Miocene-Pliocene Strike-Slip Basin Development Along the Denali Fault System in the Eastern Alaska Range

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12-2016 Miocene-Pliocene strike-slip basin development along the Denali fault system in the eastern Alaska range: Chronostratigraphy and provenance of the Mccallum formation and implications for displacement Wai Kehadeezbah Allen Purdue University

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Recommended Citation Allen, Wai Kehadeezbah, "Miocene-Pliocene strike-slip basin development along the Denali fault system in the eastern Alaska range: Chronostratigraphy and provenance of the Mccallum formation and implications for displacement" (2016). Open Access Theses. 830. https://docs.lib.purdue.edu/open_access_theses/830

This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. Graduate School Form 30 Updated

PURDUE UNIVERSITY GRADUATE SCHOOL Thesis/Dissertation Acceptance

This is to certify that the thesis/dissertation prepared

By Wai Kehadeezbah Allen

Entitled MIOCENE-PLIOCENE STRIKE-SLIP BASIN DEVELOPMENT ALONG THE DENALI FAULT SYSTEM IN THE EASTERN ALASKA RANGE: CHRONOSTRATIGRAPHY AND PROVENANCE OF THE MCCALLUM FORMATION AND IMPLICATIONS FOR DISPLACEMENT

For the degree of Master of Science

Is approved by the final examining committee:

Darryl Granger Chair Christopher L. Andronicos

Kenneth D. Ridgway

To the best of my knowledge and as understood by the student in the Thesis/Dissertation Agreement, Publication Delay, and Certification Disclaimer (Graduate School Form 32), this thesis/dissertation adheres to the provisions of Purdue University’s “Policy of Integrity in Research” and the use of copyright material.

Approved by Major Professor(s): Kenneth D. Ridgway

Approved by: Indrajeet Chaubey 11/26/2016 Head of the Departmental Graduate Program Date

MIOCENE-PLIOCENE STRIKE-SLIP BASIN DEVELOPMENT ALONG THE

DENALI FAULT SYSTEM IN THE EASTERN ALASKA RANGE:

CHRONOSTRATIGRAPHY AND PROVENANCE OF THE MCCALLUM

FORMATION AND IMPLICATIONS FOR DISPLACEMENT

A Thesis

Submitted to the Faculty

Purdue University

Wai K. Allen

In Partial Fulfillment of the

Requirements for the Degree

Master of Science

December 2016

Purdue University

West Lafayette, Indiana

For my family

My family continues be a source of inspiration and hope for me as I continue my academic career. The immense love and support during these important stages of my academic career are sincerely appreciated. My mother and father are survivors of the

American Indian boarding school era and I am proud and honored to continue their story.

My parents have always advocated for me to continue my education and instilled in me the cultural values of the Diné people. My mother and sister have always been two of the greatest heroines in my life. Their strength and perseverance continues to inspire me to be confident and to be a better individual every day. My father and brother have always taught me about hard work and how critical it is for others whether or not they ask for it. I am honored and privileged to say that I grew up on the same lands as my ancestors did.

Doing so profoundly affected my values as an individual and allowed me to recognize the beauty in the desert landscape of the Navajo Reservation while others would view it as desolate and empty.

iii

ACKNOWLEDGEMENTS

The friends that I have made during my journey to this point in my career have also been instrumental to my success. Most notably are Darryl Reano, Roberta Sakizzie, Felica

Ahasteen-Bryant, Hailey Bryant, Kimberle Davis, Aurelia Yazzie, Rylan Chong, Cassidy

Jay, Ruth Aronoff, Benjamin Link, Christopher Rommele, past and present Basin

Analysis group members (Mariah Romero, Lauren Colliver, Tim Henderson, Peter

Robinson, Tommy Lovell, and Patrick Brennan), Dr. Larry Braille, Dr. Jon Harbor, and

Dr. Jeffrey Trop. Their conversations and feedback were important in many aspects of my research as well as daily life as a graduate student. I also would like to thank my collaborators from the University of California-Davis and the University of Alaska-

Fairbanks: Dr. Sarah Roeske, Dr. Jeffrey Benowitz, Trevor Waldien, Patrick Terhune, and Kailyn Davis. My collaborators support throughout the completion of this research was invaluable. I would also like to thank my thesis committee members (Dr. Christopher

Andronicos, Dr. Darryl Granger, and Dr. Kenneth D. Ridgway) for serving on my committee and providing important feedback on my thesis and ideas for future research. I would like to sincerely thank my advisor and mentor, Dr. Kenneth D. Ridgway. Ken continues to be an amazing mentor and has understood my important cultural values as a

Native American. I feel very lucky to have Ken as my advisor and look forward to continue my research at Purdue. I would also like to thank research collaborators

iv involved with the Integrated Ocean Drilling Project 341. The research associated with this project widened my perspectives to how diverse fields of research can be integrated to unravel the 12-myr record of the surveyor fan system in Gulf of Alaska. My project that was a part of this effort involved close collaborations with Dr. Eva Enklemann and

Catherine Dunn at the University of Cincinnati. Their contribution to this project was integral in understanding the detrital and clast datasets by using the fission track method.

I thank them for their efforts in this project and their thoughtful and critical perspectives of the detrital and clast datasets. More detailed work associated with this project will be discussed in my future Ph.D. work. I also thank the Native American Education and

Cultural Center, Sloan Indigenous Graduate Partnership, the American Indian Science and Engineering Society, and Native American Student Association at Purdue University for their support. The Sloan program, NAECC, NASA, and Purdue AISES chapter organizations were important campus resources that allowed me to succeed as a graduate student and provided a much-needed community. I would finally like to thank the

National Science Foundation, ExxonMobil, Chevron Corporation, the Geological Society of America, Alaska Geological Survey, and Purdue University for their financial support of my Masters research. NSF support provided the opportunity for me to learn the U-Pb detrital zircon dating technique and also to conduct analysis at the Laserchron Center at the University of Arizona. There are many others not listed here that have contributed to my success, I thank you for your insights and encouragement to continue my education.

viii

Appendix C 40Ar/39Ar on Biotite in Volcanic Clasts ...... 139

Appendix D 40Ar/39Ar on Detrital Biotite ...... 143

Appendix E U-Pb Detrital Zircon Sample List for the McCallum Formation ...... 146

LIST OF TABLES

Appendix Tables Page Table 1 Datatables of Tephras Analyzed from the McCallum Formation ...... 125

Table 2 Datatables of Volcanic Clasts dated with 40Ar/39Ar Geochronology ...... 141

Table 3 Datatable for 40Ar/39Ar Analysis of Detrital Biotite ...... 145

LIST OF FIGURES

Figure ...... Page Figure 1 Generalized bedrock geology map of south-central Alaska with emphasis of

possible magmatic source areas for the McCallum Basin...... 6

Figure 2 Geologic map of the McCallum basin ...... 8

Figure 3. Composite Measured Stratigraphic Section of the McCallum Formation ...... 10

Figure 4 Photographs of Type Sections of the Lower and Upper Member of the

McCallum Formation and Facies 1- Facies 2 of the Lower Member ...... 13

Figure 5 Photographs of Facies 2- Facies 7 of the Lower and Upper Member...... 14

Figure 6 Photographs of Facies 7-Facies 10 of the Upper Member...... 15

Figure 7 Stratigraphic Correlation of Lithofacies of the McCallum Formation ...... 16

Figure 8 Detailed Measured Stratigraphic Sections of the Lower Member of the

McCallum Formation ...... 17

Figure 9 Depositional Interpretation of the Lower Member of the McCallum Formation.

...... 23

Figure 10 Detailed Measured Stratigraphic Sections of the Upper Member of the

McCallum Formation ...... 24

Figure 11 Depositional Interpretation of the Upper Member of the McCallum Formation.

...... 31

Figure 12 Probability Density Profiles of the U-Pb Detrital Zircon Samples from the

Lower Member ...... 34

Figure 13 Probability Density Profiles of the U-Pb Detrital Zircon Samples from the

Upper Member...... 36

Figure 14 Composite Probability Density Profiles of the U-Pb Detrital Zircons Samples

from the Upper and Lower Member of the McCallum Formation...... 37

Figure 15 Results of Single Grain Detrital Biotite 40Ar/39Ar Analysis and 40Ar/39Ar

Analysis of Volcanic clasts ...... 45

Figure 16 Clast Compositional.Data and Paleocurrent Data from Conglomerate of the

McCallum Formation ...... 60

Figure 17 Miocene-Pliocene strike-slip basin development models for the McCallum

basin ...... 67

Figure 18 Modern River Samples Relative age probability plots for the Nabesna River

and Cottonwood Creek Complex...... 69

xii

ABSTRACT

Allen, Wai, K. M.S., Purdue University, December 2016. Miocene-Pliocene Strike-slip Basin Development along the Denali Fault System in the Eastern Alaska Range: Chronostratigraphy and Provenance of the McCallum Formation and Implications for Displacement. Major Professor: Kenneth Ridgway.

The Denali fault system represents one of the major strike-slip faults in North America but very little is known about the amount and timing of displacement on this 2000-km- long structure. The 7.9 M 2002 Denali Earthquake emphasized the importance of this fault system for understanding the deformational record of the upper plate of the southern

Alaska convergent margin. Our analysis of the Miocene-Pliocene McCallum Formation located along the east-central part of the Denali fault provides one of the few records for

Neogene displacement as well as changes in surface and basin processes related to tectonic transport. We have established a chronostratigraphic framework for the

McCallum Formation that shows that it consists of a two-part stratigraphy that represents the progradation of alluvial-fan deposystems of an upper member over mainly lacustrine strata of a lower member. This upward coarsening progradational package has a minimum thickness of 564 m based on our measured stratigraphic sections. New ages from 40Ar/39Ar geochronology of tephras show that the lower member ranges in age from

6.1 to 5.07 Ma and that the upper member ranges from 5.03 to 3.80 Ma. U-Pb detrital zircon geochronology and 40Ar/39Ar detrital biotite ages from sandstone, and 40Ar/39Ar

xiii ages of volcanic clasts in conglomerate are all consistent with up to ~ 230 km of dextral offset of the McCallum Formation from its sources of sediment on the opposite (east) side of the Denali and Totschunda fault systems.

We present a minimum and maximum interpreted amount of displacement based on the new provenance data and modern displacement rates along the fault system. In both interpretations the McCallum basin would be located adjacent to the more northerly trending Totschunda fault in a transtensional setting during deposition of the lacustrine strata of the lower member. With strike-slip displacement of the McCallum basin, it was transported northward into a regional restraining bend. This stage of basin development was characterized by deposition of alluvial fan deposits of the upper member that were the product of the growth of a thrust belt along the eastern margin of the basin adjacent to the Denali fault. Our new data document 50 Ma Eocene strata that have been thrust over beds as young as 3 Ma along the eastern margin of the basin. Collectively, results of our study indicate significant Neogene strike-slip and thrust displacement along the Denali fault system that had been previously unrecognized and should be accounted for in

Cenozoic fault budgets and future seismic risk assessments of southern Alaska.

CHAPTER 1. MIOCENE-PLIOCENE STRIKE-SLIP BASIN DEVELOPMENT ALONG THE DENALI FAULT SYSTEM IN THE EASTERN ALASKA RANGE: CHRONOSTRATIGRAPHY AND PROVENANCE OF THE MCCALLUM FORMATION AND IMPLICATIONS FOR DISPLACEMENT

1.1 Introduction

The Denali fault system is one of the largest intercontinental dextral strike-slip fault systems in the North American Cordillera with a defined topographic expression that extends for more than 2000 km from northwestern British Columbia to south western

Alaska (St. Amand, 1957; Grantz, 1966; Lanphere, 1978; Stout and Chase, 1980; Dodds,

1992; Miller et al., 2002). Modern upper plate deformation resulting from oblique subduction along the southern Alaska convergent margin is partly accommodated by this major structure (Coney et al., 1985; Jadamec et al., 2013). Geologically the Denali fault system marks the tectonic boundary between the Precambrian-Paleozoic Yukon

Composite Terrane, interpreted as the Mesozoic continental margin of the northern cordillera, and the Mesozoic oceanic rocks of the Wrangellia Composite Terrane that are interpreted as forming in oceanic settings outboard of the continental margin. These two terranes are interpreted to have collided during the Mesozoic. The boundary between these two terranes in south central Alaska is known as the Alaska Range Suture zone.

The Cenozoic Denali fault system is located within this Mesozoic collisional zone. The

Cenozoic displacement history of the fault system is unclear. Cenozoic displacement

estimates range from several hundreds to tens of kilometers (St. Amand, 1957; Grantz,

1966; Turner, 1974; Eisbacher et al., 1976; Reed and Lanphere, 1974; Nokleberg et al.,

1985; Plafker et al., 1989). These previous interpretations are based on offset geologic and topographic features along different segments of the fault system. A more recent study suggests Oligocene displacement of 300 km based on U-Pb detrital zircon results by Benowitz et al. (2012) in the eastern Alaska Range.

One geologic marker that has been utilized by previous studies to determine the timing and amount of Cenozoic displacement along the Denali fault are sedimentary basins within and adjacent to the fault system (Trop and Ridgway, 2007). Previous basin analysis studies have focused on Eocene-Oligocene strata within basins located along the western segment of the fault system in Alaska (Colorado Creek; White Mountain basins) and basins (Burwash, Bates Lake, Sheep Creek, and Three Guardsmen basins) along the eastern segment of the fault system in Yukon Territory and British Columbia (Ridgway and Decelles, 1993a; 1993b; Ridgway et al. 1999; Trop et al. 2004). Basin analysis work in the Colorado Creek basin by Trop et al. (2004) suggests 30-33 km of post-early

Oligocene dextral displacement based on matching unique clast types to point sources across the fault. Analyses of these known Cenozoic basins suggest a major episode of

Eocene-Oligocene strike-slip displacement but provided little evidence of Neogene displacement along the fault system.

To better address the poorly understood Neogene history of displacement along the

Denali fault system. Our study focuses on the Neogene strata of the McCallum Formation in the McCallum Basin located south of the Denali fault in the eastern Alaska Range. Our

3 dataset consists of detailed measured stratigraphic sections, paleocurrent data, clast compositional data, U-Pb detrital zircon geochronology from sandstone, and 40Ar/39Ar geochronology on volcanic glass in tephras. From this dataset, we construct the first detailed chronostratigraphic framework for the McCallum Formation. Our dataset provides insight into the displacement and deformation record of this part of the Denali fault system in the last 6.1 Ma. Our work suggests that the McCallum basin experienced

60-230 km of displacement along both the Denali and Totschunda fault systems since 6.1

Ma. The displacement history interpreted for the McCallum basin is consistent with the rupture pathway of the 7.9 M 2002 Denali Earthquake.

1.2 Regional Geologic Setting of the eastern Alaska Range

The tectonic growth of the southern Alaska convergent margin is largely defined by two major collisional events in the Mesozoic and Cenozoic that have resulted in the amalgamation of three large composite terranes that are fault bounded by major strike- slip fault systems (Plafker, 1989; Plafker and Berg, 1994; Jones et al., 1977). From north to south, these terranes are the Yukon Composite Terrane, Wrangellia Composite

Terrane, and the Southern Margin composite terrane (Plafker et al., 1987; Nokleberg et al., 1994). The Yukon composite terrane is ~ 27 km thick and consists of metamorphosed

Proterozoic (?)-Paleozoic former continental margin rocks with a felsic composition

(Nokleberg et al., 1994; Brennan et al., 2011). The Denali fault system is located along the southern boundary of the Yukon composite terrane and northern boundary of the

Wrangellia composite terrane to the south (Figure 1). The Mesozoic allochthonous

Wrangellia composite terrane is a ~ 30 km thick oceanic plateau with a primarily mafic composition (Jones et al., 1977; Coney et al., 1985; Brennan et al., 2011).

The Border Ranges fault system marks the southern boundary of the Wrangellia composite terrane and northern boundary of the Southern Margin composite terrane. The

Southern Margin composite terrane is interpreted to be a Cretaceous accretionary prism that has been deformed by the active accretion of the Yakutat microplate to the southern

Alaska margin since Oligocene time (Plafker et al., 1987; Enkelmann et al., 2010). The deformation inboard of this collisional margin is partitioned along major strike-slip fault systems such as the Border Ranges, Castle Mountain, Denali, and Tintina fault systems

(Redfield and Fitzgerald, 1993; Riccio et al., 2014; Bemis et al., 2015). Displacement estimates for these major strike-slip structures vary. Late Cretaceous to Middle Eocene dextral displacement of minimum of 600 kilometers is estimated for the Hanagita fault system within the Border Ranges fault system (Pavlis and Roeske, 2007). Tens of kilometers of dextral strike-slip displacement since Cretaceous is estimated for the Castle

Mountain Fault system (Grantz, 1966; Clardy, 1974; Fuchs, 1980; Plafker, 1994). Eocene dextral displacement of 430 kilometers is estimated for the Tintina fault (Gabrielse et al.,

2006). The timing and amount of Cenozoic displacement for the Denali fault system is unclear. Previously interpreted displacement estimates for the Denali fault system vary among the eastern, central, and western segments of the fault system. Along the eastern segment of the Denali fault, 300 kilometers of displacement is estimated to have occurred since the Late Cretaceous based on geologic evidence that suggest the Nutzotin Mountain

Sequence is equivalent to the Dezadeash Formation and Kluane schist (Eisbacher, 1976).

Another study suggests ~400 kilometers of displacement based geologic evidence that suggest the Maclaren metamorphic terrane in the central Alaska Range and the Kluane schist and the Ruby Range batholith located in the Yukon Territory are equivalent

(Nokleberg et al., 1985). A more recent study suggests that there has been 300 kilometers of displacement in the last 26 Ma based on correlating U-Pb detrital zircon ages of the

Cottonwood Metamorphic Complex to U-Pb detrital zircon ages from the McCallum basin (Benowitz et al., 2012). Along the western segment of the Denali fault, 38 km of displacement in the last 38 Ma are suggested based on offset plutons along the McKinley strand of the Denali fault (Lanphere and Reed, 1974). Prior to rupture of the 2002 7.9M

Denali Earthquake, the fault system was thought to have experienced zero to tens of kilometers of displacement since late Cretaceous (Csejtey et al. 1982, 1997; Ford et al.

1998).

We informally refer to the eastern Alaska Range as the region of the Denali fault system located between the Delta River and the Alaska-Canada border. The segment of the

Denali fault in this region is defined as the east-central Denali fault. Major splays of the fault system in this region include the Totschunda fault located near the Wrangell volcanic field. This part of the fault is located along the 351 km rupture path of the 2002

M 7.9 Denali Earthquake that initiated on the previously unmapped Susitna Glacier thrust and propagated to the east along the Denali fault on to the Totschunda fault system

(Crone et al. 2004; Haessuler et al. 2004). The Totschunda fault has previously been interpreted to have been active since 2 Ma based on dextral offset of lava flows in the

Wrangell volcanic field (Richter and Matson, 1971; Bemis et al., 2015). The structural

Figure 1 Generalized bedrock geology map of south-central Alaska with emphasis of possible magmatic source areas for the McCallum Basin. Adapted from Aleinikoff et al., 1988; Beard and Barker, 1986; Richter, 1990; Ridgway et al., 2002; Trop and Ridgway, 2007; Brennan et al., 2015 and Dusel- Bacon et al., 2015. 6

7 relationship between the intersection of the Totschunda fault and the Denali fault marks the transition from transtensional to transpressional styles of deformation as material enters a regional restraining bend. The Totschunda fault likely extends via the Connector fault to the Fairweather fault in southeastern Alaska (Richter and Matson, 1971; Doser,

2014). A series of active fold and thrust belts located north and south of the Denali fault characterize this transpressional setting as the obliquity between the fault and pacific plate motion increases westward along the main strand (Vallage et al. 2014). This segment of the Denali fault system may have been active since 65 Ma based on thermochronological constraints from 40Ar/39Ar analysis on hornblende and apatite fission track analysis (Benowitz et al. 2014).

1.3 Previous work in the McCallum basin

Our study area, the McCallum basin, is located in the footwall of the McCallum Creek thrust near the headwaters of the Delta River in the eastern Alaska Range south of the

Denali fault (Figure 2). The McCallum Creek thrust is a part of south verging fold and thrust belt that parallels the Denali Fault. The McCallum basin is actively being incorporated into the proximal thrust sheets along the eastern basin margin with the western portion of the basin is still receiving sediment. Previous gravity and seismic studies within the vicinity of the basin have described the basin geometry to be 28 km long (north-west trending) and 18 km wide with basinal strata that is ~1.5 km thick

(Morin and Glen et al., 2003; Brocher et al., 2004). Previous work in the McCallum basin is limited to regional geologic mapping by Hanson (1963), Bond (1976), Stout (1976),

Ridgway et al. (2002), Nokleberg et al. (1982; 1992a; 1992b; 2015), and more recent

Figure 2 Geologic map of the McCallum basin. Measured section and sample locations are denoted by numerical symbols. Adapted from Ridgway et al. 2002, Nokleberg et al., 2015, and Waldien et al., 2014; 2015. 8

Figure 3. Composite measured stratigraphic section of the McCallum Formation showing stratigraphic positions of tephras dated with 40Ar/39Ar geochronology on volcanic glass and detrital zircon sample locations. Purple star indicates stratigraphic position of volcanic clasts dated with 40Ar/ 39Ar on biotite. Grain size abbreviations: M-clay and silt; F-Fine sand, C-coarse sand, P-pebble, B-boulder.

12 to confirm mineral identification and purity. The separates were sent to McMaster

University Nuclear Reactor in Hamilton, Ontario, Canada for irradiation. Individual grains were then laser step-heated from relatively low temperatures until reaching fusion temperatures using a 6W argon-ion laser (Sliwinski et al., 2012). For each step, isotopic ratios of Ar were analyzed using a VG3600 mass spectrometer that produce a spectrum of ages based on individual steps. A more detailed description of this method can be found in Sliwinski et al. (2012) and Benowitz et al. (2011). These 40Ar/39Ar analyses were performed by co-author Dr. Jeffrey Benowitz at the Geochronology Facility at the

University of Alaska-Fairbanks. Results of these analyses reported as inverse isochron ages with a range of MSWD values of 0.3-2.14 (Appendix B). Inverse isochron ages are calculated from an inverse isochron diagram of 36Ar/40Ar vs. 39Ar/40Ar ratios recorded during each individual heating step (Roddick, 1978; Roddick et al., 1980; Benowitz et al.,

2011). 40Ar/39Ar dating analysis of one to three aliquots of glass were performed for each tephra sample. For samples where two or more analysis were performed, composite isochrons were compiled from the individual analysis. Composite isochrons are a common technique applied in 40Ar/39Ar geochronology applications (ex. Sharp et al.,

2005; Cassata et al., 2008) to account for potential excess 40Ar and to increase overall precision. Refer to Figures 8 and 10 for locations of tephra samples that were collected for 40Ar/39Ar analysis. The stratigraphically oldest tephra age from the lower member age is 6.17 Ma ± 0.07. The stratigraphically youngest dated tephra in the upper member is

3.81 Ma ± 0.05 (Figure 3).

Figure 4. (A) The lower member type section for the McCallum Formation consists of mudstone, lignite beds (yellow arrows), and tephra beds (white arrows). Orange scale is 2 m tall. Outcrop is approximately 6 m tall. (B) The boundary between the lower and upper member of the McCallum Formation is characterized by a sharp contact (white dashed line). Bedding is steeply dipping at 56 degrees to the northeast. View is to the northeast. The McCallum Creek thrust is in the background. (C) Type section of upper member of McCallum Formation consists of 10 m thick laterally continuous conglomerate units (white arrows). (D) Facies 1 (F1) consists of clast-supported pebble conglomerate with sandstone lenses and is commonly overlain with lignite (White arrows). Rock hammer for scale. (E) Facies 2 (F2) consists of grey massive volcaniclastic sandstone and lignite (Also see Figure 5A). In this section, white tephra beds (F4; blue arrows) and laminated mudstone (F3; orange arrows) are steeply dipping. Person for scale. (F) SEM image of tephra consists primarily of volcanic glass with cuspate (white arrows) and vesicular textures (orange arrow

Figure 5. (A) Lignite is common in Facies 2 (F2) and ranges from wood to plant sized fragments. Locally this fragments are disorganized. (B) Individual laminae (white arrows) within well-laminated mudstone and siltstone characterize Facies 3. Rock-hammer for scale. (C) Facies 4 (F4) consists of tephra (yellow arrows; also see Figures 4E; 4F) and have average thicknesses of 1m with a range of 6-1m. Facies 5 (F5) consists of interbedded lignite with tephra. (D) Facies 6 is characterized by boulder-cobble, conglomerate (white arrows) horizontally stratified sandstone beds (yellow arrows). (E) Locally tephra beds (F11) are present within Facies 6. Person for scale. (F) Facies 7 is characterized by well-organized cobble-pebble conglomerate with lenticular sandstone lenses and is commonly grades into Facies 8 (F8).

Figure 6 (A) Clasts in conglomerate of Facies 7 are subrounded and locally imbricated (yellow arrows). (B) Facies 8 is characterized by crudely horizontally stratified coarse sandstone with granule conglomerate lenses (F8) and is interbedded with Facies 7 (F7; Figure 5F). (C) Facies 8 is characterized by sandstone with granular to pebble conglomerate lenses. Clasts of this facies are locally imbricated (blue arrows). (D) Facies 9 (F9) consists of crudely horizontally stratified coarse sandstone with granule conglomerate lenses. Clasts in the conglomerate are subrounded. Rock hammer for scale. (F) Facies 10 (F10) is characterized by sandstone with minor siltstone and lignite.

Figure 7 The stratigraphy of the McCallum Formation was correlated based on lithofacies analysis, and 40Ar/39Ar dates on tephra samples. Sample locations for U-Pb detrital zircon and 40Ar/39Ar biotite analysis are indicated next to each measured section. Numbers above each

measured section and sample location correspond to geographic locations in Figure 2. See text or detailed facies descriptions. 16

Figure 8 Detailed measured sections from the lower member show lithology, facies distribution, 39Ar/40Ar tephra and U-Pb detrital zircon sample locations. Each measured section number correlates with their respective geographic locations on Figure 2. Each facies number correlates with their respective detailed facies description in the text. Both measured section and facies numbers also correlate with their location within their interpreted depositional system (Figure 9).

19 major eruptive events (e.g., Suthren, 1985; Smith, 1991). The abundant, disorganized woody detritus in the volcaniclastic sandstone may represent trees/forests that were destroyed during major eruptions and rapidly incorporated into fluvial systems, similar to processes documented during the 1980 eruption of Mount St. Helens (Waitt, 1981).

Facies 3: Well-laminated mudstone with subordinate sandstone and plant fragments

Description:

This facies is the most common facies in the lower member forming over 33.8 % of the total lithofacies. Grey laminated mudstone is the most common rock type of this lithofacies. Laminations are defined by subtle changes in grain size and organic rich layers. Fluid escape structures locally disrupt the laminations. More siltstone-rich beds are brown in color and rich in mica and organic detritus. Locally, the siltstone-rich beds contain climbing ripple stratification and thin laminations with plant fragments.

Sandstone-rich beds are very fine grained and are interbedded with organic rich layers

(Figure 5b). Sandstone bed thicknesses range from 30 to 3 cm. Locally, sandstone beds contain ripple cross stratification and normal grading. This facies is best exposed in sections PROP-01 and PHE-01 (Figure 8).

Interpretation:

Mudstone of Facies 3 is interpreted to have been deposited through suspension fallout processes common in lacustrine environments. Common preservation of laminations within the mudstone indicate deposition by low energy gravity settling processes (e.g.,

Talbot et al., 1996; Schnurrenberger et al., 2003). The laminations that characterize this facies may represent seasonal varves that are common in lacustrine deposits in temperate climates (Fouch and Dean, 1982; Ridgway et al., 2007). The thin, normally graded and ripple laminated beds of fine sandstone are interpreted as lacustrine turbidity current deposits. The presence of fluid escape structures suggests an abundance of pore water in the interstices of the mudstone and formed as a result of localized rapid deposition. The dominance of this facies in the lower member is interpreted to represent widespread shallow lacustrine environments.

Facies 4: Tephra

Description:

Volcanic ash deposits are commonly in the lower member and have average thicknesses of 1m (Figure 4e; Figure 5c). These deposits are laterally continuous at the scale of the outcrop and have a white matrix that contains abundant vesicular volcanic glass shards, biotite phenocrysts, and minor sanidine (Figure 4f). These beds commonly have sharp basal contacts and contain laminations that normally grade into fine-grained organic rich layers at the tops of the beds. Two distinct tephra deposits can be traced throughout the lower member (Figure 7). This facies makes up 4.3 % of the lower member and is best exposed in sections PROP-01 and PHE-01 (Figure 8). The stratigraphically lowest dated tephra in the lower member has an 40Ar/39Ar age of 6.17 ±

0.07 Ma (HP2; measured section #1; Figure 8) and the stratigraphically highest dated

21 tephra in the lower member has an age of 5.07 ± 0.05 Ma (PROP-01; measured Section

#3; Figure 8).

Interpretation:

The preservation of laminations and euhedral phenocrysts within this facies both suggest a lack of extensive reworking by fluvial processes. The absence of flattening/welded fabrics, the laterally continuous bed geometries, the sharp lower contacts, and gradational upper contacts are common characteristics of air-fall tephras deposited during volcanic eruptions (Smith, 1991). We interpret Facies 4 to represent air-fall tephra deposited in mainly lacustrine environments.

Facies 5: Lignite with thin tephra layers

Description:

Lignite strata, that often contain interbedded tephra layers, are common throughout the lower member. This facies has average bed thicknesses of 20 cm. These deposits commonly contain laminated tephras (Figure 5c). This facies makes up 1.9% of the lower member and is best exposed at measured section PHE-01 (Figure 8).

Interpretation:

Facies 5 is interpreted to represent deposition in swamps, marshes, and other wet overbank areas of the McCallum basin. The common association with thin tephras suggests frequent volcanic airfall events in these environments. The preservation of

Figure 9 The lower member is interpreted to represent a highly vegetated lacustrine depositional environment. Active volcanism from the nearby Wrangell Volcanic Field provided the basin with airfall tephra deposits and volcaniclastic sandstone. The McCallum basin would have been located 79 km east of its present location at 6.1 Ma based on current slip rates along the Denali fault system. Measured section numbers are indicated alongside representative stratigraphic sections and their respective facies. See text for a detailed description of the facies. Numbers correspond to specific measured sections in Figure

8. 23

Figure 10 Detailed measured sections from the upper member show lithology, facies distribution, 39Ar/40Ar tephra and U-Pb detrital zircon sample locations. Each measured section number correlates with their respective geographic locations on Figure 2. Each facies number correlates with their respective detailed facies description in the text. Both measured section and facies numbers also correlate with their location within their interpreted depositional system (Figure 11).

26 channels (e.g., Collison, 1996; Nichols et al., 2007). The sandstone layers that cap the conglomerate units are interpreted as lower flow velocity deposition after the main channel had avulsed to a different part of the channel complex. The lack of lignite in

Facies 6 suggests that channel avulsion and/or migration was a common process in this fluvial system (e.g., Nichols et al., 2007). This facies is interpreted to represent proximal braided stream facies within a stream-dominated alluvial fan system. This alluvial-fan interpretation is partly based on the restriction of this facies to the immediate footwall of the McCallum Creek thrust fault and that our mapping shows that the boulder conglomerate of Facies 6 transitions to cobble-pebble conglomerate of Facies 7 over ~

1.5 km.

Facies 7: Organized clast-supported conglomerate with sandstone

Description:

This facies consists mainly of imbricated cobble to pebble size, clast-supported conglomerate with subordinate lenticular sandstone lenses (Figures 5f; 6a). The conglomerate contains sub-rounded clasts that have an average maximum particle size of

9 cm and range from 16-5 cm. The conglomerate packages are dominated by horizontal stratification in broad 60-50 m wide lenticular units that are 12-10 m thick. Medium to coarse-grained, horizontally stratified sandstone lenses (50-15 cm) are interbedded with the conglomerate (Figure 5f). Locally, dacite clasts with well-preserved biotite phenocrysts occur within the conglomerate. These clasts were dated and are discussed in a later section. This facies makes up 30.5% of the upper member and is best exposed at

27 the CALL-01 and CALL-03 measured sections where it is 276 m thick (Figure 4c; Figure

9). This facies grades eastward into coarser-grained conglomerate of Facies 6 and westward into finer grained conglomerate of Facies 8.

Interpretation:

The clast-supported conglomerate with horizontal stratification and lenses of lenticular sandstone of Facies 7 are indicative of deposition by stream flow processes. These are characteristics of gravels transported as bedload by traction currents under hydrodynamic stable flow conditions to form longitudinal bars (Collison, 1996; Nichols et al., 2007).

Imbrication is best developed across the top of longitudinal bars in high discharge areas of stream flow (Collison, 1996). Reduction in flow velocities allow for sand to be deposited through rapid saltation or suspension processes on the tops of gravel-rich bars

(Collison, 1996). Laterally continuous conglomerate units with sharp basal contacts and the lack of evidence for lateral accretion are consistent with deposition in shallow braided channels of a fluvial system.

Facies 8: Well-organized, sandy clast-supported conglomerate with sandstone

Description:

This facies consist of well-sorted, clast-supported, pebble to granule conglomerate with abundant sandstone lenses (Figure 6b and 6c). Subrounded imbricated clasts in the conglomerate have an average maximum particle size of 6 cm and range from 8-4.5 cm.

Coarse-grained sandstone lenses are 20-5 cm thick and often contain trough cross

28 stratification. These lenses are discontinuous at width scales of 6 to 5 m. This facies makes up 35.4% of the upper member and is best exposed at the CALL-01 and PHE-02 measured sections (Figures 6b; 6c). Facies 8 grades eastward into coarser-grained conglomerate of Facies 7 and westward into the sandstone-dominated Facies 9.

Interpretation:

Lithologically, Facies 8 is similar to Facies 2 of the lower member in that it is organized, contains imbricated clasts, lenticular sandstone lenses, and trough cross-stratification. As discussed earlier, these features are indicators of stream flow processes. The size of clasts and thickness of conglomerate beds and sandstone content in the facies are typical of distal facies of braided stream deposits (e.g., Nichols, 2007). Facies 8 is interpreted to represent the distal part of a stream-dominated alluvial-fan system.

Facies 9: Sandstone with minor granular conglomerate lenses

Description:

This lithofacies is characterized by stratified, coarse-grained sandstone (Figure 6d).

Mainly granular conglomerate lenses are common in this lithofacies with local pebble conglomerate lenses that have an average maximum particle size of 4 cm with a range of

7 to 3 cm. Low angle to horizontal stratification is common in this facies. Average bed thickness of this Facies is 10 m. This facies makes up 7.7% of the upper member and is best exposed at the CALL-01 measured section where it is 80 m thick (Figure 6d). Facies

9 grades eastward into coarser-grained conglomerate of Facies 6 and westward into the siltstone-lignite dominated Facies 10.

Interpretation:

Thick-bedded sandstone with lenticular granular conglomerate lenses is a product of sandy bedload channels (Nichols et al., 2007). In these systems, sand is deposited mainly on mid-channel bars with gravel lenses deposited as basal lag (Nichols et al., 2007).

Subordinate conglomerate deposits in Facies 4 suggest that typical stream-flow velocities were insufficient to mobilize coarse gravel material and favored transport of finer sand- sized sediment. This sandstone-dominated facies is interpreted to represent channel deposits located in the medial-distal region of a stream-dominated alluvial-fan system.

Horizontally, stratified sandstones are common products of mobile braided river systems with well-developed sandflats (Collison, 1996).

Facies 10: Fine-grained sandstone with siltstone and lignite

Facies 10 represents the finest-grained sediment documented in the upper member. See the description of Facies 3 for the lower member for a more detailed description and interpretation. Average bed thicknesses of Facies 10 are 4.5 m and are best exposed in measured section RAIN-01 (Figure 6e). This facies accounts for 6.7% of the upper member.

Figure 11 The upper member is interpreted to represent a stream dominated alluvial fan depositional environment. Rapid basin subsidence allowed 31 for the preservation of tephra deposits within this high-energy environment. Strata of the upper member prograde basinward over the lower member. The McCallum basin would have been located 65 km east of its present location 5.0 Ma based on modern slip rates along the Denali fault system. Measured section numbers are indicated alongside representative stratigraphic sections and their respective facies. See Figure 2 for the geographic location of the measured section. See text for a detailed description of each facies.

Figure 12 Probability density profiles of the detrital zircon samples from the lower member. Eleven detrital zircon samples were analyzed from the lower (Figure 12) and upper member (Figure 13) of the McCallum Formation. Probability density plots represent results for each analysis graphically. Individual plots are arranged in stratigraphic order and labeled with their respective sample name and maximum depositional age. Peak ages are denoted with their respective ages above their graphical peak. Pie diagrams show relative Cenozoic (yellow), Mesozoic (blue), Paleozoic (green), and Precambrian (purple) grain percentages for each sample. Each individual plots are organized with two separate plots that show age distributions (x-axis) between 0-550 Ma (inset plot) and 0-3250 Ma (outer plot). Inset plots display histograms with bin widths of 5 Ma and the probability density profile (red line). The outermost plot displays the overall histogram profile for the respective sample. The y-axis for each plot indicates the number of grains that each histogram bar. Refer to Figure 3 for information regarding the stratigraphic position of each sample.

Figure 13 Probability density profiles of detrital zircon samples from the upper member. Refer to Figure 12 for information on how profiles are organized. Overall there is no difference in age populations from the lower to upper member. Noticeable trends is the general increase in the percentage of Mesozoic grains and the decrease in the percentage of Cenozoic grains upsection.

Figure 14 Composite probability density profile plots representing the upper and lower member of the McCallum basin. Peak ages are shown above each graph. For an in depth explanation of the probability density profiles refer to Figure 11. The lower member contains larger Cenozoic and Precambrian age populations of zircons. The number of Mesozoic grains increases from the lower member to upper member. A summary of the entire detrital record (11 samples) for the McCallum Formation is the lower most group of probability plots. Above these plots are possible magmatic sources associated with the Yukon Composite Terrane (YCT) and Wrangellia Composite Terrane (WCT). Refer to text for more information of these sources and locations.

Peak age populations contributing less than 10% are referred to as minor peak age populations. Individual zircons with U/Th ratios < 10 are interpreted to represent igneous crystallization ages whereas zircons with U/Th ratios > 10 are interpreted to have formed as a result of metamorphism processes (Gehrels, 2012). Zircons with U/Th values > 10 account for 1% (n= 22 grains) of our total detrital zircon dataset and were excluded for the purpose of determining potential igneous sources of the McCallum Formation.

1.5.2.1.2 U-Pb Detrital Zircon Age Distribution for the McCallum Formation:

The McCallum Formation contains detrital zircon age populations with varying abundances of Cenozoic (Cz), Mesozoic (Mz), Paleozoic (Pz), and Precambrian (Pc) aged grains (Figures 12; 13; 14). Individual relative age probability plots (Figures 12 and

13) for each sample are organized by their relative stratigraphic positions. Key observations for each individual sample are presented in stratigraphic order beginning with samples from the lower member.

1.5.2.1.3 Detrital Zircon Record of the Lower Member:

Zircons (n=1479) were extracted and analyzed from six samples from the lower member of the McCallum Formation (Figure 3; Figure 8; Figure 12). The zircon age data (n=312) of the stratigraphically lowest sample (GC2-4m) records a single peak age at 124 Ma that represents 99.7% of the entire population (Figure 12). Mesozoic (Mz) age grains are the most abundant with minor Cenozoic (Cz) age grains (Cz 0.3%, Mz 99.7%). The next stratigraphically highest sample is GC1-1m. The zircon age data (n=315) of this sample

39 records a single dominant peak age at 123 Ma with minor peak ages at 6, 58, 81, 88, 100,

159, 195, and 230 Ma (Figure 8 and Figure 12). The 123 Ma peak age makes up 73% of this sample. Mesozoic age grains are the most abundant with minor Cenozoic, Paleozoic

(Pz), and Precambrian (Pc) age grains (Cz 2%, Mz 95%, Pz 1% and Pc 3%). The next stratigraphically highest sample is PROP-01-21.5m (Figure 2 and Figure 3). The zircon age data (n=261) of this sample record three dominant peak ages at 26, 50, and 205 Ma with minor peak ages at 104, 165, 183, 303, 324, and 347 Ma (Figure 12). The peak age of 26 Ma makes up 17% of the sample, the peak age of 50 Ma makes up 32% of the sample, and the peak age of 205 Ma makes up 18% of the sample. Cenozoic age grains are the most abundant with less abundant Mesozoic age grains with minor Paleozoic and

Precambrian age grains (Cz 57%, Mz 38%, Pz 3%, and Pc 2%). The next stratigraphically highest sample is CALL-02-11m (Figure 2 and Figure 3). Zircon age data (n= 241) from this sample record dominant peak ages at 91, 160, 181, and 195 Ma with minor peak ages at 53, 107, 123, 130, 135, 255, 311, 328, 354, 425, and 1804 Ma

(Figure 12). Dominant peak ages account for 50% of the total sample population including 91 (13%), 160 (13%), 181 (11%), and 195 Ma (13%). Overall, Mesozoic age grains are the most abundant with minor Cenozoic, Paleozoic, and Precambrian age grains (Cz 6%, Mz 72%, Pz 10%, and Pc 12%). The next stratigraphically highest sample is PHE-01-37m (Figure 2 and Figure 3). Zircon age data (n= 97) of this sample record two dominant peak ages at 88 and 92 Ma with minor peak ages at 5, 81, 97, 107, 112,

126, 140, 154, 166, 173, 184, 201, and 1838 Ma (Figure 12). Peak age 88 Ma makes up

14% of the sample population and peak age 92 Ma makes up 15% of the sample population. Mesozoic age grains are the most abundant with minor Cenozoic, Paleozoic,

40 and Precambrian age grains (Cz 9%, Mz 74%, Pz 6%, and Pc 11%). The highest stratigraphic sample (060514-WKA-01) in the lower member was collected at the contact of the lower and upper member of the McCallum Formation (Figure 2, Figure 3, and

Figure 7). Zircon age data (n= 253) record two dominant peak ages at 5 and 191 Ma with minor peak ages at 55, 77, 93, 98, 106, 122, 156, 165, 283, 318, 360, 1038, 1624, and

1841 Ma (Figure 12). Peak age 5 Ma makes up 34% of the sample population and peak age 191 Ma makes up 10% of the sample population. Mesozoic age grains are the most abundant with less abundant Cenozoic age grains with minor Paleozoic and Precambrian age grains (Cz 36%, Mz 44%, Pz 10%, and Pc 10%).

1.5.2.1.4 Maximum Depositional Age of the Lower Member:

The maximum depositional age (MDA) of the six samples from the lower member of the

McCallum Formation range from 5 to 53 Ma (Figure 12). The MDA for each sample is located in Figure 12; note that there are two MDAs of 5 Ma and one of 6 Ma. The general

MDA for the lower member is interpreted as 5 Ma based on these datasets (Figure 12) and is consistent with tephra ages obtained by 40Ar/ 39Ar geochronology on volcanic glass in the lower member (Figure 3 and Figure 7). The ages of these tephras range from 5.07 ±

0.05 Ma to 6.17 ± 0.07 Ma as discussed in an earlier section.

1.5.2.1.5 Summary for the Lower Member:

Collectively, Mesozoic aged grains are the most common in the lower member with less abundant Cenozoic, Paleozoic, and Precambrian aged grains (Mz 72%, Cz 18%, Pz 5%,

Pc 5%) (Figure 12). Some specific trends in the detrital zircon populations of the lower member that we consider important for interpreting the provenance of the McCallum

Formation are outlined here. The two stratigraphically lowest samples (GC1-1m and

GC2-4m) are dominated by 123 and 124 Ma grains (37%). Detrital zircons of this age are only found in minor amounts in the rest of the overlying formation in both the lower and upper members (Figures 12; 13). In the next stratigraphically highest sample (PROP-01-

21.5m) there is an introduction of two distinct new populations of 26 and 50 Ma. There is also the introduction of minor populations of zircon grains with peak ages of 303 to 347

Ma. In the next stratigraphically highest sample (CALL-02-11) there is a broad group of

Mesozoic grains with peak ages from 91-195 Ma. Both of these trends in detrital zircon populations continue in the two stratigraphically younger samples analyzed from the lower member (Figure 12). Precambrian and Paleozoic detrital zircons make up only 12% of the total detrital zircons analyzed from the lower member.

1.5.2.1.6 Detrital Zircon Record of the Upper Member:

Zircons (n=904) were extracted and analyzed from five samples from the upper member

(Figure 13). The zircon age data (n= 288) of the stratigraphically lowest sample (061414-

WKA-01) record two dominant peak ages at 26 and 158 Ma with minor peak ages at 5,

87, 93, 103, 158, 182, 187, 200, 231, and 294 Ma (Figure 13). The peak age at 26 Ma makes up 34% of the sample and the peak age at 158 Ma makes up 28% of the sample.

Mesozoic age grains are the most abundant with less abundant Cenozoic age grains and minor Paleozoic and Precambrian age grains (Cz 38%, Mz 56%, Pz 2%, and Pc 4%). The

42 next stratigraphically highest sample is CALL03-30m (Figure 13). Detrital zircon age data (n= 111) record dominant peak ages at 26, 99, 155, 187, and 295 Ma with minor peak ages at 6, 66, 90, and 199 Ma (Figure 13). The dominant peak ages of this sample make up the following percentages of this sample population 26 (15%), 99 (16%), 155

(26%), 187 (11%) and 295 Ma (10%). Mesozoic age grains are the most abundant with minor Cenozoic, Paleozoic, and Precambrian age grains (Cz 21%, Mz 66%, Pz 11%, Pc

2%). The next highest stratigraphic sample is CALL03-60m (Figure 13). Detrital zircon age data (n= 115) record dominant peak ages at 26, 100, 157, 181, and 302 Ma with minor peak ages at 5, 55, 61, 199, and 263 Ma (Figure 13). The dominant peak ages of this sample make up the following percentages of this sample population 26 (17%), 100

(16%), 157 (22%), 181 (10%) and 302 Ma (11%). Mesozoic age grains are the most abundant with minor Cenozoic, Paleozoic, and Precambrian age grains (Cz 28%, Mz

53%, Pz 14%, Pc 5%). The next stratigraphically highest sample is CALL03-88m (Figure

13). Detrital zircon age data (n= 112) record dominant peak ages at 26, 100, 163, and 306

Ma with minor peak ages at 5 and 64 Ma (Figure 13). The dominant peak ages of this sample make up the following percentages: 26 (29%), 100 (13%), 163 (20%), and 306

Ma (13%). Mesozoic age grains are the most abundant with minor Cenozoic and

Paleozoic aged grains (Cz 29%, Mz 44%, Pz 17%). Precambrian grains in this sample account for <1% of the zircon population. The next highest stratigraphic sample of the upper member is PHE-02-6.8 (Figure 13). Detrital zircon age data (n= 278) record dominant peak ages at 86, 94, 159, and 190 Ma with minor peak ages at 54, 60, 76, 103,

131, 141, 216 233, 321, 344, 352, and 1777 Ma (Figure 13). A distinct change in this sample is the lack of 5-6 Ma and 26 Ma detrital zircon age populations documented in the

43 underlying samples. Dominant peak ages of this sample makeup the following percentages of the total sample age distribution: 86 (15%), 94 (13%), 159 (14%), and 190

(10%). Mesozoic age grains are the most abundant with minor Cenozoic, Paleozoic, and

Precambrian age grains (Cz 4%, Mz 81%, Pz 7%, Pc 8%).

1.5.2.1.7 Maximum Depositional Age:

The maximum depositional age (MDA) of each individual sample from the upper member of the McCallum Formation ranges from 5 Ma to 55 Ma. The MDA for the each sample is shown in Figure 13; note that four of the samples have an MDA of 5 Ma. The general maximum depositional age for the entire upper member is interpreted as 5 Ma

(Figure 14). This MDA is consistent with tephras ages of 3.8 ± 0.05 Ma to 5.0 ± 0.10 Ma obtained by 40Ar/ 39Ar geochronology for the upper member (Figure 3 and Figure 7).

1.5.2.1.8 Summary of Upper Member Detrital Zircon Age Data:

In summary, the detrital zircon record of the upper member contains abundant Mesozoic aged grains with less common Cenozoic, Paleozoic, and Precambrian aged grains (Mz

63%, Cz 24%, Pz 8%, Pc 4%; Figure 13). Key observations from the detrital zircon record of the upper member include: (1) upward increasing trends of Mesozoic,

Paleozoic, and Precambrian aged grains, (2) upward decreasing trend of Cenozoic aged grains, (3) dominant Mesozoic age zircon populations and their respective percentage of the total upper member zircon population include: 26 Ma (18%), 81-107 (25%), 140-165

Figure 15 Probability density function plot of single grain biotite 40Ar/39Ar ages from three sandstone samples collected from the upper and lower member of the McCallum formation (red curve). All three samples record overlapping dominant Oligocene peak age (~28 Ma). The Oligocene peak age of these samples coincides with average biotite 40Ar/39Ar ages of two dacite clasts in conglomerate of the upper member (yellow rectangle).

47 with the Taylor Mountain Batholith (208-216 Ma) (Dusel-Bacon et al., 2009; Day et al.,

2014; Dusel-Bacon et al., 2015) that are exposed near the southern border between the

Eagle and Tanacross quadrangles (Figure 1). The youngest potential primary igneous sources include mid-Late Cretaceous and Paleocene plutons north of the Denali fault associated with the central Alaska Range igneous belt. Two main age distributions are associated with these plutons: 64-37 Ma and 65-110 Ma (Wilson et al., 1985; Brennan and Ridgway, 2015; Dusel-Bacon et al., 2015). The 64-37 Ma distribution includes plutons in the central Alaska Range and east-central Alaska (Figure 1; pale pink map pattern). Plutons associated with the 65-110 Ma distribution are exposed in the Healy,

Mt. Hayes, Big Delta, Eagle, and Tanacross quadrangles (Figure 1; red map pattern).

1.5.2.3.2 Potential Sedimentary and Recycled Sources North of the Denali Fault:

The oldest potential source of recycled zircons north of the Denali fault are Proterozoic?-

Paleozoic metamorphic and metasedimentary rocks of the Yukon composite terrane.

These mainly schistose rocks are the most common rock type currently exposed north of the Denali fault (Plafker and Berg 1994; Day et al. 2014; Dusel-Bacon et al. 2015). These rocks have a light purple map pattern in Figure 1 and are exposed in the Mt. McKinley,

Kantishna Hills, Fairbanks, Healy, Big Delta, Mt. Hayes, Eagle, and Tanacross quadrangles. Common U-Pb detrital zircon ages are primarily between 2000-1700 Ma and minor populations between 2700-2500 Ma (Dusel-Bacon and Williams, 2009;

Brennan and Ridgway, 2015). Another potential source of recycled zircons includes the

Upper Cretaceous sedimentary strata of the lower Cantwell Formation located in the

Healy quadrangle (Figure 2; light brown map pattern). Zircon ages from the lower

Cantwell Formation have bulk detrital populations dominated by Precambrian aged grains (Pc 45%, Mz 39%, Pz 16%). Common age populations include 583-2753 Ma

(39%) with other age populations at 188-199 (36%), 351-386 (16%) (Brennan and

Ridgway, 2015). The youngest potential source of reworked zircons is from the Neogene strata of the Tanana basin (Ridgway et al., 2007). The Usibelli Group and Nenana

Formation bulk detrital zircon age distribution consists of mainly Mesozoic aged zircons

(Mz 52%, Pc 22%; Cz 15%, Pz 11%; Brennan and Ridgway, 2015). Common peak age distributions in these strata are at 77-111 Ma, 158-166 Ma, and 184-223 Ma for Mesozoic populations, 1117-2684 Ma for Precambrian age populations, 55-65 Ma for Cenozoic age populations, and 346-353, 365-369, 460, and 593 Ma for Paleozoic age populations

(Brennan and Ridgway, 2015).

1.5.2.3.3 Potential Primary Magmatic Source Areas South of the Denali Fault:

The oldest potential igneous sources areas located south of the Denali fault system are the igneous rocks of the Mid-Pennsylvanian to Early Permian Skolai arc located in the

Gulkana and Nabesna quadrangles (Figure 1; dark green map pattern). This arc is represented by an assemblage of gabbro, diorite, tonalite, and granodiorite intrusions with

U-Pb ages of 290-320 Ma (Richter et al., 1975; Mackevett, 1978; Gardner et al. 1988;

Beard and Barker 1989; Plafker and Berg 1994). These rocks are also exposed in the hanging walls of thrust sheets that border the northeastern margin of the McCallum basin

(Figures 2; Slana River sequence). The next youngest set of plutons that may have

49 contributed sediment to the McCallum basin are the Upper Jurassic (175-135 Ma) calc- alkaline plutonic rocks of the Chitina arc (Plafker et al., 1989; Nokleberg et al., 1994;

Roeske et al., 2003). These rocks are best exposed in the McCarthy quadrangle (Figure 1;

Richter, 1976; MacKevett, 1978; Plafker and Berg, 1994). Related rocks are the Upper

Triassic to Lower Jurassic igneous rocks known as the Talkeetna arc exposed in the

Talkeetna Mountains quadrangle (purple map pattern on Figure 1). Magmatism associated with the Talkeetna arc occurred between 201-153 Ma with two distinct plutonic events during 201-181 Ma and 177-153 Ma (Onstott et al. 1989; Plafker and

Berg, 1994; Amato et al., 2007; Rioux et al., 2007; Rioux et al., 2010). The next youngest group of igneous rocks are the Cretaceous White Mountain granitoid belt is located in the

Nabesna and McCarthy quadrangles (pink and red pattern on Figure 1). Recently published U-Pb zircon ages from the Nabesna Pluton (117.6 ± 1 Ma; 118.2 ± 0.6) and

Klein Creek Pluton (126 ± 1 Ma; 123.4 ± 0.8 Ma) are consistent with Early Cretaceous magmatism (Graham et al. 2016). Previous studies had the age of this belt ranging from

113-105 Ma based on K/Ar ages (Richter, et al., 1975; Snyder et al., 2007). These rocks are associated with the Early Cretaceous Chisana arc (140-115 Ma) that intruded the

Wrangell composite terrane (Plafker and Berg, 1994). The next youngest group of igneous rocks is the Cretaceous-Paleogene igneous rocks of the Central Alaska Range igneous belt. Plutons in this belt have U-Pb crystallization ages ranging from 110-55 Ma

(Figure 1; Reed and Lanphere, 1972, 1973; Lanphere and Reed, 1985; Wallace and

Engebretson, 1984; Moll-Stalcup, 1994) and are broadly exposed from the southwest to northeast from south of the Denali fault and into the Yukon composite terrane (red and pale pink map patterns in Figure 1). The Cretaceous plutons of this belt are exposed in

50 the Talkeetna Mountains, Healy, Mt. Hayes, Big Delta, Eagle, Tanacross, and Nabesna quadrangles (red map pattern in Figure 1). The Paleocene-Oligocene plutons associated with the Central Alaska Range igneous belt are exposed in the Talkeetna, Talkeetna

Mountains, Mount McKinley, and Healy quadrangles (pale pink map pattern in Figure 1).

These intermediate to felsic plutons have U-Pb crystallization ages ranging from 73-50

Ma and 43-37 Ma (Moll-Stalcup, 1994; Hung, 2008). The Wrangell volcanic belt

(Oligocene-Present) is the youngest of the potential igneous sources for the McCallum

Formation. This in the eastern Alaska Range this belt is ~200 km long and trends northwestward from the Alaska-Yukon border to near the intersection of the Totschunda

Fault and Denali Fault (Preece and Hart, 2004). The Wrangell volcanic belt is located in the Gulkana, Nabesna, and McCarthy quadrangles (brown map pattern in Figure 1). This belt has been active since 26 Ma and consists of lava flows, sedimentary, pyroclastic, and intrusive rocks (Richter, 1976; Richter et al., 1990; Richter, 1995; Trop et al., 2012).

1.5.2.3.4 Potential Sedimentary and Recycled Sources South of the Denali Fault:

There are two main potential sedimentary and metasedimentary sources that may have potential to contribute recycled Mesozoic, Paleozoic, and Precambrian age detrital zircons to the McCallum basin. These are the Kahiltna assemblage and the Nutzotin

Mountain sequence. The Upper Jurassic-Cretaceous Kahiltna assemblage is exposed in the Mt. McKinley, Healy, Mt. Hayes, Talkeetna, and Talkeetna Mountains quadrangles located west of the McCallum basin (Figure 1; pale green map pattern). In the Kahiltna assemblage, Mesozoic aged zircons are the most abundant (Mz 74%, Pc 15%, Pz 11%).

124-122 Ma age range is unique for plutons located both north and south of the Denali fault in south central Alaska. The best fit for such a plutonic source for these ages is the

White Mountain granitoid belt located in the Nabesna quadrangle (Figure 1). Newly published U-Pb zircon ages from these plutons range between 126-117 Ma (Graham et al., 2016). One pluton, the Klein Creek pluton has U-Pb zircon ages of 126-123 Ma similar to the detrital zircon ages in our two lowest stratigraphic samples from the

McCallum Formation. The Klein Creek pluton is currently located 230 km to the southeast of the McCallum basin along the Denali and Totschunda fault systems (Figures

1; 17a). The possibility that the McCallum basin and the White Mountain granitoid belt were in closer proximity prior to Neogene strike-slip displacement seems feasible using modern displacement rates of 13 mm/yr along the Denali fault system (Matmon et al.,

2006; Mériaux et al., 2009). Using this displacement rate and 6.1 Ma age of the oldest tephra in the McCallum Formation (Figure 3), the McCallum basin would have been located at a minimum of 79 km to the southeast on the southside of the Totschunda fault during the Late Miocene (Figure 17b). We interpret that at the start of the deposition of the McCallum Formation the basin was located farther to the southeast along the

Totschunda fault system and received sediment directly or indirectly (recycled) from the

White Mountain granitoid belt across the Totschunda fault (Figure 17b).

The introduction of 50 Ma and 26 Ma detrital zircons in the next highest stratigraphic sample (PROP-01-21.5m; Figure 12) of the McCallum Formation is attributed to source rocks related to the exhumation and erosion of Eocene volcanic rocks and the Oligocene components related to the growth of the Wrangell volcanic belt. Eocene volcanic rocks

53 consisting of flows, dikes, sills, and vitric ash flow tuff are currently exposed in the hanging wall of the McCallum thrust fault system between Hoodoo and Gunn Creeks

(Figure 2; Nokleberg et al., 1992b). Previously reported ages from these rocks are mainly in the 49 Ma range based on K-Ar isotopic whole rock analysis of rhyodacite tuff

(Nokleberg et al., 1992b). The 26 Ma detrital zircon population and the 28 Ma detrital biotite cooling ages from sandstone of the McCallum Formation are attributed to sediment contribution from rocks that represent magmatism associated with the initiation of the Wrangell volcanic belt (Richter, 1990). The pioneering work of Richter (1990) reported K-Ar ages of lavas of 26-23 Ma from Sonya Creek and Rocker Creek fields of the Wrangell volcanic belt. Figure 17b shows the locations of these volcanic fields relative to our interpreted restored position of the McCallum basin at 6.1 Ma. These older components of the Wrangell volcanic field east of the Totschunda fault and may have supplied sediment to the nearby Late Miocene McCallum basin. If this interpretation is correct, it would be consistent with 79 to 230 km of Neogene displacement suggested by the oldest tephra age of the McCallum Formation (6.1 Ma) and the unique 123-124 Ma age populations of the lowest detrital zircon samples of the McCallum Formation. In addition more recent studies of the Wrangell volcanic belt also document that 26 Ma detrital zircons are being transported in the modern Chisana and Nabesna Rivers (Figures

17b; 18). Collectively, the detrital zircon populations and the detrital biotite ages from sandstone are consistent with the McCallum basin receiving large amounts of igneous detritus eroded from the older rocks of the Wrangell volcanic belt. In the stratigraphically highest sample of the lower member of the McCallum Formation, 060514-WKA-01, there is a distinct population of 6-5 Ma zircons (Figure 12). This population is found in

54 most of the samples from both the lower and upper members. We interpret this detritus to have been originally derived from the northern and most active part of the Wrangell volcanic belt. Lavas dated from the large shield volcano, Mount Blackburn, for example, have K-Ar ages of 3- 4.48 Ma (Figure 17a; Richter, 1990; 1995).

The detrital zircon record of the upper member of the McCallum Formation contains many of the same detrital zircon populations as discussed for the lower member (Figures

13; 14) and we interpret no major change in the provenance of the sand-sized detritus for the upper member. The 26 Ma and 6-5 Ma populations present in the lower member for example are observed in all of the samples analyzed from the upper member except for sample PHE-02-6.8m (Figure 13). The consistent occurrence of these detrital zircon populations may be a function of recycling of the proximal part of the McCallum basin along the thrust belt that defines the eastern margin of the basin (Figure 2; Waldien et al.,

2014; 2015). The 50 Ma population that we attribute to sediment derivation from Eocene volcanic rocks during deposition of the lower member was not observed in samples from the upper member suggesting limited sediment contribution from these sources during the later stages of basin development. The 66-55 Ma detrital zircon population is recognized in all the samples from the upper member. We interpret these zircons as having being derived from the central Alaska Range igneous belt that contains 73-50 Ma plutons.

These plutons are currently exposed west of the McCallum basin in the Healy, Talkeetna

Mountains, and Talkeetna quadrangles (Figure 1). Age populations with a range of 216-

155 Ma detrital zircons are recognized in both the lower and upper members and are especially well developed in the CALL03 samples from the upper member (Figure 13).

These detrital zircon populations overlap in age with two potential source areas located south of the Denali fault system. The first potential source is the plutons of the Late

Triassic to Early Jurassic Talkeetna arc (Amato et al., 2007; Rioux et al, 2007; 2010).

These plutons are currently exposed southwest of the McCallum basin in the Talkeetna

Mountains quadrangle (Figure 1). Another potential source is the calc-alkaline plutonic rocks of the Chitina arc that range in age from 175-135 Ma (Plafker et al., 1989;

Nokleberg et al., 1994; Roeske et al., 2003). These plutons are exposed in the McCarthy quadrangle (Figure 1). We prefer an interpretation of the plutons of the Talkeetna arc as the source for these detrital zircons in the McCallum Formation due to their proximity to the basin and that the Wrangell volcanic field would serve as the barrier to northward sediment transport from the Chitina batholith. Another small but consistent population of detrital zircons with peak ages that range from 295-330 Ma are present in all the samples but two samples from the McCallum Formation (Figures 12; 13). We interpret this population to represent sediment contribution from igneous rocks of the Wrangellia

Composite Terrane. This suite of rocks underlies much of south-central Alaska and are well dated in the northeastern corner of the Gulkana quadrangle southeast of the

McCallum basin (Figure 1). In this area and throughout southern Alaska, the Mid-

Pennsylvanian to Early Permian Skolai arc rocks have U-Pb ages of 290-320 Ma (Beard and Barker, 1989) and appear to be the likely source of detrital zircons of this age in the

McCallum Formation. These rocks are also exposed in the hangingwalls of the thrust faults that form the northern margin of the McCallum basin (Figure 2).

The general low percentages of Precambrian and Paleozoic age zircons (12%) suggest that there was limited contribution of sediment from the Precambrian and Paleozoic metamorphic and metasedimentary rocks of the Yukon composite terrane located north of the Denali fault system (Figure 1). This may be a function of the eastern Alaska Range being significant enough topography to have maintained a drainage divide between sediment sources north and south of the Denali fault system. Thermochronologic studies of the Alaska Range immediately west of the Delta River (Figure 1) indicate that it has been exhuming since 24 Ma (Benowitz et al., 2014). From our perspective, it is also important to note that the majority of detrital zircons documented in the McCallum

Formation are interpreted to have been derived from igneous rocks currently located mainly south (Talkeetna arc and Wrangell volcanic field; Figure 1) and mainly west

(Central Alaska Range and Paleocene-Oligocene igneous rocks; Figure 1) of the

McCallum basin. These relationships may suggest that these source rocks extend in the subsurface between the glacial alluvium that covers much of the Gulkana and southern half of the Mount Hayes quadrangles adjacent to the McCallum basin (Figure 1) and may have been exposed during Late Miocene-Pliocene deposition of the McCallum

Formation. Another hypothesis is that some Late Miocene-Pliocene rivers may have flowed northward and eastward in the area prior to Pleistocene reorganization of drainage systems associated with Northern Hemisphere glaciation. Additional research needs to be done to test either of these hypotheses.

The detrital record is not sensitive enough to delineate a specific amount of strike-slip displacement but these data lead us to suggest a possible range from 79 to 230 km of

57 potential offset of the McCallum basin along the Denali and Totschunda fault system since the Late Miocene. The 230 km estimate is the required amount of displacement for the McCallum basin to be located directly adjacent to the White Mountain granitoid belt during deposition of the lower member. Modern displacement rates require the 79 km estimate based on the oldest tephra age of the McCallum Formation (6.17 ± 0.07 Ma). It is possible that the 123-124 Ma detrital zircons were sourced by a large fluvial system with headwaters in the White Mountain granitoid belt, such a depositional system may have been capable of transporting zircons long distances and therefore reducing the need for strike-slip displacement of the basin from its source of sediment. We think this is unlikely for two reasons. First, the unimodal population 123-124 Ma zircons suggest there was little mixing of detritus from different sources, which would be suspected in a large fluvial system. Second, the mainly lacustrine lithofacies of the lower member, which contains this 123-124 detrital zircon age populations, is a depositional environment that would be expected to be dominated by local sources of sediment. We cannot rule out, of course, that there may be yet unrecognized 123-124 Ma plutons located west of the

Denali-Totschunda fault system. It possible that this portion of the belt was tectonically transported with the McCallum basin and provided sediment to the basin. Even in this scenario, we argue that because of the unique age of the White Mountain granitoid belt that both the basin and yet unrecognized plutons were probably transported 79 to 230 km from the offset equivalent, main cluster of plutons located on the east side of the

Totschunda fault (Nabesna quadrangle, Figure 1).

59 up <1% of the total tuff clast distribution. These clasts are contain a pink aphanitic matrix with well-preserved biotite phenocrysts. Two of these clasts were collected for 40Ar/39Ar analysis of biotite and will be discussed in a later section. Sedimentary, metasedimentary, and plutonic clasts are the minor clast types of the McCallum Formation. Sedimentary clasts make up 6% of the total clast distribution for the McCallum Formation and are dominated by chert clasts that are commonly tan but are also black and green in color.

&KHUWFODVWVPDNHXSRIWKHWRWDOVHGLPHQWDU\FODVWGLVWULEXWLRQ³2WKHUVHGLPHQWDU\

FODVWV´PDNHXSRIWKHWRWDOVHGLPHQWDU\FODsts and are most commonly siltstone and fine-grained, sandstone clasts. Metasedimentary clast types make up 5% of the total clast distribution and are dominated by quartzite clasts that account for 64% of this clast type.

Other metasedimentary clasts include argillite and metasiltstone clasts that make up 36% of this clast type. Schist clasts make up 3% of the total clast distribution and are commonly mica rich, grey, and foliated. Plutonic clasts make up 3% of the total clast distribution and are commonly granodiorite, granite, and diorite. Plutonic clast textures often contain visible hornblende and biotite phenocrysts with a quartz and plagioclase rich matrix.

Clast compositional data (n= 351) were collected at three stratigraphic positions within the lower member (Figure 16). Key observations in the lower member include: (1) metabasalt is a dominant clast type and accounts for 56% of the total clast distribution of the lower member, (2) upsection trends include increase in tuff clasts, tuff clasts account for 17% of the total clast distribution, (3) No sedimentary, plutonic, or schist clasts are present in the total clast distribution of the lower member.

Figure 16 Histograms show variation in clast composition at 16 different stratigraphic positions in the McCallum Formation (n-number of clasts counted). Clast composition data were recorded almost exclusively from the upper member. Note the upsection increase in plutonic, chert, schist, and metasedimentary clasts. See text for description of clast types. Rose diagrams were constructed using Stereonet 9.5 program designed by Allmendinger et al. (2012) and Cardozo et al. (2013). Rose petals have a 15° width. Red arrow shows mean paleocurrent direction. N values (n=81 total) are denoted next to petals to indicate the number of measurements per location. Paleocurrent measurements indicated a dominant southwest paleoflow direction. See text for descriptions of paleocurrent data.

61 61

(Figure 2). Upsection differences in clast composition include the introduction of plutonic, schist, metasedimentary, and sedimentary clast types. Local sediment sourcing from Mid-Pennsylvanian to Upper Triassic volcanic strata of the Wrangellia composite terrane exposed in the thrust sheets that form the eastern margin of the McCallum basin

(Figure 2). The general stratigraphy of the Wrangell composite terrane in the thrust sheets of north of basin include volcanic and sedimentary rocks related to the late Paleozoic

Skolai arc (Figure 2; Slana River sequence and Eagle Creek Formation) and are overlain by basaltic rocks associated with Late Triassic rifting followed by the emplacement of

Cretaceous granitic plutons and deposition of Eocene volcanic rocks. The Slana River sequence consists of the Slana Spur Formation and a mixed volcaniclastic unit that consists of andesitic lava flows, tuff, breccia, and argillite (Figure 2; Richter and Jones,

1973; Richter, 1976; Jones et al., 1977; Nokleberg et al., 1982, 1985; 2015). This unit is

700-1400 m thick and accounts for a majority of rocks exposed north of the McCallum basin (Nokleberg et al., 2015). Locally, Early Permian (?) andesite, dacite, and rhyolite stocks, dikes, sills, and small plutons intrude the Slana River sequence and are interpreted to have developed coeval with volcanic rocks of the Slana Spur Formation. (Figure 2, pink map pattern; Nokleberg et al., 2015). Thickness for this unit is unknown. The early

Permian Eagle Creek formation overlies the Slana River sequence and consists of argillite and limestone with a mixture of coral, bryozoan, brachiopod, echinoid, crinoid, and fusulinid fragments (Figure 2, blue map pattern; Bond, 1976; Richter et al., 1977). This unit is approximately 900 m thick (Nokleberg et al., 2015). Overlying the Eagle Creek

Formation are basaltic rocks related to Late Triassic rifting or possible mantle plume upwelling (Richter and Jones, 1975; Nokleberg et al., 1985; Nokleberg et al., 2015).

These rocks include the Upper Triassic Nikolai greenstone that was later intruded by coeval gabbro, metagabbro, diabase dikes and mafic and ultramafic sills that are related to late-staged magmatism (Figure 2; Richter and Jones, 1975; Nokleberg et al., 1982,

1985). These rocks are estimated to be more than 1000 m thick and make up a majority of the clast composition for the McCallum Formation (Nokleberg et al., 2015). Cenozoic intrusions located north and east of the McCallum basin include Early to mid-Cretaceous granite and granodiorite plutons (Figure 2; bright green map pattern). The age of these plutons is poorly constrained. A single K-Ar age of 110 Ma was produced by Nokleberg et al. (1992b). This age can be interpreted as either the timing of pluton emplacement or indicate the age of a metamorphic event. The thickness of this unit is unknown. Along the eastern margin of the McCallum basin lies a distinct outcrop of Eocene volcanic rocks

(Figure 2; red map pattern). Common rock types are ash-flow tuff, breccia, lava flows, dikes and sills with minor volcanic sandstone (Nokleberg et al. 2015). The outcrop thickness of this unit is estimated to be a few hundred meters (Nokleberg et al. 2015).

Local sediment derivation for clast compositional data is also consistent with southwest- directed paleocurrent indicators (Figure 16).

Dacite clasts within the upper member suggest exposure and erosion of Oligocene volcanic strata during alluvial fan deposition. The 26-28 Ma 40Ar/39Ar biotite cooling ages from the dacite clasts are consistent with 26 Ma detrital zircon peak ages and the 28

Ma 40Ar/39Ar detrital biotite cooling ages from sandstone of the McCallum Formation

(Figures 12; 13). All three datasets indicate that the McCallum basin was receiving detritus from the older parts of the Wrangell volcanic belt as discussed earlier.

Figure 17 Schematic depositional models are used to illustrate the strike-slip basin development of the McCallum basin based on chronostratigraphic and provenance analysis of the McCallum Formation. Passive markers indicate maximum (yellow) and minimum (red) displacement estimates based on provenance analysis and modern slip rates respectively. (A) The modern structural configuration of the eastern Alaska Range highlights a region of Neogene volcanism and transtension between the Totschunda and Border Ranges fault systems. The junction of the Totschunda and Denali faults marks the start of a regional restraining bend. Northwest of this junction deformation is characterized by thrust deformation north and south of the Denali fault as rock is transported into the regional restraining bend. The rupture path of the 7.9 M 2002 Denali Earthquake is also highlighted to show active tectonics along the fault system. (B) Stage 1- 6.1 Ma: During regional lacustrine deposition of the lower member, sediment was likely sourced from the Klein Creek pluton, Sonya Creek, and Rocker Creek areas north of the Totschunda fault based on recently published ages by Graham et al. (2015). Modern river samples from the Chisana and Nabesna Rivers contain young U-Pb detrital zircon ages (5 and 25 Ma) similar to the detrital zircon record of the McCallum Formation. The McCallum basin is interpreted to have been located 79-230 km southeast of its present position. (C) Stage 2- 5.0 Ma: During strike-slip transport of the McCallum basin into the regional restraining bend, rocks from Wrangellia Composite Terrane were exposed in thrust sheets and supplied sediment to alluvial fan systems. The McCallum basin is interpreted to have been located approximately 65 km southeast of its present position. (D) Stage 3- Modern Depositional Setting: the McCallum basin continues to develop as a transpressional foreland basin in the footwall of the thrust belt. The Copper River basin represents the distal part of this basin. Our interpretation requires that the Totschunda fault has been active for at least the last 6.2 Ma and is consistent with the rupture record of the 2002 Denali Earthquake. These reconstructions are based on modern slip rates from Meriaux et al. (2009) and Matmon et al. (2006). Modern structural configuration and geologic units are derived from Wilson et al. (2016), Vallage et al. (2014), and Trop et al. (2012). Ages of specific plutons and domes in the eastern Alaska Range are from Graham et al. (2016) and Richter et al. (1990).

68 68

.Figure 18 Relative age probability plots of the Nabesna and Cottonwood Creek Complex. Inset graph shows age distributions between 0-550 Ma with 5 Ma bin widths. The red curve in the inset graph is a probability density profile of the age distribution. The outer graph shows age distributions between 0-3250 Ma with 20 Ma bin widths. The vertical axes denote the number of grains for each sample. Histograms for each graph show relative number of grains. Refer to Figure 29 for the geographic locations of thse modern river samples. Important peak age populations in the Cottonwood Creek Metamorphic Complex sample include 26 Ma. This same age population accounts for 10% of the detrital record of the McCallum Formation. The Nabesna River Modern River sample show small age populations of 5 Ma with a dominance of 118 Ma age population. Both are populations found in the detrital record of the McCallum Formation.

70 segment along the main strand of the Denali fault that extends to the Canada border separates the Yukon composite terrane from the Nutzotin Mountain sequence. The southern segment of the Denali fault system extends along the Totschunda fault to the

Canada border and separates the Nutzotin Mountains sequence from the Wrangellia composite terrane. These two segments of the fault system merge northwestward into a single strand of the Denali fault system that separates the Yukon composite terrane and the Wrangellia composite terrane (Figure 17a). This segment of the fault extends to the junction where it splays into the Talkeetna, Denali/ McKinley, and Hines Creek faults

(Figure 17a). A series of active south-verging thrust faults are located on the south side of this segment of the Denali fault (e.g., McCallum Creek Thrust, Slate Creek Thrust).

South of the Totschunda fault intersection with the Denali fault is a zone of Neogene volcanism and region of transtension between the Totschunda fault and the Border

Ranges fault system (Figure 17a). Our focus is on the Denali fault system between the

Delta River and Wrangell volcanic belt because it marks a tectonic transition from transtensional to transpressional styles of deformation as material enters a regional restraining bend (Figure 17a). As described in an earlier section, during the 7.9M Denali

Earthquake in 2002 the rupture path transferred from the main strand of the Denali fault onto the Totschunda fault in the eastern Alaska Range.

Our study area, the McCallum basin, is currently located in the footwall of the McCallum

Creek thrust south of the Denali fault in the transpressional part of the fault system

(Figure 17a). This north dipping thrust is a part of an active south verging fold and thrust belt that parallels the east-central segment of the Denali fault (Ridgway et al., 2002;

72 ages of 123±126 Ma (e.g., Graham et al., 2016). This pluton is part of the Lower

Cretaceous White Mountain granitoid suite (Richter, 1990; Snyder et al., 2007; Graham et al., 2016). The 230 km of maximum dextral displacement is the required displacement if the McCallum basin was located directly adjacent and across the fault from the Klein

Creek pluton at the start of deposition of the lower member of the McCallum Formation.

As discussed in the provenance section an unequivocal solution to the amount of strike- slip displacement based on detrital zircon signatures is not possible due to potential long distances of fluvial sediment transport and recycling of sediment through multiple stages of erosion and redeposition. Aware of these potential complications, we submit that this is a reasonable interpretation because the 123-124 Ma unimodal detrital zircon peak suggest very little mixing of sediment from different sources that would be expected from a large integrated fluvial watershed system and also that much of the lower member is characterized by shallow lacustrine, peat swamp, and low-gradient fluvial environments that would be dominated by local sediment sources.

A second key provenance signal is the dominant peak population of 26 Ma detrital zircons in the sandstone of the McCallum Formation (Figure 12) as well as the 28 Ma

40Ar/ 30Ar ages from detrital biotite in sandstone (Figure 15), and the 26 to 28 Ma

40Ar/39Ar ages from volcanic clasts in conglomerate (Figure 15). Collectively these data sets all suggest that a major component of Oligocene volcanic detritus was transported and deposited in the McCallum basin. The best known match for potential sources of this

73 age are the Oligocene volcanic rocks of Rocker Creek (~26 Ma) and Sonya Creek (~23

Ma) documented by Richter (1990). Both of these volcanic fields are located east of the

Totschunda fault and are part of the Wrangell volcanic belt (Figures 1; 17b). If these volcanic fields were the source of the Oligocene detritus in the McCallum basin, the amount of displacement required would be on the order of 230 km, consistent with the amount required in the Klein Creek pluton were the main source of the 123 -124 Ma detrital zircon population in the McCallum Formation. Our maximum displacement interpretation based on two different detrital signals is consistent with the recent study of

Benowitz et al. (2012) that suggested that the Cottonwood metamorphic complex, located within the eastern Denali fault system directly north of the Klein Creek pluton, and the

Rocker Creek and Sonya Creek volcanic fields (Figure 17b), as a possible source of 26

Ma detrital zircons to the McCallum basin.

Collectively, there are several lines of new data that indicate that the McCallum basin provides a faithful marker of significant Neogene strike-slip displacement along the eastern Denali fault system. Due to the intrinsic uncertainty in the pathway from source rock to sediment deposition into the basin detrital zircon geochronology is not a precise tool for determining the specific amount of strike-slip displacement across a fault system, and as shown on the paleogeographic reconstruction in Figure 17b we have positioned the basin to accommodate both the minimum and maximum interpreted amount of displacement. In both interpretations the McCallum basin would have been located adjacent to the more northerly trending Totschunda fault in a transtensional setting during

77 strata and metamorphic rocks (Eisbacher, 1976; Nokleberg et al., 1985). Along the central segment of the fault, a previous study has estimated 38 km of displacement during the last 38 Ma based on offset plutons across the Denali fault (Lanphere and Reed, 1974).

A basin analysis study by Trop et al. (2004) of the middle Eocene ± Late Cretaceous

Colorado Creek basin strata indicated 30-33 km of Cenozoic strike-slip displacement along the central segment of the Denali fault based on matching limestone clasts containing Devonian conodonts in conglomerate with potential sources across the fault.

Prior to the 7.9 M 2002 Denali Earthquake the Denali fault system was even thought to be inactive by some researchers (Ford et al. 1998; Csejtey et al. 1997; Csejtey et al.

1982). Estimates of the amount and timing of strike-slip displacement on the Totschunda fault are also poorly documented and unclear. Bemis et al. (2015) and Richter and

Matson (1971) interpreted this fault as a young structure (~ 2 Ma) whereas Milde et al.

(2014) suggested that the fault was a Cretaceous structure.

Our analysis of the McCallum Formation provides new information on the geologic history of both these major fault systems. Results of our study based on the chronostratigraphy and provenance of the McCallum Formation indicate that there has been 79 to 230 km of Neogene strike-slip displacement along the east-central Denali and

Totschunda fault systems. To our knowledge, this is the first geologic documentation of

Neogene displacement along the entire fault system. Our results also indicate that the

Totschunda fault has been active for at least 6 Ma and that the rupture path of the 2002

Denali earthquake must have been a common displacement pathway since the Late

Miocene start of deposition of the lower member of the McCallum Formation. Repeated

78 displacement along the Denali-Totschunda fault system are required to restore the

McCallum basin to a position proximal to its sources of sediment on the opposite side of the fault system. Collectively our data indicate significant Neogene strike-slip and thrust displacement along the Denali fault system that has been previously unrecognized and should be accounted for in the Cenozoic fault budgets for the upper plate of the southern

Alaska convergent margin and in future seismic risks assessment of south central Alaska.

1.7 Conclusion:

Sedimentology, provenance, and geochronology of the McCallum Formation provides new insight into Miocene-Pliocene strike-slip basin development of the McCallum basin and the displacement history of the Denali fault system in the eastern Alaska Range. Our dataset consists of measured stratigraphic sections, paleocurrent data, clast composition data from conglomerate, U-Pb detrital zircon geochronology from sandstone,

40Ar/ 39Ar geochronology on volcanic glass, 40Ar/ 39Ar geochronology on detrital biotite, and 40Ar/ 39Ar geochronology on volcanic clasts.

New sedimentological and geochronologic data from the McCallum Formation document a two-part chronostratigraphy consisting of a lower and upper member with a minimum thickness of 564 m. The lower member has a minimum thickness of 181 m and is characterized primarily by laminated mudstone with minor pebble conglomerate, lignite, and tephra layers. We interpret the lower member to represent a lacustrine depositional system containing heavily vegetated peat swamps, shallow lakes, and low energy fluvial systems. Tephra ages for the lower member range from 6.17 to 5.08 Ma. The upper

79 member has a minimum thickness of 383 m and is characterized by cobble conglomerate with sandstone lenses interbedded with granular conglomerate and minor tephra. We interpret the upper member to represent a wet-alluvial fan environment with well- developed braided stream systems. Tephra ages for the upper member range from 5.01 to

3.80 Ma. Our lithofacies analysis of the McCallum Formation documents the progradation of the upper member alluvial fan strata over the lacustrine strata of the lower member.

Provenance analyses of U-Pb detrital zircons from sandstone and clast compositional data suggest two separate sources of sediment during deposition of the McCallum Formation.

Clast compositional data and paleocurrent indicators from the McCallum Formation indicate local sediment derivation from exhumed and eroded lithologies located within proximal thrust sheets north of the McCallum basin. Sandstone provenance analysis from the lower member indicate derivation of unique sources of sediment related to the White

Mountain granitoid belt and older strata of the Wrangell volcanic belt (26 and 123-124

Ma detrital zircon populations) that are located south of the Denali fault and north of the

Totschunda fault. Sandstone provenance analysis from the upper member document relatively unchanged sources of sediment with the exception of the absence of 123-124

Ma age population. This long term sandstone provenance record is consistent with

40Ar/ 39Ar geochronology on detrital biotite ages of 28 Ma and 40Ar/ 39Ar geochronology on biotite in volcanic clasts with 27-28 Ma ages. Collectively, our provenance analysis of clasts in conglomerate and sandstone from the McCallum Formation indicate that

80 sediment is derived primarily from igneous sources located south of the Denali fault system.

Stratigraphic and provenance analysis of the McCallum Formation indicate basin development was coeval with 79 to 230 km of strike-slip basin transport since 6.1 Ma based on modern displacement rates. The McCallum Formation documents three stages of basin development. The first stage of basin development documents the location of the basin 79-230 km southeast of its current position based on the oldest tephra age of the lower member (6.1 Ma) and unique provenance sources (123-124 Ma; 26 Ma detrital zircon populations). During regional lacustrine deposition of the lower member, sediment was likely sourced from the Klein Creek pluton, Sonya Creek, and Rocker Creek areas north of the Totschunda fault and south of the Denali fault. Continuation of basin transport at 5.0 Ma (oldest tephra age from upper member) is marked by the development of alluvial fan systems of the upper member that prograde over the lacustrine strata of the lower member. Active south-verging thrust belt development on south side of the Denali fault sourced the conglomerates of these alluvial fan systems. During this stage, the basin was located 65 km southeast of its current position. The continuation of basin transport to its current position marks the final stage of basin development. During this stage, the continuation of basinward thrust fault propagation deforms and incorporates the eastern basin margin of McCallum basin in to the thrusts faults. Alpine glaciation erodes and covers much of the basin with Quaternary deposits. This basin transport model is consistent with the rupture record of the 2002 M 7.9 Denali Earthquake and suggests the

Totschunda fault has been active since 6.1 Ma. Our research on the McCallum basin

81 demonstrates that Neogene sedimentary basins adjacent to the Denali fault system have the potential to record the Neogene displacement and deformation history of this major fault system.

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APPENDICES

112

Appendix A Measured Stratigraphic Sections

113

114

115

116

117

118

119

120

121

122

123

Appendix B 40Ar/39Ar Analysis of Volcanic Glass from Tephras

Tephra Sample Measured GPS Age Name Section Location (Ka) Location Lat. Long. WAITUFF PHE-02 63.2046 -145.5457 3808 ± 54

02HODO CALL-01 63.2305 -145.6316 4630 ± 54

08HODO CALL-03 63.2253 -145.6244 4882 ± 151

19HODO 061414-WKA01 63.2362 -145.6073 5055 ± 105

01HODO PROP-01 63.21869 -145.43903 5079 ± 56

GC1-36M GC1 N 63° 12' W 145° 21' 5858 ± 24.6" 39.3" 192

01GUNN HP2 63.2069 145.4006 6174 ± 75

*Samples were analyzed by Dr. Jeffrey A. Benowitz at the University of Alaska-

Fairbanks

Isochrons of each dataset are presented first followed by their raw dataset for each analysis is shown on the following pages. Ages are reported as Ka.

124

125

WAITUFF GL#L1 Weighted average of J from standards = 8.775e-05 +/- 2.011e-07

Laser Cumul 40Ar/3 37Ar/3 36Ar/3 % 40*/3 Power ative 9Ar +/- 9Ar +/- 9Ar +/- Atm. +/- Ca/K +/- Cl/K +/- 9K +/- Age +/-

(mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 243.18 2.75 0.4209 0.02 0.7401 0.01 89.93 1.58 0.77 0.05 0.00 0.00 24.49 3.88 3868 612. 500 0.025 842 793 3 994 4 509 108 606 258 497 91 201 073 425 .8 94 133.09 0.96 0.3670 0.01 0.3680 0.00 81.72 1.27 0.67 0.01 0.00 0.00 24.32 1.72 3843 271. 1000 0.1114 215 171 3 063 8 615 016 644 363 951 982 046 991 095 .42 57 92.325 0.45 0.3448 0.00 0.2307 0.00 73.84 0.80 0.63 0.01 0.00 0.00 24.14 0.76 3814 120. 1500 0.2691 5 1 1 594 5 258 694 001 282 09 998 026 406 516 .09 75 65.228 0.38 0.3453 0.00 0.1412 0.00 63.95 0.49 0.63 0.01 0.01 0.00 23.50 0.37 3713 58.7 2000 0.5594 65 326 2 555 1 127 831 833 377 019 018 025 454 232 .17 6 56.386 0.24 0.00 0.1094 0.00 57.33 0.77 0.80 0.00 0.01 0.00 24.05 0.45 3799 72.0 2500 0.782 17 393 0.4367 382 7 152 831 605 154 702 048 02 004 636 .26 2 57.658 0.32 0.5865 0.00 0.1113 0.00 56.99 1.33 1.07 0.01 0.00 0.00 24.79 0.78 3917 124. 3000 0.8891 95 722 7 78 1 267 019 813 672 432 922 038 651 726 .05 23 69.083 0.51 0.9712 0.01 0.1391 0.00 59.44 1.51 1.78 0.03 0.00 0.00 28.02 1.07 4425 169. 5000 0.9724 15 193 6 661 9 366 925 654 335 052 977 034 092 393 .78 41 124.41 1.79 2.7157 0.05 0.3046 0.01 72.20 2.21 4.99 0.10 0.01 0.00 34.64 2.81 5469 443. 9000 1 454 378 5 663 8 027 361 595 26 43 004 174 094 22 .79 37

Integrat 78.992 0.18 0.5129 0.00 0.1839 0.00 68.80 0.36 0.94 0.00 0.01 0.00 24.64 0.29 3893 47.9 ed 94 953 1 313 9 103 065 444 146 574 002 013 495 877 .13 8

Table 1 Datatables of Tephras Analyzed from the McCallum Formation

125

126

WAITUFF GL#L2 Weighted average of J from standards = 8.775e-05 +/- 2.011e-07

Laser Cumul 40Ar/3 +/- 37Ar/3 +/- 36Ar/3 +/- % +/- Ca/K +/- Cl/K +/- 40*/3 +/- Age +/- Power ative 9Ar 9Ar 9Ar Atm. 9K (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 500 0.1353 180.49 1.32 0.3318 0.01 0.5319 0.00 87.08 1.28 0.609 0.02 0.00 0.00 23.31 2.34 3683 369. 958 13 6 16 3 837 336 453 06 129 988 135 611 335 .43 82 1000 0.515 65.511 0.24 0.3424 0.00 0.1444 0.00 65.13 0.92 0.628 0.00 0.00 0.00 22.83 0.61 3607 97.6 94 238 8 366 4 205 572 078 55 673 984 027 544 883 .57 7 1500 0.7626 49.311 0.22 0.4636 0.00 0.0838 0.00 50.18 1.19 0.850 0.01 0.01 0.00 24.55 0.60 3879 95.7 17 281 575 3 201 567 874 92 056 112 025 728 704 .3 9 2000 0.8786 50.954 0.32 0.6911 0.01 0.089 0.00 51.53 1.87 1.268 0.03 0.01 0.00 24.69 0.97 3900 153. 31 834 3 838 327 229 602 75 375 048 071 405 23 .88 43 2500 0.9284 56.304 0.86 1.1196 0.04 0.1214 0.01 63.58 5.55 2.056 0.08 0.01 0.00 20.50 3.14 3240 496. 29 214 4 589 1 073 632 312 01 434 038 173 787 45 .19 38 3000 0.9567 64.025 1.32 1.4032 0.05 0.1244 0.01 57.26 6.51 2.577 0.09 0.01 0.00 27.37 4.21 4323 664. 85 676 7 14 2 433 792 136 37 449 165 208 402 195 .72 48 5000 0.989 78.560 1.52 2.0101 0.07 0.1413 0.01 52.98 6.97 3.693 0.13 0.01 0.00 36.97 5.53 5837 871. 91 155 6 108 7 873 604 332 61 079 267 269 314 197 .45 99 9000 1 130.72 4.33 8.1576 0.29 0.3101 0.02 69.61 6.24 15.05 0.53 0.01 0.00 39.93 8.32 6304 1311 892 071 8 074 9 939 785 339 495 967 883 53 938 472 .95 .87

Integrat 76.008 0.19 0.6203 0.00 0.1754 0.00 68.16 0.67 1.138 0.00 0.01 0.00 24.19 0.51 3822 82.4 ed 32 728 9 484 3 175 366 168 83 888 051 028 942 944 .83 4

126

127

WAITUFF GL#L3 Weighted average of J from standards = 8.775e-05 +/- 2.011e-07

Laser Cumul 40Ar/3 +/- 37Ar/3 +/- 36Ar/3 +/- % +/- Ca/K +/- Cl/K +/- 40*/3 +/- Age +/- Power ative 9Ar 9Ar 9Ar Atm. 9K (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 500 0.1072 416.05 4.89 0.3342 0.01 1.3317 0.01 94.58 0.73 0.61 0.02 0.01 0.00 22.53 3.10 3560 489. 816 959 3 166 2 718 376 183 342 14 017 098 844 321 .7 77 1000 0.4344 90.261 0.64 0.3204 0.00 0.2221 0.00 72.70 0.52 0.58 0.00 0.01 0.00 24.63 0.52 3891 83.5 15 538 5 458 204 53 033 812 841 014 041 398 919 .4 1 1500 0.6902 57.857 0.43 0.3739 0.00 0.1158 0.00 59.12 1.17 0.68 0.01 0.01 0.00 23.64 0.70 3735 111. 48 04 5 552 1 243 438 73 633 014 065 047 371 892 .13 88 2000 0.822 54.998 0.47 0.4997 0.01 0.1022 0.00 54.86 1.27 0.91 0.03 0.01 0.00 24.81 0.73 3920 116. 58 916 9 738 253 771 906 736 19 129 049 748 818 .36 48 2500 0.887 55.740 0.95 0.6672 0.02 0.1059 0.00 56.09 2.65 1.22 0.04 0.01 0.00 24.47 1.53 3865 242. 78 487 2 485 4 531 537 159 484 564 04 123 128 727 .73 58 3000 0.9218 62.215 1.15 0.8946 0.04 0.1409 0.01 66.86 4.66 1.64 0.08 0.01 0.00 20.62 2.92 3257 461. 19 503 6 358 5 014 169 028 262 007 025 186 025 622 .93 91 5000 0.9837 63.126 0.97 1.1663 0.04 0.1293 0.00 60.41 2.77 2.14 0.07 0.01 0.00 24.99 1.80 3949 284. 22 83 5 021 2 625 085 963 186 39 044 084 998 034 .16 08 9000 1 172.78 5.87 4.1197 0.15 0.4764 0.02 81.30 3.82 7.58 0.29 0.00 0.00 32.39 6.72 5115 1061 388 731 881 7 758 405 823 113 31 888 302 229 853 .24 .03

Integrat 108.70 0.44 0.5163 0.00 0.2861 0.00 77.75 0.41 0.94 0.00 0.01 0.00 24.17 0.47 3819 75.8 ed 26 616 8 487 1 177 85 521 784 895 044 025 93 728 .65 2

127

128

08HODO GL#L1 Weighted average of J from standards = 8.775e-05 +/- 2.011e-07

Laser Cumul 40Ar/3 +/- 37Ar/ +/- 36Ar/ +/- % +/- Ca/K +/- Cl/K +/- 40*/3 +/- Age +/- Power ative 9Ar 39Ar 39Ar Atm. 9K (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 500 0.0152 1561.5 131.7 1.4639 0.33 5.1439 0.45 97.33 2.84 2.688 0.60 0.01 0.01 41.59 44.67 6565 7039 0011 4606 1 008 6 898 897 894 85 691 632 646 419 972 .71 .93 1000 0.0739 1112.9 29.75 1.2528 0.08 3.5825 0.10 95.11 1.30 2.300 0.15 0.00 0.00 54.39 14.60 8581 2299 2748 459 6 233 9 703 663 308 87 133 77 411 509 724 .55 .01 1500 0.1892 578.80 13.98 1.1975 0.05 1.8139 0.04 92.59 0.69 2.199 0.10 0.00 0.00 42.87 4.238 6767 667. 603 636 9 695 9 515 794 901 27 467 327 234 766 52 .93 76 2000 0.4459 230.85 3.406 1.7644 0.03 0.6601 0.01 84.44 1.41 3.241 0.06 0.00 0.00 35.94 3.322 5674 523. 297 71 3 284 5 458 89 422 53 041 475 13 036 26 .65 73 2500 0.7563 71.606 0.693 3.8090 0.05 0.1338 0.00 54.80 1.77 7.007 0.09 0.00 0.00 32.43 1.318 5121 207. 64 02 3 143 2 448 925 777 9 488 445 074 344 94 .72 98 3000 0.8377 53.077 0.880 5.9644 0.13 0.0673 0.01 36.60 6.57 10.99 0.24 0.00 0.00 33.77 3.553 5332 560. 32 32 6 007 7 184 259 33 025 069 221 206 315 82 .97 34 5000 0.9352 52.703 1.468 6.3177 0.18 0.0817 0.01 44.86 5.93 11.64 0.33 0.00 0.00 29.17 3.248 4607 512. 67 94 1 238 4 082 768 636 408 765 759 212 06 3 .13 37 9000 1 66.040 2.071 10.338 0.33 0.1284 0.01 56.19 8.11 19.10 0.61 0.02 0.00 29.13 5.476 4600 863. 96 97 51 272 1 855 194 258 926 95 269 335 104 21 .89 8

Integrat 250.71 1.748 3.6446 0.03 0.7293 0.00 85.85 0.63 6.704 0.05 0.00 0.00 35.54 1.623 5612 256. ed 588 95 8 117 9 73 809 551 75 749 607 069 332 6 .06 28 128

129

08HODO GL#L2

Weighted average of J from standards = 8.775e-05 +/- 2.011e-07

Laser Cumul 40Ar/3 +/- 37Ar/3 +/- 36Ar/3 +/- % +/- Ca/K +/- Cl/K +/- 40*/3 +/- Age +/- Power ative 9Ar 9Ar 9Ar Atm. 9K (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 500 0.1027 788.56 9.29 0.7785 0.05 2.5934 0.03 97.18 0.764 1.429 0.10 0.01 0.00 22.24 6.07 3514 959. 083 664 3 654 5 398 063 27 29 385 141 365 381 668 .2 09 1000 0.3291 275.05 1.50 0.9223 0.02 0.8106 0.01 87.06 1.450 1.693 0.04 0.00 0.00 35.58 4.01 5618 632. 779 84 9 35 4 391 988 8 56 318 635 107 464 134 .57 38 1500 0.5345 110.56 0.87 1.5877 0.02 0.2655 0.00 70.86 2.196 2.916 0.05 0.00 0.00 32.23 2.44 5091 385. 908 76 9 918 4 846 768 06 65 366 68 136 884 666 .04 82 2000 0.6634 62.916 1.09 2.4057 0.06 0.1122 0.01 52.43 6.398 4.421 0.12 0.00 0.00 29.96 4.06 4732 641. 92 516 5 742 5 375 138 09 73 412 855 193 552 65 .51 39 2500 0.7468 52.884 1.06 3.3920 0.10 0.0946 0.01 52.40 9.337 6.238 0.19 0.00 0.00 25.21 4.97 3983 785. 51 287 9 496 7 68 04 68 97 351 958 23 912 707 .73 33 3000 0.8074 47.144 1.32 3.8583 0.15 0.0592 0.02 36.47 18.30 7.098 0.28 0.00 0.00 30.01 8.68 4739 1370 32 052 9 7 3 922 412 065 96 964 587 373 181 96 .81 .56 5000 0.9138 48.366 0.79 4.7366 0.11 0.0773 0.01 46.44 8.421 8.720 0.20 0.01 0.00 25.97 4.10 4102 648. 6 948 8 174 383 872 71 33 641 136 206 196 917 .52 35 9000 1 53.880 1.09 7.3545 0.16 0.0973 0.01 52.29 10.87 13.56 0.30 0.01 0.00 25.82 5.91 4079 932. 75 693 2 243 5 99 433 126 498 115 651 334 42 039 .21 55

Integrat 190.99 0.94 2.5822 0.02 0.5465 0.00 84.45 0.841 4.746 0.04 0.00 0.00 29.73 1.62 4696 256. ed 118 771 4 205 59 641 05 7 061 889 075 65 59 .39 68 129

130

08HODO GL#L3 Weighted average of J from standards = 8.775e-05 +/- 2.011e-07

Laser Cumul 40Ar/3 +/- 37Ar/3 +/- 36Ar/3 +/- % +/- Ca/K +/- Cl/K +/- 40*/3 +/- Age +/- Power ative 9Ar 9Ar 9Ar Atm. 9K (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 500 0.1451 740.16 11.15 0.8199 0.07 2.4208 0.04 96.64 0.894 1.505 0.13 0.01 0.00 24.85 6.66 3925 1052 674 594 3 321 7 097 418 08 33 448 499 51 209 706 .82 .03 1000 0.4865 206.91 2.034 1.0942 0.02 0.5858 0.00 83.63 0.812 2.009 0.04 0.00 0.00 33.87 1.72 5349 272. 138 8 7 211 5 791 693 02 39 063 61 209 837 834 .56 51 1500 0.6692 83.486 1.119 2.2821 0.05 0.1770 0.01 62.46 4.265 4.194 0.09 0.00 0.00 31.37 3.59 4955 566. 92 42 7 028 5 227 45 62 24 255 465 169 667 225 .07 52 2000 0.7596 63.353 0.976 3.6101 0.13 0.1013 0.01 46.83 6.966 6.641 0.24 0.00 0.00 33.75 4.45 5330 702. 35 8 6 203 6 5 154 44 07 35 593 294 431 687 73 2500 0.822 54.066 2.127 4.1903 0.19 0.0938 0.02 50.68 11.43 7.711 0.35 0.00 0.00 26.72 6.29 4221 992. 71 4 6 253 5 122 213 76 56 536 6 46 904 368 .97 95 3000 0.8667 51.517 2.665 4.6417 0.26 0.0418 0.02 23.27 15.30 8.544 0.49 0.01 0.00 39.63 8.17 6257 1288 57 25 3 712 4 674 049 109 95 337 071 627 64 561 .21 .41 5000 0.9403 58.857 1.680 5.6677 0.17 0.0881 0.01 43.49 8.533 10.44 0.32 0.01 0.00 33.37 5.13 5270 810. 68 02 6 492 6 715 088 46 136 354 086 384 684 74 .48 05 9000 1 65.709 1.859 9.9019 0.29 0.1112 0.02 48.81 9.424 18.29 0.54 0.02 0.00 33.85 6.31 5346 995. 08 74 6 468 5 116 137 87 667 834 165 575 724 446 .23 61

Integrat 212.77 1.423 2.7168 0.02 0.6130 0.00 85.04 0.720 4.994 0.05 0.00 0.00 31.87 1.56 5033 247. ed 829 46 9 787 6 639 71 42 69 134 859 126 325 489 .39 05 130

131

19HODO GL#L2

Weighted average of J from standards = 8.775e-05 +/- 2.011e-07

Laser Cumul 40Ar/3 +/- 37Ar/3 +/- 36Ar/3 +/- % +/- Ca/ +/- Cl/K +/- 40*/3 +/- Age +/- Power ative 9Ar 9Ar 9Ar Atm. K 9K (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 500 0.0368 363.00 21.22 0.4206 0.07 1.1792 0.09 95.99 4.767 0.77 0.14 - 0.00 14.55 17.33 2300 2737 475 709 4 846 1 044 081 71 205 406 0.006 753 668 237 .52 .44 11 1000 0.0665 883.92 55.60 0.9077 0.08 2.9206 0.19 97.63 2.507 1.66 0.15 0.014 0.01 20.93 22.21 3308 3506 516 118 8 305 3 829 27 12 672 258 54 401 786 643 .07 .85 1500 0.1239 606.07 18.91 0.5789 0.03 1.8595 0.07 90.66 2.318 1.06 0.06 - 0.00 56.62 14.17 8931 2230 517 321 2 795 5 483 128 2 267 97 0.000 521 005 501 .7 .55 69 2000 0.1942 529.36 17.07 0.4583 0.03 1.6296 0.06 90.96 1.960 0.84 0.07 - 0.00 47.82 10.49 7547 1653 778 005 2 909 6 308 748 04 123 177 0.000 443 802 896 .67 .36 13 2500 0.31 301.28 4.806 0.3068 0.01 0.8666 0.02 85.00 2.212 0.56 0.03 - 0.00 45.19 6.710 7132 1056 769 4 9 763 7 636 237 08 322 236 0.001 241 137 34 .41 .98 56 3000 0.4682 190.85 2.668 0.2752 0.01 0.5095 0.01 78.89 2.093 0.50 0.03 - 0.00 40.28 4.037 6360 636. 647 19 889 4 524 092 05 505 468 0.000 181 961 72 .14 27 75 5000 0.933 73.199 0.562 0.2089 0.00 0.134 0.00 54.09 1.911 0.38 0.00 0.000 0.00 33.59 1.424 5304 224. 93 18 7 457 483 362 19 348 839 82 077 477 55 .85 62 9000 1 68.076 2.175 0.6043 0.04 0.1464 0.03 63.52 13.49 1.10 0.08 - 0.00 24.82 9.223 3922 1455 04 74 7 787 6 139 783 203 941 791 0.001 474 858 59 .11 .44 04

Integrat 215.28 1.390 0.3246 0.00 0.6045 0.00 82.97 0.907 0.59 0.01 0.000 0.00 36.65 1.969 5787 310. ed 579 68 709 2 766 488 61 573 302 17 091 602 99 .46 82 131

132

19HODO GL#L3 Weighted average of J from standards = 8.775e-05 +/- 2.011e-07

Laser Cumul 40Ar/ +/- 37Ar/ +/- 36Ar/ +/- % +/- Ca/K +/- Cl/K +/- 40*/3 +/- Age +/- Power ative 39Ar 39Ar 39Ar Atm. 9K (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 500 0.0098 398.44 46.64 2.3529 0.33 1.0569 0.14 78.34 6.01 4.324 0.60 0.032 0.02 86.42 26.04 1361 4088 541 18 015 4 786 306 042 43 781 12 263 828 68 6.16 .02 1000 0.0283 448.13 32.98 2.9749 0.25 1.4939 0.11 98.46 2.80 5.470 0.46 - 0.00 6.896 12.60 1090. 1992 549 741 4 199 7 78 424 514 1 432 0.000 821 33 825 25 .66 01 1500 0.0537 427.27 19.42 2.0858 0.14 1.2500 0.06 86.41 1.77 3.832 0.27 0.006 0.00 58.12 8.063 9168. 1268 983 655 933 2 235 532 897 81 482 65 688 617 2 68 .64 2000 0.0926 331.83 11.23 1.6026 0.07 0.9673 0.03 86.11 1.59 2.943 0.14 0.010 0.00 46.13 5.533 7281. 871. 548 406 4 946 6 72 125 434 95 612 56 524 589 63 18 56 2500 0.1538 228.88 4.851 1.2863 0.04 0.5978 0.02 77.14 2.13 2.362 0.07 0.006 0.00 52.35 5.028 8261. 791. 808 89 6 194 1 08 239 833 45 709 03 273 913 66 08 59 3000 0.2307 172.89 3.398 1.2402 0.03 0.4535 0.01 77.46 2.38 2.277 0.06 0.006 0.00 38.98 4.209 6155. 663. 573 87 5 377 2 654 582 997 69 208 34 208 811 61 04 44 3500 0.3514 114.73 1.814 1.1094 0.03 0.2767 0.00 71.21 2.04 2.037 0.06 0.003 0.00 33.04 2.404 5217. 379. 299 05 7 331 4 902 543 103 32 122 08 13 275 84 8 2 4000 0.5178 77.775 1.006 0.8257 0.01 0.1570 0.00 59.61 1.57 1.515 0.03 0.002 0.00 31.41 1.294 4961. 204. 65 31 698 8 46 696 5 94 118 42 085 45 12 04 09 5000 0.9411 39.025 0.236 0.6982 0.01 0.0422 0.00 31.87 1.88 1.281 0.02 0.002 0.00 26.58 0.754 4198. 119. 68 9 157 6 25 207 555 9 126 37 074 027 33 5 01 9000 1 51.783 1.044 6.0046 0.14 0.0921 0.01 51.68 7.37 11.06 0.25 0.013 0.00 25.11 3.867 3966. 610. 48 96 7 014 9 303 384 084 466 933 59 33 199 8 83 31

Integrat 109.63 0.560 1.2894 0.01 0.2617 0.00 70.47 0.73 2.368 0.02 0.004 0.00 32.39 0.824 5115. 130. ed 78 19 6 137 5 303 038 48 13 091 33 061 637 22 88 5 132

133

01HODO GL#L1 Weighted average of J from standards = 3.464e- 03 +/- 1.319e-05

Laser Cumul 40Ar/ 37Ar/ 36Ar/ % Ca/ 40*/ Power ative 39Ar +/- 39Ar +/- 39Ar +/- Atm. +/- K +/- Cl/K +/- 39K +/- Age +/- (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 5.3753 0.04 0.2480 0.00 0.0151 0.00 83.15 0.71 0.45 0.00 0.00 0.00 0.900 0.04 5614. 258. 1000 0.2929 7 347 3 228 1 014 043 277 518 419 428 008 88 148 49 09 1.7011 0.00 0.00 0.00 51.67 0.62 0.48 0.00 0.00 0.00 0.807 0.01 5035. 73.1 2000 0.922 6 801 0.2625 142 0.003 004 395 399 174 261 477 003 9 176 85 7 0.04 1.4761 0.01 0.0167 0.00 88.22 1.32 2.71 0.02 0.00 0.00 0.644 0.07 4018. 462. 3000 0.9784 5.4978 521 1 212 4 024 429 464 128 229 613 01 58 428 97 64 15.028 0.21 4.5407 0.06 0.0510 0.00 98.16 1.84 8.35 0.12 0.01 0.00 0.275 0.27 1718. 1737 4000 0.9932 23 51 2 657 9 099 936 295 84 294 029 035 45 863 55 .51 - - 26.195 0.23 4.3122 0.05 0.0988 0.00 110.2 3.99 7.93 0.09 0.00 0.00 2.698 1.04 16923 6599 6000 0.997 28 769 4 034 5 357 8214 823 654 293 992 06 61 744 .79 .73 - - 40.058 0.35 4.3530 0.05 0.00 100.6 2.60 8.01 0.09 0.00 0.00 0.273 1.04 1710. 6539 8000 1 2 173 2 057 0.1376 369 8209 707 183 336 966 092 87 672 32 .76

3.3986 0.01 0.00 0.0088 0.00 76.21 0.44 0.76 0.00 0.00 0.00 0.801 0.01 4995. 102. Integrated 8 348 0.4181 17 1 005 795 097 739 312 482 003 45 619 68 54 133

134

01HODO GL#L2 Weighted average of J from standards = 3.464e- 03 +/- 1.319e-05

Laser Cumul 40Ar/3 37Ar/3 36Ar/3 % Ca/ 40*/ Power ative 9Ar +/- 9Ar +/- 9Ar +/- Atm. +/- K +/- Cl/K +/- 39K +/- Age +/- (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 6.4363 0.03 0.6360 0.00 0.0186 0.00 85.10 0.43 1.16 0.00 0.00 0.00 0.954 0.03 5949 194. 400 0.0667 6 786 4 386 3 01 573 511 757 708 44 011 66 122 .08 25 2.6416 0.01 0.2661 0.00 0.0058 0.00 65.58 0.67 0.48 0.00 0.00 0.00 0.01 5602 119. 900 0.5356 7 264 4 23 7 006 798 721 843 422 465 009 0.899 92 .8 46 1.3994 0.00 0.2660 0.00 0.00 43.61 0.61 0.48 0.00 0.00 0.00 0.772 0.00 4815 61.0 1400 0.8521 2 673 9 151 0.0021 003 3 259 833 277 479 004 49 981 .43 7 2.3302 0.01 0.5346 0.00 0.0053 0.00 67.21 1.20 0.98 0.00 0.00 0.00 0.754 0.02 4703 184. 2000 0.9125 3 79 7 365 8 009 202 434 141 671 495 006 59 967 .93 69 4.8998 0.03 0.9878 0.00 0.0139 0.00 82.72 1.09 1.81 0.01 0.00 0.00 0.841 0.05 5246 345. 3000 0.9522 5 392 9 644 1 018 917 809 391 184 526 007 71 549 .24 37 3.4811 0.04 1.6865 0.01 0.0096 0.00 78.90 1.51 3.09 0.03 0.00 0.00 0.729 0.05 4545 347. 5000 0.9896 2 078 7 799 9 017 159 161 832 31 683 011 07 574 .08 07 8.9133 0.10 1.4438 0.01 0.0290 0.00 95.20 1.45 2.65 0.02 0.00 0.00 0.426 0.13 2661 816. 8000 1 3 168 4 525 2 045 139 381 195 804 746 017 73 097 .64 27

2.6692 0.00 0.4011 0.00 0.00 68.16 0.36 0.73 0.00 0.00 0.00 0.840 0.01 5238 68.0 Integrated 5 738 8 144 0.0062 003 936 356 631 264 483 004 43 045 .28 1 134

135

01HODO GL#L3 Weighted average of J from standards = 3.464e- 03 +/- 1.319e-05

Laser Cumul 40Ar/ 37Ar/ 36Ar/ % Ca/ 40*/ Power ative 39Ar +/- 39Ar +/- 39Ar +/- Atm. +/- K +/- Cl/K +/- 39K +/- Age +/- (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 5.1772 0.04 0.2694 0.00 0.0144 0.00 82.48 0.82 0.49 0.00 0.00 0.00 0.901 0.04 5619 273. 500 0.1461 4 518 1 351 4 018 632 654 442 644 408 009 7 388 .57 04 2.1837 0.01 0.2365 0.00 0.0044 0.00 60.72 0.78 0.43 0.00 0.00 0.00 0.846 0.01 5273 750 0.5065 1 863 1 279 9 007 963 979 404 511 453 008 03 896 .16 118 1.5483 0.00 0.2275 0.00 0.0024 0.00 47.19 1.19 0.41 0.00 0.00 0.00 0.802 0.01 4999 116. 1000 0.772 7 602 8 098 9 006 009 95 765 18 469 006 14 877 .96 81 1.4648 0.00 0.2751 0.00 0.0021 0.00 43.03 0.50 0.50 0.00 0.00 0.00 0.817 0.00 5096 60.1 1250 0.8863 5 875 3 239 7 003 934 831 492 438 489 006 63 967 .4 6 1.8639 0.02 0.3817 0.00 0.0037 0.00 58.81 1.66 0.70 0.00 0.00 0.00 0.755 0.03 4710 210. 1500 0.9351 6 283 2 483 6 01 66 145 059 886 507 01 62 383 .36 62 3.3353 0.03 0.7179 0.00 0.00 76.90 1.62 1.31 0.01 0.00 0.00 0.763 0.05 4761 355. 2000 0.9632 8 891 3 905 0.0088 018 488 382 798 662 517 012 84 708 .56 38 9.7957 0.08 2.0516 0.01 0.0307 0.00 91.39 1.44 3.76 0.03 0.00 0.00 0.841 0.14 5246 895. 3000 0.983 3 658 6 884 8 047 37 593 998 467 654 009 72 392 .31 76 10.419 0.12 4.8319 0.05 0.0340 0.00 92.93 1.15 8.89 0.10 0.01 0.00 0.736 0.12 4589 777. 5000 0.9962 53 567 3 911 3 041 883 195 628 92 133 02 16 483 .24 21 25.086 0.23 3.9930 0.04 0.0812 0.00 94.47 1.46 7.34 0.07 0.01 0.00 1.389 0.37 8651 2319 8000 1 42 828 9 06 2 124 102 83 748 492 508 031 3 34 .15 .56

2.7341 0.00 0.00 0.0064 0.00 69.20 0.39 0.68 0.00 0.00 0.00 0.833 0.01 5192 Integrated 9 987 0.375 168 4 004 459 824 826 309 476 004 08 148 .56 74.1 135

136

GC1-36M GL#1

Weighted average of J from standards = 7.892e-05 +/- 1.911e-06

Laser Cumul 40Ar/3 +/- 37Ar/3 +/- 36Ar/3 +/- % +/- Ca/K +/- Cl/K +/- 40*/3 +/- Age +/- Power ative 9Ar 9Ar 9Ar Atm. 9K (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 500 0.0367 484.19 3.70 1.397 2.46 1.5709 0.02 95.85 1.11 2.565 4.52 0.02 0.00 20.08 5.40 2853 767. 395 727 027 5 105 609 078 84 318 181 207 315 229 .87 07 1000 0.1593 306.72 1.77 0.0638 0.69 0.9206 0.01 88.70 1.05 0.117 1.27 0.02 0.00 34.63 3.24 4918 460. 006 061 4 209 8 201 738 497 13 322 093 494 926 .9 84 1500 0.3247 240.39 1.29 - 0.52 0.6817 0.00 83.82 0.68 - 0.96 0.02 0.00 38.87 1.66 5520 235. 151 258 0.1614 515 9 649 485 187 0.296 335 378 088 445 372 .08 88 4 19 2000 0.4941 185.79 0.88 - 0.46 0.4920 0.00 78.28 0.70 - 0.84 0.02 0.00 40.33 1.34 5726 190. 445 06 0.3287 137 3 49 309 879 0.603 616 41 067 3 262 .87 34 5 06 2500 0.6756 119.32 0.53 - 0.54 0.2631 0.00 65.21 1.07 - 1.00 0.02 0.00 41.48 1.30 5890 185. 425 732 0.4859 749 2 443 055 627 0.891 388 265 074 767 946 .55 62 6 37 3000 0.834 78.588 0.48 0.4677 0.34 0.1285 0.00 48.30 1.41 0.858 0.63 0.02 0.00 40.62 1.15 5768 163. 75 181 8 618 4 38 229 37 59 562 316 054 666 054 .5 1 5000 0.956 67.820 0.34 - 0.33 0.0901 0.00 39.35 1.54 - 0.62 0.02 0.00 41.09 1.08 5834 153. 95 531 0.5402 856 5 353 976 12 0.990 074 227 062 309 024 .62 13 82 9000 1 68.264 1.00 1.9861 1.22 0.1006 0.01 43.33 4.32 3.649 2.25 0.02 0.00 38.72 3.02 5498 429. 22 585 2 661 1 004 222 179 38 699 074 131 132 945 .37 52

Integrat 171.99 0.35 - 0.21 0.4501 0.00 77.36 0.38 - 0.39 0.02 0.00 38.92 0.67 5527 164. ed 186 007 0.0155 565 9 237 21 478 0.028 569 307 03 819 108 .7 07 5 53 136

137

138

01GUNN WR#L2 Weighted average of J from standards = 8.716e-05 +/- 2.113e-07

Laser Cumul 40Ar/3 +/- 37Ar/3 +/- 36Ar/3 +/- % +/- Ca/K +/- Cl/K +/- 40*/3 +/- Age +/- Power ative 9Ar 9Ar 9Ar Atm. 9K (mW) 39Ar meas. meas. meas. 40Ar (ka) (ka) 400 0.0334 733.89 8.92 0.1527 0.01 2.4021 0.04 96.72 1.61 0.28 0.01 0.00 0.00 24.04 11.91 3772 1867 724 982 7 048 6 764 39 961 034 923 447 281 484 586 .85 .75 700 0.1226 379.54 8.05 0.1402 0.00 1.1715 0.03 91.21 1.89 0.25 0.01 0.00 0.00 33.34 7.243 5230 1134 182 769 8 648 407 389 184 742 189 676 134 767 23 .42 .42 1000 0.2593 182.30 2.91 0.1338 0.00 0.4898 0.01 79.40 1.74 0.24 0.00 0.00 0.00 37.54 3.271 5888 512. 687 302 1 424 2 3 147 77 556 778 614 069 996 37 .46 17 1300 0.4039 113.55 2.02 0.1275 0.00 0.2527 0.00 65.78 1.41 0.23 0.00 0.00 0.00 38.84 2.002 6091 313. 926 153 5 447 8 537 513 491 405 82 56 053 749 44 .59 47 1700 0.5581 82.715 1.17 0.1423 0.00 0.1519 0.00 54.27 1.03 0.26 0.00 0.00 0.00 37.80 1.162 5929 182. 55 554 7 363 2 294 847 771 126 667 604 041 903 56 .02 01 2100 0.677 68.786 0.89 0.1511 0.00 0.1015 0.00 43.64 0.85 0.27 0.01 0.00 0.00 38.75 0.883 6077 138. 85 227 8 598 8 202 026 525 743 098 552 033 549 25 .19 27 3000 0.8064 67.637 0.87 0.1585 0.00 0.0967 0.00 42.25 0.82 0.29 0.00 0.00 0.00 39.04 0.861 6122 134. 25 587 3 403 2 191 445 418 091 739 6 022 472 44 .46 85 5000 0.9291 90.981 1.03 0.1770 0.00 0.1779 0.00 57.79 1.15 0.32 0.00 0.00 0.00 38.39 1.234 6020 193. 49 68 9 413 3 362 343 351 497 757 591 044 244 62 .35 28 8000 1 163.30 1.64 0.2015 0.00 0.4223 0.00 76.42 1.43 0.36 0.01 0.00 0.00 38.50 2.454 6037 384. 243 972 1 6 809 075 13 98 101 542 047 397 64 .81 27

Integrat 152.12 0.73 0.1508 0.00 0.3880 0.00 75.37 0.61 0.27 0.00 0.00 0.00 37.45 0.984 5874 154. ed 852 485 1 167 1 347 417 992 674 306 587 022 959 16 .31 74

138

139

Appendix C 40Ar/39Ar on Biotite in Volcanic Clasts

CLASTS Elv. Rock Mine Lithology (m) Type ral Location Integra Plate # MS % of Inverse Suppliment ted au of WD 39Ar Isochron al Name Lat Long Age Age ste Relea Min 40Ar/36/ MS # of Figur (°N) (°W) (Ma) (Ma) ps se Age Ari WD Ste es (Ma) ps ClastX 63.236 145.607 1020 Dacite Biotit Conglome 28.1 ± 28.7 6 1.13 93.7 N/A N/A N/A N/ Ax BI#L1 2 3 e rate 0.2 ± 0.2 out A of 8 Clast41 63.230 145.631 ? Dacite Biotit Conglome 26.6 ± 26.7 10 1.53 98.9 N/A N/A N/A N/ Ax 01 5 6 e rate 0.1 ± 0.1 out A BI#L1 of 12

*Plateau ages of these two samples are on following page and are followed by their raw datasets

*40Ar/39Ar analyses were performed by co-author Dr. Jeffrey A. Benowitz

139

140

141

CLASTX BI#L1

Weighted average of J from standards = 8.775e-05 +/- 2.011e-07

Laser Cumula 40Ar/3 +/- 37Ar/3 +/- 36Ar/3 +/- % +/- Ca/K +/- Cl/K +/- 40*/39 +/- Ag +/- Power tive 9Ar 9Ar 9Ar Atm. K e (mW) 39Ar meas. meas. meas. 40Ar (M (M a) a) 500 0.0176 475.39 22.84 0.1460 0.03 1.5011 0.07 93.31 2.04 0.26 0.06 0.01 0.00 31.791 9.85 5.0 1.5 352 917 6 477 4 896 286 522 802 381 957 596 51 973 2 5 1000 0.0626 278.67 8.620 0.0513 0.01 0.4256 0.02 45.13 2.20 0.09 0.02 0.01 0.00 152.89 7.76 24. 1.2 44 17 6 505 456 247 263 425 761 666 301 102 043 02 1 1500 0.1805 224.46 2.924 0.0274 0.00 0.1233 0.00 16.23 0.75 0.05 0.01 0.01 0.00 187.98 2.99 29. 0.4 22 09 6 75 5 597 958 894 038 376 721 14 926 572 49 7 2000 0.3207 207.68 2.609 0.0147 0.00 0.0718 0.00 10.21 0.81 0.02 0.00 0.01 0.00 186.44 2.89 29. 0.4 813 7 2 504 2 577 877 199 701 925 596 129 023 251 24 5 2500 0.4462 199.41 3.339 0.0320 0.00 0.0548 0.00 8.131 0.71 0.05 0.01 0.01 0.00 183.17 3.39 28. 0.5 258 99 9 925 7 492 33 767 889 697 78 116 456 183 74 3 3000 0.5536 194.63 2.964 0.0416 0.00 0.0465 0.00 7.072 0.90 0.07 0.01 0.01 0.00 180.84 3.27 28. 0.5 495 65 3 932 9 599 91 338 639 711 595 133 631 303 37 1 5000 0.843 192.34 1.300 0.0592 0.00 0.0341 0.00 5.251 0.33 0.10 0.00 0.01 0.00 182.21 1.39 28. 0.2 096 8 471 9 218 35 398 863 865 905 061 995 695 59 2 9000 1 191.23 2.695 0.0227 0.00 0.0359 0.00 5.552 0.69 0.04 0.01 0.01 0.00 180.58 2.86 28. 0.4 177 19 703 3 45 62 156 165 29 815 086 824 989 33 5

Integrat 208.10 1.016 0.0393 0.00 0.0976 0.00 13.85 0.28 0.07 0.00 0.01 0.00 179.24 1.05 28. 0.1 ed 499 91 8 274 205 954 301 226 504 767 042 199 942 12 8

Table 2 Datatables of Volcanic Clasts dated with 40Ar/39Ar Geochronology

141

142

C4101 BI#L1

Weighted average of J from standards = 8.775e-05 +/- 2.011e-07

Laser Cumul 40Ar/3 +/- 37Ar/3 +/- 36Ar/3 +/- % +/- Ca/K +/- Cl/K +/- 40*/39 +/- Ag +/- Power ative 9Ar 9Ar 9Ar Atm. K e (mW) 39Ar meas. meas. meas. 40Ar (M (M a) a) 500 0.0051 947.87 56.98 0.0717 0.10 3.0105 0.19 93.85 2.52 0.13 0.19 0.01 0.00 58.252 24.22 9.1 3.8 624 929 4 476 777 45 568 164 223 241 858 86 079 9 1 1000 0.0112 818.71 39.84 0.2239 0.07 2.4103 0.12 86.99 1.75 0.41 0.13 0.00 0.00 106.47 15.26 16. 2.3 556 65 1 461 685 626 214 091 694 782 81 664 6 76 9 1500 0.0285 217.27 5.459 0.0091 0.02 0.1338 0.02 18.20 3.28 0.01 0.05 0.01 0.00 177.69 8.419 27. 1.3 933 33 4 956 5 437 634 385 676 424 972 245 757 99 88 1 2000 0.0527 201.89 3.154 0.0296 0.02 0.0751 0.01 10.99 1.97 0.05 0.03 0.01 0.00 179.68 4.873 28. 0.7 962 26 8 087 352 218 138 445 829 61 205 377 13 19 6 2500 0.09 190.96 2.451 0.0312 0.01 0.0611 0.00 9.464 1.37 0.05 0.03 0.01 0.00 172.86 3.439 27. 0.5 501 97 3 688 6 892 3 503 73 097 959 116 843 47 13 4 3000 0.1345 182.50 2.899 0.0551 0.01 0.0490 0.00 7.942 1.41 0.10 0.02 0.01 0.00 167.98 3.711 26. 0.5 48 25 177 6 876 55 232 111 16 8 148 847 47 37 8 3500 0.1855 187.43 2.403 0.0562 0.00 0.0470 0.00 7.415 0.74 0.10 0.01 0.01 0.00 173.51 2.633 27. 0.4 203 22 4 786 4 479 04 994 32 442 949 121 327 63 23 1 4000 0.2693 181.22 2.320 0.0472 0.00 0.0330 0.00 5.384 0.45 0.08 0.00 0.01 0.00 171.44 2.347 26. 0.3 1 41 8 516 3 283 59 652 675 947 74 09 062 73 91 7 4500 0.4154 174.99 0.828 0.0426 0.00 0.0223 0.00 3.775 0.35 0.07 0.00 0.01 0.00 168.36 1.016 26. 0.1 386 92 3 269 7 212 68 783 822 495 768 061 314 31 43 6 5000 0.6142 175.52 1.468 0.0526 0.00 0.021 0.00 3.533 0.19 0.09 0.00 0.01 0.00 169.30 1.460 26. 0.2 562 86 5 285 118 29 673 66 523 649 047 143 42 58 3 6000 0.952 176.05 0.766 0.0410 0.00 0.0189 0.00 3.183 0.15 0.07 0.00 0.01 0.00 170.42 0.791 26. 0.1 831 96 9 167 8 092 82 347 54 306 6 027 913 78 75 2 9000 1 174.32 1.961 0.0529 0.01 0.0317 0.00 5.373 1.52 0.09 0.02 0.01 0.00 164.93 3.241 25. 0.5 103 73 8 259 1 9 44 409 721 31 706 121 207 51 9 1

Integrat 186.76 0.544 0.0461 0.00 0.0591 0.00 9.363 0.18 0.08 0.00 0.01 0.00 169.25 0.602 26. 0.1

ed 133 57 8 178 8 117 73 331 474 327 691 023 21 18 57 1 142

143

Appendix D 40Ar/39Ar on Detrital Biotite

26HODO, 05HODO, 33HODO Detrital BI Weighted average of J from standards = 3.377e-03 +/- 8.438e-06 MMHB-1 523.5 Grai +/- 37Ar/3 +/- 36Ar/3 +/- % +/- Ca/K +/- Cl/K +/- 40*/39 +/- Age +/- n # 9Ar 9Ar Atm. K meas. meas. 40Ar (Ma) (Ma)

1 12.009 - 0.30 0.1654 0.07 72.981 30.138 - 0.56 - 0.01 18.105 20.485 106. 117. 26HOD 73 0.2721 826 6 425 5 03 0.499 54 0.003 579 87 81 95 49 O-BI 8 32 08 2 641.05 1.9862 4.91 - 3.83 174.71 41.305 3.649 9.04 - 0.12 325.03 512.27 1335 1486 26HOD 963 5 464 2.5679 584 797 62 61 303 0.050 681 199 399 .03 .22 O-BI 12 3 0.0560 0.0161 0.00 0.0427 0.00 74.293 1.9902 0.029 0.00 0.002 0.00 4.3695 0.3391 26.4 2.03 26HOD 2 8 361 4 115 86 2 69 663 04 019 4 9 O-BI 4 0.8503 0.0362 0.02 0.1204 0.00 78.460 3.9859 0.066 0.04 0.028 0.00 9.7718 1.8208 58.5 10.7 26HOD 8 694 6 648 02 9 57 943 61 165 7 3 1 3 O-BI 5 0.0486 0.0189 0.00 0.0214 0.00 57.741 1.3529 0.034 0.00 0.001 0.00 4.6421 0.1503 28.0 0.9 26HOD 2 8 117 7 051 39 1 83 214 98 008 4 2 3 O-BI 6 0.4662 0.1835 0.01 0.1535 0.00 79.623 3.0381 0.336 0.02 0.024 0.00 11.607 1.7344 69.2 10.1 26HOD 3 5 63 3 598 88 8 83 992 21 089 68 3 9 6 O-BI 7 0.0616 0.0166 0.00 0.0630 0.00 74.613 1.0340 0.030 0.00 0.007 0.00 6.3367 0.2599 38.1 1.55 26HOD 8 2 336 3 087 19 4 49 617 47 018 4 9 6 O-BI 8 0.1084 0.0247 0.00 0.0413 0.00 70.177 2.4887 0.045 0.01 0.001 0.00 5.1919 0.4353 31.3 2.6 26HOD 2 7 579 5 148 14 45 063 27 021 7 2 O-BI 9 2.7451 0.1248 0.09 0.1889 0.01 76.630 7.6112 0.229 0.16 0.034 0.00 17.023 5.5989 100. 32.2 26HOD

9 2 129 2 988 18 2 05 753 61 344 51 6 73 2 O-BI 143

144

10 0.0726 0.0491 0.00 0.0281 0.00 57.847 2.6042 0.090 0.00 0.002 0.00 6.0648 0.3765 36.5 2.25 26HOD 7 7 493 8 127 46 3 23 905 63 022 6 9 4 O-BI 11 0.0600 0.0235 0.00 0.0463 0.00 77.747 1.3822 0.043 0.00 0.006 0.00 3.9205 0.2441 23.7 1.47 26HOD 1 8 337 6 084 67 6 27 618 88 019 6 O-BI 12 0.0422 0.0330 0.00 0.0428 0.00 77.550 1.8850 0.060 0.00 0.008 0.00 3.6601 0.3078 22.1 1.85 26HOD 4 6 321 104 74 3 66 589 15 021 9 1 4 O-BI 13 0.1351 0.0189 0.01 0.0395 0.00 77.932 6.7712 0.034 0.02 0.002 0.00 3.3086 1.0173 20.0 6.12 26HOD 7 485 5 343 92 8 69 724 8 054 2 2 O-BI 14 0.0526 0.0178 0.00 0.0321 0.00 67.484 2.813 0.032 0.00 0.002 0.00 4.5735 0.3963 27.6 2.38 26HOD 8 2 409 3 134 11 7 751 07 027 8 4 2 O-BI 15 0.1567 - 0.01 0.0328 0.00 67.002 5.8691 - 0.02 0.020 0.00 4.7760 0.8532 28.8 5.11 33HOD 5 0.0064 438 2 288 26 5 0.011 638 3 075 9 1 3 O-BI 7 87 16 0.1308 0.0313 0.01 0.0292 0.00 71.174 8.1939 0.057 0.03 0.001 0.00 3.4973 0.9963 21.1 5.99 33HOD 6 7 904 3 337 07 6 55 494 13 062 1 5 6 O-BI 17 12.598 0.9254 0.18 0.8458 0.06 101.27 5.3661 1.699 0.33 0.038 0.00 - 13.248 - 81.5 33HOD 3 1 339 5 211 469 1 1 693 58 896 3.1470 61 19.2 O-BI 6 6 18 0.0947 0.0450 0.00 0.0532 0.00 76.537 2.3741 0.082 0.01 0.004 0.00 4.8198 0.4884 29.1 2.92 33HOD 8 4 923 2 167 32 2 65 693 15 031 2 4 O-BI 19 38.568 1.0428 1.73 0.2155 0.30 83.602 113.07 1.914 3.18 0.028 0.05 12.486 86.488 74.4 505. 33HOD 86 3 582 7 852 54 536 87 969 5 697 18 32 3 06 O-BI 20 235.34 4.0047 1.79 2.7011 0.84 102.12 8.7962 7.368 3.30 0.088 0.04 - 69.087 - 445. 33HOD 843 8 575 688 9 91 306 2 915 16.663 56 104. 53 O-BI 4 38 21 0.2457 0.0574 0.01 0.0768 0.00 87.472 3.0653 0.105 0.02 0.000 0.00 3.2508 0.7963 19.6 4.79 33HOD 6 3 573 3 278 43 8 39 887 73 047 9 8 O-BI 22 423.33 1.2182 2.03 2.0821 1.11 73.204 13.636 2.237 3.73 - 0.06 225.37 161.54 1019 558. 33HOD 811 4 469 8 792 6 78 22 98 0.013 955 195 02 .88 23 O-BI 98 23 3.5386 0.5056 0.09 0.3994 0.01 95.570 3.8603 0.928 0.16 0.121 0.00 5.4711 4.7719 32.9 28.5 33HOD 4 2 9 972 62 2 11 893 98 498 7 1 9 1 O-BI 24 2.4425 0.2246 0.05 0.3884 0.01 81.188 2.6668 0.412 0.09 0.098 0.00 26.592 3.7989 154. 21.2 33HOD 5 7 192 44 53 1 31 53 33 278 83 6 98 1 O-BI 25 0.1983 0.0757 0.01 0.1007 0.00 90.473 2.9394 0.139 0.02 0.015 0.00 3.1355 0.9678 18.9 5.83 33HOD

6 7 13 9 333 3 4 03 074 78 08 8 1 8 O-BI 144

145

26 0.2836 0.0686 0.01 0.1584 0.00 87.926 1.4964 0.126 0.01 0.005 0.00 6.4275 0.7977 38.7 4.75 05HOD 4 7 018 2 281 3 3 01 868 33 035 4 9 O-BI 27 40.629 1.1444 0.29 1.5593 0.13 92.185 2.5092 2.101 0.53 0.028 0.00 39.086 12.952 223. 69.6 05HOD 57 3 01 9 362 3 7 57 315 43 737 42 25 43 3 O-BI 28 884.10 2.6594 2.46 6.3328 2.76 91.878 4.1139 4.888 4.53 0.406 0.18 165.71 110.66 800. 431. 05HOD 504 3 487 6 364 26 3 88 973 24 713 397 975 94 84 O-BI 29 354.63 8.3897 1.18 10.220 1.19 98.610 1.3953 15.48 2.20 0.108 0.02 42.784 43.275 243. 230. 05HOD 496 9 969 3 226 99 3 586 902 38 284 01 91 2 12 O-BI 30 0.0579 0.0141 0.00 0.0424 0.00 82.450 1.4698 0.026 0.00 0.000 0.00 2.6684 0.2239 16.1 1.35 05HOD 1 8 395 3 077 08 4 03 724 11 013 2 3 7 O-BI 31 1.6017 0.3728 0.02 0.6038 0.00 97.116 0.6168 0.684 0.04 0.020 0.00 5.2976 1.1360 31.9 6.79 05HOD 9 716 5 641 99 7 22 986 87 091 1 7 6 O-BI

Table 3 Datatable for 40Ar/39Ar Analysis of Detrital Biotite

145

146

Appendix E U-Pb Detrital Zircon Sample List for the McCallum Formation

Sample Member Geographic Location GPS Location Names

PHE-02-6.8 Upper Member East of Phelan Creek, AK N63° 12' W148° 32' 20.1" 24.3" CALL03- Upper Member McCallum Creek, AK N63° 13' W 145° 37' 88m* 29.28" 5.1" CALL03- Upper Member McCallum Creek, AK N 63° 13' W 145° 37' 60m* 27.5" 21" CALL03- Upper Member McCallum Creek, AK N 63° 13' W 145° 37' 30m* 44.04" 43.68" 061414- Upper Member McCallum Creek, AK N 63° W145° 36' WKA-01 14'18.2" 13.4" 060514- Contact b/w West of Phelan Creek, AK N 63° W145°33'36. WKA-01 members 12'48.4" 9" PHE-01-37 Lower Member West of Phelan Creek, AK N W145° 63°12'46.37 33'05.6" " CALL-02-11 Lower Member Tributary of McCallum N W145°37'09. Creek, AK 63°13'53.6" 8" PROP-01- Lower Member Hoodoo Creek, AK N W145°26'18. 21.5 63°13'9.3" 4" GC1-1m Gun Creek Along Tributary of Gunn N 63° 12' W 145° 21' Creek, AK 24.6" 39.3" GC2-4.5m Gun Creek West side of Gulkana N 63° 13' W 145° 19' Glacier 3.6" 6.96" HP2-171m Volcaniclastic Hoodoo Pass, AK N 63° 12' W 145° 24' 33.7" 6.8"

* Sample analyzed at Washington State University