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Abstract The North American craton interior preserves a >1 Ga history of near surface processes that inform ongoing debates regarding timing and drivers of continental‐scale deformation and erosion associated with far‐field orogenesis. We tested various models of structural inversion on a major segment of the Midcontinent Rift along the Douglas Fault in northern Wisconsin, which accommodated ≳10 km of total vertical displacement. U‐Pb detrital zircon and vein calcite Δ₄₇/U‐Pb thermochronometry from the hanging wall constrain the majority of uplift (≳8.5 km) and deformation to 1052–1036 Ma during the Ottawan phase of the Grenvillian orogeny. Combined U‐Pb zircon dates, Δ₄₇/U‐Pb calcite thermochronometry, and field data that document syn‐ to early post‐depositional deformation in the footwall constrain a second stage of uplift (1–1.5 km) ca. 995–980 Ma during the Rigolet phase of the Grenvillian orogeny. A minor phase of Appalachian far‐field orogenesis is associated with minimal thrust reactivation. Our combined analyses identified the 995–980 Ma Bayfield Group as a Grenvillian foreland basin with an original thickness 0.5–2 km greater than currently preserved. By quantifying flexural loading and other subsidence mechanisms along the Douglas Fault, we identify dynamic subsidence as a mechanism that could be consistent with the development of late‐Grenvillian transcontinental fluvial systems. Minimal post‐Grenvillian erosion (0.5–2 km) in this part of the craton interior has preserved the Bayfield Group and equivalent successions, limiting the magnitude of regional erosion that can be attributed to Neoproterozoic glaciation. 

Abstract Mafic intrusions, lava flows, and felsic plutons in southwestern Laurentia have been hypothesized to be associated with the emplacement of a late Mesoproterozoic (Stenian Period) large igneous province. Improved geochronologic data resolve distinct episodes of mafic magmatism in the region. The ca. 1,098 Ma main pulse of southwestern Laurentia large igneous province (SWLLIP) magmatism is recorded by mafic intrusions across southeastern California to central Arizona. A younger episode of volcanism resulted in eruptions that formed the ca. 1,082 Ma Cardenas Basalt, which is the uppermost unit of the Unkar Group in the Grand Canyon. With the updated geochronological constraints, we develop new paleomagnetic data from mafic sills in the SWLLIP. Overlapping poles between the Death Valley sills and rocks of similar age in the Midcontinent Rift are inconsistent with large‐scale Cenozoic vertical axis rotations in Death Valley. We also develop a new paleomagnetic pole from the ca. 1,082 Ma Cardenas Basalt (pole longitude = 183.9°E, pole latitude = 15.9°N,  = 7.4°,N = 18). The new paleomagnetic data are consistent with the pole path developed from time‐equivalent rocks of the Midcontinent Rift, supporting interpretations that changing pole positions are the result of rapid equatorward motion. These data add to the record of Laurentia's rapid motion from ca. 1,110 to 1,080 Ma that culminated in collisional Grenvillian orogenesis and the assembly of Rodinia. 

Abstract The paleogeography of Laurentia throughout the Neoproterozoic is critical for reconstructing global paleogeography due to its central position in the supercontinent Rodinia. We develop a new paleomagnetic pole from red siltstones and fine‐grained sandstones of the early Neoproterozoic Jacobsville Formation which is now constrained to be ca. 990 Ma in age. High‐resolution thermal demagnetization experiments resolve detrital remanent magnetizations held by hematite. These directions were reoriented within siltstone intraclasts and pass intraformational conglomerate tests—giving confidence that the magnetization is detrital and primary. An inclination‐corrected mean paleomagnetic pole position for the Jacobsville Formation indicates that Laurentia's motion slowed down significantly following the onset of the Grenvillian orogeny. Prior rapid plate motion associated with closure of the Unimos Ocean between 1,110 and 1,090 Ma transitioned to slow drift of Laurentia across the equator in the late Mesoproterozoic to early Neoproterozoic. We interpret the distinct position of this well‐dated pole from those in the Grenville orogen that have been assigned a similar age to indicate that the ages of the poles associated with the Grenville Loop likely need to be revised to be younger due to prolonged exhumation. 

Abstract The Southwestern Laurentia large igneous province (SWLLIP) comprises voluminous, widespread ca 1.1 Ga magmatism in the southwestern United States and northern Mexico. The timing and tempo of SWLLIP magmatism and its relationship to other late Mesoproterozoic igneous provinces have been unclear due to difficulties in dating mafic rocks at high precision. New precise U-Pb zircon dates for comagmatic felsic segregations within mafic rocks reveal distinct magmatic episodes at ca. 1098 Ma (represented by massive sills in Death Valley, California, the Grand Canyon, and central Arizona) and ca. 1083 Ma (represented by the Cardenas Basalts in the Grand Canyon and a sill in the Dead Mountains, California). The ca. 1098 Ma magmatic pulse was short-lived, lasting 0.25−0.24+0.67 m.y., and voluminous and widespread, evidenced by the ≥100 m sills in Death Valley, the Grand Canyon, and central Arizona, consistent with decompression melting of an upwelling mantle plume. The ca. 1083 Ma magmatism may have been generated by a secondary plume pulse or post-plume lithosphere extension. The ca. 1098 Ma pulse of magmatism in southwestern Laurentia occurred ~2 m.y. prior to an anomalous renewal of voluminous melt generation in the Midcontinent Rift of central Laurentia that is recorded by the ca. 1096 Ma Duluth Complex layered mafic intrusions. Rates of lateral plume spread predicted by mantle plume lubrication theory support a model where a plume derived from the deep mantle impinged near southwestern Laurentia, then spread to thinned Midcontinent Rift lithosphere over ~2 m.y. to elevate mantle temperatures and generate melt. This geodynamic hypothesis reconciles the close temporal relationships between voluminous magmatism across Laurentia and provides an explanation for that anomalous renewal of high magmatic flux within the protracted magmatic history of the Midcontinent Rift. 

Abstract Inclination is the angle of a magnetization vector from horizontal. Clastic sedimentary rocks often experience inclination shallowing whereby syn‐ to post‐depositional processes result in flattened detrital remanent magnetizations relative to local geomagnetic field inclinations. The deviation of recorded inclinations from true values presents challenges for reconstructing paleolatitudes. A widespread approach for estimating flattening factors (f) compares the shape of an assemblage of magnetization vectors to that derived from a paleosecular variation model (the elongation/inclination [E/I] method). Few studies exist that compare the results of this statistical approach with empirically determined flattening factors and none in the Proterozoic Eon. In this study, we evaluate inclination shallowing within 1.1 billion‐year‐old, hematite‐bearing red beds of the Cut Face Creek Sandstone that is bounded by lava flows of known inclination. Taking this inclination from the volcanics as the expected direction, we found that detrital hematite remanence is flattened withwhereas the pigmentary hematite magnetization shares a common mean with the volcanics. Using the pigmentary hematite direction as the expected inclination results in. These flattening factors are consistent with those estimated through the E/I methodsupporting its application in deep time. However, all methods have significant uncertainty associated with determining the flattening factor. This uncertainty can be incorporated into paleomagnetic poles with the resulting ellipse approximated with a Kent distribution. Rather than seeking to find “the flattening factor,” or assuming a single value, the inherent uncertainty in flattening factors should be recognized and incorporated into paleomagnetic syntheses. 

Abstract New geochronologic and paleomagnetic data from the North American Midcontinent Rift (MCR) reveal the synchronous emplacement of the Beaver River diabase, the anorthosite xenoliths within it, and the Greenstone Flow—one of the largest lava flows on Earth. A U‐Pb zircon date of 1091.83  0.21 Ma (2) from one of the anorthosite xenoliths is consistent with the anorthosite cumulate forming as part of the MCR and provides a maximum age constraint for the Beaver River diabase. Paired with the minimum age constraint of a cross‐cutting Silver Bay intrusion (1091.61  0.14 Ma; 2), these data tightly bracket the age of the Beaver River diabase to be 1091.7  0.2 Ma (95% CI), coeval with the eruption of the Greenstone Flow (1091.59  0.27 Ma; 2)—which is further supported by indistinguishable tilt‐corrected paleomagnetic pole positions. Geochronological, paleomagnetic, mineralogical and geochemical data are consistent with a hypothesis that the Beaver River diabase was the feeder system for the Greenstone Flow. The large areal extent of the intrusives and large estimated volume of the volcanics suggest that they represent a rapid and voluminous ca. 1,092 Ma magmatic pulse near the end of the main stage of MCR magmatism. 

Abstract Apparent polar wander paths (APWPs) synthesized from paleomagnetic poles provide the most direct data for reconstructing past paleogeography and plate motions for times earlier than ca. 200 Ma. In this contribution, we describe a new method for APWP synthesis that extends the paleomagnetic Euler pole analysis of Gordon et al. (1984,https://doi.org/10.1029/TC003i005p00499) by placing it within the framework of a Bayesian inverse problem. This approach incorporates uncertainties in pole positions and age that are often ignored in standard treatments. The paleomagnetic Euler poles resulting from the inversions provide estimates for full‐vector plate motion (both latitude and longitude) and associated uncertainty. The method allows for inverting for one or more Euler poles with the timing of changepoints being solved as part of the inversion. In addition, the method allows the incorporation of true polar wander rotations, thus providing an avenue for probabilistic partitioning of plate tectonic motion and true polar wander based on paleomagnetic poles. We show example inversions on synthetic data to demonstrate the method's capabilities. We illustrate application of the method to Cenozoic Australia paleomagnetic poles which can be compared to independent plate reconstructions. A two‐Euler pole inversion for the Australian record recovers northward acceleration of Australia in the Eocene with rates that are consistent with plate reconstructions. We also apply the method to constrain rapid rates of motion for cratonic North America associated with the Keweenawan Track of late Mesoproterozoic paleomagnetic poles. The application of Markov chain Monte Carlo methods to estimate paleomagnetic Euler poles can open new directions in quantitative paleogeography. 

Abstract Theca. 1.83 Ga Trans‐Hudson orogeny resulted from collision of an upper plate consisting of the Hearne, Rae, and Slave provinces with a lower plate consisting of the Superior province. While the geologic record ofca. 1.83 Ga peak metamorphism within the orogen suggests that these provinces were a single amalgamated craton from this time onward, a lack of paleomagnetic poles from the Superior province following Trans‐Hudson orogenesis has made this coherency difficult to test. We develop a high‐quality paleomagnetic pole for northeast‐trending diabase dikes of the post‐Penokean orogen East‐Central Minnesota Batholith (pole longitude: 265.8°; pole latitude: 20.4°; A₉₅: 4.5°; K: 45.6 N: 23) whose age we constrain to be 1,779.1 ± 2.3 Ma (95% CI) with new U‐Pb dates. Demagnetization and low‐temperature magnetometry experiments establish dike remanence be held by low‐Ti titanomagnetite. Thermochronology data constrain the intrusions to have cooled below magnetite blocking temperatures upon initial emplacement with a mild subsequent thermal history within the stable craton. The similarity of this new Superior province pole with poles from the Slave and Rae provinces establishes the coherency of Laurentia following Trans‐Hudson orogenesis. This consistency supports interpretations that older discrepant 2.22–1.87 Ga pole positions between the provinces are the result of differential motion through mobile‐lid plate tectonics. The new pole supports the northern Europe and North America connection between the Laurentia and Fennoscandia cratons. The pole can be used to jointly reconstruct these cratonsca. 1,780 Ma strengthening the paleogeographic position of these major constituents of the hypothesized late Paleoproterozoic supercontinent Nuna. 

2024 SWLLIP manuscript release for submission 

Publication release of code, data, figures, and manuscript