South Georgia and Gondwana's Pacific Margin: Lost in translation?

摘要

The geology of South Georgia has long been interpreted as the product of processes acting at the Pacific margin of Gondwana in Jurassic and earlier times. This placement requires 1600 km of translation of South Georgia to its present location, for half of which there is no evidence. Assuming this means that 800 km of the translation cannot have occurred, it requires that those processes acted at a location much further east, within the interior of Gondwana. One such location could have been at the southern edge of the Deseado Terrane, which collided and sutured with Gondwana in Carboniferous times. Later, in this location, South Georgia would have experienced shearing and extension during the earliest stages of breakup of the supercontinent, eventually to form part of the ensuing ocean's northern margin. These, or possibly more recent tectonic events on the lengthening northern margin of the Scotia Sea, led to the northward obduction of ophiolitic rocks onto the island. A history like this reduces South Georgia to a peripheral role in the paleoceanographic development of Drake Passage, and strengthens the case for Eocene connection between the Pacific and Atlantic oceans.