Sequence stratigraphy in extraterrestrial settings: The Jezero crater, Mars

The analysis of high-resolution images provided by the Perseverance rover indicates the presence of a Gilberttype deltaic complex in the western part of the Jezero crater, which includes fluvial topsets, as well as subaqueous clinoforms. While previously considered to be genetically related, the topsets and the foresets are separated by subaerial unconformities and belong to different sedimentation cycles (depositional sequences) and systems tracts. Based on the stratal stacking patterns observed at Kodiak butte, the clinoforms belong to fallingstage systems tracts, as indicated by the downstepping trajectory of the clinoform rollovers, the occasional preservation of offlap, and the sharp-based nature of the clinoforms. In contrast, the topsets are part of the lowstand systems tracts of the overlying depositional sequences, and are separated from the underlying foresets by truncation surfaces (i.e., subaerial unconformities).The possible environments for the deposition of clinoforms in the Jezero crater range from lacustrine to marine. In the latter case, a connection between the Jezero Basin and a northern ocean can be inferred, allowing for the possibility of tidal processes influencing the patterns of deposition within the deltaic complex. This may explain the rhythmites observed in the deltaic foresets, although other explanations for the cyclic changes in lithology and energy conditions, such as seasonal variations in fluvial discharge and sediment load, are also possible. The location of the Jezero crater in the shoreline area of the Isidis Basin, which is a bay of the northern ocean, may have created a configuration of interconnected embayments able to amplify the otherwise small tidal range expected from the two moons of the planet. Clarification of the paleogeography at the time of deltaic progradation (c. 3.6-3.8 Ga) has major implications for the strategy of exploration for early life forms on Mars. The acquisition of rock samples from the Jezero Basin and the northern ocean are essential to gain further insight into the early land-ocean interaction and possible co-evolution of life and environments on Mars.