New results of stable isotope and petrographic studies of Jurassic glendonites from Siberia. (2nd October 2019)

• Record Type: Journal Article
• Authors: Vasileva, Kseniia Y.; Rogov, Mikhail A.; Ershova, Victoria B.; Pokrovsky, Boris G.
• Is Part Of: GFF. Volume 141:Number 4(2019)
• Page Start: 225
• Page End: 232
• Publication Date: 2019-10-02
• Subjects: Glendonites -- stable isotopes -- paleoclimate -- diagenesis; Geology -- Scandinavia -- Periodicals; Geology -- Periodicals; 554.8
• DOI: 10.1080/11035897.2019.1641549
• Languages: English
• ISSNs: 1103-5897

Abstract

ABSTRACT: We present the results of an optical microscopy, cathodoluminoscopy and isotopic study on nine glendonite concretions (calcite pseudomorphs replacing metastable hexahydrate ikaite) from Lower-Middle Jurassic sediments of Northeast Russia (Anabar Bay and Lena River region). Glendonite concretions are mainly found within Late Pliensbachian, Toarcian, Aalenian, Bajocian and Lower Bathonian clastic sediments, correlating to episodes of global climatic cooling as determined by independent paleoclimate proxy data. Stable carbon and oxygen isotopic values of glendonite concretions suggest that the primary source of carbon was derived from diagenetically altered organic matter, and the source of oxygen was from seawater. The secondary diagenetic cement is characterized by a significantly lighter δ 18 O and significantly heavier δ 13 C signature than the isotopic characteristics of the bulk rock glendonite concretion. This secondary diagenetic cement is thought to have precipitated rapidly during burial diagenesis and since it occupies a significant volume of the glendonite concretion, it has the potential to significantly influence the isotopic composition of bulk rock glendonites.