NEW K-AR ISOTOPIC AGES OF SCHISTS FROM NORDENSKOLD COAST, ANTARCTIC PENINSULA - OLDEST PART OF THE TRINITY PENINSULA GROUP

K-Ar whole-rock dating of five samples of quartz-mica schist from the Nordenskjold Coast, eastern Graham Land, provides the first unequivoca l evidence of pre-Triassic (> 249 +/- 7 Ma) deposition of a sequence r egarded as part of the Trinity Peninsula Group (TPG). A maximum age ra nge of latest Carboniferous (< c. 300 Ma)-Permian for deposition of th e Nordenskjold Coast sequence is indicated, and a polymetamorphic, pol ydeformational history for the TPG in northern Graham Land. However, t he possibility exists that the rocks dated here from the Nordenskjold Coast are part of a hitherto-unrecognized metamorphic basement unrelat ed to and older than the mainly Triassic TPG outcrops farther north. T he new ages confirm the existence of a previously poorly-defined regio nal metamorphic event in the Antarctic Peninsula at about 245-250 Ma a go.