Change search
ReferencesLink to record
Permanent link

Direct link
Palaeoenvironmental significance of Toarcian black shales and event deposits from southern Beaujolais, France
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
Show others and affiliations
2013 (English)In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 150, no 4, 728-742 p.Article in journal (Refereed) Published
Abstract [en]

New sedimentological, biostratigraphical and geochemical data recording the Toarcian Oceanic Anoxic Event (T-OAE) are reported from a marginal marine succession in southern Beaujolais, France. The serpentinum and bifrons ammonite zones record black shales with high (1-10 wt %) total organic carbon contents (TOC) and dysoxia-tolerant benthic fauna typical of the 'Schistes Carton' facies well documented in contemporaneous nearby basins. The base of the serpentinum ammonite zone, however, differs from coeval strata of most adjacent basinal series in that it presents several massive storm beds particularly enriched in juvenile ammonites and the dysoxia-tolerant, miniaturized gastropod Coelodiscus. This storm-dominated interval records a marked negative 5 parts per thousand carbonate and organic carbon isotope excursion being time-equivalent with that recording storm-and mass flow-deposits in sections of the Lusitanian Basin, Portugal, pointing to the existence of a major tempestite/turbidite event over tropical areas during the T-OAE. Although several explanations remain possible at present, we favour climatically induced changes in platform morphology and storm activity as the main drivers of these sedimentological features. In addition, we show that recent weathering, most probably due to infiltration of O-2-rich meteoric water, resulted in the preferential removal of C-12-enriched organic carbon, dramatic TOC loss and total destruction of the lamination of the black shale sequence over most of the studied exposure. These latter observations imply that extreme caution should be applied when interpreting the palaeoenvironmental significance of sediments lacking TOC enrichment and lamination from outcrops with limited surface exposures.

Place, publisher, year, edition, pages
2013. Vol. 150, no 4, 728-742 p.
Keyword [en]
Toarcian Oceanic Anoxic Event, Schistes Carton, oxygen-deficiency, organic-rich deposits, weathering, carbon isotope excursion, ammonites, event deposits
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-204094DOI: 10.1017/S0016756812000970ISI: 000320195600008OAI: diva2:637862
Available from: 2013-07-23 Created: 2013-07-22 Last updated: 2013-10-01Bibliographically approved

Open Access in DiVA

fulltext(1685 kB)220 downloads
File information
File name FULLTEXT01.pdfFile size 1685 kBChecksum SHA-512
Type fulltextMimetype application/pdf

Other links

Publisher's full text
By organisation
In the same journal
Geological Magazine
Natural Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 220 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 226 hits
ReferencesLink to record
Permanent link

Direct link