A positive trend in seawater 87Sr/86Sr values over the Early-Middle Frasnian boundary (Late Devonian) recorded in well-preserved conodont elements from the Holy Cross Mountains, Poland

John, Eleanor H., Cliff, Robert and Wignall, Paul B. 2008. A positive trend in seawater 87Sr/86Sr values over the Early-Middle Frasnian boundary (Late Devonian) recorded in well-preserved conodont elements from the Holy Cross Mountains, Poland. Palaeogeography, Palaeoclimatology, Palaeoecology 269 (3-4) , pp. 166-175. 10.1016/j.palaeo.2008.04.031

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Abstract

Over the Early–Middle Frasnian boundary interval (Late Devonian), the oceans experienced major changes in global carbon cycling and nutrient dynamics with a prominent positive carbon isotope shift at the base of the Palmatolepis punctata Zone (Middle Frasnian). The aim of this study was to construct seawater 87Sr/86Sr ratio curves for the Pa. transitans–Pa. hassi zonal interval using well-preserved conodont apatite from two sections in the Holy Cross Mountains, south-central Poland. The final curves suggest that seawater 87Sr/86Sr values were steady at ~ 0.70794–0.70799 during the transitans Zone but began to rise in the early punctata Zone towards a value of ~ 0.70814 in the late punctata Zone (an increase of ~ 0.0002). The increase in seawater 87Sr/86Sr values over the Early–Middle Frasnian boundary appears to be the second of two prominent short-term rises in 87Sr/86Sr values, which led to an overall shift in values from a Givetian plateau of between ~ 0.70780 and 0.70785 to a Late Frasnian plateau of between 0.7080 and 0.7082. Correlation with a regional positive δ13C anomaly and evidence for eutrophication in the marine environment suggests that the causes of these phenomena may be linked and that the positive 87Sr/86Sr shift was caused by an increase in the continental flux of Sr to the oceans, i.e., the weathering flux. A possible explanation for an increase in the weathering flux is the denudation of a new Acadian–Eovariscan orogen, which would have been mostly weathered in the humid, warm tropical/equatorial region.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Publisher:	Elsevier
ISSN:	0031-0182
Date of Acceptance:	22 April 2008
Last Modified:	06 Jul 2023 15:45
URI:	https://orca.cardiff.ac.uk/id/eprint/160700

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