Fluctuations of wind strength and momentary direction recorded by supercritical climbing wind ripple strata, Gale crater, Mars

Direct evidence of microscale atmospheric dynamics is rarely preserved in the geological record, yet those few examples provide valuable insight to how fundamental atmospheric and sediment transport processes operate. Climbing wind ripple strata (specifically termed supercritical climbing translatent strata) were identified for the first time on Mars by the Curiosity rover within a sequence of aeolian sandstones in Gale crater. These sedimentary structures uniquely record the momentary palaeowind direction and are directly attributable to an event lasting a few minutes. Here, interstratified packages of climbing and planar wind ripple strata are described and are interpreted to result from fluctuating wind speed that varied sediment transport rates, combined with flow separation and expansion associated with a leeward slope. These conditions caused the rapid deposition of sediment onto migrating wind ripples, resulting supercritical angles of climb, recording a gusting wind that originated from the south that lasted a matter of minutes.