Skip to Main Content
Skip Nav Destination
GEOREF RECORD

On using carbon and oxygen isotope data from glendonites as paleoenvironmental proxies; a case study from the Permian system of eastern Australia

Tracy D. Frank, Stephanie G. Thomas and Christopher R. Fielding
On using carbon and oxygen isotope data from glendonites as paleoenvironmental proxies; a case study from the Permian system of eastern Australia
Journal of Sedimentary Research (November 2008) 78 (11): 713-723

Abstract

Glendonites, calcite pseudomorphs after ikaite (CaCO (sub 3) .6H (sub 2) O), feature prominently in fine-grained, glacially influenced Permian marine strata of eastern Australia, which accumulated in a series of extensional basins that occupied polar to temperate latitudes along the southeastern margin of Gondwana. Because ikaite formation in the marine environment requires near-freezing temperatures, high alkalinity, and elevated concentrations of orthophosphate, the presence of glendonites in ancient strata implies a particular array of paleoenvironmental conditions. A petrographic and geochemical study was carried out to assess the veracity of isotopic data from glendonites as proxy indicators of ancient ocean chemistry, sea-floor temperature, and diagenesis. In thin section, glendonites consist of inclusion-zoned, equant to bladed calcite crystals, interpreted as the ikaite replacement phase, enclosed in a matrix of calcite and minor chalcedony and pyrite cements. Carbon and oxygen isotope data show a negative covariance, with delta (super 18) O values ranging from -22.5 to +0.3 per mil and delta (super 13) C values from -27.7 to -4.5 per mil V-PDB. Of the calcite phases examined, the ikaite replacement phase is the most enriched in (super 18) O and most depleted in (super 13) C; enclosing cements possess lower delta (super 18) O and higher delta (super 13) C values and are interpreted to have formed during later stages of burial diagenesis. The delta (super 18) O values of the ikaite replacement phase do not correspond to formation with Permian seawater at near-freezing temperatures unless isotopic disequilibrium is assumed. The delta (super 13) C values are similar to the carbon isotope composition of bulk organic matter in the host sediment, and suggest that the alkalinity and orthophosphate necessary for ikaite stability were generated in the zone of suboxic to anoxic diagenesis. Results indicate that although delta (super 18) O and delta (super 13) C values from glendonites are useful for understanding early to late diagenetic processes, they are not ideal proxies for seawater chemistry and temperature.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 78
Serial Issue: 11
Title: On using carbon and oxygen isotope data from glendonites as paleoenvironmental proxies; a case study from the Permian system of eastern Australia
Affiliation: University of Nebraska-Lincoln, Department of Geosciences, Lincoln, NE, United States
Pages: 713-723
Published: 200811
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 50
Accession Number: 2009-015019
Categories: StratigraphyIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 plates, 1 table, geol. sketch map
S29°00'00" - S10°00'00", E138°00'00" - E153°00'00"
Secondary Affiliation: Southern Methodist University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 200909
Close Modal

or Create an Account

Close Modal
Close Modal