2022/2023 Meetings

The AEG Southern Nevada Chapter holds dinner meetings eight times per year.  Meetings are currently being held on the second Tuesday of the month at the Embassy Suites Las Vegas located at 4315 University Center Drive (Near UNLV between Harmon Avenue and Flamingo Road) in Las Vegas, Nevada.  Each meeting features a presentation regarding a pertinent geological, environmental, or other relevant science-based issue.

Check-in and Socialize 6:00 to 6:30 pm

Dinner: 6:30 pm

Presentation: 7:15 to 8:00 pm

 

Members:  $35.00

Non-members:  $40.00

Students: $17.00 (Do not Pay in Advance)

Student Non-members: $20.00 (Do not Pay in Advance)

Walk-ins: $45.00

Vegetarian options are available.  Just let us know when you

register!

Payment for attending required at the time of registration.

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Tuesday - November 8, 2022

 6:00 to 8:00 p.m. PST

"Geologic Mapping, Geochronology, and Fault Characterization

in the Las Vegas Basin"

By:  Seth Dee,

Geologic Mapping Program Manager, Nevada Bureau of Mines and Geology,

University of Nevada, Reno

Abstract:

A recent investigation into the seismic hazard of the Las Vegas basin includes a new surficial geology and Quaternary fault map, luminescence dating, and paleoseismic investigations of the Las Vegas Valley fault system (LVVFS) and Frenchman Mountain fault system (FMFS). The new 1:50,000 scale map involved the compilation of twenty published 1:24,000 scale maps and new geologic mapping. The compilation utilized historical aerial imagery, lidar, and a new orthophoto mosaic and DEM derived from 1965 aerial stereo photos. This new mapping improves the accuracy of Quaternary fault locations and yields a consistent characterization of surficial units displaced by the faults. The mapping was accompanied by 37 new luminescence ages to better constrain the age of offset stratigraphy. The luminescence data includes ages from the fine-grained ground water discharge deposits of the Las Vegas Formation (LVF) as well as alluvial fan deposits.   

The LVVFS is a set of east-facing, northerly striking, intra-basin fault scarps up to 30 m high that displace LVF and alluvial fan deposits within the Las Vegas metropolitan area. Two paleoseismic trenches were excavated across the Eglington-Decatur fault, the westernmost in the LVVFS and the only fault with a continuous section of undeveloped scarps. The trenches exposed broadly warped LVF stratigraphy with 4-5 m of displacement and no evidence for brittle faulting.  Luminescence and radiocarbon ages constrain the age of warp formation as occurring between ~27 and ~8 ka, with no displacement for the preceding ~300,000 years. Preliminary displacement rates derived from the trench results have significant temporal variability, a shorter-term rate of ~0.15 –0.18 mm/yr and a maximum longer-term rate of ~0.03 mm/yr.

The FMFS is an arcuate, west-dipping, range-bounding normal and dextral-oblique fault on the eastern side of the Las Vegas basin. The entire length of the FMFS was remapped during this investigation utilizing lidar data and the pre-development orthophoto mosaic. The new mapping identified scarps along a southern section of the fault that displace an alluvial fan surface of probable late-Pleistocene, and adjacent fault kinematics documenting dextral-oblique slip. These observations confirm a component of dextral slip along the southern FMFS and extends the total fault length with evidence for Quaternary displacement to ~33 km. We also conducted a paleoseismic investigation of a previously excavated fault exposure in a late-Pleistocene alluvial fan along the northern section of the FMFS. Logging of the excavation documents evidence for three paleoearthquakes with luminescence ages from colluvial wedge deposits ranging from ~54 to ~25 ka. Scarp profiling conducted during previous investigations prior to widespread development coupled with new luminescence ages from displaced deposits yield a preliminary, vertical slip rate estimate of 0.11-0.20 mm/yr.

Bio: 

Seth Dee is the Geologic Mapping Program Manager for the Nevada Bureau of Mines and Geology (NBMG) at the University of Nevada, Reno. In that role he oversees the funding, production, and publication of geologic maps across the state; with an emphasis on applying mapping as a tool to understand crustal deformation, geologic hazards, landscape evolution, and natural resource management in Nevada. His research interests include understanding the timing and kinematics of Cenozoic crustal extension in the Basin and Range, the characterization of active faults and seismic hazards, and the age and climatic origins of alluvial fan and glacial deposits. Prior to joining NBMG in 2014 he worked in engineering geology, first for William Lettis and Associates and Fugro Consultants Inc. in Denver, CO, and subsequently for Lettis Consultants International in Walnut Creek, CA. His 8 years in consulting geology included domestic and international projects characterizing geologic hazards for large infrastructure projects and geotechnical site assessments. Seth attended the University of Oregon where he received a M.S. in geological sciences and the University of Puget Sound where he received a B.S. in geology.

Thank you to this month's sponsors!

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October 11, 2022
"SNWA Well System Management Program and Well Performance and Repair Case Study" by Jason Mace, Hydrologist II
November 8, 2022
“Geologic Mapping, Geochronology, and Fault Characterization in the Las Vegas Basin” By Seth Dee, Geologic Mapping Program Manager, Nevada Bureau of Mines and Geology, Reno, Nevada.
November 9, 2022
½ day field trip led by Seth Dee to fault locations in Las Vegas valley.  
January 10, 2023
“Legionella Occurrence Monitoring in Las Vegas Valley Groundwater” by Ariel Atkinson, R&D Process Systems Engineer, Water Quality Research and Development, Southern Nevada Water Authority, Las Vegas
February 7, 2023
AEG Jahns Lecturer Vince Cronin, Emeritus Professor of Geology, Baylor University, Waco, Texas. Lecture TBD.​
March 14, 2023
“Pharmaceuticals and Illicit Drugs in Surface Waters of the World’s Rivers, Including the Las Vegas Wash” by Douglas Sims, Dean, School of Science, Engineering, and Mathematics, CSN.
March 18 and 19, 2023
Joint field trip to location in Mojave Desert with Southern California and Inland Empire AEG chapters. Location TBD.
April 11, 2023
 “The Stillwater Scarp, Central Nevada – Coseismic Gravitational Failure on a 1,200-M-High Range-Front Escarpment” by James McCalpin, President, GEO-HAZ Consulting, Inc., Crestone, Colorado. (Winner of 2022 AEG Publication Award.)
May 9, 2023
“Water Issues in Southern Nevada and the Colorado River Basin” by Kyle Roerink, Executive Director, Great Basin Water Network, Reno, Nevada

May 27, 2023

Annual Field Trip: TBD

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