Search results for "mesozoic"

Mise en évidence de corps d'origine cosmique probable au sein de la formation de Carnot (République Centrafricaine)

1992

Resume Deux etudes realisees independamment l'une de l'autre, ont permis de mettre en evidence, au sein de la Formation de Carnot, formation fluviatile mesozoique, d'une part des spherules magnetiques recuperees dans les residus d'un forage (zone de Boyali), d'autre part une anomalie magnetique tres localisee (sur 270 metres de long) traduisant la presence d'un corps decametrique a forte magnetisation remanente (zone de Gambondo). Ces deux elements magnetiques ont une origine cosmique probable. Ils correspondent a des micrometeorites et a une meteorite ayant atteint l'ouest de la Republique Centrafricaine entre l'Albien et le Maastrichtien.

Deep-rooted “thick skinned” model for the High Atlas Mountains (Morocco). Implications for the structural inheritance of the southern Tethys passive …

2006

A re-interpretation of the deep structure of the High Atlas is presented through integration of geophysical and geological data, highlighting the architectural significance of the southern Tethys palaeomargin. Previous crustal models suggest the occurrence of a flat intra-crustal detachment at a depth of � 20 km, a zone where surface thrusts merge and below which the lower High Atlas crust appears continuous. However, within this study seismic refraction data, electrical resistivity surveys and gravity modelling all appear to detect a jump in crustal thickness between the High Atlas and the northern plains. We interpret these data as penetration by thrusts within the ‘‘South-Atlasic fault’’…

Séries condensées et indice de préservation d'unité biostratigraphique: exemple de l'ennoiement de la plate-forme nord-bourguignonne (France) au Call…

1999

Abstract Several depositional environments associated with Callovian-Oxfordian condensed series of the southeast of the Paris Basin are defined. As sedimentation rates were very low, variations in palaeodepth, which were synchronous at regional scale, were taken to directly reflect fluctuations in accommodation potential. Within a major trend toward increased accommodation potential, five sharp upturns and one sharp downturn are detected. A biostratigraphic unit preservation index is denned to quantify and discuss the low preservation of sediments in these condensed series. This index is seen to vary with accommodation potential.

3D structural modeling and restoration of the Apennine-Maghrebian chain in Sicily: Application for non-cylindrical fold-and-thrust belts

2019

International audience; Thirteen seismic reflection profiles and field observations have been used to build a three-dimensional watertight geological model of the sub-surface architecture of the Trapanese carbonate platform unit of the Apennine-Maghrebian chain in the Mt. Kumeta and Mt. Rocca Busambra (NW Sicily, Italy). Either a single step or a two-step thrust-fault deformation model is acceptable on the basis of seismic interpretation but the integration of 3D model reconstruction and 3D geomechanical restoration, validates only the scenario with a single stage of deformation.The 3D model highlights along strike variations of the structural style for the Trapanese unit where pre-existing…

Succession et remplacements de communautés à brachiopodes en régime de sédimentation discontinue (Jurassique Moyen, Bourgogne, France)

1993

Abstract Sequence stratigraphy throws a new and seminal light on the fossil record and helps in determining the respective role played by external control (community replacement) and internal control (paleoecological succession) in the temporal “train” of marine benthic paleocommunities. Five brachiopod-dominated communities (C1–C5) are recognized and their temporal “train” described, during the uppermost Bathonian-lower Callovian interval in Burgundy. The first series (C1–C3) exhibits a trend interpreted as a paleoecological succession and the next two (C3–C4, C4–C5) as community replacements. Within the scope of sequence stratigraphy, the paleoecological succession comes at the end of a t…

A possible bridge between Adria and Africa: New palaeobiogeographic and stratigraphic constraints on the Mesozoic palaeogeography of the Central Medi…

2010

Abstract Dinosaur records in central and southern Italy testify to the occurrence of a diverse dinosaur fauna on the Apennine and Apulian carbonate platforms at least from the Tithonian to the Santonian. Most of the palaeogeographic reconstructions show these domains as topographically isolated areas, separated by deep pelagic basins and far from emerged continental areas. Thus, they hardly justify the long-lasting occurrence of these terrestrial vertebrates. Recent studies on the Mesozoic Panormide Carbonate Platform (western Sicily) yielded important stratigraphical and palaeontological data, which provide evidence for a convincing explanation of this unresolved problem. The recent discov…

Mesozoic tectonics and volcanism from Tethyan rifted continental margins in western Sicily

2009

Tectonic and volcanic features from the Jurassic-Cretaceous carbonate successions of Rocca Busambra, Balatelle Mount and Vicari-Roccapalumba (central-western Sicily), are here described. These areas represent the easternmost outcrops of the Trapanese domain in Sicily. The Trapanese succession consists of shallow to deep-water Meso-Cenozoic deposits formed in a carbonate platform to pelagic plateau depositional setting. Detailed field work and structural analysis detected indicate the occurrence of paleofaults with different orientation, unconformity surfaces, lateral facies changes, resedimented materials and volcanic products (pillow lavas and tuffitic deposits). These data combined with f…

Evoluzione tettonica mesozoica-terziaria della Sicilia centro-settentrionale

2009

Sequence stratigraphy of a mesozoic carbonate platform-to-basin system in Western sicily

2009

Abstract Sequence stratigraphic studies of the Triassic through Paleogene carbonate successions of platform, slope and basin in western Sicily (Palermo and Termini Imerese Mountains) have identified a sedimentary cyclicity mostly caused by relative oscillations of sea level. The stratigraphic successions of the Imerese and Panormide palaeogeographic domains of the southern Tethyan continental margin were studied with physical-stratigraphy and facies analysis to reconstruct the sedimentary evolution of this platform-to-basin system. The Imerese Basin is characterized by a carbonate and siliceous-calcareous succession, 1200–1400m thick, Late Triassic to Eocene in age. The strata display a typ…

The complex nature of progenetic species — examples from Mesozoic ammonites

1991

Several examples of progenetic species among Mesozoic ammonites are investigated. The ammonites are Middle Jurassic kosmoceratids, Upper Jurassic oppeliids, and Upper Cretaceous scaphites. As assessed through outgroup comparison, the progenetic species in each of these examples is characterized by small size at maturity and the presence of morphological features typical of those of the juveniles of more primitive species. However, in none of these examples is the progenetic species a duplicate form of the juvenile stage of more primitive species. There are at least three kinds of features of progenetic species that differ from those of the juveniles of more primitive species: (1) symplesiom…