Stratigraphic relationships within Martian polar cap deposits

Abstract

Deposits of layered ice and dust accumulate on the smooth and banded terrains of the north and south polar cap deposits, while erosion of equator-facing slopes of layered terrain expose these layers. Banded terrain occurs at exposures of irregular layers resulting from slight erosion of the feather edges of layers deposited on pole-facing trough walls. These deposits unconformably overlap onto adjacent layered terrain. Stripping of layers occurs in areas of strong, multidirectional wind, forming striped terrain. Local wind scour has also produced steep scarps with crescentic planform, often associated with dune fields positioned immediately downwind. Unconformities are common within layered deposits in areas of complex topography at the north pole. These indicate that episodes of deposition of 5–10 layers alternate with slight erosion of pole-facing trough walls. Troughs that strike north-south alternate between erosional widening and deepening and depositional infilling, creating multiple unconformities. Troughs near the equatorward limit of polar deposits increase in relief by deposition on adjacent smooth terrain and, locally, by erosional deepening. Troughs may migrate poleward, replacing the relief increase by depositional infilling when they near the poles.