Late ordovician climbing dune assemblages, the signature of glacial outburst ?

PosterMeltwater-related processes have long been recognized as first-order geomorphic mechanisms in both subglacial and proglacial environments. Among them, glacial outburst or jökulhlaups (the Icelandic term for “glacial flood”) represent short-term events (1-15 days, e.g. Snorrason et al., 2002) with major erosional and depositional impacts. They emanate either from the catastrophic drainage of glacially dammed lakes or from the drainage or collapse of subglacial reservoirs

The Late Palaeozoic glaciation subsurface record, Chaco Basin (Bolivia)

Late Palaeozoic glaciation is the longest of the Phanerozoic era. It is recorded in numerous Gondwanian basins, some having a high petroleum potential like the Chaco Basin. In this basin, the quality of the available seismic, well and outcrop data permits to characterise the Late Palaeozoic glacial record. Palaeovalleys >500 m deep and ~7 km wide have here been analysed. Focusing on the glaciogenic Carboniferous deposits, the seismic data with well-ties and their outcrop analogues provide new sedimentological insights. The palaeovalley infill is imaged as a chaotic seismic facies overlain by an aggrading-prograding prism, interpreted as tillites covered by a fluvio-deltaic system respectively. Tillites form both under the ice and during rapid ice recession whereas fluvio-deltaic systems can only originate from a stable ice margin and last until the ice sheets withdraw inland. These two depositional modes are repeated several times generating the progressive burial of the Carboniferous palaeovalleys. This succession of erosions and fills records major glacial stages containing a series of glacial and interglacial phases from the Late Devonian to the Early Permian. Depicting the Late Palaeozoic glacial history of the Chaco Basin seems crucial for the localisation of potential good reservoirs

The Messinian Salinity Crisis in the Dacic Basin (SW Romania) and early Zanclean Mediterranean-Eastern Paratethys high sea-level connection

International audienceNew field observations and fossil analyses complete and clarify the strong impact of the Mediterranean sea-level changes linked to the peak of the Messinian Salinity Crisis on the Dacic Basin in southwestern Romania. In addition to the Gilbert-type fan delta already evidenced along the Danube River in the area of Turnu Severin, a new Gilbert-type fan delta is described northward. Early Zanclean bottomset beds are evidenced and dated based on nannofossils at the junction of the two coalescing Gilbert-type fan deltas. A clear sedimentological, morphological and chronologic differentiation is established in the area between the Carpathians Late Miocene piedmont alluvial fans and the early Zanclean Gilbert-type fan deltas. The early Zanclean age of the Hinova clays, where the bottomset beds of the Gilbert-type fan deltas are mostly developed, is confirmed by the occurrence of nannofossil markers of Subzone NN12b and a Bosphorian mollusk macrofauna. Early Zanclean inflow of Mediterranean marine waters into the Dacic Basin is also supported by the record of planktonic foraminifers. In the Dacic Basin, the Messinian Salinity Crisis resulted in the cutting of the Iron Gates by a Carpathians river. Fluvial erosion also affected the residual Pannonian Basin and probably catched the paleo-Tisza River which contributed to the erosion of the Iron Gates and to the fluvial drainage of the partly desiccated Dacic Basin. Arguments are reinforced in favor of a marine gateway between the Mediterranean and Dacic Basin through the Balkans before and after the Messinian Salinity Crisis

An Early Cretaceous vertebrate assemblage from the Cabao Formation of NW Libya

Fossil vertebrates from the Cabao Formation discovered in the area of Nalut in northwestern Libya include the hybodont shark Priohybodus, the crocodilian Sarcosuchus, an abelisaurid, a baryonichine spinosaurid and a large sauropod with spatulate teeth. The Cabao Formation may be Hauterivian to Barremian in age, although an earlier Berriasian to Valanginian age cannot be excluded. Its dinosaur assemblage is reminiscent of that of the El Rhaz and Tiouraren formations of Niger and strongly differs from both the Cenomanian assemblages of Morocco and Egypt and the Late Aptian to Albian fauna of Tunisia. Fossil vertebrates may be an important tool to establish the stratigraphical framework of the poorly dated Early Cretaceous continental deposits of Afric

New insights on the Sorbas Basin (SE Spain): the onshore reference of the Messinian Salinity Crisis

International audienceThe Sorbas Basin is the land reference of the Messinian Salinity Crisis (MSC) that affected the Mediterranean Sea in the latest Miocene. Its stratigraphy has been re-visited using calcareous nannofossils and planktonic foraminifers, which provide a reliable biostratigraphic frame and lead to particularly specify the relationships between the Sorbas and Zorreras members with Yesares evaporites.The evaporites overlie a shallowing upward sequence ending with the deposition of the Reef Unit and Terminal Carbonate Complex (TCC) on the periphery of the basin. The reefal carbonates of the TCC are overlain by clastic deposits that are foreset beds of post-MSC Gilbert-type fan deltas developed on the northern edge of the basin. These sedimentary structures are separated from reefal carbonates and the Reef Unit by the Messinian Erosional Surface (MES). The various facies of the Sorbas Member have been correlated with the bottomset beds of the Gilbert-type fan deltas despite some differences in palaeobathymetry. In the southeastern periphery of the basin, the MES separates the Sorbas Member from the Yesares gypsums. In the central part of the basin, a hiatus characterizes the contact between these members. The Zorreras Member postdates the MSC and entirely belongs to Zanclean. Its white “Lago Mare” layers are lagoonal deposits, the fauna of which is confirmed to result from Mediterranean–Paratethys high sea-level exchange after the post-MSC marine reflooding of the Mediterranean Basin.This study allows to re-assert the two-step scenario of the MSC (Clauzon et al., 1996) with the following events:- at 5.971–5.600 Ma, minor sea-level fall resulting in the desiccation of this peripheral basin with secondary fluctuations;- at 5.600–5.460 Ma, significant subaerial erosion (or lack of sedimentation) caused by the almost complete desiccation of the Mediterranean Sea;- instantaneous marine reflooding, accepted at 5.460 Ma, followed by continuing sea-level rise

New Insights on the Sorbas Basin (SE Spain): the onshore reference of the Messinian Salinity Crisis

The Sorbas Basin is the land reference of the Messinian Salinity Crisis (MSC) that affected the Mediterranean Sea in the latest Miocene. Its stratigraphy has been re-visited using calcareous nannofossils and planktonic foraminifers, which provide a reliable biostratigraphic frame and lead to particularly specify the relationships between the Sorbas and Zorreras members with Yesares evaporites. The evaporites overlie a shallowing upward sequence ending with the deposition of the Reef Unit and Terminal Carbonate Complex (TCC) on the periphery of the basin. The reefal carbonates of the TCC are overlain by clastic deposits that are foreset beds of post-MSC Gilbert-type fan deltas developed on the northern edge of the basin. These sedimentary structures are separated from reefal carbonates and the Reef Unit by the Messinian Erosional Surface (MES). The various facies of the Sorbas Member have been correlated with the bottomset beds of the Gilbert-type fan deltas despite some differences in palaeobathymetry. In the southeastern periphery of the basin, the MES separates the Sorbas Member from the Yesares gypsums. In the central part of the basin, a hiatus characterizes the contact between these members. The Zorreras Member postdates the MSC and entirely belongs to Zanclean. Its white "Lago Mare" layers are lagoonal deposits, the fauna of which is confirmed to result from Mediterranean-Paratethys high sea-level exchange after the post-MSC marine reflooding of the Mediterranean Basin. This study allows to re-assert the two-step scenario of the MSC (Clauzon et al., 1996) with the following events: - at 5.971-5.600 Ma, minor sea-level fall resulting in the desiccation of this peripheral basin with secondary fluctuations; - at 5.600-5.460 Ma, significant subaerial erosion (or lack of sedimentation) caused by the almost complete desiccation of the Mediterranean Sea; - instantaneous marine reflooding, accepted at 5.460 Ma, followed by continuing sea-level rise

Mesozoic eustacy record on western Tethyan margins

2° Congrès Français de sédimentologie - Livret-guide de l'excursion post-congrès en fosse vocontienne (23-24 novembre 1989

Introduction :Miocene - Pliocene geodynamics and paleogeography in the Mediterranean region : eustasy - tectonics interference

International audienc