Short-term environmental changes in the Cretaceous Tethyan Ocean: micropalaeontological evidence from the Early Albian Oceanic Anoxic Event 1b

ABSTRACT To better understand the linkage between climate and ocean circulation under greenhouse conditions we have studied calcareous nannofossils, palynomorphs and benthic foraminifera from the Early Albian Oceanic Anoxic Event 1b black shale (OAE 1b) in the Vocontian Basin (SE France). We propose that monsoonal activity resulting from precessional forcing and modulated by eccentricity‐driven temperature changes represents the driving factor of OAE 1b formation in low latitudes. With the onset of OAE 1b, increasingly warm and humid conditions, stronger winds and enhanced terrestrial input led to higher surface water productivity. Therefore, increased productivity is an important factor for OAE 1b formation in the Vocontian Basin. However, monsoonally forced productivity changes are a regional climate signal only. The supraregional occurrence of the OAE 1b is probably due to a reduction of deep water formation in the low latitudes under extremely warm and humid conditions, leading to enhanced preservation of organic matter.