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Complete Report for Pyramid Lake fault zone (Class A) No. 1669

Brief Report ||Partial Report

citation for this record: Adams, K.Kenneth, compiler, 1999, Fault number 1669, Pyramid Lake fault zone, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, http://earthquakes.usgs.gov/hazards/qfaults, accessed 08/29/2014 10:03 AM.

Synopsis This long, nearly continuous dextral zone consists of: (1) northwest-striking down-to-the-northeast and -southwest intra basin faults extending from about 15 km south of Fernley northwest to near southern margin of Pyramid Lake; (2) northwest- to northeast-trending intermontane lineaments and small faults in eastern Virginia Range near south end of zone; and (3) a north-northeast trending zone of faults that diverges from main zone near Nixon and extends into southern part of Winnemucca Dry Lake basin. The right-lateral Pyramid Lake fault zone may be structurally related to the left-lateral Olinghouse fault zone [1668], because they appear to merge near White Horse Canyon on east side of Pah Rah Range. Detailed topical studies of the fault zone, reconnaissance photogeologic mapping, and regional geologic mapping are the sources of data. Trench investigations have been conducted on central part of fault zone, but detailed studies of scarp morphology have not been completed.

Name comments Refers to faults mapped by Russell (1885 #3549), Slemmons (1968, unpublished Reno 1? X 2? sheet), Bonham (1969 #2999), Bell and Slemmons (1979 #104), Anderson and Hawkins (1984 #2404), Bell (1984 #105; 1984 #107), Greene and others (1991 #3487), and Yount and others (1993 #1608) on east side of Pah Rah and Virginia Ranges. Apparently named by Bell and Slemmons (1979 #104); includes Nixon fault zone of dePolo (1998 #2845).

Fault ID Comments:
Refers to fault R15B (Pyramid Lake fault zone) and R17 (Nixon fault zone) of dePolo (1998 #2845).
County(s) and State(s) STOREY COUNTY, NEVADA
LYON COUNTY, NEVADA
WASHOE COUNTY, NEVADA
Physiographic province(s) BASIN AND RANGE
Reliability of location Good
Compiled at 1:100,000 scale.

Comments: Fault locations are based on 1:250,000-scale map of Bell (1984 #105) that was produced from photogeologic analysis of 1:40,000-scale low sun-angle aerial photography, supplemented with 1:12,000-scale aerial photography of selected areas, several low-altitude aerial reconnaissance flights, and field reconnaissance of major structural and stratigraphic relationships.

Geologic setting This long, nearly continuous dextral zone consists of: (1) northwest-striking down-to-the-northeast and -southwest intra basin faults extending from about 15 km south of Fernley northwest to near southern margin of Pyramid Lake; (2) northwest- to northeast-trending intermontane lineaments and small faults in eastern Virginia Range near south end of zone; and (3) a north-northeast trending zone of faults that diverges from main zone near Nixon and extends into southern part of Winnemucca Dry Lake basin (Slemmons, 1968, unpublished Reno 1? X 2? sheet, Bonham, 1969 #2999; Bell and Slemmons, 1979 #104; Bell, 1984 #105; 1984 #107; Anderson and Hawkins, 1984 #2404; Greene and others, 1991 #3487). The right-lateral Pyramid Lake fault zone may be structurally related to the left-lateral Olinghouse fault zone [1668], because they appear to merge near White Horse Canyon on east side of Pah Rah Range (Sanders and Slemmons, 1996 #1229). A highly conjectural estimate of 32 km of cumulative right-lateral offset on the fault zone is based on apparent offset of northern outcrop limit of a group of Cenozoic tuffs (Bonham, 1969 #2999).

Length (km) 45 km.
Average strike N13°W
Sense of movement Dextral

Comments: (Bonham, 1969 #2999; Bell and Slemmons, 1979 #104; Bell, 1981 #2875; 1984 #107; Anderson and Hawkins, 1984 #2404; Yount and others, 1993 #1608)

Dip Direction NE; SW
Paleoseismology studies Anderson and Hawkins (1984 #2404) excavated three trenches across central part of Pyramid Lake fault zone. Their study suggests repeated Holocene displacements of alluvial, eolian, and lacustrine deposits.

Site 1669-1: One trench was excavated across a 5-m-high southwest-facing scarp with a maximum slope angle of 20? near southern end of an 800-m-long shutter ridge. The trench exposed alluvial fan gravel deposits, lacustrine silt and sand, eolian silt (loess), and colluvium and slope wash deposits. All units except the overlying colluvium and slope wash deposits have been faulted. Anderson and Hawkins (1984 #2404) reported at least three, probably four, and possibly five Holocene faulting events based on structural and stratigraphic relations exposed in the trench. The earliest faulting event occurred after 9855 + 380 yr, but before deposition of Mazama tephra (6,845?50 yr, Bacon, 1983 #3787). The two most recent events are reported to have occurred at about 2 ka and within last several hundred years. Two additional events (at 3-4 ka and 5-6 ka) are inferred from juxtaposition of disparate stratigraphic units and from correlation with trenches 1669-2.

Site 1669-2: Two trenches were excavated across a small graben and associated sag pond. One was excavated immediately adjacent to the southwest end of the other because of caving problems. The trenches exposed a faulted sequence of alluvial fan deposits of probable Holocene age with intercalated pods, lenses, and beds of Mazama tephra (6,845?50 yr, Bacon, 1983 #3787). Anderson and Hawkins (1984 #2404) reported at least three and possibly four post-Mazama faulting events based on faulting and folding of Mazama tephra layer, scarp-derived colluvial wedge, correlation with the trench at site 1669-1, complex juxtaposition of stratigraphic units, and faulting of an alluvial fan unit with a moderately-developed soil. This sequence was overlain by unfaulted colluvium, that is probably only a few hundred years old based on similarities with modern wash deposits. Anderson and Hawkins (1984 #2404) suggested that the most recent event along this section of the fault zone may have occurred within last few hundred years based on stratigraphic and structural relations exposed in the trenches.

Geomorphic expression Intrabasin faults are expressed by sag ponds, echelon left-stepping fault scarps, elongate depressions and troughs, offset stream channels, vegetation lineaments, linear gullies, transcurrent buckles (folds), and rhombohedral and wedge-shaped enclosed depressions. Intermontane structures at south end of zone are likely expressed by topographic lineaments. The northeast-striking faults at north end of zone are expressed by west-facing fault scarps on latest Pleistocene lacustrine deposits (Bell and Slemmons, 1979 #104; Bell, 1981 #2875; 1984 #105, Anderson, 1984 #2404).

Age of faulted surficial deposits Holocene; late Pleistocene; Quaternary; Tertiary. Bell and Slemmons (1979 #104) and Anderson and Hawkins (1984 #2404) reported faulted Holocene and late Pleistocene sediments; mapping of Bonham (1969 #2999) shows faulted Quaternary-Tertiary gravels along this zone; and mapping of Greene and others (1991 #3487) shows faults displacing Tertiary bedrock.
Historic earthquake
Most recent prehistoric deformation Latest Quaternary (<15 ka)

Comments: Anderson and Hawkins (1984 #2404) showed convincing stratigraphic evidence exposed in trenches for several post-Mazama (6,845?50 yr, Bacon, 1983 #3787) faulting events. Similar timing for the most recent event is indicated by Bell (1984 #105), Slemmons (1968, unpublished Reno 1? X 2? sheet), and Dohrenwend and others (1996 #2846).

Recurrence interval

Comments: Anderson and Hawkins (1984 #2404) reported the possibility of as many as five surface-faulting events in about the last 7500 yr. However, it is possible there were only three post-Mazama (6,845?50 yr, Bacon, 1983 #3787) faulting events.
Slip-rate category Between 1.0 and 5.0 mm/yr

Comments: The slip-rate category assignment is based on data from Briggs (2002 #5877) who indicates that post Lahontan (13 ka) channels and ridges are offset 27-33 m indicating a minimum slip rate of 2.1-2.5 mm/yr. However, lower slip rates are reported in earlier studies. E.J. Bell (in Bell, 1984 #107, p. 409) reported a late Cenozoic slip rate of 0.7 mm/yr for the last 22 Ma and a slip rate of 0.3 mm/yr for the last 80,000 years. Later, dePolo and others (1997 #1367) reported a slip rate of 0.4 to 1.1 mm/yr. The basis of either set of data is not known.
Date and Compiler(s) 1999
Kenneth Adams, Piedmont Geosciences, Inc.
References #2404 Anderson, L.W., and Hawkins, F.F., 1984, Recurrent Holocene strike-slip faulting, Pyramid Lake fault zone, western Nevada: Geology, v. 12, no. 11, p. 681-684.

#3787 Bacon, C.R., 1983, Eruptive history of Mount Mazama and Crater Lake Caldera, Cascade Range, USA: Journal of Volcanology and Geothermal Research, v. 18, p. 57-115.

#104 Bell, E.J., and Slemmons, D.B., 1979, Recent crustal movements in the central Sierra Nevada-Walker Lane region of California-Nevada—Part II, The Pyramid Lake right-slip fault zone segment of the Walker Lane: Tectonophysics, v. 52, p. 571-583.

#2875 Bell, J.W., 1981, Quaternary fault map of the Reno 1° by 2° quadrangle, Nevada-California: U.S. Geological Survey Open-File Report 81-982, 62 p., http://pubs.er.usgs.gov/publication/ofr81982.

#105 Bell, J.W., 1984, Quaternary fault map of Nevada—Reno sheet: Nevada Bureau of Mines and Geology Map 79, 1 sheet, scale 1:250,000.

#107 Bell, J.W., 1984, Guidebook for selected Nevada earthquake areas (field trip 18), in Lintz, J., Jr., ed., Western geological excursions: Reno, Nevada, University of Nevada, Mackay School of Mines, 1984 Annual Meetings of the Geological Society of America, Guidebook, v. 4, p. 387-472.

#2999 Bonham, H.F., 1969, Geology and mineral deposits of Washoe and Storey Counties, Nevada: Nevada Bureau of Mines and Geology Bulletin 70, 140 p., 1 pl., scale 1:250,000.

#5877 Briggs, R.W., and Wesnousky, S.G., 2002, Slip rate and Holocene earthquake recurrence Pyramid Lake and Olinghouse fault zones, western Nevada, USA: AEG News, v. 45, Program with abstracts, p. 57.

#2845 dePolo, C.M., 1998, A reconnaissance technique for estimating the slip rate of normal-slip faults in the Great Basin, and application to faults in Nevada, U.S.A.: Reno, University of Nevada, unpublished Ph.D. dissertation, 199 p.

#1367 dePolo, C.M., Anderson, J.G., dePolo, D.M., and Price, J.G., 1997, Earthquake occurrence in the Reno-Carson City urban corridor: Seismological Research Letters, v. 68, p. 401-412.

#2846 Dohrenwend, J.C., Schell, B.A., Menges, C.M., Moring, B.C., and McKittrick, M.A., 1996, Reconnaissance photogeologic map of young (Quaternary and late Tertiary) faults in Nevada, in Singer, D.A., ed., Analysis of Nevada's metal-bearing mineral resources: Nevada Bureau of Mines and Geology Open-File Report 96-2, 1 pl., scale 1:1,000,000.

#3487 Greene, R.C., Stewart, J.H., John, D.A., Hardyman, R.F., Silberling, N.J., and Sorensen, M.L., 1991, Geologic map of the Reno 1° by 2° quadrangle, Nevada and California: U.S. Geological Survey Miscellaneous Field Studies Map MF-2154-A, scale 1:250,000.

#3549 Russell, I.C., 1885, Geological history of Lake Lahontan—A Quaternary lake of northwestern Nevada: U.S. Geological Survey Monograph 11, 288 p.

#1229 Sanders, C.O., and Slemmons, D.B., 1996, Geomorphic evidence for Holocene earthquakes in the Olinghouse fault zone, western Nevada: Bulletin of the Seismological Society of America, v. 86, p. 1784-1792.

#1608 Yount, J.C., Bell, J.W., dePolo, C.M., Ramelli, A.R., Cashman, P.H., and Glancy, P.A., 1993, Neotectonics of the Walker Lane, Pyramid Lake to Tonopah, Nevada—Part II Road log, in Lahren, M.M., Trexler, J.H., Jr., and Spinosa, C., eds., Crustal evolution of the Great Basin and the Sierra Nevada: Reno, Mackay School of Mines, University of Nevada, Geological Society of America, Cordilleran/Rocky Mountain section meeting, Reno, Nevada, May 19-21, 1993, Guidebook, p. 391-408.