Search results for " Paleontology"
showing 10 items of 893 documents
Introducing the Human Factor in Predictive Modelling: a Work in Progress
2012
International audience; In this paper we present the results of a study into integrating socio-cultural factors into predictive modelling. So far, predictive modelling has largely neglected the social and cultural dimensions of past landscapes. To maintain its value for archaeological research, therefore, it needs new methodologies, concepts and theories. For this study, we have departed from the methodology developed in the 1990s during the Archaeomedes Project. In this project, cross-regional comparisons of settlement location factors were made by analyzing the environmental context of Roman settlements in the French Rhône Valley. For the current research, we expanded the set of variables…
High-resolution clay mineralogy as a proxy for orbital tuning: example of the Hauterivian-Barremian transition in the Betic Cordillera (SE Spain).
2012
11 pages; International audience; The response of clay mineral assemblages to potential orbital forcing is tested in Mesozoic hemipelagic marl- limestone rhythmites of the Río Argos section (Betic Cordillera, Southeastern Spain). Along the section, marls are pervasively enriched in kaolinite and illite, whereas limestones are enriched in smectite-rich illite/smectite mixed-layers, suggesting that marl-limestone alternations are produced by cyclic high-frequency fluctuations of continental runoff. Spectral analyses show that clay mineral assemblages evolve accordingly to precession, obliquity and eccentricity cycles. Durations of ammonite zones are assessed at 535 kyr for the Late Hauterivia…
The end of the Messinian salinity crisis: Evidences from the Chelif Basin (Algeria).
2007
How did the Messinian Salinity Crisis end is a matter of intense debate between two opposite concepts i.e., the generalised dilution event, the so-called Lago–Mare, followed by the sudden restoration of the marine conditions at the base of the Zanclean, or the early partial or complete marine refill that would have happened earlier during the upper Messinian. The Chelif Basin of Northwestern Algeria, one of the greatest Messinian marginal basins of the Mediterranean, provides an exceptional opportunity to study in detail how this major paleoenvironmental change occurred through continuous sedimentary records of the Miocene–Pliocene boundary. Five sections representative of both the central …
Smithian shoreline migrations and depositional settings in Timpoweap Canyon (Early Triassic, Utah, USA).
2014
AbstractIn Timpoweap Canyon near Hurricane (Utah, USA), spectacular outcrop conditions of Early Triassic rocks document the geometric relationships between a massive Smithian fenestral-microbial unit and underlying, lateral and overlying sedimentary units. This allows us to reconstruct the evolution of depositional environments and high-frequency relative sea-level fluctuations in the studied area. Depositional environments evolved from a coastal plain with continental deposits to peritidal settings with fenestral-microbial limestones, which are overlain by intertidal to shallow subtidal marine bioclastic limestones. This transgressive trend of a large-scale depositional sequence marks a lo…
Mapping of large-scale diapir structures at the paleo-ice tongue bed in western Latvia from geophysical investigations and borehole data
2022
Abstract This study comprises the investigation of the complex and deformed Late Pleistocene sedimentary sequence in western Latvia composed of sandy sediments that are protruded by large-scale clayey silt diapirs and covered by glaciotectonically disturbed discontinuous patches of the Late Weichselian till. We use detailed measurements by ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) combined with borehole data and sedimentological investigations at the Baltic Sea cliffs to map and characterize the large-scale deformation structures and discontinuous till patches. We distinguish the intriguing and previously not detected characteristics of the spatial distribut…
Climatic fluctuations and seasonality during the Late Jurassic (Oxfordian–Early Kimmeridgian) inferred from delta18O of Paris Basin oyster shells.
2008
10 pages; International audience; Oxygen isotope data from biostratigraphically well-dated oyster shells from the Late Jurassic of the eastern Paris Basin are used to reconstruct the thermal evolution of western Tethyan surface waters during the Early Oxfordian–Early Kimmeridgian interval. Seventy eight oyster shells were carefully screened for potential diagenetic alteration using cathodoluminescence microscopy. Isotope analyses were performed on nonluminescent parts of shells (n=264). Intra-shell δ18O variability was estimated by microsampling along a transect perpendicular to the growth lines of the largest oyster shell. The sinusoidal distribution of the δ18O values along this transect …
Continental-scale temperature variability during the past two millennia
2013
Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructi…
Middle Triassic sharks from the Catalan Coastal ranges (NE Spain) and faunal colonization patterns during the westward transgression of Tethys
2020
Abstract Palaeogeographic changes that occurred during the Middle Triassic in the westernmost Tethyan domain were governed by a westward marine transgression of the Tethys Ocean. The transgression flooded wide areas of the eastern part of Iberia, forming new epicontinental shallow-marine environments, which were subsequently colonized by diverse faunas, including chondrichthyans. The transgression is recorded by two successive transgressive–regressive cycles: (1) middle–late Anisian and (2) late Anisian–early Carnian. Here, we describe the chondrichthyan fauna recovered from several Middle Triassic stratigraphic sections (Pelsonian-Longobardian) located at the Catalan Coastal Basin (western…
Palynofacies and calcareous nannofossils in the Upper Kimmeridgian, southeastern Paris basin (France)
2005
AbstractThe Upper Kimmeridgian Members “Calcaires blancs supérieurs” and the “Marnes à exogyres supérieures” of the southeastern Paris basin were investigated for their palynofacies and calcareous nannofossils. These members display alternating limestone-marl lithotypes and represent shallow marine palaeoenvironments. The lower carbonate member is interpreted as a proximal palaeoenvironment (palaeobathymetry = 5 to 10 m), where storm and swell deposits were prevalent and the salinity was occasionally weak. The relative richness of brown phytoclasts in this part is favoured by good preservation related to restricted conditions. These conditions would explain the dominance of the nannofoss…
Les pistes d’archosauriens : Kayentapus ubacensis nov. isp. (théropodes) et crocodylomorphes du Bathonien des Grands-Causses (France). Conséquences p…
2018
Resume Deux sites a traces de pas tridactyles II–IV de theropodes et de « probables » sauropodes des Grands Causses, sommairement decrits en 2006, sont ici reetudies. Il s’agit des sites du Capelan (commune de Meyrueis, Lozere) et de la Garene (commune de La Roque-Sainte-Marguerite, Aveyron), tous deux d’âge Bathonien. En 2012, l’un d’entre eux (Le Capelan) a fait l’objet d’une fouille et d’un agrandissement, permettant la decouverte de nombreuses traces. Dans le site du Capelan, 102 epireliefs concaves, compris entre 11 et 36 cm de longueur, appartiennent a, au moins, 21 pistes; la plus longue etant visible sur 37 metres. Dans l’ensemble, ces empreintes sont presque aussi longues que large…