I 06°07 '3 0" 35"52'30" IJ rnfr,n fJ o ncl la~m.t b~ R J li eus St ,~t1gra ph1c s6cl1ons draft ed... more I 06°07 '3 0" 35"52'30" IJ rnfr,n fJ o ncl la~m.t b~ R J li eus St ,~t1gra ph1c s6cl1ons draft ed b 1 M. W Woo ld ri dge and R.
Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Con... more Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. Free Downloads NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. Non-members will have access to guidebook papers two years after publication. Members have access to all papers. This is in keeping with our mission of promoting interest, research, and cooperation regarding geology in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download. Road logs, mini-papers, maps, stratigraphic charts, and other selected content are available only in the printed guidebooks. Copyright Information Publications of the New Mexico Geological Society, printed and electronic, are protected by the copyright laws of the United States. No material from the NMGS website, or printed and electronic publications, may be reprinted or redistributed without NMGS permission. Contact us for permission to reprint portions of any of our publications. One printed copy of any materials from the NMGS website or our print and electronic publications may be made for individual use without our permission. Teachers and students may make unlimited copies for educational use. Any other use of these materials requires explicit permission. This page is intentionally left blank to maintain order of facing pages.
GSA Annual Meeting in Seattle, Washington, USA - 2017, 2017
Snowmelt-fed springs and small (0.5 km 2) upland catchments in alpine areas of the western USA co... more Snowmelt-fed springs and small (0.5 km 2) upland catchments in alpine areas of the western USA contribute significantly to the quantity and inorganic chemistry of water delivered to downstream basins but have not been studied extensively. Mineral weathering, transit time, and hydrologic mixing control the solute chemistry of waters that drain the upland zone of Niwot Ridge, Colorado Front Range and adjacent areas in the granitic core of the southern Rocky Mountains. Water in 37 springs sampled in this study flows in generally short, steep paths (~0.3 km) through shallow regolith with mean transit times (MTT) of weeks to months, producing solutions dominated by Si, Ca 2+ , Na + and HCO 3-, locally SO 4 2-. Rock type is a significant control on spring, surface-and shallow groundwater chemistry and plagioclase (oligoclase) is the major source of dissolved Na + and Si. Concentrations of Ca 2+ exceed stoichiometric predictions of oligoclase weathering by ~3.5x; excess Ca 2+ likely represents weathering of eolian material, vein calcite, or trace minerals. Concentrations of base cations and Si increase slowly with estimated MTT of 0.2 yr for Niwot Ridge spring waters, and several years for shallow groundwater sampled by wells. Chemical weathering of silicate minerals is slow with estimated rates of ~2.0 and 0.2 pmol m-2 s-1 for oligoclase and This article is protected by copyright. All rights reserved. microcline, respectively; the most mineralized spring waters are saturated only with respect to kaolinite and montmorillonite. More than 50% of the dissolved base cations + Si measured in Boulder Creek at Orodell (~25 km downstream) accumulate before water emerges from alpine springs on Niwot Ridge. Warming global temperatures are shifting more highelevation precipitation to rain, potentially changing runoff patterns, transit time, and solute loads. Acquisition of solutes by alpine waters thus has implications far beyond small upland catchments.
Infrequent, large magnitude geomorphic events generate quantifiable change on geologically short ... more Infrequent, large magnitude geomorphic events generate quantifiable change on geologically short timescales and are crucial to understanding landscape evolution. Airborne lidar surveys and field measurements were used to investigate floodplain erosion and deposition along a 19.5 km reach of Fourmile Creek, Colorado that was devastated by severe flooding in 2013 that followed a 2010 wildfire. More than 350 mm of rain fell on the Fourmile catchment from September 9-15, 2013, generating discharge that exceeded bankfull for >120 hr at the Orodell gage, with unit stream power >300 W m-2 throughout the study reach. Debris flows occurred on steep hillslopes and tributary channels in the most intensely burned areas. Lidar difference measurements and field studies highlight zones of local deposition along the study reach, but demonstrate overall net erosion of ~0.25 m for the 19.5 km reach of Fourmile floodplain, mainly by channel widening. Tributary junctions where debris-flow sediment entered the floodplain and local decreases in unit stream power controlled some zones of deposition. Overall, mass balance calculations show that a total sediment loss of ~91,000-161,000 m 3 from the Fourmile Creek floodplain and hillslopes, which is broadly consistent with channel
... DAVID P. DETHIER,1 STEPHANIE K. KAMPF,2 DAVID A. SAWYER3, AND JAMES R. BUDAHN3 1Department of... more ... DAVID P. DETHIER,1 STEPHANIE K. KAMPF,2 DAVID A. SAWYER3, AND JAMES R. BUDAHN3 1Department of Geosciences, Williams College, Williamstown, Massachusetts 01267, ddethier ... A full description of the WD-XRF technique was given by Taggart and Siems (2002). ...
... Bill Braddock, a retired structural geologist in the Univ. of Colorado geology department, he... more ... Bill Braddock, a retired structural geologist in the Univ. of Colorado geology department, helped with the interpre-tation below. The Dakota Group in this area consists of the basal Lytle Fin.(sandstone and conglomerate) and the overlying South Platte Fm. ... The Lytle Fm. ...
Geological Society of America Bulletin, Jun 1, 1988
Erosion surfaces in the Espanola basin formed before 350 ka and between 350 and 240, 240 and 130,... more Erosion surfaces in the Espanola basin formed before 350 ka and between 350 and 240, 240 and 130, and 130 and 80 ka, probably in response to climatic change and regional uplift. The surfaces are cut on Miocene, Pliocene, and Pleistocene deposits and range from about 200 m to 15 m above the present Rio Chama/Rio Grande system. Periods when the surfaces formed were dated using varnish-cation ratios from exposed clasts, the mass of soil carbonate, and amino-acid ratios in Pleistocene gastropods from underlying deposits. Thorium/uranium ages from soil carbonate were used to calibrate a local curve for varnish-cation ratios. The range in age determined for a given surface, although derived from different dating techniques, implies that parts of the surface were sites of erosion or aggradation after the surface formed. From 1.1 Ma to present, denudation rates averaged 10 cm/1,000 yr from weakly lithified sandstone, less than 7 cm/1,000 yr from indurated tuff and boulder gravel, and about 4 cm/1,000 yr from tuff and basalt. Erosion surfaces were preserved as upland benches and terraces by stream incision during periods of pluvial climate and regional uplift, but our data do not permit clear separation of the two causes.
I 06°07 '3 0" 35"52'30" IJ rnfr,n fJ o ncl la~m.t b~ R J li eus St ,~t1gra ph1c s6cl1ons draft ed... more I 06°07 '3 0" 35"52'30" IJ rnfr,n fJ o ncl la~m.t b~ R J li eus St ,~t1gra ph1c s6cl1ons draft ed b 1 M. W Woo ld ri dge and R.
Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Con... more Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. Free Downloads NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. Non-members will have access to guidebook papers two years after publication. Members have access to all papers. This is in keeping with our mission of promoting interest, research, and cooperation regarding geology in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download. Road logs, mini-papers, maps, stratigraphic charts, and other selected content are available only in the printed guidebooks. Copyright Information Publications of the New Mexico Geological Society, printed and electronic, are protected by the copyright laws of the United States. No material from the NMGS website, or printed and electronic publications, may be reprinted or redistributed without NMGS permission. Contact us for permission to reprint portions of any of our publications. One printed copy of any materials from the NMGS website or our print and electronic publications may be made for individual use without our permission. Teachers and students may make unlimited copies for educational use. Any other use of these materials requires explicit permission. This page is intentionally left blank to maintain order of facing pages.
GSA Annual Meeting in Seattle, Washington, USA - 2017, 2017
Snowmelt-fed springs and small (0.5 km 2) upland catchments in alpine areas of the western USA co... more Snowmelt-fed springs and small (0.5 km 2) upland catchments in alpine areas of the western USA contribute significantly to the quantity and inorganic chemistry of water delivered to downstream basins but have not been studied extensively. Mineral weathering, transit time, and hydrologic mixing control the solute chemistry of waters that drain the upland zone of Niwot Ridge, Colorado Front Range and adjacent areas in the granitic core of the southern Rocky Mountains. Water in 37 springs sampled in this study flows in generally short, steep paths (~0.3 km) through shallow regolith with mean transit times (MTT) of weeks to months, producing solutions dominated by Si, Ca 2+ , Na + and HCO 3-, locally SO 4 2-. Rock type is a significant control on spring, surface-and shallow groundwater chemistry and plagioclase (oligoclase) is the major source of dissolved Na + and Si. Concentrations of Ca 2+ exceed stoichiometric predictions of oligoclase weathering by ~3.5x; excess Ca 2+ likely represents weathering of eolian material, vein calcite, or trace minerals. Concentrations of base cations and Si increase slowly with estimated MTT of 0.2 yr for Niwot Ridge spring waters, and several years for shallow groundwater sampled by wells. Chemical weathering of silicate minerals is slow with estimated rates of ~2.0 and 0.2 pmol m-2 s-1 for oligoclase and This article is protected by copyright. All rights reserved. microcline, respectively; the most mineralized spring waters are saturated only with respect to kaolinite and montmorillonite. More than 50% of the dissolved base cations + Si measured in Boulder Creek at Orodell (~25 km downstream) accumulate before water emerges from alpine springs on Niwot Ridge. Warming global temperatures are shifting more highelevation precipitation to rain, potentially changing runoff patterns, transit time, and solute loads. Acquisition of solutes by alpine waters thus has implications far beyond small upland catchments.
Infrequent, large magnitude geomorphic events generate quantifiable change on geologically short ... more Infrequent, large magnitude geomorphic events generate quantifiable change on geologically short timescales and are crucial to understanding landscape evolution. Airborne lidar surveys and field measurements were used to investigate floodplain erosion and deposition along a 19.5 km reach of Fourmile Creek, Colorado that was devastated by severe flooding in 2013 that followed a 2010 wildfire. More than 350 mm of rain fell on the Fourmile catchment from September 9-15, 2013, generating discharge that exceeded bankfull for >120 hr at the Orodell gage, with unit stream power >300 W m-2 throughout the study reach. Debris flows occurred on steep hillslopes and tributary channels in the most intensely burned areas. Lidar difference measurements and field studies highlight zones of local deposition along the study reach, but demonstrate overall net erosion of ~0.25 m for the 19.5 km reach of Fourmile floodplain, mainly by channel widening. Tributary junctions where debris-flow sediment entered the floodplain and local decreases in unit stream power controlled some zones of deposition. Overall, mass balance calculations show that a total sediment loss of ~91,000-161,000 m 3 from the Fourmile Creek floodplain and hillslopes, which is broadly consistent with channel
... DAVID P. DETHIER,1 STEPHANIE K. KAMPF,2 DAVID A. SAWYER3, AND JAMES R. BUDAHN3 1Department of... more ... DAVID P. DETHIER,1 STEPHANIE K. KAMPF,2 DAVID A. SAWYER3, AND JAMES R. BUDAHN3 1Department of Geosciences, Williams College, Williamstown, Massachusetts 01267, ddethier ... A full description of the WD-XRF technique was given by Taggart and Siems (2002). ...
... Bill Braddock, a retired structural geologist in the Univ. of Colorado geology department, he... more ... Bill Braddock, a retired structural geologist in the Univ. of Colorado geology department, helped with the interpre-tation below. The Dakota Group in this area consists of the basal Lytle Fin.(sandstone and conglomerate) and the overlying South Platte Fm. ... The Lytle Fm. ...
Geological Society of America Bulletin, Jun 1, 1988
Erosion surfaces in the Espanola basin formed before 350 ka and between 350 and 240, 240 and 130,... more Erosion surfaces in the Espanola basin formed before 350 ka and between 350 and 240, 240 and 130, and 130 and 80 ka, probably in response to climatic change and regional uplift. The surfaces are cut on Miocene, Pliocene, and Pleistocene deposits and range from about 200 m to 15 m above the present Rio Chama/Rio Grande system. Periods when the surfaces formed were dated using varnish-cation ratios from exposed clasts, the mass of soil carbonate, and amino-acid ratios in Pleistocene gastropods from underlying deposits. Thorium/uranium ages from soil carbonate were used to calibrate a local curve for varnish-cation ratios. The range in age determined for a given surface, although derived from different dating techniques, implies that parts of the surface were sites of erosion or aggradation after the surface formed. From 1.1 Ma to present, denudation rates averaged 10 cm/1,000 yr from weakly lithified sandstone, less than 7 cm/1,000 yr from indurated tuff and boulder gravel, and about 4 cm/1,000 yr from tuff and basalt. Erosion surfaces were preserved as upland benches and terraces by stream incision during periods of pluvial climate and regional uplift, but our data do not permit clear separation of the two causes.
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