High palaeolatitude (Hodh, Mauritania) recovery of graptolite faunas after the Hirnantian (end Ordovician) extinction event

Marine shales directly overlying lower Hirnantian (uppermost Ordovician) glacially related sediments in Mauritania (North-West Africa) have produced a rich graptolite fauna spanning the Ordovician-Silurian boundary in an area of high palaeolatitude. The lowermost transgressive sandy shales are barren of graptolites, but overlying shales show a sudden appearance of a diverse fauna indicative of the terminal Ordovician persculptus Zone, suggesting that with improving conditions, colonisation by a relatively cold-tolerant fauna was possible. This fauna is replaced by a low diversity assemblage dominated by long ranging taxa, probably representing the basal Silurian acuminatus and atavus Zones. With the extinction of the persculptus Zone fauna, conditions were still hostile to warm water Silurian graptolites, and a Normalograptus fauna was again established. A sudden influx of fairly diverse taxa marks the base of the acinaces Zone and the establishment of a typical Lower Silurian fauna with the establishment of warmer water conditions

High palaeolatitude (Hodh, Mauritania) recovery of graptolite faunas after the Hirnantian (top Ordovician) extinction event

Marine shales directly overlying lower Hirnantian (uppermost Ordovician) glacially related sediments in Mauritania (northwest Africa) have produced a rich graptolite fauna spanning the Ordovician–Silurian boundary in an area of high palaeolatitude. The lowermost transgressive sandy shales are barren of graptolites, but overlying shales show a sudden appearance of a diverse fauna indicative of the terminal Ordovician persculptus Zone, suggesting that with improving conditions, colonisation by a relatively cold-tolerant fauna was possible. This fauna is replaced by a low-diversity assemblage dominated by long-ranging taxa, probably representing the basal Silurian acuminatus and atavus Zones. With the extinction of the persculptus Zone fauna, conditions were still hostile to warm water Silurian graptolites, and a Normalograptus fauna was again established. A sudden influx of fairly diverse taxa marks the base of the acinaces Zone and the establishment of a typical Lower Silurian fauna with the establishment of warmer water conditions

Paleovalley and fault-controlled depocentres in the Late-Ordovician glacial record of the Murzuq Basin (central Libya).

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The Devonian of the Hodh area (Islamic Republic of Mauritania) : Paleontology and stratigraphy

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Late Cenozoic Sedimentary Evolution of the Antalya Basin, Southern Turkey

International audienceThe Late Cenozoic Antalya Basin developed unconformably on a foundered basement comprising Mesozoic autochthonous carbonate platform(s) overthrust by the Lycian Nappes, the Antalya Nappes and the Alanya Massif metamorphics within the Isparta Angle, southern Turkey. The present configuration of the basin consists of three distinct parts, referred herein as the Aksu, Köprüçay and Manavgat sub-basins, respectively, which are divided by the north-south-trending Kırkkavak Fault and the westward-verging Aksu Thrust. The Miocene fill of each sub-basin is characterized by thick accumulations of non-marine to marine clastics with locally developed coralgal reefs and reefal shelf carbonates. Based on lithostratigraphic and chronostratigraphic considerations, integrated with previously established data, the Miocene fill of the Antalya Basin is reorganized into nine formations and twelve members. A total of nineteen facies have been distinguished within this stratigraphic framework. The stratigraphic organization and the time and space relationships of these facies indicate contrasting styles of sedimentation characterized by several facies associations representing deposition in colluvial and alluvial fan/fan delta with coralgal reefs, reefal shallow carbonate shelf, base of fault-controlled fore reef slope and clastic open marine shelf environments in the tectonically active sub-basins. The coralgal reefs, which occur as small, isolated patch reefs developed on progradational alluvial fan/fan delta conglomerates, and the reefal shelf carbonates represent small to large scale, transgressive-regressive cycles which are closely associated with the complex interaction between sporadic influxes of coarse terrigeneous clastics derived from the tectonically active basin margins and/or related to the eustatic sea level changes during Late Burdigalian-Langhian and Late Tortonian-Messinian times. With regard to structural history, the Antalya Neogene basins exhibit contrasting behaviour according to their position within the Isparta Angle. West of Antalya, the Lycian Basin is linked to the eastwards advance of the overlying Lycian Nappes up to the Burdigalian; in the centre of the Isparta Angle, the Aksu and Köprüçay sub-basins are younger (Serravalian-Tortonian) and exhibit intense deformation, reflecting west-directed compressional events of Late Miocene to Lower Pliocene age. In contrast, the Manavgat sub-basin situated further east is only weakly deformed, and even farther east, the Ermenek and Mut basins are almost undeformed. Thus the evolution of the Neogene Antalya basins highlights the fundamental structural asymmetry of the Isparta Angle

Facies architecture and depositional evolution of alluvial fan to fan-delta complexes in the tectonically active Miocene Köprüçay Basin, Isparta anlge, Turkey

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