Tassy A.,Center Europeen Of Recherche Et Denseignement Des Geosciences Of Lenvironnement Cerege |
Tassy A.,CNRS Paris Institute of Earth Sciences |
Fournier F.,Center Europeen Of Recherche Et Denseignement Des Geosciences Of Lenvironnement Cerege |
Munch P.,Montpellier University |
And 17 more authors.
Marine and Petroleum Geology | Year: 2014
The interpretation of high-resolution 2D marine seismic profiles together with the analysis of sea-bottom cores allowed a stratigraphic and structural framework of the Provence continental shelf to be proposed. The integration of onshore and offshore stratigraphy, structure and geomorphology provided new insights into Messinian paleotopography and paleohydrography. A geological map of the offshore Provence continental shelf, isobath map of the base Plio-Quaternary surface are presented for the first time in this area. The base Plio-Quaternary surface is a polyphased unconformity that is composed of deep canyons developed by fluvial erosion during the Messinian event, and wave-cut surfaces formed during post-Messinian transgressions. The study evidenced a deep, E-W-trending canyon (Bandol canyon) connected to the head of the Cassidaigne canyon, and filled with up to 600m-thick Plio-Quaternary deposits. The development of canyons on the Provence margin during the Messinian event was dominantly controlled by the lithology and structure of pre-Messinian formations. A map of the Messinian paleo-drainage network is proposed to explain the presence of deep canyons in the Eastern area and the lack of incision in the Western area. An underground karst drainage scheme is proposed, linked with the current submarine Port-Miou spring. © 2014 Elsevier Ltd.
Staines-Urias F.,Geological Survey of Denmark |
Staines-Urias F.,Center Europeen Of Recherche Et Denseignement Des Geosciences Of Lenvironnement Cerege |
Gonzalez-Yajimovich O.,Autonomous University of Baja California |
Beaufort L.,Center Europeen Of Recherche Et Denseignement Des Geosciences Of Lenvironnement Cerege
Quaternary Research (United States) | Year: 2015
Nannofossil assemblages from core MD02-2510 provide a ~. 22. ka record of past oceanographic variability in Alfonso Basin (Gulf of California, east subtropical Pacific). In this area, environmental conditions depend on a monsoonal system heavily influenced by changes in the location of the ITCZ and nearby atmospheric pressure centers. To reconstruct nutricline depth and ENSO-like variability, two ecological indexes were calculated based on the relative abundance of the three dominant coccolith species. The late glacial period is characterized by intensified wind-driven upwelling, high primary productivity and La Niña-like conditions. An environmental shift occurs during the glacial-interglacial transition, El Niño-like conditions intensify, nutricline deepens and surface productivity declines. The late Holocene is characterized by a persistent increase in nutricline depth and dominance of El Niño-like conditions. The fluctuations in the composition of the coccolith assemblages can be related to orbital-scale fluctuations in the average position of the ITCZ. However, while the ENSO-like signal that overprints the record varies in response to orbital forcing, on suborbital time scales the relation between ENSO-like conditions and the average position of the ITCZ and the North Pacific High changes, suggesting that the development of persistent El Niño-like conditions is strongly dependent on the specific climatic background. © 2015 University of Washington.