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Full-Text Articles in Physical Sciences and Mathematics
Geochemistry And Mineralogy Of Late Quaternary Loess In The Upper Mississippi River Valley, Usa: Provenance And Correlation With Laurentide Ice Sheet History, Daniel R. Muhs, E. Arthur Bettis Iii, Gary L. Skipp
Geochemistry And Mineralogy Of Late Quaternary Loess In The Upper Mississippi River Valley, Usa: Provenance And Correlation With Laurentide Ice Sheet History, Daniel R. Muhs, E. Arthur Bettis Iii, Gary L. Skipp
United States Geological Survey: Staff Publications
The midcontinent of North America contains some of the thickest and most extensive last-glacial loess deposits in the world, known as Peoria Loess. Peoria Loess of the upper Mississippi River valley region is thought to have had temporally varying glaciogenic sources resulting from inputs of sediment to the Mississippi River from different lobes of the Laurentide Ice Sheet. Here, we explore a new method of determining loess provenance using K/Rb and K/Ba values (in K-feldspars and micas) in loess from a number of different regions in North America. Results indicate that K/Rb and K/Ba values can distinguish loess originating from …
The Geochemistry Of Loess: Asian And North American Deposits Compared, Daniel R. Muhs
The Geochemistry Of Loess: Asian And North American Deposits Compared, Daniel R. Muhs
United States Geological Survey: Staff Publications
Loess is widely distributed over Asia and North America and constitutes one of the most important surficial deposits that serve as terrestrial records of the Quaternary. The oldest Pleistocene loess in China is likely ∼2.6 Ma, thus spanning much or all of the Pleistocene. In North America, most loess is no older than the penultimate glacial period, with the exception of Alaska, where the record may go back to ∼3.0 Ma. On both continents, loess deposits date primarily to glacial periods, and interglacial or interstadial periods are represented by paleosols. Both glacial and non-glacial sources of silts that comprise the …
Geochemical Evidence For Seasonal Controls On The Transportation Of Holocene Loess, Matanuska Valley, Southern Alaska, Usa, Daniel R. Muhs, James R. Budahn, Gary Skipp, John P. Mcgeehin
Geochemical Evidence For Seasonal Controls On The Transportation Of Holocene Loess, Matanuska Valley, Southern Alaska, Usa, Daniel R. Muhs, James R. Budahn, Gary Skipp, John P. Mcgeehin
United States Geological Survey: Staff Publications
Loess is a widespread Quaternary deposit in Alaska and loess accretion occurs today in some regions, such as the Matanuska Valley. The source of loess in the Matanuska Valley has been debated for more than seven decades, with the Knik River and the Matanuska River, both to the east, being the leading candidates and the Susitna River, to the west, as a less favorable source. We report here new stratigraphic, mineralogic, and geochemical data that test the competing hypotheses of these river sources. Loess thickness data are consistent with previous studies that show that a source or sources lay to …
Loess Records, Daniel R. Muhs, Stephen R. Cattle, Onn Crouvi, Denis-Didier Rousseau, Jimin Sun, Marcelo A. Zárate
Loess Records, Daniel R. Muhs, Stephen R. Cattle, Onn Crouvi, Denis-Didier Rousseau, Jimin Sun, Marcelo A. Zárate
United States Geological Survey: Staff Publications
Loess is aeolian sediment, dominated by silt-sized particles, that is identifiable in the field as a distinct sedimentary body. It covers a significant portion of the land surface of the Earth and as such constitutes one of the most important archives of long-term dust deposition. Large tracts of loess cover Europe, Asia, South America, and North America, and smaller loess bodies are found covering parts of Africa, the Middle East, New Zealand, and Australia. Loess thickness, particle size, and carbonate content decrease downwind from sources, trends that are powerful tools for reconstructing paleowinds. Many loess sections consist of relatively thick …
Radiocarbon Dating Loess Deposits In The Mississippi Valley Using Terrestrial Gastropod Shells (Polygyridae, Helicinidae, And Discidae), Jeffrey S. Pigati, John Mcgeehin, Daniel R. Muhs, David A. Grimley, Jeffrey C. Nekola
Radiocarbon Dating Loess Deposits In The Mississippi Valley Using Terrestrial Gastropod Shells (Polygyridae, Helicinidae, And Discidae), Jeffrey S. Pigati, John Mcgeehin, Daniel R. Muhs, David A. Grimley, Jeffrey C. Nekola
United States Geological Survey: Staff Publications
Small terrestrial gastropod shells (mainly Succineidae) have been used successfully to date late Quaternary loess deposits in Alaska and the Great Plains. However, Succineidae shells are less common in loess deposits in the Mississippi Valley compared to those of the Polygyridae, Helicinidae, and Discidae families. In this study, we conducted several tests to determine whether shells of these gastropods could provide reliable ages for loess deposits in the Mississippi Valley. Our results show that most of the taxa that we investigated incorporate small amounts (1–5%) of old carbon from limestone in their shells, meaning that they should yield ages that …
The Geologic Records Of Dust In The Quaternary, Daniel R. Muhs
The Geologic Records Of Dust In The Quaternary, Daniel R. Muhs
United States Geological Survey: Staff Publications
Study of geologic records of dust composition, sources and deposition rates is important for understanding the role of dust in the overall planetary radiation balance, fertilization of organisms in the world’s oceans, nutrient additions to the terrestrial biosphere and soils, and for paleoclimatic reconstructions. Both glacial and non-glacial processes produce fine-grained particles that can be transported by the wind. Geologic records of dust flux occur in a number of depositional archives for sediments: (1) loess deposits; (2) lake sediments; (3) soils; (4) deep-ocean basins; and (5) ice sheets and smaller glaciers. These archives have several characteristics that make them highly …
Loess Origin, Transport, And Deposition Over The Past 10,000 Years, Wrangell-St. Elias National Park, Alaska, Daniel R. Muhs, James R. Budahn, John P. Mcgeehin, E. Arthur Bettis Iii, Gary Skipp, James B. Paces, Elisabeth A. Wheeler
Loess Origin, Transport, And Deposition Over The Past 10,000 Years, Wrangell-St. Elias National Park, Alaska, Daniel R. Muhs, James R. Budahn, John P. Mcgeehin, E. Arthur Bettis Iii, Gary Skipp, James B. Paces, Elisabeth A. Wheeler
United States Geological Survey: Staff Publications
Contemporary glaciogenic dust has not received much attention, because most research has been on glaciogenic dust of the last glacial period or non-glaciogenic dust of the present interglacial period. Nevertheless, dust from modern glaciogenic sources may be important for Fe inputs to primary producers in the ocean. Adjacent to the subarctic Pacific Ocean, we studied a loess section near Chitina, Alaska along the Copper River in Wrangell-St. Elias National Park, where dust has been accumulating over the past ~10,000 years. Mass accumulation rates for the fine-grained (<20 >µm) fraction of this loess section are among the highest reported for the …20>
The Geologic Records Of Dust In The Quaternary, Daniel R. Muhs
The Geologic Records Of Dust In The Quaternary, Daniel R. Muhs
United States Geological Survey: Staff Publications
Study of geologic records of dust composition, sources and deposition rates is important for understanding the role of dust in the overall planetary radiation balance, fertilization of organisms in the world’s oceans, nutrient additions to the terrestrial biosphere and soils, and for paleoclimatic reconstructions. Both glacial and non-glacial processes produce fine-grained particles that can be transported by the wind. Geologic records of dust flux occur in a number of depositional archives for sediments: (1) loess deposits; (2) lake sediments; (3) soils; (4) deep-ocean basins; and (5) ice sheets and smaller glaciers. These archives have several characteristics that make them highly …
Isotopic Evidence For The Diversity Of Late Quaternary Loess In Nebraska: Glaciogenic And Nonglaciogenic Sources, John N. Aleinikoff, Daniel R. Muhs, E. Arthur Bettis Iii, William C. Johnson, C. Mark Fanning, Rachel Benton
Isotopic Evidence For The Diversity Of Late Quaternary Loess In Nebraska: Glaciogenic And Nonglaciogenic Sources, John N. Aleinikoff, Daniel R. Muhs, E. Arthur Bettis Iii, William C. Johnson, C. Mark Fanning, Rachel Benton
United States Geological Survey: Staff Publications
Pb isotope compositions of detrital K-feldspars and U-Pb ages of detrital zircons are used as indicators for determining the sources of Peoria Loess deposited during the last glacial period (late Wisconsin, ca. 25–14 ka) in Nebraska and western Iowa. Our new data indicate that only loess adjacent to the Platte River has Pb isotopic characteristics suggesting derivation from this river. Most Peoria Loess in central Nebraska (up to 20 m thick) is non-glaciogenic, on the basis of Pb isotope ratios in K-feldspars and the presence of 34-Ma detrital zircons. These isotopic characteristics suggest derivation primarily from the Oligocene White River …
A Late Quaternary Record Of Eolian Silt Deposition In A Maar Lake, St. Michael Island, Western Alaska, Daniel R. Muhs, Thomas A. Ager, Josh Been, J. Platt Bradbury, Walter E. Dean
A Late Quaternary Record Of Eolian Silt Deposition In A Maar Lake, St. Michael Island, Western Alaska, Daniel R. Muhs, Thomas A. Ager, Josh Been, J. Platt Bradbury, Walter E. Dean
United States Geological Survey: Staff Publications
Recent stratigraphic studies in central Alaska have yielded the unexpected finding that there is little evidence for full-glacial (late Wisconsin) loess deposition. Because the loess record of western Alaska is poorly exposed and not well known, we analyzed a core from Zagoskin Lake, a maar lake on St. Michael Island, to determine if a full-glacial eolian record could be found in that region. Particle size and geochemical data indicate that the mineral fraction of the lake sediments is not derived from the local basalt and is probably eolian. Silt deposition took place from at least the latter part of the …
Quaternary Loess-Paleosol Sequences As Examples Of Climate-Driven Sedimentary Extremes, Daniel R. Muhs, E. Arthur Bettis Iii
Quaternary Loess-Paleosol Sequences As Examples Of Climate-Driven Sedimentary Extremes, Daniel R. Muhs, E. Arthur Bettis Iii
United States Geological Survey: Staff Publications
Loess is a widespread, wind-transported, silt-dominated deposit that contains geologic archives of atmospheric circulation and paleoclimate on continents. Loess may cover as much as 10% of the Earth’s land surface. It is composed mainly of quartz, feldspars, and clay minerals, with varying amounts of carbonate minerals. The geochemistry of loess differs from region to region, depending on source materials, but all loess is very high in SiO2 with lesser amounts of other major elements. Trends in loess downwind from source areas include systematic decreases in thickness and amounts of sand and coarse silt, and increases in amounts of fine silt …
Geochemical Variations In Peoria Loess Of Western Iowa Indicate Paleowinds Of Midcontinental North America During Last Glaciation, Daniel R. Muhs, E. Arthur Bettis Iii
Geochemical Variations In Peoria Loess Of Western Iowa Indicate Paleowinds Of Midcontinental North America During Last Glaciation, Daniel R. Muhs, E. Arthur Bettis Iii
United States Geological Survey: Staff Publications
Peoria Loess deposited in western Iowa during the last glacial maximum (LGM) shows distinct geochemical and particle-size variations as a function of both depth and distance east of the Missouri River. Geochemical and particle-size data indicate that Peoria Loess in western Iowa probably had two sources: the Missouri River valley, and a source that lay to the west of the Missouri River. Both sources indicate that LGM paleowinds in western Iowa had a strong westerly component, similar to interpretations of previous workers. A compilation of loess studies in Iowa and elsewhere indicates that westerlv winds were dominant during loess transport …