Geologic map of the Ennis 30' x 60' quadrangle, Gallatin and Madison Counties, Montana

Kellogg, Karl S.; Williams, V.S.

doi:10.3133/ofr97851

Cited by 8 publications

(16 citation statements)

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“…The Northern Madison Range is a~50 km long NW-SE trending basement-cored uplift exhumed along the Laramide-aged steeply dipping Spanish Peaks Fault, which was last active during the Late Cretaceous (Figure 1b; Garihan, Schmidt, Young, & Williams, 1983;Kellogg & Harlan, 2007). The Precambrian rocks coring the range are 3.3-2.7 Ga granitoid orthogneiss (Weyand, 1989) with intercalated quartzite, metasedimentary schist, local ultramafic units and several generations of mafic dykes (Ault et al, 2012;Condit et al, 2015;Kellogg & Williams, 2000;Vuke, 2013;Vuke et al, 2002). At least the northwestern two-thirds of the range was strongly affected by Late Palaeoproterozoic high-grade thermotectonism (~0.8-1.2 GPa, 700-800°C, Ault et al, 2012;Condit et al, 2015), during the later portions of the Big Sky orogeny (1.75-1.71 Ga).…”

Section: Northern Madison Range and Gallatin Canyonmentioning

confidence: 99%

“…These dykes are sparse but several are shown on regional maps (e.g. Kellogg & Williams, 2000). The next youngest mafic dykes occur in the nearby Tobacco Root Mountains, located directly to the west of the Northern Madison Range, where one deformed dyke metamorphosed to granulite facies (Grt+CpxAEOpx+Hbl+Pl+Qz+Ilm; all mineral abbreviations after Whitney & Evans, 2009) crystallized at 2.06 Ga (Mueller et al, 2004).…”

Section: Mafic Dyke Generationsmentioning

confidence: 99%

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Fracturing, fluid flow and shear zone development: Relationships between chemical and mechanical processes in Proterozoic mafic dykes from southwestern Montana, USA

Condit

Mahan

2017

Journal Metamorphic Geology

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Fluids can play an important role in the localization of deformation in the deep crust, yet the specific mechanisms active during the complex interactions between metasomatism, metamorphism and deformation remain elusive. Precambrian metagabbronorite dykes in southwest Montana contain fractures filled with Hbl±Grt and discrete cm‐scale shear zones with well‐preserved strain gradients. This system offers an ideal opportunity to constrain the chemical and mechanical processes that facilitated strain localization. An early M1 assemblage of Grt1+Cpx1+Pl1+Qz developed at conditions of 0.51–0.85 GPa and 500–700°C and is preserved largely as a static replacement of relict igneous phases (Opx, Pgt, Pl) in coronitic textures. An M2 assemblage characterized by Grt2+Pl2±Cpx2+Hbl+Scp+Qz developed at 0.86–1.00 GPa and 660–730°C coincided with fluid flow and deformation associated with shear zone development. Microstructural observations in marginal protomylonite/mylonite and laminated ultramylonite suggest a shear zone evolution that involved (1) nucleation from pre‐existing fractures that were sites for major fluid infiltration, (2) initial widening coincident with grain‐size reduction by microfracturing, dislocation creep, and synkinematic metamorphic reaction by solution transfer, and (3) a switch in the dominant deformation mechanisms active in the ultramylonite from grain‐size insensitive mechanisms to grain‐size sensitive granular flow accommodated by fluid‐assisted diffusion. Throughout this evolution, the effective bulk compositions of the rock volumes responding to metamorphism changed through a combination of mechanical and metasomatic processes.

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Section: Northern Madison Range and Gallatin Canyonmentioning

confidence: 99%

Section: Mafic Dyke Generationsmentioning

confidence: 99%

Fracturing, fluid flow and shear zone development: Relationships between chemical and mechanical processes in Proterozoic mafic dykes from southwestern Montana, USA

Condit

Mahan

2017

Journal Metamorphic Geology

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“…Septic locations were mapped by masking the Big Sky Water and Sewer District boundary GIS layer over a 2006 structure layer supplied by the Gallatin County Planning District. Geologic maps, acquired from the Montana Bureau of Mines and Geology [Kellog and Williams, 2005] were used to determine the percent geology with higher potential for N weathering in each reach contributing area (Ackerman-Montross et al, manuscript in preparation, 2011). LULC and terrain characteristics were then extracted as variables in BiSN.…”

Section: Land Cover Analysismentioning

confidence: 99%

Quantifying watershed sensitivity to spatially variable N loading and the relative importance of watershed N retention mechanisms

Gardner

McGlynn

Marshall

2011

Water Resources Research

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[1] The link between watershed nitrogen (N) loading and watershed nitrate (NO 3 À ) export is poorly understood yet critical to addressing the growing global problem of watershed N enrichment. We introduce the Big Sky nutrient export model (BiSN) which incorporates spatial stream water chemistry, data from instream tracer additions and geologic weathering experiments, and terrain and land use analysis to quantify the spatial variability of watershed sensitivity to N loading and the relative importance of upland, riparian, and instream N retention (storage, removal, or transformation) across land use/land cover (LULC) and landscape positions. Bayesian Markov chain Monte Carlo (MCMC) methods were used for model specification and were helpful in assessing model and parameter uncertainty and advancing understanding of the primary processes governing watershed NO 3 À export. Modeling results revealed that small amounts of wastewater loading occurring in watershed areas with short travel times to the stream had disproportionately large impacts on watershed nitrate (NO 3 À ) export compared to spatially distributed N loading or localized N loading in watershed areas with longer travel times. In contrast, spatially distributed N inputs of greater magnitude (terrestrial storage release and septic systems) had little influence on NO 3

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“…16. Kellogg, K.S., and Williams, V.S., 2000, Geologic map of the Ennis 30'×60' quadrangle, Madison and Gallatin Counties, Montana, and Park County, Wyoming: U.S. Geological Survey Geologic Investigations Series I-2690, scale 1:100,000.…”

Section: ____________________________________________________________mentioning

confidence: 99%

Earth science studies in support of public policy development and land stewardship — Headwaters Province, Idaho and Montana

Lund¹

2007

Circular

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Geologic map of the Ennis 30' x 60' quadrangle, Gallatin and Madison Counties, Montana

Cited by 8 publications

References 0 publications

Fracturing, fluid flow and shear zone development: Relationships between chemical and mechanical processes in Proterozoic mafic dykes from southwestern Montana, USA

Fracturing, fluid flow and shear zone development: Relationships between chemical and mechanical processes in Proterozoic mafic dykes from southwestern Montana, USA

Quantifying watershed sensitivity to spatially variable N loading and the relative importance of watershed N retention mechanisms

Earth science studies in support of public policy development and land stewardship — Headwaters Province, Idaho and Montana

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