Depositional History of the Otis Peak Formation, Western Fan, Jezero Crater, Mars
Samantha Gwizd, Kathryn M. Stack, Michael P. Lamb, Libby R. W. Ives, Sanjeev Gupta, Alicia Vaughan, Steven Sholes, Rachel Kronyak, Nicolas Randazzo, Justin I. Simon, Larry Crumpler, Jim Rice, Briony Horgan, Linda Kah, Natalie Cavallo, Nathan Williams, Robert Barnes, Opal Ciancolo, Cathy Quantin‐Nataf, Olivier Beyssac, Vivian Sun, David Shuster, Joana R. C. Voigt, James F. Bell, Justin Maki, Kirsten Siebach, Marion NachonAbstract
The Mars 2020 Perseverance rover mission spent ∼250 sols investigating the Otis Peak formation (OPfm), a sequence of rocks containing the youngest recorded interval of sediment deposition via aqueous activity on Jezero crater’s western fan. This study uses orbiter and rover observations to interpret the formation and emplacement history of the OPfm. Orbiter images reveal a series of superimposed fan‐shaped to elongate crosscutting deposits on the western fan's upper surface that highlights a complex, prolonged depositional history. Perseverance and Ingenuity observations reveal that the OPfm comprises: planar bedded and cross‐stratified sandstones and pebble conglomerates, which are the main lobe‐ and ridge‐forming units, a boulder conglomerate that overlies the sandstone to pebble conglomerate, and a massive mafic unit whose boulders armor the western fan. We interpret the sandstone to be pebble conglomerate facies and the boulder conglomerate to have formed via fluvial deposition in an alluvial fan emanating from Neretva Vallis. The boulders armoring the fan have previously been interpreted as detrital clasts transported into the crater via Neretva Vallis, but we consider an alternative hypothesis that the majority may represent the degraded remnants of a younger igneous unit emplaced in situ within the crater. This study provides a depositional model for a fluvial system capable of transporting boulders on Mars and new insights into the extraordinary preservation of the Jezero western fan.