The Hydrogeomorphic History of Garu Crater: Implications and Constraints on the Timing of Large Late‐Stage Lakes in the Gale Crater Region

Abstract

AbstractPaleolake deposits offer a valuable record for constraining ancient Martian environments and climate. Gale crater provides extensive evidence for a long and complex history of lakes; however, the exact timing, source of water, and climate under which these large lakes persisted are still unclear. We examined the geomorphology and mineralogy of Garu crater, an ∼30 km diameter crater ∼150 km to the east of Gale crater with an age of ∼3.5 Ga (Hesperian). Garu hosts a large NE‐prograding sedimentary deposit that emanates from an incised bedrock canyon. Based on detailed geomorphic analysis, we infer it to be a Gilbert‐type delta that records steadily rising water levels over 104–105 years. This aggradational stage is followed by a period of rapid desiccation, which is evidenced by a lack of post‐depositional incision into the delta. Coupled surficial and groundwater modeling and paleo‐flow analysis suggest that the highest mapped lake stand in Garu would have been coeval with one of the largest late‐stage lakes in Gale. Both lake stands would have been supported by groundwater and surface runoff, under a semiarid climate. Unlike Gale, there is no spectral evidence for salts in Garu, which suggests that lacustrine sedimentation in Garu occurred after the deposition of the sulfate layers within Gale's central sedimentary mound. The hydrogeomorphologic record of Garu crater suggests that the climatic conditions that allowed for late Hesperian lakes in Gale crater were not isolated, and other nearby craters and basins may have responded to similar forcings from a regionally integrated hydrologic system.