Integrated Rhaetian foraminiferal and conodont biostratigraphy from the Slovenian Basin, eastern Southern Alps
Conodonts and re-deposited shallow-water benthic foraminifera co-occur in the Upper Norian-Rhaetian Slatnik Formation of the Slovenian Basin (Southern Alps). The Mt. Kobla and Mt. Slatnik sections were investigated in order to give the first direct correlation between these two groups. The Norian-Rh...
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Veröffentlicht in: | Swiss Journal of geosciences 2012-10, Vol.105 (3), p.435-462 |
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Sprache: | eng |
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Zusammenfassung: | Conodonts and re-deposited shallow-water benthic foraminifera co-occur in the Upper Norian-Rhaetian Slatnik Formation of the Slovenian Basin (Southern Alps). The Mt. Kobla and Mt. Slatnik sections were investigated in order to give the first direct correlation between these two groups. The Norian-Rhaetian boundary (NRB) is placed at the First Appearance Datum of the conodont
Misikella posthernsteini
and is approached with the First Occurrence of the foraminifer
Involutina turgida
. An association of
Trocholina turris
with duostominids is a good marker for the Rhaetian. Careful revision of literature combined with our data culminated in reambulation of stratigraphical ranges for several foraminiferal species. The foraminiferal Triassic-Jurassic boundary (TJB) can be defined with the Last Occurrence of
Galeanella tollmanni
, “
Sigmoilina
”
schaeferae
or duostominids. The absence of the uppermost Rhaetian
Misikella ultima
conodont zone and the close coincidence of foraminiferal and conodont TJB could point to the presence of hiati in the upper part of the Slatnik Formation. Consequently, the exact pattern of disappearance of Late Triassic foraminifera at the boundary could not be observed. It is clear, however, that the foraminiferal assemblage was decimated for reef-dwelling foraminifera, duostominids and most of the platform-dwelling foraminifera. Biotic changes at the TJB are best explained as a result of a biocalcification crisis. |
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ISSN: | 1661-8726 1661-8734 |
DOI: | 10.1007/s00015-012-0117-1 |