Episodic and Declining Fluvial Processes in Southwest Melas Chasma, Valles Marineris, Mars

Abstract

There is abundant evidence for aqueous processes on Noachian terrains across Mars; however, key questions remain about whether these processes continued into the Hesperian as the martian climate became less temperate. One region with an extensive Hesperian sedimentary record is Valles Marineris. We use high‐resolution image and topographic data sets to investigate the fluvial systems in the southwest Melas basin, Valles Marineris, Mars. Fluvial landforms in the basin exist across a wide area, and some are preserved as inverted channels. The stratigraphy of the basin is complex: Fluvial landforms are preserved as planview geomorphic features and are also interbedded with layered deposits in the basin. The fluvial morphologies are consistent with formation by precipitation‐driven runoff. Fluvial processes in the basin were episodic, suggesting multiple wet and dry periods. During dry periods, mantling material accumulated, and significant volumes of sediment were eroded, inverting fluvial channels. During wet periods, inverted channels and mantling material infilling valleys were incised by further fluvial erosion. These trends for episodic fluvial processes are similarly reflected in the central depression of the southwest Melas basin, previously described as a paleolake. Ultimately, fluvial processes in the basin gradually shut down, becoming geographically restricted, and then ceased entirely. We show that branching valley networks are also present on the plateaus above Melas and Ius Chasma, which converge on the heads of tributary canyons. These suggest that precipitation‐driven runoff processes also extended onto the plateaus of Valles Marineris.

Aram Dorsum: An Extensive Mid‐Noachian Age Fluvial Depositional System in Arabia Terra, Mars

“…By "channel body," we mean a sedimentary body produced by deposition during lateral and vertical accretion of depositional elements in a migrating fluvial channel over geological timescales (Friend et al, 1979). Also, Aram Dorsum is similar in many details (such as the overall ridge pattern, presence of a resistant "capping" layer and visible layering, vertical stacking, and the presence of polygonal fracturing in and around the central ridge) to other inverted fluvial channels in Arabia Terra (Davis et al, 2019(Davis et al, , 2016 and elsewhere on Mars (e.g., Burr et al, 2010;Davis et al, 2018;Newsom et al, 2010). Importantly, however, analysis of the Aram Dorsum ridge shows that it comprises multiple erosion-resistant ridge segments that exist at different stratigraphic levels (e.g., Figures 5d and 6a).…”

Ancient Martian Aeolian Sand Dune Deposits Recorded in the Stratigraphy of Valles Marineris and Implications for Past Climates

“…Basin floor units largely consist of prominent light‐toned sedimentary layered deposit mounds and lower‐lying basin fill. The canyon interiors comprise numerous geologic units of various terrain ages and origins (e.g., alluvial fans, structural massifs, and lava flows) (Davis et al, 2018; Fortezzo et al, 2016; Okubo, 2010). Surficial units of dark‐toned capping mantle materials and low albedo sand dunes are common to the study area (Chojnacki, Burr, & Moersch, 2014; Weitz et al, 2012).…”

Groundwater Control and Process Variability on the Equatorial Layered Deposits of Kotido Crater, Mars

“…Many sites in the equatorial regions of Mars (roughly within 30°north and south) host light-toned layered deposits, including Valles Marineris and the chaotic terrains (Al-Samir et al, 2017;Baioni & Tramontana, 2017;Chapman & Tanaka, 2001;Davis et al, 2018;Flahaut, Quantin, Allemand, Thomas, & Le Deit, 2010;Fueten et al, 2008Fueten et al, , 2014Fueten et al, , 2017Glotch & Rogers, 2007;Le Deit et al, 2008;Lucchitta et al, 1992;Murchie et al, 2009;Noel et al, 2015;Quantin et al, 2005;Weitz et al, 2012Weitz et al, , 2008, interior crater deposits (Allen & Oehler, 2008; Kite et al, 2013;Le Deit et al, 2013;Lewis et al, 2008;Murana, 2018;Pondrelli et al, 2015Pondrelli et al, , 2011Zabrusky et al, 2012), the northern rim of Hellas basin (Ansan et al, 2011;Day et al, 2016;Moore & Wilhelms, 2007;Salese et al, 2016;Wilson et al, 2007), and the intercrater plains of Arabia Terra and Meridiani Planum (Grotzinger et al, 2005;McLennan et al, 2005;Pondrelli et al, 2015). Dismissing the fluvio-deltaic deposits, they are grouped under the informal name of Equatorial Layered Deposits (ELDs; Hynek et al, 2002;Okubo et al, 2009) and are included in the Hesperian and Noachian highland undivided unit of the most recent global geological map (Tanaka et al, 2014).…”