Trace element content and coordinates for factors at DSDP Hole 72-516F

This study involves samples of Santonian to Eocene age (Cores 516F-125 to 516F-38) taken from the Rio Grande Rise in the South Atlantic Ocean. These samples are from DSDP Site 516 occupied during Leg 72 of the Glomar Challenger (details given in site chapter, Site 516, this volume). Only Santonian to Paleocene cores have been well sampled, and analyses of the Eocene samples are preliminary results. Results of the trace element analyses (Mg, Sr, Mn, Ni, Fe, Na, K) of the carbonate fraction and CaCO3 percentage for each sample can be found in Renard and others (1983). Whole geochemical data are treated by the statistical method of correspondence analysis. Oxygen and carbon isotopic ratios measured on samples close to the Cretaceous/Tertiary boundary are not used in this study.

Late Weichselian fluvial evolution of the southern Kara Sea

Glaciations had a profound impact on the global sea-level and particularly on the Arctic environments. One of the key questions related to this topic is, how did the discharge of the Siberian Ob and Yenisei rivers interact with a proximal ice sheet? In order to answer this question high-resolution (1-12 kHz), shallow-penetration seismic profiles were collected on the passive continental margin of the Kara Sea Shelf to study the paleo-drainage pattern of the Ob and Yenisei rivers. Both rivers incised into the recent shelf, leaving filled and unfilled river channels and river canyons/valleys connecting to a complex paleo-drainage network. These channels have been subaerially formed during a regressive phase of the global sea-level during the Last Glacial Maximum. Beyond recent shelf depths of 120 m particle transport is manifested in submarine channel-levee complexes acting as conveyor for fluvial-derived fines. In the NE area, uniform draping sediments are observed. Major morphology determining factors are (1) sea-level fluctuations and (2) LGM ice sheet influence. Most individual channels show geometries typical for meandering rivers and appear to be an order of magnitude larger than recent channel profiles of gauge stations on land. The Yenisei paleo-channels have larger dimensions than the Ob examples and could be originated by additional water release during the melt of LGM Putoran ice masses. Asymmetrical submarine channel-levee complexes with channel depths of 60 m and more developed, in some places bordered by glacially dominated morphology, implying deflection by the LGM ice masses. A total of more than 12,000 km of acoustic profiles reveal no evidence for an ice-dammed lake of greater areal extent postulated by several workers. Furthermore, the existence of the channel-levee complexes is indicative of unhindered sediment flow to the north. Channels situated on the shelf above 120-m water depth exhibit no phases of ponding and or infill during sea-level lowstand. These findings denote the non-existence of an ice sheet on large areas of the Kara Sea shelf.