TY - GEN

T1 - DEMISE AND AFTERMATH OF TRIASSIC SHALLOW-WATER RAMPS/PLATFORMS IN THE WESTERN TETHYS REALM

AU - Gawlick, Hans-Jürgen

AU - Missoni, Sigrid

PY - 2021

Y1 - 2021

N2 - The Triassic passive continental margin sedimentary evolution in the Western Tethyan realm,very well preserved in the central Northern Calcareous Alps, is characterized by the demiseand aftermath of three main shallow-water carbonate ramp/platform cycles:1) Late Early Triassic to Middle Anisian carbonate ramp evolution (upper Werfen,Gutenstein and Steinalm carbonate ramp), deposited in an epicontinental sea (graben).2) Latest Ladinian to earliest Carnian carbonate platform evolution (Wetterstein CarbonatePlatform), formed in a passive continental margin setting.3) Late Triassic (Norian-Rhaetian) Hauptdolomit/Dachstein Carbonate Platform evolution,and its Late Carnian carbonate ramp forerunner (passive continental margin).The Northern Calcareous Alps as part of the Eastern Alps is one of the most prominent Alpineareas. Together with the Western Carpathians, the Southern Alps and the Dinarides, theyconstituted an up to 700 km wide and approximately 2000 km long shelf strip of thenorthwestern Tethys margin. The Triassic sedimentation was controlled by Early to earlyMiddle Triassic extension, the break-up of the Neo-Tethys in the early Middle Triassic (MiddleAnisian) and the formation of huge carbonate platforms in the late Middle to Late Triassic.After siliciclastic dominated (latest Permian to) Early Triassic sedimentation intense shallowwatercarbonate production started slightly before the Early/Middle Triassic boundary. Afterdeposition of more open marine influenced late Early Triassic limestones, in cases intercalatedwith siliciclastic sedimentary rocks in the Early-Middle Anisian shallow-water carbonates weredeposited first under restricted and later under more open marine conditions (carbonateramps). The Late Anisian final break-up of the Neo-Tethys Ocean led to the drowning of thisshallow-water ramp deposits. In the frame of the final break-up of the Neo-Tethysa horst-and-graben morphology formed and deep-water conditions prevail during Late Anisianto Late Ladinian times. Only in short time spans during the latest Anisianresp. the Anisian/Ladinian boundary some shallow-water carbonates were formedon morphological highs, acting as nucleus for the later evolving Wetterstein Carbonate Platform.This platform started to form in the Late Ladinian, and resulted in the complex latest Ladinianto earliest Carnian platform - basin pattern (Wetterstein Carbonate Platform evolution).After the demise of the Wetterstein Carbonate Platform and partial drowning of this platformby siliciclastic input in the Middle Carnian again shallow-water carbonate production startedin the Late Carnian. These Late Carnian shallow-water carbonate ramp deposits (Waxeneckramp evolution) resulted in the evolution of the huge Norian Hauptdolomit/DachsteinLimestone Carbonate Platform, with its classical lagoonal sediments - restricted lagoon(Hauptdolomit), open lagoon (Dachstein Limestone with Lofer cycles) - the reefs belt and itstransition to the open shelf area (Hallstatt facies). In the Rhaetian the carbonate factories wereagain influenced by siliciclastic input, and a deep lagoon (Kössen Basin) was formed.At the Triassic/Jurassic boundary shallow-water carbonate production endedand the Hauptdolomit/Dachstein Carbonate Platform drowned. Beside all sedimentologicalfeatures the controlling factors of ramp/platform evolution will be discussed as the roleof tectonics, ocean acidification, climate changes, stepwise mass extinctions and sea-levelfluctuations.

AB - The Triassic passive continental margin sedimentary evolution in the Western Tethyan realm,very well preserved in the central Northern Calcareous Alps, is characterized by the demiseand aftermath of three main shallow-water carbonate ramp/platform cycles:1) Late Early Triassic to Middle Anisian carbonate ramp evolution (upper Werfen,Gutenstein and Steinalm carbonate ramp), deposited in an epicontinental sea (graben).2) Latest Ladinian to earliest Carnian carbonate platform evolution (Wetterstein CarbonatePlatform), formed in a passive continental margin setting.3) Late Triassic (Norian-Rhaetian) Hauptdolomit/Dachstein Carbonate Platform evolution,and its Late Carnian carbonate ramp forerunner (passive continental margin).The Northern Calcareous Alps as part of the Eastern Alps is one of the most prominent Alpineareas. Together with the Western Carpathians, the Southern Alps and the Dinarides, theyconstituted an up to 700 km wide and approximately 2000 km long shelf strip of thenorthwestern Tethys margin. The Triassic sedimentation was controlled by Early to earlyMiddle Triassic extension, the break-up of the Neo-Tethys in the early Middle Triassic (MiddleAnisian) and the formation of huge carbonate platforms in the late Middle to Late Triassic.After siliciclastic dominated (latest Permian to) Early Triassic sedimentation intense shallowwatercarbonate production started slightly before the Early/Middle Triassic boundary. Afterdeposition of more open marine influenced late Early Triassic limestones, in cases intercalatedwith siliciclastic sedimentary rocks in the Early-Middle Anisian shallow-water carbonates weredeposited first under restricted and later under more open marine conditions (carbonateramps). The Late Anisian final break-up of the Neo-Tethys Ocean led to the drowning of thisshallow-water ramp deposits. In the frame of the final break-up of the Neo-Tethysa horst-and-graben morphology formed and deep-water conditions prevail during Late Anisianto Late Ladinian times. Only in short time spans during the latest Anisianresp. the Anisian/Ladinian boundary some shallow-water carbonates were formedon morphological highs, acting as nucleus for the later evolving Wetterstein Carbonate Platform.This platform started to form in the Late Ladinian, and resulted in the complex latest Ladinianto earliest Carnian platform - basin pattern (Wetterstein Carbonate Platform evolution).After the demise of the Wetterstein Carbonate Platform and partial drowning of this platformby siliciclastic input in the Middle Carnian again shallow-water carbonate production startedin the Late Carnian. These Late Carnian shallow-water carbonate ramp deposits (Waxeneckramp evolution) resulted in the evolution of the huge Norian Hauptdolomit/DachsteinLimestone Carbonate Platform, with its classical lagoonal sediments - restricted lagoon(Hauptdolomit), open lagoon (Dachstein Limestone with Lofer cycles) - the reefs belt and itstransition to the open shelf area (Hallstatt facies). In the Rhaetian the carbonate factories wereagain influenced by siliciclastic input, and a deep lagoon (Kössen Basin) was formed.At the Triassic/Jurassic boundary shallow-water carbonate production endedand the Hauptdolomit/Dachstein Carbonate Platform drowned. Beside all sedimentologicalfeatures the controlling factors of ramp/platform evolution will be discussed as the roleof tectonics, ocean acidification, climate changes, stepwise mass extinctions and sea-levelfluctuations.

M3 - Conference contribution

SN - 978-80-244-5950-9

BT - aftermath of Triassic shallow-water carbonate ramps/platforms in the Western Tethys realm 4 DEMISE AND AFTERMATH OF TRIASSIC SHALLOW-WATER RAMPS/PLATFORMS IN THE WESTERN TETHYS REALM

ER -