T120 Cratonic Assembly in the Precambrian: Forming the Core of Modern and Ancient Landmasses

Monday, 23 October 2017
8:00 AM - 12:00 PM
Room 604

SHOULD THE "GRENVILLE FRONT" IN THE CENTRAL U.S. BE ERASED FROM GEOLOGIC MAPS?

Paper number: T120-5
Program: Technical Sessions
Time: 9:00 AM – 9:15 AM

Authors

Abstract

Two prominent Precambrian geologic features of central North America are the Midcontinent Rift (MCR) and Grenville Front. The MCR, an extensive band of buried igneous and sedimentary rocks that outcrop near Lake Superior, records a major rifting event at ~1.1 Ga that failed to split North America. In Canada, the Grenville Front is the landward extent of deformation of the fold and thrust belt from the Grenville orogeny, the sequence of events from ca. 1.3–0.98 Ga culminating in the assembly of the supercontinent of Rodinia. In the central United States, lineated gravity anomalies extending southward along the trend of the front in Canada have been interpreted as a buried Grenville Front. However, we argue that these anomalies delineate the eastern arm of the MCR extending from Michigan to Alabama, for multiple reasons. First, gravity anomalies along this trend are similar to those along the remainder of the MCR, and quite different from those across the Grenville Front in Canada. Second, the Precambrian deformation observed on seismic reflection profiles cannot confidently be assigned to the Grenville orogeny and deformation is recorded at least 100 km west of the "front". Third, during the Grenville orogeny deformational events from Texas to Canada were not synchronous or caused by the same plate interactions. Hence the commonly-inferred position of the "Grenville Front" in the east-central United States is part of the Midcontinent Rift, and should not be mapped as a separate entity.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-302435

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