LITHOFACIES, FLOW DIRECTIONS, AND PRELIMINARY DEPOSITIONAL INTERPRETATIONS OF LEDGE-FORMING SANDSTONES AT ALAGNAK, JEZERO CRATER, MARS

Abstract

International audienceThe Mars 2020 Perseverance rover is exploring a sedimentary deposit interpreted to be theremnants of a delta within Jezero crater, a 45 km diameter Late Noachian-aged crater. During itsexploration of the “lower delta” exposure of the western delta/fan in Jezero crater, Mars (Fig. 1), Perseveranceacquired image and composition data from Alagnak, a ~2 m thick, well-exposed outcrop of clastic sedimentaryrock located at Cape Nukshak (Fig. 1).This outcrop was thoroughly documented from multiple angles at a cm-scale by the Mastcam-Z camerasystem [1] and the Supercam Remote Micro-Imager (RMI) [2] on the Perseverance rover. Dip and strikemeasurements of sedimentary beds were collected from 3D reconstructions of Mastcam-Z stereo-imagescollected using the Planetary Robotics software tools PRoViP and PRo3D [3].In this study, we examine the physical sedimentology and stratigraphic context of the Alagnakoutcrop. The preliminary depositional interpretation of Alagnak is as a prograding, subaqueous fan builtthrough the deposition of many, meter-scale, gravity driven, sediment-rich flows. Flow directions rangedbetween NNE and SW, with principal directions toward SE and E