The Precambrian of northern New Mexico is part of an extensive 1,800 to 1,500 m.y. terrane stretching from Colorado through northern New Mexico into central Arizona. Three lithostratigraphic sequences are present in New Mexico. The oldest consists of 1,760 to 1,720 m.y. metamorphosed bimodal volcanic and volcaniclastic rocks to which no basement has been recognized. This juvenile crust developed as a magmatic arc complex and represents an early period of crustal instability. Between 1,755 and 1,700 m.y., the volcanogenic sequence was intruded by voluminous, coeval granodiorites and tonalites which stabilized the early crust. Unconformably overlying the volcano-plutonic terrane is a thick sequence of metamorphosed quartz arenites and subordinate argillites, the Ortega Group, which accumulated on a stable continental shelf. The inner shelf was dominated by tidal processes with subordinate reworking by storm and fair-weather waves. Storm processes were responsible for deposition on the outer shelf. The Ortega shelf sloped gently to the south and experienced an overall transgression which culminated in drowning of the outer shelf with onlap of black basinal muds from the south. Stable shelf sedimentation resulted from prolonged thermal subsidence following cratonization of the juvenile volcanogenic crust by intrusion of granitoid plutons.
The third lithostratigraphic sequence, the Marquenas Quartzite, consists of polymictic meta conglomerates and texturally-immature meta sandstones deposited in a braided-alluvial environment. These terrigenous sediments were supplied from the south and pebble compositions indicate derivation from the underlying volcanogenic and shelf sequences. The Marquenas Quartzite signifies cannibalization of the underlying magmatic arc and shelf. succession in response to deformation of the cratonic margin to the south.
The transition from arc volcanism to stable-shelf sedimentation and subsequent deformation of the craton margin in northern New Mexico has been recognized in central Arizona and southern Wisconsin between 1,800 and 1,630 m.y. This common crustal evolution suggests that a proto-North American craton margin opening to the south existed from central Arizona and northern New Mexico into southern Wisconsin at ca. 1,700 m.y. and was destroyed between 1,660 m.y. and 1,630 m.y. / Ph. D.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/82629 |
| Date | January 1984 |
| Creators | Soegaard, Kristian |
| Contributors | Geology, Eriksson, Kenneth, Bambach, Richard K., Read, J. Frederick, Simpson, C., Sinha, A. Krishna |
| Publisher | Virginia Polytechnic Institute and State University |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation, Text |
| Format | x, 193 leaves, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 11888333 |
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