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Year Published: 2018

Geology and geologic history: Overview of the geology of the San Francisco Bay region

The geology of San Francisco and the surrounding northern and central California area has played a pivotal role in the development of our understanding of Earth processes, especially the process of tectonic accretion at a continental margin and the development of transform plate margins. The Franciscan Complex, which underlies most (or perhaps...

Johnson, A. Kenneth; Bartow, Greg W.; Graymer, Russell

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Year Published: 2018

Flushing of the deep Pacific Ocean and the deglacial rise of atmospheric CO2 concentrations

During the last deglaciation (19,000–9,000 years ago), atmospheric CO2increased by about 80 ppm. Understanding the mechanisms responsible for this change is a central theme of palaeoclimatology, relevant for predicting future CO2 transfers in a warming world. Deglacial CO2 rise hypothetically tapped an accumulated deep Pacific carbon...

Du, Jianghui; Haley, Brian; Mix, Alan; Walczak, Maureen; Praetorius, Summer K.
Du, J., Haley, B., Mix, A., Walczak, M., Praetorius, S: Flushing of the deep Pacific Ocean and the deglacial rise of atmospheric CO2 concentrations. Nature Geoscience. 10.1038/s41561-018-0205-6 (2018)

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Year Published: 2018

Global and Arctic climate sensitivity enhanced by changes in North Pacific heat flux

Arctic amplification is a consequence of surface albedo, cloud, and temperature feedbacks, as well as poleward oceanic and atmospheric heat transport. However, the relative impact of changes in sea surface temperature (SST) patterns and ocean heat flux sourced from different regions on Arctic temperatures are not well constrained. We modify ocean-...

Praetorius, Summer K.; Rugenstein, Maria A.; Persad, Geeta; Caldeira, Ken
Praetorius, S., Rugenstein, M. Persad, G. Caldeira, K. Global and Arctic climate sensitivity enhanced by changes in North Pacific heat flux, Nature Communications 9: 3124 (2018).

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Year Published: 2018

Carving Grand Canyon’s inner gorge: A test of steady incision versus rapid knickzone migration

A recent study posits that much of the 240-m-deep inner gorge of Grand Canyon was carved between 500 and 400 ka via passage of a migrating knickzone with incision rates of ~1600 m/Ma during that time period; this was based on dating of a ca. 500 ka travertine deposit perched on the rim of the inner gorge, near Hermit Rapid, and a ca. 400 ka...

Crow, Ryan S.; Karlstrom, Karl E.; Crossey, Laura J.; Polyak, Victor; Asmerom, Yemane; McIntosh, William C.
Ryan S. Crow, Karl E. Karlstrom, Laura J. Crossey, Victor J. Polyak, Yemane Asmerom, William C. McIntosh; Carving Grand Canyon’s inner gorge: A test of steady incision versus rapid knickzone migration. Geosphere doi: https://doi.org/10.1130/GES01562.1

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Year Published: 2018

Geoelectric hazard maps for the Pacific Northwest

Maps of extreme value, horizontal component geoelectric field amplitude are constructed for the Pacific Northwest United States (and parts of neighboring Canada). Multidecade long geoelectric field time series are calculated by convolving Earth surface impedance tensors from 71 discrete magnetotelluric survey sites across the region with...

Love, Jeffrey J.; Lucas, Greg M.; Kelbert, Anna; Bedrosian, Paul A.

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Year Published: 2018

Outburst floods provide erodability estimates consistent with long-term landscape evolution

Most current models for the landscape evolution over geological timescales are based on semi-empirical laws that consider riverbed incision proportional to rock erodability (dependent on lithology) and to the work performed by water flow (stream power). However, the erodability values obtained from these models are entangled with poorly known...

Garcia-Castellanos, Daniel; O'Connor, Jim E.
Garcia-Castellanos, D., and O'Connor, J.E., 2018, Outburst floods provide erodability estimates consistent with long-term landscape evolution: Scientific Reports, https://doi.org/10.1038/s41598-018-28981-y.

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Year Published: 2018

Breaching of strike-slip faults and successive flooding of pull-apart basins to form the Gulf of California seaway from ca. 8–6 Ma

The geologic record of the formation of marine basins during continental rifting is uncommonly preserved. Using GIS-based paleotectonic maps, we show that marine basin formation in the Gulf of California–Salton trough oblique rift (Mexico and the United States) occurred in a stepwise manner as crustal thinning lowered elevations within the Gulf of...

Umhoefer, Paul J.; Darin, Michael H.; Bennett, Scott E. K.; Skinner, Lisa A.; Dorsey, Rebecca J.; Oskin, Michael E.
Umhoefer, P. J., Darin, M. H., Bennett, S. E., Skinner, L. A., Dorsey, R. J., & Oskin, M. E. (2018). Breaching of strike-slip faults and successive flooding of pull-apart basins to form the Gulf of California seaway from ca. 8–6 Ma. Geology, 46(8), 695-698.

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Year Published: 2018

Geochemical characterization and modeling of regional groundwater contributing to the Verde River, Arizona between Mormon Pocket and the USGS Clarkdale gage

We use synoptic surveys of stream discharge, stable isotopes, and dissolved noble gases to identify the source of groundwater discharge to the Verde River in central Arizona. The Verde River more than doubles in discharge in Mormon Pocket over a 1.4 km distance that includes three discrete locations of visible spring input to the river and other...

Beisner, Kimberly R.; Gardner, W. Payton; Hunt, Andrew G.
Beisner, K.R., Gardner, W.P., Hunt, A.G., (2018) Geochemical characterization and modeling of regional groundwater contributing to the Verde River, Arizona between Mormon Pocket and the USGS Clarkdale gage, Journal of Hydrology. vol. 564, p. 99-114. https://doi.org/10.1016/j.jhydrol.2018.06.078

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Year Published: 2018

Rapid 3-D analysis of rockfalls

Recent fatal and damaging rockfalls in Yosemite National Park indicate the need for rapid response data collection methods to inform public safety and assist with management response. Here we show the use of multiple-platform remote sensing methods to rapidly capture pertinent data needed to inform management and the public following a several...

Stock, Greg M.; Guerin, A.; Avdievitch, Nikita N.; Collins, Brian D.; Jaboyedoff, Michel
Stock, G.M., Guerin, A., Avdievitch, N., Collins, B.D., Jaboyedoff, M., 2018, Rapid 3-D analysis of rockfalls, GSA Today, Groundwork, v. 28, https://doi.org/10.1130/GSATG374GW.1.

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Year Published: 2018

Against the current— The Mojave River from sink to source: The 2018 Desert Symposium field trip road log

The Mojave River evolved over the past few million years by “fill and spill” from upper basins near its source in the Transverse Ranges to lower basins. Each newly “spilled into” basin in the series? sustained a long-lived lake but gradually filled with Mojave River sediment, leading to spill to a yet lower elevation? basin. The Mojave River...

Miller, David M.; Reynolds, R.E.; Groover, Krishangi D.; Buesch, David C.; Brown, H. J.; Cromwell, Geoffrey; Densmore-Judy, Jill; Garcia, A.L.; Hughson, D.; Knott, J.R.; Lovich, Jeffrey E.
Miller, D.M., Reynolds, R.E., Groover, K., Buesch, D.C., Brown, H.J., Cromwell, G.A., Densmore, J., Garcia, A.L., Hughson, D., Knott, J.R., and Lovich, J., 2018, Against the current-The Mojave River from sink to source; The 2018 Desert Symposium Field Trip Road Log: California, Desert Symposium meeting in April of 2018.

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Year Published: 2018

World distribution of uranium deposits

Deposit data derived from IAEA UDEPO (http://infcis.iaea.org/UDEPO/About.cshtml) database with assistance from P. Bruneton (France) and M. Mihalasky (U.S.A.). The map is an updated companion to "World Distribution of Uranium Deposits (UDEPO) with Uranium Deposit Classification, IAEA Tech-Doc-1629". Geology was derived from L.B. Chorlton,...

Fairclough, M. C.; Irvine, J. A.; Katona, L. F.; Simmon, W. L.; Bruneton, P.; Mihalasky, Mark J.; Cuney, M.; Aranha, M.; Pylypenko, O.; Poliakovska, K.
Fairclough, M.C., Irvine, J.A., Katona, L.F., and Slimmon, W.L., 2018, World distribution of uranium deposits, second edition: International Atomic Energy Agency, Vienna, Austria.

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Year Published: 2018

Assessing rockfall susceptibility in steep and overhanging slopes using three-dimensional analysis of failure mechanisms

Rockfalls strongly influence the evolution of steep rocky landscapes and represent a significant hazard in mountainous areas. Defining the most probable future rockfall source areas is of primary importance for both geomorphological investigations and hazard assessment. Thus, a need exists to understand which areas of a steep cliff are more likely...

Matasci, Battista; Stock, Greg M.; Jaboyedoff, Michael; Carrea, Dario; Collins, Brian D.; Guérin, Antoine; Matasci, G.; Ravanel, L.
Matasci B., Stock G.M., Jaboyedoff M., Carrea D., Collins B.D., Guerin A., Matasci G., Ravanel L., 2018, Assessing rockfall susceptibility in steep and overhanging slopes using three-dimensional analysis of failure mechanisms: Landslides, Vol. 15(5), 859–878 .