A comparative study of the Rio Grande and Kenya rifts

Keller, G. Randy; Khan, M. Aftab; Morganc, Paul; Wendlandt, Richard F.; Baldridge, W. Scott; Olsen, Kenneth H.; Prodehl, C.; Braile, L. W.

doi:10.1016/0040-1951(91)90050-3

Cited by 49 publications

(7 citation statements)

References 62 publications

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“…The Rio Grande rift forms a tectonically well-defined eastern side of the southeastern Colorado Plateau. It is one of the classic continental rifts of the world with similar size and geometry of half-graben basins, rift flanks, and transfer zones as the East African rift (Keller et al 1991). Parts of the rift have been shown to be collapsed Laramide highlands (e.g., Cather 1983).…”

Section: 5°nmentioning

confidence: 99%

Tectonics of the Colorado Plateau and Its Margins

Karlstrom

Wilgus

Thacker

et al. 2022

Annu. Rev. Earth Planet. Sci.

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The Cenozoic Colorado Plateau physiographic province overlies multiple Precambrian provinces. Its ∼2-km elevation rim surrounds an ∼1.6-km elevation core that is underlain by thicker crust and lithospheric mantle, with a sharp structural transition ∼100 km concentrically inboard of the physiographic boundary on all but its northeastern margin. The region was uplifted in three episodes: ∼70–50 Ma uplift above sea level driven by flat-slab subduction; ∼38–23 Ma uplift associated with voluminous regional magmatism and slab removal, and less than 20 Ma uplift associated with inboard propagation of basaltic magmatism that tracked convective erosion of the lithospheric core. Neogene uplift helped integrate the Colorado River from the Rockies at 11 Ma to the Gulf of California by ∼5 Ma. The sharp rim-to-core transition defined by geological and geophysical data sets suggests a young transient plateau that is uplifting as it shrinks to merge with surrounding regions of postorogenic extension. ▪ The Colorado Plateau's iconic landscapes were shaped during its 70-million-year, still-enigmatic, tectonic evolution characterized by uplift and erosion. ▪ Uplift of the Colorado Plateau from sea level took place in three episodes, the youngest of which has been ongoing for the past 20 million years. ▪ Tectonism across the Colorado Plateau's nearest plate margin (the base of the plate!) is driving uplift and volcanism and enhancing its rugged landscapes. ▪ The bowl-shaped Colorado Plateau province is defined by ongoing uplift and an inboard sweep of magmatism around its margins. ▪ The keel of the Colorado Plateau is being thinned as the North American plate moves southwest through the underlying mantle. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 50 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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Section: 5°nmentioning

confidence: 99%

Tectonics of the Colorado Plateau and Its Margins

Karlstrom

Wilgus

Thacker

et al. 2022

Annu. Rev. Earth Planet. Sci.

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“…The RGR is a narrow zone of lithospheric extension that extends >1000 km from Colorado into northern Mexico (Baldridge et al, 1984). It trends roughly northsouth, parallel to the axis of the Rocky Mountains Research Paper (Keller et al, 1991;Pazzaglia and Hawley, 2004;Fig. 1.…”

Section: ■ Geologic Backgroundmentioning

confidence: 91%

Thermochronological transect across the Basin and Range/Rio Grande rift transition: Contrasting cooling histories in contiguous extensional provinces

et al. 2021

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The Basin and Range and Rio Grande rift (RGR) are regions of crustal extension in southwestern North America that developed after Laramide-age shortening, but it has not been clear whether onset and duration of extension in these contiguous extensional provinces were the same. We conducted a study of exhumation of fault blocks along a transect from the southeastern Basin and Range to across the RGR in southern New Mexico. A suite of 128 apatite and 63 zircon (U-Th)/He dates (AHe and ZHe), as well as 27 apatite fission-track (AFT) dates, was collected to investigate the cooling and exhumation histories of this region. Collectively, AHe dates range from 3 to 46 Ma, ZHe dates range from 2 to 288 Ma, and AFT dates range from 10 to 34 Ma with average track lengths of 10.8–14.1 µm. First-order spatiotemporal trends in the combined data set suggest that Basin and Range extension was either contemporaneous with Eocene–Oligocene Mogollon-Datil volcanism or occurred before volcanism ended ca. 28 Ma, as shown by trends in ZHe data that suggest reheating to above 240 °C at that time. AHe and ZHe dates from the southern RGR represent a wider range in dates that suggest the main phase of cooling occurred after 25 Ma, and these blocks were not reheated after exhumation. Time-temperature models created by combining AHe, AFT, and ZHe data in the modeling software HeFTy were used to interpret patterns in cooling rate across the study area and further constrain magmatic and/or volcanic versus faulting related cooling. The Chiricahua Mountains and Burro Mountains have an onset of rapid extension, defined as cooling rates in excess of >15 °C/m.y., at ca. 29–17 Ma. In the Cookes Range, a period of rapid extension occurred at ca. 19–7 Ma. In the San Andres Mountains, Franklin Mountains, Caballo Mountains, and Fra Cristobal range, rapid extension occurred from ca. 23 to 9 Ma. Measured average track lengths are longer in Rio Grande rift samples, and ZHe dates of >40 Ma are mostly present east of the Cookes Range, suggesting different levels of exhumation for the zircon partial retention zone and the AFT partial annealing zone. The main phase of fault-block uplift in the southern RGR occurred ca. 25–7 Ma, similar to what has been documented in the northern and central sections of the rift. Although rapid cooling occurred throughout southern New Mexico, thermochronological data from this study with magmatic and volcanic ages suggest rapid cooling was coeval with magmatism in the Basin and Range, whereas in the Rio Grande rift cooling occurred during an amagmatic gap. These observations support a model where an early phase of extension was facilitated by widespread ignimbrite magmatism in the southeastern Basin and Range, whereas in the southern Rio Grande rift, extension started later and continues today and may have occurred between local episodes of basaltic magmatism. These differences in cooling history make the Rio Grande rift tectonically distinct from the Basin and Range. We infer based on geologic and thermochronological evidence that the onset of extension in the southern Rio Grande rift occurred at ca. 27–25 Ma, significantly later than earlier estimates of ca. 35 Ma.

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“…The Rio Grande rift is a mid-to late-Cenozoic continental rift system in the southwestern United States that separates the Colorado Plateau and Basin and Range to the west from the stable North American interior to the east (e.g., Chapin & Cather, 1994;Keller et al, 1991;Tweto, 1979). The surface expression of the rift (Figures 1 and 2) consists of a series of elongate axial basins that form a north-south trending topographic depression through central Colorado and New Mexico before broadening into southern New Mexico and northern Mexico.…”

Section: Tectonic Settingmentioning

confidence: 99%

Lithospheric Signature of Late Cenozoic Extension in Electrical Resistivity Structure of the Rio Grande Rift, New Mexico, USA

2019

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We present electrical resistivity models of the crust and upper mantle from two‐dimensional (2‐D) inversion of magnetotelluric (MT) data collected in the Rio Grande rift, New Mexico, USA. Previous geophysical studies of the lithosphere beneath the rift identified a low‐velocity zone several hundred kilometers wide, suggesting that the upper mantle is characterized by a very broad zone of modified lithosphere. In contrast, the surface expression of the rift (e.g., high‐angle normal faults and synrift sedimentary units) is confined to a narrow region a few tens of kilometers wide about the rift axis. MT data are uniquely suited to probing the depths of the lithosphere that fill the gap between surface geology and body wave seismic tomography, namely the middle to lower crust and uppermost mantle. We model the electrical resistivity structure of the lithosphere along two east‐west trending profiles straddling the rift axis at the latitudes of 36.2 and 32.0°N. We present results from both isotropic and anisotropic 2‐D inversions of MT data along these profiles, with a strong preference for the latter in our interpretation. A key feature of the anisotropic resistivity modeling is a broad (~200‐km wide) zone of enhanced conductivity (<20 Ωm) in the middle to lower crust imaged beneath both profiles. We attribute this lower crustal conductor to the accumulation of free saline fluids and partial melt, a direct result of magmatic activity along the rift. High‐conductivity anomalies in the midcrust and upper mantle are interpreted as fault zone alteration and partial melt, respectively.

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A comparative study of the Rio Grande and Kenya rifts

Cited by 49 publications

References 62 publications

Tectonics of the Colorado Plateau and Its Margins

Tectonics of the Colorado Plateau and Its Margins

Thermochronological transect across the Basin and Range/Rio Grande rift transition: Contrasting cooling histories in contiguous extensional provinces

Lithospheric Signature of Late Cenozoic Extension in Electrical Resistivity Structure of the Rio Grande Rift, New Mexico, USA

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