British Antarctic Survey, United Kingdom

Analysis of the morphology and stratigraphy of the Antarctic Peninsula Pacific margin offshore from Adelaide Island shows 3 main evolutionary stages, from the Late Miocene to the Recent, which represent the growth phase of the margin under glacial influence. The oldest, transitional stage (SU4, latest Miocene-Early Pliocene), represents the first progradational unit over the outer shelf and slope, above the Base of the Glacial Margin Sequences. This unit contains drift facies on the rise, and it represents an important change in the depositional style. The middle, progradational glacial margin stage contains two units (SU 3 & 2, Early to Late Pliocene). SU3 is composed of 3 progradational wedges (a, b & c) although the youngest one (a) is the thickest and represents the most important progradational stage of the margin. SU2 includes both progradational and aggradational deposits and it recorded a significant change in the margin growth pattern. The youngest aggradational glacial margin stage (SU1, Quaternary) recorded the last change in the depositional style of the margin, with upward and outward growth of a relatively thick sediment wedge. These stratigraphic results show a complex, multi-step evolution of the margin, although their precise chronology and details of their paleoenviornmental significance remain uncertain. Resolving these uncertainties in this area and elsewhere on the Antarctic continental margin will require improved ship-based drilling technology, to provide better recovery of glacially-derived sediments, and integrated studies to understand the evolution of the entire Antarctic continental margin, its relation with paleoenvironmental and paleoceanographic changes, and its global linkages.