CONSTRAINING MARTIAN SEDIMENTATION VIA ANALYSIS OF STRATAL PACKAGING, INTRACRATER LAYERED DEPOSITS, ARABIA TERRA, MARS

Craters within Arabia Terra, Mars, contain hundreds of meters of layered strata showing systematic alternation between slope- and cliff-forming units. This geomorphic pattern suggests rhythmic deposition of either distinct lithologies or lithologies that experienced differential cementation. Potential origins of these intercrater layered deposits include lacustrine deposition, aeolian deposition, volcanic airfall deposition, and/or impact surge deposition. On Earth, rhythmically deposited strata can be interpreted by examining the behavior of stratal packaging, wherein the interplay of tectonics, sediment deposition and changes in base level results in systematic and predictable stratal patterns. Keeping in mind the fundamental differences between Earth and Mars (e.g. basin generation via impact and a largely extinct tectonic regime on Mars which demands that packaging of layered strata primarily reflects sediment influx and base level change), similar analysis of stratal packaging may also provide information on martian sedimentary deposition

In a recent study, Lewis et al. (2008) used orbital HiRise imagery and MOLA topographic profiles to examine rhythmic bedding in Becquerel Crater, Arabia Terra. They attributed hierarchical, 10:1 bundles of strata to reflect astronomical forcing of regional climate and environmental conditions. This study, however, examines only small portions of the dramatically rhythmic successions in Arabia Terra, most of which do not show this distinct hierarchical packaging. Here, we present a reanalysis of Becquerel Crater, and compare results with additional crater successions that show very different visual display of strata. Through integration of high-resolution images with MOLA altimetry data, combined with geometric relationships, we estimate stratigraphic thickness to construct stratigraphic columns. These stratigraphic columns, when analyzed for component and cycle thickness, identify distinct intervals and patterns used to interpret and compare stratal packaging. The results of these analyses begin to define a range of depositional processes that may have affected early martian surfaces, extending our understanding of martian sedimentary environments and geologic history.