Crustal features of the Claritas Rise region indicate a mobile lithosphere on early Mars

Abstract Ancient Martian orogenesis remains controversial, ranging from mantle plumes to continental-scale gravity sliding to plate tectonism. Here, we consider Claritas Rise, an ancient, complex, Martian orogeny, as a case study in mountain building resulting from mobile lithospheric activity, using a geologic synthesis of comparative planetology. Claritas's juxtaposed serpentine and carbonate rocks, along a structurally controlled margin, compares to Earth's serpentine mélanges (e.g., Altai) that result from continental collisional processes. A less dense, older, deformed felsic/feldspathic crust may cause Claritas's gravity lows, as occurs in Earth's convergent plate boundary settings (e.g., Himalayas, Japan, Andes). This geochemically matches its regionally elevated incompatibles, potassium and thorium, relative to younger embaying lava flows. Claritas’ tectonic structures geometrically resemble the transtensional-extensional features of the Baikal Rift System located in southeastern Russia. Steeply dipping beds along a northeast-oriented ridge of Claritas also contain blocks resembling Earth's olistostromes. A mega-geomorphological pattern of landforms, including Claritas at its center, approximates that of the Western United States (i.e., where denser mafic Farallon Plate subducted beneath the buoyant, mafic/felsic North American Plate). An ancient mobile lithosphere offers a unifying explanation for these Earth counterparts on Mars while also addressing other features of interest, including crustal thickness differences across the topographic dichotomy and andesite-granite detections.