Comparisons of High-Resolution Organic Paleoenvironmental Records in Five Lake Erie Sediment Cores Sampled Over a 21 Year Period

We compared paleoenvironmental records of five sediment cores sampled at 1982, 1988, 1991 (two cores) and 2003 at approximately the same locations from Eastern Basin of Lake Erie to evaluate the effects on paleoenvironmental interpretations from spatial variability, that is the uneven distribution of the sediments, and the temporal variability, that is the diagenetic changes of the sediments. The high sedimentation rates of these cores (1.0cm-1.7cm/year) allow us to reconstruct annual climate changes. The paleoenvironmental proxies include total organic carbon, calcite contents, stable carbon isotopes of organic carbon and calcite, stable nitrogen isotopes, the atomic ratios of carbon and nitrogen, as well as stable oxygen isotopes of calcite. The absolute values of these proxies differ among different cores. By comparing the proxies at corresponding ages and depths, the difference seems mainly due to the uneven sediment distributions and is irrelevant of diagensis. The overall temporal patterns of paleoenvironmental proxies are consistent in multiple cores, providing strong evidence of the reliability of paleoenvironmental reconstruction on decadal scale. However, the year-to-year differences in proxies differ among different cores, questioning the reliability of reconstructing paleoenvironemental changes on annual scale. This study suggests that temporal resolution of paleoenvironmental reconstruction may be much lower compared to sediment rate and the analysis of multiple cores may be required for the studies aiming at a temporal resolution equal to sedimentation rate.