engleski

Boundary architecture between Triassic epeiric and isolated carbonate platform succession of Karst Dinarides

Affected by the rifting processes and separation from the Gondwana, a noticeable tectonic activity took place on the Adria Microplate during Early-Middle Triassic, creating uplifts, exposure and/or discontinuities in shallow-water carbonate sequence of the Karst Dinarides. As a consequence, some closely related non-marine sedimentary records were formed, thus producing various types of boundary architecture between two distinctive Karst Dinaridic platform megacycles ; the lower one, with the epeiric carbonate platform features, ranging from the Paleozoic to the Middle Triassic, and upper one, with the isolated carbonate platform features, ranging from the Late Triassic to the end of the Cretaceous. Four types of boundary architecture can be distinguished between these two large-scale platform megacycles: (1) the first type ranges from the Upper Ladinian to the Lower-Middle Rhaetian and is characterized by the presence of a few meters thick interval of regressive/transgressive breccia-conglomerates, containing fragments and pebbles of the Upper Ladinian "Diplopora limestones", overlain by the upper part of the Main Dolomite sequence ; (2) the second type ranges from the Upper Ladinian to the Lower Norian and comprises a few tens of meters thick interval of carbonate bauxites and laterites, ending with few meters thick interval of transgressive conglomerates, containing pebbles of bauxites, laterites and/or Ladinian limestones, overlain by the whole Main Dolomite sequence ; (3) the third type ranges from the Upper Anisian to the Lower Norian, starting with a few decimeters thick interval of regressive breccias, containing fragments of Anisian limestones, overlain by a few tens of meters thick interval of fine-grained reddish argillaceous limestone/siltstones, gradually and/or sharply overlain by the whole Main Dolomite sequence ; (4) the fourth type is characterized by a distinctive disconformity, where the Upper Scythian dolomites ("Campiler Schichten") are overlain by the lower part of the Main Dolomite sequence, starting with a few centimeters thick interval of transgressive conglomerates, containing pebbles of the Upper Scythian dolomites. Therefore, during Early-Middle Triassic, tectonicaly triggered uplifts on the "dinaridic part" of the Adria Microplate took place partly diachronously, interrupting shallow-water platform sedimenation in the former epeiric carbonate platform regime. After non-marine environmental conditions that lasted until the middle-upper Late Triassic, due diachronous transgression the shallow-water platform sedimentation was restored, but now in an isolated carbonate platform regime.

Early-Middle Triassic; Karst Dinarides; boundary architecture; platform megacycles

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