Tectonics Completed
The Southern Rocky Mountains of northern New Mexico, Colorado and southern Wyoming consist of a broad array of Proterozoic-basement-cored structural uplifts and flanking sedimentary basins. Many of these uplift-basin systems involved some degree of Late Cretaceous to Eocene crustal contraction when they initially formed during the Laramide Orogeny. Recent research has demonstrated that elements of the modern mountain-valley landscape resulted from tectonic modification of the Laramide structural framework during Oligocene to Quaternary crustal extension. Much of the extensional strain has been accommodated by normal faulting resulting in mountain block surface uplift, partly reflecting complex processes of tectonic inheritance from Proterozoic through Laramide structural features.
A Task of the Cenozoic Landscape Evolution of the Southern Rocky Mountains Project.
The mid to late Cenozoic extension may be broadly coeval with, but more spatially diffuse and regionally extensive, the discrete Rio Grande rift that transects the Southern Rocky Mountains as far north as Leadville, Colorado. For example, the broad basins of South, Middle, and North Parks may have acquired their modern topographic form chiefly by extensional modification of earlier Laramide structures. Several volcanic centers of diverse age and composition are scattered throughout the southern Rockies that may have vented along, or were otherwise influenced by, faults of similar or older age. Such structures and associations can be difficult to recognize in volcanic settings, requiring detailed mapping and field observations. Linkages between the kinematics (slip vectors) and age of young faults and the form and evolution of adjacent landscapes may exist, but they need to be systematically investigated in the Southern Rocky Mountains with the assistance of powerful new tools such as lidar and thermochronology.
Although previous research has suggested that many large-displacement and laterally extensive late Cenozoic normal faults in the Rio Grande rift and elsewhere in the Rocky Mountain region are inherited from older structures, detailed geologic data that test these claims and reveal mechanisms of structural inheritance are generally lacking. Moreover, robust criteria for testing the influence of structural inheritance are lacking.
The Laramide Orogeny in the southern Rockies has commonly been viewed as a distinct tectonic episode that was followed by a period of tectonic quiescence before latest Oligocene inception crustal extension associated with the Rio Grande rift. In contrast, recent research suggests that crustal deformation, transitional in nature between contractional (Laramide) and extensional regimes (Rio Grande rift), continued throughout late Eocene and Oligocene time. Details of this transitional tectonic phase, including temporal and spatial changes in deformational style, fault geometry, associated kinematics, and paleostress regimes have not been systematically addressed across the region.
Understanding the structural-geologic character of the present-day landscape is important for assembling the tectonic evolution of the Southern Rocky Mountains. It is also important for understanding and quantifying the natural resources that the populous of the region depends on. Refinement of our knowledge of the structural-geologic framework through mapping and topical research bears on:
- Understanding numerous resources such as groundwater aquifers and hydrocarbon and reservoirs by quantifying their physical boundary conditions—rock types, petrophysical properties, depths and lateral extents
- Identification of faults and the role they play in hosting geothermal and metallic mineral resources as well as the nature of seismic hazards they may pose
- Documentation of the current state of landscape substrates that support ecosystems that are rapidly changing
Objectives
We will characterize geologic structures as evidence for tectonic evolution and linkages to landscape change at representative locations throughout the southern Rocky Mountains. Rates of deformation and associated mountain-block rock and surface uplift will be determined in a variety of physiographic settings in rocks and deposits of diverse age using tools such as thermochronolgy. Fundamental to this research is detailed (1:50,000 and larger scale) geologic mapping of key areas to adequately document the local structural-geologic frameworks. The mapping and characterization of these frameworks, supplemented by various complementary lines of research, will help establish and assess the spatial and temporal tectonic, geologic, and landscape evolution of mountain block surface uplifts and adjacent basins and valleys over a broad region of the southern Rocky Mountains. Map and other observational data that bear directly on the relative roles of Laramide contractional versus later Cenozoic extensional deformation in controlling paleo and modern landscapes are a particular focus.
- Overview
The Southern Rocky Mountains of northern New Mexico, Colorado and southern Wyoming consist of a broad array of Proterozoic-basement-cored structural uplifts and flanking sedimentary basins. Many of these uplift-basin systems involved some degree of Late Cretaceous to Eocene crustal contraction when they initially formed during the Laramide Orogeny. Recent research has demonstrated that elements of the modern mountain-valley landscape resulted from tectonic modification of the Laramide structural framework during Oligocene to Quaternary crustal extension. Much of the extensional strain has been accommodated by normal faulting resulting in mountain block surface uplift, partly reflecting complex processes of tectonic inheritance from Proterozoic through Laramide structural features.
A Task of the Cenozoic Landscape Evolution of the Southern Rocky Mountains Project.
The mid to late Cenozoic extension may be broadly coeval with, but more spatially diffuse and regionally extensive, the discrete Rio Grande rift that transects the Southern Rocky Mountains as far north as Leadville, Colorado. For example, the broad basins of South, Middle, and North Parks may have acquired their modern topographic form chiefly by extensional modification of earlier Laramide structures. Several volcanic centers of diverse age and composition are scattered throughout the southern Rockies that may have vented along, or were otherwise influenced by, faults of similar or older age. Such structures and associations can be difficult to recognize in volcanic settings, requiring detailed mapping and field observations. Linkages between the kinematics (slip vectors) and age of young faults and the form and evolution of adjacent landscapes may exist, but they need to be systematically investigated in the Southern Rocky Mountains with the assistance of powerful new tools such as lidar and thermochronology.
Although previous research has suggested that many large-displacement and laterally extensive late Cenozoic normal faults in the Rio Grande rift and elsewhere in the Rocky Mountain region are inherited from older structures, detailed geologic data that test these claims and reveal mechanisms of structural inheritance are generally lacking. Moreover, robust criteria for testing the influence of structural inheritance are lacking.
The Laramide Orogeny in the southern Rockies has commonly been viewed as a distinct tectonic episode that was followed by a period of tectonic quiescence before latest Oligocene inception crustal extension associated with the Rio Grande rift. In contrast, recent research suggests that crustal deformation, transitional in nature between contractional (Laramide) and extensional regimes (Rio Grande rift), continued throughout late Eocene and Oligocene time. Details of this transitional tectonic phase, including temporal and spatial changes in deformational style, fault geometry, associated kinematics, and paleostress regimes have not been systematically addressed across the region.
Understanding the structural-geologic character of the present-day landscape is important for assembling the tectonic evolution of the Southern Rocky Mountains. It is also important for understanding and quantifying the natural resources that the populous of the region depends on. Refinement of our knowledge of the structural-geologic framework through mapping and topical research bears on:
- Understanding numerous resources such as groundwater aquifers and hydrocarbon and reservoirs by quantifying their physical boundary conditions—rock types, petrophysical properties, depths and lateral extents
- Identification of faults and the role they play in hosting geothermal and metallic mineral resources as well as the nature of seismic hazards they may pose
- Documentation of the current state of landscape substrates that support ecosystems that are rapidly changing
Objectives
We will characterize geologic structures as evidence for tectonic evolution and linkages to landscape change at representative locations throughout the southern Rocky Mountains. Rates of deformation and associated mountain-block rock and surface uplift will be determined in a variety of physiographic settings in rocks and deposits of diverse age using tools such as thermochronolgy. Fundamental to this research is detailed (1:50,000 and larger scale) geologic mapping of key areas to adequately document the local structural-geologic frameworks. The mapping and characterization of these frameworks, supplemented by various complementary lines of research, will help establish and assess the spatial and temporal tectonic, geologic, and landscape evolution of mountain block surface uplifts and adjacent basins and valleys over a broad region of the southern Rocky Mountains. Map and other observational data that bear directly on the relative roles of Laramide contractional versus later Cenozoic extensional deformation in controlling paleo and modern landscapes are a particular focus.