Triassic intraplatform basins versus Middle-Late Jurassic mélanges and nappes in the Western Tethys Realm: Renaissance of Mojsiscovics? or “What is written in the sedimentary successions?”

To reconstruct the Triassic–Jurassic geodynamic evolution through time and space and to distinguish the various lithologies, a high-resolution litho- and biostratigraphy is the necessary base. In cases various lithologies are defined as basin-wide useable formations, in other cases several formations are united into a group, because the included formations are characterized by facies transitions, mixed lithologies, or are not mappable lithostratigraphic units. To invent for identical lithostratigraphic units in different countries/areas independent formations with definition of a separate type-section confuse only readers, hamper the scientific progress, and result often in regional insufficient interpretations which cannot be easily compared with the over-regional tectonostratigraphic evolution, i.e. the geodynamic evolution of the birth and death of an oceanic realm (Wilson cycle). In the Neo-Tethys Wilson cycle the carbonate dominated passive continental margin evolution started in the Middle Triassic (Pelsonian) and ended in the Middle Jurassic with obduction of Neo-Tethys derived ophiolites. During this evolution carbonate platforms were formed predominantly in the Late Triassic (Wetterstein and Dachstein Carbonate platforms). For passive continental margin settings, an intraplatform basin is defined as a deep-water depositional realm situated between two carbonate platforms with lively carbonate production. A basin between the continental realm, i.e. the shore line and a platform (or rising reef-rims) is defined as deep lagoon or empty bucket. After the demise of the Middle Anisian shallow-water carbonate ramp and the formation of a horst-and-graben morphology no significant long-lasting shallow-water carbonate production can be recognized. This change was termed Reifling turnover, and can be traced throughout the whole Western Tethys Realm. The late Middle Anisian to Early Carnian deep-water sedimentary rocks cannot be attributed as “intraplatform basin”, because during this time span no huge carbonate platforms existed. In the latest Ladinian respectively in the Early Carnian the first important carbonate platform cycle started with the evolution of the Wetterstein Carbonate platforms established predominantly on top of preexisting morphological highs and started from there to prograde rapidly towards the basins (grabens/halfgrabens) formed during the Late Anisian extension. Carbonate production of the Wetterstein Carbonate Platform evolution stopped abruptly around the Julian 1/2 boundary and not all preexisting deep-water areas could be filled by the carbonates of this platform. During the short time span of several independent Wetterstein Carbonate platforms also short-living intraplatform basins could be recognized. Carbonate production recovered during the Late Carnian and gave rise for the evolution of the huge Norian-Rhaetian Hauptdolomite/Dachstein Carbonate Platform. The enormous carbonate production of this platform was able to fill all remaining older depressions in the shelf area already in the Early Norian. After the demise of the Dachstein Carbonate Platform during the Triassic/Jurassic mass extinction a hemipelagic shelf evolved (Early-Middle Jurassic). The Middle-Late Jurassic is characterized by ophiolite obduction and the formation of various mélanges and nappe thrusting. Trench-like basins were formed in front of the newly formed nappe stack, and by the erosional products predominantly of the imbricated outer shelf (Triassic deep-water limestones). In cases deep-water Hallstatt nappes were bulldozed by the obducting ophiolites to the foreland.