Palaeomagnetism of Late Cretaceous-Paleocene igneous rocks from the western part of the Antarctic Peninsula (Argentine Islands Archipelago)

摘要

A collection of 360 oriented samples of igneous rocks from the western part of the Antarctic Peninsula (Argentine Islands Archipelago, Penola Strait area), has yielded well-defined palaeomagnetic directions. Age determinations by various methods showed a Late Cretaceous-Paleocene time interval for the rocks studied. The characteristic remanent magnetisation (ChRM) was isolated by a stepwise thermal demagnetisation mostly in the temperature interval 450-580°C. It is evidently a primary magnetisation. The rocks along the coastline of the western part of the Antarctic Peninsula (AP) were emplaced during the Cretaceous Normal Superchron while the rocks from the islands with reversed polarity are of Paleocene. New Cretaceous (112-85 Ma) and Paleocene (60 Ma) palaeomagnetic poles for the passive continental margin of the Antarctic Peninsula fit well with a synthetic East Antarctica apparent polar wander path and confirms that the AP did not undergo latitudinal displacement for the last 100 Ma. The palaeomagnetic pole for 60 Ma shows a slight shift from palaeopoles obtained for the South Shetland Islands which implies that the South Shetland block is characterized by own tectonic evolution and probable anticlockwise rotation during the Paleocene.