Stratigraphic Anomalies in the Martian North Polar Layered Deposits

Asmin Pathare

(Planatary Science Institute)

We have identified numerous examples of anomalous trough stratigraphy within the North Polar Layered Deposits (NPLD). According to the standard model of NPLD stratigraphy, troughs can be divided into three main units: (1) Layered Terrain, which exhibit fine-scale laminae upon equatorward-facing (EWF) trough slopes; (2) Banded Terrain, more diffuse layers located on poleward-facing (PWF) trough walls; and (3) Smooth Terrain, which span the featureless regions between the troughs.

However, our preliminary survey of NPLD trough stratigraphy has revealed numerous exposures of Layered Terrain on PWF trough slopes. Even more surprisingly, several complex troughs also exhibit EWF Banded Terrain, which is also discordant with the standard model. Whereas the presence of PWF Banded Terrain argues against recent net deposition in the NPLD, the existence of EWF Banded Terrain suggests a corresponding lack of recent net sublimation (otherwise, the Layered Terrain that presumably underlies the Banded Terrain would be revealed). The implications of these anomalies for the mass balance history of the NPLD will be discussed.

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