scholarly journals The Chief Joseph dike swarm of the Columbia River flood basalts, and the legacy data set of William H. Taubeneck

Geosphere ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 1082-1106
Author(s):  
Matthew C. Morriss ◽  
Leif Karlstrom ◽  
Morgan W.M. Nasholds ◽  
John A. Wolff
Keyword(s):  
Large Scale ◽  
Columbia River ◽  
Flood Basalt ◽  
Continental Flood Basalt ◽  
Data Set ◽  
Average Width ◽  
Near Surface ◽  
Surface Flows ◽  
Dike Swarm ◽  
Stress Changes

Abstract The Miocene Columbia River Basalt Group (CRBG) is the youngest and best studied continental flood basalt province on Earth. The 210,000 km3 of basaltic lava flows in this province were fed by a series of dike swarms, the largest of which is the Chief Joseph dike swarm (CJDS) exposed in northeastern Oregon and southwestern Washington. We present and augment an extensive data set of field observations, collected by Dr. William H. Taubeneck (1923–2016; Oregon State University, 1955–1983); this data set elucidates the structure of the CJDS in new detail. The large-scale structure of the CJDS, represented by 4279 mapped segments mostly cropping out over an area of 100 × 350 km2, is defined by regions of high dike density, up to ∼5 segments/km−2 with an average width of 8 m and lengths of ∼100–1000 m. The dikes in the CJDS are exposed across a range of paleodepths, from visibly feeding surface flows to ∼2 km in depth at the time of intrusion. Based on extrapolation of outcrops, we estimate the volume of the CJDS dikes to be 2.5 × 102–6 × 104 km3, or between 0.1% and 34% of the known volume of the magma represented by the surface flows fed by these dikes. A dominant NNW dike segment orientation characterizes the swarm. However, prominent sub-trends often crosscut NNW-oriented dikes, suggesting a change in dike orientations that may correspond to magmatically driven stress changes over the duration of swarm emplacement. Near-surface crustal dilation across the swarm is ∼0.5–2.7 km to the E-W and ∼0.2–1.3 km to the N-S across the 100 × 350 km region, resulting in strain across this region of 0.4%–13.0% E-W and 0.04%–0.3% N-S. Host-rock partial melt is rare in the CJDS, suggesting that only a small fraction of dikes were long-lived.

scholarly journals Supplemental Material: The Chief Joseph dike swarm of the Columbia River flood basalts, and the legacy data set of William H. Taubeneck

2020 ◽  
Author(s):  
M.C. Morriss ◽  
et al.
Keyword(s):  
Pacific Northwest ◽  
Large Scale ◽  
Columbia River ◽  
Flood Basalts ◽  
Data Set ◽  
Dike Swarm ◽  
Columbia River Basalt ◽  
Legacy Data ◽  
Columbia River Basalt Group ◽  
Columbia River Flood Basalts

Supplemental Plates. Plate S1: Large-scale map of entire extent of Chief Joseph dike swarm. Also incorporates dikes of Ice Harbor, Steens, and Monument swarms. Plate S1 represents the most complete record of dikes related to Columbia River Basalt Group (CRBG) event known. Plate S2: Simplified map of CRBG-related dikes across the inland Pacific Northwest. Dikes are colored by their orientation and dike line density is also shown. Plate S3: Simplified map of CRBG-related dikes across the inland Pacific Northwest.<br>

scholarly journals Supplemental Material: The Chief Joseph dike swarm of the Columbia River flood basalts, and the legacy data set of William H. Taubeneck

2020 ◽  
Author(s):  
M.C. Morriss ◽  
et al.
Keyword(s):  
Pacific Northwest ◽  
Large Scale ◽  
Columbia River ◽  
Flood Basalts ◽  
Data Set ◽  
Dike Swarm ◽  
Columbia River Basalt ◽  
Legacy Data ◽  
Columbia River Basalt Group ◽  
Columbia River Flood Basalts

Supplemental Plates. Plate S1: Large-scale map of entire extent of Chief Joseph dike swarm. Also incorporates dikes of Ice Harbor, Steens, and Monument swarms. Plate S1 represents the most complete record of dikes related to Columbia River Basalt Group (CRBG) event known. Plate S2: Simplified map of CRBG-related dikes across the inland Pacific Northwest. Dikes are colored by their orientation and dike line density is also shown. Plate S3: Simplified map of CRBG-related dikes across the inland Pacific Northwest.<br>

scholarly journals Supplemental Material: The Chief Joseph dike swarm of the Columbia River flood basalts, and the legacy data set of William H. Taubeneck

2020 ◽  
Author(s):  
M.C. Morriss
Keyword(s):  
Pacific Northwest ◽  
Large Scale ◽  
Columbia River ◽  
Flood Basalts ◽  
Data Set ◽  
Dike Swarm ◽  
Columbia River Basalt ◽  
Legacy Data ◽  
Columbia River Basalt Group ◽  
Columbia River Flood Basalts

Supplemental Plates. Plate S1: Large-scale map of entire extent of Chief Joseph dike swarm. Also incorporates dikes of Ice Harbor, Steens, and Monument swarms. Plate S1 represents the most complete record of dikes related to Columbia River Basalt Group (CRBG) event known. Plate S2: Simplified map of CRBG-related dikes across the inland Pacific Northwest. Dikes are colored by their orientation and dike line density is also shown. Plate S3: Simplified map of CRBG-related dikes across the inland Pacific Northwest.<br>

Analytic investigations of the effects of near‐surface three‐dimensional galvanic scatterers on MT tensor decompositions

Geophysics ◽  
1991 ◽  
Vol 56 (4) ◽  
pp. 496-518 ◽  
Author(s):  
R. W. Groom ◽  
R. C. Bailey
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Magnetic Scattering ◽  
Impedance Tensor ◽  
Data Set ◽  
Near Surface ◽  
Eigenvalue Estimates ◽  
Polarization Azimuth ◽  
Local Current ◽  
Scattering Operators

An outcropping hemispherical inhomogeneity embedded in a two‐dimensional (2-D) earth is used to model the effects of three‐dimensional (3-D) near‐surface electromagnetic (EM) “static” distortion. Analytical solutions are first derived for the galvanic electric and magnetic scattering operators of the heterogeneity. To represent the local distortion by 3-D structures of fields which were produced by a large‐scale 2-D structure, these 3-D scattering operators are applied to 2-D electric and magnetic fields derived by numerical modeling to synthesize an MT data set. Synthetic noise is also included in the data. These synthetic data are used to study the parameters recovered by several published methods for decomposing or parameterizing the measured MT impedance tensor. The stability of these parameters in the presence of noise is also examined. The parameterizations studied include the conventional 2-D parameterization (Swift, 1967), Eggers’s (1982) and Spitz’s (1985) eigenstate formulations, LaTorraca et al.’s (1986) SVD decomposition, and the Groom and Bailey (1989) method designed specifically for 3-D galvanic electric scattering. The relationships between the impedance or eigenvalue estimates of each method and the true regional impedances are examined, as are the azimuthal (e.g., regional 2-D strike, eigenvector orientation and local strike) and ellipticity parameters. The 3-D structure causes the conventional 2-D estimates of impedances to be site‐dependent mixtures of the regional impedance responses, with the strike estimate being strongly determined by the orientation of the local current. For strong 3-D electric scattering, the local current polarization azimuth is mainly determined by the local 3-D scattering rather than the regional currents. There are strong similarities among the 2-D rotation estimates of impedance and the eigenvalue estimates of impedance both by Eggers’s and Spitz’s first parameterization as well as the characteristic values of LaTorraca et al. There are striking similarities among the conventional estimate of strike, the orientations given by the Eggers’s, Spitz’s (Q), and LaTorraca et al.’s decompositions, as well as the estimate of local current polarization azimuth given by Groom and Bailey. It was found that one of the ellipticities of Eggers, LaTorraca et al., and Spitz is identically zero for all sites and all periods, indicating that one eigenvalue or characteristic value is linearly polarized. There is strong evidence that this eigenvalue is related to the local current. For these three methods, the other ellipticity differs from zero only when there are significant differences in the phases of the regional 2-D impedances (i.e., strong 2-D inductive effects), implying the second ellipticity indicates a multidimensional inductive response. Spitz’s second parameterization (U), and the Groom and Bailey decomposition, were able to recover information regarding the actual regional 2-D strike and the separate character of the 2-D regional impedances. Unconstrained, both methods can suffer from noise in their ability to resolve structural information especially when the current distortion causes the impedance tensor to be approximately singular. The method of Groom and Bailey, designed specifically for quantifying the fit of the measured tensors to the physics of the parameterization, constraining a model, and resolving parameters, can recover much of the information in the two regional impedances and some information about the local structure.

scholarly journals Supplemental Material: The Chief Joseph dike swarm of the Columbia River flood basalts, and the legacy data set of William H. Taubeneck

2020 ◽  
Author(s):  
M.C. Morriss
Keyword(s):  
Columbia River ◽  
Google Earth ◽  
Flood Basalts ◽  
Data Set ◽  
Dike Swarm ◽  
River Flood ◽  
Legacy Data ◽  
Columbia River Flood Basalts

Supplemental Google Earth file: Mapped dike steps, en echelon segmentation, and cross-cutting dikes. Mapped dike steps, en echelon segmentation, and cross-cutting dikes.<br>

scholarly journals Reshuffling the Columbia River Basalt chronology—Picture Gorge Basalt, the earliest- and longest-erupting formation

Geology ◽  
2020 ◽  
Vol 48 (4) ◽  
pp. 348-352 ◽  
Author(s):  
Emily B. Cahoon ◽  
Martin J. Streck ◽  
Anthony A.P. Koppers ◽  
Daniel P. Miggins
Keyword(s):  
National Park ◽  
Columbia River ◽  
Flood Basalt ◽  
Temporal Context ◽  
Broad Area ◽  
Subsequent Evolution ◽  
Continental Flood Basalt ◽  
Columbia River Basalt ◽  
Geochemical Significance ◽  
Columbia River Basalt Group

Abstract The Columbia River Basalt Group (CRBG) is the world’s youngest continental flood basalt province, presumably sourced from the deep-seated plume that currently resides underneath Yellowstone National Park in the northwestern United States. The earliest-erupted basalts from this province aid in understanding and modeling plume impingement and the subsequent evolution of basaltic volcanism. We explore the Picture Gorge Basalt (PGB) formation of the CRBG, and discuss the location and geochemical significance in a temporal context of early CRBG magmatism. We report new ARGUS-VI multicollector 40Ar/39Ar incremental heating ages from known PGB localities and additional outcrops that we can geochemically classify as PGB. These 40Ar/39Ar ages range between 17.23 ± 0.04 Ma and 16.06 ± 0.14 Ma, indicating that PGB erupted earlier and for longer than other CRBG main-phase units. These ages illustrate that volcanism initiated over a broad area in the center of the province, and the geochemistry of these early lavas reflects a mantle source that is distinct both spatially and temporally. Combining ages with the strongest arc-like (but depleted) geochemical signal of PGB among CRBG units indicates that the shallowest metasomatized backarc-like mantle was tapped first and concurrently, with later units (Steens and Imnaha Basalts) showing increased influence of a plume-like source.

scholarly journals Supplemental Material: The Chief Joseph dike swarm of the Columbia River flood basalts, and the legacy data set of William H. Taubeneck

2020 ◽  
Author(s):  
M.C. Morriss ◽  
et al.
Keyword(s):  
Columbia River ◽  
Flood Basalts ◽  
Data Set ◽  
Dike Swarm ◽  
River Flood ◽  
Legacy Data ◽  
Columbia River Flood Basalts

Supplemental ArcGIS Shapefiles. Shapefiles for mapped dikes used in maps throughout paper.<br>

scholarly journals Thickness Characteristics of Pāhoehoe Lavas in the Deccan Province, Western Ghats, India, and in Continental Flood Basalt Provinces Elsewhere

2021 ◽  
Vol 8 ◽  
Author(s):  
Stephen Self ◽  
Tushar Mittal ◽  
Anne Elizabeth Jay
Keyword(s):  
Columbia River ◽  
Flood Basalt ◽  
Flow Fields ◽  
Lava Flows ◽  
Basalt Lava ◽  
Continental Flood Basalt ◽  
Quantitative Basis ◽  
Simple Flows ◽  
Lava Morphology ◽  
Central Atlantic

Constraining the eruption rates of flood basalt lava flows remains a significant challenge despite decades of work. One potential observable proxy for eruption rates is flood basalt lava-flow lobe thicknesses, a topic that we tackle here quantitatively. In this study, we provide the first global compilation of pāhoehoe lava-lobe thicknesses from various continental flood basalt provinces (∼ 3,800 measurements) to compare characteristic thicknesses within and between provinces. We refer to thin lobes (∼ ≤5 m), characteristic of “compound” lavas, as hummocky pāhoehoe lava flows or flow-fields. Conversely, we term thicker lobes, characteristic of “simple” flows, as coming from sheet-lobe-dominated flows. Data from the Deccan Traps and Columbia River flood-basalt provinces are archetypal since they have the most consistent datasets as well as established chemo- and litho-stratigraphies. Examining Deccan lobe thicknesses, we find that previously suggested (and disputed) distinct temporal and regional distributions of hummocky pāhoehoe and sheet-lobe-dominated flow fields are not strongly supported by the data and that each geochemically defined formation displays both lobe types in varying amounts. Thin flow-lobes do not appear to indicate proximity to source. The modal lobe thickness of Deccan formations with abundant “thin” lava-lobes is 8 m, while the mode for sheet-lobe-dominated formations is only 17 m. Sheet-lobes up to 75–80 m are rare in the Deccan and Columbia River Provinces, and ones &gt;100 m are exceptional globally. For other flood basalt provinces, modal thickness plots show a prevalence toward similar lobe thicknesses to Deccan, with many provinces having some or most lobes in the 5–8 m modal range. However, median values are generally thicker, in the 8–12 m range, suggesting that sheet-lobes dominate. By contrast, lobes from non-flood basalt flow-fields (e.g., Hawai’i, Snake River Plain) show distinctly thinner modes, sub-5 m. Our results provide a quantitative basis to ascertain variations in gross lava morphology and, perhaps, this will in future be related to emplacement dynamics of different flood basalt provinces, or parts thereof. We can also systematically distinguish outlier lobes (or regions) from typical lobes in a province, e.g., North American Central Atlantic Magmatic Province lava-lobes are anomalously thick and are closely related to feeder-intrusions, thus enabling a better understanding of conditions required to produce large-volume, thick, flood basalt lava-lobes and flows.

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