Development of the southern reaches of Laurentia
- Geological Survey, Denver, CO (United States). Federal Center
Laurentia, the Late Proterozoic continental fragment that now forms the core of North America, has a long and complex history, much of which involves development along its southern margin. The southernmost parts of the Archean continental core are the Wyoming and Superior cratons, both of which contain gneisses that record crust-forming events in the interval 3.8--3.1 Ga as well as greenstone belts that reflect continental growth in the interval 2.8--2.6 Ga. Each of these cratonic elements was assembled and stabilized prior to deposition of passive margin sequences along their southern flanks during the interval [approximately]2.5--1.9 Ga. Between [approximately]1.8 Ga and 1.6 Ga arc-related sedimentary and volcanic rocks were accreted to the southern margin of the Laurentian core during a complex series of tectonic episodes that included events locally referred to as the Penokean, Ivanpah, Yavapai, and Mazatzal orogenies, resulting in the addition of a belt of continental crust at least 1,000 km wide. Voluminous highly evolved granite and rhyolite were emplaced along this southern marginal belt between [approximately] 1.45 and 1.35 Ga under conditions of general tectonic stability, or perhaps dispersed regional extension. This same interval was also marked by onset of deposition of thick Middle Proterozoic sedimentary sequences along the western and southern margins of Laurentia. The eastern margin of Laurentia contains the complexly deformed and metamorphosed rocks of the 1.25 to 1.1 Ga Grenville orogen which, according to recent reconstructions, may record a collision with cratonic elements in western South America. The 2,000 km-long Midcontinent rift system in central Laurentia opened and filled with basalt and sediments at about the same time as the end of Grenville activity.
- OSTI ID:
- 5933141
- Report Number(s):
- CONF-9303212--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 25:1; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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