Copyright. Alana Marie Crown

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2 Copyright By Alana Marie Crown 2016

3 Detrital zircon geochronology of roof pendants, southern Sierra Nevada batholith, Tulare County, California: Insights into Paleoproterozoic through Cretaceous provenance of the western margin of Cordilleran North America and its Cretaceous syn-magmatic architecture By Alana M. Crown A Thesis Submitted to the Department of Geological Sciences California State University Bakersfield In Partial Fulfillment for the Degree of Masters of Science in Geology Spring 2016

4 Detrital zircon geochronology of roof pendants, southern Sierra Nevada batholith, Tulare County, California: Insights into Paleoproter<?zoic through Cretaceous provenance of the western margin of Cordilleran North America and its Cretaceous syn-.magmatic architecture By Alana M. Crown This thesis has been accepted on behalf of the Department of Geological Sciences by their supervisory committee: Graham D.M. Andrews, PhD., Committee Chair Sarah R. Brown, PhD.

5 Acknowledgements I would like to thank my husband, Andrew Crown, and my kids, Parker and Rebekah Crown for their enormous support and encouragement throughout this journey. A special thanks to Raina Chan and Diana Caldwell who helped me with my kids and making it easier to finish my thesis without worrying about if they were taken care of properly. Others who have helped along the journey with encouragement and support were my mom Cathey Eide, my sister Heather Mikaee, and friends Shannon Morton, Kristin Koehler, and Karla Lopez. A special thanks to Nick Moreno, who not only encouraged and supported me, but helped with rock crushing and mineral separation as well as SEM work. I would like to thank Grant Obenshain who provided key photographs for the project, and thank you to JoAnna and Billy Pounds, Zachary Martindale, and Alyssa Kaess who all participated in the project with field mapping and sample selection. Thank you to Dr. William Krugh and Dr. Sarah Brown who provided excellent feedback on my thesis and are a part of my committee. An extra thanks to Dr. Brown who went to the LaserChron Lab-University of Arizona with me and helped sort all my zircon data. Thank you Elizabeth Powers, Sue Holt, and Andrea Medina who provided encouragement and administrative help that could have easily slowed me down. I would like to thank the NSF CSUB CREST grant as well as the CSUB Student Research Scholar fund for the financial and academic support of this project. Finally, I would like to thank Dr. Graham Andrews. Thank you for your unspoken encouragement that always had me striving for the absolute best. I would like to express my appreciation for your extensive knowledge in all subjects and making this project an awesome experience. Thank you for your help in not only making me a better geologist, but a better scholar overall.

6 Abstract The fragmented Paleozoic passive margin of Cordilleran North America, its Precambrian basement, and its Mesozoic cover are preserved in metasedimentary and metavolcanic crustal fragments known as roof pendants within the Sierra Nevada batholith. This study sets out to test between different models of the architecture of Paleozoic terranes with regard to the intra-arc proto-kern Canyon Fault using detrital zircon geochronology; however, the absence of Paleozoic deposits precludes the use of these roof pendants to test between different models of terrane architecture. Five roof pendants in the southern Sierra Nevada batholith were sampled. Pendants west of the fault include Late Paleoproterozoic, Neoproterozoic, and Early Cretaceous metaturbidites and psammites. Pendants east of the fault include closely-related Early Cretaceous metasandstones and metavolcanic rocks. The Paleoproterozoic and Neoproterozoic metasedimentary rocks extend the depositional history of the southern Sierra, and the 1,700 Ma Corral Creek metagraywacke maybe the oldest rock within the Sierra Nevada batholith. The Cretaceous metasedimentary and metavolcanic rocks were deposited proximal to a felsic caldera, probably in an intra-arc graben developed along the proto-kern Canyon fault. Detrital zircon were supplied along the intra-arc graben from the south and southeast, from east of the graben in Nevada, and from magmatic sources within the graben. The depositional setting was probably analogous to present-day intra-arc graben in Japan and the southwest Pacific.

7 Contents List of Tables and Figures... 1 Highlights Introduction Geological Setting Pre-Cambrian Assembly of North America Passive Margin of Western North America Late Paleozoic Active Margin Mesozoic Active Margin Methods U-Pb isochron systems Analytical Techniques Sample selection and preparation Detrital zircon geochronology Isoplot and maximum depositional ages Results and Preliminary Interpretation Durwood Meadows roof pendant (AC01; 35 59'6.49"N, '38.56"W) Preliminary Interpretation of AC Durwood Meadows roof pendant (AC02; 35 59'8.18"N, '36.92"W) Preliminary Interpretation of AC Alder Creek roof pendant (AC03; 35 59'6.4"N, '50.6"W) Preliminary Interpretation of AC Durwood Meadows roof pendant (AC04; 35 59'28.74"N, '37.04"W) Preliminary Interpretation of AC Fairview roof pendant (AC08; 35 57'26.90"N, '38.26"W)... 51

8 3.5.1 Preliminary Interpretation of AC Kernville roof pendant (AC09; 35 47'3.83"N, '40.79"W) Preliminary Interpretation of AC Corral Creek roof pendant (AC11; 35 51'10.15"N, '8.78"W) Preliminary Interpretation of AC Discussion Sierra Nevada roof pendants Corral Creek roof pendant Kernville roof pendant Durwood Meadows and Alder Creek roof pendants Fairview roof pendant Summary The proto-kern Canyon fault An intra-arc volcanic graben within the Cretaceous Sierra Nevada arc? Conclusions Appendix A (AC01 data) Appendix B (AC02 data) Appendix C (AC03 data) Appendix D (AC04 data) Appendix E (AC08 data) Appendix F (AC09 data) Appendix G (AC11 data) References

9 List of Tables and Figures Figure 1 Normalized probability plot from Chapman et al. (2015). 5 Figure 2 Two mutually exclusive terrane models. 6 Figure 3 Archean Craton map of North America. 9 Figure 4 Paleogeographic map of early Mesoproterozoic. 10 Figure 5 Paleogeographic map of late Mesoproterozoic. 11 Figure 6 Paleogeographic map of late Neoproterozoic. 12 Figure 7 Paleogeographic map of Middle Ordovician. 13 Figure 8 Paleogeographic map of Late Devonian. 14 Figure 9 Paleogeographic map of Middle Pennsylvanian. 16 Figure 10 Paleogeographic map of Early Permian. 17 Figure 11 Paleogeographic map of Early Triassic. 18 Figure 12 Paleogeographic map of Late Jurassic. 20 Figure 13 Paleogeographic map of Late Cretaceous. 21 Figure 14 Decay chain of Uranium series. 24 Figure 15 Decay chain of Actinium series. 25 Figure 16 Example of a Wetherill concordia. 28 Figure 17 Example of a discordia with Pb loss. 28 Figure 18 Example of a discordia with U loss. 29 Figure 19 Example of Pb/Pb isochron. 29 Figure 20 Example of backscattered-electron images of zircons. 34 Figure 21 Comparison of SIMS and LA-ICP-MS sample volumes. 35 Figure 22 Example of probability density chart of Catalina Schist. 37 Figure 23 Example of probability density chart of Grand Canyon. 38 Figure 24 Geologic map of study area. 41 Figure 25 Field photo of AC Figure 26 Probability density plot of AC Figure 27 Weighted mean averages of samples. 43 Figure 28 Probability density plot of AC Figure 29 Field photo of AC Figure 30 Probability density plot of AC Figure 31 Field photo of AC Figure 32 Probability density plot of AC Figure 33 Field photo of AC Figure 34 Probability density plot of AC Figure 35 Field photo of AC Figure 36 Probability density plot of AC Figure 37 Field photo of AC Figure 38 Close up images of AC11 57 Figure 39 Probability density plot of AC

10 Figure 40 Zircon provenance map of North America. 59 Figure 41 Map of Pinto Mountains and Normalized plot of Mojave province. 61 Figure 42 Stacked normalized probability plot of samples. 62 Figure 43 Stacked normalized probability plot of roof pendants. 64 Figure 44 Geologic map showing Precambrian provinces of southwestern U.S. 67 Figure 45 Simplified map of Cretaceous southwest North America. 68 Figure 46 Map of roof pendants in Sierra Nevada. 69 Figure 47 Simple geological map of Lake Isabella. 70 Figure 48 Map showing locations of metamorphic roof pendants. 71 Figure 49 Google earth map of analogous arc in Japan. 75 Figure 50 Google earth map of analogous arc in New Zealand. 76 Table 1 Table of common methods of U-Pb dating. 33 2

11 Highlights Detrital zircon geochronology reveals that two Sierra Nevada roof pendants east of the Kern Canyon fault have Cretaceous maximum depositional ages. Three roof pendants immediately west of the Kern Canyon fault have Cretaceous, Neoproterozoic, and Paleoproterozoic maximum depositional ages, respectively. A ca. 1,700 Ma volcanogenic turbidite deposit in the Corral Creek roof pendant correlates with volcanism in the Mojave, and may be the oldest rock exposed in the Sierra Nevada. The Paleozoic terrane architecture of the southern Sierra Nevada batholith is not elucidated by studies of these roof pendants. During batholith assembly in the mid-cretaceous, a marine or lacustrine intra-arc basin existed in the southern Sierra Nevada and received sediment from local volcanism, and from distal sources in the Great Basin and the Mojave. 3

12 1. Introduction The fragmented Paleozoic passive margin of Cordilleran North America is preserved in keellike roof pendants within the Mesozoic Sierra Nevada batholith along with the remnants of volcanic arcs, subduction complexes, and ophiolites. Previous workers have conducted extensive detrital zircon geochronology in the Neoproterozoic to Paleozoic passive margin stratigraphy, including within Sierran roof pendants, of metasedimentary and metavolcanic rocks in the Cordillera (Fig. 1). The mechanisms by which the passive margin of North America evolved to an active and then transcurrent margin are not thoroughly understood. Detrital zircon geochronology can date and test models of zircon provenance; for example, to distinguish between accretion of exotic (i.e. non-north American) arc terranes and transcurrent shuffling of dismembered passive margin blocks. Many studies conclude that the Cordilleran margin is composed of crustal fragments of various terrane types and ages that have been displaced huge distances during transcurrent motion due to oblique subduction (Gehrels et al., 1995). Within the Sierra Nevada and the California-Nevada border region are five laterally continuous, NNW-SSE striking, Paleozoic tectonostratigraphic terranes separated by strike-slip faults; from east (inner shelf) to west (abyssal): Snow Lake, Inyo, El Paso, Shoofly-Kernville, and Calaveras terranes. The architecture of the different Paleozoic terranes remains controversial (c.f., Memeti et al., 2010; Chapman et al., 2012, 2015; Paterson et al., 2014). The role of the proto-kern Canyon fault (pkcf; Busby-Sera and Saleeby, 1990) in accommodating Paleozoic juxtaposition of different terranes is one such unknown (Fig. 2). The Shoofly-Kernville and Calaveras terranes are to the west in both models A and B (Fig. 2). However, in model A the El Paso terrane is truncated by the (pkcf), and juxtaposed against the Shoofly-Kernville, and the Snow Lake terrane is almost absent in the southern Sierra Nevada west of the El Paso terrane as a result of major dextral (Paleozoic) and sinistral (Mesozoic) faulting. If this model is correct, then the pkcf is likely to be significantly older than commonly inferred (i.e. Cretaceous) and may be an Early Paleozoic or even Neoproterozoic structural feature. In contrast, model B infers that both Shoofly-Kernville and Snow Lake terranes are continuous and only slightly offset across the pkcf (Fig. 2). These models are mutually exclusive and can be tested by determining the age and provenance of roof pendants west and east of the 4

13 pkcf. However, before a successful test can be conducted, the roof pendants must be shown to be Paleozoic, and not Mesozoic. This study sets out to test between these models using detrital zircon geochronology to establish the age and provenance of Sierra Nevadan roof pendants either side of the pkcf. I investigate the age and provenance of marine metasedimentary and metavolcaniclastic rocks in five roof pendants in the Fairview area of the southern Sierra Nevada batholith. There, pendants are comprised of quartzites, phyllites, metagraywackes, and marbles, which have been intruded and engulfed by Cretaceous dioritic, granodioritic, and granitic plutons. The rocks within the roof pendants were deposited on the Paleozoic continental shelf and slope of western North America, and Mesozoic marine supracrustal basins. They now straddle the north-south trending intra-batholithic Kern Canyon fault (KCF) and the pkcf, and are now strongly deformed and metamorphosed. 5

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16 1.1 Geological Setting Pre-Cambrian Assembly of North America The Sierra Nevada batholith was emplaced along the western edge of North America into attenuated Proterozoic crust and thick Paleozoic sedimentary cover. North America is composed of a core Archean shield fringed by Paleoproterozoic arcs and orogens (Fig. 3) that are source terranes for siliciclastic sediment throughout the western North American continental margin (Whitmeyer and Karlstrom, 2007; Gehrels and Pecha, 2014). The Canadian Shield, which includes the >2,500 Ma Hearne, Rae, Slave, Superior, Wyoming, and Medicine Hat cratons, was assembled in the Paleoproterozoic (2,500 1,600 Ma) and resulted in the formation of the Wopmay (2,000 1,850 Ma) and Trans-Hudson (1,900 1,800 Ma) orogens. Accretion of cratonic blocks (Mojave) and island arc terranes (Yavapai, Mazatzal) continued along the (now) southwestern margin from 1,800 1,600 Ma (Figs 3 and 4). Some basement below the Sierra Nevada may date from this period. The collisions of Amazonia and Baltica with North America (Laurentia) led to the formation of the supercontinent Rodinia and the Grenville orogen in the eastern and southern United States at about 1,100 1,000 Ma Passive Margin of Western North America The present-day southwest United States was a shallow marine basin at 1,100 Ma (Mesoproterozoic) into which the Pahrump Group sedimentary sequence was deposited (Fig. 5). The Pahrump Group underlies, and may form parts of, the Neoproterozoic to Early Paleozoic sequences in Sierra Nevadan roof pendants. No sooner was Rodinia formed than intraplate rifting in the Midcontinent Rift system attempted to sunder it. Although rifting failed to achieve continental break-up, bimodal volcanism in the Great Lakes region became a source of 1,100 1,000 Ma sediment, perecontemporaneous with syn-collisional Grenville magmatism and high-grade metamorphism (1, Ma). The western passive margin of Laurentia formed at Ma when Gondwanaland (East Antarctica and Australia) rifted off Laurentia (Fig. 6) and formed the Panthalassan ocean basin. The shallow marine Pahrump basin foundered and became a deeper water continental shelf and slope sequence. The Sierra Nevada lie along the inferred shelf-slope transition 8

17 (Fig. 6) and Neoproterozoic-Paleozoic facies in Nevada and California support the change in paleoenvironment (Fig. 2). The passive margin continued uninterrupted through the Early Paleozoic (e.g., Fig. 7) accumulating kilometers of sediment in Nevada and eastern California. The shelf (i.e. south-central California and central Nevada) accumulated significant detritus from the Mesoproterozoic Grenville, Yavapai, and Mazatzal provinces in the Laurentian hinterland (Fig. 1). This contrasts with the distal slope and abyssal successions that record supply from exclusively Paleoproterozoic (e.g., Trans-Hudson) and Archean sources. This probably reflects the difficulty in supplying coarse siliciclastic detritus beyond the shelf, and that distal Paleozoic environments accumulated most of their coarse sediment when they were proximal Neoproterozoic shelf sequences before rifting of Rodinia at ca. 650 Ma, and their foundering. Paleozoic sediment transport was dominantly east to west (Fig. 7) from sources in present-day Arizona, New Mexico, Wyoming, and Colorado, and probably from the southern Grenville province in central Texas and northeast Mexico. One notable exception to this pattern is the supply of ca. 1,900 Ma Wopmay orogen-age detritus in the Ordovician (Gehrels et. al., 1995; Gehrels and Pecha, 2014). The Wopmay orogen in the Canadian Northwest Territories is far to the north of southern California (Fig. 3). This period represents a unique phase of north to south sediment transport along the passive margin, and Wopmay-age detrital zircons are a useful tracer of the reworking of Ordovician shelf sedimentary rocks in Late Paleozoic and Mesozoic orogenesis Late Paleozoic Active Margin The passive margin continued uninterrupted into the Devonian when marginal arcs began to intrude into the Panthalassan ocean basin from the north and south (Fig. 8A), in a process analogous to present-day South America where the Caribbean and Scotia arcs have intruded the Atlantic Ocean basin from the Pacific (Fig. 8B). The arrival of exotic arcs and their unification as a continuous arc-trench system coincided with collapse of the passive margin and deformation, uplift, and erosion of the passive margin sedimentary succession in the Antler orogeny (ca Ma; DeCelles, 2004). The Antler orogen was centered in present-day western and central Nevada and was marked by the eastward-directed thrusting of passive margin sediments along the Roberts Mountain thrust. The displaced rocks form 9

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24 the Roberts Mountain allochthon (Baldrige, 2004). The Roberts Mountain allochthon extended from present-day southern Idaho to central Nevada forming the first Cordilleran highland (the Antler Mountains) and a deep, east-facing foreland basin on the remnants of the passive margin. By the Middle to Late Pennsylvanian (Fig. 9) the eroded remnants of the Antler orogen began to be overlain by shallow marine strata, and erosion and resedimentation of passive margin detritus was suspended. Development of the Antler highlands and foreland basin represents the final phase when first-cycle detrital zircon (i.e. eroded and transported from igneous or metamorphic source rock) could be sourced from the Archean Wyoming craton and Paleo-Mesoproterozoic Yavapai, Mazatzal, and Grenville provinces to the east. From the Late Paleozoic onwards the primary source of detritus to the present-day southern Sierra Nevada region was from locally-sourced, Neoproterozoic and Paleozoic passive margin rocks, or primary Cordilleran plutonic suites. Beginning in the Early Permian ( Ma) the southern margin of Laurentia became a transcurrent, dominantly oblique left-slip margin (Fig. 10) associated with the Mojave-Sonora megashear that allowed for translation of the Caborca terrane (possibly part of the Mojave block) to its present-day location in Sonora, Mexico. During the same period, continued collisions of fringing island arcs against the western margin of Laurentia rejuvenated the Antler orogen (the Sonoman orogen) and inverted and deformed the old Antler foreland basin as the Golconda allochthon in the late Permian and early Triassic (ca Ma; Fig. 11). The Caborca and Sonoman highlands formed long-lived barriers initially only in the south, but progressively further north (Figs 10 & 11). This supplied firstcycle zircon sediments from the east, that gradually incorporated those sediments into the developing Cordilleran active margin through the rest of the Mesozoic (DeCelles, 2004). 16

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28 1.1.4 Mesozoic Active Margin Triassic prebatholithic rocks in the Sierra Nevada are interpreted as the remnants of volcanic arcs (e.g., Tioga Pass caldera, Mono County; Schweickert and Lahren, 1999), abyssal sedimentary sequences (e.g., Calaveras complex; Chapman et al., 2012), and subduction complexes and sequences of oceanic lithosphere (e.g., Kings-Kaweah ophiolite belt; Saleeby, 2011) that were formed on, or accreted to, the western active margin of Laurentia (Fig. 11). Continued crustal shortening associated with the northward-propagating Cordilleran arc in the south (i.e. California and southern Nevada) and accretion of fringing island arcs in the north (i.e. northern Nevada and Idaho) rejuvenated the Antler-Sonoman highlands in the Nevadan orogeny (central Nevada from ca Ma). This initiated deformation of the Early Paleozoic passive margin and Late Paleozoic Mesozoic foreland basins in Utah and eastern Idaho during the Sevier orogeny from ca Ma (Fig. 12; Baldrige, 2004). Cratonic sediment sources were now everywhere cut-off from the Cordilleran margin and probably buried under the developing Sevier foreland basin. Instead, local sources of detritus were once again uplifted and eroded remnants of the Neoproterozoic and Early Paleozoic passive margin (i.e. Antler-Sonoman-Nevadan orogenic belt in Nevada) and Mesozoic magmatic sources in the Cordilleran arc (Fig. 11). An arc-trench system developed along the western edge of present day North America (Fig. 12) during the Jurassic (ca Ma) and is inferred to be analogous to the present-day Indonesian orogenic system (DeCelles, 2004). Both areas share active magmatic arcs, a similar plate convergence, transitional arc-retroarc regimes from contractional to transtensional, and a complex array of large and small sedimentary basins (Fig. 12; DeCelles, 2004). The Cordilleran arc continued to take shape through the construction of a composite batholith that included the formation of juvenile continental crust, crystallization of juvenile magmatic zircons, and recycling passive margin zircons (Antler, Sonoman, Nevadan, Cordilleran orogenies). 20

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31 During the Cretaceous, the Franciscan accretionary prism, the Great Valley forearc basin, and the Sierra Nevada magmatic arc co-evolved on the margins of western North America in response to subduction of the Farallon plate, a remnant of the Panthalassan ocean basin (Fig. 13). The Sierra Nevada batholith was emplaced primarily in the Cretaceous ( Ma) as it engulfed the Neoproterozoic to early Cretaceous metasedimentary and metavolcaniclastic succession now preserved in the roof pendants (Saleeby et al., 1990). As the Farallon slab flattened due to the subduction of progressively younger, more buoyant oceanic lithosphere and the subduction of the eastern-half of the Shatsky Rise aseismic ridge (Fig. 13), the locus of magmatism migrated eastwards across the present-day Sierra Nevada between Ma (Nadin and Saleeby, 2008; Saleeby et al., 2008). By the Paleocene, the arc had migrated across Nevada and Arizona into Utah and Colorado, and magmatism ceased in California. Slab flattening led to contemporaneous eastward-expansion of the Cordilleran orogenic belt through basement-cored uplifts in the craton (Laramide orogeny), and crustal thickening in Nevada to produce the elevated Nevadaplano (ca Ma; Baldridge, 2004; Saleeby et al., 2008). The intra-arc pkcf (Busby-Spera and Saleeby, 1990) was active in the southern Sierra Nevada by at latest 95 Ma, contemporaneous with active volcanism (Erskine Canyon) in the area (Nadin and Saleeby, 2008). The present-day Sierra Nevada were at or below sea level throughout the middle part of the Cretaceous. Abundant first cycle sediment was generated in the voluminous magmatism associated with the construction of the arc, and was supplemented by continued cycling of Neoproterozoic Late Paleozoic sediment from the actively uplifting and eroding Cordilleran hinterland (Fig. 13). 23

32 2. Methods Zircon (ZrSiO4) is an accessory mineral with a higher density, stability, melting point, and hardness than other minerals that commonly occur with it (e.g. quartz and feldspar). Because of these properties, zircon can survive through many rock cycles and is resistant to weathering and alteration (Fedo et al., 2003). In addition, zircon will retain its chemical and isotopic information through metamorphism, weathering, erosion and transport, and analyzed zircons are calibrated against other zircons of known age (Bowring and Schmitz, 2003). Zircons are common in intermediate to felsic igneous rocks and typically crystallize from magmas with greater than 60% SiO2 (Cawood et al., 2012), and they occur in almost all siliciclastic sedimentary rocks (Fedo et al., 2003). Zircon readily incorporates U and Hf into its structure but excludes Pb, making it an excellent U-Pb geochronometer (Finch and Hancher, 2003). Detrital zircon U-Pb geochronology is a high precision dating technique that informs on the maximum age of sedimentary deposits as the deposit cannot be older than youngest zircon included (Fedo et al., 2003). It can also determine the ages and compositions of parent rocks (provenance), and test paleogeographic reconstructions that inform on Earth s geologic history (Fedo et al., 2003). 2.1 U-Pb isochron systems There are three isotopic measurements used in U-Pb dating with two isotopes of U and one isotope of Th that are radioactive and decay to produce different isotopes of Pb. These can be shown by two decay chains: the uranium series ( 238 U to 206 Pb; Fig. 14), and the actinium series ( 235 U to 207 Pb; Fig. 15). 24

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35 The decay series can also be represented by: U 8 He + Pb by decay, λ 238 = yr, τ1 = yr U 7 He + Pb λ 235 = yr, τ1 = yr 2 With a ratio of: 235 U = 238 U Th 6 He + Pb 4 λ 232 = yr, τ1 = yr 2 Since 232 Th has such a long half-life (τ 1/2), it is generally not used in dating of anything younger than the very oldest rocks. 204 Pb is a stable non-radiogenic isotope of Pb and two isochron equations can be generated using the decay constants (λ238 and λ235) and respective ratios to obtain independent dates from the U-Pb system. ( 206 Pb 204 ) Pb t ( 207 Pb 204 ) Pb t = ( 206 Pb 204 ) Pb o = ( 207 Pb 204 ) Pb o + ( + ( 238 U 204 ) Pb t 235 U 204 ) Pb t (e tλ 238 1) (1) (e tλ 235 1) (2) 27

36 If these two independent dates are the same, I can conclude that they are concordant. Additionally, a Wetherill concordia diagram (Fig. 16) can be constructed from the Pb isotopes and the curve can be calculated by the following: ( ( 206 Pb U 238 ) = 207 Pb U 235 ) = 206 Pb ( 204 ) Pb 207 Pb ( 204 ) Pb 206 Pb ( 204 ) Pb t 238 U ( 204 ) Pb t 207 Pb ( 204 ) Pb t 235 U ( 204 ) Pb t o o = (e tλ 238 1) (3) = (e tλ 235 1) (4) I can solve for the ratios 206 Pb * / 238 U and 207 Pb * / 235 U to calculate t (time). If a zircon crystal that originally crystallized from magma and continues in a closed system with no loss or gain of U or Pb, then from the time of crystallization to the present the ratios of 206 Pb * / 238 U and 207 Pb * / 235 U will plot on concordia and the age of the zircon can be determined from its position on the plot. Discordant ages will not plot on concordia (Fig. 17); however, discordant ages from the same rock will plot along a chord called the discordia. The discordia is usually extrapolated to both ends to intersect the concordia to give a maximum and minimum intercept age. As shown in Figure 17, to is interpreted as the age that the zircon crystallized, and t* is the age of a later event (such as metamorphism) that represents any Pb loss. The most apparent cause of discordant ages is Pb loss, when soluble Pb begins to occupy or dissolves from generated radiation space within the crystal from U decay. Metamorphic events can also cause U loss where discordant points would plot above concordia (Fig. 18), and extrapolation of the discordia back to the two points where it intersects concordia, would give two ages: t* the possible metamorphic event and to representing the initial crystallization age of the zircon. 28

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39 Pb-Pb isochrons can be represented by combining equations (1) and (2): 207 Pb 207 Pb ( 204 ) ( Pb 204 ) t Pb o 206 Pb 206 Pb ( 204 ) ( Pb 204 ) t Pb o = ( 235 U ) 235 1) 238 U [(etλ ] (e tλ 238 1) (5) Assuming that the 206 Pb and 207 Pb ages are the same, and using the ratio of then equation (5) can be used for a group of lines that have a slope (m): 235 U = 238 U m = 1 [(etλ238 1) (e tλ 235 1) ] and passes through ( Pb ) Pb o, ( 206 Pb 204 ) Pb o shown by Figure

40 2.2 Analytical Techniques Isotope dilution thermal-ion mass spectrometer (ID-TIMS), secondary ion mass spectrometer (SIMS), and laser ablation inductively-coupled plasma mass spectrometer (LA-ICP-MS) are the three techniques commonly used to analyze and date detrital zircons. Table 1 lists the advantages and disadvantages of each technique. The most precise technique is ID-TIMS where zircon crystals are dissolved in acid, and then analyzed; however, spatial resolution on each crystal is lost and the technique is slow and expensive (Gehrels and Vervoort, 2010). The SIMS technique attains high spatial resolution by using a beam of oxygen ions to ablate a polished zircon, and generates precise measurements capable of resolving several ages within a single zircon crystal (Fig. 20). It can also be advantageous in better understanding the growth history of a zircon crystal by analyzing and dating zonation in an individual zircon. The LA-ICP-MS best for finding trace elements and varied U-Pb isotopic ratios. It is also an ideal dating tool as it is quicker, inexpensive, and more widely available (e.g., University of Arizona). The LA-ICP-MS destroys more of each crystal than the SIMS (Fig. 21); however, the LA- ICP-MS can analyze more samples in a shorter amount of time (Table 1). If more precision is needed, LA-ICP-MS can be used as a first step and then a SIMS or ID-TIMS method can be used on a sub-set of samples. Comparison between SIMS and LA-ICP-MS has shown that each of the dating techniques to be accurate (0.1-1%) and suitable to use for U-Pb geochronological dating. The LA-ICP-MS is better for provenance and terrane studies when a large number of samples need to be analyzed and all sources need to be identified. 2.3 Sample selection and preparation I selected 11 samples from six roof pendants in the southern Sierra Nevada of Tulare County, Fairview Quadrangle. I completed the required stages of mineral separation on 9 of the 11 samples (2 sample were duplicates) for detrital zircon analysis at California State University Bakersfield (CSUB). I crushed and pulverized rock samples and then separated the denser detritus using a water table (e.g., Wilfley table). I magnetically separated the samples with Franz magnetic separator to avoid any bias that can occur through the positive correlation between Pb loss, U content, and the magnetic susceptibilities of detrital zircons (Sláma and Kosler, 2012). Heavy liquid mineral separation was done with in order to separate zircon 32

41 more thoroughly. Individual zircons were selected in an unbiased manner by pouring since preference for larger grains, shape, or color in sample selection can skew results (Hay and Dempster, 2009) in addition to changing the number of grains per sample (the most common n-value greater than 100. Once zircons were selected and poured, they underwent mounting in a 1 epoxy mold in a random representation of the total zircon population and mounted with primary standards as per Arizona LaserChron Center (Gehrels et al., 2006). I followed these steps with standard polishing procedures, and executed each of the mineral separation stages carefully to retain the highest number of zircons to analyze. I imaged polished grain mounts at CSUB by back-scatter scanning electron microscope (SEM) and cathodoluminescence (CL) to detect defects, impurities (e.g., pyrite), and zoning patterns within zircons to ensure precise locations were used for laser analyses. I collected data at the Arizona LaserChron Center University of Arizona (UAz; Tucson, Arizona) using their multi-collector LA-ICP-MS. My LA-ICP-MS analyses used a laser beam of 30 μm diameter to ablate the sample material, carried in helium gas into the plasma source and the isotopes analyzed with a multicollector mass spectrometer (Gehrels et al., 2006). I gathered the necessary U-Pb isotopic data through the LA-ICP-MS, and further specifics of the instrument and procedures used can be found in Gehrels et al. (2008). The data collected were filtered at Arizona LaserChron Center to exclude <10% precision and >30% discordance, and then plotted on a Wetherill concordia (Johnston et al., 2009). I then re-imaged the grain mounts at CSUB using the SEM with CL to confirm that analyses were restricted to zircons and confirm that ablation pits were wholly within zircon grains. 33

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45 2.4 Detrital zircon geochronology Two different interpretations of the detrital zircon geochronological data can be made: the crystallization age and the depositional age (Cawood et al., 2012). The youngest detrital zircon grains will provide the maximum depositional age through age distribution probability density plots and histograms that show differences in crystallization age detrital zircon populations (e.g. Figs 22 and 23). Because zircon only crystallizes during magmatism and high-temperature metamorphism, peaks can be correlated to magmatic and metamorphic events of regional scale and significance, such as convergent (arc), collisional, and extensional tectonic settings (Cawood et al., 2012). Patterns in the probability density curves are controlled by the volumes of magma or high-grade metamorphic rock generated in each tectonic setting and their preservation potential, the ease in which zircons of various ages and origins become incorporated into the sedimentary record through time, and the size of the sedimentary catchment area. Because zircons are so robust, they can be recycled through sedimentary systems many times. The qualitative analysis of ages that represent each source component within the population of the host rock link them to known geological events or certain areas (Fedo, 2003; Sláma, 2012). A quantitative approach will then relate or link ages to specific geological terrains and sources by obtaining a representation of the overall detrital zircon population. Until recently detrital zircon provenance studies required zircon populations of n = analyses spots, whereas it is now typical to use n (Pullen, 2014). My data sets had 2 of the 9 samples that had insufficient number of zircons for data analysis. Three of the samples have n-values of as low as 54 67, but were sufficient enough for interpretation because of the quality of data and identifying zircons of certain ages. The other 4 samples had zircon populations n

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48 2.4.1 Isoplot and maximum depositional ages I processed my data by plotting detrital zircon ages as histograms with superimposed probability density plots (PDP) using Isoplot (Ludwig, 1999). The histograms strictly plot ages whereas the PDPs incorporate errors or the uncertainty associated with each age analyses. The relative height of the PDP is dependent on the error of the data plot and the probability of the next possible data point of the next analyzed zircon. I also used Isoplot to generate a stacked normalized probability distribution of 7 samples that had a sufficient detrital zircon age population (Ludwig, 2003). These stacked Normalized plots can be compared visually with other age distributions (e.g. Figs 1, 22, & 23). I first determined maximum depositional ages by finding the weighted mean average (WMA) of the youngest cluster of ages (i.e. n 3) by using Isoplot (Ludwig, 1999; 2003) and following the procedures in Gehrels (2013). Single zircon ages (i.e. n 2) can occur as Pb loss and/or inheritance. This is why statistical adequacy of n 3 is used because discordance and Pb loss is unlikely for 3 or more grains of a zircon population (Gehrels et al., 2008; Pullen, 2014). In addition, clustering of ages gives more significance to analyzed depositional ages and provides a more robust detrital zircon statistical age analysis. One of my samples had a maximum depositional age with a cluster of n = 2 (AC04), and I determined that this was satisfactory due to the stratigraphic and depositional context of the other two other samples within the same roof pendant (AC01 and AC02) that had the same depositional age. This should be done for each situation individually on any analyses that may have any discrepancies due to Pb loss, inclusions, inheritance, or geological implications. 40

49 3. Results and Preliminary Interpretation 3.1 Durwood Meadows roof pendant (AC01; 35 59'6.49"N, '38.56"W) A large-volume sample of a volcaniclastic metaquartzite in the Durwood Meadows roof pendant (Fig. 24) was chosen to obtain the coarsest-grained material possible from a small road cut (Fig. 25). Zircons obtained (n = 57) record multiple age probability density peaks (Fig. 26): principal peak at ~1,850 Ma (Paleoproterozoic) secondary peak at ~95 Ma (Cenomanian) minor peaks at ~2,050 Ma (Paleoproterozoic) and ~2,700 Ma (Neoarchean) Preliminary Interpretation of AC01 The maximum depositional age of AC01, and therefore the Durwood Meadows roof pendant succession, is inferred to have a weighted mean average (WMA) of ca Ma (±3.8 Ma (2σ), with mean standard weighted deviation (MSWD) 2.6; Fig. 27A) based on a single cluster of Cenomanian (Early Cretaceous) zircon (n = 3). The prominent ca. 1,850 Ma population is derived from the Trans-Hudson orogen (northern plains region; Fig. 3). The secondary peak ca. 2,100 Ma is derived from the Wopmay orogen (Northwest Territories, Canada; Fig. 3; Whitmeyer and Karlstrom, 2007); it is a distinctive age population. Zircon greater than ca. 2,500 Ma are derived ultimately from Archean cratonic rocks, the most proximal of which is the Wyoming craton possibly Mojave (Colorado and eastern Utah; Figs 3 and 4). There is a prominent age gap between the Albian (ca. 100 Ma) and the Paleoproterozoic (ca. 1,850 Ma). 41

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53 3.2 Durwood Meadows roof pendant (AC02; 35 59'8.18"N, '36.92"W) A large-volume sample of phyllite and semi-pelite was chosen to obtain the coarsest-grained material possible in the Durwood Meadows roof pendant (Fig. 24). The zircons obtained (n = 200) record multiple age probability density peaks (Fig. 28): principal peak at ~260 Ma (Permian) secondary peaks at ~115 and ~140 Ma (Early Cretaceous) minor peaks at ~95 Ma (Cenomanian), ~200 Ma (Triassic), ~350 and ~480 Ma (Paleozoic), ~1,100-1,200 Ma and ~1,350Ma (Mesoproterozoic), and ~1,750 Ma (Paleoproterozoic) Preliminary Interpretation of AC02 The maximum depositional age of AC02, is inferred to have a WMA of ca Ma (±2.2 Ma (2σ), MSWD 0.4; Fig. 27B) based on a single cluster of Cenomanian (Early Cretaceous) zircon (n = 3). Older peaks at ca. 1,100 Ma are likely derived from the Grenville orogen (eastern North America; Fig. 5) and mid-continent rift (Great Lakes region; Whitmeyer and Karlstrom, 2007). The ca. 1,700 Ma population is probably derived from the Yavapai- Mazatzal arc domains or Mojavia (southwestern United States; Fig. 5). 45

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55 3.3 Alder Creek roof pendant (AC03; 35 59'6.4"N, '50.6"W) A large-volume sample of phyllite and semi-pelite was chosen to obtain the coarsest-grained material possible from a small road cut (Fig. 29) in the Alder Creek roof pendant (Fig. 24). Abundant zircon (n = 353) record multiple age probability density peaks (Fig. 30): principal peak at ~1,850 Ma (Paleoproterozoic) secondary peaks at ~100 Ma (Albian, Early Cretaceous) and ~2,050 Ma (Paleoproterozoic) minor peaks at 321 Ma (Early Pennsylvanian; a single grain), ~1,100-1,200 Ma, ~1,300-1,500 Ma, and ~1,600 Ma (Mesoproterozoic), and ~2,700 Ma (Neoarchean) Preliminary Interpretation of AC03 The maximum depositional age of AC03, and therefore the entire Alder Creek roof pendant succession, is inferred to have a WMA of ca Ma (±1.3 Ma (2σ), MSWD 1.4; Fig. 27C) based on a single cluster of Albian (Early Cretaceous) zircon (n = 4). Older age peaks at ca. 1,100 1,200 Ma and ca. 1,300 1,500 Ma are also likely derived from the Grenville orogen (Fig. 5), the mid-continental rift, and the mid-continental anorogenic granitoid province (MCAGP; central and southwestern United States), respectively (Whitmeyer and Karlstrom, 2007). The ca. 1,600 Ma population is probably derived from the Yavapai-Mazatzal arc domains or Mojavia (Fig. 3), and the prominent ca. 1,850 Ma population is derived from the Trans-Hudson orogen (Fig. 3). Zircon greater than ca. 2,500 Ma are from the Wyoming or Mojave cratons (Fig.3). The secondary peak at ca. 2,100 Ma is derived from the Wopmay orogen (Figs 3 and 7; Whitmeyer and Karlstrom, 2007). There is a prominent age gap between the Albian (ca. 100 Ma) and the Mesoproterozoic (ca. 1,100 Ma), except for a single 321 Ma zircon. This is unusual because Late Mississippian and Early Pennsylvanian zircon crystallization events are very limited in North America (Fig. 9; Gehrels and Pecha, 2014). It is likely to be derived from either (i) the earliest part of the Alleghenian orogen ( Ma) in the eastern United States, or (ii) from isolated island arc magmatism off board of the western margin of North America (e.g., Klamath arc), prior to the Sonoma (Golconda) orogeny (Nevada and northern California; Fig. 9). 47

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57 3.4 Durwood Meadows roof pendant (AC04; 35 59'28.74"N, '37.04"W) A large-volume sample of the upper volcaniclastic metaquartzite was chosen to obtain the coarsest-grained material possible (Fig. 31) in the Durwood Meadows roof pendant (Fig. 24). Zircons obtained (n = 54) record multiple age probability density peaks (Fig. 32): principal peak at ~1,850 Ma (Paleoproterozoic) secondary peaks at ~100 Ma (Cenomanian) and 206 Ma (Late Triassic; a single grain) minor peaks at ~1,200, ~1,350 Ma, and ~1,450 Ma (Mesoproterozoic) and ~2,050 Ma (Paleoproterozoic) and ~2,700 Ma (Neoarchean) Preliminary Interpretation of AC04 The maximum depositional age of AC04, is inferred to have a WMA of ca Ma (±2.4 Ma (2σ), MSWD 0.27; Fig. 27D) based on Albian (Early Cretaceous) zircon (n = 2). Older age peaks at ca. 1,200, ca. 1,350 Ma, and ca. 1,450 Ma are also likely derived from the Grenville orogen (Fig. 5), and the MCAGP respectively (Whitmeyer and Karlstrom, 2007). The prominent ca. 1,850 Ma population is derived from the Trans-Hudson orogen (Fig. 3), and zircon ages greater than c. 2,500 Ma are from the Wyoming or Mojave cratons (Fig. 3). The secondary ca. 2,100 Ma peak is derived from the Wopmay orogen (Figs 3 and 7; Whitmeyer and Karlstrom, 2007). 49

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59 3.5 Fairview roof pendant (AC08; 35 57'26.90"N, '38.26"W) A large-volume sample of the metagraywacke was chosen to obtain the coarsest-grained material possible from a small road cut (Fig. 33) in the Fairview roof pendant (Fig. 24) that is surrounded by younger plutonic suites within the southern Sierra Nevada batholith (Nadin and Saleeby, 2008) including Brush Creek and Peppermint Meadow ( Ma) to the north, and Kern River pluton ( Ma) to the south. To the east, on the opposite side of the KCF, is the much younger Castle Rock pluton (95 84 Ma). Zircons obtained (n = 231) record multiple age probability density peaks (Fig. 34): principal peak at ~120 Ma (Aptian, Early Cretaceous) secondary peaks at ~95 Ma (Cenomanian), ~145 Ma (Late Jurassic), and ~1,050 Ma (Mesoproterozoic) minor peaks at ~1,200 and 1,350 Ma (Mesoproterozoic) and ~1,700 Ma (Paleoproterozoic) Preliminary Interpretation of AC08 The maximum depositional age of AC08 is inferred have WMA of ca Ma (±1.6 Ma (2σ), MSWD 0.91; Fig. 27E) based on a strong cluster of Albian (Early Cretaceous) zircons (n = 8). Peaks at ca. 1,200 Ma and ca. 1,350 are also likely derived from the Grenville orogen (Fig. 5), and the MCAGP (Whitmeyer and Karlstrom, 2007). The ca. 1,700 Ma population is probably derived from the Yavapai-Mazatzal or Mojave domains (Fig. 5). 51

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62 3.6 Kernville roof pendant (AC09; 35 47'3.83"N, '40.79"W) A large-volume sample of a metaquartzite semi-pelite was chosen to obtain the coarsestgrained material possible from a small outcrop (Fig. 35) in the Kernville roof pendant (Fig. 24). The pendant lies in the middle of intrusive plutons including to the west, Kern River ( Ma) and to the east, Cannell Creek and Goldledge (95 84 Ma; Nadin and Saleeby, 2008). Zircons obtained (n = 224) record multiple age probability density peaks (Fig. 36): principal peak at ~1,050 Ma (Mesoproterozoic) secondary peaks at ~1,150 Ma (Mesoproterozoic) minor peaks at ~1,350 and ~1,450 Ma (Mesoproterozoic) and ~1,700 Ma (Paleoproterozoic) Preliminary Interpretation of AC09 The maximum depositional age of AC09 is inferred to be ca. 946 Ma (±22 Ma (2σ), MSWD 1.5; Fig. 27F) based on a cluster of the youngest Neoproterozoic zircons (n = 6). The Kernville pendant has a clear Grenville signature with the principal peak of ca. 1,100 1,200 Ma. The minor peak activity between ca. 1,350 and ca. 1,450 Ma correlates to the MCAGP (Whitmeyer and Karlstrom, 2007) and the ca. 1,700 Ma population is probably derived from the Yavapai-Mazatzal arc domains or Mojavia (Fig. 5). Zircon ages greater than ca. 2,500 Ma are from the Wyoming or Mojave cratons (Fig. 4). There is a prominent quiescence from ca. 2,000 2,400 Ma. 54

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64 3.7 Corral Creek roof pendant (AC11; 35 51'10.15"N, '8.78"W) A large-volume sample of the Corral Creek roof pendant (Fig. 24) along a small outcrop near the Kern River was chosen to obtain the coarsest-grained material possible from a volcanogenic, plagioclase and quartz-rich, immature, metagraywacke unit, originally assigned to the Mesozoic Kings sequence by Saleeby and Busby-Spera (1988; Figs 37 and 38). Zircons obtained (n = 67) record multiple age probability density peaks (Fig. 39): principal peak ~at 2,550 Ma (Neoarchean) secondary peak at ~ 1,700 Ma (Paleoproterozoic) minor peaks at ~93 Ma (Cretaceous; single grain), ~161 Ma (Jurassic; single grain), ~251 Ma (Triassic; single grain), and ~1,850 Ma (Paleoproterozoic) Preliminary Interpretation of AC11 The maximum depositional age of AC11 is inferred to have a WMA of ca. 1,713 Ma (±7 Ma (2σ), MSWD 1.4; Fig. 27G) based on a strong cluster of Paleoproterozoic zircons (n = 9). The zircon population ca. 1,700 Ma is derived from the Mojave province that has age equivalents in the Yavapai and Mazatzal provinces, but incorporates an immature sequence of volcanogenic sediments (Barth et al., 2009; Fig. 40). The Corral Creek pendant also has a principal peak ca. 2,500 Ma that correlates to the Wyoming and Mojave cratons (Whitmeyer and Karlstrom, 2007; Figs 3, 4, and 5). The Mesoproterozoic Grenville orogeny (1,200 1,000 Ma) is absent in AC11 making it highly unlikely that this sample can be younger than 1,200 Ma. Minor zircon population at ca. 1,850 Ma is indicative of the Trans-Hudson orogenic event (Whitmeyer and Karlstrom, 2007; Figs 3 and 40). Single grain populations were not used because of the insufficient clustering of ages (i.e. n 3) and the evidence of the immaturity of the formation itself concluded that those zircon ages were most likely from Pb loss or another anomalous single grain inclusion. 56

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69 4. Discussion 4.1 Sierra Nevada roof pendants Corral Creek roof pendant The volcanogenic, plagioclase and quartz-rich, immature, metagraywacke unit (AC11) in the informally named Corral Creek pendant (Late Paleoproterozoic), closely correlates with the Pinto Mountain Group located in the Pinto Mountains (southeast of the San Bernardino Mountains, Mojave province; Wooden et al., 2013; Figs 41A and B). The PDP of AC11 shows that Corral Creek does not contain Grenville zircons (1,300 1,000 Ma) or MCAGP zircons (1,550 1,350 Ma) which indicates that the minimum depositional age is >1,000 Ma and is probably >1,350 Ma (cf. AC09; Fig. 42). Moreover, the immature composition of the metaturbidite suggests that the minimum depositional age is close to the maximum of c. 1,713 Ma. If this is correct, then this deposit is an example of syn-yavapai arc volcanism along the western margin of the Mojave block (e.g., Fig. 4), as well as the contemporaneous magmatism and metamorphism in the Mojave crustal province (e.g., Whitmeyer and Karlstrom, 2007; Wooden et al., 2013). These arc and arc accretion events occurred during the growth of the supercontinent Rodinia around a core composed of the Laurentian, East Antarctic, and Australian continents. Ca. 1,700 Ma rocks are preserved in the San Gabriel and San Bernardino Mountains (Barth et al., 2000; 2009) and eastern Mojave Desert (Strickland et al., 2012). Mojavia is inferred to have 2,600 2,400 Ma cratonic Mojave basement (Wooden et al., 2013), and the >2,500 Ma is not necessarily from Wyoming and thus AC11 can be explained as being solely from Mojavia as shown in Figures 3 and 4. If sample AC11 is indeed from a Paleoproterozoic deposit, then it is probably the oldest exposed rock in the Sierra Nevada, and extends the stratigraphic record in this region beyond previous estimates (e.g., Neoproterozoic; Memeti et al., 2010). 61

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72 If the Corral Creek pendant is Cretaceous then it still needs to be sourced from 1,700 Ma and 2,500 Ma rocks exclusively because of the immaturity of the formation. This concludes that it must come from Mojave basement (i.e. in the south) and not from Nevada (i.e. in the northeast) where Grenville zircons are ubiquitous in Neoproterozoic and Paleozoic rocks (e.g., Fig. 40). If it were sourced from Nevada, it would look like the Fairview pendant (AC08; Figs 34 and 42) Kernville roof pendant The Kernville pendant (AC09) is a Neoproterozoic psammite that has a maximum depositional age of ca. 946 Ma. It is inferred to form part of the Neoproterozoic Paleozoic continental slope of the passive margin (Figs 1, 2, 36, and 42; Chapman et al., 2012; 2015). Sample AC09 has a very strong Grenville peak and weaker 1,800 1,700 Ma and ca. 2,400 Ma peaks, and is most likely sourced primarily from Laurentia after 1,100 Ma. It has a similar zircon population distribution to member A of the <787 Ma Horse Thief Springs Formation of the Pahrump Group in Death Valley (Mahon et al., 2014), and may be a distal, slope-ward correlative. I infer that it is definitely younger than 1,100 Ma (Grenville), has a depositional age between ca Ma (Neoproterozoic), and is probably a distal part of the Pahrump Group Durwood Meadows and Alder Creek roof pendants The adjacent Durwood Meadows and Alder Creek roof pendants contain similar rocks that yield nearly identical mid-cretaceous depositional ages, and I infer them to be different remnants of the same sedimentary basin. The different samples (AC01, AC02, AC03, and AC04) do not have identical zircon populations (Fig. 43). Sample AC01 does not contain ca. 1, Ma zircons that are common in the other three samples. Sample AC02 does not contain ca. 2,000 Ma zircons are common in the other three samples; however, it is dominated by Permian (ca. 260 Ma) zircons that are all but absent in the others. Samples AC03 and AC04 contain ca. 1,800 Ma zircons probably derived from the Wopmay orogen in northern Canada and transported to the southwest Laurentian passive margin in the Ordovician. The only ages that are common to all four samples are Early to mid-cretaceous and ca. 2,500 Ma. 64

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74 The presence of different age populations (Fig. 43) indicates variability in sediment source and supply into the basin. Wopmay and Grenville zircons were mostly supplied from the east from the Paleozoic passive margin sequence that was uplifted and eroded in Nevada (Fig. 13). Conversely, the absence of Grenville-aged or Wopmay and Trans-Hudson-aged zircons suggests supply from the Mojave Desert region in the south (Fig. 44). Ca. 2,500 Ma zircons could be sourced from either or both Nevada or the Mojave Desert. Permian zircons in AC02 were likely sourced from the nascent Cordilleran arc (Fig. 10; Saleeby and Dunne, 2015) that continued to evolve northwards in the Early Triassic (Fig. 11); the closest Permian arc rocks are exposed in the southeastern margins of the Sierra Nevada (Saleeby and Dunne, 2015). The ubiquity of Cretaceous zircons suggests a contemporaneous local source. The rocks in the Durwood Meadows and Alder Creek roof pendants are dominated by medium-grained turbidites and water-deposited felsic volcaniclastic deposits, including ignimbrites and pumice-rich breccias. Epidotized, probably andesitic, peperites intrude felsic volcaniclastic rocks at Durwood Meadows, indicating that intermediate magmas actively intruded the non-lithified, submarine sediment package. Therefore, I infer that mid- Cretaceous (ca Ma) deposition was into a marine or deep lacustrine basin proximal to a volcanic center above the developing batholith (Fig. 45). Previously these rocks were assigned to the Jurassic Kings sequence marine succession (Saleeby and Busby-Spera, 1986; Busby-Spera and Saleeby, 1990) and the Paleozoic Mesozoic marine metasedimentary rocks of the Big Meadow metamorphic belt of Ross (1995). The presence of thick beds of felsic volcaniclastic rocks suggest deposition in proximity to a major caldera similar to the ca. 100 Ma Minarets and Merced Peak calderas in the Ritter Range pendant (Fig. 46; Patterson et al., 2014) and the ca. 196 Ma and ca. 136 Ma Mineral King caldera in the Mineral King pendant (e.g., Busby, 2012). The Minarets and Merced Peak calderas are too far away from the Durwood Meadows and the Alder Creek roof pendants to be plausible sources, and the presence of peperite indicates contemporaneous local volcanism; therefore, a local volcanic source is likely. The roof pendants are proximal to and contemporaneous with the felsic Erskine Canyon subaqueous volcanic sequence in the adjacent Lake Isabella area to the south ( Ma; Saleeby et al., 2008; Fig. 47) as well as the Oak Creek Pass metavolcanics further to the southwest (Fig. 48; Chapman et al., 66

75 2012). The Erskine Canyon Formation, the Durwood Meadows, and the Alder Creek roof pendants are contemporaneous with plutonic components of the southern Sierra Nevada batholith (Nadin and Saleeby, 2008; Saleeby et al., 2008), including the Sherman Pass pluton suite ( Ma), the Kern River plutonic suite ( Ma), and the Castle Rock plutonic suite (95 84 Ma; Figs 24 and 47). The volcanic rocks are much too young to correlate with the Ma subaerial volcanic and sedimentary Goldstein Peak Formation to the northwest (Clemens-Knott and Saleeby, 2013) Fairview roof pendant A psammitic bed (AC08) within a turbiditic sequence in the informally named Fairview pendant has a Cretaceous maximum depositional age of ca. 112 Ma. This age is similar to those of the Durwood Meadows and Alder Creek rook pendants east of the KCF, and it likely correlates with them and formed in a similar depositional environment. The zircon population in AC08 (Fig. 34) is superficially similar to some of those at Durwood Meadows and Alder Creek; Fig. 43), with Permian and Grenville peaks, but completely lacks the strong 1,800 2,100 Ma peaks (Yavapai, Mazatzal, Trans-Hudson, later Mojavia) found there. AC08 is, however, remarkably similar to AC09 (Neoproterozoic Kernville roof pendant; Fig. 43) when the >800 Ma part of the age spectrum is examined. Based on this remarkable similarity, I infer that the sediment in the Fairview pendant was most likely originally sourced from exposures of Kernville terrane metasediments (e.g., AC09) either locally or to the immediate southeast such that small populations of Permian zircons from the southeastern margin of the Sierra Nevada and proximal Cretaceous volcanogenic zircon were supplied as well. Therefore, the Fairview pendant developed synchronously with, or slightly earlier than, the Durwood Meadows Alder Creek basin, but with a distinctly different and more restricted, local source that did not include the Mojavia to the south. 67

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81 4.1.5 Summary Sierran roof pendants contain sedimentary rocks with a diverse range of depositional ages and sediment provenances. In addition to the Paleoproterozoic, Neoproterozoic, and Cretaceous deposits identified here, Paleozoic, Triassic, and Jurassic sedimentary and volcanic sequences are known. Saleeby and Busby-Spera (1986) and Saleeby et al. (1987) assigned most metasedimentary rocks in the southern Sierran roof pendants to the Triassic- Jurassic Kings sequence, and fossiliferous, marine Jurassic rocks are known in parts of the Lake Isabella roof pendant (e.g., Fig. 47). Both studies, and Saleeby et al. (2008), acknowledge the likely presence of Paleozoic rocks within the roof pendants, where they are probably complexly in-folded with the Kings sequence. Late Neoproterozoic and Paleozoic rocks are essential components of many other roof pendants such that they form the fundamental parts of terranes formed of different parts of the Paleozoic passive margin (Fig. 2). My results, therefore, extend the depositional history of southern Sierran roof pendants, and the sedimentary basins that they are fragments of, significantly. Based on (1) the proximity of the different roof pendants, (2) the recycling of Kernville terrane rocks into the adjacent Cretaceous basin(s), and (3) the known deformation within the roof pendants (e.g., Saleeby and Busby-Spera, 1986), I infer that it is possible that most parts of the Paleozoic and Mesozoic sedimentary basin architecture was developed on Paleo- to Neoproterozoic basement that was more extensive than previously thought. Given the difficulty of identifying similar looking rocks of vastly different ages in the field, it is very likely that more Proterozoic rocks exist in other pendants and other parts of these pendants. 4.2 The proto-kern Canyon fault The Durwood Meadows and Alder Creek pendants that lie to the east of the pkcf (Fig. 24; Busby-Spera and Saleeby, 1990) and both have Cretaceous depositional ages. Two of the three adjacent roof pendants west of the pkcf yield very different ages (Fig. 42) and the third is Cretaceous as well. Because none of the roof pendants sampled have Paleozoic depositional ages, and only one (AC09) is inferred to form part of the Laurentian passive margin, I cannot test between different terrane models (Figs 1 and 2). The only appropriate sample, AC09, is located on the west side of the pkcf; however, it is inferred to be located 73

82 there in both models, and therefore does not discriminate between them. Other roof pendants need to be sampled elsewhere to determine which, if any, are suitable for testing between the different models. 4.3 An intra-arc volcanic graben within the Cretaceous Sierra Nevada arc? The continental arc that was along the Cordilleran margin from Mexico to Oregon in the Early Cretaceous was a low-standing topographic feature (Sharman et al., 2014) that was emplaced in an extensional setting (Busby, 2012) similar to that of other low-standing arcs like the Ryukyu-Kyushu arc (Japan; Fig. 49) and the Taupo-Kermadec-Tonga arc (SW Pacific; Fig. 50). Both arcs are characterized by submarine (e.g., Kika) or low-lying, subaerial silicic calderas (e.g., Taupo) concentrated along a prominent intra-arc rift over a nascent batholith. The intra-arc graben are receptacles for (1) contemporaneous volcanogenic sediment from the rift margins (e.g., Ryukyu arc front), (2) along-rift transport from adjacent calderas within the rift, and (3) terrigenous sediment from outside the arctrench system (e.g., turbidites from mainland China or Japan). In the early Late Cretaceous the Sierra Nevadan arc was uplifted rapidly to >2 km above sea level (e.g., Surpless, 2015), and the sediment catchment area for the Great Valley forearc basin transitioned from regional (including the Sierran arc and adjacent parts of Nevada and Arizona) to local (the Sierran arc only). At ca Ma subaqueous sedimentation and volcanism was prevalent in the southern Sierra Nevada arc in and around the Durwood Meadows, Alder Creek, Fairview, and Lake Isabella (Erskine Canyon Formation) roof pendants. Whether or not these were submarine or lacustrine at this time is still unknown. Regardless, sediment sources included local arc volcanics and Kernville terrane rocks, medial parts of the Sierran basement (i.e. Permian rocks in the southeast Sierra Nevada), and distal sources to the south (Mojave) and east and northeast (Death Valley area, Nevada). One way that distal and medial sediment could have been sourced simultaneously from the south and southeast (i.e. along strike of the arc) and the east and northeast (i.e. perpendicular to the strike of the arc) is if a strike-parallel intra-arc graben existed within the Sierra Nevada through the Durwood Meadows Alder Creek and Lake Isabella areas and beyond, analogous to those in the Ryukyu-Kyushu and Taupo-Kermadec-Tonga arcs (Figs 49 and 50). 74

83 If such a graben existed, it would have been parallel to and located along the KCF that was active from at latest 95 Ma (Nadin and Saleeby, 2008). Between ca. 95 to 80 Ma the KCF was an east-side-up, dextral, reverse-oblique fault (Fig. 47); i.e. transpressional. I propose that prior to ca. 95 Ma (ca Ma) the KCF was locally transtensional and that a transtensional, syn-volcanic graben opened above it: this is now preserved as fragments in the Durwood Meadows, Alder Creek, and Lake Isabella roof pendants. Transtensional volcanic graben like this existed within the Sierra Nevadan arc during the Early and Middle Jurassic, and exist today in the Aeolian, Philippine, and Sumatran arcs (Busby, 2012 and references therein). The transition from transtension to transpression along the KCF, and the cessation of Erskine Canyon-age volcanism may be contemporaneous with the beginning of subduction of the conjugate of the Shatsky Rise under southern California at ca. 95 Ma (e.g., Liu et al., 2010; Nadin et al., 2016). 75

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