Controls on development of Mid-Triassic ramps: Examples from southern Hungary

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During Mid-Triassic time the palaeogeographical-tectonic setting of the northern Tethyan passive margin and epicontinental basins favoured the ramp morphology, as broad flat areas were available for flooding and establishment of carbonate sedimentation. Throughout this time, in what is now southern Hungary, homoclinal ramps developed, which also exhibit some evidence of partial distal steepening. The nearly 1 km thick Anisian-Ladinian Muschelkalk carbonates are grouped into six depositional units. In each ramp unit facies types were identified representing coastal sabkhas, inner ramp peritidal facies, backshoal lagoons, oolite shoals, storm to fair-weather influenced mid-ramps, proximal to distal shell beds and low-energy outer ramps. Mid- and inner ramp carbonates make up the majority of the successions. The deepest outer ramp facies correspond to the peak transgression of a second-order Triassic sea-level rise. In the Hungarian Muschelkalk three major transgressive-regressive sequences were identified. In Germany, Poland and Spain much thinner and slightly coarser Muschelkalk carbonate successions were formed in the same Mid-Triassic interval. The major sediment redistribution processes were related to storms that generated coquinas, and mud flow deposits. Slow, early diagenesis and the predominance of unstable muddy substrate led to the formation of small-scale slumps, slides and plastic deformation. The fauna reflects the prevalence of carbonate mud and temporarily high-stress conditions. A non 'cool water' origin of this ramp is inferred from the presence of evaporites, early dolomization of inner ramp carbonates, the biota and the palaeogeographical setting. The major controlling factors of Mid-Triassic ramps were the gentle antecedent morphology, the subtropical climate, the high production of carbonate mud and the lack of reef-building organisms, as well as the passive margin setting, which resulted in a moderate and relatively uniform subsidence rate over a wide area.

Original languageEnglish
Pages (from-to)339-367
Number of pages29
JournalGeological Society Special Publication
Publication statusPublished - Dec 1 1998


ASJC Scopus subject areas

  • Water Science and Technology
  • Ocean Engineering
  • Geology

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