Publications
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Climatic and limnologic setting of Elk Lake
Elk Lake is located on the Itasca moraine near the source of the Mississippi River in northwestern Minnesota. The basin is in calcareous glacial drift, and the lake water is a dilute solution of calcium and magnesium bicarbonate. Low-magnesian calcite formed by precipitation from the lake water has been a major component of the sediment throughout the lake’s history. The sediment also is laminated
Authors
R.O. Megard, J. Platt Bradbury, Walter E. Dean
Environment of deposition of CaCO3 in Elk Lake, Minnesota
Elk Lake is near the present forest-prairie border in northwestern Minnesota, and is also located on the boundary between hard-water lakes that are typical of once-glaciated parts of the north-central United States and more saline prairie lakes of western Minnesota and the Dakotas. The sediments of the prairie lakes just west of Elk Lake are unusual in that they commonly contain high-Mg calcite an
Authors
Walter E. Dean, R.O. Megard
Physical properties, mineralogy, and geochemistry of Holocene varved sediments from Elk Lake, Minnesota
Elk Lake in northwestern Minnesota is situated close to a climatically sensitive ecotone, the forest-prairie border, that migrated back and forth over the drainage basin of the lake during the Holocene. The entire postglacial (Holocene) sediment record in the deepest part of Elk Lake is composed of annual layers (varves) that record the seasonal pulses of many sediment components, and, most import
Authors
Walter E. Dean
Sulfidization and magnetization above hydrocarbon reservoirs
Post-depositional iron-sulfide (Fe-S) minerals that are related to hydrocarbon seepage have changed the original magnetizations at Cement oil field (Anadarko basin, Oklahoma), at Simpson oil field (North Slope basin, Alaska), and above deep Cretaceous oil and gas reservoirs, south Texas coastal plain. At Cement, ferrimagnetic pyrrhotite (Fe7S8) formed with pyrite and marcasite in Permian red beds.
Authors
Richard L. Reynolds, Martin B. Goldhaber, Michele L. Tuttle
The potential response of eolian sands to greenhouse warming and precipitation reduction on the Great Plains of the U.S.A.
Sand dunes and sand sheets are extensive on the semi-arid GreatPlains but are at present stabilized by a sparse vegetation cover. Use of a dune mobility index, which incorporates wind strength and the ratio of mean annual precipitation to potential evapotranspiration, shows that under predicted greenhouse climate effects of increased temperature and reduced precipitation, sand dunes and sand sheet
Authors
D.R. Muhs, P.B. Maat
Strontium isotope characterization of the Ash Meadows ground-water system, southern Nevada, USA
No abstract available.
Authors
Zell E. Peterman, John S. Stuckless, Shannon A. Mahan, Brian D. Marshall, E. D. Gutentag, J. S. Downey
Isotopic studies of fracture coatings at Yucca Mountain, Nevada, USA
No abstract available.
Authors
Brian D. Marshall, J. F. Whelan, Zell E. Peterman, Kiyoto Futa, Shannon A. Mahan, John S. Stuckless
U-Th-Pb, Rb-Sr, and Sm-Nd isotopic systematics of lunar troctolitic cumulate 76535: Implications on the age and origin of this early lunar, deep-seated cumulate
No abstract available.
Authors
Wayne R. Premo, M. Tatsumoto
Isotopic ages and characteristics of ancient (pre-Serenitatis) lunar crustal rocks at Apollo 17
No abstract available.
Authors
Wayne R. Premo, M. Tatsumoto
Role of chemical change in the paleomagnetic record
To produce an outline of how either to isolate or capitalize on changes in magnetic properties resulting from chemical changes, the workshop, “Effects of Chemical Changes on Magnetization,” was held in Santa Fe, N. Mex. from August 13 to 16. It was sponsored by the Institute for Rock Magnetism (IRM) in Minneapolis, Minn., and funded by the National Science Foundation. Graduate students and establi
Authors
S. Banerjee, Richard L. Reynolds
Isotopic signatures of black tektites from the K‐T boundary on Haiti: Implications for the age and type of source material
U‐Th‐Pb, Rb‐Sr, and Sm‐Nd isotopic signatures of corroded, but unaltered, black glassy tektites from Cretaceous‐Tertiary (K‐T) boundary rock on Haiti are not consistent with their derivation from an impact on MOR‐derived oceanic crust or continental regions involving middle Proterozoic or older crustal material. Two single‐grain and two batches of these tektites yielded present‐day ∍Nd = −3.0 to −
Authors
Wayne R. Premo, G. A. Izett
Allochthonous impact-shocked rocks and superimposed deformations at the Beaverhead site in southwest Montana
Upward-pointing shatter cones in sandstones of uncertain age (Middle Proterozoic? to Lower Cambrian?) and older crystalline basement rocks are exposed over an area of approximately 25 × 8 km in southwestern Montana. These shatter cones, together with pseudotachylites and breccias of various types (particularly in basement gneisses), are inferred to be products of a meteorite or cometary impact. Ho
Authors
R.B. Hargraves, Karl S. Kellogg, P.S. Fiske, S.B. Hougen