Precambrian basement geology of North and South Dakota

Abstract

Combined analysis of drill-hole, gravity, and magnetic data indicates that the buried Precambrian basement rocks of the Dakotas can be divided into several lithotectonic terranes. Eastern North Dakota and northeastern South Dakota are underlain by Archean gneiss. Except for the Black Hills region of South Dakota, where Archean rocks are also exposed, the western third of both Dakotas is underlain mainly by Early Proterozoic gneiss and metasedimentary rocks. Part of this region is underlain by Archean crust with an Early Proterozoic tectonic overprint. A broad transition zone of strongly overprinted Archean crust occurs between the Proterozoic rocks to the west and the Archean rocks to the east. South central South Dakota is underlain by an Early Proterozoic batholith. Early Proterozoic felsic volcanic rocks occur in southeast South Dakota. The bootheel portion of South Dakota contains a diverse assemblage of basement rocks that are partly Archean in age.Churchill Province rocks of the Trans-Hudson foldbelt project into the western Dakotas. The Thompson nickel belt and the Pickwitonei gneiss belt correlate with the western and eastern halves, respectively, of the transition between Archean and Proterozoic crust, and the Archean Glennie – Hanson Lake microcontinent of the Churchill Province likely extends into western North Dakota. Archean rocks of Minnesota extend into the eastern Dakotas, and the Wyoming craton extends to the Black Hills region. The Cheyenne foldbelt projects into southwest South Dakota. The Penokean foldbelt of Michigan and Wisconsin does not extend into the Dakotas, but it most likely extends into northwest Iowa.Tectonic evolution of the Early Proterozoic terrane in the Dakotas was most likely similar to plate tectonic models for the evolution of the Trans-Hudson foldbelt in the Churchill Province. As in the Churchill Province, the western Dakotas are underlain by Early Proterozoic rocks, but it is not known whether these rocks formed as a result of rifting and subsequent closure of a once extensive Archean crust or as a result of collision of once widely separated blocks of Archean crust.

Southern extension of the Churchill Province (Trans-Hudson orogenic belt) Midcontinent Strategic and Critical Minerals Project, 1985 workshop report

“…This domain is delineated by a series of relatively high-amplitude, north-south trending magnetic anomalies and may continue south to the southern terminus of the Trans-Hudson orogenic belt in southern South Dakota. To the west of another probable shear zone, the Glennie Lake domain continues southward to about 41 N., bounded on the west by the southern extension of the LaRonge-Lynn Lake volcanic arc domain which continues to about 50 N. An Archean microplate similar to the Hanson Lake block has also been identified beneath Phanerozoic sediments in North Dakota by Klasner and King (1986) who cited a 2900 Ma zircon age for gneiss cored in north-central North Dakota (Peterman and Goldich, 1982). Other such Archean microplates may also exist.…”

“…The southern extension of the Trans-Hudson orogenic belt has been recently investigated by others (1979, 1985), Peterman and Zartman (1985), and Klasner and King (1986). Since the Precambrian rocks of the orogenic belt are buried beneath Phanerozoic sediments in southern Manitoba and Saskatchewan and the Dakotas, its extent and composition must be inferred by interpretation of potential field geophysical data, limited deep reflection seismic data, and sparse drill data.…”

“…Most active workers (e.g. Lewry and others, 1985;Green and others, 1985;Klasner and King, 1986) consider the Hanson Lake block to be an Archean microcontinent that was accreted to North America during the Trans-Hudson orogeny.…”

Electromagnetic image of the Trans-Hudson orogen — THO94 transect

“…Green et al (1985) suggested that the anomaly is caused by pieces of hydrated oceanic type crustal material, which also explains the low seismic velocity observed. Klasner and King (1986) interpreted the geochronologies similarly to Peterman (1981) in revealing Paleoproterozoic rocks, mainly gneiss of unknown origin, but they could not find any evidence of oceanic crust. From the drill cores obtained above the location of the NACP by Jones and Savage (1986) in northern North Dakota, the rocks are mostly granodioritic to tonalitic gneiss.…”

“…Later, based on this and other data, a continental-scale suture zone of Hudsonian age was proposed to transect the continent; it was named the THO by Hoffman (1981). Klasner and King (1986), in their study of the nature of the Precambrian basement rocks from the Dakotas, considered the NACP anomaly an important tectonic feature and used it to correlate the buried part of the THO in the Dakotas with the Precambrian terranes that surface in northern Saskatchewan and Manitoba. Thus, the NACP anomaly has played a significant part in the discovery of the extent of the THO, and even today it remains a significant element of the THO that requires explanation in any evolutionary model proposed for the orogen's development and history.…”