Crustal and uppermost mantle structure in the central U.S. encompassing the Midcontinent Rift

Shen, Weisen; Ritzwoller, M. H.; Schulte-Pelkum, V.

doi:10.1002/jgrb.50321

Cited by 48 publications

(64 citation statements)

References 95 publications

(146 reference statements)

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“…Additional thickening may also have occurred via magmas added to the base of the crust. The crustal thickening in GLIMPCE lines A and C is consistent with observations of crustal thickening elsewhere along the MCR (Shen et al, 2013).…”

Section: Tectonic Implicationssupporting

confidence: 85%

North America’s Midcontinent Rift: When rift met LIP

et al. 2015

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Rifts are segmented linear depressions that are filled with sedimentary and igneous rocks; they form by extension and often evolve into plate boundaries. Flood basalts, a class of large igneous provinces (LIPs), are broad regions of extensive volcanism formed by sublithospheric processes. Typical rifts are not filled with flood basalts, and typical flood basalts are not associated with significant crustal extension and faulting. North America's Midcontinent Rift (MCR) is an unusual combination, because its 3000-km length formed during a continental breakup event 1.1 Ga, but it contains an enormous volume of igneous rocks that are mostly flood basalt. We show that MCR volcanic rocks are significantly thicker than other flood basalts, due to their deposition in a narrow rift rather than across a broad region, giving the MCR a rift's geom etry but a LIP's magma volume. Structural modeling of seismic-reflection data shows that LIP volcanics were deposited during two phases-an initial rift phase where flood basalts filled a fault-controlled extending basin and a postrift phase where LIP volcanics and sediments were deposited in a thermally subsiding sag basin without associated faulting. The crust thinned during the initial rifting phase and then rethickened during the postrift phase and later compression, yielding the present thicker crust observed seismologically. The restriction of extension to a single normal fault in each rift segment, steeply inward-dipping rift shoulders with sharp hinges, and persistence of volcanism after rifting ended gave rise to a deep flood basalt-filled rift geometry not observed in other presently active or ancient rifts. The unusual coincidence of a rift and LIP arose when a new rift associated with continental breakup interacted with a mantle plume or overrode anomalously hot or fertile upper mantle.

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Section: Tectonic Implicationssupporting

confidence: 85%

North America’s Midcontinent Rift: When rift met LIP

et al. 2015

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“…Beneath station SPMN, which occupies the urban gap in the SM line (Figure b), Shen et al [] inferred a Moho at a depth of 47.6 ± 5.6 km, which represents the middle of our STL, while the error bar of Shen et al [] comprises the thickness of our STL. The corresponding RF for SPMN indeed shows a weaker, broader P ‐to‐ S converted wave than for transportable array stations away from the MGA [ Shen et al , ].…”

Section: Discussionmentioning

confidence: 95%

Distinct crustal structure of the North American Midcontinent Rift from P wave receiver functions

et al. 2016

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Eighty‐two broadband seismic stations of the Superior Province Rifting Earthscope Experiment (SPREE) collected 2.5 years of continuous seismic data in the area of the high gravity anomaly associated with the Midcontinent Rift (MCR). Over 100 high‐quality teleseismic earthquakes were used for crustal P wave receiver function analysis. Our analysis reveals that the base of the sedimentary layer is shallow outside the MCR, thickens near the flanks where gravity anomalies are low, and shallows again in the MCR's center where the gravity anomalies peak. This pattern is similar to that found from local geophysical studies and is consistent with reverse faulting having accompanied the cessation of rifting at 1.1 Ga. Intermittent intracrustal boundaries imaged by our analysis might represent the bottom of the MCR's mostly buried dense volcanic layers. Outside the MCR, the Moho is strong, sharp, and relatively flat, both beneath the Archean Superior Province and the Proterozoic terranes to its south. Inside the MCR, two weaker candidate Mohos are found at depths up to 25 km apart in the rift's center. The intermediate layer between these discontinuities tapers toward the edges of the MCR. The presence of this transitional layer is remarkably consistent along the strike of the MCR, including beneath its jog in southern Minnesota, near the Belle Plaine Fault. We interpret these results as evidence for extensive underplating as a defining characteristic of the rift, which remains continuous along the Minnesota jog, where due to its orientation, it is minimally affected by the reverse faulting that characterizes the NNE striking parts of the rift.

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“…We [Pollitz and Snoke, 2010;Moschetti et al, 2010aMoschetti et al, , 2010bShen et al, 2013b;2013a] as well as numerous regional-scale studies. In the eastern U.S. there are no broad-scale high-resolution models to compare with but there are marked similarities to surface wave results in New England , the south central U.S. [Pollitz and Mooney, 2014], and to body wave tomography results [Schmandt and Humphreys, 2010;Burdick et al, 2014;Schmandt and Lin, 2014], including low-velocity region beneath the central and northern Appalachian Mountains and in the vicinity of the Gulf Coast.…”

Section: Comparison To Other Modelsmentioning

confidence: 99%

Lithospheric records of orogeny within the continental U.S.

Porter

Liu

Holt

2016

Geophysical Research Letters

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In order to better understand the tectonic evolution of the North American continent, we utilize data from the EarthScope Transportable Array network to calculate a three‐dimensional shear velocity model for the continental United States. This model was produced through the inversion of Rayleigh wave phase velocities calculated using ambient noise tomography and wave gradiometry, which allows for sensitivity to a broad depth range. Shear velocities within this model highlight the influence of orogenic and postorogenic events on the evolution of the lithosphere. Most notable is the contrast in crustal and upper mantle structure between the relatively slow western and relatively fast eastern North America. These differences are unlikely to stem solely from thermal variations within the lithosphere and highlight both the complexities in lithospheric structure across the continental U.S. and the varying impacts that orogeny can have on the crust and upper mantle.

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Crustal and uppermost mantle structure in the central U.S. encompassing the Midcontinent Rift

Cited by 48 publications

References 95 publications

North America’s Midcontinent Rift: When rift met LIP

North America’s Midcontinent Rift: When rift met LIP

Distinct crustal structure of the North American Midcontinent Rift from P wave receiver functions

Lithospheric records of orogeny within the continental U.S.

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