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Book Chapter

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

By
Christopher G. Daniel
Christopher G. Daniel
Department of Geology, Bucknell University, Lewisburg, Pennsylvania 17837, USA
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James V. Jones III
James V. Jones III
U.S. Geological Survey Alaska Science Center, 4210 University Drive, Anchorage, Alaska 99508, USA
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Christopher L. Andronicos
Christopher L. Andronicos
Department of Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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Mary Beth Gray
Mary Beth Gray
Department of Geology, Bucknell University, Lewisburg, Pennsylvania 17837, USA
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Published:
January 01, 2013

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.

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Contents

GSA Field Guide

Classic Concepts and New Directions: Exploring 125 Years of GSA Discoveries in the Rocky Mountain Region

Lon D. Abbott
Lon D. Abbott
Department of Geological Sciences University of Colorado Boulder, Colorado 80305 USA
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Gregory S. Hancock
Gregory S. Hancock
Department of Geology College of William and Mary Williamsburg, Virginia 23187 USA
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Geological Society of America
Volume
33
ISBN electronic:
9780813756332
Publication date:
January 01, 2013

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