Influence of climate and oceanography on Cretaceous sedimentation in the North Atlantic.

Abstract

Sedimentation in the North Atlantic Ocean underwent fundamental changes during the Cretaceous. From a Late Jurassic restricted basin regime, characterized by a large influx of siliciclastics, to a Mid – Late Cretaceous widening basin with open circulation and a prominent biogenic component. A systematic analysis of sediment and mineral composition of the Cretaceous cores in IODP sites was made. The study covers; Moroccan offshore, Iberian offshore, Celtic Sea Basin, Grand Banks, Blake Bahama Basins, and Demerara Rise Basins. This dissertation aims to enhance the understanding of the effect of climatic and oceanographic changes on the general sedimentary infill of the North Atlantic during the Cretaceous. The western and eastern Early Cretaceous North Atlantic commenced as wet and humid, the northern North Atlantic was prone to strong terrigenous deposition. Aptian large eustatic sea level rise, shoaling CCD and heating climate led to widespread clay deposition. The climatic and oceanographic changes led to OAE formation, from the Aptian onward. The western and southeastern margins behave differently. Continued warming climate, eustatic sea level rise and shoaling CCD were responsible for the continued shale deposition and carbonate deposition on the eastern margin influenced by upwelling. Turonian change to a ventilated margin caused by the deep water connection to the South Atlantic and cooling climate led to a carbonate dominated western North Atlantic and a zeolitic clay dominance in the southeastern North Atlantic. The Late Cretaceous was characterized by marl deposition in the western margin, and clay deposition in the southeastern North Atlantic. The western and northern continental humidity, continental weathering and high temperatures created optimum surface for high oceanic primary production. Ventilated oceans on the southeastern North Atlantic margin led to adverse conditions; less nutrient input and shoaling CCD leading to large-scale clay deposition.