UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY AERIAL PHOTOGRAPHIC INTERPRETATION OF LINEAMENTS AND FAULTS IN LATE CENOZOIC DEPOSITS IN THE EASTERN PART OF THE BENTON RANGE 1:100,000 QUADRANGLE AND THE GOLDFIELD, LAST CHANCE RANGE, BEATTY, AND

ABSTRACT Lineaments and faults in Quaternary and late Tertiary deposits in the southern part of the Walker Lane are potentially active and form patterns that are anomalous with respect to the typical fault patterns in most of the Great Basin. Little work has been done to identify and characterize these faults, with the exception of those in the Death ValleyFurnace Creek (DVFCFZ) fault system and those in and near the Nevada Test Site. Four maps at a scale of 1:100,000 summarize the existing knowledge about these lineaments and faults based on extensive aerial-photo interpretation, limited field investigations, and published geologic maps. The lineaments and faults in all four maps can be divided geographically into two groups. The first group includes west-to north-trending lineaments and faults associated with the DVFCFZ and with the Pahrump fault zone in the Death Valley Junction quadrangle. The second group consists of north-to east-northeast-trending lineaments and faults in a broad area that lies east of the DVFCFZ and north of the Pahrump fault zone. Preliminary observations of the orientations and sense of slip of the lineaments and faults suggest that the least principal stress direction is west-east in the area of the first group and northwest-southeast in the area of the second group

Constraints on present-day Basin and Range deformation from space geodesy

We use new space geodetic data from very long baseline interferometry and satellite laser ranging combined with other geodetic and geologic data to study contemporary deformation in the Basin and Range province of the western United States. Northwest motion of the central Sierra Nevada block relative to stable North America, a measure of integrated Basin and Range deformation, is 12.1±1.2 mm/yr oriented N38°W±5° (one standard error), in agreement with previous geological estimates within uncertainties. This velocity reflects both east-west extension concentrated in the eastern Basin and Range and north-northwest directed right lateral shear concentrated in the western Basin and Range. Ely, Nevada is moving west at 4.9±1.3 mm/yr relative to stable North America, consistent with dip-slip motion on the north striking Wasatch fault and other north striking normal faults. Comparison with ground-based geodetic data suggests that most of this motion is accommodated within ∼50 km of the Wasatch fault zone. Paleoseismic data for the Wasatch fault zone and slip rates based on seismic energy release in the region both suggest much lower slip rates. The discrepancy may be explained by some combination of additional deformation away from the Wasatch fault itself, aseismic slip, or a seismic rate that is anomalously low with respect to longer time averages. Deformation in the western Basin and Range province is also largely confined to a relatively narrow boundary zone and in our study area is partitioned into the eastern California shear zone, accommodating 10.7±1.6 mm/yr of north-northwest directed right-lateral shear, and a small component (∼1 mm/yr) of west-southwest - east-northeast extension. A slip rate budget for major strike-slip faults in our study area based on a combination of local geodetic or late Quaternary geologic data and the regional space geodetic data suggests the following rates of right-lateral slip: Owens Valley fault zone, 3.9±1.1 mm/yr; Death Valley-Furnace Creek fault zone, 3.3±2.2 mm/yr; White Mountains fault zone in northern Owens Valley, 3.4±1.2 mm/yr; Fish Lake Valley fault zone, 6.2±2.3 mm/yr. In the last few million years the locus of right-lateral shear in the region has shifted west and become more north trending as slip on the northwest striking Death Valley-Furnace Creek fault zone has decreased and is increasingly accommodated on the north-northwest striking Owens Valley fault zone

The ecology of dust: local- to global-scale perspectives

Emission and redistribution of dust due to wind erosion in drylands drives major biogeochemical dynamics and provides important aeolian environmental connectivity at scales from individual plants up to the global scale. Yet, perhaps because most relevant research on aeolian processes has been presented in a geosciences rather than ecological context, most ecological studies do not explicitly consider dust-driven processes. To bridge this disciplinary gap, we provide a general overview of the ecological importance of dust, examine complex interactions between wind erosion and ecosystem dynamics from the plant-interspace scale to regional and global scales, and highlight specific examples of how disturbance affects these interactions and their consequences. Changes in climate and intensification of land use will both likely lead to increased dust production. To address these challenges, environmental scientists, land managers and policy makers need to more explicitly consider dust in resource management decisions

Multiple oxygen and sulfur isotopic analyses on water-soluble sulfate in bulk atmospheric deposition from the southwestern United States

Sulfate is a major component of bulk atmospheric deposition (including dust, aerosol, fog, and rain). We analyzed sulfur and oxygen isotopic compositions of water-soluble sulfate from 40 sites where year-round dust traps collect bulk atmospheric deposition in the southwestern United States. Average sulfur and oxygen isotopic compositions (δ34S and δ18O) are 5.8 ± 1.4 (CDT) and 11.2 ± 1.9 (SMOW) (n = 47), respectively. Samples have an oxygen 17 anomaly (Δ 17O), with an average value of 1.0 ± 0.6‰. Except for a weak positive correlation between δ18O and Δ17O values (r2 ≈ 0.4), no correlation exists for δ18O versus δ34S, Δ 17O versus δ34S, or any of the three isotopic compositions versus elevation of the sample site. Exceptional positive Δ 17O values (up to 4.23‰) are found in samples from sites in the vicinity of large cities or major highways, and near-zero Δ 17O values are found in samples close to dry lakes. Comparison of isotopic values of dust trap sulfate and desert varnish sulfate from the region reveals that varnish sulfate has average isotopic values that are ∼4.8‰ lower for δ18O, ∼2.1‰ higher for δ34S , and ∼0.3‰ lower for Δ 17O than those of the present-day bulk deposition sulfate. Although other factors could cause the disparity, this observation suggests a possibility that varnish sulfate may have recorded a long-term atmospheric sulfate deposition during the Holocene or Pleistocene, as well as the differences between sulfur and oxygen isotopic compositions of the preindustrial bulk deposition sulfate and those of the industrial era

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects

In a semi-arid, upland setting on the Colorado Plateau that is underlain by nutrient-poor Paleozoic eolian sandstone, alternating episodes of dune activity and soil formation during the late Pleistocene and Holocene have produced dominantly sandy deposits that support grass and shrub communities. These deposits also contain eolian dust, especially in paleosols. Eolian dust in these deposits is indicated by several mineralogic and chemical disparities with local bedrock, but it is most readily shown by the abundance of titaniferous magnetite in the sandy deposits that is absent in local bedrock. Magnetite and some potential plant nutrients (especially, P, K, Na, Mn, and Zn) covary positively with depth (3–4 m) in dune-crest and dune-swale settings. Magnetite abundance also correlates strongly and positively with abundances of other elements (e.g., Ti, Li, As, Th, La, and Sc) that are geochemically stable in these environments. Soil-property variations with depth can be ascribed to three primary factors: (1) shifts in local geomorphic setting; (2) accumulation of relatively high amounts of atmospheric mineral dust inputs during periods of land-surface stability; and (3) variations in dust flux and composition that are likely related to changes in dust-source regions. Shifts in geomorphic setting are revealed by large variations in soil texture and are also expressed by changes in soil chemical and magnetic properties. Variable dust inputs are indicated by both changes in dust flux and changes in relations among magnetic, chemical, and textural properties. The largest of these changes is found in sediment that spans late Pleistocene to early Holocene time. Increased dust inputs to the central Colorado Plateau during this period may have been related to desiccation and shrinkage of large lakes from about 12 to 8 ka in western North America that exposed vast surfaces capable of emitting dust. Soil properties that result from variable dust accumulation and redistribution in these surficial deposits during the late Quaternary are important to modern ecosystem dynamics because some plants today utilize nutrients deposited as long ago as about 12–15 ky and because variations in fine-grained (silt) sediment, including eolian dust, influence soil-moisture capacity

Physical, chemical, ecological and age data and trench logs from surficial deposits at Hatch Point, southeastern Utah

This report presents data and describes the methodology for physical, chemical and ecological measurements of sediment, soil, and vegetation, as well as age determinations of surficial deposits at Hatch Point, Canyon Rims area, Colorado Plateau, southeastern Utah. The results presented in this report support a study that examines geomorphic and soil factors that may influence boundaries between shrubland and grassland ecosystems in the study area. Shrubland ecosystems dominated by sagebrush (Artemisia tridentata) and grassland ecosystems dominated by native perennial grasses (for example, Hilaria jamesii and Sporabolis sp.) are high-priority conservation targets for the Federal Bureau of Land Management (BLM) and other resource managers because of their diversity, productivity, and vital importance as wildlife habitat. These ecosystems have been recognized as imperiled on a regional scale since at least the mid-1990s due to habitat loss (type conversions), land-use practices, and invasive exotic plants. In the Intermountain West, the exotic annual cheatgrass (Bromus tectorum) is recognized as one of the most pervasive and serious threats to the health of native sagebrush and grassland ecosystems through effects on fire regimes and resource conditions experienced by native species

The Ecology of Dust

Wind erosion and associated dust emissions play a fundamental role in many ecological processes and provide important biogeochemical connectivity at scales ranging from individual plants up to the entire globe. Yet, most ecological studies do not explicitly consider dust-driven processes, perhaps because most relevant research on aeolian (wind-driven) processes has been presented in a geosciences rather than an ecological context. To bridge this disciplinary gap, we provide a general overview of the ecological importance of dust, examine complex interactions between wind erosion and ecosystem dynamics from the scale of plants and surrounding space to regional and global scales, and highlight specific examples of how disturbance affects these interactions and their consequences. It is likely that changes in climate and intensification of land use will lead to increased dust production from many drylands. To address these issues, environmental scientists, land managers, and policy makers need to consider wind erosion and dust emissions more explicitly in resource management decisions