Glaciology Commons^™

Transition From Contraction To Extension In The Northeastern Basin And Range: New Evidence From The Copper Mountains, Nevada, Jeffrey M. Rahl, Allen J. Mcgrew, Kenneth A. Foland

Department of Earth, Environment and Sustainability Faculty Publications

New mapping, structural analysis, and 40Ar/39Ar dating reveal an unusually well‐constrained history of Late Eocene extension in the Copper Mountains of the northern Basin and Range province. In this area, the northeast‐trending Copper Creek normal fault juxtaposes a distinctive sequence of metacarbonate and granitoid rocks against a footwall of Upper Precambrian to Lower Cambrian quartzite and phyllite. Correlation of the hanging wall with footwall rocks to the northwest provides an approximate piercing point that requires 8–12 km displacement in an ESE direction. This displaced fault slice is itself bounded above by another normal fault (the Meadow Fork Fault), which brings …

Strontium Isotopic Signatures Of The Streams And Lakes Of Taylor Valley, Southern Victoria Land, Antarctica: Chemical Weathering In A Polar Climate, W. B. Lyons, Carmen A. Nezat, Larry V. Benson, Thomas D. Bullen, Elizabeth Y. Graham, Jesicca Kidd, Kathleen A. Welch, James M. Thomas

United States Geological Survey: Staff Publications

We have collected and analyzed a series of water samples from three closed-basin lakes (Lakes Bonney, Fryxell, and Hoare) in Taylor Valley, Antarctica, and the streams that flow into them. In all three lakes, the hypolimnetic waters have different ⁸⁷Sr/⁸⁶Sr ratios than the surface waters, with the deep water of Lakes Fryxell and Hoare being less radiogenic than the surface waters. The opposite occurs in Lake Bonney. The Lake Fryxell isotopic ratios are lower than modern-day ocean water and most of the whole-rock ratios of the surrounding geologic materials. A conceivable source of Sr to the system …

Quartzite Fabric Transition In A Cordilleran Metamorphic Core Complex, Allen J. Mcgrew, Martin Casey

Department of Earth, Environment and Sustainability Faculty Publications

Photomicrographs 143A-143F record fabric variations in quartzite with increasing structural depth in a > 1 km thick, amphibolite-facies, normal-sense shear zone in the East Humboldt metamorphic core complex, Nevada (Figure 143.1). This shear zone and the overlying detachment system unroofed an infrastructure of high-grade, migmatitic gneiss during Oligocene to early Miocene extension (Dallmeyer and others, 1986; Wright and Snoke, 1993; McGrew and Snee, 1994). Thermobarometric constraints from near the base of the mylonitic zone record deformation conditions of 550°- 620°C and 300-400 MPa (Hurlow and others, 1991). Sample WBC6 (l43A and 143B) characterizes the mylonitic zone, whereas sample 8706-1 (143C and …

Lead Isotopes And Selected Metals In Ice From Law Dome, Antarctica, K. J. R. Rosman, W. Chisholm, C. F. Boutron, S. Hong, R. Edwards, Vin Morgan, Peter N. Sedwick

OES Faculty Publications

The isotopic composition. of Pb and the concentrations of Pb, Ba and Bi were measured in selected ice-core samples from Law Dome, East Antarctica, to a depth of 1196 m. The range of concentrations found in decontaminated ice was 0.03-1.5 pg g^-1 for Pb, 0.9-6.1 pg g^-1 for Ba and 0.4-17 fg g^-1 for Bi, excluding the deepest sample which contained ∼1 ppm of rock dust. The abundances of all four stable lead isotopes were measured and gave ²⁰⁶Pb/²⁰⁷Pb ratios ≤ ∼1.23. A value of ²⁰⁸Pb/²⁰⁷Pb = 2.78 was measured in …

Sem Analysis Of Quartz Sand Grain Surface Textures Indicates Alluvial/Colluvial Origin Of The Quaternary "Glacial" Boulder Clays At Huangshan (Yellow Mountain), East-Central China, P. E. Helland, Pei-Hua Huang, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

Geomorphic features and Pleistocene deposits on Huangshan have been attributed to glaciation. Recent reassessment questions this interpretation. As part of the reassessment, quartz sand grains from deposits identified as glacial boulder clays (till composed of boulders in a clay or silt matrix) were analyzed by scanning electron microscope for evidence of their sedimentary history. Surface textures found on the boulder-clay grains were compared with those on grains with known sedimentary histories including glacial, grus, colluvial, and alluvial grains. The analysis shows that the grains lack typical glacial textures. The surface textures present indicate a complex history. Non-uniformly weathered grain surfaces …

A Strategy For Monitoring Glaciers, Andrew G. Fountain, Robert M. Krimmel, Dennis C. Trabant

Geography Faculty Publications and Presentations

Glaciers are important features in the hydrologic cycle and affect the volume, variability, and water quality of runoff. Assessing and predicting the effect of glaciers on water resources require a monitoring program to provide basic data for this understanding. The monitoring program of the U.S. Geological Survey employs a nested approach whereby an intensively studied glacier is surrounded by less intensively studied glaciers and those monitored solely by remote sensing. Ideally, each glacierized region of the United States would have such a network of glaciers. The intensively studied glacier provides a detailed understanding of the physical processes and their temporal …

Grand Tour-Part 2: Petrogenesis And Thermal Evolution Of Deep Continental-Crust: The Record From The East Humboldt Range, Nevada, Allen J. Mcgrew, Mark T. Peters

Department of Earth, Environment and Sustainability Faculty Publications

The northern part of the East Humboldt Range, Nevada, provides a rare opportunity to explore the petrogenetic environment of deep levels in the middle crust during both large-scale Mesozoic contraction and Cenozoic regional extension. On this segment of the field trip, we will explore evidence bearing on the character of the metamorphic and magmatic history of this terrane, and attempt to link these constraints to the rheology and tectonic evolution of the middle crust during the Mesozoic and Cenozoic.

The Grand Tour Of The Ruby-East Humboldt Metamorphic Core Complex, Northeastern Nevada: Part 1-Introduction & Road Log, Arthur W. Snoke, Keith A. Howard, Allen J. Mcgrew, Bradford R. Burton, Calvin G. Barnes, Mark T. Peters, James E. Wright

Department of Earth, Environment and Sustainability Faculty Publications

The purpose of this geological excursion is to provide an overview of the multiphase developmental history of the Ruby Mountains and East Humboldt Range, northeastern Nevada. Although these mountain ranges are commonly cited as a classic example of a Cordilleran metamorphic core complex developed through large-magnitude, mid-Tertiary crustal extension, a preceding polyphase Mesozoic contractional history is also well preserved in the ranges. An early phase of this history involved Late Jurassic two-mica granitic magmatism, high-temperature but relatively low-pressure metamorphism, and polyphase deformation in the central Ruby Mountains. In the northern Ruby Mountains and East Humboldt Range, a Late Cretaceous history …

Nearly Synchronous Climate Change In The Northern Hemisphere During The Last Glacial Termination, Larry V. Benson, James Burdett, Steve Lund, Michaele Kashgarian, Scott Mensing

United States Geological Survey: Staff Publications

The climate of the North Atlantic region underwent a series of abrupt cold/warm oscillations when the ice sheets of the Northern Hemisphere retreated during the last glacial termination (17,700–11,500 years ago). Evidence for these oscillations, which are recorded in European terrestrial sediments as the Oldest Dryas/Bølling/ Older Dryas/Allerød/Younger Dryas vegetational sequence, has been found in Greenland ice cores. The geographical extent of many of these oscillations is not well known, but the last major cold event (the Younger Dryas) seems to have been global in extent. Here we present evidence of four major oscillations in the hydrological balance of the …

Hydrogeology And Stable Isotope Investigations Of A Landfill Impacted Site In Southwest Michigan, Eliot Anong Atekwana

Dissertations

The Cork Street landfill in the City of Kalamazoo is unlined and constructed in glacial drift material. Although water quality in some of the landfill monitoring wells is poor, the degree of the landfill’s influence to groundwater, wetlands and Davis Creek located downgradient of the landfill is unknown. The objective of this study is to evaluate the degree of the landfill’s impact in this region through hydrologic and stable isotope analysis.

Site characterization using geophysical surveys and specific conductance measurements indicates highly conductive shallow groundwater probably attributable to groundwater contamination. Hydrologic evaluation of this region shows that groundwater flows towards …

The Origin And Evolution Of The Southern Snake Range Decollement, East Central Nevada, Allen J. Mcgrew

Department of Earth, Environment and Sustainability Faculty Publications

Regional and local stratigraphic, metamorphic, and structural constraints permit reconstruction of the southern Snake Range extensional deformational system in east central Nevada. The dominant structure of the range, the southern Snake Range décollement (SSRD), operated during Oligocene and Miocene extensional deformation to exhume a footwall of multiply deformed metasedimentary and plutonic rocks. Intrusion of three plutons (∼160 Ma, 79.1 ± 0.5 Ma, and 36 ± 1 Ma, respectively) and development of two cleavages preceded the onset of extensional deformation. Plastic deformation of lower plate metasedimentary rocks accompanied the early phases of regional extension and produced bedding-parallel grain shape foliations and …

First Annual Report On The Geology Of The State Of Maine, Lucius H. Merrill, Edward H. Perkins

Maine Collection

First Annual Report on the Geology of the State of Maine by Lucius H. Merrill, State Geologist and Edward H. Perkins, Assistant Geologist, Augusta, 1930.

Articles: Maine Granites / Report on Feldspar Quarries Visited Aug. 21-24, 1929 / Coal / Petroleum and Natural Gas in Maine / The Minerals of Maine / Minerals of Maine Index, By Mineral Names / Minerals of Maine, Index by Towns / Minerals Found at Bennett's Quarry Buckfield, Maine / List of Minerals Found at Newry, Maine / List of Minerals Found in Rumford, Maine / The Natural History of Maine Minerals (Perkins) / …