Geology of Parks and Federal Lands of the Southwest

GMEG - Geology and Geophysics

Geology of Parks and Federal Lands of the Southwest

TASK 6 - Geologic and geomorphic framework of the lower Colorado River valley

Statement of Problem: The lower Colorado River valley is a critical but increasingly imperiled resource. The river supplied the water and energy necessary for opening the West to human settlement on a massive scale, and it will become even more crucial in the future to sustain a large and growing population in the southwest, especially in the face of climate change. The lower Colorado River supplies water to 22 million people and provides critical habitat to many endemic and endangered fish species as well as migrating birds along the Pacific Flyway. The river forms the state boundaries between California, Arizona, and Nevada, and the international boundary with Mexico, making it a international shared resource. In the valley itself, rapid urban growth, water diversion, recreation, and agriculture compete with national parks, wildlife refuges, tribal lands, and wilderness areas for space and resources. All of these are affected strongly by patterns of development, water consumption, and climate changes within the upstream watershed, which includes over 600,000 km of southwestern North America. Balancing the demands on the river requires scientific information about the geologic materials, processes, and history of the valley.

Davis Dam on the Lower Colorado River, Arizona and Nevada

This task supports surficial and some bedrock geologic mapping along the lower Colorado River corridor in support of land management by multiple interests and agencies. Mapping on this task takes place within Lake Mead National Recreation Area, the Havasu National Wildlife Refuge, the Fort Mojave and Chemehuevi Indian Reservations, land managed by the Bureau of Land Management, and in numerous municipalities in California, Arizona, and Nevada (see index map).

Geologic mapping within the Lake Mead National Recreation is covered in task 2. The emphasis of task 6 is mapping and topical studies along the lower Colorado River downstream of LMNRA.

Objectives: Fluvial deposits in the lower Colorado River Valley form the substrate for habitat and urban growth along the Colorado River corridor. DOI and other agencies have pressing needs for scientific information to guide policy decisions to help sustain ecosystems. For example, a major interagency ecosystem restoration program – the 50-year, Lower Colorado River Multi Species Conservation Program, managed by the U.S. Bureau of Reclamation and funded by users of Colorado River water – seeks opportunities to develop or enhance fluvial habitat along the valley for species endangered by dams and other river engineering. Nearly all these habitat elements (for example, natural levees, sand bars, oxbow lakes) are fluvial features formed by the natural operation of the river and its floodplain. Geologic mapping in the valley can provide a basis for understanding the natural processes and evolution of floodplain habitats, and inform their management and the construction of simulated new habitats. In addition, surficial geologic maps of fluvially segregated deposits on the floodplain surface can provide guidance for the planting of species in appropriate soil conditions (manager, Havasu National Wildlife Refuge, personal comm. 2005).

The lower Colorado River valley is also the locus of explosive urban growth. The population of Mohave County – whose largest cities, Bullhead City and Lake Havasu City, are along the lower Colorado River – increased by 66% between 1990 and 2000 (U.S. Census Bureau), and population growth has accelerated since 2000. Other rapidly growing urban areas along the river corridor include Laughlin, NV, Yuma, AZ, and San Luis Rio Colorado and Mexicali, Mexico. Many Indian nations, including the Fort Mojave and Chemehuevi tribes, also own critical portions of the river valley and have plans for developing their resources. Geologic mapping of the deposits on the floodplain and adjacent piedmonts, at the scale of 7.5’ quadrangles, can help delineate the distribution of flood-prone areas, surficial and subsurface materials, and other information relevant to urban planning.

The lower Colorado River is the source of much of the water to a large and growing population in the arid and semiarid southwest. Because the Colorado River is a rare example of an influent, or “losing” stream (one that supplies flow to the groundwater, rather than being fed by it), the movement of Colorado River water into local aquifers in the valley is controlled largely by the distribution of geologic materials. The arrangement of geologic materials in the subsurface also controls the movement of groundwater contamination and pollutants. This is a particular concern at the site of a project to contain a plume of chromium migrating towards the river at the head of Lake Havasu, near Topock, AZ. Surficial geologic mapping of the deposits in the lower Colorado River valley contributes to better groundwater management in the region, and this task provides input on the geologic framework for groundwater modeling. In addition to the habitat, urban planning, and water-related issues mentioned above, other geologic issues affect management along the lower Colorado River that could be aided by surficial mapping at 1:24,000 scale, including:
estimating the potential for seismic activity (construction of nuclear power plants in the valley was proposed during the 1970s, and may be revived) and managing river bank erosion and sedimentation in the river (millions of dollars are spent annually dredging sediment in some areas, while the river is sediment starved in others). The objective of task 6 is to conduct new mapping and work with collaborators in the state geologic surveys to delineate and better understand the geologic materials and processes of the lower Colorado River valley, with a particular objective of providing science relevant to the needs of DOI bureaus, tribes, and other agencies.

Methodology: (examples of methods, software, laboratory, etc.)

This task uses surficial geologic mapping at 1:24,000 scale to provide the resolution necessary to contribute to planning and to a better understanding of the stratigraphy and flood hazards. Washes tributary to the Colorado River are incised up to tens of meters into alluvial deposits consisting of complexly interfingering and in some places structurally deformed Colorado River sediments and locally derived fan materials. The stratigraphic complexity requires both field study and use of aerial photographs and other remote sensing in order to geologically map and understand the implications for geologic history and for stakeholders. Mapping of the lower Colorado River valley requires significant field mapping and stratigraphic study, supported by sedimentologic, paleontologic studies, and dating by luminescence, cosmogenic isotopes, C-14, tephrochronology, and paleomagnetic methods. We also plan to analyze recently obtained core material from near Topock, AZ, to look for possible diatom, ostracode, and pollen proxies for paleoclimate and paleoecology. Work is being done collaboratively with the DOI Topock Project (Peter Martin, WRD), and the Lower Colorado River Science on the DOI Landscape Project (Andrea Alpine and Charles Van Riper, BRD), and the Southwest Climate History Project (John Barron, ESD program).

Task Products

Dorsey, R. J., Housen, B. A., Janecke, S. U., McDougall, K., Fanning, M., Fluette, A., Axen, G. J., and Shirvell, C. R., 2006, Chronostratigraphy of the Fish Creek-Vallecito Basin, SW Salton Trough: a high-fidelity record of slip on the West Salton Detachment Fault and subsidence in its upper plate: EOS Transactions, American Geophysical Union, v. 87, no. 52, suppl. 26.

Dorsey, Rebecca J., Fluette, Amy L., Housen, Bernard A., McDougall, Kristin A., Janecke, Susanne U., Axen, Gary J., Shirvell, Catherine, 2006, Chronology of late Miocene to early Pliocene sedimentation at Split Mt. Gorge, western Salton Trough: Implications for development of the Pacific-North America Plate boundary; Lithospheric Rupture in the Gulf of California - Salton Trough Region, http://www.rcl-cortez.wustl.edu, p. 59.

Malmon, D. V., Howard, K., Lundstrom, S., and Felger, T., 2006, Response of the Colorado River to a late Pleistocene pulse of fine-grained sediment: EOS, American Geophysical Union Transactions v. 87(52). Fall Meeting Supplement, Abstract H11B-1255.

McDougall, K., 2006, Late Neogene marine incursions and the ancestral Gulf of California; Lithospheric Rupture in the Gulf of California - Salton Trough Region, http://www.rcl-cortez.wustl.edu, p. 59.

Dorsey, R. J., Fluette, A., McDougall, K., Housen, B. A., Janecke, A. U., Axen, G. J., and Shirvell, C. R., 2007, Chronology of Miocene-Pliocene deposits at Split Mountain Gorge, Southern California: a record of regional tectonics and Colorado River evolution: Geology v.35, no.1, p. 57-60.

Howard, K,A., Stock, G., Rockwell, T., Schafer, J., Webb, R. H., 2007, Holocene cyclical switching of Colorado River delta water alternatively to the Sea of Cortez or to the Salton Sink: EOS, American Geophysical Union Transactions v. 88(23). Joint Assembly Supplement, Abstract H44A-05.

Howard, K. A. and Malmon, D. V., 2007, Stratigraphy of Colorado River deposits in lower Mohave Valley, Arizona and California, in Reynolds, R. E., editor, Wild, Scenic and Rapid, a trip down the Colorado River trough, Field trip guide and abstracts from the 2007 Desert Symposium: Northridge, California State University, and LSA Associates, p.50–56.

Kimbrough, D., Grove, M., Gehrels, G., Dorsey, R., House, K.P., Howard, K., Pearthree, P. A., Spencer, J. E., Mahoney, B., 2007, Detrital zircon record of Colorado River incision: Eos American Geophysical Union Transactions, v. 88 (23), Joint Assembly Supplement, Abstract T41C-03.

Kirby, S. M., Janecke, S. U., Dorsey, R. J., Housen, B. A., Langenheim, V. E., McDougall, K., Steely, A. N., 2007, Pleistocene Brawley and Ocotillo formations: evidence for initial strike-slip deformation along the San Felipe and San Jacinto fault zones, southern California: Journal of Geology, v. 115, p. 43-62.

Malmon, D. V., Felger, T., and Howard, K. A., 2007. Floodplain lakes and alluviation cycles of the lower Colorado River, in Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border—Monitoring, Modeling, and Forecasting Change Within the Arizona-Sonora Transboundary Watersheds, U.S. Geological Survey Circular 1322.

Malmon, D. V. and Howard, K. A, 2007, Overview; the Chemehuevi Formation along the lower Colorado River, in Reynolds, R. E., editor, Wild, Scenic and Rapid, a trip down the Colorado River trough, Field trip guide and abstracts from the 2007 Desert Symposium: Northridge, California State University, and LSA Associates, p.57–60

Malmon, D., 2007, Preliminary observations of geochemical properties of Colorado River and related sediments, in Reynolds, R. E., editor, Wild, Scenic and Rapid, a trip down the Colorado River trough, Field trip guide and abstracts from the 2007 Desert Symposium: Northridge, California State University, and LSA Associates, p.61–62

Nagler, P. L., Glenn, E. P., Howard, K. A., and Webb, R. H., 2007, A water budget for riparian vegetation on the lower Colorado River: the myth of water salvage: EOS, American Geophysical Union Transactions v. 88(23). Joint Assembly Supplement, Abstract H44A-08.

Reynolds, R. E., Faulds, J., House, P. K., Howard, K. A., Malmon, D., Miller, C. F., and Pearthree, P. A., 2007, Wild, scenic and rapid trip down the Colorado River trough; Desert Symposium field trip 2007, in Reynolds, R. E., editor, Wild, Scenic and Rapid, a trip down the Colorado River trough, Field trip guide and abstracts from the 2007 Desert Symposium: Northridge, California State University, and LSA Associates, p.5–32.

Chesley, J., Sanchez, C. A., Asmerom, Y., and Malmon, D., 2008, Discerning Sources of Metal Contamination in the Colorado River from Isotopic Ratio Measurements, American Chemical Society, meeting Las Vegas, NV, September 2008.

Delong, S. B., Johnson, J.P., Whipple, K. X., Post, D. F., Rossi, M. R., Malmon, D. V., Chu, D., Hellerstein, J., Klues, K., Levis, P., and Martin, R., 2008, Environmental monitoring of hydrology and channel headwall erosion in a semiarid discontinuous arroyo network, Page Ranch, Arizona, EOS (American Geophysical Union, Dec. 2008), v. 89, no. 53, Abstract H43F-1075.

Howard, K. A. and Malmon, D. V., 2008, Boulders Deposited by Pliocene and Pleistocene floods on the lower Colorado River, in Reynolds, R. E., editor, Trough to trough; The Colorado River and the Salton Sea, Proceedings of the 2008 Desert Symposium: Northridge, California State University, Desert Studies Consortium and LSA Associates, Inc., p. 112

Howard, K. A., Lundstrom, S. C., Malmon, D. V., and Hooke, S. J., 2008, Age, distribution, and formation of late Cenozoic paleovalleys of the lower Colorado River and their relation to river aggradation and degradation, in Reheis, M. C., Herschler, R., and Miller, D. M., editors, Late Cenozoic Drainage History of the Southwestern Great Basin and Lower Colorado River Region: Geologic and Biotic Perspectives: Geological Society of America Special Paper 439, 391– 410.

Lundstrom, S. C., Mahan, S., Paces, J., Hudson, M., House, P. K., Malmon, D., Blair, J. L., and Howard, K. A., 2008, Late Pleistocene aggradation and degradation of the lower Colorado River: Perspectives from the Cottonwood area and other reconnaissance below Boulder Canyon, in Reheis, M. C., Hershler, R., and Miller, D. M., editors, Late Cenozoic Drainage History of the Southwestern Great Basin and Lower Colorado River Region: Geologic and Biotic Perspectives, p.
409-430.

Malmon, D. V, Dunne, T., and Reneau, S. L., 2008, Stochastic analysis of particle trajectories through river valleys, EOS (American Geophysical Union, Dec. 2008), v. 89, no. 53, Abstract H51J-06.

Malmon, D. V., Felger, T. J., and Howard, K. A, 2008, Geologic controls on floodplain lakes in the lower Colorado River: Colorado River Basin Science and Resource Management Symposium, Scottsdale, AZ, November 18-20, 2008

Malmon, D. V., Shafroth, P. B., and House, P. K., 2008, Interdisciplinary Mapping along the Lower Colorado River: Importance to climate science, habitat restoration, and urban planning in National Wildlife Refuges and other Public Lands, poster presentation at USFWS-USGS conference: Effects of climate change on fish, wildlife and habitats in the arid and semiarid southwestern United States, Aug. 2008, Tucson, AZ,
http://www.fws.gov/southwest/Climatechange

McDougall, K., 2008, Late Neogene marine incursions and the ancestral Gulf of California, in Reheis, M. C., Herschler, R., and Miller, D. M., editors, Late Cenozoic Drainage History of the Southwestern Great Basin and Lower Colorado River Region: Geologic and Biotic Perspectives: Geological Society of America Special Paper 439, 355– 374.

Nagler, P. L., Glenn, E. P., Hinojosa-Huerta, O., Zamora F., and Howard, K. A., 2008, Vegetation dynamics and evapotranspiration in the riparian corridor in the delta of the Colorado River, Mexico: Journal of Environmental Management, v, 88, p. 864–874, doi:10.1016/j.jenvman.2007.04.010.

Malmon, D. V., Howard, Keith A., and Priest, Susan S., 2009, Geologic map of the Needles 7.5' quadrangle, California and Arizona: U.S. Geological Survey Scientific Investigations Map 3062, scale 1;24,000, 1 sheet, includes 31 p. pamphlet [http://pubs.usgs.gov/sim/3062/].

Malmon, D. V., Howard, K. A., Martin, P.M., McGeehin, J.P., Wan, E., and Mahan, S., 2009, the stratigraphic record of the lower Colorado River - Possible climate connections: in Pacific Climate Workshop PACLIM 2009 workshop.

Malmon, D. V., Howard, P. K., House, S. C., Lundstrom, and Pearthree, P. A., 2009, The Chemehuevi Formation - a geologic example of extraordinary sediment loading in the Colorado River during the late Pleistocene: Geological Society of America Abstracts with Programs, v. 41, no. 7, p. 574.

Malmon, D. V., 2009, Geologic record of the lower Colorado River – possible climate connections, 2009: PACLIM 2009 Pacific Climate conference, Monterey, CA, April 19-22, 2009.

McDougall, Kristin, 2009, Update on microfossil studies in the northern Gulf of California and Salton Trough, MARGINS workshop “Rupturing of continental lithosphere in the Gulf of California-Salton Trough region, Charleston, South Carolina, April, 2009.

Sanchez, C. A., Chesely, J., Asmerom, Y., and Malmon, D., 2009, Tracing the sources of Uranium in the Colorado River basin: Lake Mead Science Symposium, Las Vegas, Nevada, January 13-14, 2009.

Malmon, D. V., Felger, T. J., and Howard, K. A., 2010, Geologic considerations for the placement and design of backwater restoration sites along the lower Colorado River, in Melis, T. S., Hamill, J. F., Coggins, L. G. Jr., Grams, P. E., Kennedy, T. A., Kubley, D. M., and Ralston, B. E.,. editors, Proceedings of the Colorado River Basin Science and Resource Management Symposium, Scottsdale, Arizona: U.S. Geological Survey Scientific Investigations Report 2010- 5135, p. 307-315.

Report, Planned: McDougall, K., 2010, Update on microfossils studies in the northern Gulf of California, Salton Trough, and lower Colorado River, USGS

Map, Planned: John, B. E., Howard, K. A., Nielson, J. E., and Miller, J. G., 2011, Geologic map of the Topock 7.5-minute quadrangle, Arizona and California, USGS, Scientific Investigations Map

Map, Planned: Malmon, D. V., and Priest, S. S., 2011, Surficial geologic map of the Castle Rock 7.5' quadrangle, California and Arizona, USGS

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TASK 6 - Geologic and geomorphic framework of the lower Colorado River valley Statement of Problem: The lower Colorado River valley is a critical but increasingly imperiled resource. The river supplied the water and energy necessary for opening the West to human settlement on a massive scale, and it will become even more crucial in the future to sustain a large and growing population in the southwest, especially in the face of climate change. The lower Colorado River supplies water to 22 million people and provides critical habitat to many endemic and endangered fish species as well as migrating birds along the Pacific Flyway. The river forms the state boundaries between California, Arizona, and Nevada, and the international boundary with Mexico, making it a international shared resource. In the valley itself, rapid urban growth, water diversion, recreation, and agriculture compete with national parks, wildlife refuges, tribal lands, and wilderness areas for space and resources. All of these are affected strongly by patterns of development, water consumption, and climate changes within the upstream watershed, which includes over 600,000 km of southwestern North America. Balancing the demands on the river requires scientific information about the geologic materials, processes, and history of the valley.
Davis Dam on the Lower Colorado River, Arizona and Nevada		This task supports surficial and some bedrock geologic mapping along the lower Colorado River corridor in support of land management by multiple interests and agencies. Mapping on this task takes place within Lake Mead National Recreation Area, the Havasu National Wildlife Refuge, the Fort Mojave and Chemehuevi Indian Reservations, land managed by the Bureau of Land Management, and in numerous municipalities in California, Arizona, and Nevada (see index map). Geologic mapping within the Lake Mead National Recreation is covered in task 2. The emphasis of task 6 is mapping and topical studies along the lower Colorado River downstream of LMNRA.
Objectives: Fluvial deposits in the lower Colorado River Valley form the substrate for habitat and urban growth along the Colorado River corridor. DOI and other agencies have pressing needs for scientific information to guide policy decisions to help sustain ecosystems. For example, a major interagency ecosystem restoration program – the 50-year, Lower Colorado River Multi Species Conservation Program, managed by the U.S. Bureau of Reclamation and funded by users of Colorado River water – seeks opportunities to develop or enhance fluvial habitat along the valley for species endangered by dams and other river engineering. Nearly all these habitat elements (for example, natural levees, sand bars, oxbow lakes) are fluvial features formed by the natural operation of the river and its floodplain. Geologic mapping in the valley can provide a basis for understanding the natural processes and evolution of floodplain habitats, and inform their management and the construction of simulated new habitats. In addition, surficial geologic maps of fluvially segregated deposits on the floodplain surface can provide guidance for the planting of species in appropriate soil conditions (manager, Havasu National Wildlife Refuge, personal comm. 2005). The lower Colorado River valley is also the locus of explosive urban growth. The population of Mohave County – whose largest cities, Bullhead City and Lake Havasu City, are along the lower Colorado River – increased by 66% between 1990 and 2000 (U.S. Census Bureau), and population growth has accelerated since 2000. Other rapidly growing urban areas along the river corridor include Laughlin, NV, Yuma, AZ, and San Luis Rio Colorado and Mexicali, Mexico. Many Indian nations, including the Fort Mojave and Chemehuevi tribes, also own critical portions of the river valley and have plans for developing their resources. Geologic mapping of the deposits on the floodplain and adjacent piedmonts, at the scale of 7.5’ quadrangles, can help delineate the distribution of flood-prone areas, surficial and subsurface materials, and other information relevant to urban planning. The lower Colorado River is the source of much of the water to a large and growing population in the arid and semiarid southwest. Because the Colorado River is a rare example of an influent, or “losing” stream (one that supplies flow to the groundwater, rather than being fed by it), the movement of Colorado River water into local aquifers in the valley is controlled largely by the distribution of geologic materials. The arrangement of geologic materials in the subsurface also controls the movement of groundwater contamination and pollutants. This is a particular concern at the site of a project to contain a plume of chromium migrating towards the river at the head of Lake Havasu, near Topock, AZ. Surficial geologic mapping of the deposits in the lower Colorado River valley contributes to better groundwater management in the region, and this task provides input on the geologic framework for groundwater modeling. In addition to the habitat, urban planning, and water-related issues mentioned above, other geologic issues affect management along the lower Colorado River that could be aided by surficial mapping at 1:24,000 scale, including: estimating the potential for seismic activity (construction of nuclear power plants in the valley was proposed during the 1970s, and may be revived) and managing river bank erosion and sedimentation in the river (millions of dollars are spent annually dredging sediment in some areas, while the river is sediment starved in others). The objective of task 6 is to conduct new mapping and work with collaborators in the state geologic surveys to delineate and better understand the geologic materials and processes of the lower Colorado River valley, with a particular objective of providing science relevant to the needs of DOI bureaus, tribes, and other agencies. Methodology: (examples of methods, software, laboratory, etc.) This task uses surficial geologic mapping at 1:24,000 scale to provide the resolution necessary to contribute to planning and to a better understanding of the stratigraphy and flood hazards. Washes tributary to the Colorado River are incised up to tens of meters into alluvial deposits consisting of complexly interfingering and in some places structurally deformed Colorado River sediments and locally derived fan materials. The stratigraphic complexity requires both field study and use of aerial photographs and other remote sensing in order to geologically map and understand the implications for geologic history and for stakeholders. Mapping of the lower Colorado River valley requires significant field mapping and stratigraphic study, supported by sedimentologic, paleontologic studies, and dating by luminescence, cosmogenic isotopes, C-14, tephrochronology, and paleomagnetic methods. We also plan to analyze recently obtained core material from near Topock, AZ, to look for possible diatom, ostracode, and pollen proxies for paleoclimate and paleoecology. Work is being done collaboratively with the DOI Topock Project (Peter Martin, WRD), and the Lower Colorado River Science on the DOI Landscape Project (Andrea Alpine and Charles Van Riper, BRD), and the Southwest Climate History Project (John Barron, ESD program). Task Products Dorsey, R. J., Housen, B. A., Janecke, S. U., McDougall, K., Fanning, M., Fluette, A., Axen, G. J., and Shirvell, C. R., 2006, Chronostratigraphy of the Fish Creek-Vallecito Basin, SW Salton Trough: a high-fidelity record of slip on the West Salton Detachment Fault and subsidence in its upper plate: EOS Transactions, American Geophysical Union, v. 87, no. 52, suppl. 26. Dorsey, Rebecca J., Fluette, Amy L., Housen, Bernard A., McDougall, Kristin A., Janecke, Susanne U., Axen, Gary J., Shirvell, Catherine, 2006, Chronology of late Miocene to early Pliocene sedimentation at Split Mt. Gorge, western Salton Trough: Implications for development of the Pacific-North America Plate boundary; Lithospheric Rupture in the Gulf of California - Salton Trough Region, http://www.rcl-cortez.wustl.edu, p. 59. Malmon, D. V., Howard, K., Lundstrom, S., and Felger, T., 2006, Response of the Colorado River to a late Pleistocene pulse of fine-grained sediment: EOS, American Geophysical Union Transactions v. 87(52). Fall Meeting Supplement, Abstract H11B-1255. McDougall, K., 2006, Late Neogene marine incursions and the ancestral Gulf of California; Lithospheric Rupture in the Gulf of California - Salton Trough Region, http://www.rcl-cortez.wustl.edu, p. 59. Dorsey, R. J., Fluette, A., McDougall, K., Housen, B. A., Janecke, A. U., Axen, G. J., and Shirvell, C. R., 2007, Chronology of Miocene-Pliocene deposits at Split Mountain Gorge, Southern California: a record of regional tectonics and Colorado River evolution: Geology v.35, no.1, p. 57-60. Howard, K,A., Stock, G., Rockwell, T., Schafer, J., Webb, R. H., 2007, Holocene cyclical switching of Colorado River delta water alternatively to the Sea of Cortez or to the Salton Sink: EOS, American Geophysical Union Transactions v. 88(23). Joint Assembly Supplement, Abstract H44A-05. Howard, K. A. and Malmon, D. V., 2007, Stratigraphy of Colorado River deposits in lower Mohave Valley, Arizona and California, in Reynolds, R. E., editor, Wild, Scenic and Rapid, a trip down the Colorado River trough, Field trip guide and abstracts from the 2007 Desert Symposium: Northridge, California State University, and LSA Associates, p.50–56. Kimbrough, D., Grove, M., Gehrels, G., Dorsey, R., House, K.P., Howard, K., Pearthree, P. A., Spencer, J. E., Mahoney, B., 2007, Detrital zircon record of Colorado River incision: Eos American Geophysical Union Transactions, v. 88 (23), Joint Assembly Supplement, Abstract T41C-03. Kirby, S. M., Janecke, S. U., Dorsey, R. J., Housen, B. A., Langenheim, V. E., McDougall, K., Steely, A. N., 2007, Pleistocene Brawley and Ocotillo formations: evidence for initial strike-slip deformation along the San Felipe and San Jacinto fault zones, southern California: Journal of Geology, v. 115, p. 43-62. Malmon, D. V., Felger, T., and Howard, K. A., 2007. Floodplain lakes and alluviation cycles of the lower Colorado River, in Proceedings of a USGS Workshop on Facing Tomorrow’s Challenges Along the U.S.-Mexico Border—Monitoring, Modeling, and Forecasting Change Within the Arizona-Sonora Transboundary Watersheds, U.S. Geological Survey Circular 1322. Malmon, D. V. and Howard, K. A, 2007, Overview; the Chemehuevi Formation along the lower Colorado River, in Reynolds, R. E., editor, Wild, Scenic and Rapid, a trip down the Colorado River trough, Field trip guide and abstracts from the 2007 Desert Symposium: Northridge, California State University, and LSA Associates, p.57–60 Malmon, D., 2007, Preliminary observations of geochemical properties of Colorado River and related sediments, in Reynolds, R. E., editor, Wild, Scenic and Rapid, a trip down the Colorado River trough, Field trip guide and abstracts from the 2007 Desert Symposium: Northridge, California State University, and LSA Associates, p.61–62 Nagler, P. L., Glenn, E. P., Howard, K. A., and Webb, R. H., 2007, A water budget for riparian vegetation on the lower Colorado River: the myth of water salvage: EOS, American Geophysical Union Transactions v. 88(23). Joint Assembly Supplement, Abstract H44A-08. Reynolds, R. E., Faulds, J., House, P. K., Howard, K. A., Malmon, D., Miller, C. F., and Pearthree, P. A., 2007, Wild, scenic and rapid trip down the Colorado River trough; Desert Symposium field trip 2007, in Reynolds, R. E., editor, Wild, Scenic and Rapid, a trip down the Colorado River trough, Field trip guide and abstracts from the 2007 Desert Symposium: Northridge, California State University, and LSA Associates, p.5–32. Chesley, J., Sanchez, C. A., Asmerom, Y., and Malmon, D., 2008, Discerning Sources of Metal Contamination in the Colorado River from Isotopic Ratio Measurements, American Chemical Society, meeting Las Vegas, NV, September 2008. Delong, S. B., Johnson, J.P., Whipple, K. X., Post, D. F., Rossi, M. R., Malmon, D. V., Chu, D., Hellerstein, J., Klues, K., Levis, P., and Martin, R., 2008, Environmental monitoring of hydrology and channel headwall erosion in a semiarid discontinuous arroyo network, Page Ranch, Arizona, EOS (American Geophysical Union, Dec. 2008), v. 89, no. 53, Abstract H43F-1075. Howard, K. A. and Malmon, D. V., 2008, Boulders Deposited by Pliocene and Pleistocene floods on the lower Colorado River, in Reynolds, R. E., editor, Trough to trough; The Colorado River and the Salton Sea, Proceedings of the 2008 Desert Symposium: Northridge, California State University, Desert Studies Consortium and LSA Associates, Inc., p. 112 Howard, K. A., Lundstrom, S. C., Malmon, D. V., and Hooke, S. J., 2008, Age, distribution, and formation of late Cenozoic paleovalleys of the lower Colorado River and their relation to river aggradation and degradation, in Reheis, M. C., Herschler, R., and Miller, D. M., editors, Late Cenozoic Drainage History of the Southwestern Great Basin and Lower Colorado River Region: Geologic and Biotic Perspectives: Geological Society of America Special Paper 439, 391– 410. Lundstrom, S. C., Mahan, S., Paces, J., Hudson, M., House, P. K., Malmon, D., Blair, J. L., and Howard, K. A., 2008, Late Pleistocene aggradation and degradation of the lower Colorado River: Perspectives from the Cottonwood area and other reconnaissance below Boulder Canyon, in Reheis, M. C., Hershler, R., and Miller, D. M., editors, Late Cenozoic Drainage History of the Southwestern Great Basin and Lower Colorado River Region: Geologic and Biotic Perspectives, p. 409-430. Malmon, D. V, Dunne, T., and Reneau, S. L., 2008, Stochastic analysis of particle trajectories through river valleys, EOS (American Geophysical Union, Dec. 2008), v. 89, no. 53, Abstract H51J-06. Malmon, D. V., Felger, T. J., and Howard, K. A, 2008, Geologic controls on floodplain lakes in the lower Colorado River: Colorado River Basin Science and Resource Management Symposium, Scottsdale, AZ, November 18-20, 2008 Malmon, D. V., Shafroth, P. B., and House, P. K., 2008, Interdisciplinary Mapping along the Lower Colorado River: Importance to climate science, habitat restoration, and urban planning in National Wildlife Refuges and other Public Lands, poster presentation at USFWS-USGS conference: Effects of climate change on fish, wildlife and habitats in the arid and semiarid southwestern United States, Aug. 2008, Tucson, AZ, http://www.fws.gov/southwest/Climatechange McDougall, K., 2008, Late Neogene marine incursions and the ancestral Gulf of California, in Reheis, M. C., Herschler, R., and Miller, D. M., editors, Late Cenozoic Drainage History of the Southwestern Great Basin and Lower Colorado River Region: Geologic and Biotic Perspectives: Geological Society of America Special Paper 439, 355– 374. Nagler, P. L., Glenn, E. P., Hinojosa-Huerta, O., Zamora F., and Howard, K. A., 2008, Vegetation dynamics and evapotranspiration in the riparian corridor in the delta of the Colorado River, Mexico: Journal of Environmental Management, v, 88, p. 864–874, doi:10.1016/j.jenvman.2007.04.010. Malmon, D. V., Howard, Keith A., and Priest, Susan S., 2009, Geologic map of the Needles 7.5' quadrangle, California and Arizona: U.S. Geological Survey Scientific Investigations Map 3062, scale 1;24,000, 1 sheet, includes 31 p. pamphlet [http://pubs.usgs.gov/sim/3062/]. Malmon, D. V., Howard, K. A., Martin, P.M., McGeehin, J.P., Wan, E., and Mahan, S., 2009, the stratigraphic record of the lower Colorado River - Possible climate connections: in Pacific Climate Workshop PACLIM 2009 workshop. Malmon, D. V., Howard, P. K., House, S. C., Lundstrom, and Pearthree, P. A., 2009, The Chemehuevi Formation - a geologic example of extraordinary sediment loading in the Colorado River during the late Pleistocene: Geological Society of America Abstracts with Programs, v. 41, no. 7, p. 574. Malmon, D. V., 2009, Geologic record of the lower Colorado River – possible climate connections, 2009: PACLIM 2009 Pacific Climate conference, Monterey, CA, April 19-22, 2009. McDougall, Kristin, 2009, Update on microfossil studies in the northern Gulf of California and Salton Trough, MARGINS workshop “Rupturing of continental lithosphere in the Gulf of California-Salton Trough region, Charleston, South Carolina, April, 2009. Sanchez, C. A., Chesely, J., Asmerom, Y., and Malmon, D., 2009, Tracing the sources of Uranium in the Colorado River basin: Lake Mead Science Symposium, Las Vegas, Nevada, January 13-14, 2009. Malmon, D. V., Felger, T. J., and Howard, K. A., 2010, Geologic considerations for the placement and design of backwater restoration sites along the lower Colorado River, in Melis, T. S., Hamill, J. F., Coggins, L. G. Jr., Grams, P. E., Kennedy, T. A., Kubley, D. M., and Ralston, B. E.,. editors, Proceedings of the Colorado River Basin Science and Resource Management Symposium, Scottsdale, Arizona: U.S. Geological Survey Scientific Investigations Report 2010- 5135, p. 307-315. Report, Planned: McDougall, K., 2010, Update on microfossils studies in the northern Gulf of California, Salton Trough, and lower Colorado River, USGS Map, Planned: John, B. E., Howard, K. A., Nielson, J. E., and Miller, J. G., 2011, Geologic map of the Topock 7.5-minute quadrangle, Arizona and California, USGS, Scientific Investigations Map Map, Planned: Malmon, D. V., and Priest, S. S., 2011, Surficial geologic map of the Castle Rock 7.5' quadrangle, California and Arizona, USGS