Abstract
This study presents the results of the conodont biostratigraphy and microfacies analysis carried out on the pelagic limestones of the Upper Triassic Dovško Section in Slovenia, which represents the eastern part of the Slovenian Basin. The age of the section ranges from the Lacian 1 to the Alaunian 1. The Lacian part of the succession is predominantly characterized by the representatives of the genus Ancyrogondolella. Transitional morphologies towards Alaunian faunas first appear in the Lacian 3 and become common during the Lacian-Alaunian transition. This evolutionary development coincides with a shift in microfacies from a dominantly radiolarian-bearing mudstone-wackestone-packstone to a filament- dominated wackestone-packstone, and the formation of small neptunian dykes, which may reflect environmental perturbations and/or a change in basin geometry. The proliferation of the genera Epigondolella and Mockina is observed in the Alaunian part of the section, though the genus Ancyrogondolella is still present in this interval. Systematic description of the conodont taxa is provided, and seven new species and two new subspecies are established. The new advances will be of great value in further biostratigraphic studies, especially in areas without ammonoid faunas, and in the reconstruction of the paleogeography of the Slovenian Basin.
Highlights
The Norian is the longest age of the Triassic, the fine subdivision of this ca. 20 Ma long time-span is not yet solved
This study presents the results of the conodont biostratigraphy and microfacies analysis carried out on the pelagic limestones of the Upper Triassic Dovško Section in Slovenia, which represents the eastern part of the Slovenian Basin
The documentation of the diversity, morphological variability and temporal distribution of the conodont taxa allows an insight into the evolutionary trends that characterize the faunas allowing the fine subdivision of the Lacian to lower Alaunian interval
Summary
The Norian is the longest age of the Triassic, the fine subdivision of this ca. 20 Ma long time-span is not yet solved. Important is the Lacian-Alaunian (lowermiddle Norian) transition, which is characterized by evident turnovers in several marine fossil groups, such as corals (Roniewicz, 2011), ammonoids (Krystyn, 2003) and conodonts (Karádi, 2018; Orchard, 2018). These faunal turnovers seem to coincide with changes in sedimentation in the Tethyan Realm, resulting in the formation of sedimentary breccias and slump structures in the early Alaunian and stratigraphic gaps in condensed Alaunian successions (Karádi, 2018).
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