RECENT MORAINES OF THE GERLACHE STRAIT, ANTARCTICA

While mapping the coastal deposits in the Gerlache Strait of the Antarctic Peninsula, we observed several “conspicuous ridges at sea level” (CRASL). These arc-shaped deposits are (20-100) m in length and (5-20) m in width. Usually, located directly in front of a glacier, these features were only observed in the intertidal zone. Three hypotheses for their origin are considered: 1) recessional moraines, 2) detached spits, and 3) partially submerged pro-talus ramparts. In order to determine which of these hypotheses best explains their origin, we compared the grain size, angularity, length of the axes, and petrology of the “CRASL” deposits with surface samples taken from modern moraine, beach, and talus-slope deposits in the area.

In addition to documenting their sedimentological characteristics, their distribution was mapped throughout the Gerlache Strait. Preliminary data suggests that they vary in size, occur on both sides of the strait, and have no specific orientation. Coupled with relative sea-level curves for the area, our data suggests these “CRASL”s represent recent recessional moraines. If these “CRASL”s represent recessional moraines that have undergone reworking into arc-shaped ridges and/or spits; they may indicate recent (100s of years) retreat of tide-water glaciers along the Gerlache Strait. Currently, we are attempting to place some constraints on their age using anthropogenic structures built on many of these “CRASL”s.