Archaeocyathan limestone blocks of likely Antarctic origin in Gondwanan tillite from the Falkland Islands

Abstract

Cambrian limestone clasts containing a rich, well-preserved archaeocyathan fauna have been recovered from the late Carboniferous Fitzroy Tillite Formation of the Falkland Islands. Since neither Cambrian strata nor limestone are present anywhere in the indigenous rock succession, the clasts are regarded as exotic erratics introduced during the Permo-Carboniferous Gondwana-wide glaciation. Most recent reconstructions of Gondwana rotate the Falklands into proximity with the Eastern Cape, South Africa and the Ellsworth Mountains, Antarctica. In both of these areas, Permo-Carboniferous diamictites correlated with the Fitzroy Tillite Formation also contain rare, exotic clasts of archaeocyathan limestone. The Transantarctic Mountains seem the most likely source for all of these unusual erratics. This interpretation sustains the requirement for substantial rotation of the Falklands microplate into Gondwana reconstructions and illustrates the extent of the late Carboniferous ice sheet. Apparent differences in the tillite clast assemblages between East and West Falkland suggest variable provenance within the regional ice-flow regime