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Articles 31 - 60 of 94
Full-Text Articles in Geology
The Distribution Of Naturally Occurring Soil Radionuclides And Radon Potential Of Northwest Oregon, Stuart Graham Ashbaugh
The Distribution Of Naturally Occurring Soil Radionuclides And Radon Potential Of Northwest Oregon, Stuart Graham Ashbaugh
Dissertations and Theses
Radon, a naturally occurring radioactive gas produced as one of the decay products of soil/rock uranium and thorium, is considered to be a leading cause of pulmonary disease. Gamma spectrometry of 146 samples of soil were used to quantify radon source potential relative to lithology by measuring Bi214 activity of the U238 decay series. Additional soil radio nuclide data (Th232, Ac228, K40 and C137 ) were used to help identify regional source provenance geochemistry and soil development. Ac228, Bi214 and Th232 activities in northwest Oregon soils range from five …
A Hydrologic Analysis Of Government Island, Oregon, Scott Gregory Bittinger
A Hydrologic Analysis Of Government Island, Oregon, Scott Gregory Bittinger
Dissertations and Theses
Government Island, located in the Columbia River approximately 16 km (10 mi) upstream of the confluence with the Willamette River, is a wetland mitigation site prompted by expansion of the southwest quadrant of Portland International Airport. The purpose of the study is to predict water levels in two enclosed lowland areas, Jewit Lake and Southeast Pond, based on levels of the Columbia River, precipitation, and evapotranspiration. Mitigation is intended to convert 1.13 km2 (237 acres) of seasonally flooded wetland to 1.27 km2 (267 acres) of semi-permanently flooded wetland and seasonally flooded wetland.
Flooding of the wetland is most …
Analysis Of Perched Groundwater Bodies Beneath The Radioactive Waste Management Complex At The Idaho National Engineering Laboratory, Alan V. Jones
Analysis Of Perched Groundwater Bodies Beneath The Radioactive Waste Management Complex At The Idaho National Engineering Laboratory, Alan V. Jones
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
The migration of radionuclides and volatile chemicals through a thick sequence of unsaturated basalts and sedimentary interbeds has been documented in the Subsurface Disposal Area (SDA) at the Radioactive Waste Management Complex (RWMC) of the Idaho National Engineering Laboratory (INEL). The three mechanisms by which this migration may have occurred are seasonal infiltration from the ground surface within the SDA; flood events in 1962, 1969, and 1982; and the lateral movement of water from the spreading areas located nearby. It is currently thought that the contaminants migrated through the unsaturated sediments and basalt flows during the three flood events.
Transducers …
Groundwater And Surface-Water Interactions Along Lower Medano Creek, Great Sand Dunes National Monument, Colorado, Gregg L. Hadlock
Groundwater And Surface-Water Interactions Along Lower Medano Creek, Great Sand Dunes National Monument, Colorado, Gregg L. Hadlock
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
The objectives of this investigation are as follows: 1) review the existing hydrogeologic data for the San Luis Valley, the Great Sand Dunes Monument, and Medano Creek; 2) review the surface-water data that have been collected on Medano Creek; 3) collect or review previously collected water-level data obtained in the area of lower Medano Creek and correlate them with the surface-water data; 4) conduct constant-head permeameter tests on sand samples collected near the ground surface along lower Medano Creek; 5) produce a conceptual model of lower Medano Creek; and 6) produce a numerical model of lower Medano Creek that will …
Late Quaternary Glacial Geology, Shoreline Morphology, And Tephrochronology Of The Lliamna/Naknek/Brooks Lake Area, Southwestern Alaska, Karen B. Stilwell
Late Quaternary Glacial Geology, Shoreline Morphology, And Tephrochronology Of The Lliamna/Naknek/Brooks Lake Area, Southwestern Alaska, Karen B. Stilwell
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
This study focuses on the late-Wisconsin Brooks Lake glaciation, lake-level fluctuations, and volcanic deposits in the lliamna/Naknek/Brooks Lake area on the northern Alaska Peninsula, southwestern Alaska. The Brooks Lake glaciation consists of five stades, from youngest to oldest: Kvichak, Iliamna, Newhalen, Iliuk, and Ukak. This thesis reassigns the type Mak Hill moraine to a pre-late-Wisconsin glaciation, and considers the moraine enclosing Naknek Lake an early-late-Wisconsin deposit correlative to either the Kvichak stade, lliamna stade, or both. The presence in the Iliamna Lake valley, and the absence in the Naknek Lake valley of a two-fold earliest-late-Wisconsin Kvichak/Iliamna glacial sequence suggest that …
The Quaternary Geology Of The Eastern Side Of The Greys River Valley And The Neotectonics Of The Greys River Fault In Western Wyoming, L. C. Allen Jones
The Quaternary Geology Of The Eastern Side Of The Greys River Valley And The Neotectonics Of The Greys River Fault In Western Wyoming, L. C. Allen Jones
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
The Greys River fault is the easternmost active normal fault associated with Basin and Range extension in the lntermountain seismic belt. It is a north-south trending normal fault, located in the Sevier-age fold and thrust belt of western Wyoming, and bounds the west side of the Wyoming Range. The fault is at least 54 km long, and juxtaposes Permo-Pennsylvanian Wells Formation against various Triassic formations. Throw ranges from 100-1000 m. Seismic reflection data suggest that the Greys River fault is a listric normal fault that soles into the Darby thrust at depth. The fault offsets late Quaternary deposits on the …
An Understanding Of Factors Controlling Isotopic Ratios Of Wine As A Potential Surrogate Of Past Precipitation, Eric Alan Caldwell
An Understanding Of Factors Controlling Isotopic Ratios Of Wine As A Potential Surrogate Of Past Precipitation, Eric Alan Caldwell
UNLV Theses, Dissertations, Professional Papers, and Capstones
Precipitation, vapor water, ground water, soil water, grape berry and grape leaf water, grape must, and vintage wines were collected from northern California for stable isotopic analysis. An understanding of factors controlling isotopic ratios of wine allows evaluation of wine as a surrogate of past precipitation. Stable isotopic compositions of grape berry waters collected at Charles Krug Winery in Napa Valley. CA range from -31 to -17 per mil in 8D and +7.2 to +15.3 per mil in 8180, and plot along a transpiration line of slope 2. 7. Grape leaf waters range from -25 to +5 per mil in …
A Petrographic And Fluid Inclusion Study Of The Purple Vein And Post/Betze Orebodies, Carlin, Nevada, Jan B. Lamb
A Petrographic And Fluid Inclusion Study Of The Purple Vein And Post/Betze Orebodies, Carlin, Nevada, Jan B. Lamb
UNLV Theses, Dissertations, Professional Papers, and Capstones
The Purple Vein (Meikle Mine) and Post/Betze orebodies, two Carlin-type, gold deposits, display important differences in size, alteration, silicification, pyritization, and gold grade. A core hole was examined from each deposit to gather petrographic and microthermometric data to determine the mineral paragenesis, to determine fluid pressure, temperature, and composition to compare of the two orebodies, and to determine depths of formation.
The parageneses determined were divided into three stages. (1) The Early Mineralization Stage contains quartz, pyrobitumen, barite, sphalerite, sulfosalts, quartz, and pyrite in the Purple Vein deposit and consists of calcite in the Post/Betze deposit. High salinity basinal brines, …
Geology Of The Ogallala/High Plains Regional Aquifer System In Nebraska: Field Trip No. 6, Robert F. Diffendal Jr.
Geology Of The Ogallala/High Plains Regional Aquifer System In Nebraska: Field Trip No. 6, Robert F. Diffendal Jr.
Robert F. Diffendal, Jr., Publications
This guide is mostly figures with a reference section containing some of the pertinent literature on the Cenozoic geology we will see over the next four days. We will make all 17 stops if the weather is reasonably good and the roads are passable. On the first day, April 29, we will try to get to stops 1–5, the more distal parts of the Ogallala and younger deposits in Nebraska. On April 30, we will try to visit stops 6–9. Stops 10–15, in areas closer to the sediment sources of the Ogallala and some of the younger units, will be …
A Feasibility Study For Using Computerized Water Well Records To Delineate Areas Of Recharge-Discharge Potential, Lauren D. Hughes
A Feasibility Study For Using Computerized Water Well Records To Delineate Areas Of Recharge-Discharge Potential, Lauren D. Hughes
Masters Theses
A method for delineating areas of recharge-discharge potential has been developed utilizing computerized water well records. The methodology is based on the vertical head differences found between wells with shallow depths of submergence and those with deeper depths of submergence. The residual values generated represent the magnitude of vertical potential and can be contoured to delineate areas of recharge-discharge potential. Well data were obtained from the Kalamazoo County Groundwater Database. Well selection was based on depth of submergence and total well depth.
The methodology was tested in Texas and Schoolcraft Townships, the Donnell Lake Study Area, and Kalamazoo County. Regularly …
Geophysical Investigation At The Mouth Of The St. Joseph River Valley And Adjacent Lake Michigan Shoreline In St. Joseph And Benton Harbor, Michigan, David L. Seng
Masters Theses
A combination of geophysical methods were employed in an attempt to characterize a small section of the shoreline of the St. Joseph, Michigan, region of the Lake Michigan shoreline. Electrical resistivity and Ground Penetrating Radar profiles conducted along the shoreline and within the nearshore environment reveal a buried valley of the ancestral St. Joseph river. This valley represents incision of the channel during lowered lake levels at the end of the Pleistocene.
Lakeward dipping radar reflectors are identified throughout the study site. Within the buried valley the reflectors are not glacial till as is the case outside the inferred valley …
Hydrogeochemical Delineation Of A Groundwater Flow System, Berrien County, Michigan, Patrick J. Bartnik
Hydrogeochemical Delineation Of A Groundwater Flow System, Berrien County, Michigan, Patrick J. Bartnik
Masters Theses
The objective of this study was to examine the possibility of determining groundwater flow directions from natural variations in groundwater chemistry. Groundwater samples were analyzed for major cation and anion concentrations. These data were to have been contoured and then compared with groundwater flow maps generated by conventional methods. The purpose was to determine whether a correlation could be drawn between the two methods. However, the results of the study did not allow for this comparison.
The plotted major cation and anion data did not lend themselves to contouring, which suggests that greater control may be required during the selection …
Vertical Resolution Of A Seismic Survey In Stratigraphic Sequences Less Than 100 M Deep In Southeastern Kansas, Richard Daniel J. Miller, Neil Lennart Anderson, Howard Randall Feldman, Evan K. Franseen
Vertical Resolution Of A Seismic Survey In Stratigraphic Sequences Less Than 100 M Deep In Southeastern Kansas, Richard Daniel J. Miller, Neil Lennart Anderson, Howard Randall Feldman, Evan K. Franseen
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
A 400-m long, 12-fold high-resolution common depth point (CDP) reflection seismic profile was acquired across shallow converging Pennsylvanian strata in the Independence area of southeastern Kansas. One of the principal objectives was to determine practical vertical resolution limits in an excellent shallow seismic-data area with borehole control. The dominant frequency of the CDP stacked data is in excess of 150 Hz based on peak-to-peak measurements. Interference phenomena observed on stacked seismic data incorporated with models derived from log and drill-hole information suggest a practical vertical resolution limit of about 7 m, or one-third of the dominant wavelength. The data suggest …
Sks Splitting Beneath Southern California, Kelly H. Liu, Paul M. Davis, Stephen S. Gao
Sks Splitting Beneath Southern California, Kelly H. Liu, Paul M. Davis, Stephen S. Gao
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Measurements of SKS phase splitting were obtained from nineteen seismic stations in southern California. The fast polarization directions are 53° at the southern end of the Great Valley, 82 ± 8° in the western Transverse Ranges and northern Peninsular Ranges, 95 ± 4° in Mojave Desert, and 70° on San Clemente Island. The splitting time ranges from 0.8 to 1.8 seconds, which is consistent with an anisotropic layer of 100 to 200 km thick for 4% anisotropy.
Late Cretaceous Foraminifera As Indicators Of Sequence Boundaries, Book Cliffs, Utah, U.S.A., Kimberly A. Smith
Late Cretaceous Foraminifera As Indicators Of Sequence Boundaries, Book Cliffs, Utah, U.S.A., Kimberly A. Smith
OES Theses and Dissertations
Foraminiferal assemblages were described from three different depositional settings within the Upper Cretaceous (Campanian) Blackhawk Formation of Utah (known marginal marine environments, known marine environments, and along a suspected sequence boundary). Assemblages from the known marginal marine setting (as defined by sedimentologic-stratigraphic criteria) consisted of entirely agglutinated taxa dominated by Textularia sp. A. Assemblages from the known marine environment consisted of a mix of calcareous and agglutinated species, dominated by calcareous species (e.g., Gavelinella talaria). The foraminiferal assemblages from these known environments provide independent evidence that these sampled areas are characterized by marginal marine and fully marine deposits.
The foraminiferal …
Task Ii Completion Report: Independent Groundwater Characterization And Monitoring Program In Boyd County
Conservation and Survey Division: Faculty and Staff Publications
No abstract provided.
A Search For The Seasonal Variability On The Depositional Fluxes Of 7Be And 210Pb, M. Baskaran
A Search For The Seasonal Variability On The Depositional Fluxes Of 7Be And 210Pb, M. Baskaran
Environmental Science and Geology Faculty Research Publications
Investigations of the atmospheric fallout of 7Be and 210Pb in many places around the globe indicate that there are seasonal variations on the depositional fluxes of these nuclides: high in winter in a few places, while in most places the high occurs in spring. However, these earlier studies did not address quantitatively the corresponding seasonal variations of the amount of precipitation during these periods. Data on the depositional fluxes of 7Be and 210Pb in Galveston, Texas, during the years 1989–1991 indicate that the seasonal variation is not uniform from year to year, and the amount of …
1995, Spatial And Temporal Variability Of Late Neogene Equatorial Pacific Carbonate, T. K. Hagelberg, Nicklas G. Pisias, Larry A. Mayer, N. J. Shackleton, Alan C. Mix
1995, Spatial And Temporal Variability Of Late Neogene Equatorial Pacific Carbonate, T. K. Hagelberg, Nicklas G. Pisias, Larry A. Mayer, N. J. Shackleton, Alan C. Mix
Affiliate Scholarship
High-resolution, continuous records of GRAPE wet bulk density (a carbonate proxy) from Ocean Drilling Program Leg 138 provide one the opportunity for a detailed study of eastern equatorial Pacific Ocean carbonate sedimentation during the last 6 m.y. The transect of sites drilled spans both latitude and longitude in the eastern equatorial Pacific from 90° to 110°W and from 5°S to 10°N. Two modes of variability are resolved through the use of Empirical Orthogonal Function (EOF) analysis. In the presence of large tectonic and climatic boundary condition changes over the last 6 m.y., the dominant mode of spatial variability in carbonate …
Seismic Stratigraphy Of The Eastern Equatorial Pacific Ocean: Paleoceanographic Implications, Stephen F. Bloomer, Larry A. Mayer, Ted C. Moore Jr
Seismic Stratigraphy Of The Eastern Equatorial Pacific Ocean: Paleoceanographic Implications, Stephen F. Bloomer, Larry A. Mayer, Ted C. Moore Jr
Affiliate Scholarship
The collection of Leg 138 well-log and shipboard physical-property data, in conjunction with high-resolution seismic profiles, provides an opportunity to understand the paleoceanographic significance of seismic reflectors and to gain insight into the paleoceanographic evolution of the eastern equatorial Pacific Ocean. A series of eight reflectors or reflector packages were traced between two transects connecting five Leg 138 sites. By generating synthetic seismograms at each of these sites and comparing these to the field records, the origin of these seismic reflectors was determined in terms of physical-property variations and other core measurements. In particular, these reflectors were usually associated with …
Paleoceanography Of The Eastern Equatorial Pacific During The Neogene: Synthesis Of Leg 138 Drilling Results, Nicklas G. Pisias, Larry A. Mayer, Alan C. Mix
Paleoceanography Of The Eastern Equatorial Pacific During The Neogene: Synthesis Of Leg 138 Drilling Results, Nicklas G. Pisias, Larry A. Mayer, Alan C. Mix
Affiliate Scholarship
The primary objective of Leg 138 was to provide detailed information about the ocean's response to global climate change during the Neogene. Two north-south transects were drilled (95° and 110°W) within the region of equatorial divergence-driven upwelling (and thus high accumulation rates and resolution) and spanning the major equatorial ocean current boundaries (and thus recording a high-amplitude signal of the response of the sediment to climatically and/or tectonically driven changes in ocean circulation). The Neogene is marked by a number of well-known climatic and tectonic events (the closing of the Isthmus of Panama, the onset of North Atlantic Deep Water …
Hydrocarbons And Mineral Resources Of The Uinta Basin, Utah And Colorado, United States Department Of The Interior, Indian Affairs Bureau
Hydrocarbons And Mineral Resources Of The Uinta Basin, Utah And Colorado, United States Department Of The Interior, Indian Affairs Bureau
Mines and Mineral Resources
The Uinta Basin holds special fascination for economic geologists because of its rich and diverse assemblage of mineral and hydrocarbon resources. Due to their presence in rocks of the basin, much effort has been put into assessing and exploiting uranium, phosphate, gold, copper, coal, and evaporite minerals. However, the basin is probably best noted for its extensive and very rich accumulations of hydrocarbons such as, oil, gas, bituminous sandstones, oil shale (shale oil), and gilsonite and other solid and semi-solid hydrocarbon species. More importantly, several of these commodities have proven to be a major source of wealth and resources for …
Bones Of Puffinus Lherminieri Lesson (Aves: Procellaridae) And Two Other Vertebrates From Cueva Del Agua, Mona Isalnd, Puerto Rico (West Indies), Angel M. Nieves-Rivera, John M. Mylroie, Donald A. Mcfarlane
Bones Of Puffinus Lherminieri Lesson (Aves: Procellaridae) And Two Other Vertebrates From Cueva Del Agua, Mona Isalnd, Puerto Rico (West Indies), Angel M. Nieves-Rivera, John M. Mylroie, Donald A. Mcfarlane
WM Keck Science Faculty Papers
From a dive in Cueva del Agua, Mona Island, Puerto Rico, twelve un-mineralized bones of Puffinus Lherminieri Lesson, one of Cyclura stejnegeri Stejneger, and one of Moormops blainvilii Leach were collected. The subfossil evidence confirms that P. Lherminieri was a common species on Mona Island. Cyclura stejnegeri and M. blainvilii probably became trapped and died in the pool chamber.
Geomorphic And Geochemical Evidence For The Source Of Sand In The Algodones Dunes, Colorado Desert, Southeastern California, Daniel R. Muhs, Charles A. Bush, Scott D. Cowherd, Shannon Mahan
Geomorphic And Geochemical Evidence For The Source Of Sand In The Algodones Dunes, Colorado Desert, Southeastern California, Daniel R. Muhs, Charles A. Bush, Scott D. Cowherd, Shannon Mahan
United States Geological Survey: Staff Publications
The Algodones dunes of southeastern California comprise one of the largest active dune fields in the United States. The source of sand of the Algodones dunes is controversial, and the source of stabilized aeolian sand in the adjacent East Mesa area has not been investigated at all. We used mineralogical compositions and trace element concentrations to ascertain the most likely source of sand for these active and stabilized dunes. Results indicate that alluvium derived from the San Bernardino Mountains, which enters the Salton trough to the northwest of the dune fields, and alluvium derived from the Chocolate Mountains, which is …
Source Of The Northeastern Idaho Batholith: Isotopic Evidence For A Paleoproterozoic Terrane In The Northwestern U.S., Paul A. Mueller, Robert Duncan Shuster, K. A. D'Arcy, A. L. Heatherington, A. P. Nutman, I. S. Williams
Source Of The Northeastern Idaho Batholith: Isotopic Evidence For A Paleoproterozoic Terrane In The Northwestern U.S., Paul A. Mueller, Robert Duncan Shuster, K. A. D'Arcy, A. L. Heatherington, A. P. Nutman, I. S. Williams
Geography and Geology Faculty Publications
The northeastern portion of the Idaho batholith (NIB) intruded Proterozoic rocks of the Belt-Purcell supergroup between SO and 90 Ma. Whole-rock Sm-Nd isotopic analyses of batholithic rocks yield depleted mantle model ages (T oM) between 1. 72 and 1.93 Ga and values of eNd between -17. 7 and - 21.2, similar to associated metamorphic rocks and within the range for Belt-Purcell sedimentary rocks. Premagmatic zircons from one sample of the NIB were analyzed individually using the SHRIMP ion microprobe and yielded a single age population at 1.74 Ga. This apparently single-aged source contrasts with the range of ages reported for …
Geologic Map Of Morrill County, Nebraska, James B. Swinehart, Robert F. Diffendal Jr.
Geologic Map Of Morrill County, Nebraska, James B. Swinehart, Robert F. Diffendal Jr.
Robert F. Diffendal, Jr., Publications
Morrill County, Nebraska, is perhaps the most geologically interesting county in the panhandle of Nebraska. Surficial deposits of alluvium, colluvium, loess, and eolian sand of Quaternary age cover large parts of the county. Holocene and latest Pleistocene(?) eolian sand as much as 150 It thick covers much of the area north of North Platte Valley and mantles Quaternary alluvial deposits to the south. A thin veneer of loess overlies bedrock in the uplands of the southern part of the county. Alluvium underlies the valley floors and caps river and stream terraces. Two units of older Quaternary alluvium are exposed in …
Bermuda Solution Pipe Soils: A Geochemical Evaluation Of Eolian Parent Materials, Stanley R. Herwitz, Daniel R. Muhs
Bermuda Solution Pipe Soils: A Geochemical Evaluation Of Eolian Parent Materials, Stanley R. Herwitz, Daniel R. Muhs
United States Geological Survey: Staff Publications
Solution pipes found in the Quaternary eolian and marine carbonates of Bermuda are filled with reddish to reddish-brown soil material. The bulk of the soil is composed of clay and silt-sized quartz and aluminosilicate clay minerals. The carbonates are of high purity and, therefore, are not likely to have been the parent material. Previous workers have hypothesized that Saharan dust may have been the soil parent material. The fine-grained component of loess from the Mississippi River Valley of North America also could have contributed. Paleoclimate models indicate that both North Africa and North America could have been important source areas …
Resource News-Summer 1995
Conservation and Survey Division: Faculty and Staff Publications
No abstract provided.
Organic Facies And Maturation Of Jurassic/Cretaceous Rocks, And Possible Oil-Source Rock Correlation Based On Pyrolysis Of Asphaltenes, Scotian Basin, Canada, Prasanta K. Mukhopadhyay, John A. Wade, Michael A. Kruge
Organic Facies And Maturation Of Jurassic/Cretaceous Rocks, And Possible Oil-Source Rock Correlation Based On Pyrolysis Of Asphaltenes, Scotian Basin, Canada, Prasanta K. Mukhopadhyay, John A. Wade, Michael A. Kruge
Department of Earth and Environmental Studies Faculty Scholarship and Creative Works
This paper establishes source rock characterization and oil-oil and oil-source rock correlations of selected organic-rich shale source rocks and selected light oils and condensates from Jurassic and Cretaceous formations of the Scotian Basin. Multiple source rocks of Kerogen Types IIA (oil-prone), IIA-IIB (oil- and condensate-prone), IIB (condensate and gas prone), III (gas-prone), and IV (nonsource) are identified in various stratigraphic horizons. Vitrinite reflectance and Tmax data indicate variable maturation histories, in different parts of the basin, which are related to differences in lithology-related heat conductivity and the presence of older sediments closer to areas of rifting. Multiple linear regression …
Long-Term, Storm-Dominated Sediment Dynamics Of East Beach And Sandy Point, San Salvador Island, Bahamas, Rebecca L. Beavers, H. Allen Curran, Willian T. Fox
Long-Term, Storm-Dominated Sediment Dynamics Of East Beach And Sandy Point, San Salvador Island, Bahamas, Rebecca L. Beavers, H. Allen Curran, Willian T. Fox
Geosciences: Faculty Publications
Reprinted from: Mark Boardman (ed.), Proceedings of the 7th Symposium on the Geology of the Bahamas and Other Carbonate Regions: San Salvador, Bahamian Field Station
Evidence Of Active Dune Sand On The Great Plains In The 19th Century From Accounts Of Early Explorers, Daniel R. Muhs, Vance T. Holliday
Evidence Of Active Dune Sand On The Great Plains In The 19th Century From Accounts Of Early Explorers, Daniel R. Muhs, Vance T. Holliday
United States Geological Survey: Staff Publications
Eolian sand is extensive over the Great Plains of North America, but is at present mostly stabilized by vegetation. Accounts published by early explorers, however, indicate that at least parts of dune fields in Nebraska, Colorado, Kansas, New Mexico, and Texas were active in the 19th century. Based on an index of dune mobility and a regional tree-ring record, the probable causes for these periods of greater eolian activity are droughts, accompanied by higher temperatures, which greatly lowered the precipitationto- evapotranspiration ratio and diminished the cover of stabilizing vegetation. In addition, observations by several explorers, and previous historical studies, indicate …