International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

LOWER CRETACEOUS SECTION OF THE TERNBERG NAPPE (NORTHERN CALCAREOUS ALPS, UPPER AUSTRIA): FACIES-CHANGES, BIOSTRATIGRAPHY AND PALEOECOLOGY

Pages: 227 - 237

Authors: ALEXANDER LUKENEDER, DANIELA REHAKOVA

Abstract: Lithological, sedimentological and paleoecological studies of the Lower Cretaceous (KB1-A section, Ternberg Nappe, Northern Calcareous Alps, Upper Austria) uncovered rich spectra of Early Berriasian to Late Valanginian macro- and microfaunal elements in addition to microfloral members. The evaluation of the thin sections indicates a change from a calpionellid facies to an echinoid facies within the Steinmühl Formation whereas the Schrambach Formation consists of mudstones with rare microfossils. Several compositional changes in calcareous dinoflagellate and calpionellid assemblages (bio-events) are detected at the Austrian KB1-A section. They correspond to eustatic sea-level fluctuations observed in Lower Cretaceous sections of the Western Carpathians and correlate with the Nozdrovice Breccia (Nozdrovice Event) at the end of the Late Berriasian (Calpionellopsis Zone) and with the Oravice Turbidite Event at the Early Valanginian (Calpionellites Zone). The surface of the topmost bed of the Steinmühl Formation (latest Early Valanginian) is characterized by an accumulation of pygopids, partly eroded ammonoids with crinoidal epifaunas, and belemnites with Acrothoracica burrows. Additionally, a probably small biostratigraphic gap in the calpionellid subzonation between the Steinmühl- and the Schrambach Formations show a sedimentation stop (omission) during the pygopid accumulation.

Keywords: Early Cretaceous, Austria, Ternberg Nappe, paleoenvironment, sea-level fluctuations, microfossils, ammonoids

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