Outline of the geology and hydrogeology of Cape Range, Carnarvon Basin, Western Australia

WA Museum Records and Supplements | Updated 9 years ago

Abstract: Cape Range is composed of a sequence of predominantly calcareous sedimentary rocks of Palaeocene-Pliocene age, overlain by Pliocene-Ilolocene alluvial, littoral, and shallow water marine sediments on the coastal plain, which borders the range. It is a gentle anticline resulting from inversion of fault movement on an underlying fault. The uplift has occurred intermittently since the Late Cretaceous and has affected sedimentation. The range emerged as an island probably in the Pliocene and karstification is inferred to have rapidly extended down for about 100 m in karst-prone limestone and gradually extended laterally as the range emerged. During the lowsLand of sea level in the Pleistoeene the karstifieation is presumed to have extended further offshore and been accompanied by deep erosion and establishment of the present-day drainage system. The present regional water table occurs below the level of karstification in the central part of the range and witllin cavernous limestone around its margin. The groundwater is believed to occur as a lens of fresh groundwater overlying seawater as on some oceanic islands. The remnant cave syslcm in the central part of the range is inferred to have provided a relatively stable habitat for a diverse subaerial cave fauna since the Pliocene, whereas water-filled cave system on the coastal plain, which is the habitat of aquatic troglobites, has probably extended and been subject to marked variation in the hydrogeological regime as the range has risen, and in response to ehanges in climate and sea level.