Recurrent deformations of aeolian desert dunes in the cretaceous of the South China Block: Trigger mechanisms variability and implications for aeolian reservoirs

Abstract

Deposits of aeolian dunes accumulated in Cretaceous intramontane deserts in the South China Block underwent recurrent deformation processes affecting their toesets and foreset sediments. The Mid-Cretaceous Matoushan Formation preserves examples of soft-sediment deformation deformations associated with theropod tracks in aeolian dune apron sandstones. The Late Cretaceous Tangbian Formation in the Xinjiang Basin, shows (i) seismites associated with dry interdune laminated deposits and sand injection into the interdune laminated facies generating intraclast breccias, (ii) mass-flow deposits associated with heavy rains, generating interbedding of non-deformed and deformed intervals in aeolian dune foresets. Deformed intervals display a variety of deformation styles including thrust duplexes, upturned and deformed stratification, recumbent folds and microfolds and liquefied intervals. covered by overlying draa mega cross-bedded sets. Animal tracks, seismites, monsoon rains and earthquakes are proposed as the main trigger mechanisms of the failures that led to deformation. Hydroseismicity associated with monsoon rains is a probable (but difficult to prove) trigger mechanism; this process could be an important deformation agent in the case of large-scale deformation recorded in ancient erg sequences. Mass-wasting deposits in ancient erg (extensive sandy deserts characterized by aeolian dunes) sequences constitute significant heterogeneities for hydrocarbon migration and its architectural variability could determine the development of effective sedimentary traps in aeolian reservoirs.