N. J. Hassold

Grain size evidence for variations in delivery of terrigenous sediments to a Middle Pleistocene interrupted sapropel from ODP Site 969, Mediterranean Ridge

Grain size distributions of the <63-μm terrigenous fraction of closely spaced sediment samples were measured across an interrupted sapropel sequence at ODP Site 969 on the Mediterranean Ridge to explore possible climate-related changes in delivery of wind-borne particles. Size distribution patterns are generally typical of hemipelagic sediment with a subordinate amount of eolian material. However, the eolian fraction increases in the sapropel layers, which contrasts with findings from elsewhere in the Mediterranean but is consistent with other work at this location.

Do magnetic fabrics of marine deposits preserve orbital forcing? A test case in the Southern Ocean, Antarctic Peninsula

The anisotropy of magnetic susceptibility (AMS), or magnetic fabric, of marine sediments is related to depositional current strength; higher AMS values indicate stronger currents. We have collected a 3.1 m.y. record of AMS data from the abyssal silts of Drift 4 (Ocean Drilling Program Site 1101) on the Pacific margin of the Antarctic Peninsula. Spectral analyses of these data show strong, uniform, 100 k.y. and 400 k.y. power in-phase with minima in Earth’s eccentricity throughout the long record. However, significant variability related to the 40 k.y. period of obliquity is absent. The unchanging strong 100 k.y. power and the apparent absence of 40 k.y. variability in the AMS record are in contrast to the behavior of most other paleoclimatic proxies for late Pliocene and Pleistocene time.