Circum-Tharsis wrinkle ridges at Lunae Planum: Morphometry, formation, and crustal implications

Formation and modification of wrinkle ridges in the central Tharsis region of Mars as constrained by detailed geomorphological mapping and landform analysis

“…In contrast, the thickskinned model does not require an additional mechanism to absorb the footwall shortening, because rocks below the decollement are ductile lower crustal rocks below the brittle-ductile transition (Allemand and Thomas, 1995;Mueller and Golobek, 2004). Observations supporting the thin-skinned model (i.e., decollements are within the brittle upper crust) include short dimensions (i.e., only a few km wide) of wrinkle ridges (Karagoz et al, 2022b), while observations supporting the thick-skinned models on Mars come from unidirectionally dipping thrusts that bound parallel wrinkle ridges on sloping terrain on Mars (Golombek et al, 2001). More recently, Andrews-Hanna (2020) uses a Monte Carlo boundary-element model to show that the topographic profiles of wrinkle ridges, if they still represent the original fold shapes, can be explained by a range of subsurface thrust configurations involving thin-and thick-skinned styles of deformation.…”

“…In map view, individual wrinkle ridges display consistent eastward convex shapes (Fig. 5A), which implies eastward transport direction of the landform system as it represents a thinskinned fold-and-thrust belt (e.g., Allemand and Thomas, 1995;Karagoz et al, 2022aKaragoz et al, , 2022bcf. Mueller and Golombek, 2004).…”

“…One would also expect that thermal contraction due to magma cooling below the Tharsis rise would have generated a crustal-scale stress field leading to the formation of compressional structures with horizontal wavelengths similar to the thickness of the Tharsis crust on the order of 10s of kilometers. This expectation is inconsistent with the highly localized deformation expressed by the wrinkle ridges bounded by flat inter-ridge plains (see Karagoz et al, 2022a, Karagoz et al, 2022b. Finally, heterogeneous cooling is expected due to multiple intrusions in different times and at different locations below the Tharsis rise, which would require superposition of compressional structures with different orientations that crosscut one another.…”

“…Their interpretation is supported by the similar morphology of martian wrinkle ridges with a suite of thrust-related folds on Earth. Several researchers show that scarps bounding wrinkle ridges appear to offset crater rims and crater floors at a few localities in the Tharsis region (Allemand and Thomas, 1995;Karagoz et al, 2022a, Karagoz et al, 2022b. Cole and Andrews-Hanna (2017) interpret a ridgeforming landform cutting obliquely across beddings exposed on a steep trough wall of Valles Marineris as a thrust zone, because it can be projected below a nearby wrinkle ridge.…”

“…Second, in all the quantitative models for wrinkle-ridge formation, topographic profiles are regarded as representing the original fold shapes that can be used for inverting the geometry, slip magnitude, and decollement depth of the inferred subsurface thrusts (e.g., Schultz, 2000;Mueller and Golombek, 2004;Andrews-Hanna, 2020;Karagoz et al, 2022bcf. Mège and Reidel 2001).…”