Stratigraphy, correlation, depositional setting, and geophysical characteristics of the Oligocene Snowshoe Mountain Tuff and Creede Formation in two cored boreholes

Larsen, Daniel; Nelson, Philip H.

doi:10.1130/0-8137-2346-9.159

Cited by 5 publications

(5 citation statements)

References 20 publications

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“…Figure 18 shows the same for pelletal limestones from CCM-1. The overall stable isotope systematics at CCM-1 for lacustrine carbonates are very similar to those for the deeper levels of CCM-2, which is not surprising considering the stratigraphic correlations between the two sites by Larsen and Nelson (1994) (see Figure 11). The 813C and 818O values of micrites and pellets from individual thin sections in CCM-1 tend to fall in clusters or show an inverse covariance as in CCM-2.…”

Section: Stable Isotope Systematics For Lacustrine Carbonates From Ccm-2supporting

confidence: 62%

“…Stratigraphic sections of CCM-1 and CCM-2 showing the distribution of the different lacustrine carbonate occurrences are shown in Figure 10. In Figure 10 the two columns have been indexed to the H tuff (of Larsen and Nelson, 1994) to facilitate comparison. Carbonate lamellae are abundant in the sedimentary siltstones to depths of approximately 1560 feet in the CCM-2 core and 935 feet in the CCM-1 core.…”

Section: Description Of Lacustrine Carbonate Occurrences In the Creedmentioning

confidence: 99%

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Preliminary scientific results of the Creede Caldera Continental Scientific Drilling Program: Stable isotope geochemistry of the Creede Formation and implications for the origin of fluids responsible for hydrothermal vein minerals in the Creede mining district

Rye¹,

Bethke²,

Finkelstein³

2001

Open-File Report

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This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product, or firm names in this report is for descriptive purposes only and does not imply endorsement by the U.S. Government. SULFUR ISOTOPE GEOCHEMISTRY Stable isotope systematics of sulfur-bearing vein minerals from the Creede mining district. The main stage sulfides in the veins at Creede are characterized by a narrow range of 534S values (-2±2%o) typical of volcanic or magmatic sulfur in a Tertiary volcanic environment; the vein barites, however, show a very large range of 534S values from about 4 to 44%o (Rye et al., 1988). The aqueous sulfate and sulfide species in the hydrothermal fluids were not in isotopic equilibrium and each sulfur specie was derived from different sources with profoundly different histories. The isotope data on the barites at Creede are so unusual for a hydrothermal deposit in a Tertiary volcanic environment that we have long known that some factor was present at Creede that normally does not exist in such hydrothermal systems. The sulfur and oxygen isotope data on hydrothermal barites are summarized in Figure 2 (Rye et al., 1988). The isotopic composition of the barites varies from north to south in the district with values from the northern mineralized areas being lower in both 534S and 518O. The data fall in a triangle that can best be interpreted as a mixture of three components. The lower apex (518O = 2%0 ; 534S = 1%0) is interpreted as deep sulfate from the hydrothermal system. The right apex (518O = 20 %0 ; 534S = 35 %o) is a critical one; the combination of large sulfur and oxygen values require that the sulfate went through a bacteriogenic reducing cycle in a sedimentary environment, interpreted to be the Creede Formation. The top apex (818O = 8%0 ; 534S = 48 %o) has even larger sulfur but lower oxygen values. Rye et al. (1988) interpreted the top apex to represent sulfate that had evolved by bacteriogenic reduction but had undergone further isotopic evolution by oxygen isotope exchange with ore fluids and thermochemical reduction of sulfate in the presence of organic matter. This further evolution occurred as lake water or Creede Formation pore fluids mixed with deeply circulating ore solutions in the southern part of the district. Bacteriogenic reduction of sulfate in a sedimentary environment produces diagenetic pyrite if iron is available. Therefore, the formation of diagenetic pyrite in the Creede Formation is a requirement of the hypothesis that the hydrothermal sulfate underwent a bacteriogenic cycle in the Lake Creede sediments. The search for such pyrite was one of the principal objectives of the drilling program. Drilling was critical to such a search because Creede Formation rocks exposed at the surface have been oxidized and any diagenetic pyrite removed by weathering. other component was a nearly fresh meteoric water with a 8D of about-110%o and a 818O of about-15%o, respectively. Thes...

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Section: Stable Isotope Systematics For Lacustrine Carbonates From Ccm-2supporting

confidence: 62%

Section: Description Of Lacustrine Carbonate Occurrences In the Creedmentioning

confidence: 99%

Preliminary scientific results of the Creede Caldera Continental Scientific Drilling Program: Stable isotope geochemistry of the Creede Formation and implications for the origin of fluids responsible for hydrothermal vein minerals in the Creede mining district

Rye¹,

Bethke²,

Finkelstein³

2001

Open-File Report

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“…The Creede flora was deposited within the Creede caldera, the youngest of seven calderas nested within La Garita (Lipman, 2000). The history of the Oligocene Lake Creede (Bethke and Hay, 2000;Larsen and Lipman, 2016) provides data on paleolimnology based in part on two drill cores penetrating >700 m through the caldera lake deposits (Larsen and Nelson, 2000). The depth of the lake fluctuated at times by tens of meters, with waters variously saturated with carbonates and saline mixtures (Larsen and Lipman, 2016).…”

Section: Regional Geological Setting Of the Five Paleogene Floras In mentioning

confidence: 99%

Pollen evidence of floristic turnover forced by cool aridity during the Oligocene in Colorado

Leopold

Zaborac-Reed

2019

Geosphere

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New pollen data from four Oligocene floras in volcanic landscapes of Colo rado record important climatic shifts that reshaped the local flora and promoted the development of subarid vegetation types. We combined new pollen data with previous megafossil evidence to assess vegetation changes during the Eocene-Oligocene Transition (EOT). Pollen data are the basis for updating the list of flora identified at Creede. Local extinctions in response to lower sum mer rainfall abruptly removed many of the exotic woody taxa of eastern North American and Asian affinity. This loss was followed by the appearance of xeric shrubland taxa of the Ponderosa pinefir woodland and sagebrush flora that characterize the Colorado area today. Telltale genera appear and suggest an understory of shrubs such as Artemisia, Elaeagnus, Ribes, Ephedra, Jamesia, and Shepherdia. Poaceae are also present. Significantly, herbaceous taxa of the Asteraceae, Rosaceae, Cucurbitaceae, Euphorbiaceae, and Caryophyllaceae make their first appearances in the fossil record of Colorado here. The new Oligocene pollen data record a significant drop in summer rainfall and a climatic cooling at 33.8 Ma of several degrees that relates to the Oi1 glaciation in Antarctica. The particular taxa that continued after the EOT were a basis for estimating changes in soil moisture during this time. The condi tions in Colorado are reminiscent of Wolfe's "terminal Eocene event." This re markable shift precipitated the development of a local pollen and megafossil flora more "modern" in aspect (e.g., a larger proportion of extant local genera are present). The impressive floristic turnover was probably a response to the increasingly continental climate that embraced the area during the Oligocene.

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“…Creede Formation.-Sedimentary deposits that accumulated within the caldera basin have been well described (Emmons and Larsen, 1923;Steven and Ratté, 1965;Crossey, 1996, 2000;Finkelstein and others, 1999;Heiken and others, 2000;Larsen and Nelson, 2000;Larsen and Lipman, 2016). These deposits consist largely of finely laminated shale and sandstone that represent shallow-to deep-water deltaic and lake deposits in the central moat, and alluvial slope wash, fanglomerate, and stream conglomerates and sandstones along margins of the caldera and resurgently uplifted core.…”

Section: Postcaldera Sedimentation and Volcanismmentioning

confidence: 98%

Field-trip guide to continental arc to rift volcanism of the southern Rocky Mountains—Southern Rocky Mountain, Taos Plateau, and Jemez Mountains volcanic fields of southern Colorado and northern New Mexico

Thompson¹,

Turner²,

Lipman³

et al. 2022

Scientific Investigations Report

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Stratigraphy, correlation, depositional setting, and geophysical characteristics of the Oligocene Snowshoe Mountain Tuff and Creede Formation in two cored boreholes

Cited by 5 publications

References 20 publications

Preliminary scientific results of the Creede Caldera Continental Scientific Drilling Program: Stable isotope geochemistry of the Creede Formation and implications for the origin of fluids responsible for hydrothermal vein minerals in the Creede mining district

Preliminary scientific results of the Creede Caldera Continental Scientific Drilling Program: Stable isotope geochemistry of the Creede Formation and implications for the origin of fluids responsible for hydrothermal vein minerals in the Creede mining district

Pollen evidence of floristic turnover forced by cool aridity during the Oligocene in Colorado

Field-trip guide to continental arc to rift volcanism of the southern Rocky Mountains—Southern Rocky Mountain, Taos Plateau, and Jemez Mountains volcanic fields of southern Colorado and northern New Mexico

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