Sample records for late cenozoic tectonic

  1. Late Cenozoic sedimentary and tectonic history of south Buton, Indonesia (United States)

    Fortuin, A. R.; De Smet, M. E. M.; Hadiwasastra, S.; Van Marle, L. J.; Troelstra, S. R.; Tjokrosapoetro, S.

    A description and interpretation are given of the Upper Cenozoic sedimentary record of south Buton. Various sections and outcrops were studied and sampled for their microfossil content, to provide age and paleobathymetrical data. Together with information from the literature, these data from the base for a geohistory analysis to evaluate the vertical motions. Deposition started some 11 Ma ago, after the main deformation of the island, which was related to the collision of a microplate carrying Buton, with the southeast arm of Sulawesi. Coarse and fine terrigenous debris accumulated in a rapidly subsiding foreland basin; subsidence may have exceeded 100 cm/ka. When the rate of subsidence decreased a late Miocene-early Pliocene period of quiet pelagic sedimentation followed. From the late Pliocene onwards (around 3.5 Ma BP) an overall uplift took place, with rates between 30-120 cm/ka. This drastic change is explained by the collision of Buton with a submerged microcontinent that presently forms the Tukang Besi platform, situated southeast of Buton, which interaction resulted in wrench type tectonics and a clockwise rotation of over 60° for south Buton.

  2. Late Cenozoic Tectonic Deformation in the Dongsha Islands and Adjacent Sea Area

    Institute of Scientific and Technical Information of China (English)

    WU Shiguo(吴时国); LIU Zhan(刘展); WANG Wanyin(王万银); GUO Junhua(郭军华); T. Lüdmann; H. K. Wong


    Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magnetic and drilling wells data led to the discovery of three post-fault sequences (V, VI, VII). Extensive tectonic uplift, magma activity and erosion occurred in Dongsha Island and the adjacent area, where most of the faults in the northeastern SCS were still active during Pliocene and Quaternary. Two groups of faults trending NEE and NW were developed during Late Cenozoic. We conclude that three important tectonic movements, especially Dongsha movement (4.4-5.2 Ma) and Liuhua movement (1.4-1.89 Ma), controlled the structural framework in the Dongsha rise; whose deformation in the east is stronger than that in the west and whose stress field variation suggests that the tectonic uplift in the study area contributed to magmato-tectonic events correlated to the main collision phases between the East China and Taiwan 5-3 and 3-0 Ma ago.

  3. Late Cenozoic tectonic deformation in the Tianshan Mountain and its foreland basins

    Institute of Scientific and Technical Information of China (English)

    ZHANG Peizhen


    @@ The magnificent Tianshan Mountain has owned its respects and high praise since the beginning of ancient Chinese civilization. When the history wheeled into the 1990s, a large group of earth scientists once again focused their sights on the Tianshan Mountain, the most spectacular Cenozoic rejuvenated intra-plate mountain building. Why does such strong tectonic deformation occur in the continental interior several thousand kilometers away from plate boundaries? What are the pattern and magnitude of the tectonic deformation? What factors dominate tectonic deformation in the continental interior? How do the dynamic processes at the depth dictate tectonic deformation near the surface? The Tianshan Mountain provides a natural laboratory to answer these important scientific questions.

  4. Permian to late Cenozoic evolution of northern Patagonia: Main tectonic events, magmatic activity, and depositional trends (United States)

    Uliana, M. A.; Biddle, K. T.

    The late Paleozoic to late Cenozoic evolution of northern Patagonia was influenced significantly by events that occurred while the area was part of the South American sector of Gondwanaland. Late Paleozoic to Middle Triassic subduction along the edge of the supercontinent formed a broad convergent-margin system that is the underpinning of northern Patagonia. Deformation (Gondwanidian orogeny) associated with the subduction is recognized in both the forearc and the convergent backarc areas. Regional extension, accompanied by bimodal volcanism, began in the Late Triassic and led to the formation of a number of north-northwest trending rift basins in Patagonia, which generally followed the Gondwanidian basement grain. Continued extension in the Jurassic and Early Cretaceous led to the opening of the Rocas Verdes marginal basin in southern Chile and, ultimately, to the opening of the South Atlantic Ocean. Once oceanic crust began to form, faulting and volcanism declined in Patagonia. During the late Early Cretaceous to the Late Cretaceous, sags over the rift basins coalesced to form a broad backarc basin behind the volcanic arc to the west. These sags are suggestive of thermally driven subsidence. Subsidence of the evolving Atlantic margin allowed extensive marine transgressions to take place from the east. The stratigraphic record of northern Patagonia reflects these events. The upper Paleozoic to upper Mesozoic sedimentary sequences were deposited in basins directly associated with convergent activity along the margin of Gondwanaland or in rift basins created during its breakup. Even though the Tertiary evolution of Patagonia was dominated by events along the western margin of South America, the patterns of sediment transport, thickness, and general shoreline position were still influenced by the locations of the Mesozoic rifts formed during the breakup of Gondwanaland.

  5. Late Cenozoic tectonics and volcanism along the North Anatolian Fault: new structural and geochemical data (United States)

    Adiyaman, Özlem; Chorowicz, Jean; Arnaud, O. Nicolas; Gündogdu, M. Niyazi; Gourgaud, Alain


    Different types of volcanic activity have developed along the North Anatolian Fault zone (NAF) in Turkey. Detailed analysis of satellite images and Digital Elevation Models (DEMs), and field observations have been made in order to understand the tectonics and the distribution of volcanic vents. In the Anatolian block, some faults are oblique to the NAF, and delimit extensional escape wedges. Vents rooted on open tension fractures show that emplacement of the volcanism is related to tensional fracturing of the Anatolian continental block, which we attribute to the onset of free borders in the south and west. Along the NAF, earliest extension ( ϑ1) is directed S to SSW and the latest ( ϑ2) towards W to WSW, parallel to the sinistral slip along the NAF. Major and trace element geochemical data indicate that the dominant calc-alkaline rocks are associated with various alkaline lavas. K-Ar ages of the volcanics range from 22 to 8.5 Ma in Galatia Massif, 900 to 100 ka in Niksar and 3 to 12 ka in Erzincan. Isotopic and trace element data are interpreted as reflecting a dominantly lithospheric mantle source, slightly mixed with asthenospheric liquids. Most magmas were fractionated and contaminated by continental crust during their ascent. ϑ1 and ϑ2 tectono-volcanic events have propagated through time and space from west to east. The ϑ1 extension is late Oligocene in the Galatia Massif, late Miocene in Niksar and late Pliocene in Erzincan. The ϑ2 extension and strike-slip event along the NAF began in the late Miocene in the Galatia Massif, early Pliocene in Niksar and Quaternary in Erzincan. Signature from an asthenospheric source in the second event in the three regions suggests that an ancient suture zone (Galatia Massif) and/or the lithospheric NAF transform (Niksar and Erzincan) have served to channel small quantities of asthenospheric melts existing at the base of the lithosphere.

  6. Late Cenozoic-recent tectonics of the southwestern margin of the Tibetan Plateau, Ladakh, northwest India (United States)

    Bohon, Wendy

    The Himalayan orogenic system is one of the youngest and most spectacular examples of a continent-continent collision on earth. Although the collision zone has been the subject of extensive research, fundamental questions remain concerning the architecture and evolution of the orogen. Of particular interest are the structures surrounding the 5 km high Tibetan Plateau, as these features record both the collisional and post-collisional evolution of the orogen. In this study we examine structures along the southwestern margin of the Tibetan Plateau, including the Karakoram (KFS) and Longmu Co (LCF) faults, and the Ladakh, Pangong and Karakoram Ranges. New low-temperature thermochronology data collected from across the Ladakh, Pangong and Karakoram Ranges improved the spatial resolution of exhumation patterns adjacent to the edge of the plateau. These data show a southwest to northeast decrease in cooling ages, which is the trailing end of a wave of decreased exhumation related to changes in the overall amount of north-south shortening accommodated across the region. We also posit that north-south shortening is responsible for the orientation of the LCF in India. Previously, the southern end of the LCF was unmapped. We used ASTER remotely sensed images to create a comprehensive lithologic map of the region, which allowed us to map the LCF into India. This mapping shows that this fault has been rotated into parallelism with the Karakoram fault system as a result of N-S shortening and dextral shear on the KFS. Additionally, the orientation and sense of motion along these two systems implies that they are acting as a conjugate fault pair, allowing the eastward extrusion of the Tibet. Finally, we identify and quantify late Quaternary slip on the Tangtse strand of the KFS, which was previously believed to be inactive. Our study found that this fault strand accommodated ca. 6 mm/yr of slip over the last ca. 33-6 ka. Additionally, we speculate that slip is temporally

  7. A Late Cretaceous and Cenozoic reconstruction of the Southwest Pacific region: Tectonics controlled by subduction and slab rollback processes (United States)

    Schellart, W. P.; Lister, G. S.; Toy, V. G.


    A Cenozoic tectonic reconstruction is presented for the Southwest Pacific region located east of Australia. The reconstruction is constrained by large geological and geophysical datasets and recalculated rotation parameters for Pacific-Australia and Lord Howe Rise-Pacific relative plate motion. The reconstruction is based on a conceptual tectonic model in which the large-scale structures of the region are manifestations of slab rollback and backarc extension processes. The current paradigm proclaims that the southwestern Pacific plate boundary was a west-dipping subduction boundary only since the Middle Eocene. The new reconstruction provides kinematic evidence that this configuration was already established in the Late Cretaceous and Early Paleogene. From ˜ 82 to ˜ 52 Ma, subduction was primarily accomplished by east and northeast-directed rollback of the Pacific slab, accommodating opening of the New Caledonia, South Loyalty, Coral Sea and Pocklington backarc basins and partly accommodating spreading in the Tasman Sea. The total amount of east-directed rollback of the Pacific slab that took place from ˜ 82 Ma to ˜ 52 Ma is estimated to be at least 1200 km. A large percentage of this rollback accommodated opening of the South Loyalty Basin, a north-south trending backarc basin. It is estimated from kinematic and geological constraints that the east-west width of the basin was at least ˜ 750 km. The South Loyalty and Pocklington backarc basins were subducted in the Eocene to earliest Miocene along the newly formed New Caledonia and Pocklington subduction zones. This culminated in southwestward and southward obduction of ophiolites in New Caledonia, Northland and New Guinea in the latest Eocene to earliest Miocene. It is suggested that the formation of these new subduction zones was triggered by a change in Pacific-Australia relative motion at ˜ 50 Ma. Two additional phases of eastward rollback of the Pacific slab followed, one during opening of the South Fiji

  8. Chronological dating and tectonic implications of late Cenozoic volcanic rocks and lacustrine sequence in Oiyug Basin of southern Tibet

    Institute of Scientific and Technical Information of China (English)


    Reconstruction of uplift history of the Tibetan Plateau is crucial for understanding its environmental impacts. The Oiyug Basin in southern Tibet contains multiple periods of sedimentary sequences and volcanic rocks that span much of the Cenozoic and has great potential for further studying this issue. However, these strata were poorly dated. This paper presents a chronological study of the 145 m thick and horizontally-distributed lacustrine sequence using paleomagnetic method as well as a K-Ar dating of the underlying volcanic rocks. Based on these dating results, a chronostratigraphic framework and the basin-developmental history have been established for the past 15 Ma, during which three tectonic stages are identified. The period of 15-8.1 Ma is characterized by intense volcanic activities involving at least three major eruptions. Subsequently, the basin came into a tectonically quiescent period and a lacustrine sedimentary sequence was developed. Around 2.5 Ma, an N-S fault occurred across the southern margin of the basin, leading to the disappearance of the lake environment and the development of the Oiyug River. The Gyirong basin on northern slope of the Himalayas shows a similar basin developmental history and thus there is a good agreement in tectonic activities between the Himalayan and Gangdise orogenic belts. Therefore, the tectonic evolution stages experienced by the Oiyug Basin during the past 15 Ma could have a regional significance for southern Tibet. The chronological data obtained from this study may provide some constraints for further studies with regard to the tectonic processes and environmental changes in southern Tibetan Plateau.

  9. Influence of Large Igneous Provinces on Svalbard tectonics and sedimentation from the Late Mesozoic through Cenozoic: Insight from (U-Th)/He zircon and apatite thermochronology (United States)

    Barnes, Christopher; Schneider, David; Majka, Jaroslaw


    Svalbard, the northwestern sub-aerial exposure of the Barents Shelf, offers significant insight into the geodynamics of the High Arctic. The tectonics and sedimentation on Svalbard from the Late Mesozoic through Cenozoic can be attributed to two Large Igneous Provinces: the High Arctic Large Igneous Province (HALIP; 130-90 Ma) and the North Atlantic Large Igneous Province (NAIP; 62-55 Ma). The relationship between the HALIP and the tectonics of the High Arctic remains somewhat unclear, whereas the NAIP is directly linked to opening of the North Atlantic Ocean. This study attempts to establish links between the HALIP and geodynamics of the High Arctic, and reveals the far-field tectonic consequences of the NAIP on Svalbard and the High Arctic. We focus on the Southwestern Caledonian Basement Terrane of Svalbard, characterized by the West Spitsbergen Fold and Thrust Belt, formed during the Eurekan Orogeny (c. 55-33 Ma). Crystalline basement was sampled from four regions (Prins Karls Forland, Oscar II Land, Wedel Jarlsberg Land, and Sørkapp Land) for the purpose of zircon and apatite (U-Th)/He thermochronometry which allows for resolution of thermal events below 200°C. We forward model our datasets using HeFTy software to produce temperature-time histories for each of these regions, and compare these thermal models with Svalbard stratigraphy to resolve the geodynamics of Svalbard from the Late Mesozoic through Cenozoic. The Cretaceous stratigraphy of Svalbard is characterized by a short-lived Mid-Cretaceous sub-aerial unconformity (c. 129 Ma) and a significant Late Cretaceous unconformity (c. 105-65 Ma). Our thermal models reveal a Mid-Cretaceous heating event, suggesting an increasing geothermal gradient coeval with development of the first unconformity. This may indicate that short-lived domal-uplift, related to the arrival of the HALIP plume, was a primary control on Svalbard tectonics and sedimentary deposition throughout the Mid-Cretaceous. Late Cretaceous

  10. Structure and tectonic evolution of the NE segment of the Polish-Ukrainian Carpathians during the Late Cenozoic: subsurface cross-sections and palinspastic models (United States)

    Kuśmierek, Jan; Baran, Urszula


    The discrepant arrangement of the Carpathian nappes and syntectonic deposits of the Carpathian Foredeep reveals the oroclinal migration of the subduction direction of the platform margin during the Late Cenozoic. Formation of the nappes was induced by their detachment from disintegrated segments of the European Platform; the segments were shortened as a result of their vertical rotation in zones of compressional sutures. It finds expression in local occurrence of the backward vergence of folding against the generally forward vergence toward the Carpathian Foredeep. The precompressional configuration of sedimentation areas of particular nappes was reconstructed with application of the palinspastic method, on the basis of the hitherto undervalued model which emphasizes the influence of the subduction and differentiated morphology of the platform basement on the tectonic evolution of the fold and thrust belt. Superposition of the palaeogeographic representations and the present geometry of the orogen allows understanding of the impact of the magnitudes of tectonic displacements on the differentiation of the geological structure in the NE segment of the Carpathians. The differentiation has inspired different views of Polish and Ukrainian geologists on structural classification and evolution of the frontal thrusts.

  11. Plate flexure and volcanism: Late Cenozoic tectonics of the Tabar-Lihir-Tanga-Feni alkalic province, New Ireland Basin, Papua New Guinea (United States)

    Lindley, I. D.


    Late Cenozoic Tabar-Lihir-Tanga-Feni (TLTF) alkaline volcanism, New Ireland Basin, PNG, is associated with extensional cracks along the crests of flexed ridges developed on the New Ireland Microplate (New name). The tectonic alignment of the TLTF volcanic arc is essentially perpendicular to the flexed ridges, suggesting that fractures parallel to the direction of maximum horizontal compression facilitated the rapid ascent of alkaline magmas from the mantle region, perhaps 60-70 km depth. The mainly Pliocene to Pleistocene volcanoes were localized at the intersection of ridge-parallel Kabang structures and arc-parallel Niffin structures, suggesting that the Kabang-Niffin structural intersections underlying each of the TLTF island groups provided a well developed, clustered network of open conduits which tapped the mantle source region. Periodic post-Miocene locking and unlocking along the strike-slip Kilinailau Fault (New name) are thought to have functioned as a valve, turning on (Pliocene) and then turning off (Pleistocene) volcanic activity, respectively. Partial locking of the Kilinailau Fault during the Pliocene resulted in the accumulation of intraplate stresses within the New Ireland Microplate, and caused plate flexure and ridge development, plate-cracking along ridge crests and the development of arc-parallel regional fractures parallel to the direction of maximum compression. Unlocking of the Kilinailau Fault in the Pleistocene resulted in the release of intraplate stresses in the New Ireland Microplate and a cessation of volcanic activity across most of the TLTF arc. The style and scale of plate flexure and cracking, accompanied by within-plate alkaline volcanism from equally spaced ridge-top eruptive centers confined to a narrow, linear volcanic arc are unknown from any other tectonic province.

  12. Mesozoic and Cenozoic tectonic evolution of the Longmenshan fault belt

    Institute of Scientific and Technical Information of China (English)

    WANG; ErChie


    The giant earthquake(Ms=8.0) in Wenchuan on May 12,2008 was triggered by oblique convergence between the Tibetan Plateau and the South China along the Longmenshan fault belt.The Longmenshan fault belt marks an important component of the tectonic and geomorphological boundary between the eastern and western part of China and has a protracted tectonic history.It was first formed as an intracontinental transfer fault,patitioning the differential deformation between the Pacific and Tethys tectonic domains,initiated in late Paleozoic-early Mesozoic time,then served as the eastern boundary of the Tibetan Plateau to accommodate the growth of the plateau in Cenozoic.Its current geological and geomorphological frameworks are the result of superimposition of these two tectonic events.In Late Triassic,the Longmenshan underwent left-slip oblique NW-SE shortening due to the clockwise rotation of the Yangtze Block,which led to the flexural subsidence of the Sichuan foreland basin,but after that,the subsidence of the Sichuan Basin seems no longer controlled by the tectonic activity of the Longmenshan fault belt.The Meosozoic tectonic evolution of the Songpan-Ganzi fold belt differs significantly compared with that of the Yangtze Platform,featured by intensive northeast and southwest shortening and resulted in the close of the Paleo-Tethys.Aerial photos taken immediately after main shock of the giant May 12,2008 earthquake have documented extensive rock fall and landslides that represent one of the most destructive aspects of the earthquake.Both rock avalanches and landslides delivered a huge volume of debris into the middle part of the Minjiang River,and formed many dammed lakes.Breaching of these natural dams can be catastrophic,as occurred in the Diexi area along the upstream of the Minjiang River in the year of 1933 that led to devastating floodings.The resultant flood following the breaching of these dams flowed through and out of the Longmenshan belt into the Chengdu Plain

  13. Mesozoic and Cenozoic tectonic evolution of the Longmenshan fault belt

    Institute of Scientific and Technical Information of China (English)

    WANG ErChie; MENG QingRen


    The giant earthquake (MS=8.0) in Wenchuan on May 12, 2008 was triggered by oblique convergence between the Tibetan Plateau and the South China along the Longmenshan fault belt. The Longmenshan fault belt marks an important component of the tectonic and geomorphological boundary between the eastern and western part of China and has a protracted tectonic history. It was first formed as an intracontinental transfer fault, patitioning the differential deformation between the Pacific and Tethys tectonic domains, initiated in late Paleozoic-early Mesozoic time, then served as the eastern boundary of the Tibetan Plateau to accommodate the growth of the plateau in Cenozoic. Its current geological and geomorphological frameworks are the result of superimposition of these two tectonic events. In Late Triassic, the Longmenshan underwent left-slip oblique NW-SE shortening due to the clockwise rotation of the Yangtze Block, which led to the flexural subsidence of the Sichuan foreland basin, but after that, the subsidence of the Sichuan Basin seems no longer controlled by the tectonic activity of the Longmenshan fault belt. The Meosozoic tectonic evolution of the Songpan-Ganzi fold belt differs significantly compared with that of the Yangtze Platform, featured by intensive northeast and southwest shortening and resulted in the close of the Paleo-Tethys. Aerial photos taken immediately after main shock of the giant May 12, 2008 earthquake have documented extensive rock fall and landslides that represent one of the most destructive aspects of the earthquake. Both rock avalanches and landslides delivered a huge volume of debris into the middle part of the Minjiang River, and formed many dammed lakes. Breaching of these natural dams can be catastrophic, as occurred in the Diexi area along the upstream of the Minjiang River in the year of 1933 that led to devastating floodings. The resultant flood following the breaching of these dams flowed through and out of the Longmenshan belt

  14. The Late Cenozoic tectonic deformation in the Western Qaidam Basin and its implications%柴达木盆地西部地区晚新生代构造变形及其意义

    Institute of Scientific and Technical Information of China (English)

    张涛; 宋春晖; 王亚东; 郑海军; 张志高; 吴松; 孟庆泉; 方小敏


    青藏高原东北缘构造变形研究是认识整个青藏高原隆升过程、机制以及印欧板块碰撞远程效应的重要途径。受控于昆仑山断裂、阿尔金断裂、祁连山断裂的柴达木盆地,新生代地层发育,较完整地记录了高原东北缘的构造变形信息。尤其柴达木盆地西部地区,构造变形强烈,晚新生代地层出露完整,是研究其晚新生代构造变形历史及驱动机制的理想地区。文中应用平衡剖面和古地磁构造旋转方法,结合最新的磁性地层年代,定量恢复该地区的构造变形历史。结果表明,在挤压应力的控制下该地区自22 Ma以来,构造变形主要表现为地层缩短与构造旋转,且其强度呈阶段性增长,具体又可划分为3个阶段:22~9.1 Ma构造活动平静期、9.1~2.65Ma构造变形相对加强期、2.65Ma以来构造变形顶峰期。研究表明,造成柴西地区地层持续缩短和顺时针旋转的关键推动力是印欧板块晚新生代的持续向北推挤、昆仑山—祁曼塔格山向柴达木盆地强烈挤压推覆以及阿尔金左旋走滑断裂大规模的复活。%The research of tectonic deformation of northeastern Tibetan Plateau is an important way to recognize the process and mechanism of the entire plateau uplift,and the remote effects of Indo-European plate collision,too.The Qaidam Basin is bounded by the Kunlun fault,Altyn Tagh fault and Qilian fault to the northwest,south and northeast,respectively,developed the thick Cenozoic sediments and have recorded the tectonic deformation information of northeastern Tibet.Especially,the western Qaidam Basin has undergone strong tectonic deformation and well exposed the Late Cenozoic strata,which is the ideal area to study the Late Cenozoic tectonic deformation history and driving mechanism.Combined with the latest high-precision paleomagnetic age,the balanced cross-section restoration and paleomagnetic structure rotation were used to reconstruct the

  15. Late Mesozoic-Cenozoic sedimentary basins of active continental margin of Southeast Russia: Paleogeography, tectonics, and coal-oil-gas presence

    Energy Technology Data Exchange (ETDEWEB)

    Kirillova, G.L. [Russian Academy of Science, Khabarovsk (Russian Federation). Far Eastern Branch


    After mid-Jurassic collision of the Siberian and Chinese cratons. a latitudinal system of post-collision troughs developed along the Mongol-Okhotsk suture, filled with terrigenous coal-bearing molasse. The dispersion of Pangea and creation of oceans during the Late Jurassic are correlated to the emergence of the East Asian submeridional rift system with volcano-terrigenous coal-bearing deposits. Foreland and flexural basins were formed along the margin of the rigid massifs during the Late Jurassic to Berriasian. During the Valanginian-mid-Albian an oblique subduction of the Izanagi plate beneath the Asian continent occurred, producing a transform margin type, considerable sinistral strike slip displacements, and formation of pull-apart basins filled with turbidites. The Aptian is characterized by plate reorganization and formation of epioceanic island arcs, fore-arc and back-arc basins in Sakhalin and the Sikhote-Alin, filled with volcanoclastics. By the end of the Albian, the East Asian marginal volcanic belt began to form due to the subduction of the Kula plate beneath the Asian continent. During the Cenomanian-Coniacian shallow marine coarse clastics accumulated in the fore-arc basins, which were followed by continental deposits in the Santonian-Campanian. From the Coniacian to the Maastrichtian, a thermal subsidence started in rift basins, and continental oil-bearing clastics accumulated. Widespread elevation and denudation were dominant during the Maastrichtian. This is evidenced by thick sediments accumulated in the Western Sakhalin fore-arc basin. During the Cenozoic, an extensive rift belt made up of a system of grabens, which were filled with lacustrine-alluvial coal-and oil-bearing deposits, developed along the East Asian margin.

  16. Mesozoic/Cenozoic tectonic events around Australia (United States)

    Müller, R. Dietmar; Gaina, Carmen; Tikku, Anahita; Mihut, Dona; Cande, Steven C.; Stock, Joann M.

    We use an absolute and relative plate motion model for the plates around Australia to identify major plate tectonic events, evaluate their causes, and investigate their effects on anomalous intraplate subsidence or uplift and on the history of oceanic crustal accretion. An event at ˜136 Ma is marked by the onset of sea floor spreading between Greater India and Australia. At about this time long-lived subduction east of Australia ceased, probably due to subduction of the Phoenix-Pacific spreading ridge, changing this plate boundary to a transform margin. Between 130 and 80 Ma, Australia and East Antarctica moved eastward in the Atlantic-Indian mantle hotspot reference frame. This can be plausibly linked to ridge push from the NW-SE oriented spreading center NW of Australia and to the inferred geometry and continued subduction of the Phoenix plate beneath the West Antarctic margin. A drastic change in spreading direction between the Indian and Australian plates from NE-SW to N-S occurred at about 99 Ma, possibly caused by a change in absolute motion of the Pacific Plate. Chron 27 (˜61 Ma) marks the onset of relative motion between East and West Antarctica, and a change in the relative motion between Australia and Antarctica. It may be linked to the subduction of a segment of the Neo-Tethyan Ridge. Both events caused anomalous subsidence on the Northwest Shelf of Australia. The almost stationary position of Australia w.r.t. the mantle from ˜80 Ma to ˜40 Ma may reflect the progressive subduction of the Pacific-Phoenix ridge to the east of New Zealand preceding 80 Ma, resulting in a diminished trench suction force east of Australia. Preliminary reconstructions to close the Pacific-Australian plate circuit based on recently collected geophysical data indicate that a tectonic event at 43 Ma may mark the onset of renewed subduction east of Australia. At the same time spreading in the Wharton Basin between India and Australia ceased, and tectonic reactivation is

  17. Late Mesozoic-Cenozoic sedimentary basins of active continental margin of Southeast Russia: palaeography, tectonics, and coal-oil-gas presence

    Energy Technology Data Exchange (ETDEWEB)

    Kirillova, G.L. [Russian Academy of Sciences, Khabarovsk (Russian Federation). Institute of Tectonics and Geophysics


    Various settings took place during the Late Mesozoic: divergent, convergent, collisional, and transform. After mid-Jurassic collision of the Siberian and Chinese cratons, a latitudinal system of post-collision troughs developed along the Mongol-Okhotsk suture (the Uda, Torom basins and others), filled with terrigenous coal-bearing molasse. The dispersion of Pangea, creation of oceans during the Late Jurassic is correlated to the emergence of the East Asian submeridional rift system with volcano-terrigenous coal-bearing deposits (the Amur-Zeya basin). At that time, to the east there existed an Andean-type continental margin. Foreland (Upper Bureya, Partizansk, and Razdolny) and flexural (Sangjiang-Middle Amur) basins were formed along the margin of the rigid massifs during the Late Jurassic to Berriasian. During the Valanginian-mid-Albian an oblique subduction of the lzanagi plate beneath the Asian continent occurred, producing a transform margin type, considerable sinistral strike slip displacements, and formation of pull-apart basins filled with turbidites (the Sangjiang- Middle Amur basin). The Aptian is characterized by plate reorganization and formation of epioceanic island arcs, fore-arc and back-are basins in Sakhalin and the Sikhote-Alin (the Alchan and Sangjiang-Middle Amur basins), filled with volcanoclastics. During the mid-Albian a series of terranes accreted to the Asian continental margin. By the end of the Albian, the East Asian marginal volcanic belt began to form due to the subduction of the Kula plate beneath the Asian continent. During the Cenomanian-Coniacian shallow marine coarse clastics accumulated in the fore-arc basins, which were followed by continental deposits in the Santonian-Campanian. From the Coniacian to the Maastrichtian, a thermal subsidence started in rift basins, and continental oil-bearing clastics accumulated (the Amur-Zeya basin). Widespread elevation and denudation were dominant during the Maastrichtian. This is evidenced by

  18. Pre-Cenozoic tectonic framework of Central America

    Energy Technology Data Exchange (ETDEWEB)

    Horne, G.S.


    Central America (C.A.) lies along the junctions of five crustal plates at the western edge of the Caribbean. Major fault zones divide it into at least three blocks, each of which has experienced a distinct tectonic history. Although the region has been dominated by plate interactions during the Cenozoic, paleogeographic and palinspastic relations among the various blocks is increasingly obscure and conjectural back through the Phanerozoic. Pre-Mesozoic rocks are unknown in southern C.A., but are widespread as metamorphic basement complexes in northern C.A. The Maya basement consists of Precambrian igneous massifs and Lower Paleozoic metasedimentary sequences cut by mid-Paleozoic plutons, unconformably overlain locally by Upper Paleozoic terrestrial-to-marine strata. The Chorotega-Choco basement is a Late Mesozoic ophiolite sequence accreted with Upper Cretaceous and Lower Tertiary deep marine volcanic and sedimentary strata into a forearc subduction complex along the Pacific margin. By contrast, Mesozoic successions on the Maya and Chortis blocks are cratonic and grossly similar, consisting of basal transgressive clastics, one or more thick Lower Cretaceous rudistid limestone units, and fluvial-deltaic terrigenous redbed sequences; sections vary in detail locally, and evaporites are common on the Maya block. The Late Cretaceous along the Maya-Chortis boundary was characterized by plate collision, ophiolite obduction, and sinistral block translation.

  19. On tectonic movement in the South China Sea during the Cenozoic

    Institute of Scientific and Technical Information of China (English)

    LIN Changsong; CHU Fengyou; GAO Jinyao; TAN Yonghua


    The tectonic movement taking place at the end of Cretaceous and the beginning of Cenozoic had opened the Ce-nozoic phase of polycyclic tectonic movements, then the whole crust of the South China Sea had been mainly subjected to the regional stress field of tectonic tension, which was characterized by rifting depression. Seven times of regional tectonic movement and sedimentation had been assembled into a geological development history of polycyclic oscillation. Especially, the tectonic movements were strongly intensified at the end of Cretacious and the beginning of Paleagene, between Late Eocene and Mid-Oligocene, during Mid- and Late Miocene. These three times of tectonic movement had built the most important regional tectonic interfaces in the South China Sea. Crust movements of the South China Sea were the result and epitome of interaction of the Eurasia, Pacific and Indo-Australia plates, that is, they were introduced by polycyclic changes of directions, rates and strengths of lithospheric movements and asthenospheric flows across the Pacific and Indo-Australia plates.

  20. Biogeographical consequences of Cenozoic tectonic events within East Asian margins: a case study of Hynobius biogeography.

    Directory of Open Access Journals (Sweden)

    Jun Li

    Full Text Available Few studies have explored the role of Cenozoic tectonic evolution in shaping patterns and processes of extant animal distributions within East Asian margins. We select Hynobius salamanders (Amphibia: Hynobiidae as a model to examine biogeographical consequences of Cenozoic tectonic events within East Asian margins. First, we use GenBank molecular data to reconstruct phylogenetic interrelationships of Hynobius by bayesian and maximum likelihood analyses. Second, we estimate the divergence time using the bayesian relaxed clock approach and infer dispersal/vicariance histories under the 'dispersal-extinction-cladogenesis' model. Finally, we test whether evolutionary history and biogeographical processes of Hynobius should coincide with the predictions of two major hypotheses (the 'vicariance'/'out of southwestern Japan' hypothesis. The resulting phylogeny confirmed Hynobius as a monophyletic group, which could be divided into nine major clades associated with six geographical areas. Our results show that: (1 the most recent common ancestor of Hynobius was distributed in southwestern Japan and Hokkaido Island, (2 a sister taxon relationship between Hynobius retardatus and all remaining species was the results of a vicariance event between Hokkaido Island and southwestern Japan in the Middle Eocene, (3 ancestral Hynobius in southwestern Japan dispersed into the Taiwan Island, central China, 'Korean Peninsula and northeastern China' as well as northeastern Honshu during the Late Eocene-Late Miocene. Our findings suggest that Cenozoic tectonic evolution plays an important role in shaping disjunctive distributions of extant Hynobius within East Asian margins.

  1. Eurasia as the scene of the Late Cenozoic tectogenesis

    Directory of Open Access Journals (Sweden)

    G.F. Ufimtsev


    Full Text Available This paper attempts to review the descriptions on the genetic series of neotectonic forms in Eurasia. Morphotectonically, the Eurasian continental block exhibits a radial-concentric pattern consisting of four kinds of tectonic units: platforms, rejuvenated and youthful mobile belts, and the continent-ocean transition zones. Vast areas of young and ancient platforms, such as Siberia, have experienced slow-rate Late-Cenozoic uplift and little interior deformation. The youthful orogenic belts are clustered into the giant Alpine-Himalayan megabelt. The rejuvenated mountain belts are characterized by a variety of structural-morphological types of orogens, such as domelike uplifts, block uplifts and intermountain basins. The continent-ocean transition zones in Eastern Asia, including marginal rifts and extensional basins, are resulted from interaction between the continental block and Pacific Ocean and Philippine Sea since the Late Cenozoic. One of the conspicuous features of Eurasia is that most areas lie in the largest geoid depression of the Earth, and the NS trending Uralian-Oman lineament expresses a break on the geoid slope, implying a relationship to deep structure, including density inhomogeneities, downward to the core-mantle interface. Besides, the Eurasian continent fully demonstrates morphotectonic and recent geodynamic features of the Northern Hemisphere of the Earth, just in contrast to that of the Southern Hemisphere. It is best to view the surface morphotectonics and deep structure of the Earth as a geodynamic ensemble which has spawned the large-scale geomorphic features on the surface.

  2. Polyphase tectonic events and Cenozoic basin-range coupling in the Tianshan Belt, Northwestern China

    Energy Technology Data Exchange (ETDEWEB)

    Shu, L.S.; Wang, B.; Yang, F.; Lu, H.F.; Charvet, J.; Laurent-Charvet, S. [Nanjing University, Nanjing (China). Dept. of Earth Science


    Studies show that the Tianshan orogenic belt was built in the late stage of the Palaeozoic, as evidenced by the Permian red molasses and foreland basins; which are distributed in parallel with the Tianshan belt, indicating that an intense folding and uplifting event took place. During the Triassic, this orogenic belt was strongly eroded, and basins were further developed. The folding and faulting of Mesozoic sedimentary rocks, spontaneous combustion of Jurassic coal layers and formation of sintered rocks, the Cenozoic earthquakes and active faulting, and the unique mosaic pattern of basin-range framework of Xinjiang are all products of tectonism since the Neogene.

  3. Characteristics, structural styles and tectonic implications of Mesozoic-Cenozoic faults in the eastern Heilongjiang basins (NE China) (United States)

    Zhao, Xueqin; Chen, Hanlin; Zhang, Fengqi; Sun, Mingdao; Yang, Jianguo; Tan, Baode


    The Eastern Heilongjiang Basins (EHBs) are the assemblage of a series of meso-Cenozoic residual basins located in the northeastern corner of China. The deformation pattern of the EHBs has significant implications for the history of the Pacific Plate subduction beneath the Eurasia since the Late Mesozoic. In this paper, research on the characteristics and structural styles of the meso-Cenzoic faults in the EHBs has been conducted on the basis of a comprehensive analysis of field geology, drilling data and seismic reflection profiles. As a result, five different stages of the meso-Cenozoic faults in the EHBs have been recognized. These are in accordance with the time and relevant characteristics of fault movements, i.e. the early-stage of the Early Cretaceous normal fault, the early-stage of the Late Cretaceous thrust fault, the late-stage of the Late Cretaceous thrust fault, the Cenozoic synsedimentary normal fault and the late-stage Cenozoic shear fault. A regional geological section has been generated across the EHBs by linking four local seismic profiles together. A step-by-step reconstruction has been made to help better understand the Mesozoic-Cenozoic tectonic evolution of the EHBs. Two phases of extension (rifting) in the early Cretaceous Period and the Paleogene, respectively, are demonstrated to be interfered with two phases of regional uplift (compression) and erosion in the Late Cretaceous Period. The complicated development of multiple fault systems within the EHBs has reflected the evolution of a complex tectonic subduction of the Pacific Plate beneath the Eurasia since the Cretaceous Period.

  4. Mid-Cenozoic tectonic and paleoenvironmental setting of the central Arctic Ocean (United States)

    O'Regan, M.; Moran, K.; Backman, J.; Jakobsson, M.; Sangiorgi, F.; Brinkhuis, Henk; Pockalny, Rob; Skelton, Alasdair; Stickley, Catherine E.; Koc, N.; Brumsack, Hans-Juergen; Willard, Debra A.


    Drilling results from the Integrated Ocean Drilling Program's Arctic Coring Expedition (ACEX) to the Lomonosov Ridge (LR) document a 26 million year hiatus that separates freshwater-influenced biosilica-rich deposits of the middle Eocene from fossil-poor glaciomarine silty clays of the early Miocene. Detailed micropaleontological and sedimentological data from sediments surrounding this mid-Cenozoic hiatus describe a shallow water setting for the LR, a finding that conflicts with predrilling seismic predictions and an initial postcruise assessment of its subsidence history that assumed smooth thermally controlled subsidence following rifting. A review of Cenozoic tectonic processes affecting the geodynamic evolution of the central Arctic Ocean highlights a prolonged phase of basin-wide compression that ended in the early Miocene. The coincidence in timing between the end of compression and the start of rapid early Miocene subsidence provides a compelling link between these observations and similarly accounts for the shallow water setting that persisted more than 30 million years after rifting ended. However, for much of the late Paleogene and early Neogene, tectonic reconstructions of the Arctic Ocean describe a landlocked basin, adding additional uncertainty to reconstructions of paleodepth estimates as the magnitude of regional sea level variations remains unknown.

  5. Cenozoic structures and the tectonic evolution of the eastern North Sea

    DEFF Research Database (Denmark)

    Clausen, O.R.; Nielsen, S.B.; Egholm, D.L.


    Abundant seismic sections and well data from the Cenozoic succession in the eastern North Sea area generally reveal normal faulting, salt tectonics and localized tectonic inversion. However, inferences on the Cenozoic dynamic evolution of the region require thorough analysis of interactions between...... or cover tectonism took place. Our objectives are thus 1) to analyze the interaction between basement and cover structures, and if possible 2) to relate the structures to the regional tectonic evolution. The Zechstein evaporites pinch out onto the Ringkøbing-Fyn High, which in the eastern North Sea...... influencede.g. Miocene deposition and controlled the generation of second order faults. The latter detached along the top Chalk Group due to the topography generated during faulting, i.e. they are second order detachment surfaces. We conclude that the regional tectonic significance of the Cenozoic structures...

  6. Late Cenozoic structure and stratigraphy of south-central Washington

    Energy Technology Data Exchange (ETDEWEB)

    Reidel, S.P. [Westinghouse Hanford Co., Richland, WA (United States)]|[Washington State Univ., Pullman, WA (United States). Dept. of Geology; Campbell, N.P. [Yakima Valley Coll., WA (United States); Fecht, K.R.; Lindsey, K.A. [Westinghouse Hanford Co., Richland, WA (United States)


    The structural framework of the Columbia Basin began developing before Columbia River Basalt Group (CRBG) volcanism. Prior to 17.5 Ma, the eastern part of the basin was a relatively stable area, with a basement of Paleozoic and older crystalline rock. The western part was an area of subsidence in which large volumes of sediment and volcanic rocks accumulated. Concurrent with eruption of the CRBG, anticlinal ridges of the Yakima Fold Belt (YFB) were growing under north-south compression. Topographic expression of these features was later masked by the large volume of CRBG basalt flowing west from fissures in the eastern Columbia Basin. The folds continued to develop after cessation of volcanism, leading to as much as 1,000 m of structural relief in the past 10 million years. Post-CRBG evolution of the Columbia Basin is recorded principally in folding and faulting in the YFB and sediments deposited in the basins. The accompanying tectonism resulted in lateral migration of major depositional systems into subsiding structural lows. Although known late Cenozoic faults are on anticlinal ridges, earthquake focal mechanisms and contemporary strain measurements indicate most stress release is occurring in the synclinal areas under north-south compression. There is no obvious correlation between focal mechanisms for earthquakes whose foci are in the CRBG and the location of known faults. High in situ stress values help to explain the occurrence of microseismicity in the Columbia Basin but not the pattern. Microseismicity appears to occur in unaltered fresh basalt. Faulted basalt associated with the YFB is highly brecciated and commonly altered to clay. The high stress, abundance of ground water in confined aquifers of the CRBG, and altered basalt in fault zones suggest that the frontal faults on the anticlinal ridges probably have some aseismic deformation. 85 refs.

  7. Paleoenvironmental reconstruction of the late Cenozoic Qaidam Basin, China (United States)

    Zhang, C.; Wang, Y.; Li, Q.; Wang, X.; Deng, T.; Tseng, Z. J.; Takeuchi, G.; Xie, G.; Xu, Y.


    Reconstruction of paleoenvironments in the Tibetan region is important to understanding the linkage between tectonic force and climate change. Here we report new isotope data from the Qaidam Basin, China, which is located on the northeastern Tibetan Plateau, including stable C and O isotope analyses of a wide variety of late Cenozoic mammalian tooth enamel samples (including deer, giraffe, horse, rhino, and elephant), and O isotope compositions of phosphate (δ18Op) in fish bone samples. Mammalian tooth enamel δ13C values, when combined with fossil assemblage and other geological evidence, indicate that the Qaidam Basin was warmer and more humid during the late Miocene and early Pliocene, and that there was lush C3 vegetation with significant C4 components at that time, although the C4 plants were not consistently utilized. In contrast, the modern Qaidam Basin is dominated by C3 plants. Fish bone δ18Op values showed statistically significant enrichment from the Tuxi-Shengou-Naoge interval (late Miocene) to the Yahu interval (early Pliocene) and from the Yahu interval to the present day. This most likely reflects increases in the δ18O of lake water over time, as a result of increased aridification of the Qaidam Basin. Assuming that mammals drank exclusively from the lake, temperatures were calculated from average δ18Op values and average δ18Ow derived from large mammal tooth enamel δ18O. Temperatures were also estimated from δ18Op and δ18Ow estimated from co-ocurring large mammal tooth enamel δ18O. The temperature estimates were all lower than the average temperature of the modern Qinghai Lake surface water during the summer, and mostly too low to be reasonable, indicating that the fish and the large mammals were not in equilibrium with the same water. Assuming the relationship between salinity and δ18Ow observed for the modern Qinghai Lake and its surrounding lakes and ponds applied in the past, we calculated the paleosalinities of lake waters to be ~0 to

  8. The deformation and tectonic evolution of the Huahui Basin, northeast China, during the Cretaceous-Early Cenozoic (United States)

    Huang, Shiqi; Dong, Shuwen; Zhang, Yueqiao; Zhang, Fuqin; Huang, Dezhi; Wei, Shi; Li, Zhenhong; Miao, Laicheng; Zhu, Mingshuai


    The Cretaceous Huahui basin lies along the Dunhua-Mishan fault (Dun-Mi fault), which is one of the northern branches of Tan-Lu fault in northeastern China. The study of the formation and the tectonic movements that took place in the basin can provide very important information for deciphering the tectonic evolution of northeastern China during Cretaceous-Early Cenozoic. The field analysis of fault-slip data collected from different units in the basin, demonstrates changes in the paleo-stress state that reveals a three-stage tectonic movement during the Cretaceous-Early Cenozoic. The earliest tectonic movement was NW-SE extension, which was responsible for the formation of the basin and sedimentary infilling during the Early Cretaceous. Dating of the andesite in the fill indicates it began during about 119.17 ± 0.80 Ma. The extensional structures formed in the Latest Early Cretaceous imply that this tectonic movement lasted until the beginning of the Late Cretaceous. The second stage began during the Late Cretaceous when the tectonic stress state changed and was dominated by NW-SE compression and NE-SW extension, which caused the inversion of the extensional basin. This compression folded the Early Cretaceous deposits and reactivated pre-existing faults and uplifted pre-existing granite in the basin. The strata and the unconformity in the basin shows that this compressive phase probably took place during the Late Cretaceous and ended in the Early Paleogene by a compressional regime with NE-SW compression and NW-SE extension that constitutes the third stage. The tectonic stress fields documented in the Huahui basin provide insight into the influences of plate tectonics on the crustal evolution of northeastern China during the Cretaceous to Early Cenozoic. These results show that the development of Huahui basin was controlled by the northwestward subduction of the paleo-Pacific plate during the Cretaceous, and later by the far-field effects of India-Asia collision in

  9. Cenozoic structures and the tectonic evolution of the eastern North Sea

    DEFF Research Database (Denmark)

    Clausen, O.R.; Nielsen, S.B.; Egholm, D.L.


    Abundant seismic sections and well data from the Cenozoic succession in the eastern North Sea area generally reveal normal faulting, salt tectonics and localized tectonic inversion. However, inferences on the Cenozoic dynamic evolution of the region require thorough analysis of interactions between....... These structures have in the last decades been an integrated part of the discussions about subsidence and uplift of not only the interior of the basin but also of the basin margin. Abundant 2D and 3D seismic data and new depositional models enable detailed analysis and reinterpretation of where and when basement...... or cover tectonism took place. Our objectives are thus 1) to analyze the interaction between basement and cover structures, and if possible 2) to relate the structures to the regional tectonic evolution. The Zechstein evaporites pinch out onto the Ringkøbing-Fyn High, which in the eastern North Sea...

  10. Late-Paleozoic emplacement and Meso-Cenozoic reactivation of the southern Kazakhstan granitoid basement (United States)

    De Pelsmaeker, Elien; Glorie, Stijn; Buslov, Mikhail M.; Zhimulev, Fedor I.; Poujol, Marc; Korobkin, Valeriy V.; Vanhaecke, Frank; Vetrov, Evgeny V.; De Grave, Johan


    The Ili-Balkhash Basin in southeastern Kazakhstan is located at the junction of the actively deforming mountain ranges of western Junggar and the Tien Shan, and is therefore part of the southwestern Central Asian Orogenic Belt. The basement of the Ili-Balkhash area consists of an assemblage of mainly Precambrian microcontinental fragments, magmatic arcs and accretionary complexes. Eight magmatic basement samples (granitoids and tuffs) from the Ili-Balkhash area were dated with zircon U-Pb LA-ICP-MS and yield Carboniferous to late Permian (~ 350-260 Ma) crystallization ages. These ages are interpreted as reflecting the transition from subduction to (post-) collisional magmatism, related to the closure of the Junggar-Balkhash Ocean during the Carboniferous-early Permian and hence, to the final late Paleozoic accretion history of the ancestral Central Asian Orogenic Belt. Apatite fission track (AFT) dating of 14 basement samples (gneiss, granitoids and volcanic tuffs) mainly provides Cretaceous cooling ages. Thermal history modeling based on the AFT data reveals that several intracontinental tectonic reactivation episodes affected the studied basement during the late Mesozoic and Cenozoic. Late Mesozoic reactivation and associated basement exhumation is interpreted as distant effects of the Cimmerian collisions at the southern Eurasian margin and possibly of the Mongol-Okhotsk Orogeny in SE Siberia during the Jurassic-Cretaceous. Following tectonic stability during the Paleogene, inherited basement structures were reactivated during the Neogene (constrained by Miocene AFT ages of ~ 17-10 Ma). This late Cenozoic reactivation is interpreted as the far-field response of the India-Eurasia collision and reflects the onset of modern mountain building and denudation in southeast Kazakhstan, which seems to be at least partially controlled by the inherited basement architecture.

  11. On the late Cenozoic evolution of the Norwegian Arctic continental margin (United States)

    Sverre Laberg, Jan; Rydningen, Tom Arne; Lasabuda, Amando


    The Cenozoic development of the Norwegian Arctic is inferred to include two main landscape-forming events; 1) the early Cenozoic onset of rifting and still ongoing sea-floor spreading resulting in the formation of the Norwegian - Greenland Sea; and 2) the late Cenozoic global climate deterioration resulting in the growth and decay of large ice sheets repeatedly covering the onshore as well as the continental shelf areas. The rifting and subsequent sea-floor spreading are interpreted to have resulted in two contrasting pre-glacial landscape types surrounding the newly formed ocean; i) a margin-parallel ridge onshore part of Northern Norway from rift-flank uplift, and ii) a mainly low-lying platform area in the SW Barents Sea where less influence of uplift in this period is seen. The landscapes were later exposed to glacial erosion during a tectonically "passive" period. In order to quantify the landscape development during the glaciations we have utilized the mass-balance approach where the volume of the erosional products have been estimated. From this, we quantified the sedimentation rate, erosion rate and total erosion of the source area. During the late Cenozoic, the continental margin off the SW Barents Sea exemplifies an area of very high sediment input corresponding to an estimated average erosion of the shelf area of 0.4 mm/yr, much of which is related to subglacial erosion of Mesozoic - Cenozoic sedimentary rocks beneath large paleo-ice streams preserving the pre-glacial "lowland" areas here. In contrast, the North Norwegian margin experienced markedly lower input, 0.03 mm/yr of erosion of crystalline rocks in a pre-glacial "highland" representing a low-ice-flow sector of the Fennoscandian Ice Sheet, resulting in an alpine relief. This implies up to one order of magnitude variation in average glacial erosion rates along the northwestern sector of the Fennoscandian-Barents Sea ice sheets. We interpret the following factors as the main control on the glacial

  12. Late Cenozoic Paleoceanography of the Central Arctic Ocean

    Energy Technology Data Exchange (ETDEWEB)

    O' Regan, Matt, E-mail: [School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, Wales (United Kingdom)


    The Arctic Ocean is the smallest and perhaps least accessible of the worlds oceans. It occupies only 26% of the global ocean area, and less than 10% of its volume. However, it exerts a disproportionately large influence on the global climate system through a complex set of positive and negative feedback mechanisms directly or indirectly related to terrestrial ice and snow cover and sea ice. Increasingly, the northern high latitude cryosphere is seen as an exceptionally fragile part of the global climate system, a fact exemplified by observed reductions in sea ice extent during the past decades [2]. The paleoceanographic evolution of the Arctic Ocean can provide important insights into the physical forcing mechanisms that affect the form, intensity and permanence of ice in the high Arctic, and its sensitivity to these mechanisms in vastly different climate states of the past. However, marine records capturing the late Cenozoic paleoceanography of the Arctic are limited - most notably because only a single deep borehole exists from the central parts of this Ocean. This paper reviews the principal late Cenozoic (Neogene/Quaternary) results from the Arctic Coring Expedition to the Lomonosov Ridge and in light of recent data and observations on modern sea ice, outlines emerging questions related to three main themes: 1) the establishment of the 'modern' Arctic Ocean and the opening of the Fram Strait 2) the inception of perennial sea ice 3) The Quaternary intensification of Northern Hemisphere glaciations.

  13. Late-Cenozoic relief evolution under evolving climate: a review (United States)

    Champagnac, Jean-Daniel; Valla, Pierre; Herman, Fred


    The present review is an attempt to summarize quantitative evidence of Late Cenozoic changes in topographic relief on Earth. We first define different meanings of the word "relief", as it is commonly used, and detail the metrics used to quantify it. We then specify methodological tools used to quantify relief change (primarily lowtemperature thermochronometry and terrestrial cosmogenic nuclides), and analyze published evidence for different regions. Our review first show that relief changes and rates of changes are more important at mid-, than high- or low-latitudes, and appear to be insensitive to mean precipitation rates. We also show that relief change is positive (relief increases) in most of the reported cases (~80%). We subsequently define two functional relationships between relief and erosion, depending on the chosen definition of relief, and propose a conceptual model of landscape memory. We conclude, following others, that erosion rates depends non-linearly on relief evolution, itself being a function of the spatial distribution and rates of erosion. The relief increases documented in this review may be related led to erosion rate increases during the same timescales. Lastly, we discuss the importance of glacial and periglacial processes on Late Cenozoic relief and erosion rate changes, and stress the importance of frost shattering and glacial erosion at mid- and high-latitudes.

  14. Cenozoic tectonic reorganizations of the Death Valley region, southeast California and southwest Nevada (United States)

    Fridrich, Christopher J.; Thompson, Ren A.


    The Death Valley region, of southeast California and southwest Nevada, is distinct relative to adjacent regions in its structural style and resulting topography, as well as in the timing of basin-range extension. Cenozoic basin-fill strata, ranging in age from greater than or equal to 40 to approximately 2 million years are common within mountain-range uplifts in this region. The tectonic fragmentation and local uplift of these abandoned basin-fills indicate a multistage history of basin-range tectonism. Additionally, the oldest of these strata record an earlier, pre-basin-range interval of weak extension that formed broad shallow basins that trapped sediments, without forming basin-range topography. The Cenozoic basin-fill strata record distinct stratigraphic breaks that regionally cluster into tight age ranges, constrained by well-dated interbedded volcanic units. Many of these stratigraphic breaks are long recognized formation boundaries. Most are angular unconformities that coincide with abrupt changes in depositional environment. Deposits that bound these unconformities indicate they are weakly diachronous; they span about 1 to 2 million years and generally decrease in age to the west within individual basins and regionally, across basin boundaries. Across these unconformities, major changes are found in the distribution and provenance of basin-fill strata, and in patterns of internal facies. These features indicate rapid, regionally coordinated changes in strain patterns defined by major active basin-bounding faults, coincident with step-wise migrations of the belt of active basin-range tectonism. The regionally correlative unconformities thus record short intervals of radical tectonic change, here termed "tectonic reorganizations." The intervening, longer (about 3- to 5-million-year) interval of gradual, monotonic evolution in the locus and style of tectonism are called "tectonic stages." The belt of active tectonism in the Death Valley region has abruptly

  15. Wrench-Slip Reversals and Structural Inversions: Cenozoic Slide-Rule Tectonics in Sundaland

    Directory of Open Access Journals (Sweden)

    H.D. Tjia


    Full Text Available DOI: 10.17014/ijog.v1i1.174Most of continental Southeast Asia, that is, Sundaland and Indosinia, achieved a relative tectonic stability by the beginning of the Cenozoic. Since then a strong tectonic activity in Sundaland has been restricted to existing regional fault zones and to regional slow, vertical crustal movements elsewhere that produced small to very large sedimentary basins. On the other hand, regional deformation of Indosinia as a consequence of ductile shearing has continued into the Paleogene. Since the Oligocene, the northern part of Sundaland and Indosinia have been extruded differentially towards southeast along the Red River, Wang Chao (or Mae Ping, or Tonle Sap, and Three Pagodas - Axial Malay fault zones. The initial cause has been attributed to hard collision between Subplate India with Megaplate Eurasia. Plate dynamics in the region have changed substantially since Mid-Miocene as to force wrench-slip reversals along the major fault zones in Sundaland as well as in Indosinia. Concomitant structural inversions are demonstrated on seismic sections. In the core of Sundaland, earlier transtensional wrenching was succeeded by transpressive strike-slip faulting that on major faults of the Malay Basin manifested in reversals of sense. From the Hinge-line fault eastward, the transtensional left wrench slip was succeeded by transpressional dextral slip, while in the region to its west the wrench-slip kinematics was an earlier transtensional right slip followed by transpressional left slip. In the Strait of Malacca and eastern margin of Sumatra, right-lateral wrenching in the Neogene has been common. In certain places it could be established a wrench-slip of transtensional character in Oligocene-Early Miocene, and the transpressional wrench movement occurred mainly during the Middle to Late Miocene. The remarkable coincidence of termination of spreading of the South China Basin in Langhian, and that of the West Philippine and Caroline

  16. Wrench-Slip Reversals and Structural Inversions: Cenozoic Slide-Rule Tectonics in Sundaland

    Directory of Open Access Journals (Sweden)

    H.D. Tjia


    Full Text Available DOI: 10.17014/ijog.v1i1.174Most of continental Southeast Asia, that is, Sundaland and Indosinia, achieved a relative tectonic stability by the beginning of the Cenozoic. Since then a strong tectonic activity in Sundaland has been restricted to existing regional fault zones and to regional slow, vertical crustal movements elsewhere that produced small to very large sedimentary basins. On the other hand, regional deformation of Indosinia as a consequence of ductile shearing has continued into the Paleogene. Since the Oligocene, the northern part of Sundaland and Indosinia have been extruded differentially towards southeast along the Red River, Wang Chao (or Mae Ping, or Tonle Sap, and Three Pagodas - Axial Malay fault zones. The initial cause has been attributed to hard collision between Subplate India with Megaplate Eurasia. Plate dynamics in the region have changed substantially since Mid-Miocene as to force wrench-slip reversals along the major fault zones in Sundaland as well as in Indosinia. Concomitant structural inversions are demonstrated on seismic sections. In the core of Sundaland, earlier transtensional wrenching was succeeded by transpressive strike-slip faulting that on major faults of the Malay Basin manifested in reversals of sense. From the Hinge-line fault eastward, the transtensional left wrench slip was succeeded by transpressional dextral slip, while in the region to its west the wrench-slip kinematics was an earlier transtensional right slip followed by transpressional left slip. In the Strait of Malacca and eastern margin of Sumatra, right-lateral wrenching in the Neogene has been common. In certain places it could be established a wrench-slip of transtensional character in Oligocene-Early Miocene, and the transpressional wrench movement occurred mainly during the Middle to Late Miocene. The remarkable coincidence of termination of spreading of the South China Basin in Langhian, and that of the West Philippine and Caroline

  17. Meso-Cenozoic tectonics of the Central Kyrgyz Tien Shan (Central Asia), based on apatite fission track thermochronology.


    Glorie, Stijn


    Apatite fission track thermochronology on the Kyrgyz Tien Shan basement revealed a polyphased thermal history of the study-area. We interpret the Mesozoic and Cenozoic cooling-events as periods of tectonic reactivation.

  18. Provenance Constraints on the Mesozoic-Cenozoic Tectonic Evolution of the Queen Charlotte Islands Region (United States)

    Mahoney, J.; Haggart, J. W.; Kimbrough, D.; Grove, M.


    The medial Cretaceous magmatic arc system of western North America was flanked by a series of forearc basins extending from Mexico to Alaska. Cretaceous strata in the Queen Charlotte Islands of northwest British Columbia are unique in this series of basins, as these strata have been displaced from the arc system by formation of the extensional Queen Charlotte basin in Cenozoic time. This displacement complicates reconstruction of the forearc basin, and makes it difficult to evaluate the controls on basin evolution. Sedimentologic, paleontologic, and detrital zircon analyses of forearc strata represented by the Valanginian- Campanian Queen Charlotte Group (QCG) constrain basin evolution and provide a framework for an interpretation of the Mesozoic-Cenozoic tectonic evolution of the Queen Charlotte Islands region. Basin subsidence initiated in Valanginian time with a marine transgression over irregular topography consisting of extensional fault blocks of pre-Cretaceous strata. Locally derived conglomerates at the base of the Longarm Formation are overlain by shallow marine shelf deposits that represent a westward-deepening, fining-upward transgressive succession with an eastern depositional edge that migrated eastward during Valanginian to Aptian time. West-directed paleocurrents and a unimodal detrital zircon population of 120-175 Ma grains provide the first linkage between the Cretaceous QCG and unroofed Jura-Cretaceous plutons of the Coast Plutonic Complex to the east. This initial transgressive sequence is superseded by a second pulse of clastic detritus in early Albian time, characterized by an easterly-derived, fossiliferous shallow-shelf sandstone (Haida Formation), fine-grained, outer shelf to upper slope strata (Bearskin Bay Formation), and mass-sediment gravity flows (Skidegate Formation). The unimodal zircon population (ca 140-175 Ma) in the lower Haida Formation is interpreted to reflect renewed uplift of Jura-Cretaceous arc plutons by contractional

  19. Late Cenozoic magnetic polarity stratigraphy in the Jiudong Basin, northern Qilian Mountain

    Institute of Scientific and Technical Information of China (English)

    赵志军; 方小敏; 李吉均


    Late Cenozoic sediments in the Hexi Corridor, foreland depression of the Qilian Mountain preserved reliable records on the evolution of the Northern Tibetan Plateau. Detailed magnetic polarity dating on a 1150 m section at Wenshushan anticline in the Jiudong Basin, west of Hexi Corridor finds that the ages of the Getanggou Formation, Niugetao Formation and Yumen Conglomerate are>11-8.6 Ma, 8.6-4.5 Ma and 4.5-0.9 Ma respectively. Accompanying sedimentary analysis on the same section suggests that the northern Tibetan Plateau might begin gradual uplift since 8.6-7.6 Ma, earlier than the northeastern Tibetan Plateau but does not suppose that the plateau has reached its maximum elevation at that time. The commencement of the Yumen Conglomerate indicates the intensive tectonic uplift since about 4.5 Ma.

  20. The tectonic uplift of the Hua Shan in the Cenozoic

    Institute of Scientific and Technical Information of China (English)


    Six granite samples were collected from sixdifference elevation locations at the Hua Shah in a mainridge of the Qinling Mountain. Apatite and zircon separatedfrom these six samples were dated by the fission track tech-nique. An assessment of the Cenozoic uplift or exhumationrate was obtained from the altitude difference of samplingsamples dated by fission track, and from the difference offission track dates of both apatite and zircon for a sample.The preliminary results suggest that the beginning of upliftof the Hua Shan was as early as 68.2 MaBP and the upliftrates for different periods are 0.02-0.19 mm/a (from theelevation difference) or 0.12-0.16 mm/a (from two mineralfission track dates). The average uplift rate is 0.12 mm/a(from the elevation difference) or 0.14 mm/a (from two min-eral fission track dates). The uplift of the Hua Shan mightaccelerate since (17.8+2.0) MaBP, and the average uplift rateis about 0.19 mm/a.

  1. Tectonic stress field and its effect on hydrocarbon migration and accumulation in Mesozoic and Cenozoic in Kuqa depression, Tarim basin

    Institute of Scientific and Technical Information of China (English)

    ZENG; Lianbo; TAN; Chengxuan; ZHANG; Mingli


    Through rock acoustic emission experiments and structural deformation analysis, the tectonic stages in Meso-Cenozoic in the Kuqa depression of the Tarim basin are firstly divided. Then, combining with rock magnetic fabric analysis and memory information, the distribution characteristics of tectonic stress field of every tectonic stage are quantificationally resumed. At the same time, according to the distribution relation of tectonic stress field of hydrocarbon formation stage by the finite element numerical simulation method and the known hydrocarbon reservoirs, the effects of tectonic stress field on hydrocarbon migration and accumulation are further analyzed. The Kuqa depression has mainly experienced six tectonic movements since Mesozoic. Except that the tectonic stress field of the Early Yanshan stage (208-135 Ma) showed northeast-southwest extensional stress field where the orientation of the maximum principal compressive stress (σ1) was northwest-southeast, the others were compressive stress field where the orientations of the maximum principal compressive stress (σ1) were near north-south. Along with the closure of the paleo-Tethys ocean, the Kuqa depression in the Indosinian stage (250-208 Ma) was in strong compressive circumstance with apparently big maximum principal stress (σ1) magnitude. Due to the equilibrium adjustment of interior Eurasia, the Kuqa depression in the Early Yanshan stage (208-135 Ma) was in weak extensional circumstance with apparently small maximum principal stress (σ1) magnitude. From the Late Yanshan stage (135-65 Ma) on, with a series of collision events occurring at the south edge of Eurasia, the Kuqa depression was in compressive circumstance again in which the maximum principal stress (σ1) magnitude was from small to big in turn. The Late Himalayan stage (2.6-0.7 Ma) was the main tectonic deformation stage with the biggest principal compressive stress (σ1) magnitude. Tectonic stress field plays a dominant role in

  2. Jurassic extension and Cenozoic inversion tectonics in the Asturian Basin, NW Iberian Peninsula: 3D structural model and kinematic evolution (United States)

    Uzkeda, Hodei; Bulnes, Mayte; Poblet, Josep; García-Ramos, José Carlos; Piñuela, Laura


    We constructed a geological map, a 3D model and cross-sections, carried out a structural analysis, determined the stress fields and tectonic transport vectors, restored a cross section and performed a subsidence analysis to unravel the kinematic evolution of the NE emerged portion of the Asturian Basin (NW Iberian Peninsula), where Jurassic rocks crop out. The major folds run NW-SE, normal faults exhibit three dominant orientations: NW-SE, NE-SW and E-W, and thrusts display E-W strikes. After Upper Triassic-Lower Jurassic thermal subsidence, Middle Jurassic doming occurred, accompanied by normal faulting, high heat flow and basin uplift, followed by Upper Jurassic high-rate basin subsidence. Another extensional event, possibly during Late Jurassic-Early Cretaceous, caused an increment in the normal faults displacement. A contractional event, probably of Cenozoic age, led to selective and irregularly distributed buttressing and fault reactivation as reverse or strike-slip faults, and folding and/or offset of some previous faults by new generation folds and thrusts. The Middle Jurassic event could be a precursor of the Bay of Biscay and North Atlantic opening that occurred from Late Jurassic to Early Cretaceous, whereas the Cenozoic event would be responsible for the Pyrenean and Cantabrian ranges and the partial closure of the Bay of Biscay.

  3. Late cenozoic vertical movements of non-volcanic islands in the Banda Arc area (United States)

    De Smet, M. E. M.; Fortuin, A. R.; Tjokrosapoetro, S.; Van Hinte, J. E.

    During onshore campaigns of the Snellius-II Expedition late Cenozoic sections were recorded and systematically sampled on the non-volcanic outer Banda Arc Islands of Timor, Buton, Buru, Seram and Kai. Microfaunal studies provided age and palaeobathymetric data to construct geohistory diagrams. Geohistory analysis of field and laboratory data allows to calculate rates of vertical movements of the island basements. The vertical movements were intermittent and differed widely from place to place in the arc; short periods of uplift alternated with longer periods of tectonic rest or subsidence and lateral variations in timing and magnitude seem to be more the rule than the exception. Movements affected larger segments of the arc at about the same time, especially since the late Pliocene, when widespread vertical movements started, which led to the present configuration of the arc. Rates of uplift or subsidence differed within each segment. On an intermediate scale, deformation has the character of tilting or doming of whole islands or parts of islands. On a local scale, various types of deformation occur. Calculated duration of uplift pulses is in the order of a million years where less than 50 cm·ka -1 of vertical movements are involved. Sections, however, with a high time stratigraphic resolutions show pulses of uplift with a duration of only some hundreds of thousands of years and rates of more than 500 cm·ka -1. The duration of such pulses therefore is comparable to that of eustatic third order sea level changes. But because their amplitude is an order of magnitude larger, this implies that in tectonically active areas eustatic signals, preserved in the sedimentary record, will be overprinted by tectonics, i.e. will be difficult to disentangle from the tectonic signal.

  4. Impact of Cenozoic strike-slip tectonics on the evolution of the northern Levant Basin (offshore Lebanon) (United States)

    Ghalayini, Ramadan; Daniel, Jean-Marc; Homberg, Catherine; Nader, Fadi H.; Comstock, John E.


    Sedimentary basins adjacent to plate boundaries contain key tectonic and stratigraphic elements to understand how stress is transmitted through plates. The Levant Basin is a place of choice to study such elements because it flanks the Levant Fracture System and the Africa/Anatolia boundary. This paper uses new high-quality 3-D seismic reflection data to unravel the tectonic evolution of the margin of this basin during the Cenozoic, the period corresponding to the formation of the Levant Fracture System, part of the Africa/Arabia plate boundary. Four major groups of structures are identified in the interpreted Cenozoic units: NW-SE striking normal faults, NNE-SSW striking thrust-faults, ENE-WSW striking dextral strike-slip faults, and NNE trending anticlines. We demonstrate that all structures, apart of the NW-SE striking normal faults, are inherited from Mesozoic faults. Their reactivation and associated folding started during the late Miocene prior to the Messinian salinity crisis due to a NW-SE compressional stress field. No clear evidence of shortening at present-day offshore Lebanon and no large NNE-SSW strike-slip faults parallel to the restraining bend are found indicating that the Levant Fracture System is mainly contained onshore at present day. The intermittent activity of the interpreted structures correlates with the two stages of Levant Fracture System movement during late Miocene and Pliocene. This paper provides a good example of the impact of the evolution of plate boundaries on adjacent basins and indicates that any changes in the stress field, as controlled by the plate boundary, will affect immediately the preexisting structures in adjacent basins.

  5. The Late Cenozoic Geology Of Southeastern Virginia And The Great Dismal Swamp (United States)

    US Fish and Wildlife Service, Department of the Interior — The objectives of this field trip are to acquaint the participants with the late Cenozoic stratigraphic, paleontologic and geomorphic features of the Great Dis ma 1...

  6. Plate tectonics in the late Paleozoic

    Directory of Open Access Journals (Sweden)

    Mathew Domeier


    Full Text Available As the chronicle of plate motions through time, paleogeography is fundamental to our understanding of plate tectonics and its role in shaping the geology of the present-day. To properly appreciate the history of tectonics—and its influence on the deep Earth and climate—it is imperative to seek an accurate and global model of paleogeography. However, owing to the incessant loss of oceanic lithosphere through subduction, the paleogeographic reconstruction of ‘full-plates’ (including oceanic lithosphere becomes increasingly challenging with age. Prior to 150 Ma ∼60% of the lithosphere is missing and reconstructions are developed without explicit regard for oceanic lithosphere or plate tectonic principles; in effect, reflecting the earlier mobilistic paradigm of continental drift. Although these ‘continental’ reconstructions have been immensely useful, the next-generation of mantle models requires global plate kinematic descriptions with full-plate reconstructions. Moreover, in disregarding (or only loosely applying plate tectonic rules, continental reconstructions fail to take advantage of a wealth of additional information in the form of practical constraints. Following a series of new developments, both in geodynamic theory and analytical tools, it is now feasible to construct full-plate models that lend themselves to testing by the wider Earth-science community. Such a model is presented here for the late Paleozoic (410–250 Ma together with a review of the underlying data. Although we expect this model to be particularly useful for numerical mantle modeling, we hope that it will also serve as a general framework for understanding late Paleozoic tectonics, one on which future improvements can be built and further tested.

  7. Plate tectonics in the late Paleozoic

    Institute of Scientific and Technical Information of China (English)

    Mathew Domeier; Trond H. Torsvik


    As the chronicle of plate motions through time, paleogeography is fundamental to our understanding of plate tectonics and its role in shaping the geology of the present-day. To properly appreciate the history of tectonicsdand its influence on the deep Earth and climatedit is imperative to seek an accurate and global model of paleogeography. However, owing to the incessant loss of oceanic lithosphere through subduction, the paleogeographic reconstruction of‘full-plates’ (including oceanic lithosphere) becomes increasingly challenging with age. Prior to 150 Ma w60% of the lithosphere is missing and re-constructions are developed without explicit regard for oceanic lithosphere or plate tectonic principles;in effect, reflecting the earlier mobilistic paradigm of continental drift. Although these ‘continental’ re-constructions have been immensely useful, the next-generation of mantle models requires global plate kinematic descriptions with full-plate reconstructions. Moreover, in disregarding (or only loosely applying) plate tectonic rules, continental reconstructions fail to take advantage of a wealth of additional information in the form of practical constraints. Following a series of new developments, both in geo-dynamic theory and analytical tools, it is now feasible to construct full-plate models that lend themselves to testing by the wider Earth-science community. Such a model is presented here for the late Paleozoic (410e250 Ma) together with a review of the underlying data. Although we expect this model to be particularly useful for numerical mantle modeling, we hope that it will also serve as a general framework for understanding late Paleozoic tectonics, one on which future improvements can be built and further tested.

  8. Late Cenozoic Uplift of the Chinese South Tian Shan: Insight from Magnetostratigraphy and Sedimentology (United States)

    Chen, X.; Chen, H.; Cheng, X. G.; Zhongyue, S.; Lin, X.


    The South Tian Shan in the Central Asia is an intracontinental orogeny reactivated in the late Cenozoic by far-field effect of continuous India-Aisa convergence. However, its uplift time and process remains controversial. Here, Magnetostratigraphic and Sedimentological work in the Cenozoic Tierekesazi Profile in the South Tian Shan foreland was taken to figure out these problems. The Cenozoic sediment reveals a section of generally upwardly increasing particle sizes triggered by uplift of Tian Shan. Based on increasing particle size and water power, the Cenozoic succession could be divided into four lithofacies: (i) Paleogene marine lithofacies from the Paleogene Aertashi to Eocene-Oligocene Bashibulake Formation, (ii) lacustrine to fluvial (plain) lithofacies from the early Miocene Keziluoyi Formation to the middle of middle Miocene Pakabulake Formations, (iii) alluvial sand-gravel sheet lithofacies in the upperpart of middle Miocene Pakabulake Formation, and (iv) conglomerate lithofacies from the Neogene Atushi to Quaternary Xiyu Formation. Our magnetostratigraphic results, combined with biostratigraphic correlations, provide the chronologic constraints for each lithofacies and also the sediment accumulation rates (SAR). These results indicate lithofacies (i) aged ca. 65-34 Ma, lithofacies (ii) aged ca. 22.1-12 Ma, lithofacies (iii) aged ca. 12-5.2 Ma, and lithofacies (iv) aged ca. 5.2 Ma-present (?), with SARs increasing from lithofacies (i) to (iv). Regional correlation of SAR from foreland of South Tian Shan has suggested a linkage of the sedimentary event to the tectonic activity along South Tian Shan. We propose that the earliest Miocene event may represent the initial response of the far-field effect of Indian-Eurasian convergence, but more directly and likely marks the initial underthrusting of the Tarim block beneath the South Tian Shan. The mid-Miocene and Mio-Pliocene boundary events have different structural expression in the opposite regions east and

  9. Climate vs. tectonic induced variations in Cenozoic sediment supply from western Scandinavia

    DEFF Research Database (Denmark)

    Gołędowski, Bartosz; Nielsen, S.B.; Clausen, O.R.

    -wide stress relaxation explains European Palaeocene basin inversions. Nature, 2005. 435(7039): p. 195-198. 9. Vejbæk, O.V. and C. Andersen, Post mid-Cretaceous inversion tectonics in the Danish Central Graben. Bulletin of the Geological Society of Denmark, 2002. 49: p. 129-144. 10. Nielsen, S.B., R......-up (Paleocene-Early Eocene) this link is quite striking, especially in the northern British Isles and in the Faeroe-Shetland Platform where sediment production pulses can be correlated with well documented periods of tectonic activity (e.g. magmatism). However, during the subsequent Cenozoic epochs this link...... on a particular rudimentary understanding of the Davisian cyclic landscape evolution model, which does not consider the occurrence of flexural isostasy or glacial buzzsaw processes. Observations of small scale sedimentary structures of ambiguous origin and activity of salt-related structures is not evidence...

  10. Active faults paragenesis and the state of crustal stresses in the Late Cenozoic in Central Mongolia

    Directory of Open Access Journals (Sweden)

    V. A. Sankov


    Full Text Available Active faults of the Hangay-Hentiy tectonic saddle region in Central Mongolia are studied by space images interpretation, relief analysis, structural methods and tectonic stress reconstruction. The study results show that faults activation during the Late Cenozoic stage was selective, and a cluster pattern of active faults is typical for the study region. Morphological and genetic types and the kinematics of faults in the Hangay-Hentiy saddle region are related the direction of the ancient inherited structural heterogeneities. Latitudinal and WNW trending faults are left lateral strike-slips with reverse or thrust component (Dzhargalantgol and North Burd faults. NW trending faults are reverse faults or thrusts with left lateral horizontal component. NNW trending faults have right lateral horizontal component. The horizontal component of the displacements, as a rule, exceeds the vertical one. Brittle deformations in fault zones do not conform with the Pliocene and, for the most part, Pleistocene topography. With some caution it may be concluded that the last phase of revitalization of strike slip and reverse movements along the faults commenced in the Late Pleistocene. NE trending disjunctives are normal faults distributed mainly within the Hangay uplift. Their features are more early activation within the Late Cenozoic and the lack of relation to large linear structures of the previous tectonic stages. According to the stress tensor reconstructions of the last phase of deformation in zones of active faults of the Hangay-Hentiy saddle using data on tectonic fractures and fault displacements, it is revealed that conditions of compression and strike-slip with NNE direction of the axis of maximum compression were dominant. Stress tensors of extensional type with NNW direction of minimum compression are reconstructed for the Orkhon graben. It is concluded that the activation of faults in Central Mongolia in the Pleistocene-Holocene, as well as

  11. Surface uplift and atmospheric flow deflection in the Late Cenozoic southern Sierra Nevada (United States)

    Mix, H.; Caves, J. K.; Winnick, M.; Ritch, A. J.; Reilly, S.; Chamberlain, C. P.


    Given the intimate links between topography, tectonics, climate and biodiversity, considerable effort has been devoted to developing robust elevation histories of orogens. In particular, quantitative geochemical reconstructions using stable oxygen and hydrogen isotopes have been applied to many of the world's mountain belts. Yet after decades of study, determining the Cenozoic surface uplift history of the Sierra Nevada remains a challenge. While geological and geophysical evidence suggests the southern Sierra underwent 1-2 km of Late Cenozoic surface uplift, stable isotope paleoaltimetry studies to date have been restricted to the Basin and Range interior. Recent advances in atmospheric modeling have suggested that such stable isotope records from leeward sites can be affected by the complicating role that sufficiently elevated topography such as the southern (High) Sierra plays in diverting atmospheric circulation. In order to examine the potential role of these terrain blocking effects, we produced stable isotope records from three Late Cenozoic sedimentary basins in the Eastern Sierra and Basin and Range: 1) Authigenic clay minerals in the Mio-Pliocene Verdi Basin (VB), 2) Fluvial and lacustrine carbonates from the Plio-Pleistocene Coso Basin (CB), and 3) Miocene to Holocene pedogenic, fluvial and lacustrine carbonates of Fish Lake Valley (FLV). Whereas both the VB (near present-day Reno) and CB (southern Owens Valley) receive input of water directly from the Sierra crest, FLV is a region of proposed reconvergence of moisture in the Basin and Range. The oxygen isotope records in both CB and FLV increase during the Neogene by approximately 2 ‰, while the hydrogen isotope record of the VB decreases by <10 ‰. These results are consistent with a modestly-elevated Paleogene Sierra of 2 km over which air masses traversed and underwent orographic rainout and Rayleigh distillation. A Neogene pulse of uplift in the southern Sierra could have driven modern flow

  12. K-Ar geochronology of the late cenozoic volcanic rocks of the Cordillera Occidental, southernmost Peru (United States)

    Tosdal, Richard M.; Farrar, Edward; Clark, Alan H.


    Twenty-four K-Ar radiometric ages are presented for late Cenozoic continental volcanic rocks of the Cordillera Occidental of southernmost Perú (lat. 16° 57'-17° 36'S). Rhyodacitic ignimbrite eruptions began in this transect during the Late Oligocene and continued episodically through the Miocene. The development of andesitic-dacitic strato volcanoes was initiated in the Pliocene and continues to the present. The earliest ignimbrite flows (25.3-22.7 Ma) are intercalated in the upper, coarsely-elastic member of the Moquegua Formation and demonstrate that this sedimentary unit accumulated in a trough, parallel to Andean tectonic trends, largely in the Oligocene. More voluminous ash-flow eruptions prevailed in the Early Miocene (22.8-17.6 Ma) and formed the extensively preserved Huaylillas Formation. This episode was coeval with a major phase of Andean uplift, and the pyroclastics overlie an erosional surface of regional extent incised into a Paleogene volcano-plutonic arc terrain. An age span of 14.2-8.9 Ma (mid-Late Miocene) is indicated for the younger Chuntacala Formation, which again comprises felsic ignimbrite flows, largely restricted to valleys incised into the pre-Huaylillas Formation lithologies, and, at lower altitudes, an extensive aggradational elastic facies. The youngest areally extensive ignimbrites, constituting the Sencca Formation, were extruded during the Late Miocene. In the earliest Pliocene, the ignimbrites were succeeded by more voluminous calcalkaline, intermediate flows which generated numerous large and small stratovolcanoes; these range in age from 5.3 to 1.6 Ma. Present-day, or Holocene, volcanism is restricted to several large stratovolcanoes which had begun their development during the Pleistocene (by 0.7 Ma). The late Oligocene/Early Miocene (ca. 22-23 Ma) reactivation of the volcanic arc coincided with a comparable increase in magmatic activity throughout much of the Cordilleras Occidental and Oriental of the Central Andes.

  13. Petrogenesis of Late Cenozoic basaltic rocks from southern Vietnam (United States)

    An, A.-Rim; Choi, Sung Hi; Yu, Yongjae; Lee, Der-Chuen


    Major and trace element concentrations, and Sr-Nd-Hf-Pb isotopic compositions of Late Cenozoic (4.1 to 13.8 Ma) basaltic rocks from southern Vietnam have been determined to understand the nature of their mantle source. The volcanic rocks are composed of tholeiite basalt, alkaline basanite, trachybasalt, basaltic trachyandesite, and trachyandesite. The alkaline rocks show light rare earth element (LREE) enrichment, with (La/Yb)N = 10.3-29.8. The tholeiite basalts are distinguished by much lower values (8.8-9.5) of (La/Yb)N. On a primitive mantle-normalized trace element distribution diagram, they show oceanic island basalt (OIB)-like large-ion lithophile element enrichment without high field strength element depletion. However, some samples exhibit positive anomalies in K and Pb and negative anomalies in Sm, suggesting K-rich residual amphibole in the source. The samples contain Sr (87Sr/86Sr = 0.703794-0.704672), Nd (ɛNd = + 1.7-5.7), Hf (ɛHf = + 4.0-10.9), and Pb (206Pb/204Pb = 18.23-18.75; 207Pb/204Pb = 15.53-15.59; 208Pb/204Pb = 38.32-38.88) isotopes, plotting among OIBs, with depleted mid-ocean ridge basalt mantle-enriched mantle type 2 (DMM-EM2) characteristics. There are no discernible isotopic differences between tholeiite and the alkaline series, reflecting the same source. The Nd and Hf isotopic compositions are coupled, and plot along the mantle-crust array, ruling out the possibility of lithospheric mantle in the source. Plots of NiO against the Fo numbers of olivines from the basaltic rocks are within the range of Hainan and Hawaiian basalt olivines, implying that hybrid pyroxenite is present in the source. Also note that the estimated primary melt compositions fall within the experimental field defined by partial melting of silica-poor eclogite and peridotite. The effective melting pressure (Pf) and melting temperature (T) of the primary melts are Pf = 29.6-32.8 kbar and T = 1470-1480 °C. We suggest that Vietnamese basaltic rocks may be produced by

  14. Mount Kenya volcanic activity and the Late Cenozoic landscape reorganisation in the upper Tana fluvial system

    NARCIS (Netherlands)

    Veldkamp, A.; Schoorl, J.M.; Wijbrans, J.R.; Claessens, L.F.G.


    Volcanic–fluvial landscape interaction of the late Cenozoic Mt Kenya region in the upper Tana catchment has been reconstructed. The oldest newly dated phonolite flow is 5.78 Ma (40Ar/39Ar), placing the initiation of Mt Kenya volcanic activity within the Late Miocene, much earlier than reported befor

  15. Influence of late Cenozoic mountain building on ocean geochemical cycles (United States)

    Raymo, Maureen E.; Ruddiman, William F.; Froelich, Philip N.


    In a steady-state ocean, input fluxes of dissolved salts to the sea must be balanced in mass and isotopic value by output fluxes. For the elements strontium, calcium, and carbon, rivers provide the primary input, whereas marine biogenic sedimentation dominates removal. Dissolved fluxes in rivers are related to rates of continental weathering, which in turn are strongly dependent on rates of uplift. The largest dissolved fluxes today arise in the Himalayan and Andean mountain ranges and the Tibetan Plateau. During the past 5 m.y., uplift rates in these areas have increased significantly; this suggests that weathering rates and river fluxes may have increased also. The oceanic records of carbonate sedimentation, level of the calcite compensation depth, and δ13C and δ87Sr in biogenic sediments are consistent with a global increase in river fluxes since the late Miocene. The cooling of global climate over the past few million years may be linked to a decrease in atmospheric CO2 driven by enhanced continental weathering in these tectonically active regions.

  16. Book Review: Late Cenozoic Climate Change in Asia: Loess, Monsoon and Monsoon-arid Environment Evolution (United States)

    Clemens, Steven C.


    Loess-Paleosol deposits drape >500,000 km2 of eastern China, spanning environments from the humid, monsoon-influenced regions near the coast to the arid, westerlies-dominated regions inland. Sections, up to hundreds of meters thick, are exposed in deeply incised river valleys and can be accessed as well by drilling. Combined, the high sedimentation rates and extensive geographic coverage make these sections unique among global terrestrial sediment archives. The Chinese loess-paleosol sequences, and the arid interior regions to the northwest, record diverse aspects of geologic and environmental change ranging from the tectonic evolution of the Tibetan Plateau (106 year time scale) through glacial-interglacial scale changes in global ice volume and greenhouse gasses (105 year time scale) on down through the orbital (104 years) to millennial and centennial scale events (103-102 year) relevant to the underpinnings of human interactions with changing environmental pressures. 'Late Cenozoic Climate Chang in Asia: Loess, Monsoon and Monsoon-arid Environment Evolution' is a timely contribution that synthesizes findings derived from the extensive work in these areas, places the findings in the broader context of global climate change and helps to define avenues for future research.

  17. Late Cenozoic Vertical Motions of the Coachella Valley Using Apatite U-Th/He and 4/3He Thermochronometry (United States)

    Mason, C. C.; Spotila, J. A.; Fame, M. L.; Dorsey, R. J.; Shuster, D. L.


    The Coachella Valley of southern California (USA) is a late Cenozoic transform-related sedimentary basin created by top-to-the-east extension on the West Salton detachment fault and dextral strike-slip offset on the San Andreas fault (Axen and Fletcher, 1998), which has continued to subside as a result of northeastward tilting since initiation of the San Jacinto fault ca. 1.2 Ma. Though it is generally agreed that these large regional faults are responsible for creation of high relief and deep subsidence in the Coachella Valley, the timing, magnitude, and geometries of fault offsets on these structures are still debated. This project applies an integrated source-to-sink approach to investigate tectonic models for evolution of the Pacific-North American plate boundary as recorded in the world-class natural laboratory of the Coachella Valley. In this study we integrate new thermochronometry-constrained kinematic models with tectonostratigraphic interpretations to help quantify the timing, rates, and magnitudes of tectonically driven vertical crustal motions and resulting mass fluxes. We sampled bedrock for U-Th/He (A-He) thermochronometry in the Mecca Hills, Santa Rosa, San Jacinto, and Little San Bernardino Mountains in both spatially focused and widely distributed areas. We also present new results from apatite 4/3He thermochronometry to help constrain the most recent exhumation histories. A-He results reveal spatially variable exhumation ages. The southwest Santa Rosa Mountains experienced late Miocene-early Pliocene exhumation along their southwest flank, while new A-He ages from ranges bounding Coachella Valley reveal complex uplift histories. We integrate our data set with previously published thermochronometric data to improve a regional synthesis of late Cenozoic vertical motions of the Coachella Valley.


    Institute of Scientific and Technical Information of China (English)

    张会平; 张培震; 郑德文; 郑文俊; 陈正位; 王伟涛


    stepwise style. North eastern Tibet offers both a missing link in our understanding of Tibet's overall growth and it has long been regarded as an ideal field laboratory for studies of both how and why high, regionally extensive plateaux grow and how such terrains affect regional climate. Tectonically, it lies in the transition between two contrasting styles of topography and associated deformation. South of ca. 35° N as far east as ca. 100° E,the plateau's surface is relatively gentle, and obvious manifestations of major thrust faulting and horizontal shortening of the upper crust are sparse. Here, eastward lateral, or "channel," flow of a weak lower crust into previously thinner crust that lay east of Tibet offers a testable hypothesis for how this part of the Tibetan Plateau has developed. Northwest of this area,more rugged topography of the Qilian Shan,with numerous fault-bounded ranges and intermontane basins,resembles that of the Tibetan Plateau, Tien Shan and other, older intracontinental belts like the Rocky Mountains of Laramide time in the western USA. Late Cenozoic uplift and landscape evolution of the Qilian Shan in north eastern Tibetan Plateau was continuously fed by the upward and outward growth of the Tibetan Plateau since the collision. Timing and style of uplift of the Qilian Shan to its present elevation, and its bearing of the slip of the Altyn Tagh fault have been the focus of considerable research aimed at understanding the strain portioning during continental plate collision and the influence of topographic growth on global/regional atmospheric circulation and climatic conditions in Asia. Geomorphometric indices, like slope, local relief and longitudinal profiles, reveal high-relief steep marginal ranges,and sub-summit low-relief intermontane basins in the Qilian Shan in the north eastern Tibetan Plateau. Comparison of rates of regional uplift and erosion suggests that the marginal ranges are approaching a topographic steady state. Further

  19. The uplifting process of the Bogda Mountain during the Cenozoic and its tectonic implication

    Institute of Scientific and Technical Information of China (English)

    WANG ZongXiu; LI Tao; ZHANG Jin; LIU YongQing; MA ZongJin


    Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China The Tianshan Mountains have undergone its initial orogeny, extension adjusting and re-orogeny since the Late Paleozoic. The re-orogeny and uplifting process of the orogeny in the Mesozoic and Cenozoic are two of most important events in the geological evolution of Euro-Asian continent, which resulted in the formation of the present range-and-basin pattern in topography of the Tianshan Mountains and its adjacent areas. Thermochronology results by the method of fission-track dating of apatite suggest three obvious uplifting stages of the Bogad Mountain Chain re-orogeny during the Cenozoic, i.e. 5.6-19 Ma, 20-30 Ma, and 42-47 Ma. The strongest uplifting stage of the mountain is the second one at 20-30 Ma, when the mountain uplifted as a whole, and the beginning of re-orogeny was no less than 65Ma. Furthermore, our studies also show that the uplifting types of the mountain are variable in the different time periods, including uplifting of mountain as a whole and differential uplifting. The apparently diversified uplifting processes of the mountain chain are characterized by the migration (or transformation) of the uplifting direction of the mountain from west to east and from north to south, and the main process of mountain extending is from north to south.

  20. Structural deformation pattern within the NW Qaidam Basin in the Cenozoic era and its tectonic implications (United States)

    Mao, Liguang; Xiao, Ancheng; Zhang, Hongwei; Wu, Zhankui; Wang, Liqun; Shen, Ya; Wu, Lei


    The Qaidam Basin is located in the northeastern Tibetan Plateau and provides an excellent field laboratory in understanding the history and mechanism of the plateau growth. It deformed widely over the northwest during the Cenozoic but with little thrust loading along the margins, where no foreland depression is observed. Based on satellite images, seismic and borehole data, we investigated the structural deformation pattern (including the structural style and timing of deformation) and its formation mechanism within the northwestern Qaidam Basin during the Cenozoic era. Mapping of surface geology shows that the modern Qaidam Basin is characterized by five SE-trending anticlinal belts. Each belt consists of several right-step en echelon anticlines with plenty of normal and strike-slip faults crossing the crests. Those anticlines are generally dominated by double fault systems at different depths: an upper thrust fault system, controlling the anticlines identified on the surface and a lower dextral transpressional fault system characterized by typical flower structures. They are separated by weak layers in the upper Xiaganchaigou or the Shangganchaigou formations. The upper system yields shortening strain 2-5 times larger than that of the lower system and the additional strain is interpreted to be accommodated by hinge-parallel elongation in the upper system. Growth strata indicate that deformation within the Qaidam Basin initiated in the middle Miocene ( 15 Ma) and accelerated in the late Miocene ( 8 Ma). A simple Riedel-P-Shear model is used to explain the deformation mechanism within the northwestern Qaidam Basin.

  1. U-Pb zircon geochronology of the Paleogene - Neogene volcanism in the NW Anatolia: Its implications for the Late Mesozoic-Cenozoic geodynamic evolution of the Aegean (United States)

    Ersoy, E. Yalçın; Akal, Cüneyt; Genç, Ş. Can; Candan, Osman; Palmer, Martin R.; Prelević, Dejan; Uysal, İbrahim; Mertz-Kraus, Regina


    The northern Aegean region was shaped by subduction, obduction, collision, and post-collisional extension processes. Two areas in this region, the Rhodope-Thrace-Biga Peninsula to the west and Armutlu-Almacık-Nallıhan (the Central Sakarya) to the east, are characterized by extensive Eocene to Miocene post-collisional magmatic associations. We suggest that comparison of the Cenozoic magmatic events of these two regions may provide insights into the Late Mesozoic to Cenozoic tectonic evolution of the Aegean. With this aim, we present an improved Cenozoic stratigraphy of the Biga Peninsula derived from a new comprehensive set of U-Pb zircon age data obtained from the Eocene to Miocene volcanic units in the region. The compiled radiometric age data show that calc-alkaline volcanic activity occurred at 43-15 Ma in the Biga Peninsula, 43-17 Ma in the Rhodope and Thrace regions, and 53-38 Ma in the Armutlu-Almacık-Nallıhan region, which are slightly overlapping. We discuss the possible cause for the distinct Cenozoic geodynamic evolution of the eastern and western parts of the region, and propose that the Rhodope, Thrace and Biga regions in the north Aegean share the same Late Mesozoic to Cenozoic geodynamic evolution, which is consistent with continuous subduction, crustal accretion, southwestward trench migration and accompanying extension; all preceded by the Late Cretaceous - Paleocene collision along the Vardar suture zone. In contrast, the Armutlu-Almacık-Nallıhan region was shaped by slab break-off and related processes following the Late Cretaceous - Paleocene collision along the İzmir-Ankara suture zone. The eastern and western parts of the region are presently separated by a northeast-southwest trending transfer zone that was likely originally present as a transform fault in the subducted Tethys oceanic crust, and demonstrates that the regional geodynamic evolution can be strongly influenced by the geographical distribution of geologic features on the

  2. Origin and geodynamic setting of Late Cenozoic granitoids in Sulawesi, Indonesia (United States)

    Maulana, Adi; Imai, Akira; Van Leeuwen, Theo; Watanabe, Koichiro; Yonezu, Kotaro; Nakano, Takanori; Boyce, Adrian; Page, Laurence; Schersten, Anders


    Late Cenozoic granitoids are widespread in a 1600 km long belt forming the Western and Northern Sulawesi tectono-magmatic provinces. They can be divided into three rock series: shoshonitic (HK), high-K felsic calc-alkaline (CAK), and normal calc-alkaline to tholeiitic (CA-TH). Representative samples collected from eleven plutons, which were subjected to petrography, major element, trace element, Sr, Nd, Pb isotope and whole-rock δ18O analyses, are all I-type and metaluminous to weakly peraluminous. The occurrence of the two K-rich series is restricted to Western Sulawesi, where they formed in an extensional, post-subduction tectonic setting with astenospheric upwelling providing thermal perturbation and adiabatic decompression. Two parental magma sources are proposed: enriched mantle or lower crustal equivalent for HK magmas, and Triassic igneous rocks in a Gondwana-derived fragment thrust beneath the cental and northern parts of Western Sulawesi for CAK magmas. The latter interpretation is based on striking similarities in radiogenic isotope and trace element signatures. CA-TH granitoids are found mostly in Northern Sulawesi. Partial melting of lower-middle crust amphibolites in an active subduction environment is the proposed origin of these rocks. Fractional crystallization and crustal contamination have played a significant role in magma petrogenesis, particularly in the case of the HK and CAK series. Contamination by organic carbon-bearing sedimentary rocks of the HK and CAK granitoids in the central part of Western Sulawesi is suggested by their ilmenite-series (reduced) character. The CAK granitoids further to the north and CA-TH granitoids in Northern Sulawesi are typical magnetite-series (oxidized). This may explain differences in mineralization styles in the two regions.

  3. Cenozoic Subsidence Features of Beitang Sag and Relationship with Tectonic Evolution

    Institute of Scientific and Technical Information of China (English)

    Zhang Tingting; Wang Hua; Yue Yong; Huang Chuanyan; Zhang Liwei


    Based on the application of the EBM basin modeling software and 2-D seismic profiles, the Paleogene and Neogene shubsidence histories of the Beitang(北塘) sag are simulated with the backstripping technique,and the relationship between subsidence character and tectonic revolution is discussed.Moreover,the result of the basin modeling reveals that the subsidence history of the Beitang sag has the characteristics of several geological periods,and these succeeding periods have shown certain inheritance and difference characteristics.At the early (Es3) and middle (Es2-Es1) rifting periods,the subsidence reaction of the Beitang sag was mainly in the charge of tectonic activity,while at the late (Ng-Nm+Q) rifting period-post rifting period and post rifting subsidence-acceleration period-the subsidence type is mainly that of thermal subsidence or regional depression effect; from the beginning of the subsidence history to the end,the reason for the basin subsidence has changed from tectonic activity to non-tectonic activity.

  4. Cenozoic volcanism and lithospheric tectonic evolution in Qiangtang area, northern Qinghai-Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    CHI Xiaoguo; LI Cai; JIN Wei


    Following the collision between the Indian and Eurasian plates, the Cenozoic volcanic activities are rather frequent in the Qiangtang area of northern Qinghai-Tibet Plateau. They can be divided into four series: alkaline basalt series, high-K calc-alkaline series, shoshonitic series and peralkaline potassic-ultrapotassic series. Geochemical data suggest that the magma sources of Cenozoic volcanic rocks have transferred from spinel Iherzolite mantle in the early stage to garnet peridotite enriched mantle (EM2) in the later stage. The high Mg# number and extremely high Cr-Ni-Co abundance of high-K calc-alkaline and shoshonitic series andesites in the Qiangtang area indicate that the primary magma might be derived from subduction of continent lithosphere from the Lhasa block. Incompatible element ratios of La/Rb, Zr/Rb, Rb/Nb, K/Nb,Pb/La and K/La of peralkaline potassic-ultrapotassic series lavas in northern Qinghai-Tibet Plateau are lower than island arc volcanic rocks and higher than and similar to oceanic island basalts. This signature indicates that the primary magma derive from a paleo-mantle wedge interfused by fluids derived from asthenosphere and/or subducted mantle lithosphere. But the above element ratios of ultrapotassic lavas in southern Tibet and ultrapotassic lamprophyres in eastern Tibet are higher than and similar to island arc volcanic rocks, which means that the primary magma sources contained a large quantity of crust contaminant from fluids and/or melts derived from subducted continent lithosphere. The studies result supports that the indian continental .lithosphere has underthrust beneath Tibet to about the middle of the plateau, and Eurasian (Qaidam basin) mantle lithosphere has underthrust beneath the Qiangtang area of northern Tibet Plateau. In the paper we demonstrate further that the pulsing cycles of potassic-ultrapotassic volcanism of the Qinghai-Tibet Plateau result from an asthenospher pulsing upwelling caused by the intraplate subduction

  5. Features and dynamic mechanisms of Cenozoic tectonic migration and its impact on the hydrocarbon accumulation in the northern South China Sea

    Institute of Scientific and Technical Information of China (English)

    YIN Zhengxin; CAI Zhourong; WAN Zhifeng; LYU Baofeng


    The northern continental margin of the South China Sea (SCS) is located within the tectonic system of Southeast Asia, an area with a great deal of tectonic migration due to the regional tectonic movements. The available geological and geophysical data of the area are comprehensively analyzed in order to demonstrate the typical migration patterns of the Cenozoic tectonics in the northern SCS caused by the episodes of the Cenozoic tectonic movement. Furthermore, the lateral variation characteristics of the strata and the differ-ent evolution patterns of the main basins' features are assessed. It primarily focus on: (1) the Cenozoic epi-sodic rifting from north to south in the continental margin of the northern SCS; (2) the rifting and depression time of the main basins progressively become younger as one goes from north to south, signifying that the migration of both the tectonics and the sediments within the northern SCS travelled from north to south during the Cenozoic; and (3) the lateral tectonic migration on the direction of EW is not regular in total, but in some local areas the trending of the tectonic migration is from west to east. The analysis of the tectonic migration features of the northern SCS, in combination with the regional tectonic evolution background, indicates that the observed remote lagging effect, resulted from the India-Eurasia plate collision, is the main dynamic mechanism involved in the tectonic migration within the northern SCS. The tectonic migration has significant influence on both the organization of petroleum deposits and on the hydrocarbon accumulation within the basins in the northern SCS; comprehensive understanding of this dynamic system is of great reference value in predicting the hydrocarbon accumulation and has the potential to have an enormous impact in discovering new deep reservoirs for the future oil-gas exploration.

  6. Late Cenozoic sedimentary process and its response to the slip history of the central Altyn Tagh fault, NW China

    Institute of Scientific and Technical Information of China (English)

    陈正乐; 张岳桥; 陈宣华; 王小凤; A.S.Ramon; W.B.Zack


    The ENE-striking Altyn Tagh fault (ATF), extending along the northern edge of the Tibetan Plateau, is one of the major important strike-slip faults, and has been known as one of the key areas to debate the eastward extrusion and crustral shortening models of the Tibetan Plateau during and after India-Asia collision. This paper mainly presents new evidence of Late Cenozoic sedimentary process to reconstruct the slip history of the ATF during the Late Cenozoic. Field measurements and laboratory analyses of the sedimentary characteristics in the Late Cenozoic basins in the central Altyn Tagh fault suggest that Late Cenozoic sedimentary sequence should be divided into three units according to facies changes. The paleo-topography reconstruction shows that the sedimentation in these basins was tightly related with the fault, indicating that the ATF has experienced at least three stages of strike slipping in the Late Cenozoic. New geological data from the Late Cenozoic sedimentary basins and the formation of th

  7. Pattern and timing of late Cenozoic rapid exhumation and uplift of the Helan Mountain,China

    Institute of Scientific and Technical Information of China (English)


    The Helan Mountain, an intraplate deformation belt in the North China Craton, is located in the northern portion of the China North-South seismic belt, and at the northwestern margin of the Ordos Block. The Cenozoic deformation history of the Helan Mountain is characterized by extension along the eastern Helan Mountain fault (EHSF), resulting in the exhumation and uplift of the Helan Mountain, relative to the rifting of the adjacent Yinchuan Basin. Here we present new apatite fission track (AFT) data from several transects adjacent to the EHSF in the central and northern Helan Mountain. AFT ages from the northern Helan Mountain (Dawukou and Zhengyiguan transects) range from 10 Ma to 89 Ma, whereas AFT ages from the southern Helan Mountain (Suyukou transect) are greater than 71 Ma. The AFT data analysis reveals initiation of rapid uplift and exhumation of the Helan Mountain at 10–12 Ma. Additionally, a plot of the AFT ages versus their mean track length shows a distinctive "boomerang" pattern indicating that the Helan Mountain experienced a discrete phase of accelerated exhumation beginning at 10-12 Ma. Spatially, AFT samples systematically increase in age away from the EHSF and are consistent with late Cenozoic exhumation that was slow in the southwestern Helan Mountain and rapid in the northeastern Helan Mountain, as well more rapid adjacent to the EHSF and slower away from the EHSF. Obviously, the spatial distribution of late Cenozoic exhumation indicates that normal faulting of the EHSF is related to southwestward tilting and rapid exhumation of the Helan Mountain beginning at 10–12 Ma. The uplift and exhumation of the Helan Mountain was a response to the intensive extension of the northwestern margin of the Ordos Block in the late Cenozoic; this occurred under a regional extensional stress field oriented NW-SE along the Yinchuan-Jilantai-Hetao and the Weihe-Shanxi graben systems adjacent to the Ordos Block.

  8. Gulf stream: velocity fluctuations during the late cenozoic. (United States)

    Kaneps, A G


    Biostratigraphic analysis of seven piston cores from the southeastern Blake Plateau suggests that the upper Miocene to Recent sedimentary section at this location represents a history of deposition of calcareous ooze alternating with current-induced nondeposition or erosion. This record is primarily a result of long-term fluctuations in the velocity of the western boundary current or Gulf Stream, which sweeps the plateau. High-velocity phases of this current system, as signaled by hiatuses in the section, lie within the time limits 4.8 to 6.1, 3.9 to 4.4, 2.3 to 2.9, and 0 to 1.5 million years before present (B.P.). These time intervals are coeval with dated episodes of climatic decline and glaciation. The most intense acceleration of the Gulf Stream, as indicated by deep erosion of the Blake Plateau, occurred in the latest Miocene to earliest Pliocene (4.8 to 6.1 million years B.P.) in conjunction with a major expansion of the Antarctic ice cap. Subsequent accelerations of the Gulf Stream coincide with early Pliocene cooling in the Southern Hemisphere, worldwide expansion of high-altitude-high-latitude glaciers in the late Pliocene, and the classical glaciations of the Pleistocene. An additional, protracted increase in the average velocity of the Gulf Stream, which began in the late Miocene and culminated in the mid-Pliocene (about 3.8 million years B.P.), can be attributed to the gradual emergence of the Central American isthmus.

  9. Cenozoic sediment flux in the Qaidam Basin, northern Tibetan Plateau, and implications with regional tectonics and climate (United States)

    Bao, Jing; Wang, Yadong; Song, Chunhui; Feng, Ying; Hu, Chunhua; Zhong, Sirui; Yang, Jiwei


    As the largest Mesozoic-Cenozoic terrestrial intermountain basin in the northern Tibetan Plateau, the Qaidam Basin is an ideal basin to examine the influences of regional tectonics and climate on sediment flux. Research conducted over the last two decades has provided abundant information about paleoclimatology and tectonic histories. In this study, we used the restoration of seven balanced cross-sections and compiled thickness data of ten outcrop sections and four boreholes to reconstruct the basin boundaries, develop isopach maps, and calculate the sediment flux in the Qaidam Basin. Our results show that the sediment flux in the Qaidam Basin increased gradually between 53.5 and 35.5 Ma, decreased to its lowest value from 35.5 to 22 Ma, increased between 22 and 2.5 Ma, and then increased dramatically after 2.5 Ma. By comparing the changes in the sediment flux with our reconstructed shortening rate in the Qaidam Basin, and the records of regional tectonic events and regional and global climate changes, we suggest that the gradual increase in the sediment flux from 53.5 to 40.5 Ma was controlled by both the tectonic uplift of the Tibetan Plateau and the relatively warm and humid climate, and that the high sediment flux from 40.5 to 35.5 Ma was mainly controlled by tectonics. The low sediment flux from 35.5 to 22 Ma was a response to the relatively cold and arid climate in a stable tectonic setting. The relatively high sediment flux between 22 and 15.3 Ma was related to tectonic activity and the warm and humid climate. The intense tectonic uplift of the northern Tibetan Plateau and the frequent climate oscillations after 15.3 Ma, particularly the glacial-interglacial cycles after 2.5 Ma, caused the high sediment flux after 15.3 Ma and the dramatic increase after 2.5 Ma, respectively.

  10. Late Cenozoic Deformation of the Coastal Cordillera, Northern Chilean Forearc, 18- 25°S (United States)

    Allmendinger, R. W.; González, G.; Loveless, J. P.; Carrizo, D.


    Overlying the only part of the South American continental crust that is in direct contact with the subducting Nazca Plate, the Coastal Cordillera of northern Chile and southern Peru should provide the most complete geological record of the coupling between the two plates. This record of coupling is exquisitely preserved in the hyperarid Atacama Desert. This preservation is both one of the major advantages and major challenges of working in this region: On the positive side, exposure of geomorphic surfaces is complete and unencumbered by erosion or vegetation, and brittle saline soils preserve subtle deformation features that would quickly be obliterated in more humid environments. On the negative side, ancient geomorphic features are just as fresh as Recent one and the lack of organic material precludes radiocarbon dating, a traditional tool of paleoseismology. During the last several years, we have concentrated on documenting three fundamental characteristics of late Cenozoic forearc deformation: (1) NS shortening on reverse faults striking at a high angle to, and dextral-reverse faults striking oblique to, the continental margin; (2) N-striking normal faults of the forearc and their reactivation, locally, as reverse faults; and (3) extensive suites of tension cracks. Reverse faults striking at a high angle to the margin are present between 19 and 21.5°S, straddling the topographic symmetry plane that marks the axis of the Bolivian orocline. Limited dating of tuffs and surfaces shows that these structures have been active for at least the last 6 Ma. At least 5 of these structures -- Atajaña, Pisagua, Iquique north and south, and Barranco Alto -- cut the Pleistocene marine terraces of the coastal platform, producing 20 to 50 m of vertical offset. A forearc crustal earthquake just south of Pisagua in March 2007 demonstrates that margin parallel shortening continues to the present and that permanent deformation occurs during the interseismic part of the plate

  11. Cenozoic geodynamics of the Ross Sea region, Antarctica: Crustal extension, intraplate strike-slip faulting, and tectonic inheritance (United States)

    Salvini, Francesco; Brancolini, Giuliano; Busetti, Martina; Storti, Fabrizio; Mazzarini, Francesco; Coren, Franco


    An integrated study of onshore and offshore geology of the Ross Sea region (namely, Victoria Land, north of Ross Island, and the Ross Sea, Antarctica) has revealed a complex, post-Eocene tectonic framework. Regional NW-SE right-lateral, strike-slip faults are the outstanding feature of this framework and overprint an older Mesozoic extensional event, responsible for formation of N-S basins in the Ross Sea. The Cenozoic framework includes kinematic deformation and reactivation along the NW-SE faults, including formation of pull-apart basins, both positive and negative flower structures, and push-up ridges. N-S extensional faults are well developed between NW-SE faults and indicate E-W extension during the Cenozoic, produced by the NW-SE right-lateral strike-slip motion together with regional crustal extension. NNW-SSE compression, induced by the right-lateral, strike-slip kinematics, is indicated by locally inverted NE-SW faults and basins. The evolution, geometry, and location of the Rennick Graben and the Lanterman Range fit well into this model. Variations in the deformational style across the region can be linked to corresponding variations in the bulk crustal rheology, from brittle behavior in the west, to ductile deformation (at subseismic-scale resolution) near the Eastern Basin. A semibrittle region that favors N-S clustering of Cenozoic magmatic activity lies in between. In this region, Cenozoic volcanoes develop at the intersections of the NW-SE and the major N-S faults. The NW-SE faults cut almost continually from the Ross Sea to East Antarctica through lithospheric sectors with different rheology and thickness. At least two of the NW-SE faults correspond to older Paleozoic terrane boundaries in northern Victoria Land. The NW-SE faults link in the Southern Ocean with major transform faults related to the plate motions of Australia, New Zealand, and Antarctica.

  12. Continental deformation accommodated by non-rigid passive bookshelf faulting: An example from the Cenozoic tectonic development of northern Tibet (United States)

    Zuza, Andrew V.; Yin, An


    Collision-induced continental deformation commonly involves complex interactions between strike-slip faulting and off-fault deformation, yet this relationship has rarely been quantified. In northern Tibet, Cenozoic deformation is expressed by the development of the > 1000-km-long east-striking left-slip Kunlun, Qinling, and Haiyuan faults. Each have a maximum slip in the central fault segment exceeding 10s to ~ 100 km but a much smaller slip magnitude (~rigid-body motion and flow-like distributed deformation end-member models for continental tectonics. Here we propose a non-rigid bookshelf-fault model for the Cenozoic tectonic development of northern Tibet. Our model, quantitatively relating discrete left-slip faulting to distributed off-fault deformation during regional clockwise rotation, explains several puzzling features, including the: (1) clockwise rotation of east-striking left-slip faults against the northeast-striking left-slip Altyn Tagh fault along the northwestern margin of the Tibetan Plateau, (2) alternating fault-parallel extension and shortening in the off-fault regions, and (3) eastward-tapering map-view geometries of the Qimen Tagh, Qaidam, and Qilian Shan thrust belts that link with the three major left-slip faults in northern Tibet. We refer to this specific non-rigid bookshelf-fault system as a passive bookshelf-fault system because the rotating bookshelf panels are detached from the rigid bounding domains. As a consequence, the wallrock of the strike-slip faults deforms to accommodate both the clockwise rotation of the left-slip faults and off-fault strain that arises at the fault ends. An important implication of our model is that the style and magnitude of Cenozoic deformation in northern Tibet vary considerably in the east-west direction. Thus, any single north-south cross section and its kinematic reconstruction through the region do not properly quantify the complex deformational processes of plateau formation.

  13. Impact of rock uplift on rates of late Cenozoic Rocky Mountain river incision (United States)

    Riihimaki, Catherine A.; Anderson, Robert S.; Safran, Elizabeth B.


    The high relief of the modern Rocky Mountain landscape formed in the late Cenozoic by downcutting of a fluvial network that links a series of easily eroded sedimentary basins across relatively resistant crystalline cores of adjacent ranges. Using a numerical model of fluvial erosion and the flexural isostatic response to the associated unloading, we first calculate the expected pattern and pace of incision caused by rock uplift related to migration of the Yellowstone hot spot and to growth of the northern portion of the Rio Grande rift. Calculated incision rates are <60 m/Myr, and total depth of erosion of sedimentary basins is <300 m, well below the long-term incision rates and amounts of erosion interpreted from the geologic record. Broad-scale tilting of the region toward the east, accomplished by a gradient in rock uplift of ˜1 km along the north-south axis of the central Rockies, declining to zero 1000 km to the east, can account for the additional erosion needed to match observations. In each modeling scenario, stream incision is nonsteady, with rock uplift outpacing erosion for <1 Myr in perimeter basins and 1-5 Myr in interior basins. Three factors dominate the spatial and temporal pattern of regional landscape evolution: (1) the time since uplift began, (2) the uplift pattern, and (3) the distribution of relatively resistant bedrock within the region. Our results suggest that the spatial variability in late Cenozoic exhumation can be explained by a long-lived transience in the stream network response to these various late Cenozoic geophysical events.

  14. Biostratigraphy and geochronology of the late Cenozoic of Córdoba Province (central Argentina) (United States)

    Cruz, Laura Edith


    In the last twenty years, several geological and stratigraphical studies have been undertaken in Córdoba Province, and they have provided useful bases for biostratigraphic work in the late Cenozoic. However, paleontological contributions have been limited to preliminary analyses of mammal assemblages, or specific discoveries. The aim of this work is to contribute to biostratigraphic knowledge of Argentina through the study of late Cenozoic mammals from Córdoba Province. Five localities have been analyzed: San Francisco, Miramar, Río Cuarto, Isla Verde, and Valle de Traslasierra. Through biostratigraphic analysis the first records of several taxa were established, and mammal assemblages with the description and correlation of the sedimentary strata were confirmed. Finally, three Assemblage Zones (Biozonas de Asociación) were proposed: 1) Neosclerocalyptus paskoensis-Equus (Amerhippus) assemblage zone with type area and profile based on the San Francisco locality, referred to the Lujanian (late Pleistocene-early Holocene), and comparable to the Equus (Amerhippus) neogeus Biozone of Buenos Aires Province; 2) Neosclerocalyptus ornatus-Catonyx tarijensis assemblage zone with type area and profile based on the San Francisco locality, referred to the Ensenadan (early Pleistocene) and comparable to the Mesotherium cristatum Biozone of Buenos Aires Province, and 3) Nonotherium hennigi-Propanochthus bullifer assemblage zone with type area and profile based on the Los Sauces river, Valle de Traslasierra, referred to the Montehermosan-Chapadmalalan interval (Pliocene), and comparable to the Trigodon gaudryi, Neocavia depressidens and/or Paraglyptodon chapadmalensis Biozones of Buenos Aires Province.

  15. Petrology of some Mexican mesozoic-cenozoic plutons: Sources and tectonic environments (United States)

    Stein, G.; Lapierre, H.; Monod, O.; Zimmermann, J.-L.; Vidal, R.


    In central and southern Mexico, three Late Mesozoic to Early Tertiary plutonic suites have been investigated. They record the evolution of the Mexican Pacific margin through space and time and more specifically its crustal thickness. In Central Mexico the La Angostura pluton (110-100 Ma) is calc-alkaline and intrudes a Late Jurassic-Early Cretaceous exotic arc, represented by the Guanajuato magmatic sequence. Both pluton and country rocks were affected by a greenschist facies metamorphism. Their high ɛNd(i) and low ɛSr(i) values are more or less similar to those of the Guanajuato arc tholeiitic rocks and suggest that both the calc-alkaline intrusions and the arc tholeiitic suite were derived from a mantle source essentially uncontaminated by a crustal component. The La Angostura calc-alkaline plutonic rocks could represent the remnants of the mature stage of this arc before its tectonic emplacement on the western margin of the North American craton. In the vicinity of the La Angostura pluton, the Eocene (ɛ50 Ma) Comanja and La Estancia granodiorites are chemically similar to volcanic arc granites and their low ɛNd(i) and high ɛSr(i) ratios suggest that they were derived from a mantle source highly contaminated by continental crust. Finally, the youngest plutonic suite (38 Ma), exposed near Zihuatanejo ranges from gabbro to granodiorite and displays calc-alkaline compositional features. Their ɛNd(i) and ɛSr(i) ratios indicate that the Zihuatanejo plutonic suite was derived from a mantle source which has been weakly contaminated by subducted sediments and/or continental crust. The contrasting petrology, chemistry and isotopic ratios of the Comanja-La Estancia granodiorites and the Zihuatanejo gabbro-granodiorite suite reflect a difference in thickness of their continental basement.

  16. Cretaceous-Cenozoic Geological Evolution of Tibet: Tectonic Interpretations and Outstanding Questions (Invited) (United States)

    Kapp, P. A.; Decelles, P. G.; Ding, L.; van Hinsbergen, D. J.


    The India-Asia collision, although profound, is only the most recent in a series of orogenic events that has modified the architecture of the Asian lithosphere. For instance, large parts of central Tibet (Lhasa and Qiangtang terranes) underwent >50% upper-crustal shortening, and likely substantial elevation gain, between Cretaceous and Eocene time in response to Lhasa - Qiangtang continental collision and Andean-style orogenesis along the southern margin of Asia. Findings by independent groups of Gangdese-arc-age detrital zircons in 52-50 Ma Tethyan Himalaya (TH) strata indicate that TH-Asia collision was ongoing by this time. This collision timing is consistent with multiple other, albeit less direct lines of evidence and suggests that a magmatic flare-up within the Gangdese arc (culminated at 52-51 Ma) occurred during subduction of TH lithosphere. Low-temperature thermochronologic data indicate that very low erosion rates, and likely plateau-like conditions considering the shortening history, were established in large parts of central Tibet at or by 50-45 Ma. The temporal-spatial distribution of subsequent shortening and exhumation is consistent with plateau growth northward and southward from central Tibet since the Eocene. The Cenozoic magmatic record of Tibet shows intriguing temporal-spatial patterns. Between 45 Ma and 30 Ma, volcanism swept >600 km northward from the Indus-Yarlung suture (IYS) and then back southward between 30 Ma and 25 Ma. These magmatic sweeps may have been produced by underthrusting and subsequent rollback of subducting TH lithosphere. Recent stratigraphic and structural studies suggest localized extension and elevation loss along the IYS at ~25 Ma, which is explainable in a slab rollback scenario, followed within a few million years by uplift back to near-modern elevations, perhaps in response to breakoff of TH lithosphere and northward underthrusting of Indian lithosphere. This hypothesis of TH - Indian lithosphere subduction can

  17. Relating the Seismic Character of the Crust and Upper Mantle to Late-Cenozoic Extension in Southwestern N.A. (United States)

    Thurner, S.; Frassetto, A.; Porter, R.; Zandt, G.


    A recent tectonic reconstruction (McQuarrie and Wernicke, 2005) places detailed constraints on the magnitude and scope of late-Cenozoic extension throughout Southwestern North America. This project seeks to better understand the distribution of extension throughout the crust and upper mantle and elucidate the transition from the highly extended Basin and Range to the relatively unextended Colorado Plateau. To this end, we present teleseismic receiver functions generated from 31 broadband seismometers associated with EarthScope's BigFoot Array, TriNet, and PASSCAL stations deployed across Southern California and Arizona. We employ the common-conversion-point stacking method to analyze variations in lithospheric structure. Additionally, in regions with clear converted wave reverberations we analyze the trade-off between crustal thickness and bulk Vp/Vs to improve our view of how crustal thickness and Vp/Vs relate to different tectonic environments and degree of extension. Our preliminary estimates indicate crustal thicknesses of ~25-30 km in eastern California increasing to ~40- 45 km within the southern Colorado Plateau. The transition between thin to thick crust appears to occur over as little as 20 km. Crustal Vp/Vs varies considerably, with Vp/Vs greater than 1.8 near the Transverse Ranges and Colorado Plateau, and less than 1.8 in the southern Basin and Range. We also view a change in the nature of the Moho approaching the Colorado Plateau. Initial calculations indicate the amplitude of the converted wave from the Moho is twice as strong beneath the Mojave and Southern Basin and Range than the Colorado Plateau. Additionally, we observe laminated crust in the western Mojave Desert approaching the Transverse Ranges.

  18. Unraveling tectonics and climate forcing in the late-Neogene exhumation history of South Alaska (United States)

    Valla, Pierre; Champagnac, Jean-Daniel; Shuster, David; Herman, Frédéric; Giuditta Fellin, Maria


    The southern Alaska range presents an ideal setting to study the complex interactions between tectonics, climate and surface processes in landscape evolution. It exhibits active tectonics with the ongoing subduction/collision between Pacific and North America, and major active seismogenic reverse and strike-slip faults. The alpine landscape, rugged topography and the important ice-coverage at present reveal a strong glacial imprint associated with high erosion and sediment transport rates. Therefore, the relative importance of climatically-driven glacial erosion and tectonics for the observed late-exhumation history appears to be quite complex to decipher. Here, we first perform a formal inversion of an extensive bedrock thermochronological dataset from the literature to quantify the large-scale 20-Myr exhumation history over the entire southern Alaska. We show that almost half of the variability within the thermochronological record can be explained by modern annual precipitations spatial distribution, the residuals clearly evidencing localized exhumation along major tectonic structures of the frontal fold and thrust belt. Our results confirm high exhumation rates in the St Elias "syntaxis" and frontal zones for the last 0-2 Myr, where major ice fields and high precipitation rates likely sustained high exhumation rates; however the impact of late Cenozoic glaciations is difficult to constrain because of the low resolution on the exhumation history older than ~2 Myr. On the contrary, our inversion outcomes highlight that north of the Bagley Icefield the long-term exhumation has remained quite slow and continuous over the last ~20 Myr, with no late-stage signal of exhumation change since the onset of glaciations despite a clear glacial imprint on the landscape. We thus focus on the Granite Range (Wrangell-St Elias National Park, Alaska), an area presenting a strong glacial imprint but minor tectonic activity with only localized brittle deformation. We sampled four

  19. Meso-Cenozoic intraplate contraction in Central and Western Europe: a unique tectonic event? (United States)

    Kley, Jonas; Jähne, Fabian; Malz, Alexander


    From the British Isles to Poland, Europe experienced contractional deformation in Late Cretaceous and Paleogene time. The closest contemporaneous plate margins were the incipient Mid-Atlantic rift in the west and northwest, and the Mediterranean system of subduction zones in the south. Each of these plate margins was located more than 1000 km away from the site of deformation. This tectonic event thus represents an outstanding example of large-scale intraplate shortening and may serve as a template for comparison with modern examples. Its effects are seen in a ca. 500 km wide strip that stretches in NW-SE-direction along the Tornquist Line, a regional fault zone separating thick lithosphere of the Baltic Shield from much thinner lithosphere to the southwest. Most faults and folds also trend NW-SE, but some are linked by large N-S-striking transfer zones. In the southeast, the shortening structures are truncated by the Neogene Carpathian thrust front; their original extent is unknown. In the west, the fault zones fan out into more northerly trends in the Central North Sea and more easterly trends in the Channel area before dying out on the shelf. Late Cretaceous (ca. 90-70 Ma) shortening dominates from Poland to the North Sea, while the main shortening event in Southern Britain is of Paleogene age. Many Late Cretaceous to Paleogene structures have been conditioned by Permian or Triassic through Early Cretaceous extensional faulting, whereas some large basement uplifts and reverse faults have no demonstrable inheritance from earlier extension. The thick, mobile Zechstein salt has modified extensional and contractional structures, but both extend beyond its depositional borders. Even where thick evaporates underlie the Mesozoic sedimentary cover, the basement is typically involved in the deformation, except for localized thin-skinned imbricate thrusting and salt-cored anticlines. Different structural styles do not appear to correlate with the magnitude of shortening

  20. Time variability in Cenozoic reconstructions of mantle heat flow: plate tectonic cycles and implications for Earth's thermal evolution. (United States)

    Loyd, S J; Becker, T W; Conrad, C P; Lithgow-Bertelloni, C; Corsetti, F A


    The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by approximately 0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past.

  1. Climate vs. tectonic induced variations in Cenozoic sediment supply from western Scandinavia

    DEFF Research Database (Denmark)

    Gołędowski, Bartosz; Nielsen, S.B.; Clausen, O.R.

    ) changed the erosional regime in western Scandinavia from fluvial (inefficient in tectonically stable settings, almost regardless of the amount of precipitation) to glacial. Glacial erosion is much more effective and is apparently able to outpace tectonic processes responsible for development of high...

  2. Diets and environments of late Cenozoic mammals in the Qaidam Basin, Tibetan Plateau: Evidence from stable isotopes (United States)

    Zhang, Chunfu; Wang, Yang; Li, Qiang; Wang, Xiaoming; Deng, Tao; Tseng, Zhijie J.; Takeuchi, Gary T.; Xie, Gangpu; Xu, Yingfeng


    The timing history and driving mechanisms of C4 expansion and Tibetan uplift are hotly debated issues. Paleoenvironmental evidence from within the Tibetan Plateau is essential to help resolve these issues. Here we report results of stable C and O isotope analyses of tooth enamel samples from a variety of late Cenozoic mammals, including deer, giraffe, horse, rhino, and elephant, from the Qaidam Basin in the northeastern Tibetan Plateau. The enamel-δ13C values are <-8‰ for modern samples and ≤-7‰ for fossils, except for one late Miocene rhino (CD0722, with δ13C values up to -4.1‰). If the Qaidam Basin was as arid as today in the Mio-Pliocene, these data would indicate that the majority of the animals had C3 diets and only a few individuals (besides the exceptional rhino CD0722) may have consumed some C4 plants. Based on geological evidence, however, the Qaidam Basin was probably warmer and more humid during the late Miocene and early Pliocene than today. Thus, these δ13C values likely indicate that many individuals had significant dietary intakes of C4 plants, and the Qaidam Basin had more C4 plants in the late Miocene and early Pliocene than today. Moreover, the Qaidam Basin likely had much denser vegetation at those times in order to support such large mammals as rhinos and elephants. While the δ18O values did not increase monotonously with time, the range of variation seems to have increased considerably since the early Pliocene, indicating increased aridification in the basin. The mean δ18O values of large mammals and those reconstructed for local meteoric waters display a significant negative shift in the late Miocene, consistent with the marine δ18O record which shows a cooling trend in the same period. Taken together, the isotope data suggest a warmer, wetter, and perhaps lower Qaidam Basin during the late Miocene and early Pliocene. Increased aridification after the early Pliocene is likely due to a combined effect of regional tectonism, which

  3. Late Cenozoic continuous aridification in the western Qaidam Basin: evidence from sporopollen records

    Directory of Open Access Journals (Sweden)

    Y. F. Miao


    Full Text Available Cenozoic climate changes in inner Asia provide a basis for understanding linkages between global cooling, the Tibetan Plateau uplift, and possibly the development of the East Asian monsoon. Based on the compiled palynological results from the western Qaidam Basin, this study reconstructed an 18 Ma record of changing vegetation and paleoclimates since the middle Miocene. Thermophilic taxa percentages were highest between 18 and 14 Ma and decreased after 14 Ma, corresponding closely with the Middle Miocene Climatic Optimum (MMCO between 18 and 14 Ma and the following global climatic cooling. After 3.6 Ma, the thermophilic taxa percentages further decreased, showing the inevitable relations with the ice-sheets enlargement in the North Hemisphere. During the same period of time, the increase in xerophytic taxa percentages and decrease in conifers percentages imply aridification in both the basin and surrounding mountains since 18 Ma. These results indicate that global cooling mainly controlled the climate change from a relative warm-wet stage to a cold-dry stage during the late Cenozoic at the western Qaidam Basin, and that the Tibetan Plateau uplift also contributed in contrast to the East Asian summer monsoon.

  4. Geological characteristics and evolution of the eastern Qinghai-Tibetan plateau since the late Cenozoic

    Institute of Scientific and Technical Information of China (English)


    The eastern edge of the Qinghai-Tibetan plateau developed an integrated series of late Cenozoic lacustrine,loess,red and moraines deposits.Various genetic sediments recorded rich information of Quaternary palaeoenvironment changes.Xigeda Pliocene lacustrine deposits,formed during 4.2 Ma B.P.-2.6 Ma B.P.,experienced nine periodic warm-cold stages.Eolian deposition in western Sichuan began at 1.15 Ma B.P.,and the loess-soil sequences successively record fourteen palaeomonsoon change cycles.Red clay in the Chengdu plain record five stages of paleoclimatic change stages since 1.13 Ma B.P..There was an old glacial period of 4.3 Ma the eastern Qinghai-Tibetan plateau.During the Quaternary,there were five extreme paleoclimatic events corresponding to five glaciations.

  5. Late Cenozoic genus Fupingopollenites development and its implications for the Asian summer monsoon (ASM) evolution (United States)

    Miao, Y.; Song, C.; Fang, X.; Meng, Q.; Zhang, P.; Wu, F.; Yan, X.


    An extinct palynomorph, Fupingopollenites, was used as the basis for a discussion of the late Cenozoic Asian summer monsoon (ASM) evolution and its possible driving forces. Based on the spatial and temporal variations in its percentages across Inner and East Asia, we found that Fupingopollenites mainly occurred in East Asia, with boundaries to the NE of ca. 42°N, 135°E and NW of ca. 36°N, 103°E during the Early Miocene (ca. 23-17 Ma). This region enlarged westwards, reaching the eastern Qaidam Basin (ca. 36°N, 97.5°E) during the Middle Miocene (ca. 17-11 Ma), before noticeably retreating to a region bounded to the NW at ca. 33°N, 105°E during ca. 11-5.3 Ma. The region then shrank further in the Pliocene, with the NE boundary shrinking southwards to about 35°N, 120°E; the area then almost disappeared during the Pleistocene (2.6-0 Ma). The flourishing and subsequent extinction of Fupingopollenites is indicative of a narrow ecological amplitude with a critical dependence on habitat humidity and temperature (most likely mean annual precipitation (MAP) >1000 mm and mean annual temperature (MAT) >10°C). Therefore, the Fupingopollenites geographic distribution can indicate the humid ASM evolution during the late Cenozoic, revealing that the strongest ASM period occurred during the Middle Miocene Climate Optimum (MMCO, ~17-14 Ma), after which the ASM weakened coincident with global cooling. We argue that the global cooling played a critical role in the ASM evolution, while the Tibetan Plateau uplifts made a relatively small contribution. This result was supported by a Miocene pollen record at the Qaidam Basin, inner Asia and the contemporaneously compiled pollen records across the Eurasia.

  6. A Late Cenozoic Kinematic Model for Deformation Within the Greater Cascadia Subduction System (United States)

    Wilson, D. S.; McCrory, P. A.


    Relatively low fault slip rates have complicated efforts to characterize seismic hazards associated with the diffuse subduction boundary between North America and offshore oceanic plates in the Pacific Northwest region. A kinematic forward model that encompasses a broader region, and incorporates seismologic and geodetic as well as geologic and paleomagnetic constraints offers a tool for constraining fault rupture chronologies—all within a framework tracking relative motion of the Juan de Fuca, Pacific, and North American plates during late Cenozoic time. Our kinematic model tracks motions as a system of rigid microplates, bounded by the more important mapped faults of the region or zones of distributed deformation. Though our emphasis is on Washington and Oregon, the scope of the model extends eastward to the rigid craton in Montana and Wyoming, and southward to the Sierra Nevada block of California to provide important checks on its internal consistency. The model reproduces observed geodetic velocities [e.g., McCaffrey et al., 2013, JGR], for 6 Ma to present, with only minor reorganization for 12-6 Ma. Constraints for the older deformation history are based on paleomagnetic rotations within the Columbia River Basalt Group, and geologic details of fault offsets. Since 17 Ma, our model includes 50 km of N-S shortening across the central Yakima fold and thrust belt, substantial NW-SE right-lateral strike slip distributed among faults in the Washington Cascade Range, 90 km of shortening on thrusts of Puget Lowland, and substantial oroclinal bending of the Crescent Formation basement surrounding the Olympic Peninsula. This kinematic reconstruction provides an integrated, quantitative framework with which to investigate the motions of various PNW forearc and backarc blocks during late Cenozoic time, an essential tool for characterizing the seismic risk associated with the Puget Sound and Portland urban areas, hydroelectric dams, and other critical infrastructure.

  7. Late Cenozoic evolution of the East China continental margin: Insights from seismic, gravity, and magnetic analyses (United States)

    Shang, Lu-Ning; Zhang, Xun-Hua; Jia, Yong-Gang; Han, Bo; Yang, Chuan-Sheng; Geng, Wei; Pang, Yu-Mao


    Seismic reflection profiles reveal the structural characteristics beneath the East China Sea shelf margin and the Okinawa Trough, and provide new constraints on the Late Cenozoic evolution of the East China continental margin. The Frontal Shelf Basin between the Taiwan-Sinzi Uplift and the trough axis occupies the western half of the Northern-Middle Okinawa Trough. In this basin, the Middle-Late Miocene sediments are confined to grabens or half-grabens dominated by listric faults, whereas the overlying Pliocene-Quaternary sequence is characterized by a uniform thickness and dense planar-type faults, suggesting that rifting of the Northern-Middle Okinawa Trough initiated during the Middle Miocene but slowed down during the earliest Pliocene. Since that time, the opening of the Okinawa Trough has been dominated by diffuse rifting. The Southern Okinawa Trough is predominately filled by Quaternary sediments, indicating that its back-arc rifting began during the earliest Pleistocene. Contractional structures identified in the pre-Quaternary sequence beneath the continental slope, along with an erosional Pleistocene-pre-Pleistocene unconformity in the Southern Okinawa Trough, demonstrate the existence of pre-rifting compression and uplifting in this region. We use this evidence and previously published results, to propose an evolutionary model of the East China continental margin during the Late Cenozoic. The Northern-Middle Okinawa Trough began rifting during the Middle Miocene on a paleo-uplift. The Luzon Arc initially impinged upon the Eurasian continental margin during the Late Miocene near the southeastern end of the Miyako Fault Belt and activated the proto-Taiwan Orogeny in today's Southern Okinawa Trough and adjacent regions. During the Late Miocene-Pliocene, the orogeny quickly propagated southwestward along with the west-northwest-moving Philippine Sea Plate. Subsequently, the rifting of the Southern Okinawa Trough was initiated during the earliest Pleistocene

  8. Tectonic Setting and Nature of the Provenance of Sedimentary Rocks in Lanping Mesozoic-Cenozoic Basin: Evidence from Geochemistry of Sandstones

    Institute of Scientific and Technical Information of China (English)

    李志明; 刘家军; 胡瑞忠; 何明勤; 刘玉平; 李朝阳


    The geochemical composition of sandstones in the sedimentary basin is controlled mainly by the tectonic setting of the provenance,and it is therefore possible to reveal the tectonic setting of the provenance and the nature of source rocks in terms of the geochemical composition of sandstones. The major elements,rare-earth elements and trace elements of the MesozoicCenozoic sandstones in the Lanping Basin are studied in this paper,revealing that the tectonic settings of the provenance for Mesozoic-Cenozoic sedimentary rocks in the Lanping Basin belong to a passive continental margin and a continental island arc. Combined with the data on sedimentary facies and palaeogeography,it is referred that the eastern part of the basin is located mainly at the tectonic setting of the passive continental margin before Mesozoic,whereas the western part may be represented by a continental island arc. This is compatible with the regional geology data. The protoliths of sedimentary rocks should be derived from the upper continental crust,and are composed mainly of felsic rocks,mixed with some andesitic rocks and old sediment components. Therefore,the Lanping Mesozoic-Cenozoic Basin is a typical continental-type basin. This provides strong geochemical evidence for the evolution of the paleo-Tethys and the basin-range transition.

  9. Cenozoic landforms and post-orogenic landscape evolution of the Balkanide orogen: Evidence for alternatives to the tectonic denudation narrative in southern Bulgaria (United States)

    Gunnell, Y.; Calvet, M.; Meyer, B.; Pinna-Jamme, R.; Bour, I.; Gautheron, C.; Carter, A.; Dimitrov, D.


    Continental denudation is the mass transfer of rock from source areas to sedimentary depocentres, and is typically the result of Earth surface processes. However, a process known as tectonic denudation is also understood to expose deep-seated rocks in short periods of geological time by displacing large masses of continental crust along shallow-angle faults, and without requiring major contributions from surface erosion. Some parts of the world, such as the Basin and Range in the USA or the Aegean province in Europe, have been showcased for their Cenozoic tectonic denudation features, commonly described as metamorphic core-complexes or as supradetachment faults. Based on 22 new apatite fission-track (AFT) and 21 helium (AHe) cooling ages among rock samples collected widely from plateau summits and their adjacent valley floors, and elaborating on inconsistencies between the regional stratigraphic, topographic and denudational records, this study frames a revised perspective on the prevailing tectonic denudation narrative for southern Bulgaria. We conclude that conspicuous landforms in this region, such as erosion surfaces on basement-cored mountain ranges, are not primarily the result of Paleogene to Neogene core-complex formation. They result instead from "ordinary" erosion-driven, subaerial denudation. Rock cooling, each time suggesting at least 2 km of crustal denudation, has exposed shallow Paleogene granitic plutons and documents a 3-stage wave of erosional denudation which progressed from north to south during the Middle Eocene, Oligocene, Early to Middle Miocene, and Late Miocene. Denudation initially prevailed during the Paleogene under a syn-orogenic compressional regime involving piggyback extensional basins (Phase 1), but subsequently migrated southward in response to post-orogenic upper-plate extension driven by trench rollback of the Hellenic subduction slab (Phase 2). Rare insight given by the denudation pattern indicates that trench rollback


    Directory of Open Access Journals (Sweden)

    Victor D. Mats


    Full Text Available The publication presents a review of alterations of stagnant elements of the Baikal region that occurred during formation and development of the Baikal rift from the Late Cretaceous. Nowadays the natural complex contains the elements varying in age and genesis as they developed during three large stages. In the course of the regional evolution, peneplains altered into uplifted platoes, alpinetype and goltsy mountain ranges; humid quasitropics and subtropics developed into arid zones with the Mediterraneantype climate and moderate and nival zones which were subjected to recurrent mountainandvalley glaciations. Water basins became ultradeep and hosted water species populations which are unique in terms of the biodiversity and endemic features. The main stages of environmental alterations were separated by phases of tectonic movement and tectonic inversions. The alterations’ review is based on consecutive series of cartographic representations of the paleogeographic scenarios.

  11. Late Cretaceous fluvial systems and inferred tectonic history, central Utah

    Energy Technology Data Exchange (ETDEWEB)

    Lawton, T.F.


    Upper Campanian nonmarine sedimentary rocks exposed between the Wasatch Plateau and the Green River in central Utah record a tectonic transition from thin-skinned deformation in the thrust belt to basement-cored uplift in the foreland region. Sandstones within the section consist of two distinct compositional suites, a lower quartzose petrofacies and an upper lithic petrofacies. The volcanic lithic grains of the Farrer and Tuscher Formations were derived from more distal arc sources to the southwest, and transported through the thrust belt somewhere west of the Kaiparowits region, where time-equivalent sedimentary rocks are also rich in volcanic lithic fragments. Disappearance of volcanic lithics and appearance of pebbles at the top of the Tuscher Formation is interpreted to reflect a latest Campanian reorganization of drainage patterns that marked initial growth of the San Rafael swell and similar basement uplifts to the south of the swell. Contemporaneous fluvial systems that deposited the uppermost part of the Price River Formation in the Wasatch Plateau were apparently unaffected by the uplift and continued to flow northeast. Depositional patterns thus indicate that initial growth of the San Rafael swell was probably concurrent with late deformation in the thrust belt. Depositional onlap across the Mesaverde Group by a largely post-tectonic assemblage of fluvial and lacustrine strata (North Horn Formation) indicates a minimum late Paleocene age for growth of the San Rafael swell and deformation within the thrust belt.

  12. Cenozoic tectonics of western North America controlled by evolving width of Farallon slab. (United States)

    Schellart, W P; Stegman, D R; Farrington, R J; Freeman, J; Moresi, L


    Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench migration. Using a global subduction zone data set and three-dimensional numerical subduction models, we show that slab width (W) controls these modes and the partitioning of subduction between them. Subducting plate velocity scales with W(2/3), whereas trench velocity scales with 1/W. These findings explain the Cenozoic slowdown of the Farallon plate and the decrease in subduction partitioning by its decreasing slab width. The change from Sevier-Laramide orogenesis to Basin and Range extension in North America is also explained by slab width; shortening occurred during wide-slab subduction and overriding-plate-driven trench retreat, whereas extension occurred during intermediate to narrow-slab subduction and slab-driven trench retreat.

  13. Long-term stability of global erosion rates and weathering during late-Cenozoic cooling. (United States)

    Willenbring, Jane K; von Blanckenburg, Friedhelm


    Over geologic timescales, CO(2) is emitted from the Earth's interior and is removed from the atmosphere by silicate rock weathering and organic carbon burial. This balance is thought to have stabilized greenhouse conditions within a range that ensured habitable conditions. Changes in this balance have been attributed to changes in topographic relief, where varying rates of continental rock weathering and erosion are superimposed on fluctuations in organic carbon burial. Geological strata provide an indirect yet imperfectly preserved record of this change through changing rates of sedimentation. Widespread observations of a recent (0-5-Myr) fourfold increase in global sedimentation rates require a global mechanism to explain them. Accelerated uplift and global cooling have been given as possible causes, but because of the links between rates of erosion and the correlated rate of weathering, an increase in the drawdown of CO(2) that is predicted to follow may be the cause of global climate change instead. However, globally, rates of uplift cannot increase everywhere in the way that apparent sedimentation rates do. Moreover, proxy records of past atmospheric CO(2) provide no evidence for this large reduction in recent CO(2) concentrations. Here we question whether this increase in global weathering and erosion actually occurred and whether the apparent increase in the sedimentation rate is due to observational biases in the sedimentary record. As evidence, we recast the ocean dissolved (10)Be/(9)Be isotope system as a weathering proxy spanning the past approximately 12 Myr (ref. 14). This proxy indicates stable weathering fluxes during the late-Cenozoic era. The sum of these observations shows neither clear evidence for increased erosion nor clear evidence for a pulse in weathered material to the ocean. We conclude that processes different from an increase in denudation caused Cenozoic global cooling, and that global cooling had no profound effect on spatially and

  14. Late Cenozoic pollen records and paleoclimate in the western Qaidam Basin, Northern Tibetan Plateau (United States)

    Miao, Y.


    Y. F. Miao1, X. M. Fang2*, F. L. Wu2, M. T. Cai2, C. H. Song3, Q. Q. Meng3 1 Key Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Institute, Chinese Academy of Sciences, Lanzhou, 730000, China 2 Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100085, China 3 School of Earth Science, Lanzhou University, Lanzhou, 730000, China * Corresponding author, E-mail address: (X.M. Fang). Abstract: Cenozoic climate changes in inner Asia provide a basis for understanding linkages between global cooling, the Tibetan Plateau uplift, and possibly the development of the East Asian monsoon. Based on a compilation of palynological results from the western Qaidam Basin, this study reconstructed a 15 million years (Ma) record of changing vegetation and paleoclimates spanning the middle Miocene to present (comprising two series: ~18-5 Ma and ~3.1-0 Ma, respectively). The thermophilic percentages were highest between 18 and 14 Ma, and decreased after 14 Ma, closely corresponding to the Middle Miocene Climatic Optimum (MMCO) between 18 and 14 Ma and the following global climatic cooling between 14 and 5 Ma. At the same time, decreases in the xerophytic and coniferous taxa percentages, and the increasing logarithmic ratio of non-arboreal pollen to arboreal pollen (ln (NAP/AP)), reveal the continuous aridification across both the basin and surrounding mountains. Between ~3.1-0 Ma, the percentages of the thermophilic, xerophytic and coniferous pollen as well as the ln (NAP/AP) imply further cooling and drying in this region since 3.1 Ma. We argue that these vegetation and climate patterns during the late Cenozoic western Qaidam Basin are primarily a result of the global cooling, with the Tibetan Plateau uplift and East Asian summer monsoon having contributions of lesser importance.

  15. The Tectonic Event of the Cenozoic in the Tasman Area, Western Pacific, and Its Role in Eocene Global Change (United States)

    Collot, J.; Sutherland, R.; Rouillard, P.; Patriat, M.; Roest, W. R.; Bache, F.


    . Together, these evidences form a tectonic event, which is manifest as a regional Eocene-Oligocene unconformity, and which is named the "Tectonic Event of the Cenozoic in the Tasman Area" (TECTA). Studying the absolute timing of TECTA and the relative timing of its sub-events will allow to better understand its role and relation to Eocene global change.

  16. Taxonomic review of the late Cenozoic megapodes (Galliformes: Megapodiidae) of Australia (United States)

    Prideaux, Gavin J.


    Megapodes are unusual galliform birds that use passive heat sources to incubate their eggs. Evolutionary relationships of extant megapode taxa have become clearer with the advent of molecular analyses, but the systematics of large, extinct forms (Progura gallinacea, Progura naracoortensis) from the late Cenozoic of Australia has been a source of confusion. It was recently suggested that the two species of Progura were synonymous, and that this taxon dwarfed into the extant malleefowl Leipoa ocellata in the Late Pleistocene. Here, we review previously described fossils along with newly discovered material from several localities, and present a substantial taxonomic revision. We show that P. gallinacea and P. naracoortensis are generically distinct, describe two new species of megapode from the Thylacoleo Caves of south-central Australia, and a new genus from Curramulka Quarry in southern Australia. We also show that L. ocellata was contemporaneous with larger species. Our phylogenetic analysis places four extinct taxa in a derived clade with the extant Australo-Papuan brush-turkeys Talegalla fuscirostris, L. ocellata, Alectura lathami and Aepypodius bruijnii. Therefore, diversity of brush-turkeys halved during the Quaternary, matching extinction rates of scrubfowl in the Pacific. Unlike extant brush-turkeys, all the extinct taxa appear to have been burrow-nesters. PMID:28680676

  17. Taxonomic review of the late Cenozoic megapodes (Galliformes: Megapodiidae) of Australia (United States)

    Shute, Elen; Prideaux, Gavin J.; Worthy, Trevor H.


    Megapodes are unusual galliform birds that use passive heat sources to incubate their eggs. Evolutionary relationships of extant megapode taxa have become clearer with the advent of molecular analyses, but the systematics of large, extinct forms (Progura gallinacea, Progura naracoortensis) from the late Cenozoic of Australia has been a source of confusion. It was recently suggested that the two species of Progura were synonymous, and that this taxon dwarfed into the extant malleefowl Leipoa ocellata in the Late Pleistocene. Here, we review previously described fossils along with newly discovered material from several localities, and present a substantial taxonomic revision. We show that P. gallinacea and P. naracoortensis are generically distinct, describe two new species of megapode from the Thylacoleo Caves of south-central Australia, and a new genus from Curramulka Quarry in southern Australia. We also show that L. ocellata was contemporaneous with larger species. Our phylogenetic analysis places four extinct taxa in a derived clade with the extant Australo-Papuan brush-turkeys Talegalla fuscirostris, L. ocellata, Alectura lathami and Aepypodius bruijnii. Therefore, diversity of brush-turkeys halved during the Quaternary, matching extinction rates of scrubfowl in the Pacific. Unlike extant brush-turkeys, all the extinct taxa appear to have been burrow-nesters.

  18. Features of Late Cenozoic Deepwater Sedimentation in Southern Qiongdongnan Basin,Northwestern South China Sea

    Institute of Scientific and Technical Information of China (English)

    Yuan Shengqiang; Yao Genshun; Lü Fuliang; Hu Bing; He Xiaosu; Wang Bin; Li Li


    Based on high resolution 2D and 3D seismic data acquired in recent years,using sequence stratigraphy analysis and geophysical methods,we discuss the features of Late Cenozoic deepwater sedimentation in the southern Qiongdongnan (琼东南) basin.The study area entered a bathyal slope environment in the Miocene.The channel developed in the Sanya (三亚) Formation was controlled by a fault break,and its shingled seismic characteristics represent multiple erosion and fill,which may indicate that turbidite current developed in the slope environment.The polygon faults found in mudstone of the Meishan (梅山) Formation represent the deepwater hungry sedimentary environment.The large-scale channels developed on the top of HuangUu (黄流) Formation could be the result of a big sea level drop and an increase of sediment supply.The fantastic turbidite channel developed in Late Quaternary in the slope environment has "fan-like" body and long frontal tiny avuision channel The analysis of these features suggests that the sediment supply of the study area in the post-rifting period was dominant from the Vietnam uplift in the southwest.These deepwater sedimentary features could be potential reservoirs or migration pathways for deepwater petroleum systems.

  19. The Curious Decoupling of Magmatism and Plate Tectonics During the Cenozoic in Western North America: Insight From the NAVDAT Database (United States)

    Glazner, A. F.; Walker, J. D.; Farmer, G. L.; Bowers, T. D.


    Since the widespread acceptance of plate tectonics, magmatism in the western U.S. has been explained by subduction along the west coast of North America and destruction of the subduction system by development of the San Andreas transform fault system. However, re-analysis of space-time patterns of magmatism in western North America calls many of these inferred patterns of magmatism into question. Animation of space-time patterns found in the developing NAVDAT dataset (which currently hosts about 10,000 Cenozoic age and/or geochemical analyses;, demonstrates that: (1) subduction-type (e.g., intermediate) volcanism is poorly linked to the subduction system; (2) there is little evidence that slab windows controlled magmatism; (3) magmatism was clearly migratory, but not in ways that can be explained by plate-tectonic processes; and (4) magmatism was migratory at length scales ranging from 1000s of km (continental) to 10s of km (county). Several space-time patterns are evident in the NAVDAT animations, including: (1) a sweep from Montana into Nevada from 50 to about 20 Ma; (2) a clockwise sweep around the Colorado Plateau from New Mexico to southern Nevada, from about 30 to 15 Ma; (3) a burst of magmatism at about 16 Ma in northern Nevada, followed by outward sweeps to Yellowstone, central Oregon, and the Sierra Nevada; (4) a burst of magmatism in the Sierra Nevada at 3.5 Ma; and (5) several local migrations, including from Phoenix north onto the Colorado Plateau and from the San Francisco Bay area north to the Geysers geothermal field. Some of these patterns have been tied to specific events (e.g., impingement of the Yellowstone plume and Pliocene delamination), but the others are difficult to relate to plate-tectonic events. They may be caused by local tectonic events (propagating rifts?), minor convective rolls in the asthenosphere, lithospheric delamination, or delamination of a flat Laramide slab. Whatever their origin, database animation

  20. Orthorhombic faults system at the onset of the Late Mesozoic-Cenozoic Barents Sea rifting (United States)

    Collanega, Luca; Breda, Anna; Massironi, Matteo


    The structures of the Late Mesozoic/Cenozoic Barents Sea rifting have been investigated with multichannel 3D seismics, covering an area of 7700 sqKm in the Hoop Fault Complex, a transitional area between the platform and the marginal basins. The main structural lineaments have been mapped in a time domain 3D surface and their activity ranges have been constrained through the sin-sedimentary thickness variations detected in time-thickness maps. Two main fault systems have been identified: an orthorhombic fault system consisting of two fault sets trending almost perpendicularly one to the other (WNW-ESE and NNE-SSW) and a graben/half-graben system, elongated approximately N-S in the central part of the study area. While the graben/half-graben system can be explained through the theory of Anderson, this landmark theory fails to explain the simultaneous activity of the two fault sets of the orthorhombic system. So far, the models that can better explain orthorhombic fault arrangements are the slip model by Reches (Reches, 1978; Reches, 1983; Reches and Dieterich, 1983) and the odd-axis model by Krantz (Krantz, 1988). However, these models are not definitive and a strong quest to better understand polymodal faulting is actual (Healy et al., 2015). In the study area, the presence of both a classical Andersonian and an orthorhombic system indicates that these models are not alternative but are both effective and necessary to explain faulting in different circumstances. Indeed, the Andersonian plain strain and the orthorhombic deformation have affected different part of the succession during different phases of the rifting. In particular, the orthorhombic system has affected only the Late Mesozoic-Cenozoic interval of the succession and it was the main active system during the initial phase of the rifting. On the other hand, the graben/half-graben system has affected the whole sedimentary succession, with an increasing activity during the development of the rifting. It has

  1. Late Cretaceous-Early Palaeogene tectonic development of SE Asia (United States)

    Morley, C. K.


    -South China Sea) is preferred. Lying between the two subduction related arcs, the Khorat Basin is of predominantly Late Jurassic-Early Cretaceous age but stratigraphic and apatite fission track data also indicates deposition of 1-2 km of Late Cretaceous sediments. The synformal basin geometry probably arose due to the dynamic topography created by converging Tethyan and Palaeo-Pacific subduction zones. The Aptian-Albian slowing of basin subsidence and onset of evaporite deposition coincides with collision of the Mawgyi and Woyla island arcs. Extensive Palaeogene deformation and exhumation (3 + km in places) affected all margins of the Khorat Plateau. Deformation includes folds of the Phu Phan uplift, and strike-slip faults, thrusts and folds on the southern and eastern margins. South of the Khorat Plateau outcrop, and seismic reflection data from the Ton Le Sap Basin (Cambodia), and the Gulf of Thailand, indicate syn-depositional fault-controlled subsidence was important during Cretaceous deposition. The hot, thickened crust developed during the Late Cretaceous-Palaeogene events follows the weak (Indosinian), crustal-scale Inthanon and Sukhothai zones, which persistently guided the location of later structures including Cenozoic extensional, and post-rift basins, and influenced the widespread occurrence of low-angle normal faults, metamorphic core complexes, and eastern Gulf of Thailand super-deep post-rift basins.

  2. A high-resolution multi-proxy record of late Cenozoic environment change from central Taklimakan Desert, China

    Directory of Open Access Journals (Sweden)

    X. Wang


    Full Text Available The Taklimakan Desert in the Tarim Basin is the largest desert in Central Asia, and is regarded as one of the main dust sources to the Northern Hemisphere. Late Cenozoic sedimentary sequences with intercalated in-situ aeolian dune sands in this area preserve direct evidence for the Asian desertification. Herein, we report a high-resolution multi-proxy climatic record from the precise magnetostratigraphic dated Hongbaishan section in the central Taklimakan Desert. Our results show that a fundamental climate change, characterized by significant cooling, enhanced aridity, and intensified atmospheric circulation, occurred at 2.8 Ma. Good correlations between climate records in the dust sources and downwind areas suggest a broadly consistent climate evolution of northwestern China during the late Cenozoic, which is probably driven by the uplift of the Tibet Plateau and the Northern Hemisphere glaciation.

  3. Magnetostratigraphic and paleoenvironmental records for a Late Cenozoic sedimentary sequence drilled from Lop Nor in the eastern Tarim Basin (United States)

    Chang, Hong; An, Zhisheng; Liu, Weiguo; Qiang, Xiaoke; Song, Yougui; Ao, Hong


    The Tarim Basin, one of the largest inland basins in the world, is situated in the northwestern China and to the north of the Tibetan Plateau. Continuous Cenozoic deposits have accumulated in this basin, which are crucial for investigating the growth of the Tibetan Plateau and the paleoclimatic evolution in Asian interior. Here we report the magnetostratigraphic and paleoenvironmental records for a Late Cenozoic sedimentary sequence drilled from Lop Nor in the eastern Tarim Basin. Magnetostratigraphic results show that this core has recorded a magnetic polarity sequence from C3Bn to C1n, covering an age range from ca. 7 Ma to the present. Decreased magnetic susceptibility occurred after ca. 5.6-5.1 Ma, which was interpreted to indicate an enhancement of aridity in the Tarim Basin since this period. We attribute this aridification to the combined effect of global climate cooling and the uplift of the Northern Tibetan Plateau since the late Miocene.

  4. Late Cenozoic Geology and Paleo-environment Change in the Eastern Edge of Qinghai-Xizang Plateau

    Institute of Scientific and Technical Information of China (English)

    ZHAO Zhizhong; MIAO Qi; JIANG Fuchu; QIAO Yansong; WANG Shubing; YAO Haitao; WANG Yan; LI Chaozhu; FU Jianli; LIU Zongxiu; LI Mingze


    There are late Cenozoic lacustrine deposits and loess and red clay and moraines in eastern edge of the Qinghai-Xizang Plateau. Various genetic sediments recorded rich information on late Cenozoic paleo-environment changes. Xigeda lacustrine formed during 4.2 Ma B.P.-2.6 Ma B.P. There were 9 periodic warm-cold alternations. Eolian deposition in western Sichuan began at 1.15 Ma B.P. The loess-soil sequences recorded successively 14 paleo-monsoon climate cycles. Laterite in Chengdu plain recorded 5 stages of paleoclimatic stages since 1.13 Ma B.P. There was an old glacial period of 4.3 Ma B.P. In eastern Qinghai-Xizang Plateau. During Quaternary, there are 5 extreme paleoclimatic events corresponding with 5 glaciations.

  5. Mongolian plateau: Evidence for a late Cenozoic mantle plume under central Asia (United States)

    Windley, Brian F.; Allen, Mark B.


    The 2500 x 700 km Mongolian plateau (average elevation 2000 m) is situated between the Altai orogen and the Siberian craton and occupies much of Mongolia and Transbaikalia in Russia. The plateau is characterized by (1) basin and range topography and two major domes(Hentai, 600 x 300 km, and Hangai, 800 x 550 km), where altitudes reach 3905 m; (2) lithosphere that is thinner than adjacent areas (minimum ˜50 km); (3) elevated heat flow (up to 120 mW/m2); (4) dominantly alkaline basaltic volcanism in the form of cones, lava fields, and volcanic plateaus mostly of Miocene-Quaternary age, and (5) rifts, including Baikal (main evolution in the Pliocene-Quaternary), Tunka (Oligocene-early Miocene), and Hobsogol (Pliocene-Quaternary). Existing models explain these features in terms of diapiric upwelling of a mantle asthenolith below the main rifts and/or as a long-distance effect of the India-Asia collision. We propose that the late Cenozoic uplift of the whole Mongolian plateau and associated rifting, magmatism, high heat flow, and lithospherec thinning are not externally driven by the India-Asia collision, but are the expression of the interaction of a mantle plume with overlying lithosphere. Some rifts link and interact with major strike-slip faults, such as the Bolnai. Such faults may be the major expression of the India-Asia collision in this region.

  6. Cenozoic Sedimentation and Tectonic Deformation in the Central Part of the Potiguar Basin

    Directory of Open Access Journals (Sweden)

    Elissandra Nascimento Moura-Lima


    Full Text Available Neogene and Quaternary sedimentary covers occur along the Brazilian coast and have been frequently describedtogether as a single unit. The study of Brazilian sedimentary basins concentrates on their rift phase, whereas the post-riftphase has been considered a tectonic quiescent period. In the Potiguar basin, although post-rift Cretaceous units are wellinvestigated, the Neogene and Quaternary sedimentary covers, as well as their identifi cation and differentiation, are still poorly known. A few previous studies have demonstrated that post-rift sedimentary units with no apparent deformation have a complexdeformation pattern in all scales of observation. The study of this deformation, however, did not include Neogene and Quaternary units.The main aim of the present study is the characterization of Neogene and Quaternary sedimentary units that outcrop in the central partof the Potiguar Basin, State of Rio Grande do Norte, Brazil, and related tectonics. The study has concentrated on the description ofthe Barreiras Formation and overlying Quaternary alluvial, marine, and aeolian deposits at 1:100,000 scale. Facies analyses, grain sizestudies, and luminescence dating were carried out. Ten informal and formal lithostratigraphic sedimentary units were described, inaddition to the Precambrian crystalline basement. The main results indicate that several Quaternary alluvial deposits were previouslymapped as the Miocene Barreiras Formation. It was possible to locate the new boundaries of the Quaternary sedimentary deposits andtheir stratigraphic relationships with older units. In addition, it was possible to identify the major fault systems in the basin that show NW- and NE-trending directions, which coincide with macro landforms. It follows that these major fault systems, mainly the NW trending system, control the deposition of Neogene and Quaternary sedimentary units.

  7. Fault zone evolution in a Cenozoic inversion tectonic setting, SE Korea (United States)

    Kim, Young-Seog; Lee, Minjoo; Han, Seung-Rok


    The Korean peninsula has been considered as a tectonically safe region from earthquakes, because it is located in a stable margin of the Eurasian plate. However, more than 30 Quaternary faults have recently been reported from the southeastern part of the Korean peninsula. The studied fault zone is an N-S trending fault located in the northern extent of the Quaternary Eupcheon Fault, which composed of several fault gouges indicating multiple deformations. The fault zone (fault core) is exposed over 1 km long and the thickness is up to 2m. The fault gouge zone is composed of several different colored gouge bands. Well-exposed vertical and horizontal sections are analyzed so as to understand the characteristics of the fault and fault zone evolution. The analyzed kinematic indicators such as cleavages, lineations and slickenlines suggest that the fault underwent early normal slip under SE extension and was later reactivated under NNW compression resulting in inversion tectonics. Major fault zones do not cross-cut each other; instead, the fault gouges within the fault zone split and merge into other fault zones. Fault rocks developed in this fault zone show asymmetrical features including lens-shaped breccias blocks in gouge zones, and asymmetric distributions of grain size and fracture density, indicating mature fault system and asymmetric fault zone evolution. The hanging wall block of the fault shows relatively highly damaged fracture patterns indicating that the hanging wall is weaker than footwall. Therefore, detailed analysis of fault and fracture patterns, and characteristics of fault zones must be very useful in evaluation of fault zone evolution and characteristics of foundation.

  8. Apatite fission-track thermochronological constraints on the pattern of late Mesozoic-Cenozoic uplift and exhumation of the Qinling Orogen, central China (United States)

    Chen, Hong; Hu, Jianmin; Wu, Guoli; Shi, Wei; Geng, Yingying; Qu, Hongjie


    The Qinling Orogen of central China was formed by intracontinental collision between the North and South China Blocks. The orogen comprises several micro-blocks bounded by sutures and faults, and has undergone long-term intracontinental deformation since the Late Triassic. The micro-blocks include the southern margin of the North China Block (S-NCB), the Northern Qinling Belt (NQB), the Southern Qinling Belt (SQB), and the northern margin of the South China Block (N-SCB). Under a uniform tectonic setting in late Mesozoic-Cenozoic, these micro-blocks have been subjected to a range of deformation styles, as demonstrated by their structural deformation, history of magmatism, and the development of sedimentary basins. To investigate the differences among the micro-blocks and to quantify their uplift and exhumation, we obtained 45 rock samples from eight Mesozoic granites in these micro-blocks, and conducted apatite fission-track (AFT) thermochronological modeling. The results reveal that the Qinling Orogen underwent four distinct stages of rapid cooling histories during the late Mesozoic-Cenozoic, and showed variation in uplift and exhumation whereby the intracontinental deformation started in the south (the N-SCB) and propagated to the north (S-NCB). In the first stage, during the Late Jurassic-Early Cretaceous (ca. 160-120 Ma), rock cooling occurred mainly in the N-SCB, attributed to the clockwise rotation and northward subduction of the South China Block beneath the Qinling Orogen. In the second stage, compression- and extension-related uplift was initiated during the late Early Cretaceous-early Late Cretaceous (ca. 120-90 Ma) in the SQB, consistent with the southward subduction of the North China Block and broadly extensional deformation in the eastern China continent. In the third stage, a gentle regional-scale cooling event that occurred during the latest Cretaceous-Paleocene (ca. 90-50 Ma) started in the NQB and became widespread in the Qinling Orogen. This

  9. Advances in Structural Geology and Tectonics in the Late 20th Century: A Review

    Institute of Scientific and Technical Information of China (English)


    Based on analyses of the share of documents of structural geology and tectonics in the GeoRef system over 100 years in the last century, and the historical change of international (31 years) and domestic (16 years) document counts of various topics in structural geology and tectonics, the position of structural geology and tectonics in the geosciences is evaluated and the major advaces in fields of plate tectonics, continental dynamics and global dynamics are reviewed. Our attention mainly focuses on the advances in studies of structural analysis, deformation mechanisms and rheology of rocks,contractional tectonics and late- and post-orogenic extensional collapse in orogens, large-scale strikeslip faults and indentation-extrusion tectonics, active tectonics and natural hazards. The relationships of structural geology and tectonics with petrology and geochronology are also discussed in terms of intersection of scientific disciplines. Finally, some suggestions are proposed for the further development of structural geology and tectonics in China.

  10. Progress in Understanding the Cenozoic Tectonic Evolution of the Western United States (United States)

    Wernicke, B.


    During Cenozoic time the North American plate underwent two fundamental changes in its mode of interaction with oceanic plates to its west. The first was decoupling of the relatively cold Laramide slab from its base beginning near 45 Ma. The pattern of foundering is inferred primarily by intense intraplate magmatism that migrated more-or-less symmetrically northward from Mexico and southward from the Pacific Northwest through Oligocene and early Miocene time, eventually reaching the latitude of Las Vegas near 15 Ma. The magmatism was accompanied by lithospheric extension, expressed as a system of highly localized core complexes within much broader magmatic belts that were oriented at a high angle to the plate boundary at any given time. The deep crust was clearly weak enough to flow in complementary fashion to upper crustal strain. The second change was the gradual transition from a convergent margin with the Farallon plate to a transtensional one with the Pacific plate. The extensional component of Pacific-North America relative motion was especially strong from 20 to 10 Ma, giving rise to more broadly distributed intraplate extension, tearing the Sierra Nevada-Great Valley block off of North America at 15 Ma. As relative plate motion became more parallel to the margin, extension in the Basin and Range slowed and intraplate deformation became concentrated in the eastern California shear zone and Walker Lane fault system along the western side of the province. To the south, at 6 Ma North America ceded the Baja Peninsula to the Pacific plate opening up the Gulf of California. Two areas of recent observational progress in understanding the relationship between these two major changes and the evolution of the North American lithosphere include paleoaltimetry studies and large-scale continuous GPS studies, both of which powerfully limit the range of physical models applicable to the plate boundary deformation zone. For example, paleoaltimetry studies suggest that the

  11. Heavy mineral compositions and zircon U-Pb ages of Cenozoic sandstones in the SW Qaidam basin, northern Tibetan Plateau: Implications for provenance and tectonic setting (United States)

    Zhu, Wen; Wu, Chaodong; Wang, Jialin; Zhou, Tianqi; Li, Jijun; Zhang, Changhao; Li, Linlin


    The Qaidam basin is the largest intermountain basin within the Tibetan Plateau. The spatio-temporal evolution of the basin and the provenances of the deposits in the SW Qaidam basin were greatly influenced by the boundary ranges. Comprehensive research is needed to identify the relationships between the basin and the surrounding ranges. Therefore, 4682 heavy mineral data from 70 wells and 720 detrital zircon ages from 8 samples were used to investigate the provenances of the deposits in the SW Qaidam basin and to further constrain the tectonic evolution of the boundary ranges. The heavy mineral data, zircon U-Pb ages, and paleocurrent data indicate that the Qimen Tagh Range and the Altyn Tagh Range were two provenances of the sediments deposited in the SW Qaidam basin during the Cenozoic. The variations of heavy mineral assemblages and ZTR index (100 ∗ (zircon + tourmaline + rutile)/total transparent heavy minerals) on the northern flank of the Qimen Tagh Range suggest that the Qimen Tagh Range experienced rapid uplift in the Early to Middle Miocene. Furthermore, according to the greatly increased quantities of epidote and hornblende sourced from the Altyn Tagh Range and the obvious decrease in the ZTR index values, the Altyn Tagh Range underwent fast uplift in the Late Oligocene to Early Miocene. In addition, based on the ages of the granitic plutons in the Altyn Tagh Range and the zircon ages in the Ganchaigou and Qigequan sections, the strike-slip movement of the Altyn Tagh Fault (ATF) initiated during or no later than the Middle Eocene, resulting in the ATF offsets of ca. 200 km between the Middle Eocene and the Miocene and of ca. 345 km between the Middle Eocene and the present.

  12. Late Cretaceous tectonic framework of the Tibetan Plateau (United States)

    Wu, Zhenhan; Barosh, Patrick J.; Ye, Peisheng; Hu, Daogong


    New research, coupled with previous data, reveals the Late Cretaceous paleo-geography, and related paleo-tectonic movement of the Tibetan Plateau. A vast ocean, the Neo-Tethys Ocean, perhaps as wide as ∼7000 km, existed between the Indian and Eurasian Continental Plates in the early Late Cretaceous. In addition, a Himalaya Marginal Sea lay along the border of the Indian Plate and other marginal seas were present to the north in both the southern Lhasa and southwestern Tarim Blocks. Northward subduction of the Neo-Tethys Oceanic Plate along the Yalung-Zangbu Suture closed most of the ocean and led to intensive thrusting, tight folding, magmatic plutonism and volcanic eruptions in the central plateau to the north. A magmatic arc up to 500 km wide formed across the southern margin of the continental plate in central Tibet and its varying granitic composition appears to reflect the depth to the subducted plate and define its geometry. A series of large, chiefly north-dipping thrust systems also developed across central Tibet. These include thrusts along the Yalung-Zangbu and Bangong-Nujiang Sutures, the North Gangdese and North Lhasa Thrusts in the Lhasa Block, the Qiangtang and North Tangula Thrusts in the Qiangtang block, the Hoh-Xil and Bayan Har Thrusts in the Hoh-Xil Block, as well as the sinistral-slip South Kunlun and Altyn Tagh Faults in northern Tibet. Uplifts formed above the hanging walls of the major thrusts and their eroded debris formed thick red-beds in basins below them. The central Tibetan Plateau maintained a low elevation and coastal vegetation was dominant during the Late Cretaceous.

  13. Neogene marine isotopic evolution and the erosion of Lesser Himalayan strata: Implications for Cenozoic tectonic history (United States)

    Myrow, Paul M.; Hughes, Nigel C.; Derry, Louis A.; Ryan McKenzie, N.; Jiang, Ganqing; Webb, A. Alexander G.; Banerjee, Dhiraj M.; Paulsen, Timothy S.; Singh, Birendra P.


    An extensive, northward deepening blanket of Neoproterozoic and Cambrian sedimentary rocks once extended from the Himalayan margin far onto the Indian craton. Cambrian deposits of this "upper Lesser Himalayan" succession, which include deposits of the "outer" Lesser Himalaya tectonic unit, are enriched in radiogenic 187Os. They make up part of a proximal marine facies belt that extends onto the craton and along strike from India to Pakistan. By contrast, age-equivalent facies in the Tethyan Himalaya are more distal in nature. Neoproterozoic to Cambrian strata of the upper Lesser Himalayan succession are now missing in much of the Lesser Himalaya, with their erosion exposing older Precambrian Lesser Himalayan strata. We suggest that exhumation and weathering of the upper Lesser Himalaya and related strata caused dramatic changes in the 187Os/188Os and 87Sr/86Sr Neogene record of seawater starting at ∼ 16 Ma. First-order estimates for the volume of upper Himalayan strata, as well as the volume of all LH rock eroded since this time, and geochemical box modeling, support this idea. Exhumation at 16 Ma is a fundamental event in the evolution of the Himalayan orogeny and the geochemical evolution of the oceans, and will be a critical part of the construction of future models of Himalayan thrust belt evolution.

  14. Response of Cenozoic turbidite system to tectonic activity and sea-level change off the Zambezi Delta (United States)

    Castelino, Jude A.; Reichert, Christian; Jokat, Wilfried


    Submarine fans and turbidite systems are important and sensitive features located offshore from river deltas that archive tectonic events, regional climate, sea level variations and erosional process. Very little is known about the sedimentary structure of the 1800 km long and 400 km wide Mozambique Fan, which is fed by the Zambezi and spreads out into the Mozambique Channel. New multichannel seismic profiles in the Mozambique Basin reveal multiple feeder systems of the upper fan that have been active concurrently or consecutively since Late Cretaceous. We identify two buried, ancient turbidite systems off Mozambique in addition to the previously known Zambezi-Channel system and another hypothesized active system. The oldest part of the upper fan, located north of the present-day mouth of the Zambezi, was active from Late Cretaceous to Eocene times. Regional uplift caused an increased sediment flux that continued until Eocene times, allowing the fan to migrate southwards under the influence of bottom currents. Following the mid-Oligocene marine regression, the Beira High Channel-levee complex fed the Mozambique Fan from the southwest until Miocene times, reworking sediments from the shelf and continental slope into the distal abyssal fan. Since the Miocene, sediments have bypassed the shelf and upper fan region through the Zambezi Valley system directly into the Zambezi Channel. The morphology of the turbidite system off Mozambique is strongly linked to onshore tectonic events and the variations in sea level and sediment flux.

  15. 冀中坳陷中北部新生代构造演化特征%Cenozoic tectonic evolution in the north-central Jizhong Depression

    Institute of Scientific and Technical Information of China (English)

    董大伟; 李理; 刘建; 李继岩


    On the basis of fine seismic interpretation ,various methods including fault throw method ,fault activity intensity method,balanced cross-section technique and physical simulation are adopted in this paper to analyze the Cenozoic tec -tonic characteristics and evolution process as well as the forming mechanism of structures .The results show that the north-central part of Jizhong Depression was dominated by extensional structures in the Cenozoic ,with strike-slip structure style also occurring .In Baxian Sag ,tilting and sliding fault terrace structural styles were predominant .While Raoyang Sag was dominated by anticline structural style except for its northernmost part where strike-slip structure style was common .The extensional intensity shows large diversity in different periods in both Baxian Sag and Raoyang Sag ,strictly controlled by the activity of boundary faults .Raoyang Sag was controlled by Liulu ,Hejian,and Maxi faults from south to north .The ex-tension of sag as characterized by transition from “south being larger than central-north” in Ek-Es4 to “central-north being larger than south” in Es3 -Ed.Baxian Sag was controlled by the diversity of Niudong fault activity along strike ,fea-turing in the tectonic evolution of “strong early stage but weak middle and late stages” in south,“weak early stage strong middle stage and weak late stage”in the central ,and “weak early stage but strong middle and late stages” in north .The physics simulation experiment validates the fault development process of research area .The experiment result has strong similarity with the development characteristics of the faults ,demonstrating the correctness of tectonic geometry and kine-matics characteristic analysis .On the basis of above research ,the tectonic evolution process of Raoyang Sag and Baxian Sag is divided into three stages ,namely weak early stage ,strong middle stage ,and fair late stage .Finally,the mechanism and deep background of tectonic

  16. Mesozoic - Cenozoic tectonic evolution of southwestern Tian Shan: Evidence from detrital zircon U/Pb and apatite fission track ages of the Ulugqat area, Northwest China

    NARCIS (Netherlands)

    Yang, W.; Jolivet, M.; Dupont-Nivet, G.; Guo, Z.


    The Late Tertiary tectonic and topographic evolution of the Tian Shan Range has beenwidely studied as it represents a key example of active intra-continentalmountain belts. Recent studies have shown that both the general tectonic framework of Tian Shan and some of its actual topographic features wer

  17. The Kuqa late Cenozoic fold-thrust belt on the southern flank of the Tian Shan Mountains (United States)

    Li, Yue-Jun; Wen, Lei; Zhang, Hong-An; Huang, Tai-Zhu; Li, Hui-Li; Shi, Yuan-Yuan; Meng, Qing-Long; Peng, Geng-Xin; Huang, Shao-Ying; Zhang, Qiang


    The Kuqa fold-thrust belt (KFTB), a late Cenozoic fold-thrust belt on the southern flank of the Tian Shan Mountains, consists of several deformation zones trending nearly W-E. The main décollement fault of the KFTB gradually rises southwards. There are three regional main décollement faults in the Triassic dark mudstone, Paleogene gypsum salt (Kumugeliemu Formation), and Neogene gypsum salt (Jidike Formation), respectively, and possibly a fourth in the Jurassic coalbed. Laterally, thin-skinned structures are developed in the main segments of the KFTB, whereas thick-skinned structures are in the root zone. Vertically, the structural deformation above the Cenozoic gypsum-salt layers (Paleogene gypsum salt in the middle segment of the KFTB and Neogene gypsum salt in the eastern segment) is characterized by décollement folding, whereas that below is characterized by thrusting. The KFTB was resulted from the late Cenozoic intra-continental orogeny in the Tian Shan area under the far-field effect of the India-Asia collision. The deformation of KFTB began (folding and thrusting) ca. 23 Ma, when the far-field effect of the India-Asia collision reached the Tian Shan area. The deformation of KFTB accelerated ca. 10, 5-2, and 1-0 Ma. In general, the evolution of the KFTB is forward propagating, and the hinter parts of the KFTB continue to deform, while its front propagates southwards.

  18. Late Cenozoic acceleration of erosion in the Southern Central Andes revealed by low-temperature thermochronology (United States)

    Franziska Stalder, Nadja; Herman, Frédéric; Reiners, Peter W.; Aguilar, German


    The Earth's topography is shaped by feedback mechanisms between tectonics, climate, and surface processes. To understand the influence of these interactions on mountain building processes, one can quantify the temporal and spatial history of exhumation using thermochronology. The Andes are a suitable natural laboratory to study such feedbacks, because they result from the steady subduction of the Nazca plate below the South American plate and their meridional extent crosses several global climate zones. Furthermore, the recent growth of regional low-temperature thermochronological studies led to an extensive data coverage, which can now be inverted to estimate the exhumation history at the scale of a mountain range. In this study, we present a total of 172 new thermochronological AHe, ZHe, and AFT bedrock ages filling remaining data gaps between 26°S and 34°S latitude. To avoid dating of emplacement ages instead of exhumation, ZHe and AFT analyses are restricted to pre-Miocene intrusions only present in the northern part of the study area. From about 31°S to 34°S, the study area covers a key transitional zone where topography decreases, precipitation increases, and the subduction regime changes from flat to steep dip angle. ZHe and AFT ages to the north of 33°S indicate erosion rates lower than 0.2 mm/yr since the Paleogene, except for few localized areas showing middle-to-late Miocene increased exhumation in their AHe ages. To the south of 33°S, two AHe age-elevation profiles reveal ages between 0.5 to 3.5 Ma and suggest intensified erosion during the Plio-Pleistocene relative to the northern area, with southward increasing rates from about 1.3 mm/yr to 3.8 mm/yr. The transition occurs more than 150 km south of the tectonic change in the subduction regime. However, the establishment of the modern atmospheric circulation pattern in the late Pliocene led to increased moisture transport to the North and the initiation of glaciations. Higher precipitation and

  19. Monazite age spectra in the Late Cenozoic strata of the Changjiang delta and its implication on the Changjiang run-through time

    Institute of Scientific and Technical Information of China (English)

    FAN Daidu; LI Congxian; Yokoyama Kazumi; ZHOU Baochun; LI Baohua; WANG Qiang; YANG Shouye; DENG Bing; WU Guoxuan


    The Late Cenozoic strata are 313 m thick, revealed by the drilling core PD-99 in the south Changjiang delta. Monazite chemical dating shows that 350-500-Ma monazites predominate in the Pliocene and 100-275-Ma monazites in the Quaternary, indicating a great change of their provenance. The first presence horizon of monazites younger than 25 Ma is just above the Matruyama/Gauss boundary (~2.58 Ma), whch is exactly when uplift of the Tibetan Plateau began to influence deposition in the East China Sea. Variations in contents of monazites younger than 25 Ma can be divided into two sections. The Early-Middle Pleistocene with less <25 Ma monazites corresponds with rapid uplift of the Tibetan Plateau, and the Late Pleistocene with more <25 Ma monazites parallels the peak uplift of the Tibetan Plateau. This study demonstrates that chemical dating of monazites in the river-mouth strata is a useful method to explore changes of river drainage basins, and deconvolute multistage tectonic and magmatic activity histories in the provenance areas.

  20. Fission track evidence for the Mesozoic-Cenozoic tectonic uplift of Mt. Bogda, Xinjiang, Northwest China

    Institute of Scientific and Technical Information of China (English)

    SHEN Chuanbo; MEI Lianfu; PENG Lei; ZHANG Shiwan; LIU Lin; TANG Jiguang


    Fission-track dating evidence from 5apatite samples and 4 zircon samples, and modeled time-temperature thermal history indicate that since Late Jurassic-Cretaceous (150 -106 Ma), the uplift process of Mt. Bogda can be divided into four stages of thermal evolution: 150 - 106, 75 -65, 44 -24and 13 -9 Ma. Before 44- 24 Ma, the cooling rate and uplifting rate of the southern and northern segments of Mt. Bogda are almost the same, showing that the uplifting of Mt. Bogda is an overall process.Since 44 - 24 Ma, the uplifting of the southern and northern segments of Mt. Bogda has shown differences. During 42 - 11 Ma, the northern segment of Mt. Bogda was at a steady stage, with the cooling rate being 0.03℃/Ma and the uplifting rate being 0. 001 mm/a. From 11 Ma to the present, the northern segment of Mt. Bogda was at a rapid cooling and uplifting stage, with the cooling rate being 5.72℃/Ma and the uplifting rate being 0.19 mm/a. However, the southern segment of Mt. Bogda has been at a rapid cooling and uplifting stage since 26 Ma, with the cooling rate being 1.24℃/Ma and the uplifting rate being 0.041 mm/a during 26 -9 Ma; 4.88℃/Ma and 0. 163 mm/a from 9 Ma till now.

  1. Late Cenozoic exhumation of New Zealand: inversion from bedrock thermochronological ages (United States)

    Jiao, Ruohong; Herman, Frédéric; Seward, Diane


    In the SW Pacific, the present subaerial land area of New Zealand straddles the boundary between the Australian and Pacific Plates. This margin has been converging since the mid-Eocene-late Oligocene, leading to a period of widespread crustal deformation and exhumation. During the past decades, the exhumation of the New Zealand basement has been the basis of many thermochronological studies, resulting in a large number of data from the Palaeozoic and Mesozoic bedrocks. We compiled the cooling ages from multiple thermochronological systems (i.e. apatite and zircon (U-Th)/He, apatite and zircon fission-track, K-feldspar, muscovite, biotite and hornblende 40Ar/39Ar or K-Ar) that yielded cooling events younger than 25 Ma, and formally inverted this data set to estimate the large-scale temporal and spatial variations in the exhumation rates of New Zealand during the late Cenozoic. The exhumation results show good agreement with the predicted off-shore sedimentation rates, while the thermal model used in the inversion is in part constrained by the present-day observed surface heat flow. The modelling results indicate crustal exhumation from the earliest Miocene (just prior to 20 Ma). But from ~10 Ma, a moderate acceleration of exhumation is observed at most sites, coincident with an important change in the orientation of the Pacific motion relative to the Australian Plate. Since the Quaternary, rapid exhumation has occurred in the Southern Alps along the west coast of South Island, with the highest rates in the central part of range. In this region, our estimates of the million-year-scale exhumation rates are in general coincidence with those previously estimated over shorter (i.e. 0.1 Ma and 10 ka) time scales, as well as with the contemporary rock uplift rates derived from GPS data, confirming exhumational steady-state in the orogeny. In contrast in eastern North Island, the predicted Quaternary exhumation rates are much lower than the recent rock uplift rates measured

  2. Dike orientations in the late jurassic independence dike swarm and implications for vertical-axis tectonic rotations in eastern California (United States)

    Hopson, R.F.; Hillhouse, J.W.; Howard, K.A.


    Analysis of the strikes of 3841 dikes in 47 domains in the 500-km-long Late Jurassic Independence dike swarm indicates a distribution that is skewed clockwise from the dominant northwest strike. Independence dike swarm azimuths tend to cluster near 325?? ?? 30??, consistent with initial subparallel intrusion along much of the swarm. Dike azimuths in a quarter of the domains vary widely from the dominant trend. In domains in the essentially unrotated Sierra Nevada block, mean dike azimuths range mostly between 300?? and 320??, with the exception of Mount Goddard (247??). Mean dike azimuths in domains in the Basin and Range Province in the Argus, Inyo, and White Mountains areas range from 291?? to 354?? the mean is 004?? in the El Paso Mountains. In the Mojave Desert, mean dike azimuths range from 318?? to 023??, and in the eastern Transverse Ranges, they range from 316?? to 051??. Restoration for late Cenozoic vertical-axis rotations, suggested by paleodeclinations determined from published studies from nearby Miocene and younger rocks, shifts dike azimuths into better agreement with azimuths measured in the tectonically stable Sierra Nevada. This confirms that vertical-axis tectonic rotations explain some of the dispersion in orientation, especially in the Mojave Desert and eastern Transverse Ranges, and that the dike orientations can be a useful if imperfect guide to tectonic rotations where paleomagnetic data do not exist. Large deviations from the main trend of the swarm may reflect (1) clockwise rotations for which there is no paleomagnetic evidence available, (2) dike intrusions of other ages, (3) crack filling at angles oblique or perpendicular to the main swarm, (4) pre-Miocene rotations, or (5) unrecognized domain boundaries between dike localities and sites with paleomagnetic determinations. ?? 2008 The Geological Society of America.

  3. End Late Paleozoic tectonic stress field in the southern edge of Junggar Basin

    Directory of Open Access Journals (Sweden)

    Wei Ju


    Full Text Available This paper presents the end Late Paleozoic tectonic stress field in the southern edge of Junggar Basin by interpreting stress-response structures (dykes, folds, faults with slickenside and conjugate joints. The direction of the maximum principal stress axes is interpreted to be NW–SE (about 325°, and the accommodated motion among plates is assigned as the driving force of this tectonic stress field. The average value of the stress index R′ is about 2.09, which indicates a variation from strike-slip to compressive tectonic stress regime in the study area during the end Late Paleozoic period. The reconstruction of the tectonic field in the southern edge of Junggar Basin provides insights into the tectonic deformation processes around the southern Junggar Basin and contributes to the further understanding of basin evolution and tectonic settings during the culmination of the Paleozoic.

  4. The Miocene mammal Necrolestes demonstrates the survival of a Mesozoic nontherian lineage into the late Cenozoic of South America. (United States)

    Rougier, Guillermo W; Wible, John R; Beck, Robin M D; Apesteguía, Sebastian


    The early Miocene mammal Necrolestes patagonensis from Patagonia, Argentina, was described in 1891 as the only known extinct placental "insectivore" from South America (SA). Since then, and despite the discovery of additional well-preserved material, the systematic status of Necrolestes has remained in flux, with earlier studies leaning toward placental affinities and more recent ones endorsing either therian or specifically metatherian relationships. We have further prepared the best-preserved specimens of Necrolestes and compared them with newly discovered nontribosphenic Mesozoic mammals from Argentina; based on this, we conclude that Necrolestes is related neither to marsupials nor placentals but is a late-surviving member of the recently recognized nontherian clade Meridiolestida, which is currently known only from SA. This conclusion is supported by a morphological phylogenetic analysis that includes a broad sampling of therian and nontherian taxa and that places Necrolestes within Meridiolestida. Thus, Necrolestes is a remnant of the highly endemic Mesozoic fauna of nontribosphenic mammals in SA and extends the known record of meridiolestidans by almost 45 million years. Together with other likely relictual mammals from earlier in the Cenozoic of SA and Antarctica, Necrolestes demonstrates the ecological diversity of mammals and the mosaic pattern of fauna replacement in SA during the Cenozoic. In contrast to northern continents, the Cenozoic faunal history of SA was characterized by a long period of interaction between endemic mammalian lineages of Mesozoic origin and metatherian and eutherian lineages that probably dispersed to SA during the latest Cretaceous or earliest Paleocene.

  5. Cenozoic tectonic evolution leading to the Choco-South America collision (Panama-Colombia), from seismic profiles interpretations (United States)

    Barat, F.; Maurin, T.; Auxietre, J.; Mercier de Lépinay, B.; Salmon, P.; Sosson, M. M.


    The Choco Block is located in eastern Panama and western Colombia, at the western boundary of the Caribbean Plate (CP), and is mainly characterized by a Late Cretaceous-Paleogene volcanic arc overlying the Caribbean Large Igneous Province (CLIP). This block was accreted to South American plate (SAP) during Middle to Late Miocene. Geological, chronological and structural data are scarce in the Choco Block. Our study aims at reconstructing the evolution at a local scale, to provide new constraints to the regional scale tectonic processes that have occurred since the Paleogene. In that perspective, we have interpreted offshore seismic reflection profiles. This interpretation was supported by biostratigraphic data from two wells. We focused our studies in the Uraba Gulf area, a triple junction between the Choco Block, the SAP and the Caribbean oceanic plateau. This poorly understood zone offers rare observation of two accretionary wedges, the North Panama Deformed Belt (NPDB), and the Sinu Belt, located at the margins of the Choco Block and the SAP, respectively. They are the results of two opposite convergent zones, and collide along the active Uramita strike-slip Fault Zone (UFZ), a suture zone between the Choco Block and the SAP. This area may provide information on the ages of both accretionary wedges, on the tectonic processes responsible for the disappearance of the CP, and on the late formation of the Choco Block. Our results evidence a northward propagating deformation along the Choco Block, miocene or older in the South of the Uraba Gulf, pliocene in the North of the Uraba Gulf, and active along the northern margin of Panama. This deformation is the result of the progressive accretion of Choco Block along the SAP. At the Uraba triple junction, a thick sedimentary sequence was deposited since late Miocene. North verging progradations suggest that sediments came from the drainage of the western cordillera of Colombia by a Paleo-Sinu river and actual Atrato river

  6. Late Cenozoic Stratigraphy and Paleomagnetic Chronology of the Zanda Basin, Tibet, and Records of the Uplift of the Qinghai-Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    MENG Xiangang; ZHU Dagang; SHAO Zhaogang; YANG Chaobin; HAN Jianen; YU Jia; MENG Qingwei; LU Rongping


    The characteristics of Late Cenozoic tectonic uplift of the southern margin of the Qinghai-Tibet Plateau may be inferred from fluvio-lacustrine strata in the Zanda basin, Ngari, Tibet.Magnetostratigraphic study shows that the very thick fluvio-lacustrine strata in the basin are 5.89-0.78 Ma old and that their deposition persisted for 5.11 Ma, I.e. starting at the end of the Miocene and ending at the end of the early Pleistocene, with the Quaternary glacial stage starting in the area no later than 1.58 Ma. Analysis of the sedimentary environment indicates that the Zanda basin on the southern Qinghai-Tibet Plateau began uplift at ~5.89 Ma, later than the northern Qinghai-Tibet Plateau. Presence of gravel beds in the Guge and Qangzê Formations reflects that strong uplift took place at ~5.15 and ~2.71 Ma, with the uplift peaking at ~2.71 Ma.

  7. New insights into late Neogene glacial dynamics, tectonics, and hydrocarbon migrations in the Atlantic-Arctic gateway region. (United States)

    Knies, J.; Baranwal, S.; Fabian, K.; Grøsfjeld, K.; Andreassen, K.; Husum, K.; Mattingsdal, R.; Gaina, C.; De Schepper, S.; Vogt, C.; Andersen, N.


    Notwithstanding the recent IODP drilling on the Lomonosov Ridge, the Late Cenozoic history of the Arctic Ocean still remains elusive. The tectonic processes leading to the development of the only deep-water connection to the Arctic Ocean via the Fram Strait are still poorly understood. Also, the influence of the gateway region on changes in Arctic-Atlantic ocean circulation, uplift/erosion on the adjacent hinterland, as well as glacial initiation and its consequences for the petroleum systems in the regions, remain unclear. By revisiting Ocean Drilling Program (ODP) Leg 151, holes 911A and 910C and interpreting new multi-channel seismic data, we have now established a new comprehensive chronological framework for the Yermak Plateau and revealed important paleoenvironmental changes for the Atlantic-Arctic gateway during the late Neogene. The improved chronostratigraphic framework is established through continuous paleomagnetic and biostratigraphic data as well as selected intervals with stable ?18O and ?13C data derived from benthic foraminifera Cassidulina teretis. Supported by acoustic profiling, the new data indicate a continuous late Miocene/early Pliocene age (~5-6 Ma) for the base of both holes. The depositional regime north (Yermak Plateau) and south of the Fram Strait (Hovgaard Ridge) was rather shallow during the late Miocene and water mass exchange between the Arctic and Atlantic was restricted. Ice sheets on the Svalbard Platform evolved during the late Miocene, however did not reach the coastline before 3.3 Ma. Migration of gaseous hydrocarbons occurred prior to the intensification of the Northern Hemisphere Glaciations (~2.7 Ma) as indicated by high-amplitude reflections, corroborating the occurrence of greigite mineralization and stable carbon isotope excursions in planktic/benthic foraminifera. The data indicate that Pleistocene erosion and uplift in the Barents Sea region had probably only minor effects on reservoir leakages than previously thought.

  8. Late Cenozoic onset of the latitudinal diversity gradient of North American mammals (United States)

    Marcot, Jonathan D.; Fox, David L.; Niebuhr, Spencer R.


    The decline of species richness from equator to pole, or latitudinal diversity gradient (LDG), is nearly universal among clades of living organisms, yet whether it was such a pervasive pattern in the geologic past remains uncertain. Here, we calculate the strength of the LDG for terrestrial mammals in North America over the past 65 My, using 27,903 fossil occurrences of Cenozoic terrestrial mammals from western North America downloaded from the Paleobiology Database. Accounting for temporal and spatial variation in sampling, the LDG was substantially weaker than it is today for most of the Cenozoic and the robust modern LDG of North American mammals evolved only over the last 4 My. The strength of the LDG correlates negatively with global temperature, suggesting a role of global climate patterns in the establishment and maintenance of the LDG for North American mammals.

  9. Late Cenozoic Bryozoa from diamictites of Cape Lamb, Vega Island, Antarctic Peninsula

    Directory of Open Access Journals (Sweden)

    Adamonis Susana


    Full Text Available Bryozoans were found in upper Cenozoic diamictite debris that crops out at the southwestern tip of Cape Lamb, Vega Island. The diamictite is the youngest deposit on the island and richly composed of foraminifers, brachiopods and scallops. The foraminifera assemblage recovered from the Cape Lamb diamictite and 87Sr/86Sr isotopic age obtained from the pectinid Adamussium colbecki in the nearby locality of Terrapin indicates a Pleistocene age for this deposit. The main goal of this contribution is to present a bryozoan assemblage of Microporella stenoporta Hayward et Taylor, Hippothoa flagellum Manzoni, Ellisina antarctica (Kluge, Micropora notialis Hayward et Ryland and an indeterminate crisiid constituting the first record of these bryozoan taxa in Cenozoic diamictites of the Antarctic Peninsula.

  10. Late Cenozoic stress state distributions at the intersection of the Hellenic and Cyprus Arcs, SW Turkey (United States)

    Över, Semir; Özden, Süha; Pınar, Ali; Yılmaz, Hüseyin; Kamacı, Züheyr; Ünlügenç, Ulvi Can


    The history of the Late Cenozoic stress regime was determined for an area between the gulfs of Fethiye and Antalya. Fault kinematic analysis and inversion of focal mechanisms of shallow earthquakes reveal significant evolution of the regional stress regime in SW Anatolia, i.e., the area of interaction between the Hellenic and Cyprus arcs, from the Mio-Pliocene to the present time. Fault kinematic analysis yields two different normal faulting stress regimes along the southwestern part of Fethiye-Burdur Fault zone, e.g., in and around Çameli Basin (Zone A1) and two different strike-slip to normal faulting stress regimes characterized by a roughly orthogonal set of extensional axes between Fethiye and Demre (Zone B) with an older NW-SE σ3 axis for Mio-Pliocene and a younger NE-SW σ3 axis for Plio-Quaternary time. Inversion of focal mechanisms of the earthquakes occurring in Zone A1 provides an extensional stress state with approximately N-S σ3 axis. Inversion of those occurring in Zone B, south of Zone A1, yields a dominantly strike-slip stress state with a NE-SW σ3 axis and a NW-SE σ1 axis respectively. The inversion slip vectors from fault planes yield a consistent normal faulting stress regime in Burdur Basin and its surroundings (i.e., along the northeastern part of Fethiye-Burdur Fault Zone, (Zone A2)) during Plio-Quaternary, continuing into recent time as indicated by earthquake focal mechanism inversions. Both states have a consistent NW-SE σ3 axis. Fault kinematic analysis indicates NW-SE extension acting in Zone C (subarea between Demre and Antalya), south of Zone A2, during Mio-Pliocene time. The inversion of focal mechanisms yields normal faulting also characterized by a consistent NW-SE σ3 axis. The nearly orthogonal extensional stress regimes (NW-SE and NE-SW) obtained by inversion of both measured and seismic faults seem to have been acting contemporaneously with each other at different intensities from the Mio-Pliocene onwards in SW Turkey. This

  11. Tectonic and climate driven fluctuations in the stratigraphic base level of a Cenozoic continental coal basin, northwestern Andes (United States)

    Silva Tamayo, J. C.; Sierra, G. M.; Correa, L. G.


    Changes in the sedimentologic and stratigraphic characteristics of the coal-bearing middle Oligocene-late Miocene siliciclastic Amagá Formation, northwestern Colombia, reflect major fluctuations in the stratigraphic base level within the Amagá Basin, which paralleled three major stages of evolution of the middle Cenozoic Andean Orogeny. These stages, which are also traceable by the changes in the compositional modes of sandstones, controlled the occurrence of important coal deposits. The initial stage of evolution of the Amagá Basin was related to the initial uplift of the Central Cordillera of Colombia around 25 Ma, which promoted moderate subsidence rates and high rates of sediment supply into the basin. This allowed the development of aggradational braided rivers and widespread channel amalgamation resulting in poor preservation of both, low energy facies and geomorphic elements. The presence of poorly preserved Alfisols within the scarce flood plains and the absence of swamp deposits suggest arid climate during this stage. The compositional modes of sandstones suggest sediment supply from uplifted basement-cored blocks. The second stage of evolution was related to the late Oligocene eastward migration of the Pre-Andean tholeitic magmatic arc from the Western Cordillera towards the Cauca depression. This generated extensional movements along the Amagá Basin, enhancing the subsidence and increasing the accommodation space along the basin. As a result of the enhanced subsidence rates, meandering rivers developed, allowing the formation of extensive swamps deposits (currently coal beds). The excellent preservation of Entisols and Alfisols within the flood plain deposits suggests rapid channels migration and a humid climate during deposition. Moderate to highly mature channel sandstones support this contention, and point out the Central Cordillera of Colombia as the main source of sediment. Enhanced subsidence during this stage also prevented channels

  12. Investigating Cenozoic climate change in tectonically active regions with a high-resolution atmospheric general circulation model (ECHAM5) (United States)

    Mutz, Sebastian; Ehlers, Todd; Li, Jingmin; Werner, Martin; Stepanek, Christian; Lohmann, Gerrit


    Studies of Cenozoic palaeo-climates contribute to our understanding of contemporary climate change by providing insight into analogues such as the Pliocene (PLIO), and by evaluation of GCM (General Circulation Models) performance using the Mid-Holocene (MH) and the Last Glacial Maximum (LGM). Furthermore, climate is a factor to be considered in the evolution of ecology, landscapes and mountains, and in the reconstruction of erosion histories. In this study, we use high-resolution (T159) ECHAM5 simulations to investigate pre-industrial (PI) and the the above mentioned palaeo-climates for four tectonically active regions: Alaska (St. Elias Range), the US Northwest Pacific (Cascade Range), western South America (Andes) and parts of Asia (Himalaya-Tibet). The PI climate simulation is an AMIP (Atmospheric Model Intercomparison Project) style ECHAM5 experiment, whereas MH and LGM simulation are based on simulations conducted at the Alfred Wegner Institute, Bremerhaven. Sea surface boundary conditions for MH were taken from coupled atmosphere-ocean model simulations (Wei and Lohmann, 2012; Zhang et al, 2013) and sea surface temperatures and sea ice concentration for the LGM are based on GLAMAP project reconstructions (Schäfer-Neth and Paul, 2003). Boundary conditions for the PLIO simulation are taken from the PRISM (Pliocene Research, Interpretation and Synoptic Mapping) project and the employed PLIO vegetation boundary condition is created by means of the transfer procedure for the PRISM vegetation reconstruction to the JSBACH plant functional types as described by Stepanek and Lohmann (2012). For each of the investigated areas and time slices, the regional simulated climates are described by means of cluster analyses based on the variability of precipitation, 2m air temperature and the intra-annual amplitude of the values. Results indicate the largest differences to a PI climate are observed for LGM and PLIO climates in the form of widespread cooling and warming

  13. Tectonic setting of Late Cenozoic gold mineralization in the gold belt of Costa Rica

    Energy Technology Data Exchange (ETDEWEB)

    Deruyter, V.D.


    The Gold Belt of Costa Rica is a northwest-elongated zone 15 km wide by 120 km long containing numerous auriferous quartz veins and pyritic silicified patterns upon which abundant small mines are developed. Gold veins are related principally to northeast-southwest and north-south striking, steeply dipping faults. Higher grade ore and thicker veins invariably occur at intersections of these fracture orientations, indicating simultaneous opening at the time of gold introduction. Restriction of gold veins to the northwest-trending arc of Miocene Aguacate Group andesite volcanic rocks, a product of Cocos Plate subduction, suggested approximately coeval formation, but recognition by the writer of the important role played by 2-5 m.y. old altered, gold mineralized rhyolite dikes intruded along north-south gold vein structures and intimately involved with high grade ores at the Esperanza Mine and Rio Chiquito prospect, for example, suggest a much younger period of fracturing and gold introduction. The rhyolite intrusions are more brittle and stockwork mineralized than andesite host rocks and form bulk tonnage gold targets. Initiation of right-lateral movement along the north-south Panama Fracture Zone at 5 m.y.a. within the pattern of northeastward Cocos Plate subduction may have tapped rhyolites from subvolcanic magma chambers into new faults.


    Institute of Scientific and Technical Information of China (English)

    曹代勇; 张杰林; 关英斌; 钱光谟; 吴国强; 韩远方; 赵志明


    The structural deformation of Lu' an mining area is characterized by a remarkable feature of zoning along E-W direction, in the east.limb of Qinshui basin, Shanxi Province, China. The regional tectonic stress fields and basement tectonics are two fundamental factors to control the cover tectonic framework. This paper uses the finite-element method with a elastic-plastic plan problem model to simulate the three periods of stress fields resulting from field geological study. Based on these works, the formation and evolution of tectonic framework of Lu' an mining area have been discussed.

  15. Plate tectonic history of the Arctic (United States)

    Burke, K.


    Tectonic development of the Arctic Ocean is outlined, and geological maps are provided for the Arctic during the mid-Cenozoic, later Cretaceous, late Jurassic, early Cretaceous, early Jurassic and late Devonian. It is concluded that Arctic basin history is moulded by the events of the following intervals: (1) continental collision and immediately subsequent rifting and ocean formation in the Devonian, and continental rifting ocean formation, rapid rotation of microcontinents, and another episode of collision in the latest Jurassic and Cretaceous. It is noted that Cenozoic Arctic basin formation is a smaller scale event superimposed on the late Mesozoic ocean basin.

  16. Plate tectonic history of the Arctic (United States)

    Burke, K.


    Tectonic development of the Arctic Ocean is outlined, and geological maps are provided for the Arctic during the mid-Cenozoic, later Cretaceous, late Jurassic, early Cretaceous, early Jurassic and late Devonian. It is concluded that Arctic basin history is moulded by the events of the following intervals: (1) continental collision and immediately subsequent rifting and ocean formation in the Devonian, and continental rifting ocean formation, rapid rotation of microcontinents, and another episode of collision in the latest Jurassic and Cretaceous. It is noted that Cenozoic Arctic basin formation is a smaller scale event superimposed on the late Mesozoic ocean basin.

  17. Middle-Late Eocene structure of the southern Levant continental margin — Tectonic motion versus global sea-level change (United States)

    Segev, Amit; Schattner, Uri; Lyakhovsky, Vladimir


    During the Paleogene greenhouse episode Earth experienced the warmest period of the Cenozoic while global sea level rose by more than 100 m. However, geological evidence from the Levant margin, northwestern Arabian plate, indicates that throughout this period seabed deepening exceeded 1000 m. Lithology from Israel, Syria, Lebanon and Jordan is mainly pelagic and neritic, interfered by occasional fossil sub-marine slumps. In order to understand this dissimilarity we quantify the vertical tectonic motion of the Levant continental margin through the Paleogene. The margin began to take shape during the Late Permian and it was reactivated during the Oligocene. Based on information from outcrops, drillholes, seismic reflection and refraction, gravity, and previous publications, a multi-layered model of the Levant lithosphere was established. Layers include the Moho, top of the crystalline basement and covering sediments up to the Late Eocene. The model was restored horizontally by 100 km along the younger Dead Sea transform. Assuming local isostatic compensation, vertical restoration yielded the paleo-bathymetry which prevailed across northwestern Arabia during the Middle-Late Eocene. Results show that following the margin subsidence the Cretaceous Levantine platform became ramp shaped during the Eocene. Most parts of the central Levant were submerged under ~ 200 to ~ 1800 m of water, while the paleo-bathymetric gradients ranged from ~ 2° at the shelf to ~ 6° at the slope. The apparent dissimilarity between sea level and our tectonic-based calculations is up to an order of magnitude. These differences may be resolved by accounting for vertical tectonic motions and sediment supply rates. Our results stress the importance of the presented crustal structure. As opposed to the backstripping procedure, the structural map of the top Eocene interface was constructed upwards from the well established top Turonian (Judea Group) interface since only scarce and sporadic outcrops

  18. Thermochronology of Mesozoic Sandstone from the Beipiao Basin and Its Implication to Meso-Cenozoic Tectonic Evolution of the Eastern Yan-Liao Orogenic Belt

    Institute of Scientific and Technical Information of China (English)

    YAN Yi; LIN Ge; XIA Bin; LI Zi'an; LI Zhongcheng


    Combining the single-grain low-temperature apatite fission track with high-temperature zircon U-Pb dating of sandstone can better reveal the temporal association between the source and depositional site, and identify both the age component of the source terrain and subsequent thermo-tectohic events after deposition. This paper introduces the singlegrain zircon U-Pb dating and fission track (FT) dating of sediments from the Beipiao basin in Northeast China. The U-Pb ages of 18 single zircon grains collected from the early Jurassic Beipiao Formation range from 194.3±2.9 to 233.8±4.2 Ma and most of apatite FI ages are about 30-40 Ma, indicating that the eastern part of the Yan-Liao orogenic belt experienced an obvious tectonic seesawing during Meso-Cenozoic time. The eastern part of Liaoning Province (the Liaodong block)uplifted in the early Mesozoic (230-190 Ma) and formed a geological landscape of high mountains, while the western part of the province (the Liaoxi area) subsided relatively and thousand-meter-scale sediments were deposited. During the Cenozoic (30-40 Ma), the Liaoxi area uplifted as a whole, and the Xialiaohe Basin sank intensively. The topographic landscape had a great change: high mountains in the west and east of Liaoning Province and low plains in the central area.

  19. Magnetostratigraphy of Late Cenozoic fossil mammals in the northeastern margin of the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)


    A number of fossil mammals have been found in the very thick Cenozoic stratigraphy of the Guide Basin in the northeastern margin of the Tibetan Plateau. Some of these are of great significance in mammal evolution and stratigraphic correlation on and around the Tibetan Plateau and North China. However, the chronology of these mammals is poorly constrained. Dating of the mammals will not only place precise age constraints on the mammals, but also provide much information on the related stratigraphy that records the uplift process of the Tibetan Plateau. Detailed paleomagnetism of the upper part of the Cenozoic stratigraphy at He'erjia and Lajigai north of Guide County has revealed magnetic chrons that can be correlated to Gauss and 3An chrons, determining the section spanning about 3.1-6.5 Ma and the first, second and third layers of fossil mammals at about 5.25, 5.1 and 4.4 Ma, respectively. Ages of the significant genus Gazella kueitensis and the Chinese elephant Anancus sinensis are firstly constrained at about 5.25 MaBP and 4.4 Ma, respectively. The mammalian evolution and the associated increase in coarse sediments and sedimentation rate may suggest that the northeastern Tibetan Plateau was uplifted rapidly at that time, and the eastern Tibetan Plateau with its neighboring regions was not high enough to stop mammal exchange between the northern and southern sides of the Tibetan Plateau.

  20. Late Mesozoic basin and range tectonics and related magmatism in Southeast China

    Directory of Open Access Journals (Sweden)

    Dezi Wang


    Full Text Available During the Late Mesozoic Middle Jurassic–Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacific Plate subduction. Basin tectonics consists of post-orogenic (Type I and intra-continental extensional basins (Type II. Type I basins developed in the piedmont and intraland during the Late Triassic to Early Jurassic, in which coarse-grained terrestrial clastic sediments were deposited. Type II basins formed during intra-continental crustal thinning and were characterized by the development of grabens and half-grabens. Graben basins were mainly generated during the Middle Jurassic and were associated with bimodal volcanism. Sediments in half-grabens are intercalated with rhyolitic tuffs and lavas and are Early Cretaceous in age with a dominance of Late Cretaceous–Paleogene red beds. Ranges are composed of granitoids and bimodal volcanic rocks, A-type granites and dome-type metamorphic core complexes. The authors analyzed lithological, geochemical and geochronological features of the Late Mesozoic igneous rock assemblages and proposed some geodynamical constraints on forming the basin and range tectonics of South China. A comparison of the similarities and differences of basin and range tectonics between the eastern and western shores of the Pacific is made, and the geodynamical evolution model of the Southeast China Block during Late Mesozoic is discussed. Studied results suggest that the basin and range terrane within South China developed on a pre-Mesozoic folded belt was derived from a polyphase tectonic evolution mainly constrained by subduction of the western Pacific Plate since the Late Mesozoic, leading to formation of various magmatism in a back-arc extensional setting. Its geodynamic mechanism can compare with that of basin and range tectonics in the eastern shore of the Pacific. Differences of basin and range

  1. Late Eocene clay boron-derived paleosalinity in the Qaidam Basin and its implications for regional tectonics and climate (United States)

    Ye, Chengcheng; Yang, Yibo; Fang, Xiaomin; Zhang, Weilin


    The Qaidam Basin, located on the northeastern Tibetan Plateau and containing Cenozoic sediments with a maximum thickness of 12,000 m, is an ideal place to study the phased uplift of the NE Tibetan Plateau and regional climate change. The estimation of the paleosalinity of sedimentary environments not only helps to evaluate the evolution of lakes in this region but offers insights into contemporaneous climate change. We present detailed geochemical and mineralogical investigations from the lacustrine interval of the Hongliugou section in the northern Qaidam Basin to reconstruct salinity fluctuations in the paleolake during the late Eocene era ( 42.0-35.5 Ma). The clay mineral assemblages mainly contain smectite, illite, chlorite, kaolinite and irregular illite/smectite mixed layers. Clay boron-derived paleosalinity estimates (equivalent boron content, Couch's paleosalimeter and B/Ga ratios) along with other proxies sensitive to salinity changes (e.g., Rb/K ratios and ostracod assemblages) collectively indicate an overall brackish sedimentary environment with a higher-salinity period at approximately 40.0-39.2 Ma. This higher-salinity period indicates a more arid environment and is probably related to global cooling. However, the global cooling in late Eocene cannot explain the overall stable long-term salinity pattern, implying that other factors exist. We propose that the migration of the Yiliping depression depocenter in the northern Qaidam and increased orographic rainfall induced by late Eocene tectonic activity at the northern margin of the basin might have partly offset the increase in salinity driven by global cooling.

  2. Late Alpine to recent thick-skinned tectonics of the central Swiss Molasse Basin, Canton of Bern, Switzerland (United States)

    Mock, Samuel; Allenbach, Robin; Wehrens, Philip; Reynolds, Lance; Kurmann-Matzenauer, Eva; Michael, Salomè; Herwegh, Marco


    The Swiss Molasse Basin (SMB) forms part of the North Alpine Foreland Basin. It is a typical peripheral foreland basin, which developed in Paleogene and Neogene times in response to flexural bending of the European lithosphere induced by the orogenic loading of the advancing Alpine thrust wedge. The tectonics of the SMB and the role of Paleozoic and Mesozoic structures are still poorly understood. It is widely accepted that during the main deformation phase of the Jura fold-and-thrust belt, the SMB was riding piggy-back above a major detachment horizon situated within Triassic evaporites. In recent years it has been observed that the Jura fold-and-thrust belt is today deforming in a thick-skinned tectonic style. As for the western and central SMB, most authors still argue in favor of a classical foreland type, thin-skinned style of deformation. Based on the geological 3D modeling of seismic interpretations, we present new insights into the structural configuration of the central SMB. Revised and new interpretations of 2D reflection seismic data from the 1960s to the 1980s reveal a major strike-slip fault zone affecting not only the Mesozoic and Cenozoic cover, but also the crystalline basement beneath. The fault zone reactivated late Paleozoic synsedimentary normal faults bounding a Permo-Carboniferous trough. Basement-involved thrusting observed in the southern part of the SMB seems to be controlled by the presence of slightly inverted Permo-Carboniferous troughs as well. These observations, combined with a compiled structural map and the distribution of recent earthquake hypocenters suggest a late stage, NNW-SSE directed, compressional thick-skinned and strike-slip dominated tectonic activity of the central SMB, post-dating the main deformation phase of the Jura fold-and-thrust belt. This still ongoing deformation might be related to the slab rollback of the European plate and the associated lower crustal delamination as recently suggested by Singer et al. (2014

  3. Cenozoic ecological history of South East Asian peat mires based on the comparison of coals with present day and Late Quaternary peats

    Directory of Open Access Journals (Sweden)

    Robert J. Morley


    Full Text Available Tropical peat swamps are more widespread in Sundaland than in any other equatorial region. Also, Cenozoic deposits from the area are rich in coals. The developmental pattern of present day peat swamps from the region has often been used to help clarify that of coals in the geological record. This paper initially reviews the ecology of present day ombrotrophic, rheotrophic and brackish mangrove peat swamps, and their pattern and timing of development during the Holocene and latest Pleistocene based on palynological studies. Then, it attempts to examine the developmental pattern of the peats which led to the formation of Cenozoic coals across the region, based on both published and unpublished datasets generated during the course of hydrocarbon exploration programmes. It is concluded that Cenozoic coals reflect a greater variety of peat forming settings than occurs in the region today. Extensive brackish water peats formed during the Middle and Late Eocene and Middle and Late Miocene, these often being laterally very extensive. Rheotrophic peats also formed widely through most of the Cenozoic. Ombrotrophic kerapah type peats are first recognised in the Late Oligocene, based on their content of common Casuarina type and Dacrydium pollen, and were particularly common during the Early and Late Miocene in the Sunda shelf region. Kerapah peats sometimes developed great thickness. Basinal peats, on the other hand, increased in representation during the course of the Miocene. No convincing evidence for doming in Cenozoic peats has yet been noted, but on the other hand, no really thick coals, which may have been formed from basinal peats, have so far been studied. As a consequence, examples of doming in the rock record from this area are probably yet to be found.

  4. Tectonic model for the Late Paleozoic of southeastern New England

    Energy Technology Data Exchange (ETDEWEB)

    Wintsch, R.P.; Sutter, J.F.


    Hornblende and biotite /sup 40/Ar//sup 39/Ar age spectra from rocks in south-central Connecticut help define a Permian-Triassic cooling curve for the area. Together with petrologic and structural information, a time-temperature-pressure-strain path is established. Similar data for the Narragansett basin in Rhode Island and Massachusetts allow correlation of the late Paleozoic histories of the two areas. Together, these data suggest that in the late Paleozoic, south-central New England was part of a fold-thrust belt, and the Narragansett basin was a retroarc foreland basin. NW-SE compression during the final assembly of Pangaea resulted in SE directed thrusting, causing the development of clastic wedges in adjacent Rhode Island and Massachusetts in the Late Carboniferous-Early Permian. A clockwise rotation of this deformation from NW to NNE led to northward underthrusting and concomitant uplift of both eastern Connecticut and Rhode Island in the Permian and Triassic.

  5. Cenozoic tectonic and climatic events in southern Iberian Peninsula: Implications for the evolutionary history of freshwater fish of the genus Squalius (Actinopterygii, Cyprinidae). (United States)

    Perea, Silvia; Cobo-Simon, Marta; Doadrio, Ignacio


    Southern Iberian freshwater ecosystems located at the border between the European and African plates represent a tectonically complex region spanning several geological ages, from the uplifting of the Betic Mountains in the Serravalian-Tortonian periods to the present. This area has also been subjected to the influence of changing climate conditions since the Middle-Upper Pliocene when seasonal weather patterns were established. Consequently, the ichthyofauna of southern Iberia is an interesting model system for analyzing the influence of Cenozoic tectonic and climatic events on its evolutionary history. The cyprinids Squalius malacitanus and Squalius pyrenaicus are allopatrically distributed in southern Iberia and their evolutionary history may have been defined by Cenozoic tectonic and climatic events. We analyzed MT-CYB (510 specimens) and RAG1 (140 specimens) genes of both species to reconstruct phylogenetic relationships and to estimate divergence times and ancestral distribution ranges of the species and their populations. We also assessed their levels of genetic structure and diversity as well as the amount of gene flow between populations. To investigate recent paleogeographical and climatic factors in southern Iberia, we modeled changes-through-time in sea level from the LGM to the present. Phylogenetic, geographic and population structure analyses revealed two well-supported species (S. malacitanus and S. pyrenaicus) in southern Iberia and two subclades (Atlantic and Mediterranean) within S. malacitanus. The origin of S. malacitanus and the separation of its Atlantic and Mediterranean populations occurred during the Serravalian-Tortonian and Miocene-Pliocene periods, respectively. These divergence events occurred in the Middle Pliocene and Pleistocene in S. pyrenaicus. In both species, Atlantic basins possessed populations with higher genetic diversity than Mediterranean, which may be explained by the Janda Lagoon. The isolation of S. malacitanus was

  6. Coupling between tectonics and surface processes in the Congo Basin: Cretaceous-Cenozoic sedimentation and erosion triggered by climatic and tectonic factors (United States)

    de Putter, Thierry; Mees, Florias; Bayon, Germain; Ruffet, Gilles; Smith, Thierry; Delvaux, Damien


    Cretaceous to Recent evolution of the Congo Basin in Central Africa is still poorly documented although its history over the last 75 Myr has potentially recorded global and major regional events, including the Paleocene-Eocene Thermal Maximum at 56 Ma and the Miocene aperture of the Western branch of the East African Rift System along its eastern border at 25 Ma. Available data for associated off-shore deposits show that in parallel, the Congo River delta experienced a starvation period during the Mid- to Late Cretaceous and Paleogene, with endorheic lacustrine to desert environments in the upstream basin, followed by a period marked by high rates of drainage and sediment supply in the Neogene. Here, we combine new observations on the recent tectonic evolution with newly obtained 39Ar-40Ar ages for cryptomelane from Katanga (Kasekelesa) and Kasaï (Mt Mwatshimwa) and the preliminary results of the Landana condensed section ( 45 m) Paleogene-Neogene sequence. The maximum burial in the Congo Basin is estimated at 80 Ma and was followed by the removal of at least 900-1500 m of sediments (Sachse et al., 2012). Soon after the 39Ar-40Ar ages reveal that a major (Campanian or older) surface formed in the Kasai and Katanga before 76 Ma, followed by at least two younger Eocene denudation episodes, during the Lutetian ( 45 Ma) and the Priabonian ( 35 Ma) and more Mio-Pliocene denudation surfaces during the Mio-Pliocene (De Putter et al., 2016). The older surface likely belongs to the subcontinental 'African Surface' that had previously not been identified for Central Africa. During this long-lasting erosional history of the central part of the Congo Basin, the Landana section along the Atlantic coast recorded a condensed ( 45 m) sequence of Paleogene-Neogene sediments. The first 25m are shallow marine carbonates with little detrital input, recording slightly increasing weathering from the Danian to the Lutetian (Bayon et al., 2016). Whether this section had a physical

  7. Mesozoic-Cenozoic inversion of the Turpan-Hami Basin, northwest China

    Energy Technology Data Exchange (ETDEWEB)

    Cao, D.; Zhang, P.; Jin, K.; Qian, G.; Mei, M.; Tang, Y.; Shao, L. [China University of Mining and Technology, Beijing (China). Beijing Graduate School


    The Turpan-Hami basin, rich in coal and petroleum, is a superimposed basin of three types in different tectonic environments. The basin has undergone a complex tectonic-sedimentary evolution, in which two important stages were the negative inversion from a foredeep to an extensional basin during Early Mesozoic and the positive inversion to a thrust foreland basin in Late Mesozoic-Early Cenozoic. The early normal faults residues are recognized with the addition of tectonic-sedimentary analysis to confirm the basin extension during Jurassic time and its subsequent tectonic inversion. 4 refs., 6 figs.

  8. New allocyclic dimensions in a prograding carbonate bank: Evidence for eustatic, tectonic, and paleoceanographic control (late Neogene, Bahamas) (United States)

    Lidz, B.H.; McNeill, D.F.


    The deep-sea record, examined recently for the first time in a shallow-depocenter setting, has unveiled remarkable evidence for new sedimentary components and allocyclic complexity in a large, well-studied carbonate bank, the western Great Bahama Bank. The evidence is a composite foraminiferal signature - Paleocene to early Miocene (allogenic or reworked) and late Miocene to late Pliocene (host) planktic taxa, and redeposited middle Miocene shallow benthic faunas. Ages of the oldest and youngest planktic groups range from ??? 66 to ??? 2 Ma. The reworked and redeposited taxa are a proxy for significant sediment components that otherwise have no lithofacies or seismic resolution. The composite signature, reinforced by a distinctive distribution of the reworked and redeposited faunas, documents a much more complex late Neogene depositional system than previously known. The system is more than progradational. The source sequences that supplied the constituent bank-margin grains formed at different water depths and over hundreds of kilometers and tens of millions of years apart. New evidence from the literature and from data obtained during Ocean Drilling Program (OOP) Leg 166 in the Santaren Channel (Bahamas) support early interpretations based on the composite fossil record and provide valuable new dimensions to regional allocyclicity. The middle Miocene taxa were confined to the lower part of the section by the latest Miocene-earliest Pliocene(?) lowstand of sea level. An orderly occurrence of the allogenic taxa is unique to the global reworked geologic record and appears to have been controlled by a combination of Paleogene-early Neogene tectonics at the source, eustatic changes, and late Neogene current activity at the source and across the bank. The allogenic taxa expand the spatial and temporal range of information in the northern Bahamas by nearly an order of magnitude. In essence, some of the major processes active in the region during ??? 64 m.y. of the

  9. Episodes of environmental stability versus instability in Late Cenozoic lake records of Eastern Africa. (United States)

    Trauth, Martin H; Bergner, Andreas G N; Foerster, Verena; Junginger, Annett; Maslin, Mark A; Schaebitz, Frank


    Episodes of environmental stability and instability may be equally important for African hominin speciation, dispersal, and cultural innovation. Three examples of a change from stable to unstable environmental conditions are presented on three different time scales: (1) the Mid Holocene (MH) wet-dry transition in the Chew Bahir basin (Southern Ethiopian Rift; between 11 ka and 4 ka), (2) the MIS 5-4 transition in the Naivasha basin (Central Kenya Rift; between 160 ka and 50 ka), and (3) the Early Mid Pleistocene Transition (EMPT) in the Olorgesailie basin (Southern Kenya Rift; between 1.25 Ma and 0.4 Ma). A probabilistic age modeling technique is used to determine the timing of these transitions, taking into account possible abrupt changes in the sedimentation rate including episodes of no deposition (hiatuses). Interestingly, the stable-unstable conditions identified in the three records are always associated with an orbitally-induced decrease of insolation: the descending portion of the 800 kyr cycle during the EMPT, declining eccentricity after the 115 ka maximum at the MIS 5-4 transition, and after ∼ 10 ka. This observation contributes to an evidence-based discussion of the possible mechanisms causing the switching between environmental stability and instability in Eastern Africa at three different orbital time scales (10,000 to 1,000,000 years) during the Cenozoic. This in turn may lead to great insights into the environmental changes occurring at the same time as hominin speciation, brain expansion, dispersal out of Africa, and cultural innovations and may provide key evidence to build new hypotheses regarding the causes of early human evolution. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Tectonic implications of Late Paleozoic stratigraphic distribution in Northeast China and adjacent region

    Institute of Scientific and Technical Information of China (English)

    WANG ChengWen; SUN YueWu; LI Ning; ZHAO GuoWei; MA XiaoQin


    An analysis of the distribution of the Late Paleozoic strata on Northeast Chinaand adjacent region re-veals a zonal pattern of the distribution around the core of the Jiamusi-Mongolia Block. The main part of Late Paleozoic marine strata in this area is considered the continental margin deposits of the Jia-musi-Mongolia Block by analyzing the stratigraphic contact relationship, lithofacies, etc. The results are exhibited in a series of tectonic paleogeographic maps. This presents an important proof for the foundation of the Jiamusi-Mongolia Block, and confines the forming time of Jiamusi-Mongolia Block to the Late Silurian.

  11. Tectonic lineaments in the cenozoic volcanics of southern Guatemala: Evidence for a broad continental plate boundary zone (United States)

    Baltuck, M.; Dixon, T. H.


    The northern Caribbean plate boundary has been undergoing left lateral strike slip motion since middle Tertiary time. The western part of the boundary occurs in a complex tectonic zone in the continental crust of Guatemala and southernmost Mexico, along the Chixoy-Polochic, Motogua and possibly Jocotan-Chamelecon faults. Prominent lineaments visible in radar imagery in the Neogene volcanic belt of southern Guatemala and western El Salvador were mapped and interpreted to suggest southwest extensions of this already broad plate boundary zone. Because these extensions can be traced beneath Quaternary volcanic cover, it is thought that this newly mapped fault zone is active and is accommodating some of the strain related to motion between the North American and Caribbean plates. Onshore exposures of the Motoqua-Polochic fault systems are characterized by abundant, tectonically emplaced ultramafic rocks. A similar mode of emplacement for these off shore ultramafics, is suggested.

  12. Late Cenozoic surficial deposits and valley evolution of unglaciated northern New Jersey (United States)

    Stanford, S.D.


    Multiple alluvial, colluvial, and eolian deposits in unglaciated northern New Jersey, and the eroded bedrock surfaces on which they rest, provide evidence of both long-term valley evolution driven by sustained eustatic baselevel lowering and short-term filling and excavation of valleys during glacial and interglacial climate cycles. The long-term changes occur over durations of 106 years, the short-term features evolve over durations of 104 to 105 years. Direct glacial effects, including blockage of valleys by glacial ice and sediment, and valley gradient reversals induced by crustal depression, are relatively sudden changes that account for several major Pleistocene drainage shifts. After deposition of the Beacon Hill fluvial gravel in the Late Miocene, lowering of sea level, perhaps in response to growth of the Antarctic ice sheet, led to almost complete dissection of the gravel. A suite of alluvial, colluvial, and eolian sediments was deposited in the dissected landscape. The fluvial Bridgeton Formation was deposited in the Raritan lowland, in the Amboy-Trenton lowland, and in the Delaware valley. Following southeastward diversion of the main Bridgeton river, perhaps during Late Pliocene or Early Pleistocene glaciation, northeastward drainage was established on the inactive Bridgeton fluvial plain. About 30 to 45 m of entrenchment followed, forming narrow, incised valleys within which Late Pleistocene deposits rest. This entrenchment may have occurred in response to lowered sea level caused by growth of ice sheets in the northern hemisphere. Under periglacial conditions in the Middle and Late Pleistocene, valleys were partially filled with alluvium and colluvium. During interglacials slopes were stabilized by vegetation and the alluvial and colluvial valley-fill was excavated by gullying, bank erosion, and spring sapping. During Illinoian and late Wisconsinan glaciation, the lower Raritan River was diverted when glacial deposits blocked its valley, and the

  13. Progress in faunal correlation of Late Cenozoic fluvial sequences 2000 4: the report of the IGCP 449 biostratigraphy subgroup (United States)

    Schreve, D. C.; Keen, D. H.; Limondin-Lozouet, N.; Auguste, P.; Santisteban, Juan I.; Ubilla, M.; Matoshko, A.; Bridgland, D. R.; Westaway, R.


    Vertebrate and invertebrate faunal biostratigraphy is a well-tested method for establishing relative chronologies for fluviatile sequences that has proved useful in many parts of the world. The robust bones and teeth of large mammals are commonly found in fluviatile deposits, whereas small vertebrates can be readily recovered through systematic sieving of calcareous sediments, as can molluscs, the other major faunal group that has been used for biostratigraphical analysis of fluvial sequences. Because of their rapid and quantifiable rates of evolution, extinction, body mass change and dispersal during the Late Cenozoic, mammals are especially useful for ordering the fragmentary terrestrial sequence of interglacials and glacials, and proposing correlation with the global marine climatostratigraphic record. Other groups (e.g. reptiles and amphibians, ostracods) are as yet only in the initial stages of development as a dating tool, whereas some (e.g. fish, birds) still require substantial development in order to fully explore their utility. As part of IGCP 449, vertebrate and molluscan assemblages have made important contributions to datasets from a number of areas, notably northern France, central Germany, the Czech Republic and the Ukraine. Further south, mammalian assemblages have proved useful in separating discrete periods of climatic change in Iberia and Syria. At greater distances from the core area of fluvial biostratigraphical archives, significant contributions have come from South America (Uruguay River), South Africa (Vaal) and Australia (Riverine Plain and Lake Eyre drainage basin).

  14. Late Cretaceous- Cenozoic history of deciduousness and the terminal Cretaceous event. (United States)

    Wolfe, J.A.


    Deciduousness in mesic, broad-leaved plants occurred in disturbed, middle-latitude environments during the Late Cretaceous. Only in polar environments in the Late Cretaceous was the deciduous element dominant, although of low diversity. The terminal Cretaceous event resulted in wide-spread selection for plants of deciduous habit and diversification of deciduous taxa, thus leaving a lasting imprint on Northern Hemisphere vegetation. Various environmental factors have played important roles in subsequent diversification of mesic, broad-leaved deciduous taxa and in origination and decline of broad-leaved deciduous forests. Low diversity and rarity of mesic deciduous plants in the post-Cretaceous of the Southern Hemisphere indicate that the inferred 'impact winter' of the terminal Cretaceous event had little effect on Southern Hemisphere vegetation and climate. -Author

  15. Late Carboniferous tectonic subsidence in South Wales: implications for Variscan basin evolution and tectonic history in SW Britain

    Energy Technology Data Exchange (ETDEWEB)

    Burgess, P.M.; Gayer, R.A. [University of Cardiff, Cardiff (United Kingdom). Dept. of Earth Sciences


    Detailed stratigraphic data were used to backstrip seven sections from the Carboniferous South Wales coal basin. Resulting tectonic subsidence curves for the interval 319-305 Ma (Namurian-Westphalian D) are convex-up, indicating increasing subsidence rate with time, with rates between 130 and 250 m Ma{sup -1} suggesting a foreland basin setting. Forward modelling of subsidence due to flexural loading in front of a propagating orogenic wedge shows that an orogenic load migrating in a north-northeasterly direction across SW England between 319 and 305 Ma could have generated the backstripped subsidence patterns. Sensitivity tests show that while many of the forward model parameters are poorly constrained, and the model results non-unique, backstripped subsidence patterns allow reasonable constraint on the different model cases, so that model predictions can be treated as one possibility in a limited range. The predicted load evolution is consistent with current knowledge of tectonic and stratigraphic features of SW England. These results suggest that subsidence in other Late Carboniferous UK basins may also have been influenced by flexure due to a propagating orogenic load.

  16. Trends, Rhythms, and Aberrations in Global Climate during the Cenozoic: The Interplay between Tectonic and Orbital forcing (Milutin Milankovic Medal Lecture) (United States)

    Zachos, James C.


    Prior to the mid-nineties much of our understanding of early Neogene and Paleogene climate was based on relatively low-resolution reconstructions. As a consequence, under-sampled periodic climate variability appeared as noise in global records (i.e., stacks), limiting our ability to fully evaluate mechanisms of past climate change. Efforts to address this limitation began in earnest with Ocean Drilling Program Leg 154, one of the first to successfully recover high-quality stratigraphically complete and relatively expanded successions of Paleogene pelagic sediments, allowing for astronomical tuning and the development of detailed paleoclimatic records extending back into the Oligocene. The strategies implemented during this Leg to locate, recover, and tune Paleogene sequences were adapted by subsequent ODP/IODP expeditions, ultimately contributing to the development of high-resolution astronomically-tuned climate records extending back to the Cretaceous. The collective contributions of these expeditions provided the necessary framework for characterizing climate variability on orbital time scales throughout the Cenozoic, including the major transitions and aberrations, the Oligocene-Miocene (O/M), Eocene-Oligocene Transition (EOT), and the Paleocene-Eocene Thermal Maximum (PETM). In this presentation I will review the most recent advances in reconstructing past climates on orbital time scales, and how these advances are altering our understanding of the triggering mechanisms for these major climate transitions, and discuss how the interplay between tectonic processes and orbital forcing as well as physical and geochemical feedbacks contributed to drive the more rapid and extreme aberrations.

  17. Tectonic Evolution of the Tianhuan Depression and the Western Margin of the Late Triassic Ordos

    Institute of Scientific and Technical Information of China (English)

    LI Xiangbo; LIU Huaqing; WANYAN Rong; WEI Lihua; LIAO Jianbo; FENG Ming; MA Yuhu; BAI Yunlai


    The Ordos Basin is one of the most important oil and gas basins in China. Based on surface outcrop, key exploratory wells and seismic reflection data and by using the technology of "prototype basin recovery", seismic profile "layer flattening" and "restoration of balanced section", and other methods, the sedimentary boundary, structure and the evolution history of the Tianhuan depression on the western margin of the Ordos Basin are reestablished. The following results have been obtained. (1) The west boundary of the Late Triassic Ordos Basin was far beyond the scope of the current basin. The basin is connected with the Late Triassic Hexi Corridor Basin, and its western margin did not have tectonic characteristics of a foreland basin. (2) The Tianhuan depression was first formed in the Late Jurassic. At the late stage it was impacted by the late Yanshanian and Himalayan tectonic movement and the depression axis gradually moved eastwards to the present location with a cumulative migration distance of ~30 kin. (3) Eastward migration of the depression axis caused adjustment and even destruction of the originally formed oil and gas reservoirs, so that oil and gas remigrated and aggregated, resulting in secondary structural reservoirs formed at high positions on the western flank of the depression.

  18. Tectonic Evolution of the North Depression of the South Yellow Sea Basin Since Late Cretaceous

    Institute of Scientific and Technical Information of China (English)

    LI Nan; LI Weiran; LONG Haiyan


    On the basis of subsidence history analysis and balanced cross-section analysis, the vertical uplift/subsidence history and horizontal extension/compression history of the north depression of the south Yellow Sea basin are quantitatively studied. The results show that the tectonic evolution of the north depression of the south Yellow Sea basin since late Cretaceous can be divided into a rifting phase (late Cretaceous to Paleogene) and a post-rifting phase (Neogene to Quaternary). The rifting phase can be further subdivided into an initial rifting stage (late Cretaceous), an intensive rifting stage (Paleocene), a rifting termination stage (Eocene), and an inversion-uplifting stage (Oligocene). Together, this division shows the characteristics of an episodic-evolved intracontinental rift-depression basin. The deformation of the north depression of the south Yellow Sea basin since late Cretaceous was mainly fault-related. The horizontal extension and tectonic subsidence were controlled by the activity of faults. The differential evolution of faults also caused variations in local uplift/subsidence movements and the regional heterogeneity in extension. The late Cretaceous initial rifting of the north depression of the south Yellow Sea basin is related to the Pacific-Eurasia convergence. From the Paleocene intensive rifting stage to present, the Pacific-Eurasia convergence and India-Eurasia convergence have played important roles in the evolution of this region.

  19. Tectonic evolution of the north depression of the south Yellow Sea basin since late Cretaceous (United States)

    Li, Nan; Li, Weiran; Long, Haiyan


    On the basis of subsidence history analysis and balanced cross-section analysis, the vertical uplift/subsidence history and horizontal extension/compression history of the north depression of the south Yellow Sea basin are quantitatively studied. The results show that the tectonic evolution of the north depression of the south Yellow Sea basin since late Cretaceous can be divided into a rifting phase (late Cretaceous to Paleogene) and a post-rifting phase (Neogene to Quaternary). The rifting phase can be further subdivided into an initial rifting stage (late Cretaceous), an intensive rifting stage (Paleocene), a rifting termination stage (Eocene), and an inversion-uplifting stage (Oligocene). Together, this division shows the characteristics of an episodic-evolved intracontinental rift-depression basin. The deformation of the north depression of the south Yellow Sea basin since late Cretaceous was mainly fault-related. The horizontal extension and tectonic subsidence were controlled by the activity of faults. The differential evolution of faults also caused variations in local uplift/subsidence movements and the regional heterogeneity in extension. The late Cretaceous initial rifting of the north depression of the south Yellow Sea basin is related to the Pacific-Eurasia convergence. From the Paleocene intensive rifting stage to present, the Pacific-Eurasia convergence and India-Eurasia convergence have played important roles in the evolution of this region.

  20. Dating the Late Cenozoic glacial sequence, Pieman River basin, western Tasmania, Australia (United States)

    Augustinus, Paul C.


    The Pieman River basin, western Tasmania, displays one of the most complete Middle to Early Pleistocene glacial sequences from a Southern Hemisphere mid-latitude site. Most of the glacial deposits exceed the 14C limit, although mapping of the depositional units using morphostratigraphic, post-depositional weathering criteria and magnetostratigraphy, shows that the sediments of the Boco and Bobadil glaciation were deposited during the Brunhes normal chron (ferricretes and peat developed within and upon the sediment bodies whereby the deposits of the Boco and Bobadil glaciation are shown to be broadly correlative with Oxygen Isotope Stages 6 and 8, respectively. An older mid-Pleistocene glacial event (Animal Creek Glaciation) has also been recognised and dated to >275 kyr. Late Last (Margaret) Glaciation advances in the Pieman basin are much more restricted in extent and display evidence for multiple stillstand-readvance phases during the decay of the system, with most of the ice having disappeared by ˜14 kyr BP.

  1. Chapter B: Regional Geologic Setting of Late Cenozoic Lacustrine Diatomite Deposits, Great Basin and Surrounding Region: Overview and Plans for Investigation (United States)

    Wallace, Alan R.


    Freshwater diatomite deposits are present in all of the Western United States, including the Great Basin and surrounding regions. These deposits are important domestic sources of diatomite, and a better understanding of their formation and geologic settings may aid diatomite exploration and land-use management. Diatomite deposits in the Great Basin are the products of two stages: (1) formation in Late Cenozoic lacustrine basins and (2) preservation after formation. Processes that favored long-lived diatom activity and diatomite formation range in decreasing scale from global to local. The most important global process was climate, which became increasingly cool and dry from 15 Ma to the present. Regional processes included tectonic setting and volcanism, which varied considerably both spatially and temporally in the Great Basin region. Local processes included basin formation, sedimentation, hydrology, and rates of processes, including diatom growth and accumulation; basin morphology and nutrient and silica sources were important for robust activity of different diatom genera. Only optimum combinations of these processes led to the formation of large diatomite deposits, and less than optimum combinations resulted in lakebeds that contained little to no diatomite. Postdepositional processes can destroy, conceal, or preserve a diatomite deposit. These processes, which most commonly are local in scale, include uplift, with related erosion and changes in hydrology; burial beneath sedimentary deposits or volcanic flows and tuffs; and alteration during diagenesis and hydrothermal activity. Some sedimentary basins that may have contained diatomite deposits have largely been destroyed or significantly modified, whereas others, such as those in western Nevada, have been sufficiently preserved along with their contained diatomite deposits. Future research on freshwater diatomite deposits in the Western United States and Great Basin region should concentrate on the regional

  2. The Cenozoic Diversity of Agglutinated Foraminifera - Evidence for a late Oligocene to early Miocene diversification event (United States)

    Kaminski, Michael; Setoyama, Eiichi; Kender, Sev; Cetean, Claudia


    The agglutinated foraminifera are among the most abundant micro-organisms in the deep marine environment and have a diversity record extending back to the late Precambrian. We present an updated diversity curve for agglutinated foraminiferal genera based on the stratigraphic ranges of all the agglutinated genera recognized as valid in the classification of Kaminski (2014). The data set for this analysis is based on the stratigraphic ranges of agglutinated genera published in Foraminiferal Genera and their Classification, which has been subsequently updated based on published studies and our new observations. The mean standing diversity of agglutinated foraminiferal genera was compiled by counting the number of boundary crossers rather than the number of genera in each stage. In this study, we report the stratigraphic and geographical occurrence of a benthic foraminiferal diversification event that has previously received little attention. In the latest Oligocene to earliest Miocene a number of trochospiral agglutinated genera with alveolar or canaliculate walls first appeared in the fossil record. Our studies of late Oligocene of the Congo fan, offshore Angola (Kender et al., 2008; Cetean and Kaminski, 2011) have revealed a diverse assemblage that includes new taxa of deep-water agglutinated foraminifera. In a biostratigraphic study of the Miocene foraminiferal assemblages Kender et al. (2008) noted steadily increasing diversity and proportions of infaunal agglutinated foraminiferal morphotypes over the lower Miocene interval. The proportion of infaunal agglutinated foraminifera assigned to the order Textularida increased dramatically in the lower mid-Miocene, suggesting expansion of the oxygen minimum zone into deeper waters. In addition to the trochospiral alveolar genera, several species of Reticulophragmium and Cyclammina display rapid diversification into numerous separate lineages that are at present not reflected in our generic diversity record owing to

  3. Cenozoic stratigraphy of the Sahara, Northern Africa (United States)

    Swezey, Christopher S.


    This paper presents an overview of the Cenozoic stratigraphic record in the Sahara, and shows that the strata display some remarkably similar characteristics across much of the region. In fact, some lithologies of certain ages are exceptionally widespread and persistent, and many of the changes from one lithology to another appear to have been relatively synchronous across the Sahara. The general stratigraphic succession is that of a transition from early Cenozoic carbonate strata to late Cenozoic siliciclastic strata. This transition in lithology coincides with a long-term eustatic fall in sea level since the middle Cretaceous and with a global climate transition from a Late Cretaceous–Early Eocene “warm mode” to a Late Eocene–Quaternary “cool mode”. Much of the shorter-term stratigraphic variability in the Sahara (and even the regional unconformities) also can be correlated with specific changes in sea level, climate, and tectonic activity during the Cenozoic. Specifically, Paleocene and Eocene carbonate strata and phosphate are suggestive of a warm and humid climate, whereas latest Eocene evaporitic strata (and an end-Eocene regional unconformity) are correlated with a eustatic fall in sea level, the build-up of ice in Antarctica, and the appearance of relatively arid climates in the Sahara. The absence of Oligocene strata throughout much of the Sahara is attributed to the effects of generally low eustatic sea level during the Oligocene and tectonic uplift in certain areas during the Late Eocene and Oligocene. Miocene sandstone and conglomerate are attributed to the effects of continued tectonic uplift around the Sahara, generally low eustatic sea level, and enough rainfall to support the development of extensive fluvial systems. Middle–Upper Miocene carbonate strata accumulated in northern Libya in response to a eustatic rise in sea level, whereas Upper Miocene mudstone accumulated along the south side of the Atlas Mountains because uplift of the

  4. Late Quaternary river channel migrations of the Kura River in Transcaucasia - tectonic versus climatic causes (United States)

    von Suchodoletz, Hans; Gärtner, Andreas; Hoth, Silvan; Umlauft, Josefine; Godoladze, Tea; Faust, Dominik


    Large-scale river channel migrations either in the form of avulsions or combing, i.e. progressive lateral migrations, are global phenomena during the Late Quaternary. Such channel migrations were triggered by tectonics, climate change, human activity or a combination of those factors. River channel migrations have the potential to cause significant human and economic losses. Thus, a more thorough knowledge about underlying causes and process rates is essential. Furthermore, such studies will elucidate the sensitivity or robustness of rivers to different external and internal forcing-agents, i.e. they help to identify the dominant drivers of regional landscape evolution. The Caucasus region is part of the active collision zone between the Africa-Arabian and the Eurasian plates, and is characterized by high current tectonic activity. Furthermore, significant environmental changes took place during the Late Quaternary, i.e. the shrinking or even disappearance of glaciers in the Greater and Lesser Caucasus or fundamental changes of the vegetation cover varying between woodland and grassland-dominated vegetation. The Kura River is the main gaining stream of the Transcaucasian Depression located between the Greater Caucasus Mountains in the north and the Lesser Caucasus Mountains in the south, and receives several tributaries from both mountain ranges. This study focusses on the middle course of the Kura River in eastern Georgia, SE of the city of Tbilisi. Integration of fluvial geomorphology, geochronology, heavy mineral analyses and seismo-tectonic analyses demonstrates that this part of the Kura River underwent large-scale channel migrations up to >10 km during Late Pleistocene and Holocene. It is interpreted that these movements followed both tectonic and climatic triggers: Whereas SW-ward migrations were caused by tectonic uplift in and SW-directed advance of the Kura fold and thrust belt as part of the Greater Caucasus, NE-ward migrations occurred during cold

  5. Paleo-tectonogeomorphology during Late Cretaceous to Early Cenozoic in Liupanshan Area%六盘山地区晚白垩世-新生代初期古构造运动

    Institute of Scientific and Technical Information of China (English)

    黄建军; 吴建勇; 吴竹明; 朱鲁生; 林秀斌


    现今中国西部印度-欧亚板块碰撞影响的地区在碰撞之前的构造地貌格局是地学界很关注的问题,对先期古构造地貌格局的了解有助于将先期构造事件从后期印度-欧亚板块碰撞事件中剥离出来.本文选现今青藏高原东北缘的六盘山东麓出露的寺口子剖面新生界底部沉积物,通过详尽的沉积学及古水流方向研究,认为六盘山在晚白垩世-新生代初期存在古构造地貌高地,这为Kohistan-Dras岛弧及冈瓦纳大陆的碎片向欧亚大陆聚合在六盘山地区的反映.%The tectonogeomorphology of the area pre-dating the Indian-Eurasian collision in west China draws dramatic attentions of geologists, the understanding of former tectonogeomorphology will help us to rule out the previous tectonic events from the collision. We select the sediments at the bottom of Cenozoic sequences in Sikouzi section, which were re-vealed in the east of Liupanshan situated in the northeast of the Tibetan Plateau, to reveal the pre-dating tectonogeomor-phology of Liupan Shan. Based on detailed sedimentologic and paleocurrent studies, we suggest that a geomorphologic relief existed in Liupanshan during late Cretaceous to early Cenozoic,which possibly resulted from the far-field effects of the assembly of Kohistan-Dras Arc and Gondwana fragments to Eurasian continent.

  6. Compression-extension transition of continental crust in a subduction zone: A parametric numerical modeling study with implications on Mesozoic-Cenozoic tectonic evolution of the Cathaysia Block (United States)

    Chan, Lung Sang; Gao, Jian-Feng


    The Cathaysia Block is located in southeastern part of South China, which situates in the west Pacific subduction zone. It is thought to have undergone a compression-extension transition of the continental crust during Mesozoic-Cenozoic during the subduction of Pacific Plate beneath Eurasia-Pacific Plate, resulting in extensive magmatism, extensional basins and reactivation of fault systems. Although some mechanisms such as the trench roll-back have been generally proposed for the compression-extension transition, the timing and progress of the transition under a convergence setting remain ambiguous due to lack of suitable geological records and overprinting by later tectonic events. In this study, a numerical thermo-dynamical program was employed to evaluate how variable slab angles, thermal gradients of the lithospheres and convergence velocities would give rise to the change of crustal stress in a convergent subduction zone. Model results show that higher slab dip angle, lower convergence velocity and higher lithospheric thermal gradient facilitate the subduction process. The modeling results reveal the continental crust stress is dominated by horizontal compression during the early stage of the subduction, which could revert to a horizontal extension in the back-arc region, combing with the roll-back of the subducting slab and development of mantle upwelling. The parameters facilitating the subduction process also favor the compression-extension transition in the upper plate of the subduction zone. Such results corroborate the geology of the Cathaysia Block: the initiation of the extensional regime in the Cathaysia Block occurring was probably triggered by roll-back of the slowly subducting slab. PMID:28182640

  7. Thick-skinned tectonics and basement control on geometry, kinematics and mechanics of fold-and-thrust belts. Insights from some cenozoic belts worldwide (United States)

    Lacombe, Olivier; Bellahsen, Nicolas


    Fold-and-thrust belts (FTBs) form either in lower and upper plates at the expense of proximal parts of former passive margins during collision or within the upper plate of subduction orogens. In contrast, inner parts of mountain belts are likely made of stacked units from the distal passive margin domains that have undergone continental subduction and HP-LT metamorphism. There are increasing lines of evidence that the basement is involved in shortening in many FTBs worldwide, either pervasively (across the entire belt; tectonic inversion may even occur more forelandward than the mountain front) or mainly in their innermore domains where this basement is commonly exhumed. For thick-skinned FTBs that developed from former passive margins, the occurrence of weak mechanical layers within the proximal margin lithosphere (the middle and most of the lower crust are expectedly ductile) may explain that contractional deformation be distributed within most of the crust giving rise to basement-involved tectonic style. In contrast, because these weak crustal levels are usually lacking in distal parts of the margins as a result of thinning, these stronger lithospheric domains are more prone to localized deformation/subduction. Less understandable this way is the occurrence of thick-skinned wide domains within cold and strong interiors of upper plates of subduction zones, such as the Paleocene Laramide orogenic belt or the active Sierras Pampeanas belt. Structural, geophysical and thermochronological investigations within Cenozoic thick-skinned (or basement-involved thin-skinned) FTBs provide evidence for how the pre-orogenic and syn-orogenic deformation of the basement may control the geometry, kinematics and mechanics of FTBs. In this contribution, we examine some examples of FTBs where the basement is known to be involved in shortening and we review some aspects of the control exerted by the basement on the deformation. This control is demonstrated (1) at the scale of the

  8. Distinct phases of eustatic and tectonic forcing for late Quaternary landscape evolution in southwest Crete, Greece

    Directory of Open Access Journals (Sweden)

    V. Mouslopoulou


    Full Text Available The extent to which climate, eustasy and tectonics interact to shape the late Quaternary landscape is poorly known. Alluvial fans often provide useful indexes that allow the decoding of information recorded on complex coastal landscapes, such as those of the eastern Mediterranean. In this paper we analyse and date (using infrared stimulated luminescence (IRSL dating a double alluvial fan system on southwest Crete, an island straddling the forearc of the Hellenic subduction margin, in order to constrain the timing and magnitude of its vertical deformation and discuss the factors contributing to its landscape evolution. The studied alluvial system is exceptional because each of its two juxtaposed fans records individual phases of alluvial and marine incision, thus providing unprecedented resolution in the formation and evolution of its landscape. Specifically, our analysis shows that the fan sequence at Domata developed during Marine Isotope Stage (MIS 3 due to five distinct stages of marine transgressions and regressions and associated river incision, in response to sea-level fluctuations and tectonic uplift at averaged rates of  ∼ 2.2 mm yr−1. Interestingly, comparison of our results with published tectonic uplift rates from western Crete shows that uplift during 20–50 kyr BP was minimal (or even negative. Thus, most of the uplift recorded at Domata must have occurred in the last 20 kyr. This implies that eustasy and tectonism impacted the landscape at Domata over mainly distinct time intervals (e.g. sequentially and not synchronously, with eustasy forming and tectonism preserving the coastal landforms.

  9. Phosphorites, Co-rich Mn nodules, and Fe-Mn crusts from Galicia Bank, NE Atlantic: Reflections of Cenozoic tectonics and paleoceanography (United States)

    González, Francisco Javier; Somoza, Luis; Hein, James R.; Medialdea, Teresa; León, Ricardo; Urgorri, Victoriano; Reyes, Jesús; Martín-Rubí, Juan Antonio


    A wide variety of marine mineral deposits were recovered from 750 to 1400 m water depths on Galicia Bank, Iberian margin. Mineral deposits include: (1) carbonate fluorapatite phosphorite slabs and nodules that replaced limestone and preserved original protolith fabric. (2) Ferromanganese vernadite crusts with high Mn and Fe (Mn/Fe = 1) contents, and thick stratabound layers consisting mainly of Mn (up to 27% MnO) and Fe (15% Fe2O3), which impregnated and replaced the phosphorite. (3) Co-rich Mn nodules are composed of romanechite and todorokite laminae. Mn-rich layers (up to 58% MnO) contain up to 1.8% Co. (4) Goethite nodules with Fe up to 67% Fe2O3 have low Mn and trace metals. We interpret this mineralization paragenesis to be related to major changes in oceanographic and tectonic regimes. Three phosphatization generations formed hardgrounds dated by 87Sr/86Sr isotopes as late Oligocene, early Miocene, and latest early Miocene. During the latest early Miocene, the hardground was fractured and breached due to regional intraplate tectonism, which was coeval with a widespread regional erosional unconformity. The stratabound layers and Co-rich manganese nodules were derived from low-temperature geothermally driven hydrothermal fluids, with fluid conduits along reactivated faults. During middle and late Miocene, the introduction of vigorous deep water flow from the Arctic generated growth of hydrogenetic ferromanganese crusts. Finally, growth of diagenetic Fe-rich nodules (late Pliocene) was promoted by the introduction of hypersaline Mediterranean Outflow Water into the Atlantic Ocean.

  10. Quantitative Research on Longmen Shan Uplift Caused by Late Cenozoic Isostatic Rebound%龙门山晚新生代均衡反弹隆升的定量研究

    Institute of Scientific and Technical Information of China (English)

    王岩; 刘少峰


    Longmen Shan is located at the boundary between the Sichuan Basin and the eastern margin of Tibetan Plateau, representing the steepest gradient of any edges of the plateau. Its uplifting process and mechanism are important scientific issues studied by international geologists. Especially after the large amount of denudation such as landslides and debris flows since Late Cenozoic, Longmen Shan did not reduce the elevation, but continually uplifted. This article discussed three popular geodynamic mechanisms about Longmen Shan tectonic uplift in Late Cenozoic, i. e. channel flow in the lower crust, crustal shortening deformation and crustal isostatic rebound. The uplift of Longmen Shan in Late Cenozoic is related to isostatic rebound associated with erosion. The erosion denuded crustal rocks gradually, and the space occupied by the original erosional material was replaced by air, which led the lithosphere or crust to produce negative load and caused uplift of the mountain. Combining with digital elevation model data, this research revealed that the coseismic deformation caused by repeated large seismic events and isostatic rebound induced by rapid surface erosion, such as earthquake, landslide and debris flow, might be a new geodynamic mechanism to drive ongoing mountain building of Longmen Shan. The elevation of Longmen Shan nowadays may be controlled by tectonic and erosion-induced isostatic rebound effects, and the contribution of erosion-induced isostatic rebound on the uplift of Longmen Shan is about 30%.%龙门山位于青藏高原东缘与四川盆地的交接部位,是青藏高原周边山脉中地形梯度变化最大的山脉,其隆升过程和机制一直是国际地学界关注的焦点.晚新生代经过大量的滑坡、泥石流等快速剥蚀作用,龙门山的高程却不断升高.讨论了龙门山构造隆升的3种地球动力学机制,即下地壳通道流机制、地壳挤压缩短变形机制、地壳均衡反弹机制.晚新生代龙门山的

  11. The Role of Late-Cenozoic Lava Flows in the Evolution of the Owyhee River Canyon, Oregon (United States)

    Brossy, C. C.; House, P. K.; Ely, L. L.; O'Connor, J. E.; Safran, E. B.; Bondre, N.; Champion, D. E.; Grant, G.


    Over the last 2 Ma, at least six lava flows entered the canyon of the Owyhee River in southeastern Oregon, dramatically and repeatedly altering the river's course and profile. A combination of geochronologic, geochemical, and paleomagnetic analyses accompanied by extensive field mapping shows that these lava flows erupted from upland vents 10s of km from the river, entered the canyon via tributary or rim, and formed blockages sufficient to create lakes. Thick deltas of pillow lavas and rising passage zones in the head of the dams and subaerial lavas downstream of the dam indicate effective damming. The presence of fine grained laminated sediments deposited in the lakes suggests the dams were fairly long lived. Pending OSL dates and ongoing field study of these sediments will shed light on the nature and duration of dam construction and removal. Lava-water interaction during dam construction was extensive, and thick pillow lava deltas are common. In contrast to rivers in other locations, we did not find evidence of pyroclastics such as cinders associated with the dams. The three oldest intracanyon lava flows: the lower undivided Bogus lavas (>1.92 ± 0.22 Ma), the Bogus Rim (1.92 ± 0.22 Ma), and the Greeley Bar lavas (>780 ka), all record the filling of a wide, deep canyon, damming of the Owyhee River, and creation of extensive lakes at elevations 230 to 310 m above the modern river. The three younger lava flows, the Clarks Butte (248 ± 45 ka), the Saddle Butte (~125 ka), and the West Crater (60-90 ka), record the occurrence of similar events but in a narrower, deeper canyon similar to the modern one. Overall, this array of late Cenozoic intracanyon lava flows provides key insights into the long-term incision history of the canyon, possibly including the effect of integration with the Snake River, and supports a model of long-term, regional landscape evolution that is strongly linked to lava-water interactions.

  12. Onset and ending of the late Palaeozoic ice age triggered by tectonically paced rock weathering (United States)

    Goddéris, Yves; Donnadieu, Yannick; Carretier, Sébastien; Aretz, Markus; Dera, Guillaume; Macouin, Mélina; Regard, Vincent


    The onset of the late Palaeozoic ice age about 340 million years ago has been attributed to a decrease in atmospheric CO2 concentrations associated with expansion of land plants, as plants both enhance silicate rock weathering--which consumes CO2--and increase the storage of organic carbon on land. However, plant expansion and carbon uptake substantially predate glaciation. Here we use climate and carbon cycle simulations to investigate the potential effects of the uplift of the equatorial Hercynian mountains and the assembly of Pangaea on the late Palaeozoic carbon cycle. In our simulations, mountain uplift during the Late Carboniferous caused an increase in physical weathering that removed the thick soil cover that had inhibited silicate weathering. The resulting increase in chemical weathering was sufficient to cause atmospheric CO2 concentrations to fall below the levels required to initiate glaciation. During the Permian, the lowering of the mountains led to a re-establishment of thick soils, whilst the assembly of Pangaea promoted arid conditions in continental interiors that were unfavourable for silicate weathering. These changes allowed CO2 concentrations to rise to levels sufficient to terminate the glacial event. Based on our simulations, we suggest that tectonically influenced carbon cycle changes during the late Palaeozoic were sufficient to initiate and terminate the late Palaeozoic ice age.

  13. Multistage late Cenozoic evolution of the Amargosa River drainage, southwestern Nevada and eastern California Society of America. All rights reserved (United States)

    Menges, C.M.


    Stratigraphic and geomorphic analyses reveal that the regional drainage basin of the modern Amargosa River formed via multistage linkage of formerly isolated basins in a diachronous series of integration events between late Miocene and latest Pleistocene-Holocene time. The 275-km-long Amargosa River system drains generally southward across a large (15,540 km 2) watershed in southwestern Nevada and eastern California to its terminus in central Death Valley. This drainage basin is divided into four major subbasins along the main channel and several minor subbasins on tributaries; these subbasins contain features, including central valley lowlands surrounded by highlands that form external divides or internal paleodivides, which suggest relict individual physiographic-hydrologic basins. From north to south, the main subbasins along the main channel are: (1) an upper headwaters subbasin, which is deeply incised into mostly Tertiary sediments and volcanic rocks; (2) an unincised low-gradient section within the Amargosa Desert; (3) a mostly incised section centered on Tecopa Valley and tributary drainages; and (4) a west- to northwest-oriented mostly aggrading lower section along the axis of southern Death Valley. Adjoining subbasins are hydro-logically linked by interconnecting narrows or canyon reaches that are variably incised into formerly continuous paleodivides. The most important linkages along the main channel include: (1) the Beatty narrows, which developed across a Tertiary bedrock paleodivide between the upper and Amargosa Desert subbasins during a latest Miocene-early Pliocene to middle Pleistocene interval (ca. 4-0.5 Ma); (2) the Eagle Mountain narrows, which cut into a mostly alluvial paleodivide between the Amar-gosa Desert and Tecopa subbasins in middle to late Pleistocene (ca. 150-100 ka) time; and (3) the Amargosa Canyon, which formed in late middle Pleistocene (ca. 200140 ka) time through a breached, actively uplifting paleodivide between the Tecopa

  14. Late Miocene to recent plate tectonic history of the southern Central America convergent margin (United States)

    Morell, Kristin D.


    New plate reconstructions constrain the tectonic evolution of the subducting Cocos and Nazca plates across the southern Central American subduction zone from late Miocene to recent. Because of the strong relationships between lower and upper (Caribbean) plate dynamics along this margin, these constraints have wide-ranging implications for the timing and growth of upper plate deformation and volcanism in southern Central America. The reconstructions outline three important events in the Neogene history of this margin: (1) the coeval development of the Panama Triple Junction with the initiation of oblique subduction of the Nazca plate at ˜8.5 Ma; (2) the initiation of seamount and rough crust subduction beginning at ˜3-4 Ma; and (3) Cocos Ridge subduction from ˜2 to 3 Ma. A comparison of these events with independent geologic, geomorphic, volcanic, and stratigraphic data sets reveals that the timing, rates, and origin of subducting crust directly impacted the Neogene growth of upper plate deformation and volcanism in southern Central America. These analyses constrain the timing, geometry, and causes of a number of significant tectonic and volcanic processes, including rapid Plio-Quaternary arc-fore arc contraction due to Cocos Ridge subduction, the detachment of the Panama microplate at ˜1-3 Ma, and the late Miocene cessation of mantle-wedge-derived volcanism across ˜300 km of the subduction zone.

  15. Tectonic transition associated with Kazakhstan Orocline in the Late Paleozoic: magmatic archives of western Chinese Tianshan (United States)

    Cai, Keda


    Kazakhstan accretionary system was a principle component of the Central Asian Orogenic Belt (CAOB) that is one of the largest accretionary orogens on earth. The Kazakhstan composite continent could have been established in the Early Paleozoic by the Kazakhstan accretionary system in the form of progressively amalgamations of diverse tectonic units, such as continental ribbon, accretionary prim, oceanic remnant and arc material. Subsequently, the composite continent was bended to form a spectacular U-shaped architecture that probably occurred in the Late Paleozoic. The western Chinese Tianshan is situated on the south wing of the Kazakhstan Orocline, featured by extensive magmatim, intense deformation and voluminous mineralization. Our new geochronological and geochemical data suggest a noticeable magmatic gap between Late Devonian and Early carboniferous and contrasting magma sources of these magmatic rocks. The significant shifts correspond to the tectonic transition from terrane amalgamation to mountain bending in the Early Paleozoic. This study was financially supported by the Major Basic Research Project of the Ministry of Science and Technology of China (2014CB448000), Xinjiang outstanding youth scientific grant (2013711003) and the Talent Awards to KDC from the China Government under the 1000 Talent Plan.

  16. Late Triassic - Early Jurassic successions of the Atuel depocenter: sequence stratigraphy and tectonic controls

    Directory of Open Access Journals (Sweden)

    Silvia Lanés


    Full Text Available Biostratigraphic correlations of the Late Triassic - Early Jurassic successions of the Atuel depocenter allowed determining the accommodation changes and the possible tectonic controls on sedimentation. The Rhaetian - late Early Sinemurian deposits contain facies of slope-type fan deltas, braided fluvial systems and low sinuosity rivers with alternate bars deposited during a synrift phase. The late Early Sinemurian - Toarcian series host facies of intermediate (Gilbert to shelf type fan deltas, braided and low sinuosity fluvial systems, wave-dominated estuaries, transgressive storm-dominated and turbidite-influenced marine shelves which record the sag phase. According to different criteria two stratigraphic schemes are proposed, the first one considering tectosedimentary units (TSU and the second one using "Exxon-like" sequences. In the first scheme the synrift TSU matches the actual Precuyo Mesosequence and the sag TSU is partly equivalent to the Cuyo Mesosequence, mainly keeping the current mesosequence scheme for the Neuquén basin but assigning the fandeltaic deposits to the Precuyo Mesosequence. The second sequence scheme considers the whole Late Triassic - Early Jurassic succession as a part of the Cuyo Mesosequence, where the synrift deposits composes the detached lowstand system tract (LST and most of the sag deposits makes the transgressive system tract (TST. The basal sequence boundary does not crop out, the flooding surface at the TST base and the maximum flooding surface at the TST top are respectively marked by the lowest estuarine levels and by black shales with suboxic-compatible bivalves (Bositra sp..

  17. Paleoecologies and paleoclimates of late cenozoic mammals from Southwest China: Evidence from stable carbon and oxygen isotopes (United States)

    Biasatti, Dana; Wang, Yang; Gao, Feng; Xu, Yingfeng; Flynn, Lawrence


    increased significantly after ˜3.5 Ma. The oxygen isotope results from Yuanmou (Xiaohe Formation) show a positive shift after ˜8.5 Ma, which is similar in timing and magnitude to δ 18O shifts observed in horses and rhinos from the Linxia Basin and in fossils and paleosols from Pakistan and Nepal, suggesting a shift toward a drier climate at the northeast, southeast, and southern borders of the Tibetan Plateau during the late Miocene. Taken together, the carbon and oxygen isotope data indicate a general drying of the local climate over time and a change from a largely dense-forest environment at ˜8 Ma to a more open environment with a mosaic of forests and grasslands after 3-4 Ma in the Yuanmou region. Intra-tooth δ 13C and δ 18O variations within individual fossil teeth from Yuanmou suggest a stronger seasonality of rainfall at ˜1.7 Ma than in the late Miocene. The spatial and temporal δ 13C and δ 18O variations observed in mammalian teeth from Yunnan likely reflect changes in regional climate and/or tectonics, but more data are needed to fully explore the significance of the regional patterns in the δ 18O and δ 13C data in relation to climate and tectonic evolution of the region.

  18. Tectonic control on the Late Quaternary hydrography of the Upper Tiber Basin (Northern Apennines, Italy) (United States)

    Benvenuti, Marco; Bonini, Marco; Moroni, Adriana


    We examine the intramontane Upper Tiber Basin in the Northern Apennines (central Italy), where sub-orthogonal fault systems forced river deviation and the abandonment of alluvial fans since the late Middle Pleistocene. Archaeological material, spanning the Middle Palaeolithic-Iron Age, was collected mostly from the surface of the Late Quaternary alluvial landforms and related deposits (MUP and HOL units). This information contributed to the partial dating of seven major stages of drainage development. Normal faults parallel and transverse to the basin trend were active at different times and conditioned the valley pattern of the Middle (MUP1-2)-Late (MUP3) Pleistocene Tiber, Singerna, Sovara and Tignana rivers, which still flow today into the basin. The MUP1 and the MUP3 fans were beheaded by the displacement of their feeder valleys along the basin-transverse Carmine and Montedoglio faults. In some cases, the former feeder rivers underwent stream piracy but their courses mostly deviated in response of the topographic gradient created by faulting, as well as through the incision of new valleys that exploited the lithological contrast along the fault lines. The MUP3 Tignana fan was abandoned mostly due to the activity of the basin-parallel, dip-slip Sansepolcro fault. Subsidence driven by the basin-parallel Anghiari and Sansepolcro fault systems also provided the accommodation space for the MUP3 and HOl1-2 Afra fans between Late Pleistocene and early-mid Holocene. This study exemplifies the interplay between longitudinal and transverse fault systems, and the Late Quaternary hydrographic evolution of an extensional basin settled in the axial zone of an active fold-and-thrust belt. Although the faulting has interacted with the forcing exerted by the Late Quaternary climate fluctuations on the basin drainage systems, the tectonic rates are sufficiently high to represent the prime controller on base-level change and drainage routing patterns.

  19. Late Mesozoic and Cenozoic thermotectonic evolution of the central Brooks Range and adjacent North Slope foreland basin, Alaska: Including fission track results from the Trans-Alaska Crustal Transect (TACT) (United States)

    O'Sullivan, P. B.; Murphy, J.M.; Blythe, A.E.


    Apatite fission track data are used to evaluate the thermal and tectonic history of the central Brooks Range and the North Slope foreland basin in northern Alaska along the northern leg of the Trans-Alaska Crustal Transect (TACT). Fission track analyses of the detrital apatite grains in most sedimentary units resolve the timing of structures and denudation within the Brooks Range, ranging in scale from the entire mountain range to relatively small-scale folds and faults. Interpretation of the results indicates that rocks exposed within the central Brooks Range cooled rapidly from paleotemperatures 110?? to 50??C during discrete episodes at ???100??5 Ma, ???60??4 Ma, and ???24??3 Ma, probably in response to kilometer-scale denudation. North of the mountain front, rocks in the southern half of the foreland basin were exposed to maximum paleotemperatures 110??C in the Late Cretaceous to early Paleocene as a result of burial by Upper Jurassic and Cretaceous sedimentary rocks. Rapid cooling from these elevated paleotemperatures also occurred due to distinct episodes of kilometer-scale denudation at ???60??4 Ma, 46??3 Ma, 35??2 Ma, and ???24??3 Ma. Combined, the apatite analyses indicate that rocks exposed along the TACT line through the central Brooks Range and foreland basin experienced episodic rapid cooling throughout the Late Cretaceous and Cenozoic in response to at least three distinct kilometer-scale denudation events. Future models explaining orogenic events in northern Alaska must consider these new constraints from fission track thermochronology. Copyright 1997 by the American Geophysical Union.

  20. Late Quaternary tectonic landforms and fluvial aggradation in the Saryu River valley: Central Kumaun Himalaya (United States)

    Kothyari, Girish Ch.; Luirei, Khayingshing


    The present study has been carried out with special emphasis on the aggradational landforms to explain the spatial and temporal variability in phases of aggradation/incision in response to tectonic activity during the late Quaternary in the Saryu River valley in central Kumaun Himalaya. The valley has preserved cut-and-fill terraces with thick alluvial cover, debris flow terraces, and bedrock strath terraces that provide signatures of tectonic activity and climate. Morphostratigraphy of the terraces reveals that the oldest landforms preserved south of the Main Central Thrust, the fluvial modified debris flow terraces, were developed between 30 and 45 ka. The major phase of valley fill is dated between 14 and 22 ka. The youngest phase of aggradation is dated at early and mid-Holocene (9-3 ka). Following this, several phases of accelerated incision/erosion owing to an increase in uplift rate occurred, as evident from the strath terraces. Seven major phases of bedrock incision/uplift have been estimated during 44 ka (3.34 mm/year), 35 ka (1.84 mm/year), 15 ka (0.91 mm/year), 14 ka (0.83 mm/year), 9 ka (1.75 mm/year), 7 ka (5.38 mm/year), and around 3 ka (4.4 mm/year) from the strath terraces near major thrusts. We postulate that between 9 and 3 ka the terrain witnessed relatively enhanced surface uplift (2-5 mm/year).

  1. Late cenozoic evolution of Fortymile Ash: Major change in drainage pattern in the Yucca Mountain, Nevada region during late miocene volcanism

    Energy Technology Data Exchange (ETDEWEB)

    Lundstrom, S.C. [Geological Survey, Las Vegas, NV (United States); Warren, R.G. [Los Alamos National Lab., NM (United States)


    Analysis of sedimentary provenance and altitude distribution of volcanic strata along Fortymile Wash, the primary desert wash east of Yucca Mountain, NV, indicates a major change in surface drainage basins related to late Miocene volcanic disruption. This event resulted in the establishment of the modern Fortymile Wash basin before 3 Ma, and probably by latest Miocene time. An understanding of this event is useful for evaluation of extensive alluviation east of Yucca Mountain and its relation to paleoclimate, hydrology and tectonics. To the northeast of Yucca Mountain, Fortymile Wash provides southward surface drainage from 60% of the area of the 11 Ma Timber Mountain caldera via Fortymile Canyon, a major breach in the caldera wall. In the southeast caldera moat, the distribution of volcanic units that predate and include the 9.4 Ma Thirsty Canyon Group and the characteristics of intercalated sediments indicate a northward paleoslope and sediment transport from a major drainage divide near Dome Mountain, a shield volcano now deeply incised by Fortymile Canyon. Eruption of the Thirsty Canyon Group from the Black Mountain area, 10 km northwest of the Timber Mountain caldera, is likely to have dammed a counterclockwise drainage system of the east moat. Following drainage disruption, the east moat filled with sediment up to the level of a new southward outlet at the saddle between Dome Mountain and the onlapping rhyolite of Shoshone Mountain. An older canyon south of this saddle received the overflow from the east moat and became the throughgoing Fortymile Canyon, integrating the east moat basin with a lower base level in Jackass Flats. Well-integrated southward drainage existed by the time the trachybasalt flows of Buckboard Mesa (2.8 Ma) were emplaced, because basal elevations of these flows slope southward about 100 m above modern Fortymile Wash.

  2. Late Mesozoic crust-mantle interaction and lower crust components in South China: A geochemical study of mafic granulite xenoliths from Cenozoic basalts

    Institute of Scientific and Technical Information of China (English)

    YU; Jinhai; (于津海); XU; Xisheng; (徐夕生); ZHOU; Xinmin; (周新民)


    Mafic granulite xenoliths collected from Cenozoic basalts in SE China can be classified as magmatic granulite and cumulate granulite. Magmatic granulites are characterized by highly concentrated Al2O3, K2O, P2O5, Ba, Sr, Pb and REE, and low contents of Nb, Zr, Hf and Th, and have an incompatible element abundance pattern similar to that of continental arc basalts. Cumulate granulites aredepleted in K2O, P2O5, Rb, Cs and Ba. These granulite xenoliths were the products of crystallization and recrystallization of the basaltic magma underplating into crust-mantle boundary in Late Mesozoic. Sr and Nd isotopic compositions and variation trend of these mafic rocks are the result of crust-mantle mixing and controlled by assimilation and fractional crystallization process (AFC). However,trace element and major element variations were mainly controlled by fractionalcrystallization. The granulites are similar in geochemistry to surface Late Mesozoic gabbro and basalt in the study area, suggesting a close petrogenetic link between them. Late Mesozoic basaltic magma activities are the most important cause for the formation of extensive contemporaneous granite and rhyolite in the study area. This study and previous data indicate that the lower crust beneath South China is composed of a variety of Paleo- to Meso-proterozoic metamorphic rocks and Late Mesozoic mafic granulites.

  3. Tectonic implications for the occurrence of ocean floor, hotspot, and island arc materials within accretionary prisms: Examples from the Mesozoic-Cenozoic NW Pacific Rim (United States)

    Ogawa, Y.; Hirano, N.; Hirano, N.; Taniguchi, H.; Taniguchi, H.; Taniguchi, H.


    On-land Mesozoic-Cenozoic accretionary prisms exposed in Japan commonly have basaltic rocks incorporated as blocks into melanges or fault zones during a prolonged history of subduction and/or obduction. Chemical signatures of these basaltic rocks and their mode of occurrence with sedimentary covers and/or associated sedimentary rocks indicate that most of these isolated small basaltic blocks consistently display a WPB chemistry, whereas large slabs of basaltic rocks around the Izu Arc collision zone show MORB chemistry with rare examples of IAT, BABB, and/or WPB affinities. Comparing with the present uniformitarian examples of convergent plate boundaries in the western Pacific that we know through the DSDP and ODP projects and submersible and seismic surveys, we can interpret some of the basaltic material with WPB affinity in the Japanese accretionary prisms as relict edifices of seamounts with hotspot origin. These hotspot-related basaltic rocks are commonly associated with reefal limestones and were incorporated into continental margin melanges either by submarine sliding from the downgoing oceanic plate or by shallow-level offscraping along decollement surfaces during the subduction of oceanic plates. Older, uplifted parts of the fossil accretionary prisms on the continent side further inward from the trench where the deeper levels of accreted material are exposed include larger amounts of basaltic blocks. This observation suggests that significant amount of underplating might have occurred in the deeper levels of oceanic crust along decollement zones at structurally lower depths. The metamorphic belts (e.g.Sambagawa, Chichibu, Shimanto etc.) have commonly alkaline rocks or plateau-type E-MORB basalts without any trace of N-MORB rocks with rare special exceptions. Besides these ordinary accretionary prism examples formed by a simple plate subduction system, another type of accretion resulting from island arc or ridge collision is observed to have occurred in

  4. 库鲁克塔格南部山前带中-新生代构造演化史--来自磷灰石裂变径迹的证据%Meso-Cenozoic Tectonic Evolution History in the Southern Piedmont Zone of Kuruktag---the Evidence Taken from Apatite Fission Track

    Institute of Scientific and Technical Information of China (English)

    刘阵; 张洪美; 何金有; 何登发; 温佳霖; 马渭; 王永飞


    Based on analysis of apatite fission track data and thermal history modeling, and combined with field geological survey, the Meso—Cenozoic tectonic evolution history in the southern piedmont zone of Kuruktag has been studied. Results showed that the formation had the characteristics of keeping the Kelatong attitude from Kuruktag uplift to the southern pied-mont direction. The age of apatite in the southern piedmont zone of Kuruktag recorded the two tectonic cooling events in 182Ma and 167—142 Ma, and the simulation of fission track thermal history indicated that Hercynian tectonic uplifted, Early—Middle Jurassic formation descended, Late Jurassic—Early Cretaceous tectonic uplifted, and Late Cenozoic tectonic uplifted, etc. Comprehensive study showed that the southern piedmont zone had been affected commonly by the early tec-tonic uplift that created in Hercynian and Yanshan movement, the Himalaya movement mainly caused the strong thrust at the upper part of fault. From the viewpoint of deposition, the deposition center of early—middle Jurassic is located in the ancient position of Queerqueke mountain.%通过对磷灰石裂变径迹数据的分析和热史模拟,结合野外地质调查,研究了库鲁克塔格南部山前带中—新生代构造演化史。结果显示,从库鲁克塔格隆起到南部山前带方向,地层具有稳定克拉通地层产状的特征。库鲁克塔格南部山前带磷灰石年龄记录了182Ma和167—142Ma两期构造冷却事件,裂变径迹热史模拟反映出海西期构造抬升、早—中侏罗世埋藏沉降、晚侏罗世—白垩纪初构造抬升和新生代晚期构造抬升等演化阶段。综合研究表明,南部山前带普遍受到海西期和燕山运动早期构造抬升的影响,喜马拉雅运动主要造成了研究区断裂上盘的强烈逆冲推覆;早—中侏罗世埋藏沉降阶段,从沉积角度看,沉积中心位于却尔却克山所在的古位置。

  5. Segmentation of the eastern North Greenland oblique-shear margin – regional plate tectonic implications

    DEFF Research Database (Denmark)

    Andreasen, Arne Døssing; Stemmerik, Lars; Dahl-Jensen, T.


    a highly complex, Paleozoic–early Cenozoic pre-opening setting. However, due to extreme ice conditions, very little is known about the offshore areas seawards of – and between – the peninsulas. Consequently, prevailing structural-tectonic models of the margin tend to be significantly oversimplified...... and inadequate. We present the first, combined onshore–offshore, model of the margin integrating onshore outcrops with potential field data, new offshore seismic reflection data and receiver-function analysis of seismic broad band data. The results reveal a margin which is far more complex than previously...... anticipated. In particular, we interpret strong margin segmentation along N/NE-striking fault structures. The structures are likely to have formed by Late Mesozoic–early Cenozoic strike-slip tectonics and have continued to be active during the late Cenozoic. A more than 8 km deep sedimentary basin...

  6. Cenozoic tectonics in the Buruanga Peninsula, Panay Island, Central Philippines, as constrained by U-Pb, 40Ar/39Ar and fission track thermochronometers (United States)

    Walia, M.; Yang, T. F.; Knittel, U.; Liu, T.-K.; Lo, C.-H.; Chung, S.-L.; Teng, L. S.; Dimalanta, C. B.; Yumul, G. P.; Yuan, W. M.


    Buruanga Peninsula forms the westernmost part of Panay Island, Central Philippines and is a part of the Palawan Continental Terrane (PCT), which was formerly attached to south-eastern China. It acted as the leading edge of the continental fragment and collided with the Philippine Mobile Belt (PMB) followed by convergence beneath the latter. Dating of the collision is crucial for understanding the evolution of the archipelago. Samples collected from Buruanga Peninsula were dated using U-Pb, 40Ar/39Ar and fission track dating (FTD) techniques to constrain the timing of the tectonic events related to the collision of the PMB with the PCT. These techniques have enabled us to obtain ages over a range of closure temperatures from about 700 °C to about 110 °C. Paleoproterozoic and Permian zircon U-Pb ages from Saboncogon Formation emphasize derivation of the western part of Buruanga Peninsula from SE China; zircon and apatite fission track ages of 51 Ma and 16 Ma, respectively, constrain the exhumation of this formation. The age data suggest tectonic events at ~ 14 Ma, ~ 11-12 Ma and about 7-8 Ma following intrusive activity at about 18 Ma. Uplift and exhumation at ~ 14 Ma are thought to be the result of subduction of low-density crustal rocks, at 11 Ma to be the result of isostatic uplift as a consequence of crustal thickening and at ~ 8 Ma to be due to the isostatic re-equilibration of the sediments overlying the former suture. Hence, collision is constrained to have started at about 14-15 Ma and to have ended before 8 Ma. Multi-element patterns of the 18 Ma Patria-Diorite from Buruanga Peninsula show enrichment in LILE (Rb, Sr, and K) and LREE and depletion in HFSE elements (Ti, Nb, and Ta) similar to those from Luzon volcanics and the volcanic rocks of Negros Island. These arc-signatures indicate a subduction related environment for the emplacement of this intrusive body and show that the diorite belongs to the PMB. The age constraints of the present study neither

  7. Tectonic, magmatic, and metallogenic evolution of the Late Cretaceous arc in the Carpathian-Balkan orogen (United States)

    Gallhofer, Daniela; Quadt, Albrecht von; Peytcheva, Irena; Schmid, Stefan M.; Heinrich, Christoph A.


    The Apuseni-Banat-Timok-Srednogorie Late Cretaceous magmatic arc in the Carpathian-Balkan orogen formed on the European margin during closure of the Neotethys Ocean. It was subsequently deformed into a complex orocline by continental collisions. The Cu-Au mineralized arc consists of geologically distinct segments: the Apuseni, Banat, Timok, Panagyurishte, and Eastern Srednogorie segments. New U-Pb zircon ages and geochemical whole rock data for the Banat and Apuseni segments are combined with previously published data to reconstruct the original arc geometry and better constrain its tectonic evolution. Trace element and isotopic signatures of the arc magmas indicate a subduction-enriched source in all segments and variable contamination by continental crust. The magmatic arc was active for 25 Myr (~92-67 Ma). Across-arc age trends of progressively younger ages toward the inferred paleo-trench indicate gradual steepening of the subducting slab away from the upper plate European margin. This leads to asthenospheric corner flow in the overriding plate, which is recorded by decreasing 87Sr/86Sr (0.70577 to 0.70373) and increasing 143Nd/144Nd (0.51234 to 0.51264) ratios over time in some segments. The close spatial relationship between arc magmatism, large-scale shear zones, and related strike-slip sedimentary basins in the Timok and Pangyurishte segments indicates mild transtension in these central segments of the restored arc. In contrast, the Eastern Srednogorie segment underwent strong orthogonal intraarc extension. Segmental distribution of tectonic stress may account for the concentration of rich porphyry Cu deposits in the transtensional segments, where lower crustal magma storage and fractionation favored the evolution of volatile-rich magmas.

  8. Magnetostratigraphy of the late Cenozoic Laojunmiao anticline in the northern Qilian Mountains and its implications for the northern Tibetan Plateau uplift

    Institute of Scientific and Technical Information of China (English)

    FANG; Xiaomin; ZHAO; Zhijun; LI; Jijun; YAN; Maodu; PAN; Ba


    Cenozoic sediments in the foreland basin--Jiuquan Basin in west Hexi Corridor recorded tectonic uplift information of the Qilian Mountains. High resolution paleomagnetic dating of the Laojunmiao (LJM) section across the central LJM anticline in the southern Jiuquan Basin reveals ages of the Getanggou Member, Niugetao Member in the Shulehe Formation, the Yumen Conglomerate, Jiuquan Conglomerate and Gobi Formation at >13-8.3 Ma, 8.3-4.9 Ma, 3.66-0.93 Ma, 0.84-0.14 Ma and 0.14-0 Ma, respectively. Sedimentary evolution study suggests that the Qilian Mountains should begin to rise gradually since ~8-6.6 Ma, accompanied by sedimentary environments changing from lacustrine mudstones-sandstones to alluvial conglomerates. Rapid uplift of the Qilian Mountains began at ~3.66 Ma, followed by a series of stepwise or intermittent intensive uplifts at about <1.8-1.23 Ma, 0.93-0.84 Ma and 0.14 Ma, which finally resulted in the present high Qilian Mountains.

  9. The Cenozoic volcanism in the Kivu rift: Assessment of the tectonic setting, geochemistry, and geochronology of the volcanic activity in the South-Kivu and Virunga regions (United States)

    Pouclet, A.; Bellon, H.; Bram, K.


    The Kivu rift is part of the western branch of the East African Rift system. From Lake Tanganyika to Lake Albert, the Kivu rift is set in a succession of Precambrian zones of weakness trending NW-SE, NNE-SSW and NE-SW. At the NW to NNE turn of the rift direction in the Lake Kivu area, the inherited faults are crosscut by newly born N-S fractures which developed during the late Cenozoic rifting and controlled the volcanic activity. From Lake Kivu to Lake Edward, the N-S faults show a right-lateral en echelon pattern. Development of tension gashes in the Virunga area indicates a clockwise rotation of the constraint linked to dextral oblique motion of crustal blocks. The extensional direction was W-E in the Mio-Pliocene and ENE-WSW in the Pleistocene to present time. The volcanic rocks are assigned to three groups: (1) tholeiites and sodic alkali basalts in the South-Kivu, (2) sodic basalts and nephelinites in the northern Lake Kivu and western Virunga, and (3) potassic basanites and potassic nephelinites in the Virunga area. South-Kivu magmas were generated by melting of spinel + garnet lherzolite from two sources: an enriched lithospheric source and a less enriched mixed lithospheric and asthenospheric source. The latter source was implied in the genesis of the tholeiitic lavas at the beginning of the South-Kivu tectono-volcanic activity, in relationships with asthenosphere upwelling. The ensuing outpouring of alkaline basaltic lavas from the lithospheric source attests for the abortion of the asthenospheric contribution and a change of the rifting process. The sodic nephelinites of the northern Lake Kivu originated from low partial melting of garnet peridotite of the sub-continental mantle due to pressure release during swell initiation. The Virunga potassic magmas resulted from the melting of garnet peridotite with an increasing degree of melting from nephelinite to basanite. They originated from a lithospheric source enriched in both K and Rb, suggesting the

  10. The role of tectonics and climate in the late Quaternary evolution of a northern Amazonian River (United States)

    Cremon, Édipo Henrique; Rossetti, Dilce de Fátima; Sawakuchi, André de Oliveira; Cohen, Marcelo Cancela Lisboa


    The Amazon basin has most of the largest rivers of the world. However, works focusing the geological evolution of the trunk river or its tributaries have been only partly approached. The Branco River constitutes one of the main northern Amazonian tributaries. A previous work proposed that, before flowing southward into the Negro-Amazon Rivers, the Branco River had a southwest to northeast course into the Caribbean Sea. The present work aimed to establish if the proposed change in the course of this river is supported by morphological and sedimentological data. Other goals were to discuss the factors influencing river development and establish its evolution over time within the chronological framework provided by radiocarbon and optically stimulated luminescence dating. The work considered the entire course of the Branco River downstream of the Precambrian Guiana Shield, where the river presumably did not exist in ancient times. The river valley is incised into fluvial sedimentary units displaying ages between 100 and 250 ky old, which record active and abandoned channels, crevasse splay/levees, and point bars. The sedimentary deposits in the valley include two alluvial plain units as old as 18.7 ky and which intersects a Late Pleistocene residual megafan. These characteristics suggest that a long segment of the Branco River was established only a few thousand years ago. Together with several structural anomalies, these data are consistent with a mega-capture at the middle reach of this river due to tectonic reactivation in the Late Pleistocene. This integrated approach can be applied to other Amazonian tributaries to unravel how and when the Amazonian drainage basin became established.

  11. Cenozoic lithospheric evolution of the Bohai Bay Basin, eastern North China Craton: Constraint from tectono-thermal modeling (United States)

    Liu, Qiongying; He, Lijuan; Huang, Fang; Zhang, Linyou


    It is well established that the lithosphere beneath the eastern North China Craton (NCC) had been thinned before the Cenozoic. A 2D multi-phase extension model, in which the initial crustal and lithospheric thicknesses are variable, is presented to reconstruct the initial thicknesses of the crust and lithosphere in the early Cenozoic and to further investigate the lithospheric evolution beneath the eastern NCC through the Cenozoic. We conduct thermal modeling along three profiles from east to west in the Bohai Bay Basin, which is the center of the lithospheric destruction and thinning of the NCC. Using multiple constraints, such as tectonic subsidence, the present-day heat flow and the Moho depth, we determine the initial crustal and lithospheric thicknesses of the Bohai Bay Basin before the Cenozoic rift to be 33-36 km and 80-105 km, respectively. The model results show that the most rapid lithospheric thinning during the Cenozoic occurred in the middle Eocene for most depressions, and the thinning activity ceased at the end of the Oligocene, reaching a minimum lithospheric thickness of 53-74 km, followed by a thermal relaxation phase. Combined with previous studies, we infer that the lithosphere beneath the eastern NCC experienced two stages of alternating thinning and thickening: notable thinning in the Early Cretaceous and Paleogene, and thickening in the Late Cretaceous and late Cenozoic. We believe that thermo-chemical erosion, together with extension, was probably the major mechanism of the significant lithospheric removal during the Mesozoic, whereas the Cenozoic lithospheric thinning was mainly dominated by tectonic extension in the eastern NCC; lithospheric thickening was generally a result of thermal cooling.

  12. The epilog of the western paleo-Pacific subduction: Inferred from spatial and temporal variations and geochemistry of the Late Cretaceous to Early Cenozoic silicic magmatism in coastal South China (United States)

    Chen, Cheng-Hong; Lee, Chi-Yu; Shinjo, Ryuichi


    The Late Cretaceous to Early Cenozoic magmatism in the South China coastal area produced some amounts of rhyolitic rocks in two phases, which may be used to unravel the geohistory of the epilog of the paleo-Pacific plate subduction system. Essence of the Phase I rocks is the high temperature rhyolite (A-type)-trachydacite association in north Fujian (95-91 Ma) that was coeval with regional A-type granites. They succeeded the vast rhyolite-dacite-andesite (RDA) associations and I-type granitoids (113.5-96 Ma) and preceded the silicic-dominating rhyolite/basalt bimodal suites or monolithologic rhyolite in Zhejiang (89-86 Ma). Phase II rocks include (a) the RDA association or rhyolite alone in some drifted continental fragments nearby (83-56 Ma) and (b) the following rift-basin related rhyolite-trachyte/basalt bimodal suites in Guangdong and west Taiwan (56-38 Ma). The silicic volcanism, spatially changed from a NE-SW to the nearly E-W direction after 83 Ma, may reflect tectonic-driven eruptions occurred in the post-orogenic extensional (Phase I), resumed plate subducting (Phase IIa) and continental margin rifting (Phase IIb) stages. Rhyolitic rocks basically are shoshonitic to high-K calc-alkaline affinities while the Phase IIa RDA associations are mostly concentrated in the high-K to medium-K calc-alkaline series. All these rocks generally possess a continental arc character in tectonic discrimination diagrams, except shoshonitic rocks that have within-plate signatures. Based on the trace element and Nd-Pb isotope data, A-type rocks are suggested to have derived from mixing between trachydacitic (or syenitic) magmas and crustal melts of various sources under the high temperature condition (±metasomatism), and the succeeding silicic rocks are derivatives of the contaminated lithospheric mantle melts through crystal fractionation. On the other hand, Phase II silicic rocks are mainly the fractionation products of mafic magmas originated either from the lithospheric or

  13. Tectonic evolvement of metamorphic complexes at Jilin paleocontinental margin during the transition from late Archaean to early Proterozoic

    Institute of Scientific and Technical Information of China (English)

    SUN Zhongshi; DENG Jun; JIANG Yanguo; WANG Jianping; WANG Qingfei; WEI Yanguang


    The kinematics and dynamical process of tectonic evolvement of metamorphic complexes at the interim from late Archaean to early Proterozoic is one of the key problems in geosciences. For the disputation on the genesis of metamorphic complexes at the margin of Jilin palaeocontinent, this paper takes the example of Banshigou region, Jilin Province to discuss the dynamical evolution of palaeocontinent during the transition from late Archaean to early Proterozoic (2600-2000 Ma). On the time sequence, from center to palaeocontinental margin, it shows a series of dynamical movements including underplating, horizontal movement, subduction, intraplate extension and separation. And its corresponding sequence of kinematical modes is as follows: vertical movement, horizontal movement, extension and shearing in contact zone,uplift-sliding movement in paleocontinental margin and interformational sliding, resulting in such tectonite sequence, tectonic gneiss, gneissic complex, gneissic complex-mylonite, mylonite and fracture cleavage-mylonite, which consist of the main body of metamorphic complexes. Their palaeostresses are: < 20, 20.40, 21.72, 28.80 and 30.8-69.8 MPa respectively. The deformational metamorphic temperature is between hornblende and low-grade greenschist facies. The general deformational characters of Jilin palaeocontinent reflect a complete dynamic system of crust evolution, which indicates that the formation of the metamorphic complexes and the tectonic evolution are altered from vertical movement to compression to extension. It also indicates a continuous tectonic transformation from deep to shallow, and from ductile to brittle. The transformation between different dynamic mechanisms not only forms tectonic rocks, but also benefits the linking up, exchange and enrichment with rock-forming minerals and ore-forming elements.This research is helpful to classifying regional tectonic events and making further study on the evolution of palaeocontinental dynamics.

  14. Synthesis of Late Cretaceous-Quaternary tectonic, sedimentary and magmatic processes and basin formation related to episodic subduction-collision in the easternmost Mediterranean region (United States)

    Robertson, Alastair; Kinnaird, Timothy; McCay, Gillian; Palamakumbura, Romesh; Taslı, Kemal


    Mesozoic oceanic crust of the easternmost Mediterranean has experienced northwards subduction during Late Cretaceous-Cenozoic, either continuously or discontinuously based on kinematic evidence. Much of the existing information on sedimentation within the easternmost Mediterranean oceanic basin comes from the non-emplaced continental margins of the Levant and North Africa. In addition, sedimentary basins related to plate convergence are recorded along the northern margin of the Southern Neotethyan ocean, mainly in the Kyrenia Range of northern Cyprus and its extension into the Misis Mountains of southern Turkey, coupled with the adjacent submerged areas. In a setting of only incipient continental collision such as the easternmost Mediterranean the sedimentary basins would be expected to remain entirely submarine. In contrast, the Kyrenia Range has been strongly uplifted and subaerially exposed during Late Pliocene-Quaternary time. This allows the recognition of a number of discrete phases of sedimentary basin formation: 1. Late Cretaceous (Campanian-Maastrichtian): silicic volcanism to create a subaqueous volcaniclastic apron; 2. Maastrichtian-Paleocene: pelagic carbonate deposition interspersed with proximal gravity flows and within-plate type alkaline volcanics; 3. Early Eocene: large-scale sedimentary melange (olistostrome) emplacement; 4. Late Eocene-Late Miocene: terrigenous gravity-flow deposition in a deep-water fault dissected 'fore arc' setting. Initial, Late Eocene non-marine coarse clastic alluvial fan deposition was succeeded by Oligocene-Miocene deep-marine siliciclastic gravity flow deposits, fining and shallowing upwards during the Late Miocene; 5. Messinian: localised precipitation of evaporites in small fault-controlled basins; 6. Pliocene: shallow-marine siliciclastic-carbonate deposition in a shelf-depth, overall regressive setting; 7. Latest Pliocene to mid-Pleistocene: gravitational accumulation of coarse talus along a strongly uplifting

  15. Detrital zircon and apatite fission track data in the Liaoxi basins: Implication to Meso-Cenozoic thermo-tectonic evolution of the northern margin of the North China Craton

    Indian Academy of Sciences (India)

    Yi Yan; Xiaoqiong Hu; Ge Lin; Weiliang Liu; Zhengjiang Song


    Detrital zircon and apatite fission track (ZFT and AFT) data of the sandstones collected from the Liaoxi basins served as a significant probe to study the Meso-Cenozoic thermo-tectonic reactivation events in the northern margin of the North China Craton. All sandstones show wide ZFT and AFT age spectrum and most of ZFT and AFT ages are younger than depositional age of respective host rocks, which suggest widespread track resetting of the host rocks in the Liaoxi basins after deposition. This hot geothermal status in the Liaoxi basins deduced from ZFT and AFT data is temporal consistent with the lithospheric evolution of the North China Craton, which implies that the lithosphere under the northern margin of the North China Craton underwent similar thermo-tectonic destruction process as the intracratonic Bohai Sea. The young ZFT peak age, which ranges from ∼50Ma to 20 Ma, to some extend, provides a temporal constraint on the time that lithosphere significantly thinned and following reverse of the Liaoxi basins and uplift of the eastern part of the Yan-Liao Orogenic Belt. Exhumation of 1.5–2 km can be estimated in the eastern part of the Yan-Liao Orogenic Belt since ∼30Ma to 10 Ma.

  16. The Cenozoic tectonic evolution of the west Qinling: Constraints on the uplift and deformation of the Tibetan Plateau%西秦岭新生代以来地质构造过程对青藏高原隆升和变形的约束

    Institute of Scientific and Technical Information of China (English)

    郭进京; 韩文峰; 李雪峰


    The Cenozoic tectonic and geomorphological processes of the west Qinling as a part of Qinghai - Tibetan plateau could provide some constraints on the uplift and deformation model of the Qinghai - Tibetan plateau. Based on the analysis of the Cenozoic sedimentary strata and its deformation features, regional fault framework and its kinematics, and geomorphological records, we could reach the following preliminary understanding. (1) Based on their rock composition, spatial distribution and tectonic deformation characteristics, we can divide the Late Mesozoic - Cenozoic red bed sedimentary strata in the west Qinling into the Late Jurassic - Early Cretaceous, the Late Cretaceous - Paleogene and the Neogene three tectonic strata units, which corresponds to three tectonic evolution stages. (2)The fault-thrusting and fold-shortening of K_2-E strata in the west Qinling occurred at the end of Eocene, synchronous with the crust shortening and thrusting in the Qinghai - Tibetan plateau, which may indicate that the compressive tectonic stress from the collisional convergence between the India plate and the Eurasia plate have been transmitted to the west Qinling. (3)The west Qinling had undergone a relatively tectonic stable period since the Neogene, in which extensive erosion and planation occurred, and finally main planation surface and associated Neogene sedimentary strata consisting of red conglomerate and red clay were formed before 3.6 Ma. This planation surface at present-day decreased gradually from 3200 m in the west to 1200 m in the east, which can be interpreted as continuous uplift in the eastward expansion of the Qinghai - Tibetan plateau. (4) The structural deformation transition from thrusting-shortening to extension-strike slip at 13 - 14 Ma or 8 Ma in the south Tibet have not appeared widely in the west Qinling, whereas fault thrusting predominated the total Cenozoic tectonic history and left-lateral strike-slip only occurred in the northern boundary fault of

  17. New paleomagnetic data from late Paleozoic sedimentary rocks of Novaya Zemlya Archipelago: tectonic implications (United States)

    Abashev, Victor V.; Metelkin, Dmitry V.; Mikhaltsov, Nikolay E.; Vernikovsky, Valery A.; Matushkin, Nikolay Yu.


    New paleomagnetic data for Novaya Zemlya archipelago were obtained by processing the samples collection gathered during the 2014 field season. The paleomagnetic directions and paleomagnetic poles were determined from the Paleozoic sedimentary complexes located on the Southern Island (Upper Permian) and the Northern Island (Lower and Upper Devonian, Upper Carboniferous) of the archipelago. Positive fold and reversal tests indicate that the isolated paleomagnetic directions correspond to the primary magnetization components. The corresponding paleomagnetic pole are in good agreement with poles obtained earlier in the 1980s by E.L. Gurevich and I.A. Pogarskaya. Considering the confidence ovals, the paleomagnetic poles obtained for the sites of the Northern Island are located close to the corresponding path segment of the APWP of Europe. This means that at least since the early Devonian, the northern part of Novaya Zemlya Archipelago had a position that was close to its current position relatively to the Arctic margin of Europe and has not undergone significant shifts or rotations. However, the upper Permian paleomagnetic pole for the Southern Island is very different from the corresponding part of the European APWP. We are considering this pole position within a model, involving significant intraplate movement between the structures of the European and Siberian tectonic provinces until the Late Cretaceous. The sinistral strike-slips inferred by the model could have caused or were accompanying the opening of the Mesozoic rift system in Western Siberia. This event has reached its maximum within the South Kara basin and resulted in the north-westward (in geographic coordinates) displacement of the southern part of the Novaya Zemlya Archipelago in relation to the Arctic margin of Europe and in the deformation of the Pay-Khoy-Novaya Zemlya margin, which caused its modern curved form. The study was supported by the Russian Science Foundation, grant No. 14-37-00030 and the

  18. Late Cenozoic Chemical Weathering and Environmental Changes Recorded in the Co Ngoin Sediments, Central Qinghai-Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    CHEN Shiyue; JIN Zhangdong; WANG Sumin; SHEN Ji


    A series of faulted inland basins were developed in the central Qinghai-Tibet Plateau, among which the Co Ngoin Basin containing thick lacustrine sediments is located in the peripheral area of the Indian monsoon. In this paper, we present the weathering history and paleoclimatic changes in the last 2.8 Ma based on studies of high-resolution temporal distributions of Sr, Rb and Zr concentrations, Rb/Sr and Zr/Rb ratios and δ 13C and TOC for the Co Ngoin sediments, in combination with the sediment properties, grain size distribution and clay mineralogy. The sedimentary records indicate three environmental stages in the last 2.8 Ma. At the core depth of 197-170 m (about 2.8-2.5 Ma), low-intensity chemical weathering in the Co Ngoin catchment was experienced under warm-dry to cool-wet climate conditions with relatively low Sr concentration and high Rb/Sr and Zr/Rb ratios. The sudden occurrence of both subalpine coniferous forest and coarse sand and gravel sediments in the Co Ngoin core reflects a strong tectonic uplift. The high Sr concentrations and low Rb/Sr and Zr/Rb ratios reflect a relatively strong chemical weathering between 2.5 Ma and 0.8 Ma (at the core depth of 170-38.5m) under a temperate/cool and wet climate, characterized by mud and silt with fine sand, probably indicating a stable process of denudation and planation of the plateau. Above the depth of 38.5 m (about 0.8-0 Ma), the coarsening of sediments indicates a strong tectonic uplift and a relatively low intensity of chemical weathering as supported by the record of sediments having relatively low Sr concentrations and high Rb/Sr and Zr/Rb ratios. Since then, the plateau has taken the shape of the modern topographic pattern above 4000 m a.s.1.

  19. Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 2. Implications for magma production rates and subduction erosion (United States)

    Schindlbeck, J. C.; Kutterolf, S.; Freundt, A.; Straub, S. M.; Vannucchi, P.; Alvarado, G. E.


    Pacific drill sites offshore Central America provide the unique opportunity to study the evolution of large explosive volcanism and the geotectonic evolution of the continental margin back into the Neogene. The temporal distribution of tephra layers established by tephrochonostratigraphy in Part 1 indicates a nearly continuous highly explosive eruption record for the Costa Rican and the Nicaraguan volcanic arc within the last 8 Myr. The widely distributed marine tephra layers comprise the major fraction of the respective erupted tephra volumes and masses thus providing insights into regional and temporal variations of large-magnitude explosive eruptions along the southern Central American Volcanic Arc (CAVA). We observe three pulses of enhanced explosive volcanism between 0 and 1 Ma at the Cordillera Central, between 1 and 2 Ma at the Guanacaste and at >3 Ma at the Western Nicaragua segments. Averaged over the long-term the minimum erupted magma flux (per unit arc length) is ˜0.017 g/ms. Tephra ages, constrained by Ar-Ar dating and by correlation with dated terrestrial tephras, yield time-variable accumulation rates of the intercalated pelagic sediments with four prominent phases of peak sedimentation rates that relate to tectonic processes of subduction erosion. The peak rate at >2.3 Ma near Osa particularly relates to initial Cocos Ridge subduction which began at 2.91 ± 0.23 Ma as inferred by the 1.5 Myr delayed appearance of the OIB geochemical signal in tephras from Barva volcano at 1.42 Ma. Subsequent tectonic re-arrangements probably involved crustal extension on the Guanacaste segment that favored the 2-1 Ma period of unusually massive rhyolite production.

  20. Block and shear-zone architecture of the Minnesota River Valley subprovince: Implications for late Archean accretionary tectonics (United States)

    Southwick, D.L.; Chandler, V.W.


    The Minnesota River Valley subprovince of the Superior Province is an Archean gneiss terrane composed internally of four crustal blocks bounded by three zones of east-northeast-trending linear geophysical anomalies. Two of the block-bounding zones are verified regional-scale shears. The geological nature of the third boundary has not been established. Potential-field geophysical models portray the boundary zones as moderately north-dipping surfaces or thin slabs similar in strike and dip to the Morris fault segment of the Great Lakes tectonic zone at the north margin of the subprovince. The central two blocks of the subprovince (Morton and Montevideo) are predominantly high-grade quartzofeldspathic gneiss, some as old as 3.6 Ga, and late-tectonic granite. The northern and southern blocks (Benson and Jeffers, respectively) are judged to contain less gneiss than the central blocks and a larger diversity of syntectonic and late-tectonic plutons. A belt of moderately metamorphosed mafic and ultramafic rocks having some attributes of a dismembered ophiolite is partly within the boundary zone between the Morton and Montevideo blocks. This and the other block boundaries are interpreted as late Archean structures that were reactivated in the Early Proterozoic. The Minnesota River Valley subprovince is interpreted as a late accretionary addition to the Superior Province. Because it was continental crust, it was not subductible when it impinged on the convergent southern margin of the Superior Craton in late Archean time, and it may have accommodated to convergent-margin stresses by dividing into blocks and shear zones capable of independent movement.

  1. Late stage thermal history of the Songliao Basin and its tectonic implications: Evidence from apatite fission track (AFT) analyses

    Institute of Scientific and Technical Information of China (English)


    Apatite Fission Track (AFT) data from the Songliao Basin indicates that the late stage tectonic movements in the Songliao Basin have zoning in space and episodes in time. The late stage tectonic movements started from the east part of the basin and migrated westward. AFT ages in the east part of the basin are older than those in the west part of the basin, suggesting that the uplift occurred earlier in the east than in the west. The denudation thickness in the east part of the basin is significantly greater than that in the centre and west. The thermal history evolved two episodes of rapid cooling and subsequent slow cooling processes. Age-depth relationship derived from the AFT data indicates a four-episode denudation history. Further Monte Carlo random simulation of the AFT data reveals the four changing points of the thermal evolution at 65 Ma, 43.5 Ma, 28 Ma and 15 Ma, respectively. The uplifting and denudation rates from different episodes of evolution are proportional to the plate convergence rate. Based on the above analyses and the regional geologic background, it is concluded that the late stage thermal events in the Songliao Basin are the far field response to the subduction of the Pacific Plate under the Eurasian Plate. The first episode of the rapid cooling probably started at the end of the Nenjiang Formation, climaxed at the end of the Cretaceous and ceased at the Late Eocene. The subsequent slow cooling lasts another 15 Ma. The first episode of the evolution is the far field response to the major episode of the Yanshan Movement and subsequent series of the tectonic reorganization, especially the directional change of the Pacific Movement and also the subduction of the Indian Plate underneath the Eurasian Plate. While the second episode of the evolution is the far field response to the extension and closure of the Sea of Japan. Extension led to the migration and converging of the mantle heat flow to the Sea of Japan and resulted in the rapid cooling

  2. Formation and evolution of yardangs activated by Late Pleistocene tectonic movement in Dunhuang, Gansu Province of China (United States)

    Wang, Yanjie; Wu, Fadong; Zhang, Xujiao; Zeng, Peng; Ma, Pengfei; Song, Yuping; Chu, Hao


    Developed in the Anxi-Dunhuang basin, the yardangs of Dunhuang (western China) are clearly affected by tectonic movement. Based on fieldwork, this study ascertained three levels of river terrace in the area for the first time. Through the analysis of river terraces formation and regional tectonic movement, the study ascertained that the river terraces were formed mainly by Late Pleistocene tectonic uplift, which had activated the evolution of yardangs in the study area. By electron spin resonance (ESR) dating and optically stimulated luminescence (OSL) dating, the starting time and periodicity of the evolution of the yardangs were determined. The river terraces designated T3, T2 and T1 began to evolve at 109.0 ˜98.5, 72.9 ˜66.84 and 53.2 ˜38.0 kaBP, respectively, which is the evidence of regional neotectonic movement. And, the formation of the yardangs was dominated by tectonic uplift during the prenatal stage and mainly by wind erosion in the following evolution, with relatively short stationary phases. This research focused on the determination of endogenic processes of yardangs formation, which would contribute to further understanding of yardangs formation from a geological perspective and promote further study of yardang landform.

  3. Formation and evolution of yardangs activated by Late Pleistocene tectonic movement in Dunhuang, Gansu Province of China

    Indian Academy of Sciences (India)

    Yanjie Wang; Fadong Wu; Xujiao Zhang; Peng Zeng; Pengfei Ma; Yuping Song; Hao Chu


    Developed in the Anxi-Dunhuang basin, the yardangs of Dunhuang (western China) are clearly affected by tectonic movement. Based on fieldwork, this study ascertained three levels of river terrace in the area for the first time. Through the analysis of river terraces formation and regional tectonic movement, the study ascertained that the river terraces were formed mainly by Late Pleistocene tectonic uplift, which had activated the evolution of yardangs in the study area. By electron spin resonance (ESR) dating and optically stimulated luminescence (OSL) dating, the starting time and periodicity of the evolution of the yardangs were determined. The river terraces designated T3, T2 and T1 began to evolve at 109.0∼98.5, 72.9∼66.84 and 53.2∼38.0 kaBP, respectively, which is the evidence of regional neotectonic movement.And, the formation of the yardangs was dominated by tectonic uplift during the prenatal stage and mainly by wind erosion in the following evolution, with relatively short stationary phases. This research focused on the determination of endogenic processes of yardangs formation, which would contribute to further understanding of yardangs formation from a geological perspective and promote further study of yardang landform.

  4. 山西晚新生代古地理环境变迁与新构造运动响应%Evolution of Late Cenozoic Geography and Environment in Shanxi Province and the Neotectonic Response

    Institute of Scientific and Technical Information of China (English)

    闫小兵; 李自红; 郭瑾; 赵晋泉; 陈文; 扈桂让; 苏宗正


    系统解读了山西晚新生代古地理古环境特征,结合近年来笔者的研究给出了各时代古地理分布图。上新世的构造运动和地理环境演化奠定了现今地理环境的基础,尤其是奠定了现今地貌、水系的轮廓。早更新世地理环境最突出的事件是各断陷盆地中的湖泊广泛发育,出现淹没整个盆地的大湖景观;黄土广泛发育,但主要堆积于吕梁山分水岭以西;黄河在早更新世已经发育,并形成5级阶地。中更新世古地理的主要事件是湖泊的衰退,黄土堆积范围几乎遍布全省,厚可达200 m左右,表明气候较早更新世进一步明显变干。晚更新世古地理的主要特征是湖泊消亡,其地理环境更加接近现代。最后,笔者预测未来山西断陷盆地将持续断陷,各盆地内水系不再外流,形成贯通的大湖景观,类似现今的贝加尔湖。%The Late Cenozoic paleogeography of Shanxi was affected by geomorphology,rivers, sedimentary environment,animals,plants,climate,loess,and ancient human activities during the Pliocene and Pleistocene epochs,from about 5.5 million to 12 thousand years ago.The evolution of the paleogeography formed the basis of the modern geography and environment,particularly the modern landscape and water systems.Understanding the ancient environment is also of great importance for effective environmental protection and for predicting future climate.Using infor-mation from our recent field investigations conducted throughout Shanxi Province,this paper sys-tematically gives explanatory notes on the paleogeographical and paleoenvironmental characteris-tics for all epochs of the late Cenozoic in Shanxi Province.During tectonic movements in the early Pliocene,the Shanxi rift zone began to subside.In the Datong,Xinding,Taiyuan,and Linfen areas a rift basin began to form,with the corresponding emergence of small lakes.In the middle and late Pliocene,these basins formed

  5. Thermotectonic history of Mt Logan, Yukon Territory, Canada: implications of multiple episodes of middle to late Cenozoic denudation (United States)

    O'Sullivan, Paul B.; Currie, Lisel D.


    The extreme relief of the St. Elias Mountains, including Mt. Logan, is suggestive of a young mountain belt. New apatite fission track data indicate that the Mt. Logan massif experience rapid low-temperature cooling during three distinct periods: during the middle Eocene, Middle Miocene and Pliocene. Each cooling episode, the magnitude of which varies due to temporal variations in recorded paleogeothermal gradients, can be tentatively linked to a tectonic cause. Eocene cooling may be due to re-equilibration of isotherms following normal faulting, caused by a combination of thermal weakening of the crust and a decrease in regional compressional stress, due to the ˜ 43 Ma change in relative motions between the Pacific and North American plates. The cause of Miocene cooling is problematic, and could reflect denudation in response to initial underplating of the Yakutat terrane, or a recorded change in heat flow unrelated to denudation. Pliocene cooling reflects erosion due to surface uplift that produced the spectacular present-day topography of the St. Elias Mountians. This surface uplift is probably related to the coeval significant change in relative motion between the North American and Pacific plates and/or resistance to subduction by the Yakutat terrane.

  6. Late Eocene to Early Miocene Andean uplift inferred from detrital zircon fission track and U-Pb dating of Cenozoic forearc sediments (15-18°S) (United States)

    Decou, A.; von Eynatten, H.; Dunkl, I.; Frei, D.; Wörner, G.


    Timing, amount, and mechanisms of uplift in the Central Andes have been a matter of debate in the last decade. Our study is based on the Cenozoic Moquegua Group deposited in the forearc basin between the Western Cordillera and the Coastal Cordillera in southern Peru from ˜50 to ˜4 Ma. The Moquegua Group consists mainly of mud-flat to fluvial siliciclastic sediments with upsection increasing grain size and volcanic intercalations. Detrital zircon U-Pb dating and fission track thermochronology allow us to refine previous sediment provenance models and to constrain the timing of Late Eocene to Early Miocene Andean uplift. Uplift-related provenance and facies changes started around 35 Ma and thus predate major voluminous ignimbrite eruptions that started at ˜25 by up to 10 Ma. Therefore magmatic addition to the crust cannot be an important driving factor for crustal thickening and uplift at Late Eocene to Early Oligocene time. Changes in subduction regime and the subducting plate geometry are suggested to control the formation of significant relief in the area of the future Western Cordillera which acts as an efficient large-scale drainage divide between Altiplano and forearc from at least 15.5 to 19°S already at ˜35 Ma. The model integrates the coincidence of (i) onset of provenance change no later than 35 Ma, (ii) drastic decrease in convergence rates at ˜40, (iii) a flat-subduction period at around ˜40 to ˜30 Ma leading to strong interplate coupling, and (iv) strong decrease in volcanic activity between 45 and 30 Ma.

  7. Cenozoic faults and faulting phases in the western Tarim Basin (NW China): Effects of the collisions on the southern margin of the Eurasian Plate (United States)

    Li, Yue-Jun; Zhang, Qiang; Zhang, Guang-Ya; Tian, Zuo-Ji; Peng, Geng-Xin; Qiu, Bin; Huang, Zhi-Bin; Luo, Jun-Cheng; Wen, Lei; Zhao, Yan; Jia, Tie-Gan


    The Bachu Rise in the western Tarim Basin is the fore-bulge of the Kunlun late Cenozoic intra-continental foreland basin system formed under the far-field effect of India-Asia collision. Cenozoic faults and faulting are abnormally developed in the Bachu Rise and its adjacent area. Taking the Niaoshan-Gudongshan area on the southern boundary of the Bachu Rise as the key study area, 5 Cenozoic faulting phases were identified in the Bachu Rise and its adjacent area after careful seismic interpretation. They are end Cretaceous ∼ beginning Paleogene (ca. 65 Ma) décollement-thrusting, end Paleogene ∼ beginning Neogene (ca. 23 Ma) décollement-thrusting, end Miocene ∼ beginning Pliocene (ca. 5 Ma) basement-involved thrusting, late Pliocene ∼ early Pleistocene (ca. 3-2 Ma) normal faulting, middle Pleistocene ∼ Holocene (ca. <1.5 Ma) décollement-thrusting and strike-slip faulting. The Middle Cambrian and Paleogene gypsum-salt layers serve as the two main décollement layers in the study area. Thrusting of ca. 65 Ma was under the far-field effect of the collision between Lhasa (part of the Cimmerian Continent) and Asia; and the other 4 Cenozoic faulting phases were all under the far-field effect of the India-Asia collision. The late Cenozoic faulting is characterized by pulse thrust. There is one tectonic pause between each two successive thrust pulses. The compressive tectonic stress is weaker and even evolved into a slight tensional tectonic stress and forms normal fault in the tectonic pauses.

  8. Layer-block tectonics of Cenozoic basements and formation of intra-plate basins in Nansha micro-plate,southern South China Sea

    Institute of Scientific and Technical Information of China (English)

    LIU Hailing; XIE Guofa; LIN Qiujin; ZHENG Hongbo; LIU Yingchun


    Layer-block tectonics (LBT) concept, with the core of pluralistic geodynamic outlook and multi-layer-sliding tectonic outlook, is one of new keys to study 3-dimensional solid and its 4-dimensional evolution history of global tectonic system controlled by global geodynamics system. The LBT concept is applied to study the lithospheric tectonics of the southern South China Sea (SCS). Based on the analysis of about 30 000 km of geophysical and geological data, some layer-blocks in the Nansha micro-plate can be divided as Nansha ultra-crustal layer-block, Zengmu crustal layer-block, Nanwei (Rifleman bank)-Andu (Ardasier bank) and Liyue (Reed bank)-North Palawan crustal layer-blocks, Andu-Bisheng and Liyue-Banyue basemental layer-blocks. The basic characteristics of the basemental layer-blocks have been dicussed, and three intra-plate basin groups are identified. The intra-plate basins within Nansha micro-plate can be divided into three basin groups of Nanwei-Andu, Feixin-Nanhua, and Liyue-North Palawan based on the different geodynamics. In the light of pluralistic geodynamic concept, the upheaving force induced by the mid-crust plastic layer is proposed as the main dynamical force which causes the formation of the intra-plate basins within the Nansha micro-plate. Finally, models of a face-to-face dip-slip-detachment of basemental layer-block and a unilateral dip-slip-detachment of basemental layer-block are put forward for the forming mechanisms of the Nanwei-Andu and Liyue-North Palawan intra-plate basin groups, respectively.

  9. Cenozoic evolution of the eastern Danish North Sea

    Energy Technology Data Exchange (ETDEWEB)

    Huuse, M.; Lykke-Andersen, H.; Michelsen, O.


    This paper provides a review of recent high-resolution and conventional seismic investigations in the eastern Danish North Sea and destribes their implications for the development of the eastern North Sea Basin. The results tomprise detailed timestructure maps of four major unconformities in the eastern Danish North Sea: the Top Chalk surface (mid-Paleogene), near top Oligocene, the mid-Miocene unconformity, and base Quatemary. The maps show that the eastem Danish North Sea has been affected by fauldng and salt diapirism throughout the Cenozoic. Carbonate mounds, erosional valleys and pockmark- or karstlike struttures were identitied at the top of the Upper Cretaceous-Danian Chalk Group. Strike-parallel erosional features and depositional geometries observed at near top Oligocene and at the mid-Miocene unconformity indicate that these major sequence boundarics tan be attributed to large-scale lateral changes in sediment supply directions. Increases in sediment flux to the southeastern North Sea at the Eocene/Oligocene transition and in the post-Middle Miocene appear to correlate with similar events world wide and with long term {delta} {sup 18} O increases, indicating forting by global factors, i.e. eustasy and climate. Stratal geometries observed on the seismic data indicate that the socalled `Neogene uplift' of the Bastern Danish North Sea may have been hundreds of metres less than previously suggested. lt is argued that late Cenozoic uplift of the basin margin and of mountain peaks in southern Norway may have been caused entirely by isostatic uplift of the trust in response to accelerated late Cenozoic denudation and dissection of topography created in the Paleogene. The late Cenozoic periods of accelerated denudation and incision rates were most likely driven by climatic deterioration and long term eustatic lowering rather than active late Cenozoic tectonics, the cause of which is conjectural. A series of shallow thrust struttures and an associated system

  10. Late Mesozoic-Cenozoic décollement structure and its deep geological background in western Shandong,China

    Institute of Scientific and Technical Information of China (English)

    Li Li; Dalai Zhaong; Xiupeng Shi; Zibo Tang; Qiuyuan Hu; Yi Xu; Zhiwei Li


    Data from seismic reflection profiles,drilling,stratigraphy,structural deformation studies and physical rock properties reveal the existence of drcollement structures in both shallow and deep levels in western Shandong,China.The most outstanding shallow décollement structures occur along the regional unconformity surface between the Cambrian and Archean,and the disconformity surface between the Carboniferous and Ordovician.The drcollement structure surface manifests as a fault zone with cataclastic rocks and asymmetrical folds.Some of the cataclastic rocks underwent dynamic metamorphism and hydrothermal alteration,including silicification,marbleization and specularite mineralization.Above the decollement structure,the bottom of the Cambrian might be missing or overprinted because of decollement.The striations,asymmetrical folds and boudinage structures indicate the direction of the main décollement tothe NNW and NNE.A deep level decollement structure occurs at a depth of 12-22 km and up to 30 km distance to the south.The early Cretaceous and Eocene are two main periods of activity,with the Cretaceous decollement probably initiated by mantle upwelling derived from subduction and collision of the Yangtze Plate with the North China Plate along the Tancheng-Lujiang Fault in the late Triassicearly Jurassic.This circumstance implies a multidirection of subduction and collision of these two plates in the early late Mesozoic.(C) 2009 National Natural Science Foundation of China and Chinese Academy of Sciences.Published by Elsevier Limited and Science in China Press.All rights reserved.

  11. The mapping methods and division of tectonic units of the regional tectonic map in the eastern China seas and adjacent regions

    Institute of Scientific and Technical Information of China (English)

    YIN Yanhong; ZHANG Xunhua; WEN Zhenhe; GUO Zhenxuan


    The geological-geophysical map series of the eastern China seas and adjacent region (1:1 000 000) will be published in the late half year of 2009. The regional tectonic map is one of the main professional maps. The Mapping methods, the division method of geological tectonic units and the main geological tectonic units are mainly discussed. The strata from Pliocene to Holocene are peeled off so as to display the Pre-Pliocene structures. In basins, isopaches are drawn for the Cenozoic deposits. The plate tectonic theory and present tectonic pattern are adopted as the priorities in tectonic division. As to the division of intraplate tectonic units, it is a revision, complement and improvement of previous dividing systems, and the nomenclature for each tectonic unit follows the current system in China. The first-order tectonic unit is plate (Pacific Plate, Eurasian Plate and Philippine Sea Plate). The second-order tectonic unit is tectonic domain (East Asian continental tectonic domain,East Asian continental margin tectonic domain and west Pacific tectonic domain). The Philippine Sea Plate and the west part of the Pacific Plate are called the West Pacific tectonic domain. The part of the Eurasian Plate involved in this study area can be further divided into East Asian continental tectonic domain and East Asian continental margin tectonic domain. The East Asian continental margin domain is composed of the Ryukyu island arc, the Okinawa Trough back-arc basin and the back-arc basin of Sea of Japan. The East Asian continental tectonic domain in this study area is composed of the Sino-Korea Massif, the Changjiang River (Yangtze) Massif and South China Massif. In turn, these massifs consist of basins, folded belts or uplift zones. The basins,the folded belts or the uplift zones are further divided into uplifts and depressions made up of sags and swells.

  12. Ar-Ar geochronology of Late Mesozoic volcanic rocks from the Yanji area,NE China and tectonic implications

    Institute of Scientific and Technical Information of China (English)

    LI ChaoWen; GUO Feng; FAN WeiMing; GAO XiaoFeng


    Ar-Ar dating results of late Mesozoic-Cenozoic volcanic rocks from the Yanji area, NE China provide a new volcano-sedimentary stratigraphic framework. The previously defined "Triassic-Jurassic" volcanic rocks(including those from Sanxianling, Tuntianying, Tianqiaoling and Jingouling Fms.)were erupted during 118-106Ma,corresponding to Early Cretaceous. The new eruption age span is slightly younger than the main stage(130-120 Ma)of the extensive magmatism in the eastern Central Asian Orogenic Belt and its adjacent regions. Subduction-related adakites occurring in the previously defined Quanshuicun Fm. Were extruded at ca.55 Ma. Based on these new Ar-Ar ages, the late Mesozoic to Palaeocene volcano-sedimentary sequences is rebuilt as:Tuopangou Fm., Sanxianling/Tuntianying Fm.(118-115 Ma),Malugou/Tianqiaoling Fm.(K1),Huoshanyan/Jingouling Fm.(108-106 Ma),Changcai Fm.(K2),Quanshuicun Fm.(~55 Ma)and Dalazi Fm. Our results suggest that subduction of the Palaeo-Pacific Ocean beneath the East Asian continental margin occurred during 106to 55 Ma. Consistent with the paleomagnetic observations and magmatic records which indicated that the Izanagi-Farallon ridge subduction beneath the southwestern Japan took place during 95-65 Ma.

  13. Ar-Ar geochronology of Late Mesozoic volcanic rocks from the Yanji area, NE China and tectonic implications

    Institute of Scientific and Technical Information of China (English)


    Ar-Ar dating results of late Mesozoic-Cenozoic volcanic rocks from the Yanji area, NE China provide a new volcano-sedimentary stratigraphic framework. The previously defined “Triassic-Jurassic” volcanic rocks (including those from Sanxianling, Tuntianying, Tianqiaoling and Jingouling Fms.) were erupted during 118―106 Ma, corresponding to Early Cretaceous. The new eruption age span is slightly younger than the main stage (130―120 Ma) of the extensive magmatism in the eastern Central Asian Orogenic Belt and its adjacent regions. Subduction-related adakites occurring in the previously defined Quanshuicun Fm. were extruded at ca. 55 Ma. Based on these new Ar-Ar ages, the late Mesozoic to Palaeocene volcano-sedimentary sequences is rebuilt as: Tuopangou Fm., Sanxianling/Tuntianying Fm. (118―115 Ma), Malugou/Tianqiaoling Fm. (K1), Huoshanyan/Jingouling Fm. (108―106 Ma), Changcai Fm. (K2), Quanshuicun Fm. (~55 Ma) and Dalazi Fm. Our results suggest that subduction of the Pa- laeo-Pacific Ocean beneath the East Asian continental margin occurred during 106 to 55 Ma, consistent with the paleomagnetic observations and magmatic records which indicated that the Izanagi-Farallon ridge subduction beneath the southwestern Japan took place during 95―65 Ma.

  14. Geomorphic and Fish Genetics Constraints on Late Cenozoic Long Wavelength Topographic Evolution of the Hangay Mountains, Central Mongolia (United States)

    Wegmann, K. W.; Tamra, M.; Sabaj Pérez, M.; Lopresti, M.; Cole, M. B.; Gosse, J. C.; Smith, S. G.; Bayasgalan, G.; Ancuta, L. D.; McDannell, K. T.; Gallen, S. F.


    The Hangay Mountains stand 1.5 - 2 km above adjacent lowlands and the timing and cause of their high elevation is debated. As part of a broad collaborative project, we synthesize several data sets that collectively suggest the Hangay increased in elevation during the mid-to-late Miocene, while topographic relief, one metric commonly associated with active mountain ranges, remained largely unchanged. The topographic crest of the Hangay forms the drainage divide between the Selenga River and internal drainage of the Mongolian Depression of Lakes (MDL) and northern Gobi. Synthetic drainage divides for the Hangay were created by filtering digital topography in the spectral domain (50 - 200 km wavelengths) using a 2D-FFT function. The co-location of the synthetic and modern divides suggests that the Hangay divide is in a stable, equilibrium configuration. This assumption is corroborated by chi-maps of steady-state river channel elevations that exhibit nearly equal values across water divides. An exception to both of these metrics occurs in the northwest Hangay where the Bulnay fault crosses a low divide between the western Selenga basin and the MDL. Recent basalt vesicle paleoaltimetry results allow for ~1 km of surface uplift of the central Hangay in the past ~ 10 Ma. These same basalt flows in-filled late Miocene valleys cut into basement with a minimum of 800 m of local relief; similar to the amount of modern, post-glacial relief along the drainage divide. mtDNA analyses from > 250 combined Stone Loaches (Barbatula), Grayling (Thymallus), and Eurasian Dace (Leuciscus) samples from both sides of the continental drainage divide are supportive of Miocene surface uplift. Molecular genetic differences between the loach populations across the divide suggest that they separated from a common ancestor between 20 and 11 Ma. This date is consistent with the timing of surface uplift and valley incision preserved in the Miocene basalt flows. The dace and grayling populations on

  15. An overview of the Mesozoic-Cenozoic magmatism and tectonics in Eastern Paraguay and central Andes (Western Gondwana): Implications for the composition of mantle sources (United States)

    Omarini, Ricardo H.; Gasparon, Massimo; De Min, Angelo; Comin-Chiaramonti, Piero


    The amalgamation of the Western Gondwana (including the Greater Gondwana supercraton) occurred at 600 Ma during the Brazilian - Pan African orogeny. A plate junction related to this event is marked by the Transbrazilian lineament which separates the South American continent into two sectors: the Eastern Paraguay-Brazilian and Central Andean domains. An overview of the geodynamic data from these two sectors indicates that the two domains were subjected to distinct evolutions from the Proterozoic to the present. The Andean domain is characterized by long-lived subduction processes linked to the convergence and consequent collision of microplates since the Middle Proterozoic (western Amazonian Craton) with a peak at about 600-580 Ma. The Paraguay-Brazilian domain remained relatively stable but was affected by extension episodes that reactivated ancient (Early and Middle Proterozoic) suture zones. These different geodynamic evolutions seem to reflect broadly distinct mantle compositions. In the subduction zones of the Andean domain the mantle was deeply modified by metasomatic processes following the subduction of oceanic plates. Consequently, the Andean type magma sources show a clear HIMU imprint inherited from the MORB, whereas the Paraguay-Brazilian sector shows a prevalent EMI and subordinate EMII character. The petrological data mainly from Mesozoic and Cenozoic magmatic events in the two sectors are reviewed to investigate the current mantle plume and mantle dome models for the uprising of the asthenospheric (or sub-lithospheric) material.

  16. Late Paleozoic tectonic evolution and concentrated mineralization in Balkhash and West Junggar, western part of the Central Asian Orogenic Belt (United States)

    Dong, Shuwen; Chen, Xuanhua; Chen, Zhengle


    The Central Asia Orogenic Belt (CAOB) is an important area with significant growth of the crust and metallogeny in the Late Paleozoic. The Balkhash-Junggar tectono-metallogenic belt consists of the Balkhash, the West Junggar, and the East Junggar tectono-metallogenic belts in western part of the Central Asian Orogenic Belt (CAOB). According to the structural geological relationship, the East Junggar, the West Junggar, and the Balkhash belts are considered to be once a continuous E-W-trending tectono-metallogenic belt in Late Carboniferous. The West Junggar belt is featured with NE-trending left-lateral strike-slip faulting tectonic system (WJTS), while the left-lateral strike-slip faults are E-W-trending in the Balkhash belt. The WJTS consists of the Darabut, the Mayile, and the Baerluke faults, and the blocks among them. All these left-lateral strike-slip faults are forming due to the transition of tectonic settings from syn-collisional orogeny to post-collisional extension during the closure of the ocean (the Junggar Sea) in Late Carboniferous, with significant intrusion of batholiths and crust growth occurred in this period. These faults are truncated by the right-lateral strike-slip faults, such as the Chingiz-Junggar fault, and the Central Balkhash fault in Mesozoic. The Balkhash-Junggar tectono-metallogenic belt is important for the occurrence of many well-known super-large and large porphyry Cu-Mo deposits (such as the Kounrad, the Aktogai, the Borly, and the Baogutu deposits), large skarn Cu deposits (in the Sayak ore-filed), large rare metal deposits (such as the East Kounrad, the Zhanet, and the Akshatau deposits), and large gold deposits (such as the Hatu deposit). Zircon U-Pb ages, Re-Os isotopic dating of molybdenites, 40Ar/39Ar thermochronology of hornblendes, muscovites, biotites, and K-feldspars, and zircon and apatite fission track (FT) and (U-Th)/He dating and thermal history modeling, provide a multidisciplinary approach to constrain the whole

  17. Late Cretaceous-Cenozoic Evolution of the Central Andean Foreland Basin System in the Eastern Cordillera to Subandean Zone, Southern Bolivia (United States)

    Calle, A.; Horton, B. K.; Anderson, R. B.; Long, S. P.


    Evaluation of foreland basin deposystems and provenance across southern Bolivia reveals punctuated growth of the central Andean orogenic wedge. New and published sedimentology, provenance data, stratigraphy, subcrop mapping, and apatite (U-Th)/He thermochronometry along two transects (19.5, 21°S) from the easternmost Eastern Cordillera (EC) to the western Subandean Zone (SAZ) shed light on Late Cretaceous-Miocene thrust belt and foreland basin dynamics. Sediment dispersal patterns are constrained by paleocurrents, detrital zircon U-Pb geochronology, sandstone petrography, and conglomerate clast compositions. Spatial and temporal changes in the Andean thrust belt are recorded in asymmetric foreland basin thicknesses, facies distributions, and provenance within the EC (Incapampa and Camargo synclines) and SAZ (El Rosal and Entre Rios synclines). The >4 km uppermost Cretaceous-lower Miocene EC succession and ~2.5 km upper Oligocene-Miocene SAZ clastic successions record a shift from fluvial backbulge to pedogenic forebulge deposition. Braided, meandering, and lacustrine foredeep deposition records the most-rapid subsidence, with a later shift to progradational braided and alluvial fan deposition in the wedge-top zone. Growth strata preserved in EC and SAZ wedge-top deposits suggest unsteady eastward advance of the deformation front. Distal foreland deposits show west-directed paleocurrents with >1 Ga detrital zircon populations. Emerging Andean sources are indicated by east-directed paleocurrents, 36-25 Ma), Interandean Zone (IAZ, ~22-7 Ma) and SAZ (<6 Ma) can be linked to eastward passage of a flexural forebulge, recorded as a 50-200 m thick condensed zone in EC and SAZ basin fill. Integrated assessment of basin architecture, provenance, and exhumation highlights the potential influence of pre-Cenozoic IAZ heterogeneities on orogenic wedge growth.

  18. Sedimentary and tectonic evolution of the arc zone of Southwestern Ecuador during Late Cretaceous and early Tertiary times (United States)

    Jaillard, Etienne; Ordoñez, Martha; Berrones, Gerardo; Bengtson, Peter; Bonhomme, Michel; Jimenez, Nelson; Zambrano, Italo


    The eastern part of the "Celica basin" of southwesternmost Ecuador exhibits Late Cretaceous to Tertiary sediments which belong to the magmatic arc paleogeographic zone. Important N-S to NE-trending faults separate a western, mainly Late Cretaceous series (Río Playas) from an eastern succession (Catamayo-Gonzanamá) of (?) Late Cretaceous to early Tertiary age. The analysis of these sediments indicates a complex geologic history, which recorded the main stages of the early tectonic evolution of the Andes. In the Río Playas area, a submarine andesitic volcanic pile (Celica Fm) represents the products of a volcanic arc of probably Albian age. It is apparently overlain by a thick, early Late Cretaceous series of volcanic flows and coarse-grained volcaniclastic high-density turbiditic beds (Alamor Fm), the deposition of which might result from the Mochica phase (late Albian-early Cenomanian) Deformation, uplift and erosion (early Peruvian phase) are followed by the sedimentation of unconformable marls and greywackes of marine open shelf to deltaic environment. These comprise Santonian and/or Campanian fine- to mediumgrained deposits (Naranjo Fm), abruptly overlain (late Peruvian phase ?) by fan-delta coarse-grained marine deposits of latest Cretaceous age (Casanga Fm) They are locally capped by undated, partly volcaniclastic red beds, indicating an important regression/uplift of latest Cretaceous-early Tertiary age. In the Catamayo-Gonzanamá area, thick subaerial andesitic volcanic rocks (Sacapalca Fm) are intruded by Paleocene to early Eocene plutons and are overlain by undated fluvial red beds. They express uplift movements of latest Cretaceous-early Tertiary age. To the South, these are capped by slumped lacustrine black shales and greywackes of possible Maastrichtian-Paleocene age (Gonzanamá Fm) Farther north, the Sacapalca volcanics and red beds are overlain by variegated shales, sandstones and conglomerates, dated as latest Oligocene-early Miocene (Catamayo Fm

  19. Mesozoic-Cenozoic Basin Features and Evolution of Southeast China

    Institute of Scientific and Technical Information of China (English)


    The Late Triassic to Paleogene (T3-E) basin occupies an area of 143100 km2, being the sixth area of the whole of SE China; the total area of synchronous granitoid is about 127300 km2; it provides a key for understanding the tectonic evolution of South China. From a new 1:1500000 geological map of the Mesozoic-Cenozoic basins of SE China, combined with analysis of geometrical and petrological features, some new insights of basin tectonics are obtained. Advances include petrotectonic assemblages,basin classification of geodynamics, geometric features, relations of basin and range. According to basin-forming geodynamical mechanisms, the Mesozoic-Cenozoic basin of SE China can be divided into three types, namely: 1) para-foreland basin formed from Late Triassic to Early Jurassic (T3-J1)under compressional conditions; 2) rift basins formed during the Middle Jurassic (J2) under a strongly extensional setting; and 3) a faulted depression formed during Early Cretaceous to Paleogene (K1-E)under back-arc extension action. From the rock assemblages of the basin, the faulted depression can be subdivided into a volcanic-sedimentary type formed mainly during the Early Cretaceous (K1) and a red-bed type formed from Late Cretaceous to Paleogene (K2-E). Statistical data suggest that the area of all para-foreland basins (T3-J1) is 15120 km2, one of rift basins (J2) occupies 4640 km2, and all faulted depressions equal to 124330 km2 including the K2-E red-bed basins of 37850 km2. The Early Mesozoic(T3-J1) basin and granite were mostly co-generated under a post-collision compression background,while the basins from Middle Jurassic to Paleogene (J2-E) were mainly constrained by regional extensional tectonics. Three geological and geographical zones were surveyed, namely: 1) the Wuyishan separating zone of paleogeography and climate from Middle Jurassic to Tertiary; 2) the Middle Jurassic rift zone; and 3) the Ganjiang separating zone of Late Mesozoic volcanism. Three types of basin

  20. Climatic and tectonic controls on Late Triassic to Middle Jurassic sedimentation in northeastern Guangdong Province, South China (United States)

    Pang, Chong-Jin; Li, Zheng-Xiang; Xu, Yi-Gang; Wen, Shu-Nv; Krapež, Bryan


    Stratigraphic analyses document climatic and tectonic controls on the filling of a Late Triassic to early Middle Jurassic (T3-J2) basin that developed on top of a young orogenic belt in southeastern South China. About 2700 m of Carnian to Bajocian sedimentary rocks is documented in the Meizhou region, Guangdong Province. The Carnian to Rhaetian sequence is characterized by deltaic facies that are succeeded by Hettangian fluvial, shallow marine and volcaniclastic facies, and by Sinemurian to early Toarcian interdistributary bay and floodplain facies. The late Toarcian to Bajocian sequence comprises proximal alluvial to lacustrine facies that changed upwards to fluvial facies. Fossil assemblages indicate that climatic conditions changed from tropical/subtropical warm humid, to temperate humid, and then to hot arid through the Late Triassic to the Middle Jurassic. Climatically induced changes (e.g., in precipitation, vegetation and erosion) exerted a strong influence on sediment supply, whereas tectonics played a dominant role in stratigraphic evolution, accommodation generation, sedimentation pattern and volcanism. Tectonostratigraphic analysis shows that the T3-J2 basin was initiated on an orogenic belt during late-stage orogeny, and evolved into shallow-marine and volcanic environments and then back to terrestrial facies during the post-orogenic stage. This was followed by regional uplift and the development of a basin-and-range province. The order of these events is similar to that of the central Rocky Mountains, western North America during the Palaeogene. The Mesozoic basin of South China and the Eocene basins of the central Rocky Mountains highlight the importance of subduction-related subsidence above young and broad orogens.

  1. Cenozoic intracontinental deformation of the Kopeh Dagh Belt, Northeastern Iran (United States)

    Chu, Yang; Wan, Bo; Chen, Ling; Talebian, Morteza


    Compressional intracontinental orogens represent large tectonic zones far from plate boundaries. Since intracontinental mountain belts cannot be framed in the conventional plate tectonics theory, several hypotheses have been proposed to account for the formations of these mountain belts. The far-field effect of collision/subduction at plate margins is now well accepted for the origin and evolution of the intracontinental crust thickening, as exemplified by the Miocene tectonics of central Asia. In northern Iran, the Binalud-Alborz mountain belt witnessed the Triassic tectonothermal events (Cimmerian orogeny), which are interpreted as the result of the Paleotethys Ocean closure between the Eurasia and Central Iran blocks. The Kopeh Dagh Belt, located to the north of the Binalud-Alborz Belt, has experienced two significant tectonic phases: (1) Jurassic to Eocene rifting with more than 7 km of sediments; and (2) Late Eocene-Early Oligocene to Quaternary continuous compression. Due to the high seismicity, deformation associated with earthquakes has received more and more attention; however, the deformation pattern and architecture of this range remain poorly understood. Detailed field observations on the Cenozoic deformation indicate that the Kopeh Dagh Belt can be divided into a western zone and an eastern zone, separated by a series of dextral strike-slip faults, i.e. the Bakharden-Quchan Fault System. The eastern zone characterized by km-scale box-fold structures, associated with southwest-dipping reverse faults and top-to-the NE kinematics. In contrast, the western zone shows top-to-the SW kinematics, and the deformation intensifies from NE to SW. In the northern part of this zone, large-scale asymmetrical anticlines exhibit SW-directed vergence with subordinate thrusts and folds, whereas symmetrical anticlines are observed in the southern part. In regard to its tectonic feature, the Kopeh Dagh Belt is a typical Cenozoic intracontinental belt without ophiolites or

  2. Late Pleistocene and Holocene uplift history of Cyprus: implications for active tectonics along the southern margin of the Anatolian microplate (United States)

    Harrison, R.W.; Tsiolakis, E.; Stone, B.D.; Lord, A.; McGeehin, J.P.; Mahan, S.A.; Chirico, P.


    The nature of the southern margin of the Anatolian microplate during the Neogene is complex, controversial and fundamental in understanding active plate-margin tectonics and natural hazards in the Eastern Mediterranean region. Our investigation provides new insights into the Late Pleistocene uplift history of Cyprus and the Troodos Ophiolite. We provide isotopic (14C) and radiogenic (luminescence) dates of outcropping marine sediments in eastern Cyprus that identify periods of deposition during marine isotope stages (MIS) 3, 4, 5 and 6. Past sea-levels indicated by these deposits are c. 95±25 m higher in elevation than estimates of worldwide eustatic sea-level. An uplift rate of c. 1.8 mm/year and possibly as much as c. 4.1 mm/year in the past c. 26–40 ka is indicated. Holocene marine deposits also occur at elevations higher than those expected for past SL and suggest uplift rates of c. 1.2–2.1 mm/year. MIS-3 marine deposits that crop out in southern and western Cyprus indicate uniform island-wide uplift. We propose a model of tectonic wedging at a plate-bounding restraining bend as a mechanism for Late Pleistocene to Holocene uplift of Cyprus; uplift is accommodated by deformation and seismicity along the margins of the Troodos Ophiolite and re-activation of its low-angle, basal shear zone.

  3. Regional post-late Miocene thrust faulting in offshore central California-implications for wrench-style tectonics

    Energy Technology Data Exchange (ETDEWEB)

    Crouch, J.K.; Bachman, S.


    High-resolution, deep-penetration seismic reflection data have recently been collected in the offshore Santa Maria basin, northern Santa Barbara Channel, and off Point Conception, California. These data reveal major post-late Miocene east-over-west thrust faulting in offshore central California. Recognizable on both dip and strike lines, the thrust faults are generally imbricate and curve downward to a basal sole thrust at depths of 1.5-3 km (4900-9800 ft). The offshore Santa Maria basin is generally regarded as a wrench-style basin. However, the Hosgri and other northwest-trending faults with the basin appear to be predominantly thrust rather than strike-slip faults. Also, detailed mapping within the basin indicates that the overall structural pattern does not fit accepted models of wrench tectonics; for example, folds have a preferred asymmetry and their axes closely paralleled faults rather than lie en echelon to them. It is concluded that the folds and faults as well as the present morphology of the offshore Santa Maria basin are largely due to post-late Miocene northeast-southwest compression. Similar conclusions can be drawn from the onshore Santa Maria basin on the basis of field relations and well data. These data, and the conclusions drawn from them, raise questions as to the validity of the generally accepted notion that all California Neogene basins are products of wrench-style tectonics.

  4. Late Quaternary tectonics and active ground deformation in the Catania urban area (eastern Sicily): New constraints from a geological investigation (United States)

    Catalano, Stefano; Pavano, Francesco; Romagnoli, Gino; Tortorici, Giuseppe


    New surface and subsurface geological data on the Catania urban area, in eastern Sicily, are here illustrated by a detailed geological map of the city and by four significant cross-sections. Our study aims at defining the prolongation of the principal regional Late Quaternary tectonic features, beneath the city. The resulting geometry of the investigated structures completes the tectonic pictures of two different stages of deformation. The earlier structural association, ranging in age from 600 to 125 ka, consists of a transpressive dextral belt that include E-W oblique thrust ramp, located to the south and the north of the city respectively, connected by a wide NE-SW oriented anticline crossing the urban area. The younger structural association developed since the Late Pleistocene and includes a set of ENE-trending folds that originated at the hangingwall of a main thrust ramp running just beneath the old town (Catania Thrust Ramp). These contractional features have been active during the last 60 ka and their geometry is consistent with the active ground deformation observed by the available geodetic data (GPS vectors and DInSAR analyses). The entire set of the recent structures are bordered to the north by a dextral transfer zone, reactivating part of the previous E-W alignment, that now represents the tectonic boundary with the Mt. Etna Volcano transtensional domain. Our data suggest that the Catania Thrust Ramp could play a main role in the active deformation pattern of the region, thus representing a potential seismotectonic feature to be carefully investigated for the re-evaluation of the seismic hazard of the area.

  5. Paleothermal structure of the Point San Luis slab of central California: Effects of Late Cretaceous underplating, out-of-sequence thrusting, and late Cenozoic dextral offset (United States)

    Underwood, Michael B.; Laughland, Matthew M.


    Late Cretaceous shale and sandstone turbidites of the Point San Luis "slab" are isoclinally folded, locally sheared, and faulted, but their severity of stratal disruption is relatively mild when compared to adjacent polymictic mélange of the Franciscan Complex. We tested the interpretation of a trench-slope basin origin for these strata by documenting their paleothermal structure, including contacts between turbidites and mélange. Values of mean random vitrinite reflectance (Rm) from turbidites are 0.9-1.7% estimates of maximum paleotemperature are 135°-200°C. Mélange matrix samples yield Rm values of 1.1-2.5%, with an average of 1.5%, and peak temperatures between 160° and 240°C. The turbidite-over-mélange contact is locally "cooler over warmer" and was folded after peak heating. The relatively high paleotemperatures cast doubt on a shallow slope basin model (i.e., 1-2 km burial depth). We suggest, instead, that thermal maturation of the Point San Luis slab occurred much deeper in an accretionary prism (10-15 km), where offscraped trench wedge deposits were faulted against underplated mélange. The paleothermal structure was offset and tilted after peak heating by two out-of-sequence faults. Late Oligocene to Pliocene strata rest unconformably above the Franciscan, and there is a significant gap in thermal maturity across this unconformity, with no evidence to show that Franciscan rocks were reset thermally following the main episode of uplift and erosion. Three-dimensional orientations of isoreflectance surfaces on opposite sides of the San Gregorio-San Simeon-Hosgri fault system also can be used to test interpretations of strike-slip neotectonics. The failure to match these geometries among suspected piercing points at Point San Luis, Cambria, and Point Sur favors a suggestion that differential, post thermal peak, dextral offset of Franciscan basement has not exceeded 10-15 km.

  6. Apatite Fission Track Evidence for the Mesozoic-Cenozoic Tectonic Uplift of Aqishan-Yamansu Area, East Tianshan:With Discussion of Tectonic Activity and Geological Disposal of Radioactive Waste%阿齐山--雅满苏地区中-新生代构造隆升裂变径迹证据:兼论构造活动对核废选址场的意义

    Institute of Scientific and Technical Information of China (English)

    刘红旭; 王永文; 赵建; 颜丹平; 何建国; 陈峰; 高洪雷; 所世鑫; 王勋; 张晓; 曹清艳


    Tectonic activity is a fundamental discriminant factor in site assessment for radioactive waste. The tectonic activity of geological repository of radioactive waste which is located at Aqishan-Yamasu in the East Tianshan was evaluated through model studying the uplift and exhumation history by the apatite fission track dating. The result shows that apatite fission track pool-age data range from 81.7 to 51.4 Ma which recorded a cooling event of the East Tianshan during the Late Cretaceous to Eocene, which is consistent with a tectonic uplift and denudation event in the Late Cretaceous in the Tianshan. The mean track lengths range from 13.60±0.11 to 14.36±0.10 μm with the standard deviations of 0.98 ~1.22 μm, which suggests that most tracks didn’ t experience thermal annealing process after they were formed. Based on evaluated geothermal gradient, the mean exhumation rate in the East Tianshan during the Late Cretaceous to Eocene was calculated to reach 270~580 m/Ma. The geological data and further temperature-time modeling of apatite was conducted, indicating that an exhumation event existed from the Late Cretaceous to Eocene (84~49 Ma); after 50 Ma, the crust of the east Tianshan has been in a steady state, and the Cenozoic tectonic activity in Aqishan-Yamansu area has become significantly weaker than other area of Tianshan. The study shows that the geomorphologic features of present Tianshan inherit that from the Late Cretaceous, and weak tectonic activity conforms to the tectonic requirements of geological disposal of radioactive waste.%构造活动性是核废处置场评价的一项基本判别要素。文中通过对东天山阿齐山-雅满苏地区磷灰石裂变径迹测年及构造隆升剥蚀过程的模拟来评价核废处置场的构造活动性。结果表明阿齐山-雅满苏地区样品磷灰石裂变径迹年龄集中分布在81.7~51.4 Ma之间,反映出东天山地区晚白垩世-始新世存在一次明显的构造冷却事件,这与

  7. Geochemical and Sr-Nd-Pb isotopic characteristics of Late Cenozoic leucite lamproites from the East European Alpine belt (Macedonia and Yugoslavia) (United States)

    Altherr, R.; Meyer, H.-P.; Holl, A.; Volker, F.; Alibert, C.; McCulloch, M. T.; Majer, V.

    In the East European Alpine belt, leucite-sanidine-phlogopite-olivine-bearing volcanic rocks of Late Cenozoic age occur at eight localities within the Vardar suture zone and at one locality in the Southern Carpathian fold-and-thrust belt. Most of these volcanics are characterized by high Mg# (66.6-78.6), high abundances of Ni (117-373 ppm) and Cr (144-445 ppm) as well as high primary K2O contents (5.63-7.01 %) and K2O/Na2O values (1.93-4.91). Rocks with more differentiated compositions are rare. A lamproite affinity of these rocks is apparent from their relatively low contents of Al2O3 (9.9-14.3 wt%) and CaO (6.2-8.3 wt%) in combination with high abundances of Rb (85-967 ppm), Ba (1,027-4,189 ppm), Th (18.9-76.5 ppm), Pb (19-54 ppm), Sr (774-1,712 ppm) and F (0.16-0.52 wt%), and the general lack of plagioclase. Although eruption of the magmas took place in post-collisional extensional settings, significant depletions of Nb and Ta relative to Th and La, low TiO2 contents (0.92-2.17 %), low ratios of Rb/Cs, K/Rb and Ce/Pb as well as high ratios of Ba/La and Ba/Th suggest close genetic relationships to subduction zone processes. Whereas Sr and Nd isotope ratios show relatively large variations (87Sr/86Sr = 0.7078-0.7105, 143Nd/144Nd = 0.51242-0.51215), Pb isotope ratios display a very restricted range with 206Pb/204Pb = 18.68-18.88 and variable but generally high Δ7/4 (11-18) and Δ8/4 (65-95) values. The observed petrographic, geochemical and isotopic characteristics are best explained by a genetic model involving preferential melting of phlogopite-rich veins in an originally depleted lithospheric mantle source, whereby the metasomatic enrichment of the mantle source is tentatively related to the addition of components from subducted sediments during consumption of Tethyan oceanic lithosphere.

  8. The mesozoic-cenozoic tectonics of part of the northeastern margin of the Parana Basin: apatite fission tracks; A tectonica meso-cenozoica de parte da borda nordeste da Bacia do Parana: tracos de fissao em apatita

    Energy Technology Data Exchange (ETDEWEB)

    Fracalossi, Carlos Pinto [PETROBRAS (Brazil). Unidade de Negocio Sergipe Alagoas. Gerencia de Avaliacao e Acompanhamento Geologico], e-mail:; Godoy, Daniel Francoso [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Rio Claro, SP (Brazil). Pos-Graduacao em Geologia Regional], e-mail:; Hackspacher, Christian [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Rio Claro, SP (Brazil). Dept. de Petrologia e Metalogenia


    The possible development of thermal events in the central portion of Sao Paulo state was described based on apatite fission track analysis. Using apatites of sedimentary rocks of the Parana Basin, modeling the thermal history was made possible due to the homogeneity of the data. Every thermal history begins with a total annealing of fission tracks, related to the Serra Geral magmatism, evolving into a cooling period. In addition to cooling after the magmatism (Early Cretaceous) two other periods of cooling were also detected, registered in the Late Cretaceous/Paleocene and Eocene, driven as much by uplift with tectonic denudations by faulting. The nearest portion of the edge of the basin (external to the Dome of Pitanga), registered a period of warming over the Paleocene that can be attributed to the increase in the geothermal gradient. The periods of cooling have a regional and temporal relationship with the tectonic events that occurred in the southeastern Brazil and were described in the crystalline basement. The period of warming, registered in the Late Cretaceous/Paleocene, has local occurrence and can be found only in the southern portion of the studied area. (author)

  9. Late Miocene volcanism and intra-arc tectonics during the early development of the Trans-Mexican Volcanic Belt (United States)

    Ferrari, Luca; Conticelli, Sandro; Vaggelli, Gloria; Petrone, Chiara M.; Manetti, Piero


    The early stage of the Trans-Mexican Volcanic Belt (hereafter TMVB) is marked by widespread, mafic to intermediate, volcanism emplaced between 11 and 7 Ma from the Pacific coast to the longitude of Mexico City, to the north of the modern volcanic arc. Petrological and geochronological data support the hypothesis that this volcanism made up a unique late Miocenic central Mexican comagmatic province. Mafic lavas at the mouth of the Gulf of California and along the northwestern sector of the TMVB made up the Nayarit district, which includes calc-alkaline to transitional varieties. The central sector of the TMVB is characterized by two basaltic districts: the Jalisco-Guanajuato and the Queretaro-Hidalgo, which are distinguished from the westernmost ones by their lower Nb/La and generally lower HFSE/LILE values, as well as by spider diagrams characterized by larger negative spikes at Th, Ta, Nb, and Ti. The surface occurrence of the late Miocene basalts appears to be controlled by pre-existing zones of crustal weakness that channeled the mafic magmas. Field observations suggest that these structures have been reactivated in a transtensional fashion induced by differential tectonic motion of crustal blocks to the south and to the north of the TMVB. Starting from ˜12 Ma the TMVB separates a northern tectonic domain, subject to the developing divergent Pacific-North America plate boundary, from a southern tectonic domain, characterized by oblique subduction of the Rivera and Cocos plates. Apparently, far field stresses related to these complex plate boundaries reactivated older suture zones, allowing rapid uprise of mantle-derived magmas. The subduction-related signature shown by Miocene mafic lavas of the Jalisco-Guanajuato district argues against the existence of mantle plumes beneath this sector of the North America plate. On the other hand, the occurrence in the western TMVB and in the Guadalajara region of a large volume of mafic magmas, which sometimes show

  10. Modulation of Late Cretaceous and Cenozoic climate by variable drawdown of atmospheric pCO2 from weathering of basaltic provinces on continents drifting through the equatorial humid belt

    Directory of Open Access Journals (Sweden)

    D. V. Kent


    Full Text Available The small reservoir of carbon dioxide in the atmosphere (pCO2 that modulates climate through the greenhouse effect reflects a delicate balance between large fluxes of sources and sinks. The major long-term source of CO2 is global outgassing from sea-floor spreading, subduction, hotspot activity, and metamorphism; the ultimate sink is through weathering of continental silicates and deposition of carbonates. Most carbon cycle models are driven by changes in the source flux scaled to variable rates of ocean floor production, but ocean floor production may not be distinguishable from being steady since 180 Ma. We evaluate potential changes in sources and sinks of CO2 for the past 120 Ma in a paleogeographic context. Our new calculations show that decarbonation of pelagic sediments by Tethyan subduction contributed only modestly to generally high pCO2 levels from the Late Cretaceous until the early Eocene, and thus shutdown of this CO2 source with the collision of India and Asia at the early Eocene climate optimum at around 50 Ma was inadequate to account for the large and prolonged decrease in pCO2 that eventually allowed the growth of significant Antarctic ice sheets by around 34 Ma. Instead, variation in area of continental basalt terranes in the equatorial humid belt (5° S–5° N seems to be a dominant factor controlling how much CO2 is retained in the atmosphere via the silicate weathering feedback. The arrival of the highly weatherable Deccan Traps in the equatorial humid belt at around 50 Ma was decisive in initiating the long-term slide to lower atmospheric pCO2, which was pushed further down by the emplacement of the 30 Ma Ethiopian Traps near the equator and the southerly tectonic extrusion of SE Asia, an arc terrane that presently is estimated to account for 1/4 of CO2 consumption from all basaltic provinces that account for ~1/3 of the total CO2 consumption by continental silicate weathering (Dessert et al., 2003. A negative climate

  11. Structure and sediment budget of Yinggehai-Song Hong basin, South China Sea: Implications for Cenozoic tectonics and river basin reorganization in Southeast Asia (United States)

    Lei, Chao; Ren, Jianye; Sternai, Pietro; Fox, Matthew; Willett, Sean; Xie, Xinong; Clift, Peter D.; Liao, Jihua; Wang, Zhengfeng


    The temporal link between offshore stratigraphy and onshore topography is of key importance for understanding the long-term surface evolution of continental margins. Here we present a grid of regional, high-quality reflection seismic and well data to characterize the basin structure. We identify fast subsidence of the basin basement and a lack of brittle faulting of the offshore Red River fault in the Yinggehai-Song Hong basin since 5.5 Ma, despite dextral strike-slip movement on the onshore Red River fault. We calculate the upper-crustal, whole-crustal, and whole-lithospheric stretching factors for the Yinggehai-Song Hong basin, which show that the overall extension observed in the upper crust is substantially less than that observed for the whole crust or whole lithosphere. We suggest that fast basement subsidence after 5.5 Ma may arise from crustal to lithospheric stretching by the regional dynamic lower crustal/mantle flow originated by collision between India-Eurasia and Indian oceanic subduction below the Eurasian margin. In addition, we present a basin wide sediment budget in the Yinggehai-Song Hong basin to reconstruct the sedimentary flux from the Red River drainage constrained by high-resolution age and seismic stratigraphic data. The sediment accumulation rates show a sharp increase at 5.5 Ma, which suggests enhanced onshore erosion rates despite a slowing of tectonic processes. This high sediment supply filled the accommodation space produced by the fast subsidence since 5.5 Ma. Our data further highlight two prominent sharp decreases of the sediment accumulation at 23.3 Ma and 12.5 Ma, which could reflect a loss of drainage area following headwater capture from the Paleo-Red River. However, the low accumulation rate at 12.5 Ma also correlates with drier and therefore less erosive climatic conditions.

  12. Detailed geologic field mapping and radiometric dating of the Abanico Formation in the Principal Cordillera, central Chile: Evidence of protracted volcanism and implications for Cenozoic tectonics (United States)

    Mosolf, J.; Gans, P. B.; Wyss, A. R.; Cottle, J. M.


    the Abanico Formation in addition to the revision of the prevailing tectonic models for the Principal Cordillera, including the timing of eastward arc migration.

  13. Exhuming the Meso–Cenozoic Kyrgyz Tianshan and Siberian Altai-Sayan: A review based on low-temperature thermochronology

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    Stijn Glorie


    Full Text Available Thermochronological datasets for the Kyrgyz Tianshan and Siberian Altai-Sayan within Central Asia reveal a punctuated exhumation history during the Meso–Cenozoic. In this paper, the datasets for both regions are collectively reviewed in order to speculate on the links between the Meso–Cenozoic exhumation of the continental Eurasian interior and the prevailing tectonic processes at the plate margins. Whereas most of the thermochronological data across both regions document late Jurassic–Cretaceous regional basement cooling, older landscape relics and dissecting fault zones throughout both regions preserve Triassic and Cenozoic events of rapid cooling, respectively. Triassic cooling is thought to reflect the Qiangtang–Eurasia collision and/or rifting/subsidence in the West Siberian basin. Alternatively, this cooling signal could be related with the terminal terrane-amalgamation of the Central Asian Orogenic Belt. For the Kygyz Tianshan, late Jurassic–Cretaceous regional exhumation and Cenozoic fault reactivations can be linked with specific tectonic events during the closure of the Palaeo-Tethys and Neo-Tethys Oceans, respectively. The effect of the progressive consumption of these oceans and the associated collisions of Cimmeria and India with Eurasia probably only had a minor effect on the exhumation of the Siberian Altai-Sayan. More likely, tectonic forces from the east (present-day coordinates as a result of the building and collapse of the Mongol-Okhotsk orogen and rifting in the Baikal region shaped the current Siberian Altai-Sayan topography. Although many of these hypothesised links need to be tested further, they allow a first-order insight into the dynamic response and the stress propagation pathways from the Eurasian margin into the continental interior.

  14. Thick-skinned tectonics within the intracontinental easternmost Atlas foreland-and-thrust belt (Tunisia): Meso-Cenozoic kinematics and implications for regional geodynamics (United States)

    Belkhiria, W.; Boussiga, H.; Inoubli, M. H.


    The transition zone between western and central Mediterranean domains presents a key area to investigate kinematic interactions within the adjacent orogen systems such as the easternmost Atlas foreland-and-thrust belt. Gravity and seismic data revealed a highly structured basement, characterizing a series of structural highs and lows delimited by high-angle N-S, E-W, and NW-SE extensional faults. This basement architecture is inherited from successive extensional events related to the openings of the Triassic-Early Cretaceous Tethys oceans (i.e., Alpine Tethys, Ligurian Tethys, and Mesogea). Throughout this period, this mosaic of continental blocks significantly controlled the thickness and facies distributions. Early stages of diapirism took place along these basement faults and allowed maximum subsidence in minibasins revealed by the development of growth strata. In response to the Late Cretaceous-Eocene shortenings, these extensional faults have been reactivated as trasnpressional shear zones, giving rise to narrow pop-up structures. In addition, gravity modeling indicates crustal thinning and deep-rooted faults affecting the crust south of the Zaghouan Thrust and along E-W transfer zones. From the late Miocene, a drastic change in the stress regime is attributed to the effect of the adjacent Sicily channel on the study area. This promotes crustal thinning, basin subsidence, and channeling up of mantle-derived helium along lithospheric-scale weak zones. Our results give rise to new insights into the reactivation of inherited weakness zones of southern Tethys margin in response to the complex interaction between African and Eurasian plates accommodated by subduction, rollback, collision, and slab segmentation.

  15. Paleomagnetism of the Late Paleogene and Neogene rocks of the Serbian Carpatho-Balkanides: Tectonic implications

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    Marović Milun


    Full Text Available This paper focuses on results of the paleomagnetic research conducted in the territory of Serbian Carpatho-Balkanides, within the following basinal domains: Babušnica-Koritnik (the Oligocene deposits, Žagubica (the upper part of the Lower Miocene and the lower part of the Middle Miocene deposits and Dacian (the Pontian deposits. The clockwise rotations are established for each basinal region: Babušnica-Koritnik 10°, Žagubica 5-10° and Dacia 5-20°. On the basis of these results and the available data on rotations in the Romanian Southern Carpathians, new tectonic implications are discussed as a contribution to understanding the genesis of the Paleogene-Neogene and Neogene fabric of the Carpatho-Balkanides in Serbia. It is shown that this region has been subjected not only to vertical, but also to horizontal mobility during the latest stage of its geological development.

  16. Quaternary volcanism, tectonics, and sedimentation in the Idaho National Engineering Laboratory area

    Energy Technology Data Exchange (ETDEWEB)

    Hackett, W.R.; Smith, R.P.


    In this article, we discuss the regional context and describe localities for a two-day field excursion in the vicinity of the Idaho National Engineering Laboratory (INEL). We address several geologic themes: (1) Late Cenozoic, bimodal volcanism of the Eastern Snake River Plain (ESRP), (2) the regional tectonics and structural geology of the Basin and Range province to the northwest of the ESRP, (3) fluvial, lacustrine, and aeolian sedimentation in the INEL area, and (4) the influence of Quaternary volcanism and tectonics on sedimentation near the INEL.

  17. Quaternary volcanism, tectonics, and sedimentation in the Idaho National Engineering Laboratory area

    Energy Technology Data Exchange (ETDEWEB)

    Hackett, W.R.; Smith, R.P.


    In this article, we discuss the regional context and describe localities for a two-day field excursion in the vicinity of the Idaho National Engineering Laboratory (INEL). We address several geologic themes: (1) Late Cenozoic, bimodal volcanism of the Eastern Snake River Plain (ESRP), (2) the regional tectonics and structural geology of the Basin and Range province to the northwest of the ESRP, (3) fluvial, lacustrine, and aeolian sedimentation in the INEL area, and (4) the influence of Quaternary volcanism and tectonics on sedimentation near the INEL.

  18. Late Quaternary loess landscape evolution on an active tectonic margin, Charwell Basin, South Island, New Zealand (United States)

    Hughes, Matthew W.; Almond, Peter C.; Roering, Joshua J.; Tonkin, Philip J.


    Loess deposits constitute an important archive of aeolian deposition reflecting wider patterns of glacial atmospheric circulation, and more localised interactions between riverine source areas, loess trapping efficiency and geomorphic controls on erosion rate. Conceptual models have been formulated to explain the coeval evolution of loess mantles and associated landscapes (loess landscape models) but none apply to areas of tectonically induced base-level lowering. This study uses an age sequence of alluvial fill terraces in the Charwell Basin, north-eastern South Island New Zealand, which straddles the transpressive Hope Fault, to investigate geomorphic controls on loess landscape evolution in an active tectonic region. We hypothesize that the more evolved drainage networks on older terraces will more effectively propagate base-level lowering by way of a greater areal proportion of steep and convex hillslopes and a smaller proportion of non-eroding interfluves. Eventually, as the proportion of interfluves diminishes and hillslope convexity increases, terraces shift from being net loess accumulators to areas of net loess erosion. We investigate the nature of erosion and the geomorphic thresholds associated with this transition. Morphometric analysis of alluvial terraces and terrace remnants of increasing age demonstrated geomorphic evolution through time, with a decrease in extent of original planar terrace tread morphology and an increase in frequency of steeper slopes and convexo-concave land elements. The number of loess sheets and the thickness of loess increased across the three youngest terraces. The next oldest (ca. 150 ka) terrace remnant had the greatest maximum number of loess sheets (3) and loess thickness (8 m) but the loess mantle was highly variable. A detailed loess stratigraphic analysis and the morphometric analysis place this terrace in a transition between dominantly planar, uniformly loess-mantled landforms and loess-free ridge and valley terrain

  19. Petrogenesis and tectonic implication of the Late Triassic post-collisional volcanic rocks in Chiang Khong, NW Thailand (United States)

    Qian, Xin; Wang, Yuejun; Feng, Qinglai; Zi, Jian-Wei; Zhang, Yuzhi; Chonglakmani, Chongpan


    The volcanic rocks exposed within the Chiang Khong-Lampang-Tak igneous zone in NW Thailand provide important constraints on the tectonic evolution of the eastern Paleotethys ocean. An andesite sample from the Chiang Khong area yields a zircon U-Pb age of 229 ± 4 Ma, significantly younger than the continental-arc and syn-collisional volcanic rocks (ca. 238-241 Ma). The Chiang Khong volcanic rocks are characterized by low MgO (1.71-6.72 wt.%) and high Al2O3 (15.03-17.76 wt.%). They are enriched in LILEs and LREEs and depleted in HFSEs, and have 87Sr/86Sr (i) ratios of 0.7050-0.7065, εNd (t) of - 0.32 to - 1.92, zircon εHf (t) and δ18O values of 3.5 to - 11.7 and 4.30-9.80 ‰, respectively. The geochemical data for the volcanic rocks are consistent with an origin from the enriched lithospheric mantle that had been modified by slab-derived fluid and recycled sediments. Based on available geochronological and geochemical evidences, we propose that the Late Triassic Chiang Khong volcanic rocks are equivalent to the contemporaneous volcanic rocks in the Lancangjiang igneous zone in SW China. The formation of these volcanic rocks was possibly related to the upwelling of the asthenospheric mantle during the Late Triassic, shortly after slab detachment, which induced the melting of the metasomatized mantle wedge.

  20. Late Neogene stratigraphy and tectonic control on facies evolution in the Laguna Salada Basin, northern Baja California, Mexico (United States)

    Martín-Barajas, A.; Vázquez-Hernández, S.; Carreño, A. L.; Helenes, J.; Suárez-Vidal, F.; Alvarez-Rosales, J.


    The Laguna Salada Basin (LSB) in northeastern Baja California records late-Neogene marine incursions in the Salton Trough and progradation of the Colorado River delta. Early subsidence and subsequent tectonic erosion are related to evolution of the Sierra El Mayor detachment fault during late Miocene time (geothermal exploratory well on the eastern margin of LSB. Interfingering fluvial-sandstone deposits and prograding alluvial fanglomerates with coarse debris-flow and rock-avalanche deposits crudely mark the onset of vertical slip along the Laguna Salada fault and rapid uplift of Sierra Cucapa and Sierra El Mayor. Up to 2 km of Quaternary alluvial-fan and lacustrine deposits accumulated along the eastern margin of LSB, whereas lower subsidence rates produced a thinner sedimentary wedge over a ramp-like crystalline basement along the western margin. In early Pleistocene time (˜2-1 Ma), the Laguna Salada became progressively isolated from the Colorado River delta complex, and the Salton Trough by activity on the Elsinore and Laguna Salada fault zones.

  1. Modulation of Late Cretaceous and Cenozoic climate by variable drawdown of atmospheric pCO2 from weathering of basaltic provinces on continents drifting through the equatorial humid belt

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    G. Muttoni


    Full Text Available The small reservoir of carbon dioxide in the atmosphere (pCO2 that modulates climate through the greenhouse effect reflects a delicate balance between large fluxes of sources and sinks. The major long-term source of CO2 is global outgassing from sea-floor spreading, subduction, hotspot activity, and metamorphism; the ultimate sink is through weathering of continental silicates and deposition of carbonates. Most carbon cycle models are driven by changes in the source flux scaled to variable rates of ocean floor production. However, ocean floor production may not be distinguishable from being steady since 180 Ma. We evaluate potential changes in sources and sinks of CO2 for the past 120 Ma in a paleogeographic context. Our new calculations show that although decarbonation of pelagic sediments in Tethyan subduction likely contributed to generally high pCO2 levels from the Late Cretaceous until the Early Eocene, shutdown of Tethyan subduction with collision of India and Asia at the Early Eocene Climate Optimum at around 50 Ma was inadequate to account for the large and prolonged decrease in pCO2 that eventually allowed the growth of significant Antarctic ice sheets by around 34 Ma. Instead, variation in area of continental basaltic provinces in the equatorial humid belt (5° S–5° N seems to be the dominant control on how much CO2 is retained in the atmosphere via the silicate weathering feedback. The arrival of the highly weatherable Deccan Traps in the equatorial humid belt at around 50 Ma was decisive in initiating the long-term slide to lower atmospheric pCO2, which was pushed further down by the emplacement of the 30 Ma Ethiopian Traps near the equator and the southerly tectonic extrusion of SE Asia, an arc terrane that presently is estimated to account for 1/4 of CO2 consumption from all basaltic provinces that account for ~1/3 of the total CO2 consumption by continental silicate weathering (Dessert et al., 2003. A negative climate

  2. Climatic and tectonic implications of the late Miocene Jakokkota flora, Bolivian Altiplano (United States)

    Gregory-Wodzicki, Kathryn M.; McIntosh, W. C.; Velasquez, Kattia


    When compared to a database of modern foliar physiognomy and climate, the physiognomy of a new collection of dicotyledonous leaves from the 10.66±0.06 Ma Jakokkota flora, Bolivian Altiplano, implies a mean annual temperature (MAT) of 18.6-21.0±2.5°C. Similarly, a literature-derived sample of the early-middle Miocene Potosı´flora, Cordillera Oriental, implies a MAT of 21.5-21.7±2.1°C. We estimate that both floras experienced a growing season precipitation of 50±40 cm. The paleoclimate thus appears considerably warmer than the current highland climate, with MATs of 8-9°C; the paleoprecipitation is indistinguishable from modern levels. A comparison of the Miocene MATs with the modern MATs, with the effects of latitudinal continental drift and global climate change subtracted, suggests that the Jakokkota flora grew at an elevation of 590-1610±1000 m, and the Potosı´flora grew at an elevation of 0-1320±1000 m. Both paleoelevation estimates are significantly lower than the present elevations of 3940 and 4300 m, respectively, requiring a substantial component of Andean uplift since 10.7 Ma. This uplift history is consistent with two-stage tectonic models of Andean orogeny.

  3. Alluvial fan facies of the Yongchong Basin: Implications for tectonic and paleoclimatic changes during Late Cretaceous in SE China (United States)

    Chen, Liuqin; Steel, Ronald J.; Guo, Fusheng; Olariu, Cornel; Gong, Chenglin


    Late Cretaceous continental redbeds, the Guifeng Group of the Yongchong Basin in SE China have been investigated to conduct detailed fan facies description and interpretation. Tectonic activities determined the alluvial fan development along the basin margin, but the alluvial facies was linked with paleoclimate changes. The Guifeng Group is divided into the Hekou, Tangbian and Lianhe formations in ascending order. The Hekou conglomerates are typically polymict, moderately sorted with erosional bases, cut-and-fill features, normal grading and sieve deposits, representing dominant stream-flows on alluvial fans during the initial opening stage of the basin infill. The Tangbian Formation, however, is characterized by structureless fine-grained sediments with dispersed coarse clasts, and couplets of conglomerate and sandstone or siltstone and mudstone, recording a change to a playa and ephemeral lake environments with occasional stream flooding, thus indicating a basin expanding stage. The hallmark of the Lianhe Formation is disorganized, poorly sorted conglomerates lack of erosional bases, and a wide particle-size range from clay to boulders together reflect mud-rich debris-flows accumulating on fans, likely related to reactivation of faulting along the northwestern mountain fronts during a post-rift stage. The depositional system changes from stream-flows up through playa with ephemeral streams to debris-flows during the accumulation of the three formations are thus attributed to different source rocks and climatic conditions. Therefore, the fluvial-dominated fans of the Hekou Formation recorded a subhumid paleoclimate (Coniacian-Santonian Age). The dominant semiarid climate during the Campanian Age produced abundant fine-grained sediments in the playa and ephemeral lake environments of the Tangbian Formation. A climatic change towards more humidity during the late stage of the Guifeng Group (Maastrichtian Age) probably yielded high deposition rate of coarse clasts in

  4. Geochronology, geochemistry and tectonic implications of Late Triassic granites in the Mongolian Altai Mountains (United States)

    Dash, Batulzii; Boldbaatar, Enkhjargal; Zorigtkhuu, Oyun-Erdene; Yin, An


    Although the closure of the Paleo-Asian Ocean in western China and western Mongolia occurred in the Late Carboniferous and Early Permian, widespread intra-continental magmatism continued to occur across this region from the Late Permian to the end of the Triassic. In this study we document field relationships and geochemical characterization of a Late Triassic felsic intrusive complex in the western Mongolian Altai. The plutonic complex occurs as sills, dikes, and small stocks and its composition varies from biotite granite, two-mica granite, to leucogranite. Structurally, the plutonic complex occurs in the hanging wall of a segment of the regionally extensively (>1500 km long) Irtysh-Ertix-Bulgan thrust zone. As the plutonic bodies both cut and are deformed by the shear fabrics in this regional thrust shear zone, the duration of felsic magmatism and regional thrusting was temporally overlapping. This suggests that magmatism was coeval with crustal thickening. Major- and trace-element data and isotopic analysis of granitoid samples from our study area indicate that the felsic intrusions were derived from partial melting of meta-sediments, with the biotite and two-mica granite generated through vapor-absent melting and the leucogranite from flux melting. Although the Mongolian Altai intrusions were clearly originated from anatexis, coeval granite in the Chinese Altai directly west of our study area in the hanging wall of the Irtysh-Ertix-Bulgan thrust was derived in part from mantle melting. To reconcile these observations, we propose a Himalayan-style intracontinental-subduction model that predicts two geologic settings for the occurrence of felsic magmatism: (1) along the intracontinental thrust zone where granite was entirely generated by anatexis and (2) in the hanging wall of the intracontinental thrust where convective removal and/or continental subduction induced mantle melting.

  5. Provenance analysis of the Late Paleozoic sedimentary rocks in the Xilinhot Terrane, NE China, and their tectonic implications (United States)

    Han, Jie; Zhou, Jian-Bo; Wilde, Simon A.; Song, Min-Chun


    The Xilinhot Terrane is located in the eastern segment of the Central Asian Orogenic Belt in NE China, and is a key to a hotly debated issue on the Paleozoic tectonic evolution of this giant progenic belt. To constrain the tectonic evolution of the Xilinhot Terrane in the Late Paleozoic, we undertook zircon U-Pb dating and geochemical analyses of the Zhesi and Benbatu formations in the Suolun and Xi Ujimqin areas in the Xilinhot Terrane. Samples of the Benbatu Formation yield detrital zircon U-Pb ages ranging from 2659 Ma to 316 Ma, with four age populations at: 2659-1826 Ma, 1719-963 Ma, 590-402 Ma, and 396-316 Ma, whereas samples from the Zhesi Formation yield detrital zircon U-Pb ages ranging from 1967 Ma to 250 Ma, with four age populations at: 1967-1278 Ma, 971-693 Ma, 561-403 Ma, and 399-250 Ma. The age groups of both the Benbatu and Zhesi formations in the Xilinhot Terrane are similar to those in other parts of the Central Asian Orogenic Belt (CAOB). This evidence indicates that the Xilinhot Terrane is a microcontinent, and not an accretionary complex as previously thought. Furthermore, the youngest zircon grains in the Benbatu and Zhesi formations yield weighted mean 206Pb/238U ages of 322 ± 12 Ma (MSDW = 0.12, n = 4) and 257 ± 2.8 Ma (MSDW = 1.6, n = 8), respectively. Combined with fossil data, our new data suggest that the Benbatu and Zhesi formations in the Xilinhot Terrane were possibly deposited at ∼322 Ma and ∼257 Ma, respectively. Based on the provenance of the Carboniferous-Permian sandstones came from the blocks of NE China, we speculate that the Xilinhot Terrane is the western part of the Songliao block.

  6. Late Eocene Myanmar tectonics constrained by magnetostratigraphy of the Yaw Formation, Chidwin Basin, Kalewa (United States)

    Dupont-Nivet, Guillaume; Licht, Alexis; Bernard, Annabelle; Roperch, Pierrick; Win, Zaw; Jaeger, Jean-Jacques; Aung, Day Wa; Kaythi, Myat; Hnin Swe, Hnin; Poblete, Fernando


    Sedimentary basins in Myanmar have recorded key events of the India-Asia collision including associated geodynamic movements and paleoclimatic records. In particular, Paleogene deposits provide invaluable insight on the accretion of the Burma terrane, its rotation associated with the alleged extrusion of Indochina and the formation of the Indo-Burman ranges. They also yield unique records of monsoonal intensity during the growth of the Tibetan Plateau and a rich paleontological assemblage including some of the earliest primates. However, understanding the potential relations between these recorded events is strongly hindered by insufficient age control on these deposits. As part of the Myanmar Geodynamic & Paleoclimate Initiative and the ERC "MAGIC" project, our initial focus is to date Paleogene deposits of Myanmar with better accuracy using magnetostratigraphy. We present preliminary results from the Chindwin Basin where we sampled a 400-meter section of the top of the Yaw formation recording a major sedimentological facies transition previously estimated roughly as Eocene to Oligocene in age. Detailed rock magnetic analyses enabled to identify and isolate primary Characteristic Remanent Magnetizations of normal and reversed polarities carried by iron sulfides, iron carbonates and/or iron oxides. A correlation to the Geomagnetic Polarity Time Scale can be proposed suggesting deposition between the base of chrons C16n2n and the base of C13r (36.3 and 34.8 Ma). This age suggests the facies transition may be more likely associated with regional tectonics such as the Indo-Burman uplift rather than sea-level drop linked to ice-sheet formation at the Eocene-Oligocene Transition at 33.9 Ma. In addition, the mean observed paleomagnetic declination (13.3+/-3.7°) is statistically indistinguishable from declinations expected by geodynamic models with limited vertical-axis rotations of the Burma terrane and therefore supports little to no rotational extrusion since 35 Ma.

  7. Sedimentary-tectonic evolution from late Palaeozoic to Triassic in south of North China block

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    Chen, S. [University of Petroleum, Dongying (China). Dept of Resource


    The sedimentary facies of some typical profiles as in Hancheng, Jiyuan, Denfeng and Huainan, and the characteristic of regional palaeogeography in the south of North China block were researched. The result shows that the research area had an evolution from the epeiric sea to a lake basin during Palaeozoic to Triassic. This transition was controlled by the collision progeny of Qinling orogenic belt directly. The collision began along the Shangnan-Zhenping-Tongbai line, making the south of North China block compressed and subsided, and transferred from a structural high land to an epeiric sea in Late Carboniferous. The western part of North Qinling began to uplift and became a source of terrigenous clastic sediments to North China basin. In the Permian, the compression strengthened further and the North Qinling-North Huaiyang structural belt uplifted, making the epeiric sea transits to a marginal lake basin. In the Triassic, the Qinling orogenic belt uplifted rapidly and the large scale depression lake basin developed in its north side, and the centre of the basin also transferred to the orogenic belt in the Late Triassic. 7 refs., 4 figs.

  8. Tectonic significance of paleobotanically estimated climate and altitude of the late Eocene erosion surface, Colorado (United States)

    Gregory, Kathryn M.; Chase, Clement G.


    Erosion beveled the Laramide Front Range uplift in Colorado to a surface of low relief by the end of the Eocene. This study uses J. A. Wolfe's new multivariate climate analysis techniques to determine the paleoelevation of this regional surface by examining the overlying 35 Ma Florissant flora. A multiple regression model explaining 93.3% of the variance in mean annual temperature was developed using Wolfe's dataset of 31 leaf physiognomic character states for 86 modern vegetation sites. These character states were scored on 29 species collected from one facies of the Florissant Lake Beds. The paleotemperature estimate of mean annual temperature (10.7 ±1.5 °C) derived from these data, when combined with sea-level temperature and terrestrial lapse rate, implies a late Eocene paleoelevation of 2.4-2.7 km. Pliocene uplift is thus not required to explain the present elevation of 2.5 km. It is unclear when and why the southern Rocky Mountains achieved this elevation. Magmatic crustal thickening can explain the late Eocene high elevation of the southern Rockies, but neither this mechanism nor compressive thickening explains why the Great Plains, which are tied to the Florissant elevation by the Wall Mountain Tuff, were also high. This paleoelevation estimate indicates that regional surfaces of planation could be formed at high elevation in the Eocene, probably because of peculiarities of the Eocene climate.

  9. Late Cretaceous to middle Tertiary tectonic history of the northern Rio Grande Rift, New Mexico (United States)

    Kelley, Shari A.; Duncan, Ian J.


    Apatite fission track ages for samples collected from three mountain ranges on the eastern margin of the Rio Grande rift are used to examine the late Cretaceous to middle Miocene uplift and erosional history of north central New Mexico. The dates indicate that uplift and erosion was in progress in the Sandia Mountains near Albuquerque and in the Taos Range portion of the Sangre de Cristo Mountains near Taos at least 30-35 m.y. ago. Uplift and erosion continued in the Sandia Mountains at a relatively constant rate (81 m/m.y.) until 15 Ma; the rate of uplift and erosion in this area has approximately tripled in the past 15 m.y. (230 m/m.y.). Igneous activity in the Taos Range has largely obscured the early Tertiary uplift and erosional history of this portion of the Sangre de Cristo Mountains. A fission track date from one of the middle Tertiary intrusions in the Taos Range is used to calculate the cooling rate due to uplift and erosion in this area for the past 14 m.y. (210 m/m.y.). The uplift and erosion rates derived from the fission track data for the past 14-15 m.y. are similar to those obtained from other geological evidence. In contrast to the Oligocene to Miocene ages found in the other two areas, the apatite fission track ages from the Santa Fe Range portion of the Sangre de Cristo Mountains near Santa Fe are Late Cretaceous to early Eocene. These dates record the cooling of the area due to uplift and erosion during the Laramide event. The preservation of these older ages indicates that the Santa Fe Range was a low-lying area during the Oligocene to Miocene, while the surrounding areas (Sandia Mountains and Taos Range) underwent uplift and erosion. Volcanic activity occurred in the vicinity of the two areas of positive relief. Localized crustal extension associated with the volcanism may have contributed, in part, to the uplift of these areas. Using simple, two-dimensional thermal models, we found that the apparent denudation rates derived from the fission

  10. Late Pleistocene to Historical Activity of the Hovd Fault (Mongolian Altay) from Tectonic Geomorphology and Paleoseismology (United States)

    Ferry, M. A.; Battogtokh, D.; Ritz, J. F.; Kurtz, R.; Braucher, R.; Klinger, Y.; Ulzibat, M.; Chimed, O.; Demberel, S.


    Active tectonics of western Mongolia is dominated by large strike-slip fault systems that produced great historical earthquakes: the Bulnay fault (Mw 8.1 and 8.4 in 1905), the Fu-Yun fault (Mw 8.0 in 1931) and the Bogd fault (Mw 8.1 in 1957). Central to these faults is the Altay Range that accommodates ~4 mm/yr of right-lateral motion. An earthquake of similar magnitude occurred in 1761 and has been attributed to the Hovd fault were seemingly fresh surface rupture was reported in 1985. Here, we study the Ar-Hötöl section of the Hovd fault where surface rupture was described over a length of ~200 km. Detailed mapping of stream gullies from high-resolution Pleiades satellite images show a consistent pattern of right-lateral offsets from a few meters to ~500 m. At Climbing Rock, we surveyed a gully offset by 75 ± 5 m. The associated surface was sampled for 10Be profile which yields an exposure age of 154 ± 20 ka. The resulting minimal right-lateral slip rate ranges 0.4-0.6 mm/yr. However, drainage reconstruction suggests this surface may have recorded as much as 400 ± 20 m of cumulative offset. This implies the Hovd fault may accommodate as much as 2.6 ± 0.4 mm/yr, which would make it the main active fault of the Altay. At a smaller scale, TLS topography documents offsets in the order of 2.5-5 m that likely correspond to the most recent surface-rupturing event with Mw ~8. A value of 2.8-3.0 m is reconstructed from a Uiger grave dated AD 750-840. At Marmot Creek and Small Creek, short drainages flow across the fault and form ponds against the main scarp. Two paleoseimic trenches reveal similar stratigraphy with numerous peat layers that developed over alluvial sands. The fault exhibits near vertical strands affecting pre-ponding units as well as a well-developed peat unit radiocarbon-dated AD 1465-1635. This unit likely corresponds to the ground surface at the time of the last rupture. It is overlain with a sandy pond unit on top of which a second continuous peat

  11. The Late Cretaceous Alkaline Igneous Province in the Iberian Peninsula, and its tectonic significance (United States)

    Rock, N. M. S.


    The Iberian Province consists of the following: the three subvolcanic, syenitic, major intrusive complexes of Monchique, Sines and Sintra in W. and SW Portugal, together with their basanitic/lamprophyric minor intrusive suites; basanitic volcanic complexes around Lisbon; at least some of a widespread suite of basanitic to theralitic minor intrusives in west central Portugal; about 80 small basanitic/lamprophyric to nepheline syenitic intrusions scattered through the Pyrenees, NE Spain, the French Corbières, and off the coast of NW Spain; and the Ormonde Seamount of the Gorringe Bank off the SW coast of Portugal. Most of these occurrences have been dated isotopically or from field evidence as Late Cretaceous. Geological and petrological details of the various occurrences are compiled and reviewed. Primary basanitic magmas were probably parental to the entire Province, and generated syenitic magmas by differentiation processes; oversaturated rocks were produced by alkali loss and perhaps also by crustal involvement. The Iberian Province is related to the opening of the N. Atlantic, specifically that of the Bay of Biscay.


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    V. D. Mats


    Full Text Available The article reviews three typical concepts concerning the age of the Baikal rift (BR which development is still underway: 5 Ma (the BR development start in the Late Pliocene, 30 Ma (Miocene or Oligocene, and 60–70 Ma (the Late Cretaceous. Under the concept of the young BR age (Pliocene–Quaternary [Artyushkov, 1993; Nikolaev et al., 1985; Buslov, 2012], according to E.V. Artyushkov, BR is not a rift, but a graben due to the fact that the pre‐Pliocene structure of BR does not contain any elements that would be indicative of tensile stresses. However, field studies reported in [Lamakin, 1968; Ufimtsev, 1993; Zonenshain et al., 1995; Mats, 1993, 2012; Mats et al., 2001] have revealed that extension structures, such as tilted blocks and listric faults, are abundant in the Baikal basin (BB, and thus do not supportE.V. Artyushkov’s argumentation. The opinion that BR is young is shared by M.M. Buslov [2012]; he refers to studies of  Central Asia and states that only the Pliocene‐Quaternary structure of BB is a rift, while the oldest Cenozoic structures (Upper Cretaceous – Miocene are just fragments of the large Cenozoic Predbaikalsky submontane trough (PBT which are not related to the rift. However, the coeval Cenozoic lithological compositions, thicknesses of sediment layers and types of tectonic structures in PBT and BB have nothing in common. Across the area separating PBT and BB, there are no sediments or structures to justify a concept that BR and PBT may be viewed as composing a single region with uniform structures and formations. The idea of the Pliocene‐Quaternary age of BR should be rejected as it contradicts with the latest geological and geophysical data. Seismic profiling in BB has revealed the syn‐rift sedimentary bed which thickness exceeds 7.5 km. Results of drilling through the 600‐metre sedimentary sequence of Lake Baikal suggest the age of 8.4 Ma [Horiuchi et al., 2004], but M.M. Buslov believes

  13. Evidence for subduction-related magmatism during the Cretaceous and Cenozoic in Myanmar (United States)

    Sevastjanova, Inga; Sagi, David Adam; Webb, Peter; Masterton, Sheona; Hill, Catherine; Davies, Clare


    Myanmar's complex geological history, numerous controversies around its tectonic evolution and the presence of prospective hydrocarbon basins make it a key area of interest for geologists. Understanding whether a passive or an active margin existed in the region during the Cenozoic is particularly important for the production of accurate basin models; active Cenozoic subduction would imply that hydrocarbon basins in the forearc experienced extension due to slab rollback. The geology of Myanmar was influenced by the regional tectonics associated with the Cretaceous and Cenozoic closure of the Neotethys Ocean. During this time, India travelled rapidly from Gondwana to Asia at speeds up to 20 cm/yr. To accommodate the north-eastward motion of India, the Neotethys Ocean was consumed at the subduction zone along the southern margin of Eurasia. Based on our Global Plate Model, this subduction zone can reasonably be expected to extend for the entire width of the Neotethys Ocean as far as Myanmar and Southeast Asia at their eastern extent. Moreover, a) Cretaceous volcanism onshore Myanmar, b) the middle Cenozoic arc-related extension in the Present Day eastern Andaman Sea and c) the late Cenozoic uplift of the Indo-Burman Ranges are all contemporaneous with the subduction ages predicted by the global plate motions. However, because of the geological complexity of the area, additional evidence would augment interpretations that are based on structural data. In an attempt to reduce the uncertainty in the existing interpretations, we have compiled published zircon geochronological data from detrital and igneous rocks in the region. We have used published zircon U-Pb ages and, where available, published Hf isotope data and CL images (core/rim) in order to distinguish 'juvenile' mantle-derived zircons from those of reworked crustal origin. The compilation shows that Upper Cretaceous and Cenozoic zircons, which are interpreted to have a volcanic provenance, are common across the

  14. Regionwide Geodynamic Analyses of the Cenozoic Carbonate Burial in Sri Lanka Related to Climate and Atmospheric CO2

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    Amila Sandaruwan Ratnayake


    Full Text Available Asian tectonism and exhumation are critical components to develop modern icehouse climate. In this study, stratigraphic sections of eight wells in the Mannar and Cauvery basins were considered. The author demonstrated that this local system records a wealth of information to understated regional and global paleoclimatic trends over the Cenozoic era. The lithostratigraphic framework has been generally characterized by deposition of carbonate-rich sediments since the Middle Cenozoic. Geological provenance of carbonate sediments had probably related to local sources from Sri Lankan and Indian land masses. The main controlling factor of carbonate burial is rather questionable. However, this carbonate burial has indicated the possible link to the Middle to Late Cenozoic global climatic transition. This major climatic shift was characterized by long-term reduction of atmospheric carbon dioxide concentration over the Cenozoic era. Consequently, this geological trend (carbonate burial has a straightforward teleconnection to the global cooling towards the glaciated earth followed by the development of polar ice sheets that persist today.

  15. Sichuan Basin and beyond: Eastward foreland growth of the Tibetan Plateau from an integration of Late Cretaceous-Cenozoic fission track and (U-Th)/He ages of the eastern Tibetan Plateau, Qinling, and Daba Shan (United States)

    Yang, Zhao; Shen, Chuanbo; Ratschbacher, Lothar; Enkelmann, Eva; Jonckheere, Raymond; Wauschkuhn, Bastian; Dong, Yunpeng


    Combining 121 new fission track and (U-Th)/He ages with published thermochronologic data, we investigate the Late Cretaceous-Cenozoic exhumation/cooling history of the eastern Tibetan Plateau, Qinling, Daba Shan, and Sichuan Basin of east central China. The Qinling orogen shows terminal southwestward foreland growth in the northern Daba Shan thrust belt at 100-90 Ma and in the southern Daba Shan fold belt at 85-70 Ma. The eastern margin of Tibetan Plateau experienced major exhumation phases at 70-40 Ma (exhumation rate 0.05-0.08 mm/yr), 25-15 Ma (≤1 mm/yr in the Pengguan Massif; 0.2 mm/yr in the imbricated western Sichuan Basin), and since 11-10 Ma along the Longmen Shan ( 0.80 mm/yr) and the interior of the eastern Tibetan Plateau (Dadu River gorge, Min Shan; 0.50 mm/yr). The Sichuan Basin records two basin-wide denudation phases, likely a result of the reorganization of the upper Yangtze River drainage system. The first phase commenced at 45 Ma and probably ended before the Miocene; >1 km of rocks were eroded from the central and eastern Sichuan Basin. The second phase commenced at 12 Ma and denudated the central Sichuan Basin, Longmen Shan, and southern Daba Shan; more than 2 km of rocks were eroded after the lower Yangtze River had cut through the Three Gorges and captured the Sichuan Basin drainage. In contrast to the East Qinling, which was weakly effected by late Cenozoic exhumation, the West Qinling and Daba Shan have experienced rapid exhumation/cooling since 15-13 Ma, a result of growth of the Tibetan Plateau beyond the Sichuan Basin.

  16. The Alpine tectonic evolution of the Danube Basin and its northern periphery (southwestern Slovakia

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    Hók Jozef


    Full Text Available The tectonic evolution of the pre-Cenozoic basement, as well as the Cenozoic structures within the Danube Basin (DB and its northern periphery are presented. The lowermost portion of the pre-Cenozoic basement is formed by the Tatricum Unit which was tectonically affected by the subduction of the Vahicum / Penninicum distal continental crust during the Turonian. Tectonically disintegrated Tatricum overlaid the post-Turonian to Lower Eocene sediments that are considered a part of the Vahicum wedge-top basin. These sediments are overthrust with the Fatricum and Hronicum cover nappes. The Danube Basin Transversal Fault (DBTF oriented along a NW–SE course divided the pre-Neogene basement of the DB into two parts. The southwestern part of the DB pre-Neogene basement is eroded to the crystalline complexes while the Palaeogene and Mesozoic sediments are overlaid by the Neogene deposits on the northeastern side of the DBTF. The DBTF was activated as a dextral fault during the Late Oligocene – Earliest Miocene. During the Early Miocene (Karpatian – Early Badenian it was active as a normal fault. In the Middle – Late Miocene the dominant tectonic regime with NW – SE oriented extension led to the disintegration of the elevated pre-Neogene basement under the simple and pure shear mechanisms into several NE – SW oriented horst and graben structures with successive subsidence generally from west to east. The extensional tectonics with the perpendicular NE – SW orientation of the Shmin persists in the Danube Basin from the ?Middle Pleistocene to the present.

  17. Mesozoic and Cenozoic Cooling History of the Qiangtang Block, Northern Tibet, China: New Constraints from Apatite and Zircon Fission Track Data

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    Chunyan Song


    Full Text Available This study used a new set of zircon and apatite fission track ages to quantitatively document the tectonic evolution and cooling histories of the Qiangtang block of the central Tibetan Plateau. The results indicate that the Qiangtang block underwent three cooling stages at ~148 - 73, ~50 - 20, and ~20 - 0 Ma. The three-stage cooling history and tectonic exhumation were controlled by the closure of the Bangong-Nujiang Suture during the Late Jurassic-Late Cretaceous, the India-Asia collision in the Paleogene, and the underthrusting of the India Plate during the Late Cenozoic. In addition to revealing the Late Jurassic-Late Cretaceous cooling events, the annealing patterns of the zircon fission track samples indicate different burial depths, which may help identify the Jurassic basin characteristics of the Qiangtang block. The apatite fission track (AFT ages range from 60 ¡_ 5 Ma to 26 ¡_ 3 Ma, with a mean age of 44 Ma. These ages indicate that the Cenozoic exhumation of the Qiangtang block may have started in the Eocene. Inverse modeling of the AFT data shows that the Qiangtang block had a relatively slow cooling rate of approximately 0.5 - 1¢XC Myr-1 from 50 to 20 Ma. After ~20 Ma, most of the samples show evidence for a rapid cooling stage with a cooling rate of 4 - 6¢XC Myr-1.

  18. Petrogenesis and tectonic implications of the Early Carboniferous to the Late Permian Barleik plutons in the West Junggar (NW China) (United States)

    Liu, Bo; Han, Bao-Fu; Ren, Rong; Chen, Jia-Fu; Wang, Zeng-Zhen; Zheng, Bo


    The Paleozoic accretionary orogenesis and continental crustal growth in Central Asia are thought to have close relationship with the evolution of the Paleo-Asian Ocean (PAO). The well-exposed plutons in the northern Barleik Mountains of the West Junggar region, NW China, may provide essential insights into the evolution of the Junggar Ocean, a branch of the PAO, and mechanism of continental crustal growth. Our work on the Barleik plutons indicates an early suite of 324-320 Ma diorite and a late suite of 314-259 Ma quartz syenite and granitic porphyry. All the plutons are characterized by high-K calc-alkaline to shoshonitic signatures, varying depletion in Nb, Ta, Sr, P, Eu, and Ti, low initial 87Sr/86Sr ratios (0.70241-0.70585), strongly positive εNd(t) values (+ 5.7-+7.7), and young one-stage Nd model ages (390-761 Ma), suggesting that they resulted from different batches of magma that were produced by fractional crystallization of a metasomatized mantle source with minor crustal contamination. The diorite is coeval with the youngest arc magmatic rocks, indicating a subduction-related origin. By contrast, the quartz syenite and granitic porphyry are geochemically similar to A2-type granites, with high Zr, Ga, and FeOT/[FeOT + MgO], and are coeval with the widespread plutons in the West Junggar. This, together with the occurrence of Late Carboniferous fluvial deposits and the lack of < 320 Ma ophiolitic and subduction-related metamorphic lithologies, definitively indicates a post-collisional setting after the closure of the Junggar Ocean. Slab breakoff accompanied by asthenospheric upwelling and basaltic underplating is a possible geodynamic process that is responsible for the post-collisional magmatism and vertical crustal growth in the region. Thus a tectonic switch from subduction to post-collision started at the end of the Early Carboniferous ( 320 Ma), probably as a result of the final closure of the Junggar Ocean.

  19. Late Carboniferous to early Permian sedimentary–tectonic evolution of the north of Alxa, Inner Mongolia, China: Evidence from the Amushan Formation

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    Haiquan Yin


    Full Text Available The late Paleozoic evolution of the Wulijishanhen (WSH-Shangdan (SD area near to the Chaganchulu Ophiolite belt is reinterpreted. Analysis of the upper Carboniferous to lower Permian sedimentary sequence, biological associations, detrital materials, sandstone geochemistry and volcanic rocks indicates that the SD area was an epicontinental sea and rift during the late Paleozoic rather than a large-scale ocean undergoing spreading and closure. This study reveals that the actual evolution of the study area is from the late Carboniferous to the early Permian. The fusulinids Triticites sp. and Pseudoschwagerina sp. in the limestones demonstrate that the Amushan Formation develops during the late Carboniferous to the early Permian. The limestones at the base of the SD section indicate that it is a stable carbonate platform environment, the volcanic rocks in the middle of the sequence support a rift tectonic background, and the overlying conglomerates and sandstones are characteristic of an epicontinental sea or marine molasse setting. The rift volcanism made the differences in the fossil content of the SD and WSH sections and led to two sections expose different levels within the Amushan Formation and different process of tectonic evolution. Moreover, the geochemical characteristics and detrital materials of the sandstones show that the provenance and formation of the sandstones were related to the setting of active continental margin. The quartz-feldspar-lithic fragments distribution diagram indicates that the material source for the sandstones was a recycled orogenic belt. Thus, the source area of the sandstones may have been an active continental margin before the late Carboniferous–early Permian. The characteristics of the regional tectonic evolution of the area indicate that the region may form a small part of the Gobi–Tianshan rift of southern Mongolia.

  20. Late Archean-Early Proterozoic timing for an Andean-style porphyry Cu-Mo deposit at Malanjkhand, Central Indian Tectonic Zone: implications for a Late Archean supercontinent (United States)

    Stein, H. J.; Zimmerman, A.; Hannah, J. L.; Markey, R. J.


    Eight Re-Os ages from six molybdenite samples representative of Cu-Mo mineralization in a highly deformed quartz reef and granite host rock comprising the large Malanjkhand deposit were obtained using ID-NTIMS. These data provide a clear Late Archean-Early Proterozoic age for this recently discovered deposit and by implication a minimum age for its hosting terrane, the Central Indian Tectonic Zone (CITZ), a continental scale structure separating peninsular India from northern India. The CITZ was previously inferred to be Middle Proterozoic or younger. Molybdenite dating indicates that stringer mineralization in the quartz reef and disseminated mineralization in the granite were contemporaneous at 2493 ± 8 Ma (2493.1 ± 1.4 Ma based on regression without uncertainty in the 187Re decay constant, MSWD = 0.5, n = 5). Additional molybdenite was precipitated during at least two pulses of reworking (ěrb1 12480 and ěrb1 12450 Ma) that we suggest configured the elongate quartz reef as the CITZ developed in response to NW-directed oblique convergence of a landmass from the south. Previously unrecognized petrographic evidence coupled with high Re concentrations for molybdenites (400-650 ppm) suggest that Malanjkhand is a porphyry Cu-Mo deposit of classic Andean-type, forming in a subduction-accretionary setting that includes involvement of mantle. We suggest that the CITZ may provide a median segment of an extensive and continuous Late Archean-Early Proterozoic orogenic belt that may include portions of the Moyar, Bhavani, Palghat, and Cauvery shear zones in southern India, the Eastern Ghats orogenic belt along the eastern side of India, and connecting to the Aravalli-Delhi belt extending through northwest India. This now folded orogenic belt could be related to the assembly of a Late Archean supercontinent whose eastward margin included East Antartica (Napier complex) at 2.5 Ga. In addition, we suggest that the Vestfold Hills complex (East Antartica) was part of this

  1. Emplacement ages, geochemical and Sr-Nd-Hf isotopic characterization of Mesozoic to early Cenozoic granitoids of the Sikhote-Alin Orogenic Belt, Russian Far East: Crustal growth and regional tectonic evolution (United States)

    Jahn, Bor-ming; Valui, Galina; Kruk, Nikolai; Gonevchuk, V.; Usuki, Masako; Wu, Jeremy T. J.


    Late Cretaceous. The apparently regular progression of granitic intrusion ages from 80 to 56 Ma in the Taukha Terrane may reflect oblique underflow of the Paleo-Pacific plate beneath the Eurasian continental margin. Subduction was not only manifested by granitic intrusion, but also by abundant silicic volcanism. The Late Cretaceous Paleo-Pacific plate motion probably changed from parallel or sub-parallel to oblique relative to the continental margin of the Sikhote-Alin, leading to the change of magmatic source region and geochemical characteristics of the derived igneous rocks. Late Cretaceous rapid sea-floor spreading at ca. 100 Ma induced highly active subduction and led to voluminous magmatism in the entire Circum-Pacific realm. Finally, the present age and isotopic study lends support to the hypothesis of geologic and tectonic correlation between Sikhote-Alin and SW Japan.

  2. Evolución tectónica, paleogeográfica y metalogénica durante el Cenozoico en los Andes de Chile norte y central e implicaciones para las regiones adyacentes de Bolivia y Argentina Tectonic, paleogeographic, and metallogenic evolution during the Cenozoic in the Andes of Central and Northern Chile and implication for the adjacent regions of Bolivia and Argentina

    Directory of Open Access Journals (Sweden)

    Reynaldo Charrier


    southern Peru to central Chile and formed the boundary between two paleogeographical domains with dissimilar geological evolutions during the rest of the Cenozoic. The western domain was characterized by erosion and sedimentation processes. The eastern domain also included significant erosional episodes, but was characterized by different evolutions north and south of ~27°S. Northward of this latitude, within the Altiplano-Puna realm, the magmatic arc remained in a fixed position, coinciding with the current active arc, and was bordered by a back-arc foreland basin; whereas southward of ~27°S a succession of magmatic arcs developed with a prominent eastward migration. The Late Eocene to Late Oligocene- Early Miocene was characterized by the development of an extensive intra-arc extensional basin, the Abanico Basin. A succession of volcanic and volcaniclastic rocks, with minor sedimentary intercalations, up to 3,000 m thick were deposited within this basin. At about the boundary between the Oligocene and the Miocene a compressive tectonism affected the whole orogen rejuvenating the core of the Incaic Cordillera and resulted in the tectonic inversion of the Abanico Basin; leading to the syntectonic sedimentation on both sides of the new elevated terrain. The beginning of this tectonism is coincident with the Pehuenche orogeny, but the compression extended until the Early Pliocene. During the Early to Middle Miocene the deformation extended to the east with the development of foreland fold and thrust belts and basins. Within the western domain in northern Chile, area of the current Central Depression and Precordillera, the accumulation of thick sedimentary deposits from the western slope of the Incaic Cordillera originated the Tarapacá and Atacama pediments; whereas an extensive peneplanation developed in central Chile. In Late Miocene the prolonged development of the east-verging fold and thrust belts and the generation of overthrusts deep under the Cordillera, which

  3. Inversión y reactivación tectónicas cretácicocenozoicas en el Noroeste Argentino: influencia de las heterogeneidades del basamento neoproterozoico-paleozoico inferior Cretaceous-Cenozoic tectonic inversion and reactivation in Northwestern Argentina: Influence of Neoproterozoic-Lower Paleozoic basement heterogeneities

    Directory of Open Access Journals (Sweden)

    Fernando Hongn


    basement structural features have influenced in different ways the development of later both extensional Cretaceous and contractional Cenozoic structures. Tectonic inversion of normal faults related to the Cretaceous rift has been frequently addressed as the main mechanism for explaining double-vergent and retrovergent structures in the hinterland of the Andean orogen in northwestern Argentina. This paper proposes that basement structures played a primary role in the nucleation of both Cretaceous normal faults showing Cenozoic tectonic inversion and Cenozoic reverse faults. A regional section between the Domeyko Cordillera (Chile and the Santa Bárbara System (nearly at 24º-25ºSL shows portions with opposite Cenozoic vergence, each one related to different controls made by previous structures. The inversion of Mesozoic rift-related faults mainly influenced the geometry and vergence of the Cenozoic structures linked to Andean shortening in the Domeyko Cordillera, in the Calchaquí Valleys region and in the Santa Bárbara System. Reactivation of structures and heterogeneities formed during the Neoproterozoic-lower Paleozoic tectonic evolution of the basement controlled the Andean contractional structures in the Puna. Reactivation of Neoproterozoic-lower Paleozoic basement heterogeneities not only contributes to changes in attitude and vergence but also to the irregular time distribution showed by the Andean shortening since many of the reactivated or inverted (positive and negative inversion structures record superposed movements from the Cretaceous up to the Quaternary.

  4. Late Cretaceous ARC to MORB compositional switch in the Quebradagrande Complex, Colombian Andes: understanding the long term tectonic evolution of a magmatic arc. (United States)

    Jaramillo, J. S.; Cardona, A.; Zapata, S.; Valencia, V.


    The spatial and compositional characters of arc rocks are sensible markers of the tectonic changes experienced by convergent margins and therefore provide a fundamental view to the continuous tectonic evolution of active margins. The Early to Late Cretaceous tectonic evolution of the Northern Andes have been related to the growth and accretion of different continental and oceanic arc systems that were juxtaposed at the beginning of the Andean Orogeny in the Late Cretaceous. The Quebradagrande Complex is a tectonostratigraphic unit made of mafic to intermediate plutonic rocks, basic to intermediate volcanic flows and associated marine sedimentary rocks that have been related to a single Albian arc or back-arc environment that discontinuously outcrops along the western margin of the Central Cordillera of Colombia. New field, geochronological and geochemical data from the plutonic and volcanic rocks of the Quebradagrande complex shows that the pre-90-80 Ma volcanic arc rocks are intruded by ca. 90 Ma pyroxene gabbroic and hornblende dioritic plutons with medium to pegmatitic grain size characterized by a contrasting MORB-type signature. We related the compositional change to a transient modification of the convergent margin system, where and extensional roll-back related configuration or the subduction of an oceanic ridge allows the flux of the astenospheric mantle. This continental magmatic arc was subsequently deformed due to the collision and accretion of an allocthonous oceanic arc that migrate from the southeast Pacific at the beginning of the Andean orogeny.

  5. Terrestrial ferromanganese ore concentrations from mid-european basement blocks and their implication concerning the environment of formation during the late cenozoic (northern Bavaria, F.R.G.) (United States)

    Dill, Harald


    Terrestrial Fe-Mn concentrations from the Hercynian Basement in Central Europe may be categorized into five principal types: ferricretes sensu stricto, pebble iron ores, ferruginous conglomerates and breccias (Fe-Mn cement), Fe replacement ores and limonitic gossans of vein-type deposits. The four types first mentioned are true supergene, whereas the last-mentioned type of Fe-Mn mineralization is suggested to have been generated by ascending hydrothermal fluids which reacted with ground waters. A sequence of minerals common to all the different host-rock lithologies may be established: Fe silcretes, goethite, poorly hydrated Mn oxides and intensively hydrated modifications of manganomelane. The Fe-Mn enrichments, irrespective of their host rocks, were taken as remnants of hydromorphic paleosoils of nonlateritic origin (Plio-Pleistocene). The more silicified equivalents are assumed to be precursor of these concretions. The most significant controls on Fe-Mn enrichments are considered to be the host-rock lithology, the local and regional geomorphology and the Cenozoic climatic conditions.

  6. A synthesis of Cenozoic sedimentation in the North Sea

    DEFF Research Database (Denmark)

    Anell, Ingrid Anna Margareta; Thybo, Hans; Rasmussen, E.S.


    margins have undergone. While the North Sea has been mapped locally, we present the first regional mapping of the Cenozoic sedimentary strata. Our study provides a new regional sub-division of the main seismic units in the North Sea together with maps of depocentres, influx direction and source areas. Our......The North Sea Basin contains an almost complete record of Cenozoic sedimentation, separated by clear regional unconformities. The changes in sediment characteristics, rate and source, and expression of the unconformities reflect the tectonic, eustatic and climatic changes that the North Sea and its...... characteristics of many unconformities indicate that they were generated by eustatic sea-level fall, often in conjunction with other processes. Early Cenozoic unconformities, however, relate to tectonism associated with the opening of the North Atlantic. From observation on a regional scale, we infer...

  7. Late Paleozoic tectonics of the Solonker Zone in the Wuliji area, Inner Mongolia, China: Insights from stratigraphic sequence, chronology, and sandstone geochemistry (United States)

    Shi, Guanzhong; Song, Guangzeng; Wang, Hua; Huang, Chuanyan; Zhang, Lidong; Tang, Jianrong


    The geology in the Wuliji area (including the Enger Us and Quagan Qulu areas) is important for understanding the Late Paleozoic tectonics of the Solonker Zone. Ultramafic/mafic rocks in the Enger Us area, previously interpreted as an ophiolitic suture, are actually lava flows and sills in a Permian turbiditic sequence and a small body of fault breccia containing serpentinite. Subduction zone features, such as accretionary complexes, magmatic arc volcanics or LP/HP metamorphism are absent. Early Permian N-MORB mafic rocks and Late Permian radiolarian cherts accompanied by turbidites and tuffeous rocks indicate a deep water setting. In the Quagan Qulu area, outcrops of the Late Carboniferous to Permian Amushan Formation are composed of volcano-sedimenary rocks and guyot-like reef limestone along with a Late Permian volcano-sedimentary unit. A dacite lava in the Late Permian volcano-sedimentary unit yields a zircon U-Pb age of 254 Ma. The gabbros in the Quagan Qulu area are intruded into the Amushan Formation and caused contact metamorphism of country rocks. Sandstones in the Upper Member of the Amushan Formation contain detrital clasts of volcanic fragments and mineral clasts of crystalline basement rocks (i.e. biotite, muscovite and garnet). Geochemical analysis of volcaniclastic sandstones shows a magmatic affinity to both continental island arc (CIA) and active continental margin (ACM) tectonic settings. A Late Permian incipient rift setting is suggested by analyzing the lithostratigraphic sequence and related magmatism in the Wuliji area. The volcano-sedimentary rocks in the Wuliji area experienced a nearly N-S shortening that was probably related to the Early Mesozoic nearly N-S compression well developed in other areas close to the Wuliji area.

  8. Significant Cenozoic faulting, east margin of the Española Basin, Rio Grande rift, New Mexico (United States)

    Vernon, James H.; Riecker, Robert E.


    Tectonic interpretation of the east margin of the Española Basin, Rio Grande rift, New Mexico, has been controversial. Previous authors have disagreed as to whether significant faulting defines the boundary between the basin and the Sangre de Cristo Mountains. A more recent geophysical basin transect that suggests no significant faulting and held observation of faceted spurs along the western Sangre de Cristo Mountain front indicating a faulted margin motivate our study. The east margin of the Española Basin for about 37 km north of Santa Fe, New Mexico, is marked by a complex array of significant, late Cenozoic high-angle faults. Locally, three parallel, north-trending, high-angle faults cut Precambrian basement and Tertiary basin-fill rocks along the basin margin. Elsewhere along the margin, tilted fault blocks and intersecting faults occur. Fault area, fault attitude with depth, magnitude of fault motion, and timing of fault motion remain uncertain. However, faults studied in detail are 1-2 km long, have minimum dip-slip motion of 33-100 m, and underwent movement during the late Cenozoic. Potentially significant tectonic and seismic hazard implications arise from the possibility of post-150 ka fault motion.

  9. Cenozoic uplift of the Tibetan Plateau: Evidence from the tectonic–sedimentary evolution of the western Qaidam Basin

    Directory of Open Access Journals (Sweden)

    Yadong Wang


    Full Text Available Geologists agree that the collision of the Indian and Asian plates caused uplift of the Tibet Plateau. However, controversy still exists regarding the modes and mechanisms of the Tibetan Plateau uplift. Geology has recorded this uplift well in the Qaidam Basin. This paper analyzes the tectonic and sedimentary evolution of the western Qaidam Basin using sub-surface seismic and drill data. The Cenozoic intensity and history of deformation in the Qaidam Basin have been reconstructed based on the tectonic developments, faults growth index, sedimentary facies variations, and the migration of the depositional depressions. The changes in the sedimentary facies show that lakes in the western Qaidam Basin had gone from inflow to still water deposition to withdrawal. Tectonic movements controlled deposition in various depressions, and the depressions gradually shifted southeastward. In addition, the morphology of the surface structures in the western Qaidam Basin shows that the Cenozoic tectonic movements controlled the evolution of the Basin and divided it into (a the southern fault terrace zone, (b a central Yingxiongling orogenic belt, and (c the northern fold-thrust belt; divided by the XI fault (Youshi fault and Youbei fault, respectively. The field data indicate that the western Qaidam Basin formed in a Cenozoic compressive tectonic environment caused by the India–Asia plate collision. Further, the Basin experienced two phases of intensive tectonic deformation. The first phase occurred during the Middle Eocene–Early Miocene (Xia Ganchaigou Fm. and Shang Ganchaigou Fm., 43.8–22 Ma, and peaked in the Early Oligocene (Upper Xia Ganchaigou Fm., 31.5 Ma. The second phase occurred between the Middle Miocene and the Present (Shang Youshashan Fm. and Qigequan Fm., 14.9–0 Ma, and was stronger than the first phase. The tectonic–sedimentary evolution and the orientation of surface structures in the western Qaidam Basin resulted from the Tibetan

  10. Shallow-source aeromagnetic anomalies observed over the West Antarctic Ice Sheet compared with coincident bed topography from radar ice sounding - New evidence for glacial "removal" of subglacially erupted late Cenozoic rift-related volcanic edifices (United States)

    Behrendt, John C.; Blankenship, D.D.; Morse, D.L.; Bell, R.E.


    Aeromagnetic and radar ice sounding results from the 1991-1997 Central West Antarctica (CWA) aerogeophysical survey over part of the West Antarctic Ice Sheet (WAIS) and subglacial area of the volcanically active West Antarctic rift system have enabled detailed examination of specific anomaly sources. These anomalies, previously interpreted as caused by late Cenozoic subglacial volcanic centers, are compared to newly available glacial bed-elevation data from the radar ice sounding compilation of the entire area of the aeromagnetic survey to test this hypothesis in detail. We examined about 1000 shallow-source magnetic anomalies for bedrock topographic expression. Using very conservative criteria, we found over 400 specific anomalies which correlate with bed topography directly beneath each anomaly. We interpret these anomalies as indicative of the relative abundance of volcanic anomalies having shallow magnetic sources. Of course, deeper source magnetic anomalies are present, but these have longer wavelengths, lower gradients and mostly lower amplitudes from those caused by the highly magnetic late Cenozoic volcanic centers. The great bulk of these >400 (40-1200-nT) anomaly sources at the base of the ice have low bed relief (60-600 m, with about 80%10 million years ago. Eighteen of the anomalies examined, about half concentrated in the area of the WAIS divide, have high-topographic expression (as great as 400 m above sea level) and high bed relief (up to 1500 m). All of these high-topography anomaly sources at the base of the ice would isostatically rebound to elevations above sea level were the ice removed. We interpret these 18 anomaly sources as evidence of subaerial eruption of volcanoes whose topography was protected from erosion by competent volcanic flows similar to prominent volcanic peaks that are exposed above the surface of the WAIS. Further, we infer these volcanoes as possibly erupted at a time when the WAIS was absent. In contrast, at the other extreme

  11. Shallow-source aeromagnetic anomalies observed over the West Antarctic Ice Sheet compared with coincident bed topography from radar ice sounding—new evidence for glacial "removal" of subglacially erupted late Cenozoic rift-related volcanic edifices (United States)

    Behrendt, John C.; Blankenship, Donald D.; Morse, David L.; Bell, Robin E.


    Aeromagnetic and radar ice sounding results from the 1991-1997 Central West Antarctica (CWA) aerogeophysical survey over part of the West Antarctic Ice Sheet (WAIS) and subglacial area of the volcanically active West Antarctic rift system have enabled detailed examination of specific anomaly sources. These anomalies, previously interpreted as caused by late Cenozoic subglacial volcanic centers, are compared to newly available glacial bed-elevation data from the radar ice sounding compilation of the entire area of the aeromagnetic survey to test this hypothesis in detail. We examined about 1000 shallow-source magnetic anomalies for bedrock topographic expression. Using very conservative criteria, we found over 400 specific anomalies which correlate with bed topography directly beneath each anomaly. We interpret these anomalies as indicative of the relative abundance of volcanic anomalies having shallow magnetic sources. Of course, deeper source magnetic anomalies are present, but these have longer wavelengths, lower gradients and mostly lower amplitudes from those caused by the highly magnetic late Cenozoic volcanic centers. The great bulk of these >400 (40-1200-nT) anomaly sources at the base of the ice have low bed relief (60-600 m, with about 80%WAIS >10 million years ago. Eighteen of the anomalies examined, about half concentrated in the area of the WAIS divide, have high-topographic expression (as great as 400 m above sea level) and high bed relief (up to 1500 m). All of these high-topography anomaly sources at the base of the ice would isostatically rebound to elevations above sea level were the ice removed. We interpret these 18 anomaly sources as evidence of subaerial eruption of volcanoes whose topography was protected from erosion by competent volcanic flows similar to prominent volcanic peaks that are exposed above the surface of the WAIS. Further, we infer these volcanoes as possibly erupted at a time when the WAIS was absent. In contrast, at the other

  12. Evidence of Arid to Semi-arid Climate Near Western Pacific Warm Pool During Sea-Level Lowstands: Caliche Surfaces in Late Cenozoic Carbonates of Nansha Islands, South China Sea (United States)

    Gong, S.; Mii, H.; Horng, C.; Huang, F.; Chi, W.; Yui, T.; Torng, P.; Huang, S.; Wang, S.; Wu, J.; Yang, K.


    Whether the climate of tropical seas during glacial periods became cold and dry has been an open debate. Models by different authors proposed the tropical sea-surface temperature (SST) during the Last Glacial Maximum (LGM) to be about 2\\deg lower, or 5-6\\deg lower than present. The controversy partly arise from disparate reconstructions of temperature from stable oxygen isotope archives of marine sediments. In this paper, we provide field evidence of semi-arid or arid climate during late Cenozoic sea-level lowstands from an atoll located in central South China Sea near the Western Pacific Warm Pool (WPWP). Lower rainfall and higher evaporation associated with the dry conditions might have resulted in less meteoric water component in the surface sea-water, and this factor should be taken into considerations in deciphering temperature from isotopic records. Taiping Islet (Itu Aba), located at N10\\deg 23' and E114\\deg 22' is part of the Nansha (Spratly) Islands near the northwestern margin of the Western Pacific Warm Pool. Rock cores of a borehole at Taiping became accessible to the authors in the recent years. We identified at least four subaerial exposure surfaces (SES) in the late Cenozoic carbonates. Caliche deposits are recognized on each of the four surfaces on the basis of alveolar texture, micro-rhizolith, caliche glaebules and corroded limestone nodules in reddish matrix (terra-rossa). Caliche developed on limestones typically forms in semi-arid to arid areas with annual precipitation from about 500 to 1000mm, while the modern annual rainfall of Nansha Island is 1800-2100mm. The occurrence of the Nansha caliche suggests the climate was much drier than present during the sea-level lowstands represented by the four SES. During the sea-level falls, reduced surface area of South China Sea with continental shelves exposed might have resulted in less moistures in the atmosphere and therefore less precipitation and higher evaporation rates. As a result, the

  13. Timing and tectonic processes associated to the Late Cretaceous to Paleogene transition from collision to subduction in the Northern margin of Colombia (United States)

    Cardona, A.; Montes, C.; Bayona, G.; Jaramillo, S.; Lopez-Martinez, M.; Silva, J.; Valencia, V.; Vanegas, J.; Zapata, S.


    Large scale plate tectonic scale models of the Caribbean-South American interactions have suggest the existence of different Late Cretaceous to Eocene collisional and subduction events associated to the Caribbean and South American plates interactions. We integrate field, petrological and geochronological results from igneous, metamorphic and sedimentary rocks from northeastern Colombia Guajira and Santa Margin in order to accurately discriminate the timing and understand with more details the processes associated to the evolution from collision to subduction and oblique convergence between the Caribbean and South America. Geochronological data from metamorphic units in the Santa Marta and Guajira regions document Late Cretaceous and Early Paleocene deformational events link to the collision of the Caribbean plate margin and the subsequent inversion of the upper plate during subduction initiation. Contemporaneous with these metamorphic events, inland basins experienced two major peaks of subsidence that can be related to the advance and overthrusting of the continental plate within the same tectonic scenario of collision and renewed subductions. This was followed by the construction of an Early Eocene magmatic arc located within the upper plate in a near trench position. Shallow and "fore arc" melting was related to the early astenospheric influx under the upper plate during the early stages of subduction. Another Late Eocene-Oligocene deformation is related to thrusting of the arc, exhumation and inland migration of deformation. This event may be related to major changes in the rates and directions of plate convergence between the Caribbean and South American plates.

  14. Geochemistry of Late Triassic pelitic rocks in the NE part of Songpan-Ganzi Basin, western China: Implications for source weathering, provenance and tectonic setting

    Directory of Open Access Journals (Sweden)

    Yan Tang


    Full Text Available Major, trace and rare earth element (REE concentrations of Late Triassic sediments (fine-grained sandstones and mudstones from Hongcan Well 1 in the NE part of the Songpan-Ganzi Basin, western China, are used to reveal weathering, provenance and tectonic setting of inferred source areas. The Chemical Index of Alteration (CIA reflects a low to moderate degree of chemical weathering in a cool and somewhat dry climate, and an A-CN-K plot suggests an older upper continental crust provenance dominated by felsic to intermediate igneous rocks of average tonalite composition. Based on the various geochemical tectonic setting discrimination diagrams, the Late Triassic sediments are inferred to have been deposited in a back-arc basin situated between an active continental margin (the Kunlun-Qinling Fold Belt and a continental island arc (the Yidun Island Arc. The Triassic sediments in the study area underwent a rapid erosion and burial in a proximal slope-basin environment by the petrographic data, while the published flow directions of Triassic turbidites in the Aba-Zoige region was not supported Yidun volcanic arc source. Therefore, we suggest that the Kunlun-Qinling terrane is most likely to have supplied source materials to the northeast part of the Songpan-Ganzi Basin during the Late Triassic.

  15. Major phases of salt tectonics within the Central European Basin System (United States)

    Maystrenko, Yuriy; Scheck-Wenderoth, Magdalena; Bayer, Ulf


    The Central European Basin System (CEBS) covers the area of the Southern and Northern Permian basins and contains up to 12 km of Permian to Cenozoic deposits. Initiated in the Early Permian, the Central European Basin System accumulated Lower Permian clastics overlain by significant amount of Upper Permian (Zechstein) salt. Post-Permian differentiation of the basin system was controlled by variable regional stress conditions including Late Triassic extension, a Mid-Late Jurassic-Early Cretaceous regional erosional event, Early Cretaceous transtension and Late Cretaceous-Early Tertiary compression. These tectonic phases not only provoked regional shifts in subsidence and erosion but also triggered the mobilisation of the Zechstein salt which had an important impact on sedimentation and the subsequent deformation of Mesozoic and Cenozoic strata within the CEBS. Salt rise strongly influenced the Meso-Cenozoic structural evolution in terms of mechanical decoupling of the sedimentary cover from its basement. Consequently, the CEBS displays a wide variety of salt structures (walls, diapirs and pillows) with structural amplitudes of up to 9 km. This makes it a classical site to study the interaction of salt movements, deposition and tectonics. A combined approach of subsidence analysis and seismic interpretation has been used to unravel the mechanisms controlling basin evolution and the related salt pathways. Subsidence analysis includes 3D backstripping with salt redistribution in response to the changing load conditions in the salt cover. The results of 3D modelling of salt movements and seismic data indicate that the primary initiation of salt movements occurred during the Triassic. The Triassic regional extensional event initiated a phase of salt movements within the Triassic depocenters of the Central European Basin System, such as the Glueckstadt Graben, Horn Graben, the Fjerritslev Trough and the adjacent Himmerland Graben of the Norwegian-Danish Basin, and the

  16. Tectonic and climatic controls on late quaternary sedimentary processes in a neotectonic intramontane basin. (The Pitalito Basin, South Colombia).

    NARCIS (Netherlands)

    Bakker, J.


    The present study deals with the influence of tectonics and climatic changes on sedimentation patterns in the Quaternary Pitalito Basin (lat. 1°52'N, long. 76°02'W). This intramontane sedimentary basin is 15 km in width and 20 kin in length and is located in the Eastern Cordillera of the southern Co

  17. From Flysch to Molasse-Sedimentary and Tectonic Evolution of Late Caledonian-Early Hercynian Foreland Basin in North Qilian Mountains

    Institute of Scientific and Technical Information of China (English)


    The Late Caledonian to Early Hercynian North Qilian orogenic belt in northwestern China is an elongate tectonic unit situated between the North China plate in the north and the Qaidam plate in the south. North Qilian started in the latest Proterozoic to Cambrian as a rift basin on the southern margin of North China, and evolved later to an archipelagic ocean and active continental margin during the Ordovician and a foreland basin from Silurian to the Early and Middle Devonian. The Early Silurian flysch and submarine alluvial fan, the Middle to Late Silurian shallow marine to tidal flat deposits and the Early and Middle Devonian terrestrial molasse are developed along the corridor Nanshan. The shallowing-upward succession from subabyssal flysch, shallow marine, tidal flat to terrestrial molasse and its gradually narrowed regional distribution demonstrate that the foreland basin experienced the transition from flysch stage to molasse stage during the Silurian and Devonian time.

  18. Norway and adjacent sedimentary basins during Cenozoic times - sediment fluxes, accumulation rates and mass balance

    DEFF Research Database (Denmark)

    Gołędowski, Bartosz; Nielsen, S.B.; Clausen, O.R.


    is in agreement with the so-called ICE hypothesis (Nielsen et al., 2009) which suggests the longevity of the Scandinavian mountains and do not impose tectonic rejuvenation of topography in Cenozoic times. Such episodes of tectonic uplift have been previously suggested as the controlling factors of erosion rates...

  19. Late Cenozoic evolution in the Pamir-Tian Shan convergence: New chronological constraints from the magnetostratigraphic record of the southwestern Tianshan foreland basin (Ulugqat area) (United States)

    Qiao, Qingqing; Huang, Baochun; Biggin, Andrew J.; Piper, John D. A.


    The northeastern Pamir-Tian Shan convergence zone is a key region for understanding ongoing intracontinental mountain building. A detailed magnetostratigraphic study combined with color reflectance variations of continental sediments from the 1120 m-thick Sankeshu Section in the south west sector of the Tianshan Foreland Basin of western China yields important insights into the tectonic evolution of this zone. Correlation with the geomagnetic polarity time scale identifies deposition lasting from 16.7 to 2.6 Ma with a marked increase in sedimentation rate at 7 Ma. A further rapid increase occurred after 2.6 Ma with influx of the conglomeratic Xiyu Formation. Observed height-dependent changes of rock magnetic parameters (shape parameter T and AMS ellipsoid parameters) show that these sediments were influenced by weak deformation, with the sediments accumulated before 11 Ma recording a signature of compressive deformation from northward indentation by the Pamir. The succession of sedimentary events in the foreland basin is comparable to previous investigations of magnetostratigraphic and sedimentological analyses, and with thermochronology collectively showing that deformation in the Tian Shan region has been concentrated in Miocene and later times. The regional correlations resulting from these analyses show that sedimentary events correlate with the episodic nature of regional uplift with the latter inducing climatic changes that are in turn recorded in the sediment record.

  20. Mesozoic-Cenozoic thermal history of Turpan-Hami Basin: apatite fission track constraints

    Institute of Scientific and Technical Information of China (English)

    ZHU Wenbin; WAN Jinglin; SHU Liangshu; SUN Yan; GUO Jichun; WANG Feng


    Apatite fission track dating is carried out on nine samples collected from the central part (Lianmuqin section) and from both northern and southern margins of Turpan-Hami Basin. The fission-track ages of seven Jurassic samples are distinctly younger than depositional ages. In contrast, the fission-track ages of two Cretaceous samples are older than, or as old as depositional ages. These observations indicate that the Jurassic samples have been annealed or partially annealed, whereas the Cretaceous samples have not been annealed.The further thermal modelling results show that Turpan-Hami Basin experienced a Late Cretaceous period (120-100 Ma) of tectonic uplift with rapid cooling and exhumation of sediments. The samples underwent a Cenozoic period of reburial and re-heating and were exhumed again at 10-8 Ma.

  1. Late Cretaceous-Cenozoic subduction-collision history of the Southern Neotethys: new evidence from the Çağlayancerit area, SE Turkey (United States)

    Akıncı, Ahmet Can; Robertson, Alastair H. F.; Ünlügenç, Ulvi Can


    Evidence of the subduction-collision history of the S Neotethys is well exposed in the frontal part of the SE Anatolian thrust belt and the adjacent Arabian continental margin. The foreland succession in the study area begins with Eocene shelf carbonates, ranging from shallow marine to deeper marine, without sedimentary input from the Tauride continent to the north. After a regional hiatus (Oligocene), sedimentation resumed during the Early Miocene with terrigenous gravity-flow deposition in the north (Lice Formation) and shallow-marine carbonates further south. Clastic detritus was derived from the Tauride continent and oceanic accretionary material. The base of the overriding Tauride allochthon comprises ophiolite-derived debris flows, ophiolite-related mélange and dismembered ophiolitic rocks. Above this, the regional-scale Bulgurkaya sedimentary mélange (an olistostrome) includes blocks and dismembered thrust sheets of metamorphic rocks, limestone and sandstone, which include Late Cretaceous and Eocene foraminifera. The matrix is mainly strongly deformed Eocene-Oligocene mudrocks, hemipelagic marl and sandstone turbidites. The thrust stack is topped by a regionally extensive thrust sheet (Malatya metamorphic unit), which includes greenschist facies marble, calcschist, schist and phyllite, representing Tauride continental crust. Beginning during the Late Mesozoic, the S Neotethys subducted northwards beneath a backstop represented by the Tauride microcontinent (Malatya metamorphic unit). Ophiolites formed within the S Neotethys and accreted to the Tauride active margin. Large-scale sedimentary mélange developed along the Tauride active margin during Eocene-Oligocene. On the Arabian margin, a sedimentary hiatus and tilting (Oligocene) is interpreted to record initial continental collision. The Early Miocene terrigenous gravity flows represent a collision-related flexural foreland basin. Southward overthrusting of the Tauride allochthon took place during Early

  2. Paleogeographic and tectonic implications of the first paleomagnetic results from the Middle Late Cambrian Mesón Group: NW Argentina (United States)

    Spagnuolo, Cecilia M.; Rapalini, Augusto E.; Astini, Ricardo A.


    The first paleomagnetic data from autochthonous Cambrian rocks in NW Argentina is reported to constrain the apparent polar wander path (APWP) of Gondwana during the Early Paleozoic. The paleomagnetic pole (Lat 4.5°S; Long 359.0°E; dp = 5.5; dm = 8.8; n = 26) was obtained from the red to purple sandstones of the Campanario Formation. These rocks present a characteristic remanence carried by fine-grained hematite. The pole indicates that during the Late Cambrian, rocks now exposed in the Eastern Cordillera of NW Argentina were deposited at relatively low latitudes (≈26°S), consistent with intense chemical alteration during wet and warm climates, as indicated from petrography of apparent first-cycle quarzites of the Mesón Group. However, the pole position is anomalous with respect to the most accepted apparent polar wander paths for Gondwana, suggesting that the study area (22°50'S, 65°00'W) underwent clockwise rotation of 38° ± 8°, likely related to the Cenozoic central Andes rotation pattern characteristic of the region.

  3. Late Cretaceous-Cenozoic exhumation history of Tiantangzhai region of Dabieshan Orogen: Constraints from (U-Th)/He and fission track analysis

    Institute of Scientific and Technical Information of China (English)


    Integrated fission track and (U-Th)/He analysis is carried out on 6 apatite and 6 zircon samples from a near vertical section in The Tiantangzhai region at the core of the present Dabieshan orogen. The result shows that the region experienced cooling/exhumation during the Late Cretaceous and Early Tertiary period. Age-elevation relationships for different dating systems and different minerals suggest a pulse of rapid exhumation at ~110 Ma before present, preserved in the structurally highest samples. At lower elevations, ages begin to decrease with decreasing elevation, suggesting lower exhumation rates since 90 Ma. Two periods of different exhumation rates are identified since 90 Ma. The average apparent exhumation rate for the period of 43.4-22.5 is 0.062 km/Ma, whereas that for the period of 76.4-47.4 Ma is 0.039 km/Ma.

  4. Late Cretaceous to recent tectonic evolution of the North German Basin and the transition zone to the Baltic Shield/southwest Baltic Sea (United States)

    Al Hseinat, M.; Hübscher, C.


    In this study we investigate the Late Cretaceous to recent tectonic evolution of the southwestern Baltic Sea based on a dense grid of seismic reflection profiles. This area covers the Baltic Sea sector of the salt influenced North German Basin and its transition to the salt free Baltic Shield across the Tornquist Zone. The Upper Cretaceous to recent structural evolution is discussed by means of individual seismic sections and derived high-resolution time-structure maps of the main horizons, i.e., the Upper Cretaceous, Tertiary and Pleistocene. The Upper Cretaceous and Tertiary layers reveal numerous significant faults throughout the study area. Several of these faults propagate upwards across the unconsolidated Pleistocene sediments and occasionally penetrate the surface. The salt influenced North German Basin reveals three major fault trends: NW-SE, N-S and NNE-SSW. Several of these faults are located directly above basement (sub-salt) faults and salt pillows. The majority of these faults are trending N-S to NNE-SSW and parallel the direction of the Glückstadt Graben faults. In the salt free Tornquist Zone, we identify two major shallow fault trends, which are NW-SE and NE-SW. The majority of these faults are located above basement faults, following the direction of the Tornquist Zone. We conclude that generally basement tectonics controls activation and trends of shallow faults. If salt is present, the ductile salt layer causes a lateral shift between the sub- and supra-salt faults. Major plate reorganisation related to the Africa-Iberia-Europe convergence and the subsequent Alpine Orogeny caused reactivation of pre-existing faults and vertical salt movement in the Late Cretaceous. The change of stress orientation from NE-SW to a NW-SE during Neogene caused another phase of fault and salt tectonic reactivation. We explain that the ice-sheet loading and/or present-day stress field may have acted in combination, causing the recent tectonics and upward extension of

  5. Geochronological and sedimentological evidences of Panyangshan foreland basin for tectonic control on the Late Paleozoic plate marginal orogenic belt along the northern margin of the North China Craton (United States)

    Li, Jialiang; Zhou, Zhiguang; He, Yingfu; Wang, Guosheng; Wu, Chen; Liu, Changfeng; Yao, Guang; Xu, Wentao; Zhao, Xiaoqi; Dai, Pengfei


    There is a wide support that the Inner Mongolia Palaeo-uplift on the northern margin of the North China Craton has undergone an uplifting history. However, when and how did the uplift occurred keeps controversial. Extensive field-based structural, metamorphic, geochemical, geochronological and geophysical investigations on the Inner Mongolia Palaeo-uplift, which suggested that the Inner Mongolia Palaeo-uplift was an uplifted region since the Early Precambrian or range from Late Carboniferous-Early Jurassic. The geochemical characteristics of the Late Paleozoic to Early Mesozoic intrusive rocks indicated that the Inner Mongolia Palaeo-uplift was an Andean-type continental margin that is the extensional tectonic setting. To address the spatial and temporal development of the Inner Mongolia Palaeo-uplift, we have carried out provenance analysis of Permian sedimentary rocks which collected from the Panyangshan basin along the northern margin of the North China Craton. The QFL diagram revealed a dissected arc-recycled orogenic tectonic setting. Moreover, the framework grains are abundant with feldspar (36-50%), indicating the short transport distance and unstable tectonic setting. Detrital zircon U-Pb analysis ascertained possible provenance information: the Precambrian basement ( 2490 and 1840 Ma) and continental arc magmatic action ( 279 and 295 Ma) along the northern margin of the North China Craton. The projection in rose diagrams of the mean palaeocurrent direction, revealing the SSW and SSE palaeoflow direction, also shows the provenance of the Panyangshan basin sources mainly from the Inner Mongolia Palaeo-uplift. The andesite overlying the Naobaogou Formation has yielded U-Pb age of 277.3 ± 1.4 Ma. The additional dioritic porphyry dike intruded the Naobaogou and Laowopu Formations, which has an emplacement age of 236 ± 1 Ma. The above data identify that the basin formed ranges from Early Permian to Middle Triassic (277-236 Ma). Accordingly, the Inner Mongolia

  6. Late Pleistocene-Holocene uplift driven terrace formation and climate-tectonic interplay from a seismically active intraplate setting: An example from Kachchh, Western India (United States)

    Prizomwala, S. P.; Das, Archana; Chauhan, G.; Solanki, T.; Basavaiah, N.; Bhatt, Nilesh; Thakkar, M. G.; Rastogi, B. K.


    Fluvial terrace formation is often regulated by external forcings like climate, tectonic and eustatic changes. These terraces, particularly in a dryland environment, preserves the discrete signatures of these external forcings, thus enabling us to reconstruct the fluvial response to the late Quaternary palaeoenvironmental changes and factors governing them. The present study focuses on reconstructing the aggradation/incision phases in the Lotia River which is located in the eastern segment of the Northern Hill Range (NHR) of the Kachchh Peninsula. The Lotia river drains through Mesozoic rocks before cutting across the Kachchh Mainland Fault (KMF) and finally debouch in the Banni Plains. Reconstruction based on tectonic geomorphology, sedimentology, sediment geochemistry, mineral magnetic, and OSL chronology suggests the fluvial response to monsoon variability archived during the last 15 ka. The time frame was also marked by incision enhanced by uplift along the KMF, which led to strath terrace formation. The accommodation space thus created was filled by an aggradational event between 14.8 ka and 10.6 ka. Sedimentological and geochemical parameters have also suggested that the time period between 12.5 ka and 11.5 ka showed a decline in the monsoon strength, which coincides with 'Younger Dryas'. It has been observed that the sediments spanning between 10.6 ka and 7.8 ka are absent from the archive, which is most likely the manifestation of the early Holocene optimum that led to severe erosional processes. The period between 7.8 ka and 3.3 ka is marked as another aggradational phase with fluctuating climatic conditions. At 3.3 ka, the region has experienced an incision of 4 m, which led to the formation of Holocene terrace T1, most likely due to tectonic uplift. During the last 3.3 ka, another pulsative uplift has occurred, which led to the formation of unpaired Holocene terrace T2, along with tilting of the Lotia basin. Based on the OSL chronology of bedrock strath

  7. Successor Characteristics of the Mesozoic and Cenozoic Songliao Basins

    Institute of Scientific and Technical Information of China (English)

    LI Zhongquan; Timothy KUSKY; YING Danlin; GUO Xiaoyu; LI Hongkui


    The Songliao basin is a complex successor basin that was initiated in the Mesozoic and experienced multiple periods of reactivation. Based on seismic and drilling data, as well as regional geologic research, we suggest that the Songliao basin contains several different successor basins resting on top of Carboniferous-Permian folded strata forming the basement to the Songliao basin. These basins include the Triassic-Mid Jurassic Paleo-foreland basin, the Late Jurassic-Early Cretaceous downfaulted basin, and an early Cretaceous depressed basin (since the Denglouku Group). This paper presents a systematic study of the basin-mountain interactions, and reveals that there are different types of prototype basin at different geologic times. These prototype basins sequentially superimposed and formed the large Songliao basin. Discovery of the Triassic-early Middle Jurassic paleo-foreland basin fills a Triassic-early Middle Jurassic gap in the geologic history of the Songliao basin. The paleoforeland basin, downfaulted basin, and depressed thermal subsidence basin all together represent the whole Mesozoic-Cenozoic geologic history and deformation of the Songliao basin. Discovery of the Triassic-early Middle Jurassic paleo-foreland basin plays an important role both for deep natural gas exploration and the study of basin-mountain coupling in north China and eastern China in general. This example gives dramatic evidence that we should give much more attention to the polyphase tectonic evolution of related basins for the next phase of exploration and study.

  8. Mesozoic-Cenozoic mafic magmatism in Sanandaj-Sirjan Zone, Zagros Orogen (Western Iran): Geochemical and isotopic inferences from Middle Jurassic and Late Eocene gabbros (United States)

    Deevsalar, R.; Shinjo, R.; Ghaderi, M.; Murata, M.; Hoskin, P. W. O.; Oshiro, S.; Wang, K. L.; Lee, H. Y.; Neill, I.


    One of the consequences of Neo-Tethys ocean subduction beneath the Central Iranian Micro-continent (CIMC) is the development of rare gabbroic intrusions in the Malayer-Boroujerd Plutonic Complex (MBPC) located in the Sanandaj-Sirjan Zone (SaSZ) of the Zagros Orogenic belt. The MBPC is a suite of extensive felsic and lesser mafic magmatic products in the northern SaSZ with geochemical signatures of arc-like magmatism during the Middle Jurassic (Ghorveh-Aligudarz arc) and intraplate type in the Late Eocene. Middle Jurassic gabbros (non-cumulate and cumulate) have low-Ti concentrations (non-cumulates belong to common liquid line of descent, with complementary trace element patterns. Much of the variation between samples can be modeled by fractional crystallization (FC) of a common parent; only one cumulate gabbro from this suite exhibits isotopic evidence of contamination, probably by Rb-depleted crustal materials. The Late Eocene gabbros have relatively high-Ti (> 1 wt.%) and display isotopically depleted Sr-Nd values (initial 87Sr/86Sr: 0.7044-0.7087, εNd(t): 1.9 -+3.2, barring one crustally-contaminated sample). OIB-like trace element characteristics such as enriched HFSE, and only minor enrichment of LILE and LREE, reflect a within-plate character and asthenospheric source. Trace element modeling indicates small degree melting (fmelting: 0.05) of upper mantle lherzolite (garnet:spinel 3:1) followed by higher degree melting (fmelting: 0.15) at shallower depths (garnet:spinel 4.5:2). The Eocene parental magma underwent FC of olivine and clinopyroxene. We propose that Eocene asthenospheric upwelling was triggered by slab tearing in response to slab-rollback, which is elsewhere reported to have triggered a 'flare-up' of extension-related magmatism across Iran. Three stages of tectono-magmatic evolution in the Ghorveh-Aligudarz arc segment of the N-SaSZ are represented by: 1) arc-like magmatism during active subduction of the Neo-Tethys seaway at Middle Jurassic, 2

  9. Evolution process of the Late Silurian–Late Devonian tectonic environment in Qimantagh in the western portion of east Kunlun, China: Evidence from the geochronology and geochemistry of granitoids

    Indian Academy of Sciences (India)

    Nana Hao; Wanming Yuan; Aikui Zhang; Yunlei Feng; Jianhui Cao; Xiaoning Chen; Xueqin Cheng; Xuanxue Mo


    The East Kunlun Orogenic Belt has undergone a composite orogenic process consisting of multiple orogenic cycles and involving many types of magmatic rocks spread over the whole district. However, due to bad natural geographical conditions and complex superimposed orogenic processes, most of the Caledonian orogenic traces were modified by the late tectonic uplift and denudation, so these rocks are poorly studied. Multiperiodic magmatic activity during the Late Silurian (approximately 420 Ma)–Late Devonian (approximately 380 Ma) exists in the Qimantagh area. We obtained 5 zircon U–Pb ages from the Late Silurian–Late Devonian granitoids in the Qimantagh area. Those ages are 420.6 ± 2.6 Ma(Nalingguole biotite monzogranite), 421.2 ± 1.9 Ma (Wulanwuzhuer potassium granite), 403.7 ± 2.9 Ma (Yemaquan granodiorite), 391.3 ± 3.2 Ma (Qunli granite porphyry), and 380.52 ± 0.92 Ma (Kayakedengtage granodiorite). These granitoids belong to the sub-alkaline, high-K calc-alkaline, metaluminous or weakly or strongly peraluminous series. The rocks are right oblique types, having overall relative LREE enrichment and HREE depletion, though rocks from different times may exhibit different degrees of Eu anomalies or overall moderate Eu depletion. The rocks are rich in large ion lithophile elements (LILE), such as Rb, Th, and K, and high field strength elements (HFSE), such as Zr and Hf, and are depleted in Ba, Nb, Ta, Sr, P, Eu, and Ti. The rocks have complex composition sources. The Late Silurian granitoids are mainly crust-derived. Most of the Devonian granitoids are crust-mantle mixed-source and only some parts of them are crust-derived, especially the Middle Devonian granitoids. Those mid-acidic and acidic intrusive rocks are formed in a post-collision tectonic setting, lithosphere delamination may have occurred in the Early Devonian (407 Ma), and the study area subsequently experienced an underplating of the mantle-derived magma at least until the Late Devonian (380 Ma).

  10. Tectonic and eustatic controls of late quaternary shelf sedimentation along the Central California (Santa Cruz) continental margin: high-resolution seismic stratigraphic evidence (United States)

    Mullins, Henry T.; Nagel, David K.; Dominguez, Laura L.


    A high-resolution "uniboom", seismic stratigraphic investigation of a portion of the central California continental shelf has demonstrated that depositional patterns and sequences are controlled largely by an interplay of glacioeustatic sea-level fluctuations superimposed on local tectonics. Wrench tectonics, associated with active right-lateral shear along the San Gregorio fault zone, and the Pigeon Point Basement High control the location, distribution and overall geometry of depositional sequences via en echelon folding and differential subsidence. Areas of relatively thick and thin late Quaternary sediments conform in large part with structures produced during wrenching. Glacioeustatic sea-level oscillations have also shaped depositional patterns and sequences. Correlation of our seismic stratigraphic data with a southern California continental margin sea-level curve, suggests that during the last glacial maximum, approximately 18,000 yrs ago, a relative lowstand resulted in the erosion of a distinct unconformity upon which late Quaternary sediments have accumulated. A rapid rise of sea level to a relative stillstand, approximately 12,000 yrs ago, produced a concave-up, marine terrace profile across the mid-shelf, that has since been infilled with as much as 22 m of Holocene clastic sediments. A relative drop of sea level, approximately 11,000 yrs ago, allowed sediments to build seaward as a series of prograding clinoforms that form the basal sequences of the late Quaternary sediment fill. The succeeding Holocene transgression partially eroded the top of this earlier regressive sequence, and has now established a typical, wave-graded shelf along which sediments fine in a seaward direction to water depths of 90-100 m. At greater shelf water depths, surface sediments coarsen and appear to be relicts of previous relative sea-level lowstands. The presence of now submerged and buried marine terraces along both the central and southern California continental margins

  11. Parallel Extension Tectonics (PET): Early Cretaceous tectonic extension of the Eastern Eurasian continent (United States)

    Liu, Junlai; Ji, Mo; Ni, Jinlong; Guan, Huimei; Shen, Liang


    The present study reports progress of our recent studies on the extensional structures in eastern North China craton and contiguous areas. We focus on characterizing and timing the formation/exhumation of the extensional structures, the Liaonan metamorphic core complex (mcc) and the Dayingzi basin from the Liaodong peninsula, the Queshan mcc, the Wulian mcc and the Zhucheng basin from the Jiaodong peninsula, and the Dashan magmatic dome within the Sulu orogenic belt. Magmatic rocks (either volcanic or plutonic) are ubiquitous in association with the tectonic extension (both syn- and post-kinematic). Evidence for crustal-mantle magma mixing are popular in many syn-kinematic intrusions. Geochemical analysis reveals that basaltic, andesitic to rhyolitic magmas were generated during the tectonic extension. Sr-Nd isotopes of the syn-kinematic magmatic rocks suggest that they were dominantly originated from ancient or juvenile crust partly with mantle signatures. Post-kinematic mafic intrusions with ages from ca. 121 Ma to Cenozoic, however, are of characteristic oceanic island basalts (OIB)-like trace element distribution patterns and relatively depleted radiogenic Sr-Nd isotope compositions. Integrated studies on the extensional structures, geochemical signatures of syn-kinematic magmatic rocks (mostly of granitic) and the tectono-magmatic relationships suggest that extension of the crust and the mantle lithosphere triggered the magmatisms from both the crust and the mantle. The Early Cretaceous tectono-magmatic evolution of the eastern Eurasian continent is governed by the PET in which the tectonic processes is subdivided into two stages, i.e. an early stage of tectonic extension, and a late stage of collapse of the extended lithosphere and transformation of lithospheric mantle. During the early stage, tectonic extension of the lithosphere led to detachment faulting in both the crust and mantle, resulted in the loss of some of the subcontinental roots, gave rise to

  12. Re-examination of geophysical data off Northwest India: Implications to the Late Cretaceous plate tectonics between India and Africa.

    Digital Repository Service at National Institute of Oceanography (India)

    Ramana, M.V.; Desa, M.; Ramprasad, T.

    processes. Late Cretaceous seafloor spreading between India and Africa formed the Mascarene Basin, and the plate reconstruction models depict unequal crustal accretion in this basin. Re-interpretation of magnetic data in the Gop and Laxmi Basins suggests...

  13. Cenozoic tectono-thermal history of the Tordrillo Mountains, Alaska: Paleocene-Eocene ridge subduction, decreasing relief, and late Neogene faulting (United States)

    Benowitz, Jeff A.; Haeussler, Peter J.; Layer, Paul W.; O'Sullivan, Paul B.; Wallace, Wes K.; Gillis, Robert J.


    Topographic development inboard of the continental margin is a predicted response to ridge subduction. New thermochronology results from the western Alaska Range document ridge subduction related orogenesis. K-feldspar thermochronology (KFAT) of bedrock samples from the Tordrillo Mountains in the western Alaska Range complement existing U-Pb, 40Ar/39Ar and AFT (apatite fission track) data to provide constraints on Paleocene pluton emplacement, and cooling as well as Late Eocene to Miocene vertical movements and exhumation along fault-bounded blocks. Based on the KFAT analysis we infer rapid exhumation-related cooling during the Eocene in the Tordrillo Mountains. Our KFAT cooling ages are coeval with deposition of clastic sediments in the Cook Inlet, Matanuska Valley and Tanana basins, which reflect high-energy depositional environments. The Tordrillo Mountains KFAT cooling ages are also the same as cooling ages in the Iliamna Lake region, the Kichatna Mountains of the western Alaska Range, and Mt. Logan in the Wrangell-St. Elias Mountains, thus rapid cooling at this time encompasses a broad region inboard of, and parallel to, the continental margin extending for several hundred kilometers. We infer these cooling events and deposition of clastic rocks are related to thermal effects that track the eastward passage of a slab window in Paleocene-Eocene time related to the subduction of the proposed Resurrection-Kula spreading ridge. In addition, we conclude that the reconstructed KFATmax negative age-elevation relationship is likely related to a long period of decreasing relief in the Tordrillo Mountains.

  14. A tale of two eras: Pliocene-Pleistocene unroofing of Cenozoic and late Archean zircons from active metamorphic core complexes, Solomon Sea, Papua New Guinea (United States)

    Baldwin, Suzanne L.; Ireland, Trevor R.


    U/Pb ion microprobe analyses of zircons from gneisses and granodiorites exposed in the D'Entrecasteaux Islands, and from conglomerate sections of the Goodenough No. 1 well in the adjacent Trobriand Basin, provide constraints on the age of magmatism, peak metamorphism, and nature of rocks unroofed during initial stages of metamorphic core complex formation in the Solomon Sea. The youngest populations of zircons from felsic gneisses and granodiorites indicate late Pliocene 206Pb*/238U ages. No inherited zircons were identified in the granodiorites, and the 206Pb*/238U ages (1.65 ± 0.18 Ma; 1.98 ± 0.08 Ma [2σ]) are interpreted as crystallization ages. These synkinematically emplaced granodiorites, intruded into actively extending continental crust, are some of the youngest known granitoids currently exposed at the Earth' surface. Zircon ages from felsic gneisses (2.63 ± 0.16 Ma; 2.72 ± 0.28 Ma [2σ]) are interpreted to date zircon growth subsequent to eclogite facies metamorphism. Felsic gneiss samples also contained zircon xenocrysts from Cretaceous-Miocene protoliths. In striking contrast, zircons from igneous and metamorphic clasts from the Goodenough No. 1 well indicate a single population with a 207Pb*/206/Pb* age of 2781 ± 9 Ma (2σ). We speculate that they are derived from basement rocks unroofed during initial stages of development of the D&Entrecasteaux metamorphic core complexes. These results provide the first direct evidence for the existence of Archean protoliths in the basement rocks of southeastern Papua New Guinea.

  15. Cenozoic tectono-thermal history of the Tordrillo Mountains, Alaska: Paleocene-Eocene ridge subduction, decreasing relief, and late Neogene faulting (United States)

    Benowitz, Jeff A.; Haeussler, Peter J.; Layer, Paul W.; O'Sullivan, Paul B.; Wallace, Wes K.; Gillis, Robert J.


    Topographic development inboard of the continental margin is a predicted response to ridge subduction. New thermochronology results from the western Alaska Range document ridge subduction related orogenesis. K-feldspar thermochronology (KFAT) of bedrock samples from the Tordrillo Mountains in the western Alaska Range complement existing U-Pb, 40Ar/39Ar and AFT (apatite fission track) data to provide constraints on Paleocene pluton emplacement, and cooling as well as Late Eocene to Miocene vertical movements and exhumation along fault-bounded blocks. Based on the KFAT analysis we infer rapid exhumation-related cooling during the Eocene in the Tordrillo Mountains. Our KFAT cooling ages are coeval with deposition of clastic sediments in the Cook Inlet, Matanuska Valley and Tanana basins, which reflect high-energy depositional environments. The Tordrillo Mountains KFAT cooling ages are also the same as cooling ages in the Iliamna Lake region, the Kichatna Mountains of the western Alaska Range, and Mt. Logan in the Wrangell-St. Elias Mountains, thus rapid cooling at this time encompasses a broad region inboard of, and parallel to, the continental margin extending for several hundred kilometers. We infer these cooling events and deposition of clastic rocks are related to thermal effects that track the eastward passage of a slab window in Paleocene-Eocene time related to the subduction of the proposed Resurrection-Kula spreading ridge. In addition, we conclude that the reconstructed KFATmax negative age-elevation relationship is likely related to a long period of decreasing relief in the Tordrillo Mountains.

  16. Cenozoic uplift and subsidence in the North Atlantic region

    DEFF Research Database (Denmark)

    Anell, Ingrid Anna Margareta; Thybo, Hans; Artemieva, Irina


    , time and amplitude (where possible) of topographic changes in the North Atlantic region during the Cenozoic (65-0 Ma). Our compilation is based on published results from reflection seismic studies, AFT (apatite fission track) studies, VR (vitrinite reflectance) trends, maximum burial, sediment supply...... studies, mass balance calculations and extrapolation of seismic profiles to onshore geomorphological features. The integration of about 200 published results reveal a clear pattern of topographic changes in the North Atlantic region during the Cenozoic: (1) The first major phase of Cenozoic regional...... and the surrounding areas. (2) A regional increase in subsidence in the offshore marginal areas of Norway, the northern North Sea, the northern British Isles and west Greenland took place in the Eocene (ca 57-35 Ma). (3) The Oligocene and Miocene (35-5 Ma) were characterized by regional tectonic quiescence, with only...

  17. Seismic tomographic constraints on plate-tectonic reconstruction of Nazca subduction under South America since late Cretaceous (~80 Ma) (United States)

    Chen, Yi-Wei; Wu, Jonny; Suppe, John; Liu, Han-Fang


    Our understanding of the global plate tectonics is based mainly on seafloor spreading and hotspot data obtained from the present earth surface, which records the growth of present ocean basins. However, in convergent tectonic settings vast amounts of lithosphere has been lost to subduction, contributing to increasing uncertainty in plate reconstruction with age. However, subducted lithosphere imaged in seismic tomography provides important information. By analyzing subducted slabs we identify the loci of subduction and assess the size and shape of subducted slabs, giving better constrained global plate tectonic models. The Andean margin of South America is a classic example of continuous subduction up to the present day, providing an opportunity to test the global plate prediction that ~24×10e6 km2 (4.7% of earth surface) lithosphere has been subducted since ~80 Ma. In this study, we used 10 different global seismic tomographies and Benioff zone seismicity under South America. To identify slabs, we first compared all data sets in horizontal slices and found the subducted Nazca slab is the most obvious structure between the surface and 750 km depth, well imaged between 10°N and 30°S. The bottom of the subducted Nazca slab reaches its greatest depth at 1400 km at 3°N (Carnegie Andes) and gradually shallows towards the south with 900 km minimum depth at 30°S (Pampean Andes). To assess the undeformed length of subducted slab, we used a refined cross-sectional area unfolding method from Wu et al. (in prep.) in the MITP08 seismic tomography (Li et al., 2008). Having cut spherical-Earth tomographic profiles that parallel to the Nazca-South America convergence direction, we measured slab areas as a function of depth based on edges defined by steep velocity gradients, calculating the raw length of the slab by the area and dividing an assumed initial thickness of oceanic lithosphere of 100km. Slab areas were corrected for density based on the PREM Earth model

  18. Late Cenozoic volcanism in the western Woodlark Basin area, SW Pacific: the sources of marine volcanic ash layers based on their elemental and Sr-Nd isotope compositions (United States)

    Lackschewitz, K. S.; Mertz, D. F.; Devey, C. W.; Garbe-Schönberg, C.-D.


    between 1.5 to 3 Ma. The Lusancay Islands can be excluded as a source for the volcanogenic layers found during Leg 180. Generally, the volcanogenic layers indicate much calc-alkaline rhyolitic volcanism in eastern Papua since 3.8 Ma. Starting at 135 ka, however, peralkaline tephra layers appear. This geochemical change in source characteristics might reflect the onset of a change in geotectonic regime, from crustal subduction to spreading, affecting the D'Entrecasteaux Islands region. Initial 143Nd/144Nd ratios as low as 0.5121 and 0.5127 for two of the tephra layers are interpreted as indicating that D'Entrecasteaux Islands volcanism younger than 2.9 Ma occasionally interacted with the Late Archean basement, possibly reflecting the mobilisation of the deep continental crust during active rift propagation.

  19. Late Pliocene To Pleistocene Tectonic Activity In SW Portugal: The S.Teotónio-Aljezur- Sinceira Fault System And Evidence For Coastal Uplift (United States)

    Figueiredo, P.; Cabral, J.; Rockwell, T.


    mainly by Mesozoic limestones and exhibits a generally lower topography accented by karstic morphology. In both areas, little work has been done to map the sequence of marine terraces, nor to determine their ages, although the majority of them are likely Pleistocene. The highest raised marine deposits reach an altitude of 370 m ~13 km inland and may be as old as Pliocene in age. Inland, the Säo Teotónio-Aljezur-Sinceira fault system (STASFS) extends NNE-SSW for 50 km, parallel and close to the southwest Portuguese coast, and controls the development of several small Cenozoic tectonic basins. It comprises onshore faults which may relate to the ongoing plate boundary deformation. This fault system expresses primarily sinistral strike-slip with a minor reverse component. Four cenozoic strike-slip basins occur along the STASFS, generally with lengths of less than 5 km and a maximum width of 1.5 km, filled with Miocene to Pleistocene sediments. In some areas, fault-related post-Pliocene vertical displacements of up to 100 m may have occurred, but generally they only reach a few tens of meters. This coastal region is therefore particularly appropriate for establishing the offshore-onshore link through a detailed neotectonic study of the active faults, including exploration with paleoseismological techniques, and the vertical deformation field using marine terraces as a reference frame.

  20. Cenozoic seawater Sr/Ca evolution (United States)

    Sosdian, Sindia M.; Lear, Caroline H.; Tao, Kai; Grossman, Ethan L.; O'Dea, Aaron; Rosenthal, Yair


    Records of seawater chemistry help constrain temporal variations in geochemical processes that impact the global carbon cycle and climate through Earth's history. Here we reconstruct Cenozoic seawater Sr/Ca (Sr/Casw) using fossil Conus and turritellid gastropod Sr/Ca. Combined with an oxygen isotope paleotemperature record from the same samples, the gastropod record suggests that Sr/Caswwas slightly higher in the Eocene (˜11.4 ± 3 mmol/mol) than today (˜8.54 mmol/mol) and remained relatively stable from the mid- to late Cenozoic. We compare our gastropod Cenozoic Sr/Casw record with a published turritellid gastropod Sr/Casw record and other published biogenic (benthic foraminifera, fossil fish teeth) and inorganic precipitate (calcite veins) Sr/Caswrecords. Once the uncertainties with our gastropod-derived Sr/Casw are taken into account the Sr/Casw record agrees reasonably well with biogenic Sr/Caswrecords. Assuming a seawater [Ca] history derived from marine evaporite inclusions, all biogenic-based Sr/Casw reconstructions imply decreasing seawater [Sr] through the Cenozoic, whereas the calcite vein Sr/Casw reconstruction implies increasing [Sr] through the Cenozoic. We apply a simple geochemical model to examine the implications of divergence among these seawater [Sr] reconstructions and suggest that the interpretation and uncertainties associated with the gastropod and calcite vein proxies need to be revisited. Used in conjunction with records of carbonate depositional fluxes, our favored seawater Sr/Ca scenarios point to a significant increase in the proportion of aragonite versus calcite deposition in shelf sediments from the Middle Miocene, coincident with the proliferation of coral reefs. We propose that this occurred at least 10 million years after the seawater Mg/Ca threshold was passed, and was instead aided by declining levels of atmospheric carbon dioxide.

  1. Phylogeographic heterogeneity of the brown macroalga Sargassum horneri (Fucaceae) in the northwestern Pacific in relation to late Pleistocene glaciation and tectonic configurations. (United States)

    Hu, Zi-Min; Uwai, Shinya; Yu, Shen-Hui; Komatsu, Teruhisa; Ajisaka, Tetsuro; Duan, De-Lin


    Pleistocene glacial oscillations and associated tectonic processes are believed to have influenced the historical abundances and distribution of organisms in the Asia Northwest Pacific (ANP). Accumulating evidence indicates that factors shaping tempospatial population dynamics and distribution patterns of marine taxa vary with biogeographical latitude, pelagic behaviour and oceanographic regimes. To detect what kinds of historical and contemporary factors affected genetic connectivity, phylogeographic profiles of littoral macroalga Sargassum horneri in the ANP were analysed based on mitochondrial (Cox3) and chloroplast (rbcL) data sets. Five distinct clades were recovered. A strong signature of biogeographical structure was revealed (Φ(CT) = 0.487, P architecture in S. horneri, initially shaped by historical geographic isolation during the late Pleistocene ice age and physical biogeographical barriers, can be complicated by oceanographic regimes (ocean surface currents) and relocating behaviour such as oceanic drifting.


    Institute of Scientific and Technical Information of China (English)

    王飞; 孙东怀; 张月宝; 李再军; 王鑫; 李宝峰; 吴晟; 郭峰


    兰州盆地位于青藏高原与黄土高原过渡地带,晚新生代全球降温和青藏高原的构造隆升对这—地区的温度、降水和高程产生了显著的影响.利用红度温度和磁化率-降水转换函数并结合古生物、地层地貌资料对兰州盆地过去8Ma的温度、降水和高度的半定量重建,结果表明:8.3~3.5Ma兰州盆地气候较为暖湿,期间经历了3个阶段两次显著的降温和变干过程,年均温度从16.7±2.9℃降低到11.9±3.2℃,年均降水从1150±350mm减小至500±100mm,这一时期盆地的冷干化可能受到全球降温和高原隆升的双重影响,但盆地海拔可能一直维持在1000m以下;3.5~1.7Ma盆地经历了青藏运动的A,B和C三幕,形成了一级山麓剥蚀面,代表了兰州盆地演化的新高度,海拔可能达到了1400 ~1600m,年均温度变为6.0±2.5℃,年均降水为240±40mm;1.70 ~0.45Ma山麓剥蚀面海拔达到1791 ~1991m,年均温度和年均降水分别为4.7±3.8℃和145±135mm;0.45 ~0Ma期间青藏高原再次隆起使兰州盆地继续抬升,达到现今的高度,并最终形成了目前的地貌格局,年均温度为5.2±4.8℃,年均降水为363±237mm,现今的气候特征也由此形成.%Lanzhou Basin located between Tibetan plateau and Loess Plateau, where the Cenozoic uplift of Tibetan Plateau and the global cooling have significant impact on its paleoelevation and paleoclimate. Quantitative reconstruction of Late Cenozoic paleoclimate and paleoelevation of Lanzhou Basin is not only helpful to understand the contribution of uplift of Tibetan Plateau and the global cooling during Late Cenozoic to regional climate evolution, respectively, but also necessary to discuss the coupled relationship between the tectonic and climate. Abundant evidence proved that the change of magnetic susceptibility and redness of the Chinese loess are controlled by pedogenesis, which is the product of climate change. Based on the research about the

  3. Late Miocene-Pliocene geomorphological evolution of the Xiaoshuizi peneplain in the Maxian Mountains and its tectonic significance for the northeastern Tibetan Plateau (United States)

    Li, Jijun; Ma, Zhenhua; Li, Xiaomiao; Peng, Tingjiang; Guo, Benhong; Zhang, Jun; Song, Chunhui; Liu, Jia; Hui, Zhengchuang; Yu, Hao; Ye, Xiyan; Liu, Shanpin; Wang, Xiuxi


    As a remnant elevated peneplain, the Tangxian planation surface is widely distributed in North China and the Ordos Plateau. Further into the Tibetan Plateau (TP), the Main planation surface can also be traced across this, the highest plateau on the Earth's surface. What the relation is between these two planation surfaces and whether they represent the remnants of a unique planation surface remains open to question. As the intermediate region between the low-altitude North China and the high-altitude TP, the Maxian Mountains and such bilateral basins located in the northeastern TP margin retain a series of well-preserved geomorphic features such as planation surfaces, pediment surface, and the fluvial terraces of the Yellow River. When and how the Xiaoshuizi peneplain was formed are crucial questions to elucidate the geomorphic evolution of the northeastern TP and infer the tectonic history of the TP. Here we present two parallel red clay-loess drill cores from the uplifted Xiaoshuizi bedrock peneplain in the Maxian Mountains, which document both the upper formation age of the planation surface and the evolution of Asian aridification. Based on the integration of high-resolution magnetostratigraphy analysis and Pliocene mammal fossils, we demonstrate that the red clay-loess succession deposited on the Xiaoshuizi peneplain probably began to accumulate at 6.9 Ma, implying that the Xiaoshuizi peneplain had begun to form before this. These results support the hypothesis that the Xiaoshuizi planation surface is equivalent to Tangxian planation surface of North China and Main planation surface of the TP. Furthermore, the onset of red clay sequence may indicate that the Xiaoshuizi peneplain was ultimately destroyed by the intensive tectonic uplift of the northeastern TP before 6.9 Ma. Taking into account the synchronous Late Miocene red clay deposition between the Xiaoshuizi peneplain and central Chinese Loess Plateau (CLP), we propose that the onset of interior Asian

  4. Late Paleozoic sedimentation and tectonics of rift and limited ocean basin at southern margin of the Qinling

    Institute of Scientific and Technical Information of China (English)

    孟庆任; 张国伟; 于在平; 梅志超


    The rifting and occurrence of limited oceanic basin at southern margin of Qinling separated south Qinling from Yangtze Block in late Paleozoic. Detailed sedimentary studies were carried out at two localities at southern flank of this rift-limited oceanic basin zone. and depositional architectures were then established accordingly. The results show that tectono-sedimentary stories are differing in different positions but clearly demonstrate spatial development of the rift. It is obvious that the rift in west part of Mianlue underwent two developmentary phases, early rapid subsidence and late slow subsidence, and there occurred breakup unconformity between the seccessions of the two subsidence phases. Combined with the data of structural, geochemical and chronological studies on the ophiolitic complex within the Mianlue zone. it is demonstrated that the rifting-drifting transition occurred, leading to the development of limited oceanic basin during the late Paleazoic. Spatial and temporal evolution of the

  5. A Paleomagnetic Study of Late Cretaceous Ophiolites in SE Turkey: implications for palaeolatitudes of S Neotethyan spreading centers and emplacement-related tectonic rotations (United States)

    Mualla, Cinku; Timur, Ustaömer; Osman, Parlak; Mumtaz, Hisarli


    Two E-W trending ophiolite belts crop out in SE Turkey, The southerly located ophiolites (Hatay, Koçali) were emplaced onto the Arabian Platform in Late Cretaceous whereas the northerly located ophiolites (Göksun, İspendere, Kömürhan, Guleman) were underthrust the S Tauride margin (i.e. Malatya-Keban Platform) in Late Cretaceous. Different tectonic models exist in the literature for the origin of these different ophiolite belts that we test here by a detailed palaomagnetic study: a) all the ophiolites in Turkey, including those in the study area were rooted from a single ocean basin to the N (i.e. the N Neotethyan Ocean Basin); b) all the ophiolites in SE Turkey were derived from the S Neotethyan Ocean Basin; c) the two ophiolite belts in SE Turkey are believed to have rooted from two different ocean basins; the Berit ocean to the north and the S Neotethys to the S. Our palaeomagnetic study from 72 different sites was focused on to the sheeted dyke complex, cumulate gabbros and extrusive sequences where available of each ophiolite from the N and S belts. We also sampled the unconformable cover units to distinguish emplacement related tectonic rotations from post-emplacement tectonic rotations. Here we report our first results obtained from the Göksun Ophiolite of the northern belt and the Hatay Ophiolite of the southern belt. Rock magnetic experiments showed evidence od magnetite/titanomagnetite as the main magnetic carriers at the majority of sites. Progressive thermal and alternating demagnetization revealed that the characteristic remanent component is removed between 500 and 580 ?C or 30-100 mT, respectively. Our new paleomagnetic results from the ophiolitic rocks emplaced in Arabian platform and the SE Anatolia show important implications to the spreading centre of the former ocean (s). Large counterclockwise rotations up to 100° are obtained from the sheeded dykes of the Hatay ophiolite in the Arabian plate with a paleolatitude of ˜16° , in contrast

  6. Evidence of Last Interglacial sea-level oscillations and recent tectonism in the Late Pleistocene Falmouth Formation of Jamaica (United States)

    Skrivanek, A.; Dutton, A.; Stemann, T.


    The timing and rates of sea-level change during Marine Isotope Stage 5e (MIS 5e) are poorly constrained. Across the Caribbean, many MIS 5e reefs are exposed above modern sea level, and have been studied extensively to understand sea level and ice sheet dynamics during an interglacial climate. This study investigates potential evidence for sub-orbital sea-level oscillations in the limestone Falmouth Formation from the northern and southwestern coastlines of Jamaica, a tectonically active island on the northern boundary of the Caribbean Plate. Vertical exposures of MIS 5e reefs contain multiple facies transitions that are sometimes associated with sharp unconformities. Outcrops at East Rio Bueno contain a distinct change in coral taxonomy from an assemblage of in situ Montastraea spp., Siderastrea and Diploria sp. encrusted by coralline algae, next to a repeated succession of Porites furcata, Acropora cervicornis, coralline algae and Porites astreoides, to in situ P. furcata. This is overlain by a fining-upwards sequence of coral rubble, a laterally persistent layer of small in situ Siderastrea and a ~1-m thick caprock. Near Oracabessa, a unit dominated by Acropora palmata clearly transitions into in situ Montastraea spp., Siderastrea, Colpophyllia natans, and Diploria sp. overlain by A. cervicornis. An abrupt vertical displacement of the sequence, indicating faulting, was observed at Oracabessa. Along the south coast, transitions in coral assemblages were also noted upsection. Common facies observed include in situ A. palmata and/or rubble, with a trend of reduction in algal encrustation upsection, capped by head corals and a regressive beach unit. The structure and composition of reefs preserved in the Falmouth Formation provide detailed information about sea-level behavior during MIS 5e, that will be used to test the hypothesis that sub-orbital sea-level oscillations occurred during the MIS 5e highstand. Evidence of tectonic activity along portions of the northern

  7. Cretaceous–Cenozoic burial and exhumation history of the Chukchi shelf, offshore Arctic Alaska (United States)

    Craddock, William H.; Houseknecht, David W.


    Apatite fission track (AFT) and vitrinite reflectance data from five exploration wells and three seafloor cores illuminate the thermal history of the underexplored United States Chukchi shelf. On the northeastern shelf, Triassic strata in the Chevron 1 Diamond well record apatite annealing followed by cooling, possibly during the Triassic to Middle Jurassic, which is a thermal history likely related to Canada Basin rifting. Jurassic strata exhumed in the hanging wall of the frontal Herald Arch thrust fault record a history of probable Late Jurassic to Early Cretaceous structural burial in the Chukotka fold and thrust belt, followed by rapid exhumation to near-surface temperatures at 104 ± 30 Ma. This history of contractional tectonism is in good agreement with inherited fission track ages in low-thermal-maturity, Cretaceous–Cenozoic strata in the Chukchi foreland, providing complementary evidence for the timing of exhumation and suggesting a source-to-sink relationship. In the central Chukchi foreland, inverse modeling of reset AFT samples from the Shell 1 Klondike and Shell 1 Crackerjack wells reveals several tens of degrees of cooling from maximum paleo-temperatures, with maximum heating permissible at any time from about 100 to 50 Ma, and cooling persisting to as recent as 30 Ma. Similar histories are compatible with partially reset AFT samples from other Chukchi wells (Shell 1 Popcorn, Shell 1 Burger, and Chevron 1 Diamond) and are probable in light of regional geologic evidence. Given geologic context provided by regional seismic reflection data, we interpret these inverse models to reveal a Late Cretaceous episode of cyclical burial and erosion across the central Chukchi shelf, possibly partially overprinted by Cenozoic cooling related to decreasing surface temperatures. Regionally, we interpret this kinematic history to be reflective of moderate, transpressional deformation of the Chukchi shelf during the final phases of contractional tectonism in the

  8. Restoration of Late Neoarchean-Early Cambrian tectonics in the Rengali orogen and its environs (eastern India): The Antarctic connection (United States)

    Bhattacharya, A.; Das, H. H.; Bell, Elizabeth; Bhattacharya, Atreyee; Chatterjee, N.; Saha, L.; Dutt, A.


    Geological mapping and P-T path reconstructions are combined with monazite chemical age and Secondary Ion Mass Spectrometric (SIMS) U-Pb zircon age determinations to identify crustal domains with distinctive evolutionary histories in the Rengali orogen sandwiched between two Grenvillian-age metamorphic belts, i.e. the Eastern Ghats Granulite Belt (EGGB) in the south, and the amphibolite facies Gangpur Schist Belt (GSB) in the north, which in turn forms a collar along the NW/W margins of the Paleo/Mesoarchean Singhbhum Craton (SC) north of the Rengali orogen. Anatectic gneisses in the orogen core exhibit multi-phase Neoarchean/Paleoproterozoic deformation, metamorphic P-T histories and juvenile magma emplacement events. The high-grade belt is inferred to be a septum of the Bastar Craton (BC). The flanking supracrustal belt in the orogen - dominated by quartz-muscovite schists (± staurolite, kyanite, garnet pyrophyllite), inter-bedded with poorly-sorted and polymict meta-conglomerate, and meta-ultramafic/amphibolite bands - evolved along P-T paths characterized by sub-greenschist to amphibolite facies peak P-T conditions in closely-spaced samples. The supracrustal rocks and the anatectic gneisses of contrasting metamorphic P-T histories experienced D1, D2 and D3 fabric-forming events, but the high-angle obliquity between the steeply-plunging D3 folds in the anatectic gneisses and the gently-plunging D3 folds in the supracrustal unit suggests the two lithodemic units were tectonically accreted post-S2. The supracrustal belt is inferred to be a tectonic mélange formed in an accretionary wedge at the tri-junction of the Bastar Craton, the Eastern Ghats Granulite Belt and the Singhbhum Craton; the basin closure synchronous with the assembly of EGGB and the Singhbhum Craton-Gangpur Schist belt composite occurred between 510 and 610 Ma. Based on the available evidence across the facing coastlines of the Greater India landmass and the Australo-Antarctic blocks at ~ 500 Ma

  9. The Cenozoic evolution of the San Joaquin Valley, California (United States)

    Bartow, J. Alan


    homocline, the western limb of the valley syncline between the Stockton arch and Panoche Creek, consists of a locally faulted homocline with northeast dips. Deformation is mostly late Cenozoic, is complex in its history, and has included up-to-the-southwest reverse faulting. The west-side fold belt, the southwestern part of the valley syncline between Panoche Creek and Elk Hills and including the southern Diablo and Temblor Ranges, is characterized by a series of folds and faults trending slightly oblique to the San Andreas fault. Paleogene folding took place in the northern part of the belt; however, most folding took place in Neogene time, during which the intensity of deformation increased southeastward along the belt and southwestward toward the San Andreas fault. The Maricopa-Tejon subbasin and the south-margin deformed belt are structurally distinct, but genetically related, regions bounded by the Bakersfield arch on the north, the San Emigdio Mountains on the south, the Tehachapi Mountains on the east, and the southeast end of the fold belt on the west. This combined region, which is the most deformed part of the basin, has undergone significant late Cenozoic shortening through north-directed thrust faulting at the south margin, as well as extreme Neogene basin subsidence north of the thrust belt. The sedimentary history of the San Joaquin basin, recorded in terms of unconformity-bounded depositional sequences, has been controlled principally by tectonism, but it has also been controlled by eustatic sea-level changes and, to a lesser degree, by climate. Plate tectonic events that had an influence on the basin include (1) subduction during the early Tertiary that changed from oblique to normal convergence in the later part of the Eocene, (2) the mid-Oligocene encounter of the Pacific-Farallon spreading ridge with the trench, and the consequent establishment of the San Andreas transform, (3) the northwestward migration of the Mendocino triple junction that in

  10. A subdued topography among the high relief, tectonic-active island ---registered middle to late Pleistocene climatic changes in Taiwan (United States)

    Liew, P.; Chen, B.


    The island of Taiwan is geographically in the frontal zone of the Asian monsoon region, and is geologically located in the collision boundary between the Philippine Sea plate and the Eurasian plate. A Holocene uplifting rate of up to 10mm/yr in the eastern coast has been documented in this high relief mountainous island, and active folds and thrusts are common. When tracing the rivers backward to the mountain, one often encounters a subdued topography, covered by primary lateritic soil, above the higher river terrace and below the rugged mountains, and is referred to as lateritic highland (LH) by a previous author. Studies in paleoclimatology and geomorphology enable us to refine the possible age and origin of this remarkable topography. The penultimate glacial-interglacial cycle and the last interglacial period should be the major interval for the development of lateritic highland. LH may be looked upon as a reference surface for studying the dynamic evolution of the tectonic landscape of Taiwan. It shows that the lower uplifting rate is the most important factor for the preservation of the LH topography in this island. Based on the morphology of LH, different deformation styles are recognized in north and south Chiayi (near tropic of cancer), in western Taiwan. To the north, platforms originating from piedmont LH are well developed, whereas to the south, platforms and piedmont LH are hardly visible. This contrast is probably due to a lithological variance between them.

  11. Holocene late Pleistocene non-tropical carbonate sediments and tectonic history of the western rift basin margin of the southern Gulf of California (United States)

    Halfar, Jochen; Godinez-Orta, Lucio; Goodfriend, Glenn A.; Mucciarone, David A.; Ingle, James C.; Holden, Peter


    Using high-resolution seismic reflection profiling and dating of (1) shallow marine vibracores and (2) sediments collected from uplifted marine terraces we reconstruct the tectonic history and sediment accumulation patterns of Holocene to late Pleistocene warm-temperate to subtropical carbonates in the southern Gulf of California, Mexico. The study was conducted in the vicinity of La Paz where carbonates form along the fault bounded narrow western shelf of the tectonically active Gulf of California rift basin. The non-tropical nature of the setting is responsible for (1) poor cementation of the bioclastic carbonates, and (2) a composition which is dominated by rhodoliths (coralline red algae), corals and mollusks. Unrimmed carbonate flats forming in small pocket bays and a rhodolith bioherm, which has a surface area of more than 20 km 2 and is up to 16 m thick, constitute the major carbonate factories. Holocene carbonate accumulation rates were deduced from seismic and core data and are highest on the rhodolith bioherm (260 cm/ka) and in subtidal zones of pocket bays (210 cm/ka), and lowest on the inner and middle shelf (100 cm/ka). Taken together, rates of carbonate accumulation are intermediate in magnitude between higher rates recorded in fully tropical carbonate settings and lower rates typical of cool-water carbonates. Seismic reflection profiles demonstrate that Isla Espiritu Santo in the center of the study area is a west dipping fault block, which is tectonically influenced by two distinct faults, the La Paz and Espiritu Santo faults. The latter fault accommodates at least 700 m of east-side down normal offset, and forms a steep eastern escarpment leading into the La Paz slope basin. Some of the sediments produced in the shallow carbonate factories of the narrow La Paz shelf are transported across this escarpment and are redeposited in the slope basin at a water depth of 750 m. Uranium-series dates of marine terraces exposed on Isla Espiritu Santo indicate

  12. The Cenozoic geological evolution of the Central and Northern North Sea based on seismic sequence stratigraphy

    Energy Technology Data Exchange (ETDEWEB)

    Jordt, Henrik


    This thesis represents scientific results from seismic sequence stratigraphic investigations. These investigations and results are integrated into an ongoing mineralogical study of the Cenozoic deposits. the main results from this mineralogical study are presented and discussed. The seismic investigations have provided boundary conditions for a forward modelling study of the Cenozoic depositional history. Results from the forward modelling are presented as they emphasise the influence of tectonics on sequence development. The tectonic motions described were important for the formation of the large oil and gas fields in the North Sea.

  13. Altered volcanic ash layers of the Late Cretaceous San Felipe Formation, Sierra Madre Oriental (Northeastern Mexico): Usbnd Pb geochronology, provenance and tectonic setting (United States)

    Velasco-Tapia, Fernando; Martínez-Paco, Margarita; Iriondo, Alexander; Ocampo-Díaz, Yam Zul Ernesto; Cruz-Gámez, Esther María; Ramos-Ledezma, Andrés; Andaverde, Jorge Alberto; Ostrooumov, Mikhail; Masuch, Dirk


    A detailed petrographic, geochemical, and Usbnd Pb geochronological study of altered volcanic ash layers, collected in eight outcrops of the Late Cretaceous San Felipe Formation (Sierra Madre Oriental, Northeastern Mexico), has been carried out. The main objectives have been: (1) to establish a deposit period, and (2) to propose a reliable provenance-transport-deposit-diagenetic model. These volcano-sedimentary strata represent the altered remains of vitreous-crystalline ash (main grains: quartz + K-feldspar (sanidine) + Na-plagioclase + zircon + biotite; groundmass: glass + calcite + clinochlore + illite) deposited and preserved in a shallow, relatively large in area, open platform environment. Major and trace element geochemistry indicate that parent volcanism was mainly rhyodacitic to rhyolitic in composition. Discrimination diagrams suggest a link to continental arc transitional to extension tectonic setting. Usbnd Pb geochronology in zircon has revealed that the volcanic ash was released from their sources approximately during the range 84.6 ± 0.8 to 73.7 ± 0.3 Ma, being transported to the depocenters. Burial diagenesis process was marked by: (a) a limited recycling, (b) the partial loss of original components (mainly K-feldspar, plagioclase, biotite and glass), and (c) the addition of quartz, calcite, illite and clinochlore. The location of the source area remains uncertain, although the lack of enrichment in Zr/Sc ratio suggests that ashes were subjected to relatively fast and short-distance transport process. El Peñuelo intrusive complex, at 130-170 km west of the depocenters, is the nearest known zone of active magmatism during the Upper Cretaceous. This intermediate to felsic pluton, characterized by a geochemical affinity to post-orogenic tectonic setting, could be linked to the volcanic sources.

  14. Late Cretaceous volcanic arc system in Southwest Korea: Occurrence, lithological characteristics, SHRIMP zircon U-Pb age, and tectonic implications (United States)

    Koh, Hee Jae; Kwon, Chang Woo


    In the southwest region of the Korean Peninsula, four large volcanoes, the Buan, Seonunsan, Wido, and Beopseongpo, with a maximum diameter of ca 20 km, form a distinct topographic undulation along the NE-SW-trending Hamyeol Fault. These volcanics comprise various types of pyroclastic, sedimentary, and lava/intrusive rocks, and are interpreted as remnants of calderas resulting from various volcanic eruptions, indicating that Hamyeol Fault, together with crustal extension, played an important role in volcano formation in this region. SHRIMP U-Pb ages of zircon isolated from each volcanics are as follows. For Buan Volcanics, Cheonmasan Tuff 87.23 ±0.92 Ma, Udongje Tuff 86.79 ±0.71 Ma, Seokpo Tuff 87.30 ±0.99 Ma and Yujeongje Tuff 86.66 ±0.93 Ma. For Seonunsan Volcanics, Gyeongsusan Tuff 84.9 ±1.1 Ma and Yeongije Tuff 86.61 ±0.67 Ma. These ages indicate that the four volcanics were formed in the Late Cretaceous. The ages are comparable to those of the volcanic rocks of the Aioi and Arima groups in Southwestern Japan, suggesting that the Late Cretaceous volcanic arc systems developed in a NE-SW direction from the Japanese Islands to the southwestern part of the Korean Peninsula caused by regional magmatism together with crustal deformation as reflected by occurrence of the volcanic rocks along the Hamyeol Fault.


    Institute of Scientific and Technical Information of China (English)



    对我国新生代晚期的剑齿象(Stegodon)进行再研究,提出了下列几点看法:1)依据Stegodon的特征,可将已命名的中国剑齿象种分为3类.一类为有效的剑齿象种,包括晚中新世的S.licenti Teilhard&Trasseart,1937;上新世的S.zdanskyi Hopwood,1935和S.officinalisHopwood,1935;上新世晚期至更新世早期的S.zhaotongensis Chow&Zhai,1962;更新世的S.chiai Chow& Zhai,1962,S.orientalis Owen,1870,S.sinensis Owen,1870和S.huananensis sp.n.等种.另一类是从剑齿象属中分出,归入到其他属或科的种.属于这一类的有可能置入真象类( Elephantoidae)的Stegodon parahypsilophus He,1984,S.guizhouensis Li&Wen,1986,Stegodon cf.S.hypsilophus和S.primitium Liu et al.,1973以及归入Stegolophodon的Stegodon baoshanensis Yun,1975.第三类为属种分类位置未定的种,以S.wushanensis Huang et al.,1991为代表.2)南亚更新世的S.elephantoides (Clift),1828可能在我国不存在.3)我国的剑齿象化石相当丰富,发现于东经99°以东、北纬38°以南的广大地区(包括山西、陕西和甘肃以及华中、华南、西南和部分华东等地区),生存时代为晚中新世晚期至更新世.4)在新生代晚期我国的剑齿象可能经历了3次大的由北向南的扩散和迁移事件.第一次发生在晚中新世,第二次在晚中新世晚期至早上新世早期,第三次在更新世早期.5)剑齿象可能起源于亚洲.S.licenti是我国出现时代最早的剑齿象,也可能是剑齿象最原始的一种.%The Chinese Stegodon was first recorded by Owen in 1870. He described two species; Stegodon orientalis and S. Sinensis based on the three teeth brought in by dealers for medicinal purposes (Osborn, 1942). Since then, a great number of materials (mainly including teeth) belonging to Stegodon have been collected from the late Cenozoic of China and about 20 species have been named. They were revised several times by paleontologists ( Hopwood, 1935; Young, 1935, 1938; Osborn, 1942

  16. Transitional changes in microfossil assemblages in the Japan Sea from the Late Pliocene to Early Pleistocene related to global climatic and local tectonic events (United States)

    Itaki, Takuya


    Many micropaleontological studies based on data from on-land sections, oil wells, and deep-sea drilling cores have provided important information about environmental changes in the Japan Sea that are related to the global climate and the local tectonics of the Japanese Islands. Here, major changes in the microfossil assemblages during the Late Pliocene to Early Pleistocene are reviewed. Late Pliocene (3.5-2.7 Ma) surface-water assemblages were characterized mainly by cold-temperate planktonic flora and fauna (nannofossils, diatoms, radiolarians, and planktonic foraminifera), suggesting that nutrient-rich North Pacific surface waters entered the Japan Sea via northern straits. The common occurrence of Pacific-type deep-water radiolarians during this period also suggests that deep water from the North Pacific entered the Japan Sea via the northern straits, indicating a sill depth >500 m. A weak warm-water influence is recognized along the Japanese coast, suggesting a small inflow of warm water via a southern strait. Nannofossil and sublittoral ostracod assemblages record an abrupt cooling event at 2.75 Ma that correlates with the onset of the Northern Hemisphere glaciation. Subsequently, cold intermediate- and deep-water assemblages of ostracods and radiolarians increased in abundance, suggesting active ventilation and the formation of the Japan Sea Proper Water, associated with a strengthened winter monsoon. Pacific-type deep-water radiolarians also disappeared around 2.75 Ma, which is attributed to the intermittent occurrence of deep anoxic environments and limited migration from the North Pacific, resulting from the near-closure or shallowing of the northern strait by a eustatic fall in sea level and tectonic uplift of northeastern Japan. A notable reduction in primary productivity from 2.3 to 1.3 Ma also suggests that the nutrient supply from the North Pacific was restricted by the near-closure of the northern strait. An increase in the abundance of subtropical

  17. Fission track dating of the Cenozoic uplift in Mabian area, southern Sichuan Province, China

    Institute of Scientific and Technical Information of China (English)

    AN YanFen; HAN ZhuJun; WAN JingLin


    The apparent ages of samples are obtained from fission track dating of apatite samples collected from the fault zones in Mabian area, southern Sichuan Province.In addition, thermal history is simulated from the obtained data by applying AFTSolve Program, to acquire the thermal evolution history of the samples.The result shows that tectonically the Mabian area was relatively stable between 25 and 3 Ma, compared to the inner parts and other marginal areas of the Tibetan Plateau.The studied area had little response to the rapid uplift events that occurred for several times in the Tibetan Plateau during 25-3 Ma.The latest thermal event related to the activity of the Lidian fault zone (about 8 Ma) is later than that of the Ebian fault zone (18-15 Ma ) to the west, indicating to some extent that the evolution of fault activity in the Mabian area has migrated from west to east.The latest extensive tectonic uplift occurred since about 3 Ma.As compared with the Xianshuihe fault zone, the Mabian area is closer to the eastern margin of the plateau, while the time of fast cooling event in this area is later than that in the southeast segment of the Xianshuihe fault zone (3.6-3.46 Ma).It appears to support the assumption of episodic uplift and stepwise outward extension of the eastern boundary of the Tibetan Plateau in late Cenozoic.

  18. Fission track dating of the Cenozoic uplift in Mabian area, southern Sichuan Province, China

    Institute of Scientific and Technical Information of China (English)


    The apparent ages of samples are obtained from fission track dating of apatite samples collected from the fault zones in Mabian area, southern Sichuan Province. In addition, thermal history is simulated from the obtained data by applying AFT Solve Program, to acquire the thermal evolution history of the samples. The result shows that tectonically the Mabian area was relatively stable between 25 and 3 Ma, compared to the inner parts and other marginal areas of the Tibetan Plateau. The studied area had little response to the rapid uplift events that occurred for several times in the Tibetan Plateau during 25-3 Ma. The latest thermal event related to the activity of the Lidian fault zone (about 8 Ma ) is later than that of the Ebian fault zone (18-15 Ma ) to the west, indicating to some extent that the evolution of fault activity in the Mabian area has migrated from west to east. The latest extensive tectonic uplift occurred since about 3 Ma. As compared with the Xianshuihe fault zone, the Mabian area is closer to the east- ern margin of the plateau, while the time of fast cooling event in this area is later than that in the southeast segment of the Xianshuihe fault zone (3.6-3.46 Ma ). It appears to support the assumption of episodic uplift and stepwise outward extension of the eastern boundary of the Tibetan Plateau in late Cenozoic.

  19. MORVEL构造板块的转动张量%Inertia Tensor for MORVEL Tectonic P lates

    Institute of Scientific and Technical Information of China (English)



    NNR-MORVEL56板块运动模型描述了全球56个构造板块在无整体旋转参考架下的角速度运动参数. 这些板块可以近似描述为单位球上的无重叠球面多边形区域. 用ITRF速度场计算这56个板块相对于无整体旋转参考架下的绝对运动时, 板块的几何参数起着至关重要的作用. 详细给出了计算板块几何参数的方法并且编写了FORTRAN90程序以供参考, 使得计算单位球上板块的面积和转动惯性张量得以实现. 文中的计算方法和程序主要采用球面三角算法和自适应辛普森双积分算法, 并对全球56个板块的几何参数进行了计算, 得到了较为可靠的计算结果.%The NNR (No-Net-Rotation)-MORVEL (Mid-Ocean Ridge VELocity) 56 is a set of angular velocities describing the motions of 56 plates relative to a No-Net-Rotation reference frame. These plates can be adjusted in terms of non-overlapping polygonal regions, separated by plate boundaries on a unit sphere. During the calculation on the kinematic parameters for these 56 plates in a NNR reference frame using the International Terrestrial Reference Frame ( ITRF) velocity field, the geometric parameters of tectonic plates play a significant role in establishing an absolute plate motion model based on space geodesy results. The computational method for these geometric parameters implemented as a FORTRAN90 program is described in this paper, allowing an evaluation of the area and the inertia tensor of a polygonal region on a unit sphere. This program is mainly built on a triangulation algorithm and the adaptive Simpson 's double integral method for spherical polygons, which produces highly reliable results for all 56 modern plates.

  20. Reconstructing geographical boundary conditions for palaeoclimate modelling during the Cenozoic (United States)

    Baatsen, Michiel; van Hinsbergen, Douwe J. J.; von der Heydt, Anna S.; Dijkstra, Henk A.; Sluijs, Appy; Abels, Hemmo A.; Bijl, Peter K.


    Studies on the palaeoclimate and palaeoceanography using numerical model simulations may be considerably dependent on the implemented geographical reconstruction. Because building the palaeogeographic datasets for these models is often a time-consuming and elaborate exercise, palaeoclimate models frequently use reconstructions in which the latest state-of-the-art plate tectonic reconstructions, palaeotopography and -bathymetry, or vegetation have not yet been incorporated. In this paper, we therefore provide a new method to efficiently generate a global geographical reconstruction for the middle-late Eocene. The generalised procedure is also reusable to create reconstructions for other time slices within the Cenozoic, suitable for palaeoclimate modelling. We use a plate-tectonic model to make global masks containing the distribution of land, continental shelves, shallow basins and deep ocean. The use of depth-age relationships for oceanic crust together with adjusted present-day topography gives a first estimate of the global geography at a chosen time frame. This estimate subsequently needs manual editing of areas where existing geological data indicate that the altimetry has changed significantly over time. Certain generic changes (e.g. lowering mountain ranges) can be made relatively easily by defining a set of masks while other features may require a more specific treatment. Since the discussion regarding many of these regions is still ongoing, it is crucial to make it easy for changes to be incorporated without having to redo the entire procedure. In this manner, a complete reconstruction can be made that suffices as a boundary condition for numerical models with a limited effort. This facilitates the interaction between experts in geology and palaeoclimate modelling, keeping reconstructions up to date and improving the consistency between different studies. Moreover, it facilitates model inter-comparison studies and sensitivity tests regarding certain

  1. Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting (United States)

    Etheve, Nathalie; Frizon de Lamotte, Dominique; Mohn, Geoffroy; Martos, Raquel; Roca, Eduard; Blanpied, Christian


    Based on field work and seismic reflection data, we investigate the Cenozoic tectono-sedimentary evolution offshore and onshore Ibiza allowing the proposal of a new tectonic agenda for the region and its integration in the geodynamic history of the West Mediterranean. The late Oligocene-early Miocene rifting event, which characterizes the Valencia Trough and the Algerian Basin, located north and south of the study area respectively, is also present in Ibiza and particularly well-expressed in the northern part of the island. Among these two rifted basins initiated in the frame of the European Cenozoic Rift System, the Valencia Trough failed rapidly while the Algerian Basin evolved after as a back-arc basin related to the subduction of the Alpine-Maghrebian Tethys. The subsequent middle Miocene compressional deformation was localized by the previous extensional faults, which were either inverted or passively translated depending on their initial orientation. Despite the lateral continuity between the External Betics and the Balearic Promontory, it appears from restored maps that this tectonic event cannot be directly related to the Betic orogen, but results from compressive stresses transmitted through the Algerian Basin. A still active back-arc asthenospheric rise likely explains the stiff behavior of this basin, which has remained poorly deformed up to recent time. During the late Miocene a new extensional episode reworked the southern part of the Balearic Promontory. It is suggested that this extensional deformation developed in a trans-tensional context related to the westward translation of the Alboran Domain and the coeval right-lateral strike-slip movement along the Emile Baudot Escarpment bounding the Algerian Basin to the north.

  2. Testing alternative tectonic models of Palaeotethys in the E Mediterranean region: new U-Pb and Lu-Hf isotopic analyses of detrital zircons from Late Carboniferous and Late Triassic sandstones associated with the Anatolide and Tauride blocks (S Turkey) (United States)

    Ustaömer, Timur; Ayda Ustaömer, Petek; Robertson, Alastair; Gerdes, Axel


    Alternative tectonic models of Palaeotethys during Late Palaeozoic-Early Mesozoic time infer: 1. southward subduction beneath the north margin of Gondwana; 2. northward subduction beneath the south margin of Eurasia, or 3. double subduction (northwards and southwards), at least during Late Carboniferous. U-Pb and Lu-Hf isotopic analysis of detrital zircons, extracted from sandstones, can provide strong indications of age and identity of source terranes. Here, we consider the provenance of both Late Carboniferous and Late Triassic sandstones from both relatively allochthonous and relatively autochthonous units that are all spatially associated with the Anatolide and Tauride continental blocks. The relatively allochthonous units are sandstones (3 samples) from the Late Carboniferous Aladaǧ Nappe (Tauride; in the east), the Konya Complex (Anatolide; central area) and the Karaburun Mélange (Tauride-related; in the west). The relatively autochthonous units are Late Triassic sandstones (4 samples) from the Üzümdere Formation, the Kasımlar Formation (both western Taurides) and the Güvercinlik Formation (Karaburun Peninsula-Tauride related; far west). The Late Carboniferous sandstones from the three relatively allochthonous units are dominated by Precambrian zircon populations, the age distribution of which suggests derivation from two contrasting source regions: First, a NE African-type source (i.e. Saharan craton) for the sandstones of the Konya Mélange and the Aladaǧ Nappe because these sediments have prominent zircon populations dated at 0.5-0.7, 0.8 and 0.9-1.1 Ga. Palaeozoic zircons are minimal in the sandstones of the Aladaǧ Nappe and the Konya Complex (3 and 5% of the whole data, respectively) and are confined to Cambrian to Ordovician. Secondly, a contrasting NW African-type source is inferred for sandstone from the Karaburun Mélange because of the marked absence of Tonian-Stenian zircons and the predominance of ~2 Ga zircons over ~2.5 Ga zircons. In

  3. Detrital Zircon Provenance Record of Pre-Andean to Modern Tectonics in the Northern Andes: Examples from Peru, Ecuador, and Colombia (United States)

    George, S. W. M.; Jackson, L. J.; Horton, B. K.


    Detrital zircon U-Pb age distributions from modern rivers and Mesozoic-Cenozoic basin fill in the northern Andes provide insights into pre-Andean, Andean, and active uplift and exhumation of distinctive sediment source regions. Diagnostic age signatures enable straightforward discrimination of competing sediment sources within the Andean magmatic arc (Western Cordillera-Central Cordillera), retroarc fold-thrust belt (Eastern Cordillera-Subandean Zone), and Amazonian craton (composed of several basement provinces). More complex, however, are the mid/late Cenozoic provenance records generated by recycling of basin fill originally deposited during early/mid Mesozoic extension, late Mesozoic thermal subsidence, and early Cenozoic shortening. Although subject to time-transgressive trends, regionally significant provenance patterns in Peru, Ecuador, and Colombia reveal: (1) Triassic-Jurassic growth of extensional subbasins fed by local block uplifts (with commonly unimodal 300­-150 Ma age peaks); (2) Cretaceous deposition in an extensive postrift setting fed by principally cratonic sources (with common 1800-900 Ma ages); and (3) Cenozoic growth of a broad flexural basin fed initially fed by magmatic-arc rocks (100-0 Ma), then later dominance by thrust-belt sedimentary rocks with progressively greater degrees of basin recycling (yielding diverse and variable age populations from the aforementioned source regions). U-Pb results from modern rivers and smaller subbasins prove useful in evaluating source-to-sink relationships, downstream mixing relationships, hinterland-foreland basin connectivity, paleodrainage integration, and tectonic/paleotopographic reconstructions. Most but not all of the elevated intermontane basins in the modern hinterland of the northern Andes contain provenance records consistent with genesis in a broader foreland basin developed at low elevation. Downstream variations within modern axial rivers and Cenozoic axial basins inform predictive models of

  4. Cenozoic rift formation in the northern Caribbean (United States)

    Mann, P.; Burke, K.


    Rifts form in many different tectonic environments where the lithosphere is put into extension. An outline is provided of the distribution, orientation, and relative ages of 16 Cenozoic rifts along the northern edge of the Caribbean plate and it is suggested that these structures formed successively by localized extension as the Caribbean plate moved eastward past a continental promontory of North America. Evidence leading to this conclusion includes (1) recognition that the rifts become progressively younger westward; (2) a two-phase subsidence history in a rift exposed by upthrusting in Jamaica; (3) the absence of rifts east of Jamaica; and (4) the observation that removal of 1400 km of strike-slip displacement on the Cayman Trough fault system places the Paleogene rifts of Jamaica in an active area of extension south of Yucatan where the rifts of Honduras and Guatemala are forming today.

  5. Foraminifera in Cenozoic Paleoenvironments

    Institute of Scientific and Technical Information of China (English)

    Brian McGowran


    Paleontologists search the fossil record for evidence of age, ancient environments, phylogenetic reconstructions and ancient communities. Cenozoic foraminifera preserve evidence for all of these simultaneously from the water column and from at, above and below the sediment/water interface. As our understanding of foraminiferal assemblages and their place in the strata (biofacies) becomes more sophisticated, so are foraminiferal biofacies challenged to contribute to more subtle problems in Cenozoic earth and life history. Progress is described as a series of five "integrations". (Ⅰ) The quantification of foraminiferal biofacies was an advance on simple presences and absences of species meeting such questions as marine or nonmarine, or shallow or deep. (Ⅱ) Foraminiferal shells carry geochemical signals especially isotopes of oxygen (temperature, ice volume), carbon (nutrition and the carbon cycle), and strontium (seawater ratios through time). (Ⅲ) From modern foraminiferal biology we have lifestyle insights leading to a model of oceans and paleo-oceans called the trophic resource continuum, a valuable way into greenhouse-icehouse comparisons and contrasts. (Ⅳ) Biofacies changes in space and time are sometimes abrupt with little evidence of diachrony, and sometimes gradual. These patterns are clarified in the context of sequence stratigraphy (which they enrich in turn). (Ⅴ) The paleobiological counterpart of sequence stratigraphy is evolutionary paleoecology, reconstructing communities in deep time. The foraminifera are perfectly suited to investigate the possibility (or likelihood) that global environmental shifts have controlled community turnover in the pelagic, neritic and terrestrial realms.

  6. The Palos Verdes Fault offshore southern California: late Pleistocene to present tectonic geomorphology, seascape evolution and slip rate estimate based on AUV and ROV surveys (United States)

    Brothers, Daniel S.; Conrad, James E.; Maier, Katherine L.; Paull, Charles K.; McGann, Mary L.; Caress, David W.


    The Palos Verdes Fault (PVF) is one of few active faults in Southern California that crosses the shoreline and can be studied using both terrestrial and subaqueous methodologies. To characterize the near-seafloor fault morphology, tectonic influences on continental slope sedimentary processes and late Pleistocene to present slip rate, a grid of high-resolution multibeam bathymetric data, and chirp subbottom profiles were acquired with an autonomous underwater vehicle (AUV) along the main trace of PVF in water depths between 250 and 600 m. Radiocarbon dates were obtained from vibracores collected using a remotely operated vehicle (ROV) and ship-based gravity cores. The PVF is expressed as a well-defined seafloor lineation marked by subtle along-strike bends. Right-stepping transtensional bends exert first-order control on sediment flow dynamics and the spatial distribution of Holocene depocenters; deformed strata within a small pull-apart basin record punctuated growth faulting associated with at least three Holocene surface ruptures. An upper (shallower) landslide scarp, a buried sedimentary mound, and a deeper scarp have been right-laterally offset across the PVF by 55 ± 5, 52 ± 4 , and 39 ± 8 m, respectively. The ages of the upper scarp and buried mound are approximately 31 ka; the age of the deeper scarp is bracketed to 17–24 ka. These three piercing points bracket the late Pleistocene to present slip rate to 1.3–2.8 mm/yr and provide a best estimate of 1.6–1.9 mm/yr. The deformation observed along the PVF is characteristic of strike-slip faulting and accounts for 20–30% of the total right-lateral slip budget accommodated offshore Southern California.

  7. Floor-age constraining of a tectonic paroxysm of the Pyrenean orogen. Late Middle Eocene mammal age of a faulted karstic filling of the Quercy phosphorites, south-western France (United States)

    Astruc, Jean Guy; Escarguel, Gilles; Marandat, Bernard; Simon-Coinçon, Régine; Sigé, Bernard

    Breaking effects of a Pyrenean compressive tectonic phase are recognised in northern Pyrenean foreland, such as in the Quercy Jurassic limestone platform. The age of this phase still remains poorly constrained. In the so-called Quercy phosphorites area, within the Prajoux-Mémerlin paleokarst system near the city of Cajarc, a clay filling shows a strike slip fault effect, close to N-S direction. According to an analysis of the mammal fauna and inferred chronology of the polyphased paleokarst infilling, the age of the faulted clay is late Middle Eocene, with a mammal age estimate of 41.5 Ma. This provides reliable precise floor-age constraining for the involved sismo-tectonic paroxysm, seemingly related to the Pyrenean tectonic compressive phase.

  8. Tectonic evolution of the southern margin of the Amazonian craton in the late Mesoproterozoic based on field relationships and zircon U-Pb geochronology

    Directory of Open Access Journals (Sweden)



    Full Text Available New U-Pb zircon geochronological data integrated with field relationships and an airborne geophysical survey suggest that the Nova Brasilândia and Aguapeí belts are part of the same monocyclic, metaigneous and metasedimentary belt formed in the late Mesoproterozoic (1150 Ma-1110 Ma. This geological history is very similar to the within-plate origin of the Sunsás belt, in eastern Bolivia. Thus, we propose that the Nova Brasilândia, Aguapeí and Sunsás belts represent a unique geotectonic unit (here termed the Western Amazon belt that became amalgamated at the end of the Mesoproterozoic and originated through the reactivation of a paleo-suture (Guaporé suture zone in an intracontinental rift environment. Therefore, its geological history involves a short, complete Wilson cycle of ca. 40 Ma. Globally, this tectonic evolution may be related with the final breakup of the supercontinent Columbia. Mafic rocks and trondhjemites in the northernmost portion of the belt yielded U-Pb zircon ages ca. 1110 Ma, which dates the high-grade metamorphism and the closure of the rift. This indicates that the breakup of supercontinent Columbia was followed in short sequence by the assembly of supercontinent Rodinia at ca. 1.1-1.0 Ga and that the Western Amazon belt was formed during the accretion of the Arequipa-Antofalla basement to the Amazonian craton.

  9. Constraining the Late Mesozoic and Early Tertiary Tectonic Evolution of Southern Mexico: Structure and Deformation History of the Tierra Caliente Region. (United States)

    Cabral-Cano; Draper; Lang; Harrison


    We analyze the structure and assess the deformation history of the Tierra Caliente Metamorphic Complex (TCMC) of southern Mexico, where Laramide accretion of exotic terranes is in debate. The TCMC consists of a south-plunging antiform fault that is bounded on both its eastern and western flanks. Tierra Caliente Metamorphic Complex rocks show at least two phases of compressional deformation. The first and most prominent records a mean tectonic transport direction of 068 degrees. This phase is responsible for east-verging asymmetrical folding and thrusting of both metamorphic and superjacent sedimentary rocks. The second phase has an average transport direction of 232 degrees and is restricted to the western portion of the TCMC. A third phase is responsible for normal faulting. Lack of discernible deformation before Late Cretaceous time indicates that the main deformation phase is coincident with Laramide orogenesis elsewhere in the North American Cordillera. The stratigraphy, structure, and deformational history of the TCMC do not require accretion of exotic terranes. We explain the Mesozoic tectonostratigraphic evolution of the TCMC in terms of deposition and deformation of Mesozoic volcanic and sedimentary strata over the attenuated continental crust of the North American plate.

  10. Cretaceous-Cenozoic tectonic history of the Jiaojia Fault and gold mineralization in the Jiaodong Peninsula, China: constraints from zircon U-Pb, illite K-Ar, and apatite fission track thermochronometry (United States)

    Deng, Jun; Wang, Changming; Bagas, Leon; Carranza, Emmanuel John M.; Lu, Yongjun


    The Jiaojia Fault (JJF) in the Jiaodong area of eastern China is an important NNE-trending structure that is subsidiary to the regional Tancheng-Lujiang (Tan-Lu) Fault Zone, and hosts >1200 t of gold reserves contained in disseminated and stockwork ore, dominantly in the footwall of the fault. We present new zircon U-Pb, apatite fission track, and illite K-Ar data along the JJF and have delineated its tectonic history focusing on its formation and reactivation. Zircon U-Pb dating shows that the Shangzhuang granite is a composite body with ages between 132 ± 1 and 127 ± 1 Ma. Illite K-Ar ages for the fault's gouge range from 83 ± 2 to 68 ± 2 Ma, and the measured apatite fission track ages for ores are between 55 and 21 Ma. Previous zircon U-Pb geochronology and structural studies suggest that the JJF was originally activated in the Jurassic during 160-150 Ma as a sinistral fault. The JJF was a normal fault in the Early Cretaceous due to NW-SE orientated tension and NE-SW compression, which lasted from 135 to 120 Ma. This was followed by sinistral strike-slip faulting due to NW-SE compression and NE-SW tension during 120-110 Ma, and it changed to normal displacement at ca. 110 Ma. Our apatite fission track data analysis and thermal modeling of representative samples suggest that there was a subsequent dextral reactivation of the fault at ca. 55 Ma. Previous age data of ca. 130-110 Ma for gold mineralization along the JJF coincides with the Early Cretaceous magmatism and is coeval with the transition from normal faulting to sinistral strike-slip faulting of the JJF in Early Cretaceous, which is interpreted to be due to changing direction of the subducting Pacific Plate.

  11. 柴达木盆地西部地区新生代演化特征与青藏高原隆升%Cenozoic Uplift of the Tibetan Plateau: Evidence from tectonic-sedimentary evolution of the Western Qaidam Basin

    Institute of Scientific and Technical Information of China (English)

    王亚东; 张涛; 迟云平; 刘艳蕊; 张志高; 李仕远; 方小敏; 张跃中


    通过对柴达木盆地西部地区(柴西地区)地震剖面构造-沉积相演化的分析,结合基底岩性及区域构造运动历史,重建了柴西地区新生代构造-沉积动态演化框架.柴西地区新生代以来一直处在印欧板块碰撞所引起的青藏高原阶段性隆升的挤压构造背景下,经历了两大构造变形期:第一变形期主要发育在古近纪,变形高峰在下干柴沟组上段,第二变形期发育在新近纪-第四纪,变形强度日益加剧.剖面沉积相的变化体现柴西地区经历了水进-静水沉降-水退的过程,平面沉积相演变是沉积中心受构造运动控制的直接结果;受构造演化控制柴西地区以Ⅺ号(油狮断裂)和油北断裂为分界线,由南至北地表形态表现为3种不同样式:柴西南区断裂发育,柴西中部为英雄岭新生造山带,柴西北区主要发育冲断褶皱.柴西地区构造-沉积演化特征是对青藏高原阶隆升的响应,同时记录了青藏高原向北间歇性蔓延生长的过程.%on the basis of the analysis of structure and sedimentary evolution of the seismic section in Western Qaidam Basin and combining the basement lithology, faults distribution and history of tectonic movement, we reconstructed the dynamical evolution framework of structure and sedimentation of Western Qaidam Basin during the Cenozoic. Our results suggested that Western Qaidam Basin was under the compression tectonicbackground of the Tibetan Plateau uplift caused by the collision of India and Eurasia in the Cenozoic and underwent two violent periods of tectonic deformation. The Western Qaidam Basin had undergone two periods of tectonic deformation. The first ocurred in the Paleocene, and reached the peak at the E23; the second was in the Neocene-Quaternary, and the deformation intensified rapidly. The forces transmitted from the south to the north,while the tectonic deformation spread from the west to the east, which indicated that the thrust of the

  12. Cenozoic uplift of West Qinling, northeast margin of Tibetan plateau-a detrital apatite fission track record from the Tianshui basin

    Institute of Scientific and Technical Information of China (English)

    WANG Xiuxi; LI Jijun; SONG Chunbui; ZHANG Jun; ZHAO Zhijun; GAO Junping; PAN Meihui


    The Cenozoic sedimentation in the Tianshui basin, which is located at the junction of the Liupanshan and West Qinling, northeast margin of the Tibetan plateau,provides a record for the regional tectonism and exhumation history of the surrounding mountains. Thermochronologic study on the detrital apatite grains from sandstones at Yaodian, near Tianshui, has revealed two rapid tectonic uplift-exhumation events of the source area, which happened at 23.7 and 14.1 Ma, respectively. The fast exhumation(0.34 mm/a) at 23.7 Ma, which recorded the tectonic uplift ofWest Qinling, led to the formation of the Neogene Tianshuibasin and initiated the reception of alluvial deposits. This event is most likely in response to the synchronous tectonism of the Tibetan plateau. The source region experienced another rapid exhumation (1.05 mm/a) at 14.1 Ma, when the Tianshui basin began to depress broadly and fluvial-lacustrine sediments dominated the Late Miocene.

  13. Melt source and evolution of I-type granitoids in the SE Tibetan Plateau: Late Cretaceous magmatism and mineralization driven by collision-induced transtensional tectonics (United States)

    Yang, Li-Qiang; Deng, Jun; Dilek, Yildirim; Meng, Jian-Yin; Gao, Xue; Santosh, M.; Wang, Da; Yan, Han


    We report new whole-rock geochemical and Sr-Nd-Pb isotope and zircon U-Pb age and Hf isotope data of the Hongshan intrusive suite in the Triassic Yidun Terrane, eastern Tibet. These data allow us to explore the possible causative links between the magmatism and the coeval Cu-Mo mineralization in the region. The Hongshan intrusive rocks have SiO2 of 65.06-73.60 wt.%, K2O of 3.17-6.41 wt.%, and P2O5 of 0.11-0.39 wt.%, enriched in Rb, Th, and U, and depleted in Ba, Sr, P, Ti, Nb, and Eu. These rocks are of high-K calc-alkaline to shoshonite series, showing geochemical signatures of metaluminous to slightly peraluminous I-type granite. Magmatic zircons separated from four samples yielded weighted mean 206Pb/238U ages of 79 ± 0.7 Ma, 78 ± 0.5 Ma, 77 ± 0.8 Ma, and 76 ± 0.8 Ma. Low MgO (0.42-1.47 wt%), low HREE and Y, varying εHf(t) (- 9.5 to - 2.2), and negative εNd(t) (- 7.7 to - 5.8) suggest that magmas of the late Cretaceous Hongshan plutons were most likely generated by partial melting and mixing of ~ 20% juvenile lower crust-derived melts, represented by the ca. 215 Ma basaltic andesite from the southern Yidun Terrane, with ancient basement-derived melts represented by the Baoshan S-type granitic melts from the Zhongza Block. We consider that partial melting processes are capable of removing chalcophile elements (such as Cu) and leaving siderophile metals (such as Mo) as residue in the lower crust of the Yidun Terrane, consequently inducing porphyry Cu-Mo mineralization. This consideration enables us to propose that the Triassic subduction-modified, copper-rich lithosphere was crucial for the giant copper mineralization that occurred in the Yidun Terrane during the late Cretaceous. Lithospheric-scale, transtensional faulting, developed as a result of collision-induced escape tectonics in SE Tibet, triggered asthenospheric upwelling, which in turn caused intra-plate extension and magmatism during the late Cretaceous, forming the Hongshan and coeval I

  14. Geochronology and Geochemistry of Middle-Late Ordovician Granites and Gabbros in the Erguna Region, NE China:Implications for the Tectonic Evolution of the Erguna Massif

    Institute of Scientific and Technical Information of China (English)

    Shuo Zhao; Wenliang Xu; Wei Wang; Jie Tang; Yihan Zhang


    Zircon U-Pb ages, Hf isotope data and whole-rock major and trace element data for the Middle to Late Ordovician gabbros and granites in the Erguna Massif, NE China were presented in this paper. The petrogenesis of these rocks and the Early Paleozoic tectonic evolution of the massif were discussed. Zircons from the granites and gabbros are of magmatic origin based on their cathodolumi-nescence (CL) images. The206Pb/238U ages obtained from 20 spots on zircons from the granites range from 446±9 to 464±10 Ma, yielding a weighted mean age of 455±10 Ma; and 16 spots on zircons from the gabbros range from 465±10 to 466±7 Ma, yielding a weighted mean age of 465±2 Ma. Chemically, the Late Ordovician granites in the Erguna Massif are weakly peraluminous and similar to A-type granites. The granites and gabbros are all enriched in light rare earth elements and large ion lithophile elements (e.g., Rb, K), and depleted in heavy rare earth elements and high field strength elements (e.g., Nb, Ta, and Ti); they all exhibit marked negative Eu anomalies. Their zirconεHf(t) values range mainly from +1.86 to +6.21 (for the granites) and +1.39 to +3.89 (for the gabbros), except for one spot with a value of -0.27 (for a gabbro). TheTDM1 ages for the gabbros andTDM2 ages for the granites vary from 928 to 1 091 Ma and from 1 287 to 1 675 Ma, respectively. It is concluded that the primary magma of the granites could have been derived by partial melting of Mesoproterozoic newly accreted crustal ma-terial, whereas the primary magma of the gabbros originated by partial melting of a depleted mantle wedge that had been metasomatized by fluids derived from a subducted slab. These Middle-Late Or-dovician granites and gabbros constitute a typical bimodal igneous rock association, implying an exten-sional environment that was probably related to the post-collisional development of the Erguna and Xing’an massifs in the early Early Paleozoic.

  15. Sequence framework of two different kinds of margins and their response to tectonic activity during the Middle-Late Triassic, Ordos Basin

    Institute of Scientific and Technical Information of China (English)


    Two kinds of margin respectively occur in the Ordos Basin during the Middle-Late Triassic (Yanchang Age), one is foreland margin developed under the background of flexural subsidence by thrusting intensively in the southwest margin, and the other is intracratonic basin margin by stable subsidence in northern and central parts of the basin. The Middle-Late Triassic Yanchang Formation can be divided into four regional third-order sequences, which are separated by gentle angular unconformity or regional erosion surface, made up of lowstand system tract (LST), expanding system tract (EST) and highstand system tract (HST) from lower to upper within a sequence. But there are distinct differences of the sequence framework between the southwest margin and northern and central parts of the basin. The southwest margin develops heavy conglomerate layer and unconformity as a result of orogeny by thrusting, and the intracratonic basin margin by stable subsidence in the northern and central parts grows aggradational sandstone, conglomerate in fluvio-delta system and parallel unconformity. The depositional framework of southwest margin reflects the tectonic evolution from flexural subsidence by thrusting to rebounded uplift. The formation of sequence boundary is related to the resilient uplift and erosion. The sequence stratigraphic framework and depositional system tract configuration in the foreland basin are controlled by structural activity of the fold and thrust belt, and the sequence succession reflects episodic thrusting of the Middle-Late Triassic toward the foreland basin. The sequence evolution in northern and central parts reflects the depositional succession of fluvio-delta system under intracratonic background, composed of coarse-grained sediment in braided channel deposit at the lower, meandering channel deposit in the middle and fine-grained sediment in the flood plain at the upper, dominated by lake level fluctuation. During the deposit of the LST in the

  16. Early to late Yanshanian I-type granites in Fujian Province, SE China: Implications for the tectonic setting and Mo mineralization (United States)

    Yang, Yu-Long; Ni, Pei; Yan, Jun; Wu, Chang-Zhi; Dai, Bao-Zhang; Xu, Ying-Feng


    existing data, suggest that the tectonic setting of the early Yanshanian (∼143 Ma) highly fractionated I-type Dayang granite was a back-arc that formed in response to the westward subduction of the Paleo-Pacific Plate, and that the late Yanshanian (∼133 Ma) Juzhou granite formed in a continental arc setting in response to rollback of the Paleo-Pacific Plate toward the coastline. The Mo mineralization in the Makeng ore area was probably the result of the exsolution of Mo-bearing fluids from the Dayang granitic magmas due to extensive fractional crystallization.

  17. From folding to transpressional faulting: the Cenozoic Fusha structural belt in front of the Western Kunlun Orogen, northwestern Tibetan Plateau (United States)

    Wang, Cong; Cheng, Xiao-Gan; Chen, Han-Lin; Li, Kang; Fan, Xiao-Gen; Wang, Chun-Yang


    Fusha structural belt (FSB) is one of the most important tectonic units in front of the Western Kunlun Orogen, northwestern Tibetan Plateau (NW China), in which the Kekeya oil field was discovered in 1971. However, there is no new oil field discovered since then due to the unclarity of the intense and complex Cenozoic deformation in this area. Based on field investigation, seismic interpretation and Continuous Electromagnetic Profile data, we analyze in detail the Cenozoic deformation history, emphasizing on the spatial and temporal variation of the deformation of the FSB in this paper. The result suggests that the FSB was dominated by two deformation events, (1) early (Miocene-early Pliocene) folding event expressed by anticline, with the western segment E-W orienting, while the eastern segment NWW-SEE orienting and (2) later (since late Pliocene) transpressional faulting event that destroyed and divided the earlier anticline into a number of fault blocks. The transpressional faulting caused dextral strike-slip reverse fault, with the dip angles decreasing eastward from ~90° to reserved. Based on the spatial variation of structural characteristics, we propose that the fault block traps and anticline traps in the eastern segment and fault block traps in western segment are favorable for hydrocarbon accumulation.

  18. European Cenozoic rift system (United States)

    Ziegler, Peter A.


    The European Cenozoic rift system extends from the coast of the North Sea to the Mediterranean over a distance of some 1100 km; it finds its southern prolongation in the Valencia Trough and a Plio-Pleistocene volcanic chain crossing the Atlas ranges. Development of this mega-rift was paralleled by orogenic activity in the Alps and Pyrenees. Major rift domes, accompanied by subsidence reversal of their axial grabens, developed 20-40 Ma after beginning of rifting. Uplift of the Rhenish Shield is related to progressive thermal lithospheric thinning; the Vosges-Black Forest and the Massif Central domes are probably underlain by asthenoliths emplaced at the crust/mantle boundary. Evolution of this rift system, is thought to be governed by the interaction of the Eurasian and African plates and by early phases of a plate-boundary reorganization that may lead to the break-up of the present continent assembly.

  19. The origin of Cenozoic magmatism of Libya (United States)

    Stuart, Finlay; Masoud, Abdelmoniem; Mark, Darren


    significantly earlier (20-10 Ma). The Cenozoic basaltic volcanism in Libya appears to be related to reactivation of ancient structures during the passive rifting that has been produced in response to interaction of African and European plates since the late Mesozoic.


    Institute of Scientific and Technical Information of China (English)


    This paper is concentrated on Cenozoic volcanism and geothermal resources in Northeast China. There are a lot of Cenozoic volcanoes, a large area of volcanic rocks, a large number of active faults and rich geothermal resources in Northeast China. The time and space characteristics of Cenozoic volcanism and the space distribution characters of hot springs and high geothermal flux regions in Northeast China are described and discussed on the basis of geological, geothermal, drilling and volcanological data. It is revealed that the hot springs and high geothermal flux regions are re lated to the Cenozoic volcanism, rifting and faulting in Northeast China. It is especially emphasized that the hot springs and high geothermal anomaly areas are controlled by active deep faults. It is proposed that the Cenozoic volcanism re gions, rift basins, active fault belts, activated plate suture zones and large earthquake occurrence points are the best areas for prospecting geothermal resources. The geothermal resources in younger volcanic zones are richer than those in older volcanic belts. The hot springs and active or activated faults might be a very good clue for looking for geothermal resources.

  1. I. Cenozoic geology of Iran: An integrated study of extensional tectonics and related volcanism. II. Ediacaran stratigraphy of the North American Cordillera: New observations from eastern California and northern Utah (United States)

    Verdel, Charles


    I. The late Oligocene to Miocene collision of Arabia and Eurasia was preceded by ~175 My of subduction of Neotethyan oceanic crust. Associated magmatic activity includes late Triassic(?) to Jurassic plutons in the Sanandaj-Sirjan zone of southern Iran, limited Cretaceous magmatism in the Alborz Mountains of northern Iran, and widespread Eocene volcanism across central Iran. Metamorphic core complexes of Eocene age have recently been recognized in widely separated parts of Iran, suggesting that Tertiary volcanism was related to extension. Geochemical data indicate that Eocene volcanism was typical of continental arcs and was followed by less voluminous Oligocene basaltic volcanism of the type often associated with back-arc basins. This set of observations suggests that mid-Mesozoic plutons in southern Iran are the remnants of an original volcanic arc that was only weakly developed because of slow subduction rate. Magmatic activity largely ceased in southern and central Iran during the Cretaceous and shifted to the north, suggesting a period of flat slab subduction. Subsequent slab-rollback during the Eocene extended the overriding plate, forming metamorphic core complexes and inducing pressure-release melting of partially hydrated lithospheric mantle and upwelling of asthenosphere. II. The Ediacaran Period spans from the base of cap carbonates overlying glacial deposits of the Marinoan "Snowball Earth" event to the Precambrian-Cambrian boundary, ~635 to 542 Ma. Sediments deposited during the rifting of southwest Laurentia, which are now exposed in a relatively narrow belt in the western US, are one of the best records on earth of the geological, geochemical, and geobiological events that occurred during this period. Evidence for one of the most significant of these, the final oxygenation of the oceans, is found within the upper Johnnie Formation in the southern Great Basin. C isotope data from thick, basinal facies of the Johnnie Fm. in the Panamint Range provide a

  2. Mesozoic-Cenozoic Tectonic Evolution of the Kuqa Basin:Evidence from Apatite Fission-Track Data%库车盆地中新生代构造演化:磷灰石裂变径迹证据

    Institute of Scientific and Technical Information of China (English)

    罗梦; 朱文斌; 郑碧海; 朱晓青


    Fourteen samples were collected from the Kuqa River section for apatite fission track analysis in order to investigate the thermal history of the Kuqa Basin and its sedimentary provenance. By comparing the apparent ages of samples with the related strata ages, the samples can be divided into two groups: the annealed group and the detrital group (unreset samples). The AFT ages become younger from 136 Ma to 93. 7 Ma from the Tianshan Mountain to the Kuqa Basin, probably recording a basin-ward propagation of the thrust-fold belt. Samples 09dk-6, 09dk-7, 09dk-8 and 09dk-ll failed the X2 test likely due to the subsequent tectonic deformation. The youngest ages extracted from these samples probably record the latest activities of the Kuruli Syncline, Jiesidelike Anticline and the A'ge Fault at 74. 4 Ma, 24. 2 Ma and 50. 8 Ma, respectively. The detrital samples have three peak ages at 250 Ma, 160 Ma and 100 Ma respectively. Thermal history modeling reveals four periods of denudation at 250 Ma, 160 Ma, 100 Ma and 20 Ma in the Kuqa basin and the Tianshan Mountains. The multi-stage denudation is linked to far-field effects resulted from the collision and accretion of terranes along the southern Asian continental margin.%通过对库车河剖面14个样品磷灰石裂变径迹的测试,研究了库车盆地及其源区的构造演化.根据表观年龄和地层年龄关系,将结果分成8个退火样品和6个碎屑样品.退火样品年龄从北向南从136~93.7Ma,记录了构造发育自造山带向盆地扩展的运动样式.其中09dk-6,09dk-7,09dk-8和09dk-11未通过x2检验,分析认为与后期构造活动有关,分解得到最年轻的年龄组记录了库如力向斜,捷斯德里克背斜和阿合断层分别在74.4Ma、24.2 Ma和50.8 Ma的最新一期活动.碎屑磷灰石得到了250Ma、160Ma和100 Ma3个明显的静态峰.结合热模拟研究表明,研究区存在250Ma、160Ma、100Ma和20 Ma四期构造隆升,是对亚洲南缘多期地体碰撞增生的响应.


    Directory of Open Access Journals (Sweden)



    Full Text Available Seep-carbonates are generally related to hydrocarbon seepage on continental margins. Modern cold seeps are abundant in actively deforming tectonic settings, suggesting that tectonics is one of the major controlling factor on fluid emissions. Hydrocarbon seepages areconsidered major geological sources of atmospheric methane, one of the most important green-house gases, and have also been related to climate changes. However, the interplaybetween tectonics and climate change in forcing seepage is not clearly understood. Miocene seep-carbonates, formed in a collisional settingsuch as that ofthe Salsomaggiore area of the Northern Apennines(Italy, provide an opportunitytoassess accumulation and release of methane in response to tectonics and climate change along a convergent margin. Thestudiedseep-carbonatesarerelated to fluid emissions of various intensities coeval with tectonic pulses.Newplanktonic foraminiferal biostratigraphic datareveals thatdepositionof these seep-carbonatesislate Serravallian-early Tortonian in age and partiallycoeval with the Miller’s global cooling event Mi 5 (as used below. These seep-carbonates were deposited in two stages with different seepage modes. During the first stage, local tectonic pulses at the onset of the Mi5 event may have producedslow seepage, whereas during the second stage regional tectonics and more extreme climatic conditions (coolest peak of Mi5 event may have resulted inafast and more intense seepage as suggested by increasing occurrence of chaotic facies. In the Salsomaggiore Ridge, tectonics and the Mi5 cooling event actively concurredtothe deposition of seep-carbonates in both stages.

  4. Tectonic geomorphology

    National Research Council Canada - National Science Library

    Burbank, Douglas West; Anderson, Robert S


    Tectonic geomorphology is the study of the interplay between tectonic and surface processes that shape the landscape in regions of active deformation and at times scales ranging from days to millions of years...

  5. Paleomagnetism of Late Jurassic to Early Cretaceous red beds from the Cardamom Mountains, southwestern Cambodia: Tectonic deformation of the Indochina Peninsula (United States)

    Tsuchiyama, Yukiho; Zaman, Haider; Sotham, Sieng; Samuth, Yos; Sato, Eiichi; Ahn, Hyeon-Seon; Uno, Koji; Tsumura, Kosuke; Miki, Masako; Otofuji, Yo-ichiro


    Late Jurassic to Early Cretaceous red beds of the Phuquoc Formation were sampled at 33 sites from the Sihanoukville and Koah Kong areas of the Phuquoc-Kampot Som Basin, southwestern Cambodia. Two high-temperature remanent components with unblocking temperature ranging 650°-670 °C and 670-690 °C were identified. The magnetization direction for the former component (D = 5.2 °, I = 18.5 ° with α95 = 3.1 ° in situ) reveals a negative fold test that indicates a post-folding secondary nature. However, the latter component, carried by specular hematite, is recognized as a primary remanent magnetization. A tilt-corrected mean direction of D = 43.4 °, I = 31.9 ° (α95 = 3.6 °) was calculated for the primary component at 11 sites, corresponding to a paleopole of 47.7°N, 178.9°E (A95 = 3.6 °). When compared with the 130 Ma East Asian pole, a southward displacement of 6.0 ° ± 3.5 ° and a clockwise rotation of 33.1 ° ± 4.0 ° of the Phuquoc-Kampot Som Basin (as a part of the Indochina Block) with respect to East Asia were estimated. This estimate of the clockwise rotation is ∼15° larger than that of the Khorat Basin, which we attribute to dextral motion along the Wang Chao Fault since the mid-Oligocene. The comparison of the herein estimated clockwise rotation with the counter-clockwise rotation reported from the Da Lat area in Vietnam suggests the occurrence of a differential tectonic rotation in the southern tip of the Indochina Block. During the southward displacement of the Indochina Block, the non-rigid lithosphere under its southern tip moved heterogeneously, while the rigid lithosphere under the Khorat Basin moved homogeneously.

  6. A-type granitoid in Hasansalaran complex, northwestern Iran: Evidence for extensional tectonic regime in northern Gondwana in the Late Paleozoic (United States)

    Azizi, Hossein; Kazemi, Tahmineh; Asahara, Yoshihiro


    The Hasansalaran plutonic complex is one of the main intrusive bodies with a wide range of granite, monzonite, diorite and syenite that crop out in northwest Iran. This body includes Paleozoic granitoids that are surrounded and cut by Cretaceous granitoids. Zircon U-Pb age dating shows that the crystallization of this body occurred at 360 Ma ago in the Early Carboniferous. Whole rock compositions of the investigated intrusive body, show high contents of Ga (11.1-76.3 ppm), Zr (73.5-1280 ppm), Zn (43.7-358 ppm), Y(17.9-177 ppm), enrichment of rare earth elements (REEs) together with high Ga/Al ratios and a strong Eu negative anomaly, fairly consistent with typical A-type signature. The low εNd(t = 360 Ma) value (< + 3) and high variation of 87Sr/86Sr(initial) ratios are evidence of the role of the continental component for the evolution of A-type granitoids in the Hasansalaran area. Because of the high contents of Ta, Yb, Nb and Y, all samples are plotted in the within-plate tectonic regime without interfering oceanic released fluids in the subduction zone. These high Nb content rocks (37.2-342 ppm without one sample) are classified as A1-type granitoids. Based on the distribution of A1- and A2-type granitoids in the Late Paleozoic in northwest Iran, the existence of some gabbroic rocks with tholeiitic to alkali composition and a long gap for magmatic activities in the area from 550 to 360 Ma (approximately 180 my.a.) between the Zagros and Tabriz faults, we suggest a new thematic model for evolution of northwest Iran in the Late Paleozoic. Based on our model, the upwelling of a mantle plume, probably due to the proto-Tethys oceanic rollback activity beneath northern Gondwana, had a crucial role in the uplifting of the continental crust and resulted in the crystallization of A-type granitoids with some gabbroic rocks in northwest Iran.

  7. Performative Tectonics

    DEFF Research Database (Denmark)

    Holst, Malene Kirstine; Mullins, Michael; Kirkegaard, Poul Henning


    This paper studies two digital generative tools in terms of Performative Tectonics. Performative Tectonics is a term developed in the paper, which links the contemporary development of digital tools to the tectonic tradition of architecture. Within the theoretical framework of this definition...

  8. 滇西哀牢山构造带:结构与演化%The Ailaoshan Belt in Western Yunnan:Tectonic Framework and Tectonic Evolution

    Institute of Scientific and Technical Information of China (English)

    刘俊来; 唐渊; 宋志杰; Tran My Dung; 翟云峰; 吴文彬; 陈文


    The Ailaoshan tectonic zone is the most significant lineament in the eastern Tibet (Southeast Asia) , which separates the Yangtze-South China and the Indochina blocks. Information on multi-stage complex tectonic evolution is preserved in the rocks in the tectonic zone. Late Archean Neoproterozoic high grade metamorphic rock series, Cenozoic tectono-magmatic assemblages (shearing deformation structures) , Late Permian - Early Triassic Jinping-Song Da rifting rock sequences and Early Carboniferous-Early Triassic Ailaoshan tectonic melange were well developed from east to west along the Ailaoshan tectonic zone. The various tectonic units of different characteristics are separated by fault structures mainly developed in Cenozoic. Granitic intrusions of various stages which were formed due to allochthonous emplacement or mingmatization are widespread along the tectonic belt. The Ailaoshan tectonic belt has multiple tectonic natures during different geologic history stages. On the whole, it has experienced three important tectonic stages, I. E. Pre-tethys, Tethys, and Cenozoic intracontinental stages. During the Pre-tethys evolution until Early Paleozoic, the major part of the belt (especially along the eastern zone) had affinity to the Yangtze block, and preserved records of Late Archean Neoproterozoic crustal evolution. Since the Late Paleozoic-Early Mesozoic the tectonic belt became a part of the Tethyan domain with the opening of Paleotethys. The belt was evolved into a tectonic domain with different nature from that of the South China-Yangtze plate. Subsequent closure of the Ailaoshan Ocean in from Early Carboniferous and the Jinping-Song Da Ocean since Early Permian resulted in the formation of the paleo-Ailaoshan orogenic belt. The closure of the Tethyan oceans made Yangtze-South China block and Indochina block to become a unified continent. Interaction between the Indian and the Eurasian plates had a sound influence on the Ailaoshan belt. There are Early Cenozoic

  9. Cenozoic plant diversity of Yunnan: A review

    Directory of Open Access Journals (Sweden)

    Yongjiang Huang


    Full Text Available Yunnan in southwestern China is renowned for its high plant diversity. To understand how this modern botanical richness formed, it is critical to investigate the past biodiversity throughout the geological time. In this review, we present a summary on plant diversity, floristics and climates in the Cenozoic of Yunnan and document their changes, by compiling published palaeobotanical sources. Our review demonstrates that thus far a total of 386 fossil species of ferns, gymnosperms and angiosperms belonging to 170 genera within 66 families have been reported from the Cenozoic, particularly the Neogene, of Yunnan. Angiosperms display the highest richness represented by 353 species grouped into 155 genera within 60 families, with Fagaceae, Fabaceae, Lauraceae and Juglandaceae being the most diversified. Most of the families and genera recorded as fossils still occur in Yunnan, but seven genera have disappeared, including Berryophyllum, Cedrelospermum, Cedrus, Palaeocarya, Podocarpium, Sequoia and Wataria. The regional extinction of these genera is commonly referred to an aridification of the dry season associated with Asian monsoon development. Floristic analyses indicate that in the late Miocene, Yunnan had three floristic regions: a northern subtropical floristic region in the northeast, a subtropical floristic region in the east, and a tropical floristic region in the southwest. In the late Pliocene, Yunnan saw two kinds of floristic regions: a subalpine floristic region in the northwest, and two subtropical floristic regions separately in the southwest and the eastern center. These floristic concepts are verified by results from our areal type analyses which suggest that in the Miocene southwestern Yunnan supported the most Pantropic elements, while in the Pliocene southwestern Yunnan had abundant Tropical Asia (Indo–Malaysia type and East Asia and North America disjunct type that were absent from northwestern Yunnan. From the late Miocene to

  10. River history and tectonics. (United States)

    Vita-Finzi, C


    The analysis of crustal deformation by tectonic processes has gained much from the clues offered by drainage geometry and river behaviour, while the interpretation of channel patterns and sequences benefits from information on Earth movements before or during their development. The interplay between the two strands operates at many scales: themes which have already benefited from it include the possible role of mantle plumes in the breakup of Gondwana, the Cenozoic development of drainage systems in Africa and Australia, Himalayan uplift in response to erosion, alternating episodes of uplift and subsidence in the Mississippi delta, buckling of the Indian lithospheric plate, and changes in stream pattern and sinuosity along individual alluvial channels subject to localized deformation. Developments in remote sensing, isotopic dating and numerical modelling are starting to yield quantitative analyses of such effects, to the benefit of geodymamics as well as fluvial hydrology.

  11. Plate tectonic setting and genetic types of gas (oil)-bearing basins in China

    Institute of Scientific and Technical Information of China (English)

    张一伟; 陈发景; 陆克政; 漆家福


    The plate tectonic setting and genetic types of the gas (oil)-bearing basins in China are studied. Based on the history of break-up and amalgamation of Pangea, the three tectonic evolutionary megastages can be divided and the sedimentary basins in China are classified as Palaeozoic and Meso-Cenozoic basins. The Palaeozoic gas(oil)-bearing basins are mainly located in intracratonic basins, on which different types of Meso-Cenozoic basins are superimposed, and located in cratonic marginal basins and aulacogens destroyed with a slight degree, (n contrast, the Mesozoic and Cenozoic gas (oil)-bearing basins mainly formed in extensional foreland and intracontmental shortening flexural basins.

  12. Early cenozoic differentiation of polar marine faunas.

    Directory of Open Access Journals (Sweden)

    J Alistair Crame

    Full Text Available The widespread assumption that the origin of polar marine faunas is linked to the onset of major global cooling in the Late Eocene-Early Oligocene is being increasingly challenged. The Antarctic fossil record in particular is suggesting that some modern Southern Ocean taxa may have Early Eocene or even Paleocene origins, i.e. well within the Early Cenozoic greenhouse world. A global analysis of one of the largest marine clades at the present day, the Neogastropoda, indicates that not only is there a decrease in the number of species from the tropics to the poles but also a decrease in the evenness of their distribution. A small number of neogastropod families with predominantly generalist trophic strategies at both poles points to the key role of seasonality in structuring the highest latitude marine assemblages. A distinct latitudinal gradient in seasonality is temperature-invariant and would have operated through periods of global warmth such as the Early Cenozoic. To test this concept a second global analysis was undertaken of earliest Cenozoic (Paleocene neogastropods and this does indeed show a certain degree of faunal differentiation at both poles. The Buccinidae, s.l. is especially well developed at this time, and this is a major generalist taxon at the present day. There is an element of asymmetry associated with this development of Paleocene polar faunas in that those in the south are more strongly differentiated than their northern counterparts; this can in turn be linked to the already substantial isolation of the southern high latitudes. The key role of seasonality in the formation of polar marine faunas has implications for contemporary ecosystem structure and stability.

  13. Cenozoic Tectonic Evolution and its Influence on Uranium Ore-forming Processes in the Xiazhuang Ore Field, Northern Guangdong Province%粤北下庄矿田新生代构造演化及其对铀成矿的影响

    Institute of Scientific and Technical Information of China (English)

    王军; 赖中信; 张辉仁; 汤世凯; 杨坤光


    also provides a brief summary for the applications of the HPT to address various important geological and geophysical problems such as rheology and fracture mechanics of polyphase rocks, formation and extraction of partial melt, brittle-ductile transition, dynamic recrystallization and development of lattice preferred orientation, and seismic properties of deformed rocks. The recent installation of a HPT in the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, introduces to China a new high technology in the Earth Sciences, and promises to have a large positive impact on the experimental studies of structural geology, tectonics and geodynamics. 20. Oma) intermittent faulting and uplifting, Ⅲ(20.0 -2. 2Ma) frequent small scale hydrothermal activities. ESR ages of hydrothermal quartz and U-Pb ages of pitchblender from 331, 335, 336 uranium deposits demonstrate that the U mineralization took place no later than 60 Ma ± , which is consistent with the first stage deformation. The second and third stage deformation resulted in uplifting and frequent faulting. The NNE, NEE and the EW-trending structures exhibit chess-board pattern in horizontal and graben-like pattern vertically. The structures aggravated weathering, leaching and denudation processes, and finally destroyed the pre-exist metallogenic environment. Thus, study of the Cenozoic tectonic evolution may contribute to the understanding of the tectonic controls on the uranium ore forming processes.%粤北南岭地区是我国重要的花岗岩型铀矿产地,通过野外地质调查与构造变形研究,结合34件石英脉体电子自旋共振(ESR)测年研究,论述了粤北地区下庄矿田的新生代构造演化期次.构造变形研究与ESR年龄测定显示:新生代主要发生了三幕构造变形,第Ⅰ幕(65.5~55.0Ma)为地块的差异升降运动,断裂活动规模大;第Ⅱ幕(40.3~20.0Ma)为间歇性的升降运动,总体为上升趋势;第Ⅲ幕(20.0~2.2Ma)表现为断裂

  14. Phanerozoic tectonic evolution of the Circum-North Pacific (United States)

    Nokleberg, Warren J.; Parfenov, Leonid M.; Monger, James W.H.; Norton, Ian O.; Khanchuk, Alexander I.; Stone, David B.; Scotese, Christopher R.; Scholl, David W.; Fujita, Kazuya


    the ancestral margins of present-day Northeast Asia and northwestern North America. The rifting resulted in the fragmentation of each continent and the formation of cratonal and passive continental-margin terranes that eventually migrated and accreted to other sites along the evolving margins of the original or adjacent continents. (2) From about the Late Triassic through the mid-Cretaceous, a succession of island arcs and tectonically paired subduction zones formed near the continental margins. (3) From about mainly the mid-Cretaceous through the present, a succession of igneous arcs and tectonically paired subduction zones formed along the continental margins. (4) From about the Jurassic to the present, oblique convergence and rotations caused orogenparallel sinistral and then dextral displacements within the upper-plate margins of cratons that have become Northeast Asia and North America. The oblique convergences and rotations resulted in the fragmentation, displacement, and duplication of formerly more nearly continuous arcs, subduction zones, and passive continental margins. These fragments were subsequently accreted along the expanding continental margins. (5) From the Early Jurassic through Tertiary, movement of the upper continental plates toward subduction zones resulted in strong plate coupling and accretion of the former island arcs and subduction zones to the continental margins. Accretions were accompanied and followed by crustal thickening, anatexis, metamorphism, and uplift. The accretions resulted in substantial growth of the North Asian and North American Continents. (6) During the middle and late Cenozoic, oblique to orthogonal convergence of the Pacifi c plate with present-day Alaska and Northeast Asia resulted in formation of the modern-day ring of volcanoes around the Circum-North Pacific. Oblique convergence between the Pacific plate and Alaska also resulted in major dextral-slip faulting in interior and southern Alaska and along the western p

  15. Relating Cenozoic North Sea sediments to topography in southern Norway:

    DEFF Research Database (Denmark)

    Anell, Ingrid Anna Margareta; Thybo, Hans; Stratford, Wanda Rose


    sources for progradational influx of clastic sediments from Scotland, the Shetland platform and, to a lesser degree, southwestern Norway. The Eocene sedimentation pattern was similar to the Palaeocene, with lower rates of accumulation associated with flooding and tectonic quiescence. Sediment influx from...... the Shetland platform continued throughout the Cenozoic while supply from southern Norway increased markedly around the Eocene–Oligocene, coeval with the greenhouse–icehouse transition. Mass balance calculations of sediment and eroded rock volumes suggest that while some topography along the western margin...

  16. Constraining the vertical surface motions of the Hampshire Basin, south England During the Cenozoic (United States)

    Smith, Philip; England, Richard; Zalasiewicz, Jan


    The potential effect of rising sea level on the UK has received considerable attention in recent years. However, the ongoing long-term changes in surface topography of the UK driven by regional tectonics and the mechanisms responsible are not fully understood. It is thought that glacial loading/unloading is the primary influence. However, this is inconsistent with present-day vertical surface motions recorded from Continuous Global Positioning Stations (CGPS) across the UK. The lateral variations in the present day motions are too complex to be explained by glacial isostatic rebound. We are investigating the hypothesis that the vertical motions of SE England also reflect the long term tectonic history by backstripping the Cenozoic geological record. So far the Paleogene stratigraphic record of the Hampshire basin in southern England has been investigated and using a series of deep boreholes that reach the chalk basement, a 2-D backstripping method has been applied. Subsidence analysis of cliff sections and boreholes reveal the Hampshire Basin was tectonically subsiding at a steady rate from 56.5Ma and any major periods of uplift and denudation to the present day state must have occurred from the mid Oligocene onwards. At this time the northern and western regions of the UK were believed to be uplifting as evidenced by heavy mineral transport directionns and sediment drainage patterns. A rapid increase in tectonic subsidence from 42Ma recorded by the three Isle of Wight sections in close proximity to an existing Variscan fault, thought to reactivate as a thrust during the Cenozoic, suggests a compressional stress regime in this region. The stress pattern observed from the tectonic subsidence data and evidence from drainage patterns supports a model in which the UK was uplifting in the north and west while the south east was subsiding. As this pattern is similar to the present day vertical surface motions and pre-dates glaciation, we propose glacial unloading as a

  17. Extension structural records in the Qinshui basin (North China) since the Late Mesozoic (United States)

    Wang, Ying; Zhang, Qinglong; Zhu, Wenbin; Wang, Liangshu; Xie, Guoai; Liu, Chao; Zou, Xu


    Qinshui basin has abundant coal-bed methane resources and has been undergoing intensive intracontinental rifting and extensional tectonics since the Late Mesozoic. Some fractures, which were previously considered as conjugate shear fractures, are interpreted as joint sets with extension characteristics, for the first time in the Qinshui basin. The widely distributed joint sets with stable attitudes can be divided into four sets. This paper presents updated results of fault-slip datasets collected in different zones of the Qinshui basin and addresses the changes in the direction of extensional stresses since the Late Mesozoic. Based on the analysis results of the slickenline of normal faults, joint sets in the field, and focal mechanism solutions data from the Shanxi Province, we identified four main directions of extension since the Late Mesozoic in the Qinshui basin: (1) Early Cenozoic ENE-WSW (85 ± 15°) extension; (2) Palaeogene NNE-SSW (30 ± 5°) extension; (3) Miocene NW-SE (135 ± 15°) extension; and (4) Late Pliocene-quaternary NNW-SSE (170 ± 5°) extension. The principal extension directions in the Qinshui basin seem to have undergone a counterclockwise rotation from the Early Cenozoic to the Miocene. We prefer that the extension deformation events in the Qinshui basin since the Late Mesozoic were mainly related to the back-arc spreading induced by westward subduction of the paleo-Pacific plate under the Eurasian continent.

  18. Cenozoic Carbonate Stratigraphy of the Yucatan Shelf, Southern Gulf of Mexico (United States)

    Ortega-Nieto, A.; Urrutia-Fucugauchi, J.


    The Yucatan shelf in the southern Gulf of Mexico has developed as a large shallow ramp shelf, tectonically stable that preserves a continuous sedimentary record for the Late Mesozoic and Cenozoic. We present the preliminary results of a study involving well stratigraphy, X-ray diffraction and petrography of the Cenozoic sequence sampled in the UNAM-5, UNAM-6 and UNAM-7 exploratory boreholes drilled in the southwestern and southern sectors of the Yucatan state. The boreholes were drilled as part of the Chicxulub Drilling Project aimed to investigate the formation and characteristics of the large crater, formed by an asteroid impact at the Cretaceous/Paleogene (K/Pg) boundary. Our study aims to investigate the stratigraphic relations, textural changes and characteristics of the sedimentary units, to identify events associated with the evolution of the platform during the Cenozoic. We constructed detailed stratigraphic columns for the three borehole cores and prepared samples collected across the stratigraphic section for petrography and clay analyses. The petrographic studies were made at different depths above the K/Pg boundary to recognize textural variations, the identification of dolomite was made by the method of staining thin sections, and the dolomite fabrics were analyzed to identify the nature and shape of their crystal boundaries. The method of X-ray diffraction was used to identify clay types. The three boreholes cross the K/Pg boundary at different depths. The stratigraphic column is formed, from bottom to top, of a limestone sequence with evaporites nodules, little contents of benthic foraminifera, scarce planktic foraminifera and oogonia fossils suggesting internal lagoonal environments that vary to outer lagoon. This sequence is underlain by limestones with different degrees of dolomitization that in many cases present poorly preserved microfossil contents. Above this sequence, there is a clay bed identified as palygorskita, which has a variable

  19. Pacific plate slab pull and intraplate deformation in the early Cenozoic (United States)

    Butterworth, N. P.; Müller, R. D.; Quevedo, L.; O'Connor, J. M.; Hoernle, K.; Morra, G.


    Large tectonic plates are known to be susceptible to internal deformation, leading to a~range of phenomena including intraplate volcanism. However, the space and time dependence of intraplate deformation and its relationship with changing plate boundary configurations, subducting slab geometries, and absolute plate motion is poorly understood. We utilise a buoyancy-driven Stokes flow solver, BEM-Earth, to investigate the contribution of subducting slabs through time on Pacific plate motion and plate-scale deformation, and how this is linked to intraplate volcanism. We produce a series of geodynamic models from 62 to 42 Ma in which the plates are driven by the attached subducting slabs and mantle drag/suction forces. We compare our modelled intraplate deformation history with those types of intraplate volcanism that lack a clear age progression. Our models suggest that changes in Cenozoic subduction zone topology caused intraplate deformation to trigger volcanism along several linear seafloor structures, mostly by reactivation of existing seamount chains, but occasionally creating new volcanic chains on crust weakened by fracture zones and extinct ridges. Around 55 Ma, subduction of the Pacific-Izanagi ridge reconfigured the major tectonic forces acting on the plate by replacing ridge push with slab pull along its northwestern perimeter, causing lithospheric extension along pre-existing weaknesses. Large-scale deformation observed in the models coincides with the seamount chains of Hawaii, Louisville, Tokelau and Gilbert during our modelled time period of 62 to 42 Ma. We suggest that extensional stresses between 72 and 52 Ma are the likely cause of large parts of the formation of the Gilbert chain and that localised extension between 62 and 42 Ma could cause late-stage volcanism along the Musicians volcanic ridges. Our models demonstrate that early Cenozoic changes in Pacific plate driving forces only cause relatively minor changes in Pacific absolute plate motion

  20. Pacific Plate slab pull and intraplate deformation in the early Cenozoic

    Directory of Open Access Journals (Sweden)

    N. P. Butterworth


    Full Text Available Large tectonic plates are known to be susceptible to internal deformation, leading to a range of phenomena including intraplate volcanism. However, the space and time dependence of intraplate deformation and its relationship with changing plate boundary configurations, subducting slab geometries, and absolute plate motion is poorly understood. We utilise a buoyancy driven Stokes flow solver, BEM-Earth, to investigate the contribution of subducting slabs through time on Pacific Plate motion and plate-scale deformation, and how this is linked to intraplate volcanism. We produce a series of geodynamic models from 62 to 42 Ma in which the plates are driven by the attached subducting slabs and mantle drag/suction forces. We compare our modelled intraplate deformation history with those types of intraplate volcanism that lack a clear age progression. Our models suggest that changes in Cenozoic subduction zone topology caused intraplate deformation to trigger volcanism along several linear seafloor structures, mostly by reactivation of existing seamount chains, but occasionally creating new volcanic chains on crust weakened by fracture zones and extinct ridges. Around 55 Ma subduction of the Pacific-Izanagi ridge reconfigured the major tectonic forces acting on the plate by replacing ridge push with slab pull along its north-western perimeter, causing lithospheric extension along pre-existing weaknesses. Large scale deformation observed in the models coincides with the seamount chains of Hawaii, Louisville, Tokelau, and Gilbert during our modelled time period of 62 to 42 Ma. We suggest that extensional stresses between 72 and 52 Ma are the likely cause of large parts of the formation of the Gilbert chain and that localised extension between 62 and 42 Ma could cause late-stage volcanism along the Musicians Volcanic Ridges. Our models demonstrate that early Cenozoic changes in Pacific plate driving forces only cause relatively minor changes in Pacific

  1. Pacific plate slab pull and intraplate deformation in the early Cenozoic

    Directory of Open Access Journals (Sweden)

    N. P. Butterworth


    Full Text Available Large tectonic plates are known to be susceptible to internal deformation, leading to a~range of phenomena including intraplate volcanism. However, the space and time dependence of intraplate deformation and its relationship with changing plate boundary configurations, subducting slab geometries, and absolute plate motion is poorly understood. We utilise a buoyancy-driven Stokes flow solver, BEM-Earth, to investigate the contribution of subducting slabs through time on Pacific plate motion and plate-scale deformation, and how this is linked to intraplate volcanism. We produce a series of geodynamic models from 62 to 42 Ma in which the plates are driven by the attached subducting slabs and mantle drag/suction forces. We compare our modelled intraplate deformation history with those types of intraplate volcanism that lack a clear age progression. Our models suggest that changes in Cenozoic subduction zone topology caused intraplate deformation to trigger volcanism along several linear seafloor structures, mostly by reactivation of existing seamount chains, but occasionally creating new volcanic chains on crust weakened by fracture zones and extinct ridges. Around 55 Ma, subduction of the Pacific-Izanagi ridge reconfigured the major tectonic forces acting on the plate by replacing ridge push with slab pull along its northwestern perimeter, causing lithospheric extension along pre-existing weaknesses. Large-scale deformation observed in the models coincides with the seamount chains of Hawaii, Louisville, Tokelau and Gilbert during our modelled time period of 62 to 42 Ma. We suggest that extensional stresses between 72 and 52 Ma are the likely cause of large parts of the formation of the Gilbert chain and that localised extension between 62 and 42 Ma could cause late-stage volcanism along the Musicians volcanic ridges. Our models demonstrate that early Cenozoic changes in Pacific plate driving forces only cause relatively minor changes in Pacific

  2. Late Pleistocene to Holocene alluvial tableland formation in an intra-mountainous basin in a tectonically active mountain belt - A case study in the Puli Basin, central Taiwan

    NARCIS (Netherlands)

    Tseng, Chia Han; Lüthgens, Christopher; Tsukamoto, Sumiko; Reimann, Tony; Frechen, Manfred; Böse, Margot


    The morphology in Taiwan is a product of high tectonic activity at the convergent margin and East Asian monsoon climate. Tablelands are prominent geomorphic features in the Puli Basin in central Taiwan. These tablelands provide an archive to understand links between past climatic evolution and te

  3. Cenozoic Uplift, Erosion and Dynamic Support of Madagascar (United States)

    Stephenson, Simon; White, Nicky


    The physiography of Madagascar is characterised by high-elevation but low-relief topography; 42% of the landscape is above 500 m in elevation. Eocene (marine) nummulitic (marine) limestones at elevations of ˜400 m above sea level and newly dated, emergent 125 ka coral reefs suggest that Madagascar has experienced differential vertical motions during Cenozoic times. Malagasy rivers are often deeply incised and contain steepened reaches, implying that they have responded to changes in regional uplift rate. However, low temperature thermochronology and 10Be derived erosion rates suggest that both Cenozoic and Recent average denudation rates have been low. Extensive laterite-capped, low-relief surfaces also suggest that there have been long periods of tectonic quiescence. In contrast, the modern landscape is characterised by erosional gullies (i.e. lavaka), with very high local erosion rates. To bridge the gap between this disparate evidence, we inverted 2566 longitudinal river profiles using a damped non-negative, least-squares linear inversion to determine the history of regional uplift. We used a simplified version of the stream power erosional law. River profiles were extracted from the 3 arc-second Shuttle Radar Topography Mission (SRTM) digital elevation model. Calibration of the stream power erosional law is based upon Cenozoic limestones and new radiometrically dated marine terraces. The residual misfit between observed and calculated river profiles is small. Results suggest that Malagasy topography grew diachronously by 1-2 km over the last 15-20 Ma. Calculated uplift and denudation are consistent with independent observations. Thus drainage networks contain coherent signals that record regional uplift. The resultant waves of incision are the principal trigger for modern erosional processes. Admittance calculations, the history of basaltic volcanism and nearby oceanic residual age-depth measurements all suggest that as much as 0.8 - 1.1 km of Cenozoic uplift

  4. Tectonics of China: Continental scale cataclastic flow (United States)

    Gallagher, John J., Jr.

    Stratigraphic, structural, and earthquake evidence indicates that cataclastic flow, that is, flow by brittle mechanisms (e.g., fracture and slip), was dominant in China from late Paleozoic. This process has operated over a range of scales including the continental scale. China is made up of large brittle basement elements immersed in ductile zones which are analogous to porphyroclasts (large, often brittle fragments) surrounded by fluxion (foliation or flow) structures in cataclastic rocks, respectively. This basement fabric for China is seen on Landsat imagery and on tectonic maps and is comparable to cataclastic rock fabrics seen in fault zones, on outcrops, and in thin sections. Brittle basement elements are broken into two or more large rigid blocks, and the dimensions of elements and blocks are within 1 order of magnitude of each other. Ductile zones are made up of fragments which are many orders of magnitude smaller than the ductile zones. Rigid blocks and fragments are identified, and their dimensions are measured through earthquake, fault, and fracture patterns. Rigid basement blocks are surrounded by earthquakes. The sedimentary rocks over the basement faults at the block boundaries seem to be affected by fault movements because they are characterized by facies changes, thickness changes, high-angle faults, and forced folds. Ductile basement zones are earthquake prone, and deformation of the ductile basement affects the overlying sedimentary rocks, as is demonstrated by unconformities and by a wide variety of structures. Thrust faults, buckle folds, and strike slip faults are common in and adjacent to western ductile zones. Structures are most intensely developed where ductile zones abut brittle elements. Both brittle elements and ductile zones are rifted and cut by strike slip faults in eastern China. The mechanical fabric of China and the boundary conditions acting on China are now and always have been determined by its plate tectonic history. This

  5. Dinosaur tectonics

    DEFF Research Database (Denmark)

    Graversen, Ole; Milàn, Jesper; B. Loope, David


    to crustal scale tectonics associated with plate tectonics and foreland fold-thrust belts. A structural analysis of the dinosaur tracks shows the timing and direction of the forces exercised on the substrate by the animal's foot during the stride. Based on the structural analysis, we establish a scenario...... of the undertrack. The total length of the tectonic disturbance created by the dinosaur is up to three times that of the original footprint. Early, near-surface cementation gave the substrate the rheological properties necessary for development of the observed structures....

  6. Tectonic evolution of the Western Eger rift: a tale of two faults (United States)

    Tomasek, Jan; Kley, Jonas; Fischer, Tomáš; Štěpančíková, Petra


    The Eger Rift and Cheb basin in northwestern Bohemia are part of the European Cenozoic Rift System. They are associated with earthquake swarms, voluminous CO2 outgassing and Quaternary mantle-derived volcanism. The Eger Graben, of which the Cheb basin is traditionally considered a subbasin, contains a Cenozoic volcano-sedimentary record no thicker than 500 m. The structure of the extensional system is dominated by two large faults: (1) the ENE-striking Krušné Hory Fault (KHF), which delimits the northwestern shoulder of the Eger rift and has accommodated tilting and uplift of the Erzgebirge, creating a present day elevation difference of 700 m; (2) the NNW-striking Mariánské Lázně Fault (MLF), which is the master fault of the Cheb basin. First-order structural relationships indicate that the MLF has cross-cut the Eger rift at right angle and offset it with dominantly normal sense of motion. These relationships suggest that activity on the MLF was accentuated late in the history of the rift, around early Pliocene time, reflecting a fundamental change of the governing stress field. We aim to constrain, in conjunction with a Czech companion project focussing on tectonic geomorphology and seismology, the tectonic evolution of the two basins, and in particular the kinematics and timing of the Krušné Hory (Erzgebirge) and Mariánské Lázně bounding faults over Late Cenozoic time. This will be done by modelling the subsidence of the basins from stratigraphic and structural data. Rift shoulder uplift, exhumation and fault offsets will be constrained by low-T thermochronology, especially (U-Th)/He on apatite (AHe). 2D cross-sections and restorable structural 3D models will delimit the range of possible fault geometries and constrain the magnitude of fault displacements, their gradients and the deep architecture of the large faults. The Cheb basin forms an approximate semi-ellipse in map view, suggesting it is a half-graben bounded by a listric, WSW-dipping MLF

  7. Subsidence history and forming mechanism of anomalous tectonic subsidence in the Bozhong depression, Bohaiwan basin

    Institute of Scientific and Technical Information of China (English)

    XIE; XiNong


    [1]Li D S.Tectonic framework of the Bohai Gulf and coastal basins.Mar Sci,1982,1:82-93[2]Li S T.Basin geodynamics background of formation of huge petroleum systems (in Chinese).Earth Sci-J China Univ Geosci,2004,29(5):505-512[3]Allen M B,Macdonald D I M,Zhao X,et al.Early Cenozoic two-phase extension and late Cenozoic thermal subsidence and inversion of the Bohai basin,northern China.Mar Petrol Geol,1997,14(7/8):951-972[4]Gong Z S,Wang G C.Neotectonism and late hydrocarbon accumulation in Bohai Sea.Acta Pet Sin (in Chinese),2001,22(2):1-8[5]Hu S B,O'Sullivan P B,Raza A,et al.Thermal history and tectonic subsidence of the Bohai Basin,northern China:a Cenozoic rifted and local pull-apart basin.Phys Earth Planet Int,2001,126:221-235[6]Ren J Y,Tamaki K,Li S T,et al.Late Mesozoic and Cenozoic rifting and its dynamic setting in Eastern China and adjacent areas.Tectonophysics,2002,344:175-205[7]Li D S.Tectonics of Petroliferous Basins in China (in Chinese).Beijing:Petroleum Industry Press,2002.674[8]Xu J,Ma Z J,Deng Q D,et al.Regional tectonic conditions for intensive subsidence of the middle Bohai Sea since Oligocene.Acta Pet Sin (in Chinese),2004,25(5):11-16[9]Sclater J G,Christie P A F.Continental stretching:an explanation of the post Mid-Cretaceous subsidence of the central North Sea basin.J Geophys Res,1980,85:3711-3739[10]Xie X N,Müller R D,Li S T,et al.Origin of anomalous tectonic subsidence along the northern South China Sea Margin and its relationship to dynamic topography.Mar Pet Geol,2006,23(7):745-765[11]White N.Recovery of strain-rate variation from inversion of subsidence data.Nature,1993,366(6454):449-452[12]White N.An inverse method for determining lithosphere strain rate variation on geological time scales.Earth Planet Sci Lett,1994,122:351-371[13]Xie X N,Bethke C M,Li S T,et al.Overpressure and Petroleum generation and accumulation in the Dongying Depression of the Bohaiwan Basin,China.Geofluids,2001,1(4):257-271[14]Hall R.Reconstructing Cenozoic SE

  8. Kinematics of syn-tectonic unconformities and implications for the tectonic evolution of the Hala'alat Mountains at the northwestern margin of the Junggar Basin, Central Asian Orogenic Belt

    Directory of Open Access Journals (Sweden)

    Delong Ma


    Full Text Available The Hala'alat Mountains are located at the transition between the West Junggar and the Junggar Basin. In this area, rocks are Carboniferous, with younger strata above them that have been identified through well data and high-resolution 3D seismic profiles. Among these strata, seven unconformities are observed and distributed at the bases of: the Permian Jiamuhe Formation, the Permian Fengcheng Formation, the Triassic Baikouquan Formation, the Jurassic Badaowan Formation, the Jurassic Xishanyao Formation, the Cretaceous Tugulu Group and the Paleogene. On the basis of balanced sections, these unconformities are determined to have been formed by erosion of uplifts or rotated fault blocks primarily during the Mesozoic and Cenozoic. In conjunction with the currently understood tectonic background of the surrounding areas, the following conclusions are proposed: the unconformities at the bases of the Permian Jiamuhe and Fengcheng formations are most likely related to the subduction and closure of the Junggar Ocean during the late Carboniferous–early Permian; the unconformities at the bases of the Triassic Baikouquan and Jurassic Badaowan formations are closely related to the late Permian–Triassic Durbut sinistral slip fault; the unconformities at the bases of the middle Jurassic Xishanyao Formation and Cretaceous Tugulu Group may be related to reactivation of the Durbut dextral slip fault in the late Jurassic–early Cretaceous, and the unconformity that gives rise to the widely observed absence of the upper Cretaceous in the northern Junggar Basin may be closely related to large scale uplift. All of these geological phenomena indicate that the West Junggar was not calm in the Mesozoic and Cenozoic and that it experienced at least four periods of tectonic movement.

  9. Everyday Tectonics

    DEFF Research Database (Denmark)

    Beim, Anne; Hvejsel, Marie Frier


    to critically juxtapose the two concepts, everyday architecture and tectonics in this paper. We ask ourselves if everyday architecture can be qualified by means of general tectonic considerationsmethod and which strategies are needed to reveal its potential?. To aAnswerring theseese questions entails...... a clarification of concepts. Methodologically we pursue this clarification through a rereading of the essay: “Henri Lefebvre’s essay of 1972 entitled ‘The everyday and everydayness” by Henri Lefebvre (Lefebvre 1972).’ The essay offersing a general definition of the term related to everyday life...... as such and outlinea general definition of the aspects related to everyday life, how it can manifest itself in various cultural practices that can be discussed in relation to ‘everyday architecture’ and tectonic strategies or practices of tectonic methods. As such we propose the notion of ‘the everyday’ as a critical...

  10. Tectonic control on turbiditic sedimentation: The Late Cretaceous-Eocene successions in the Sinop-Boyabat Basin of north-central Turkey

    Energy Technology Data Exchange (ETDEWEB)

    Janbu, Nils Erik


    The aim of this study: Tectonics is widely recognized by geologists as the single most important factor controlling the development, filling and deformation of sedimentary basins. In general terms, the role of tectonics seems rather ''obvious'' to most geologists, because we know reasonably well as what tectonics ''can do'' as the agent of structural deformation. Therefore, the role of tectonics is often invoked as a kind of ballpark variable - as the obvious cause of ''subsidence'' or ''uplift'' - and seems to some authors even too obvious to mention. Relatively little attempt has been in sedimentological and stratigraphic studies to recognize as to what effects exactly the tectonic activity had on sedimentation in a particular basin. The principal aim of the present study has been to improve our understanding of how tectonic activity can affect deep-water turbiditic sedimentation in a particular basin, including its ''external'' influences (basin geometry, basin-margin configuration, sediment source/supply and relative sea-level change) and ''internal'' effects (basin-floor subsidence, seafloor deformation). Foreland basins are some of the most active tectonically, and the Sinop- Boyabat Basin is a fascinating case of a rift converted into a foreland basin and increasingly deformed. Summary of papers: The main part of the field study, concerned with the sedimentology and facies analysis of the turbiditic succession, is summarized in Papers 1-3, which put special emphasis on the physical character and morphodynamic evolution of the depositional systems and on the tectonic control on their development. Paper 4 focuses on the frequency distribution of bed thickness data collected by detailed logging of various turbiditic assemblages: siliciclastic deposits of nonchannelized currents (lobe and overbank facies); siliciclastic deposits of poorly

  11. Tectonic control on turbiditic sedimentation: The Late Cretaceous-Eocene successions in the Sinop-Boyabat Basin of north-central Turkey

    Energy Technology Data Exchange (ETDEWEB)

    Janbu, Nils Erik


    The aim of this study: Tectonics is widely recognized by geologists as the single most important factor controlling the development, filling and deformation of sedimentary basins. In general terms, the role of tectonics seems rather ''obvious'' to most geologists, because we know reasonably well as what tectonics ''can do'' as the agent of structural deformation. Therefore, the role of tectonics is often invoked as a kind of ballpark variable - as the obvious cause of ''subsidence'' or ''uplift'' - and seems to some authors even too obvious to mention. Relatively little attempt has been in sedimentological and stratigraphic studies to recognize as to what effects exactly the tectonic activity had on sedimentation in a particular basin. The principal aim of the present study has been to improve our understanding of how tectonic activity can affect deep-water turbiditic sedimentation in a particular basin, including its ''external'' influences (basin geometry, basin-margin configuration, sediment source/supply and relative sea-level change) and ''internal'' effects (basin-floor subsidence, seafloor deformation). Foreland basins are some of the most active tectonically, and the Sinop- Boyabat Basin is a fascinating case of a rift converted into a foreland basin and increasingly deformed. Summary of papers: The main part of the field study, concerned with the sedimentology and facies analysis of the turbiditic succession, is summarized in Papers 1-3, which put special emphasis on the physical character and morphodynamic evolution of the depositional systems and on the tectonic control on their development. Paper 4 focuses on the frequency distribution of bed thickness data collected by detailed logging of various turbiditic assemblages: siliciclastic deposits of nonchannelized currents (lobe and overbank facies); siliciclastic deposits of poorly

  12. Digital Tectonics

    DEFF Research Database (Denmark)

    Christiansen, Karl; Borup, Ruben; Søndergaard, Asbjørn;


    Digital Tectonics treats the architectonical possibilities in digital generation of form and production. The publication is the first volume of a series, in which aspects of the strategic focus areas of the Aarhus School of Architecture will be disseminated.......Digital Tectonics treats the architectonical possibilities in digital generation of form and production. The publication is the first volume of a series, in which aspects of the strategic focus areas of the Aarhus School of Architecture will be disseminated....

  13. The last interglacial period at Guantanamo Bay, Cuba and an estimate of late Quaternary tectonic uplift rate in a strike-slip regime (United States)

    Schweig, E. S.; Muhs, D. R.; Simmons, K. R.; Halley, R. B.


    Guantanamo Bay, Cuba is an area dominated by a strike-slip tectonic regime and is therefore expected to have very low Quaternary uplift rates. We tested this hypothesis by study of an unusually well preserved emergent reef terrace around the bay. Up to 12 m of unaltered, growth-position reef corals are exposed at about 40 sections examined around ˜40 km of coastline. Maximum reef elevations in the protected, inner part of the bay are ˜11-12 m, whereas outer-coast shoreline angles of wave-cut benches are as high as ˜14 m. Fifty uranium-series analyses of unrecrystallized corals from six localities yield ages ranging from ˜134 ka to ˜115 ka, when adjusted for small biases due to slightly elevated initial 234U/238U values. Thus, ages of corals correlate this reef to the peak of the last interglacial period, marine isotope stage (MIS) 5.5. Previously, we dated the Key Largo Limestone to the same high-sea stand in the tectonically stable Florida Keys. Estimates of paleo-sea level during MIS 5.5 in the Florida Keys are ~6.6 to 8.3 m above present. Assuming a similar paleo-sea level in Cuba, this yields a long-term tectonic uplift rate of 0.04-0.06 m/ka over the past ~120 ka. This estimate supports the hypothesis that the tectonic uplift rate should be low in this strike-slip regime. Nevertheless, on the southeast coast of Cuba, east of our study area, we have observed flights of multiple marine terraces, suggesting either (1) a higher uplift rate or (2) an unusually well-preserved record of pre-MIS 5.5 terraces not observed at Guantanamo Bay.

  14. From Arctic greenhouse to icehouse: the Cenozoic development of the West Greenland-Baffin Bay margin and the case for scientific drilling (United States)

    Knutz, Paul; Gregersen, Ulrik; Hopper, John R.; Dybkjær, Karen; Nøhr-Hansen, Henrik; Sheldon, Emma; Huuse, Mads


    The long-term evolution of glaciated margins plays an essential role in understanding the driving forces and interactions that determine the build-up and decay of ice sheets. The Greenland continental margin towards Baffin Bay is densely covered by industry seismic data and several exploration wells have been drilled, providing a regional stratigraphic framework for the sedimentary successions. This presentation provides an overview of the major depositional units and stratigraphy of the mid-late Cenozoic (since mid-Eocene), with examples demonstrating the different processes that have formed this margin. A sedimentary succession up to 3.5 km thick, of mid-Eocene to mid-Miocene age (mega-unit D), infills the pronounced ridge-basin structures of the rifted and tectonically inverted margin. The lower part of this interval, presumably late Eocene-Oligocene in age, is interpreted as basin-floor fan deposits, while the upper section, of early-middle Miocene age, is mainly marine mudstone. The basin infilling strata are overlain by a late Miocene-Pliocene succession consisting of two mega-units (B and C), with typical thicknesses of 0.5-1 km. The units are characterised by upslope-climbing sediment waves and along-slope trending sedimentary prisms reminiscent of giant contourite drifts. The borehole data associates the prism accumulations with a deep shelf environment influenced by strong marine currents and nearby fluvial sources. On the slope and in the deep basin of Baffin Bay the late Neogene succession is strongly influenced by mass wasting correlated with erosional scars updip. The uppermost seismic mega-unit (A) is dominated by aggradational wedges and prograding fan deposits displaying depocentres >3 km thick, formed at the terminus of palaeo-ice streams. Borehole information associates this interval with deposition of primarily diamict sediments and suggests a late Pliocene onset of major shelf based glaciations on the NW Greenland margin. The southwest margin

  15. U-Pb zircon ages and geochemistry of the Wuguan complex in the Qinling orogen, central China: Implications for the late Paleozoic tectonic evolution between the Sino-Korean and Yangtze cratons (United States)

    Chen, Longyao; Liu, Xiaochun; Qu, Wei; Hu, Juan


    The tectonic evolution of the Qinling orogen, central China, is the key to understanding the assembly of the Sino-Korean and Yangtze cratons. The Wuguan complex, between the early Paleozoic North Qinling and Mesozoic South Qinling tectonic belts, can provide important constraints on the late Paleozoic evolutionary processes in the Qinling orogen. U-Pb zircon analyses, using laser ablation-multicollector-inductively coupled plasma-mass spectrometry, reveal protolith ages of 446 ± 2 Ma for a garnet amphibolite, 368 ± 3 Ma for a meta-andesite, and 351 ± 2 Ma for a mylonitized granitic dike from the Wuguan complex. Elemental geochemistry indicates typical island arc affinities for all the above rocks, but some amphibolites of unknown age have E-MORB signatures. Detrital zircons from a metaquartzite have an age spectrum with a major peak at 462 Ma, two subordinate peaks at 828 and 446 Ma, and a youngest weighted mean age of 423 ± 5 Ma. This suggests that at least some of metasedimentary rocks from the Wuguan complex belong to the part of the Devonian turbidite sequence of the Liuling Group, which was deposited in a fore-arc basin along the southern accreted margin of the Sino-Korean craton, whereas the late Ordovician precursors of the amphibolite might be derived from the Danfeng Group. The occurrence of late Devonian-early Carboniferous arc-related rocks in the Wuguan complex implies penecontemporaneous oceanic subduction, and therefore the Paleo-Qinling Ocean was not finally closed until the early Carboniferous. On the other hand, metamorphic zircon grains from two amphibolites yielded ages of 321 ± 2 and 318 ± 3 Ma. Hence, the Wuguan complex in the Qinling orogen and the Guishan complex in the Tongbai orogen constitute a medium-pressure Carboniferous metamorphic belt that is more than 500 km long, and which was formed in the hanging wall of a subduction zone.

  16. Tectonic events reflected by palaeocurrents, zircon geochronology, and palaeobotany in the Sierra Baguales of Chilean Patagonia (United States)

    Gutiérrez, Nestor M.; Le Roux, Jacobus P.; Vásquez, Ana; Carreño, Catalina; Pedroza, Viviana; Araos, José; Oyarzún, José Luis; Pablo Pino, J.; Rivera, Huber A.; Hinojosa, L. F.


    The Sierra Baguales, situated north of the Torres Del Paine National Park in the Magallanes region of southern Chile, shows a well-exposed stratigraphic sequence ranging from the Late Cretaceous to late Pliocene, which presents a unique opportunity to study the evolution of sedimentological styles and trends, palaeoclimate changes, and tectonic events during this period. The depositional environment changed from a continental slope and shelf during the Cenomanian-Campanian (Tres Pasos Formation) to deltaic between the Campanian-Maastrichtian (Dorotea Formation) and estuarine in the Lutetian-Bartonian (Man Aike Formation). During the Rupelian, a continental environment with meandering rivers and overbank marshes was established (Río Leona Formation). This area was flooded in the early Burdigalian (Estancia 25 de Mayo Formation) during the Patagonian Transgression, but emerged again during the late Burdigalian (Santa Cruz Formation). Measured palaeocurrent directions in this Mesozoic-Cenozoic succession indicate source areas situated between the northeast and east-southeast during the Late Cretaceous, east-southeast during the middle Eocene, and southwest during the early Oligocene to early Miocene. This is confirmed by detrital zircon age populations in the different units, which can be linked to probable sources of similar ages in these areas. The east-southeastern provenance is here identified as the Antarctic Peninsula or its northeastern extension, which is postulated to have been attached to Fuegian Patagonia during the Eocene. The southwestern and western sources were exhumed during gradual uplift of the Southern Patagonian Andes, coinciding with a change from marine to continental conditions in the Magallanes-Austral Basin, as well as a decrease in mean annual temperature and precipitation indicated by fossil leaves in the Río Leona Formation. The rain shadow to the east of the Andes thus started to develop here during the late Eocene-early Oligocene ( 34

  17. U-Pb detrital zircon age patterns of Cenozoic clastic sedimentary rocks in Trinidad and its implications (United States)

    Xie, Xiangyang; Mann, Paul


    The Cenozoic evolution of northern South America can be simplified as a diachronous, west-to-east change from north-facing passive margin, to active convergence and transcurrent plate margin. As the current eastern end of the Caribbean-South America plate boundary, the Trinidad area records the most recent tectonic regime transition. Documenting the provenance of Cenozoic clastic rocks in Trinidad provides insights into the spatial and temporal relationships between mountain range uplifting, sediment dispersal, and drainage system development along the eastern end of the Caribbean-South American plate boundary. Four Eocene to Pliocene age outcropping sandstone samples were collected from Trinidad and 545 detrital zircon grains were analyzed using the U-Pb LA-ICP-MS method. A total of 404 analyses with less than 10% discordance were used for the final interpretation. Results show that the age distribution of the Eocene to the Early Oligocene samples is very restricted and dominated by Precambrian age grains with age peaks at ~ 1400 Ma, ~ 1800 Ma, and ~ 2000 Ma, typically derived from the Guyana Shield. In contrast, the Late Oligocene and younger samples show much broader and mixed age distribution that includes Mesozoic, Paleozoic, and Precambrian peaks. This age shift was interpreted as arriving of the Great Caribbean Arc and oblique collision between the South America and Caribbean plates. Continuing collision uplifted the Andes belts to the west. The Eastern Cordillera of Colombia, the Merida Andes, and the northern Venezuela coastal ranges then became the second primary sources. Offshore sedimentation switched from the passive margin with multiple small drainage systems to the active convergent and transcurrent plate margin with a single large river-dominated delivery system.

  18. Meso-Cenozoic Tectono-Thermal Evolution History in Bohai Bay Basin, North China

    Institute of Scientific and Technical Information of China (English)

    Yinhui Zuo; Nansheng Qiu; Jiawei Li; Qingqing Hao; Xiongqi Pang; Zhongying Zhao; Qi Zhu


    The thermal history of sedimentary basins is a key factor for hydrocarbon accumula-tion and resource assessment, and is critical in the exploration of lithospheric tectono-thermal evo-lution. In this paper, the Cenozoic thermal histories of nearly 200 wells and the Mesozoic thermal histories of 15 wells are modeled based on the vitrinite reflectance and apatite fission track data in Bohai Bay Basin, North China. The results show that the basin experienced Early Cretaceous and Paleogene heat flow peaks, which reveals two strong rift tectonic movements that occurred in the Cretaceous and the Paleogene in the basin, respectively. The thermal evolution history in Bohai Bay Basin can be divided into five stages including (1) the low and stable heat flow stage from the Trias-sic to the Jurassic, with the heat flow of 53 to 58 mW/m2;(2) the first heat flow peak from the Early Cretaceous to the middle of the Late Cretaceous, with a maximum heat flow of 81 to 87 mW/m2;(3) the first post-rift thermal subsidence stage from the middle of the Late Cretaceous to the Paleocene, with the heat flow of 65 to 74 mW/m2 at the end of the Cretaceous; (4) the second heat flow peak from the Eocene to the Oligocene, with a maximum heat flow of 81 to 88 mW/m2;and (5) the second thermal subsidence stage from the Neogene to present, with an average heat flow of 64 mW/m2.

  19. Relief Evolution in Tectonically Active Mountain Ranges (United States)

    Whipple, Kelin X.


    The overall aims of this 3-yr project, as originally proposed were to: (1) investigate quantitatively the roles of fluvial and glacial erosion in the evolution of relief in mountainous regions, and (2) test rigorously the quality and accuracy of SRTM topographic data in areas of rugged relief - both the most challenging and of greatest interest to geomorphic, neotectonic, and hazards applications. Natural laboratories in both the western US and the Southern Alps of New Zealand were identified as most promising. The project has been both successful and productive, despite the fact that no SRTM data for our primary field sites in New Zealand were released on the time frame of the work effort. Given the delayed release of SRTM data, we pursued the scientific questions of the roles of fluvial and, especially, glacial erosion in the evolution of relief in mountainous regions using available digital elevation models (DEMs) for the Southern Alps of New Zealand (available at both 25m and 50m pixel sizes), and USGS 10m and 30m DEMs within the Western US. As emphasized in the original proposal, we chose the emphasis on the role of glacial modification of topographic relief because there has been little quantitative investigation of glacial erosion processes at landscape scale. This is particularly surprising considering the dramatic sculpting of most mid- and high-latitude mountain ranges, the prodigious quantities of glacially-derived sediment in terrestrial and marine basins, and the current cross-disciplinary interest in the role of denudational processes in orogenesis and the evolution of topography in general. Moreover, the evolution of glaciated landscapes is not only a fundamental problem in geomorphology in its own right, but also is at the heart of the debate over Late Cenozoic linkages between climate and tectonics.


    Institute of Scientific and Technical Information of China (English)



    The Late Cenozoic deposits of the Linxia Basin in Gansu, China are relatively thick, bearing abundant mammalian fossils of different periods from the Late Oligocene to the Early Pleistocene. Until now, 172 species in 42 families of 10 orders have been found,all of which are extinct forms at the specific level and only a small number of genera have extant species. These fossils are important materials to study the evolution of mammalian faunas and their relationship with climatic and environmental backgrounds. The diversity and morphology of mammals are tightly related to climatic and environmental factors, and especially sensitive to changes of temperature, humidity and elevation. Interpretations to climatic and environmental changes reflect the evolution of mammals. Specific diversities, new records, and vanished species in the sedimentary sequence of the Linxia Basin are counted for each Chinese land mammal age. The diversity variations of mammals in the Linxia Basin were very noticeable throughout the Late Cenozoic,which are divided into different stages; the Middle Miocene,Late Miocene and Early Pleistocene have the highest diversities, the Late Oligocene and Early Miocene have the lowest, and the Pliocene has the moderate. The climatic and environmental variations of the Linxia Basin in different ages, which are judged from mammalian diversities, are highly consistent with other independent evidence, such as the result of the cenogram analysis, and closely relevant to the uplift of the Tibetan Plateau.%甘肃临夏盆地的晚新生代沉积物厚度巨大,其中富含从晚渐新世到早更新世各个时代的哺乳动物化石,目前已知包括10目42科131属172种,在种级水平上全部是绝灭类型,仅少数属有现生代表.这些化石是研究哺乳动物群演化及其与气候环境背景关系的重要材料.哺乳动物的多样性和形态特征与气候环境因素密切相关,对温度、湿度和海拔高度的变化尤其敏感.依据

  1. Role of Variscan tectonics inheritance in the Jurassic rifting of the passive margin of Adria: insights from the Canavese Zone (Western Southern Alps, Italy) (United States)

    De Caroli, Sara; Succo, Andrea; Centelli, Arianna; Barbero, Edoardo; Borghi, Alessandro; Balestro, Gianni; Festa, Andrea


    The formation of rifted continental margins by extension of continental lithosphere leading to seafloor spreading is a complex component of the plate tectonic cycle. Geological mapping, supported by multidisciplinary analyses of rifted continental margins may thus provide significant information to better understand and model the related processes, and explain the geometry of those margins as observed by means of seismic imaging. We present here our new findings on the Canavese Zone (Italian Western Alps), which is inferred to represent the remnant of the Jurassic syn-rift stretching, thinning and dismemberment of the distal passive margin of Adria, occurred during the opening of the Northern Alpine Tethys. Through multiscale and multidisciplinary, field- and laboratory-based structural, stratigraphic and petrographic studies (from geological map scale to mesoscale and microscope scale), we document that the tectonic dismemberment of the rifted continental margin of Adria did not simply result from the syn-rift Jurassic extension, but was strongly favored by the inheritance of older (Variscan and post-Variscan) tectonic stages, which controlled earlier lithospheric weakness. Our findings show the existence of two different tectonic units of the pre-Variscan basement, which were deformed, juxtaposed and exhumed already during the Variscan orogeny as constraint by (i) intrusion of early Permian granitoids, (ii) emplacement of volcanic rocks and (iii) unconformable overlie of Permian deposits on those metamorphic units. The syn-extensional (syn-rift) Jurassic faults, which affect the Mesozoic sedimentary succession, show only limited vertical displacement that was ineffective in producing and justifying the crustal thinning observed in pre-Variscan basement units. Finally, Late Cretaceous-Early Paleocene and Late Cenozoic strike-slip faulting (i.e. Alpine and Insubric tectonic stages) reactivated previously formed faults, leading to the formation of a complex tectonic

  2. 阿尔泰南缘晚石炭世淡色花岗岩的发现及其构造意义%Discovery of the Late Carboniferous Leucogranite in the Southern Altay Range and its Tectonic Implications

    Institute of Scientific and Technical Information of China (English)

    沈晓明; 张海祥; 马林


    在阿尔泰南缘的多摩拉克布拉克地区,新发现含石榴子石和白云母的淡色花岗岩侵入于早石炭世南明水组火山沉积地层中。LA-ICP-MS锆石U-Pb测年结果表明,淡色花岗岩形成于311±3 Ma的晚石炭世早期。该淡色花岗岩的发现及其年龄的确定,结合区域岩浆岩、变质岩和沉积学等资料分析,表明阿尔泰造山带南缘在~311 Ma前完成碰撞过程,并从此进入后碰撞时代。该发现为进一步研究阿尔泰造山带晚古生代构造演化提供了新的证据。%The time frame for the collision between Siberia Plate and Kazakhstan-Junggar Plate and the initiation of post-collision of the Southern Altay Range in the Late Paleozoic remain controversial. Paleozoic granitoid magmatism played an important role in the tectonic evolution of the Southern Altay Range and various origins of granitoids have been found in this region, including I-, S-, A-and M-type granitoids. Here, we report the newly discovered Duomolakebulake garnet-and muscovite-bearing leucogranite which intruded the Early Carboniferous Nanmingshui volcanic-sedimentary formation in the southern Altay Range. LA-ICP-MS zircon U-Pb dating indicates that the leucogranite was generated in the early Late Carboniferous (311±3 Ma). As an important rock type for tectonic implications, leucogranite is considered to be generated in a post-collision setting. In combination with lithology data in this region, we suggest that the collision ended prior to~311 Ma in the southern Altay Range, and then evolved into the post-collisional stage. This new discovery may shed lights on the tectonic evolution of the Altay Range in the Late Paleozoic.

  3. The Research of Cenozoic Migrant Worker Satisfaction

    Institute of Scientific and Technical Information of China (English)



    The phenomenon of Cenozoic migrant worker shortage is a realism problem of China's enterprise,and Cenozoic migrant worker has become an important force occupied the social structure.So the study of Cenozoic migrant worker's status and the demand is imperative.Understand employees"both psychological and physiological satisfaction of enterprises'environmental factors,and make some corresponding changes is of great help to reduce the employee turnover rate.This paper commenced to research from the Cenozoic migrant worker's characteristics,analyzed conditions and puts forward the corresponding countermeasures.

  4. Discovery of the Longriba Fault Zone in Eastern Bayan Har Block, China and its tectonic implication

    Institute of Scientific and Technical Information of China (English)


    Re-measured GPS data have recently revealed that a broad NE trending dextral shear zone exists in the eastern Bayan Har block about 200 km northwest of the Longmenshan thrust on the eastern margin of the Qinghai-Tibet Plateau. The strain rate along this shear zone may reach up to 4-6 mm/a. Our interpretation of satellite images and field observations indicate that this dextral shear zone corresponds to a newly generated NE trending Longriba fault zone that has been ignored before. The northeast segment of the Longriba fault zone consists of two subparallel N54°±5°E trending branch faults about 30 km apart, and late Quaternary offset landforms are well developed along the strands of these two branch faults. The northern branch fault, the Longriqu fault, has relatively large reverse component, while the southern branch fault, the Maoergai fault, is a pure right-lateral strike slip fault. According to vector synthesizing principle, the average right-lateral strike slip rate along the Longriba fault zone in the late Quaternary is calculated to be 5.4±2.0 mm/a, the vertical slip rate to be 0.7 mm/a, and the rate of crustal shortening to be 0.55 mm/a. The discovery of the Longriba fault zone may provide a new insight into the tectonics and dynamics of the eastern margin of the Qinghai-Tibet Plateau. Taken the Longriba fault zone as a boundary, the Bayan Har block is divided into two sub-blocks: the Ahba sub-block in the west and the Longmenshan sub-block in the east. The shortening and uplifting of the Longmenshan sub-block as a whole reflects that both the Longmenshan thrust and Longriba fault zone are subordinated to a back propagated nappe tectonic system that was formed during the southeastward motion of the Bayan Har block owing to intense resistance of the South China block. This nappe tectonic system has become a boundary tectonic type of an active block supporting crustal deformation along the eastern margin of the Qinghai-Tibet Plateau from late Cenozoic

  5. Discovery of the Longriba Fault Zone in Eastern Bayan Har Block, China and its tectonic implication

    Institute of Scientific and Technical Information of China (English)

    XU XiWei; WEN XueZe; CHEN GuiHua; YU GuiHua


    Re-measured GPS data have recently revealed that a broad NE trending dextral shear zone exists in the eastern Bayan Har block about 200 km northwest of the Longmenshan thrust on the eastern margin of the Qinghai-Tibet Plateau.The strain rate along this shear zone may reach up to 4-6 mm/a.Our interpretation of satellite images and field observations indicate that this dextral shear zone corresponds to a newly generated NE trending Longriba fault zone that has been ignored before.The northeast segment of the Longriba fault zone consists of two subparallel N54°±5°E trending branch faults about 30 km apart, and late Quaternary offset landforms are well developed along the strands of these two branch faults.The northern branch fault, the Longriqu fault, has relatively large reverse component, while the southern branch fault, the Maoergai fault, is a pure right-lateral strike slip fault.According to vector synthesizing principle, the average right-lateral strike slip rate along the Longriba fault zone in the late Quaternary is calculated to be 5.4±2.0 mm/a, the vertical slip rate to be 0.7 mm/a, and the rate of crustal shortening to be 0.55 mm/a.The discovery of the Longriba fault zone may provide a new insight into the tectonics and dynamics of the eastern margin of the Qinghai-Tibet Plateau.Taken the Longriba fault zone as a boundary, the Bayan Har block is divided into two sub-blocks: the Ahba sub-block in the west and the Longmenshan sub-block in the east.The shortening and uplifting of the Longmenshan sub-block as a whole reflects that both the Longmenshan thrust and Longriba fault zone are subordinated to a back propagated nappe tectonic system that was formed during the southeastward motion of the Bayan Har block owing to intense resistance of the South China block.This nappe tectonic system has become a boundary tectonic type of an active block supporting crustal deformation along the eastern margin of the Qinghai-Tibet Plateau from late Cenozoic till now

  6. Cenozoic carbon cycle imbalances and a variable weathering feedback (United States)

    Caves, Jeremy K.; Jost, Adam B.; Lau, Kimberly V.; Maher, Kate


    The long-term stability of Earth's climate and the recovery of the ocean-atmosphere system after carbon cycle perturbations are often attributed to a stabilizing negative feedback between silicate weathering and climate. However, evidence for the operation of this feedback over million-year timescales and in response to tectonic and long-term climatic change remains scarce. For example, the past 50 million years of the Cenozoic Era are characterized by long-term cooling and declining atmospheric CO2 (pCO2). During this interval, constant or decreasing carbon fluxes from the solid Earth to the atmosphere suggest that stable or decreasing weathering fluxes are needed to balance the carbon cycle. In contrast, marine isotopic proxies of weathering (i.e., 87Sr/86Sr, δ7 Li , and 187Os/188Os) are interpreted to reflect increasing weathering fluxes. Here, we evaluate the existence of a negative feedback by reconstructing the imbalance in the carbon cycle during the Cenozoic using the surface inventories of carbon and alkalinity. Only a sustained 0.25-0.5% increase in silicate weathering is necessary to explain the long-term decline in pCO2 over the Cenozoic. We propose that the long-term decrease in pCO2 is due to an increase in the strength of the silicate weathering feedback (i.e., the constant of proportionality between the silicate weathering flux and climate), rather than an increase in the weathering flux. This increase in the feedback strength, which mirrors the marine isotope proxies, occurs as transient, 1 million year timescales remains invariant to match the long-term inputs of carbon. Over the Cenozoic, this results in stable long-term weathering fluxes even as pCO2 decreases. We attribute increasing feedback strength to a change in the type and reactivity of rock in the weathering zone, which collectively has increased the reactivity of the surface of the Earth. Increasing feedback strength through the Cenozoic reconciles mass balance in the carbon cycle with

  7. Signatures of Late Quaternary sea-level changes and Neo-tectonic activity over Visakhapatnam - Gopalpur shelf, east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, K.M.; Reddy, N.P.C.; PremKumar, M.K.; Raju, Y.S.N.; Venkateswarlu, K.; Murthy, K.S.R.

    representing still stands during the late Pleistocene to Holocene. Seismic records obtained off Visakhapatnam-Pudimadaka show two distinct sedimentary units bounded by erosional unconformities. Occurrence of palaeo-channel beneath the seabed in the inner shelf...

  8. Textile Tectonics

    DEFF Research Database (Denmark)

    Mossé, Aurélie


    The meeting of architecture and textiles is a continuous but too often forgotten story of intimate exchange. However, the 2nd Ventulett Symposium hosted by the College of Architecture, within Georgia Institute of Technology, Atlanta, GA, was one of these precious moments celebrating such a marriage....... Organized by Lars Spuybroeck, principal of Nox, Rotterdam, and current Thomas W. Ventulett III distinguished chair of Architectural Design, the event was embracing the textile tectonics as a core topic, praising textiles as the key component of architecture, relying on Gottfried Semper’s understanding...... of the discipline. Inspiring time gathering some of the most exciting architects of the moment, Lars Spuybroeck, Mark Burry, Evan Douglis, Michael Hensel and Cecil Balmond were invited to discuss their understanding of tectonics. Full text available at

  9. The low-grade Canal de las Montañas Shear Zone and its role in the tectonic emplacement of the Sarmiento Ophiolitic Complex and Late Cretaceous Patagonian Andes orogeny, Chile (United States)

    Calderón, M.; Fosdick, J. C.; Warren, C.; Massonne, H.-J.; Fanning, C. M.; Cury, L. Fadel; Schwanethal, J.; Fonseca, P. E.; Galaz, G.; Gaytán, D.; Hervé, F.


    The Canal de las Montañas Shear Zone (CMSZ), southern Patagonian Andes (51-52°S), is a low-grade mylonite belt generated from felsic ignimbritic, pelitic and basaltic protoliths of the Late Jurassic-Early Cretaceous Rocas Verdes basin. The different types of rock fabrics across the CMSZ are thought to be associated with relatively intermediate and high strain conditions, characterized by the development of a narrow western belt of S-Ć-type mylonites and phyllonites interpreted as the metamorphic sole thrust of the Sarmiento Ophiolitic Complex. Highly strained rocks of the CMSZ display a reverse, continent-ward tectonic transport, with a minor dextral component of shearing. Transitional pumpellyite-actinolite and upper greenschist facies metamorphic conditions at ca. 5-6 kbar and 230-260 °C indicate that the primary shearing event occurred in a subduction zone setting. In-situ 40Ar/39Ar laserprobe chronology yielded ages of ca. 85 Ma on syntectonic phengite which are interpreted as representing cooling synchronous with mica crystallization during the main compressive deformational event. The 78-81 Ma U-Pb zircon crystallization ages of cross-cutting plutonic and hypabyssal rocks and 40Ar/39Ar amphibole age of ca.79 Ma from lamprophyric dikes within the fold-thrust belt constrain an upper age limit of the ophiolite tectonic emplacement deformation.

  10. Tectonics of Antarctica (United States)

    Hamilton, W.


    Antarctica consists of large and wholly continental east Antarctica and smaller west Antarctica which would form large and small islands, even after isostatic rebound, if its ice cap were melted. Most of east Antarctica is a Precambrian Shield, in much of which charnockites are characteristic. The high Transantarctic Mountains, along the Ross and Weddell Seas, largely follow a geosyncline of Upper Precambrian sedimentary rocks that were deformed, metamorphosed and intruded by granitic rocks during Late Cambrian or Early Ordovician time. The rocks of the orogen were peneplained, then covered by thin and mostly continental Devonian-Jurassic sediments, which were intruded by Jurassic diabase sheets and overlain by plateau-forming tholeiites. Late Cenozoic doming and block-faulting have raised the present high mountains. Northeastern Victoria Land, the end of the Transantarctic Mountains south of New Zealand, preserves part of a Middle Paleozoic orogen. Clastic strata laid unconformably upon the Lower Paleozoic plutonic complex were metamorphosed at low grade, highly deformed and intruded by Late Devonian or Early Carboniferous granodiorites. The overlying Triassic continental sedimentary rocks have been broadly folded and normal-faulted. Interior west Antarctica is composed of miogeosynclinal clastic and subordinate carbonate rocks which span the Paleozoic Era and which were deformed, metamorphosed at generally low grade, and intruded by granitic rocks during Early Mesozoic time and possibly during other times also. Patterns of orogenic belts, if systematic, cannot yet be defined; but fragmentation and rotation of crustal blocks by oroclinal folding and strike-slip faulting can be suggested. The Ellsworth Mountains, for example, consist of Cambrian-Permian metasedimentary rocks that strike northward toward the noncorrelative and latitudinally striking Mesozoic terrane of the Antarctic Peninsula in one direction and southward toward that of the Lower Paleozoic: terrane

  11. Cenozoic Methane-Seep Faunas of the Caribbean Region. (United States)

    Kiel, Steffen; Hansen, Bent T


    We report new examples of Cenozoic cold-seep communities from Colombia, Cuba, the Dominican Republic, Trinidad, and Venezuela, and attempt to improve the stratigraphic dating of Cenozoic Caribbean seep communities using strontium isotope stratigraphy. Two seep faunas are distinguished in Barbados: the late Eocene mudstone-hosted 'Joes River fauna' consists mainly of large lucinid bivalves and tall abyssochrysoid gastropods, and the early Miocene carbonate-hosted 'Bath Cliffs fauna' containing the vesicomyid Pleurophopsis, the mytilid Bathymodiolus and small gastropods. Two new Oligocene seep communities from the Sinú River basin in Colombia consist of lucinid bivalves including Elongatolucina, thyasirid and solemyid bivalves, and Pleurophopsis. A new early Miocene seep community from Cuba includes Pleurophopsis and the large lucinid Meganodontia. Strontium isotope stratigraphy suggests an Eocene age for the Cuban Elmira asphalt mine seep community, making it the oldest in the Caribbean region. A new basal Pliocene seep fauna from the Dominican Republic is characterized by the large lucinid Anodontia (Pegophysema). In Trinidad we distinguish two types of seep faunas: the mudstone-hosted Godineau River fauna consisting mainly of lucinid bivalves, and the limestone-hosted Freeman's Bay fauna consisting chiefly of Pleurophopsis, Bathymodiolus, and small gastropods; they are all dated as late Miocene. Four new seep communities of Oligocene to Miocene age are reported from Venezuela. They consist mainly of large globular lucinid bivalves including Meganodontia, and moderately sized vesicomyid bivalves. After the late Miocene many large and typical 'Cenozoic' lucinid genera disappeared from the Caribbean seeps and are today known only from the central Indo-Pacific Ocean. We speculate that the increasingly oligotrophic conditions in the Caribbean Sea after the closure of the Isthmus of Panama in the Pliocene may have been unfavorable for such large lucinids because they

  12. Cenozoic Methane-Seep Faunas of the Caribbean Region.

    Directory of Open Access Journals (Sweden)

    Steffen Kiel

    Full Text Available We report new examples of Cenozoic cold-seep communities from Colombia, Cuba, the Dominican Republic, Trinidad, and Venezuela, and attempt to improve the stratigraphic dating of Cenozoic Caribbean seep communities using strontium isotope stratigraphy. Two seep faunas are distinguished in Barbados: the late Eocene mudstone-hosted 'Joes River fauna' consists mainly of large lucinid bivalves and tall abyssochrysoid gastropods, and the early Miocene carbonate-hosted 'Bath Cliffs fauna' containing the vesicomyid Pleurophopsis, the mytilid Bathymodiolus and small gastropods. Two new Oligocene seep communities from the Sinú River basin in Colombia consist of lucinid bivalves including Elongatolucina, thyasirid and solemyid bivalves, and Pleurophopsis. A new early Miocene seep community from Cuba includes Pleurophopsis and the large lucinid Meganodontia. Strontium isotope stratigraphy suggests an Eocene age for the Cuban Elmira asphalt mine seep community, making it the oldest in the Caribbean region. A new basal Pliocene seep fauna from the Dominican Republic is characterized by the large lucinid Anodontia (Pegophysema. In Trinidad we distinguish two types of seep faunas: the mudstone-hosted Godineau River fauna consisting mainly of lucinid bivalves, and the limestone-hosted Freeman's Bay fauna consisting chiefly of Pleurophopsis, Bathymodiolus, and small gastropods; they are all dated as late Miocene. Four new seep communities of Oligocene to Miocene age are reported from Venezuela. They consist mainly of large globular lucinid bivalves including Meganodontia, and moderately sized vesicomyid bivalves. After the late Miocene many large and typical 'Cenozoic' lucinid genera disappeared from the Caribbean seeps and are today known only from the central Indo-Pacific Ocean. We speculate that the increasingly oligotrophic conditions in the Caribbean Sea after the closure of the Isthmus of Panama in the Pliocene may have been unfavorable for such large

  13. The effect of gateways on ocean circulation patterns in the Cenozoic

    NARCIS (Netherlands)

    von der Heydt, A.S.; Dijkstra, H.A.


    Both geological data and climate model studies indicate that substantially different patterns of the global ocean circulation have existed throughout the Cenozoic. In a climate model study of the late Oligocene [von der Heydt, A., Dijkstra, H.A. (2006). Effect of ocean gateways on the global ocean

  14. Analysing the Cenozoic depositional record

    DEFF Research Database (Denmark)

    Goledowski, Bartosz; Clausen, O.R.; Nielsen, S.B.

    It is well known that sediment deposition in the North Sea and on the Norwegian Shelf varied significantly during the Cenozoic as a consequence of varying erosion rate mainly in Western Scandinavia, in Scotland and in the Alps. Recent results have demonstrated that a causal relationship exists...... of variations in erosion rates. Here we present the rationale behind the project, the data available and some preliminary results. The dense seismic and well coverage in the area makes it possible to estimate the rate of deposition of matrix mass. Assuming that sediment storage is not important, this provides...

  15. Formwork tectonics

    DEFF Research Database (Denmark)

    Manelius, Anne-Mette


    På engelsk: Based on the concept of techné and framed in architectural studies of tectonics and an experimental practice of making, this paper investigates the multiple technological roles of textiles in fabric formwork for concrete in four analytical studies of experimental data of the author’s ...

  16. The chronology and tectonic style of landscape evolution along the elevated Atlantic continental margin of South Africa resolved by joint apatite fission track and (U-Th-Sm)/He thermochronology (United States)

    Wildman, Mark; Brown, Roderick; Beucher, Romain; Persano, Cristina; Stuart, Fin; Gallagher, Kerry; Schwanethal, James; Carter, Andrew


    Atlantic-type continental margins have long been considered "passive" tectonic settings throughout the entire postrift phase. Recent studies question the long-term stability of these margins and have shown that postrift uplift and reactivation of preexisting structures may be a common feature of a continental margin's evolution. The Namaqualand sector of the western continental margin of South Africa is characterized by a ubiquitously faulted basement but lacks preservation of younger geological strata to constrain postrift tectonic fault activity. Here we present the first systematic study using joint apatite fission track and apatite (U-Th-Sm)/He thermochronology to achieve a better understanding on the chronology and tectonic style of landscape evolution across this region. Apatite fission track ages range from 58.3 ± 2.6 to 132.2 ± 3.6 Ma, with mean track lengths between 10.9 ± 0.19 and 14.35 ± 0.22 µm, and mean (U-Th-Sm)/He sample ages range from 55.8 ± 31.3 to 120.6 ± 31.4 Ma. Joint inverse modeling of these data reveals two distinct episodes of cooling at approximately 150-130 Ma and 110-90 Ma with limited cooling during the Cenozoic. Estimates of denudation based on these thermal histories predict approximately 1-3 km of denudation coinciding with two major tectonic events. The first event, during the Early Cretaceous, was driven by continental rifting and the development and removal of synrift topography. The second event, during the Late Cretaceous, includes localized reactivation of basement structures as well as regional mantle-driven uplift. Relative tectonic stability prevailed during the Cenozoic, and regional denudation over this time is constrained to be less than 1 km.

  17. Recent structures and tectonic regimes of the stress-strain state of the Earth's crust in the northeastern sector of the Russian Arctic region (United States)

    Imaeva, L. P.; Imaev, V. S.; Mel'nikova, V. I.; Koz'min, B. M.


    A comprehensive investigation aimed at determining seismotectonic types of destruction and the stress-strain state of the Earth's crust in the main seismogenerating structures of the Arctic-Asian seismic belt is conducted for the territory of the northeastern sector of the Russian Arctic region. Based on the degree of activity of geodynamical processes, the regional principles for ranking neotectonic structures are elaborated, and neotectonic zoning is carried out based on the substantiated differentiation of the corresponding classes. Within the limits of the Laptev Sea, Kharaulakh, and Lena-Anabar segments, we analyzed I the structural-tectonic position of the most recent structures, II the deep structure parameters, III the parameters of the active fault system, and IV the parameters of the tectonic stress field, as revealed from tectonophysical analysis of Late Cenozoic fault and fold deformations. Based on the seismological data, the mean seismotectonic deformation tensors are calculated to determine, in combination with geological and geophysical data, the orientations of the principal stress axes and to reveal the structural-tectonic regularity for tectonic regimes of the stress-strain state of the Earth's crust in the Arctic sector of the boundary between the Eurasian and North American lithospheric plates.

  18. Depositional architecture and evolution of inner shelf to shelf edge delta systems since the Late Oliocene and their respone to the tectonic and sea level change, Pear River Mouth Basin, northern South China Sea (United States)

    Lin, Changsong; Zhang, Zhongtao; liu, Jingyan; Jiang, Jing


    The Pear River Mouth Basin is located in the northern continent margin of the South China Sea. Since the Late Oligocene, the long-term active fluvial systems (Paleo-Zhujiang) from the western basin margin bebouched into the northern continental margin of the South China Sea and formed widespread deltaic deposits in various depositional geomorphologies and tectonic settings. Based of integral analysys of abundant seismic, well logging and drilling core data, Depositional architecture and evolution of these delta systems and their respone to the tectonic and sea level change are documented in the study. There are two basic types of the delta systems which have been recognized: inner shelf delta deposited in shallow water enviroments and the outer shelf or shelf-edge delta systems occurred in deep water settings. The paleowater depths of these delta systems are around 30 to 80m (inner shelf delta) and 400-1000m (shelf-edge delta) estimated from the thickness (decompaction) of the delta front sequences. The study shows that the inner shelf delta systems are characterized by relatively thin delta forests (20-40m), numereous stacked distributary channel fills, relative coarse river mouth bar deposits and thin distal delta front or distal bar and prodelta deposits. In contrast, the outer shelf or shelf edge delta systems are characteristic of thick (300-800m) and steep (4-60) of deltaic clinoforms, which commonly display in 3D seismic profiles as "S" shape reflection. Large scale soft-sediment deformation structures, slump or debris flow deposits consisting mainly of soft-sediment deformed beds, blocks of sandstones and siltstones or mudstones widely developed in the delta front deposits. The shelf edge delta systems are typically associated with sandy turbidite fan deposits along the prodelta slopes, which may shift basinwards as the progradation of the delta systems. The delta systems underwent several regional cycles of evolution from inner shelf deltas to shelf edge

  19. Alaskan Peninsula Cenozoic stratigraphy: stratigraphic sequences and current research

    Energy Technology Data Exchange (ETDEWEB)

    Allison, R.C.; Armentrout, J.M.


    Geology of the Alaska Peninsula-Island Arc and Continental Margin, by C.A. Burk, is the principal reference for stratigraphic studies on the Alaska Peninsula. Burk mapped the Phanerozoic stratigraphy and provided a geologic history and structural interpretation of the area between Wide Bay and Unimak Island. Cenozoic rocks were mapped as three unconformity-bounded sequences. Recognition of specific formations was difficult due to similarity of lithofacies, isolated outcrops, rapid facies changes, and alteration and burial by young volcanics. Consequently, megafossil assemblages were relied upon to facilitate correlations between study areas. The three unconformity-bounded Cenozoic sequences are: (1) the Paleogene Beaver Bay Group consisting of three formations: the dominantly nonmarine Tolstoi Formation, the dominantly marine Stepovak Formation, and the volcanic Meshik Formation. Current work suggests these units are at least in part coeval facies of late Paleocene through Oligocene age. (2) The Neogene Bear Lake Formation consisting of the lower Unga Conglomerate Member and an unnamed upper member. Rapid facies changes and incorrect reports of fossil occurrence have resulted in confusion of stratigraphic relationships within this sequence of middle to late Miocene age. (3) A late Neogene informally defined upper sequence consisting of interbedded marginal marine, coastal-plain, and volcanic facies. Current work suggests this sequence is Pliocene through Pleistocene in age.

  20. Late Neoproterozoic to Carboniferous genesis of A-type magmas in Avalonia of northern Nova Scotia: repeated partial melting of anhydrous lower crust in contrasting tectonic environments (United States)

    Murphy, J. Brendan; Shellnutt, J. Gregory; Collins, William J.


    Avalonian rocks in northern mainland Nova Scotia are characterized by voluminous 640-600 Ma calc-alkalic to tholeiitic mafic to felsic magmas produced in a volcanic arc. However, after the cessation of arc activity, repeated episodes of felsic magmatism between ca. 580 Ma and 350 Ma are dominated by A-type geochemical characteristics. Sm-Nd isotopic data, combined with zircon saturation temperature estimates, indicate that these magmas were formed by high temperature (800-1050 °C) melting of the same anhydrous crustal source. Regional tectonic considerations indicate that A-type felsic magmatism was produced (1) at 580 Ma in a San Andreas-type strike slip setting, (2) at 495 Ma as Avalonia rifted off Gondwana, (3) at 465 and 455 in an ensialic island arc environment and (4) at 360-350 Ma during post-collisional, intra-continental strike-slip activity as Avalonia was translated dextrally along the Laurentian margin. These results attest to the importance of crustal source, rather than tectonic setting, in the generation of these A-type magmas and are an example of how additional insights are provided by comparing the geochemical and isotopic characteristics of igneous suites of different ages within the same terrane. They also suggest that the shallow crustal rocks in northern mainland Nova Scotia were not significantly detached from their lower crustal source between ca. 620 Ma and 350 Ma, a time interval that includes the separation of Avalonia from Gondwana, its drift and accretion to Laurentia as well as post-accretionary strike-slip displacement.

  1. Late Cenozoic cooling history of the central Menderes Massif: Timing of the Büyük Menderes detachment and the relative contribution of normal faulting and erosion to rock exhumation (United States)

    Wölfler, Andreas; Glotzbach, Christoph; Heineke, Caroline; Nilius, Nils-Peter; Hetzel, Ralf; Hampel, Andrea; Akal, Cüneyt; Dunkl, István; Christl, Marcus


    Based on new thermochronological data and 10Be-derived erosion rates from the southern part of the central Menderes Massif (Aydın block) in western Turkey, we provide new insights into the tectonic evolution and landscape development of an area that undergoes active continental extension. Fission-track and (U-Th)/He data reveal that the footwall of the Büyük Menderes detachment experienced two episodes of enhanced cooling and exhumation. Assuming an elevated geothermal gradient of 50 °C/km, the first phase occurred with an average rate of 0.90 km/Myr in the middle Miocene and the second one in the latest Miocene and Pliocene with a rate of 0.43 km/Myr. The exhumation rates between these two phases were lower and range from 0.14 to 0.24 km/Myr, depending on the distance to the detachment. Cosmogenic nuclide-based erosion rates for catchments in the Aydın block range from 0.1 to 0.4 km/Myr. The similarity of the erosion rates on both sides of the Aydın block (northern and southern flank) indicate that a rather symmetric erosion pattern has prevailed during the Holocene. If these millennial erosion rates are representative on a million-year timescale they indicate that, apart from normal faulting, erosion in the hanging wall of the Büyük Menderes detachment fault did also contribute to the exhumation of the metamorphic rocks.

  2. Fission Track Geochronology of Xiaonanchuan Pluton and the Morphotectonic Evolution of Eastern Kunlun since Late Miocene

    Institute of Scientific and Technical Information of China (English)


    Apatite fission track (AFT) thermochronology of seven samples from the Xiaonanchuan(小南川) pluton in the Kunlun (昆仑) pass area was carried out, for the purpose of determining the timing of cooling and the relation between the exhumation and the morphotectonic processes. The AFT ages yield low denudation rates of 0.020-0.035 mm/ a during the late Miocene, which correspond to a stable geomorphic and weak tectonic uplifting environment. The low denudation rates can be considered as the approximate tectonic uplifting rates. The AFT geochronology shows paroxysmally rapid cooling since the Pliocene and an apparent material unroofing of more than 3 km in the Xiaonanchuan area. This was not the result of simple denudation. The rapid cooling was coupled with the intensive orogeny since the Pliocene, which was driven by tectonic uplifting. The accelerated relief building was accompanied by a series of faulting, which caused the basin and the valley formation and sinking. The space pattern of the AFT ages also shows differential uplifting, which decreases northwardly. This trend is supported by the regional AFT data, which indicate that the exhumation decreases northwardly in eastern Kunlun. This trend also exists in east-west orientation from the western Kunlun range to the eastern. The uplifting trend is also supported by geomorphic characteristics including the elevation and the relief differences as well as the distribution of the Late Cenozoic volcanism.

  3. North Atlantic Ocean deep-water processes and depositional environments: A study of the Cenozoic Norway Basin (United States)

    Oline Hjelstuen, Berit; Andreassen, Elin V.


    Despite the enormous areas deep-water basins occupy in modern oceans, our knowledge about them remains poor. At depths of greater than 2000 m, the Cenozoic Norway Basin in the northernmost part of the Atlantic Ocean, is one such basin. Interpretation of 2D multichannel seismic data suggests a three-stage evolution for the Norway Basin. (1) Eocene-Pliocene. This time period is characterised by deposition of ooze-rich sediments in a widening and deepening basin. (2) Early-Middle Pleistocene. A significant shift in sedimentary processes and depositional environments took place in the Early Pleistocene. Mass failures initiated on the Norwegian continental slope, and three Early and Middle Pleistocene slide debrites, with maximum thicknesses of 600 m and sediment volumes of up to 25000 km3, were deposited. With ages estimated at c. 2.7-1.7 Ma, 1.7-1.1 Ma and 0.5 Ma, these slide deposits are among the largest identified worldwide, and among the oldest mapped along the entire NE Atlantic continental margin. (3) Late Pleistocene-Present. Since c. 0.5 Ma the Norway Basin has been effected by glacigenic debris flows, the Storegga Slide and hemipelagic-glacimarine sedimentation. These sedimentary processes were active during a time of repeated shelf-edge ice advances along the NE Atlantic continental margin. This study shows that deep-water basins represent dynamic depositional environments reflecting regional tectonic and climatic changes trough time.

  4. Subsidence history and forming mechanism of anomalous tectonic subsidence in the Bozhong depression, Bohaiwan basin

    Institute of Scientific and Technical Information of China (English)


    The Bozhong depression of the Bohaiwan basin belongs to a family of extensional basins in East China, but is quite different from other parts of the basin. The Cenozoic subsidence of the depression is controlled by a combination of lithospheric thinning and polycyclic strike-slip movements. Three episodic rifts have been identified, i.e. Paleocence-early Eocene, middle-late Eocene and Oligocene age. The depression underwent syn-rift and post-rift stages, but two episodic dextral movement events of the strike-slip faults modify the subsidence of the Bozhong depression since the Oligocene. The early dextral movement of the Tan-Lu fault associated with crustal extension resulted in accelerated subsidence during the time of deposition of the Dongying Formation with a maximum thickness of 4000 m. A late reactivation of dextral movement of the Tan-Lu fault began in late Miocene (about 12 Ma), which resulted in the intense subsidence of Minghuazhen Formation and Quaternary. In addition, dynamic mantle convection-driven topography also accelerated the post-rift anomalous subsidence since the Miocene (24.6 Ma). Our results indicate that the primary control on rapid subsidence both during the rift and post-rift stages in the Bozhong depression originates from a combination of multiple episodic crustal extension and polycyclic dextral movements of strike-slip faults, and dynamic topography. tectonic subsidence, strike-slip, dynamic topography, Bozhong depression, Bohaiwan basin

  5. Transcultural Tectonic Connections

    DEFF Research Database (Denmark)

    Carter, Adrian


    This paper presents an understanding of Jørn Utzon, as one of the most profound exponents of a transcultural and tectonic approach to modern architecture in the late twentieth century. The paper will examine the sources of inspiration, intersections and connections in Utzon’s architecture; which...... ruins in Mexico. The Sydney Opera House’s signature sail-like roof shells derive from knowledge of boat building in his youth and ancient Chinese and Japanese temple roofs floating above a stone base. With the choice of ceramic tiles to accentuate the sculptural character of the shells, owing its...

  6. Climate and tectonic variability during Late Quaternary in western fringe of Tibetan Plateau: case study from Trans-Himalayan ranges of Ladakh, NW India (United States)

    Phartiyal, B.


    The climate system plays an important role in the geomorphological dynamics of a region. The cold, arid, high altitude, tectonically active areas of Ladakh (India) in Trans Himalaya, western Tibetan Plateau is none exception. Noticeable change in the landscape with a shift from fluvial to lacustrine regime at 10000 yrs BP forming big open valley lakes occupying the present day river valleys is attributed to the early Holocene northward advancement of the mean latitudinal position of the summer ITCZ causing wetter conditions in this dry area. The glaciers of the Ladakh range are almost depleted and the northern range glaciers show andrastic retreat in the Quaternary time. Lakes were studied using multi-proxies, to record centennial and decadal scale climatic variability. Spatial and temporal setting of Spituk palaeolake (12600-240 cal yrs BP) along Indus River, was analyzed using multi proxies. The lake that extended for 40-50 km covering an area of 106 km2, was formed after Older Dryas as a result of river blockage by precipitation induced debris flow and seismicity. Two lake phases between 12600-9000 and 5500-3200 cal yrs BP show stable lake conditions and have synchronous relationship between high variation in monsoon intensity, high δ18O values in the Guliya core, rise in temperature and high solar insolation. High magnetic susceptibility and clay content along with diversified diatom and other freshwater algae and land derived organic matter are indicative of fresh water supply leading to high lake level from 4700 yr BP onwards in the present pro-glacial lakes studied. The multi-proxy data provides evidence of much higher and stable lake level during 3700 yr BP and 3000 yr BP onwards due to high water supply in these lake. It is in contrast to the records of weak ISM conditions and low lake level in rest of the part of Indian peninsula during the period. The study also suggests strong western disturbance activity during 4800-3000 yr BP leading to high lake

  7. Cenozoic basin thermal history reconstruction and petroleum systems in the eastern Colombian Andes (United States)

    Parra, Mauricio; Mora, Andres; Ketcham, Richard A.; Stockli, Daniel F.; Almendral, Ariel


    Late Mesozoic-Cenozoic retro-arc foreland basins along the eastern margin of the Andes in South America host the world's best detrital record for the study of subduction orogenesis. There, the world's most prolific petroleum system occur in the northernmost of these foreland basin systems, in Ecuador, Colombia and Venezuela, yet over 90% of the discovered hydrocarbons there occur in one single province in norteastern Venezuela. A successful industry-academy collaboration applied a multidisciplinary approach to the study of the north Andes with the aim of investigating both, the driving mechanisms of orogenesis, and its impact on hydrocarbon accumulation in eastern Colombia. The Eastern Cordillera is an inversion orogen located at the leading edge of the northern Andes. Syn-rift subsidence favored the accumulation of km-thick organic matter rich shales in a back-arc basin in the early Cretaceous. Subsequent late Cretaceous thermal subsidence prompted the accumulation of shallow marine sandstones and shales, the latter including the Turonian-Cenomanian main hydrocarbon source-rock. Early Andean uplift since the Paleocene led to development of a flexural basin, filled with mainly non-marine strata. We have studied the Meso-Cenozoic thermal evolution of these basins through modeling of a large thermochronometric database including hundreds of apatite and zircon fission-track and (U-Th)/He data, as well as paleothermometric information based on vitrinite reflectance and present-day temperatures measured in boreholes. The detrital record of Andean construction was also investigated through detrital zircon U-Pb geochronometry in outcrop and borehole samples. A comprehensive burial/exhumation history has been accomplished through three main modeling strategies. First, one-dimensional subsidence was used to invert the pre-extensional lithospheric thicknesses, the magnitude of stretching, and the resulting heat flow associated to extension. The amount of eroded section and

  8. 东北亚地区晚侏罗—白垩纪构造格架主体特点%Main Characteristics of Late Jurassic-Cretaceous Tectonic Framework in Northeast Asia

    Institute of Scientific and Technical Information of China (English)


    Placing the main structural features of the Northeast China into Northeast Asia area, to analyze the tectonic setting, the Northeast Asia Late Mesozoic - Paleogene tectonic evolution can be divided into three periods: 1) the Middle -Late Jurassic, extension of the Tethys Ocean and the collision between North America and ancient Eurasia continental plate, resulting in Mongolia-Okhotsk Gulf closure and the formation of large-scale deep-level thrust in Mongolia and the North China block, and a long-range stacking effect in southern Mongolia and the northern margin of the North China block. 2) Late Jurassic - Early Cretaceous, the combined effects of Tethys Ocean, the Eurasian continental plate and the Paleo-Pacific tectonic domain (including the old Pacific or Izanaqi plate) .resulted in continental crust creeping eastward, stretching and block breaking activities, which were, accompanied by development of a small rift basin group and metamorphic core complexes. 3) Early Cretaceous (Late Albian)- Neogene (Miocene), the combined effects of the tectonic domain between Tethys (later including the Indian plate), the Pacific tectonic domain (including Izanaqi plate) and Eurasia continental plate resulted in Izanaqi ocean disappeared, the collision between the Okhotsk Oceanic micro-plate and the Eurasian continent, and the formations of the Eurasian continental margin volcanic belt and the depression basin on the continental margin. During 100 - 60 Ma, the interaction between the Pacific tectonic domain (including Izanaqi plate) and the Eurasian continent, had a major influence on the eastern edge of the Eurasian continent and caused continental lithospheric-crust thinning, the change of mantle type and a strong deep magmatic activity. Meanwhile, producing a series of the surface block effects related to the continental margin faulted block activities.%将东北地区主体构造特征置于东北亚大地构造背景中进行分析,可将东北亚地区晚中生代—古

  9. Evolution of the late Quaternary San Gregorio Magno tectono-karstic basin (southern Italy) inferred from geomorphological, tephrostratigraphical and palaeoecological analyses: tectonic implications (United States)

    Aiello, G.; Ascione, A.; Barra, D.; Munno, R.; Petrosino, P.; Russo Ermolli, E.; Villani, F.


    The Pantano di San Gregorio Magno is a 4.7 km2 large tectono-karstic basin located in the axial belt of the Southern Apennines, an area affected by intense seismicity. The basin was formed in the Middle Pleistocene and is presently undissected. It is filled by lacustrine sediments (clays, silts and pyroclastic sands) passing laterally into alluvial fan deposits. Geomorphological investigations were integrated with tephrostratigraphical, palynological and palaeoecological analyses of a 61 m thick core (not reaching the bedrock). The multiproxy analysis of the S. Gregorio Magno record shows that, over the last 200k yr, the basin hosted a freshwater lake with an oscillating level. Age constraints provided by the tephrostratigraphic record allowed estimation of the sedimentation rate, which varied strongly through time. Evolution of the basin resulted from the complex combination of tectonic subsidence, karst processes and changing amounts of sedimentary inputs. The latter was influenced by allogenic contributions related both to primary and reworked volcanoclastic inputs and was climate-driven. The overall evidence, which indicates that in the long-term the accumulation rate substantially counterbalanced the accommodation space created by faulting, suggests that the basin evolution was also modulated by changing subsidence rates. Copyright

  10. The oldest record of Alligator sinensis from the Late Pliocene of Western Japan, and its biogeographic implication (United States)

    Iijima, Masaya; Takahashi, Keiichi; Kobayashi, Yoshitsugu


    The late Cenozoic fossil record of alligators in East Asia is crucial in understanding the origin and past distribution of Asian alligators that are now represented by a single species, Alligator sinensis. This study reports a partial skeleton of A. sinensis from the Late Pliocene (approximately 3.0 Ma) of western Japan. This Japanese A. sinensis is large in size (>200 cm total length), comparable to the maximum size of extant individuals. It demonstrates the oldest record of A. sinensis and wider distribution of this species in the past. Tectonic and geographic history of East Asia suggests that alligators presumably dispersed into Japan before 25 Ma or after 10 Ma, yet finally were wiped out from Japan due to the semi-isolated condition of the Japanese island arc and the deteriorated climate during the Plio-Pleistocene.

  11. Geology and tectonics of Japanese islands: A review - The key to understanding the geology of Asia (United States)

    Wakita, Koji


    The age of the major geological units in Japan ranges from Cambrian to Quaternary. Precambrian basement is, however, expected, as the provenance of by detrital clasts of conglomerate, detrital zircons of metamorphic and sedimentary rocks, and as metamorphic rocks intruded by 500 Ma granites. Although rocks of Paleozoic age are not widely distributed, rocks and formations of late Mesozoic to Cenozoic can be found easily throughout Japan. Rocks of Jurassic age occur mainly in the Jurassic accretionary complexes, which comprise the backbone of the Japanese archipelago. The western part of Japan is composed mainly of Cretaceous to Paleogene felsic volcanic and plutonic rocks and accretionary complexes. The eastern part of the country is covered extensively by Neogene sedimentary and volcanic rocks. During the Quaternary, volcanoes erupted in various parts of Japan, and alluvial plains were formed along the coastlines of the Japanese Islands. These geological units are divided by age and origin: i.e. Paleozoic continental margin; Paleozoic island arc; Paleozoic accretionary complexes; Mesozoic to Paleogene accretionary complexes and Cenozoic island arcs. These are further subdivided into the following tectonic units, e.g. Hida; Oki; Unazuki; Hida Gaien; Higo; Hitachi; Kurosegawa; South Kitakami; Nagato-Renge; Nedamo; Akiyoshi; Ultra-Tamba; Suo; Maizuru; Mino-Tamba; Chichibu; Chizu; Ryoke; Sanbagawa and Shimanto belts. The geological history of Japan commenced with the breakup of the Rodinia super continent, at about 750 Ma. At about 500 Ma, the Paleo-Pacific oceanic plate began to be subducted beneath the continental margin of the South China Block. Since then, Proto-Japan has been located on the convergent margin of East Asia for about 500 Ma. In this tectonic setting, the most significant tectonic events recorded in the geology of Japan are subduction-accretion, paired metamorphism, arc volcanism, back-arc spreading and arc-arc collision. The major accretionary

  12. Dynamic topography and the Cenozoic carbonate compensation depth (United States)

    Campbell, S. M.; Moucha, R.; Raymo, M. E.; Derry, L. A.


    The carbonate compensation depth (CCD), the ocean depth at which the calcium carbonate accumulation rate goes to zero, can provide valuable insight into climatic and weathering conditions over the Cenozoic. The paleoposition of the CCD can be inferred from sediment core data. As the carbonate accumulation rate decreases linearly with depth between the lysocline and CCD, the CCD can be calculated using a linear regression on multiple sediment cores with known carbonate accumulation rates and paleodepths. It is therefore vital to have well-constrained estimates of paleodepths. Paleodepths are typically calculated using models of thermal subsidence and sediment loading and compaction. However, viscous convection-related stresses in the mantle can warp the ocean floor by hundreds of meters over broad regions and can also vary significantly over millions of years. This contribution to paleobathymetry, termed dynamic topography, can be calculated by modeling mantle flow backwards in time. Herein, we demonstrate the effect dynamic topography has on the inference of the late Cenozoic CCD with an example from the equatorial Pacific, considering sites from IODP Expeditions 320/321. The equatorial Pacific, given its large size and high productivity, is closely tied to the global carbon cycle. Accordingly, long-term changes in the equatorial Pacific CCD can be considered to reflect global changes in weathering fluxes and the carbon cycle, in addition to more regional changes in productivity and thermohaline circulation. We find that, when the dynamic topography contribution to bathymetry is accounted for, the equatorial Pacific CCD is calculated to be appreciably shallower at 30 Ma than previous estimates would suggest, implying a greater deepening of the Pacific CCD over the late Cenozoic.

  13. Seismotectonics of the 2013 Lushan Mw 6.7 earthquake: Inversion tectonics in the eastern margin of the Tibetan Plateau (United States)

    Lu, Renqi; Xu, Xiwei; He, Dengfa; John, Suppe; Liu, Bo; Wang, Fuyun; Tan, Xibin; Li, Yingqiang


    On 20 April 2013, an unexpected Mw 6.7 earthquake occurred in Lushan County at the southern Longmen Shan, the eastern margin of the Tibetan Plateau. A high-resolution seismic reflection profile was combined with near-surface geological data, earthquake relocation and geodetic measurements, and a recent deep artificial seismic reflection profile to identify the active fault and seismotectonics of this earthquake. Three-dimensional imaging of the aftershocks was used to identify two planar faults that together form a y shape (f1 and f2). Seismic interpretations suggest that fault f1 did not break through the overlying Mesozoic and Cenozoic rocks and is a typical blind fault. Geodetic measurements suggest that the coseismic deformation is consistent with the geometry and kinematics of shear fault-bend folding. Deep seismic data indicate the syndepositional nature of fault f1 a preexisting normal fault older than the Triassic, which underwent positive inversion tectonics during the Late Cenozoic. A thrust fault f3 converges with f1 at a depth of approximately 12 km with an accumulated slip 3.6 km. This 2013 Lushan earthquake triggered by blind faults is a hidden earthquake. Blind and reactivated faults increase the potential risk and uncertainty related to earthquakes in the eastern margin of the Tibetan Plateau.

  14. Using Carbon Isotopes in Cenozoic Soil Carbonates to Quantify Primary Productivity from Mid-Latitude Regions (United States)

    Caves, J. K.; Kramer, S. H.; Ibarra, D. E.; Chamberlain, C. P.


    The carbon isotope composition of pedogenic carbonates (δ13Ccarb) from paleosols has been extensively used as a proxy to estimate atmospheric pCO2 over the Phanerozoic. However, a number of other factors - including the concentration of plant-respired CO2 and the isotopic composition of both atmospheric and plant-respired carbon - influence the δ13C of pedogenic carbonates. For example, δ13Ccarb records from the mid-latitudes in central Asia and western North America show increasing trends in δ13Ccarb despite decreasing pCO2 during the late Cenozoic, which suggests that other factors play an important role in determining the isotopic composition of pedogenic carbonates. Instead, we suggest that these records are primarily recording changes in primary productivity rather than changes in atmospheric pCO2 and therefore propose a novel use of paleosol carbonate records to understand paleo-ecosystem dynamics. Here, we compile existing paleosol carbonate records, and present three new records from Wyoming, to estimate soil respiration and primary productivity in western North America during the Paleogene and early Neogene. We observe both an overall increase in δ13Ccarb after the early Eocene, and spatially heterogeneous δ13Ccarb values across western US basins. We combine this δ13Ccarb data with compilations of atmospheric pCO2 to estimate soil respiration and plant productivity. The long-term increase in δ13Ccarb indicates a decrease in plant productivity as conditions became more arid across much of the western US, congruent with both records of regional uplift and of global cooling. Furthermore, significant spatial heterogeneity in δ13Ccarb indicates that regional factors, such as the presence of paleolakes and/or local paleotopography may have provided a second-order control on local and regional productivity. Thus, our results provide a first-order estimate linking changes in primary productivity with regional tectonics and global climatic change.

  15. The coal-bearing Cenozoic As Pontes Basin (northwestern Spain): geological influence on coal characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Cabrera, L.; Hagemann, H.W.; Pickel, W.; Saez, A. [Universitat de Barcelona, Barcelona (Spain). Dept. de Geologia Dinamica, Geofisica i Paleontologia


    Lignite deposits in the Cenozoic As Pontes strike-slip basin (northwestern Spain) were formed as a function of specific paleoclimatic conditions and tectonic evolution of the basin. During the early evolutionary stages, the presence of active normal faults and thrusts inside the basin resulted in two subbasins with distinct differences in sedimentary records, with respect to lignite seam occurrence, thickness, areal extent and lithotype development. In contrast, during the late e