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Sample records for australopithecus bahrelghazali mio-pliocene

  1. MIO-PLIOCENE CRUSTACEANS FROM THE CANARY ISLANDS, SPAIN

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    JUAN FRANCISCO BETANCORT

    2014-11-01

    Full Text Available There are few previous references to fossil crustaceans for the Neogene marine layers of the Canary Islands (Spain. The Mio-Pliocene marine sedimentary layers in the eastern islands (Gran Canaria, Fuerteventura and Lanzarote were previously characterised by the presence of numerous fossil fauna, mainly anthozoans and molluscs, which correspond to an equatorial-typepalaeoclimate, warmer than the present climate. This Mio-Pliocene transition dated between 9.3 and 4.1 Ma. In this paper, 12 fossil crustacean taxa are identified and classified, including decapods and barnacles: Balanus concavus Bronn, 1831, Balanus spongicola Brown, 1827, Balanus perforatus Bruguière, 1789, Chenolobia testudinaria Linnè, 1767, Tetraclita cf. rubescens Darwin, 1854, Callianassa matsoni Rathbun, 1935, Callianassa sp., Upogebia sp, Eriphia aff. verrucosa (Forskal, 1775 , Maja sp., Scylla michelini Milne-Edwards, 1861 and Ocypode sp. Some of these taxa mean new references for the Atlantic islands and the North African Atlantic and definitely enlarge the palaeographic distribution of Neogene crustaceans beyond the Mediterranean region, extending it to the North Atlantic. Particularly significant are the presence of Tetraclita cf. rubescens ,this being the first reported fossil occurrence of this barnacle outside the North America Pacific coasts, and Chenolobia testudinaria , indicating for the first time the existence of marine turtles in these islands during the Neogene. These results are coherent with previous research hypothesising the existence of a flow of surface water between the Pacific and Atlantic in the Mio-Pliocene transition (Central American Seaway, CAS which explains the arrival of organisms, in larval stage, from Central America to the Canary Islands.

  2. Giant bunodont Lutrinae from the Mio-Pliocene of Kenya and Uganda

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    Pickford, M.

    2005-12-01

    Full Text Available Three new species of bunodont otters are described from the Mio-Pliocene of East Africa. They are provisionally attributed to the genus Sivaonyx Pilgrim, 1931. The species described are Sivaonyx soriae, nov. sp. and Sivaonyx senutae nov. sp. from the Latest Miocene Lukeino Formation (Kenya and Sivaonyx kamuhangirei nov. sp. from the Pliocene of Kazinga and Warwire (Uganda. Additional material of the species Sivaonyx ekecaman (Werdelin, 2003 is described from Sagatia, Mabaget Formation (Kenya. The systematics of the new tribe Enhydriodontini are discussed and we report the presence of evolutionary tendencies in the bunodont African otters: increase in body size, modification of the carnassial teeth. In particular in the P4/ the protocone becomes well separated from the paracone, at the same time that an anterior valley develops.Se describen tres nuevas especies de nutrias bunodontas del Mio-plioceno de Africa oriental. Provisionalmente se adscriben al género Sivaonyx Pilgrim 1931. Las especies descritas son Sivaonyx soriae nov. sp y Sivaonyx senutae nov. sp. del Mioceno final de la formación Lukeino (Kenia, y Sivaonyx kamuhangirei nov. sp del Plioceno de Kazinga y Warwire (Uganda. También se describen nuevos fósiles de Sagatia, formación Magabet (Kenia atribuibles a la especie Sivaonyx ekecaman (Werdelin, 2003. Se discute la sistemática de la nueva tribu Enhydriotini y se señala la presencia de dos tendencias evolutivas en las nutrias bunodontas africanas: incremento de talla y modificación de las carniceras. Especialmente del P4/ en el que el protocono se va separando del paracono, al mismo tiempo que se desarrolla un valle en posición anterior.

  3. Depositional Environment of Mio-Pliocene Siwalik Sedimentary Strata from the Darjeeling Himalayan Foothills, India: A Palynological Approach.

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    Sandip More

    Full Text Available A rich and diverse palynoassemblage recovered from the Churanthi River section (26°53' 59.3" N, 88°34' 17.2" E, Darjeeling foothills Eastern Himalaya, has yielded 87 species assigned to 69 genera. The palynoassemblage is rich in angiosperm taxa (45.63% followed by gymnosperms (0.45%, pteridophytes (18.49% and fungal remains (23.88%. Based on their nearest living relatives, a wet evergreen to semi-evergreen forest under a humid tropical to sub-tropical environment during the Mio-Pliocene age has been suggested. A lot of angiosperms such as Palaeosantalaceaepites, Araliaceoipollenites, Malvacearampollis, Zonocostites, Neocouperipollis, Dicolpopollis, Palmidites, Palmaepollenites, isolated salt glands of mangrove plant leaves (Heliospermopsis and Mediaverrunites type of fungal spores, along with ichnofossils like Planolites, Palaeophycus, Skolithos, Rosselia, Ophiomorpha and Teichichnus associated with rippled mudstone-siltstone suggest an environment strongly influenced by brackish water. Primary sedimentary structures in the associated strata indicate strong wave agitation common in shallow marine setting. Some high elevation components (5.14% such as Alnipollenites, cf. Corylus (Betulaceae, Juglanspollenites, Engelhardtioipollenites (Juglandaceae, Quercoides, Cupuliferoidaepollenites, Lithocarpus, Castanopsis (Fagaceae, Abietineaepollenites (Pinaceae represent hinterland vegetation possibly transported to the prograding deltaic coastline by the rivers. Reworked palynotaxa (Striatopodocarpites sp., Striatites sp., Faunipollenites sp., Circumstriatites sp., Crescentipollenites sp., Cuneatisporites sp., Parasaccites sp., Scheuringipollenites sp., Rhizomaspora sp., Marsupipollenites sp., Lophotriletes sp. of Permian age have also been recorded in the palynoassemblage (11.55% indicating the abundance of Permian Gondwana strata in the source area.

  4. Soft-sediment deformation structures in the Mio-Pliocene Misaki Formation within alternating deep-sea clays and volcanic ashes (Miura Peninsula, Japan)

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    Mazumder, Rajat; van Loon, A. J. (Tom); Malviya, Vivek P.; Arima, Makoto; Ogawa, Yujuro

    2016-10-01

    The Mio-Pliocene Misaki Formation of the Miura Group (Miura Peninsula, Japan) shows an extremely wide variety of soft-sediment deformation structures. The most common deformation structures are load casts and associated flame structures, dish-and-pillar structures, synsedimentary faults, multilobated convolutions, chaotic deformation structures, sedimentary veins and dykes, and large-scale slides and slump scars. The formation, which accumulated in a deep-sea environment (2000-3000 m), is well exposed in and around Jogashima; it consists of relative thin (commonly dm-scale) alternations of deep-marine fine-grained sediments and volcanic ejecta that are, as a rule, coarse-grained. Since the formation represents fore-arc deposits of the Izu-Bonin and the Honsu arc collision zone, it might be expected that tectonic activity also played a role as a trigger of the soft-sediment deformation structures that abound in these sediments. This is indicated, indeed, by the abundance of soft-sediment deformations over large lateral distances that occur in numerous beds that are sandwiched between undeformed beds. On the basis of their characteristics and the geological context, these layers can be explained satisfactorily only by assuming deformation triggered by seismicity, which must be related to the Izu-Bonin and Honsu arc collision. The layers thus form deep-marine seismites.

  5. The vertebral column of Australopithecus sediba.

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    Williams, Scott A; Ostrofsky, Kelly R; Frater, Nakita; Churchill, Steven E; Schmid, Peter; Berger, Lee R

    2013-04-12

    Two partial vertebral columns of Australopithecus sediba grant insight into aspects of early hominin spinal mobility, lumbar curvature, vertebral formula, and transitional vertebra position. Au. sediba likely possessed five non-rib-bearing lumbar vertebrae and five sacral elements, the same configuration that occurs modally in modern humans. This finding contrasts with other interpretations of early hominin regional vertebral numbers. Importantly, the transitional vertebra is distinct from and above the last rib-bearing vertebra in Au. sediba, resulting in a functionally longer lower back. This configuration, along with a strongly wedged last lumbar vertebra and other indicators of lordotic posture, would have contributed to a highly flexible spine that is derived compared with earlier members of the genus Australopithecus and similar to that of the Nariokotome Homo erectus skeleton.

  6. Rodent faunas of the Mio-Pliocene continental sediments of the Teruel-Alfambra region, Spain

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    Weerd, A. van de

    1976-01-01

    In the large inland basin of Teruel-Calatayud the area around the town of Teruel is well known for its numerous remains of fossil mammals. They are found in Upper Miocene and Pliocene deposits, and some groups have already been studied in detail. Simultaneous with the collecting of fossil smaller ma

  7. Revision of the Mio-Pliocene bunodont otter-like mammals of the Indian Subcontinent

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    Pickford, M.

    2007-06-01

    Full Text Available A revision of the Enhydriodontini of the Indian Subcontinent is undertaken on the basis of previously described and recently collected bunodont otter-like fossils from the sub-Himalayan Siwalik Group. It is confirmed that, with the passage of geological time spanning the period 13 – 3 Ma, there occurred a progressive increase in body size, a reduction of the anterior part of the premolar row and an increase in degree of cheek tooth bunodonty and cusp mastoidization. Functional analysis of a snout with a partly preserved incisor battery of Enhydriodon sivalensis, reveals that it was probably a molluscivore, preying principally on bivalves, while other species of enhydriodonts were more likely to have been piscivores and cancrivores. One new species of Sivaonyx is described from the base of the Late Miocene of Pakistan. Bunodont otter-like mammals from Eurasia, Africa and North America are briefly discussed in light of the revision of the Indo-Pakistan ones. The origins and phylogenetic relationships of these mammals remains obscure. The major differences in dental anatomy indicate that these Old World otter-like mammals should not be classified in Enhydrini, but in a tribe of their own Enhydriodontini new tribe.La revisión de los Enhydriontinos del subcontinente Indio se aborda, tanto en base a los fósiles de nutrias bunodontas previamente descritos, como a los hallazgos recientemente realizados en el Grupo de los Siwaliks en el sub-Himalaya. Se confirma que durante el período de tiempo comprendido entre los 13 a 3 Ma hubo un progresivo incremento en la talla corporal, una reducción de la parte anterior de la serie premolar y un incremento en el grado de bunodoncia y mastoidización de las cúspides de los dientes. El análisis funcional de un hocico de Enhydriodon sivalensis con la batería de incisivos parcialmente conservados revela que esta especie fue parcialmente malacófaga, alimentándose principalmente de bivalvos, mientras que otras especies de enhydriontinos fueron más piscívoras y cancrívoras. En el trabajo también se describe una nueva especie de Sivaonyx procedente de la base del Mioceno Terminal de Paquistán. Los mamíferos bunodontos de tipo nutria de Eurasia, África y América del Norte son brevemente discutidos a la luz de la revisión realizada para las formas paquistaníes. El origen y relaciones filogenéticas de estos mamíferos permanecen oscuros. Las importantes diferencias en anatomía dental indican que estos mamíferos de tipo nutria del Viejo Mundo no deberían ser clasificados como Enhydrini, sino en una tribu propia, Enhydriodontini nueva tribu.

  8. Anterior dental evolution in the Australopithecus anamensis-afarensis lineage.

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    Ward, Carol V; Plavcan, J Michael; Manthi, Fredrick K

    2010-10-27

    Australopithecus anamensis is the earliest known species of the Australopithecus-human clade and is the likely ancestor of Australopithecus afarensis. Investigating possible selective pressures underlying these changes is key to understanding the patterns of selection shaping the origins and early evolution of the Australopithecus-human clade. During the course of the Au. anamensis-afarensis lineage, significant changes appear to occur particularly in the anterior dentition, but also in jaw structure and molar form, suggesting selection for altered diet and/or food processing. Specifically, canine tooth crown height does not change, but maxillary canines and P(3)s become shorter mesiodistally, canine tooth crowns become more symmetrical in profile and P(3)s less unicuspid. Canine roots diminish in size and dimorphism, especially relative to the size of the postcanine teeth. Molar crowns become higher. Tooth rows become more divergent and symphyseal form changes. Dietary change involving anterior dental use is also suggested by less intense anterior tooth wear in Au. afarensis. These dental changes signal selection for altered dietary behaviour and explain some differences in craniofacial form between these taxa. These data identify Au. anamensis not just as a more primitive version of Au. afarensis, but as a dynamic member of an evolving lineage leading to Au. afarensis, and raise intriguing questions about what other evolutionary changes occurred during the early evolution of the Australopithecus-human clade, and what characterized the origins of the group.

  9. The functional significance of the squamosal suture in Australopithecus boisei.

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    Rak, Y

    1978-07-01

    A juvenile Australopithecus boisei specimen from the Omo basin, southern Ethiopia, is found to exhibit and extraordinarily large overlap of the temporal squama on the parietal, a phenomenon shared with at least two adult specimens of A. boisei. An attempt is made to interpret the overlap as a structural (bony/ligamentous) adaptation necessitated by the unique combination of certain components of the masticatory system of A. boisei. These are: (1) the massiveness and strength of the temporalis muscle, (2) its relatively anterior location, and (3) the lateral position of the masseter muscle due to the flaring of the zygomatic arches. The effect of the temporalis muscle is to create excessive pressure on the portion of the squamosal suture along the parietal, while the lateral placement of the masseter and the resultant increase of pressure on the temporal squama via the zygomatic arch tend to "loosen" the contact between the temporal and parietal bones.

  10. Sawfishes and Other Elasmobranch Assemblages from the Mio-Pliocene of the South Caribbean (Urumaco Sequence, Northwestern Venezuela)

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    2015-01-01

    The Urumaco stratigraphic sequence, western Venezuela, preserves a variety of paleoenvironments that include terrestrial, riverine, lacustrine and marine facies. A wide range of fossil vertebrates associated with these facies supports the hypothesis of an estuary in that geographic area connected with a hydrographic system that flowed from western Amazonia up to the Proto-Caribbean Sea during the Miocene. Here the elasmobranch assemblages of the middle Miocene to middle Pliocene section of the Urumaco sequence (Socorro, Urumaco and Codore formations) are described. Based on new findings, we document at least 21 taxa of the Lamniformes, Carcharhiniformes, Myliobatiformes and Rajiformes, and describe a new carcharhiniform species (†Carcharhinus caquetius sp. nov.). Moreover, the Urumaco Formation has a high number of well-preserved fossil Pristis rostra, for which we provide a detailed taxonomic revision, and referral in the context of the global Miocene record of Pristis as well as extant species. Using the habitat preference of the living representatives, we hypothesize that the fossil chondrichthyan assemblages from the Urumaco sequence are evidence for marine shallow waters and estuarine habitats. PMID:26488163

  11. Sexual dimorphism in the face of Australopithecus africanus.

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    Lockwood, C A

    1999-01-01

    Recently discovered crania of Australopithecus africanus from Sterkfontein Member 4 and Makapansgat enlarge the size range of the species and encourage a reappraisal of both the degree and pattern of sexual dimorphism. Resampling methodology (bootstrapping) is used here to establish that A. africanus has a greater craniofacial size range than chimpanzees or modern humans, a range which is best attributed to a moderately high degree of sexual dimorphism. Compared to other fossil hominins, this variation is similar to that of Homo habilis (sensu lato) but less than that of A. boisei. The finding of moderately high dimorphism is corroborated by a CV-based estimate and ratios between those specimens considered to be male and those considered to be female. Inferences about the pattern of craniofacial dimorphism in the A. africanus face currently rely on the relationship of morphology and size. Larger specimens, particularly Stw 505, show prominent superciliary eminences and glabellar regions, but in features related in part to canine size, such as the curvature of the infraorbital surface, large and small specimens of A. africanus are similar. In this respect, the pattern resembles that of modern humans more so than chimpanzees or lowland gorillas. A. africanus may also show novel patterns of sexual dimorphism when compared to extant hominines, such as in the form of the anterior pillar. However, males of the species do not exhibit characteristics of more derived hominins, such as A. robustus.

  12. Patterns of size sexual dimorphism in Australopithecus afarensis: another look.

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    Lee, S-H

    2005-01-01

    Size sexual dimorphism is one of the major components of morphological variation and has been associated with socio-ecology and behavioral variables such as mating patterns. Although several studies have addressed the magnitude and pattern of sexual dimorphism in Australopithecus afarensis, one of the earliest hominids, consensus has yet to be reached. This paper uses assigned re-sampling method, a data re-sampling method to estimate the magnitude of sexual dimorphism without relying on individual sex assessments, to examine the fossil hominid sample from Hadar. Two questions are asked: first, whether sexual dimorphism in a selected sample of skeletal elements of A. afarensis is the same as that in living humans, chimpanzees, or gorillas; and second, whether different skeletal elements reflect variation in sexual dimorphism in the same way. All possible metric variables were used as data in applying the method, including seven variables from three elements (mandibular canine, humerus, femur). Analyses show that A. afarensis is similar in size sexual dimorphism to gorillas in femoral variables, to humans in humeral variables, and to chimpanzees in canine variables. The results of this study are compatible with the hypothesis that the pattern of sexual dimorphism in A. afarensis is different from any that are observed in living humans or apes.

  13. Australopithecus sediba at 1.977 Ma and implications for the origins of the genus Homo.

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    Pickering, Robyn; Dirks, Paul H G M; Jinnah, Zubair; de Ruiter, Darryl J; Churchil, Steven E; Herries, Andy I R; Woodhead, Jon D; Hellstrom, John C; Berger, Lee R

    2011-09-01

    Newly exposed cave sediments at the Malapa site include a flowstone layer capping the sedimentary unit containing the Australopithecus sediba fossils. Uranium-lead dating of the flowstone, combined with paleomagnetic and stratigraphic analysis of the flowstone and underlying sediments, provides a tightly constrained date of 1.977 ± 0.002 million years ago (Ma) for these fossils. This refined dating suggests that Au. sediba from Malapa predates the earliest uncontested evidence for Homo in Africa.

  14. Trabecular evidence for a human-like gait in Australopithecus africanus.

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    Meir M Barak

    Full Text Available Although the earliest known hominins were apparently upright bipeds, there has been mixed evidence whether particular species of hominins including those in the genus Australopithecus walked with relatively extended hips, knees and ankles like modern humans, or with more flexed lower limb joints like apes when bipedal. Here we demonstrate in chimpanzees and humans a highly predictable and sensitive relationship between the orientation of the ankle joint during loading and the principal orientation of trabecular bone struts in the distal tibia that function to withstand compressive forces within the joint. Analyses of the orientation of these struts using microCT scans in a sample of fossil tibiae from the site of Sterkfontein, of which two are assigned to Australopithecus africanus, indicate that these hominins primarily loaded their ankles in a relatively extended posture like modern humans and unlike chimpanzees. In other respects, however, trabecular properties in Au africanus are distinctive, with values that mostly fall between those of chimpanzees and humans. These results indicate that Au. africanus, like Homo, walked with an efficient, extended lower limb.

  15. Reconsideration of the so-called Oligocene fauna in the asphaltic deposits of Buton (Malay Archipelago) — 1. Mio-Pliocene Mollusca

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    Beets, C.

    1952-01-01

    Ever since his first experience with the remarkable “Upper Oligocene” molluscan fauna of the Isle of Buton, the present writer has endeavoured to find more convincing evidence for its age. One of the most tempting problems was why this fauna showed so few relationships to other fossil faunas or to t

  16. Studies in Neotropical Paleobotany. XV. A Mio-Pliocene palynoflora from the Eastern Cordillera, Bolivia: implications for the uplift history of the Central Andes.

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    Graham, A; Gregory-Wodzicki, K M; Wright, K L

    2001-09-01

    An assemblage of 33 fossil pollen and spores, recovered from the 3600-m high Pislepampa locality of E. W. Berry, Eastern Cordillera, Bolivia, adds considerably to our knowledge of three aspects of the region in late Neogene time: (1) the paleovegetation, (2) the paleoclimate, and (3) the paleoelevation of the Central Andes. The plant microfossils recognized are Isoetes, Lycopodium (three types), Cnemidaria, Cyathea (three types), Grammitis, Hymenophyllum, Pteris, trilete fern spores (two types), Danaea, monolete fern spores (four types), Podocarpus, Gramineae, Palmae, Ilex, cf. Oreopanax, Cavanillesia, cf. Pereskia, Compositae (three types), Ericaceae, Tetrorchidium, and unknowns (three types). The diversity of the Compositae suggest that this flora has a maximum age around the Miocene-Pliocene boundary, that is, 6-7 million years. All members of the paleocommunity presently grow in the bosque montano húmedo (cloud forest) along the eastern slope of the Central Andes of Bolivia, which occurs between MATs (mean annual temperatures) of ∼10° and 20°C. The Pislepampa flora probably represents the lower limits of this forest because the fossil leaves collected by Berry from the same locality all have entire margins, suggesting that the flora grew near the cloud forest-tropical forest transition. Presently, the lower limit of the cloud forest forest has MATs of ∼20°C, a mean annual precipitation between 1000 and 1500 mm, and that part containing most of the identified genera of fossil pollen is found at elevations ∼1200-1400 m. These conditions are thus inferred for the Pislepampa flora; however, because of the uncertainty of the magnitude of global climate change and of possible changes in the ecological range of plant genera, we estimate an error of at least ±1000 m for the paleoelevation estimate. When the total uplift is corrected for probable amounts of erosionally driven isostatic rebound, the paleoelevation estimate suggests that from one-third to one-half of the uplift of the Eastern Cordillera had occurred by the beginning of the Pliocene. This estimate is consistent with other paleoelevation estimates from the Central Andes.

  17. Comparative taphonomy, taphofacies, and bonebeds of the Mio-Pliocene Purisima Formation, central California: strong physical control on marine vertebrate preservation in shallow marine settings.

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    Robert W Boessenecker

    Full Text Available Taphonomic study of marine vertebrate remains has traditionally focused on single skeletons, lagerstätten, or bonebed genesis with few attempts to document environmental gradients in preservation. As such, establishment of a concrete taphonomic model for shallow marine vertebrate assemblages is lacking. The Neogene Purisima Formation of Northern California, a richly fossiliferous unit recording nearshore to offshore depositional settings, offers a unique opportunity to examine preservational trends across these settings.Lithofacies analysis was conducted to place vertebrate fossils within a hydrodynamic and depositional environmental context. Taphonomic data including abrasion, fragmentation, phosphatization, articulation, polish, and biogenic bone modification were recorded for over 1000 vertebrate fossils of sharks, bony fish, birds, pinnipeds, odontocetes, mysticetes, sirenians, and land mammals. These data were used to compare both preservation of multiple taxa within a single lithofacies and preservation of individual taxa across lithofacies to document environmental gradients in preservation. Differential preservation between taxa indicates strong preservational bias within the Purisima Formation. Varying levels of abrasion, fragmentation, phosphatization, and articulation are strongly correlative with physical processes of sediment transport and sedimentation rate. Preservational characteristics were used to delineate four taphofacies corresponding to inner, middle, and outer shelf settings, and bonebeds. Application of sequence stratigraphic methods shows that bonebeds mark major stratigraphic discontinuities, while packages of rock between discontinuities consistently exhibit onshore-offshore changes in taphofacies.Changes in vertebrate preservation and bonebed character between lithofacies closely correspond to onshore-offshore changes in depositional setting, indicating that the dominant control of preservation is exerted by physical processes. The strong physical control on marine vertebrate preservation and preservational bias within the Purisima Formation has implications for paleoecologic and paleobiologic studies of marine vertebrates. Evidence of preservational bias among marine vertebrates suggests that careful consideration of taphonomic overprint must be undertaken before meaningful paleoecologic interpretations of shallow marine vertebrates is attempted.

  18. Forearm articular proportions and the antebrachial index in Homo sapiens, Australopithecus afarensis and the great apes.

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    Williams, Frank L'Engle; Cunningham, Deborah L; Amaral, Lia Q

    2015-12-01

    When hominin bipedality evolved, the forearms were free to adopt nonlocomotor tasks which may have resulted in changes to the articular surfaces of the ulna and the relative lengths of the forearm bones. Similarly, sex differences in forearm proportions may be more likely to emerge in bipeds than in the great apes given the locomotor constraints in Gorilla, Pan and Pongo. To test these assumptions, ulnar articular proportions and the antebrachial index (radius length/ulna length) in Homo sapiens (n=51), Gorilla gorilla (n=88), Pan troglodytes (n=49), Pongo pygmaeus (n=36) and Australopithecus afarensis A.L. 288-1 and A.L. 438-1 are compared. Intercept-adjusted ratios are used to control for size and minimize the effects of allometry. Canonical scores axes show that the proximally broad and elongated trochlear notch with respect to size in H. sapiens and A. afarensis is largely distinct from G. gorilla, P. troglodytes and P. pygmaeus. A cluster analysis of scaled ulnar articular dimensions groups H. sapiens males with A.L. 438-1 ulna length estimates, while one A.L. 288-1 ulna length estimate groups with Pan and another clusters most closely with H. sapiens, G. gorilla and A.L. 438-1. The relatively low antebrachial index characterizing H. sapiens and non-outlier estimates of A.L. 288-1 and A.L. 438-1 differs from those of the great apes. Unique sex differences in H. sapiens suggest a link between bipedality and forearm functional morphology.

  19. Dentognathic remains of Australopithecus afarensis from Nefuraytu (Woranso-Mille, Ethiopia): Comparative description, geology, and paleoecological context.

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    Haile-Selassie, Yohannes; Melillo, Stephanie M; Ryan, Timothy M; Levin, Naomi E; Saylor, Beverly Z; Deino, Alan; Mundil, Ronald; Scott, Gary; Mulugeta Alene; Gibert, Luis

    2016-11-01

    Australopithecus afarensis is the best-known and most dimorphic species in the early hominin fossil record. Here, we present a comparative description of new fossil specimens of Au. afarensis from Nefuraytu, a 3.330-3.207 million-years-old fossil collection area in the Woranso-Mille study area, central Afar, Ethiopia. These specimens include NFR-VP-1/29, one of the most complete mandibles assigned to the species thus far and among the largest mandibles attributed to Au. afarensis, likely representing a male individual. NFR-VP-1/29 retains almost all of the distinctive archaic features documented for Au. afarensis. These features include a posteriorly sloping symphysis, a low and rounded basally set inferior transverse torus, anterosuperiorly opening mental foramen, a lateral corpus hollow bound anteriorly by the C/P3 jugae and posteriorly by the lateral prominence, and the ascending ramus arising high on the corpus. Dental morphology and metrics of the Nefuraytu specimens also falls within the range of Au. afarensis. The presence of this species at Woranso-Mille between 3.330 and 3.207 million years ago confirms the existence of this species in the area in close spatial and temporal proximity to other middle Pliocene hominin taxa such as the one represented by the Burtele foot (BRT-VP-2/73) and the recently named species Australopithecus deyiremeda. This has important implications for our understanding of middle Pliocene hominin diversity.

  20. Refinement of the time-space evolution of the giant Mio-Pliocene Río Blanco-Los Bronces porphyry Cu-Mo cluster, Central Chile: new U-Pb (SHRIMP II) and Re-Os geochronology and 40Ar/39Ar thermochronology data

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    Deckart, Katja; Clark, Alan H.; Cuadra, Patricio; Fanning, Mark

    2013-01-01

    Representing one of the largest known (estimated >5 Gt at 1 % Cu and 0.02 % Mo) porphyry system, the Río Blanco-Los Bronces deposit incorporates at least five hypabyssal intrusive and hydrothermal centres, extending for about 5 km from the Río Blanco and Los Bronces mines in the north, through the Don Luis mine, to the Sur Sur mine, La Americana and Los Sulfatos in the south. The new geochronology data, which now include data on different molybdenite vein types, confirm the U-Pb ages of the pre-mineralisation intrusions but slightly increase their age range from 8.8 to 8.2 Ma. The distinct magmatic pulses of the mineralisation-associated porphyritic intrusives (Late Porphyries) indicate an age interval instead of the previously suggested individual ages: the quartz monzonite porphyry ranges from 7.7 to 6.1 Ma (Sur Sur 5.74 ± 0.13 Ma), the feldspar porphyry shows an interval from 5.8 to 5.2 Ma and the Don Luis porphyry from 5.2 to 5.0 Ma. The new Re-Os data on distinct molybdenite vein types confirm the protracted history of Cu(-Mo) mineralisation, inferred previously. The vein development occurred at least from 5.94 to 4.50 Ma, indicating a time-span of 1.5 Ma for the hydrothermal activity. Hydrothermal minerals dated by the 40Ar/39Ar method are generally too young to record the age of early, high-temperature mineralisation. The majority of the 40Ar/39Ar data in the Río Blanco porphyry cluster record reheating by either the youngest member of the Late Porphyry suite or the post-mineralisation dacite or rhyolite plug formations at around 4.9-4.7 Ma.

  1. Like father, like son: assessment of the morphological affinities of A.L. 288-1 (A. afarensis, Sts 7 (A. africanus and Omo 119-73-2718 (Australopithecus sp. through a three-dimensional shape analysis of the shoulder joint.

    Directory of Open Access Journals (Sweden)

    Julia Arias-Martorell

    Full Text Available The postcranial evidence for the Australopithecus genus indicates that australopiths were able bipeds; however, the morphology of the forelimbs and particularly that of the shoulder girdle suggests that they were partially adapted to an arboreal lifestyle. The nature of such arboreal adaptations is still unclear, as are the kind of arboreal behaviors in which australopiths might have engaged. In this study we analyzed the shape of the shoulder joint (proximal humerus and glenoid cavity of the scapula of three australopith specimens: A.L. 288-1 (A. afarensis, Sts 7 (A. africanus and Omo 119-73-2718 (Australopithecus sp. with three-dimensional geometric morphometrics. The morphology of the specimens was compared with that of a wide array of living anthropoid taxa and some additional fossil hominins (the Homo erectus specimen KNM-WT 15000 and the H. neanderthalensis specimen Tabun 1. Our results indicate that A.L. 288-1 shows mosaic traits resembling H. sapiens and Pongo, whereas the Sts 7 shoulder is most similar to the arboreal apes and does not present affinities with H. sapiens. Omo 119-73-2718 exhibits morphological affinities with the more arboreal and partially suspensory New World monkey Lagothrix. The shoulder of the australopith specimens thus shows a combination of primitive and derived traits (humeral globularity, enhancement of internal and external rotation of the joint, related to use of the arm in overhead positions. The genus Homo specimens show overall affinities with H. sapiens at the shoulder, indicating full correspondence of these hominin shoulders with the modern human morphotype.

  2. Like Father, Like Son: Assessment of the Morphological Affinities of A.L. 288–1 (A. afarensis), Sts 7 (A. africanus) and Omo 119–73–2718 (Australopithecus sp.) through a Three-Dimensional Shape Analysis of the Shoulder Joint

    Science.gov (United States)

    Arias-Martorell, Julia; Potau, Josep Maria; Bello-Hellegouarch, Gaëlle; Pérez-Pérez, Alejandro

    2015-01-01

    The postcranial evidence for the Australopithecus genus indicates that australopiths were able bipeds; however, the morphology of the forelimbs and particularly that of the shoulder girdle suggests that they were partially adapted to an arboreal lifestyle. The nature of such arboreal adaptations is still unclear, as are the kind of arboreal behaviors in which australopiths might have engaged. In this study we analyzed the shape of the shoulder joint (proximal humerus and glenoid cavity of the scapula) of three australopith specimens: A.L. 288–1 (A. afarensis), Sts 7 (A. africanus) and Omo 119–73–2718 (Australopithecus sp.) with three-dimensional geometric morphometrics. The morphology of the specimens was compared with that of a wide array of living anthropoid taxa and some additional fossil hominins (the Homo erectus specimen KNM-WT 15000 and the H. neanderthalensis specimen Tabun 1). Our results indicate that A.L. 288–1 shows mosaic traits resembling H. sapiens and Pongo, whereas the Sts 7 shoulder is most similar to the arboreal apes and does not present affinities with H. sapiens. Omo 119–73–2718 exhibits morphological affinities with the more arboreal and partially suspensory New World monkey Lagothrix. The shoulder of the australopith specimens thus shows a combination of primitive and derived traits (humeral globularity, enhancement of internal and external rotation of the joint), related to use of the arm in overhead positions. The genus Homo specimens show overall affinities with H. sapiens at the shoulder, indicating full correspondence of these hominin shoulders with the modern human morphotype. PMID:25651542

  3. Will dragonblood survive the next period of climate change? Current and future potential distribution of Dracaena cinnabari (Socotra, Yemen)

    NARCIS (Netherlands)

    Attorre, F.; Francesconi, F.; Taleb, N.; Scholte, P.; Saed, A.; Alfo, M.; Bruno, F.

    2007-01-01

    The potential impact of climate change on Dracaena cinnabari, a spectacular relict of the Mio-Pliocene Laurasian subtropical forest in Socotra (Yemen), was analysed. Current distribution, abundance and vertical structure of D. cinnabari populations were assessed with 74 plots in nine remnant areas.

  4. Baboon feeding ecology informs the dietary niche of Paranthropus boisei.

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    Gabriele A Macho

    Full Text Available Hominins are generally considered eclectic omnivores like baboons, but recent isotope studies call into question the generalist status of some hominins. Paranthropus boisei and Australopithecus bahrelghazali derived 75%-80% of their tissues' δ(13C from C4 sources, i.e. mainly low-quality foods like grasses and sedges. Here I consider the energetics of P. boisei and the nutritional value of C4 foods, taking into account scaling issues between the volume of food consumed and body mass, and P. boisei's food preference as inferred from dento-cranial morphology. Underlying the models are empirical data for Papio cynocephalus dietary ecology. Paranthropus boisei only needed to spend some 37%-42% of its daily feeding time (conservative estimate on C4 sources to meet 80% of its daily requirements of calories, and all its requirements for protein. The energetic requirements of 2-4 times the basal metabolic rate (BMR common to mammals could therefore have been met within a 6-hour feeding/foraging day. The findings highlight the high nutritional yield of many C4 foods eaten by baboons (and presumably hominins, explain the evolutionary success of P. boisei, and indicate that P. boisei was probably a generalist like other hominins. The diet proposed is consistent with the species' derived morphology and unique microwear textures. Finally, the results highlight the importance of baboon/hominin hand in food acquisition and preparation.

  5. Evolution of brain and culture: the neurological and cognitive journey from Australopithecus to Albert Einstein.

    Science.gov (United States)

    Falk, Dean

    2016-06-20

    Fossil and comparative primatological evidence suggest that alterations in the development of prehistoric hominin infants kindled three consecutive evolutionary-developmental (evo-devo) trends that, ultimately, paved the way for the evolution of the human brain and cognition. In the earliest trend, infants' development of posture and locomotion became delayed because of anatomical changes that accompanied the prolonged evolution of bipedalism. Because modern humans have inherited these changes, our babies are much slower than other primates to reach developmental milestones such as standing, crawling, and walking. The delay in ancestral babies' physical development eventually precipitated an evolutionary reversal in which they became increasing unable to cling independently to their mothers. For the first time in prehistory, babies were, thus, periodically deprived of direct physical contact with their mothers. This prompted the emergence of a second evo-devo trend in which infants sought contact comfort from caregivers using evolved signals, including new ways of crying that are conserved in modern babies. Such signaling stimulated intense reciprocal interactions between prehistoric mothers and infants that seeded the eventual emergence of motherese and, subsequently, protolanguage. The third trend was for an extreme acceleration in brain growth that began prior to the last trimester of gestation and continued through infants' first postnatal year (early "brain spurt"). Conservation of this trend in modern babies explains why human brains reach adult sizes that are over three times those of chimpanzees. The fossil record of hominin cranial capacities together with comparative neuroanatomical data suggest that, around 3 million years ago, early brain spurts began to facilitate an evolutionary trajectory for increasingly large adult brains in association with neurological reorganization. The prehistoric increase in brain size eventually caused parturition to become exceedingly difficult, and this difficulty, known as the "obstetrical dilemma", is likely to constrain the future evolution of brain size and, thus, privilege ongoing evolution in neurological reorganization. In modern babies, the brain spurt is accompanied by formation and tuning (pruning) of neurological connections, and development of dynamic higher-order networks that facilitate acquisition of grammatical language and, later in development, other advanced computational abilities such as musical or mathematical perception and performance. The cumulative evidence suggests that the emergence and refinement of grammatical language was a prime mover of hominin brain evolution.

  6. Virtual reconstruction of the Australopithecus africanus pelvis Sts 65 with implications for obstetrics and locomotion.

    Science.gov (United States)

    Claxton, Alexander G; Hammond, Ashley S; Romano, Julia; Oleinik, Ekaterina; DeSilva, Jeremy M

    2016-10-01

    Characterizing australopith pelvic morphology has been difficult in part because of limited fossilized pelvic material. Here, we reassess the morphology of an under-studied adult right ilium and pubis (Sts 65) from Member 4 of Sterkfontein, South Africa, and provide a hypothetical digital reconstruction of its overall pelvic morphology. The small size of the pelvis, presence of a preauricular sulcus, and shape of the sciatic notch allow us to agree with past interpretations that Sts 65 likely belonged to a female. The morphology of the iliac pillar, while not as substantial as in Homo, is more robust than in A.L. 288-1 and Sts 14. We created a reconstruction of the pelvis by digitally articulating the Sts 65 right ilium and a mirrored copy of the left ilium with the Sts 14 sacrum in Autodesk Maya. Points along the arcuate line were used to orient the ilia to the sacrum. This reconstruction of the Sts 65 pelvis looks much like a "classic" australopith pelvis, with laterally flared ilia and an inferiorly deflected pubis. An analysis of the obstetric dimensions from our reconstruction shows similarity to other australopiths, a likely transverse or oblique entrance of the neonatal cranium into the pelvic inlet, and a cephalopelvic ratio similar to that found in humans today.

  7. Rapid Post-Miocene tectonic rotation associated with the San Gregorio Fault Zone in central California

    Science.gov (United States)

    Holm, Eric J.; Horns, Daniel M.; Verosub, Kenneth L.

    1991-12-01

    Paleomagnetic measurements of samples from the Mio-Pliocene Purisima Formation demonstrate that the Pomponio tectonic block of central coastal California has rotated clockwise by approximately 35° to 55° within the last 2.5 million years. The most likely interpretation of this data is that the Pomponio block is broken into several small blocks which have rotated by various amounts. The data suggest that rotations contribute to vertical deformation and secondary faulting within the central San Andreas Fault System, and that they play an important role in the accommodation of shear along the fault system.

  8. Unusual death of millipedes (Diplopoda towards the north of the Varkala Cliff section near Papanasam, Kerala, India

    Directory of Open Access Journals (Sweden)

    P.K. Sarkar

    2011-08-01

    Full Text Available The cliff section at Varkala, Kerala consisting of clay, lignite band, clay, sandy-clay, sandstone of Mio-Pliocene age. This sedimentary sequence is overlain by a thick laterite. Above the lower lignite band, in the exposed clay beds several struggling and dead millipedes can be observed. Their death is probably due to the action of dehydration related to the sulphuric water infiltration in the sediments. However, it still remains a mystery why these millipedes choose such a toxic environment to create their habitat?

  9. Late Cenozoic stress state distributions at the intersection of the Hellenic and Cyprus Arcs, SW Turkey

    Science.gov (United States)

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

    2016-12-01

    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

  10. Evolution of an Interbasin Mountain-Block Extensional Accommodation Zone Within the Central Colorado Rio Grande Rift, USA

    Science.gov (United States)

    Minor, S. A.; Caine, J. S.; Fridrich, C.; Hudson, M. R.

    2015-12-01

    Our understanding of extensional strain transfer and accommodation in continental rifts has grown considerably, but few studied transfer zones exhibit high internal topographic and structural relief. In the Rio Grande rift of Colorado the WNW-trending northern tip of the Sangre de Cristo Range separates the opposite-tilted Upper Arkansas River (UAR) and San Luis half grabens. We have investigated the development and role of faults flanking this "Poncha" intrarift mountain block in transferring extension between rift basins, mountain block surface uplift, and landscape evolution. The topographically rugged Poncha block consists of Proterozoic metamorphic and plutonic rocks overlain on its west and southwest flanks by 34.5-33-Ma volcanic rocks and alluvial deposits of the Mio-Pliocene Dry Union Formation. Similar Dry Union sediments underlie a moderately elevated, strongly dissected older piedmont along the northern front of the mountain block. All of these units are tilted 10-35º to the W and SW. A WNW-trending, right-stepping fault system > 25 km in length separates the piedmont and UAR basin from the steep northern Poncha mountain front. Slip measurements along this fault system, cutting deposits as young as ~200 ka, indicate dextral-normal oblique movement. The NNW-striking, down-to-E southern Sawatch range-front fault system forms the western terminus of the Poncha block where it juxtaposes Dry Union deposits against Sawatch Proterozoic basement rocks. Gently tilted proximal diamicton and alluvial deposits on the downthrown blocks of both range-front faults likely mark Plio-Pleistocene(?) mountain block uplift. Arrays of NNW- to WNW-striking faults cutting volcanic and Dry Union units on the flanks of the Poncha block commonly have normal-oblique slip, with greater tendency for dextral strike-slip components on WNW-striking faults. Preliminary paleomagnetic data from the volcanic rocks detect no significant vertical-axis rotation that accompanied oblique

  11. Divergence between Antarctic and South American marine invertebrates: What molecular biology tells us about Scotia Arc geodynamics and the intensification of the Antarctic Circumpolar Current

    Science.gov (United States)

    Poulin, Elie; González-Wevar, Claudio; Díaz, Angie; Gérard, Karin; Hüne, Mathias

    2014-12-01

    Continental drift processes such as major gateway openings have been historically advocated to explain the distribution of marine benthic taxa in the Southern Ocean (SO). The separation between Antarctic Peninsula and the southern tip of South America together with the onset of the Antarctic Circumpolar Current (ACC) represent the final step for the complete isolation of the Antarctic region. However, there is still controversy concerning the timing and mode of this process, and especially about the role of the Scotia Arc geodynamics in the development of a fully deep and intensified ACC circulation. Based on mitochondrial Cytochrome c Oxidase Subunit I (COI) sequences obtained from different taxa, we performed molecular comparisons between Antarctic and South American relatives to provide independent time estimations of Antarctica's isolation. We include in the analyses congeneric Antarctic and Patagonian near-shore marine benthic invertebrates including indirect developers (Nacella, Yoldia, Sterechinus, and Parbolasia) and brooders (Xymenopsis and Trophonella). Considering the levels of genetic differentiation between relatives from both regions and assuming the molecular clock hypothesis, we estimated the onset of their respective divergence. On one hand, similar levels of genetic distance in broadcast-spawners (7%-8.3%) support the hypothesis that the development of an effective barrier between Antarctica and South America occurred almost simultaneously for these groups. Divergence time estimations based on specific substitution rates indicate that the separation occurred near the Mio-Pliocene transition, long after the physical separation of both continents. Genetic distance and divergence time estimation in direct developers indicate an older separation time, close to the mid-Miocene. Even when the analyzed groups included both broadcast-spawners and brooder organisms, the divergence between Antarctic and South America lineages rather than being related to

  12. Evaluation of aquifer environment under Hazaribagh leather processing zone of Dhaka city

    Science.gov (United States)

    Zahid, Anwar; Balke, K.-D.; Hassan, M. Qumrul; Flegr, Matthias

    2006-07-01

    Hazaribagh is a densely populated area of Dhaka city where about 185 leather processing industries have been operating and discharging solid and liquid wastes directly to the low-lying areas, river and natural canals without proper treatment. The area is covered by alluvial deposits of Holocene age and is underlain by Pleistocene Madhupur clay. The Dupi Tila Formation of Mio-Pliocene age underlain by this yellowish gray to brick red clay bed serves as the main water-bearing aquifer of Dhaka city. To assess the environmental degradation as well as the groundwater environment, major anions, cations and heavy metals of water samples, heavy metals and organic carbon content of sediment samples were analyzed in this study. Analyses of tannery effluent detect high concentration of Na+, Mg2+, Cl- and SO{4/2-} followed by Ca2+, NH{4/+} and K+ with remarkable contents of some trace elements, mainly Cr, Fe, Mn, S, Ni and Pb. Higher accumulations of Cr, Al and Fe are observed in topsoil samples with significant amounts of Mn, Zn, Ni and Cu. Concentrations of ions and all the investigated trace elements of sampled groundwater were within the maximum allowable limit for drinking water of the Department of Environment, Bangladesh (DoE), and World Health Organization (WHO). However, excessive concentrations of Cr, Pb, etc., have already been reported in the shallow groundwater (10-20 m) of the area. Due to excessive withdrawal the vulnerability of groundwater contamination in deeper parts cannot be avoided for the future.

  13. Site characterization and site response in Port-au-Prince, Haiti

    Science.gov (United States)

    Hough, Susan E.; Yong, Alan K.; Altidor, Jean Robert; Anglade, Dieuseul; Given, Douglas D.; Mildor, Saint-Louis

    2011-01-01

    Waveform analysis of aftershocks of the Mw7.0 Haiti earthquake of 12 January 2010 reveals amplification of ground motions at sites within the Cul de Sac valley in which Port-au-Prince is situated. Relative to ground motions recorded at a hard-rock reference site, peak acceleration values are amplified by a factor of approximately 1.8 at sites on low-lying Mio-Pliocene deposits in central Port-au-Prince and by a factor of approximately 2.5–3 on a steep foothill ridge in the southern Port-au-Prince metropolitan region. The observed amplitude, predominant periods, variability, and polarization of amplification are consistent with predicted topographic amplification by a steep, narrow ridge. A swath of unusually high damage in this region corresponds with the extent of the ridge where high weak-motion amplifications are observed. We use ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) imagery to map local geomorphology, including characterization of both near-surface and of small-scale topographic structures that correspond to zones of inferred amplification.

  14. Impact of climate changes during the last 5 million years on groundwater in basement aquifers.

    Science.gov (United States)

    Aquilina, Luc; Vergnaud-Ayraud, Virginie; Les Landes, Antoine Armandine; Pauwels, Hélène; Davy, Philippe; Pételet-Giraud, Emmanuelle; Labasque, Thierry; Roques, Clément; Chatton, Eliot; Bour, Olivier; Ben Maamar, Sarah; Dufresne, Alexis; Khaska, Mahmoud; Le Gal La Salle, Corinne; Barbecot, Florent

    2015-09-22

    Climate change is thought to have major effects on groundwater resources. There is however a limited knowledge of the impacts of past climate changes such as warm or glacial periods on groundwater although marine or glacial fluids may have circulated in basements during these periods. Geochemical investigations of groundwater at shallow depth (80-400 m) in the Armorican basement (western France) revealed three major phases of evolution: (1) Mio-Pliocene transgressions led to marine water introduction in the whole rock porosity through density and then diffusion processes, (2) intensive and rapid recharge after the glacial maximum down to several hundred meters depths, (3) a present-day regime of groundwater circulation limited to shallow depth. This work identifies important constraints regarding the mechanisms responsible for both marine and glacial fluid migrations and their preservation within a basement. It defines the first clear time scales of these processes and thus provides a unique case for understanding the effects of climate changes on hydrogeology in basements. It reveals that glacial water is supplied in significant amounts to deep aquifers even in permafrosted zones. It also emphasizes the vulnerability of modern groundwater hydrosystems to climate change as groundwater active aquifers is restricted to shallow depths.

  15. Evidences of "Lago-Mare" episode around the Messinian-Pliocene boundary in eastern Tunisia (central Mediterranean)

    Science.gov (United States)

    Frigui, Mouna; Ben Youssef, Mohamed; Ouaja, Mohamed

    2016-11-01

    Eight stratigraphic sections, located in northeastern part of the Sahel area of Tunisia recorded evidences of "Lago-Mare" episode and events related to the Messinian-Late Pliocene interval. A comparison with previous studies carried on sections from neighboring areas and boreholes data drilled within the Gulf of Hammamet and the Gulf of Gabès, is conducted and gives useful information to characterize the Late Messinian to Late Pliocene events. The most notable feature distinguished in the studied area consists on the lack of gypsum, commonly recorded in relation with the crucial event of the Messinian Salinity Crisis. However, only lagoonal deposits, bearing messinian brackish fauna, are encountered. These sediments are usually attributed to the "Segui" formation or the so called "Mio-Pliocene continental". Thin sections samples and field observations have recognized sands, marls, clays, lacustrine limestone, some gypsum lenses, mud-cracks, lignite and Messinian brackish fauna. Similar deposits were previously described in the Kechabta basin from the Northern Tunisia and in some wells from the Gulf of Gabès and the Gulf of Hammamet. We suggest that all these facies belong to the coeval of the "Lago-Mare" facies within Eastern and Western Mediterranean basins (e.g. Sicily, Mallorca, Libya and Cyprus). Finally, four major erosional surfaces have been recorded within the Late Messinian-Late Pliocene deposits, aged post-Tortonian, intra-Messinian, Late Messinian and intra-Pliocene times. They seem to be the result of local tectonic uplifts and eustatic fluctuations.

  16. Impact of climate changes during the last 5 million years on groundwater in basement aquifers

    Science.gov (United States)

    Aquilina, Luc; Vergnaud-Ayraud, Virginie; Les Landes, Antoine Armandine; Pauwels, Hélène; Davy, Philippe; Pételet-Giraud, Emmanuelle; Labasque, Thierry; Roques, Clément; Chatton, Eliot; Bour, Olivier; Ben Maamar, Sarah; Dufresne, Alexis; Khaska, Mahmoud; La Salle, Corinne Le Gal; Barbecot, Florent

    2015-01-01

    Climate change is thought to have major effects on groundwater resources. There is however a limited knowledge of the impacts of past climate changes such as warm or glacial periods on groundwater although marine or glacial fluids may have circulated in basements during these periods. Geochemical investigations of groundwater at shallow depth (80–400 m) in the Armorican basement (western France) revealed three major phases of evolution: (1) Mio-Pliocene transgressions led to marine water introduction in the whole rock porosity through density and then diffusion processes, (2) intensive and rapid recharge after the glacial maximum down to several hundred meters depths, (3) a present-day regime of groundwater circulation limited to shallow depth. This work identifies important constraints regarding the mechanisms responsible for both marine and glacial fluid migrations and their preservation within a basement. It defines the first clear time scales of these processes and thus provides a unique case for understanding the effects of climate changes on hydrogeology in basements. It reveals that glacial water is supplied in significant amounts to deep aquifers even in permafrosted zones. It also emphasizes the vulnerability of modern groundwater hydrosystems to climate change as groundwater active aquifers is restricted to shallow depths. PMID:26392383

  17. Time scales of regional circulation of saline fluids in continental aquifers (Armorican massif, Western France

    Directory of Open Access Journals (Sweden)

    A. Armandine Les Landes

    2014-06-01

    Full Text Available In recent decades, saline fluids have been sampled worldwide at great depths in continental basements. Although some of them have been attributed to marine transgressions the mechanisms allowing their circulation is not understood. In this paper, we describe the horizontal and vertical distribution of moderately saline fluids (60 to 1400 mg L−1 sampled at depths ranging from 41 to 200 m in aquifers at the regional scale of the Armorican Massif (northwestern France. The horizontal and vertical distributions of high chloride concentrations are in good agreement with both the altitudinal and vertical limits and succession of the three major transgressions between the Mio-Pliocene and Pleistocene ages. The mean chloride concentration for each transgression area is exponentially related to the time spanned until present. It defines the potential laws of leaching of marine waters by fresh meteoric waters. The results of the Armorican aquifers provide the first observed constraints for the time scales of seawater circulation in the continental basement and the subsequent leaching by fresh meteoric waters. The general trend of increasing chloride concentration with depth and the time frame for the flushing process provide useful information to develop conceptual models of the paleo-functionning of Armorican aquifers.

  18. The Cape element in the Afrotemperate flora: from Cape to Cairo?

    Science.gov (United States)

    Galley, Chloe; Bytebier, Benny; Bellstedt, Dirk U; Linder, H Peter

    2007-02-22

    The build-up of biodiversity is the result of immigration and in situ speciation. We investigate these two processes for four lineages (Disa, Irideae p.p., the Pentaschistis clade and Restionaceae) that are widespread in the Afrotemperate flora. These four lineages may be representative of the numerous clades which are species rich in the Cape and also occur in the highlands of tropical Africa. It is as yet unclear in which direction the lineages spread. Three hypotheses have been proposed: (i) a tropical origin with a southward migration towards the Cape, (ii) a Cape origin with a northward migration into tropical Africa, and (iii) vicariance. None of these hypotheses has been thoroughly tested. We reconstruct the historical biogeography of the four lineages using likelihood optimization onto molecular phylogenies. We find that tropical taxa are nested within a predominantly Cape clade. There is unidirectional migration from the Cape into the Drakensberg and from there northwards into tropical Africa. The amount of in situ diversification differs between areas and clades. Dating estimates show that the migration into tropical East Africa has occurred in the last 17 Myr, consistent with the Mio-Pliocene formation of the mountains in this area.

  19. The Transylvanian Basin (Romania) and its relation to the Carpathian fold and thrust belt: Insights in gravitational salt tectonics

    Energy Technology Data Exchange (ETDEWEB)

    Krezsek, Csaba [SNGN ROMGAZ, 4 Unirii 551025 Medias (Romania); Bally, Albert W. [Department of Geology and Geophysics, University of Rice, 6100 South Main Street, Houston, TX 77005-1892 (United States)

    2006-05-15

    Interpretation of regional seismic profiles, stratigraphic and sedimentologic data improved insights in the evolution of the Transylvanian Basin. The basin evolution was coeval with the post-Mid-Cretaceous to recent deformation of the Carpathian Mts. Four tectonostratigraphic megasequences are differentiated: Upper Cretaceous (rift), Paleogene (sag), Lower Miocene (flexural basin) and Middle to Upper Miocene (backarc sequence dominated by gravitational tectonics). The Mid-Miocene continental collision in the Eastern Carpathians is associated with the rising Carpathians. This uplift enhanced the differential load, which, together with the high heat flow induced by Late Miocene to Pliocene arc volcanism, triggered large-scale Mio-Pliocene gravity spreading of the salt overburden. This 'mega-slide' comprises three structural domains, as follows: extensional weld (upslope), contractional folds (central) and contractional toe thrust (downslope). The diapirs in the east indicate a pre-shortening reactive/passive growth stage. The central folds are mostly the result of late shortening. Basement involved thrusting uplifted the toe thrust domain by the Late Pliocene. The Late Neogene to recent Carpathians uplift, backarc volcanism and gravity spreading are largely coeval. (author)

  20. The rise of ocean giants: maximum body size in Cenozoic marine mammals as an indicator for productivity in the Pacific and Atlantic Oceans

    Science.gov (United States)

    Vermeij, Geerat J.

    2016-01-01

    Large consumers have ecological influence disproportionate to their abundance, although this influence in food webs depends directly on productivity. Evolutionary patterns at geologic timescales inform expectations about the relationship between consumers and productivity, but it is very difficult to track productivity through time with direct, quantitative measures. Based on previous work that used the maximum body size of Cenozoic marine invertebrate assemblages as a proxy for benthic productivity, we investigated how the maximum body size of Cenozoic marine mammals, in two feeding guilds, evolved over comparable temporal and geographical scales. First, maximal size in marine herbivores remains mostly stable and occupied by two different groups (desmostylians and sirenians) over separate timeframes in the North Pacific Ocean, while sirenians exclusively dominated this ecological mode in the North Atlantic. Second, mysticete whales, which are the largest Cenozoic consumers in the filter-feeding guild, remained in the same size range until a Mio-Pliocene onset of cetacean gigantism. Both vertebrate guilds achieved very large size only recently, suggesting that different trophic mechanisms promoting gigantism in the oceans have operated in the Cenozoic than in previous eras. PMID:27381883

  1. Brittle tectonics and state of stress in the basin of Tizi n'Test (High Atlas, Morocco during the Tertiary inversion

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    Qarbous, A.

    2008-06-01

    Full Text Available During the Atlasic compressional phase, the Tizi n’Test Triassic basin underwent a tectonic inversion responsible for the reactivation of the extensional Triassic structures. Contrary to former concepts suggesting a transpressional regime, the NE-SW to WNW-ESE trending faults had a reverse displacement, while the NW-SE to NNW-SSE ones were reactivated as strike-slip faults. The reverse motion of the initially normal faults led to the uplift of the basin and its basement in a pop-up style. This inversion is also responsible for a set of footwall synclines and hanging wall anticlines with variable half-wavelength, and related to basement reverse faulting. Striation analysis with the help of software R4DT was carried out at 45 sites in order to determine the state of stress. The 25 most reliable tensors show that the main compressive stress £m1 trends NW-SE to NNE. Analysis of the spatial distribution of the £m1 axis shows a main maximum at N012 and two secondary axes at N123 and N147. In absence of an absolute or relative chronology of the events, we interpret these directions as related to two distinct events, the age of which should be, by comparison with other studies, pre-Mio-Pliocene for the N012 phase and Mio-Pliocene for the NW-SE phase.Durante la fase de compresión Atlásica, la cuenca Triásica de Tizi n’Test ha sufrido un proceso de inversión tectónica responsable de la reactivación de las estructuras extensionales Triásicas. A diferencia de las teorías anteriores que hablaban de un régimen transpresivo, las fallas NE-SO a ONO-ESE han sido inversas, mientras que las de direcciones NO-SE a NNO-SSE han sido reactivadas en su mayoría como fallas de desgarre. El juego inverso de las fallas inicialmente normales provocó el levantamiento de la cuenca y su zócalo paleozoico mediante un estilo de “pop-upâ€�. Esta inversión también generó un conjunto de sinclinales en los compartimientos inferiores y

  2. Impact of the Megalake Chad on climate and vegetation during the late Pliocene and the mid-Holocene

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    C. Contoux

    2013-03-01

    Full Text Available Given the growing evidence for megalakes in the geological record, assessing their impact on climate and vegetation is important for the validation of paleoclimate simulations and therefore the accuracy of model/data comparison in lacustrine environments. Megalake Chad (MLC occurrences are documented for the mid-Holocene but also for the Mio-Pliocene (Schuster et al., 2009. The surface covered by water would have reached up to ~350 000 km2 (Ghienne et al., 2002; Schuster et al., 2005; Leblanc et al., 2006 making it an important evaporation source, possibly modifying the climate and vegetation in the Chad basin. We investigated the impact of such a giant continental water area in two different climatic backgrounds within the Paleoclimate Model Intercomparison Project phase 3 (PMIP3: the late Pliocene (3.3 to 3 Ma, i.e. the mid-Piacenzian warm period and the mid-Holocene (6 kyr BP. In all simulations including a MLC, precipitation is drastically reduced above the lake surface because deep convection is inhibited by colder air above the lake surface. Meanwhile, convective activity is enhanced around the MLC, because of the wind increase generated by the flat surface of the megalake, transporting colder and moister air towards the eastern shore of the lake. Effect of the MLC on precipitation and temperature is not sufficient to widely impact vegetation patterns. Nevertheless, tropical savanna is present in the Chad Basin in all climatic configurations, even without the MLC presence, showing that the climate itself is the driver of favourable environments for sustainable hominid habitats.

  3. Depósitos epitermales de baja sulfuración ricos en sulfuros de metales base, distrito aurífero La Carolina, San Luis, Argentina

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    Gallard-Esquivel María Cecilia

    2011-12-01

    Full Text Available Low-sulfidation epithermal base-metal sulfide-rich deposits, La Carolina gold-bearing district,San Luis, Argentina. La Carolina gold-bearing district is located at the western end of the Metallogenetic Belt of San Luis, which is spatially and genetically related to the mesosilicic volcanism of mio-pliocene age. The volcanic arc experienced an eastward migration, due to the flattening of the Nazca plate in the segment 27°-33°S, known as the Pampean flat-slab. At La Carolina, the volcanic activity occurred between 8.2 and 6.3 Ma. It encompasses lavas and pyroclastics of andesitic, dacitic, latitic and trachytic composition. The mesosilicic magmas belong to normal to high-k calc-alkaline and shoshonitic suites. Structural analysis shows that previous structures have strongly controlled the emplacement of volcanic rocks and related mineral deposits at La Carolina allowing to define a pullapart.In this gold-bearing district there are eigth small mineralized prospects. The mineralogy consists of pyrite, arsenic rich pyrite, galena, sphalerite, marcasite, melnikovite, chalcopyrite, pyrrhotite, arsenopyrite, tennantitetetrahedrite, digenite, covellite, bornite, pyrargiryte, hessite, silvanite, pearceite, argirodite, gold, silver, greigite, boulangerite, jamesonite and electrum. The gangue consists of quartz, calcite, chalcedony and minor adularia.The hydrothermal alteration is widespread and comprise phyllic and argillic mineral assemblages characterized by sericite, illite, interstratified I/S, and silicic; propylitic alteration is also present as an outer halo. Fluid inclusions studies show that the formation temperatures range between 230º to 330º C. Boiling and mixing with meteoric water led to mineral precipitation. Based on the mineralogy, textures, hydrothermal alteration, formation temperatures,fluid chemistry and prospective geochemistry the mineralizations have been classified as low-sulfidation epithermal base-metal sulfide-rich deposits.

  4. Timing and sources of neogene and quaternary volcanism in South-Central Guatemala

    Science.gov (United States)

    Reynolds, James H.

    1987-08-01

    Five new and six existing radiometric age dates place constraints on the timing of volcanic episodes in a 1400-km 2 area east of Guatemala City. The source of the voluminous Miocene rhyolitic welded tuffs was the newly discovered Santa Rosa de Lima caldera, in the northern part of the area, not fissure eruptions as was previously believed. Resurgence during the Pliocene included the eruption of more silicic tuffs, followed by post-collapse volcanism around the perimeter. Volcanism in the southern part of the area occurred along the Neogene volcanic front. The sources for these Late Miocene and Pliocene andesitic lavas were not fissure eruptions, as was once believed, but were four large volcanic centers, Cerro Pinula, Ixhuatán, Teanzul, and Cerro La Gabia. The Santa Rosa de Lima caldera structure deflects the Jalpatagua Fault forming tensional fractures along which eruptions in the Quaternary Cuilapa-Barbarena cinder cone field took place. Pleistocene ash flows were erupted from Ixhuatán and Tecuamburro volcanoes in the southern part of the area. Tephras from Ayarza, Amatitlán, and Atitlán blanket the northern and central portions. Present-day activity is restricted to hot springs around the northern and eastern base of Tecuamburro volcano. Based on the work in this area it is proposed that rocks of the Miocene Chalatenango Formation throughout northern Central America were erupted from calderas behind the Neogene volcanic front. Rocks of the Mio-Pliocene Bálsamo Formation in Guatemala and El Salvador were erupted from discrete volcanic centers along the Neogene volcanic front. Pliocene rocks of the Cuscatlán Formation probably represent post-collapse volcanism around earlier caldera structures.

  5. Probing atomic scale transformation of fossil dental enamel using Fourier transform infrared and nuclear magnetic resonance spectroscopy: a case study from the Tugen Hills (Rift Gregory, Kenya).

    Science.gov (United States)

    Yi, Haohao; Balan, Etienne; Gervais, Christel; Ségalen, Loïc; Roche, Damien; Person, Alain; Fayon, Franck; Morin, Guillaume; Babonneau, Florence

    2014-09-01

    A series of fossil tooth enamel samples was investigated by Fourier transform infrared (FTIR) spectroscopy, (13)C and (19)F magic-angle spinning nuclear magnetic resonance (MAS NMR) and scanning electron microscopy (SEM). Tooth remains were collected in Mio-Pliocene deposits of the Tugen Hills in Kenya. Significant transformations were observed in fossil enamel as a function of increasing fluorine content (up to 2.8wt.%). FTIR spectroscopy revealed a shift of the ν1 PO4 stretching band to higher frequency. The ν2 CO3 vibrational band showed a decrease in the intensity of the primary B-type carbonate signal, which was replaced by a specific band at 864cm(-1). This last band was ascribed to a specific carbonate environment in which the carbonate group is closely associated to a fluoride ion. The occurrence of this carbonate defect was consistently attested by the observation of two different fluoride signals in the (19)F NMR spectra. One main signal, at ∼-100ppm, is related to structural F ions in the apatite channel and the other, at -88ppm, corresponds to the composite defect. These spectroscopic observations can be understood as resulting from the mixture of two phases: biogenic hydroxylapatite (bioapatite) and secondary fluorapatite. SEM observations of the most altered sample confirmed the extensive replacement of the bioapatite by fluorapatite, resulting from the dissolution of the primary bioapatite followed by the precipitation of carbonate-fluorapatite. The ν2 CO3 IR bands can be efficiently used to monitor the extent of this type of bioapatite transformation during fossilization.

  6. Vicariance and Its Impact on the Molecular Ecology of a Chinese Ranid Frog Species-Complex (Odorrana schmackeri, Ranidae).

    Science.gov (United States)

    Li, Yongmin; Wu, Xiaoyou; Zhang, Huabin; Yan, Peng; Xue, Hui; Wu, Xiaobing

    2015-01-01

    Paleogeological events and Pleistocene climatic fluctuations have had profound influences on the genetic patterns and phylogeographic structure of species in southern China. In this study, we investigated the population genetic structure and Phylogeography of the Odorrana schmackeri species complex, mountain stream-dwelling odorous frogs, endemic to southern China. We obtained mitochondrial sequences (1,151bp) of the complete ND2 gene and two flanking tRNAs of 511 individuals from 25 sites for phylogeographic analyses. Phylogenetic reconstruction revealed seven divergent evolutionary lineages, with mean pairwise (K2P) sequence distances from 7.8% to 21.1%, except for a closer ND2 distance (3.4%). The complex geological history of southern China drove matrilineal divergence in the O. schmackeri species complex into highly structured geographical units. The first divergence between lineage A+B and other lineages (C-G) had likely been influenced by the uplift of coastal mountains of Southeast China during the Mio-Pliocene period. The subsequent divergences between the lineages C-G may have followed the formation of the Three Gorges and the intensification of the East Asian summer monsoon during the late Pliocene and early Pleistocene. Demographic analyses indicated that major lineages A and C have been experienced recent population expansion (c. 0.045-0.245 Ma) from multiple refugia prior to the Last Glacial Maximum (LGM). Molecular analysis suggest that these seven lineages may represent seven different species, three described species and four cryptic species and should at least be separated into seven management units corresponding to these seven geographic lineages for conservation.

  7. Megalake Chad impact on climate and vegetation during the late Pliocene and the mid-Holocene

    Directory of Open Access Journals (Sweden)

    C. Contoux

    2013-07-01

    Full Text Available Given the growing evidence for megalakes in the geological record, assessing their impact on climate and vegetation is important for the validation of palaeoclimate simulations and therefore the accuracy of model–data comparison in lacustrine environments. Megalake Chad (MLC occurrences are documented not only for the mid-Holocene but also for the Mio-Pliocene (Schuster et al., 2009. At this time, the surface covered by water would have reached up to ~350 000 km2 (Ghienne et al., 2002; Schuster et al., 2005; Leblanc et al., 2006, making it an important evaporation source, possibly modifying climate and vegetation in the Chad Basin. We investigated the impact of such a giant continental water area in two different climatic backgrounds within the Paleoclimate Model Intercomparison Project phase 3 (PMIP3: the late Pliocene (3.3 to 3 Ma, i.e. the mid-Piacenzian warm period and the mid-Holocene (6 kyr BP. In all simulations including MLC, precipitation is drastically reduced above the lake surface because deep convection is inhibited by overlying colder air. Meanwhile, convective activity is enhanced around MLC because of the wind increase generated by the flat surface of the megalake, transporting colder and moister air towards the eastern shore of the lake. The effect of MLC on precipitation and temperature is not sufficient to widely impact vegetation patterns. Nevertheless, tropical savanna is present in the Chad Basin in all climatic configurations, even without MLC presence, showing that the climate itself is the driver of favourable environments for sustainable hominid habitats.

  8. Gravimetry contributions to the study of the complex western Haouz aquifer (Morocco): Structural and hydrogeological implications

    Science.gov (United States)

    Chouikri, Ibtissam; el Mandour, Abdennabi; Jaffal, Mohammed; Baudron, Paul; García-Aróstegui, José-Luis; Manar, Ahmed; Casas, Albert

    2016-03-01

    This study provides new elements that illustrate the benefits of combining gravity, structural, stratigraphic and piezometric data for hydrogeological purposes. A combined methodology was applied to the western Haouz aquifer (Morocco), one of the main sources of water for irrigation and human consumption in the Marrakech region. First, a residual anomaly map was calculated from the Bouguer anomaly data. The computed map provided information on the ground density variation, revealing a strong control by a regional gradient. We then used various filtering techniques to delineate the major geological structures such as faults and basins: vertical and horizontal derivatives and upward continuation. This technique highlighted news structures and provided information on their dip. The gravity anomalies perfectly delineated the basement uplifts and the sedimentary thickening in depressions and grabens. The interpretation of gravimetric filtering, geological and hydrogeological data then highlighted two types of groundwater reservoirs, an unconfined aquifer hosted in conglomeratic mio-pliocene and quaternary rocks, covering the entire western Haouz and a deep confined aquifer contained in cenomanian-turonian limestone and eocene dolomitic formations in the south. Combining piezometric and residual anomaly maps revealed that groundwater flow and storage was in perfect agreement with the structures showing a negative anomaly, while structures with positive anomalies corresponded to groundwater divides. The study of gravity gradient zones by contact analysis enhanced the existing structural pattern of the study area and highlighted new structures, mainly oriented N70 and N130. The results of this study present a common framework and provide a notable step forward in the knowledge of the geometry and the groundwater flow pattern of the western Haouz aquifer, and will serve as a solid basis for a better water resource management.

  9. Paratethys forcing of the Messinian Salinity Crisis

    Science.gov (United States)

    Krijgsman, Wout; Van Baak, Christiaan; Flecker, Rachel; Grothe, Arjen; Marzocchi, Alice; Stoica, Marius; Vasiliev, Iuliana

    2016-04-01

    During the Messinian Salinity Crisis (5.97-5.33 Ma), there is increasing evidence for the presence of fresh water input, not only during the final Lago-mare stage but even during times of evaporite formation. Here we present new strontium isotopic data from two well-dated Messinian sections in the Black and Caspian seas, which show remarkably similar Sr-values as the ones recorded in the Mediterranean during the final phase of the salinity crisis. This strongly suggests that a major fresh water pulse in the Mediterranean originated from the Paratethys. It highlights the importance of a Mediterranean-Black Sea connection during the entire MSC, adding an enormous drainage basin to the Mediterranean water balance. The presence of Paratethyan fauna in the Mediterranean Lago-Mare deposits has fuelled long-lasting controversies over the connectivity between the Mediterranean and Paratethys and contemporary sea level drops in both basins. We furthermore use results of sub-precessional climate simulations to calculate the freshwater budget of the Mediterranean and Paratethys in the Messinian. Using these numerical constraints, we propose a Mediterranean outflow pump as an alternative scenario for the most dramatic hydrological changes in the MSC. This "pump" mechanism significantly enhanced Paratethyan inflow to the Mediterranean, creating 1) suitable conditions for gypsum to form and 2) Lago-mare fauna to migrate and thrive. When the Mediterranean sea level finally reached the height of the Gibraltar sill, Mediterranean outflow restarted there and enhanced exchange with the Atlantic. During this reorganisation of the circulation, brackish and hypersaline waters were pumped out of the Mediterranean, and open marine conditions were re-established without major flooding at the Mio-Pliocene boundary.

  10. Arsenic concentrations in soils and sediments of the southern Pampean Plain, within Claromecó River Basin (Argentina)

    Science.gov (United States)

    Sosa, N. N.; Datta, S.; Zarate, M.

    2015-12-01

    The Pampean plain is an extensive flatland covering ~1000000 km2 of central and northern Argentina. The region, dominated by Neogene and quaternary volcanoclastic loess and loess-like deposits, shows one of the highest groundwater As concentrations of the world which cause serious problems to human health. The oxidising and high pH conditions of the Pampean groundwater leads to the dissolution of volcanic glass and Fe oxy-hydroxides and the release of As to water. Variation of As content related to lithogenic factors is evident from our study in Claromecó River Basin (Southern Pampean plain): the Mio-Pliocene fluvial facies (MPFF) show low As content (2.6mg/kg) compared to the Late Pleistocene fluvial facies (11.6mg/kg; LPFF). Furthermore, the pedogenic calcrete and the paleosols developed in fluvial facies present significantly different As content: 3.9 mg/Kg in MPFF pedogenic calcrete and 16.5 mg/Kg in LPFF paleosols. Modern soils show the highest As content, especially in the illuvial horizons (23.3 mg/Kg) controlled by grain size and clay mineralogy constituents. Preliminary results demonstrate a sedimentological control embarking differences in As concentrations. These differences are probably attributed to a major hydraulic gradient during the MPFF, which is reflected in grain size and in fluvial structures, which probably was followed by washed out sediments. A geomorphological control was observed through an increase of As concentrations from the interfluves (MPFF) to the valleys (LPFF) as well as from the upper to the lower basin zone within the LPFF. Pedogenic calcrete and paleosols developed in MPFF and LPFF respectively reflect the different geomorphological conditions showing high As content in LPFF paleosols (attributed to Fe oxy-hydroxides). This study relates mineralogy and sedimentological environment to groundwater, surface water from wetlands to understand the hydrochemical processes in controlling As within the Claromecó basin.

  11. Inherited weaknesses control deformation in the flat slab region of Central Argentina

    Science.gov (United States)

    Stevens, A.; Carrapa, B.; Larrovere, M.; Aciar, R. H.

    2015-12-01

    The Sierras Pampeanas region of west-central Argentina has long been considered a geologic type-area for flat-slab induced thick-skinned deformation. Frictional coupling between the horizontal subducting plate and South American lithosphere from ~12 Ma to the present provides an obvious causal mechanism for the basement block uplifts that characterize this region. New low temperature thermochronometry data show basement rocks from the central Sierras Pampeanas (~ longitude 66 ̊ W) including Sierras Cadena de Paiman, Velasco and Mazan retain a cooling history of Paleozoic - Mesozoic tectonics events. Results from this study indicate that less than 2 km of basement has been exhumed since at least the Mesozoic. These trends recorded by both apatite fission track (AFT) and apatite helium (AHe) thermochronometry suggest that recent Mio-Pliocene thick-skinned deformation associated with flat-slab subduction follow inherited zones of weakness from Paleozoic terrane sutures and shear zones and Mesozoic rifting. If a Cenozoic foreland basin exisited in this region, its thickness was minimal and was controlled by paleotopography. Pre-Cenozoic cooling ages in these ranges that now reach as high as 4 km imply significant exhumation of basement rocks before the advent of flat slab subduction in the mid-late Miocene. It also suggests that thick-skinned deformation associated with flat slab subduction may at least be facilitated by inherited crustal-scale weaknesses. At the most, pre-existing zones of weakness may be required in regions of thick-skinned deformation. Although flat-slab subduction plays an important role in the exhumation of the Sierras Pampeanas, it is likely not the sole mechanism responsible for thick-skinned deformation in this region. This insight sheds light on the interpretation of modern and ancient regions of thick-skinned deformation in Cordilleran systems.

  12. Vicariance and Its Impact on the Molecular Ecology of a Chinese Ranid Frog Species-Complex (Odorrana schmackeri, Ranidae.

    Directory of Open Access Journals (Sweden)

    Yongmin Li

    Full Text Available Paleogeological events and Pleistocene climatic fluctuations have had profound influences on the genetic patterns and phylogeographic structure of species in southern China. In this study, we investigated the population genetic structure and Phylogeography of the Odorrana schmackeri species complex, mountain stream-dwelling odorous frogs, endemic to southern China. We obtained mitochondrial sequences (1,151bp of the complete ND2 gene and two flanking tRNAs of 511 individuals from 25 sites for phylogeographic analyses. Phylogenetic reconstruction revealed seven divergent evolutionary lineages, with mean pairwise (K2P sequence distances from 7.8% to 21.1%, except for a closer ND2 distance (3.4%. The complex geological history of southern China drove matrilineal divergence in the O. schmackeri species complex into highly structured geographical units. The first divergence between lineage A+B and other lineages (C-G had likely been influenced by the uplift of coastal mountains of Southeast China during the Mio-Pliocene period. The subsequent divergences between the lineages C-G may have followed the formation of the Three Gorges and the intensification of the East Asian summer monsoon during the late Pliocene and early Pleistocene. Demographic analyses indicated that major lineages A and C have been experienced recent population expansion (c. 0.045-0.245 Ma from multiple refugia prior to the Last Glacial Maximum (LGM. Molecular analysis suggest that these seven lineages may represent seven different species, three described species and four cryptic species and should at least be separated into seven management units corresponding to these seven geographic lineages for conservation.

  13. Tectonic evolution of the El Salvador Fault Zone. Insights from analogue experiments.

    Science.gov (United States)

    Alonso-Henar, Jorge; Schreurs, Guido; Jesús Martínez-Díaz, José; Álvarez-Gómez, José Antonio

    2014-05-01

    The El Salvador Fault Zone (ESFZ) is an active, c. 150 km long and 20 km wide segmented, dextral strike-slip fault zone within the El Salvador Volcanic Arc striking N90°-100°E. Although several studies have investigated the surface expression of the ESFZ, little is known about its structure at depth and its kinematic evolution. Our analysis of structural field data, remote sensing images and morphometric indices reveals a trenchward migration of the volcanic arc and furthermore suggests that not all structures within the ESFZ can be explained within the current tectonic context, but require a phase of extension or an extensional component of deformation at some stage in the evolution of the ESFZ. Such an extension and trenchward migration of the volcanic arc could be related to subduction roll-back of the Cocos Plate beneath the Chortis Block in Mio-Pliocene times. Such a possible evolution leads to open questions that we address in our research: Is the ESFZ a neo-formed fault zone, i.e. did it form during one phase of strike-slip or transtensional deformation, or do the structures in the ESFZ reflect a two-phase evolution, i.e. an early phase of extension overprinted by a later phase of strike-slip or transtension? Did subduction roll-back occur beneath El Salvador? We carried out analogue model experiments to test whether or not an early phase of extension is required to form the present-day fault pattern in the ESFZ. Analogue modeling is an effective tool in testing various hypotheses, as it allows the experimenter to control specific parameters and to test their influence on the resulting structures. Our experiments suggest that a two-phase tectonic evolution best explains the ESFZ: an early pure extensional phase linked to a segmented volcanic arc is necessary to form the main structures of the ESFZ and can explain the shallow geometry of the fault zone. This extensional phase is followed by a strike-slip dominated regime, which results in inter

  14. Tectonic activity revealed by morphostructural analysis: Development of the Sierra de la Candelaria range, northwestern Argentina

    Science.gov (United States)

    Barcelona, H.; Peri, G.; Tobal, J.; Sagripanti, L.; Favetto, A.

    2014-12-01

    The tectonically active broken foreland of NW Argentina is a recent analog of the eastern margin of the Puna plateau during Mio-Pliocene times and likely of other broken forelands worldwide. In order to evaluate active tectonism in the broken foreland of the NW Argentine Andes, we examined the complex geomorphology in the vicinity of the basement-cored Sierra de la Candelaria range at ˜26°S and deciphered multiple episodes of crustal deformation spanning the Pliocene to the Quaternary. Digital elevation models, satellite images and geological data within a GIS environment allowed us to analyze the terrain, drainage networks, river dynamics and structure, as well as to obtain detailed geomorphological mapping, active tectonic indices, longitudinal river profiles and structural sections. Three morphostructural segments were defined based on the structural features, the differential vertical dissection pattern over the basement, the faulted Pliocene to recent deposits, the stepwise propagation of anticlines and the distortion over the fluvial system. By combining the several lines of evidence, we concluded that the Sierra de la Candelaria range was subjected to a multi-stage development. The first stage uplifted the central segment concomitant with the formation of the surrounding ranges and with the main partition phase of the foreland. After a significant time lapse, the mountain range was subjected to southward thick-skinned growth and northward growth via stepwise thin-skinned deformation and exerted control over the dynamics of the Río Rosario. Taking into account the surrounding basins and ranges of the Sierra de la Candelaria, the southern Santa Bárbara System is characterized by partially isolated intramontane basins (Choromoro and Rosario) limited by shielded ranges that caused moisture block and shows continuous deformation. These features were related to early stages of a broken foreland evolution model and modern analogs were found at the northern

  15. Past changes of the North African monsoon intensity between 5 and 6.2 My, impact of the Messinian Salinity Crisis (MSC)

    Science.gov (United States)

    Ségueni, F.; Colin, C.; Siani, G.; Frank, N.; Blamart, D.; Kissel, C.; Liu, Z.; Richter, T.; Suc, J.

    2006-12-01

    A high resolution multiproxy study by oxygen isotope record (δ18O) on benthic foraminifera (Cibicides wuellerstorfii), magnetic susceptibility, clay mineralogy (DRX), major - trace elements (XRF core scanner and ICPMS) and Rb/Sr - Nd isotopes was carried out from site ODP 659 along the Cape Verde off Africa. The aim was to reconstruct variations of African Monsoon during the Mio-Pliocene in the time interval from 5 My to 6,2 My. Chronology was established by linear interpolation between 3 bio-events based on calcareous nannoplancton zones, 2 glacial stages TG12 and TG22 identified on δ18O records and by tuning the δ18O and magnetic susceptibility records to the orbital parameter of obliquity and precession. Results indicate that between 5 to 6.2 My variability in the eolian input from Sahara and the coastal upwelling intensity are anti-correlated and make it possible to retrace the evolution of northern African Monsoon. The latter co- varies mainly with the insolation received by the earth at low latitude during the summer. Maximal insolation enhance summer monsoonal effects by increasing wetter conditions on Sahel and NE dominance wind system cause a reduced eolian input and an increased biogenic sea surface productivity by coastal upwelling. On the other hand, minimal insolation reinforce winter monsoon that create a more arid climate on Sahel and stronger westward winds that increase eolian flux on Cap Verde with a reduced upwelling effect on sea surface productivity. At a longer time scale, the end of the MSC is correlated with a major change of the African Monsoon intensity. Finally, the δ18O record on C.wuellerstorfii suggests that global eustatic processes didn't play a key role in the MSC history. Nevertheless, transition between glacial stage TG12 and the interglacial TG11 seems to correspond to a major event within the MSC, and associated to the beginning of the upper evaporite deposits. Thus, the facies of the Lago Mare of the upper evaporites would

  16. Using 10Be cosmogenic surface exposure dating to determine the evolution of the Purgatorio active fault in the Andean forearc, southern Peru

    Science.gov (United States)

    Carlos, Benavente; Swann, Zerathe; Laurence, Audin; Fabrizio, Delgado; Marianne, Saillard; Sarah, Hall R.; Aster Team

    2015-04-01

    Active transpressive deformation has been occurring along the Andean hyperarid forearc for the last 3 Myrs but many of these faults are still not described even if able to produce large damaging earthquakes. Active faulting along the northern part of the Arica Bend can be recognized due to the presence of well-preserved and sharp fault scarps indicating recent surface slip. During the Mio-Pliocene, deposition within the forearc continental basins resulted in the formation of vast fan deposits and conglomerates of the Moquegua Formation, which can be considered as bedrock in this exposure study (~45-4 Ma; Tosdal et al., 1984; Sebrier et al., 1988a; Roperch et al., 2006). The typical vertical Purgatorio fault scarps offset both the Moquegua bedrock and several younger geomorphic features associated with Moquegua formation outcroping vertically along the fault scarp. These samples are well-suited to the application of in situ produced cosmogenic radionuclides for surface exposure dating, as the hyperarid region has extremely low erosion rates. We sampled the scarp away from any significant drainage so as to avoid possibly disturbed areas. The sampling did involve extracting quarzite conglomeratic material along the bedrock scarp and on the upper surrounding crests. The aim has been to measure Berylium-20 TCN (Terrestrial in situ Cosmogenic Nuclides) concentrations to determine exposure age as a function of height on the scarp. This has been successfully employed on one scarp in Italy based on Chlorine-36 TCN (Palumbo et al., 2004). However, slow faults behaviour remains unclear and more contributions are needed. Quaternary activity of the Purgatorio fault system was evidenced by Hall et al. (2008). They highlighted a vertical offset of about ~100 m for a pediment surface intercepted by the fault, and dated at ~280 ka. Considering that the pediment surface is horizontal, this would gave a maximum of ~0.3 mm/yr of vertical deformation since 280 ka. Our new data provide

  17. Eroding and Inflating the Atacama Desert, Chile: Insights Through Cosmogenic 10-Be, 26-Al and 21-Ne

    Science.gov (United States)

    Heimsath, A. M.; Jungers, M. C.; Amundson, R.; Balco, G.; Shuster, D. L.

    2010-12-01

    quantify surface chronologies as well as the processes shaping these unusual landscapes. To do so we have combined standard surface exposure dating with an application of the burial and profile-dating methodology to surfaces that are expanding by salt inflation. Profiles of these nuclides are used to test simple end-member models for the timescale of surface inflation and initial results support Mio-Pliocene ages for landscapes previously dated by other methods. We also use profiles and burial-age methods to date and better estimate potential inheritance in the nuclide signals for extensive cobble deposits thought to originate from the Andes prior to the onset of hyperaridity. Preliminary results support Miocene deposition, which may suggest a significantly more recent onset time for hyperaridity than others have estimated.

  18. Are There High Meteorite Concentrations in the Atacama Desert/Chile?

    Science.gov (United States)

    Scherer, P.; Delisle, G.

    1992-07-01

    We have visited numerous regions of the Atacama desert between Copiapo (27 degrees, 15'S) and Calama (22 degrees, 25'S) to assess their potential as a high-yield meteorite concentration surface, easily exploitable by search efforts within a reasonable time frame. According to our observations, this desert is characterized by the following features: a) A high percentage of the desert consists of sloping surfaces on which soil movement occurs, presumably by very infrequent, though heavy rain. b) Vast areas of the desert are covered by a dm-thick sand layer of dark colour. Since the sand is too coarse-grained to be transported by wind it presumably resulted from in-situ weathering of rock debris derived from nearby mountains. We suspect that impacting smaller objects can easily penetrate the sand layer. c) The sand layer is typically dotted by rocks, fist-size or smaller, that are covered by a thick layer of desert paint (reddish-brown to black colour). Most country rocks are of volcanic origin (rhyolite, andesite, basalt) and are typically of grey to black colour. A noticeable colour contrast in particular to potential stony meteorites is almost nonexistent. d) Soil salts with a potential to speed up weathering processes are ubiquitous near the surface. e) The Pampa de Mejillones, 45 km north of Antofagasta, is one of the few light-coloured areas in the Atacama desert. The surface, being of Mio-Pliocene age, consists of an almost continuous layer of light-brown fossil shells (bivalves and gastropodes). Fluvially transported dark rocks from adjacent outcrops rest on top. The latter material is covered again by desert paint. Few meteorite discoveries have been reported from this area (Pampa (a),(b),(c)). f) Numerous old tire tracks, in particular around mines in operation, crisscross most areas of the Atacama. Undetected objects such as large masses of iron bodies are not likely to have remained undiscovered in great numbers any more. We conclude that the potential of

  19. Quaternary Deformation of Sumba, Indonesia: Evidence from Carbonate Terraces

    Science.gov (United States)

    Dahlquist, M. P.; West, A. J.; Dolan, J. F.

    2014-12-01

    The Banda Arc of Indonesia remains one of the least understood tectonic domains on the modern Earth. The island of Sumba, located approximately 50 km south of Flores and 120 km north of the Java Trench, northwest of where it transitions into the Timor Trough, lies in a region of tectonic transition and potentially offers insights into regional dynamics. The Banda Arc is volcanically active, but Sumba itself is not volcanic. The northern coast of Sumba is covered in Quaternary coral terraces, with the rest of the island's surface geology composed of Mio-pliocene carbonates and uplifted Late Cretaceous-Oligocene forearc basin and volcanic rocks. The purpose of this study is to remotely map the topographic expression of the coral terraces and use the information gained to better understand deformation on Sumba since their deposition. The ages of the coral terraces, of which many platforms are exposed over significant areas of the island, have been constrained at Cape Luandi in north central Sumba, but uplift rates calculated from those ages may not be representative of the island as a whole. The lateral continuity of these dated terraces can help constrain the extent to which uplift of Sumba is spatially variable. Analysis of the terraces using SRTM digital elevation data with ArcGIS software makes it possible to trace the same terrace platforms over large distances, and shows that the north central part of the island has experienced the most uplift since the deposition of the terraces, forming an anticline with the east limb dipping more steeply than the west. The terraces are not well preserved on the southern half of the island. Exposure of older rocks and lack of terrace preservation, as well as a south-skewed drainage divide suggests the southern half of the island experiences greater exhumation, but this could be driven by climate or other factors and does not necessarily indicate more rapid uplift. Study of Quaternary deformation of Sumba can offer greater

  20. Extreme extension across Seram and Ambon, eastern Indonesia: evidence for Banda slab rollback

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    Pownall, J. M.; Hall, R.; Watkinson, I. M.

    2013-09-01

    The island of Seram, which lies in the northern part of the 180°-curved Banda Arc, has previously been interpreted as a fold-and-thrust belt formed during arc-continent collision, which incorporates ophiolites intruded by granites thought to have been produced by anatexis within a metamorphic sole. However, new geological mapping and a re-examination of the field relations cause us to question this model. We instead propose that there is evidence for recent and rapid N-S extension that has caused the high-temperature exhumation of lherzolites beneath low-angle lithospheric detachment faults that induced high-temperature metamorphism and melting in overlying crustal rocks. These "Kobipoto Complex" migmatites include highly residual Al-Mg-rich garnet + cordierite + sillimanite + spinel + corundum granulites (exposed in the Kobipoto Mountains) which contain coexisting spinel + quartz, indicating that peak metamorphic temperatures likely approached 900 °C. Associated with these residual granulites are voluminous Mio-Pliocene granitic diatexites, or "cordierite granites", which crop out on Ambon, western Seram, and in the Kobipoto Mountains and incorporate abundant schlieren of spinel- and sillimanite-bearing residuum. Quaternary "ambonites" (cordierite + garnet dacites) emplaced on Ambon were also evidently sourced from the Kobipoto Complex migmatites as demonstrated by granulite-inherited xenoliths. Exhumation of the hot peridotites and granulite-facies Kobipoto Complex migmatites to shallower structural levels caused greenschist- to lower-amphibolite facies metapelites and amphibolites of the Tehoru Formation to be overprinted by sillimanite-grade metamorphism, migmatisation, and limited localised anatexis to form the Taunusa Complex. The extreme extension required to have driven Kobipoto Complex exhumation evidently occurred throughout Seram and along much of the northern Banda Arc. The lherzolites must have been juxtaposed against the crust at typical

  1. Doubts and Speculation of the Use of Stone Balls%石球用途的质疑与猜测

    Institute of Scientific and Technical Information of China (English)

    司新国

    2012-01-01

    The stone ball is one of common important stoneware types in the Paleolithic site. The stone ball is the first product of labor of Australopithecus undoubtedly, But we have no reason to think of the Australopithecus creating any objects as tools. Worship of the sun and the moon and the fruit may become the power of Australopithecus building stone balls.%石球是旧石器时代遗址中常见的、重要的石器类型之一。石球无疑是古猿的最初劳动产品,但我们没有理由把古猿创造的任何器物都视为工具。对日月的崇拜、对果实的崇拜有可能成为古猿打造石球的动力。

  2. Development of the palatal size in Pan troglodytes, Hominids and Homo sapiens.

    Science.gov (United States)

    Arnold, W H; Zoellner, A; Sebastian, T

    2004-12-01

    As the hard palate plays an important role in speech production it was the aim of this study whether similarities or dissimilarities in palatal size may allow conclusions about the ability to produce speech in the extant investigated species. The palatal size of Pan troglodytes, Homo sapiens, Australopithecus afarensis, Australopithecus africanus, Australopithecus robustus, Australopithecus boisei, Homo erectus, Homo neanderthalensis and Cro-Magnon has been investigated using euclidian distance matrix analysis (EDMA) and thin-plate-spline analysis. The results show that the palatal size of all australopithecine specimens and H. erectus is very similar to that of P toglodytes, whereas the palatal size of H. neanderthalensis more closely resembles that of H. sapiens. Postnatal development of palatal size in P troglodytes is different from that of H. sapiens. In P troglodytes not only the size of the palate changes but also the form. In H. sapiens there is little change in form, but a continuos uniform growth from infantile to adult specimens. From the results we conclude that in all australopithecine samples which have been investigated, the palatal size is similar to that of P troglodytes. Therefore, it is unlikely that austraopithecine individuals were capable of producing vowels and consonants. The palatal size of H. neandethalensis and Cro-Magnon is similar to that of H. sapiens which may indicate the possibility that they were capable of speech production.

  3. New hominin fossils from Kanapoi, Kenya, and the mosaic evolution of canine teeth in early hominins

    Directory of Open Access Journals (Sweden)

    J. Michael Plavcan

    2012-03-01

    Full Text Available Whilst reduced size, altered shape and diminished sexual dimorphism of the canine–premolar complex are diagnostic features of the hominin clade, little is known about the rate and timing of changes in canine size and shape in early hominins. The earliest Australopithecus, Australopithecus anamensis, had canine crowns similar in size to those of its descendant Australopithecus afarensis, but a single large root alveolus has suggested that this species may have had larger and more dimorphic canines than previously recognised. Here we present three new associated dentitions attributed to A. anamensis, recently recovered from the type site of Kanapoi, Kenya, that provide evidence of canine evolution in early Australopithecus. These fossils include the largest mandibular canine root in the hominin fossil record. We demonstrate that, although canine crown height did not differ between these species, A. anamensis had larger and more dimorphic roots, more like those of extant great apes and Ardipithecus ramidus, than those of A. afarensis. The canine and premolar occlusal shapes of A. anamensis also resemble those of Ar. ramidus, and are intermediary between extant great apes and A. afarensis. A. afarensis achieved Homo-like maxillary crown basal proportions without a reduction in crown height. Thus, canine crown size and dimorphism remained stable during the early evolution of Australopithecus, but mandibular root dimensions changed only later within the A. anamensis–afarensis lineage, coincident with morphological changes in the canine–premolar complex. These observations suggest that selection on canine tooth crown height, shape and root dimensions was not coupled in early hominin evolution, and was not part of an integrated adaptive package.

  4. Lucy's flat feet: the relationship between the ankle and rearfoot arching in early hominins.

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    Jeremy M DeSilva

    Full Text Available BACKGROUND: In the Plio-Pleistocene, the hominin foot evolved from a grasping appendage to a stiff, propulsive lever. Central to this transition was the development of the longitudinal arch, a structure that helps store elastic energy and stiffen the foot during bipedal locomotion. Direct evidence for arch evolution, however, has been somewhat elusive given the failure of soft-tissue to fossilize. Paleoanthropologists have relied on footprints and bony correlates of arch development, though little consensus has emerged as to when the arch evolved. METHODOLOGY/PRINCIPAL FINDINGS: Here, we present evidence from radiographs of modern humans (n = 261 that the set of the distal tibia in the sagittal plane, henceforth referred to as the tibial arch angle, is related to rearfoot arching. Non-human primates have a posteriorly directed tibial arch angle, while most humans have an anteriorly directed tibial arch angle. Those humans with a posteriorly directed tibial arch angle (8% have significantly lower talocalcaneal and talar declination angles, both measures of an asymptomatic flatfoot. Application of these results to the hominin fossil record reveals that a well developed rearfoot arch had evolved in Australopithecus afarensis. However, as in humans today, Australopithecus populations exhibited individual variation in foot morphology and arch development, and "Lucy" (A.L. 288-1, a 3.18 Myr-old female Australopithecus, likely possessed asymptomatic flat feet. Additional distal tibiae from the Plio-Pleistocene show variation in tibial arch angles, including two early Homo tibiae that also have slightly posteriorly directed tibial arch angles. CONCLUSIONS/SIGNIFICANCE: This study finds that the rearfoot arch was present in the genus Australopithecus. However, the female Australopithecus afarensis "Lucy" has an ankle morphology consistent with non-pathological flat-footedness. This study suggests that, as in humans today, there was variation in arch

  5. Neogene Uplift and Exhumation of Plutonic Bodies in the Beni Bou Ifrour Massif (Nador, northeastern Morocco)

    Science.gov (United States)

    Lebret, Noëmie; Jolivet, Laurent; Branquet, Yannick; Bourdier, Jean-Louis; Jolivet, Marc; Marcoux, Eric

    2013-04-01

    In Neogene times, the whole Mediterranean Sea was the center of an intense magmatic activity. This post-collisional magmatism produced a large amount of volcanic edifices through the Alpine belts, together with some intrusives. These plutonic bodies can be associated with skarn-type mineralization, well-known in Elba Island or Serifos Island (Cyclades), where they are generally exhumed by detachment faults. In Morocco, the plutons hosted by the Beni Bou Ifrour massif are connected to the biggest skarn-type iron concentrations of the country (production > 60 Mt, reserves ≈ 25 Mt). The purpose of this work is to explain the late uplift of this massif and subsequent exhumation of the intrusives. As a final product of the Africa-Eurasia plate convergence since ca. 70 Ma, the Rif Mountains constitute the westernmost segment of the Mediterranean Alpine belts. In the oriental part of this range, volcanic summits and Paleozoic to Mesozoic massifs outcrop in the surrounding Mio-Pliocene plains. The Beni Bou Ifrour massif, in the Nador province, consists in a dome-shaped folded Mesozoic series (Domerian to Barremian) affected by a slight epizonal regional metamorphism (ca. 14-12 Ma), dislocated by Neogene NE-SW faults and eventually sealed by upper Miocene transgressive sediments. The hosted intrusives (7.58 ± 0.03 Ma; Duggen et al., 2005) are the plutonic equivalents to the potassic calc-alkaline lavas (andesites mainly) from the surrounding "satellite" volcanic massifs. They turn out to stand in higher topographic position than the younger shoshonitic lavas of the neighboring Gourougou stratovolcano (6.12 ± 0.01 Ma; Duggen et al., 2005). Previous studies have attributed this uplift to the action of normal faults (pull-apart basins; Guillemin & Houzay, 1982), thrusting (Kerchaoui, 1985; 1995) or even of a caldeira resurgence (El Bakkali, 1995). To discriminate against those exhumation mechanisms, field work has been performed, coming along with new cross-sections to

  6. New Constraints on the Timing and Magnitude of Deformation and Basin Exhumation in the Eastern Cordillera of NW Argentina.

    Science.gov (United States)

    Trimble, J. D.; Carrapa, B.; Stockli, D. F.; Stutz, J.

    2008-12-01

    could be potentially related to the reactivation of Cretaceous relay-zone structures. Flexural-slip folding is the dominant mechanism of folding within the basin, with centimeter to meter scale fracture-rich and slickenside-rich beds of fine silts acting as primary slip-surfaces between thicker, more competent beds of coarse sand and conglomerate. A newly discovered intra-formational angular unconformity near the base of the Angastaco Fm. documents growth during the early stages of deposition. However, there is no clear evidence of continuous growth up section, implying at least two pulses of significant deformation during syn- and post- Miocene time. New apatite (U-Th)/He thermochronology (AHe) from six samples from the Eocene-Oligocene(?) Quebrada de los Colorados Fm and the Miocene Angastaco Fm (~18 Ma) in the Angastaco and surrounding Pucara and Tin Tin basins yields youngest ages between ca. 13.2 Ma (to the west) and ca. 10.3 Ma (to the east), and correlate with low Uranium content. We interpret these ages as representative of cooling following basin exhumation in the Miocene. The younging of those ages towards the east, together with structural data indicating young Mio-Pliocene deformation, suggests that those ages may be the result of eastward propagation of deformation into the foreland driving basin exhumation.

  7. Modeling along-axis variations in fault architecture in the Main Ethiopian Rift: implications for Nubia-Somalia kinematics

    Science.gov (United States)

    Erbello, Asfaw; Corti, Giacomo; Sani, Federico; Kidane, Tesfaye

    2016-04-01

    The Main Ethiopian Rift (MER), at the northern termination of the East African Rift, is an ideal locale where to get insights into the long-term motion between Nubia and Somalia. The rift is indeed one of the few places along the plate boundary where the deformation is narrow: its evolution is thus strictly related to the kinematics of the two major plates, whereas south of the Turkana depression a two-plate model for the EARS is too simplistic as extension occurs both along the Western and Eastern branches and different microplates are present between the two major plates. Despite its importance, the kinematics responsible for development and evolution of the MER is still a matter of debate: indeed, whereas the Quaternary-present kinematics of rifting is rather well constrained, the plate kinematics driving the initial, Mio-Pliocene stages of extension is still not clear, and different hypothesis have been put forward, including: polyphase rifting, with a change in direction of extension from NW-SE extension to E-W extension; constant Miocene-recent NW-SE extension; constant Miocene-recent NE-SW extension; constant, post-11 Ma extension consistent with the GPS-derived kinematics (i.e., roughly E-W to ESE-WNW). To shed additional light on this controversy and to test these different hypothesis, in this contribution we use new crustal-scale analogue models to analyze the along-strike variations in fault architecture in the MER and their relations with the rift trend, plate motion and the resulting Miocene-recent kinematics of rifting. The extension direction is indeed one of the most important parameters controlling the architecture of continental rifts and the relative abundance and orientation of different fault sets that develop during oblique rifting is typically a function of the angle between the extension direction and the orthogonal to the rift trend (i.e., the obliquity angle). Since the trend of the MER varies along strike, and consequently it is

  8. Parametric study of the impact of waste pollutants on groundwater: the case of Abidjan District (Ivory Coast)

    Science.gov (United States)

    Agnès Kouamé, Amenan; Jaboyedoff, Michel; Tacher, Laurent; Derron, Marc-Henri; Franz, Martin

    2015-04-01

    Abidjan like numerous African cities is experiencing a significant and uncontrolled population growth. The annual growth rate is estimated at 3.99% by the National Institute of Statistics. This rapid population growth also generates growing needs in general and especially for drinking water and economic activities. In the District of Abidjan, groundwater comes from the Mio-Pliocene age aquifer called "Continental Terminal". This unconfined aquifer is the main source of water supply. Its lithology consists of four levels. Actually only the two upper levels outcrop and constitute the main part of the Continental Terminal aquifer. Some recent studies report a potential overexploitation and pollution of Abidjan groundwater (Jourda, 1986, Kouame 2007, Deh, 2013). This deterioration in water quality could be due to the release of domestic and industrial waste water, pesticide and fertilizer from crops and toxic waste sites containing high doses of organochlorines, of hydrogen sulfide and sulfides. This risk is also linked to the economic activities such as car workshops, gas stations and the sand exploitation in the lagoon. To observe the likely evolution of such contaminants in the subsurface and we developed hydrogeological models that couple groundwater flow and transport with FEFLOW software. The model is composed of a sandy layer where two constant hydraulic heads of 55 m and 0.2 m are imposed on the north and the south respectively. We carried out grain size analysis of some samples (E2, E3, E4, E5, and E6) which shows particle size ranging between 0.0001 mm and 8 mm. This grain size analysis performed by sieving underwater and laser indicates that these five soils are: loamy sand with traces of clay and gravel for E2 and E5; Sandy loam with traces of clay for E3; Sand with traces of clay and gravel for E4 and Sand with traces of silt and clay for E6. Their porosity and average values of permeability coefficient K measured in the laboratory range from 0.2 to 0

  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

    Science.gov (United States)

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

    2016-09-01

    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. Crustal structure of Tolfa domes complex (northern Latium - Italy) inferred from receiver functions analysis: an interplay between tectonics and magmatism

    Science.gov (United States)

    Buttinelli, M.; Bianchi, I.; Anselmi, M.; Chiarabba, C.; de Rita, D.; Quattrocchi, F.

    2010-12-01

    The Tolfa-Cerite volcanic district developed along the Tyrrhenian passive margin of central Italy, as part of magmatic processes started during the middle Pliocene. In this area the uncertainties on the deep crustal structures and the definition of the intrusive bodies geometry are focal issues that still need to be addressed. After the onset of the spreading of the Tyrrhenian sea during the Late Miocene, the emplacement of the intrusive bodies of the Tolfa complex (TDC), in a general back-arc geodynamical regime, generally occurred in a low stretching rate, in correspondence of the junctions between major lithospheric discontinuities. Normal faults, located at the edge of Mio-Pliocene basins, were used as preferential pathways for the rising of magmatic masses from the mantle to the surface. We used teleseismic recordings at the TOLF and MAON broad band station of the INGV seismic network (located between the Argentario promontory and Tolfa-Ceriti dome complexes -TDC-) to image the principal seismic velocity discontinuities by receiver function analysis (RF's). Together with RF’s velocity models of the area computed using the teleseismic events recorded by a temporary network of eight stations deployed around the TDC, we achieve a general crustal model of this area. The geometry of the seismic network has been defined to focus on the crustal structure beneath the TDC, trying to define the main velocity changes attributable to the intrusive bodies, the calcareous basal complex, the deep metamorphic basement, the lower crust and the Moho. The analysis of these data show the Moho at a depth of 23 km in the TDC area and 20 km in the Argentario area. Crustal models also show an unexpected velocity decrease between 12 and 18 km, consistent with a slight dropdown of the Vp/Vs ratio, imputable to a regional mid-crustal shear zone inherited from the previous alpine orogenesis, re-activated in extensional tectonic by the early opening phases of the Tyrrhenian sea. Above

  11. New insights into the evolution of central Tyrrhenian margin of Italy (northern Latium off-shore area): evidences and constraints from seismic data interpretation

    Science.gov (United States)

    Buttinelli, M.; Vico, G.; Scrocca, D.; Petracchini, L.; de Rita, D.

    2009-04-01

    the formation of several small and narrow graben and half-graben basins with NW-SE and NE-SW direction of elongation, filled with up to 600m of conglomeratic, sandy and clayish sediments and a regional unconformity surface on top of the deformed basement. The sedimentation continued with the trasgressive deposition of the Plio-Pleitocene clayish units, separated by a Middle Pliocene unconformity; iii) a final stage of deformation, strictly localized around the Late Pliocene volcanic intrusions of the Tolfa and Ceriti dome complexes. This is associated with local uplift (up to 200m), normal faulting, and radial tilting of the sedimentary units strata of the Mio-Pliocene sedimentary units in the on-shore graben and half-graben filled basins, analogous to the geological setting of the basins recognised in the off-shore part of this area. Gravimetric and Magnetic anomaly data also suggest the possible presence of an off-shore intrusion just in front of the coastline of Civitavecchia city. Seismic reflection data analysis show in the same place a local perturbation of the sedimentation regime of the Plio-Pleistocene units due to the local change of basin morphology.

  12. Analyse quantitative du réseau hydrographique du bassin versant du Slănic (Roumanie

    Directory of Open Access Journals (Sweden)

    Florina Grecu

    2007-12-01

    Full Text Available L'étude porte sur le bassin versant du Slănic, un affluent du Buzău. Ce bassin de taille relativement réduite (433 km2 est situé dans la région des Carpates et des Subcarpates de la Courbure, région très active sur le plan sismique. Du point de vue lithologique, le bassin du Slănic correspond à des flyschs paléogènes et à des molasses mio-pliocènes. Ces roches peu résistantes ont facilité une forte érosion du relief. Actuellement, les précipitations présentent souvent une forte intensité, et elles se produisent fréquemment après des périodes de sécheresse. Elles sont ainsi très agressives et déclenchent une érosion intense. L'analyse de quelques paramètres morphométriques [grand nombre de segments de cours d'eau d'ordres 1 (5230 et 2 (944 ; densité élevée des segments par rapport à la superficie du bassin (environ 15 segments / km2 ; longueur moyenne réduite des segments d'ordre 1 (260 m par rapport à ceux d'ordre 2 (530 m] s'accorde avec des temps de concentration des eaux courts et une forte énergie des écoulements. La vitesse de réaction aux précipitations des segments d'ordres inférieurs est en outre favorisée par la répartition spatiale des pluies et par les conditions lithologiques.The study is focused on the Slănic basin which has a small size (433 km2. The hydrographical basin of Slănic, situated in the Carpathian and Subcarpathian Curvature, a very active from neotectonical viewpoint area, is a part of the Buzău basin. From a petrographic point of view, the Slănic hydrographic basin belongs to the paleogen flysch deposits (within the Carpathian sector and to the mio-pliocen molasse (within the Subcarpathian area latter formed by predominantely friable rocks which have encouraged deep fragmentation of the relief. Actual rainfalls are often very intensive, and they frequently occur after dry seasons. The analysis of morphometric parameters shows many elementary segments of first

  13. Integrative geomorphological mapping approach for reconstructing meso-scale alluvial fan palaeoenvironments at Alborz southern foothill, Damghan basin, Iran

    Science.gov (United States)

    Büdel, Christian; Majid Padashi, Seyed; Baumhauer, Roland

    2013-04-01

    Alluvial fans and aprons are common depositional features in general Iranian geomorphology. The countries major cities as well as settlements and surrounding area have often been developed and been built up on this Quaternary sediment covers. Hence they periodically face the effects of varying fluvial and slope-fluvial activity occurring as part of this geosystem. The Geological Survey of Iran therefore supports considerable efforts in Quaternary studies yielding to a selection of detailed mapped Quaternary landscapes. The studied geomorphologic structures which are settled up around an endorheic basin in Semnan Province represent a typical type of landform configuration in the area. A 12-km-transect was laid across this basin and range formation. It is oriented in north-south direction from the southern saltpan, called "Kavir-e-Haj Aligholi"/"Chah-e-Jam" ("Damghan Kavir"), across a vast sandy braided river plain, which is entering from the north east direction of the city of Shahroud. At its northern rim it covers alluvial sediment bodies, which are mainly constituted by broad alluvial aprons, fed by watersheds in Alborz Mountains and having their genetic origins in Mio-/Pliocene times. During this study a fully analytical mapping system was used for developing a geodatabase capable of integrating geomorphological analyses. Therefore the system must provide proper differentiation of form, material and process elements as well as geometric separation. Hence the German GMK25 system was set up and slightly modified to fit to the specific project demands. Due to its structure it offers most sophisticated standards and scale independent hierarchies, which fit very well to the software-determinated possibilities of advanced geodatabase applications. One of the main aspects of mapping Quaternary sediments and structures is to acquire a proper description and systematic correlation and categorization of the belonging mapping-objects. Therefore the team from GSI and

  14. Effects of Caribbean oceanic plateau shallow subduction on topographic uplift and exhumation of the northwestern Maracaibo block, Colombia

    Science.gov (United States)

    Sanchez, J.; Mann, P.

    2013-12-01

    central SP show several slope-break knickpoints and changes in steepness indices by factor of ~1.9, all indicative of fault control in this area; 3) perturbations in stream profiles with change in steepness indices by a factor of ~1.6 occur in the southern SP are interpreted as the expression of the active Santa-Marta Bucaramanga fault system, 4) although most of the knickpoints in SSM profiles seem to be associated with changes in bedrock lithology, the alignments, slope-breaking character, and change in steepness indices by factor of ~1.8-2.2 indicate active ENE-WSW fault control along the south-southeastern edge of the SSM, 5) generally undisturbed profiles at northern SSM suggest current quiescence in rock uplift in this area; and 6) basin modeling of the CRB constrain the most recent uplift event as Mio-Pliocene at rates of 0.15-0.18 mm/yr. We propose that the most likely tectonic mechanism to explain widespread active fault activity and uplift within the SSM and SP is oblique, low-angle (20 degrees), southeastward subduction of the Caribbean plate beneath the area. The present rate of subduction and length of slab would have initiated uplift and fault activity at Early Miocene.

  15. The promotion of geomorphosites on salt from Sovata - Praid and Turda using cultural and scientific tourism

    Science.gov (United States)

    Toma, B.; Irimus, I.; Petrea, D.

    2012-04-01

    The paper highlights the role of geomorphosites on salt, in experts and specialists training, in geography of tourism and planning, namely, the involvement of educational factor in defining managerial and marketing skills of future specialists in training. Geographical area of investigation belongs to the Transylvanian tectonic basin, overlapped to saliferous tectonic area from eastern Transylvania, represented by Praid - Sovata - Corund anticline and Sic -Cojocna - Turda anticline, analysis is focused on the Praid - Sovata and Turda diapirs. Saliferous area Praid - Sovata - Corund is situated on the contact area of the Transylvanian Basin with neo-eruptiv mountain chain of Eastern Carpathians, Calimani - Gurghiu - Harghita, and at the contact of Târnavelor Plateau with the orogen alignment of Gurghiu - Harghita Mountains. The salt body, in the horizontal plane, has a quasi-circular shape, slightly ellipsoidal, with diameters of 1.2 and 1.4 km, and is estimated to have a burial depth of 2.6 to 2.8 km. The salt massif from Praid, pierce the Mio-Pliocene blanket around and appears at the surface as diapir, flanked by sedimentary rocks that are partially covered by extrusive post-Pliocene volcanic formations and Quaternary deposits. Evaporitic deposits presents a varied lithology represented by gypsum, anhydrite, salt rock, potassium salt and celestine. The salt massif from Turda develops on the anticline Sic -Cojocna - Turda, oriented NE - SW, 2 km NE of Turda's downtown. It has an elongated shape, about 4 km, with widths ranging from 700 m to 200 m and also with a thickness ranging from 750 m to over 1000 m. In terms of stratigraphy, the salt massif is surrounded by deposits belonging to Badenian, Sarmatian and Quaternary. Due to salt dissolution by meteoric waters, carsto-saline lakes were formed, and due to ceiling collapse, because of an intensive exploitation, and infiltrations of rainwater and rivers, antropo-salted lakes were formed. The water and mud of

  16. Break-up of the Greater Indo-Australian Continent and accretion of blocks framing South and East Asia

    Science.gov (United States)

    Acharyya, S. K.

    1998-09-01

    composite block. Dislocations of the 90 °E Ridge, indicate that the main compression occurred during early Eocene which was followed by movement since late Miocene. The ophiolite trail on IBA does not represent the eastern suture of the Indian continent. As a result of Late Oligocene oblique terminal collision between Sibumasu and 1BA, Mesozoic early Eocene ophiolites. their mid-Eocene cover and trench sediments occur as klippen on IBA. Oblique convergence between IBA and the Indian plate in turn produced an active subduction regime along the western margin of the Indo-Burma mobile belt and the Andaman-Java trench. The activity produced Neogcne-Quaternary volcanism. dextral strike-slip movement in Central Burma-Andaman-Sumatran region, and opened up the Andaman sea. Northward, the Shillong massif, representing NE prolongation of the Indian sub-continent, is technically juxtaposed against the northern end of IBA. The collision of these blocks might have uplifted the Shillong massif during Mio-Pliocene. Far eastward, the convergence was orthogonal between the Australian continent and the Indonesian Arc resulting emplacement of the Lolotoi continental rocks. Maubissi exotic blocks and ophiolitic rocks as nappe over the Timor shelf which possibly remained attached to the Australian continent.

  17. Extreme extension across Seram and Ambon, eastern Indonesia: Evidence for Banda slab rollback

    Directory of Open Access Journals (Sweden)

    J. M. Pownall

    2013-04-01

    Full Text Available The island of Seram, which lies in the northern part of the 180°-curved Banda Arc, has previously been interpreted as a fold-and-thrust belt formed during arc-continent collision, which incorporates ophiolites intruded by granites thought to have been produced by anatexis within a metamorphic "sole". However, new geological mapping and a re-examination of the field relations cause us to question this model. We instead propose that there is evidence for recent N–S extension that has caused the high-temperature exhumation of hot mantle peridotites, granites, and granulites (the "Kobipoto Complex" beneath low-angle lithospheric detachment faults. Greenschist- to lower-amphibolite facies metapelites and amphibolites of the Tehoru Formation, which comprise the hanging wall above the detachment faults, were overprinted by sillimanite-grade metamorphism, migmatisation and limited localised diatexis to form the Taunusa Complex. Highly aluminous metapelitic garnet + cordierite + sillimanite + spinel + corundum + quartz granulites exposed in the Kobipoto Mountains (central Seram are intimately associated with the peridotites. Spinel + quartz inclusions in garnet, which indicate that peak metamorphic temperatures for the granulites likely approached 900 °C, confirm that peridotite was juxtaposed against the crust at typical lithospheric mantle temperatures and could not have been part of a cooled ophiolite. Some granulites experienced slight metatexis, but the majority underwent more advanced in situ anatexis to produce widespread granitic diatexites characterised by abundant cordierite and garnet xenocrysts and numerous restitic sillimanite + spinel "clots". These Mio-Pliocene "cordierite granites", which are present throughout Ambon, western Seram, and the Kobipoto Mountains in direct association with peridotites, demonstrate that the extreme extension required to have driven Kobipoto Complex exhumation must have occurred along much of the northern

  18. In Search of the Ancestors of Chinese People

    Institute of Scientific and Technical Information of China (English)

    GAO Xing; WANG Chunxue

    2010-01-01

    @@ Presently,the research on the origin of Chinese ancestors focuses on two issues,namely the origin of the first human populations in Asia and the origin of modern Chinese people.Up till now,all the fossils of Australopithecus and Homo habilis,the earliest two stages of human evolution,are from Africa,and no human fossil earlier than2.0 million years ago is available outside of this continent.

  19. Plio-Pleistocene climate-driven facial morphology in southern African australopithecines

    Science.gov (United States)

    Williams, F. L.; Christensen, B. A.

    2004-12-01

    Intensification of Northern Hemispheric Glaciation (INHG) has been cited as the driving force for climate change in southern Africa, despite the fact that rare and fragmentary continental records for the region allow for only a loose correlation between local faunal events and global climate change. Determining climatic influence from the limited climate history is exacerbated by the difficult chronology for the cave sites. The depositional history of the caves nonetheless reveals a turnover of southern African mammals, and variability, among other forcing factors, have implicated the INHG to explain the evolution of these novel forms. We suggest that evolutionary changes in southern African fauna may have also been driven by a subsequent climate event, the Onset of Walker Circulation (OWC) at ~ 2 Myr. The OWC, with enhanced high frequency climate variability, may have been more dominant than INHG in driving southern African mammalian evolution. For example, Pleistocene Australopithecus robustus, but not Pliocene Australopithecus africanus, exhibits relatively broad palates, postcanine megadonty and deep mandibular corpora that correspond to a dietary niche involving heavy mastication. These adaptations may have been selected for in unstable Pleistocene environments initiated by the OWC. Moreover, the temporal context of Australopithecus robustus, found in the Pleistocene dated caves of Swartkrans, Kromdraai and Drimolen, coincides more closely with the OWC than with the INHG.

  20. The first hominin from the early Pleistocene paleocave of Haasgat, South Africa

    Directory of Open Access Journals (Sweden)

    AB Leece

    2016-05-01

    Full Text Available Haasgat is a primate-rich fossil locality in the northeastern part of the Fossil Hominid Sites of South Africa UNESCO World Heritage Site. Here we report the first hominin identified from Haasgat, a partial maxillary molar (HGT 500, that was recovered from an ex situ calcified sediment block sampled from the locality. The in situ fossil bearing deposits of the Haasgat paleokarstic deposits are estimated to date to slightly older than 1.95 Ma based on magnetobiostratigraphy. This places the hominin specimen at a critical time period in South Africa that marks the last occurrence of Australopithecus around 1.98 Ma and the first evidence of Paranthropus and Homo in the region between ∼2.0 and 1.8 Ma. A comprehensive morphological evaluation of the Haasgat hominin molar was conducted against the current South African catalogue of hominin dental remains and imaging analyses using micro-CT, electron and confocal microscopy. The preserved occlusal morphology is most similar to Australopithecus africanus or early Homo specimens but different from Paranthropus. Occlusal linear enamel thickness measured from micro-CT scans provides an average of ∼2.0 mm consistent with Australopithecus and early Homo. Analysis of the enamel microstructure suggests an estimated periodicity of 7–9 days. Hunter–Schreger bands appear long and straight as in some Paranthropus, but contrast with this genus in the short shape of the striae of Retzius. Taken together, these data suggests that the maxillary fragment recovered from Haasgat best fits within the Australopithecus—early Homo hypodigms to the exclusion of the genus Paranthropus. At ∼1.95 Ma this specimen would either represent another example of late occurring Australopithecus or one of the earliest examples of Homo in the region. While the identification of this first hominin specimen from Haasgat is not unexpected given the composition of other South African penecontemporaneous site deposits, it represents

  1. The shape of the early hominin proximal femur.

    Science.gov (United States)

    Harmon, Elizabeth H

    2009-06-01

    Postcranial skeletal variation among Plio-Pleistocene hominins has implications for taxonomy and locomotor adaptation. Although sample size constraints make interspecific comparisons difficult, postcranial differences between Australopithecus afarensis and Australopithecus africanus have been reported (McHenry and Berger: J Hum Evol 35 1998 1-22; Richmond et al.: J Hum Evol 43 [2002] 529-548; Green et al.: J Hum Evol 52 2007 187-200). Additional evidence indicates that the early members of the genus Homo show morphology like recent humans (e.g., Walker and Leakey: The Nariokotome Homo erectus skeleton. Cambridge: Harvard, 1993). Using a larger fossil sample than previous studies and novel methods, the early hominin proximal femur is newly examined to determine whether new data alter the current view of femoral evolution and inform the issue of interspecific morphological variation among australopiths. Two- and three-dimensional data are collected from large samples of recent humans, Pan, Gorilla, and Pongo and original fossil femora of Australopithecus, Paranthropus, and femora of African fossil Homo. The size-adjusted shape data are analyzed using principal components, thin plate spline analysis, and canonical variate analysis to assess shape variation. The results indicate that femora of fossil Homo are most similar to modern humans but share a low neck-shaft angle (NSA) with australopiths. Australopiths as a group have ape-like greater trochanter morphology. A. afarensis differs from P. robustus and A. africanus in attributes of the neck and NSA. However, interspecific femoral variation is low and australopiths are generally morphologically similar. Although the differences are not dramatic, when considered in combination with other postcranial evidence, the adaptive differences among australopiths in craniodental morphology may have parallels in the postcranium.

  2. Bone strength and athletic ability in hominids: Ardipithecus ramidus to Homo sapiens

    Science.gov (United States)

    Lee, S. A.

    2013-03-01

    The ability of the femur to resist bending stresses is determined by its midlength cross-sectional geometry, its length and the elastic properties of the mineral part of the bone. The animal's athletic ability, determined by a ``bone strength index,'' is limited by this femoral bending strength in relation to the loads on the femur. This analysis is applied to the fossil record for Homo sapiens, Homo neanderthalensis, Homo erectus, Homo habilis, Australopithecus afarensis and Ardipithecus ramidus. Evidence that the femoral bone strength index of modern Homo sapiens has weakened over the last 50,000 years is found.

  3. Anthropogeny and Intellectual Evolution%人类起源与智能进化

    Institute of Scientific and Technical Information of China (English)

    吕宝忠

    2012-01-01

    The long evolutionary way for human can be traced back to about 5 million years ago, in which two "missing links", Ardipi-thecus ramidus and Australopithecus sediba , have been validated. There are two conflicted hypotheses, "out of Africa" and multire-gional origins. At present, the mixture of both hypotheses seems to be more valuable according to Neanderthal and Denisovan genome draft and other data. The ultimate explanation for being human is focused on the culture-making brain, especially in the cerebral hemisphere asymmetry, that bolsters the framework for 4 graded languages and 3 types of world.

  4. Our Magnetic Planet (Arthur Holmes Medal Lecture)

    Science.gov (United States)

    Laj, Carlo

    2015-04-01

    and Turkey) allowed to show that the main post-cretaceous geodynamical evolution of the Aegean Realm is dominated since 30 My by two phases of rotational deformation in opposite sense around two poles: one just north of Albania for the western part, the second in the South Eastern Mediterranean for the eastern part. During the sampling of Mio-Pliocene marls in Crete, using a LETI portable magnetometer to the development of which I have participated, we sampled a geomagnetic reversal registered over about 50 cm of sediments. Interestingly, some intermediate directions were clearly apparent. This gave me the idea that the dynamical directional behaviour of the reversing field could be studied. At the time, only a very few and very incomplete similar records existed. For me, this has been the beginning of an extraordinary adventure still going on today. From the accumulation of data, first from Crete, then from other worldwide spread sites, it became apparent, as illustrated in a cover of Nature, that sedimentary reversal transition paths had a tendency to coincide with the seismically cold deep regions, suggesting that a lower mantle control existed over the reversing geodynamo. This idea, sometimes greeted with scepticism, has stimulated joint efforts to test it both from different disciplines and different experimental and theoretical approaches. It is fair to say that 25 years after it was proposed, our idea is still "on the table" and discussed. We then turned to the study of the changes of the geomagnetic field intensity, still inadequately described at the time. Because measurements of traditional small cubic samples was largely too time consuming to allow surveys of the amplitude we had in mind, I adapted the u-channel measurement techniques to small access pass-through cryogenic magnetometers, and suggested to W. Goree of 2G-Enterprises a modification of the standard pick-up coil geometry (called the Laj-system by the manufacturer) to allow high spatial

  5. Fish as a proxy for African paleogeography: results from both extant and fossil taxa and prospects to constrain faunal exchange pathway through time

    Science.gov (United States)

    Otero, Olga; Joordens, Josephine; Dettai, Agnès; Christ, Leemans; Pinton, Aurélie

    2016-04-01

    : relationships between Chad and neighbouring basins throughout the Mio-Pliocene. Palaeobiogeography, Palaeoclimatology, Palaeoecology, 274 (2009): 134-139. [5] Argyriou T., Otero O., Pavlakis P., Boaz N.T. 2012 - Description and paleobiogeographical implications of new Semlikiichthys (Teleostei, Perciformes) fish material from the Late Miocene deposits of Sahabi, Libya. Geobios, 45(2012): 429-436. [6] Joordens J (Pi) - Coastal origins? A biogeographical model for mominin evolution and dispersal in Africa between 5 and 2.5 million years ago.

  6. Shape Ontogeny of the Distal Femur in the Hominidae with Implications for the Evolution of Bipedality.

    Directory of Open Access Journals (Sweden)

    Melissa Tallman

    Full Text Available Heterochrony has been invoked to explain differences in the morphology of modern humans as compared to other great apes. The distal femur is one area where heterochrony has been hypothesized to explain morphological differentiation among Plio-Pleistocene hominins. This hypothesis is evaluated here using geometric morphometric data to describe the ontogenetic shape trajectories of extant hominine distal femora and place Plio-Pleistocene hominins within that context. Results of multivariate statistical analyses showed that in both Homo and Gorilla, the shape of the distal femur changes significantly over the course of development, whereas that of Pan changes very little. Development of the distal femur of Homo is characterized by an elongation of the condyles, and a greater degree of enlargement of the medial condyle relative to the lateral condyle, whereas Gorilla are characterized by a greater degree of enlargement of the lateral condyle, relative to the medial. Early Homo and Australopithecus africanus fossils fell on the modern human ontogenetic shape trajectory and were most similar to either adult or adolescent modern humans while specimens of Australopithecus afarensis were more similar to Gorilla/Pan. These results indicate that shape differences among the distal femora of Plio-Pleistocene hominins and humans cannot be accounted for by heterochrony alone; heterochrony could explain a transition from the distal femoral shape of early Homo/A. africanus to modern Homo, but not a transition from A. afarensis to Homo. That change could be the result of genetic or epigenetic factors.

  7. First early hominin from central Africa (Ishango, Democratic Republic of Congo.

    Directory of Open Access Journals (Sweden)

    Isabelle Crevecoeur

    Full Text Available Despite uncontested evidence for fossils belonging to the early hominin genus Australopithecus in East Africa from at least 4.2 million years ago (Ma, and from Chad by 3.5 Ma, thus far there has been no convincing evidence of Australopithecus, Paranthropus or early Homo from the western (Albertine branch of the Rift Valley. Here we report the discovery of an isolated upper molar (#Ish25 from the Western Rift Valley site of Ishango in Central Africa in a derived context, overlying beds dated to between ca. 2.6 to 2.0 Ma. We used µCT imaging to compare its external and internal macro-morphology to upper molars of australopiths, and fossil and recent Homo. We show that the size and shape of the enamel-dentine junction (EDJ surface discriminate between Plio-Pleistocene and post-Lower Pleistocene hominins, and that the Ishango molar clusters with australopiths and early Homo from East and southern Africa. A reassessment of the archaeological context of the specimen is consistent with the morphological evidence and suggest that early hominins were occupying this region by at least 2 Ma.

  8. Sédimentation et tectonique dans le bassin marin Eocène supérieur-Oligocène des Alpes du Sud Sedimentation and Tectonics in the Upper Eocene-Oligocene Marine Basin in the Southern Alps

    Directory of Open Access Journals (Sweden)

    Riche P.

    2006-11-01

    'exprime nettement moins que précédemment. Le toit des grès est marqué par une surface de discontinuité fortement érosive correspondant à des canyons sous-marins de direction NE-SO. Cette surface peut être mise en relation avec l'écoulement des olistostromes qui termine le remplissage du bassin. La mise en place de ces olistostromes et des olistolithes qui les accompagnent n'est pas paléontologiquement datée : elle débute avec la fin de la sédimentation gréseuse. L'ensemble est encore affecté par une distension E-O ce qui tend à montrer que cette mise en place est antérieure à la phase de serrage miocène. La confrontation entre les observations de terrain, les expériences de sédimentation en canal et l'interprétation sismique de bassins offshore argumente les interprétations proposées. This paper is based on local field surveys performed recently by Institut Français du Pétrole (IFP and Ecole Nationale Supérieure du Pétrole et des Moteurs (ENSPM in the western part of the southern Alps nummulitic basin, to help interpret seismic data. It underlines the role of extensional tectonics during sedimentation. It questions the geodynamic interpretation of the basin as a foredeep basin in the Alpine orogenic belt. On a Mesozoic basement folded by the Pyreneo-Provençale orogeny, as early as the Lutetian the nummulitic transgression flooded the eastern area, which was subsequently obscured by the Pennine main fault during Mio-Pliocene times. It spread westward during the Upper Eocene. In the meantime, an E-W extension, shown clearly along the Var River faults and along the edge of the Pelvoux range, fragmented the fringes of the basin with blocks tilted during sedimentation. The result is fast changes of facies within the basal carbonates, which pass from platform types to slope types and to thin gravitational sediments farther into the basin. The overlying marls correspond to slope facies wrapping the inherited topography. The Gres d'Annot s. l

  9. Ontogeny of the maxilla in Neanderthals and their ancestors.

    Science.gov (United States)

    Lacruz, Rodrigo S; Bromage, Timothy G; O'Higgins, Paul; Arsuaga, Juan-Luis; Stringer, Chris; Godinho, Ricardo Miguel; Warshaw, Johanna; Martínez, Ignacio; Gracia-Tellez, Ana; de Castro, José María Bermúdez; Carbonell, Eudald

    2015-12-07

    Neanderthals had large and projecting (prognathic) faces similar to those of their putative ancestors from Sima de los Huesos (SH) and different from the retracted modern human face. When such differences arose during development and the morphogenetic modifications involved are unknown. We show that maxillary growth remodelling (bone formation and resorption) of the Devil's Tower (Gibraltar 2) and La Quina 18 Neanderthals and four SH hominins, all sub-adults, show extensive bone deposition, whereas in modern humans extensive osteoclastic bone resorption is found in the same regions. This morphogenetic difference is evident by ∼5 years of age. Modern human faces are distinct from those of the Neanderthal and SH fossils in part because their postnatal growth processes differ markedly. The growth remodelling identified in these fossil hominins is shared with Australopithecus and early Homo but not with modern humans suggesting that the modern human face is developmentally derived.

  10. Om religion og evolution

    DEFF Research Database (Denmark)

    Geertz, Armin W.

    2011-01-01

    begyndt længe før homo-arten, endog før Australopithecus, hvor man finder primitive sten redskaber og tilstedeværelse af (dog ikke kontrol over) ild, og hvor de fysiologiske og genetiske forandringer, som førte til mennesket, også var påbegyndt. Dernæst opstilles otte træk, som kan have været til stede i......, hvad man kan kalde en 'proto-religion'. Den art, som sandsynligvis har besiddet disse træk, er Homo erectus; men der kan have været ansatser til denne proto-religion endnu tidligere. Artiklen afsluttes med en diskussion af de mest kendte teorier og hypoteser, der har forsøgt at forklare, hvorfor...

  11. Human hyoid bones from the middle Pleistocene site of the Sima de los Huesos (Sierra de Atapuerca, Spain).

    Science.gov (United States)

    Martínez, I; Arsuaga, J L; Quam, R; Carretero, J M; Gracia, A; Rodríguez, L

    2008-01-01

    This study describes and compares two hyoid bones from the middle Pleistocene site of the Sima de los Huesos in the Sierra de Atapuerca (Spain). The Atapuerca SH hyoids are humanlike in both their morphology and dimensions, and they clearly differ from the hyoid bones of chimpanzees and Australopithecus afarensis. Their comparison with the Neandertal specimens Kebara 2 and SDR-034 makes it possible to begin to approach the question of temporal variation and sexual dimorphism in this bone in fossil humans. The results presented here show that the degree of metric and anatomical variation in the fossil sample was similar in magnitude and kind to living humans. Modern hyoid morphology was present by at least 530 kya and appears to represent a shared derived feature of the modern human and Neandertal evolutionary lineages inherited from their last common ancestor.

  12. Early Pleistocene hominid teeth recovered in Mohui cave in Bubing Basin, Guangxi, South China

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; Richard Potts; HOU Yamei; CHEN Yunfa; WU Huaying; YUAN Baoyin; HUANG Weiwen

    2005-01-01

    Two hominid teeth recovered in Mohui cave are morphologically distinguished from Australopithecus in Africa, but close to Homo erectus in China. These teeth are therefore provisionally assigned to Homo erectus. The associated mammalian fauna include Gigantopithecus blacki, Nestoritherium sp., Sus xiaozhu, Sus peii and Ailuropoda microta, which are typical early Pleistocene taxa in South China. The general characteristics of the Mohui faunal assemblage are similar to the Longgupo site, which is dated to 2 Ma, implying a contemporaneity for the two sites. To date, compared with the discoveries in Africa, far fewer early Pleistocene hominid fossils have been recovered in Asia, and there are intensive controversies concerning their stratigraphic provenience and typological and temporal positions. The hominid fossils from Mohui cave, with their reliable biostratigraphic positions and distinct typological features, provide important evidence regarding the issue of early human origins and evolution.

  13. The evolution of human and ape hand proportions.

    Science.gov (United States)

    Almécija, Sergio; Smaers, Jeroen B; Jungers, William L

    2015-07-14

    Human hands are distinguished from apes by possessing longer thumbs relative to fingers. However, this simple ape-human dichotomy fails to provide an adequate framework for testing competing hypotheses of human evolution and for reconstructing the morphology of the last common ancestor (LCA) of humans and chimpanzees. We inspect human and ape hand-length proportions using phylogenetically informed morphometric analyses and test alternative models of evolution along the anthropoid tree of life, including fossils like the plesiomorphic ape Proconsul heseloni and the hominins Ardipithecus ramidus and Australopithecus sediba. Our results reveal high levels of hand disparity among modern hominoids, which are explained by different evolutionary processes: autapomorphic evolution in hylobatids (extreme digital and thumb elongation), convergent adaptation between chimpanzees and orangutans (digital elongation) and comparatively little change in gorillas and hominins. The human (and australopith) high thumb-to-digits ratio required little change since the LCA, and was acquired convergently with other highly dexterous anthropoids.

  14. Homo floresiensis-like fossils from the early Middle Pleistocene of Flores.

    Science.gov (United States)

    van den Bergh, Gerrit D; Kaifu, Yousuke; Kurniawan, Iwan; Kono, Reiko T; Brumm, Adam; Setiyabudi, Erick; Aziz, Fachroel; Morwood, Michael J

    2016-06-01

    The evolutionary origin of Homo floresiensis, a diminutive hominin species previously known only by skeletal remains from Liang Bua in western Flores, Indonesia, has been intensively debated. It is a matter of controversy whether this primitive form, dated to the Late Pleistocene, evolved from early Asian Homo erectus and represents a unique and striking case of evolutionary reversal in hominin body and brain size within an insular environment. The alternative hypothesis is that H. floresiensis derived from an older, smaller-brained member of our genus, such as Homo habilis, or perhaps even late Australopithecus, signalling a hitherto undocumented dispersal of hominins from Africa into eastern Asia by two million years ago (2 Ma). Here we describe hominin fossils excavated in 2014 from an early Middle Pleistocene site (Mata Menge) in the So'a Basin of central Flores. These specimens comprise a mandible fragment and six isolated teeth belonging to at least three small-jawed and small-toothed individuals. Dating to ~0.7 Ma, these fossils now constitute the oldest hominin remains from Flores. The Mata Menge mandible and teeth are similar in dimensions and morphological characteristics to those of H. floresiensis from Liang Bua. The exception is the mandibular first molar, which retains a more primitive condition. Notably, the Mata Menge mandible and molar are even smaller in size than those of the two existing H. floresiensis individuals from Liang Bua. The Mata Menge fossils are derived compared with Australopithecus and H. habilis, and so tend to support the view that H. floresiensis is a dwarfed descendent of early Asian H. erectus. Our findings suggest that hominins on Flores had acquired extremely small body size and other morphological traits specific to H. floresiensis at an unexpectedly early time.

  15. A geometric morphometrics comparative analysis of Neandertal humeri (epiphyses-fused) from the El Sidrón cave site (Asturias, Spain).

    Science.gov (United States)

    Rosas, Antonio; Pérez-Criado, Laura; Bastir, Markus; Estalrrich, Almudena; Huguet, Rosa; García-Tabernero, Antonio; Pastor, Juan Francisco; de la Rasilla, Marco

    2015-05-01

    A new collection of 49,000 year old Neandertal fossil humeri from the El Sidrón cave site (Asturias, Spain) is presented. A total of 49 humeral remains were recovered, representing 10 left and 8 right humeri from adults, adolescents, and a juvenile (not included in the analyses). 3D geometric morphometric (GM) methods as well as classic anthropological variables were employed to conduct a broad comparative analysis by means of mean centroid size and shape comparisons, principal components analysis, and cluster studies. Due to the fragmentary nature of the fossils, comparisons were organized in independent analyses according to different humeral portions: distal epiphysis, diaphysis, proximal epiphysis, and the complete humerus. From a multivariate viewpoint, 3D-GM analyses revealed major differences among taxonomic groups, supporting the value of the humerus in systematic classification. Notably, the Australopithecus anamensis (KP-271) and Homo ergaster Nariokotome (KNM-WT 15000) distal humerus consistently clusters close to those of modern humans, which may imply a primitive condition for Homo sapiens morphology. Australopithecus specimens show a high degree of dispersion in the morphospace. The El Sidrón sample perfectly fits into the classic Neandertal pattern, previously described as having a relatively wide olecranon fossa, as well as thin lateral and medial distodorsal pillars. These characteristics were also typical of the Sima de los Huesos (Atapuerca) sample, African mid-Pleistocene Bodo specimen, and Lower Pleistocene TD6-Atapuerca remains and may be considered as a derived state. Finally, we hypothesize that most of the features thought to be different between Neandertals and modern humans might be associated with structural differences in the pectoral girdle and shoulder joint.

  16. Spinal cord evolution in early Homo.

    Science.gov (United States)

    Meyer, Marc R; Haeusler, Martin

    2015-11-01

    The discovery at Nariokotome of the Homo erectus skeleton KNM-WT 15000, with a narrow spinal canal, seemed to show that this relatively large-brained hominin retained the primitive spinal cord size of African apes and that brain size expansion preceded postcranial neurological evolution. Here we compare the size and shape of the KNM-WT 15000 spinal canal with modern and fossil taxa including H. erectus from Dmanisi, Homo antecessor, the European middle Pleistocene hominins from Sima de los Huesos, and Pan troglodytes. In terms of shape and absolute and relative size of the spinal canal, we find all of the Dmanisi and most of the vertebrae of KNM-WT 15000 are within the human range of variation except for the C7, T2, and T3 of KNM-WT 15000, which are constricted, suggesting spinal stenosis. While additional fossils might definitively indicate whether H. erectus had evolved a human-like enlarged spinal canal, the evidence from the Dmanisi spinal canal and the unaffected levels of KNM-WT 15000 show that unlike Australopithecus, H. erectus had a spinal canal size and shape equivalent to that of modern humans. Subadult status is unlikely to affect our results, as spinal canal growth is complete in both individuals. We contest the notion that vertebrae yield information about respiratory control or language evolution, but suggest that, like H. antecessor and European middle Pleistocene hominins from Sima de los Huesos, early Homo possessed a postcranial neurological endowment roughly commensurate to modern humans, with implications for neurological, structural, and vascular improvements over Pan and Australopithecus.

  17. Body mass estimates of hominin fossils and the evolution of human body size.

    Science.gov (United States)

    Grabowski, Mark; Hatala, Kevin G; Jungers, William L; Richmond, Brian G

    2015-08-01

    Body size directly influences an animal's place in the natural world, including its energy requirements, home range size, relative brain size, locomotion, diet, life history, and behavior. Thus, an understanding of the biology of extinct organisms, including species in our own lineage, requires accurate estimates of body size. Since the last major review of hominin body size based on postcranial morphology over 20 years ago, new fossils have been discovered, species attributions have been clarified, and methods improved. Here, we present the most comprehensive and thoroughly vetted set of individual fossil hominin body mass predictions to date, and estimation equations based on a large (n = 220) sample of modern humans of known body masses. We also present species averages based exclusively on fossils with reliable taxonomic attributions, estimates of species averages by sex, and a metric for levels of sexual dimorphism. Finally, we identify individual traits that appear to be the most reliable for mass estimation for each fossil species, for use when only one measurement is available for a fossil. Our results show that many early hominins were generally smaller-bodied than previously thought, an outcome likely due to larger estimates in previous studies resulting from the use of large-bodied modern human reference samples. Current evidence indicates that modern human-like large size first appeared by at least 3-3.5 Ma in some Australopithecus afarensis individuals. Our results challenge an evolutionary model arguing that body size increased from Australopithecus to early Homo. Instead, we show that there is no reliable evidence that the body size of non-erectus early Homo differed from that of australopiths, and confirm that Homo erectus evolved larger average body size than earlier hominins.

  18. The posterior border of the sphenoid greater wing and its phylogenetic usefulness in human evolution.

    Science.gov (United States)

    Braga, J; Crubézy, E; Elyaqtine, M

    1998-12-01

    The elucidation of patterns of cranial skeletal maturation and growth in fossil hominids is possible not only through dental studies but also by mapping different aspects of ossification in both extant African apes and humans. However, knowledge of normal skeletal development in large samples of extant great apes is flimsy. To remedy this situation, this paper offers an extensive survey and thorough discussion of the ossification of the posterior border of the sphenoid greater wing. Indeed, this area provides much information about basicranial skeletal maturation. We investigate three variants: the absence of the foramen spinosum and the position of both the foramen spinosum and the foramen ovale in relation to the sphenosquamosal suture. Providing original data about humans and 1,425 extant great ape skulls and using a sample of 64 fossil hominids, this study aimed to test whether different ossification patterns occurred during the course of human evolution. The incidence of three derived morphologies located on the posterior border of the sphenoid greater wing increases during human evolution at different geological periods. The evolutionary polarity of these three derived morphologies is assessed by outgroup comparison and ontogenetic methods. During human evolution, there is a clear trend for the foramen spinosum to be present and wholly located on the posterior area of the sphenoid greater wing. Moreover, in all the great ape species and in Australopithecus afarensis, the sphenosquamosal suture may split the foramen ovale. Inversely, the foramen ovale always lies wholly within the sphenoid greater wing in Australopithecus africanus, robust australopithecines, early Homo, H. erectus (and/or H. ergaster), and Homo sapiens. From ontogenetic studies in humans, we conclude that, during human evolution, the ossification of the posterior area of the sphenoid greater wing progressively surrounded the middle meningeal artery (passing through the foramen spinosum) and

  19. Ontogeny and phylogeny of femoro-tibial characters in humans and hominid fossils: functional influence and genetic determinism.

    Science.gov (United States)

    Tardieu, C

    1999-11-01

    Three different human femoro-tibial characters are selected as functionally relevant and derived hominid characters: femoral bicondylar angle, shape of the femoral distal epiphysis, and the tibial insertion of the lateral meniscus. The timing and mode of formation of these characters are investigated during human ontogeny and are shown to differ considerably. The available hominid fossils (Australopithecus afarensis and early Homo) are interpreted in the light of this ontogenetic analysis with the conclusion that, during hominid evolution, different modes of selection of these features must have occurred. In modern humans, the femoral bicondylar angle proves to be an epigenetic functional feature, which develops during early childhood growth. It is present in all australopithecines and we suggest that it developed following a change in their locomotor behavior and not upon a genomic change: the early practice of bipedal walking, with adducted knee joints, in the locomotor repertoire of infant australopithecines, was sufficient to promote this angle. Later in hominid evolution, the knee joint evolved from having a single insertion of the lateral meniscus on the tibia to a double one. While Australopithecus afarensis exhibits a single insertion, early Homo clearly exhibits a double insertion of the lateral meniscus on the tibia. The double insertion restricts the mobility of the meniscus on the tibial plateau, indicating a habitual practice of full extension movements of the knee joint. Among modern humans, the posterior insertion of the lateral meniscus appears early in fetal life. Consequently in early Homo, this new selected feature developed directly as a result of a genomic change. The derived shape of human distal femoral epiphysis includes a prominence of the lateral lip of the femoral trochlea, an elliptical profile of the lateral condyle, and an anteroposterior lengthening of the epiphysis. Analysis of human fetal and neonatal distal epiphyses shows that the

  20. A vuelo de pájaro: Una mirada a la Salud Pública de Etiopía Overview to Ethiopian’s Public Health

    Directory of Open Access Journals (Sweden)

    Liliana Palacios

    2006-03-01

    Full Text Available Pienso en Etiopía y no sé por dónde empezar, mezcla de sentimientos y mucha, pero mucha información… La vida y la muerte pueden convivir tan de cerca que cualquier experiencia se tiñe de una matiz especial. También llamada Abissinia, Etiopia sigue siendo hoy día tierra mítica y gracias a Lucy Australopithecus Afarensis es reconocida antropológicamente como el posible lugar de origen del género humano. Al mismo tiempo, es uno de los países en vías de desarrollo con indicadores de salud por debajo de la media mundial y un sistema relativamente joven que aun no termina de responder a las necesidades de su población. Al igual que otros países en las mismas características, los etíopes recurren a una mezcla de medicina tradicional vs servicios halopáticos mientras que las políticas nacionales siguen tratando de dar las pautas acordes a los lineamientos y metas mundiales, dando como resultado un panorama interesante para un salubrista público y cualquier personal sanitario interesado en la situación sanitaria de otros lugares.I think about Ethiopia and I am not clear how to start, a mixture of feelings and a lot of information is surrounding me… The life and death can stay so close that any experience has a special tone. Named Abissinia as well, Ethiopia is still today a mythic land. Due to "Lucy" Australopithecus Afarensis finding, it is acknowledged like the starting point of human being. In addition, it is one of the developing countries with core health indicators under world´ standard line and a "Fresh Health System" which still doesn’t cover properly the population’s needs. Like another country in this situation, the Ethiopian look for a mixture of Traditional medicine Vs Western one, meanwhile the National policies are trying of reach the aims and outlines fixed in the world. Like a result, there is an interesting landscape to any Public Health specialist and/or someone who can be interested in abroad sanitarian

  1. Fossil land snails of East Africa and their palaeoecological significance

    Science.gov (United States)

    Pickford, Martin

    1995-04-01

    This study deals with the Neogene and extant land snails of tropical East Africa and their implications for interpreting the paleoenvironments of the numerous localities at which they have been found. Of major significance to the study is the intimate association between the terrestrial molluscs and the rich mammalian faunas, hominoids included, of East Africa. Thus, palaeoecological reconstructions based on land snails are directly applicable to the mammalian faunas. Palaeoecological reconstructions are proposed for most of the Lower and Middle Miocene hominoids, including Proconsul, Rangwapithecus, Limnopithecus, Micropithecus, Nyanzapithecus, Kenyapithecus and others, and for the mid-Pliocene Australopithecus from Laetoli, Tanzania. The departure point for the palaeoecological reconstructions is a comprehensive study of extant terrestrial molluscs of East Africa, the habitat preferences of which are well documented. All the fossil gastropods studied comprise extant genera and even species, so the usual problems regarding the application of actualism to fossil assemblages is avoided. Furthermore, the fossil gastropod assemblages resemble extant ones, confirming their utility for such reconstructions. Among the parameters examined are rainfall, altitude, vegetation cover and type and zoogeography. A further point of interest is that the samples are more than adequate for the purposes of the study, many of the fossil localities having yielded several thousand specimens. Finally, more than 40% of the extant genera of East Africa have now been recognized in the fossil state. The molluscs are thus, by far, the best represented biological group known in the fossil record of Africa and as such hold great potential for understanding the past. This study ends with reconstructions of the palaeoecology of numerous fossiliferous localities in East Africa which have yielded molluscs and mammals. Changes through the geological column are documented and the habitat preferences

  2. Contemporary flowstone development links early hominin bearing cave deposits in South Africa

    Science.gov (United States)

    Pickering, Robyn; Kramers, Jan D.; Hancox, Philip John; de Ruiter, Darryl J.; Woodhead, Jon D.

    2011-06-01

    The Cradle of Humankind cave sites in South Africa preserve fossil evidence of four early hominin taxa: Australopithecus africanus, Australopithecus sediba, Paranthropus robustus and early Homo. In order to integrate this record into a pan-African scenario of human evolutionary history it is critical to have reliable dates and temporal ranges for the southern African hominins. In the past a lack of precise and accurate chronological data has prevented the evaluation of the temporal relationships between the various sites. Here we report new uranium-lead (U-Pb) radiometric ages obtained from sheets of calcium carbonate flowstone inter-bedded between clastic cave sediments at the site of Swartkrans, providing bracketing ages for the fossiliferous deposits. The fossil bearing units of Swartkrans, specifically the Hanging Remnant and Lower Bank of Member 1, are underlain by flowstone layers dated to 2.25 ± 0.05 Ma and 2.25 ± 0.08 Ma and capped by layers of 1.8 ± 0.01 Ma and 1.7 ± 0.07 Ma. The age bracket of the Member 1 deposits is therefore between 2.31 and 1.64 Ma. However, by combining the U-Pb with biostratigraphic data we suggest that this can be narrowed down to between 1.9 and 1.8 Ma. These data can be compared with other recently dated sites and a radiometrically dated U-Pb age sequence formed: Sterkfontein Member 4, Swartkrans Member 1, Malapa, and Cooper's D. From this new U-Pb dataset, a pattern of contemporary flowstone development emerges, with different caves recording the same flowstone-forming event. Specifically overlapping flowstone formation takes place at Swartkrans and Sterkfontein at ~ 2.29 Ma and ~ 1.77 Ma, and at Sterkfontein and Malapa at ˜ 2.02 Ma. This suggests a regional control over the nature and timing of speleothem development in cave deposits and these flowstone layers could assist in future correlation, both internal to specific deposits and regionally between sites.

  3. Functional morphology of the Neandertal scapular glenoid fossa.

    Science.gov (United States)

    Macias, Marisa E; Churchill, Steven E

    2015-01-01

    Neandertals and Homo sapiens are known to differ in scapular glenoid fossa morphology. Functional explanations may be appropriate for certain aspects of glenoid fossa morphology; however, other factors--e.g., allometry, evolutionary development--must be addressed before functional morphology is considered. Using three-dimensional geometric morphometrics, shape of the scapular glenoid fossa was compared among Neandertals, early and recent modern humans, chimpanzees, orangutans, Australopithecus afarensis, and Au. sediba. Permutation analysis revealed that side, sex, and lifestyle did not correlate with shape. Of the features we found to differ between groups, anterior glenoid rim morphology and fossa curvature did not correlate with the aforementioned shape variables; thus, a functional explanation is appropriate for these components of glenoid fossa shape. Shared morphology among recent humans and chimpanzees (to the exclusion of Neandertals and orangutans) suggests independent forces contributing to these morphological configurations. Potential explanations include adaptations to habitual behavior and locomotor adaptations in the scapulae of recent humans and chimpanzees; these explanations are supported by clinical and experimental literature. The absence of these morphological features in Neandertals may support the lack of these selective forces on their scapular glenoid fossa morphology.

  4. Assessing the paleoenvironmental potential of Pliocene to Holocene tufa deposits along the Ghaap Plateau escarpment (South Africa) using stable isotopes

    Science.gov (United States)

    Doran, Taylor Louise; Herries, Andy I. R.; Hopley, Philip J.; Sombroek, Hank; Hellstrom, John; Hodge, Ed; Kuhn, Brian F.

    2015-07-01

    The tufa deposits of the Ghaap Plateau escarpment provide a rich, yet minimally explored, geological archive of climate and environmental history coincident with hominin evolution in South Africa. This study examines the sedimentary and geochemical records of ancient and modern tufas from Buxton-Norlim Limeworks, Groot Kloof, and Gorrokop, to assess the potential of these sediments for providing reliable chronologies of high-resolution, paleoenvironmental information. Chronometric dating demonstrates that tufa formation has occurred from at least the terminal Pliocene through to the modern day. The stable isotope records show a trend toward higher, more variable δ18O and δ13C values with decreasing age from the end of the Pliocene onwards. The long-term increase in δ18O values corresponds to increasingly arid conditions, while increasing δ13C values reflect the changing proportion of C3/C4 vegetation in the local environment. Analysis of the Thabaseek Tufa, in particular, provides valuable evidence for reconstructing the depositional and chronological context of the enigmatic Taung Child (Australopithecus africanus). Collectively, the results of the present study demonstrate the potential of these deposits for developing high-precision records of climate change and, ultimately, for understanding the causal processes relating climate and hominin evolution.

  5. Chimpanzee subspecies and ‘robust’ australopithecine holotypes, in the context of comments by Darwin

    Directory of Open Access Journals (Sweden)

    S. Prat

    2010-02-01

    Full Text Available On the basis of comparative anatomy (including chimpanzees, gorillas and other primates, Darwin1 suggested that Africa was the continent from which ‘progenitors’ of humankind evolved. Hominin fossils from this continent proved him correct. We present the results of morphometric analyses based on cranial data obtained from chimpanzee taxa currently recognised as distinct subspecies, namely Pan troglodytes troglodytes and Pan troglodytes schweinfurthii, as well as Pan paniscus (bonobo. Our objective was to use a morphometric technique2 to quantify the degree of similarity between pairs of specimens, in the context of a statistical (probabilistic definition of a species.3–5 Results obtained from great apes, including two subspecies of chimpanzee, were assessed in relation to same-scale comparisons between the holotypes of ‘robust’ australopithecine (Plio-Pleistocene hominin taxa which have traditionally been distinguished at a species level, notably Paranthropus robustus from South Africa, and Paranthropus (Australopithecus/ Zinjanthropus boisei from East Africa. The question arises as to whether the holotypes of these two taxa, TM 1517 from Kromdraai6 and OH 5 from Olduvai,7 respectively, are different at the subspecies rather than at the species level.

  6. Disproportionate Cochlear Length in Genus Homo Shows a High Phylogenetic Signal during Apes' Hearing Evolution.

    Science.gov (United States)

    Braga, J; Loubes, J-M; Descouens, D; Dumoncel, J; Thackeray, J F; Kahn, J-L; de Beer, F; Riberon, A; Hoffman, K; Balaresque, P; Gilissen, E

    2015-01-01

    Changes in lifestyles and body weight affected mammal life-history evolution but little is known about how they shaped species' sensory systems. Since auditory sensitivity impacts communication tasks and environmental acoustic awareness, it may have represented a deciding factor during mammal evolution, including apes. Here, we statistically measure the influence of phylogeny and allometry on the variation of five cochlear morphological features associated with hearing capacities across 22 living and 5 fossil catarrhine species. We find high phylogenetic signals for absolute and relative cochlear length only. Comparisons between fossil cochleae and reconstructed ape ancestral morphotypes show that Australopithecus absolute and relative cochlear lengths are explicable by phylogeny and concordant with the hypothetized ((Pan,Homo),Gorilla) and (Pan,Homo) most recent common ancestors. Conversely, deviations of the Paranthropus oval window area from these most recent common ancestors are not explicable by phylogeny and body weight alone, but suggest instead rapid evolutionary changes (directional selection) of its hearing organ. Premodern (Homo erectus) and modern human cochleae set apart from living non-human catarrhines and australopiths. They show cochlear relative lengths and oval window areas larger than expected for their body mass, two features corresponding to increased low-frequency sensitivity more recent than 2 million years ago. The uniqueness of the "hypertrophied" cochlea in the genus Homo (as opposed to the australopiths) and the significantly high phylogenetic signal of this organ among apes indicate its usefulness to identify homologies and monophyletic groups in the hominid fossil record.

  7. Disproportionate Cochlear Length in Genus Homo Shows a High Phylogenetic Signal during Apes' Hearing Evolution.

    Directory of Open Access Journals (Sweden)

    J Braga

    Full Text Available Changes in lifestyles and body weight affected mammal life-history evolution but little is known about how they shaped species' sensory systems. Since auditory sensitivity impacts communication tasks and environmental acoustic awareness, it may have represented a deciding factor during mammal evolution, including apes. Here, we statistically measure the influence of phylogeny and allometry on the variation of five cochlear morphological features associated with hearing capacities across 22 living and 5 fossil catarrhine species. We find high phylogenetic signals for absolute and relative cochlear length only. Comparisons between fossil cochleae and reconstructed ape ancestral morphotypes show that Australopithecus absolute and relative cochlear lengths are explicable by phylogeny and concordant with the hypothetized ((Pan,Homo,Gorilla and (Pan,Homo most recent common ancestors. Conversely, deviations of the Paranthropus oval window area from these most recent common ancestors are not explicable by phylogeny and body weight alone, but suggest instead rapid evolutionary changes (directional selection of its hearing organ. Premodern (Homo erectus and modern human cochleae set apart from living non-human catarrhines and australopiths. They show cochlear relative lengths and oval window areas larger than expected for their body mass, two features corresponding to increased low-frequency sensitivity more recent than 2 million years ago. The uniqueness of the "hypertrophied" cochlea in the genus Homo (as opposed to the australopiths and the significantly high phylogenetic signal of this organ among apes indicate its usefulness to identify homologies and monophyletic groups in the hominid fossil record.

  8. Hard-object feeding in sooty mangabeys (Cercocebus atys and interpretation of early hominin feeding ecology.

    Directory of Open Access Journals (Sweden)

    David J Daegling

    Full Text Available Morphology of the dentofacial complex of early hominins has figured prominently in the inference of their dietary adaptations. Recent theoretical analysis of craniofacial morphology of Australopithecus africanus proposes that skull form in this taxon represents adaptation to feeding on large, hard objects. A modern analog for this specific dietary specialization is provided by the West African sooty mangabey, Cercocebus atys. This species habitually feeds on the large, exceptionally hard nuts of Sacoglottis gabonensis, stereotypically crushing the seed casings using their premolars and molars. This type of behavior has been inferred for A. africanus based on mathematical stress analysis and aspects of dental wear and morphology. While postcanine megadontia, premolar enlargement and thick molar enamel characterize both A. africanus and C. atys, these features are not universally associated with durophagy among living anthropoids. Occlusal microwear analysis reveals complex microwear textures in C. atys unlike those observed in A. africanus, but more closely resembling textures observed in Paranthropus robustus. Since sooty mangabeys process hard objects in a manner similar to that proposed for A. africanus, yet do so without the craniofacial buttressing characteristic of this hominin, it follows that derived features of the australopith skull are sufficient but not necessary for the consumption of large, hard objects. The adaptive significance of australopith craniofacial morphology may instead be related to the toughness, rather than the hardness, of ingested foods.

  9. Disproportionate Cochlear Length in Genus Homo Shows a High Phylogenetic Signal during Apes’ Hearing Evolution

    Science.gov (United States)

    Braga, J.; Loubes, J-M.; Descouens, D.; Dumoncel, J.; Thackeray, J. F.; Kahn, J-L.; de Beer, F.; Riberon, A.; Hoffman, K.; Balaresque, P.; Gilissen, E.

    2015-01-01

    Changes in lifestyles and body weight affected mammal life-history evolution but little is known about how they shaped species’ sensory systems. Since auditory sensitivity impacts communication tasks and environmental acoustic awareness, it may have represented a deciding factor during mammal evolution, including apes. Here, we statistically measure the influence of phylogeny and allometry on the variation of five cochlear morphological features associated with hearing capacities across 22 living and 5 fossil catarrhine species. We find high phylogenetic signals for absolute and relative cochlear length only. Comparisons between fossil cochleae and reconstructed ape ancestral morphotypes show that Australopithecus absolute and relative cochlear lengths are explicable by phylogeny and concordant with the hypothetized ((Pan,Homo),Gorilla) and (Pan,Homo) most recent common ancestors. Conversely, deviations of the Paranthropus oval window area from these most recent common ancestors are not explicable by phylogeny and body weight alone, but suggest instead rapid evolutionary changes (directional selection) of its hearing organ. Premodern (Homo erectus) and modern human cochleae set apart from living non-human catarrhines and australopiths. They show cochlear relative lengths and oval window areas larger than expected for their body mass, two features corresponding to increased low-frequency sensitivity more recent than 2 million years ago. The uniqueness of the “hypertrophied” cochlea in the genus Homo (as opposed to the australopiths) and the significantly high phylogenetic signal of this organ among apes indicate its usefulness to identify homologies and monophyletic groups in the hominid fossil record. PMID:26083484

  10. Unique Dental Morphology of Homo floresiensis and Its Evolutionary Implications.

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    Yousuke Kaifu

    Full Text Available Homo floresiensis is an extinct, diminutive hominin species discovered in the Late Pleistocene deposits of Liang Bua cave, Flores, eastern Indonesia. The nature and evolutionary origins of H. floresiensis' unique physical characters have been intensively debated. Based on extensive comparisons using linear metric analyses, crown contour analyses, and other trait-by-trait morphological comparisons, we report here that the dental remains from multiple individuals indicate that H. floresiensis had primitive canine-premolar and advanced molar morphologies, a combination of dental traits unknown in any other hominin species. The primitive aspects are comparable to H. erectus from the Early Pleistocene, whereas some of the molar morphologies are more progressive even compared to those of modern humans. This evidence contradicts the earlier claim of an entirely modern human-like dental morphology of H. floresiensis, while at the same time does not support the hypothesis that H. floresiensis originated from a much older H. habilis or Australopithecus-like small-brained hominin species currently unknown in the Asian fossil record. These results are however consistent with the alternative hypothesis that H. floresiensis derived from an earlier Asian Homo erectus population and experienced substantial body and brain size dwarfism in an isolated insular setting. The dentition of H. floresiensis is not a simple, scaled-down version of earlier hominins.

  11. Fossil skulls reveal that blood flow rate to the brain increased faster than brain volume during human evolution

    Science.gov (United States)

    Seymour, Roger S.; Bosiocic, Vanya; Snelling, Edward P.

    2016-08-01

    The evolution of human cognition has been inferred from anthropological discoveries and estimates of brain size from fossil skulls. A more direct measure of cognition would be cerebral metabolic rate, which is proportional to cerebral blood flow rate (perfusion). The hominin cerebrum is supplied almost exclusively by the internal carotid arteries. The sizes of the foramina that transmitted these vessels in life can be measured in hominin fossil skulls and used to calculate cerebral perfusion rate. Perfusion in 11 species of hominin ancestors, from Australopithecus to archaic Homo sapiens, increases disproportionately when scaled against brain volume (the allometric exponent is 1.41). The high exponent indicates an increase in the metabolic intensity of cerebral tissue in later Homo species, rather than remaining constant (1.0) as expected by a linear increase in neuron number, or decreasing according to Kleiber's Law (0.75). During 3 Myr of hominin evolution, cerebral tissue perfusion increased 1.7-fold, which, when multiplied by a 3.5-fold increase in brain size, indicates a 6.0-fold increase in total cerebral blood flow rate. This is probably associated with increased interneuron connectivity, synaptic activity and cognitive function, which all ultimately depend on cerebral metabolic rate.

  12. 《21世紀の医学の重要課題》一文的注释、分析及翻译(十二)

    Institute of Scientific and Technical Information of China (English)

    吴宣刚

    2001-01-01

    @@ [接上期] 原文:自然段28 人類の歴史を、猿人(australopithecus)の時代から見てみま寸と、原生人(homo sapiens)が現われたのは10~20万年前と考之られています.仮に400万年前老1日の午前0時とし、現在を24小時としますと、農業が始まったのは早いところ、例えば中国の最も早いところで23畴57分、工業が始まったのはョ一口ッパで23畴59分24秒であ9ます.アジア諸国で工業化が進み、人口が飽食したのは、ほんの1~2秒に遇ぎません.

  13. A filogênese da linguagem: novas abordagens de antigas questões

    Directory of Open Access Journals (Sweden)

    FERREIRA ROBERTO GODOFREDO FABRI

    2000-01-01

    Full Text Available A filogênese e a antropogênese da linguagem tornam-se elementos fundamentais para conhecimento anatômico e fisiológico dos mecanismos da comunicação humana, bem como suas aplicações clínicas. Durante o processo de desenvolvimento primata, importantes transformações no corpo do animal, notadamente na cabeça, ocorreram a partir da vida arborícola com implicações importantes na gênese da linguagem. A aquisição de uma postura semi-vertical do corpo, o uso exploratórios das mãos e o desenvolvimento da visão em detrimento da olfação permitiram o crescimento craniano e o aumento do encéfalo. Com o retorno do primata ao chão e o desenvolvimento da bipedia nos Australopithecus, ocorreu progressivo crescimento em leque das regiões frontais, parietais e temporais, permitindo o desenvolvimento simultâneo dos centros neuroanatômicos de linguagem, expressão facial e atividade motora manual.

  14. Estimate of the lower-limb-specific muscle parameters during bipedal walking for humans, apes and early hominids with the implications for the evolution of body proportion

    Institute of Scientific and Technical Information of China (English)

    Wang Weijie

    2007-01-01

    Modern human has different body proportion from early hominids and great apes. Comparing with others, in general, modern human adults have relatively long lower limb and heavier body weight. Since the lower limbs provide support to the whole body and play an important role in walking, it is proposed that the ratio of the lower limb to the whole body for modern human could be beneficial to bipedal walking. This study tried to estimate the muscle parameters of the lower limb in walking for the subjects with various body proportions. Using a simplified musculoskeletal model, some muscle parameters of the lower limb, e.g. muscle force, stress, work and power, were estimated for modern human adult, child, AL 288-1 (the fossil specimens of Australopithecus afarensis, 3.18 million years old) and apes. The results show that with the body proportion modern human adult spends less muscle work and power in walking than other subjects. The results imply that using the cost of transport (i.e. the muscle work of the lower limb per unit of displacement) as the criteria, the early hominids, if their body proportions were structurally similar to AL 288-1, could evolve towards what modern human adult looks like, in order to save energy during bipedal walking.

  15. Possible brucellosis in an early hominin skeleton from sterkfontein, South Africa.

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    Ruggero D'Anastasio

    Full Text Available We report on the paleopathological analysis of the partial skeleton of the late Pliocene hominin species Australopithecus africanus Stw 431 from Sterkfontein, South Africa. A previous study noted the presence of lesions on vertebral bodies diagnosed as spondylosis deformans due to trauma. Instead, we suggest that these lesions are pathological changes due to the initial phases of an infectious disease, brucellosis. The macroscopic, microscopic and radiological appearance of the lytic lesions of the lumbar vertebrae is consistent with brucellosis. The hypothesis of brucellosis (most often associated with the consumption of animal proteins in a 2.4 to 2.8 million year old hominid has a host of important implications for human evolution. The consumption of meat has been regarded an important factor in supporting, directing or altering human evolution. Perhaps the earliest (up to 2.5 million years ago paleontological evidence for meat eating consists of cut marks on animal remains and stone tools that could have made these marks. Now with the hypothesis of brucellosis in A. africanus, we may have evidence of occasional meat eating directly linked to a fossil hominin.

  16. A new horned crocodile from the Plio-Pleistocene hominid sites at Olduvai Gorge, Tanzania.

    Directory of Open Access Journals (Sweden)

    Christopher A Brochu

    Full Text Available BACKGROUND: The fossil record reveals surprising crocodile diversity in the Neogene of Africa, but relationships with their living relatives and the biogeographic origins of the modern African crocodylian fauna are poorly understood. A Plio-Pleistocene crocodile from Olduvai Gorge, Tanzania, represents a new extinct species and shows that high crocodylian diversity in Africa persisted after the Miocene. It had prominent triangular "horns" over the ears and a relatively deep snout, these resemble those of the recently extinct Malagasy crocodile Voay robustus, but the new species lacks features found among osteolaemines and shares derived similarities with living species of Crocodylus. METHODOLOGY/PRINCIPAL FINDINGS: The holotype consists of a partial skull and skeleton and was collected on the surface between two tuffs dated to approximately 1.84 million years (Ma, in the same interval near the type localities for the hominids Homo habilis and Australopithecus boisei. It was compared with previously-collected material from Olduvai Gorge referable to the same species. Phylogenetic analysis places the new form within or adjacent to crown Crocodylus. CONCLUSIONS/SIGNIFICANCE: The new crocodile species was the largest predator encountered by our ancestors at Olduvai Gorge, as indicated by hominid specimens preserving crocodile bite marks from these sites. The new species also reinforces the emerging view of high crocodylian diversity throughout the Neogene, and it represents one of the few extinct species referable to crown genus Crocodylus.

  17. Crecimiento y desarrollo: una perspectiva evolutiva

    Directory of Open Access Journals (Sweden)

    Goikoetxea Zabaleta, I.

    2011-01-01

    Full Text Available El estudio del patrón de crecimiento y desarrollo en las distintas especies fósiles del linaje humano permite interpretar de forma correcta el modelo de historia biológica de los individuos adultos e inmaduros y, además, ayuda a los investigadores a comprender mejor la evolución de nuestra especie. Los patrones de crecimiento y desarrollo de los humanos actuales y de los chimpancés son los que a día de hoy mejor se conocen y por eso son usados como modelos. Los restos de los individuos inmaduros del registro fósil contienen información que permite hipotetizar sobre estos patrones a lo largo de la evolución humana. En este trabajo se reúnen datos de individuos subadultos del registro fósil y se realiza una puesta al día sobre las hipótesis que hasta ahora se han propuesto para el patrón de crecimiento y desarrollo de las especies de los géneros Australopithecus, Paranthropus y Homo.

  18. Quantum Field Theory in Curved Spacetime

    Science.gov (United States)

    Reynolds, Sally C.; Gallagher, Andrew

    2012-03-01

    List of contributors; Foreword J. T. Francis Thackeray; 1. African genesis: an evolving paradigm Sally C. Reynolds; 2. Academic genealogy Peter Ungar and Phillip V. Tobias; Part I. In Search of Origins: Evolutionary Theory, New Species, and Paths into the Past: 3. Speciation in hominin evolution Colin Groves; 4. Searching for a new paradigm for hominid origins in Chad (Central Africa) Michel Brunet; 5. From hominoid arboreality to hominid bipedalism Brigitte Senut; 6. Orrorin and the African ape/hominid dichotomy Martin Pickford; 7. A brief history and results of 40 years of Sterkfontein excavations Ronald J. Clarke; Part II. Hominin Morphology Through Time: Brains, Bodies and Teeth: 8. Hominin brain evolution, 1925-2011: an emerging overview Dean Falk; 9. The issue of brain reorganisation in Australopithecus and early hominids: Dart had it right Ralph L. Holloway; 10. The mass of the human brain: is it a spandrel? Paul R. Manger, Jason Hemingway, Muhammad Spocter and Andrew Gallagher; 11. Origin and diversity of early hominin bipedalism Henry M. McHenry; 12. Forelimb adaptations in Australopithecus afarensis Michelle S. M. Drapeau; 13. Hominin proximal femur morphology from the Tugen Hills to Flores Brian G. Richmond and William L. Jungers; 14. Daily rates of dentine formation and root extension rates in Paranthropus boisei, KNM-ER 1817, from Koobi Fora, Kenya M. Christopher Dean; 15. On the evolutionary development of early hominid molar teeth and the Gondolin Paranthropus molar Kevin L. Kuykendall; 16. Digital South African fossils: morphological studies using reference-based reconstruction and electronic preparation Gerhard W. Weber, Philipp Gunz, Simon Neubauer, Philipp Mitteroecker and Fred L. Bookstein; Part III. Modern Human Origins: Patterns, and Processes: 17. Body size in African Middle Pleistocene Homo Steven E. Churchill, Lee R. Berger, Adam Hartstone-Rose and Headman Zondo; 18. The African origin of recent humanity Milford H. Wolpoff and Sang-Hee Lee

  19. The Vindija Neanderthal scapular glenoid fossa: comparative shape analysis suggests evo-devo changes among Neanderthals.

    Science.gov (United States)

    Di Vincenzo, Fabio; Churchill, Steven E; Manzi, Giorgio

    2012-02-01

    Although the shape of the scapular glenoid fossa (SGF) may be influenced by epigenetic and developmental factors, there appears to be strong genetic control over its overall form, such that variation within and between hominin taxa in SGF shape may contain information about their evolutionary histories. Here we present the results of a geometric morphometric study of the SGF of the Neanderthal Vi-209 from Vindjia Cave (Croatia), relative to samples of Plio-Pleistocene, later Pleistocene, and recent hominins. Variation in overall SGF shape follows a chronological trend from the plesiomorphic condition seen in Australopithecus to modern humans, with pre-modern species of the genus Homo exhibiting intermediate morphologies. Change in body size across this temporal series is not linearly directional, which argues against static allometry as an explanation. However, life history and developmental rates change directionally across the series, suggesting an ontogenetic effect on the observed changes in shape (ontogenetic allometry). Within this framework, the morphospace occupied by the Neanderthals exhibits a discontinuous distribution. The Vindija SGF and those of the later Near Eastern Neanderthals (Kebara and Shanidar) approach the modern condition and are somewhat segregated from both northwestern European (Neandertal and La Ferrassie) and early Mediterranean Neanderthals (Krapina and Tabun). Although more than one scenario may account for the pattern seen in the Neanderthals, the data is consistent with palaeogenetic evidence suggesting low levels of gene flow between Neanderthals and modern humans in the Near East after ca. 120-100 ka (thousands of years ago) (with subsequent introgression of modern human alleles into eastern and central Europe). Thus, in keeping with previous analyses that document some modern human features in the Vindija Neanderthals, the Vindija G(3) sample should not be seen as representative of 'classic'--that is, unadmixed, pre

  20. A simple rule governs the evolution and development of hominin tooth size.

    Science.gov (United States)

    Evans, Alistair R; Daly, E Susanne; Catlett, Kierstin K; Paul, Kathleen S; King, Stephen J; Skinner, Matthew M; Nesse, Hans P; Hublin, Jean-Jacques; Townsend, Grant C; Schwartz, Gary T; Jernvall, Jukka

    2016-02-25

    The variation in molar tooth size in humans and our closest relatives (hominins) has strongly influenced our view of human evolution. The reduction in overall size and disproportionate decrease in third molar size have been noted for over a century, and have been attributed to reduced selection for large dentitions owing to changes in diet or the acquisition of cooking. The systematic pattern of size variation along the tooth row has been described as a 'morphogenetic gradient' in mammal, and more specifically hominin, teeth since Butler and Dahlberg. However, the underlying controls of tooth size have not been well understood, with hypotheses ranging from morphogenetic fields to the clone theory. In this study we address the following question: are there rules that govern how hominin tooth size evolves? Here we propose that the inhibitory cascade, an activator-inhibitor mechanism that affects relative tooth size in mammals, produces the default pattern of tooth sizes for all lower primary postcanine teeth (deciduous premolars and permanent molars) in hominins. This configuration is also equivalent to a morphogenetic gradient, finally pointing to a mechanism that can generate this gradient. The pattern of tooth size remains constant with absolute size in australopiths (including Ardipithecus, Australopithecus and Paranthropus). However, in species of Homo, including modern humans, there is a tight link between tooth proportions and absolute size such that a single developmental parameter can explain both the relative and absolute sizes of primary postcanine teeth. On the basis of the relationship of inhibitory cascade patterning with size, we can use the size at one tooth position to predict the sizes of the remaining four primary postcanine teeth in the row for hominins. Our study provides a development-based expectation to examine the evolution of the unique proportions of human teeth.

  1. Recent origin of low trabecular bone density in modern humans.

    Science.gov (United States)

    Chirchir, Habiba; Kivell, Tracy L; Ruff, Christopher B; Hublin, Jean-Jacques; Carlson, Kristian J; Zipfel, Bernhard; Richmond, Brian G

    2015-01-13

    Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations.

  2. The evolutionary relationships and age of Homo naledi: An assessment using dated Bayesian phylogenetic methods.

    Science.gov (United States)

    Dembo, Mana; Radovčić, Davorka; Garvin, Heather M; Laird, Myra F; Schroeder, Lauren; Scott, Jill E; Brophy, Juliet; Ackermann, Rebecca R; Musiba, Chares M; de Ruiter, Darryl J; Mooers, Arne Ø; Collard, Mark

    2016-08-01

    Homo naledi is a recently discovered species of fossil hominin from South Africa. A considerable amount is already known about H. naledi but some important questions remain unanswered. Here we report a study that addressed two of them: "Where does H. naledi fit in the hominin evolutionary tree?" and "How old is it?" We used a large supermatrix of craniodental characters for both early and late hominin species and Bayesian phylogenetic techniques to carry out three analyses. First, we performed a dated Bayesian analysis to generate estimates of the evolutionary relationships of fossil hominins including H. naledi. Then we employed Bayes factor tests to compare the strength of support for hypotheses about the relationships of H. naledi suggested by the best-estimate trees. Lastly, we carried out a resampling analysis to assess the accuracy of the age estimate for H. naledi yielded by the dated Bayesian analysis. The analyses strongly supported the hypothesis that H. naledi forms a clade with the other Homo species and Australopithecus sediba. The analyses were more ambiguous regarding the position of H. naledi within the (Homo, Au. sediba) clade. A number of hypotheses were rejected, but several others were not. Based on the available craniodental data, Homo antecessor, Asian Homo erectus, Homo habilis, Homo floresiensis, Homo sapiens, and Au. sediba could all be the sister taxon of H. naledi. According to the dated Bayesian analysis, the most likely age for H. naledi is 912 ka. This age estimate was supported by the resampling analysis. Our findings have a number of implications. Most notably, they support the assignment of the new specimens to Homo, cast doubt on the claim that H. naledi is simply a variant of H. erectus, and suggest H. naledi is younger than has been previously proposed.

  3. Hominins, sedges, and termites: new carbon isotope data from the Sterkfontein valley and Kruger National Park.

    Science.gov (United States)

    Sponheimer, Matt; Lee-Thorp, Julia; de Ruiter, Darryl; Codron, Daryl; Codron, Jacqui; Baugh, Alexander T; Thackeray, Francis

    2005-03-01

    Stable carbon isotope analyses have shown that South African australopiths did not have exclusively frugivorous diets, but also consumed significant quantities of C4 foods such as grasses, sedges, or animals that ate these foods. Yet, these studies have had significant limitations. For example, hominin sample sizes were relatively small, leading some to question the veracity of the claim for australopith C4 consumption. In addition, it has been difficult to determine which C4 resources were actually utilized, which is at least partially due to a lack of stable isotope data on some purported australopith foods. Here we begin to address these lacunae by presenting carbon isotope data for 14 new hominin specimens, as well as for two potential C4 foods (termites and sedges). The new data confirm that non-C3 foods were heavily utilized by australopiths, making up about 40% and 35% of Australopithecus and Paranthropus diets respectively. Most termites in the savanna-woodland biome of the Kruger National Park, South Africa, have intermediate carbon isotope compositions indicating mixed C3/C4 diets. Only 28% of the sedges in Kruger were C4, and few if any had well-developed rhizomes and tubers that make some sedges attractive foods. We conclude that although termites and sedges might have contributed to the C4 signal in South African australopiths, other C4 foods were also important. Lastly, we suggest that the consumption of C4 foods is a fundamental hominin trait that, along with bipedalism, allowed australopiths to pioneer increasingly open and seasonal environments.

  4. Craniofacial biomechanics and functional and dietary inferences in hominin paleontology.

    Science.gov (United States)

    Grine, Frederick E; Judex, Stefan; Daegling, David J; Ozcivici, Engin; Ungar, Peter S; Teaford, Mark F; Sponheimer, Matt; Scott, Jessica; Scott, Robert S; Walker, Alan

    2010-04-01

    Finite element analysis (FEA) is a potentially powerful tool by which the mechanical behaviors of different skeletal and dental designs can be investigated, and, as such, has become increasingly popular for biomechanical modeling and inferring the behavior of extinct organisms. However, the use of FEA to extrapolate from characterization of the mechanical environment to questions of trophic or ecological adaptation in a fossil taxon is both challenging and perilous. Here, we consider the problems and prospects of FEA applications in paleoanthropology, and provide a critical examination of one such study of the trophic adaptations of Australopithecus africanus. This particular FEA is evaluated with regard to 1) the nature of the A. africanus cranial composite, 2) model validation, 3) decisions made with respect to model parameters, 4) adequacy of data presentation, and 5) interpretation of the results. Each suggests that the results reflect methodological decisions as much as any underlying biological significance. Notwithstanding these issues, this model yields predictions that follow from the posited emphasis on premolar use by A. africanus. These predictions are tested with data from the paleontological record, including a phylogenetically-informed consideration of relative premolar size, and postcanine microwear fabrics and antemortem enamel chipping. In each instance, the data fail to conform to predictions from the model. This model thus serves to emphasize the need for caution in the application of FEA in paleoanthropological enquiry. Theoretical models can be instrumental in the construction of testable hypotheses; but ultimately, the studies that serve to test these hypotheses - rather than data from the models - should remain the source of information pertaining to hominin paleobiology and evolution.

  5. Isotopic evidence of early hominin diets

    Science.gov (United States)

    Sponheimer, Matt; Alemseged, Zeresenay; Cerling, Thure E.; Grine, Frederick E.; Kimbel, William H.; Leakey, Meave G.; Lee-Thorp, Julia A.; Kyalo Manthi, Fredrick; Reed, Kaye E.; Wood, Bernard A.; Wynn, Jonathan G.

    2013-06-01

    Carbon isotope studies of early hominins from southern Africa showed that their diets differed markedly from the diets of extant apes. Only recently, however, has a major influx of isotopic data from eastern Africa allowed for broad taxonomic, temporal, and regional comparisons among hominins. Before 4 Ma, hominins had diets that were dominated by C3 resources and were, in that sense, similar to extant chimpanzees. By about 3.5 Ma, multiple hominin taxa began incorporating 13C-enriched [C4 or crassulacean acid metabolism (CAM)] foods in their diets and had highly variable carbon isotope compositions which are atypical for African mammals. By about 2.5 Ma, Paranthropus in eastern Africa diverged toward C4/CAM specialization and occupied an isotopic niche unknown in catarrhine primates, except in the fossil relations of grass-eating geladas (Theropithecus gelada). At the same time, other taxa (e.g., Australopithecus africanus) continued to have highly mixed and varied C3/C4 diets. Overall, there is a trend toward greater consumption of 13C-enriched foods in early hominins over time, although this trend varies by region. Hominin carbon isotope ratios also increase with postcanine tooth area and mandibular cross-sectional area, which could indicate that these foods played a role in the evolution of australopith masticatory robusticity. The 13C-enriched resources that hominins ate remain unknown and must await additional integration of existing paleodietary proxy data and new research on the distribution, abundance, nutrition, and mechanical properties of C4 (and CAM) plants.

  6. Neogene biomarker record of vegetation change in eastern Africa.

    Science.gov (United States)

    Uno, Kevin T; Polissar, Pratigya J; Jackson, Kevin E; deMenocal, Peter B

    2016-06-07

    The evolution of C4 grassland ecosystems in eastern Africa has been intensely studied because of the potential influence of vegetation on mammalian evolution, including that of our own lineage, hominins. Although a handful of sparse vegetation records exists from middle and early Miocene terrestrial fossil sites, there is no comprehensive record of vegetation through the Neogene. Here we present a vegetation record spanning the Neogene and Quaternary Periods that documents the appearance and subsequent expansion of C4 grasslands in eastern Africa. Carbon isotope ratios from terrestrial plant wax biomarkers deposited in marine sediments indicate constant C3 vegetation from ∼24 Ma to 10 Ma, when C4 grasses first appeared. From this time forward, C4 vegetation increases monotonically to present, with a coherent signal between marine core sites located in the Somali Basin and the Red Sea. The response of mammalian herbivores to the appearance of C4 grasses at 10 Ma is immediate, as evidenced from existing records of mammalian diets from isotopic analyses of tooth enamel. The expansion of C4 vegetation in eastern Africa is broadly mirrored by increasing proportions of C4-based foods in hominin diets, beginning at 3.8 Ma in Australopithecus and, slightly later, Kenyanthropus This continues into the late Pleistocene in Paranthropus, whereas Homo maintains a flexible diet. The biomarker vegetation record suggests the increase in open, C4 grassland ecosystems over the last 10 Ma may have operated as a selection pressure for traits and behaviors in Homo such as bipedalism, flexible diets, and complex social structure.

  7. Biometrical studies upon hominoid teeth: the coefficient of variation, sexual dimorphism and questions of phylogenetic relationship.

    Science.gov (United States)

    Blumenberg, B

    1985-01-01

    Sexual dimorphism as a function of variation in hominoid tooth metrics has been investigated for four groups of taxa: Recent great apes (two subfamilies), Dryopiths (one subfamily), Ramapiths (one subfamily) and hominids (one family). Gorilla, and to a lesser extent Pan, appear characterized by very high levels of sexual dimorphism and meet several criteria for statistical outliers. Recent great apes are the only group exhibiting consistently high levels of sexual dimorphism. Ramapiths are the only group characterized by low levels of sexual dimorphism and their relative canine length is most similar to Dryopiths. Both Dryopiths and hominids contain taxa with low and intermediate levels of sexual dimorphism. The Gingerich and Shoeninger hypothesis relating coefficients of variation to occlusal complexity is supported. Non-parametric statistics suggest that homogeneity of coefficient of variation profiles over most of the tooth row is characteristic of only the Dryopiths and a composite data set composed of the Dryopith plus Ramapith tooth measurements. Oxnard's model for the multifactorial basis of multiple sexual dimorphisms is also supported. The Dryopith and hominid patterns of sexual dimorphism are similar, an observation that suggests phylogenetic relationship. At the taxonomic level of subfamily or family, sexual dimorphism is a character of cladistic usefulness and possible phylogenetic valence. Assuming that breeding system and sexual dimorphism are functional correlates as many workers suggest, then Ramapithecus sp. China, Sivapithecus indicus and possibly Australopithecus boisei are good candidates for having possessed monogamous breeding/social structures. All Dryopith taxa, S. sivalensis, Sivapithecus sp. China, A. afarensis, Homo habilis and H. erectus emerge as the best candidates for having possessed a polygynous breeding/social structure. No biometrical affinities of Ramapiths with hominids can be demonstrated and some phylogenetic relationship with

  8. Barefoot on Hot Ground: Formation Temperatures of Plio-Pleistocene Soil Carbonates in East Africa Based on the Clumped Isotope in Carbonate (Δ47) Thermometer

    Science.gov (United States)

    Passey, B. H.; Eiler, J. M.; Levin, N. E.; Cerling, T. E.

    2008-12-01

    suggest that similarly high temperatures periodically characterized the environments occupied by Australopithecus, Homo, and other human relatives over the past 4 million years.

  9. Early hominid evolution and ecological change through the African Plio-Pleistocene.

    Science.gov (United States)

    Reed, K E

    1997-01-01

    The habitats in which extinct hominids existed has been a key issue in addressing the origin and extinction of early hominids, as well as in understanding various morphological and behavioral adaptations. Many researchers postulated that early hominids lived in an open savanna (Dart, 1925; Robinson, 1963; Howell, 1978). However, Vrba (1985, 1988) has noted that a major global climatic and environmental shift from mesic, closed to xeric, open habitats occurred in the late African Pliocene (approximately 2.5 m.y.a.), thus implying that the earliest hominids existed in these mesic, wooded environs. This climatic shift is also suggested to have contributed to a pulse in speciation events with turnovers of many bovid and possibly hominid species. Previous environmental reconstructions of hominid localities have concentrated on taxonomic identities and taxonomic uniformitarianism to provide habitat reconstructions (e.g., Vrba, 1975; Shipman & Harris, 1988). In addition, relative abundances of species are often used to reconstruct a particular environment, when in fact taphonomic factors could be affecting the proportions of taxa. This study uses the morphological adaptations of mammalian assemblages found with early hominids to reconstruct the habitat based on each species' ecological adaptations, thus minimizing problems introduced by taxonomy and taphonomy. Research presented here compares east and south African Plio-Pleistocene mammalian fossil assemblages with 31 extant mammalian communities from eight different habitat types. All communities are analyzed through ecological diversity methods, that is, each species trophic and locomotor adaptations are used to reconstruct an ecological community and derive its vegetative habitat. Reconstructed habitats show that Australopithecus species existed in fairly wooded, well-watered regions. Paranthropus species lived in similar environs and also in more open regions, but always in habitats that include wetlands. Homo is the

  10. Using (1)(0)Be cosmogenic isotopes to estimate erosion rates and landscape changes during the Plio-Pleistocene in the Cradle of Humankind, South Africa.

    Science.gov (United States)

    Dirks, Paul H G M; Placzek, Christa J; Fink, David; Dosseto, Anthony; Roberts, Eric

    2016-07-01

    Concentrations of cosmogenic (10)Be, measured in quartz from chert and river sediment around the Cradle of Humankind (CoH), are used to determine basin-averaged erosion rates and estimate incision rates for local river valleys. This study focusses on the catchment area that hosts Malapa cave with Australopithecus sediba, in order to compare regional versus localized erosion rates, and better constrain the timing of cave formation and fossil entrapment. Basin-averaged erosion rates for six sub-catchments draining the CoH show a narrow range (3.00 ± 0.28 to 4.15 ± 0.37 m/Mega-annum [Ma]; ±1σ) regardless of catchment size or underlying geology; e.g. the sub-catchment with Malapa Cave (3 km(2)) underlain by dolomite erodes at the same rate (3.30 ± 0.30 m/Ma) as the upper Skeerpoort River catchment (87 km(2)) underlain by shale, chert and conglomerate (3.23 ± 0.30 m/Ma). Likewise, the Skeerpoort River catchment (147 km(2)) draining the northern CoH erodes at a rate (3.00 ± 0.28 m/Ma) similar to the Bloubank-Crocodile River catchment (627 km(2)) that drains the southern CoH (at 3.62 ± 0.33 to 4.15 ± 0.37 m/Ma). Dolomite- and siliciclastic-dominated catchments erode at similar rates, consistent with physical weathering as the rate controlling process, and a relatively dry climate in more recent times. Erosion resistant chert dykes along the Grootvleispruit River below Malapa yield an incision rate of ∼8 m/Ma at steady-state erosion rates for chert of 0.86 ± 0.54 m/Ma. Results provide better palaeo-depth estimates for Malapa Cave of 7-16 m at the time of deposition of A. sediba. Low basin-averaged erosion rates and concave river profiles indicate that the landscape across the CoH is old, and eroding slowly; i.e. the physical character of the landscape changed little in the last 3-4 Ma, and dolomite was exposed on surface probably well into the Miocene. The apparent absence of early Pliocene- or Miocene-aged cave deposits and

  11. Hominid environments at Hadar from paleosol studies in a framework of Ethiopian climate change.

    Science.gov (United States)

    Aronson, James L; Hailemichael, Million; Savin, Samuel M

    2008-10-01

    The amount and seasonal distribution of paleo-rainfall is a major concern of paleoanthropology because they determine the nature of the vegetation and the structure of the ecosystem, particularly in eastern Africa. The delta(18)O and delta(13)C of paleosol carbonates are quantitative proxies of these critical features of the paleoenvironment. The Afar region of Ethiopia lies between the African and Indian summer monsoons, and is prone to profound climate change. In the western Afar, the dominant paleoenvironment of the Hadar Formation during the late Pliocene was a major meandering river's distal low, flat floodplain, on which muds accreted that were continuously transformed into vegetated soils with Bk horizons rich in CaCO(3). The mean delta(13)C of paleosols throughout the Hadar Formation translates to an average vegetative cover across the extensive floodplain of about 30% of the C(4) grasses and 70% of unspecified C(3) plants. The character of the paleosols, such as the one at Locality 333, and their delta(18)O(Carbonate) argue for a highly seasonal rainfall of about twice today's amount, implying that the C(3) plants were mostly sizeable trees and that the biome for Australopithecus afarensis was a grassy woodland. The amount of grasses abruptly increased in the lower Busidima Formation with its early Homo and artifacts to a more open grassy woodland of ca. 50% grasses. However, this transition in delta(13)C is not mirrored in the delta(18)O, which persists at a quite negative average value of -6.4 per thousand over the entire >2-Myr duration of both formations. This value for the carbonate means that the paleosoil water was a quite negative -4.1 per thousand, a significant 5 per thousand more negative than our estimate of modern rain at Hadar. We put the negative delta(18)O of paleo-Hadar's rainfall into an isotopic framework of the dynamic history of climate change in sub-Saharan northern Africa. There have been two end-member climate regimes: (1) an

  12. 沂源人牙冠的几何形态学研究%Geometric and Morphometric Analysis of Middle Pleistocene Hominin Teeth from Yiyuan, Shandong Province

    Institute of Scientific and Technical Information of China (English)

    孙承凯; 周蜜; 邢松

    2011-01-01

    Morphometric analysis of the crowns of six teeth from the Yiyuan site were compared with those of Homo erectus, archaic and late Homo sapiens from Asia, Australopithecus, African early Homo and recent Chinese. The present study shows that the Yiyuan teeth retain some primitive traits, including their trapezoidal outline shapes of the upper premolars and the straight mesial outline of the first upper molar. Other features are apomorphic, as manifested in the extent to which outline of p3 buccal cusp expands mesially and distally, the outline shape of the P4,which is close to that of the recent Chinese, the relatively large paracone size compared to the metacone in M1 , and the roundness of the buccal outline and relatively restricted metaconid of M1. Fossil teeth of early and middle Pleistocene Chinese exhibit many similarities to each other,with no obvious differences being shown, therefore Chinese Homo erectus and archaic Homo sapiens could be treated as a sample group. The teeth from Yiyuan could also be placed in this group, however these teeth are quite “evolved” compared with other sample members. It is noteworthy that M1 and M1 have a very large value of BL/MD, which surpasses each of corresponding specimens used in present study and may be meaningful in interpreting evolutionary progress.%采用形态测量分析方法对上世纪80年代发现于山东沂源的6枚人类牙齿化石齿冠外轮廓形状进行了研究,并与亚洲直立人、早期智人、晚期智人、南方古猿、非洲早期人属以及现代人进行了对比.本文发现:沂源人既保留了部分原始特征,也表现出许多进步特征.颊侧尖基底轮廓原始特征主要表现在P3和P4近似蚕豆形的外轮廓及M1近中轮廓线的平直;进步特征主要体现在:P3向近远中方向的明显扩展、颊侧尖向颊侧的突出程度减弱,P4外轮廓形状处于现代人分布范围的边缘,M1前后尖比例增大,M1颊侧外轮廓的圆隆以及下后尖的