Current interpretations of glacial history in the Transantarctic Mountains permit two vastly opposing views of Pliocene Antarctic climate and associated ice response. One view, based on the semi-lithified Sirius Formation, calls for extensive ice-sheet collapse and warm (2-5 degrees C) marine flooding in East Antarctica, with Northfagus growing nearby. A contrasting view, based on isotopically dated unconsolidated Pliocene drifts, calls for mountain overriding by an expanded ice sheet under subantarctic climatic conditions. This investigation is designed to improve our understanding of Pliocene glacial history of the Transantarctic Mountains in order to reconcile these conflicting hypotheses. Field areas are in the Dry Valleys where all Pliocene glacial morphologic features and sedimentary units occur together with ashes from nearby volcanoes. These ashes will produce a precise Pliocene chronology by the new technology of laser fusion 40Ar/39Ar dating of single crystals. The resulting glacial and tectonic history should clarify existing conflicts of Pliocene climate and ice-sheet response. This will clarify the long-term mechanics of the global climate system (particularly near 2.4 Ma), and its effect on eustatic sea level, deep-sea oxygen isotope fluctuations, and the Antarctic response to global Pliocene warmth.
