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The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of Open Access research papers by University of Strathclyde researchers, including by researchers from the Department of Computer & Information Sciences involved in mathematically structured programming, similarity and metric search, computer security, software systems, combinatronics and digital health.

The Department also includes the iSchool Research Group, which performs leading research into socio-technical phenomena and topics such as information retrieval and information seeking behaviour.


Are oxygen and carbon isotopes of mollusc shells reliable palaeosalinity indicators in marginal marine environments? A case study from the Middle Jurassic of England

Hendry, J.P. and Kalin, R.M. (1997) Are oxygen and carbon isotopes of mollusc shells reliable palaeosalinity indicators in marginal marine environments? A case study from the Middle Jurassic of England. Journal of the Geological Society, 154 (2). pp. 321-333.

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Stable isotope analyses of non-luminescent, texturally-pristine oyster calcites (Praexogyra hebridica) are presented from Bathonian inner-ramp limestones in central-eastern England. A relatively large range of values (delta(18)O=-2.0 to +2.3 parts per thousand PDB; delta(13)C=+0.9 to +3.7 parts per thousand PDB) define a crude positive covariance, which can be regionally correlated with an offshore to nearshore increase in faunal restriction. This palaeoenvironmental stress gradient has previously been interpreted as a consequence of fluctuating nearshore palaeo-salinities, due to episodic or seasonal runoff from surrounding hinterlands. Covariant delta(18)O-delta(13)C trends from euryhaline bivalves are commonly ascribed to regional salinity gradients, the most isotopically depleted examples representing the greatest influence of Fresh water. However, Bathonian palaeogeography indictates that the most isotopically-depleted oysters inhabited relatively offshore settings. Assuming an average growth temperature of 25 degrees C, these shells were secreted in near-normal sea water (delta(18)O=+0.4 parts per thousand SMOW). In contrast, isotopically heavy oyster calcites were produced in highly evaporated, nearshore lagoonal waters (delta(18)O up to +4.8 parts per thousand SMOW). Modelling the oxygen isotope and chemical evolution of residual waters during evaporation suggests that up to 65% of the nearshore water mass was lost, probably in a complex of hydrodynamically choked lagoons. Evaporites were not precipitated in the sediment, and geochemical modelling suggests that the lagoon waters may have been brackish rather than marine in origin. The regional delta(13)C trend is contrary to that predicted on the basis of palaeosalinity and may have resulted from variations in organic carbon production, decay and fixation in early diagenesis.