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Research about Rio Grande Rift

Source-linked reports with geographic coverage including Rio Grande Rift.

8 recordsLinked to original sources
USGS2018

Using high-resolution aeromagnetic surveys to map subsurface hydrogeology in sediment-filled basins: A case study over the Rio Grande Rift, Central New Mexico, USA

High-resolution aeromagnetic surveys were acquired for the Albuquerque basin in the central Rio Grande rift, a basin filled with poorly consolidated sediments. The surveys proved successful in efficiently and economically mapping previously unknown hydrogeologic features of the shallow subsurface. This success suggests that aeromagnetic methods may be useful in hydrogeologic studies of other sediment-filled basins. The aeromagnetic surveys were used primarily to delineate buried igneous rocks and to locate faults within the basin fill, both important for understanding the subsurface hydrogeology. Buried igneous rocks were recognized from their high-frequency, high-amplitude magnetic responses and characteristic map patterns. The horizontal-gradient and local wavenumber methods were used to obtain estimates of their source depths. The aeromagnetic surveys were also successfully used to locate faults within the basin fill. Magnetic signatures associated with faults are produced by the juxtaposition of sediments having differing magnetic properties rather than the products of secondary processes. Expression of faults is abundant throughout the basin, revealing patterns that cannot be mapped at the surface due to widespread cover. A fault signature recognized in the high-resolution data that has multiple inflection points is best explained by a fault with a thin magnetic layer on the upthrown block and thick magnetic layer on the downthrown block, called the thin-thick layers model. Geologically, this signature indicates erosion of the upthrown block or a growth-faulting scenario: fault-controlled sedimentation for faults that offset sediments, and successive accumulation of basalt on the downthrown block for faults that offset volcanic rocks.

New Mexico↗
USGS2014

40Ar/39Ar Geochronology, Isotope Geochemistry (Sr, Nd, Pb), and petrology of alkaline lavas near Yampa, Colorado: migration of alkaline volcanism and evolution of the northern Rio Grande rift

Volcanic rocks near Yampa, Colorado (USA), represent one of several small late Miocene to Quaternary alkaline volcanic fields along the northeast margin of the Colorado Plateau. Basanite, trachybasalt, and basalt collected from six sites within the Yampa volcanic field were investigated to assess correlations with late Cenozoic extension and Rio Grande rifting. In this paper we report major and trace element rock and mineral compositions and Ar, Sr, Nd, and Pb isotope data for these volcanic rocks. High-precision 40Ar/39Ar geochronology indicates westward migration of volcanism within the Yampa volcanic field between 6 and 4.5 Ma, and the Sr, Nd, and Pb isotope values are consistent with a primary source in the Proterozoic subcontinental lithospheric mantle. Relict olivine phenocrysts have Mg- and Ni-rich cores, whereas unmelted clinopyroxene cores are Na and Si enriched with finely banded Ca-, Mg-, Al-, and Ti-enriched rims, thus tracing their crystallization history from a lithospheric mantle source region to one in contact with melt prior to eruption. A regional synthesis of Neogene and younger volcanism within the Rio Grande rift corridor, from northern New Mexico to southern Wyoming, supports a systematic overall southwest migration of alkaline volcanism. We interpret this Neogene to Quaternary migration of volcanism toward the northeast margin of the Colorado Plateau to record passage of melt through subvertical zones within the lithosphere weakened by late Cenozoic extension. If the locus of Quaternary alkaline magmatism defines the current location of the Rio Grande rift, it includes the Leucite Hills, Wyoming. We suggest that alkaline volcanism in the incipient northern Rio Grande rift, north of Leadville, Colorado, represents melting of the subcontinental lithospheric mantle in response to transient infiltration of asthenospheric mantle into deep, subvertical zones of dilational crustal weakness developed during late Cenozoic extension that have been migrating toward, and subparallel to, the northeast margin of the Colorado Plateau since the middle Miocene. Quaternary volcanism within this northern Rio Grande rift corridor is evidence that the rift is continuing to evolve.

Colorado↗
USGS2013

Oblique transfer of extensional strain between basins of the middle Rio Grande rift, New Mexico: Fault kinematic and paleostress constraints

The structural geometry of transfer and accommodation zones that relay strain between extensional domains in rifted crust has been addressed in many studies over the past 30 years. However, details of the kinematics of deformation and related stress changes within these zones have received relatively little attention. In this study we conduct the first-ever systematic, multi-basin fault-slip measurement campaign within the late Cenozoic Rio Grande rift of northern New Mexico to address the mechanisms and causes of extensional strain transfer associated with a broad accommodation zone. Numerous (562) kinematic measurements were collected at fault exposures within and adjacent to the NE-trending Santo Domingo Basin accommodation zone, or relay, which structurally links the N-trending, right-stepping en echelon Albuquerque and Española rift basins. The following observations are made based on these fault measurements and paleostresses computed from them. (1) Compared to the typical northerly striking normal to normal-oblique faults in the rift basins to the north and south, normal-oblique faults are broadly distributed within two merging, NE-trending zones on the northwest and southeast sides of the Santo Domingo Basin. (2) Faults in these zones have greater dispersion of rake values and fault strikes, greater dextral strike-slip components over a wide northerly strike range, and small to moderate clockwise deflections of their tips. (3) Relative-age relations among fault surfaces and slickenlines used to compute reduced stress tensors suggest that far-field, ~E-W–trending σ 3 stress trajectories were perturbed 45° to 90° clockwise into NW to N trends within the Santo Domingo zones. (4) Fault-stratigraphic age relations constrain the stress perturbations to the later stages of rifting, possibly as late as 2.7–1.1 Ma. Our fault observations and previous paleomagnetic evidence of post–2.7 Ma counterclockwise vertical-axis rotations are consistent with increased bulk sinistral-normal oblique shear along the Santo Domingo rift segment in Pliocene and later time. Regional geologic evidence suggests that the width of active rift faulting became increasingly confined to the Santo Domingo Basin and axial parts of the adjoining basins beginning in the late Miocene. We infer that the Santo Domingo clockwise stress perturbations developed coevally with the oblique rift segment mainly due to mechanical interactions of large faults propagating toward each other from the adjoining basins as the rift narrowed. Our results suggest that negligible bulk strike-slip displacement has been accommodated along the north-trending rift during much of its development, but uncertainties in the maximum ages of fault slip do not allow us to fully evaluate and discriminate between earlier models that invoked northward or southward rotation and translation of the Colorado Plateau during early (Miocene) rifting.

New Mexico↗
USGS2013

Introduction in New perspectives on Rio Grande rift basins: from tectonics to groundwater

Basins of the Rio Grande rift have long been studied both for their record of rift development and for their potential as host of natural resources. Early workers described the basin geomorphology and the character of infilling sediments (e.g. Siebenthal, 1910; Bryan, 1938; Speigel and Baldwin, 1963), and subsequent research compilations provided general stratigraphic and tectonic overviews of rift basins and described their geophysical characteristics within the crust (Hawley, 1978; Riecker, 1979; Baldridge et al., 1984; Keller, 1986). Subsurface knowledge gained from hydrocarbon exploration activities coupled with detailed surface studies of basins and their flanking uplifts were presented in Geological Society of America (GSA) Special Paper 291, edited by Keller and Cather (1994a).

Colorado;New Mexico↗
USGS2007

Guides to understanding the aeromagnetic expression of faults in sedimentary basins: Lessons learned from the central Rio Grande rift, New Mexico

High-resolution aeromagnetic data acquired over several basins in the central Rio Grande rift, north-central New Mexico, prominently display low-amplitude (5–15 nT) linear anomalies associated with faults that offset basin-fill sediments. The linear anomalies give an unparalleled view of concealed faults within the basins that has significant implications for future basin studies. These implications provide the impetus for understanding the aeromagnetic expression of faults in greater detail. Lessons learned from the central Rio Grande rift help to understand the utility of aeromagnetic data for examining concealed faults in sedimentary basins in general. For example, linear anomalies in the rift can be explained entirely by the tectonic juxtaposition of magnetically differing strata rather than the product of chemical processes acting at the fault zone. Differences in layer thickness, depth to the layer(s), and magnetic susceptibility govern the variability of the anomaly shape. Further investigations of these variables using simple models provide graphical, mathematical, and conceptual guides for understanding the aeromagnetic expression of faults, including the criteria for aeromagnetic expression of faults, how to locate fault traces from aeromagnetic anomalies, the effect of fault dip, and how to assess the role of topography. The horizontal gradient method applied to reduced-to-pole aeromagnetic data is particularly effective in mapping fault locations, especially at regional scales. With our new understanding of the aeromagnetic expression of faults, we updated interpretations of faults from the aeromagnetic data for the central Rio Grande rift. These interpretations, along with the guides, should provide direction and fuel for future work in a wide variety of multidisciplinary basin-related topics.

New Mexico↗
USGS1989

Gravity anomalies of irregularly shaped two-dimensional bodies with constant horizontal density gradient

An equation to compute the gravity anomalies of two-dimensional (2-D) bodies with density contrast varying with depth (z axis) was developed by Murthy and Rao (1979). I develop an equation for computing the gravity anomalies of 2-D bodies with constant horizontal density gradient. By combining this equation with the equation of Murthy and Rao, I estimate the depth of the sedimentary basin which is adjacent to the master fault associated with the Rio Grande rift in New Mexico, where the density is assumed to decrease basinward from the fault (Cordell, 1979).

New Mexico↗
USGS1978

Guidebook to Rio Grande rift in New Mexico

Discusses the details of geologic features along the rift zone. Included are short papers on topics relative to the overall region. These papers and the road logs are of special interest to any one pursuing further study of the rift. This book is a comprehensive guide to the middle and late Cenozoic geology of the Rio Grande region of Colorado and New Mexico. Though initially used on field trips for the International Symposium on Tectonics and Magmatism of the Rio Grande rift, the guidebook will be useful to anyone interested in the Cenozoic history of the 600-mi-long area extending from central Colorado to El Paso, Texas.

New Mexico↗