The Ellsworth–Coats Land (Antarctic) Promontory of Laurentia: Global paleogeographic and environmental implications

The Ellsworth Mountains form an isolated range in central West Antarctica. They comprise an almost continuous succession of Neoproterozoic−Permian sedimentary strata deformed during the latest Paleozoic to earliest Mesozoic Gondwanide orogeny. The resulting fold-and-thrust belt terminates abruptly at both the northern and southern ends of the range. Restoration of the Gondwanide fold belt within reconstructions of Gondwana places the Ellsworth Mountains on the ‘outboard’ Pacific (Panthalassic) side of the Coats Land crustal block of the East Antarctic craton, which has been identified as a likely former fragment of Laurentia, now ∼12,000 km to the north. The Precambrian basement of the crust containing the Ellsworth Mountains is almost indistinguishable from that of southwestern Texas (southern United States), and the overlying Neoproterozoic−Cambrian strata on both continents reflect contemporaneous two-stage continental rifting and ensuing late Cambrian drift and thermal subsidence. The detrital zircon record of the lower to middle Cambrian clastic strata shares a very high statistical similarity with that of contemporaneous sandstones in Texas, therefore suggesting a likely Laurentian provenance. We propose that a former “Ellsworth−Coats Land promontory” separated from Laurentia during the late Cambrian. This interpretation has significant global paleogeographic and paleoenvironmental implications. It implies that the hypothetical Pannotia supercontinent consisting of Laurentia plus the newly amalgamated Gondwana did fleetingly exist in Cambrian times, and that the early Paleozoic marine transgression and global cooling that accompanied the radiation of multicellular life may have been driven by the opening of a passage between Laurentia and Gondwana joining the Iapetus and paleo-Pacific ocean basins to initiate Panthalassa.