Cryospheric processes in Quaternary and Cretaceous hyper‐arid plateau desert oases

Abstract

AbstractWinter supercooling of oasis waters in hyper‐arid plateau deserts leads to the formation of ice floes on oases water surfaces. Multi‐year satellite imagery from recent oases in the Badain Jaran Desert (China) reveals dynamic cryospheric processes including ice floe, ice jams abutting on border ice, hinge and transverse cracks, multiple ice lobes related to aufeis formation on the ice floe surface indicating oases water level oscillations linked with short‐term variations of the groundwater input. Oasis ice floe break up and transportation by strong desert winds produce an effective gouge and abrasion mechanism of oasis margin sediments, incorporating them both into the oasis bottom, and as supra‐ice floe debris that ultimately will be released to the bottom of the oasis as dropstones as the ice cover melts. Supercooling conditions in the Badain Jarain Desert oases suggest that anchor ice can form in the oases bottoms from fazil ice crystals generated in open supercooled oasis waters. Mud dropstones and diamicton in Cretaceous wet interdune facies from China suggest ice‐rafting processes in oases. Rounded and subangular mud intraclasts are mud boudins formed by in situ boudinage of mud interdune sediments due to the combined effect of compaction by prograding aeolian sediments and aufeis formation. Anchor ice formed in the oases bottoms lifted them up due to floatability and released them as dropstones to the oasis bottom when melted. Cryospheric processes in hyper‐arid oases are more active than expected and may play a significant role in intraclast reworking. The recognition of these processes is critical for Mesozoic palaeoclimates.