Skeletal and sedimentary structures in yardang caverns in the Mars analog, Qaidam Basin: origin and implication

Abstract

<p>Cavernous weathering features on Earth and Mars exhibit diverse morphologies, yet their formation in hyperarid environments is still poorly understood. This study investigates a novel cavernous weathering pattern, termed as <em>skeletal structure</em>, within yardang caverns of the northeastern Qaidam Basin, a terrestrial Mars analog. These skeletal structures comprise interconnected through-holes bounded by rod-like “bones”, forming polycyclic frameworks distinct from honeycombs or tafoni. Petrographic analyses reveal predominantly subangular grains across all the samples, with some orthoclase and mica crystals showing little erosional effects. When combined with granulometric data, these textural characteristics indicate fluvial transport as the primary depositional mechanism. The presence of anhydrite-cemented sandstones and halite rims within the gypsum-cemented samples suggests limited aqueous alteration during post-depositional uplift and exhumation. Integrated structural, textural, mineralogical, and geochemical evidence reconstructs a four-phase evolution for these sediments: 1) depositional accumulation, 2) burial diagenesis, 3) tectonic uplift, and 4) erosional sculpting. Wind erosion is identified as the dominant factor for skeletal structure formation, with calcium sulfate cementation weakening sandstone resistance and enabling grain disintegration by windborne sediments. In rainwater-affected zones, salt plays a dual role: anhydrite hydration enhances rock strength, while halite leaching weakens surfaces. Notably, similar cavernous weathering structures and sedimentary beddings were also observed by the Curiosity rover at the Marker Band on Mars. Based on morphological and compositional parallels with the Qaidam Basin and the Martian context, we propose that Marker Band’s skeletal structures were shaped by prolonged aeolian erosion, while its bedded formations originated from ancient fluvial processes.<br></p>