Aeolian sand-sheet deposits in the Lower Cambrian Neksø sandstone formation, Bornholm, Denmark: sedimentary architecture and genesis

The Lower Cambrian Neksø Sandstone Formation, which hitherto has been thought to be of pure fluvial origin, locally contains a significant amount of aeolian deposits. These aeolian sediments form relatively thin, tabular sand sheet deposits separated by straight to somewhat irregular erosional bounding surfaces and associated pond deposits. These bounding surfaces can be classified after rank, of after genesis. The aeolian bounding surfaces in the Neksø Sandstone Formation are probably multugenetic and signify initial ground-water-controlled deflation of the sand-sheets followed by a ground-water rise or low-energy flooding and pond sedimentation. The sand-sheets and intervening pond deposits form a multistorey succession (7 m thick) that records systematic fluctuations in available sand supply in the source area, air flow characteristics, ground-water level and aeolian accumulation rate. Apparently, the recorded sedimentary pattern reflects episodic growth of a sand-sheet deposit related to systematic climatic fluctuations.