| Summary: | The Antarctic region has significantly influenced global climate throughout the Cenozoic. In order to predict future climate change, it is important and necessary to understand past Antarctic environments and how these environments have changed through time. Unfortunately, our knowledge of Cenozoic paleoenvironments in Antarctica is limited due to the lack of exposed strata of this age. Fossil-bearing erratic boulders present in coastal moraines in McMurdo Sound, East Antarctica, are derived from strata present beneath the East Antarctic ice sheet and Ross Ice Shelf. The erratics provide a record of Paleogene fossil biotas, climate and paleoenvironment that existed on the coastal margin of the Transantarctic Mountains (TAM). Over one thousand erratics were collected from McMurdo Sound between 1991 and 1995 in an effort to increase the paleontologic and sedimentologic database for East Antarctica. Marine palynomorph (dinoflagellate cyst, acritarch and prasinophyte) assemblages present in many erratics aid in the determination of age relationships and interpretation of paleoenvironmental setting. Several age groups are recognized based on Southern Ocean dinoflagellate cyst biostratigraphy: middle to upper Eocene; upper middle to upper Eocene; ?lower Oligocene; and post-Eocene. Erratics recovered include sandstone, sandy-mudstone, conglomerate, mudstone and diamictite lithofacies. Age interpretations indicate that most sandstone, sandy-mudstone and conglomerate facies were deposited during the middle to late Eocene within coastal marine settings, proximal to the uplifting TAM. There is no direct evidence for ice influence in this environment, though mountain glaciers were likely present in higher elevations of the TAM. Sandy mudstone, mudstone and diamictite facies of Oligocene and younger age, were probably deposited in proximal glaciomarine, distal glaciomarine and subglacial environments, respectively. The suite of erratic boulders presented herein, therefore, records a transition from cool-temperate, ?ice-free, ...
|
|---|