The Three-Dimensional Stratigraphic Architecture of the Jezero Delta Front

The NASA Mars2020 rover Perseverance has been traversing stratigraphy that represents the transition from crater floor lithologies to deposits of the Jezero western delta since Sol 422 of rover operations. Here we map the 3-D geometry of stratigraphic boundaries and document the 3-D stratigraphic architecture at the sub-km to m- scale using Mastcam-Z mosaics and Planetary Robotics processing and viewing tools (PRoViP and PRo3D). Four cross-sections were constructed across the lower delta stratal units at the base of Hawksbill Gap using 3D reconstructions of Mastcam-Z data and HiRISE topography. The fine-medium-grained sandstone Devils Tanyard member (DT) is the first sedimentary unit to overlie the crater floor Maaz formation, with raisebox-0.5extextasciitilde4.5 m of alternating resistant and weathered out discontinuous bedsets concordantly overlain by the raisebox-0.5extextasciitilde5 m thick Hughes River Gap member (HRG), which lacks the recessive interlayers of DT. The 6 - 6.5 m thick Boston Knob member (BK) forms a topographic bench on the delta slopes, overlain by the raisebox-0.5extextasciitilde2.2 – 4 m thick Hogwallow Flats member (HF). The Lower and Upper Rocky Top members (RT) are at least 7 m thick. Both members pinch out to the east and are composed of moderately sorted pebbly sandstone beds 1 - 2 cm thick. Member boundaries are sub-horizontal, dipping raisebox-0.5extextasciitilde8° at the base shallowing to raisebox-0.5extextasciitilde3° up- section, consistently towards 165° – 175°. Internal beds and laminations within DT, HRG and HF dip shallowly to the north, with curvilinear laminations in DT and HRG with up to 80° of variation in dip and strike evidencing possible convolute folding or rotation during weathering of layers raisebox-0.5extextasciitilde5 – 20 cm thick. Similar structures are found in HF in which the raisebox-0.5extextasciitilde80 cm thick basal layer shows evidence of raisebox-0.5extextasciitilde4 m wavelength folding with up to 25° of rotation and erosion of fold crests. The 65 cm thick middle sub-member of HF shows low-amplitude undulations 3 – 4 m in wavelength in the interlayered resistant platy laminations and recessive intervals. The stratigraphic architecture is consistent with deposition of variable grain size fractions in delta bottomsets, from the DT to BK members, and a deepening phase or change in sediment input is evidenced by finer-grained siltstones at HF. A transition to relatively coarser-grained pebbly sandstones likely deposited by turbidity current event-beds is observed at RT.