The genesis of Lofer cycles of the Dachstein Limestone, Northern Calcareous Alps, Austria

Abstract

Peritidal carbonate platform Lofer cycles have been regarded as a record of sea-level oscillations driven by variations in the earth's orbit. Fresh analysis of a newly measured 700 m thick section from the Steinernes Meer is presented here. Estimation of stratigraphic completeness indicates that this sequence is only 0.75–9.5% complete, strongly suggesting that Milankovitch patterns are not preserved. Analysis of cycle thickness-frequency distributions reveals an exponential pattern, strongly suggestive of aperiodic, random deposition rather than periodic deposition in response to orbital forcing. Evidence for the importance of autocyclic processes (e.g. lateral migration of inter- to supratidal mudbanks and subtidal areas) and syn-sedimentary tectonic downfaulting events within this already active Late Triassic extensional zone is presented.