Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Abstract Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Muhs, D. R. Articles by Jones, J. A. Search for Related Content GeoRef GeoRef Citation

Geochemical evidence for airborne dust additions to soils in Channel Islands National Park, California

¹ U.S. Geological Survey, M.S. 980, Box 25046, Federal Center, Denver, Colorado 80225, USA
² Department of Geography, University of Illinois, Urbana, Illinois 61801, USA
³ U.S. Geological Survey, M.S. 980, Box 25046, Federal Center, Denver, Colorado 80225, USA
⁴ Department of Geosciences, 104 Wilkinson Hall, Oregon State University, Corvallis, Oregon 97331-5506, USA

View larger version (34K): [in this window] [in a new window]   Figure 1. Left: map of the western United States, showing location of Channel Islands National Park. Right: enlargement of study area shown in larger map, showing coastal southern California, Channel Islands National Park, and the southern group of Channel Islands.

View larger version (14K): [in this window] [in a new window]   Figure 2. Classification of volcanic rocks on the Channel Islands as a function of SiO2 versus Na2O + K2O, using the classification scheme of Le Bas et al. (1986, 1992). All data are from this study.

View larger version (109K): [in this window] [in a new window]   Figure 3. Geology and coastal geomorphology of Channel Islands National Park on (A) Santa Cruz Island, (B) Santa Barbara Island, (C) East Anacapa Island, and (D) all three Anacapa Islands. Photographs by the authors.

View larger version (65K): [in this window] [in a new window]   Figure 4. Aerial photograph of easternmost Santa Cruz Island, California, showing geographic features, geographic extent of silt mantles observed, and soil and bedrock sampling localities. Also shown is the geographic extent of eolian sand (eolianite) of the Potato Harbor Formation, redrawn from Weaver and Meyer (1969).

View larger version (24K): [in this window] [in a new window]   Figure 5. Soil map of Santa Barbara Island (redrawn from Johnson, 1979), showing soil sample and bedrock sample localities.

View larger version (16K): [in this window] [in a new window]   Figure 6. Soil map of East Anacapa Island (redrawn from Johnson, 1979), showing soil sample and bedrock sample localities.

View larger version (115K): [in this window] [in a new window]   Figure 7. Soils on the California Channel Islands: (A) Vertic Haploxeralfs on East Anacapa Island, showing light-colored silt mantles overlying clay-rich Bt horizons; (B) Vertic Haploxeralf on San Clemente Island, showing light-colored silt mantle overlying darker, clay-rich Bt horizon; (C) hand specimen of silt mantle from Santa Cruz Island, showing biologic soil crust on surface of silt mantle; and (D) Vertic Haploxeralfs on Santa Barbara Island, showing light-colored silt mantle overlying clay-rich Bt horizons.

View larger version (24K): [in this window] [in a new window]   Figure 8. Plot of mean particle size and degree of sorting (standard deviation of the mean particle size) of silt-enriched mantles (squares) from (A) eastern Santa Cruz Island, (B) East Anacapa Island, and (C) Santa Barbara Island. Also shown for comparison are ranges of mean particle size and degree of sorting of eolian sediments from other areas. Eastern Colorado loess data are from Muhs and Benedict (2006); northern Illinois loess data are new, from the section at Morrison, Illinois (Muhs and Bettis, 2000; Bettis et al., 2003); Chinese loess data are from the Luochuon and Xifeng sections and are from Lu et al. (2001). Mojave Desert dust data are from Reheis (2003). Chinese dune sand data are from the Taklimakan Desert and are from Wang et al. (2002); Kalahari dune sand data are from Livingstone et al. (1999); Anacapa Island shelf sediments are from Scholl (1960). All analyses were done by laser particle-size methods, except Anacapa Island shelf sediments.

View larger version (20K): [in this window] [in a new window]   Figure 9. X-ray diffractograms (glycolated, Mg-saturated) of the clay fractions of a Vertic Haploxeralf on East Anacapa Island, showing contrast in mineralogy between the silt-rich, A horizon and underlying, clay-rich, Bt horizons.

View larger version (19K): [in this window] [in a new window]   Figure 10. X-ray diffractograms (glycolated, Mg-saturated) of the clay fractions of a Vertisol on Santa Cruz Island, showing contrast in mineralogy between the silt-rich, A horizon and underlying, clay-rich, vertic horizons.

View larger version (12K): [in this window] [in a new window]   Figure 11. Ternary diagrams showing relative proportions of immobile elements Sc, Th, and La in silt fractions (53–2 µm) and clay fractions (<2 µm), of silt mantles on (A) Santa Barbara Island, (B) Santa Cruz Island, and (C) East Anacapa Island. Also shown is the range in values for these elements in local bedrock, consisting of andesite and shale (Santa Cruz Island), basalt (Santa Barbara Island), and andesite (East Anacapa Island). Field defined by Mojave Desert dust collected in traps is from data in Reheis (2003) and Reheis et al. (2002).

View larger version (12K): [in this window] [in a new window]   Figure 12. Ternary diagrams showing relative proportions of immobile elements Ta (x10), Nd, and Cr (/10) in silt fractions (53–2 µm) and clay fractions (<2 µm) of silt mantles on (A) Santa Barbara Island, (B) Santa Cruz Island, and (C) East Anacapa Island. Also shown is the range in values for these elements in local bedrock, consisting of andesite and shale (Santa Cruz Island), basalt (Santa Barbara Island), and andesite (East Anacapa Island). Field defined by Mojave Desert dust collected in traps is from data in Reheis (2003) and Reheis et al. (2002).

View larger version (13K): [in this window] [in a new window]   Figure 13. Chondrite-normalized, rare-earth element (REE) plots of volcanic rocks on the Channel Islands, showing decreasing light REE enrichment and decreasing negative Eu anomaly with increasingly mafic rock types (rhyolite to andesite to basalt).

View larger version (24K): [in this window] [in a new window]   Figure 14. Chondrite-normalized, rare-earth element (REE) plots of highly contrasting rock types (andesite and shale) on eastern Santa Cruz Island.

View larger version (18K): [in this window] [in a new window]   Figure 15. Chondrite-normalized, rare-earth element (REE) plots of silt (53–2 µm) and clay (<2 µm) fractions of silt mantles on Santa Cruz, East Anacapa, and Santa Barbara Islands.

View larger version (12K): [in this window] [in a new window]   Figure 16. Eu/Eu* versus LaN/YbN values in silt fractions (53–2 µm; circles) and clay fractions (<2 µm; solid squares), of silt mantles on (A) Santa Barbara Island, (B) East Anacapa Island, and (C) Santa Cruz Island. Also shown are the ranges in these values for bedrock, consisting of andesite and shale (Santa Cruz Island), basalt (Santa Barbara Island), and andesite (East Anacapa Island). Field defined by Mojave Desert dust collected in traps is from data in Reheis (2003) and Reheis et al. (2002).

View larger version (34K): [in this window] [in a new window]   Figure 17. Map of the northern Channel Islands, showing the extent of present offshore shelf that would have been exposed during the last glacial maximum, ca. 21–22 ka, when sea level was lowered 120 m (Bard et al., 1990) and wind roses for Channel Islands stations and offshore buoys. Map generated by the authors, using bathymetry from 1:100,000- and 1:250,000-scale U.S. Geological Survey topographic maps. Length of arm is proportional to amount of time that wind is above velocity of 5 m/s; approximate percentage figure is given for the longest arm; thus, scale for each rose differs. Number in center circle is percent of time that winds are below 5 m/s. Note that periods of record vary for each station, but all are two years or more. Geographic positions of wind roses are approximate for clarity of presentation. Wind roses generated by the authors from data from the Western Regional Climate Center (http://www.wrcc.dri.edu/channel_isl/index.html).

View larger version (32K): [in this window] [in a new window]   Figure 18. (A) Map of the western United States, showing location of Channel Islands National Park. Also shown are positions of air masses, major fronts, and surface pressures (in millibars) during Santa Ana wind conditions of 9 February 2002. (B) Map of southern California, showing location of Channel Islands National Park and dust trap localities (Reheis, 2003, 2006; Reheis et al., 1995, 2002) in the Mojave Desert. Also shown are patterns of wind direction during "Santa Ana" events. The map of wind directions is simplified from model simulations courtesy of Robert Fovell, Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles (http://www.atmos.ucla.edu/fovell/ASother/mm5/SantaAna/winds.html).