Ancient Stratigraphy Preserving a Wet-to-Dry, Fluvio-Lacustrine to Aeolian Transition Near Barth Crater, Arabia Terra, Mars

Ancient lacustrine and aeolian sediments have been separately identified in a variety of locations on Mars. In this work, we interpret the depositional history of Barth crater and its surrounding area in Arabia Terra where exposed geologic units preserve a record of lacustrine and aeolian interaction. Aeolian sandstone in the study area overlies lacustrine strata and is interbedded with easily eroded interdune deposits. The aeolian sandstone preserves dune strata with structures that indicate paleo-sediment transport toward the northwest. The aeolian unit also preserves a transition up-section from separated barchan dunes to continuous transverse dunes, capturing the development of the ancient dune field from sediment limited to sediment rich. Inverted fluvial channels provide evidence that water was delivered to the area at the same time the dune field was present, providing a simple mechanism, via wetting and cementation, for aeolian strata preservation. This example of wet-system aeolian accumulation preserves an upward drying sequence in the sedimentary record that may have been coincident with the widely hypothesized global climate transition. The terrains described in this work provide a framework for interpreting similar aeolian units in elsewhere on Mars, even where cross-strata cannot be easily resolved.