Clay mineralogy in the dababiya quarry corehole

摘要

Variations in the abundance of clay mincrals in the Dababiya Quarry Corehole, especially of detrital (i.e., terrigenous) chlorite, illite and kaolinite, together with the saddle index (tentatively used as a sedimentary rate proxy) and the "Wratio" (kaolinite versus chlorite balance), allow tentative reconstruction of the erosional history of the Saharan continent from Maastrichtian through Early Ypresian. During the Maastrichtian and Paleocene, the influx of the terrigenous minerals exhibit a stepwise decreasing trend with some pronounced changes as, for instance, around the K/Pg boundary. Erosion and transport of detrial minerals nearly creased during the Late Paleocene (resulting int the Tarawan chalk Formation). During the latest Paleocene, terrigenous clay minerals abruptly reappeared, became increasingly abundant and achieved prominence during the Early Eocene. Superimposed on this long-term trend, high frequency variations in terrigenous influx took place in the earliest Eocene (as marked by the base Dababiya Quarry Member). These were clearly related to the PETM climatic perturbations.