Marine and limnic radiocarbon reservoir corrections for studies of late- and postglacial environments in Georgia Basin and Puget Lowland, British Columbia, Canada and Washington, USA

Abstract

Models of late-glacial environmental change in coastal areas are commonly based on radiocarbon ages on marine shell and basal lake sediments, both of which may be compromised by reservoir effects. The magnitude of the oceanic reservoir age in the inland waters of the Georgia Basin and Puget Lowland of northwestern North America is inferred from radiocarbon ages on shell-wood pairs in Saanich Inlet and previously published estimates. The weighted mean oceanic reservoir correction in the early and mid Holocene is −720±90 yr, slightly smaller than, but not significantly different from, the modern value. The correction in late-glacial time is −950±50 yr. Valley-head sites yield higher reservoir values (−1200±130 yr) immediately after deglaciation. The magnitude of the gyttja reservoir effect is inferred from pairs of bulk gyttja and plant macrofossil ages from four lakes in the region. Incorporation of old carbon into basal gyttja yields ages from bulk samples that are initially about 600 yr too old. The reservoir age declines to less than 100 yr after the first millennium of lake development. When these corrections are accounted for, dates of deglaciation and late-glacial sea-level change in the study area are pushed forward in time by more than 500 yr.

Postglacial vegetation and climate dynamics in the Seymour‐Belize Inlet Complex, central coastal British Columbia, Canada: palynological evidence from Tiny Lake

“…630 a too old (cf. Hutchinson et al, 2004). The other dates obtained from the Tiny Lake core have probably not been affected by the incorporation of old carbon because this effect becomes negligible approximately 1000 a following lake inception as forest and soil development reduce the exposure and weathering rates of tills (Engstrom et al, 2000;Hutchinson et al, 2004).…”

“…BP denotes before 1950. Lateglacial reservoir effects have been observed in limnic sediments from southwestern BC and Washington and Holocene-aged old carbon effects have been observed in Alberta, possibly due to the incorporation of old carbon from carbonate reserves, graphite-containing minerals and/or marine sediments contained in exposed glacial tills (Sutherland, 1980;MacDonald et al, 1991;Hutchinson et al, 2004). No correction was applied to the basal date of 11 763 AE 87 14 C a BP (13 815 cal.…”

Relative Sea-Level Change in the Northern Strait of Georgia, British Columbia*

“…The marine reservoir correction has varied in the Strait of Georgia since late-glacial time (Hutchinson et al, 2004b).…”

Late Holocene paleoceanographic evidence of the influence of the Aleutian Low and North Pacific High on circulation in the Seymour-Belize Inlet Complex, British Columbia, Canada

“…No marine reservoir effect was applied to the bulk sediment sample derived date, since there are no studies in the variations of reservoir effects in enclosed fjords such as the SBIC. Even though areas of strong upwelling such as the east coast of Vancouver Island tend to have strong marine reservoir effects (up to 1200 years, Hutchinson et al, 2004), values for estuaries are very much affected by freshwater inflow, especially at boundaries between different ocean circulation regimes, such as the SBIC (Ingram and Southon, 1996).…”