Stable Carbon and Oxygen Isotope Records From Lake Erie Sediment Cores: Mollusc Aragonite 4600 BP–200 BP

Abstract

We present the first δ 18O and δ 13C data from mollusc aragonite from Lake Erie for the 4.6–0.2 ka (4600 BP to 200 BP 14C yrs) time interval and describe single and composite species isotope trends. Composite species δ 18O data show an almost 2.0%o increase from 3.3 to 3.0 ka followed by a nearly 2.5%o decrease at 2.8 ka. Oxygen isotope values then fluctuate by < l‰ until 0.2 ka. This trend in oxygen values is also evident in single species analyses of Sphaerium striatinurn. The most dramatic changes in isotope values, which occur from 3.3–2.8 ka, may reflect a pattern of water level changes in Lake Erie which occurred during the Nipissing flood and its lower water aftermath. Carbon isotope data show progressively more 13C enriched values from 4.6 ka (averaging–6.5‰ PDB) to the present (–0.57‰). This trend may reflect the dilution of isotopically light CO 2 from the oxidation of organic matter due to rising lake levels. The short-term increase in δ 18O values is coupled with a corresponding decrease in δ 13C values. A similar pattern for Lake Erie prior to 10.5 ka was also associated with a lowering of water levels in the lake.