testing a kinematic and geometric fault slip transfer ... · california shear zone (ecsz), which...

Testing a kinematic and geometric fault slip transfer model: Geologic and LIDAR mapping and

40Ar/39Ar Geochronology in the northern Eastern California Shear Zone, California

MS Thesis Candidate: Kevin M DeLano, [email protected]

MS Thesis Supervisor: Dr. Jeffrey Lee, [email protected]

Introduction

The spatial and temporal distribution of strain

across the Walker Lane Belt (WLB) – Eastern

California Shear Zone (ECSZ), which

accommodates ~20% of Pacific-North America plate

motion, is a major tectonic question. To characterize

the evolution of fault kinematics and determine the

mechanisms of intracontinental deformation,

geologists compare geodetic and geologic slip rates.

Across the northern ECSZ, at 37.5°N-38°N, the sum

of geologically determined fault slip rates is ~33%

of the geodetically determined NW dextral shear rate

(Frankel et al., 2011). To resolve part of this

discrepancy, Nagorsen-Rinke et al. (2013) proposed

a kinematic fault slip transfer model whereby NW

dextral shear is transferred from the Owens Valley

fault (OVF) north-northwest to the Mina deflection

via undocumented slip. To test this model, I will

accomplish new field geologic mapping and

structural, kinematic, and 40Ar/39Ar geochronology

studies to determine the faulting and volcanic

histories of the Black Mountain area and LiDAR

mapping of faults in the Volcanic Tableland. I will

use anticipated Pliocene to Pleistocene fault slip

rates for the Black Mountain area and Volcanic Tableland to address regional tectonic questions, including the

discrepancy between geodetic and geologic fault slip rates, the spatial and temporal distribution of strain in the

northern ECSZ, and the relative contributions of geodynamic forces driving deformation at the northern margin of

the ECSZ.

Background and Importance

Transform motion between the Pacific and North American plates is partitioned between the San Andreas

Fault system (~80% of the plate motion) and the WLB-ECSZ (~20% of the plate motion). Fault slip across the

Figure 1. Shaded relief map of the northern Eastern

California Shear Zone and western Basin and Range

Province, showing major Quaternary faults. Solid circles are

on the hanging wall of normal faults; arrows indicate

relative motion across strike-slip faults. Modified from Lee

et al. (2009).

DeLano – MS Thesis Proposal 2

WLB-ECSZ is characterized by a dominant set of NW-striking dextral faults, which strike sub-parallel to Pacific-

North America plate motion, and lesser NS-striking to NE-striking normal faults, and ENE-striking sinistral faults

(Fig. 1). Numerous investigations along

the WLB-ECSZ have centered on

documenting fault slip rates over geologic

and geodetic time scales. Across a NE-

striking transect of northern ECSZ at

latitude 37.5°N-38°N, a discrepancy exists

between geologic and geodetic slip rates

(Fig. 2). The sum of geologic fault slip

rates is ~33% of the geodetic NW dextral

shear rate, 10 mm/yr (Frankel et al., 2011;

Lifton et al., 2013).

To resolve part of the discrepancy,

Nagorsen-Rinke et al. (2013) proposed a

fault slip kinematic model whereby NW

dextral shear along the NNW-striking

dextral Owens Valley fault (OVF) is

transferred north-northwest to ENE-

striking faults in the Mina deflection (Fig.

3). In this kinematic model, NW dextral

shear at the northern margin of the OVF is

transferred northward via two

components: (a) one component to the

northeast along the NW-striking dextral

White Mountains fault zone (WMFZ),

which accommodates ~0.30-0.45 mm/yr

(Kirby et al., 2006) to ≥1.1 mm/yr of slip

(Lifton et al., 2013) and (b) a second

component to the northwest through the Volcanic Tableland, into the Black Mountain area, and onto faults in the

Adobe Hills via ~0.6 mm/yr ~EW-extension on NNE-striking normal faults since the Pliocene.

Fault slip rates in the Black Mountain area can be constrained because faults offset datable Miocene to

Pleistocene volcanic rock units. Slip rates in the Volcanic Tableland can be constrained via LiDAR mapping

because faults show measurable offset in the Bishop tuff, a 759 ka pyroclastic flow. Through new geologic field


mapping, structural geology, and 40Ar/39Ar geochronology in the Black Mountain area and LiDAR mapping

across the Volcanic Tableland, I will document fault slip

kinematics, magnitude of fault slip, timing of volcanism,

and fault slip rates over time. My results will allow me to

test the Nagorsen-Rinke et al. (2013) kinematic model and

address regional tectonic questions, including the local

discrepancy between geodetic and geologic slip rates, the

spatial and temporal distribution of regional strain in the

northern ECSZ, and the relative contributions of plate

boundary vs. gravitational potential energy forces in

driving deformation within this area of the ECSZ.

Geologic Setting

The northern ECSZ (Fig. 1) is a ~100-200 km wide

domain of NW dextral shear that extends from the ENE-

striking Garlock fault north to the Mina deflection, a fault

slip transfer zone that relays dextral shear from the

northern ECSZ, across a ~60 km right-stepover, to the

Central Walker Lane Belt. Starting ~12 Ma,

intracontinental Pacific-North American dextral shear

initiated on NW-striking dextral faults in the northern

ECSZ (Faulds and Henry, 2008). The Pliocene

delamination of the lithospheric root beneath the Sierra

Nevada changed regional lithospheric heat flow dynamics,

and is a proposed driver of the westward shift in E-W

extension and regional dextral shear (Jones et al., 2004).

Fault slip rates decreased on the Fish Lake Valley-Death

Valley fault zone and increased on the White Mountains-

Owens Valley fault zone (Malservisi et al., 2001;

Nagorsen-Rinke et al., 2013; Saleeby et al., 2012). Today,

overlapping NW-striking dextral faults, connected by NE-

striking normal faults, accommodate NW dextral shear (Lee et al., 2001; Faulds and Henry, 2008).

Faulting History of the Owens Valley

Exposed within the Owens Valley, a ~175 km long extensional graben, is the White Mountains-Owens Valley

fault zone, one of the major NW-striking dextral faults that accommodates shear across the ECSZ (Lee et al.,


2009). The Owens Valley fault is a ~55 km long, NNW-striking, dextral fault system (Fig. 3). Dextral slip along

the OVF, or its precursor structure, initiated ~83 Ma and accommodated 50-60 km of dextral slip during the Late

Cretaceous and early Tertiary (Glazner et al., 2005). About 3 Ma, the westward shift in regional dextral shear

reactivated the OVF as a complex system of dextral, normal, and oblique faults (Glazner et al., 2005; Stockli et

al., 2003). Since reactivation, the OVF has accommodated ~6-9 km of dextral displacement (Glazner et al., 2005)

Nagorsen-Rinke et al. (2013) proposed that the OVF transfers slip to the Mina deflection via two components: (a)

an eastward step onto the dextral White Mountains fault zone (WMFZ) and (b) a predicted northwestward step

onto a set of faults that cut across the Volcanic Tableland (Figs. 2 and 3). The WMFZ is a ~60 km long, NW-

striking, dextral-normal oblique fault system (Fig. 1). Slip along the WMFZ initiated ~12 Ma as a normal fault,

accommodated 8 km of west-down horizontal displacement, and uplifted the modern White Mountains . Since

strike-slip initiated ~3 Ma, the WMFZ has accommodated 1.5-2.5 km of dextral displacement (Stockli et al.,

2003).

Slip rates on the OVF and WMFZ appear to have varied temporally since the Pleistocene. Late Pleistocene

(80-55 ka) dextral slip on the northern OVF was calculated at 2.8 mm/yr ± error (Kirby et al., 2008), wheras the

latest Pleistocene (25 ka) dextral slip rate on the southern OVF was calculated at 1.0 ± 0.5 mm/yr (Bacon and

Pezzopane, 2007). The discrepancy in slip rates suggests that either slip on the OVF decreased during the late

Pleistocene or that slip across the southern Owens Valley is distributed across a broad deformation zone rather

than concentrated on a single fault stand. Of the latter is true, then the dextral slip rate estimate of Bacon and

Pezzopane (2007) is an underestimate for the total slip rate across the southern Owens Valley. A minimum dextral

slip rate of 1.1 ± 0.1 mm/yr since the eruption of the Bishop tuff (~759 ka) was calculated for the WMFZ (Lifton,

2013). An investigation by (Kirby et al., 2006) suggested that dextral slip rates decreased to 0.37-0.57 mm/yr

along the WMFZ since the late Pleistocene (90-60 ka). In contrast, a more recent investigation by (Lifton, 2013)

yielded late Pleistocene slip rates of 1.9 +0.5/-0.4 to 1.8 +2.8/-0.7 mm/yr, indicating that the slip rate likely

remained constant through time. Geodetic measurements yield a modern slip rate of ≥1.9 mm/yr of slip (Lifton et

al., 2013), a rate consistent with the idea that slip rates along the WMFZ have been constant through time.

North of Owens Valley and west of the WMFZ, distributed NS-striking normal faults and NW-striking

dextral faults across the Volcanic Tableland, NNE-striking normal faults exposed in the Black Mountain area, and

NW-striking normal-oblique faults exposed in the southern Adobe Hills area transfer NW dextral shear from the

OVF to sinistral faults in the Mina deflection (Fig. 3) (Nagorsen-Rinke et al., 2013). The 758.9 ± 1.8 ka Bishop

tuff, a pyroclastic flow deposit, defines the Volcanic Tableland (Bogaard and Schirnick, 1995; Sarna-Wojcicki et

al., 2000). Tectonic geomorphology clearly shows that from south to north across part of the Volcanic Tableland,

NS-striking normal faults swing into NW-striking dextral faults and in turn swing back into NS-striking normal

faults (Fig. 4). These faults cut the Bishop tuff, which provides an ideal time-datum for documenting Pleistocene

fault slip rates. North of the Volcanic Tableland, the distributed faults consolidate onto NNE-striking normal


faults in the Black Mountain area. Faults in the Black Mountain area cut Jurassic granitic basement and scattered

Miocene to Pleistocene volcanic flows and tuffs. Faults are buried under or cut Quaternary deposits.

Geologic slip rates on faults in the Volcanic Tableland and Black Mountain area have not been documented.


Based on the Nagorsen-Rinke et al. (2013) kinematic model (Fig. 3), we predict that NW-striking faults cutting

the Volcanic Tableland accommodate ~0.4 mm/yr dextral shear and that NNE-striking normal faults in the Black

Mountain area (Fig. 2) accommodate 0.6 mm/yr of ~EW-extension.

Research Plan

To test the Nagorsen-Rinke et al. (2013) fault slip kinematic model, I will accomplish new field geologic

mapping and structural, kinematic, geomorphic and 40Ar/39Ar geochronology studies to determine the faulting and

volcanic histories of the Black Mountain area and LiDAR mapping of faults across the Volcanic Tableland (Fig.

2). The combination of desert exposure, well-preserved fault geometry and geomorphic indicators, and faulting

through datable Miocene to Pleistocene volcanic rocks make the Black Mountain area and Volcanic Tableland

excellent locations to study fault kinematics within the northern ECSZ. Field geologic mapping in the Black

Mountain area will be done on 1:12,000 digital orthophotoquadrangles georeferenced to DEM contours and

supported with structural and kinematic field data.

My field focus will be to map faults that cut Miocene to Pleistocene volcanic and sedimentary rock units

which unconformably overlie Mesozoic granitic rocks (Krauskopf and Bateman, 1977). To constrain fault

geometry, kinematics, and offset, I will use use stratigraphy, bedrock orientation, fault plane and striation

orientations, cross-cutting relationships, and geomorphic indicators. Field work will be conducted from June 2 to

August 3, 2014 with advisor supervision at the beginning, middle, and end of the field season. Two field

assistants, Tucker Lance and Peter Duboyski, will accompany me for the duration of fieldwork. I will combine

40Ar/39Ar geochronology with fault offset measurements to calculate fault slip rates, a key dataset that will allow

me to determine the spatial and temporal evolution of faulting in the Black Mountain area and test and refine the

Nagorsen-Rinke et al. (2013) fault slip kinematic model.

Under the supervision of Dr. Andy Calvert, a collaborator of Dr. Jeffrey Lee, 40Ar/39Ar geochronology of

volcanic rock units cut by and depositionally overlying faults will be conducted at the USGS, Menlo Park, CA.

Two 1-week trips are needed: (1) the first week, in late Fall 2014, will be spent crushing samples, separating

appropriate minerals for 40Ar/39Ar geochronology, and packaging the mineral separates for irradiation, and (2) the

second week, in late Spring 2015, will be spent assisting with extracting the gas for 40Ar/39Ar geochronology.

To determine the faulting history of the Volcanic Tableland, I will use high-resolution LiDAR topography to

map faults and calculate the magnitude of horizontal ~EW-extension across the NS-striking normal faults and

horizontal NE-SW extension across the NW-striking faults (Fig. 4). Using simple trigonometry, I can then

calculate the magnitude of NW dextral shear across the zone of NW-striking normal-dextral oblique faults (Fig.

5). Geologic slip rates can then be calculated by dividing the magnitude of offsets by the ~759 ka age of the

Bishop tuff (Bogaard and Schirnick, 1995; Sarna-Wojcicki et al., 2000). The combination of desert exposure,

well-preserved fault geometry, and faulting through a single time datum make the Volcanic Tableland an


excellent site to document Pleistocene geologic slip rates, and to test and refine the Nagorsen-Rinke et al. (2013)

kinematic model.

My new geologic mapping, structural geology, and 40Ar/39Ar geochronology studies of the Black Mountain

area and LiDAR mapping of the Volcanic Tableland will also allow me to address regional tectonic questions,

including (a) whether the local discrepancy between geodetic and geologic slip rates is real, (b) the spatial and

temporal distribution of regional strain in the northern ECSZ, and (c) assessing the relative contributions plate

boundary vs. gravitational potential energy forces in driving deformation in this part of the ECSZ (Jones et al.,

2004; Saleeby et al., 2012).


Schedule

Spring 2014

o Defend thesis proposal (Friday May 23 at 9am)

o Start writing background of thesis?

o Investigation of faults in Volcanic Tableland from LiDAR data

o Submit GSA meeting abstract for LiDAR project

Summer 2014

o June 2 – August 3: two month field season in Black Mountain area, Mono County, CA

o August: Spend time in California

o September: Return to Washington

Fall 2014

o Select volcanic rock samples for thin sectioning and 40Ar/39Ar geochronology

o Compile geologic map, cross sections, structural data, and stratigraphic observations, and

complete limited petrography on volcanic rocks

o October - Present LiDAR mapping research at GSA in Vancouver

o Write background, methods, and preliminary results section of thesis

o October or November - First trip to USGS Menlo Park to prepare samples for 40Ar/39Ar

geochronology

Winter 2015

o Complete analyses

o Complete figures

o Finish writing background, methods, and available results

Spring 2015

o Second trip to USGS Menlo Park to complete geochronology

o Finish writing thesis

o Defend thesis in early June

Summer 2015

o Go boating, travel, celebrate

Budget

Field Work

Large pickup truck rental from Enterprise in Bishop, CA: $2807.98

K.DeLano stipend: $6000-$7000

WMRC lodging: $880 - covered

T. Lance stipend: $2000

Receieved $1000 from NCGS

40Ar/39Ar geochronology, $2160


Item Explanation Single Trip Cost Two Trip Total

Airfare Two round trip flights - Seattle to San Jose $400 $800

Ground Transportation

Two round trip airport shuttles in Washington

- Ellensburg, WA to Seattle, WA

$70 $140

Ground Transportation

Two round Caltrain tickets in California - San

Jose Airport to Menlo Park Inn

$10 $20

Hotel 12 nights at Pacific Euro Hotel @ $70/night $420 $840

Food per diem $30/day for 12 days $180 $360

Grand Total $2160

GSA funded -$1500

Remaining $616

Anticipated Support

1) USGS-EDMAP (funded). $17499 awarded to Dr. Jeffrey Lee for fieldwork only.

2) Northern California Geological Society (funded), $1000 awarded to K. DeLano for fieldwork.

3) National Center for Airborne Laser Mapping (funded), awarded to K. DeLano for LiDAR dataset across a

portion of the Volcanic Tableland for mapping faults.

4) GSA Graduate Research Grant (funded), $1500 awarded to K. DeLano to support 40Ar/39Ar geochronology

analysis at USGS, Menlo Park, CA.

5) White Mountain Research Station minigrant (funded), awarded $880 to K. DeLano to cover lodging once every

10 days during fieldwork

6) Northwest Federation of Mineralogical Societies - American Federation of Mineralogical Societies Scholarship

Foundation (funded), awarded $4000 scholarship to K. DeLano.

7) Two Central Washington University graduate student research fellowships (pending), applied for $700 and

$2800 to support 40Ar/39Ar geochronology and a summer stipend for fieldwork.

8) Central Washington University general scholarship application (pending) for funding to cover tuition expenses.

References Bacon, S.N., and Pezzopane, S.K., 2007, A 25,000-year record of earthquakes on the Owens Valley fault near Lone Pine, California:

Implications for recurrence intervals, slip rates, and segmentation models: Geological Society of America Bulletin, v. 119, no. 7-8, p. 823–847, doi: 10.1130/B25879.1.

Bogaard, P. van den, and Schirnick, C., 1995, 40Ar/39Ar laser probe ages of Bishop Tuff quartz phenocrysts substantiate long-lived silicic magma chamber at Long Valley, United States: Geology, v. 23, no. 8, p. 759, doi: 10.1130/0091-7613(1995)023<0759:AALPAO>2.3.CO;2.

Dixon, T.H., Miller, M., Farina, F., Wang, H., and Johnson, D., 2000, Present-day motion of the Sierra Nevada block and some tectonic implications for the Basin and Range province, North American Cordillera: Tectonics, v. 19, no. 1, p. 1–24.

Faulds, J.E., and Henry, C.D., 2008, Tectonic influences on the spatial and temporal evolution of the Walker Lane: An incipient transform fault along the evolving Pacific–North American plate boundary: Ores and orogenesis: Circum-Pacific tectonics,

geologic evolution, and ore deposits: Arizona Geological Society Digest, v. 22, p. 437–470.

Frankel, K.L., Dolan, J.F., Owen, L.A., Ganev, P., and Finkel, R.C., 2011, Spatial and temporal constancy of seismic strain release along an evolving segment of the Pacific–North America plate boundary: Earth and Planetary Science Letters, v. 304, no. 3-4, p. 565–576, doi: 10.1016/j.epsl.2011.02.034.


Glazner, A.F., Lee, J., Bartley, J.M., Coleman, D.S., Kylander-Clark, A., Greene, D.C., and Le, K., 2005, Large dextral offset across Owens Valley, California from 148 ma to 1872 A.D., in Stevens, C. and Cooper, J. eds., Western Great Basin Geology, 99, The Pacific Section Society of Sedimentary Geology, p. 1–35.

Jones, C.H., Farmer, G.L., and Unruh, J., 2004, Tectonics of Pliocene removal of lithosphere of the Sierra Nevada, California: Geological Society of America Bulletin, v. 116, no. 11-12, p. 1408–1422.

Kirby, E., Anandakrishnan, S., Phillips, F., and Marrero, S., 2008, Late Pleistocene slip rate along the Owens Valley fault, eastern

California: Geophysical Research Letters, v. 35, no. 1, doi: 10.1029/2007GL031970.

Kirby, E., Burbank, D.W., Reheis, M., and Phillips, F., 2006, Temporal variations in slip rate of the White Mountain Fault Zone, Eastern California: Earth and Planetary Science Letters, v. 248, no. 1-2, p. 168–185, doi: 10.1016/j.epsl.2006.05.026.

Krauskopf, K.B., and Bateman, P.C., 1977, Geologic Quadrangle Map, Glass Mountain Quadrangle, California-Nevada: U.S. Dept. of the Interior, U.S. Geological Survey, Washington DC.

Lee, J., Spencer, J., and Owen, L., 2001, Holocene slip rates along the Owens Valley fault, California: Implications for the recent evolution of the eastern California shear zone: Geology, v. 29, no. 9, p. 819–822.

Lee, J., Stockli, D.F., Owen, L.A., Finkel, R.C., and Kislitsyn, R., 2009, Exhumation of the Inyo Mountains, California: Implications for the timing of extension along the western boundary of the Basin and Range Province and distribution of dextral fault slip rates across the eastern California shear zone: Tectonics, v. 28, no. 1, doi: 10.1029/2008TC002295.

Lifton, Z.M., 2013, Understanding an evolving diffuse plate boundary with geodesy and geochronology [PhD thesis]: Georgia Institute of Technology, 108 p.

Lifton, Z.M., Newman, A.V., Frankel, K.L., Johnson, C.W., and Dixon, T.H., 2013, Insights into distributed plate rates across the

Walker Lane from GPS geodesy: Geophysical Research Letters, v. 40, p. 4620–4624, doi: 10.1002/grl.50804.

Malservisi, R., Furlong, K.P., and Dixon, T.H., 2001, Influence of the earthquake cycle and lithospheric rheology on the dynamics of the eastern California shear zone: Geophysical Research Letters, v. 28, no. 14, p. 2731–2734.

Nagorsen-Rinke, S., Lee, J., and Calvert, A., 2013, Pliocene sinistral slip across the Adobe Hills, eastern California–western Nevada: Kinematics of fault slip transfer across the Mina deflection: Geosphere, v. 9, no. 1, p. 37–53.

Saleeby, J., Le Pourhiet, L., Saleeby, Z., and Gurnis, M., 2012, Epeirogenic transients related to mantle lithosphere removal in the southern Sierra Nevada region, California, part I: Implications of thermomechanical modeling: Geosphere, v. 8, no. 6, p.

1286–1309, doi: 10.1130/GES00746.1.

Sarna-Wojcicki, A.M., Pringle, M.S., and Wijbrans, J., 2000, New 40Ar/39Ar age of the Bishop Tuff from multiple sites and sediment rate calibration for the Matuyama-Brunhes boundary: Journal of Geophysical Research: Solid Earth (1978–2012), v. 105, no. B9, p. 21431–21443.

Stockli, D.F., Dumitru, T.A., McWilliams, M.O., and Farley, K.A., 2003, Cenozoic tectonic evolution of the White Mountains, California and Nevada: Geological Society of America Bulletin, v. 115, no. 7, p. 788–816.

testing a kinematic and geometric fault slip transfer ... · california shear zone (ecsz), which...

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