Stable isotopic compositions of recent freshwater cyanobacterial carbonates from the British Isles: local and regional environmental controls

Andrews, JE, Riding, R and Dennis, PF ORCID: https://orcid.org/0000-0002-0307-4406 (1993) Stable isotopic compositions of recent freshwater cyanobacterial carbonates from the British Isles: local and regional environmental controls. Sedimentology (40). pp. 303-314. ISSN 1365-3091

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Abstract

Recent (<50 years old) freshwater cyanobacterial carbonates from diverse environments (streams, lakes, waterfalls) throughout Britain and Ireland were analysed for their stable carbon and oxygen isotope compositions. The mean δ18O value of −5–9‰ PDB for river and stream data represents calcite precipitation in equilibrium with the mean oxygen isotopic composition of precipitation in central Britain (−7–5‰SMOW) assuming a mean water temperature of 9°C. The mean δ18O of lake data, −4–5‰ PDB, is statistically different, reflecting the effects of residence time and/or variations in the oxygen isotopic composition of rainfall. Carbon isotopes have wide variations in both fluviatile and lake data sets (+ 3 to −12‰ PDB). These variations are principally controlled in the fluviatile samples by contribution of isotopically light ‘soil zone’ carbon relative to isotopically heavier carbon from limestone aquifer rock dissolution. Lake samples have the heaviest carbon isotope values, reflecting a trend toward isotopic equilibrium between atmospheric CO2 and aqueous HCO3-. We infer that isotopic compositions of ancient cyanobacterial carbonates should also record environmental information, although the effects of stabilization and diagenesis on primary δ18O values will need careful consideration. Primary carbon isotope compositions should be well preserved, although in marine samples values will be buffered by the isotopic composition of aqueous marine bicarbonate.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Environmental Sciences University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups:	Faculty of Science > Research Groups > Geosciences Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Depositing User:	Rachel Snow
Date Deposited:	03 Mar 2011 12:20
Last Modified:	13 Apr 2023 13:43
URI:	https://ueaeprints.uea.ac.uk/id/eprint/25605
DOI:	10.1111/j.1365-3091.1993.tb01765.x

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