Depositional Controls of the Layered Deposits of Arabia Terra, Mars: Hints From Basin Geometries and Stratigraphic Trends

Abstract

An extensive distribution of water‐altered equatorial layered deposits (ELDs) characterizes the densely cratered terrain of Arabia Terra (AT), Mars. The majority of these deposits reside within craters and are easily identified by laterally continuous layering. The processes that led to their formation have been widely investigated, but remain unresolved. Furthermore, their precise spatial distribution as a whole, as well as their relationship to one another individually, has yet to be fully appreciated. This work examines 1,013 craters and emphasizes 45 that were observed to contain ELDs within the eastern half of AT. We present the statistical relationships between crater characteristics (e.g., location, diameter, depth), as well as evidence supporting a southeast‐northwest facies change. The 30–2,000‐m range of measured deposit thicknesses, accompanied with individual layer thicknesses, correlate with crater elevation either due to water level differences within craters, or a proximal‐distal relationship to the source. Air fall or fluid expulsion appear to stand out among all the prevailing depositional hypotheses, however the volume required to fill these craters in an ash fall scenario is in opposition with the locations of known volcanic provinces and the volume of ash that volcanic eruptions produce. This new evidence of a regional facies change provides a unique opportunity to better understand past climate and sedimentary processes on Mars, as well as the putative groundwater level in ancient AT. Ultimately, our results do not agree well with a unified depositional method for these deposits and the possibility of mixed origins should be taken seriously.

Rivers and Lakes in Western Arabia Terra: The Fluvial Catchment of the ExoMars 2022 rover landing site

“… We find that large craters with evidence of paleolake deposits are not well integrated into the fluvial system. These craters show evidence for having been sustained by groundwater, and appear to have had contained lakes with multiple different water levels over time comparable other regional paleolake systems (Michalski et al, 2013;Schmidt et al, 2021).…”

“…From this, we interpret that large crater lakes and rimless craters hosted predominantly groundwater-controlled lakes at times when climatic conditions were conducive to a combination of high groundwater levels (Andrews-Hanna et al, 2010;Pondrelli et al, 2019;Schmidt et al, 2021) and supplementary overland water supplied through the regional fluvial network. The younger phase of fluvial activity is likely more closely associated with craters hosting well-preserved feature associated with this more intense valley network formation (e.g.…”

“…We propose that these dark deposits, when located in crater floors and associated with the channel network, represent allochthonous mafic volcaniclastic/aeolian materials (Edgett and Sarkar, 2021) that have been cemented by high stand of groundwater activity (Andrews-Hanna et al, 2007;Schmidt et al, 2021). The deposits accumulated in topographic lows associated with the ancient low-relief/wide flat floored channel network, which could have provided hydrological corridors within the regional groundwater flow (Andrews-Hanna et al, 2010, 2007, or mafic enrichment in a desert pavement-like process (Irwin III et al, 2018;Rogers et al, 2018).…”

Rivers and Lakes in Western Arabia Terra: The Fluvial Catchment of the ExoMars 2022 Rover Landing Site

“…These craters show evidence for having been sustained by groundwater, and appear to have had contained lakes with multiple different water levels over time comparable other regional paleolake systems (Michalski et al, 2013;Schmidt et al, 2021). 5.…”

“…Inlet and outlet channels are not common in large crater lakes or rimless crater lakes, despite this, the evidence from other features that supports a lake interpretation reinforcing the conclusion that groundwater has been an important driver of lake stability in the region (Michalski et al, 2013;e.g.,Salese et al, 2019;Schmidt et al, 2021). Inlet channels are seen where craters are located on a topographic rise with a large enough upslope area catchment.…”