Magnetostratigraphy of the Ludlow Member of the Fort Union Formation (Lower Paleocene) in the Williston Basin, North Dakota
D.J. Peppe et al., Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06511, USA. Pages 65-79.
To determine the geomagnetic polarity stratigraphy and the duration and age of the Ludlow Member of the Fort Union Formation (Lower Paleocene), Peppe et al. constructed a 325 meter composite lithostratigraphic section of the Upper Cretaceous Hell Creek Formation and the Lower Paleocene Ludlow and Tongue River Members of the Fort Union Formation in the Little Missouri River valley of North Dakota, USA. They analyzed paleomagnetic samples from nine of the logged sections. The principal magnetic carrier in the Ludlow Member sediments is likely titanomaghemite, as indicated by predominantly irreversible thermomagnetic curves measured from sandstone, siltstone, and carbonaceous shale samples. Peppe et al. infer that the magnetization of the samples is primary because the characteristic directions are consistent with those of the Paleocene of North America. By extrapolating the measured sediment accumulation rate from the Cretaceous-Tertiary (K-T) boundary to the top of C28n and then to the top of the Ludlow Member, they estimate the duration of the member to range from 2.31 to 2.61 million years. This is the first estimate for the duration and ag
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