HORNUNG, T., BRANDNER, R.,KRYSTYN, L., JOACHIMSKI, M.M., KEIM, L. (2007c)
Multistratigraphic
constraints on the NW Tethyan ‘Carnian Crisis’
Abstract
The ‘Carnian Crisis’ is
documented in basinal, shallow-marine and epicontinental northwestern Tethyan
facies areas by, successively, 1) a
demise of carbonate platforms and reefs in Julian 1/IIc, 2) a major faunal
and floral turnover in Late Julian and 3) a significant extinction event affecting
conodonts and ammonoids at the Julian/Tuvalian boundary. Based on the study
of 19 successions from the NW Tethys, the presence of short-lived ammonoid
and conodont taxa and the sudden absence of reef-derived debris in basinal
and shallow-marine successions document a strict synchroneity in latest Julian
1 of a carbonate productivity crisis. d18Ophos values measured on conodont
apatite display a major negative shift of 2.0 ‰ [V-SMOW] in latest Julian
1 and Julian 2 indicating climate warming and a change in seawater salinity.
This interpretation fits with changes in lithofacies and argues for humidification
and enhanced freshwater runoff (sensu Simms and Ruffell, 1989), resulting in
higher nutrient levels as the main factors of both reef disease and decline
of nektonic biodiversity in late Early Carnian time.
published in: Lucas, S.G., Spielmann, J.A.: The Global Triassic. New Mexico Museum of Natural History Bulletin, 41: 59-67 |
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