THE LATE NEOGENE ENVIRONMENT OF THE INTERIOR OF ANTARCTICA

Fossils from siltstones, peat, and marlstone interbedded with tillites from the Transantarctic Mountains (85° S), about 500 km from the South Pole, provide information about the paleoenvironment of Antarctica before the onset of the polar desert climate of today The fossil assemblage is unlike any Paleogene fossil assemblages from Antarctica and is estimated to be of late Neogene age based on derived marine diatoms. Plant fossils include wood and leaves of Nothofagus, abundant ‘seeds'of Ranunculus (buttercups) and other herbaceous taxa, flower parts, moss stems and leaves, root casts, ‘algal structures' with spores, and pollen. The insects include the skeletal parts of 3 species of beetles, including the head of a weevil, a puparium of a higher fly, and what is possibly the leg of a hemipteran. The weevil, based on characters on the mandible, is assigned to the Listroderina, but is probably not closely related to any of the living species which inhabit southern South America. The puparium is from a fly in the suborder Brachycera, possibly representing a species of Calliphoridae (blow flies). Freshwater mollusc shells are assigned to a fingernail clam, Pisidium, unrelated to the present day southern hemisphere subgenus Afropisidium, and a species of lymnaeid gastropod. Other invertebrate fossils include an ostracod species and several unidentified egg cases of annelids or arthropods. The only vertebrate fossil is a single tooth of a fish. The environment was on the margins of a glacier. Moraines deposited during glacial recession were colonized by plant and animal species dispersing inland along the Beardmore fiord. Summer temperatures were low but water in the lake had to be warm enough for freshwater molluscs to complete their life cycles. The best estimate for a mean summer temperatures is about 5° C, about 25° C lower than at the site at the present day. The polar ice sheet during this time was very reduced in size.