Environmental Magnetism of Oligocene - Miocene Glaciomarine Strata from CRP-2/2A, Victoria Land Basin, Antarctica

Analysis of the environmental magnetic properties of the 624.15-m CRP-2/2A core, from McMurdo Sound, Antarctica, suggests that the core can be divided into three intervals, based on the nature and abundance of the magnetic minerals in the sedimentary sequence. These variations in magnetic parameters do not appear to be directly related to lithological variations in the core. Above 270 metres below sea floor (mbsf), magnetite is the dominant magnetic mineral and variations in magnetic properties coincide with fluctuations in the input of volcanic glass from the McMurdo Volcanic Group. The two lowermost intervals (270 – 413 mbsf, and 413 – 624 mbsf) are marked by alternations between zones that are relatively enriched in magnetite and hematite, respectively. The two intervals are differentiated on the basis of their mean coercivity values. It is unlikely that the alternations in magnetic properties reflect fluctuations in sediment provenance. More probably they reflect changes in palaeoenvironmental conditions related to climate and weathering regime. information about changes in palaeoenvironmental conditions in a sedimentary basin and its surrounding region (Thompson & Oldfield, 1986; Verosub & Roberts, 1995). Sagnotti et al. (1998a) found alternations between zones of high and low ferrimagnetic mineral concentration in the lower Miocene strata from CRP-1. Alternating intervals of high and low magnetic mineral concentration have also been found in strata that span the Eocene Oligocene boundary in the CIROS-1 core (Sagnotti et al., 1998b). CRP-2/2A spans the Oligocene Miocene interval that is missing across an unconformity at about 366 mbsf in CIROS-1 and partially overlaps the lower Miocene strata that were recovered in CRP-1.