VARVE SEDIMENT RECORDS OF PRE-HISTORIC HUMAN DISTURBANCE, CRAWFORD LAKE, ONTARIO, CANADA: INITIAL FINDINGS

Previous work on the laminated sediments of meromictic Crawford Lake, southeast Ontario, Canada, has focused on pollen, charcoal, and stable isotope studies. Initial pollen work documented the sporadic presence of Zea (maize) pollen from varve years 1360 AD through 1680 AD in the lake sediment. These findings prompted an archaeological survey that led to the discovery of a pre-Columbian Iroquois village approximately 500 m north of the lake. Subsequent charcoal and isotope studies have aided in reconstructing a local Late-Glacial and Holocene paleoclimatic history but have not contributed to the understanding of pre-historic human impacts on the lake and its surroundings. Though the sediments of Crawford Lake have been examined in detail for paleoecological and stable isotope studies, no high-resolution sedimentologic study has examined this record of pre-historic human disturbance.

A detailed sedimentologic description of two newly collected Crawford Lake gravity cores was performed in summer of 2001. Findings from visual description, petrographic smear slide analysis, XRD, carbon coulometry, and varve thickness have quantified changes in lithological attributes coincident with the Iroquois settlement horizon and associated landscape disturbance. Preliminary results show an increase in varve thickness and carbonate content concomitant with the Iroquois settlement horizon. Future high-resolution sedimentologic and geochemical studies will further enhance our understanding of the magnitude and significance of pre-European human-environment interaction in this region.