|mhorn||Дата: Tuesday, 16.07.2013, 16:26 | Сообщение # 1|
|Krische O., Bujtor L., Gawlick H.-J. (2013) Calpionellid and ammonite biostratigraphy of uppermost Jurassic to Lower Cretaceous sedimentary rocks from the Leube quarry (Northern Calcareous Alps, Salzburg, Austria) // Austrian J. Earth Sci. Vol.106. no.1. P.26-45. |
New calpionellid and ammonite data from the Leube quarry in combination with microfacies and lithology analyses allow a new and precise biostratigraphy in Upper Tithonian and Lower Cretaceous hemipelagic sedimentary rocks of the Northern Calcareous Alps south of Salzburg (Austria). The Upper Tithonian Oberalm Formation is dated by the first occurrence of Calpionella alpina (Lorenz, 1902), Crassicollaria massutiniana (Colom, 1948) and Crassicollaria intermedia (Durand-Delga, 1957) (Crassicollaria intermedia Subzone). In the Upper Tithonian hemipelagic radiolarian wackestones several clastic cycles are intercalated, consisting of breccias beds (mass-flow deposits) and turbidites with resedimented litho- and bioclastic material from nearby carbonate platforms (Barmstein Limestone). The change from white, hemipelagic limestones to greenish, marly limestones with marl intercalations takes place in between the Upper Tithonian and Lower Berriasian part of the Oberalm Formation and is dated by the first common occurrence of Calpionella alpina (Lorenz, 1902) together with Remaniella sp. (Calpionella alpina and Remaniella Subzones). The next lithological change follows in the upper Lower Berriasian to Middle Berriasian, constrained by the first occurrences of Calpionella elliptica (Cadisch, 1932) and Remaniella cadischiana (Colom, 1948) (Calpionella elliptica and Remaniella cadischiana Subzones). Green-red marly limestones (Gutratberg beds of the Oberalm Formation with the economically important Portland cement layer) and marls with an increasing amount of sponge spicula, turbiditic layers with echinoderm remnants and detrital minerals are characteristic. The variegated marls and limestones are overlain by silty brownish to greenish marls with plant remnants and ammonites of the Schrambach Formation (Middle Berriasian). The first occurrence of Calpionellopsis sp. within calcareous turbidites defines the basis of the Upper Berriasian (Calpionellopsis Zone). These turbidites are overlain again by plant remnant bearing marls and a well bedded limestone-marl succession. Fauriella boissieri (Pictet, 1867) within the marls below the well bedded rocks indicates a Late Berriasian age (Subthurmannia boissieri Zone). The first occurrence of Calpionellites sp. together with Remaniella filipescui (Pop, 1994) in the bedded limestone-marl succession marks the beginning of the Lower Valanginian.
Middle Jurassic - Lower Cretaceous ammonites & aptychi