TY - GEN

T1 - Radiolarian response to environmental changes at the Sinemurian–Pliensbachian transition in the Northern Calcareous Alps, Austria

AU - Cifer, Tim

AU - Goričan, Špela

AU - Demény, Attila

AU - Gawlick, Hans-Jürgen

PY - 2024/1/15

Y1 - 2024/1/15

N2 - Major environmental, climate and sealevelchanges occurred in the Western Tethyan Realm during thelate Sinemurian to early Pliensbachian time interval. Here, weexamine how these changes affected the taxonomic compositionof radiolarian fauna. Radiolarian assemblages were collectedon Mount Rettenstein (Northern Calcareous Alps) froma siliceous limestone and marl succession, deposited in awell-oxygenated basin a few hundred metres in depth on thecontinental shelf at the western edge of the Neotethys Ocean.Radiolarian research was complemented with elemental andisotope geochemistry on bulk carbonate samples. The siliceousmicrofaunas below and above the stage boundary consist ofmore than 80% sponge spicules and less than 20% radiolarians,with a strong predominance of the Order Spumellaria.The Nassellaria to Spumellaria abundance ratio ranges from1:5 to 1:3. At the Sinemurian–Pliensbachian transition, a significantdrop in diversity occurred, accompanied by asubstantial change in relative abundances of radiolarian taxa.The most severely affected groups were surface-dwelling radiolarians(Angulobrachiidae, Hagiastridae, Pantanelliidae;mostly Gorgansium, Poulpidae and Ultranaporidae), whichalmost or completely disappeared. In contrast, Archaeocenosphaera,Praeconocaryomma, Zhamoidellum and Lantusbecame abundant and were apparently the most resistant toenvironmental stress. The changes in radiolarian assemblageswere local and probably induced by the end-Sinemurian sealeveldrop that transformed the area into a semi-enclosed basinwith restricted ocean circulation. The exchange of watermasses and thus radiolarian faunas with the open sea wasreduced and their productivity may have been lowered by thelower inflow of fertile waters from the ocean

AB - Major environmental, climate and sealevelchanges occurred in the Western Tethyan Realm during thelate Sinemurian to early Pliensbachian time interval. Here, weexamine how these changes affected the taxonomic compositionof radiolarian fauna. Radiolarian assemblages were collectedon Mount Rettenstein (Northern Calcareous Alps) froma siliceous limestone and marl succession, deposited in awell-oxygenated basin a few hundred metres in depth on thecontinental shelf at the western edge of the Neotethys Ocean.Radiolarian research was complemented with elemental andisotope geochemistry on bulk carbonate samples. The siliceousmicrofaunas below and above the stage boundary consist ofmore than 80% sponge spicules and less than 20% radiolarians,with a strong predominance of the Order Spumellaria.The Nassellaria to Spumellaria abundance ratio ranges from1:5 to 1:3. At the Sinemurian–Pliensbachian transition, a significantdrop in diversity occurred, accompanied by asubstantial change in relative abundances of radiolarian taxa.The most severely affected groups were surface-dwelling radiolarians(Angulobrachiidae, Hagiastridae, Pantanelliidae;mostly Gorgansium, Poulpidae and Ultranaporidae), whichalmost or completely disappeared. In contrast, Archaeocenosphaera,Praeconocaryomma, Zhamoidellum and Lantusbecame abundant and were apparently the most resistant toenvironmental stress. The changes in radiolarian assemblageswere local and probably induced by the end-Sinemurian sealeveldrop that transformed the area into a semi-enclosed basinwith restricted ocean circulation. The exchange of watermasses and thus radiolarian faunas with the open sea wasreduced and their productivity may have been lowered by thelower inflow of fertile waters from the ocean

KW - Radiolaria

KW - palaeoecology

KW - Early Jurassic

KW - Western Tethys

KW - taxonomic composition

KW - environmental crisis

M3 - Conference contribution

BT - Radiolarian response to environmental changes at the Sinemurian–Pliensbachian transition in the Northern Calcareous Alps, Austria

ER -