Construction of type curves of geomagnetic secular variation for dating lake sediments from east central North America

Abstract

Type curves of palaeomagnetic secular variations of declination and inclination through the last 12 000 radiocarbon years have been constructed by combining data from the Minnesota Lakes with parallel data from the Great Lakes. The former records were well dated by reliable radiocarbon age determinations at frequent depth increments but the curves are not so well formed as the corresponding Great Lakes curves, which, however, cannot be so accurately dated. The same characteristic features can be identified in the records from both areas, particularly in inclination. Thus the Great Lakes records have been redated by correlation of the inclination features with the Minnesota records. Inclination and declination records from both areas were then stacked and the resulting curves serve as type curves for east-central North America. Standard error bars are shown at each time increment of 40 years. Significant swings on declination and inclination curves were used for reinterpretation of Lake Erie and Lake Michigan records.