Mid-Cretaceous paleomagnetic reference field for North America: restudy of 100 Ma intrusive rocks from Arkansas

Abstract

We have obtained new paleomagnetic data from three middle Cretaceous alkalic intrusive complexes in central Arkansas: Magnet Cove and Potash Sulfur Springs intrusions and Granite Mountain stock. The directions of magnetization calculated with respect to present-day horizontal yield a mean paleopole at 192.5°E, 74.1°N (N = 20, K = 34, A95 = 5.7°). The angular dispersion (Sd) of site virtual geomagnetic poles (VGPs) is 13.6°. The revised Arkansas paleopole is combined with four other cratonic North American paleopoles of mid-Cretaceous age to yield a revised middle Cretaceous reference pole at 196°E, 71°N, A95 = 4.9°. The mean of nine paleopoles derived from overprints in rock units from the craton and craton margin, which range in age from Proterozoic to Jura-Cretaceous, is 202°E, 68°N, A95 = 8.2°. This is not different from the reference paleopole, indicating that overprinting was very widespread across North America in mid-Cretaceous time. -from Authors