Abstract

The plate tectonic and physiographic evolution of the Atlantic Ocean and its surrounding epicontinental seas resulted in prominent global paleoenvironmental changes. The main North Atlantic basin south of Iceland was part of the circumequatorial Tethys seaway from its formation in Early Middle Jurassic time until Late Cretaceous time. Then the South Atlantic Ocean opened wide enough to allow the exchange of surface as well as deep water masses. The separation of Svalbard and northeast Greenland in the Middle Oligocene created a deep water passage between the Arctic and the Norwegian Sea and the subsidence of the main platform of the aseismic volcanic Iceland-Faeroe Ridge during the Miocene allowed deep water from the Norwegian-Greenland Sea to enter the main North Atlantic basin.

The main part of the sedimentary column of the North Atlantic south of the Norwegian-Greenland Sea is composed of calcareous components of pelagic biogenic origin. Sedimentation rates of pelagic deposits have been used to quantify the influx of sediment into the North Atlantic Ocean because they are believed to record the response of the depositional environment to changes of both the ocean basin configuration and the paleoclimate during Late Mesozoic and Cenozoic time. Phases of high sediment input into the basin, 140-105 m.y., 60-40 m.y., and since 25 m.y. ago alternated with intervals when the ocean received relatively little sediment. Hiatuses were most frequent at paleodepths of 2-3 and 4-5 km. The processes generating the hiatuses removed sediment by dissolution or downslope displacement and created a distinctive depth-related accumulation pattern during the past 140 m.y.

Terrigenous detrital particles are relatively scarce and their pattern of distribution with time and depth is subdivided into three phases: 1) prior to 100 m.y. ago when almost no detritus reached the North Atlantic, 2) 100-70 m.y. ago when sediments with high terrigenous concentrations were deposited throughout the entire water covered region, and 3) the past 70 m.y. when high concentrations of detrital terrigenous components were deposited only in the deepest part of the ocean basin. Periods when high concentrations of detrital material were deposited coincided with hiatus maxima and a rapidly rising sea level.