A 1000 YEAR PALEOMAGNETIC SECULAR VARIATION RECORD (INCLINATION AND DECLINATION) FROM GLACIAL LAKE OJIBWAY VARVES

We present paleomagnetic secular variation (PSV) data from sediment cores from three lakes in northwestern Quebec, lakes de Courval, Duparquet, and Montbeillard. Each record includes varves (annually laminated sediment) from glacial Lake Ojibway, and the varves are correlated between the three sites based upon matching varve thickness patterns. The intention is to compare this record to similar records from well-dated regional sites in an effort to create an accurate and precise age model. The cores are extruded 1-meter sections of sediment. The PSV data are continuous data from a u-channel magnetometer at the Institute of Rock Magnetism at the University of Minnesota. The u-channels were demagnetized at 50 Gauss intervals. Because of the high sedimentation rate of the varves, data are at a 5 to 20 year resolution. Correlative varve sections have similar inclination values and trends. The declination values also appear robust, but the declination data from each section need rotated because successive core sections are not oriented. In the 1000 year record, there is a peak and a trough in the inclination values and a trough in the declination values. There appears to be a likely match between these sediments and a high resolution record from Lake Superior, however the Lake Superior record is not well dated. This correlation to Lake Superior records suggests the varves from Lake Ojibway date between 8600 and 9600 cal yr BP, but this age assignment is uncertain. Additional PSV data and radiocarbon dates from Lake Ojibway sediments will test and improve the certainty of this age model.