Significance of aeolian limestone lenses in quartz sand formations: an interdigitation of coastal and continental facies, Perth Basin, southwestern Australia

Abstract

In the Quaternary of the Perth Basin of southwestern Australia, the transition from coastal dune ridges to continental, siliciclastic sand hinterland is a zone of calcareous sand or limestone lenses on or within siliciclastic sand. In the Holocene sequences the transition is a zone of landward-extended and detached parabolic dunes, which in section appear as lenses of calcareous sand resting on Pleistocene quartz sand and limestone. In the Pleistocene sequences, aeolian limestone lenses are common in thick sections of yellow quartz sand. Using the Holocene coast to hinterland transition as an analogue, the limestone lenses are interpreted to be buried outliers of attenuated parabolic calcareous dunes that migrated inland over an undulating plain of yellow quartz sand from a Pleistocene coastal zone. These dunes were later buried by influxes of aeolian yellow quartz sand during glacial-age desert phases of the Pleistocene. In section these buried dunes form a zone of limestone lenses within aeolian quartz sand formations. Thus, in a given time interval limestone lenses represent the transition between coastal and hinterland continental desert environments, and record the extent that coastal dunes penetrated inland. The Pleistocene stratigraphic model of aeolian limestone lenses set within a sequence of aeolian siliciclastic sand is a distinctive style of coastal to continental transition which can be used to unravel similar sequences in the stratigraphic record where coastal-aeolian calcareous facies interdigitate with desert-aeolian siliciclastic facies.