Geochemical and palaeoecological record of the Cenomanian-Turonian Anoxic Event in the carbonate platform of the Preafrican Trough, Morocco

摘要: Abstract Geochemical analyses (major and trace elements) palaeontological studies were carried out based on rock samples thin sections collected from three outcrop (Goulmima, Ziz Tazzouguert) in the upper Cenomanian–lower Turonian carbonate platform of Preafrican Trough (South Morocco), order to determine if oxygen-depleted conditions affected platform, highlight possible impact oxygen variation production, particularly during Oceanic Anoxic Event 2 (OAE2), which took place late Cenomanian. During this interval, was composed two contrasting environments. A shallow-water environment (peritidal mid-ramp) developed East (Ziz Tazzouguert sections), characterized by a high diversity abundance benthic organisms, some cases, planktonic associated with low concentrations authigenic markers (U, Mo, V Cr: redox proxies), indicating oxic conditions. In West (Goulmima section), deeper (mid ramp/outer ramp) proxies record enrichment, an indicator reducing conditions, organisms presence Buliminidae. Bottom waters dysoxic palaeoproductivity at sea surface. Thus, Cenomanian, oxygenation relatively good over area Trough, even OAE2, except environments toward West, where bottom depleted oxygen. Cenomanian transgression, more precisely dysoxia linked influx poorly-oxygenated anoxic basins Atlantic and/or Tethys oceans. Geochemical, sedimentological disturbances are recorded lower everywhere outer-ramp platform. Palaeontological show huge decrease group diversity, disappearance foraminifera – for Buliminidae proliferated only survived. marked enrichment all sections, higher values West. This occurred response climatic change, warm seasons hot wet, induced increase chemical weathering Anti-Atlas southwest substantial input nutrients increased palaeoproductivity, finally enhanced consumption O2 owing decay organic matter. Moreover, transgression led supply additional due leaching soils.