TERRANE MAP OF THE PRECAMBRIAN BASEMENT, SOUTH DAKOTA

The terrane map of the Precambrian basement presented here is based on a compilation of South Dakota well and test-hole data, the contour map of the Precambrian surface of South Dakota, existing geophysical data (magnetic and gravity data), previously published basement maps of South Dakota and surrounding states, and published radiometric dates.

New interpretations from this study include the concept that the Wyoming boundary zone in and around South Dakota can be separated into three domains: the Cedar Creek domain, the Black Hills domain (only partially equivalent to the Black Hills domain defined by previous workers), and the Hartville domain. A new terrane, the Williston domain, is identified just east of the Cedar Creek domain. Finally, a new designation, southern Dakota domain, is proposed for terrane just north of the Yavapai suture. The southern Dakota domain encompasses the southern part of the state west of the Black Hills domain, including the region of low gravity in south-central South Dakota and the strong positive magnetic anomaly that penetrates the Superior boundary zone to the east. The southern Dakota domain is interpreted to be a magmatic terrane developed at the terminus of the southern Trans-Hudson orogen, composed mainly of volcanic centers and associated deposits and intrusions. This terrane is thought to have formed principally through modification of Trans-Hudson internides by the Yavapai orogeny.