Ökologie und systematische stellung der foraminiferen im gebankten dachsteinkalk (obertrias) des nördlichen toten gebirges (oberösterreich)

Abstract

Statistical analysis reveals the strong facies dependence of foraminifera of the backreef environment in the Upper Triassic sedimentary limestones. Six facies are distinguished on the basis of counted allochems: 1.(1) Oolite facies. Ooids indicate strong water turbulence and normal marine salinity. Vagile foraminifera with great adherence dominate (Tetrataxis, Duostomina, etc.). Glomospirella indicate the allochthonous position of ooids.2.(2) Oolitic facies. Ooids have been transported and redeposited. The heterogeneous composition of foraminifera reflects the close association with the oolite, grapestone and pellet-mud facies.3.(3) Grapestone facies. Subtidal algal mats and strong water turbulence caused the formation of grapestones. The sligjtly raised salinity affords optimum conditions for vagile miliolids (Miliolipora, Quinqueloculina).4.(4) Calcareous algal-foraminiferal-detritus facies. Undamaged Dasycladaceae indicate low turbulence. Salinity may have reached higher levels in which highly variable involutinids with big shells were developed. Their association with calcareous algae corresponds to that of Recent larger foraminifera.5.(5) Pellet-mud facies. Pellets and micritic matrix indicate the least water movement and high salinity. Strongly adapted foraminifera, such as Trochammina, Agathammina, Palaeospiroplectammina and Frondicularia, predominate.6.(6) Mud facies. The absence of pellets, because of their destruction, confirms stronger water currents than in the pellet—mud facies; salinity reaches high levels. Foraminifera with thin shells (Involutina, Nodosaria) preferred this environment.