Geochemical investigations of volcanic ash layers from southern Atlantic Legs 113 and 114

Abstract

Petrographic and geochemical investigations were carried out on 21 ash layers from four sites of ODP Legs 113 and 114. With the help of geochemical data and petrographic characterization three rock series can be distinguished for stratigraphically different ash layers from Site 701 (Leg 114) whereas the Leg 113 tephras belong to another magmatic series. Geochemical correlation of the Leg 113 tephras with possible source areas indicates that they were probably erupted from the Antarctic Peninsula. The Miocene ashes from Site 701 are probably derived from the now-extinct Discovery Arc, the precursor of the South Southwich Islands. The Pliocene ashes from the site show some affinity with the South Shetland Islands. The Quaternary ashes from Site 701 display a chemistry typical of island-arc tholeiites and are therefore most probably derived from eruptions on the South Sandwich Islands. -from Authors