Geology and Stratigraphic Correlation of the Murray and Carolyn Shoemaker Formations Across the Glen Torridon Region, Gale Crater, Mars

Abstract

The Glen Torridon (GT) region within Gale crater, Mars, occurs in contact with the southern side of Vera Rubin ridge (VRR), a well‐defined geomorphic feature that is comparatively resistant to erosion. Prior to detailed ground‐based investigation of GT, its geologic relationship with VRR was unknown. Distinct lithologic subunits within the Jura member (Murray formation), which forms the upper part of VRR, made it possible to be also identified within GT. This indicates that the strata pass across the geomorphic divide between regions. Furthermore, the cross‐bedded lower part of the overlying Knockfarril Hill member (Carolyn Shoemaker formation) also occurs within both VRR and GT. Correlation of both units demonstrates that the strata form a continuous stratigraphic succession regardless of large‐scale geomorphic expression. The lithologic change from mudstone (Jura member) to cross‐bedded sandstone (Knockfarril Hill member) heralds a significant shift in paleoenvironment from lacustrine to fluvial. The upper part of the Knockfarril Hill member consists of interbedded mudstone and sandstone that transitions to the overlying finely laminated mudstone of the Glasgow member, and a return to lacustrine deposition. In GT, the Stimson formation unconformably overlies the Glasgow member, where it demarks the southern boundary of GT. Contacts for each stratigraphic unit were defined and transferred to a high‐resolution image base to make a geologic map and cross sections perpendicular to the NE strike. Stratal dips cannot exceed 2° NW to retain the positions of stratigraphic units in the locations they are exposed throughout GT.

Evidence for Fluctuating Wind in Shaping an Ancient Martian Dune Field: The Stimson Formation at the Greenheugh Pediment, Gale Crater

“…Blunts Point and the Jura members of the Murray formation comprise the landform known as the Vera Rubin Ridge (Edgar et al, 2020;Fedo et al, 2020;Fraeman et al, 2020), which underwent some degree of diagenesis to form a prominent topographic feature (Fraeman et al, 2016(Fraeman et al, , 2020. The base of the Carolyn Shoemaker formation is coincident with the base of the Knockfarril Hill member, in the topographic low known as Glen Torridon (defined by Bennett et al, 2022). The Knockfarril Hill (Fedo et al, 2020, this issue;Caravaca et al, 2022) and the Glasgow members of the C.Shoemaker formation are located in this area.…”

“…It is composed of laminated lacustrine mudstones, with minor intraformational fluvial sediments (Edgar et al, 2020;Grotzinger, Gupta, et al, 2015;Stack et al, 2019). Conformably overlying the Murray formation is the Carolyn Shoemaker formation (also referred herein as the C.Shoemaker formation), which is composed of horizontally laminated siltstones and sandstones, and an increased proportion of fluvial and aeolian sandstones (Bennett et al, 2022). The Murray formation is subdivided into seven members, which are interpreted to record lake and lake margin environments.…”

From Lake to River: Documenting an Environmental Transition Across the Jura/Knockfarril Hill Members Boundary in the Glen Torridon Region of Gale Crater (Mars)

“…The GT sedimentary record encompasses the Jura member of the Murray formation and the Knockfarril Hill and Glasgow members of the Carolyn Shoemaker formation (Figure 2). These units are composed of mudstones (Jura member; Edgar et al., 2020; Fedo et al., 2020) and very fine‐ to medium‐grained sandstones (Knockfarril Hill and Glasgow members; Fedo et al., 2020, 2022) that are laterally discontinuous. All these deposits contain significant amounts of clay minerals (e.g., Bristow et al., 2021; Cousin et al., 2021; Thorpe et al., 2020), confirming prior detection with orbital spectrometry (e.g., Milliken et al., 2010).…”

“…A similar relationship is also seen in some intervals of the Antonine Wall outcrop with occurrences of recessive finer‐grained layer alternating with resistant and cross‐stratified sandstones (Figure 8c). This alternating/interfingering architecture is observed in GT area and was called “Flodigarry facies,” notably at Woodland Bay (e.g., Bristow et al., 2021; Edgar et al., 2020; Fedo et al., 2022; Rudolph et al., 2020). We propose that the “Flodigarry” outcrop is not a “facies” per se but rather reflects the progressive transition between facies A and B.…”

“…This map shows that both facies are observed occurring within both members mapped area, demonstrating a progressive transition between them rather than a sharp geographic boundary. Regional geological basemap afterFedo et al (2022). WB: Woodland Bay, KA: Kilmarie/Aberlady drill sites, TR: Teal Ridge, HR: Harlaw rise, and AW: Antonine Wall and Glen Etive drill site; Mf: Murray formation and CSf: Carolyn Shoemaker formation (cf., Figure2).…”