Bartlett Springs fault system, Lake Mountain section (Class A) No. 29a
Last Review Date: 2017-03-17
Compiled in cooperation with the California Geological Survey
citation for this record: Bryant, W.A., compiler, 2001, Fault number 29a, Bartlett Springs fault system, Lake Mountain section, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, https://earthquakes.usgs.gov/hazards/qfaults, accessed 05/10/2024 08:31 AM.
| Synopsis |
General:
The Bartlett Springs fault system is a major northwest-trending zone comprised of discontinuous, steeply dipping dextral strike-slip faults associated with the San Andreas fault system. The Bartlett Springs fault system can be mapped for at least 120 km from the southern side of Round Valley southeast to near Clear Lake. North of Round Valley, Herd (1978) suggested that the Lake Mountain fault may by the northern continuation of the Bartlett Springs fault system, indicating a total length of about 165 km. Lienkaemper (2010) mapped Holocene active traces of the Bartlett Springs fault system that extend for approximately 175 km. Traces of the Bartlett Springs fault system locally are delineated by geomorphic evidence of latest Pleistocene and Holocene strike-slip displacement, especially in the vicinity of Lake Pillsbury (dePolo and Ohlin, 1984; Taylor and Swan, 1986; Swan and Taylor, 1991; Bryant, 1993). The Lake Pillsbury area also is characterized by a somewhat broad, linear zone of microseismicity with focal-plane solutions that are predominantly dextral strike-slip (Dehlinger and Bolt, 1984; Castillo and Ellsworth, 1993). Taylor and Swan (1986) excavated and logged trenches across traces of the Bartlett Springs fault zone in the Lake Pillsbury area. Here they documented evidence of Holocene displacement. Taylor and Swan (1986) reported that stratigraphic relations exposed in one of their trenches can be interpreted to represent at least 3 faulting events. Taylor and Swan (1986) reported that the most recent fault rupture event occurred from 300 to 1000 yrs ago, based on their observation that the fault affects the modern soil. Swan and Taylor (1991) reported a Holocene slip rate of 1 to 2 mm/yr for the fault zone near Lake Pillsbury. Lisowski and Prescott (1989) reported a creep rate of 8 mm/yr for the 1985–1989 period near Round Valley. This 8 mm/yr creep rate at Round Valley was neither well-constrained nor supported by additional measurements (Lienkaemper, 2010). GPS measurements near Covelo (in Round Valley, but not on the original Lisowski and Prescott array site) indicate a creep rate of 0.4±1.49 mm/yr near Covelo in the Round Valley region (McFarland and others 2016). Lienkaemper (2010) reported that fault creep occurs across six GPS or alinement arrays established in 2005 across traces of the Bartlett Springs fault system. Two array sites have recorded creep rates measured for the period 2005–2015 (Lake Pillsbury array 3.21±0.12 mm/yr) and 2007–2015 (Huntington Creek array 2.22±0.55 mm/yr) (Lienkaemper, 2010; McFarland and others, 2016) across the Bartlett Springs fault zone. Sections: This fault has 4 sections. dePolo and Ohlin (1984) designated four segments for the fault system: from north to south, they are the Elk Creek fault (after CDWR, 1969), the Hot Springs shear zone (after Etter, 1979), the Chalk Mountain segment, and the Wilson fault [35] (after Lawton, 1956). Taylor and Swan (1986) divided the Bartlett Springs fault system into 6 segments from the area east of Clear Lake (north of the Wilson fault [35]) north to Round Valley, based on differences in geomorphic expression of the fault zone. These segments, from north to south include the Elk Creek, Coyote Rocks, McLeod Ridge, Twin Valley, Reister Rock, and Chalk Mountain. Lienkaemper (2010) identified two ≥ 2.5 km stepovers along the Bartlett Springs fault system: an extensional stepover near the southern end of the Bartlett Springs fault near Wilson Valley and a compressional stepover where Salmon Creek drains into the Middle Fork of the Eel River. An extensional step at Lake Pillsbury is about 2 km wide. The majority of mapping along the Bartlett Springs fault system is detailed reconnaissance in nature and very little data exists to characterize paleoseismic behavior and delineate paleoseismic segments. For this compilation, the Bartlett Springs fault system has been grouped into four principal sections and include, from north to south, the Lake Mountain section [29a] (after Herd, 1978), the Round Valley section [29b], the Elk Creek section [29c], and the Bartlett Springs section [29d]. |
| Name comments |
General: The Bartlett Springs fault system is comprised of discontinuous northwest-trending, steeply dipping faults that form a zone at least 1.5 km and possibly greater than 3 km wide. The Bartlett Springs fault system, as considered in this compilation, consists of the Lake Mountain fault zone, Round Valley fault zone, Etsel Ridge fault, Updegraff Ridge fault, and Bartlett Springs fault zone. The Bartlett Springs fault zone was first recognized by Clark (1930) as an essentially continuous zone of faulting, but was not named by him. Irwin (1960) first mapped a northwest-striking fault zone south of Lake Pillsbury, but did not name the fault. Maxwell (1974) and Etter (1979) mapped a zone of faults between Lake Pillsbury and Round Valley. Etter (1979) referred to this zone as the Hot Springs shear zone. Bolt and Oakeshott (1982) first used the name Bartlett Springs thrust fault for a structure that is associated with the unnamed fault of Irwin (1960) and the Hot Springs shear zone of Etter (1979). McLaughlin and Nilsen (1982) first used the name Bartlett Springs fault zone for the northwest-trending zone of discontinuous faults extending from the Wilson fault [35] of Lawton (1956) northwest to Herd’s (1978) Lake Mountain fault zone. The Lake Mountain fault zone was first mapped and named by Herd (1978). Traces of the Round Valley fault zone were first mapped by CDWR (1966). Jayko and others (1989) mapped a northwest-trending zone of faults along the western side of Round Valley and was first to name the Round Valley fault zone. The Etsel Ridge fault was mapped and named by Jayko and others (1989). Bryant (1993) proposed the name Updegraff Ridge fault for the zone of northwest striking faults on the eastern side of Updegraff Ridge. Section: Lake Mountain section extends from near Zenia south-southeast to the northern end of Updegraff Ridge. This section is delineated by the Lake Mountain fault zone, which was first mapped on a reconnaissance level and named by Herd (1978 #5234). Fault ID: Refers to numbers 78 (Lake Mountain fault zone), 90 (Round Valley fault zone), 91 (Etsel Ridge fault), and 92 (Bartlett Springs fault zone) of Jennings (1994) and Jennings and Bryant (2010), and numbers C6 (Bartlett Springs fault), C7 (Round Valley fault), and C8 (Lake Mountain fault) of WGNCEP (1996). |
| County(s) and State(s) |
MENDOCINO COUNTY, CALIFORNIA TRINITY COUNTY, CALIFORNIA |
| Physiographic province(s) |
PACIFIC BORDER |
| Reliability of location |
Good Compiled at 1:12,000; 1:100,000; and 1:800,000 scale. Comments: Location of principal active traces based on air photo interpretation of 1:12,000-scale aerial photographs by Lienkaemper (2010) and digital revisions to Jennings (1994). Revisions are based on regional map (fig. 3, ca. 1:880,000 scale) of Kelsey and Carter (1988) and mapping by Jayko and others (1989) at 1:100,000.
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| Geologic setting |
The Bartlett Springs fault system is a major northwest-trending zone of steeply dipping, discontinuous Quaternary-active faults in the north-central Coast Ranges. This fault system has been reported to be from 1.5 km wide (McLaughlin and others, 1990; dePolo and Ohlin, 1984) to more than 3 km wide (Etter, 1979). Taylor and Swan (1986) interpreted the Bartlett Springs fault system to be an immature zone of dextral shear related to evolution of the San Andreas fault system. Herd (1978) inferred that a system of principally dextral strike-slip faults east of the San Andreas fault zone [1] defined an intracontinental plate boundary east of Cape Mendocino. The Bartlett Springs fault system considered for this compilation extends for about 175 km from the northern end of the Lake Mountain fault zone (Herd, 1978; Kelsey and Carver, 1988) southeast to east of Clear Lake. The Bartlett Springs fault zone may complexly join with the Hunting Creek-Berryessa fault zone [35] along the Wilson fault [35] of Lawton (1956). The Bartlett Springs fault system has been variously described as a thrust fault related to the Coast Range thrust (Bolt and Oakeshott, 1982), a dextral-normal oblique fault (McLaughlin and others, 1990), and as a predominantly dextral strike-slip fault (dePolo and Ohlin, 1984; Dehlinger and Bolt, 1984; Clark, 1983; Taylor and Swan, 1986). The Bartlett Springs fault system occupies a topographic low nearly coincident with a narrow belt of Franciscan mélange and ultramafic rocks (dePolo and Ohlin, 1984). Cumulative dextral slip is not known, but the juxtaposition of different rock units of the Franciscan Complex suggests a significant strike-slip component. McLaughlin and others (1990) speculated that perhaps tens of kilometers of dextral strike-slip displacement has occurred on the fault system. Maximum vertical offset could be more than 1.5 km (southwest side down) east of Clear Lake, based on estimates of the total thickness of the Pliocene-Pleistocene Cache Formation (McLaughlin and others, 1990).
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| Length (km) | This section is 51 km of a total fault length of 160 km. |
| Average strike | N15°W (for section) versus N23°W (for whole fault) |
| Sense of movement |
Right lateral
Comments: Lienkaemper (2010), Herd (1978), and Kelsey and Carver (1988) reported that the Lake Mountain fault zone is delineated by geomorphic features indicative of dextral strike-slip displacement.
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| Dip Direction | V |
| Paleoseismology studies |
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| Geomorphic expression |
Lake Mountain fault zone is delineated by geomorphic evidence of late Pleistocene and Holocene dextral slip, such as linear closed depressions, aligned drainages, linear troughs and trenches, and aligned saddles (Lienkaemper, 2010; Kelsey and Carver, 1988). The fault zone is characterized by discontinuous traces and is locally concealed by massive landslides.
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| Age of faulted surficial deposits | Fault offsets rocks of the Mesozoic Franciscan Complex and Miocene Temblor Formation (Kelsey and Carver, 1988). Late Quaternary deposits are incompletely mapped and there is no documentation of specific localities where the Lake Mountain fault zone offsets dated late Quaternary sediment. |
| Historic earthquake | |
| Most recent prehistoric deformation |
latest Quaternary (<15 ka)
Comments: Timing of most recent paleoevent is not known. Youthful geomorphic expression indicates late Pleistocene to Holocene displacement (Lienkaemper, 2010; Kelsey and Carver, 1988).
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| Recurrence interval | |
| Slip-rate category |
Between 1.0 and 5.0 mm/yr
Comments: The geomorphic expression of the Lake Mountain fault zone reported by Herd (1978) and Kelsey and Carver (1988) is in an area of rapid erosion and mass wasting and is considered indicative of a slip rate of at least 1 mm/yr. |
| Date and Compiler(s) |
2001
William A. Bryant, California Geological Survey |
| References |
#4907 Bolt, B.A., and Oakeshott, G.B., 1982, Seismic and tectonic evaluation for Scott Dam and vicinity: Unpublished report for Pacific Gas and Electric Company, San Francisco, California, 31 p. #4908 Bryant, W.A., 1993, Bartlett Springs fault zone, Lake and Mendocino Counties, California: California Division of Mines and Geology Fault Evaluation Report FER-236, scale 1:24,000. #4909 California Department of Water Resources (CDWR), 1966, Areal geology, Round Valley drainage tunnel: Unpublished map, scale 1:24,000. #4910 California Department of Water Resources (CDWR), 1969, Areal geology, Elk Creek tunnel: Unpublished map and cross sections, scale 1:24,000. #5281 Castillo, D.A., and Ellsworth, W.L., 1993, Seismotectonics of the San Andreas fault system between Point Arena and Cape Mendocino in northern California—Implications for the development and evolution of a young transform: Journal of Geophysical Research, v. 98, no. B4, p. 6543-6560. #4912 Clark, B.L., 1930, Tectonics of the Coast Ranges of middle California: Geological Society of America Bulletin, v. 41, p. 747-828. #4913 Clark, J.T., 1983, San Andreas sense faulting, northern California Coast Ranges, California: Geological Society of America Abstracts with Programs, v. 15, no. 5, p. 418. #5230 Dehlinger, P., and Bolt, B.A., 1984, Seismic parameters along the Bartlett Springs Fault Zone in the Coast Ranges of northern California: Bulletin of the Seismological Society of America, v. 74, p. 1785-1798. #5231 dePolo, C.M., and Ohlin, N.H., 1984, The Bartlett Springs fault zone—An eastern member of the California plate boundary system: Geological Society of America Abstracts with Program, v. 16, no. 6, p. 486. #5232 Etter, S.D., 1979, Geology of the Lake Pillsbury area, northern Coast Ranges, California: Austin, University of Texas at Austin, unpublished Ph.D. dissertation, 275 p., 3 pls., scale 1:62,500. #5234 Herd, D.G., 1978, Intercontinental pl. boundary east of Cape Mendocino, California: Geology, v. 6, no. 12, p. 721-725. #4900 Irwin, W.P., 1960, Geologic reconnaissance of the northern Coast Ranges and Klamath Mountains, California, with a summary of the mineral resources: California Division of Mines Bulletin 179, 80 p., 1 pl., scale 1:500,000. #5235 Jayko, A.S., Blake, M.C., Jr., McLaughlin, R.J., Ohlin, H.N., Ellen, S.D., and Kelsey, H., 1989, Reconnaissance geologic map of the Covelo 30 x 60-minute quadrangle, northern California: U.S. Geological Survey Miscellaneous Field Studies Map MF-2001, scale 1:100,000. #7904 Jennings and Bryant, W.A., 2010, Fault activity map of California: California Geological Survey Geologic Data Map No. 6, map scale 1:750,000. #2878 Jennings, C.W., 1994, Fault activity map of California and adjacent areas, with locations of recent volcanic eruptions: California Division of Mines and Geology Geologic Data Map 6, 92 p., 2 pls., scale 1:750,000. #4094 Kelsey, H.M., and Carver, G.A., 1988, Late Neogene and Quaternary tectonics associated with northward growth of the San Andreas transform fault, northern California: Journal of Geophysical Research, v. 93, no. B5, p. 4797–4819. #5237 Lawton, J.E., 1956, Geology of the north half of the Morgan Valley and the south half of the Wilbur Springs quadrangles, California: Palo Alto, California, Stanford University, unpublished Ph.D. dissertation, 223 p., scale 1:48,000. #8181 Lienkaemper, J.J., 2010, Recently active traces of the Bartlett Springs fault, California—A digital database: U.S. Geological Survey Data Series 541, 10 p., http: //pubs.usgs.gov/ds/541/. #5238 Lisowski, M., and Prescott, W.H., 1989, Strain accumulation near the Mendocino Triple Junction, California: Eos, Transactions of the American Geophysical Union, v. 70, no. 43, p. 1332. #5239 Maxwell, J.C., 1974, Anatomy of an orogen: Geological Society of America Bulletin, v. 85, p. 1195-1204. #8430 McFarland, F.S., Lienkaemper, J.J., and Caskey, S.J., 2016, Data from theodolite measurements of creep rates on San Francisco Bay region faults, California, Version 1.8 (March 2016): U.S. Geological Survey Open-File Report 2009–1119, 21 p. #5240 McLaughlin, R.J., and Nilsen, T.H., 1982, Neogene non-marine sedimentation and tectonics in small pull-apart basis of the San Andreas fault system, Sonoma County, California: Sedimentology, v. 29, p. 865-876. #5241 McLaughlin, R.J., Ohlin, H.N., Thormohlen, D.J., Jones, D.L., Miller, J.W., and Blane, C.D., 1990, Geologic map and structure sections of the Little Indian Valley-Wilbur Springs geothermal area, northern Coast Ranges, California: U.S. Geological Survey Miscellaneous Investigations Series Map I-1706, scale 1:24,000. #5243 Swan, F.H., and Taylor, C.L., 1991, Geologic and geomorphic evidence suggesting spatial and temporal clustering of paleoseismic events along the Bartlett Springs fault zone, northern California: Geological Society of America Abstracts with Programs, v. 23, no. 2, p. 102. #5244 Swan, F.H., and Taylor, C.L., 1991, Geologic and geomorphic evidence suggesting spatial and temporal clustering of paleoseismic events along the Bartlett Springs fault zone, northern California: Seismological Research Letters, v. 62, no. 1, p. 11. #5245 Taylor, C.L., and Swan, F.H., 1986, Geological assessment of the seismic potential of the Bartlett Springs shear zone for Scott Dam, Lake County, California: Final report by Geomatrix Consultants for Pacific Gas and Electric Company, 51 p. #1216 Working Group on Northern California Earthquake Potential (WGNCEP), 1996, Database of potential sources for earthquakes larger than magnitude 6 in northern California: U.S. Geological Survey Open-File Report 96-705, 40 p. |