Magnetostratigraphy of an Upper Cretaceous succession of James Ross Basin, Antarctica

MILANESE, FLORENCIA N.; KIRSCHVINK, JOSEPH L.; OLIVERO, EDUARDO B.; RAPALINI, AUGUSTO E.

Montevideo

Congreso; III Reunión Bienal de la Asociación Latinoamericana de Paleomagnetismo y Geomagnetismo; 2013

A magnetostratigraphic study was carried out in three Upper Cretaceous sections exposed in the SE area of James Ross Basin, Antarctic Peninsula. We present preliminary results of paleomagnetism, rock magnetism and magnetofabric. Anisotropy of magnetic susceptibility studies were carried out in all collected samples and indicate a likely depositional origin (characterized by low anisotropy degrees, oblate ellipsoids and vertical K3 axes) in the two first sections, and a particular grouping of K1 axes along vertical direction (inverse magnetofabric?) in the upper section. From hysteresis loops and Lowrie-Fuller tests, Ti-poor PSD magnetite is interpreted as the characteristic remanence carrier. After combined AF+thermal demagnetization a characteristic remanence was isolated in most samples which allowed us to build preliminary local magnetostratigraphic columns. Comparison with the GPTS suggests that chrons C33R, C33N, C32R? and C32N are represented in the studied sections. Polarity change between chrones C33R and C33N, dated in 79.543 Ma, occurs in member II of the Rabot Formation (at a stratigraphic level of 120 m in the first section and 100 m in the second one), indicating that the whole formation would have deposited in middle Campanian.