Palaeomagnetic studies of the Early Permian Ingelside Formation of northern Colorado

Abstract

Palaeomagnetic results have been obtained from the Early Permian Ingelside Formation at a location just north of Owl Canyon in northern Colorado. A total of 243 stratigraphically distinct core samples were collected at a stratigraphic interval of 28 cm. Curie temperature analysis and IRM acquisition experiments indicate that hematite is the predominant carrier of remanence in these samples. All the samples were subjected to partial thermal demagnetization. A two‐step selection procedure involving the method of Helsley was applied to the partial thermally demagnetized data restricting the stable sample population to 34 samples which yielded an Early Permian pole at 45.9° N, 122.1° E (δp= 1.1, δm= 2.1, kappa = 147.3). This result is similar to other cratonic North American Permian pole positions and, when combined with other data from the Late Palaeozoic, defines a polar wander path along which the palaeomagnetic pole appeared to move systematically north‐west from a position near southern Japan during the Mississippian to near 55°N, 103°E during the Early Triassic. No normal polarity zones appear in the Ingelside section. Copyright © 1979, Wiley Blackwell. All rights reserved