Characteristics of the Lofer cyclicity in the type locality of the Dachstein Limestone (Dachstein Plateau, Austria)

摘要

In the present paper, the results of our studies in the type locality of the Dachstein Limestone are summarised in order to contribute to the correct interpretation of the Lofer cycles. In the sections studied on the Dachstein Plateau, the boundaries of the Lofer cycles are usually erosional disconformities showing karstification features. Penetration by karstic solution was not more than a few decimetres, since during the recurrent sea-level drops the platform only slightly emerged above sea level. The reddish or greenish argillaceous carbonate interlayers (facies A) cannot be interpreted as in situ palaeosol horizons. They are tidal flat deposits consisting predominantly of subtidal carbonate mud redeposited by storms that was mixed with reworked airborne fine carbonate particles and argillite and/or reworked lateritic soil, which were accumulated on the subaerially exposed platform. Rip-ups from consolidated sediment, blackened intraclasts and skeletons of tidal flat biota may have also contributed to the sediment of facies A. Erosional boundaries of most of the investigated cycles, and definite features of karstic solution beneath the disconformities, suggest periodical drops of sea level followed by a renewed transgression. This appears to confirm the allocyclic model for the explanation of the origin of the Lofer cycles.