Martian South Polar Layered Deposit stratigraphy and implications for accumulation history

Abstract

We examine the stratigraphy of the Martian South Polar Layered Deposits (SPLD) exposed on scarp walls throughout the deposit using THEMIS visible (17 m/pxl) images from the Mars Odyssey spacecraft. By correlating marker layers and packets of layers among multiple locations, we are able to identify three sequences of layers within the SPLD, each with a different areal extent. While certain layers are correlatable over hundreds of km, implying widespread deposition of polar material, the absence of several identified layer sequences in some regions, notably the Promethei Lingula region, as well as the presence of several unconformities, indicates that deposition and sublimation or erosion of these deposits has not been uniform around the SPLD. This is further supported by the fact that individual layers display variations in thickness greater than a factor of 4 over hundreds of kilometers. Using these observations we propose an internal structure for the SPLD, with individual layers roughly following a dome‐like shape toward the center of the deposit, and becoming more planar toward the margins. We infer that the SPLD underwent at least three major periods of layer accumulation; each period is distinguished by a change in areal extent of net accumulation. The changes in areal extent of the layer sequences may be due to changes in Martian climate causing episodes of significant erosion of the SPLD between the deposition of each sequence or causing wide variations in accumulation zones of the SPLD over the history of these deposits.