Critical Zone Structure Under a Granite Ridge Inferred From Drilling and Three‐Dimensional Seismic Refraction Data
Tóm tắt
Observing the critical zone (CZ) below the top few meters of readily excavated soil is challenging yet crucial to understanding Earth surface processes. Near‐surface geophysical methods can overcome this challenge by imaging the CZ in three dimensions (3‐D) over hundreds of meters, thus revealing lateral heterogeneity in subsurface properties across scales relevant to understanding hillslope erosion, weathering, and biogeochemical cycling. We imaged the CZ under a soil‐mantled ridge developed in granitic terrain of the Laramie Range, Wyoming, using data from five boreholes and a 3‐D volume (970 by 600 by 80 m) of seismic velocities generated by ordinary kriging of 25 two‐dimensional seismic refraction transects. The observed CZ structure under the ridge broadly matches predictions of two recently proposed hypotheses: the uppermost surface of weathered bedrock is consistent with subsurface weathering driven by bedrock drainage and subsurface topography defining the top of unweathered protolith is consistent with fracturing predicted from topographic and regional stresses. In contrast, differences in slope aspect along the ridge are too subtle to explain observed variations in regolith structure. Our observations suggest that multiple processes, each of which may dominate at different depths, work in concert to regulate deep CZ structure.
Từ khóa
Tài liệu tham khảo
Bell J. M.(1998).A petrographic geochemical and isotopic investigation of the Mule Creek‐Richeau Hills portion of the Sherman Batholith Laramie Wyoming(M.S.). University of Wyoming United States‐Wyoming. Retrieved fromhttp://search.proquest.com.libproxy.uwyo.edu/pqdtlocal1005743/docview/304458004/citation/6AB9176C22074928PQ/1
Bradley W. C., 1987, Geomorphic systems of North America, 215
Burrough P. A., 2015, Principles of geographical information systems
Chapin C. E., 1997, Geologic history of the Colorado Front Range, 1943
Hayes J. L.(2016).Seismic refraction studies of volcanic crust in Costa Rica and of critical zones in the southern Sierra Nevada California and Laramie Range Wyoming(PhD). University of Wyoming United States ‐‐ Wyoming. Retrieved fromhttp://search.proquest.com.libproxy.uwyo.edu/pqdtlocal1005743/docview/1801725446/abstract/9E567E53BAB84E7CPQ/4
Houston R. S. &Marlatt G.(1997).Proterozoic geology of the Granite Village area Albany and Laramie counties Wyoming compared with that of the Sierra Madre and Medicine Bow mountains of southeastern Wyoming (USGS Numbered Series No. 2159). USGS. Retrieved fromhttp://pubs.er.usgs.gov/publication/b2159
Mears B., 1993, Geology of Wyoming, 608
Moore F. E., 1960, Guide to the geology of Colorado, 217
Moser T. J., 1992, Ray bending revisited, Bulletin of the Seismological Society of America, 82, 259
Natural Resources Conservation Service(1988).Soil survey of Albany County area Wyoming. Retrieved fromhttps://www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/wyoming/albanyWY1998/albanyWY1998.pdf Accessed 12/06/2017.
Natural Resources Conservation Service(2015).Crow Creek SNOTEL site United States Department of Agriculture SNOTEL surveys. Retrieved fromhttp://wcc.sc.egov.usda.gov/nwcc/site?sitenum=1045 Accessed 07/15/2017.
Natural Resources Conservation Service(2017).United States Department of Agriculture. Web Soil Survey. Retrieved fromhttps://websoilsurvey.sc.egov.usda.gov/ Accessed 07/15/2017.
Pavich M. J., 1986, Rates of chemical weathering of rocks and minerals, 551
Scott G. R., 1986, Map showing late Eocene erosion surface, Oligocene‐Miocene paleovallys and Tertiary deposits in the Pueblo, Denver, and Greely 1° x 2° quadrangles, Colorado (Scale 1:2500,000)
St. Clair J.(2015).Geophysical investigations of underplating at the Middle American Trench weathering in the critical zone and snow water equivalent in seasonal snow(PhD). University of Wyoming United States ‐‐ Wyoming.
Ver Ploeg A. J., 2010, Preliminary geologic map of the Sherman Mountains West quadrangle, Albany County, Wyoming (sheet 1, scale 1:24,000)