Progressive opening of the northern Rio Grande rift based on fault structure and kinematics of the Tusas-Abiquiu segment in north-central New Mexico, U.S.

Analysis of spatiotemporal patterns of faulting and magmatism in the Rio Grande rift (RGR) in New Mexico and Colorado, USA, yields insights into continental rift processes, extension accommodation mechanisms, and rift evolution models. We combine new apatite (U-Th-Sm)/He and zircon (U-Th)/He thermochronometric data with previously published thermochronometric data to assess the timing of fault initiation, magnitudes of fault exhumation, and growth and linkage patterns of rift faults. Thermal history modeling of these data reveals contemporaneous rift initiation at ca. 25 Ma in both the northern and southern RGR with continued fault initiation, growth, and linkage progressing from ca. 25 to ca. 15 Ma. The central RGR, however, shows no evidence of Cenozoic fault-related exhumation as observed with thermochronometry and instead reveals extension accommodated through Late Cenozoic magmatic injection. Furthermore, faulting in the northern and southern RGR occurs along an approximately north-south strike, whereas magmatism in the central RGR occurs along the northeast to southwest trending Jemez lineament. Differences in deformation orientation and rift accommodation along strike appear to be related to crustal and lithospheric properties, suggesting that rift structure and geometry are at least partly controlled by inherited lithospheric-scale architecture. We propose an evolutionary model for the RGR that involves initiation of fault-accommodated extension by oblique strain followed by block rotation of the Colorado Plateau, where extension in the RGR is accommodated by faulting (southern and northern RGR) and magmatism (central RGR). This study highlights different processes related to initiation, geometry, extension accommodation, and overall development of continental rifts. Plain Language SummaryWe identify patterns of faulting and volcanism in the Rio Grande rift (RGR) in the western United States to better understand how continental rifts evolve. Using methods for documenting rock cooling ages (thermochronology), we determined that rifting began around 25 million years ago (Ma) in both the northern and southern RGR. Rift faults continued to develop and grow for another 10 to 15 million years. The central RGR, however, shows that rift extension occurred through volcanic activity both as eruptions at the surface and as magma injection below the surface since~15 Ma. Interestingly, RGR faulting in the north and south parts of the rift occurs on a north-south line, while volcanism in the central RGR is along a northeast to southwest line. The differences in the location and orientation of faulting and volcanic activity may be related to the thickness of the lithosphere beneath different parts of the rift. Using these patterns of faulting and magmatism, we propose the RGR evolved through a combination of (1) oblique strain-extension diagonal to the rift and (2) block rotation-where the Colorado Plateau is the rotating block. This detailed study highlights different processes related to the accommodation of extension...

Section: Northern Rgrmentioning

confidence: 99%

Section: Summary Of Thermochronometry Magmatism and Extension In Thmentioning

confidence: 99%

Section: Summary Of Thermochronometry Magmatism and Extension In Thmentioning

confidence: 99%

Section: Summary Of Thermochronometry Magmatism and Extension In Thmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Perspectives on Continental Rifting Processes From Spatiotemporal Patterns of Faulting and Magmatism in the Rio Grande Rift, USA

Abbey

Niemi

2020

Initiation and Evolution of the Shanxi Rift System in North China: Evidence From Low‐Temperature Thermochronology in a Plate Reconstruction Framework

Tan

et al. 2021

Rift initiation and evolution is a fundamental process in plate tectonics. When, how, and why a rift initiates and evolves, toward a rifted passive margin or a failed rift, are key questions in tectonics. Numerical and analog models have shown that a number of factors, including lithospheric thickness, rheology, heat flow, obliquity, heterogeneity, and strain rate, control the mode, sequence, and magnitude of continental rifting (e.g.

Late Paleozoic Flexural Extension and Overprinting Shortening in the Southern Ozark Dome, Arkansas, USA: Evolving Fault Kinematics in the Foreland of the Ouachita Orogen

Hudson

Turner

2022

Faults and folds on the southern flank of the Ozark dome in northern Arkansas, USA, record flexural extension in a foreland area followed by shortening in response to the late Paleozoic Ouachita orogeny. Map‐scale structures and an analysis of fault‐slip data collected systematically during geologic mapping demonstrate that most deformation in the area accommodated north‐south extension as the southern margin of Laurentia was flexed beneath the thrust load of the Ouachita belt, probably during Middle Pennsylvanian. Extension was concentrated in northeast‐ and west‐northwest‐trending structural zones having sets of discontinuous, often en echelon normal and strike‐slip faults and associated monoclinal folds. Reactivation of basement weaknesses that underlie these zones is indicated by their close match to oblique‐rift models in which both the proportions of normal and strike‐slip faulting and the internal extension directions vary with orientation of the zones. Subsequent propagation of north‐south Ouachita shortening into the foreland formed small‐offset strike‐slip and sparse reverse faults that overprinted older extensional structures. Strike‐slip faults were concentrated in reactivated northeast‐trending structural zones. In two areas, reverse faults and local anticlines were developed in the footwalls of older normal faults, both near intersections of northeast‐ and west‐northwest‐trending structural zones. These are interpreted as areas of incipient inversion due to compressional stress concentrations at fault‐block corners. Spatial overlap of areas of north‐south shortening and fluid flux marked by silicification or lead‐zinc mineralization indicates that regional fluid flow of brines was coeval with and may have enhanced inversion during Late Pennsylvanian to early Permian.