Deep sea-floor evidence of past ice streams off the Antarctic Peninsula

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Abstract
The past existence of a giant ice stream off the northern end of the Antarctic Peninsula is suggested by a convex-upward, elongated sediment body now at a mean water depth of 1000 m. Because of its morphological characteristics, i.e., a set of parallel to subparallel ridges and grooves to 100 km long, with an overall width of 25 km, we call this depositional body a bundle structure. We hypothesize that bundle structures form by accumulation of basal deformation till under their parent ice streams. From its location, size, and overall characteristics the bundle structure described here constitutes the best preserved, largest, deepest, and relatively low latitude evidence of giant ice streams that flowed offshore Antarctica during glacial maxima. Bundle structures reveal the very dynamic behavior of ice caps in the northern Antarctic Peninsula during the last glacial maximum, with catchment areas draining rapidly under marine-based critical subglacial conditions. Bundle structures represent a new megascale streamlined glacial landform.