δ 18O composition of conodont apatite indicates climatic cooling during the middle Pridoli
2010 (English)In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 294, 242-247 p.Article in journal (Refereed) Published
Phosphatic microfossils, such as conodonts and fish microremains (dermal scales) from the upper Silurian(Pridoli) of Lithuania have been studied for their oxygen isotope composition. The conodont colour alterationindex of the biogenic apatite did not exceed 1.5 reflecting only a minor thermal alteration. Conodontδ18Oapatite values range from 17.7 to 19.2‰ V-SMOW, with the average values around 18.3‰. Fossil apatite offish exoskeleton microremains from the same samples have lower δ18Oapatite values ranging from 15.2 to17.4‰ V-SMOW, with the average values around 16.3‰ V-SMOW. Palaeoseawater temperatures calculatedfrom conodont apatite δ18O range from 24.8–31.5 °C, those derived from fish δ18O give approximately 10 °Chigher temperatures ranging from 32.6 to 38.1 °C. The lower δ18Oapatite values of fish apatite and thus theunrealistic high palaeotemperatures are interpreted as a result of diagenetic alteration. A significant positiveshift in conodont apatite δ18O of +1.1‰ at the boundary between the Vievis and Lapės formations isobserved, coinciding with a major facies change. It is interpreted as a mid-Pridoli event within theOzarkodina eosteinhornensis Bizone, or the Ozarkodina remscheidensis Biozone reflecting a major coolingevent, which may have resulted in the formation of an ice sheet in high latitudes and a glacio-eustatic sealevelfall.
Place, publisher, year, edition, pages
2010. Vol. 294, 242-247 p.
IdentifiersURN: urn:nbn:se:uu:diva-230859DOI: 10.1016/j.palaeo.2010.03.033OAI: oai:DiVA.org:uu-230859DiVA: diva2:742145