Information on Holocene climatic variation derives largely from terrestrial evidence, whether direct human records or indications from a variety of archaeological and geological sources (Lamb 1995). With the exception of some evidence from the trace-elemental (Beck et al. 1992) and stable-isotopic (e.g., Swart et al. 1996) composition of tropical corals, comparatively little information has been derived from the marine realm. Relevant data are potentially obtainable and of value to corroborate (or otherwise test) terrestrial evidence and to investigate the linkage between marine environmental conditions and climate. One source of evidence of Holocene marine conditions in extra-tropical areas is the oxygen and carbon stable isotopic composition of mollusc-shell calcium carbonate (e.g., Eisma et al. 1981; Cohen and Tyson 1995; Hong et al. 1995; Aguirre et al. 1998; Jones and Kennett 1999). Stable isotope data obtained by ontogenetic sampling of mollusc shell can yield accurate estimates of seasonal marine temperature variation, together with indications of the timing of freshwater influxes, upwelling events, phytoplankton blooms, and the season of death of the animal investigated (e.g., Krantz et al. 1984, 1987, 1988; Krantz 1990; Jones and Allmon 1995; Hickson et al. 1999; Johnson et al. 2000). Thus, while providing high-quality temperature information for comparison with terrestrial records, stable isotope data also yield information concerning other climate-related variables. Brief, large-scale freshwater influxes are, for instance, likely to be the result of storms, for which there exists independent evidence of variation in intensity during the Holocene (Lamb 1995). Because carbon stable isotopic composition of marine shells also appears to reflect that of the atmosphere, which varies with atmospheric CO2 concentration (Beveridge and Shackleton 1994; Böhm et al. 1996), there is scope in addition for investigating the role of this last factor as a cause of climatic variation.
Abundant molluscs are present in cores of North Sea Holocene deposits taken by the British Geological Survey (BGS) as part of the Land-Ocean Evolution Perspective Study (LOEPS), a branch of the Land-Ocean Interaction Study (LOIS). This molluscan fauna (Balson et al. 1997) includes the Queen Scallop, Aequipecten opercularis, a benthic bivalve. Study of modern specimens of this species has shown it to be well suited to provision of environmental information through isotopic analysis (Hickson et al. 1999). Aequipecten opercularis deposits calcite of the outer shell layer at or near isotopic equilibrium with ambient waters and has the potential for growth throughout the year (at least in young specimens); hence it affords a full record of seasonal environmental variation.
In this paper we report the results of analysis of six 14C-dated Holocene shells and confirm that detailed environmental information can be obtained from ancient material. We discuss estimates of marine temperature in the light of indications of atmospheric temperature from terrestrial sources, present evidence of the level of atmospheric CO2 in the Holocene relative to the present day, and consider the cause of differences in occurrence and growth pattern between Holocene and modern A. opercularis in the southern North Sea.