ALBERT

Description: Late Pleistocene intermediate water ventilation history in the northeastern Pacific has been inferred from benthic foraminiferal carbon isotopic data from seven California margin basins. Secular variations in oceanic d13C recorded at North Pacific ODP Site 849 were subtracted from each basin record leaving a residual d13C history that reflects variations in ventilation. During the previous interglacial intermediate waters above 2000m contained less oxygen than they do today or Pacific deep water at Site 849 was better ventilated. Intermediate water ventilation began to improve during oxygen isotope stage 4 and continued to improve throughout stages 3 and 2. This enhanced ventilation was not contemporaneous at all depths and appears to have progressed upwards through the water column. The diachronous nature of these changes suggest that there was not simply an "on"/"off" mechanism which resulted in higher or lower ventilation in the North Pacific during the last glacial cycle.

Description: The mineralogy of the lower Oligocene to Quaternary sediments of core CRP-2/2A drilled on the continental shelf of McMurdo Sound in Ross Sea, Antarctica, was examined by the X-ray diffraction method. Quartz, plagioclase feldspar and K-feldspar are the most important non-clay minerals. Pyroxene and amphibole occur in minor amounts throughout the core. The composition of the sediments points to an origin in the Transantarctic Mountains for the majority of the detrital components. There, the plutonic and metamorphic rocks of the basement, the sediments of the Beacon Supergroup and the volcanic rocks of the Ferrar Group could serve as possible source lithologies. The distribution of the detrital minerals reflects a long-term history of successive erosion and valley incision. During the deposition of the lower part of the core, the detrital minerals were probably mainly derived from the sediments of the Beacon Supergroup, as indicated by the high quartz but relatively low feldspar abundances. In the upper c. 350 m of the core, the influence of a source in the basement became stronger and results in lower quartz contents but increasing abundance of feldspar. Some diagenetic alteration of the sediments is indicated by the occurrence of zeolites below c. 320 mbsf and of opal-CT above c. 320 mbsf.

Description: The mineralogy of the lower Oligocene (to possibly upper Eocene) sediments of core CRP-3 drilled on the continental shelf of McMurdo Sound in the Ross Sea, Antarctica, has been examined by the X-ray diffraction method. Quartz, plagioclase K- feldspar and pyroxene are the most important non-clay minerals. Amphibole occurs in minor amounts. The composition of the sediments points exclusively to an origin in the Transantarctic Mountains for the detrical components. There, the plutonic and metamorphic rocks of the basement, the sediments of the Beacon Supergroup and the volcanic rocks of the Ferrar Supergroup could serve as possible source lithologies. The distribution of the detrital minerals reflects a longterm history of successive erosion and beginning valley incision. During the deposition of the lowest part of the Cenozoic sediments of CRP-3, the majority of detrital minerals was probably derived from the sediments of the upper Beacon Supergroup (Victoria Group) and the Ferrar Supergroup, as indicated by the high quartz and pyroxene concentrations. Only a very minor proportion probably was contributed by basement rocks. From c. 620 to c. 420 mbsf the sandstone-dominated Taylor Group of the Beacon Supergroup probably acted as the main source rock and was responsible for maximum quartz concentrations and the strongly lowered feldspar and pyroxene amounts in the CRP-3 core. Above c. 420 mbsf the erosion in the valleys cutting through the Transantarctic mountains reached the level of the basement rocks and therefore the amount of basement-derived minerals like K-feldspar and amphibole in the CRP-3 sediments became more important.