Climatic control of sedimentation in bays and fjords of the northern Antarctic Peninsula

Abstract

The northern Antarctic Peninsula is dominated by strong climatic gradients, which are locally enhanced by subsidiary orographic and topographic effects. These gradients are reflected in the sediments of the bays and fjords of the region. The climate of the South Shetland Islands is relatively warm, with high levels of precipitation. This leads to a temperate glacial setting in which many glaciers terminate on land, and bay waters which are turbid with terrigenous debris. Sediments, which consist of terrigenous muds and sands with a low ice-rafted debris (IRD) content, are relatively thick (≈ 70 m) and have now filled in and almost completely mask the underlying basement topography. The Palmer Archipelago is colder than the South Shetland Islands, and is the wettest area of the Antarctic. It is heavily glaciated, and all major glaciers are grounded below sea level. Only rarely have sediment plumes been seen. The sediments, which are primarily terrigenous muds and sands with a variable IRD component, are thin (maximum ≈ 40 m) but are ponding in every available bathymetric depression. The pristine nature of the ice visible above sea level indicates that terrigenous debris is entering the bays from below sea level. Sediment gravity flows are important in redistributing sediment. The Danco Coast lies within the precipitation shadow of the Graham Land Plateau. Its climate is slightly colder, and is the driest in the study area, with less than half of the precipitation of the Palmer Archipelago. Nevertheless, it is also heavily glaciated. With few exceptions, sediments here are diatomaceous muds and oozes. They are very thin and drape across the rugged basement topography, rather than ponding in lows. Sediment gravity flow deposits are rare. These observations indicate a lower rate of production of terrigenous sediment here, a consequence of the drier climatic setting.