Classic Concepts and New Directions: Exploring 125 Years of GSA Discoveries in the Rocky Mountain Region
The Rocky Mountain Region has been the subject of continuous, exhaustive scientific work since the first organized geologic trips to the area began in the 1860s. Despite almost 150 years of scrutiny, the region's magnificent geology continues to challenge, perplex, and astound modern geoscientists. It is a testing ground for geologists and for big geologic ideas. This volume, prepared for the 2013 GSA Annual Meeting in Denver, Colorado, serves both as a progress report on what we have learned over those years of study and a guide to forthcoming scientific questions about the region. The guide's fourteen chapters, which span the region's 1.7-billion-year history, give a retrospective glimpse of early geologic ideas being forged, bring the latest mapping and analytical results from classic locations, and introduce techniques that will form the bedrock of our geologic understanding in the years to come.
Proterozoic metamorphism and deformation in the northern Colorado Front Range
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Published:January 01, 2013
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CiteCitation
Kevin H. Mahan, Julien M. Allaz, Graham B. Baird, Nigel M. Kelly, 2013. "Proterozoic metamorphism and deformation in the northern Colorado Front Range", Classic Concepts and New Directions: Exploring 125 Years of GSA Discoveries in the Rocky Mountain Region, Lon D. Abbott, Gregory S. Hancock
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Abstract
Paleoproterozoic supracrustal rocks in the region near Big Thompson Canyon, northern Colorado, have long been recognized as a spectacularly exposed example of regionally zoned metamorphism, preserving an apparently complete sequence from biotite- to migmatite-zones. Due to its location and relatively easy access, the Big Thompson Metamorphic Suite has also provided a valuable field-based educational experience for universities and colleges all along the Front Range and from elsewhere. In addition to a number of other studies, the pioneering work of William Braddock and graduate students from the University of Colorado resulted in more than a dozen M.Sc. and Ph.D. theses from the 1960s to the 1990s. Despite the volume of ground-breaking science conducted on these rocks in the past, there remain a number of fundamental questions regarding the metamorphic history and overall tectonic significance of many of the observable features. Several lines of evidence suggest there is potential for a complex tectonometamorphic history that likely spans from ~1.8 to 1.4 Ga. These include: thermochronologic and geochronologic data supporting multiple thermal and magmatic episodes, structural evidence for multiple deformation events, multiple generations of typical Barrovian minerals (e.g., staurolite), and the widespread occurrence of minerals not commonly associated with a classic Barrovian sequence (e.g., andalusite, cordierite). One purpose of this fieldtrip is to foster new ideas and stimulate new research directions that will utilize the Big Thompson Metamorphic Suite, and the Colorado Rockies in general, as field laboratories for better understanding fundamental orogenic processes.
- basement
- Colorado
- deformation
- faults
- field trips
- Front Range
- guidebook
- intrusions
- isograds
- metamorphic rocks
- metamorphism
- migmatites
- mineral assemblages
- mineral composition
- nesosilicates
- North America
- orogeny
- orthosilicates
- porphyroblastic texture
- Precambrian
- Proterozoic
- road log
- Rocky Mountains
- shear zones
- silicates
- staurolite
- tectonics
- textures
- thermochronology
- U. S. Rocky Mountains
- United States
- upper Precambrian
- Big Thompson Canyon