Search results for "Geophysic"
showing 10 items of 2684 documents
Regional Tectonic Setting and Geological Structure of the Rhenish Massif
1983
This chapter contains an outline of the geological history of the Rhenish Massif and the development of its margins and surrounding areas. Section 2.2 gives some main aspects of the development of the Variscan geosyncline and orogeny and a short description of the pre-Variscan geological history of this region. Since the end of the Variscan orogeny many different epeirogenetic processes have occurred here (Sect. 2.3). During these long geological times uplift and subsidence changed in the different parts of the Massif and in the surrounding areas.
The owl that never left! Taphonomy of Earlier Stone Age small mammal assemblages from Wonderwerk Cave (South Africa)
2022
Wonderwerk Cave, in South Africa, is an exceptional site that has yielded a large collection of small mammal fossils in a stratigraphic sequence reaching back ca. 2 million years. Taphonomic studies undertaken to date, show that Tytonidae (likely Tyto alba) was the dominant predator during the Earlier Stone Age. They produced masses of pellets that formed a dense carpet-like surface that covered the cave floor at intervals throughout the sequence. This paper compares the taphonomic signatures of five different Earlier Stone Age small mammal assemblages from Wonderwerk Cave, including assemblages not studied before, as well as a modern pellet assemblage collected from inside the cave. These …
Climatic ups and downs in a disturbed Jurassic world.
2011
4 pages; International audience; The tropical, warm, and equable climate of the Jurassic world is regularly challenged by geoscientists, especially since oxygen isotopes ( 18O) of fossil hardparts have been used to reconstruct the paleotemperature history of seawater. By applying the innovative “SiZer” (significant zero crossings of the derivatives) statistical approach to a newly compiled 18O database for the Jurassic, we demonstrate the occurrence of major and multiscale 18O changes mainly related to climate disturbances. For the first time, two long-term anomalies in 18O are identified during the Toarcian and the Late Jurassic, in conjunction with intensive volcanism in large igneous pro…
Paleoecological constraints on reef-coral morphologies in the Tortonian–early Messinian of the Lorca Basin, SE Spain
2004
Abstract Coral reefs represent one of the main carbonate factories that contributed to the control of the stratigraphic architecture of carbonate platforms, which had a widespread development during the late Miocene in the paleo-Mediterranean area. The late Miocene reef complexes of the Lorca Basin in southeastern Spain are composed of five mixed siliciclastic/carbonate units, middle Tortonian to early Messinian in age. The development of coral reefs probably ceased when the first evaporitic event occurred in the basin centre in the early Messinian. This study mainly focuses on the response of reef communities and the modifications of reef organisation to global and regional parameters. At …
Geological Setting and Paleoecology of the Upper Cretaceous Bench 19 Marine Vertebrate Bonebed at Bentiaba, Angola
2014
AbstractThe Bench 19 Bonebed at Bentiaba, Angola, is a unique concentration of marine vertebrates preserving six species of mosasaurs in sediments best correlated by magnetostratigraphy to chron C32n.1n between 71.4 and 71.64 Ma. The bonebed formed at a paleolatitude near 24°S, with an Atlantic width at that latitude approximating 2700 km, roughly half that of the current width. The locality lies on an uncharacteristically narrow continental shelf near transform faults that controlled the coastal outline of Africa in the formation of the South Atlantic Ocean. Biostratigraphic change through the Bentiaba section indicates that the accumulation occurred in an ecological time dimension within …
Warming or cooling in the Pragian? Sedimentary record and petrophysical logs across the Lochkovian–Pragian boundary in the Spanish Central Pyrenees
2016
Abstract High-resolution petrophysical correlation methods were applied, for the first time, to mid-Paleozoic rocks of the Pyrenees. The methods included magnetic susceptibility measurements (MS), gamma-ray spectrometry (GRS), and alignment of MS logs using the dynamic time-warping (DTW) algorithm. Conodont biostratigraphy provided the basic framework necessary for work with the GRS and MS logs. Despite differences in the sediment patterns and accumulation/erosion rates, the logs from two selected sections in the Spanish Central Pyrenees show a striking symmetry that correlates well with the previously published logs from the Barrandian area in the Czech Republic. The high similarity betwee…
ISOTOPIC TEMPERATURES FROM THE EARLY AND MID-PLIOCENE OF THE US MIDDLE ATLANTIC COASTAL PLAIN, AND THEIR IMPLICATIONS FOR THE CAUSE OF REGIONAL MARIN…
2017
Mean seasonal extreme temperatures on the seafloor calculated from the shell d 18 Oofthescallop Placopecten clintonius from the basal part of the early Pliocene Sunken Meadow Member (Yorktown Formation) in Virginia are very similar to those from the same horizon at the latitude of Cape Hatteras in North Carolina ( ~ 210 km to the south). The lowest and highest temperatures calculated from each shell (using d 18 O seawater ¼þ 0.7 % )givemean values for winter and summer of 8.4 6 1.1 8 C( 6 1 r ) and 18.2 6 0.6 8 CinVirginia,and8.6 6 0.4 8 Cand16.5 6 1.1 8 C in North Carolina (respective median temperatures: 13.3 8 C and 12.6 8 C). Patterns of ontogenetic variation in d 18 O, d 13 C and micro…
Landscape and fuel management in the context of prehistoric and historical occupations of Cova des Moro (Manacor, Mallorca, Spain)
2021
Abstract In this paper, the first results of charcoal analyses carried out at Cova des Moro (Manacor, Mallorca, Spain) are presented. This cave is an archaeological but also palaeontological site that provides information on endemic fauna (the extinct caprine Myotragus balearicus) before the arrival of humans and, later, the relationship between the first farmers and the landscape. Several human occupations in the cave have been documented, from the Chalcolithic (end of the 3rd millennium cal BC), the Bronze Age (2nd millennium cal BC) and, finally, the Almohad period (13th century AD), during which the cave was used for different purposes. The first results of charcoal analyses at Cova des…
Description de Artareites landii nov. (Ammonoidea) du Barrémien supérieur de Majastre (sud-est de la France) et discussion sur les Helicancylidae Hya…
2009
25 pages; Dans le secteur de Majastre (Alpes-de-Haute-Provence, SE de la France), le domaine hémipélagique du Crétacé inférieur est exposé à la faveur du décrochement du Poil. Cette position paléogéographique et paléotectonique a permis la récolte d'une faune d'ammonites diversifiée dans le niveau à « petits Barremites ». Il est précisément daté ici pour la première fois et se place entre la base de la sous-zone à Barremense et la base du biohorizon à Breistrofferi de la biozone à Vandenheckei (base du Barrémien supérieur). Au sein de cette faune, Artareites landii nov. sp. est considéré ici, par ses caractéristiques et sa position stratigraphique, comme issu du genre Dissimilites Sarkar. L…
La faune ammonitique des marnes à fossiles ferrugineux de la région de Niort, France (Oxfordien inférieur, Zone à Cordatum, Sous-Zone à Cordatum)
2009
21 pages; Une nouvelle récolte d'ammonites dans les marnes à ammonites ferrugineuses de la région de Niort (France), autrefois étudiées par de GROSSOUVRE (1922), apporte de très nombreuses informations biostratigraphiques, paléoenvironnementales et paléobiogéographiques. La faune est datée de l'Oxfordien inférieur : Zone à Cordatum, Sous-Zone à Cordatum, partie inférieure probable. De plus, elle est unique en Europe occidentale 1) par les espèces trouvées -dont certaines ne semblent connues que dans ce gisement- 2) par la domination très atypique du binôme Taramelliceras - Creniceras qui représente les 2/3 des individus. Enfin, le spectre faunique plaide en faveur d'un milieu de plate-forme…