Damp- to dry aeolian systems: Sedimentology, climate forcing, and aeolian accumulation in the Late Cretaceous Liyou Basin, South China

Abstract

Aeolian desert systems were widely distributed in South China during the Late Cretaceous. These systems developed under the control of subtropical highs and a monsoon climate. They reveal the evolution of palaeoclimate and palaeogeography and the regional palaeowind pattern in the South China interior during this period. Based on the analyses of sedimentology and facies architecture, this study examines and reassesses the aeolian succession of the Upper Cretaceous Daijiaping Formation in the southern Liyou Basin of southeast China. This aeolian desert succession records aeolian dune, dry and damp interdune and aeolian sandsheet sedimentation in streamflow, fluvial channel and overbank settings. Aeolian dune deposits comprise low-angle dune plinth strata and superimposed sets of cross-strata bounded by a hierarchy of bounding surfaces. The deposits record two morphological types of compound crescentic dunes and complex linear dunes. Palaeowind direction in the Liyou desert agrees with the subtropical high-pressure westerly and northeasterly wind pattern that existed in the mid to low latitudes of the Northern Hemisphere, in conjunction with possible monsoon climate conditions during the Late Cretaceous. The fault-bounded basin in which the succession accumulated experienced a high subsidence rate and a high supply and availability of windblown sand, which ensured hundreds of metres of thick accumulation of the dune field system. The occurrence of a near-surface water table and soft-sediment deformation in the aeolian dune foresets indicates that the monsoon rains could have recharged the groundwater system and resulted in episodes of relative water-table rise, which played an important role in the accumulation and preservation of aeolian systems in the Liyou desert basin. Gradual and progressive subsidence of the aeolian succession combined with water-table fluctuations allowed the preservation of the aeolian accumulation system.