Making the case for the Picuris orogeny: Evidence for a 1500 to 1400 Ma orogenic event in the southwestern United States

Geological Society of America Field Guides
By: , and 
Edited by: Lon D. Abbott and Gregory S. Hancock

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Abstract

The early Mesoproterozoic (ca. 1400 Ma) is an enigmatic time in the tectonic evolution of southern Laurentia. Circa 1400 Ma granites within Laurentia and multiple other continents have distinctive geochemistry consistent with crustal extension or mantle upwelling. In the southwestern United States, these granites are commonly foliated and are often spatially associated with km-scale ductile shear zones. Deformation is attributed to intracontinental tectonism driven by active convergence along the distal southern margin of Laurentia. The recent discovery of deformed and metamorphosed, ca. 1450 Ma sedimentary rocks in northern New Mexico has strengthened the case for regional deformation and orogenesis. However, important questions remain about the tectonic significance of these events and how to reconcile tectonic models with granite petrology at the regional to global scale. This trip focuses on the protolith age of Proterozoic metasedimentary rocks and the kinematics, timing, and tectonic significance of deformation, magmatism, and metamorphism for the Mesoproterozoic across different crustal levels in the southern Rocky Mountains to highlight the ongoing questions and controversies regarding the Mesoproterozoic tectonic setting of Laurentia.

This field trip will examine some of the diverse and most recently discovered evidence for ca. 1400 Ma orogenesis in the southern Rocky Mountains. We hope this trip will promote new interest and discussion about the Mesoproterozoic tectonic evolution of Laurentia. We will visit multiple outcrops in the Wet Mountains of southern Colorado and the Picuris Mountains of northern New Mexico. Stops in the Wet Mountains are arranged from north to south to examine contrasting styles of ca. 1400 Ma deformation with increasing paleodepth across the tilted Proterozoic crustal section. In the Picuris Mountains, we focus on detrital zircon geochronology and revisions to the lithostratigraphy of Paleoproterozoic and recently documented Mesoproterozoic metasedimentary rocks, the nature of regional metamorphism, and the style of deformation, ca. 1450–1400 Ma.

Additional publication details

Publication type Book chapter
Publication Subtype Book Chapter
Title Making the case for the Picuris orogeny: Evidence for a 1500 to 1400 Ma orogenic event in the southwestern United States
Series title Geological Society of America Field Guides
ISBN 9780813756332
DOI 10.1130/2013.0033(07)
Volume 33
Year Published 2013
Language English
Publisher Geological Society of America
Contributing office(s) Alaska Science Center Geology Minerals
Description 31 p.
Larger Work Type Book
Larger Work Subtype Monograph
Larger Work Title Classic concepts and new directions: Exploring 125 years of GSA discoveries in the Rocky Mountain region
First page 205
Last page 235
Country United States