Integrated stratigraphy across the Jurassic–Cretaceous boundary in the Rettenbacher section (Northern Calcareous Alps, Salzburg, Austria)

Abstract

Rettenbacher Quarry carbonate sequence in the Northern Calcareous Alps represents highly dynamic pelagic carbonate sedimentation in the lower slope environment. The section spans from upper Tithonian Crassicollaria colomi Subzone to middle Berriasian Calpionella elliptica Subzone. Radiolarian samples belong to Pseudodictyomitra carpatica Zone. Considerable redeposition of calpionellids, organic walled dinoflagellate cysts, calcareous nannofossils and foraminifera in the allodapic layers, as well as extensive normal polarity remagnetisation event with substantial clockwise rotation is documented. Quantitative predominance of genera Watznaueria and Cyclagelosphaera indicate strong nannofossil modification during diagenesis. The almost straight trend in the δ¹³C with some slight carbon-isotope perturbations is recorded at Rettenbacher. Three significant and stratigraphically important negative excursions of the δ¹³C_carb values were identified — including tentative indication of a new “Negative peak 4” in the upper part of the Elliptica Subzone — and correlated with other sections confirming stability, respectively isochronity within carbon chemostratigraphy.