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The creation of Laurentia involved accretion of crustal fragments around a central portion of Archean crust, including the Wyoming Province. The southern boundary of the Wyoming Province, the Cheyenne belt, separates Archean rocks to the north from <1.8 Ga Paleoproterozoic rocks of the Yavapai/Mojavia blocks that were previously interpreted to have collided with the southern Wyoming Province at ~1.7 Ga. Though the location of the Cheyenne belt is well-known in southern Wyoming, its location farther west, such as in the Uinta Mountains of eastern Utah, is poorly known due to conflicting U/Pb zircon ages from basement rocks of the Red Creek Quartzite and the Owiyukuts Complex. Here, we present new U/Pb zircon ages from a quartzite and felsic orthogneiss of the Owiyukuts Complex near Beaver Creek and two quartzites and an amphibolite from the structurally overlying Red Creek Quartzite from Beaver Creek and Jesse Ewing Canyon. New maximum depositional ages of the quartzites span from ~2.67 Ga to ~2.32 Ga and agree with the relative structural positions hypothesized by prior workers on the basis of structural mapping and metamorphic grade. Results also suggest that the quartzite sediments came from sources dominated by ~2.7 Ga ages, with one quartzite sample yielding ages as young as ~2.3 Ga. Two quartzites, including from both the Owiyukuts Complex and Red Creek Quartzite, have distinctly zoned zircon rims on CL images that yield high-U/Th, ~1.75 Ga ages that we interpret to represent the timing of high-grade metamorphism. Substantial Pb loss precludes estimation of the crystallization age of the felsic orthogneiss. Finally, a coarsely crystalline amphibolite sill exposed at Beaver Creek lacks a significant foliation and yields an age of 1.68 Ga, which we interpret to post-date high-grade metamorphism and deformation. In summary, our results suggest that basement of the eastern Uinta Mountains is dominated by ~2.67-2.32 Ga metasedimentary rocks, which enjoyed high-grade metamorphism at ~1.75 Ga. Given their similarities with the southern Wyoming Province and Cheyenne belt, we interpret that basement rocks in the eastern Uintas define the southern boundary of the Wyoming Province and were metamorphosed as a consequence of collision of Paleoproterozoic blocks to the south at ~1.75 Ga. 

Unconformities, or gaps in the rock record, have typically limited our understanding of Earth’s history. However, geologic processes such as erosion and burial leave a thermal imprint on the rocks below unconformities that can be recovered using thermochronology. Thermochronology uses the temperature-sensitive diffusive loss of radiogenic daughter products within a mineral to obtain information about a sample’s temperature and time evolution, or its thermal history. In the Uinta Mountains of northeastern Utah, Paleoproterozoic metamorphic rocks are nonconformably overlain by Neoproterozoic sedimentary rocks of the Uinta Mountain Group (UMG), resulting in a nearly 1 Gyr interval of missing time. The UMG is a valuable record during early stages of rifting of Rodinia along the western margin of Laurentia where, elsewhere, this early rifting is rarely preserved. In our work, we use the unconformity as an independent thermochronologic constraint: at the time of deposition of the overlying rock, the underlying rock must have been at the surface and at cool, near-surface temperatures. As deposition ensued, we expect that the underlying rocks were heated. To evaluate whether the thermal record of this burial is preserved in the underlying rock and extract information about the pre-depositional history of the region, we sampled basement rocks in depositional contact with the overlying Uinta Mountain Group in a well-characterized structural context for thermochronologic analysis. Here, we present new zircon (U-Th)/He data to constrain the thermal history of each sample. Despite the complexity of multiple episodes of deformation within the study area, these preliminary data and thermal history models support an episode of heating ca. 800-700 Ma, corresponding with deposition of the UMG. Ongoing work will evaluate the spatial heterogeneity of this thermal record within the study area and thus the ability of deep-time thermochronology to fill in the knowledge gaps left by unconformities, particularly in other localities where the sedimentary record of Neoproterozoic rifting is not preserved. 

Abstract Crystalline basement rocks of southwestern Montana have been subjected to multiple tectonothermal events since ∼3.3 Ga: the Paleoproterozoic Big Sky/Great Falls orogeny, Mesoproterozoic extension associated with Belt‐Purcell basin formation, Neoproterozoic extension related to Rodinia rifting, and the late Phanerozoic Sevier‐Laramide orogeny. We investigated the long‐term (>1 Ga), low‐temperature (erosion/burial within 10 km of the surface) thermal histories of these tectonic events with zircon and apatite (U‐Th)/He thermochronology. Data were collected across nine sample localities (n = 55 zircon andn = 26 apatite aliquots) in the northern and southern Madison ranges, the Blacktail‐Snowcrest arch, and the Tobacco Root uplift. Our zircon (U‐Th)/He data show negative trends between single aliquot date and effective uranium (a radiation damage proxy), which we interpreted with a thermal history model that considers the damage‐He diffusivity relationship in zircon. Our model results for these basement ranges show substantial cooling from temperatures above 400°C to near surface conditions between 800 and 510 Ma. Subsequent Phanerozoic exhumation culminated by ∼75 Ma. Late Phanerozoic cooling is coincident with along‐strike Sevier belt thin‐skinned thrusting in southeastern Idaho, and older than exhumation in basement‐involved uplifts of the Wyoming Laramide province. Our long‐term, low‐temperature thermal record for these southwestern Montana basement ranges shows that: (a) these basement blocks have experienced multiple episodes of upper crustal exhumation and burial since Archean time, possibly influencing Phanerozoic thrust architecture and (b) the late Phanerozoic thick‐skinned thrusting recorded by these rocks is among the earliest thermochronologic records of Laramide basement‐involved shortening and was concomitant with Sevier belt thin‐skinned thrusting. 

The development of innovative antimicrobial materials is crucial in thwarting infectious diseases caused by microbes, as drug-resistant pathogens are increasing in both number and capacity to detoxify the antimicrobial drugs used today. An ideal antimicrobial material should inhibit a wide variety of bacteria in a short period of time, be less or not toxic to normal cells, and the fabrication or synthesis process should be cheap and easy. We report a one-step microwave-assisted hydrothermal synthesis of mixed composite CuxFeyOz (Fe2O3/Cu2O/CuO/CuFe2O) nanoparticles (NPs) as an excellent antimicrobial material. The 1 mg/mL CuxFeyOz NPs with the composition 36% CuFeO2, 28% Cu2O and 36% Fe2O3 have a general antimicrobial activity greater than 5 log reduction within 4 h against nine important human pathogenic bacteria (including drug-resistant bacteria as well as Gram-positive and Gram-negative strains). For example, they induced a >9 log reduction in Escherichia coli B viability after 15 min of incubation, and an ~8 log reduction in multidrug-resistant Klebsiella pneumoniae after 4 h incubation. Cytotoxicity tests against mouse fibroblast cells showed about 74% viability when exposed to 1 mg/mL CuxFeyOz NPs for 24 h, compared to the 20% viability for 1 mg/mL pure Cu2O NPs synthesized by the same method. These results show that the CuxFeyOz composite NPs are a highly efficient, low-toxicity and cheap antimicrobial material that has promising potential for applications in medical and food safety. 

Abstract The Lower Cretaceous Blackleaf Formation in southwestern Montana records sedimentation in the Idaho‐Montana retroforeland basin of the North American Cordillera. Regional‐scale sedimentology suggests that during Albian time southwestern Montana was partially flooded by an early marine incursion of the Western Interior Seaway during deposition of the Blackleaf Formation. We use sandstone petrography, large‐n(n = 600) U‐Pb detrital zircon geochronology and mixture modelling to determine the provenance of these strata. Our analysis suggests three distinct provenance groups: Group 1 sandstones occur in the eastern region of the study area, are quartz‐rich and have zircon age‐probability peaks of ca. 110, 160, 420–450, 1050 and 1160 Ma; these sandstones match with a primarily Appalachian provenance. Group 2 sandstones occur in the western region of study area, are lithic‐rich and have peaks of ca. 110, 160, 1780, 1840, 1920, 2080 and 2700 Ma; the primary source for these sandstones was exhumed lower‐middle Palaeozoic strata from the Idaho sector of the Sevier belt. Group 3 sandstones occur in the western region of the study area, are lithic‐rich and have prominent peaks of ca. 115, 170, 430, 600, 1085, 1170, 1670 and 1790 Ma; the primary source for these sandstones was exhumed Triassic‐upper Palaeozoic strata from the Idaho sector of the Sevier belt. Our provenance data record a sharp change that coincides with the western shoreline of the seaway, and we infer that it may indicate the position of an irregular, submarine forebulge depozone influenced by dynamic subsidence during a period of reduced thrusting in the adjacent fold‐thrust belt. Albian‐aged sediments in southwestern Montana were delivered by rivers with headwaters in the Sevier belt as well as transcontinental river systems with headwaters in eastern North America. In southwestern Montana, west‐flowing transcontinental fluvial systems were flooded by the Western Interior Seaway as it encroached from the north.