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

Abstract

Winter 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.

Ice-rafted dropstones at midlatitudes in the Cretaceous of continental Iberia

“…S6). Collectively, these features are attributed to ice-rafted dropstones released from lacustrine icebergs and emplaced on the lake bottom (Le Heron, 2015;Le Heron et al, 2021;Rodríguez-López et al, 2016;Wu and Rodríguez-López, 2021). The quantified penetration depths and bending of underlying strata suggest that glacial dropstones were released into a relatively deep lake.…”

“…The widespread view of the Cretaceous Period as an archetypal super-greenhouse is being increasingly questioned by new data (Ladant and Donnadieu, 2016) suggesting that the Cretaceous cryosphere had similarities with its Pleistocene and Holocene counterparts (Rodríguez-López et al, 2022). Evidence of an active cryosphere during the Cretaceous includes glacial dropstones and ice-rafted debris (IRD) transported by icebergs both in marine deposits (Rodríguez-López et al, 2016;Alley et al, 2020) and continental plateau oases (Wu and Rodríguez-López, 2021), and high-altitude permafrost (Rodríguez-López et al, 2022). Such evidence for deep-time glacial and permafrost records is vital for understanding cryosphere dynamics on very long time scales (10 6 -10 8 yr; Le Heron et al, 2022).…”

Permafrost in the Cretaceous supergreenhouse

“…Most evidence of a Cretaceous cryosphere comes in the form of marine ice-rafted debris (IRD) from the southern 6 , 7 and northern hemispheres 8 – 11 , as well as from the recognition of marine glendonites (calcite pseudomorphs after ikaite) indicating cold temperatures during formation 12 – 15 . Additional evidence includes Cretaceous landforms in Yukon and Alaska 16 , patterned ground in China 17 , and ice-rafted dropstones in desert oases indicating cold-desert conditions in interdunes similar to those in the Badain Jaran Desert 11 . Recently, the discovery of ultra-depleted hydrogen isotopes from Antarctica has suggested glaciation of the South Pole during the Late Cretaceous 18 , and there is isotopic evidence for continental ice sheets in China during the Early Cretaceous 19 .…”

“…Most evidence of a Cretaceous cryosphere comes in the form of marine ice-rafted debris (IRD) from the southern 6,7 and northern hemispheres [8][9][10][11] , as well as from the recognition of marine glendonites (calcite pseudomorphs after ikaite) indicating cold temperatures during formation [12][13][14][15] . Additional evidence includes Cretaceous landforms in Yukon and Alaska 16 , patterned ground in China 17 , and ice-rafted dropstones in desert oases indicating colddesert conditions in interdunes similar to those in the Badain Jaran Desert 11 . Recently, the discovery of ultra-depleted hydrogen isotopes from Antarctica has suggested glaciation of the South Pole during the Late Cretaceous 18 , and there is isotopic evidence for continental ice sheets in China during the Early Cretaceous 19 .…”

Permafrost in the Cretaceous supergreenhouse

“…Most evidence of a Cretaceous cryosphere comes in the form of marine ice-rafted debris (IRD) from the southern 6,7 and northern hemispheres [8][9][10][11] , as well as from the recognition of marine glendonites (calcite pseudomorphs after ikaite) indicating cold temperatures during formation [12][13][14][15] . Additional evidence includes Cretaceous landforms in Yukon and Alaska 16 , patterned ground in China 17 , and ice-rafted dropstones in desert oases indicating colddesert conditions in interdunes similar to those in the Badain Jaran Desert 11 . Recently, the discovery of ultra-depleted hydrogen isotopes from Antarctica has suggested glaciation of the South Pole during the Late Cretaceous 18 , and there is isotopic evidence for continental ice sheets in China during the Early Cretaceous 19 .…”