Texture, Organic Carbon, and Clay Mineralogy of Western Beaufort Sea Sediments: ABSTRACT

Abstract

In the western Beaufort Sea the shelf sediments differ significantly from the slope and basin sediments in texture and in carbon and carbonate contents. The shelf is generally carpeted by positively skewed, platykurtic gravelly, sandy mud, whereas the slope and basin mostly have sandy or clean mud with symmetric and mesokurtic size-distribution curves. The predominance of muddy gravels on the shelf suggests that ice-rafting is important in transporting sediment to this region. Possibly the presence of the permanent pack ice across the slope and basin acts as an effective barrier for the movement of ice-rafted gravels to those regions. Probably the well-sorted and rounded sands associated with the slope and basin muds have been transported by turbidity currents from the sh lf margin, where it is believed they were deposited originally under turbulent conditions during geologically recent lowered sea levels. The shelf sediments have relatively lower organic carbon contents (average, 0.95%) than those of the slope and basin (average, 1.19%). However, the amount of carbonate in the shelf is higher (average, 4.8%) than in the slope and basin (average, 2.75%). The organic content is related to the clay percent whereas the carbonate content is related to the amount of calcareous shelly and lithogenous components. Clay mineral composition of the less than 2- and 4-µ sediment sizes consists predominantly of illite with significant amounts of kaolinite and almost no chlorite. It is suggested that the use of clay minerals in the inference of paleoclimates must be made with great caution because the generally accepted view related to marine End_Page 2497------------------------------ sediments is that kaolinite is a low latitude clay mineral and chlorite a high latitude one. Concentrations of uranium in the sediments range from 0.75 to 5.0 ppm and their variations seem to have no relation to the texture, organic carbon content, or clay mineralogy of the sediments. End_of_Article - Last_Page 2498------------