MAGNETOSTRATIGRAPHY OF AN UPPER CRETACEOUS SUCCESSION OF JAMES ROSS BASIN, ANTARCTIC PENINSULA

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

Mérida

Congreso; 12th Scientific Assembly of IAGA; 2013

IAGA-IUGG

A magnetostratigraphic study was carried out in three sections of the Upper Cretaceous sedimentary succession exposed in James Ross and Snow Hill islands, Antarctic Peninsula. These sections are a) HN (200m, Lower Campanian), located to the North of Hamilton Point (64º19? S; 57º23? W). It comprises the informal members I and II of the Rabot Formation; b) Re (324m), exposed at Redonda Point (64º22? S; 57º26? W) and partly stratigraphically equivalent to HN and c) SC (250m, Upper Campanian), located in a nunatak in Snow Hill Island (64º 26? 29.6?? S, 57º 12? 9.6?? W), which corresponds to the Sanctuary Cliffs Member of the Snow Hill Island Formation and is stratigraphically younger than the other two. Anisotropy of magnetic susceptibility studies were carried out in all collected samples. The magnetic fabric parameters obtained from these rocks indicate a likely depositional origin (characterized by low anisotropy degrees, oblate ellipsoids and vertical K3 axes. From the information obtained 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 that will conribute to a better chronostratigraphyof the succession. Comparison with the GPTS suggests that chrones C33R, C33N, C32R? and C32N are representedin the studied sequences and allows further chronological constraints on the biostratigraphy of the study units. Meanpaleomagnetic directions obtained from these Cretaceous units in the James Ross Basin suggest lack of meaningfultectonic rotations in the area since 80 Ma ago