The Thousand Lake Fault: Earthquake Geology of a Long-Recurrence Normal Fault at the Eastern Edge of the Basin and Range 1 2 3 4 1s 3s 1s Contact Information: Dr. Nathan A. Toke, Associate Professor Nathan Toke, David Marchetti, Christopher Bailey, Robert Biek, Joseph Phillips, Hanna Bartram, and Clayton Forster Department of Earth Science, Valley University 800 W. University Parkway, Orem, UT 84058 1 - Utah Valley University, Department of Earth Science 2 - Western State Colorado University, Geology Program 3 - College of William and Mary, Department of Geology 4 - Utah Geological Survey [email protected] http://research.uvu.edu/toke/

A Basin and Range Fault Abutting the Colorado Plateau Cumulative Long-term Fault Slip Rate Constraints from Fremont River Incision and Terrace Warping

View Looking South along TLF, near Terraces in the area of greatest slope in the Fremont River gorge have Sunglow Campground incised 100 m in about 200 kya. Incision rates across the lower gradient TLF scarp are almost certainly less than within the gorge and therefore fault slip rates are even lower during the late Pleistocene.

a 2300 • Age of Displaced Volcanics ~26 Mya (UGS and NIGL, 2012) Qt ~ 180m • Tectonic Initiation 10-16 Mya (e.g., McQuarrie and TLF Wernicke, 2005)

2200 Terr of aces Thou with a’ Qt ~ 60 m sand in 8 k Near Fault Center Lake m Remnant Qt ~ 35 m sFau lt (TL Volcanic Minimum Long Term Slip Rate ~ 0.1 mm/a Qt ~15 m F) Marchetti and Cerling, 2005: Tablelands Maximum Long Term Slip Rate ~ 0.25 mm/a 2100 3He ages - ~200 kya

Also see Bartram, 2014 F C Terrace L Remnant T ~100 m Volcanic ) Table lands l 2000 JM Terrace m s

a ~100 m

r s e t a a’ 1900 m e (

n o i 1500-2500 m t a Repka, Anderson, and Finkel, 1997: v e l 1800 CRN Terrace Ages downstream E ~0.8 mm/yr Incision Rate Estimated headwaters exhumation of 30m/Ma Thousand Lake Mt 1700 Fremont 151 +/- 24 kya FR4 120 m Rabbit Valley/ R Aquarius Plateau iv TLF er 102 +/- 16 kya Late Pleistocene Fault Slip Rate Pr FR3 80 m 1600 of Alluvial Fan Scarp ile 60 +/- 9 kya FR2 45 m a (2x Vertical Exaggeration) a’ Fremont River 2230 FR1 20 m

2225 1500 2220 15000 35000 55000 2215 Distance Downstream (meters)

Boulder Mt 2210

2205 25 50 75 100 125 150 175 200 225 250 275 Terrace sets approaching the TLF appear to show warping due to uplift of the footwall side of the fault. This observation The Thousand Lake Fault (TLF) trends north-south and dips to the west. The TLF fault zone extends for Only 3-4 meters of displacement across a fan could represent an opportunity to learn additional information about fault activity or other mechanisms of uplift that may be at least 50 km. Uplift along the east side of the fault has helped to produce the 11,000+ ft high Boulder and Thousand Lake Mountains (~1000 m of local relief). However, the Fremont River maintains a water that was abandoned 81-246 kya (Marchetti et al., 2005, active within the region (isostatic adjustments due to glaciation, sedimentation, etc.). gap across the TLF, demonstrating its competency to down-cut faster than the fault produces relief. 3He exposure ages): 0.01-0.05 mm/a. Elsewhere, Great Basin margin faults have relatively fast slip rates and high recurrence rates...

Thousand Lake Fault Paleoseismic Trenching Lines fault Thousand Lake Fault Trench - South Wall Soil Bk-III fault queried South Wall North Wall contact Units Scale: OSL Sample Soil A - Horizon 1 Sq meter Colluvial Wedge Bulk Soil Sample Bench Soil Bk-II-III Soil-A Colluvial * * * * * * * * ** *** ** *** ** ** * *** * * *** ( * **** ** ****** * * ** * ** * *** ( ( ( * ** * * * ** * * * * ( * **** ** * * *** *** * * *** *** ( * * ** ** * * * * ** * * ( (( ( ( ( * ** * ** * * * ( ( *** ** * * * * * ** *** * * ( ( ( ( (( ( * * * * * ** * * *Wedge* * ( ( (( ( ( ( * * * * * ** * * * * * * ** * ( ( ( ** * * * ** * * * (( ( ( (( ( ( ** * * * * * * **** * ** ( * * * * * * ** ** * ** * * Soil-Bk-I-II ( *** * * * **** * * ***** * ** * ** * ***** * * ** * * ** ** * * * ** * * * * * Soil Bk I-II * ** * ** * * * * * ** *** * * * ** **** * * ** * * ** * ** * *** **** * * * * * * * * ** * * * * *** *** ** * * ** ***** * ** * * * * * * * ** * * * * * * * ** ** ** *** * * * * **** ** * ** *** * * *** ** * ** **** *** ** * * *** ******** * ** *** * * **** * ** ** * * * * *** ** * * ** * *** * * * ** * **** * ** * ** Colluival Wedge *** * *** * * ** * * * * * ** ** **** *** ** * * ** * * * ** * ** * *** * *** * Soil A - Horizon * ** * * * ** * ** ** ** * ** *** ** * Soil Bk-III Fissure Fill Soil Bk-I-II Soil-Bk-III Soil Bk-III Fluvial Gravels ( ( ( ( ( ( ( (( ( (( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (( ( ( ( ( ( ( ( (( ( ( ( ( ( ( ( (( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( (( ( ( ( ( ( ( (( ( ( ( ( ( ( ( ( ( ( ( Fluvial Sand ( Clast-V Debris Flow I Debris Flow II

Paleoseismic Trench in old, abandoned fan Summary of Event Information: * Stage III soil carbonate is displaced by 0.8 to 1.2 m in each wall. * A wedge of scarp-derived colluvium overlies and mingles with a less developed soil carbonate horizon on the hanging wall. Conclusions: *The less developed soil carbonate is nearly absent on the footwall. *Both trenches have multiple fault zones, but only one is interpretable. * At least two events have ruptured the TLF since 81-246 kya *Multiple events have occurred, likely two, since the fan was active.

* Recurrence rate is on the order of 50,000 to 125,000 years/event References Trench Site Additional Fault Exposures Anderson, R.E., and Barnhard, T.P., 1986, Genetic relationship between faults and folds and determination of Laramide and neotectonic paleostress, western Colorado Plateau-transition zone, central Utah: * Slip rate appears to be lower during the late Pleistocene Tectonics, v. 5, p. 335-357. Bartram, H.C., 2014, The Geometry, Kinematics, and History of the Thousand Lake Fault System, Central Utah. Undergraduate Honors Thesis, Paper 102, College of William and Mary. Biek, R.F., 2016, Interim Geologic Map of the Bicknell Quadrangle, Wayne County, Utah, Utah Geological * Slip rate ranges from 0.01-0.25 mm/a since the mid Miocene. Survey Open-File Report 654. Doelling H. and P. Kuehne, 2007, Interim Geologic Map of the East Half of the Loa 30’ x 60’ Quadrangle, Wayne, Garfield, and Emery Counties, Utah, Utah Geological Survey Open-File Report 489. Harty, K.M., 1987, Field reconnaissance of Thousand Lake fault zone: Utah Geological and Mineral Survey, memorandum, 2 p. Hecker, S., 1993, Quaternary tectonics of Utah with emphasis on earthquake-hazard characterization: Utah Geological Survey Bulletin 127, 157 p., 6 pls., scale 1:500,000. Additional work to be done: McQuarrie, N. and B.P. Wernicke, 2005,An Animated Tectonic Reconstruction of Southwestern North America since 36 MA. Geosphere, v. 1, no. 3, 147-172. Marchetti, D. and T. Cerling, 2005, Cosmogenic 3He exposure ages of Pleistocene debris flows and desert pavements in Capitol Reef National Park, Utah, Geomorphology, v. 67, 423-435. * OSL dating of fluvial sand and silt samples just below soil B horizons Marchetti, D., Dohrenwend J.C., and T.E. Cerling, 2005, Geomorphology and rates of landscape change in the Fremont River drainage, northwestern Colorado Plateau, in Pederson, J. and Dehler, C.M. eds.,Interior Western : to better constrain the age of alluvial fan abandonment. Geological Society of America Field Guide 6, doi: 10.1130/2005.fld006(04). National Agricultural Imagery Program, 2014, NAIP imagery acquired from Utah AGRC: https://gis.utah.gov/data/aerial-photography/ Repka, J., R. Anderson, and R. Finkel, 1997, Cosmogenic dating of fluvial terraces, Fremont River, Utah, * Structure from motion topographic surveys to better constrain Earth and Planetary Science Letters, V. 152, 59-73. Additional, faulted Quaternary exposures State of Utah, 2006, Auto-Correlated 5 meter DEM, Utah AGRC: https://gis.utah.gov/data/elevation-terrain-data/ the fan’s displacement. Toke, N. and J. Phillips, Preliminary Investigation of the Thousand Lake Fault from the mid Miocene to the late Pleistocene: have been recognized along separate An Approach for Characterizing Low Slip Rate Normal Faults using Geomorphology and Paleoseismology. 2017 Annual Meeting of the Geological Society of America in Seattle, WA. Bar surface traces of the TLF. Displacements Utah Quaternary Fault and Fold Database: https://geology.utah.gov/resources/data-databases/qfaults/ * Detailed along strike cross section displacement analysis to Utah Geological Survey and Nevada Isotope Geochronology Laboratory, 2012, 40Ar/39Ar Geochronology Results for the are also meter-scale. Forsyth Reservoir, Hilgard Mountain, and Mount Terrill Quadrangles, Utah, Open-File Report 594. constrain cumulative slip distribution along the fault and better Utah Geological Survey Aerial Imagery Collection: 1950 DKT, 1958 EEZ, and 1966 EEZ https://geodata.geology.utah.gov/imagery/ Geologic Map by Biek, 2016 estimate potential earthquake magnitude.