Chapter 28: Seismic properties of the crust and uppermost mantle of the conterminous United States and adjacent Canada

Braile, L. W.; Hinze, William J.; Frese, Ralph R. B. von; Keller, G. Randy

doi:10.1130/mem172-p655

Cited by 74 publications

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“…In areas spanning the west coast of North America to the High Plains, these studies found specifi c tectonic provinces and terranes exhibiting structures with large variations in crustal thickness and changes in seismic velocities across the Moho (e.g., Braile et al, 1989;Prodehl and Lipman, 1989;Catchings and Mooney, 1991;Snelson et al, 1998;Bostock et al, 2002;Gorman et al, 2002;Li et al, 2002;Magnani et al, 2004;Keller et al, 2005;Frassetto et al, 2006;Lerch et al, 2007;Hansen and Dueker, 2009;Buehler and Shearer, 2010;Cox and Keller, 2010;Eagar et al, 2011;Hansen et al, 2011). Data from the Transportable Array can be used to investigate the crust across extensive distances to compare and connect the observations from these previous localized studies.…”

Section: Previous Investigationsmentioning

confidence: 96%

Untitled

Gilbert

2012

Geosphere

113

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Section: Previous Investigationsmentioning

confidence: 96%

Untitled

Gilbert

2012

Geosphere

113

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“…To explain this apparent discrepancy, McQuarrie and Chase (2000) invoked ~15 km thickening of 30-km-thick Colorado Plateau crust by Laramide mid-crustal fl ow eastward from the thickened Sevier hinterland, thus producing ~2 km of uplift in the Colorado Plateau. However, the crustal thickness of the Colorado Plateau is similar to much of cratonic North America (Braile et al, 1989;Mooney et al, 1998;Eaton, 2008), including areas that were near sea level in the Late Cretaceous but were largely unaffected by the Laramide orogeny (North Dakota, South Dakota, Nebraska, Kansas, Iowa, Missouri, and much of Minnesota). Kilty (2000) and Morgan (2003) also questioned the viability of the Laramide mid-crustal fl ow model on the basis of other geological and geophysical parameters.…”

Section: Laramidementioning

confidence: 97%

Diachronous episodes of Cenozoic erosion in southwestern North America and their relationship to surface uplift, paleoclimate, paleodrainage, and paleoaltimetry

2012

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The history of erosion of southwestern North America and its relationship to surface uplift is a long-standing topic of debate. We use geologic and thermochronometric data to reconstruct the erosion history of southwestern North America. We infer that erosion events occurred mostly in response to surface uplift by contemporaneous tectonism, and were not long-delayed responses to surface uplift caused by later climate change or drainage reorganization. Rock uplift in response to isostatic compensation of exhumation occurred during each erosion event, but has been quantifi ed only for parts of the late Miocene-Holocene erosion episode. We recognize four episodes of erosion and associated tectonic uplift: (1) the Laramide orogeny (ca. 75-45 Ma), during which individual uplifts were deeply eroded as a result of uplift by thrust faults, but Laramide basins and the Great Plains region remained near sea level, as shown by the lack of signifi cant Laramide exhumation in these areas; (2) late middle Eocene erosion (ca. 42-37 Ma) in Wyoming, Montana, and Colorado, which probably occurred in response to epeirogenic uplift from lithospheric rebound that followed the cessation of Laramide dynamic subsidence; (3) late Oligocene-early Miocene deep erosion (ca. 27-15 Ma) in a broad region of the southern Cordillera (including the southern Colorado Plateau, southern Great Plains, trans-Pecos Texas, and northeastern Mexico), which was uplifted in response to increased mantle buoyancy associated with major concurrent volcanism in the Sierra Madre Occidental of Mexico and in the Southern Rocky Mountains; (4) Late Miocene-Holocene erosion (ca. 6-0 Ma) in a broad area of southwestern North America, with loci of deep erosion in the western Colorado-eastern Utah region and in the western Sierra Madre Occidental. Erosion in western Colorado-eastern Utah refl ects mantle-related rock uplift as well as an important isostatic component caused by compensation of deep fl uvial erosion in the upper Colorado River drainage following its integration to the Gulf of California.Erosion in the western Sierra Madre Occidental occurred in response to rift-shoulder uplift and the proximity of oceanic base level following the late Miocene opening of the Gulf of California. We cannot estimate the amount of rock or surface uplift associated with each erosion episode, but the maximum depths of exhumation for each were broadly similar (typically ~1-3 km). Only the most recent erosion episode is temporally correlated with climate change.Paleoaltimetric studies, except for those based on leaf physiognomy, are generally compatible with the uplift chronology we propose here. Physiognomy-based paleo eleva tion data suggest that near-modern elevations were attained during the Paleogene, but are the only data that uniquely support such interpretations. High Paleogene elevations require a complex late Paleogene-Neogene uplift and subsidence history for the Front Range and western Great Plains of Colorado that is not compatible with the regional sedimentation and er...

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“…Although thin crust and high elevation have been observed elsewhere in the world (Braile et al 1989;Durrheim & Mooney 1991Assumpgg.o et al 2002), the question remains of how the higher elevations are gravitationally compensated at depth. Compensation produced by the low-density upper mantle beneath the craton is only part of the story, particularly if the lower crust beneath cratons is less mafic on average (and hence less dense and lower velocity) than is post-Archaean lower crust (Griffin & O'Reilly 1987;Durrheim & Mooney 1994;Rudnick & Fountain 1995).…”

Section: Crustal Structurementioning

confidence: 99%

Formation and evolution of Archaean cratons: insights from southern Africa

James

Fouch

2002

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Archaean cratons are the stable remnants of Earth's early continental lithosphere, and their structure, composition and survival over geological time make them unique features of the Earth's surface. The Kaapvaal Project of southern Africa was organized around a broadly diverse scientific collaboration to investigate fundamental questions of craton formation and mantle differentiation in the early Earth. The principal aim of the project was to characterize the physical and chemical nature of the crust and mantle of the cratons of southern Africa in geological detail, and to use the 3D seismic and geochemical images of crustal and mantle heterogeneity to reconstruct the assembly history of the cratons. Seismic results confirm that the structure of crust and tectospheric mantle of the cratons differs significantly from that of post-Archaean terranes. Three-dimensional body-wave tomographic images reveal that high-velocity mantle roots extend to depths of at least 200 kin, and locally to depths of 250 300 km beneath cratonic terranes. No low-velocity channel has been identified beneath the cratonic root. The Kaapvaal Craton was modified approximately 2.05Ga by the Bushveld magmatic event, and the mantle beneath the Bushveld Province is characterized by relatively low seismic velocities. The crust beneath undisturbed Archaean craton is relatively thin (c. 35-40km), unlayered and characterized by a strong velocity contrast across a sharp Moho, whereas post-Archaean terranes and Archaean regions disrupted by large-scale Proterozoic magmatic or tectonic events are characterized by thicker crust, complex Moho structure and higher seismic velocities in the lower crust. A review of Re Os depletion model age determinations confirms that the mantle root beneath the cratons is Archaean in age. The data show also that there is no apparent age progression with depth in the mantle keel, indicating that its thickness has not increased over geological time. Both laboratory experiments and geochemical results from eclogite xenoliths suggest that subduction processes played a central role in the formation of Archaean crust, the melt depletion of Archaean mantle and the assembly of early continental lithosphere. Co-ordinated geochronological studies of crustal and mantle xenoliths have revealed that both crust and mantle have experienced a multi-stage history. The lower crust in particular retains a comprehensive record of the tectonothermal evolution of the lithosphere. Analysis of lower-crustal xenoliths has shown that much of the deep craton experienced a dynamic and protracted history of tectonothermal activity that is temporally associated with events seen in the surface record. Cratonization thus occurred not as a discrete event, but in stages, with final stabilization postdating crustal formation.

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Chapter 28: Seismic properties of the crust and uppermost mantle of the conterminous United States and adjacent Canada

Cited by 74 publications

References 0 publications

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Diachronous episodes of Cenozoic erosion in southwestern North America and their relationship to surface uplift, paleoclimate, paleodrainage, and paleoaltimetry

Formation and evolution of Archaean cratons: insights from southern Africa

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