Carbonate platform sediments of the Triassic Dachstein Formation display the so-called Lofer cycles, attributed to sea-level fluctuations. The Lofer cycles have been attributed by previous authors to the Milankovitch variations of the parameters of the Earth's orbit. The Late Triassic Pedata/Pötschen Schichten represent the basinal equivalent of the Dachstein Formation. The petrographical composition of 810 calciturbidites of the Late Triassic Lacke section (Eastern Alps, Austria) was analysed to see whether the flooding/ exposure cycles of the platform could be traced into the adjacent basin. In each thin section, 200 points were counted. Seven categories of platform-bank or basin-derived grains were distinguished. The platform-bank derived input (e.g. Dasycladaceae, platform Foraminifera, pellets, Bryozoa, corals, calcisponges, microproblematica) displays a clear variation throughout the section. Spectral analysis revealed various cyclicities in the basinal sediments. The effects on the power spectra of individual debris flows and variations in sedimentation rate are evaluated. The fluctuation in calciturbidite composition along the section is conceived as a response to sea-level controlled variation in platform sediment production. After transformation into time, correspondence of several spectral peaks with Milankovitch quasi-periodicities can be suggested.
- Blackman-Tukay (BT)
- Periodicities in composition of Late Triassic calciturbidities
- Thickness versus time
- Thin-section analysis
- Time series analysis