scholarly journals Early Pennsylvanian sediment routing to the Ouachita Basin (southeastern United States) and barriers to transcontinental sediment transport sourced from the Appalachian orogen based on detrital zircon U-Pb and Hf analysis

Geosphere ◽  
2021 ◽  
Author(s):  
Isaac J. Allred ◽  
Michael D. Blum
Keyword(s):  
United States ◽  
Detrital Zircon ◽  
Eastern United States ◽  
Ouachita Mountains ◽  
Sediment Dispersal ◽  
Continental Scale ◽  
The North ◽  
Sediment Routing ◽  
Proximal Site ◽  
Central United States

Carboniferous sediment dispersal from the Appalachian orogenic system (eastern United States) has become a topic of widespread interest. However, the actual pathways for continental-scale, east-to-west sediment transfer have not been documented. This study presents detrital zircon (DZ) U-Pb ages and Hf isotopic values from the Lower Pennsylvanian (Morrowan) Jackfork Group and Johns Valley Shale of the synorogenic Ouachita deepwater basin of Arkansas to document provenance and delineate the likely sediment-routing systems within the broader context of sediment dispersal across Laurentia. Twelve (12) DZ U-Pb age distributions are interpreted to indicate that sediments were derived from the Appalachians to the east and northeast, as well as the midcontinent region to the north. All samples display prominent ca. 500– 400 Ma, 1250–950 Ma, 1550–1300 Ma, and 1800–1600 Ma grains, consistent with ultimate derivation from the Appalachian, Grenville, Midcontinent, and Yavapai-Mazatzal provinces. DZ Hf values obtained from the Ouachita Basin are similar to published Hf values from Pennsylvanian samples in the Appalachian and Illinois Basins. Age distributions are generally consistent for seven samples collected from the Jackfork Group and Johns Valley Shale in the southern Ouachita Mountains through ~2400 m of stratigraphic section and are interpreted to indicate little change in provenance during the Morrowan in this part of the system. However, samples from the most northern and most source-proximal site in Little Rock, Arkansas, exhibit modest percentages of Appalachian ages and elevated contributions of Yavapai-Mazatzal ages when compared with samples collected farther to the south and west. We interpret differences between DZ signatures to indicate distinct sediment-routing pathways to the Ouachita Basin. We infer the strong Appalachian and Grenville signals to represent an axial system flowing through the Appalachian foredeep, whereas the more diverse signals represent a confluence of rivers from the northeast through the backbulge of southern Illinois and western Kentucky and from the north across the Arkoma shelf. Collectively, the Ouachita Basin represents a terminal sink for sediments derived from much of the eastern and central United States.

scholarly journals Warm Season Response over North America to a Shutdown of the Atlantic Meridional Overturning Circulation and CO2 Increases

2012 ◽  
Vol 25 (19) ◽  
pp. 6701-6720 ◽  
Author(s):  
Bing Pu ◽  
Edward K. Vizy ◽  
Kerry H. Cook
Keyword(s):  
United States ◽  
North Atlantic ◽  
Warm Season ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Eastern United States ◽  
The North ◽  
Central United States ◽  
Moisture Fluxes ◽  
Meridional Overturning

Abstract Paleo-proxy and modeling evidence suggest that a shutdown of the Atlantic meridional overturning circulation (AMOC) would decrease North Atlantic Ocean sea surface temperatures and have far-reaching climate impacts. The authors use a regional climate model to examine the warm season response over North America to a hypothetical late-twenty-first-century shutdown of the AMOC with increased atmospheric CO2. In the future simulation, precipitation decreases over the western and central United States by up to 40% and over eastern Mexico by up to 50%. Over the eastern United States rainfall generally increases except during July. Variations in the moisture convergence associated with large-scale circulation changes dominate the rainfall variations, while evaporation plays a critical role over the northeastern United States in spring and the north-central United States in summer. During April–June the westward extension of the North Atlantic subtropical high enhances southwesterly moisture fluxes from the Gulf of Mexico into the eastern and south-central United States. Increases in low-level moisture content reduce the stability of the atmosphere. Enhanced southerly winds promote convergence over the eastern United States through the Sverdrup vorticity balance and precipitation increases. In July–August anomalous anticyclonic moisture fluxes associated with an anomalous high over the Gulf of Mexico and eastern Pacific decrease the moisture supply into the United States and Mexico. Over the central United States decreases in evaporation support decreases in low-level moisture content and increases in atmospheric stability. Over the eastern United States the Sverdrup balance weakens in summer and anomalous moisture convergence is mainly located over the East Coast.

scholarly journals Detrital zircon U-Pb data reveal a Mississippian sediment dispersal network originating in the Appalachian orogen, traversing North America along its southern shelf, and reaching as far as the southwest United States

Lithosphere ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 581-587 ◽  
Author(s):  
Alan D. Chapman ◽  
Andrew K. Laskowski
Keyword(s):  
United States ◽  
North America ◽  
Detrital Zircon ◽  
Structural Data ◽  
Trade Wind ◽  
Long Distance ◽  
Sediment Dispersal ◽  
Sediment Routing ◽  
Appalachian Orogen ◽  
Peace River Arch

AbstractRecent detrital zircon U-Pb geochronology reveals an increasing proportion of Grenville-age (ca. 0.95–1.3 Ga) and ca. 300–480 Ma grains in late Paleozoic strata of the SW United States. These grain populations are interpreted to have been sourced from the Appalachian orogen, though the precise timing, transport mechanisms, and pathway(s) of sediment dispersal remain unclear. We combine 35,796 published detrital zircon U-Pb ages from Ordovician to Pennsylvanian strata of southern Canada, northern Mexico, and the U.S. with new data (1,628 ages) from Kansas, Missouri, Montana, and South Dakota. These data are integrated with sedimentary structural data and paleogeographic reconstructions to reveal temporal and spatial patterns of the sediment routing system at continent scale. In Ordovician time, North America was partitioned into western, central, and eastern domains in which strata were derived primarily from the Peace River Arch, the Superior Craton, and the Appalachians, respectively. Silurian–Devonian time saw limited integration of these domains, corresponding with the delivery of Appalachian-derived detritus to the Midcontinent via prograding deltas and westward-flowing rivers. Appalachian detritus flowed westward in Mississippian time, accumulating in the Appalachian foreland and continuing westward through Mississippi, Arkansas, Missouri, Oklahoma, Kansas, Colorado, Arizona, and California along the continental shelf. Given that North America was at equatorial latitudes and was inundated by the Kaskaskia sea at this time, westward dispersal likely occurred by trade wind–driven longshore drift, waves, tides, and marine currents, with the possible added contribution of hurricanes. Modern analogs for the southern margin of North America during Mississippian time (e.g., the Great Barrier Reef and the east coast of South America) indicate that long-distance (>1000 km) shelf-parallel sediment transport is readily accomplished through fair-weather processes and extreme events. Finally, Appalachian-derived detritus became widespread throughout North America following regression of the Kaskaskia sea in Pennsylvanian time, likely via fluvial, deltaic, and aeolian processes.

A mactrid bivalve from Pleistocene deposits of Lake Russell, Mono Basin, California

2009 ◽  
Vol 83 (3) ◽  
pp. 496-499 ◽  
Author(s):  
Robert Hershler ◽  
Angela S. Jayko
Keyword(s):  
United States ◽  
Gulf Of California ◽  
Gulf Coast ◽  
Eastern United States ◽  
Salinity Regime ◽  
The North ◽  
Biogeographic History ◽  
Coastal Marine ◽  
Central United States ◽  
History Of

Rangia des Moulins, 1832 is a small genus of mactrid bivalves that is currently distributed in estuarine waters of the eastern United States, Gulf of Mexico, and Gulf of California (Keen, 1971; Abbott, 1974). (One congener, R. cuneata [Sowerby, 1831], was recently introduced to the Antwerp (Belgium) harbor [Verween et al., 2006].) Although these clams are euryhaline and capable of living in freshwater as adults, they require an estuarine-like salinity regime for successful reproduction and recruitment (Cain, 1973; Hopkins et al., 1974), which has constrained their ability to penetrate the North American continental interior through coastal drainages (Cain, 1974; Swingle and Brand, 1974). the Neogene and Quaternary fossil record of the genus is also restricted to coastal or near-coastal marine-influenced depositional systems, with the exception of Holocene specimens of R. cuneata from two archeological sites in the central United States which were obviously introduced by humans (Baker, 1941; Hill, 1983), and a Pleistocene(?) occurrence of this species from along the Pecos River in New Mexico (more than 800 km from the sea) which has been attributed to transport of Gulf Coast immigrants on waterfowl (Metcalf, 1980; Taylor, 1985). Here we provide fossil evidence that the biogeographic history of this predominantly brackish-coastal genus also includes avian-assisted colonization of a far inland lake in the western United States—Pleistocene Lake Russell, Mono Basin, California (Fig. 1).

An Observational Examination of Long-Lived Supercells. Part I: Characteristics, Evolution, and Demise

2006 ◽  
Vol 21 (5) ◽  
pp. 673-688 ◽  
Author(s):  
Matthew J. Bunkers ◽  
Mark R. Hjelmfelt ◽  
Paul L. Smith
Keyword(s):  
United States ◽  
The United States ◽  
Eastern United States ◽  
North Central ◽  
The North ◽  
Central United States ◽  
Bow Echo ◽  
Primary Focus ◽  
Convective Mode

Abstract Observations of supercells and their longevity across the central and eastern United States are examined, with the primary focus on understanding the properties of long-lived supercells (defined as supercells lasting ≥4 h). A total of 224 long-lived supercells, occurring in 184 separate events, are investigated. These properties are compared with those of short-lived supercells (lifetimes ≤2 h) to determine the salient differences between the two classifications. A key finding is that long-lived supercells are considerably more isolated and discrete than short-lived supercells; as a result, the demise of a long-lived supercell (i.e., the end of the supercell phase) is often signaled by a weakening of the storm’s circulation and/or a rapid dissipation of the thunderstorm. In contrast, short-lived supercells commonly experience a demise linked to storm mergers and convective transitions (e.g., evolution to a bow echo). Also noteworthy, 36% of the long-lived supercell events were associated with strong or violent tornadoes (F2–F5), compared with only 8% for the short-lived supercell events. Evolutionary characteristics of long-lived supercells vary geographically across the United States, with the largest contrasts between the north-central United States and the Southeast. For example, 86% of the long-lived supercells across the north-central United States were isolated for most of their lifetime, whereas only 35% of those in the Southeast displayed this characteristic. Not surprisingly, the convective mode was discrete for 70% of the long-lived supercell events across the north-central United States, compared with 39% for the Southeast.

scholarly journals Genetic Variation of Sclerotinia sclerotiorum from Multiple Crops in the North Central United States

PLoS ONE ◽  
2015 ◽  
Vol 10 (9) ◽  
pp. e0139188 ◽  
Author(s):  
Laura Aldrich-Wolfe ◽  
Steven Travers ◽  
Berlin D. Nelson
Keyword(s):  
United States ◽  
Genetic Variation ◽  
Sclerotinia Sclerotiorum ◽  
North Central ◽  
The North ◽  
Central United States

Evaluation of Intensity Prediction Equations (IPEs) for Small-Magnitude Earthquakes

2021 ◽  
Author(s):  
Ganyu Teng ◽  
Jack W. Baker ◽  
David J. Wald
Keyword(s):  
United States ◽  
Ground Truth ◽  
Site Amplification ◽  
Eastern United States ◽  
Prediction Equations ◽  
Small Magnitude ◽  
Intensity Prediction ◽  
Central United States ◽  
Hazard Disaggregation

Abstract This study assesses existing intensity prediction equations (IPEs) for small unspecified magnitude (M ≤3.5) earthquakes at short hypocentral distances (Dh) and explores such earthquakes’ contribution to the felt shaking hazard. In particular, we consider IPEs by Atkinson and Wald (2007) and Atkinson et al. (2014), and evaluate their performance based on “Did You Feel It” (DYFI) reports and recorded peak ground velocities (PGVs) in the central United States. Both IPEs were developed based on DYFI reports in the central and eastern United States with moment magnitudes above Mw 3.0. DYFI reports are often used as the ground truth when evaluating and developing IPEs, but they could be less reliable when there are limited responses for small-magnitude earthquakes. We first compare the DYFI reports with intensities interpolated from recorded PGVs. Results suggest a minimal discrepancy between the two when the intensity is large enough to be felt (i.e., M >2 and Dh<15  km). We then compare intensities from 31,617 DYFI reports of 3049 earthquakes with the two IPEs. Results suggest that both the IPEs match well with observed intensities for 2.0< M <3.0 and Dh<10  km, but the IPE by Atkinson et al. (2014) matches better for larger distances. We also observe that intensities from DYFI reports attenuate faster compared with the two IPEs, especially for distances greater than 10 km. We then group DYFI reports by inferred VS30 as a proxy for site amplification effects. We observe that intensities at sites with VS30 around 300 m/s are consistently higher than at sites with VS30 around 700 m/s and are also closer to the two IPEs. Finally, we conduct hazard disaggregation for earthquakes at close distances (Dh=7.5  km) using the observed records. Results suggest that earthquakes with magnitudes below M 3.0 contribute more than 40% to the occurrence of felt shaking.

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