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Sediment Supply to the South China Sea as Recorded by Sand Composition at IODP

Expedition 367/368 Sites U1499 and U1500

Thesis

Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in

the Graduate School of The Ohio State University

Caroline Mae Robinson, B.S.

Graduate Program in Earth Sciences

The Ohio State University

2018

Thesis Committee

Dr. Lawrence Krissek, Advisor

Dr. Derek Sawyer

Dr. William Ausich

Copyrighted by

Caroline Mae Robinson

2018

Abstract

IODP Expeditions 367/368 drilled the northern rifted margin of the South China

Sea (SCS) basin to investigate the timing and mechanisms of its rifting history and to explore its sediment source-to-sink processes. This study examines the mineral composition of sand intervals recovered from two adjacent sites drilled during these expeditions, in order to contribute to understanding these aspects of the evolution of the

SCS basin. The sand mineral assemblages at these two sites were interpreted in the context of sand mineral assemblages derived from major sources surrounding the SCS to evaluate the history of sediment supply and the patterns of sand transport throughout the mid-late Cenozoic. Mineral distributions in sand intervals throughout Sites U1499 and

U1500 also help to distinguish between rifting models hypothesized for this basin.

Sixty-nine samples of medium- to coarse-grained sand and sandstone intervals from Sites U1499 and U1500 were analyzed petrographically. The two sites contain similar lithostratigraphic successions, although unit boundaries occur at different depths.

Moving downcore, these units include clay; silty sand with clay and siltstone interbeds; claystone; calcareous-rich claystone; and sandstone. The base of Site U1499 contained sandstone with polymict clasts and matrix-supported breccia, overlying sandstone cobbles.

At Site U1499, thin sections from the cobble lithologic unit contain an average framework composition of Q18F74L8; shallower samples are more quartz-rich (average framework composition of Q54F38L8), and some intervals are enriched in mica. Most rock fragments in the cobble interval at Site U1499 are volcanic in origin, whereas the majority of rock fragments in the shallower sediments are plutonic.

At Site U1500, thin sections contain an average framework grain composition of

Q53F42L5, with limited variability. The majority of rock fragments shifts slightly at Site

U1500 from more metamorphic rock fragments to more sedimentary rock fragments up section. The framework grain composition of the upper sediments recovered at Site

U1499 is similar to that of the sands at Site U1500, suggesting similar sediment sources for those lithologic units.

The upcore shift from plagioclase-rich gravels to quartz-rich sands suggests a change from more proximal to more distal sediment sources. The plagioclase-rich gravels at Site U1499 may record input from granitoid basement rock in southern mainland China, from continental crust exposed during rifting, or from a local basement high formed as a result of rifting. The cobble unit also may have been deposited by a locally sourced gravity flow, based on its limited geographic distribution. The younger sediments may have been supplied by more quartz-rich sediments from the Pearl River or from mica-rich metamorphic basement rocks in Taiwan, which was uplifted during the late Miocene/early Pliocene by collision of the Luzon Arc with the Eurasian Plate.

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Dedication

This project would not have been possible without the endless support from family and friends. I would like to dedicate my thesis to my late mother, Carol Robinson. Although she was not physically here to watch it all happen, I could not have completed this work without the values of hard work, dedication, persistence, and passion she instilled in me during her time on Earth. I will continue to work hard every day to honor her legacy and make her proud.

Acknowledgments

I would first like to thank my Dad for his unending encouragement and support and a huge thanks to my entire family for driving up to Ohio to visit numerous times. I would like to thank my boyfriend, Chris Gates, for visiting me in Columbus often and for always being there for me. I would also like to thank everyone at the School of Earth

Sciences for making my experience at OSU so enjoyable. I would like to thank USSSP for the post expedition award that was used to fund this research as well as Friends of

Orton Hall that allowed me to present my masters research at both GSA and AGU.

I would especially like to thank my thesis advisor, Dr. Larry Krissek, for giving me the opportunity to obtain my master’s degree and study sedimentology under his guidance at Ohio State University. Thank you for helping me apply and encouraging me to sail on IODP Expedition 367, which will always be one of the most amazing and rewarding adventures of my life. It has been a great privilege to work with Larry and I will miss our conversations about all things sports. I would also like to thank Dr. Mike

Barton for all of his help and guidance identifying minerals in thin section and for serving on my committee for most of my time at OSU. A huge thanks to Dr. Bill Ausich for not only giving me a spot to work in his air-conditioned lab but also for stepping up to be on my committee. I would also like to thank Dr. Derek Sawyer for being on my committee and for his guidance.

Vita

2012……………………………………Ocean Lakes High School

2016……………………………………B.S. Geology, James Madison University

2017……………………………………Sedimentologist on IODP Expedition 367/368

2016 to present…………………………Graduate Teaching Associate, School of Earth

Sciences, The Ohio State University

Publications

Larsen, H.C., Mohn, G., Nirrengarten, M., Sun, Z., Stock, J., Jian, Z., Klaus, A., et al. (2018). Rapid transition from continental breakup to igneous oceanic crust in the South China Sea. Nature Geoscience, 11(10), 782-789. https://doi.org/10.1038/ s41561-018-0198-1 Sun, Z., Jian, Z., Stock, J.M., Larsen, H.C., Klaus, A., Alvarez Zarikian, C.A., and the Expedition 367/368 Scientists. (2018). South China Sea Rifted Margin. Proceedings of the International Ocean Discovery Program, 367/368: College Station, TX (International Ocean Discovery Program). https://doi.org/10.14379/ iodp.proc.367368.2018 Sun, Z., Stock, J., Klaus, A., and the Expedition 367 Scientists. (2018). Expedition 367 Preliminary Report: South China Sea Rifted Margin. International Ocean Discovery Program. https://doi.org/10.14379/iodp.pr.367.2018

Fields of Study

Major Field: Earth Sciences

Table of Contents

Abstract ...... ii Dedication ...... iv Acknowledgments...... v Vita ...... vi List of Tables ...... ix List of Figures ...... x Chapter 1. Introduction ...... 1 Chapter 2. Geologic Setting ...... 6 Geologic Summary of the South China Sea Basin ...... 6 Tectonic Overview of the South China Sea ...... 6 Rifting Models for the South China Sea ...... 10 Sources of Sediment ...... 15 The Pearl River and Southern Mainland China ...... 16 Taiwan...... 28 The Philippines ...... 31 The Red River and Vietnam ...... 35 The Mekong River and the Indochina Peninsula ...... 37 Borneo ...... 39 Oceanography and Paleoceanography ...... 41 Chapter 3. Study Region and Site Descriptions ...... 44 Study Region ...... 44 Operations and Lithostratigraphy at Sites U1499 and U1500 ...... 47 Downhole Logging Measurements at Sites U1499 and U1500 ...... 53 Chapter 4. Materials & Methods ...... 57 Materials ...... 57 Methods...... 59

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Chapter 5. Data ...... 70 Grain Size Effect on Sample Composition ...... 70 Stratigraphic Variations in Sediment Composition ...... 77 Quartz, Feldspar, and Rock Fragment Abundances ...... 77 Comparison of Framework Grain and Lithic Grain Assemblages, Site U1499 ...... 83 Lithic Grain Composition ...... 86 Documentation of Grain Types ...... 87 Stratigraphic Variations in Lithic Grain Assemblages ...... 95 Documentation of Lithic Grain Types ...... 97 Detailed Analysis of Quartz and Feldspar Framework Grains ...... 100 Comprehensive Summary of Stratigraphic Changes in Sediment Composition ...... 102 Chapter 6. Discussion ...... 110 Overall Stratigraphic Trends and Provenance Interpretations ...... 110 Implications for Correlation between Sites U1499 and U1500 ...... 123 Implications for Rifting Models...... 125 Implications for the Depositional Process of Basal Sediments at Site U1499 ...... 127 Next Steps ...... 128 Chapter 7. Conclusions ...... 130 Bibliography ...... 134 Appendix A. Sample Description Table for Site U1499 ...... 142 Appendix B. Sample Description Table for Site U1500 ...... 156 Appendix C. Raw Data from Point Counting at Sites U1499 and U1500. See Table 4 in Chapter 3 for definition of parameter abbreviations...... 160 Appendix D. Comments from thin section descriptions ...... 173 Appendix E. Calculated parameters for each sample at Site U1499. See Table 4 in Chapter 3 for definition of parameter abbreviations...... 193 Appendix F. Calculated parameters for each sample at Site U1500. See Table 4 in Chapter 3 for definition of parameter abbreviations...... 198

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List of Tables

Table 1. Summary of published literature on sand and clay mineralogy in landmasses and rivers surrounding the SCS basin...... 17 Table 2. Summary of samples selected from Site U1499...... 58 Table 3. Summary of samples selected from Site U1500...... 60 Table 4. Counted parameters list the compositional categories grains were placed into while point counting. Calculated parameters list calculations made for analysis of the point counting data...... 64 Table 5. Reproducibility results from 3 different samples showing similar mineral compositions...... 67 Table 6. Average and standard deviation calculations of framework grains in duplicate samples...... 68 Table 7. Grain composition as a function of grain size. Part A shows the data for Site U1499 and Part B shows the data for Site U1500...... 74 Table 8. Grain composition as a function of grain size for Site U1499 separated by upper sediment and basal sediment. Part A shows the data for the upper sediments in lithostratigraphic units I-VII. Part B shows the data for the basal sediments in lithostratigraphic units IXA and IXC...... 78 Table 9. The average framework grain composition and lithic grain distribution for LSUs at Sites U1499 and U1500. Part A compares the average composition of framework grains between upper sediments in LSUs I-VII and basal sediments in LSUs IXA and IXC at Site U1499. Part B compares the average composition of framework grains between each LSU at Site U1500...... 80 Table 10. The average framework grain composition and lithic grain distribution for each lithostratigraphic unit at Site U1499...... 85

List of Figures

Figure 1. Site map of the South China Sea showing all the drill sites for Expeditions 367 & 368 (designated by black dots)...... 2 Figure 2. Two magma-poor rifted margin models modified from Huismans and Beaumont (2011). Part A represents a type I rifted margin and part B represents a type II rifted margin...... 12 Figure 3. Map of the South China Sea basin and surrounding landmasses. Numbered red boxes indicate study areas discussed in this section and correlate with Table 1...... 22 Figure 4. Summary of published framework grain compositions in landmasses and rivers surrounding the SCS basin...... 23 Figure 5. Geologic map of southern mainland China, Taiwan, and the Luzon Arc. Shapefile Downloaded from the U.S. Geological Survey...... 24 Figure 6. Summary of drilling operations for Sites U1499 and U1500. Drilling operations affect the quality of sediment core recovery (Modified from Larsen et al., 2018b)...... 48 Figure 7. Simplified summary of sediment lithologies and lithostratigraphic units at Sites U1499 and U1500 (Modified from Sun et al., 2018b)...... 50 Figure 8. Downhole logging data for Site U1499B...... 55 Figure 9. Downhole logging data for Site U1500B...... 56 Figure 10. Framework grain composition for all data samples categorized by average grain size. The left triangle represents Site U1500 samples and the right triangle represents Site U1499 samples...... 72 Figure 11. Framework grain composition for Site U1499 samples categorized by average grain size. The left triangle represents the basal sediments in lithostratigraphic units IXA and IXC. The right triangle represents the upper sediments in lithostratigraphic units I- VII...... 76 Figure 12. Quartz, feldspar, and lithic grain abundances for all samples. The left triangle represents samples from Site U1500 categorized by lithostratigraphic units. The right triangle represents samples from Site U1499 divided into upper sediments and basal sediments...... 79 Figure 13. Quartz, feldspar, and lithic composition of Site U1499 upper sediments categorized by lithostratigraphic unit...... 84 Figure 14. Photomicrographs from the upper section of Site U1499 (See Table 4 for definition of parameter abbreviations). Part A. Quartz and feldspar minerals in U1499A- 4H-6 (104-106 cm); Part B. Weathered plagioclase, potassium feldspar, and quartz in U1499A-4H-6 (104-106 cm); Part C. MRF, quartz, and feldspar grains in U1499A-4H-6 (104-106 cm); Part D. Abundance of quartz grains in U1499A-6H-2 (82-84 cm); Part E. Quartz and plagioclase in U1499A-29X-1 (53-55 cm); Part F. Carbonate grain, quartz x grains and a quartzite grain in U1499A-54X-CC (15-17 cm); Part G. Abundant mica and one SRF grain in U1499A-57X-CC (31-33 cm); Part H. Calcite cement with mica, feldspars, and quartz minerals in U1499B-4R-CC (5-7 cm); Part I. Feldspar, quartz, carbonate, and a few SRF grains in U1499B-12R-1 (34-36 cm)...... 88 Figure 15. Photomicrographs of basal unit at Site U1499 (See Table 4 for definition of parameter abbreviations). Part A. VRF and plagioclase grains in U1499B-36R-1 (89-93 cm); Part B. Quartz and weathered plagioclase grains in U1499B-34R-1 (0-6 cm); Part C. MRF, inclusion filled quartz and plagioclase in U1499B-36R-1 (89-93 cm); Part D. Quartz overgrowth and plagioclase in U1499B-33R-2 (27-33 cm); Part E. Weathered plagioclase grain in U1499B-34R-1 (0-6 cm); Part F. Plagioclase showing the variation in alteration in U1499B-36R-1 (89-93 cm); Part G. Very coarse sand to granule sized plutonic rock fragment in U1499B-39R-1 (30-35 cm); Part H. Matrix within the cobbles, abundance of plagioclase, and quartz vein in U1499B-34R-1 (0-6 cm); Part I. MRF and tattered matrix in U1499B-40R-1 (43-47 cm)...... 91 Figure 16. Photomicrographs of Site U1500 grains (See Table 4 for definition of parameter abbreviations). Part A. MRF, glauconite, quartz and feldspar minerals in U1500B-54R-1 (25-27 cm); Part B. Calcite matrix and abundance of quartz grains in U1500B-54R-1 (25-27 cm); Part C. Abundance of glauconite and quartz in U1500B-54R- 1 (25-27 cm); Part D. Polycrystalline quartz, monocrystalline quartz and plagioclase in U1500B-54R-1 (25-27 cm); Part E. Mica filled in with glauconite, polycrystalline quartz and monocrystalline quartz in U1500B-54R-1 (25-27 cm); Part F. Abundance of plagioclase and quartz minerals and a SRF in U1500A-20R-CC (8-10 cm)...... 94 Figure 17. Part A shows the lithic grain composition at Site U1499. Part B represents the lithic grain composition at Site U1500...... 96 Figure 18. Thin section and grain mount photomicrographs of lithic grains (See Table 4 for definition of parameter abbreviations). Part A. Volcanic rock fragment in U1499B- 39R-1 (30-33 cm); Part B. Coarse sand sized plutonic rock fragment in U1499B-39R-1 (30-33 cm); Part C. Siltstone rock fragment in U1499B-34R-1 (0-6 cm); Part D. Volcanic rock fragment in U1499B-34R-1 (0-6 cm); Part E. Metamorphic rock fragment in U1499B-39R-1 (30-33 cm); Part F. Volcanic rock fragment in U1499B-36R-1 (89-92 cm); Part G. Metamorphic rock fragment in U1499A-54X-CC (15-17 cm); Part H. Very fine sandstone to siltstone rock fragments in U1499A-57X-CC (31-33 cm); Part I. Chert rock fragments in U1499A-4H-6 (104-106 cm)...... 98 Figure 19. Monocrystalline quartz, potassium feldspar, and plagioclase feldspar ternary diagrams for Sites U1499 and U1500. The triangle on the left represents data from Site U1500 categorized by lithostratigraphic unit. The triangle on the right represents data from Site U1499 comparing upper and basal sediments...... 101 Figure 20. Monocrystalline quartz, potassium feldspar, and plagioclase feldspar composition of Site U1499 upper sediments categorized by lithostratigraphic unit...... 103 Figure 21. Downhole plot of framework grain mineralogy and lithic grain composition at Site U1499. Each dot represents data collected from one thin section...... 105 Figure 22. Downhole plot of mica and glauconite composition at Site U1499. Each dot represents data collected from one thin section...... 106

Figure 23. Downhole plot of framework grain mineralogy and lithic grain composition with depth at Site U1500. Each dot represents data collected from one thin section. .... 107 Figure 24. Downhole plot of mica and glauconite composition at Site U1500. Each dot represents data collected from one thin section...... 108 Figure 25. QFL ternary diagram with provenance fields from Dickinson (1985) and Marsaglia & Ingersoll (1992) and all data from Site U1499...... 112 Figure 26. QFL ternary diagram with provenance fields from Dickinson (1985) and Marsaglia & Ingersoll (1992) and all data from Site U1500...... 113 Figure 27. Lithic grain ternary diagram with provenance fields from Ingersoll & Suczek (1979). Part A shows all the lithic composition data from Site U1499. Part B shows all the lithic composition data from Site U1500...... 115 Figure 28. QmKP ternary diagram of Site U1499 data with provenance fields from Marsaglia & Ingersoll (1992)...... 117 Figure 29. QFL ternary diagram of sandstones from landmasses and rivers surrounding the SCS; data acquired from published literature listed in Table 1 from Chapter 2. The dark blue circles represent the two clusters of data analyzed in this study from Site U1499 (represented in Figure 12)...... 119

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Chapter 1. Introduction

International Ocean Discovery Program (IODP) Expeditions 367 and 368 were conducted to further understand the formation of the South China Sea (SCS) basin and to better constrain the timing and mechanisms of tectonic events that led to rifting (Sun et al., 2016b). Both expeditions were focused in the northern margin of the eastern subbasin of the South China Sea, and drilling was done on four structural highs within the continent-ocean transition (Figure 1). Previous drilling in this area of the South China Sea

(conducted by Ocean Drilling Program Leg 184 and IODP Expedition 349) was unsuccessful in recovering syn-rift and post-rift sediments that would support a better understanding of magma-poor rifted margins and constrain rifting models (Sun et al.,

2016b). As a result, the goal of Expeditions 367/368 was to recover syn-rift sediment and underlying basement in the continent-ocean transition to better understand magma-poor rifted margins and the rifting mechanism that formed the South China Sea (Sun et al.,

2016b). The South China Sea basin serves as a unique and accessible location to reach those goals for several reasons: it has a relatively thin post-rift sedimentary section; previous drilling and seismic imaging was completed in the area; it has a young age of rifting compared to other well-known margins (the SCS basin formed during the mid- to late Cenozoic and rifted from the early Eocene to the early Oligocene); it is a slow to intermediate spreading rate; and it has potential to provide evidence of lithospheric

China Pearl River Taiwan

Hong Kong Myanmar Red River Laos Hainan

Luzon

Thailand Mekong South China Sea River Cambodia Philippines Vietnam

Malaysia Sarawak

Borneo Sumatra

Indonesia

Java

Figure 1. Site map of the South China Sea showing all the drill sites for Expeditions 367

& 368 (designated by black dots).

2 thinning and exhumed mantle due to rifting in a magma-poor system (Sun et al., 2016b).

The sources and transport paths of clay minerals in the South China Sea have been well documented following previous expeditions in the area because the proximal location of the South China Sea makes it a good region to directly study sediment source- to-sink relationships (Liu et al., 2016; Schroeder, Wiesner, & Liu, 2015). Although several studies have investigated the fine-grained component of the South China Sea stratigraphic record, the medium to coarse sand size fraction has not been well studied and is also important because provenance signals may vary in different grain sizes

(James, DeVaughn, & Marsaglia, 2007). Clay minerals account for less than 50% of the total sediment in the South China Sea, so the mineralogy of the majority of the sediment in this basin has been overlooked in most of the previous provenance studies (Wei et al.,

2012).

The sediments deposited in the South China Sea are transported by surface and deep water currents after having been supplied both by major rivers entering the basin, such as the Pearl River and the Red River, and from landmasses partially separating the

South China Sea from the Pacific Ocean, such as Taiwan, Luzon, and South China (Liu et al., 2008b). The present chemical and mineralogic compositions of sediments supplied by rivers entering the South China Sea are potentially different from the characteristics of those supplied during the geologic past due to changes in exposed landmasses, climate, and land use (Clift, 2016). The complex tectonic history of the South China Sea region, which includes collisions, uplift, and tilting, has also changed the paths and drainage patterns of surrounding rivers since the formation of the basin. Although these changes

3 complicate provenance interpretations, understanding sediment transport and deposition in the South China Sea will help to interpret the evolution of weathering patterns, drainage, and paleogeography throughout the Cenozoic (Clift, 2016).

The purpose of this study is to use the mineral composition of medium- to coarse- grained sand intervals at IODP Expedition 367/368 Sites U1499 and U1500 to better understand the records of sediment provenance and sediment transport carried in sediments of the South China Sea. Sand fraction mineral assemblages derived from major sources surrounding the South China Sea will be compared to the sand fraction mineral assemblages at these two sites to evaluate the history of sediment supply and potential sediment mixing, as well as the patterns of sand transport throughout the mid-late

Cenozoic. This study addresses three main questions: how the mineral composition of sand intervals changes through the stratigraphic section and why; what source regions contributed to the sand assemblages that are present; and what history of Cenozoic tectonic activity in the region (collision, rifting and uplift) is recorded by the sand assemblages.

This study also contributes to meeting some of the primary objectives of IODP

Expedition 367/368, which were to distinguish between rifting models for the SCS basin, constrain the mechanism of plate rupture and spreading, and further understand the development of Southeast Asia associated with the SCS basin during the Cenozoic (Sun et al., 2016b). The mineralogy of the sediment within the basin reflects the exposed land that was eroded at that time, providing insight into the configuration of the basin during the Cenozoic. For example, evidence of serpentinite within the sediment record overlying

4 basement rock would indicate that the basin was formed in a magma-poor rifted system

(Sun et al., 2016b). Mineral abundances and grain characteristics provide a detailed record of the processes affecting their transport and deposition, thereby helping to distinguish between rifting models. The paleogeography of Southeast Asia and the SCS basin has changed throughout the Cenozoic leading to changes in exposed landmasses and sediment transport passageways. As a result, it is important to understand the tectonic history of Southeast Asia in order to determine the sediment deposition and provenance story in this basin. Conversely, though, documenting and interpreting the composition of sands in the SCS basin also can provide information about sediment sources that were activated tectonically but that have not been recognized in previous studies.

Chapter 2. Geologic Setting

Geologic Summary of the South China Sea Basin

As one of the largest marginal seas in the Western Pacific, the South China Sea is an important resource for understanding the tectonic evolution of Asia, as well as an important laboratory for studying the sedimentary transport processes from source to sink

(Sun, 2016a; Sun et al., 2009; Ru & Pigott, 1986; Liu et al., 2010). Multiple tectonic and rifting models have been proposed for the formation and opening of the South China Sea, dating back to the 1970s (Ru & Pigott, 1986). An increase in scientific ocean drilling by the Ocean Drilling Program (ODP Expedition 184) and the International Ocean

Discovery Program (IODP Expeditions 349 and 367/368), as well as improvements in modeling software, has provided data for further interpretations addressing the specifics of the amount of volcanism during rifting and the timing of a proposed two-stage breakup discussed later in this chapter (Franke, 2013; Ru & Pigott, 1986).

Tectonic Overview of the South China Sea

The South China Sea (SCS) basin is located on the Eurasian Plate and is surrounded by four other tectonic plates, including the Philippines Plate to the east, the

Pacific Plate to the east, the Indian Plate to the west, and the Australian Plate to the south

(Wu et al., 2009). Episodes of tectonic movement caused by the surrounding tectonic

6 plates were key factors affecting the development of the SCS basin during the Eocene and the state of the basin thereafter (Sun, 2016a). The boundary of modern-day southeast mainland China was a convergent boundary for most of the Paleozoic and Mesozoic, until subduction stopped and the proto-China margin began to rift during the late

Cretaceous (Barckhausen et al., 2014). The formation of the South China Sea is related to the collision between India and Asia, west of the SCS, during the early Eocene (around

55 Ma) (Wang & Li, 2009). The Tibetan Plateau was uplifted as a result of the subduction associated with this collision, changing the regional paleoslope in East Asia toward the east, initiating the monsoon system, and ultimately having an effect on the creation of the Pacific marginal basins (Sun et al., 2016b). After subduction ceased, widespread extensional rifting formed the basin and all modern-day subbasins within the

SCS, from the Pearl River Mouth Basin in the north to the Dangerous Grounds in the southwest (Cullen et al., 2010). The age of rifting onset is poorly constrained relative to the age of subduction farther west, but SCS rifting is proposed to have occurred from the

Paleocene to the late Eocene.

Multiple theories have been proposed to explain the onset of extension in this region after a long period of collision. Although some theories are more widely accepted than others, no consensus has been reached within the scientific community (Wang & Li,

2009; Sun et al., 2016b; Cullen et al., 2010; Franke, 2013). Four often-discussed models include the collision-extrusion model, the slab pull model, the subduction zone roll-back model, and the backarc extension model (Sun et al., 2009; Cullen et al., 2010; Wang &

Li, 2009; Barckhausen et al., 2014; Sun, 2016a). Although determining the origin of

7 extensional forces that formed the SCS basin is crucial to understanding its history, this study will focus on the compositions of sediment sources active during rifting, as well as the importance of volcanism in the rifting system, as evidenced in the sediment record.

Regardless of the exact rifting mechanism that formed it, the SCS basin can be divided into three subbasins based on the age of oceanic crust and the stage of continental rifting. These subbasins are the Northwest Subbasin, the East Subbasin, and the

Southwest Subbasin (the designation of subbasins in this study is based on the subbasins classified and discussed in Barckhausen et al., 2014 and Ru & Pigott, 1986). After a long period of crustal extension, seafloor spreading was initiated and oceanic crust began to form to create the SCS basin (Barckhausen et al., 2014). Briais et al. (1993) used magnetic anomaly data to date oceanic spreading and the orientation of spreading throughout the different subbasins in the SCS and concluded that oceanic spreading and the formation of oceanic crust began during the early Oligocene (~32 Ma) in the East

Subbasin and stopped just after 30 Ma, with the spreading ridge orientation ranging from

NE-SW to WNW-ESE. Approximately 26-24 Ma the spreading ridge jumped south and propagated southwest to begin rifting the Southwest Subbasin (Briais et al., 1993).

Seafloor spreading throughout the SCS basin is estimated to have ended during the middle Miocene (~15.5 Ma; Briais et al., 1993). A more recent study of spreading age by

Barckhausen et al. (2014) confirmed the ages of spreading onset proposed by Briais at al.

(1993) but proposed that spreading ended earlier (~20.5 Ma) and that the rate of spreading was faster than previously interpreted. Li et al. (2014) proposed similar ages, with much slower spreading rates than those proposed by Barckhausen et al. (2014). Both

8 interpretations classify this spreading system as slow to intermediate, which is an important factor in distinguishing between magma-poor and magma-rich tectonic models

(Li et al., 2014). The difference in the timing of rifting between the East Subbasin and the

Southwest Subbasin is attributed to the presence of crustal blocks, presently forming

Macclesfield Bank (also called Zhongsha-Xisha), and Reed Bank, which acted as continental microplates and halted seafloor spreading in the Southwest Subbasin until sufficient rifting occurred to break the blocks into two separate entities (Sun et al., 2009;

Franke, 2013).

During the seafloor spreading that formed the SCS, which started along the eastern margin of mainland China, tectonic events on adjacent tectonic plates also affected the orientation of, and geography around, the present-day SCS marginal basin.

Australia collided with Asia during the late Oligocene (~ 25 Ma), forcing the rotation of

Borneo and closing the SCS off from the Indian Ocean to the south (Wang & Li, 2009).

The formation of the Luzon Arc and the uplift of Taiwan also helped separate the SCS from the Pacific Ocean to the east and directly affected the sediment supply to the northern section of the East Subbasin (Wang & Li, 2009). The Luzon Arc was formed during the middle to late Miocene from the subduction of post-rift eastward-moving crust of the SCS under the Philippine tectonic plate (Huang, Yuan, & Tsao, 2006). This subduction generated volcanism along the eastern margin of the SCS and formed an accretionary prism that was later deformed by the arc-continent collision (between the

Eurasian plate and the Luzon volcanic arc) that uplifted Taiwan in the early Pliocene

(Huang, Yuan, & Tsao, 2006).

Rifting Models for the South China Sea

Rifted margins are described by the amount of volcanism that takes place during continental breakup and seafloor spreading, forming two main categories: volcanic rifted margins and magma-poor rifted margins (Sun et al., 2016b). Volcanic rifted margins are defined by immense igneous activity during breakup for a duration of 1 to 3 million years

(Sun et al., 2016b). Magma-poor rifted margins lack the massive igneous activity, but rift by long-duration, ultraslow extension of the lithosphere until the thinned layer of continental rock breaks and seafloor spreading begins (Sun et al., 2016b). This hyperextension of the lithospheric crust leads to uplift and serpentinization of the mantle lithosphere as water seeps into the mantle through deep faults in the thinned crust (Sun et al., 2016b). The weakening of the mantle and thinned crust ultimately leads to breakup without the help of magmatic activity. The South China Sea basin has previously been categorized as a magma-poor rifted margin based on seismic data, which has similarities to structures identified at the magma-poor Iberia-Newfoundland margin and fails to have the easily identified structures observed in volcanic rifted margins (Sun et al., 2016b;

Larsen at al., 2018a). One major goal of IODP Expedition 367/368 was to better constrain the rifting model for the South China Sea and to determine whether it was a magma-poor rift, similar to the Iberia-Newfoundland margin, or a new category of rifted margins (Sun et al., 2016b).

Volcanic rifted margins are the dominant rifted margin type and are characterized by thick volcanic flows, a narrow continent-ocean transition zone (COT), large igneous provinces, high velocity physical property measurements within the lower crust, thicker- 10 than-normal oceanic crust, and large amounts of basaltic volcanism (Franke, 2013;

Menzies et al., 2002). These margins contain an abundance of igneous rock and prerift- to-synrift sediment eroded from the volcanic rifted margin, and these sediments include sandstones most likely containing an abundance of recycled igneous rock fragments

(Menzies et al., 2002). Volcanic rifted margins are mostly described by plume-driven models, which require the asthenospheric mantle to be anomalously hot (Franke, 2013;

Larsen at al., 2018a). Magma-poor rifted margins may contain peridotite-bearing upper mantle rocks in the case of exhumed mantle lithosphere, thinned continental crust without serpentinized mantle, detachment faults in the lower crust, evidence of extremely thinned crust in the distal margin, and steep listric faults more proximal to the margin (Franke,

2013). It is important to note that the difference between these two types of rifted margins is in the volume of volcanism, not the presence of volcanism, as even magma-poor rifted margins exhibit an increase in magmatic activity during seafloor spreading (Franke,

2013).

Although multiple models have been proposed to explain how rifting occurs and the potential stratigraphic outcomes, this study will focus on evaluating two end-member models of two-stage breakup and rifting; both models were suggested for the formation of a magma-poor rifted margin, but they would result in different lithologic sections in syn-rift sediment and basement rocks across the COT (Figure 2; Sun et al., 2016b;

Huismans & Beaumont, 2011). The type I magma-poor rifted margin model is described by: the thinning of the upper lithospheric crust in narrow areas; abundant extensional faults or shears cutting into the deep crust; the crust breaking before the mantle, exposing

A. Type I magma-poor rifted margin

Uplift Rift Serpentinized Uplift Rift Flanks mantle lithosphere Flanks

Crust Continental Oceanic

Mantle Lithosphere Lithosphere

Asthenosphere

B. Type II magma-poor rifted margin Thin Continental Crust Thin Continental Crust No rift flank uplifts Sag basins Crust Continental Mantle Oceanic Lithosphere Lithosphere

Asthenosphere

Figure 2. Two magma-poor rifted margin models modified from Huismans and Beaumont

(2011). Part A represents a type I rifted margin and part B represents a type II rifted margin.

12 serpentinized mantle lithosphere at the seafloor within the COT; and a significant time gap between the onset of seafloor spreading and the formation of normal igneous ocean crust (Figure 2A; Huismans & Beaumont, 2011; Sun et al., 2016b). The type I model is exemplified by the Iberia-Newfoundland margin and would contain serpentinized rock and evidence of serpentinization within sediment in the COT, representing the exhumed mantle lithosphere present at the seafloor. Normal igneous oceanic crust is formed at the center of the rift, seaward of the serpentinite (Huismans & Beaumont, 2011; Sun et al.,

2016b).

In contrast, the type II magma-poor rifting model does not include serpentinization or exposed mantle lithosphere and has the potential for more syn-rift magmatic activity than does type 1 (Figure 2B; Huismans & Beaumont, 2011). The type

II model is characterized by wider zones of thinned continental crust with less breakage; sedimentary sag basins formed by faulting and containing syn-rift sediments and possibly evaporites; evidence of hot oceanic lithosphere and asthenosphere moving up to remove and replace the mantle lithosphere to either side of the rift center; and no hiatus between the onset of seafloor spreading and the formation of normal oceanic crust (Figure 2B;

Huismans & Beaumont, 2011; Sun et al., 2016b). The type II model is exemplified by the

South Atlantic margin. Rifting of this style in the SCS would be indicated by the presence of continental blocks originating from mainland China such as granite, granodiorite, and biotite gneiss, as well as no evidence of serpentinization (Huismans & Beaumont, 2011).

Normal igneous oceanic crust would be present adjacent to, and seaward of, the continental crust, closer to the axis of the rift in this type of margin (Sun et al., 2016b).

A recent publication by Larsen et al. (2018a) following the joint IODP Expedition

367/368 suggests that the rifting of the SCS margin was relatively brief, fast, and produced a narrow continent-ocean transition. Basalts with a mineralogic signature of mid-ocean ridge basalt, recovered from within the continent ocean transition during

Expedition 367/368, indicate that magmatism occurred during margin breakup (Larsen et al., 2018a). The lack of magmatic evidence within sediment cores in the continent ocean transition following continental breakup also contradicts magma poor rifting models

(Larsen et al., 2018a). Larsen et al. (2018a) also suggest that the presence of similar alteration patterns between bottom sediments and underlying basalt at Site U1502 indicates that there was not a gap in time between igneous oceanic crust formation and sedimentation. Unlike volcanic rifted margins however, the stratigraphic record in the

SCS does not contain evidence of an anomalously hot asthenospheric mantle (Larsen et al., 2018a). Overall, Larsen et al. (2018a) suggest that the SCS rifted margin is not representative of either the Iberia-Newfoundland magma-poor rifted margin or the typical magma-rich rifted margin.

Evidence of each type of rifted margin discussed can be observed in seismic data and the stratigraphic record of cores extracted from the COT of a rifted margin and can be used to clarify the extent and mechanisms of rifting. Although seismic data is needed to recognize faulting and the nature of the continental crust and mantle boundaries at a rifted margin, the evidence obtained through drilling provides the direct record of lithologies overlying oceanic crust, as well as the ability to date pre-rift to syn-rift sediments that are needed to discriminate between rifting models. The abundance and

14 composition of rock fragments in the basal sediments at Site U1499 can also provide evidence for the appropriate rifting model.

Sources of Sediment

The influx of sediment to the SCS basin from surrounding landmasses and their rivers provides a challenging and unique record of source-to-sink processes and an opportunity to unravel the provenance story of sediments in the SCS basin (Liu et al.,

2016). Tectonic movement has affected the provenance story by uplifting new land masses, creating more areas susceptible to erosion, and closing the open connection of the SCS basin to the rest of the ocean by rotating landmasses to create the present semi- enclosed basin (Wang & Li, 2009).

Southern mainland China and Vietnam contain some of the largest rivers in the world that transport sediment into the SCS basin. The sediment deposited from large

Asian rivers such as the Pearl River, the Red River, and the Mekong-Lancang River, reflects the material eroded from the drainage basins; and therefore, provides a mineral signature of the eroded landmass. In this section, sediment influx to the SCS is described in order from the land masses most proximal to the drilling site locations (such as

Southern mainland China and the Pearl River), to land masses more distal from those sites (such as Borneo and Sumatra). The mineralogy of each river’s sediment is described with the landmass that those rivers flow through.

Mineralogical characteristics of the land masses surrounding the SCS basin and their river sediments have been compiled from petrologic studies of sand/sandstones, clay provenance studies, geochemical analyses of sandstones, and bedrock geology maps and 15 stratigraphic sections (Table 1; Figure 3). The sources and transport paths of clay minerals in the South China Sea have been well documented following previous expeditions in the area (Liu et al., 2016; Schroeder, Wiesner, & Liu, 2015). Although several studies have investigated the fine-grained component of the South China Sea stratigraphic record, the medium to coarse sand-size fraction has not been documented well in English-language scientific journals. Petrologic data from published studies that did conduct a mineralogical analysis on sands and sandstones are plotted on a framework grain ternary diagram (Figure 4).

The medium to coarse sand size fraction is important because provenance signals may vary in different grain sizes (James, DeVaughn, & Marsaglia, 2007). Clay minerals account for less than 50% of the total sediment in the South China Sea, so the mineralogy of the majority of the sediment in this basin has been overlooked in most of the previous provenance studies (Wei et al., 2012).

The Pearl River and Southern Mainland China

The Pearl River carries sediment from mainland China to the South China Sea.

The bedrock geology of southern mainland China consists of Mesozoic intrusive and volcanic igneous rocks to the southeast, Paleozoic sandstones, shales, and a few intrusive rocks in the center, and Cenozoic sedimentary and metamorphic rocks near the mouth of the Pearl River (Milliman & Farnsworth, 2011; Shao et al., 2016) (Figure 5). Southeast

China experienced widespread magmatic activity in the Mesozoic, forming mostly granites and rhyolites, although gabbros and basalts are also present (Li et al., 2003).

Location Study Sediment Depositional on Map Age Grain size Composition Sediment Provenance Reference Source Environment (Figure 3)

Q72F13L15 Lithic subarkose, sublitharenite, and subarkose. Pearl River Fine- Lithic grains dominated by Chengfu et Mouth Basin Delta, littoral 1 Oligocene medium volcanics (5-19%) that were NA al., 2014 (Panyu low- facies sand slightly to strongly sericitized; uplift) minor chert and metamorphic rock fragments. Upper Zhuhai formation: Q84F3L13 with majority of Pearl River volcanic rock fragments (5- Fine- Chen et al., Mouth Basin Delta, littoral 15%) and some metamorphic 1 Oligocene medium NA 2011 (Panyu low- facies rock fragments; Lower Zhuhai sand uplift) formation: Q80F3L17 with slightly more volcanic rock fragments (10-25%) Decrease in smectite from 80% Shao et al., in Oligocene to 20% in Late Oligocene – 2016 and Pearl River Oligocene and Miocene/Pliocene; increase in magmatic source rocks; 1 Range NA Cao et al., Mouth Basin Miocene CaO and a decrease in Al2O3 Miocene – carbonate 2017 across the Oligocene, Miocene source rocks boundary

Continued

Table 1. Summary of published literature on sand and clay mineralogy in landmasses and rivers surrounding the SCS basin.

Table 1 Continued

Location Study Sediment Depositional on Map Age Grain size Composition Sediment Provenance Reference Source Environment (Figure 3) Transported fine grained Pearl River Kaolinite (35-65%) avg: 46%, material in upper section main channels: Holocene Chlorite (20-35%) avg: 25%, of river to the South Liu et al., East River, 2 (surface Clay NA Illite (12-42%) avg: 26%, and China Sea. Clay mineral 2007a North River, sediments) Small smectite amount (less assemblage similar among and West River than 5%) sampling sites spanning length of river Lower Miocene: Q F L 90 3 8 Slate fragments in Taiwan – Very Fine Upper Miocene - Pliocene: Nagel et al., Miocene - Miocene sandstones Western 3 Sandstones NA Q F L 2014 Pliocene 66 19 15 supplied from Mainland Foothills 63-125 µm Upper Pliocene - Pleistocene: China Q59F18L23 Fold-thrust belt including Garzanti & Taiwan – Q63F7L30 majority of lithic sediment of Chinese Resentini, Western 3 Modern 32-500 µm NA grains shale/siltstone and chert passive margin and more 2016 Foothills sedimentary rock fragments recent foreland-basin sediments Rivers and Illite: 56% Holocene Liu et al., lakes in SW Chlorite: 41% 4 (surface Clay NA NA 2008b Taiwan and the Scarce kaolinite (1%) and sediments) Taiwan shelf Smectite (1%) Recycled orogen Yen & deposited on accretionary Lundberg, SW Taiwan 5 Holocene >63 µm NA Q F L and Lm Lv Ls 25 15 60 45 5 51 prism from the Taiwan 2006 orogen

Continued

Table 1 Continued

Location Study Sediment Depositional on Map Age Grain size Composition Sediment Provenance Reference Source Environment (Figure 3) Luzon Trough Yen & (in-between Q F L Lundberg, 6 Holocene >63 µm NA 25 31 44 Magmatic arc Taiwan and and Lm Lv Ls 2006 22 49 29 Luzon arc) Awidon Mesa Formation: Increase in feldspar grains Cagayan Basin Mathisen, Plio- Q F L from dacitic volcanism in in Luzon, 7 unknown NA 7 54 38 1984 Pleistocene Ilagan Formation: Q F L the Cordillera Central Philippines 4 26 70 mountain belt Late Eocene: tuff and some angular plagioclase grains Oligocene: volcanic lithics Zambales Early Miocene: abundant Increase in plagioclase Mountain belt Late Eocene – Schweller & plagioclase grains with few may have been from in western 8 Middle Unknown NA Karig, 1982 volcanic lithics gabbro weathering from a Luzon, Miocene Middle Miocene: abundant volcanic terrane Philippines serpentinite, volcanic and sedimentary rock fragments, and plagioclase grains Rivers Smectite: 86% Andesitic and basaltic Holocene Liu et al., throughout All over Kaolinite: 9% volcanic and sedimentary (surface Clay NA 2009 Luzon, Luzon Chlorite: 5% basement rocks in the sediments) Philippines Illite: 1% region

Continued

Table 1 Continued

Location Study Sediment Depositional on Map Age Grain size Composition Sediment Provenance Reference Source Environment (Figure 3) >62.5 µm, Q: 78% (50-95%) Island of ranged F: 13% (0.5-30%) Continental origin from a Concepcion Mindoro, 9 Late Eocene from NA L: 9% (2-12%) continental margin et al., 2012 Philippines 150-700 Q:F:L plots in continental block tectonic setting µm and recycled orogen Upper Medium- to Matrix: 6-25% Suzuki et Palawan, Granitic basement rock in 10 Cretaceous to coarse- NA Q: 39-46% al., 2000 Philippines Southern Mainland China Eocene grained L: 24-27% Lowermost samples Q46F3L51 Borges & Modern (river Lithic arenite Red River 11 63-500 µm NA Recycled Orogen Huh, 2007 bed sediments) Predominately sed and meta rock fragments Illite: 44% Liu et al., Red River and Modern (river Kaolinite: 25% Sourced from geology of 11 Clay NA 2007b tributaries bed sediments) Chlorite: 25% the drainage basin Smectite: 6% Q F L Fine- 68 8 25 Mekong River Lithic arenite Potter, 1978 12 Holocene medium- NA NA delta Majority of lithic fragments fall grained in the meta-plutonic field Illite: 35% Lower Mekong Modern (river Illite most likely sourced Liu et al., Kaolinite: 28% River and 12 surface Clay NA from granite and 2007b Chlorite: 26% tributaries sediments) metamorphic parent rock Smectite: 11%

Continued

Table 1 Continued

Location Study Sediment Depositional on Map Age Grain size Composition Sediment Provenance Reference Source Environment (Figure 3)

Fluvial Sandstones: Q70F8L22 Lukie & Wave/storm Distributary channel Large Balaguru, Klias, Borneo 13 Miocene influenced sandstones: NA range 2012 delta system Q71F0L29 Majority sublithic arenites Sublithic arenite with large abundance of quartz, less than 10% feldspar and about 20% Recycled orogen from the Early lithics; Mostly monocrystalline Eocene, Cretaceous van Hattum Unknown North Borneo 14 Miocene- NA plutonic quartz and some K- granites located in the et al., 2006 range Eocene feldspar with radiolarian chert Schwaner Mountains and Other Lithic fragments: Sunda Shelf serpentinite, granite, schist, rare acid volcanic rocks Northeast NE Borneo: Illite:77%, High illite content caused Modern (river Wang et al., Borneo and Kaolinite: 12%, Chlorite: 10% by active tectonics and 15 surface Clay NA 2011 Northwest NW Borneo: Illite: 51%, strong weathering caused sediments) Borneo Chlorite: 33%, Kaolinite: 16% by heavy precipitations

China 2 Pearl River 3 Taiwan 4 Red River Hong Kong Myanmar 5 1 6 Laos 11 Hainan

7 Luzon Thailand 8 Mekong Mindoro River South China 9 Cambodia Sea Vietnam Philippines 10 12 Palawan

13 15 Malaysia 14

Sarawak 15

Borneo

Sumatra Indonesia

Java

Figure 3. Map of the South China Sea basin and surrounding landmasses. Numbered red boxes indicate study areas discussed in this section and correlate with Table 1.

Quartz Quartz Key Pearl River Key Taiwan Offshore southern Taiwan and the Luzon Trough Pearl River Philippines (Luzon & Mindoro) Taiwan Red River Offshore southern Taiwan and the Luzon Trough Mekong River Borneo Philippines (Luzon & Mindoro) Red River Mekong River Borneo

Feldspar Lithics

Figure 4. Summary of published framework grain compositions in landmasses and rivers

surrounding the SCS basin.

110°0'0"E 115°0'0"E 120°0'0"E

25°0'0"N 25°0'0"N

20°0'0"N 20°0'0"N

15°0'0"N 15°0'0"N

10°0'0"N 10°0'0"N

Esri, Garmin, GEBCO, NOAA NGDC, and other contributors 110°0'0"E 115°0'0"E 120°0'0"E Legend

Legend Drilling Site Locations Devonian Silurian/Ordovician

DrillingRock Site Locationslithology Devonian Silurian Silurian/OrdovicianOrdovician/Cambrian LegendOphiolites and ultrabasic rocks Rock lithology Silurian Ordovician Ordovician/CambrianUpper Paleozoic Volcanic rocks Ophiolites and ultrabasicDrilling rocks Site LocationsOrdovician CambrianDevonian Upper PaleozoicLower PaleozoicSilurian/Ordovician Intrusive rocks Volcanic rocksRock lithology Cambrian ProterozoicSilurian Lower PaleozoicCenozoicOrdovician/Cambrian IntrusiveGeologic rocks Age Ophiolites and ultrabasic rocks Legend Proterozoic ArcheanOrdovicianCenozoic MesozoicUpper Paleozoic GeologicLegend Age QuaternaryVolcanic rocks Archean UndividedCambrian TertiaryMesozoic PaleozoicLower Paleozoic Drilling Site Locations Devonian Silurian/Ordovician QuaternaryDrilling Site LocationsNeogeneIntrusive rocks Devonian Silurian/Ordovician Undivided TertiaryTertiary/CretaceousProterozoicPaleozoic PrecambrianCenozoic Rock lithologyLegend Silurian Ordovician/Cambrian Rock lithologyNeogene GeologicPaleogene Age Silurian Ordovician/Cambrian Ophiolites and ultrabasic rocks Tertiary/CretaceousCretaceous/JurassicArchean Precambrian Cenozoic/MesozoicMesozoic DrillingOphiolites Site and Locations ultrabasic rocks OrdovicianDevonian Upper PaleozoicSilurian/Ordovician Paleogene CretaceousQuaternary Ordovician Upper Paleozoic RockVolcanic lithology rocks Cretaceous/JurassicJurassic/TriassicUndivided TertiaryCenozoic/MesozoicMesozoic/PaleozoicPaleozoic Volcanic rocks CambrianSilurian Lower PaleozoicOrdovician/Cambrian Cretaceous JurassicNeogene Cambrian Lower Paleozoic IntrusiveOphiolites rocks and ultrabasic rocks Jurassic/TriassicTriassic/PermianTertiary/CretaceousMesozoic/PaleozoicPaleozoic/PrecambrianPrecambrian Intrusive rocks ProterozoicOrdovician CenozoicUpper Paleozoic Jurassic TriassicPaleogene Proterozoic Cenozoic Geologic Age Volcanic rocks Triassic/PermianPermian/CarboniferousCretaceous/JurassicPaleozoic/PrecambrianGeologyCenozoic/Mesozoic not shown Geologic Age ArcheanCambrian MesozoicLower Paleozoic Triassic PermianCretaceous Archean Mesozoic QuaternaryIntrusive rocks Permian/CarboniferousCarboniferous/DevonianJurassic/TriassicGeology not shownUndeterminedMesozoic/Paleozoic age Legend Quaternary UndividedProterozoic Tertiary PaleozoicCenozoic Permian CarboniferousJurassic Undivided Tertiary Paleozoic GeologicNeogene Age Carboniferous/DevonianDevonian/SilurianTriassic/PermianUndetermined age Paleozoic/Precambrian Neogene Tertiary/CretaceousArchean PrecambrianMesozoic Drilling Site Locations DevonianTriassic Silurian/Ordovician CarboniferousQuaternary Tertiary/Cretaceous Precambrian Legend Paleogene Devonian/Silurian Permian/Carboniferous Geology not shown Paleogene Cretaceous/JurassicUndivided Tertiary Cenozoic/MesozoicPaleozoic Rock lithology SilurianPermian Cretaceous/JurassicOrdovician/Cambrian Cenozoic/Mesozoic Drilling Site Locations CretaceousNeogeneDevonian Silurian/Ordovician Carboniferous/Devonian Undetermined age Ophiolites and ultrabasic rocksCretaceous Jurassic/TriassicTertiary/Cretaceous Mesozoic/PaleozoicPrecambrian OrdovicianCarboniferous Jurassic/TriassicUpper Paleozoic Mesozoic/Paleozoic Rock lithology Jurassic PaleogeneSilurian Ordovician/Cambrian Devonian/Silurian Volcanic rocks Jurassic Triassic/PermianCretaceous/Jurassic Paleozoic/PrecambrianCenozoic/Mesozoic Cambrian Triassic/PermianLower Paleozoic Paleozoic/Precambrian Ophiolites and ultrabasic rocksTriassic CretaceousOrdovician Upper Paleozoic Intrusive rocks Triassic Permian/CarboniferousJurassic/Triassic GeologyMesozoic/Paleozoic not shown Proterozoic Permian/CarboniferousCenozoic Geology not shown Volcanic rocks PermianJurassicCambrian Lower Paleozoic Geologic Age Permian Carboniferous/DevonianTriassic/Permian UndeterminedPaleozoic/Precambrian age Archean Carboniferous/DevonianMesozoic Undetermined age Intrusive rocks CarboniferousTriassicProterozoic Cenozoic Quaternary Carboniferous Permian/Carboniferous Geology not shown Undivided TertiaryDevonian/SilurianPaleozoic Geologic Age Permian Devonian/Silurian Neogene Archean MesozoicCarboniferous/Devonian Undetermined age Tertiary/Cretaceous Precambrian Quaternary Carboniferous FigurePaleogene 5. GeologicUndivided map Tertiary of southePaleozoicDevonian/Silurianrn mainland China, Taiwan, and the Luzon Arc. Neogene Cretaceous/Jurassic Cenozoic/Mesozoic Cretaceous Tertiary/Cretaceous Precambrian Paleogene Jurassic/Triassic Mesozoic/Paleozoic Jurassic Cretaceous/Jurassic Cenozoic/Mesozoic CretaceousShapefile DownloadedTriassic/Permian from the U.S.Paleozoic/Precambrian Geological Survey. Triassic Jurassic/Triassic Mesozoic/Paleozoic Jurassic Permian/Carboniferous Geology not shown Permian Triassic/Permian Paleozoic/Precambrian Triassic Carboniferous/Devonian Undetermined age Carboniferous Permian/Carboniferous Geology not shown Permian Devonian/Silurian Carboniferous/Devonian Undetermined age 24 Carboniferous Devonian/Silurian The Pearl River presently is one of the largest Asian rivers and is the largest river flowing into the South China Sea. It enters the SCS from southern mainland China, along the northern SCS margin (Milliman & Farnsworth, 2011). The modern Pearl River is

2200 km long with an average discharge of 260 km3/yr and a basin area of 490,000 km2, making it the largest sediment source from southern mainland China into the SCS

(Milliman & Farnsworth, 2011). The modern sediment influx from the Pearl River is dominated by carbonate detritus (making up 80% of the total load); however, the composition of Pearl River sediment has changed through geologic time due to tectonic movement and the expansion of the Pearl River drainage, as well as through more recent time due to anthropogenic influence (Milliman & Farnsworth, 2011; Shao et al., 2016;

Cao et al., 2017).

Prior to building dams and organizing irrigation in this area of southern mainland

China, the sediment discharge of the Pearl River is calculated to have been 80 Mt/yr, but with anthropogenic influence the present calculated sediment load has been reduced to 25

Mt/yr (Milliman & Farnsworth, 2011). However, anthropogenic influence is rarely helpful; many of the published mineralogical studies identify changes in heavy metal contents through the Holocene reflecting the effect of human-induced pollution on the river (Heise et al., 2013; Zhou, Peng, & Pan, 2004).

The source of sediment carried by the Pearl River is expected to have changed through geologic time as the path of the river has changed. The modern Pearl River drainage is divided into three regions based on lithology and proximity to the river mouth. The upper region, on the far west side of the map in Figure 3, consists of

Mesozoic limestone and Paleozoic sandstone, shale, and a few granite intrusions. The middle region contains Paleozoic rock; and the lower region consists mostly of granites and volcanics. However, the path of the Pearl River did not always flow through all three regions of the modern drainage basin (Cao et al., 2017; Shao et al., 2016). Geochemical data, as well as an increase in the mud to sand ratio of sediments in the Pearl River

Mouth Basin from the Oligocene to the Miocene, provides evidence for the westward expansion of the Pearl River through time. During the Oligocene, the Pearl River was confined to the present lower drainage region, but its drainage basin expanded during the

Miocene (Shao et al., 2016). Therefore, the sediment transported by the Pearl River shifted from a dominance of granitic and volcanic detritus during the Oligocene to more sandstone and limestone during the Miocene, changing the signature of the Pearl River input to the SCS basin. The Pearl River drainage may have expanded due to the tectonic shift from rifting to subsidence, with an increase in sediment load during the late

Oligocene (Cao et al., 2017; Shao et al., 2016).

The Panyu low-uplift, located in the center of the Pearl River Mouth Basin

(PRMB) and directly in front of the Pearl River mouth, is an area that has been well described and analyzed because it is an important and prolific oil production site (Chen et al., 2011; Chengfu et al., 2014). Chen et al. (2011) analyzed fine- to medium-grained sandstones from the Oligocene Zhuhai Formation in this area and concluded that the average framework grain composition in the upper part of the formation was quartz rich

(Q84F3L13; Table 1; Figures 3 and 4). The lower part of the formation contained slightly more lithic grains (Q80F3L17). Overall, the majority of lithic grains identified in the

Zhuhai Formation were volcanic rock fragments, with a smaller amount of metamorphic rock fragments. These sandstones were classified as sublitharenite using McBride’s 1963 classification scheme.

A subsequent study by Chengfu et al. (2014) also sampled the Zhuhai Formation in the Panyu low-uplift and found quartz-rich sandstones with a framework grain composition of Q72F13L15 (Table 1; Figures 3 & 4). The lithic grains were also dominated by volcanic rock fragments, and minor abundances of chert grains were identified. The volcanic rock fragments were sericitized in both studies (Chen et al., 2011 and Chengfu et al., 2014), and metamorphic rock fragments were mainly comprised of phyllite, quartz schist, and quartzite. Both studies also focused on understanding the effects of diagenesis and concluded that diagenetic cements consisted of quartz (in the form of quartz overgrowth), clay (kaolinite, chlorite, smectite, illite), and various forms of calcite. It is not clear in either study how feldspar grains and volcanic rock fragments were counted and if a heavily weathered/altered feldspar grain was counted as a feldspar or clay.

The shift in sediment composition caused by the westward expansion of the Pearl

River during the Miocene was observed in geochemical analyses conducted on sediments from the PRMB which had an increase in CaO and a decrease in Al2O3 from the

Oligocene to the Miocene (Cao et al., 2017; Shao et al., 2016; Table 1; Figure 3). The geochemical data also had a decrease in smectite, from 80% during the Oligocene to 20% during the Miocene/Pliocene, which could indicate a decrease in the importance of magmatic source rocks (because smectite is an indicator of weathered magmatic rock) or

27 a decrease in chemical weathering from the Oligocene to the Miocene in this area (Shao et al., 2016).

The clay mineralogy of modern surface sediments in the Pearl River and its tributaries consists mainly of kaolinite, with subequal amounts of chlorite and illite and a small amount of smectite (Liu et al., 2007a; Table 1; Figure 3). However, samples from the northern SCS basin contain a lower abundance of kaolinite and a higher abundance of smectite, indicating that the modern Pearl River is not the main source of smectite for the

SCS basin, but does supply kaolinite (Liu et al., 2007a).

Taiwan

Taiwan lies on the northeastern side of the SCS basin, just east of southern mainland China. Taiwan was uplifted during the late Miocene/early Pliocene by the subduction at the boundary of the Luzon volcanic arc and the Eurasian plate, so sediment derived from this source could not have entered the South China Sea until after the

Miocene (Huang et al., 2006; Garzanti & Resentini, 2016). The island of Taiwan is approximately 36,000 km2 in size, and the bedrock geology of the island is complex, with a variety of lithologies (Figure 5). Taiwan can be divided into four main physiographic provinces; from west to east, these are the Coastal Plain, the Western Foothills, the

Central Range, and the Coastal Range (Nagel et al., 2014; Yen & Lundberg, 2006). The

Coastal Plain, on the western edge of the island, contains Quaternary and Neogene alluvial sediments; the Western Foothills consists of upper Miocene to Pliocene clastic sedimentary deposits; the Central Range contains Eocene to Miocene low-grade metamorphic rocks (slate and metasandstones) and more high-grade metamorphic rock 28

(schists, serpentinites, and granitoids); and the Coastal Range is composed of Miocene sedimentary rocks and volcanics (Nagel et al., 2014; Yen & Lundberg, 2006).

Taiwan presently contains several small mountainous rivers that enter the South

China Sea, as well as rivers that flow into the Taiwan Strait to the northwest and the

Pacific Ocean to the east (Liu et al., 2008a). These small rivers carry a large amount of sediment due to rapid erosion driven by frequent high intensity precipitation events, the southern Asian monsoon, the abundance of typhoons (Taiwan is located in Typhoon

Alley), the mountainous terrain, and the very active tectonic setting of Taiwan (Liu et al.,

2008a). In total, these rivers discharge between 230 and 400 Mt of sediment every year

(Liu et al., 2008a). Five major rivers discharge sediment from Taiwan into the South

China Sea, including the Yenshui River, the Erhjen River, the Kaoping River, the

Tungkang River, and the Linpian River (Liu et al., 2008a). Together these rivers transport about 70 Mt of sediment annually. Four of these rivers flow from the Western Foothills to the SCS, but the Kaoping River flows from an elevation greater than 3000 m in the

Central Range to the SCS, discharging 15-35 Mt of sediment per year (Liu et al., 2008a).

Nagel et al. (2014) examined very fine sandstones from late Miocene to late

Pleistocene formations throughout the Western Foothills province (Table 1; Figures 3 &

4). The framework grain composition of these sandstones had a decrease in quartz abundance upsection with an accompanying increase in feldspar and lithic abundances present (Composition values listed in Table 1). A shift in lithic grain composition was also observed, changing from more metamorphic rock fragments during the Miocene and lower Pliocene (Lm67Lv6Ls27) to more sedimentary rock fragments during the upper

Pliocene to Pleistocene (Lm46Lv3Ls51). Miocene sediments also contained slate and quartzite fragments, whereas younger samples contained more mudrock and siltstone lithic fragments. The slate fragments are hypothesized to have been derived from mainland China. The QFL shift from the Miocene sandstones to the Pleistocene sandstones provided evidence of a change in tectonic activity and the collision of Taiwan with the Luzon Arc, causing the uplift and growth of the landmass (Nagel et al., 2014).

Modern very fine- to medium-grained sand in the Western Foothills province was determined to have an average framework grain composition with high quartz abundance

(Q63F7L30; Garzanti & Resentini, 2016; Table 1; Figures 3 & 4). Siltstone and mudrock sedimentary rock fragments were abundant in these sands, with chert, limestone, and felsic volcanic grains also present (Garzanti & Resentini, 2016). Samples of modern sediment from some of the major rivers in western Taiwan had an average framework composition of Q47F3L49 (Garzanti & Resentini, 2016). The clay mineralogy of modern surface sediments in rivers, lakes, and the continental shelf of southwestern Taiwan consist mainly of illite (56%) and chlorite (41%), with small amounts of smectite and kaolinite (Liu et al., 2008b; Table 1; Figure 3). However, samples from the nearby SCS shelf and slope contain more smectite, abundant illite and chlorite, and a low abundance of kaolinite indicating that illite is the main clay contributed to the SCS from Taiwan (Liu et al., 2008b).

Yen & Lundberg (2006) conducted a petrographic study of very fine- to medium- grained modern sands from offshore Taiwan and the Luzon trough (Table 1; Figures 3 &

4). Sand sampled from offshore Taiwan had an average framework grain composition of

Q25F15L60, and samples farther south in the Luzon Trough contained more feldspar and fewer lithic fragments (Q25F31L44; Yen & Lundberg, 2006). Lithic fragments south of

Taiwan mainly consisted of sedimentary rock fragments and low-grade metamorphic lithic fragments, whereas samples from the Luzon Trough were rich in volcanic rock fragments most likely sourced from the eastern side of Taiwan (Yen & Lundberg, 2006).

The Philippines

The Philippines is comprised of more than 7000 islands with an area of 299,404 km2 and borders the eastern side of the SCS basin (Figure 3; White, 1996). For this study, the focus will be on the largest islands of the Philippines, such as Luzon farthest north,

Mindora located directly south of Luzon, and Palawan located southwest of Mindora

(White, 1996). Luzon formed during the middle to late Miocene from the subduction of

SCS crust under the Philippine Sea plate (Huang et al., 2006). Luzon presently contains three tectonically active mountain belts that create steep slopes and increased runoff, increasing erosion, and sediment supply to the SCS (Schweller & Karig, 1982). These mountain belts are the Sierra Madre, located on the eastern flank of Luzon; the Cordillera

Central on the northwestern side of Luzon; and the Zambales on the southwestern portion of the island (Schweller & Karig, 1982).

The Zambales contain Mesozoic ultrabasic intrusive basement rocks surrounded by Miocene sedimentary rocks, young extrusive rocks, and modern sediments (Liu et al.,

2009; Figure 5). The Cordillera Central is comprised of Cretaceous-Paleogene extrusive igneous rocks and Cenozoic intermediate intrusive igneous rocks (Liu et al., 2009). The

Sierra Madre is comprised of Mesozoic ultrabasic intrusive rocks, younger extrusive 31 rocks, and Paleozoic metamorphic rocks (Liu et al., 2009). Miocene sedimentary rocks are commonly found between mountain belts (Liu et al., 2009). Overall, igneous basement rocks, consisting of peridotite, gabbro, diorite, and other intrusives, are abundant in the mountain ranges; and sedimentary rocks, consisting of limestone, turbidite sequences, and volcaniclastics, are common in low-lying valleys and other areas

(Liu et al., 2009; Mathisen, 1984; Schweller & Karig, 1982).

The northeastern portion of Palawan contains Permian to Triassic limestone, chert, basalt, and sandstone; and Upper Cretaceous to Eocene peridotites, basalts, gabbros, and sedimentary rocks (including mudstone, sandstone, and pebbly mudstone) are present in the central and southwestern parts of the island (Suzuki et al., 2000; Figure

5). The northwestern portion of Mindoro contains Permian to Triassic metamorphic rocks, including graphite, chlorite, and mica schists and metasediments (Concepcion et al., 2012). The rest of Mindoro consists of Cenozoic volcanic and sedimentary rocks.

Several rivers presently transport sediment from Luzon into the surrounding oceans. The Cagayan River is the largest river in Luzon and transports sediment north into the Luzon Strait; and the second largest river, the Pampanga, drains into Manila Bay just south of Luzon (Liu et al., 2009). Two main rivers, the Agno River and the Vigan

River, presently flow into the South China Sea, supplying sediment from Mesozoic ultrabasic intrusive igneous rocks and Cenozoic extrusive and intrusive igneous and sedimentary rocks, respectively (Liu et al., 2009).

Sandstones from the upper Eocene to the lower/middle Miocene of the Zambales

Mountains on the western side of Luzon were analyzed petrographically by Schweller &

Karig (1982) (Table 1; Figures 3 & 4). Upper Eocene samples contained tuff with angular plagioclase grains and pumice fragments, whereas Oligocene samples contained volcanic lithic grains and unidentifiable heavily weathered grains. Lower Miocene samples contained abundant plagioclase with limited pyroxene and volcanic lithic grains. The increased plagioclase in the lower Miocene may have been the result of weathering gabbro from a volcanic terrane. Finally, the middle Miocene samples analyzed in this study contained abundant serpentinite, pyroxene, chromite, plagioclase, and volcanic and sedimentary lithic grains (Schweller & Karig, 1982).

The Cagayan basin is located between the Cordillera Central and Sierra Madre mountain belts on Luzon and contains volcanic-rich sandstones (Mathisen, 1984).

Sandstones from the Ilagan Formation and the overlying Awidon Mesa Formation range in age from Pliocene to Pleistocene and are described as lithic arkoses and feldspathic litharenites (Table 1; Figures 3 & 4). The Ilagan Formation has an average framework grain composition of Q4F26L70, whereas the Awidon Mesa Formation contains more feldspar and fewer lithic fragments (Q7F54L38). An increase in dacitic-rich volcanism within the Cordillera Central during the Pleistocene is interpreted to have supplied additional plagioclase to the Awidon Mesa Formation (Mathisen, 1984). The clay mineralogy of modern surface sediments in Luzon rivers is dominated by smectite (86%), with lesser subequal amounts of kaolinite (9%) and chlorite (5%) (Liu et al., 2009; Table

1; Figure 3). The high abundance of smectite is related to the volcanic-rich geology of

Luzon and its active tectonic setting and high rate of chemical weathering (Liu et al.,

2009).

The upper Eocene Lasala Formation in northwestern Mindoro contains gray sandstone with interbedded dark shale, limestones, and a few conglomerates and basalt flows (Concepcion et al., 2012). Its framework grain composition ranges 50-95% quartz,

0.5-30% feldspar, and 2-12% lithic fragments, classifying these sandstones as sublitharenites, quartz arenites, and arkoses (Table 1; Figures 3 & 4). These sandstones contain a clay matrix and calcite and quartz cements (evidenced by quartz overgrowth).

Feldspar grains show alteration, twinning, and zoning; polycrystalline and monocrystalline quartz grains are abundant. Lithic fragments mainly consist of basalt and chert. The framework grain composition for these samples indicates a source region of recycled orogen or transitional continental and/or craton interior, meaning that these sediments most likely were sourced from within the continental block or from a nearby landmass (Concepcion et al., 2012).

Sandstones from an upper Cretaceous to Eocene turbidite sequence in central

Palawan have a framework grain composition of abundant quartz grains and rock fragments (Suzuki et al., 2000; Table 1; Figure 3). These sandstones are classified as lithic arenites and wackes (Suzuki et al., 2000). Most feldspar grains have been altered and replaced; undulose extinction and fluid or heavy mineral inclusions were present in quartz grains; and lithic fragments are predominantly volcanic and rhyolitic with some mudstone and schist fragments (Suzuki et al., 2000). Granitic basement rock in southern mainland China is interpreted to have been the source of these sandstones due to the plutonic origin of quartz grains, as well as rhyolite lithic fragments (Suzuki et al., 2000).

The Red River and Vietnam

Vietnam borders the SCS basin to the northwest, with an area of 331,689 km2

(Tran, 1995). A large Cenozoic fault zone, the Red River fault zone, is located in the northeastern part of the country and caused the Indochina Peninsula to move southward relative to southern mainland China (towards the SCS basin) during the Tertiary (Tran,

1995). The Red River runs along the fault zone into the Gulf of Tonkin, transporting sediment eroded from present-day Vietnam and southwestern China (Tran, 1995; Borges

& Huh, 2007). The bedrock geology of northeastern Vietnam is dominated by igneous and metamorphic rocks around the Red River fault zone and the Ailao Shan-Red River shear zone, and by sedimentary rocks in the remainder of the Red River drainage basin

(Borges & Huh, 2007). Quaternary deltaic sediments and Mesozoic strata (sedimentary and volcanic-rich sedimentary rocks, including limestone, coal, sandstone, shales, and conglomerates) are present near the river mouth on the eastern and western side of the river within the Red River drainage basin (Tran, 1995). Precambrian rocks and middle

Cambrian to lower Ordovician limestones, mudstones, sandstones, and coals are located farther upstream (Tran, 1995). Mylonitic gneiss is present along the Red River shear zone

(Clift et al., 2006).

The Red River drainage basin is presently smaller than those of the Pearl River and the Mekong River, with an area of 120,000 km2; however, the Red River drainage has a large sediment yield, supplying 130,000,000 t/y of suspended sediment into the

Gulf of Tonkin (Borges & Huh, 2007). The amount of sediment supplied from the Red

River may have decreased over time due to drainage capture by the Yangtze River since 35 the Eocene and through the Oligocene and Neogene (Clift et al., 2008). The proto-Red

River was supplied by larger rivers such as the Yangtze and Mekong, carrying sediment from the eastern section of the Himalayas and the Tibetan Plateau into the Red River and out into the Gulf of Tonkin. In contrast, the modern Red River has been truncated due to the uplift of Tibet, and is supplied sediment more locally from two main tributaries, the

Lo River and the Da River (Borges & Huh, 2007; Carling, 2009). The sediment transported by the Red River is mostly produced by a combination of heavy precipitation and active uplift, and the majority of modern sediments transported to the Gulf of Tonkin are sourced from the sedimentary basins surrounding the river rather than from the metamorphic rocks in the shear zone (Clift, 2006).

Borges and Huh (2007) petrographically analyzed very fine- to medium-grained sand samples from the bed of the Red River to understand modern day weathering patterns in the drainage basin (Table 1; Figures 3 & 4). The framework grain composition of samples taken throughout the Red River and its tributaries contained low abundances of feldspars and subequal abundances of quartz and rock fragments (Borges & Huh,

2007). All of the framework grains were subangular to angular, suggesting a somewhat short transport history (Borges & Huh, 2007). The lowermost sediments collected from the Red River and its tributaries closest to the river mouth have an average framework composition of Q46F3L51 and are classified as lithic arenites (Borges & Huh, 2007). The majority of lithic grains were identified as metamorphic rock fragments, with lesser abundances of sedimentary rock fragments and little to no volcanic rock fragments

(Borges & Huh, 2007). Overall these sediments are interpreted to be sourced from a

36 recycled orogen (Borges & Huh, 2007). The clay mineralogy of modern surface sediments in the Red River consists mainly of illite (44%), with subequal amounts of kaolinite (25%) and chlorite (25%) and low abundances of smectite (6%) (Liu et al.,

2007b; Table 1; Figure 3). The clay mineralogy results indicate that the Red River sediments have undergone significant physical erosion and limited hydrolysis as compared to the more heavily chemically weathered sediments of the Pearl River and the moderately chemically weathered sediments of the Mekong River. The geology of each drainage basin is also suspected to play a role in the differences in clay mineralogy and level of weathering between these basins (Liu et al., 2007b).

The Mekong River and the Indochina Peninsula

The Indochina Peninsula borders the South China Sea along the western side of the basin and includes the southern part of Vietnam, Cambodia, Thailand, Lao PDR

(Laos), Myanmar, and the Malaysia Peninsula (Gupta, 2009). The geology of the

Indochina Peninsula is predominantly Paleozoic sedimentary rocks, including limestone; some metamorphic rocks, including schists, marbles and phyllites; Mesozoic sedimentary rocks, including sandstones and limestones; and some granites. Quaternary sediments are also abundant in the western part of the peninsula, in southern Vietnam, Cambodia, and

Thailand. Proterozoic granites and schists are also present in Lao PDR and north of the

Indochina Peninsula into China (Gupta, 2009).

The Mekong River flows through the Indochina Peninsula with a length of 4,800 km and a drainage basin area of 795,000 km2, making the Mekong the largest river flowing through SE Asia (Kubo, 2008). The Mekong River flows from headwaters in the 37 southwestern part of China to the borders of Myanmar and Thailand, through Lao PDR and Cambodia, and to the southern tip of Vietnam (Gupta, 2009). The modern Mekong

River has a mean water discharge of 475 km3/yr and a suspended sediment load estimated at 160 Mt/yr and slightly increasing through time (Kubo, 2008; Walling, 2008). The extensive length of the Mekong River includes very different terrains in the upper part of the river versus the lower part of the river. The upper part of the river flows at higher altitude in the mountainous region of southwestern China in a narrow steep valley comprised of Mesozoic granites and metasediments; the lower part of the river flows through flat and wide basins in Cambodia and Vietnam (Gupta, 2009; Walling, 2008).

The path of the Mekong River has changed significantly since the Eocene

(Carling, 2009). The proto-Mekong River was part of a larger river flowing along the path of the modern Red River, carrying sediment and water from the Himalayas and the

Tibetan Plateau (Carling, 2009). The uplift of Tibet, to its highest extent during the

Miocene, caused changes in regional slopes, with drainage separation between SE Tibet and the Indochina Peninsula causing some of the flow to be diverted to the Yangtze River while the remainder formed the proto-Mekong River (Carling, 2009).

Fine- to medium-grained sands from the Mekong River delta were analyzed petrographically by Potter (1978). The average framework grain composition of the

Mekong River sands is Q68F8L25 and classified as lithic arenites (Potter, 1978; Table 1;

Figures 3 & 4). The majority of rock fragments in the Mekong sands were sedimentary, metamorphic, and plutonic grains, with very few volcanic rock fragments (Potter, 1978).

The clay mineralogy of modern surface sediments in the Mekong River is similar to the

38 clay composition in the Red River, with an average of 35% illite, 28% kaolinite, 26% chlorite, and low abundances of smectite (avg. 11%) (Liu et al., 2007b; Table 1; Figure

3). The average smectite abundance is slightly higher than that in the Red River, and the illite content is slightly lower (Liu et al., 2007b). The abundant illite in the Mekong could be sourced from metamorphic and intrusive basement rocks in the upper Mekong basin

(Liu et al., 2007b).

Borneo

Borneo borders the South China Sea along the southern side of the basin, where it rotated to separate the SCS from the Indian Ocean during the late Oligocene (Wang & Li,

2009). The geology of Borneo includes Mesozoic intrusive and volcanic rocks, including granites in central Borneo surrounded by Cenozoic clastic sedimentary rocks and some

Mesozoic/Paleozoic sedimentary rocks, metamorphic rocks, and ophiolites (Wang et al.,

2011; Nagarajan et al., 2014). The focus of this section with be on northeastern Borneo, which is most proximal to the SCS basin and consists of Mesozoic and Quaternary sedimentary rocks (sandstones, shales, coals, and carbonates; Wang et al., 2011).

Sandstones from the Eocene-Oligocene Crocker Fan, the Trusmadi Formation, and the Crocker Formation of northeastern Borneo are classified as sublithic arenites with a majority of monocrystalline quartz grains (van Hattum et al., 2006; Table 1; Figure 3).

Lithics are the next most common framework grain, with radiolarian chert fragments in every sample and other lithics (granite, schist, and volcanic fragments) occasionally present (van Hattum et al., 2006). Feldspars are relatively uncommon, making up less than 10% of the total framework grains. The framework grain compositions of these 39 sandstones indicate a recycled orogen source, potentially from Cretaceous granite basement rocks in southwestern Borneo (van Hattum et al., 2006).

Early to late Miocene age sandstones from the Klias Peninsula and Labuan Island in northeastern Borneo exhibit framework grain compositions similar to those of the

Eocene-Oligocene Crocker Fan sandstones (Lukie & Balaguru, 2012; Table 1; Figures 3

& 4). Lower middle Miocene sandstones from the Klias Peninsula have a composition of

Q71F0L29 (Lukie & Balaguru, 2012). The overlying middle Miocene sandstones from the

Klias Peninsula and Labuan Island have framework grain compositions of Q70F8L22 and

Q86F1L13, respectively (Lukie & Balaguru, 2012). Overall these sandstones were deposited on a wave-influenced delta and were classified as sublithic arenites (Lukie &

Balaguru, 2012). Geochemical and XRF analyses were also conducted on middle

Miocene sandstones from the Tukau Formation of northeastern Borneo (Nagarajan et al.,

2014). These sandstones contain ~80% quartz, no feldspar, and minor kaolinite and illite clay minerals (Lukie & Balaguru, 2012).

The clay mineral contents of modern river sediments in northeastern Borneo are

77% illite, 12% kaolinite, 10% chlorite, and 0% smectite, whereas modern river sediments in northwest Borneo contain 51% illite, 33% chlorite, 16% kaolinite, and 0% smectite (Wang et al., 2011; Table 1; Figure 3). The high illite content in the surface sediments of northern Borneo is interpreted to result from strong physical and chemical weathering caused by heavy precipitation and active tectonics in the region (Wang et al.,

2011).

Oceanography and Paleoceanography

The evolution of surface water circulation, the East Asian Monsoon system, bathymetry, and deep water circulation in the South China Sea through geologic time has affected sediment supply, sediment composition, and sediment transport and deposition throughout the SCS basin (Wang & Li, 2009; Wang et al., 2000; Wan et al., 2007; Shao et al., 2007). Most of the published oceanographic studies of the SCS basin focus on modern patterns of circulation, which aid in understanding the present effect of the monsoon system on surface currents (Wang & Li, 2009). However, combining an understanding of the current monsoon system with evolution of the Cenozoic history of the East Asian Monsoon provides insight into surface water circulation changes through time (Wang & Li, 2009). The bathymetry of the SCS basin, which has changed through geologic time due to tectonics, controls the pathways of deep water circulation; the opening and closure of connections between the SCS and surrounding bodies of water has influenced mixing within the basin, as well as sediment transport and deposition patterns (Wang & Li, 2009).

Variations in monsoon intensity in southeastern Asia, both in the geologic past and seasonally today, affect the amount of erosion from landmasses and the patterns of sediment deposition in the SCS (Wang & Li, 2009; Wang et al., 2000; Wan et al., 2007).

The modern East Asian Monsoon system is unlike other monsoon systems in that the winter monsoon, which lasts from November to April, is more intense than the summer monsoon, which lasts from the middle of May to the middle of September (Wang & Li,

2009). This is caused by northeastern winds that push a cold air mass from Siberia into 41 the coastal region of southeast Asia during the winter monsoon (Wang & Li, 2009). Both the winter and summer monsoon systems are characterized by heavy precipitation, with the winter monsoon rains focused primarily in the southern half of the basin (centered in

Indonesia and Malaysia) and the summer monsoon rain focused in the central part of the basin (the Philippines and the Indochina Peninsula; Wang et al., 2000).

Sea surface circulation in the modern SCS basin changes seasonally due to the seasonal reversal of wind direction caused by the winter and summer monsoon systems, forming a dominant cyclonic gyre during the winter monsoon and a less dominant anticyclonic gyre during the summer monsoon (Wang & Li, 2009). Surface circulation also varies geographically between the northern and southern halves of the basin during the summer months, due to the relatively weak summer monsoon. The northern half of the basin remains in a cyclonic gyre during the summer monsoon, whereas the southern half of the basin is more affected by the southerly winds brought into the basin by the summer monsoon and circulates in an anticyclonic gyre (Wang & Li, 2009).

The East Asian Monsoon system intensified during the Miocene as the result of the uplift of the Tibetan Plateau and the expansion of the Himalayan-Tibetan orogen, which also affected the drainage patterns of the Mekong and Red Rivers (Wang et al.,

2000). Glacial/interglacial changes in global climate, atmospheric CO2 content, and other climatic factors (solar radiation, precipitation, and humidity) also have influenced the intensity of the monsoon system, which is the defining climate indicator for southeast

Asia (Wang et al., 2000). Prior to uplift of the Tibetan plateau, evaporitic basins occupied the dry, arid environment throughout China until the onset of a weak summer monsoon

42 near the Eocene/Oligocene boundary; this onset increased precipitation within the region

(Wang et al., 2000). The expansion of the Himalayan-Tibetan orogen during the Miocene increased the intensity of the winter monsoon, with periods of high strength observed at

15 mya, 8 mya, and 3 mya (Wan et al., 2007).

The bathymetry of the SCS basin has been affected by rifting and tectonic activity since the Eocene, compounded by sea level changes during glacials and interglacials

(Wang & Li, 2009). Bathymetry changes have opened and closed passageways connecting the South China Sea to the Pacific Ocean, as well as the Indian Ocean, the

East China Sea, and the Sulu Sea (Wang & Li, 2009). The SCS presently is open to the

East China Sea through the Taiwan Strait and is open to the Indian Ocean through the upper 30-40 m of the water column in the southern part of the basin; both of these passageways have closed during glacials due to a drop in sea level (Wang & Li, 2009).

The connections of the SCS basin to the Sulu Sea, through the Balabac Strait and the

Mindoro Strait, and to the Pacific Ocean, through the Bashi Strait, are much deeper and consequently remained intact during glacials (Wang & Li, 2009).

The main source of deep water in the SCS is from the Pacific Ocean through the

Bashi Strait, located between Taiwan and Luzon on the eastern side of the basin (Wang &

Li, 2009). This inflow is a portion of the West Pacific Ocean Current, forms the deep water for the entire SCS basin, and flows in a cyclonic pattern (Shao et al., 2007; Wang

& Li, 2009). This connection with the Pacific Ocean via the Bashi Strait causes sedimentation rates to be higher on the eastern side of the SCS basin and modifies sedimentary processes in the northeast portion of the basin (Shao et al., 2007).

Chapter 3. Study Region and Site Descriptions

Study Region

The joint IODP Expeditions 367 and 368 drilled at seven sites on the northern rifted margin of the South China Sea basin (Figure 1). The SCS basin is the largest marginal basin isolating Asia from the Pacific Ocean and ranges from the Equator to the

Tropic of Cancer (Wang & Li, 2009; Liu et al., 2016). A marginal basin is defined as a semi-isolated basin, with typical oceanic depths, separated from the ocean by a system of island arcs (Karig, 1971). Although a marginal basin is semi-isolated, it provides connections from the adjacent continent to the open ocean through small straits and passageways (Liu et al., 2016). The Mindoro, Balabac, and Karimata Straits, the shallow

Taiwan Strait, the deep Bashi Strait, the shallow Malacca Strait, and the deep Luzon

Strait all contribute to connecting the marginal basin of the SCS with the Sulu and Java

Seas, the East China Sea, the Philippine Sea, the Andaman Sea, and the Pacific Ocean, respectively (Qu et al., 2009). The South China Sea basin ranges from shallow water depths to greater than 4000 m in its deepest parts, and its surface area is approximately

3.5 x 1012 m2 (Qu et al., 2009).

The South China Sea is a location where processes affecting sediment source-to- sink transfer can be observed, which include deep water currents, surface water currents, monsoonal patterns, erosion from land, and fluvial input from large Asian rivers (Liu et 44 al., 2016). Due to the semi-enclosed nature of the basin, sediment transport pathways are more distinct, and provenance studies can more accurately assess where sediment originated (Liu et al., 2016). The SCS is surrounded by mainland South China to the north, Taiwan to the northeast, the Luzon arc and the other Philippines islands to the east,

Borneo and Indonesia to the south, and Malaysia, Cambodia, and Vietnam to the west.

Much of the sediment deposited in the South China Sea is supplied by major rivers entering the basin, such as the Pearl River carrying sediment from south China, the

Mekong River carrying sediment through Cambodia and the Indochina Peninsula, and the

Red River, on the northwest margin of the basin, carrying sediment through Vietnam.

Within the SCS basin, sediments also can be redistributed by oceanic currents.

Drilling during Expeditions 367/368 was completed in the northwestern portion of the East Subbasin of the SCS on four structural highs within the continent-ocean transition (COT) zone. The COT is defined as the zone between thinned continental crust that was present before rifting and oceanic crust formed as a result of seafloor spreading

(Cameselle et al., 2017). In other words, it is the area where the extended and thinned continental lithosphere is replaced by ocean crust and lithosphere formed at the spreading rifted margin (Sun et al., 2016b). The composition and thickness of the continent-ocean transition are crucial to understanding the processes and style of rifting, breakup, and seafloor spreading in a rifted margin, making it the targeted location for drilling

(Cameselle et al., 2017). IODP Expeditions 367 and 368 drilled on a broad section of

COT, extending more than 50 km due to crustal stretching prior to breakup (Larsen et al.,

2018b).

The four structural highs chosen for drilling include the outer margin high

(OMH), which is located closest to the continent and is not directly in the COT zone, and

Ridge A, Ridge B, and Ridge C moving seaward, respectively. Each basement ridge is oriented parallel to the rifted margin within the COT (Larsen et al., 2018b). Drilling on the OMH provided an opportunity to core syn-rift to post-rift sediments in an area unaffected by newly created oceanic crust. Three sites were drilled on the OMH including sites U1501, U1504, and U1505. Based on seismic data, the OMH was described as containing an abundance of shallow half-graben basins formed by extensional low angle detachment faults (Larsen et al., 2018b).

Sites U1499 and U1502 were drilled on Ridge A and Site U1500 was drilled on

Ridge B. The objective of drilling at each of these sites was to drill through the lowermost sediment to recover basement rocks in the COT to aid seismic data in differentiating between breakup and rifting models (Sun et al., 2018b; Stock et al., 2018).

Ridge A was described, based on seismic data, as a dome-like structure lacking the faults and half-grabens observed in the OMH (Larsen et al., 2018b). Seismic data also indicated fault blocks rotated toward land on normal faults that dip seaward at Ridges B and C.

Site U1503 was attempted on Ridge C, which would have been an important piece of the transect as it represents the seaward end of the COT and, therefore, full igneous oceanic crust. However, due to mechanical problems, Site U1503 was not drilled after casing was emplaced; the hole was cased and left open for future coring endeavors. The crustal thickness below these basement ridges ranges from 6-8 km, thinning seaward (Larsen et al., 2018b). Drilling across the COT, from the most landward structural high to the

46 basement high representing igneous oceanic crust, creates a transect of records to understand the extent of lithospheric thinning and the timing and onset of oceanic crust formation within the rock record to compare to seismic records and rifting models.

Operations and Lithostratigraphy at Sites U1499 and U1500

Expedition 367 recovered sediment at Site U1499 on Ridge A and Site U1500 on

Ridge B, drilling two holes at each site (Figure 6). Hole U1499A was drilled in a water depth of 3760.2 m and cored from the seafloor to 659.2 mbsf using Advanced Piston

Coring (APC) and Extended Core Barrel (XCB) methods (Sun et al., 2018b). Hole

U1499B was cored using Rotary Core Barrel (RCB) methods to a depth of 1081.8 mbsf

(Sun et al., 2018b). Hole U1500A was drilled in a water depth of 3801.7 m and cored from the seafloor to 854.6 mbsf using RCB coring, and Hole U1500B was cored to a depth of 1529.0 m also using RCB coring (Stock et al., 2018).

The poor recovery at Sites U1499 and U1500 was attributed to unconsolidated sandy intervals that could not be extracted and to the drilling techniques used (shown in

Figure 6). The sediment record recovered at these sites was affected by the method of drilling; for example, the more consolidated sediment farther downhole required different techniques than the less consolidated material. At Sites U1499 and U1500, APC recovered much more sediment (103%) than XCB drilling (60-5%) and RCB drilling

(35%); however, XCB is necessary in more consolidated intervals and RCB is necessary in well-consolidated and hard rock intervals. Casing was installed in both Hole U1499B and Hole U1500B because those holes were very deep, and the casing was necessary to keep the hole open (Figure 6). Operational details of drilling at Sites U1499 and U1500 47

Figure 6. Summary of drilling operations for Sites U1499 and U1500. Drilling operations affect the quality of sediment core recovery (Modified from Larsen et al., 2018b).

48 are described in Larsen et al. (2018b).

Sites U1499 and U1500 contain similar sequences of lithostratigraphic units, although the lithostratigraphic sequence appears to be more complete at Site U1499 and the unit boundaries occur at different depths in these two sites (Figure 7). Based on the more complete lithostratigraphic sequence at Site U1499, these units include:

Unit I -- middle-late Pleistocene aged massive dark greenish gray bioclast-rich clay with sand and thin clayey silt interbeds (Sun et al., 2018b). The silt and sand interbeds fine upward, vary in thickness from 2-5 to 15-20 cm, and are interbedded semi- regularly with massive bioturbated clay intervals; they are interpreted as distal turbidite sequences due to their erosional bases and cyclic appearance (Sun et al., 2018b).

Unit II -- alternating beds of dark greenish gray nannofossil-rich clay and greenish gray clay-rich calcareous ooze (Sun et al., 2018b), with a few very thin to medium beds of dark gray sandy silt within the nannofossil-rich clay. This unit also contains evidence of synsedimentary deformation with distinct folds, faults, and inclined bedding representing a slump deposit (Sun et al., 2018b). The interpreted depositional environment for this lithologic unit is the continental slope.

Unit IIIB -- dark greenish gray clay with thin nannofossil-rich and foraminifer- rich interbeds and thin clayey silt-to-silty sand interbeds (Sun et al., 2018b). The coarser- grained interbeds are interpreted as distal turbidites.

Unit IV -- dark greenish gray silty sand and clay, with very low recovery.

Unit V (Similar to Site U1500 Unit I) -- dark greenish gray clay with thin clayey silt and foraminifer sand interbeds, lacking abundant siliciclastic sand material (Sun et

Site U1499 Site U1500

Key Clay/claystone Silt/Siltstone Sand/Sandstone Gravel Breccia Ooze/Chalk Basalt Sediment Samples

Figure 7. Simplified summary of sediment lithologies and lithostratigraphic units at Sites

U1499 and U1500 (Modified from Sun et al., 2018b).

50 al., 2018b).

Unit VI (Similar to Site U1500 Units II and III) -- dark greenish gray fine- to medium-grained sand interbedded with silt, clay, and foraminifer-rich intervals (Sun et al., 2018b). Lithostratigraphic Units II and III at Site U1500 are very similar in composition but were divided due to the wash down zone separating the recovery and because Unit III contains mudclasts in the sandstone layers (Stock et al., 2018).

Unit VII (Similar to Site U1500 Unit IV) -- dark greenish gray to dark gray sandstone and claystone with foraminifer sandstone and siltstone interbeds (Sun et al.,

2018b). The coarser beds of sandstone and siltstone fine upward into fine-grained claystone intervals and contain parallel laminations and abundant biogenic carbonate clasts (or mudclasts) (Sun et al., 2018b). These intervals are interpreted as distal turbidite sequences. Unit IV at Site U1500 had very low recovery.

Subunit VIIIA (Similar to Site U1500 Subunit VA) -- dark brown claystone with greenish gray to gray siltstone, foraminifer sandstone interbeds, and calcareous-rich claystone (Sun et al., 2018b). The thin beds of gray laminated sandstone are interpreted as distal turbidites.

Subunit VIIIB (Similar to Site U1500 Subunit VB) -- pelagic reddish brown clay- rich nannofossil chalk and clay-rich chalk (Sun et al., 2018b). Angular to subrounded pebbles and concentric black iron-manganese nodules were observed in the lower part of this unit, embedded in nannofossil-rich claystone. The depositional environment of this lithologic unit was a deep marine environment, possibly near a hydrothermal plume on

51 the mid-ocean ridge to form manganese nodules. Unit V at Site U1500 provides the best lithostratigraphic correlation to Site U1499 at Unit VIII.

Lithostratigraphic similarities between Sites U1499 and U1500 are less obvious below Unit VIII, with the following units only recovered at Site U1499:

Subunit IXA -- gravelly sandstone, with clast size increasing downhole from granule to pebble to a matrix-supported breccia (Sun et al., 2018b). The lithology of the clasts varies throughout the subunit, and sorting decreases as the angularity increases downhole (Sun et al., 2018b). This unit is interpreted as a debris flow deposit on the continental slope, supported by an interpretation that the calcareous nannofossils in this unit were transported and reworked (Sun et al., 2018b).

Subunit IXB -- transition zone from the angular clasts in Unit IXA to the nannofossil-barren, rounded to subangular pebbles of Unit IXC (Sun et al., 2018b).

Subunit IXC -- gray to dark gray gravel with intervals of silty sand, transitioning into well-consolidated large cobbles and gravelly sandstone (Sun et al., 2018b). Five lithologies were common in the cobbles, including gray medium-grained gravelly sandstone, very dark gray fine-grained sandy siltstone, gray fine-grained sandstone, gray medium-grained low-grade metasandstone and layered gray to very dark gray medium- grained sandstone. Shipboard analysis indicated that the cobbles contain abundant mono- and polycrystalline quartz, feldspar, muscovite, and lithic grains of igneous, metamorphic, and sedimentary origin. The cobbles are interpreted as the deposit of a debris flow on the continental slope, with sediment sourced from a magmatic arc or recycled orogen (Sun et al., 2018b).

The basal lithostratigraphic units at Site U1500 differ from the basal units recovered at Site U1499, with three units only recovered at Site U1500:

Unit VI -- dark greenish gray silty claystone with biogenic carbonate and thick to very thick beds of dark gray sandstone (Stock et al., 2018). Montmorillonite content increases markedly from the upper part of Unit V to Unit VI (Stock et al., 2018). This unit is a darker green color and is more porous than what was recovered in U1499. Due to the interbeds of sand and the dark green color of the lithology, this unit is interpreted as a turbidite sequence that has undergone hydrothermal alteration.

Unit VII -- claystone that transitions in color from a very dusky red to a greenish gray in direct horizontal contact with the basalt in Unit VIII (Stock et al., 2018). The carbonate content for this unit is low and the montmorillonite content is high (Stock et al., 2018). Similarly, colored claystone intervals are identified within the basalt unit, although those claystones contain more carbonate material.

Unit VIII -- basalt with infrequent thin reddish brown well lithified claystone inclusions that contain authigenic carbonate and few nannofossils (Stock et al., 2018).

Downhole Logging Measurements at Sites U1499 and U1500

Downhole logging was conducted below casing in Holes U1499B and U1500B; these data can be used to identify characteristics of the sediment that were not recovered in low recovery zones, and to compare sand and sandstone intervals throughout the hole and between the two sites. At Hole U1499B, two logging strings were run from 651 mbsf

(at the bottom of the casing) to the bottom of good borehole conditions at 1020 mbsf (Sun et al., 2018b; Figure 8). However, borehole conditions for logging were poor at 670-710 53 m and 830-920 m (Sun et al., 2018b). Measurements acquired during logging include acoustic velocity, resistivity, bulk density, natural gamma radiation (NGR), and a formation microscanner (FMS; Sun et al., 2018b). These measurements can be used in combination with macroscopic core description, physical property measurements taken on the physical cores, and microscopic petrologic data to understand the material that was not recovered and how that material changes downhole. These data are also helpful to further understand the characteristics of the unrecovered matrix material in Subunit IXC and to compare with mineralogic signatures determined from thin sections. The logging data have a sharp increase in acoustic velocity, gamma ray, and resistivity at approximately Core 30, which is the top of lithologic Unit IX (Figure 7). However, the bulk density does not have any major change at this level.

Downhole logging measurements were made at Hole U1500B from 842 m (below casing) to 1133 m (at the bottom of good borehole conditions) (Stock et al., 2018).

Although only 291 m of logging data were acquired, a vertical seismic imager was used in addition to the logging tools used at Site U1499 to obtain a vertical seismic profile in a check shot experiment (Stock et al., 2018). Unlike the sharp peaks in the logging data for

Site U1499, the logging data for Site U1500 have little change within lithologic Units III and IV (Figure 9).

Figure 8. Downhole logging data for Site U1499B.

Figure 9. Downhole logging data for Site U1500B.

Chapter 4. Materials & Methods

Materials

Samples for this study were identified using shipboard core descriptions and core images and were requested and approved following standard procedures for an IODP shipboard scientist. Samples were taken during the Expedition 367/368 shore-based sampling party at the Gulf Coast Repository. All samples were 10 cc in volume and contained medium to coarse sand grains; however, the samples varied in lithification from unconsolidated to very well cemented.

A total of 69 samples of medium- to coarse-grained sand and sandstone intervals were selected from Holes U1499A, U1499B, U1500A, and U1500B (Figure 7). Samples were selected to examine representative sandy intervals throughout Sites U1499 and

U1500, while avoiding sandy intervals dominated by foraminifers. For Site U1499, 27 samples were taken from sandy turbidite intervals in Lithostratigraphic Units I, II, III, IV,

VI, and VII, and 23 samples were taken from the brecciated sandstone and cobbles in

Units IXA and IXC. The distribution of these samples through the lithostratigraphic units at Site U1499 is listed in Table 2 and is illustrated in Figure 7 (A more detailed sample table for Site U1499 is included in Appendix A).

Although overall core recovery was low for Site U1500, due to the use of RCB coring in soft lithologies plus washing down through several stratigraphic intervals, 19 57

Site U1499 Average Number Sedimentation LSU Unit Description Depth (mbsf) of Age Rate samples (mm/k.y.) Bioclast-rich clay with thin Hole A: 0- Middle-late Unit I 9 130 clayey silt and 48.85 Pleistocene sand interbeds Clay-rich Early- calcareous ooze Hole A: 48.85- Slump - Unit II 1 middle and nanno-rich 100.04 unknown Pleistocene clay Clay with thin Early Unit Hole A: silt and foram 2 50 Pleistocene IIIB 181.80-333.65 interbeds -Pliocene Early Unit Silty sand with Hole A: Pliocene- 1 80 IV clay interbeds 333.65-404.90 late Miocene Unit Silty sand with Hole A: Late 3 80 VI clay interbeds 469.45-618.30 Miocene Sandstone and Hole A: Unit claystone with 618.30-659.20 Late 9 80 VII siltstone Hole B: Miocene interbeds 655.00-761.70 Unit Claystone with Hole B: Early-late 1 80 VIIIA interbeds 761.70-892.10 Miocene Unit Hole B: Early Clay-rich chalk 1 8 VIIIB 892.10-929.02 Miocene Sandstone with Unit Hole B: clasts and 7 Unknown Oligocene IXA 929.02-933.28 breccia Oligocene Unit Gravel with silty Hole B: 16 Unknown (and pre- IXC sand intervals 933.35-1081.8 Oligocene)

Table 2. Summary of samples selected from Site U1499.

58 samples were selected from sand intervals within Lithostratigraphic Units III, IV, and VI.

The distribution of these samples through the lithostratigraphic units at Site U1500 is listed in Table 3 and is illustrated in Figure 7 (A more detailed sample table for Site

U1500 is included in Appendix B). Despite the low recovery, the location of Site U1500 near Site U1499 provides an opportunity to better document and correlate the stratigraphic records at these two sites, which are located on adjacent basement ridges.

This comparison is especially important because the basal sediments and basement rock recovered at Site U1500 are much different than the basal sediments and inferred basement rock at Site U1499.

Methods

This study is based on data collected by examining each sample using a petrographic microscope, so sample preparation procedures were designed to produce materials appropriate for this type of analysis. As described below, the specific steps of sample preparation were determined by the degree of lithification of that sample.

Of the 69 samples collected, 33 were sufficiently lithified to be cut into billets and made into conventional thin sections. Thin sections were prepared by a commercial vendor (Spectrum Petrographics, Inc.). Conventional thin sections were embedded with epoxy, mounted on a glass slide and ground to 30 microns, stained for potassium and calcium-bearing feldspar, and finished with a coverglass. The embedding resin used for all samples was clear Epotek 301.

Samples that were slightly to moderately lithified were sieved to collect the sand fraction, which was used to create grain mounts (or strewn slides). Of the total 69 59

Site U1500 Average Number Lithostrat. Unit Sedimentation Depth (mbsf) of Age Unit Description Rate samples (mm/k.y.) Sandstone and claystone Hole A: with thin 641.20-854.60 Late Unit III 6 120 siltstone Hole B: Miocene interbeds and 846.00-892.44 mud clasts Sandstone with Hole B: Late Unit IV claystone and 7 120-270 892.44-1233.30 Miocene siltstone interbeds Silty claystone with Hole B: Unit VI 6 unknown Oligocene sandstone and 1310.98-1370.33 biogenic carbonate

Table 3. Summary of samples selected from Site U1500.

60 samples, 25 samples were sieved to make grain mounts. These samples were disaggregated using an ultrasonic cleaner and then, if necessary, a sonic dismembrator.

Once the samples were disaggregated, they were wet-sieved twice: first, to separate the sand fraction from the fines and gravel, and then to separate the sands into 63-125 micron, 125-250 micron, and 250-500 micron fractions. Sieved sand fractions were oven- dried and then inspected with a hand lens to estimate the abundances of siliciclastic vs. biogenic (i.e., foraminifer) grains. Sieved sand fractions were also photographed with a

Leica DMS 1000 digital light microscope. The 250-500 micron size fractions of sixteen samples were dominated by foraminifers, so those samples were treated with 10% HCl to remove the biogenic carbonate grains and then were re-sieved. Grain mounts for 21 samples were made using the 250-500 micron size fraction; grain mounts for the other four samples were made using the 125-250 micron size fraction, due to the small amount of material in the 250-500 micron size fraction for those four samples. However, two of these four samples did have a small amount of 250-500 micron sized material, so grain mounts also were made of these small samples. Three of the sieved samples lacked enough material in any size fraction for a conventional grain mount, so grain mounts for those samples were produced with an optimally confined monolayer method. All grain mounts were prepared by a commercial vendor (Spectrum Petrographics, Inc.); processing included two steps of embedding the sand grains in epoxy, in order to minimize settling bias; mounting on a glass slide and grinding to 30 microns; staining for potassium and calcium-bearing feldspar; and finishing with a coverglass. The embedding

61 resin used for all samples was clear Epotek 301. Duplicate grain mounts were made for three samples, in order to assess reproducibility of the compositional data.

The remaining 11 samples had an intermediate degree of lithification and proved impossible to disaggregate without using destructive methods. As a result, those 11 samples also were made into thin sections, although they were subject to fragmentation as the thin sections were made. These thin sections were also prepared by a commercial vendor (Spectrum Petrographics, Inc.), using the same steps as were used for the well- lithified samples.

Samples were examined using a Leitz Ortholux II Pol-BK petrographic microscope, with a Swift automatic point counter used to ensure a 500 micron step size during point-counting of thin sections. A minimum of 300 grains, excluding matrix counts, were identified and counted on each thin section and grain mount (with the exception of one thin section that had a total of 260 grains counted because it lacked an abundance of grains). Point counts on thin sections were made using a modified version of the Gazzi-Dickinson method, which is the most commonly used method among sedimentary petrologists (Marsaglia et al., 1996; Dickinson et al., 1970). In the modified version of the Gazzi-Dickinson method used for this study, mineral grains were counted if they were contained in a rock fragment larger than 500 microns in a thin section, rather than counting the single large rock fragment; this modification was made to accommodate the wide range of grain sizes in some thin sections. The exceptions to this counting strategy were large chert or volcanic rock fragments, which were counted as rock fragments because of their small constituent grain sizes. Another exception to this

62 method was if the center of the cross hairs landed on the matrix of a large >500 micron sedimentary rock fragment. In this case the grain was counted as a rock fragment because a single mineral couldn’t be identified. In those cases, if the grain was larger than the step size, and the same grain was landed on twice, the grain was only counted once, and nothing was recorded the second time. Therefore, the modified Gazzi-Dickinson method was mostly used for plutonic rock fragments and metamorphic rock fragments.

Thin sections were point-counted with a step size of 500 microns horizontally, and a new transect was created by moving the thin section 1 to 2 mm vertically, depending on the abundance of grains, the size of the grains, and the shape and size of the rock chip on the thin section. The size of each grain counted was also recorded for each thin section, to better understand how the grain composition is affected by grain size. The petrographic reference, Memoir 109: A Color Guide to the Petrography of Sandstones,

Siltstones, Shales and Associated Rocks (Ulmer-Scholle et al., 2014), was used to identify minerals and rock fragments in thin section. Grains for each thin section were identified and placed into 17 monomineralic and polymineralic categories (Table 4).

Grain mounts were also point-counted with a step size of 500 microns horizontally, however unlike the technique used for thin sections, if the center of the cross hairs landed on epoxy, the closest grain to the center was identified and counted. If the center of the cross hairs was equidistant to all surrounding grains, nothing was counted, and the thin section was moved another 500 microns. In thin section, if the center of the cross hairs landed on matrix, then that position was counted as matrix and

Counted Parameters Qp: Polycrystalline quartz Qm: Monocrystalline quartz P: Plagioclase feldspar K: Potassium feldspar Lp: Plutonic rock fragments Lv: Volcanic rock fragments Lm: Metamorphic rock fragments Lsi: Siliciclastic sedimentary rock fragments (siltstone-sandstone) Chemical sedimentary rock fragments (chert, chalcedony, oolitic Lsch: limestone) Lsc: Biochemical (carbonates) Mus: Muscovite Biot: Biotite and Chlorite Glau: Glauconite Bioclasts: Siliceous and calcareous microfossils and bioclasts Opaques: Opaques (pyrite/oxides) Carb: Carbonate minerals Dense: Dense minerals (zircon, hornblende, tourmaline, pyroxene) Total Grains: Total grains counted excluding matrix Q=Qp+Qm F=P+K Lvt=Lp+Lv Lst=Lsi+Lsch+Lsc L=Lvt+Lst+Lm Calculated Parameters

QFL%Q = 100 x Q/(Q + F + L) LmLvtLst%Lm = 100 x Lm/L QFL%F = 100 x F/(Q + F + L) LmLvtLst%Lvt = 100 x Lvt/L QFL%L = 100 x L/(Q + F + L) LmLvtLst%Lst = 100 x Lst/L

QmKP%Qm = 100 x Qm/(Qm + F) QmKP%P = 100 x P/(Qm + F) QmKP%K = 100 x K/(Qm + F) %M = 100 x (Mus+Biot)/(Total Grains) %Glau = 100 x (Glau/Total Grains)

Table 4. Counted parameters list the compositional categories grains were placed into while point counting. Calculated parameters list calculations made for analysis of the point counting data.

64 the crosshairs were moved another 500 microns instead of identifying the closest grain.

Although grain boundaries were much easier to distinguish in grain mounts than in thin sections, the mineral relief was much higher in the grain mounts, which meant that relief was not always the best property to use when identifying minerals in grain mounts. Mud blobs, which were not well disaggregated during the sieving process prior to being made into grain mounts were counted as matrix and were not added to the total grain count.

Minerals were identified based on specific guiding principles formed from petrographic references and cross-verification of grain types with petrologists and sedimentologists (Dr. M. Barton, Dr. D. Elliot, and Dr. L. Krissek, personal communication). Guiding principles used to identify plagioclase and potassium feldspar grains include stain color, evidence of cleavage, blocky shape, the orientation of oxides

(along cleavage planes), twinning pattern, and/or the tattered weathered appearance of feldspar altering to clay. Staining varies among feldspar grains due to the amount of Ca,

Na, and K in the feldspar minerals, for example, albite minerals, or pure Na minerals, appear unstained in thin section and in grain mount causing stain to be only one of many guiding principles to identify feldspar in thin section. Identified unstained feldspar grains were counted as plagioclase for this study.

Biotite was identified based on the presence of pleochroism, frequent alteration to chlorite, mottled birdseye extinction, and cleavage. Guiding principles used to identify chlorite include sweeping extinction and/or mottled extinction, green-blue pleochroism, and the anomalous blue interference color. To identify carbonate minerals lacking biogenic evidence, the relief of the grain was observed as the stage was rotated to identify

65 a change in relief. Kaolinite and chert appear similar in thin section, however at high magnification the speckled appearance of kaolinite appears more linear, whereas the chert grain looks more granular. Lithic grains were also identified based on a set of guiding principles; siliciclastic rock fragments were identified based on the presence of matrix or cement and individual identifiable grains; metamorphic rock fragments were identified based on the presence of elongated and stretched quartz minerals and/or oriented mica or oxide minerals; volcanic rock fragments were identified based on the presence of plagioclase laths or shards of minerals within a fine grained matrix; plutonic rock fragments were identified based on the presence of 2 or more minerals with little to no matrix and no preferred orientation.

Duplicate grain mounts were made and point-counted for two samples selected from U1499A and one sample selected from U1499B in order to evaluate reproducibility across point counting techniques and grain mount preparation. The compositional data for these duplicate grain mounts is in Table 5. The framework grain compositions are very similar between grain mount duplicates, but the detailed lithic compositions vary more due to the low percentage of total lithic grains identified in each of these three duplicates.

The grain size distribution counted for each of these duplicate thin sections also shows very similar results which indicates precision in measuring grains under the microscope.

The average standard deviation of quartz abundance between duplicate samples was low at 3.6% and the average standard deviations of feldspar abundance and lithic abundance were calculated to be even lower, indicating that the point counting technique and identification of framework grains is reproducible, and conclusions can be drawn on

Reproducibility Core, section, Depth Average grain %Q %F %L %Lvt %Lm %Lst %M Qp/Q P/F Lp/Lvt interval (mbsf) size (µm) (cm) <63-125: 6.1% U1499A- 125-250: 37.1% 5H-6W, 44.72 250-500: 53.4% 66.9 26.1 7.0 35.0 55.0 10.0 0.3 0.0 0.7 1.0 122-124 >500: 3.5% B8T-004 max: 630

<63-125: 4.5% U1499A- 125-250: 36.6% 5H-6W, 44.72 250-500: 57.0% 72.1 23.3 4.5 46.2 38.5 15.4 1.3 0.1 0.8 1.0 122-124 >500: 1.9% B8T-005 max: 630

<63-125: 2.8% U1499A- 125-250: 45.6% 8H-4W, 70.37 250-500: 51.3% 67.8 29.6 2.6 37.5 25.0 37.5 0.3 0.1 0.9 1.0 137-139 >500: 0.31% B8T-009 max: 560

U1499A- <63-125: 4.7% 8H-4W, 125-250: 52.0% 70.37 61.0 32.5 6.4 73.7 21.1 5.3 0.3 0.1 0.9 1.0 137-139 250-500: 43.2% B8T-010 max: 490

<63-125: 0.32% U1499B- 125-250: 16.5% 9R-1W, 724 250-500: 78.5% 51.2 39.9 9.0 33.3 48.1 18.5 2.2 0.2 0.7 1.0 107-109 >500: 4.7% B8T-021 max: 840

<63-125: 1.6% U1499B- 125-250: 19.5% 9R-1W, 724 250-500: 74.4% 47.8 41.2 11.0 43.8 34.4 21.9 5.4 0.2 0.8 1.0 107-109 >500: 4.5% B8T-022 max: 630

Table 5. Reproducibility results from 3 different samples showing similar mineral compositions. 67

Reproducibility Calculations

Core, section, STDEV STDEV STDEV AVG %Q AVG %F AVG %L interval (cm) %Q %F %L

U1499A-5H-6W, 69.5 3.7 24.7 2.0 5.7 1.7 122-124

U1499A-8H-4W, 64.4 4.8 31.1 2.1 4.5 2.7 137-139

U1499B-9R-1W, 49.5 2.4 40.6 1.0 10.0 1.4 107-109 Average Standard 3.6 1.7 2.0 Deviation

Table 6. Average and standard deviation calculations of framework grains in duplicate samples.

68 variations in grain composition greater than 4% (reproducibility calculations shown in

Table. 6).

Data were analyzed using QFL ternary plots (quartz-feldspar-lithic ternary plots), as well as lithic ternary plots (total metamorphic rock fragments-total volcanic rock fragments-total sedimentary rock fragments) and QmKP ternary plots (Monocrystalline quartz, feldspar, plagioclase ternary plot). Spider plots were made to observe stratigraphic patterns of compositional change at each site. Data for Site U1499 were analyzed by comparing the average calculated mineral signature in each lithostratigraphic unit as well as comparing the average mineralogy between upper sediments and basal sediments. Data for Site U1500 were analyzed by comparing the average calculated mineral signature in each lithostratigraphic unit as well as comparing the average mineralogy between Site

U1500 and Site U1499.

Chapter 5. Data

Sixty-eight of the thin sections/grain mounts of samples from Sites U1499 and

U1500 were analyzed by point counting; the remaining three grain mounts, made from samples that had not been pretreated with HCl, were dominated by carbonate microfossils and did not contain enough siliciclastic grains for a representative population count. The original point count data and grain size data for each sample analyzed are given in Appendix C. Observations of mineral abundances, inclusions, and matrix made during point count analysis for each thin section are included in Appendix

D. The original data were used to calculate the relative abundances of quartz, feldspar, and lithic grains, as well as the relative abundances of volcanic lithic, metamorphic lithic, and sedimentary lithic grains, in order to present this compositional data on appropriate ternary diagrams and in tabular form. Appendices E and F contain those calculated abundances for Sites U1499 and U1500, respectively.

Grain Size Effect on Sample Composition

During weathering and transport, rock fragments tend to break down into smaller constituent grains, thereby creating a trend with rock fragments more abundant in coarser grained sediment and less abundant in finer grained sediments (Ingersoll et al.,

1984). As a result, a modified version of the Gazzi-Dickinson method was used in this study to minimize the effect of grain size on sample composition. However, grain sizes 70 were still measured in this study to independently assess variations in grain composition as a function of grain size. This was accomplished by measuring the size of each grain counted, and then determining an average grain size for each thin section from the distribution of grain sizes counted in that thin section.

Figure 10 shows the framework grain composition (% quartz, % feldspar, and % lithic fragments) as a function of grain size for all samples from Sites U1499 and U1500.

The Site U1499 samples include representatives from every average grain size group.

For some average grain sizes, the Site U1499 samples exhibit a wide range of compositions; for example, the group of fine and medium sand samples ranges from

9.1% to 72.1% quartz. The fine sand group and the medium and coarse sand group also shows significant variability in quartz and feldspar abundances. However, the samples in these size ranges do not have any consistent changes to greater rock fragment abundances as grain size increases.

Two samples of medium sand size from Site U1499 are enriched in lithic fragments, with lithic abundances of 30-40%. Most medium sand samples from Site

U1499 have much lower lithic abundances, generally between 0% and 10%. The two samples with higher lithic abundances also contained abundant mica grains (not reflected in Figure 10), and abundant grains classified as sedimentary rock fragments. A re-evaluation of those possible sedimentary rock fragments, however, suggests that they may have been sand and mud “clumps” that were not disaggregated during sample processing, rather than being detrital sedimentary rock fragments. If that re-evaluation is correct, then the lithic abundances for these two samples would be reduced

Site U1500 Site U1499

QuartzQuartz QuartzQuartz Key Key Quartz Very Fine and Fine Sand Very Fine and Fine Sand Fine Sand Key Fine Sand Fine and Medium Sand Fine and Medium Sand Medium SandVery Fine and Fine Sand Medium Sand Medium and Coarse Sand Medium and Coarse Sand Coarse SandFine Sand Coarse Sand Fine and Medium Sand Medium Sand Medium and Coarse Sand Coarse Sand

Feldspar Feldspar Rock Fragments Rock Fragments Feldspar Feldspar Lithics

Figure 10. Framework grain composition for all data samples categorized by average

grain size. The left triangle represents Site U1500 samples and the right triangle

represents Site U1499 samples.

Feldspar Rock Fragments

72 significantly, and their compositions would be more consistent with the rest of the medium sand samples from Site U1499.

Only one sample from Site U1499 is classified as coarse-sand sized. That sample has a high lithic fragment abundance (20.4%) but provides limited evidence of the effect of grain size on grain composition. Table 7 shows the average quartz, feldspar, and lithic fragment abundances, and their standard deviations for each grain size group at Sites U1499 and U1500. The range in quartz and feldspar average abundances at Site U1499 (Table 7A) is much larger than the changes in lithic fragment abundances, indicating that grain size has little direct impact on rock fragment abundances at Site U1499.

The compositional data indicate that the samples from Site U1499 can be separated into two main clusters: one is relatively feldspar-rich and the other is relatively quartz-rich (Figure 10). The medium sand-sized samples generally lie within the more quartz-rich cluster, whereas the very fine and fine sand-sized samples lie within the feldspar-rich cluster. The fine sand-sized samples and the fine and medium sand-sized samples extend across the full range of quartz and feldspar abundances in this study.

Lithic fragment abundances have no consistent pattern of variation with grain size, suggesting that compositional variations in the Site U1499 samples are relatively independent of sample grain size. Instead, the samples in these two clusters generally are distinguished by their stratigraphic positions, so that the dominant compositional differences are between the upper sediments and the basal sediments at Site U1499.

Similar to the sediment compositions at Site U1499, the very fine and fine sands,

Table 7. Grain composition as a function of grain size. Part A shows the data for Site

U1499 and Part B shows the data for Site U1500.

74 fine sands, fine and medium sands, and medium sands at Site U1500 cluster along the quartz-feldspar join, with <10% lithic fragments (Figure 10). The very fine and fine sand-sized samples and the fine sand-sized samples are spread relatively evenly across the cluster, whereas the medium sand-sized samples are slightly enriched in lithic fragments. Medium sands are the largest average grain size analyzed from Site U1500, but are represented by only two samples (Table 7B).

The average lithic fragment abundance for the medium sands at Site U1500, shown in Table 7B, is higher than the values for the other grain sizes at this site.

However, the small number of medium sand samples, makes it difficult to evaluate whether a relationship exists between grain size and lithic fragment abundance.

Evaluating any potential trend is further complicated by the analysis of only one fine and medium sand-sized sample from Site U1500. In general, any trend of increasing lithic fragment abundance with larger grain size at Site U1500 appears to be small. The change in average lithic fragment abundances between grain size groups (Table 7B) is much smaller than the changes in average quartz and feldspar abundances, supporting the interpretation that grain size exerts a minimal influence on sample composition at

Site U1500. Based on the limited effect of grain size on sample composition at both Site

U1499 and U1500, this study will proceed by combining the data from all grain sizes

(i.e., from all samples); results will not be separated by grain size for interpretation.

The potential effect of grain size on sample composition at Site U1499 is explored in more detail in Figure 11, where the two depth-defined sample clusters are plotted separately. The upper sediments are from Lithostratigraphic Units I-VII, and the

Units IXA & IXC Units I-VII

QuartzQuartz QuartzQuartz Key Key Quartz Very Fine and Fine Sand Very Fine and Fine Sand Fine Sand Fine Sand Fine and Medium Sand Key Fine and Medium Sand Medium Sand Very Fine and Fine Sand Medium Sand Medium and Coarse Sand Medium and Coarse Sand Coarse SandFine Sand Coarse Sand Fine and Medium Sand Medium Sand Medium and Coarse Sand Coarse Sand

FeldsparFeldspar FeldsparFeldspar Rock Fragments Rock Lithics Fragments

Figure 11. Framework grain composition for Site U1499 samples categorized by average

grain size. The left triangle represents the basal sediments in lithostratigraphic units IXA

and IXC. The right triangle represents the upper sediments in lithostratigraphic units I-

VII.

Feldspar Rock Fragments

76 basal sediments are from Lithostratigraphic Units IXA and IXC. Both the fine and medium sand-sized samples and the medium sand-sized samples in the upper sediments show a wide range of quartz and feldspar abundances, with a much smaller range of lithic fragment abundances. The fine sand-sized samples in the upper sediments show less variability than the coarse size fractions, although that difference could be the result of a small number of fine sand-sized samples (Table 8A).

The basal sediments at Site U1499 also show a wide range of compositions for the very fine and fine sand, fine and medium sand, and fine sand samples. The medium and coarse sand- sized samples and the coarse sand-sized samples both have a higher abundance of lithic grains (Table 8B), although the statistical significance of that increase is difficult to assess because there is only one sample for each of those grain size groups in the basal sediments at Site U1499. The similarity of the averages and standard deviations for each framework grain type between grain size groups indicates that grain size changes have little to no impact on sediment composition at Site U1499. This similarity supports the decision to analyze the compositional data for all samples together, rather than interpreting data separately for each grain size fraction.

Stratigraphic Variations in Sediment Composition

Quartz, Feldspar, and Rock Fragment Abundances

The quartz, feldspar, and lithic fragment abundances for all samples at Sites

U1499 and U1500 are shown in Figure 12 and Table 9, separated into lithostratigraphic units for the respective sites. A more detailed table of calculated parameters for all

B Table 8. Grain composition as a function of grain size for Site U1499 separated by upper sediment and basal sediment. Part A shows the data for the upper sediments in lithostratigraphic units I-VII. Part B shows the data for the basal sediments in lithostratigraphic units IXA and IXC.

Site U1500 Site U1499

Quartz QuartzQuartz QuartzQuartz Key Key KeyU1500 Unit III U1499 Units I-VII U1500 Unit IV U1499 Units IXA and IXC U1499 Units I-VIIU1500 Unit VI U1500 Unit III U1499 Units IXA and IXC U1500 Unit IV U1500 Unit VI U1500 Unit III U1500 Unit IV U1500 Unit VI

FeldsparFeldspar FeldsparFeldspar Rock Fragments Rock Lithics Fragments Figure 12. Quartz, feldspar, and lithic grain abundances for all samples. The left triangle

represents samples from Site U1500 categorized by lithostratigraphic units. The right

triangle represents samples from Site U1499 divided into upper sediments and basal

sediments.

Feldspar Rock Fragments

Average Composition of Framework Grains at Site U1499 Basal Sediments vs. Upper Sediments Site QFL %Q QFL %F QFL %L LmLvtLst %Lm LmLvtLst %Lvt LmLvtLst %Lst U1499 LSU n AVG STDEV AVG STDEV AVG STDEV AVG STDEV AVG STDEV AVG STDEV

I-VII 26.0 54.3 13.2 38.2 11.6 7.5 8.8 27.7 15.4 40.9 22.7 27.6 24.4 IXA & 23.0 18.0 5.7 74.3 8.0 7.6 4.9 24.5 23.5 42.0 19.8 33.5 22.6 IXC

Average Composition per Lithostratigraphic Unit at Site U1500 Site QFL %Q QFL %F QFL %L LmLvtLst %Lm LmLvtLst %Lvt LmLvtLst %Lst U1500 LSU n AVG STDEV AVG STDEV AVG STDEV AVG STDEV AVG STDEV AVG STDEV

III 6 53.5 6.9 41.6 8.0 4.9 3.0 34.2 24.8 21.0 30.5 44.8 32.7

IV 7 50.4 3.8 44.2 5.4 5.5 2.4 34.4 14.4 32.5 24.8 33.1 24.9

VI 6 54.7 4.1 39.9 4.8 5.4 1.3 41.7 13.6 45.5 12.5 12.9 11.8

Table 9. The average framework grain composition and lithic grain distribution for LSUs at Sites U1499 and U1500. Part A compares the average composition of framework grains between upper sediments in LSUs I-VII and basal sediments in LSUs IXA and

IXC at Site U1499. Part B compares the average composition of framework grains between each LSU at Site U1500.

80 samples from Site U1499 is included in Appendix E, and equivalent data for samples from Site U1500 are included in Appendix F. The data for Site U1499 indicate that basal sediments in Lithostratigraphic Units IXA and IXC are much more feldspar-rich than the quartz-rich upper sediments in LSUs I-VII (Figure 12); the upper sediments have an average framework composition of Q54F38L8, whereas the basal sediments have an average framework composition of Q18F74L8 (Table 9A). Standard deviations for each framework grain type are higher in the upper sediments than in the basal sediments.

Quartz abundances in the upper sediment group range from 41% to 75% (not including three outlier samples that are discussed below), with an average of 54.3%

(Figure 12 and Table 9A). The abundance of lithic grains in the main cluster of upper sediments is low (< 11%) and averages 7.5% of the total framework grains (Table 9A).

The compositional shift between the upper and basal sediment groups is relatively abrupt, except for one sample from the upper sediments (Unit VII) that is relatively enriched in feldspar. That feldspar-enriched sample (one of the three outlier samples) was compositionally unusual; quartz, feldspar, and rock fragments represented <10% of the total framework grains of that sample, with the framework dominated by biotite, chlorite, carbonate, and opaque minerals.

Outlier samples two and three from the upper sediments at Site U1499 (Units VI and VII) have anomalously high lithic fragment abundances. As mentioned previously, those two samples were analyzed as containing high abundances of mica and sedimentary rock fragments. However, the putative rock fragments may have been the result of

81 incomplete sample disaggregation during processing, so these samples are not considered compositionally representative of the Site U1499 upper sediments.

The basal sediments at Site U1499 are enriched in feldspar relative to the Site

U1499 upper sediments, with feldspar contents ranging from 56.3% to 88.5% and averaging 74.3% (Table 9A). Subunit IXA consists of a matrix supported breccia with large subangular clasts, transitioning into more consolidated gravel with little to matrix recovered between cobbles in Subunit IXC. The sedimentary clasts within the breccia in subunit IXA have the same appearance and mineral signature as the cobble thin sections from subunit IXC. Although the cobbles were comprised of grains of the relatively smaller sand sizes, as indicated by the grain size data discussed previously (Figures 10 and 11), approximately half of the basal sediment samples are slightly enriched in lithic grains when compared to the upper sediments. Lithic grain abundances in the basal sediments range from 0.7% to 20.4%; the average abundance of lithic grains in the basal sediments is 7.6%, which is similar to the average for the upper sediments.

Samples from Site U1500 exhibit much less compositional variability than at Site

U1499 (Figure 12 and Table 9), and the compositions for each LSU at Site U1500 are similar. LSUs III, IV, and VI at Site U1500 have average framework compositions of

Q54F42L5, Q50F44L6, and Q55F40L5, respectively, with low standard deviation values for each framework grain type. This compositional similarity across LSUs is noteworthy, because these LSUs had very different physical appearances during shipboard description. Overall, the Site U1500 samples are compositionally similar to the upper sediments at Site U1499, with less than 10% lithic grains and quartz abundances ranging

82 from 44.5% to 63.1%. This compositional similarity between Site U1500 and the upper sediments at Site U1499 supports the correlation of Units III and IV at Site U1500 with

Units VI and VII at Site U1499, discussed among shipboard scientists onboard the expedition. However, the similarity of the basal sediments at Site U1500 (Unit VI) and the younger sediments at Site U1499 calls into question the previous correlation of older units between the two sites, as Unit VI at Site U1500 was previously thought to represent an interval not recovered at Site U1499.

There is also a shift in mineral composition between LSUs within the upper sediments at Site U1499. Figure 13 shows a more detailed examination of framework grain abundances in the upper sediments at Site U1499, subdivided by lithostratigraphic unit. With the exception of Unit III, the quartz content generally increases upsection.

Comparison of Framework Grain and Lithic Grain Assemblages, Site U1499

The average QFL and LmLvtLst abundances for all lithostratigraphic units analyzed at Site U1499 are shown in Table 10. The upper sediments range from LSU VII to LSU I, and their average QFL values show a general increase in quartz abundance and a general decrease in lithic fragment abundance upsection. LSUs IXC and IXA, in the basal sediments, contain significantly less quartz and significantly more feldspar than the upper sediments.

Overall the lithic grain compositions show much more variability between lithostratigraphic units than their framework grain compositions do. LSU IXC contains abundant volcanic rock fragments; LSUs IXA and VII have subequal abundances of the three lithic grain types; LSU VI contains abundant sedimentary rock fragments; LSU IV 83

Site U1499

QuartzQuartz Key Quartz U1499 Unit I Key U1499 Unit II U1499 Unit III U1499 Unit I U1499 Unit IV U1499 Unit II U1499 Unit VI U1499 Unit VII U1499 Unit III U1499 Unit IV U1499 Unit VI U1499 Unit VII

FeldsparFeldspar Rock LithicsFragments Figure 13. Quartz, feldspar, and lithic composition of Site U1499 upper sediments

categorized by lithostratigraphic unit.

Feldspar Rock Fragments

Average Composition of Framework Grains per Lithostratigraphic Unit at Site U1499 Site QFL %Q QFL %F QFL %L LmLvtLst %Lm LmLvtLst %Lvt LmLvtLst %Lst U1499 LSU n AVG STDEV AVG STDEV AVG STDEV AVG STDEV AVG STDEV AVG STDEV

I 8 63.8 9.0 31.7 10.2 4.6 1.7 31.6 17.1 49.4 27.3 19.0 22.7

II 2 64.4 4.8 31.1 2.1 4.5 2.7 23.0 2.8 55.6 25.6 21.4 22.8

IIIB 3 49.2 4.8 46.8 4.6 4.0 0.3 22.3 9.7 57.5 17.0 20.2 14.7

IV 1 66.2 NA 27.0 NA 6.8 NA 30.0 NA 40.0 NA 30.0 NA

VI 3 51.7 21.0 33.1 3.5 15.3 19.3 16.7 19.1 21.0 12.8 62.4 31.0

VII 9 45.0 10.8 45.6 12.4 9.4 10.1 30.4 16.9 31.2 16.8 27.3 22.1

IXA 7 18.4 8.4 76.6 9.1 5.0 3.1 36.6 33.6 31.8 26.2 31.7 25.3

IXC 16 17.9 4.4 73.3 7.6 8.8 5.2 19.3 16.0 46.5 15.1 34.3 22.2

Table 10. The average framework grain composition and lithic grain distribution for each lithostratigraphic unit at Site U1499.

85 has subequal abundances of the three lithic grain types; LSUs IIIB and II contain abundant volcanic rock fragments with subequal amounts of metamorphic rock fragments and sedimentary rock fragments; and LSU I contains mostly volcanic rock fragments and metamorphic rock fragments.

Lithic Grain Composition

The lithic grain assemblage of each sample at Site U1499 is subdivided into abundances of metamorphic, total volcanic, and sedimentary rock fragments in Table 9A.

The upper sediments have an average lithic composition of Lm28Lvt41Lst28, whereas the basal sediments have an average lithic composition of Lm25Lvt42Lst34. Although the lithic compositions of the upper and lower sediments generally are similar, the basal sediments are slightly enriched in sedimentary rock fragments and volcanic rock fragments, whereas the younger sediments are slightly enriched in metamorphic rock fragments.

The lithic grain assemblage of each sample at Site U1500 is subdivided into abundances of metamorphic, total volcanic, and sedimentary rock fragments in Table 9B.

LSUs III, IV, and VI at Site U1500 have average lithic grain compositions of

Lm34Lvt21Lst45, Lm34Lvt33Lst33, and Lm42Lvt46Lst13 respectively, which exhibits much more variability than the framework grain abundances. The abundances of metamorphic lithic grains are similar for Units III and IV, but Unit III contains more sedimentary rock fragments and less volcanic rock fragments than Unit IV. The lithic grain composition of

Unit VI is very different from that of the other two units, with fewer sedimentary rock fragments and more volcanic and metamorphic rock fragments.

The standard deviation is much higher for each type of lithic grain than for the major framework grain types because the number of lithic grains counted in each sample is small. As a result of the low absolute numbers of lithic grains counted, even a small change in the absolute number of a particular lithic grain type encountered produces a large change in the percent abundance of that grain type, and generates a relatively large standard deviation.

Documentation of Grain Types

Photomicrographs were taken to document grain types encountered and counted during this study, and representative photomicrographs will be presented and described in this section. Photomicrographs of thin sections from the upper sediments of Site U1499 are shown in Figure 14; these photomicrographs are organized by depth, with Figure 14A representing the youngest sample and Figure 14I representing the oldest sample from the upper sediments. Figure 14A is a grain mount with abundant angular to subangular monocrystalline quartz grains and two polycrystalline quartz grains. Quartz grains have evidence of strain through undulatory extinction, and contain fractures and vacuoles.

Although not pictured here, quartz grains typically contain tourmaline and needle-like mineral inclusions as well as oxide mineral inclusions. Plagioclase grains stained reddish brown have evidence of twinning, and some plagioclase grains have evidence of alteration to sericite.

Figure 14B contains a weathered plagioclase grain altering to sericite but still shows evidence of twinning; a potassium feldspar grain stained yellow (appearing green

500 µm A 200 µm 200 µm Qm B C P Qm Qm P Qm

Qm P Qm Qp Lm P Qm Qm K Qp Lsch P P K Qm K 500 µm D 200 µm E 200 µm F P Qm

Qm Qm v Qm v Dense Carb v Lm Qm Qp v Qm P v Qm K Qm P Qm v P Qm K v K

200 µm 200 µm 200 µm Carb G Qm H I Carb Clay P

Lsi K K Chl Qm Lsi K Mus Lsi Biot P Mus Qm Qm P Qm

Qm K Figure 14. Photomicrographs from the upper section of Site U1499 (See Table 4 for definition of parameter abbreviations). Part A. Quartz and feldspar minerals in U1499A-

4H-6 (104-106 cm); Part B. Weathered plagioclase, potassium feldspar, and quartz in

U1499A-4H-6 (104-106 cm); Part C. MRF, quartz, and feldspar grains in U1499A-4H-6

(104-106 cm); Part D. Abundance of quartz grains in U1499A-6H-2 (82-84 cm); Part E.

Quartz and plagioclase in U1499A-29X-1 (53-55 cm); Part F. Carbonate grain, quartz grains and a quartzite grain in U1499A-54X-CC (15-17 cm); Part G. Abundant mica and one SRF grain in U1499A-57X-CC (31-33 cm); Part H. Calcite cement with mica, feldspars, and quartz minerals in U1499B-4R-CC (5-7 cm); Part I. Feldspar, quartz, carbonate, and a few SRF grains in U1499B-12R-1 (34-36 cm).

88 in cross polarized light); and several monocrystalline quartz grains containing abundant fractures and vacuoles and evidence of strain. Lithic grains in this upper section include the metamorphic rock fragment in the center of Figure 14C, comprised of quartz and potassium feldspar. Figure 14C also illustrates a blocky grain of plagioclase, as recognized by its cleavage pattern. Figure 14D illustrates the abundance of quartz in the upper section of Site U1499 with a view at low magnification.

Figure 14E is an example of a heavy mineral with high birefringence in cross- polarized light (XPL) and pleochroism from green to dark green in plane-polarized light

(PPL). This grain is tentatively identified as hornblende. Figure 14E also illustrates a polycrystalline quartz grain surrounded by monocrystalline quartz grains and plagioclase grains with an orange-brown stain. Carbonate grains are abundant in some samples from the upper sediments of Site U1499; their abundance in the original sediment cannot be assessed with any confidence, however, because carbonate grains were removed from some samples by acid dissolution if carbonate grains were observed as dominating the original sediment.

Figure 14F illustrates a medium sand-sized carbonate grain, a quartzite metamorphic rock fragment, and abundant monocrystalline quartz grains. One of the quartz grains is surrounded by sericite or calcite, which is common in the grain mounts and represents incomplete removal of the matrix sediment. Figure 14G illustrates one of the medium sand-sized samples with an anomalously high abundance of lithic fragments

(discussed earlier), containing abundant mica grains, including muscovite, chlorite, and

89 biotite, and putative sedimentary rock fragments (which may be undisaggregated fine- grained sediment).

Most of the samples from the upper sediments at Site U1499 were processed by sieving and were made into grain mounts, so the matrix material and any cement in the upper sediments could only be identified in the few thin sections from that interval. These thin sections are dominated by calcite cement, with some mud blobs and sericite, as shown in Figure 14H. Quartz grains that are most likely diagenetic in origin appear to fill gaps; these quartz grains were counted as part of the matrix rather than as quartz framework grains. Figure 14H also illustrates a potassium feldspar grain with inclusions and a long muscovite grain with high birefringence. Figure 14I has a weathered and stained plagioclase grain, sedimentary rock fragments, and fractured quartz grains.

Photomicrographs of the basal sediments at Site U1499 provide visual evidence of the difference in composition between the upper sediments and the basal sediments at this site. The plagioclase grains in the basal sediments are much more weathered and altered (all images in Figure 15). The tattered grain in Figure 15E is a particularly good example of this alteration, exhibiting several holes and alteration to sericite. Figure 15B also contains multiple weathered plagioclase grains; some are so heavily altered that they are only recognizable as feldspar based on gross morphology and evidence of original twinning. Figure 15F illustrates the varying degrees of plagioclase alteration within a single sample.

All images in Figure 15 have a higher abundance of feldspar grains relative to quartz when compared to images in Figure 14 (especially the low magnification field of

200 µm A 200 µm B 200 µm C Qm P v Qm v Qm P P v Qm v Lm Lv P P P

P P 200 µm D 200 µm E 200 µm F

P P P P

Qm P v P P

Lv Qm Qm v Qm v v

500 µm G 500 µm H 500 µm I

Megaquartz vein Lp Qm v Megaquartz P Lm P P P Qm v

Figure 15. Photomicrographs of basal unit at Site U1499 (See Table 4 for definition of parameter abbreviations). Part A. VRF and plagioclase grains in U1499B-36R-1 (89-93 cm); Part B. Quartz and weathered plagioclase grains in U1499B-34R-1 (0-6 cm); Part C.

MRF, inclusion filled quartz and plagioclase in U1499B-36R-1 (89-93 cm); Part D.

Quartz overgrowth and plagioclase in U1499B-33R-2 (27-33 cm); Part E. Weathered plagioclase grain in U1499B-34R-1 (0-6 cm); Part F. Plagioclase showing the variation in alteration in U1499B-36R-1 (89-93 cm); Part G. Very coarse sand to granule sized plutonic rock fragment in U1499B-39R-1 (30-35 cm); Part H. Matrix within the cobbles, abundance of plagioclase, and quartz vein in U1499B-34R-1 (0-6 cm); Part I. MRF and tattered matrix in U1499B-40R-1 (43-47 cm).

91 view in Figure 15H). Figure 15H also illustrates a quartz vein, which is a common diagenetic feature in most thin sections from the basal sediments. The matrix observed in the basal sediments is dominated by kaolinite and clay, with sericite and carbonate cement. The abundance of carbonate cement increases upsection through the basal sediments. Megaquartz cement, likely diagenetic in origin, is abundant, as is radial megaquartz surrounding grains. Iron oxide strands are abundant in some thin sections, although they are difficult to distinguish from reddish brown clay and pink to red feldspar stain when using transmitted light microscopy.

Lithic grains are common and easy to identify within the basal section of Site

U1499. Figure 15A contains an example of a volcanic rock fragment containing plagioclase laths and surrounded by plagioclase grains. Figure 15C illustrates a metamorphic rock fragment with mylonitic texture and a quartz grain containing several mineral inclusions. Figure 15G illustrates a very coarse sand- to granule-sized plutonic rock fragment containing polycrystalline quartz and feldspar grains.

Quartz overgrowths were common in samples from the basal sediments of Site

U1499, and an example is shown in Figure 15D. The tattered and weathered nature of the feldspars within this interval is best illustrated in Figure 15I. The dissolution and alteration of feldspars to kaolinite and sericite make grain boundaries difficult to distinguish in thin sections from the basal sediments. This difficulty is illustrated in

Figure 15I, where a metamorphic rock fragment with oriented mica and sericite minerals and quartz minerals is surrounded by kaolinite/clay matrix.

Photomicrographs also were taken of samples from Site U1500 to document common grain types and to illustrate compositional differences between Sites U1499 and

U1500 (Figure 16). Carbonate cement was present in all thin sections from Site U1500.

Quartz grains commonly were observed filling gaps created by diagenesis; this quartz was counted as matrix, rather than as quartz framework grains. Iron oxides also were observed as inclusions within grains and in the matrix.

Figure 16A illustrates a quartzite metamorphic rock fragment and abundant quartz minerals. Quartz minerals are much more abundant at Site U1500 than in the basal sediments at Site U1499 (Figure 15). The medium sand-sized stained feldspar grains in

Figures 16A, 16D, and 16F are also much less weathered and tattered than the feldspar grains in the basal sediments at Site U1499. Figure 16B is a low magnification field of view of the abundant quartz at Site U1500. Glauconite, which is not common at Site

U1499, is much more abundant at Site U1500, as shown in plane polarized light in Figure

16C. Figure 16D illustrates feldspar grains, quartz grains, and a large polycrystalline quartz grain in a sample from Site U1500,

Mica is a common constituent in Site U1500 samples, occurring as muscovite, biotite, and chlorite; the most abundant mica is biotite. Figure 16E contains a medium sand- sized muscovite grain, partially infilled by glauconite. Only one sample from Site U1500 was sieved and made into a grain mount. Figure 16F illustrates that grain mount, dominated by quartz but also containing plagioclase and mica grains and a sedimentary rock fragment.

200 A 500 B µm Carb µm

K Qm Qm v v Glau Qm v

Glau Qm Qp v Lm P Qm P v

200 C 200 D µm µm P K Qm Qm P Glau v Glau P Glau Qp

Qm v P Qp Qm

200 E 500 F µm µm P Qp Lsi Qm Qp Glau K Biot Qm Qp P Mus P

Qm Qp Qm Qm Qm

Figure 16. Photomicrographs of Site U1500 grains (See Table 4 for definition of parameter abbreviations). Part A. MRF, glauconite, quartz and feldspar minerals in

U1500B-54R-1 (25-27 cm); Part B. Calcite matrix and abundance of quartz grains in

U1500B-54R-1 (25-27 cm); Part C. Abundance of glauconite and quartz in U1500B-54R-

1 (25-27 cm); Part D. Polycrystalline quartz, monocrystalline quartz and plagioclase in

U1500B-54R-1 (25-27 cm); Part E. Mica filled in with glauconite, polycrystalline quartz and monocrystalline quartz in U1500B-54R-1 (25-27 cm); Part F. Abundance of plagioclase and quartz minerals and a SRF in U1500A-20R-CC (8-10 cm).

Stratigraphic Variations in Lithic Grain Assemblages

The average abundances of each lithic grain type, and their standard deviations, are presented in Table 9 and demonstrate the similarity in lithic grain assemblages in the upper and basal sediments at Site U1499, and in LSUs at Site U1500. The lithic assemblage abundances for each sample are plotted in Figure 17 (LmLvtLst = metamorphic rock fragments, total volcanic and plutonic rock fragments and total sedimentary rock fragments). The lithic grain data for Site U1499 are again separated into the upper sediments, containing LSUs I-VII, and the basal sediments, containing LSUs

IXA and IXC. The data for each interval show much more variability than was demonstrated by the clustered nature of their QFL abundances (Figure 12).

Samples from the basal sediments at Site U1499 (Figure 17A) mostly plot at metamorphic lithic fragment abundances <30% and generally contain more volcanic rock fragments than sedimentary rock fragments. The one basal sediment sample plotted as containing 100% metamorphic rock fragments only had one lithic fragment counted.

Lithic grain abundances in samples from the upper sediments at Site U1499 have less overall variability than the data for the Site U1499 basal sediments, and generally cluster at higher abundances of metamorphic rock fragments and higher ratios of volcanic rock fragments to sedimentary rock fragments. Almost all samples from the upper sediments contain more than 10% metamorphic rock fragments, whereas ~40% of the samples from the basal sediments contain less than 10% metamorphic rock fragments.

The lithic grain compositions for Site U1500 samples are illustrated in Figure

17B, subdivided by lithostratigraphic unit. The range of compositions for Site U1500 is 95

Lm% Lm% Key A. Site U1499 U1499 Units I-VII U1499 Units IXA and IXC Lm% Key U1499 Units I-VII U1499 Units IXA and IXC

Lvt%Lvt% Lst%Lst%

Lm%Lm% Key U1500 Unit III B. Site U1500 U1500 Unit IV Lm% U1500 Unit VI Key U1500 Unit III U1500 Unit IV U1500 Unit VI

Lvt%Lvt% Lst%Lst% Lvt% Lst%

Figure 17. Part A shows the lithic grain composition at Site U1499. Part B represents the

lithic grain composition at Site U1500.

Lvt% Lst% generally similar to the range of compositions for the upper sediments of Site U1499, although metamorphic rock fragments are somewhat more abundant at Site U1500. The lithic grain compositions also appear to shift somewhat between LSUs at Site U1500, with a slight upsection increase in both the abundance of sedimentary and metamorphic rock fragments and in the range of lithic assemblage compositions. Overall there is a slight difference in volcanic and sedimentary rock fragment abundance between LSU III and LSU VI.

Documentation of Lithic Grain Types

Lithic grains, or rock fragments, are important indicators of sediment provenance because they provide the most direct evidence of source area geology (Ulmer-Scholle et al., 2014). Therefore, lithic grains were analyzed and counted with detail in this study, including subdividing each lithic grain type into several subcategories for identification and point counting. Photomicrographs of different lithic grain types, identified during point counting of Site U1499 samples, are shown in Figure 18.

Volcanic rock fragments were subdivided into two categories: plutonic rock fragments, such as pieces of granite, gabbro, etc. that contain more than one type of mineral in a single grain, and volcanic rock fragments that contain shards or laths of plagioclase and other fragmented minerals. Figure 18A illustrates a volcanic rock fragment with weathered and tattered unoriented plagioclase laths, and Figure 18D contains a volcanic rock fragment with slightly more oriented and slightly less weathered plagioclase laths. Figure 18F contains a volcanic rock fragment with very fine unoriented plagioclase laths next to a weathered blocky plagioclase grain. Figure 18B contains a 97

Lsi

Lv Qm

Lv P

Lsch P P

Qm Lsi Lsch Qm Carb P Qp Carb P Mus Lsi K Carb Lm Qm Qm Lsch

Figure 18. Thin section and grain mount photomicrographs of lithic grains (See Table 4 for definition of parameter abbreviations). Part A. Volcanic rock fragment in U1499B-

39R-1 (30-33 cm); Part B. Coarse sand sized plutonic rock fragment in U1499B-39R-1

(30-33 cm); Part C. Siltstone rock fragment in U1499B-34R-1 (0-6 cm); Part D. Volcanic rock fragment in U1499B-34R-1 (0-6 cm); Part E. Metamorphic rock fragment in

U1499B-39R-1 (30-33 cm); Part F. Volcanic rock fragment in U1499B-36R-1 (89-92 cm); Part G. Metamorphic rock fragment in U1499A-54X-CC (15-17 cm); Part H. Very fine sandstone to siltstone rock fragments in U1499A-57X-CC (31-33 cm); Part I. Chert rock fragments in U1499A-4H-6 (104-106 cm).

98 large coarse sand-sized plutonic rock fragment containing polycrystalline quartz and plagioclase.

All of the volcanic rock fragment photomicrographs were taken from samples of the cobble unit within the basal sediments at Site U1499, because that interval contains abundant volcanic rock fragments. Younger sediments at Site U1499 contain few volcanic rock fragments, but more plutonic rock fragments. Therefore, although the total volcanic rock fragment abundances change very little between the upper and basal sediments (Figure 17A), the type of volcanic rock fragment does change upsection, from more volcanic-rich lithic fragments in the basal sediments to more plutonic-rich lithic fragments in the younger sediments (shown in Appendix C in the column ‘Lp/Lvt’).

Sedimentary rock fragments were subdivided into three categories: siliciclastic sedimentary rock fragments such as grains of siltstone or sandstone, chemical sedimentary rock fragments such as chert and chalcedony, and biochemical (carbonate) sedimentary rock fragments (which were rarely identified). Figure 18C contains an example of a siltstone sedimentary rock fragment with a clay matrix and rounded quartz grains from the basal sediments of Site U1499. Figure 18H contains two examples of siliciclastic rock fragments in a sample from Hole U1499A; one is a siltstone grain and the other is a grain of very fine sandstone. Both of these grains contain subrounded to subangular quartz minerals, a clay matrix, and calcite cement. Figure 18I illustrates two examples of chemical sedimentary rock fragments identified as chert, with microcline, plagioclase, and quartz also present.

Metamorphic rock fragments are found in both the basal and the upper sediments at Site U1499. Figure 18E shows a metamorphic rock fragment with elongated and strained quartz minerals and oriented mica minerals, in a sample from the cobble unit at the base of Site U1499. Figure 18G illustrates a metamorphic rock fragment or quartzite grain with elongated and strained quartz minerals, in a sample from the upper sediments at Site U1499.

Detailed Analysis of Quartz and Feldspar Framework Grains

Analysis of the types of quartz and feldspar framework grains in sandstones has been shown to be useful for distinguishing between potential tectonic source areas by evaluating patterns observed in samples collected from various tectonic settings

(Marsaglia & Ingersoll, 1992). As a result, the relative abundances of monocrystalline quartz, potassium feldspar, and plagioclase feldspar at Sites U1499 and U1500 are plotted in Figure 19. In general, these plots have clusters of samples similar to those identified in the respective QFL plots (Figure 12), with potassium feldspar as the least abundant of these grain types in all samples.

The QmKP compositions at Site U1500 show no pattern of consistent variation with lithostratigraphic unit, and the samples from Site U1500 are compositionally very similar to the samples from the upper sediments at Site U1499. In general, Site U1500 samples contain more monocrystalline quartz than feldspar, with monocrystalline quartz abundances between 40% and 70%. The Site U1500 samples also generally contain more plagioclase than potassium feldspar.

100

%Qm %Qm Quartz Qm% Qm% Key Key Key U1500 Unit III U1499 Units I-VII U1500 Unit IV U1499 Units IXA and IXC U1499 Units I-VIIU1500 Unit VI U1499 Units IXA and IXC U1500 Unit III U1500 Unit IV U1500 Unit VI

%KK% K% %PP% %PP%

Figure 19. Monocrystalline quartz, potassium feldspar, and plagioclase feldspar ternary

diagrams for Sites U1499 and U1500. The triangle on the left represents data from Site

U1500 categorized by lithostratigraphic unit. The triangle on the right represents data

from Site U1499 comparing upper and basal sediments.

Feldspar Rock Fragments

101

The upper sediments at Site U1499 exhibit approximately the same range of quartz abundances as the Site U1500 samples, and the majority of upper Site U1499 samples contain less than 50% plagioclase feldspar and less than 20% potassium feldspar.

The QmKP compositions of the upper sediments are clearly different from the QmKP compositions of the basal sediments, which have plagioclase abundances of 50 - 80%.

The majority of the basal sediments contain less than 20% monocrystalline quartz and have more variable potassium feldspar abundances than the upper sediments.

The QmKP compositions of samples from the upper sediments at Site U1499 are plotted in Figure 20, subdivided by lithostratigraphic unit. A trend of monocrystalline quartz abundance increasing upsection is evident, especially when comparing LSUs VII and III to LSUs I and II; a similar trend is present in the overall QFL abundances (Figure

13). Plagioclase is much more abundant than potassium feldspar in all samples.

Monocrystalline quartz grains are also more abundant than polycrystalline quartz (as shown in the raw and calculated parameter tables in Appendix C and E). Therefore, a more detailed description of the change in framework grain composition upsection at Site

U1499 is a shift from plagioclase feldspar-rich to monocrystalline quartz-rich sand.

Comprehensive Summary of Stratigraphic Changes in Sediment Composition

Ternary diagrams have been used extensively to present the compositional data collected during this study, but each ternary diagram only presents information about three sediment components. A more comprehensive summary of sediment compositions at Site U1499 is given in Figures 21 and 22, where abundances of various sediment constituents are plotted against depth downcore. This presentation clearly illustrates the 102

Site U1499

%Qm%Qm Key U1499 Unit I U1499 Unit II Quartz U1499 Unit III Key U1499 Unit IV U1499 Unit VI U1499 Unit I U1499 Unit VII U1499 Unit II U1499 Unit III U1499 Unit IV U1499 Unit VI U1499 Unit VII

%KK% %PP%

Figure 20. Monocrystalline quartz, potassium feldspar, and plagioclase feldspar

composition of Site U1499 upper sediments categorized by lithostratigraphic unit.

Feldspar Rock Fragments

103 relatively steady increase in quartz abundance and the relatively steady decrease in feldspar abundance upsection (Figure 21). The abundance of lithic grains is low and relatively uniform throughout Site U1499, except for two high abundance peaks produced by the outlier samples discussed earlier (where grains classified as sedimentary rock fragments are likely to be undisaggregated mud “clumps”). Abundances of individual lithic grain types vary irregularly through the section, although volcanic rock fragments generally are the most abundant lithic grain type in the upper 500 m and in the basal sediments, abundances of the three lithic grain types are subequal at ~500 - ~750 m, and sedimentary rock fragments are most abundant at ~750 - ~920 m.

Mica and glauconite abundances at Site U1499 (Figure 22) indicate the low abundance of glauconite throughout that site; and the low abundance of mica at Site

U1499, except for one sample in Unit VI, all of Unit VII, and the basal sediments in Unit

IXA; samples from Unit VI contain a range of 0 - 47.0% mica, samples from Unit VII contain 2.2 - 49.3% mica, and Unit IXA contains a range of 1.6 - 8.6% mica grains. The majority of mica grains counted were biotite and chlorite, with many of the biotite grains showing evidence of alteration to chlorite. Muscovite also was identified in some samples.

A comprehensive summary of sediment compositions at Site U1500 is presented in Figures 23 and 24. Quartz and feldspar abundances have little variation through the section at Site U1500, and these two minerals are relatively subequal in abundance

(Figure 23). The abundance of lithic grains increases slightly upsection from the base of

Site U1500 to ~1100 m, decreases markedly at that level, and then increases slightly

104

Figure 21. Downhole plot of framework grain mineralogy and lithic grain composition at

Site U1499. Each dot represents data collected from one thin section.

105

Figure 22. Downhole plot of mica and glauconite composition at Site U1499. Each dot represents data collected from one thin section.

106

Figure 23. Downhole plot of framework grain mineralogy and lithic grain composition with depth at Site U1500. Each dot represents data collected from one thin section.

107

Figure 24. Downhole plot of mica and glauconite composition at Site U1500. Each dot represents data collected from one thin section.

108 upsection to the top of the core. The abundances of lithic grain types vary in relatively consistent patterns. Sedimentary rock fragments generally become more abundant upsection, with several single-point decreases interrupting that trend. Volcanic rock fragments generally become less abundant upsection, with several single-point peaks superimposed on that trend. Metamorphic rock fragments are more abundant at the top of the hole and at the bottom of the hole, with abundances having a stepwise increase downcore at ~1100 m.

Abundances of mica and glauconite at Site U1500 are shown in Figure 24.

Glauconite is more abundant at Site U1500 than at Site U1499; the abundance of glauconite generally decreases upsection, with the largest decrease at ~1100 m. Mica is also more abundant at Site U1500 than at Site U1499, with the abundance of mica increasing slightly upsection at Site U1500.

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Chapter 6. Discussion

Overall Stratigraphic Trends and Provenance Interpretations

The QFL framework grain compositions of sand and sandstone samples analyzed from Site U1499 are separated into two main clusters based on compositional changes with depth (Figure 12). The data for Site U1499 indicate that the upper sediments in

Lithostratigraphic Units I-VII are much more quartz-rich than the feldspar-rich basal sediments in LSUs IXA and IXC. This shift in mineralogy can be observed in the downhole logging data for Site U1499B (Figure 8) which shows an abrupt gamma ray, resistivity, and velocity increase at the start of the basal sediments at core 30R. The majority of sandstones analyzed from the upper lithostratigraphic units are classified as arkoses and sub-arkoses, based on McBride (1963), whereas the majority of sandstones from the basal units are classified as arkoses or lithic arkoses. The majority of sands and sandstones at Site U1499 contain relatively low abundances of lithic fragments, with high abundances of feldspar and quartz grains. A trend of increasing quartz abundance upsection is also present within the upper sediments at Site U1499 (Figure 13).

Samples from three lithostratigraphic units at Site U1500 exhibit little compositional variability; all plot as arkoses and have an average framework grain composition that is very similar to that of the quartz-rich upper sediments at Site U1499

(Figure 12). The similarity of mineral composition between LSUs at Site U1500 can be 110 observed in the downhole logging data for Site U1500B (Figure 9) which shows little change in the gamma ray, resistivity, and velocity logs; however Unit VI was not logged due to hole instability.

The source of sand to the samples analyzed from Sites U1499 and U1500 can be interpreted from compositional ternary diagrams with superimposed provenance fields, as published by Dickinson (1985), Marsaglia and Ingersoll (1992), and Ingersoll and Suczek

(1979). The QFL provenance diagram (Figure 25) indicates that most of the Site U1499 samples plot within the continental block section of the diagram, with some samples indicating a plutonic or transitional arc source. The continental block source is separated into basement uplift, transitional continental and craton interior. The basal sediments indicate a basement uplift source, whereas the upper sediments primarily indicate a transitional continental source, farther from the rifting center. One sample from Unit I plots just within the recycled orogen field, further indicating an uphole shift to sediments supplied from sources other than the rifting center. Data from Site U1500 indicates subequal importance of transitional continental and basement uplift sources from within the continental block section of the QFL provenance diagram (Figure 26). Sample compositions have no clear stratigraphic trends in source area importance at Site U1500.

The continental block and dissected arc origin of these sands, as indicated in

Figures 25 and 26, is interpreted to record the formation and evolution of the SCS rifted margin. The proto SCS, which was present prior to rifting, was located near the southeastern margin of the modern basin and is hypothesized to have begun as a back-arc basin before rifting into the modern-day SCS basin (Wang & Li, 2009). This proposed

111

Quartz Quartz Quartz Key Key U1499 Units I-VII Craton U1499 Units IXA and IXC U1499 Units I-VII U1500 Unit III Interior U1500 Unit IV U1499 Units IXA and IXC U1500 Unit VI

Transitional Continental Continental Block Recycled Orogen

Basement Uplift Plutonic Arc

Transitional Arc Volcanic Arc FeldsparFeldspar Rock Lithics Fragments

Feldspar Rock Fragments Figure 25. QFL ternary diagram with provenance fields from Dickinson (1985) and

Marsaglia & Ingersoll (1992) and all data from Site U1499.

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QuartzQuartz Quartz Key U1500 Unit III Craton Key U1500 Unit IV U1500 Unit VI Interior U1500 Unit III U1500 Unit IV U1500 Unit VI Transitional Continental Continental Block Recycled Orogen

Basement Uplift Plutonic Arc

Transitional Arc Volcanic Arc

FeldsparFeldspar Rock L Fragmentsithics

Feldspar Lithics Figure 26. QFL ternary diagram with provenance fields from Dickinson (1985) and

Marsaglia & Ingersoll (1992) and all data from Site U1500.

113 history provides the opportunity for sediment supply from both a dissected arc, adjacent to the original back-arc basin, and the southern mainland China continental block consisting of Mesozoic granitic and rhyolitic basement. The Oligocene basal sediments were deposited during the initial stages of rifting, when the dissected arc was more proximal to the paleolocation of Site U1499, and when the thermal conditions of early rifting were more likely to have uplifted adjacent continental basement. The younger sediments were deposited at a location more distant from the rifting zone, and therefore, were less influenced by sediment sources activated by rifting; this change is indicated by the upsection compositional shift, away from sediment sources associated with the rift zone and early rifting and toward a larger influence of more transitional continental rock and the craton interior.

Provenance interpretations based on lithic grain compositions at Site U1499

(Figure 27A) are much more variable than the interpretations based on QFL abundances, primarily due to the low abundance of lithic grains in these samples. The majority of samples plot in and between the fields for an arc source and an arc and rifted continental margin source, with an arc and subduction complex provenance indicated for some samples. The basal sediments generally plot either within the arc and rifted continental margin provenance field or between the arc and the arc and rifted continental margin fields, whereas the upper sediments generally plot within or between the arc and the arc and subduction complex fields. Overall, the sediment sources suggested by the lithic grain provenance are consistent with those indicated by QFL provenance, indicating sand sources proximal to the rifting system for the basal sediments and potentially more distal

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Lm% Lm% Key A. Site U1499 U1499 Units I-VII U1499 Units IXA and IXC Lm% Key U1499 Units I-VII U1499 Units IXA and IXC Suture Belt

Arc and Subduction Arc Complex

Rifted Continental Arc and Rifted Margin Continental Margin Lvt%Lvt% Lst%Lst%

Lm%Lm% Key U1500 Unit III B. Site U1500 U1500 Unit IV Lm% U1500 Unit VI Key U1500 Unit III U1500 Unit IV U1500 Unit VI Suture Belt

Arc and Subduction Arc Complex

Rifted Continental Arc and Rifted Margin Continental Margin

Lvt%Lvt% LsLst%t% Lvt% Lst% Figure 27. Lithic grain ternary diagram with provenance fields from Ingersoll & Suczek

(1979). Part A shows all the lithic composition data from Site U1499. Part B shows all

the lithic composition data from Site U1500.

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Lvt% Lst% sources for the younger sediments. Provenance interpretations for Site U1500 based on lithic grain compositions are diverse (Figure 27B), primarily because the lithic component at Site U1500 is slightly more enriched in metamorphic and sedimentary rock fragments than the lithics at Site U1499. This diversity is illustrated well in the youngest sediments in LSU III at Site U1500, which indicate a rifted continental margin source; whereas lithics from LSUs IV and VI indicate an arc source, an arc and subduction complex source, or combinations of these two. Despite this diversity, the lithic composition data for Site U1500 generally indicates a range of sediment supplies similar to that for the younger sediments at Site U1499.

The relative abundances of monocrystalline quartz, potassium feldspar, and plagioclase feldspar can also be used to interpret the source of sands at Site U1499, using provenance fields designated by Marsaglia and Ingersoll (1992), (Figure 28). As described in the Data section, sands and sandstones from Site U1499 are enriched in plagioclase feldspar relative to potassium feldspar and are enriched in monocrystalline quartz grains compared to polycrystalline quartz. With very limited exceptions, the basal sediments and the younger sediments from Site U1499 form clearly separate clusters on the QmKP ternary diagram; the majority of the basal sediments indicate a continental source, and the upper sediments plot in an unlabeled provenance field. Data from Site

U1500 also plots in the unlabeled provenance field, similar to the upper sediments from

Site U1499. All three provenance diagrams (Figures 25, 26, 27, and 28) indicate a consistent set of sources for these sediments -- a continental block source and an arc and rifted continental margin source.

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%QmQm% Quartz Key U1499 Units I-VII Key U1499 Units IXA and IXC U1499 Units I-VII U1499 Units IXA and IXC

Continental

Intraoceanic %KK% %PP% Feldspar Rock Fragments

Figure 28. QmKP ternary diagram of Site U1499 data with provenance fields from

Marsaglia & Ingersoll (1992).

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The potential sources of sands recovered at Sites U1499 and U1500 also were evaluated more directly by comparing the framework grain compositions determined in this study to published data about the framework grain compositions of sands and sandstones from major landmasses and rivers adjacent to the SCS basin. Several landmasses were examined, including southern mainland China, Taiwan, the Philippines,

Vietnam, the Indochina Peninsula, and Borneo, with the goal of understanding the bedrock geology being eroded on these landmasses and the sediment each may have supplied to the SCS in the past (Table 1; Figure 3). The Pearl River, the Red River and the Mekong River are three major rivers presently emptying into the South China Sea, and the mineral signatures of sediment supplied by each to the SCS basin also were examined from published data (Table 1; Figure 3).

Published data on the framework grain mineralogy of sands and sandstones from the landmasses and rivers listed above are plotted on a QFL diagram in Figure 29 to compare the mineral signatures of sediments from potential source areas to the sand mineralogies observed in the northwestern portion of the SCS East Subbasin (i.e, at Sites

U1499 and U1500). The compositional ranges of the basal sediments and of the upper sediments at Site U1499 are indicated by the two ellipses in Figure 29, and each of the data points represents the published composition of sediment from a potential sediment source (Table 1; Figure 3). Overall, the published compositional data from adjacent landmasses does not match well with the mineral signatures of sediments analyzed from

Sites U1499 and U1500; the sands at Sites U1499 and U1500 have higher abundances of feldspar, whereas the published data indicate that sediments supplied from adjacent

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Quartz Key Pearl River Taiwan Offshore southern Taiwan and the Luzon Trough Quartz Philippines (Luzon & Mindoro) Red River Key Mekong River Pearl River Borneo Taiwan Offshore southern Taiwan and the Luzon Trough Philippines (Luzon & Mindoro) Red River Mekong River Borneo

Feldspar Lithics

Figure 29. QFL ternary diagram of sandstones from landmasses and rivers surrounding

the SCS; data acquired from published literature listed in Table 1 from Chapter 2. The

dark blue circles represent the two clusters of data analyzed in this study from Site U1499

(represented in Figure 12).

119 landmasses contain more lithic fragments and quartz. This lack of compositional agreement is especially noteworthy for the basal sediments at Site U1499, because no potential sources of sufficiently feldspar-rich sediment are evident in the published literature. Although no single potential sediment source is a convincing compositional match to the more quartz-rich upper sediments from Site U1499, those younger sediments are compositionally more similar to the local source signatures than the basal sediments at Site U1499 are. The published compositional data suggest that sediments sourced from the Pearl River, Taiwan, the island of Mindoro in the Philippines, and

Borneo may have contributed some portion of the sands found in the upper sediments at

Site U1499 and the sediments sampled at Site U1500 (Figure 29). Sediments from the

Red River, the island of Luzon in the Philippines, and the Luzon arc contain a high abundance of lithic grains, which is not consistent with the sandstone compositions at

Sites U1499 and U1500.

The Pearl River, southern mainland China, and Taiwan are the main source areas supplying sediment to the northern margin of the SCS basin today; the Pearl River input is especially important along the northern margin of the basin, southwest of the Dongsha

Islands where the Expedition 367/368 sites were drilled (Shao et al., 2016). Although the younger sediments from Site U1499 and the sediments from Site U1500, approach the composition of the Pearl River input, the basal sediments at Site U1499 suggest that the major sources of modern sediment input are not representative of at least one major feldspar-rich sediment source in the past (Figure 29). This lack of agreement between the

120 compositions of the basal sediments at Site U1499 and the published compositions of potential source areas may arise from one or more causes:

1) the published studies do not accurately document the compositions of sediments supplied from the various sources during the Oligocene; or

2) the published studies do not include all the sediment sources that were active during the Oligocene.

These two options will be considered in more detail in the next few paragraphs.

Only a few studies have been published in English examining the petrology of sandstones on landmasses surrounding the South China Sea, making it difficult to compare local source compositions with the composition of sands recovered on the northern margin of the SCS. In addition, it is crucial to understand how the compositions of the local sediment sources changed through time, in order to identify the cause of the increase in quartz abundance from the basal sediments to the upper sediments at Site

U1499. However, most of the potential sediment source areas have been described by only a few published petrologic studies (generally one to three studies each), and most of those studies examined Pleistocene to Holocene sediments. Without a more complete understanding of the compositional evolution of sediments supplied from each potential source area, it is not possible to fully assess the importance of sediment input from each source to the SCS in the past. For example, the Pearl River is known to have expanded westward from the Oligocene to the Miocene, expanding its drainage basin from granitic and volcanic rocks to regions supplying sandstone and limestone in the Miocene (Cao et al., 2017; Shao et al., 2016). This change in the composition of sediments supplied by

121 the Pearl River to the SCS is not indicated in Figure 29, because the Pearl River data points are based on studies of Oligocene sandstones.

A second option for explaining the compositional dissimilarity between the Site

U1499 basal sediments and the present-day sediment sources is that sediment may have been supplied from another source, unrecognized in the Miocene or younger and acting over a limited area. This local source would have provided sediment derived from the vicinity of the continent-ocean transition in the SCS, with an abundance of feldspar minerals as a result of the lithologies exposed during rifting, or may have been controlled by the geology exposed on the paleogeography of SE Asia prior to rifting. For example, the southeastern side of modern mainland China consists of Mesozoic granitic and rhyolitic bedrock (Figure 5), which could have supplied the northern margin of the SCS with feldspar-rich detritus if the paleogeography of the proto-SCS placed Site U1499 closer to the southeastern side of China at the onset of rifting and reduced the influence of

Pearl River input. One of the magma-poor rifting models of Huismans and Beaumont

(2011), as discussed in Chapter 2, invokes stretching of continental lithosphere, without mantle exhumation, prior to seafloor spreading and mid-ocean ridge basalt formation

(Figure 2). If SCS rifting took place as explained by this model, then the basal sediments at Site U1499 could have been sourced from localized blocks of continental lithosphere uplifted during rifting. Basement highs and submarine ridges formed by volcanic activity during rifting are another potential source for the abundant volcanic lithic fragments and plagioclase feldspar within the basal sandstone units at Site U1499.

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To summarize, the angularity of the grains, the presence of siliciclastic sedimentary rock fragments, and the vast difference in framework grain composition between the Site U1499 basal sediments and the published compositions for modern regional sediment sources suggest that the basal unit was sourced from a geographically and/or temporally restricted sediment source. Three options can be proposed for this

“local” source: 1, continental crust, disrupted and activated as a sediment source during early stages of rifting; 2, local basement highs formed during the rifting process; or 3, the

Mesozoic granitic basement of southeast China, with increased sediment supply from this region in response to paleoslope changes associated with rifting. Unfortunately, the viability of each of these options cannot be evaluated further with the data available at the present time.

Implications for Correlation between Sites U1499 and U1500

The shipboard scientists on IODP Expedition 367 determined the preliminary correlation of LSUs between Sites U1499 and U1500 based on core lithologies and physical properties. The strongest correlation between the two sites was judged to be Unit

VIII at Site U1499 correlating to Unit V at Site U1500, because these two LSUs are comprised of similar reddish-brown claystone, transitioning downhole into calcareous- rich claystone and chalk (Figure 7). The compositional results of this study, however, support an additional correlation of Units III and IV at Site U1500 with Units VI and VII at Site U1499.

Based on shipboard data, Unit VI at Site U1500 was interpreted to represent an interval not recovered at Site U1499, due to the differences in its physical appearance, as 123 well as the difference in units recovered below the well-correlated Unit VIII at Site

U1499 and Unit V at Site U1500. Unit VI at Site U1500 contains porous dark gray sandstone and dark greenish gray silty claystone, which transitions downhole into a thin unit of claystone and then into mid-ocean ridge basalt. At Site U1499, Unit IXA consists of brownish to greenish sandstone with pebble-sized clasts and matrix-supported breccia, underlain by the cobble unit (Sun et al., 2018b; Figure 7).

However, the compositional results of this study support a revised interpretation of lithostratigraphic correlations between these two sites. These revised correlations highlight differences in overall lithostratigraphy between the two sites, potentially arising from differences in their tectonic settings within the evolving SCS basin. The framework grain composition of Unit VI at Site U1500 is similar to the compositions of Units III and

IV at Site U1500, and all of these units are compositionally similar to the upper sediments at Site U1499 (see Figure 12). As a result, the entire sedimentary section at

Site U1500 is compositionally similar and directly overlies mid-ocean ridge basalt, with limited evidence of sediment supplied from uplifted continental basement. These characteristics support the interpretation that the paleolocation of Site U1500 was closer to the rifting center and influenced by the formation of oceanic crust, whereas the basal units at Site U1499 were influenced more by the rifting mechanisms on the flank of the

COT. Although the entire sedimentary section at Site U1500 has similar QFL compositions, Unit VI does contain a higher abundance of volcanic lithic fragments

(Figure 17), which is consistent with that unit’s stratigraphic proximity to the underlying mid-ocean ridge basalt.

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Alternatively, the sandstones and claystones of Unit VI at Site U1500 could represent the unrecovered matrix from the interval of sandstone cobbles in Unit IX at Site

U1499, or could be present -- but uncored -- below the cobble unit at the base of Site

U1499. Neither of these alternative lithostratigraphic correlation schemes can be evaluated further with the data and cores presently available.

Implications for Rifting Models

The sediment records recovered at Sites U1499 and U1500, as well as at the four sites drilled during Expedition 368, contained no evidence of exhumed and serpentinized mantle, suggesting that rifting in the SCS basin took place via a different mechanism than had been proposed previously. Evidence of serpentinization in the mantle lithosphere within the COT would have indicated that the margin rifted via processes similar to those that formed the type I, magma-poor, Iberia-Newfoundland margin, with extreme thinning and breaking of continental crust and the exposure of mantle lithosphere in the COT

(Huismans & Beaumont, 2011; Figure 2). Instead of evidence of serpentinization, an unexpected interval of sedimentary cobbles, which records local sediment sources of continental block and arc and rifted margin composition, was recovered at the base of

Site U1499, and mid-ocean ridge basalt, representing ocean crust formation, was recovered at the base of Site U1500 (Figure 7). The presence of these two lithologies at the bases of Sites U1499 and U1500 provide evidence for a different type of rifted margin along the SCS basin.

The type II magma-poor rifted margin described by Huismans and Beaumont

(2011) provides a better explanation for the basal records recovered at Sites U1499 and 125

U1500 because the type II margin does not involve uplift and exposure of the mantle lithosphere; instead, the type II margin is characterized by laterally extensive thinned continental crust, located above hot asthenospheric mantle (Figure 2). This model also includes the possibility of magmatism during rifting and the formation of sag basins, where syn- and post-rift sediments can be deposited. The type I rifting model does not account for magmatism contemporaneous with rifting or the formation of sag basins

(Huismans & Beaumont, 2011). The abundant feldspars in the basal units at Site U1499, which could not be explained by inputs from known sediment sources around the SCS basin, may have been sourced from the thinned continental crust associated with the type

II rifting model (Huismans & Beaumont, 2011). The mid-ocean ridge basalt at the base of

Site U1500 records syn-rift magmatism, which also is consistent with the type II model

(Larsen et al., 2018a). The SCS basin also contains evidence of sag basins; one of the largest and deepest sag basins in the Pearl River mouth basin, the Baiyun Sag, is located on the northern margin of the SCS basin (Tang, Yang, & Hu, 2018; Figure 1). Another deep sag basin is detected in seismic data just landward of the outer margin high; it is interpreted to have formed during the Eocene to Oligocene, consistent with the early stage of SCS rifting (Larsen et al., 2018b). Overall, the composition and inferred source of the basal sediments at Site U1499, the presence of basalt at the base of Site U1500, the presence and inferred ages of sag basins, and the absence of evidence of serpentinization all support an interpretation of this region as a type II magma-poor rifted margin.

126

Implications for the Depositional Process of Basal Sediments at Site U1499

Evidence from a suite of boreholes around Site U1499 indicates that the sandstone cobbles recovered at the base of Site U1499 have a geographically restricted distribution.

Site U1499 is located on Ridge A, but an equivalent cobble interval was not recovered at either Site U1502, which is located to the east of Site U1499 on Ridge A, or at Site

U1500, which is located seaward of Ridge A on Ridge B (Figure 1). Sandstones containing pebble-sized clasts and glauconite were recovered in the basal units of Site

U1501 (Larsen et al., 2018a), located landward of Ridge A on the Outer Margin High, which is a prominent basement high within the COT (Larsen et al., 2018b). Igneous basement was not recovered at Site U1501, however, so the stratigraphic position of the pebble-sized clasts relative to any possible basalt is unknown. The sandstone basal unit at

Site U1501 is described as well-consolidated and feldspar-rich, with variations in grain size from fine-grained sandstone to conglomerates (Larsen et al., 2018b). Some of the sandstone contains finely laminated intervals, as does the sandstone in the basal unit at

Site U1499. Core images of this interval at Site U1501, taken during shipboard core description, appear similar to core images of the basal sediments at Site U1499 (Larsen et al., 2018b).

The sandstone unit recovered at Site U1501 is similar to the cobble unit recovered at Site U1499 both physically and compositionally and, especially, in having similar high feldspar abundances. The limited geographic distribution of this coarse-grained unit between Site U1501 and U1499 and its absence on the structural highs at Sites U1500 and U1502, suggests that this unit may represent a gravity flow deposit sourced locally 127 from uplifted continental lithologies. The variations in weathering and roundness present among grains in a single thin section suggest that grains from multiple sources were mixed before and/or during transport, even over a relatively short distance. The two sandstone units at Site U1499 and U1501 are lithologically unique among sites drilled in the COT, suggesting that they may be related.

Next Steps

The results of this project have identified the following questions, which could be addressed with additional data as described below:

1) What are the geographic extents of the compositionally distinctive lithostratigraphic groupings identified at Sites U1499 and U1500 (i.e., the compositional distinction between the basal sediments at Site U1499 and the upper sediments at Site

U1499 + the sediments at Site U1500)?

This question can be addressed by conducting petrographic analyses of sandstones from other drill sites in the SCS basin (ODP Expedition 184 and IODP Expeditions 349 and 367/368). Extending the study of sand framework grain compositions across the entire continent-ocean-transition will support correlations of lithostratigraphic units, as well as provide insights into rifting processes and mechanisms across the Northern and

Eastern subbasins.

2) How have the compositional signatures of the various potential sediment sources evolved through time? How can this information improve the interpretations of source area contributions to the SCS basin in the past?

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This question can be addressed by conducting a more complete compositional analysis of sands derived from landmasses surrounding the SCS basin, as recorded in fluvial and/or marine sediments of various ages from the SCS basin and from terrestrial outcrops. The compilation of published data for this study was complicated by the fact that the techniques used for grain identification and for point counting were not described in all papers cited. As a result, it would be helpful for one research group to conduct the compositional analysis across all locations, in order to ensure consistency in the analytical methods used.

3) How can information about the locations and movements of depocenters be combined with lithostratigraphic and sediment compositional data to better understand the evolution of source-to-sink processes and pathways in the developing SCS basin?

Seismic data can provide excellent insights into regional patterns of deposition across the COT and within the depositional basins near the main sediment sources, such as the Pearl River Mouth Basin, whereas lithostratigraphic and sediment compositional data can provide information about source area compositions and depositional processes.

Extensive seismic imaging has been completed across the SCS basin, and the recent focus of IODP drilling in the SCS has provided ample material to better characterize, correlate, and interpret sediment lithologies, compositions, and depositional environments.

Integrating these data sets will support more robust interpretations from local to basinwide scales and will also support better interpretations of seismic data from parts of the basin that have not yet been drilled.

129

Chapter 7. Conclusions

This study was conducted to help address the overarching objectives of IODP

Expedition 367/368: to distinguish between rifting models for the SCS basin, to constrain the mechanism of plate rupture and spreading, and to further understand the development of Southeast Asia associated with the SCS basin during the Cenozoic (Sun et al., 2016b).

The mineral compositions of sand and sandstone intervals from IODP Expedition

367/368 Sites U1499 and U1500, located in the northern margin of the East Subbasin in the South China Sea, were analyzed petrographically to determine the provenance and supply histories of sediment deposited in the SCS basin through geologic time.

The framework grain composition of sand and sandstone intervals at Site U1499 can be separated into two main clusters (Figure 12): the more feldspar-rich basal sediments (Q18F74L8) and the quartz-rich upper sediments (Q54F38L8). Within the upper sediments at Site U1499, the abundance of quartz minerals increases upsection (Figure

13). Although the abundance of lithic fragments throughout Site U1499 is low and the composition of lithic fragments is much more variable than the framework grain composition, volcanic grains are the most abundant lithic fragments (Figure 17A). Site

U1500 sands had a mineral composition similar to that of the upper sediments at Site

U1499, with little compositional variability (Q53F42L5; Figure 12). An upsection shift

130 from more metamorphic and volcanic rock fragments to more sedimentary rock fragments is present at Site U1500 (Figure 17B).

Based on the data collected in this study, the major conclusions regarding sediment provenance and its implications for further understanding the development of the SCS during the Cenozoic are as follows:

• The compositional ternary diagrams with superimposed provenance fields

(Figures 25, 26, 27, and 28) indicate a continental block and an arc and rifted

continental margin source. Basal sediments at Site U1499 plot within the

basement uplift provenance field and plot closer to the arc and rifted continental

margin field, indicating that the basal sediments were influenced by sediment

sources activated by rifting closer to the rifting center. The upper sediments plot

within the transitional continental source, indicating a shift away from sources

associated with rifting and toward more transitional continental rock and the

craton interior.

• The sand mineralogy of adjacent source regions, compiled from the published

literature, does not match well with the mineral signature observed in sand and

sandstone intervals at Sites U1499 and U1500 (Figure 29). In particular, the

published compositions of potential sources areas have higher abundances of

lithic fragments and quartz and lower abundances of feldspar than the feldspar-

rich basal sediments at Site U1499. The upper sediments at Site U1499 and the

sediments at Site U1500 are compositionally more similar to the published

131

compositions of sediments from the Pearl River and Taiwan, due to the upsection

increase in quartz abundance at these sites.

• The published studies of potential sediment sources may not accurately document

the compositions of sediments supplied from the various sources during the

Oligocene due to the limited database of petrologic studies on sand in

surrounding landmasses and the lack of data representing compositional changes

through geologic time.

• Potential local sources for the feldspar-rich basal units at Site U1499 include:

o The southeastern side of modern mainland China which consists of

Mesozoic granitic and rhyolitic bedrock (Figure 5). Supplying sediment

from this source would indicate a change in paleogeography of the

northern margin of the proto-SCS closer to the southeastern side of China.

o The thinned continental lithosphere associated with the type II magma-

poor rifting system described by Huismans and Beaumont (2011) (Figure

2).

o The basement highs and submarine ridges formed by volcanic activity

during rifting.

• Unit VI at Site U1500 may represent the unrecovered matrix within the sandstone

cobbles in Unit IX at Site U1499 or may be present below Unit IX. Wireline

logging data was not collected within Unit VI at Site U1500, so that neither of

these hypotheses can be evaluated.

132

• The geographically restricted distribution of Unit IX in the COT suggests that

this unit may represent a gravity flow deposit sourced locally from uplifted

continental lithosphere.

• Overall the Type II magma-poor rifting model described by Huismans and

Beaumont (2011) is most consistent with the sediment record at Sites U1499 and

U1500 due to the lack of exhumed and serpentinized mantle and the potential

role of thinned continental crust as a local sediment source (Figure 2).

133

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Appendix A. Sample Description Table for Site U1499

Bottom Top Total IODP Notes during processing Core Sect. Type of Depositional Exp Site Hole Core Sect. Offset Meters Sample (sieving or from Spectrum LSU Sample Descrip. Ages Type Half analysis Environment (cm) Below ID Petrographics) Seafloor

Medium-fine grained Sieved; acid bath & resieved WDGE1 Grain Sand with bioclasts; Middle-late Distal turbidite 367 U1499 A 2 H 5 W 84 14.36 half of sample-still all shells - I 6961222 Mount poorly sorted; very dark Pleistocene sequence DID NOT use sample. gray; thin bed

Sieved; acid bath & resieved - dissolved half of sample and Silty sand with WDGE1 Grain then half of the other half - foraminifers; greenish Middle-late Distal turbidite 367 U1499 A 3 H 6 W 119 25.71 I 6962892 Mount minimal material, looks like gray; fine sand - silt sized Pleistocene sequence coated forams and mudclasts - grains; very thin bed DID NOT use sample.

Sieved; acid bath & resieved half of sample; good Silty sand with siliciclastics; dissolved the WDGE1 Grain foraminifers; greenish Middle-late Distal turbidite 367 U1499 A 4 H 6 W 104 35.06 other half of the sample to add I 6964242 Mount gray; fine sand - clay Pleistocene sequence to the amount. Double sized grains; very thin bed embedded and stained for plagioclase and K-feldspar.

142

Sieved; not a lot of material, not going to sieve and do acid Dark greenish gray sand; WDGE1 Grain Middle-late Distal turbidite 367 U1499 A 4 H 7 W 65 36.17 bath - majority siliciclastics. I fine to very coarse sand; 6964372 Mount Pleistocene sequence Double embedded and stained very thin bed for plagioclase and K-feldspar.

Sieved; acid bath and resieved Dark greenish gray sand; WDGE1 Grain half of sample; good to go. Middle-late Distal turbidite 367 U1499 A 5 H 5 W 49 42.51 I coarse sand; quartz sand; 6965412 Mount Double embedded and stained Pleistocene sequence medium bed for plagioclase and K-feldspar.

Sieved; no need for acid bath; Dark greenish gray sand; WDGE1 Grain Duplicate sample was made. Middle-late Distal turbidite 367 U1499 A 5 H 6 W 122 44.74 I fine-coarse sand; fining 6965762 Mount Double embedded and stained Pleistocene sequence upward structure; thin bed for plagioclase and K-feldspar.

Sieved; no need for acid bath; small amount of material for >250 micrometers-going to be made using the optimally confined monolayer method with plagioclase and K- Dark greenish gray clayey WDGE1 Grain feldspar staining; much more Middle-late Distal turbidite 367 U1499 A 5 H 7 W 56 45.58 I sand; silt-fine sand; fining 6965942 Mount material for the >125 Pleistocene sequence upward; very thin bed micrometer grain size; sent both to be made into grain mounts. >125 micrometer grain size double embedded and stained for plagioclase and K-feldspar.

143

Sieved; acid bath & resieved half of sample; good amount of siliciclastics. Dissolved the Dark greenish gray clayey WDGE1 Grain Middle-late Distal turbidite 367 U1499 A 6 H 1 W 8 45.8 other half of the sample to add I sand; silt-fine sand; fining 6966042 Mount Pleistocene sequence to the amount. Double upward; thick bed embedded and stained for plagioclase and K-feldspar.

Sieved; acid bath & resieved half of sample; looks great. Dark gray clayey sand; WDGE1 Grain Dissolved the other half of the Middle-late Distal turbidite 367 U1499 A 6 H 2 W 82 47.84 I silt-fine sand; parallel 6966662 Mount sample to add to the amount. Pleistocene sequence lamination; thick bed Double embedded and stained for plagioclase and K-feldspar.

Dark gray sandy silt; silt- Continental Sieved; no need for acid bath; coarse sand; Early- slope; slumping WDGE1 Grain Duplicate sample was made. 367 U1499 A 8 H 4 W 137 70.39 II interlamination structure; middle of weakly 6969862 Mount Double embedded and stained thick bed; fining upward Pleistocene consolidated for plagioclase and K-feldspar. within each lamination sediments

Sieved; acid bath & resieved half of sample, looks great ready to go; the >250 size looked like all forams so I Very dark greenish gray Early WDGE1 Grain dissolved the lower size; I also silty sand; fine sand; Distal turbidite 367 U1499 A 29 X 1 W 53 259.95 IIIB Pleistocene 6985322 Mount dissolved the >250 size. I sent fining upward; medium sequence -Pliocene both to be made into grain bed mounts. Double embedded and stained for plagioclase and K- feldspar.

144

Sieved; acid bath & resieved half of sample; looks great - Very dark greenish gray lots of siliciclastics. Dissolved Early WDGE1 Grain silty sand; fine-medium Distal turbidite 367 U1499 A 29 X 1 W 75 260.17 the other half of the sample to IIIB Pleistocene 6985362 Mount sand; fining upward; sequence add to the amount. Double -Pliocene medium bed embedded and stained for plagioclase and K-feldspar.

Deep marine Early environment; Sieved; no need for acid bath. Dark greenish gray silty WDGE1 Grain Pliocene- low recovery - 367 U1499 A 39 X CC W 39 357.5 Double embedded and stained IV sand; clay-coarse sand; 6988672 Mount late more sand in for plagioclase and K-feldspar. medium bed Miocene hemipelagic composition

Deep marine environment; Sieved; no need for acid bath. Dark greenish gray sand; WDGE1 Grain Late low recovery - 367 U1499 A 54 X CC W 15 502.07 Double embedded and stained VI fine-medium sized sand; 6990072 Mount Miocene more sand in for plagioclase and K-feldspar. medium bed hemipelagic composition

Deep marine environment; Sieved; no need for acid bath. Dark greenish gray sand; WDGE1 Grain Late low recovery - 367 U1499 A 56 X CC W 19 521.51 Double embedded and stained VI clay-fine sand; medium 6990092 Mount Miocene more sand in for plagioclase and K-feldspar. bed hemipelagic composition Deep marine environment; Sieved; no need for acid bath. Dark greenish gray sand; WDGE1 Grain Late low recovery - 367 U1499 A 57 X CC W 31 532.07 Double embedded and stained VI fine-medium sand; thin 6990212 Mount Miocene more sand in for plagioclase and K-feldspar. bed hemipelagic composition

145

Sieved; acid bath & resieved half of the >250 size sample; not a ton of material - appears to be almost all forams - not going to use the >250 size. Dissolved the >125 size, still Light greenish gray silty WDGE1 Grain Late Distal turbidite 367 U1499 A 67 X 1 W 119 629.21 not a lot of material but looks VII claystone with 6990962 Mount Miocene sequence like siliciclastics. Sent the nannofossils; thin bed >125 sample - going to be made using the optimally confined monolayer method with plagioclase and K- feldspar staining.

Sieved; acid bath and resieved entire sample; the 125 size looks better but neither have a lot of material; sent the >125 Dark greenish gray WDGE1 Grain Late Distal turbidite 367 U1499 A 69 X CC W 36 648.48 size sample - going to be made VII sandstone; very fine-fine 6991152 Mount Miocene sequence using the optimally confined sand; medium bed monolayer method with plagioclase and K-feldspar staining.

Sieved; acid bath & resieved entire sample; >250 micrometer size appears to be Dark greenish gray WDGE1 Grain Late Distal turbidite 367 U1499 A 71 X CC W 13 651.35 coated forams - not a ton of VII sandstone; very fine-fine 6991252 Mount Miocene sequence material - after resieving not sand; medium bed enough material - DID NOT use sample.

Sieved; Acid bath and resieved; had coated forams; Very dark greenish gray WDGE1 Grain lots of siliciclastics. Dissolved Late Distal turbidite 367 U1499 B 3 R 3 W 59 668.1 VII sandstone; very fine- 6991622 Mount entire sample. Double Miocene sequence coarse sand; medium bed embedded and stained for plagioclase and K-feldspar.

146

Second batch, originally going to be sieved but too lithified to Very dark greenish gray WDGE1 Thin Late Distal turbidite 367 U1499 B 4 R CC W 5 674.47 break apart. Double embedded VII sandstone; fine-coarse 6991662 Section Miocene sequence and stained for plagioclase and sand; thin-med bed K-feldspar.

Sieved; acid bath & resieved half of sample; looks great, lots Grayish green sand with of siliciclastics and mica; WDGE1 Grain biogenic carbonate; Late Distal turbidite 367 U1499 B 9 R 1 W 74 723.67 dissolved the other half of the VII 6991712 Mount medium-coarse sand; thin- Miocene sequence sample to add to the amount. med bed Double embedded and stained for plagioclase and K-feldspar.

Sieved; acid bath & resieved half of sample; looks great - lots of siliciclastics and mica. Very dark gray claystone; WDGE1 Grain Dissolved the other half of the clay-silt; (sandy material Late Distal turbidite 367 U1499 B 9 R 1 W 107 723.99 VII 6991732 Mount sample to add to the amount; in core section photo 106- Miocene sequence Duplicate sample was made. 112 cm; thin bed) Double embedded and stained for plagioclase and K-feldspar.

Sieved; acid bath & resieved half of sample; a lot of micas, looks great but not a lot of Dark gray sandstone; WDGE1 Grain material. Dissolved the other Late Distal turbidite 367 U1499 B 10 R 3 W 11 734.8 VII medium sand; medium 6992042 Mount half of the sample to add to the Miocene sequence bed amount. Double embedded and stained for plagioclase and K- feldspar.

Very dark greenish gray Sieved; no need for acid bath. WDGE1 Grain sandstone; fine-medium Late Distal turbidite 367 U1499 B 12 R 1 W 34 752.36 Double embedded and stained VII 6992102 Mount sand; clasts of claystone; Miocene sequence for plagioclase and K-feldspar. zoophycus; medium bed

147

Second batch, originally going to be sieved but too lithified to gray sandstone; fine- WDGE1 Thin VIII Early-late Distal turbidite 367 U1499 B 13 R 4 W 94 766.38 break apart. Double embedded medium sized sand; 6992892 Section A Miocene sequence and stained for plagioclase and laminations; thin bed K-feldspar.

Double embedded, small slide Deep marine Reddish brown claystone; size, cover slip, trimmed to environment; WDGE1 Thin VIII clay-granule; nodules Early 367 U1499 B 30 R 2 W 55 928.58 size, K-feldspar and hydrothermal 7009312 Section B (manganese); mudclasts; Miocene Plagioclase staining, no plume on mid- thick bed orientation. ocean ridge

Second batch, originally going to be sieved but too lithified to Olive brown sandstone Continental WDGE1 Thin 367 U1499 B 30 R 2 W 104 929.06 break apart. Double embedded IXA with gravel; clay-granule Oligocene Slope; Debris 7009482 Section and stained for plagioclase and sized grains; medium bed flow deposit K-feldspar.

Second batch, originally going to be sieved but too lithified to Olive brown sandstone Continental WDGE1 Thin 367 U1499 B 30 R 2 W 128 929.29 break apart. Double embedded IXA with gravel; clay-granule Oligocene Slope; Debris 7009592 Section and stained for plagioclase and sized grains; medium bed flow deposit K-feldspar.

Second batch, originally going Olive brown sandstone to be sieved but too lithified to with gravel; clay-granule Continental WDGE1 Thin 367 U1499 B 30 R 3 W 0 929.36 break apart. Double embedded IXA sized grains; subangular Oligocene Slope; Debris 7009612 Section and stained for plagioclase and to rounded sand to granule flow deposit K-feldspar. sized clasts of green color

148

Greenish gray sandstone with gravel; clay to very Second batch, originally going coarse sand; thick bed; to be sieved but too lithified to Continental WDGE1 Thin subangular to rounded 367 U1499 B 30 R 3 W 38 929.74 break apart. Double embedded IXA Oligocene Slope; Debris 7009732 Section sand to granule sized and stained for plagioclase and flow deposit clasts of shale and K-feldspar. sandstone with green alteration halos

Dark reddish brown sandy claystone with gravel; clay-pebble sized; very Double embedded, small slide thick bed; angular to size, cover slip, trimmed to subrounded granule-to Continental WDGE1 Thin 367 U1499 B 30 R 4 W 77 931.23 size, K-feldspar and IXA pebble-sized clasts of Oligocene Slope; Debris 7010152 Section Plagioclase staining, no sandstone, conglomerate, flow deposit orientation. black to brownish shale, carbonate, jasper, and quartz; some greenish- white alteration halos

Dark reddish brown sandy claystone with gravel; clay-pebble sized; very Second batch, originally going thick bed; angular to to be sieved but too lithified to Continental WDGE1 Thin subrounded granule-to 367 U1499 B 30 R 5 W 23 931.99 break apart. Double embedded IXA Oligocene Slope; Debris 7010372 Section pebble-sized clasts of and stained for plagioclase and flow deposit sandstone, conglomerate, K-feldspar. black to brownish shale, carbonate, jasper, and quartz

149

Dark reddish brown sandy claystone with gravel; clay-pebble sized; very Second batch, originally going thick bed; angular to to be sieved but too lithified to Continental WDGE1 Thin subrounded granule-to 367 U1499 B 30 R 5 W 91 932.66 break apart. Double embedded IXA Oligocene Slope; Debris 7010532 Section pebble-sized clasts of and stained for plagioclase and flow deposit sandstone, conglomerate, K-feldspar. black to brownish shale, carbonate, jasper, and quartz

Continental Slope; Debris flow deposit; Embedded, small slide size, Gray gravel; pebble to cobbles sourced Oligocene TSB170 Thin cover slip, trimmed to size, K- cobble sized; gravel from magmatic 367 U1499 B 32 R 1 W 3 946.05 IXC (and pre- 10952 Section feldspar and Plagioclase lithology is coarse-grained arc or recycled Oligocene) staining, no orientation. sandstone with clay orogen possibly coming from Continental shelf

Continental Slope; Debris flow deposit; Embedded, small slide size, Gray gravel; pebble to cobbles sourced Oligocene TSB170 Thin cover slip, trimmed to size, K- cobble sized; gravel from magmatic 367 U1499 B 32 R 1 W 58 946.62 IXC (and pre- 10992 Section feldspar and Plagioclase lithology is fine-medium arc or recycled Oligocene) staining, no orientation. grained sandstone orogen possibly coming from Continental shelf

150

Continental Slope; Debris flow deposit; Embedded, small slide size, Gray gravel; pebble to cobbles sourced Oligocene TSB170 Thin cover slip, trimmed to size, K- cobble sized; gravel from magmatic 367 U1499 B 32 R 1 W 88 946.91 IXC (and pre- 11042 Section feldspar and Plagioclase lithology is fine-medium arc or recycled Oligocene) staining, no orientation. grained sandstone orogen possibly coming from Continental shelf

Continental Slope; Debris flow deposit; Embedded, small slide size, Light gray gravel; pebble cobbles sourced Oligocene TSB170 Thin cover slip, trimmed to size, K- to cobble sized; gravel from magmatic 367 U1499 B 33 R 1 W 19 955.97 IXC (and pre- 11062 Section feldspar and Plagioclase lithology is medium arc or recycled Oligocene) staining, no orientation. grained sandstone orogen possibly coming from Continental shelf

Continental Slope; Debris flow deposit; Embedded, small slide size, Gray gravel; pebble to cobbles sourced Oligocene CUTS17 Thin cover slip, trimmed to size, K- cobble sized; gravel from magmatic 367 U1499 B 33 R 2 W 7 956.97 IXC (and pre- 312312 Section feldspar and Plagioclase lithology is medium- arc or recycled Oligocene) staining, no orientation. coarse grained sandstone orogen possibly coming from Continental shelf

151

Continental Slope; Debris flow deposit; Embedded, small slide size, Gray gravel; pebble to cobbles sourced Oligocene CUTS17 Thin cover slip, trimmed to size, K- cobble sized; gravel from magmatic 367 U1499 B 33 R 2 W 27 957.18 IXC (and pre- 312322 Section feldspar and Plagioclase lithology is medium-very arc or recycled Oligocene) staining, no orientation. coarse-grained sandstone orogen possibly coming from Continental shelf

Continental Slope; Debris flow deposit; Embedded, small slide size, Gray gravel; pebble to cobbles sourced Oligocene CUTS17 Thin cover slip, trimmed to size, K- cobble sized; gravel from magmatic 367 U1499 B 34 R 1 W 0 965.46 IXC (and pre- 312212 Section feldspar and Plagioclase lithology is medium-very arc or recycled Oligocene) staining, no orientation. coarse-grained sandstone orogen possibly coming from Continental shelf

Continental Slope; Debris flow deposit; Embedded, small slide size, Bluish gray gravel; pebble cobbles sourced Oligocene CUTS17 Thin cover slip, trimmed to size, K- to cobble sized; gravel from magmatic 367 U1499 B 34 R 1 W 50 965.95 IXC (and pre- 312232 Section feldspar and Plagioclase lithology is medium-very arc or recycled Oligocene) staining, no orientation. coarse-grained sandstone orogen possibly coming from Continental shelf

152

Continental Slope; Debris flow deposit; Embedded, small slide size, Bluish gray gravel; pebble cobbles sourced Oligocene CUTS17 Thin cover slip, trimmed to size, K- to cobble sized; gravel from magmatic 367 U1499 B 34 R 1 W 87 966.31 IXC (and pre- 312252 Section feldspar and Plagioclase lithology is medium- arc or recycled Oligocene) staining, no orientation. coarse grained sandstone orogen possibly coming from Continental shelf

Continental Slope; Debris flow deposit; Embedded, small slide size, Gray gravel; pebble to cobbles sourced Oligocene CUTS17 Thin cover slip, trimmed to size, K- cobble sized; gravel from magmatic 367 U1499 B 34 R 2 W 11 966.99 IXC (and pre- 312342 Section feldspar and Plagioclase lithology is medium- arc or recycled Oligocene) staining, no orientation. grained sandstone orogen possibly coming from Continental shelf

Continental Slope; Debris flow deposit; Embedded, small slide size, Brown gravel; cobble cobbles sourced Oligocene TSB170 Thin cover slip, trimmed to size, K- sized; gravel lithology is from magmatic 367 U1499 B 36 R 1 W 51 985.35 IXC (and pre- 11562 Section feldspar and Plagioclase medium-very coarse- arc or recycled Oligocene) staining, no orientation. grained sandstone orogen possibly coming from Continental shelf

153

Continental Slope; Debris flow deposit; Yellowish brown to very Embedded, small slide size, cobbles sourced dark gray gravel; pebble Oligocene TSB170 Thin cover slip, trimmed to size, K- from magmatic 367 U1499 B 36 R 1 W 89 985.73 IXC to cobble sized; gravel (and pre- 11602 Section feldspar and Plagioclase arc or recycled lithology is medium-very Oligocene) staining, no orientation. orogen possibly coarse-grained sandstone coming from Continental shelf

Continental Slope; Debris flow deposit; Double embedded, small slide Dark gray gravel; cobble cobbles sourced size, cover slip, trimmed to Oligocene TSB170 Thin sized; gravel lithology is from magmatic 367 U1499 B 36 R 1 W 100 985.84 size, K-feldspar and IXC (and pre- 11612 Section coarse to very coarse arc or recycled Plagioclase staining, no Oligocene) sandstone orogen possibly orientation. coming from Continental shelf

Continental Slope; Debris flow deposit; Black gravel; pebble Embedded, small slide size, cobbles sourced sized; gravel lithology is Oligocene CUTS17 Thin cover slip, trimmed to size, K- from magmatic 367 U1499 B 37 R 1 W 105 995.62 IXC siltstone with parallel (and pre- 312412 Section feldspar and Plagioclase arc or recycled lamination; max grain size Oligocene) staining, no orientation. orogen possibly is medium sand coming from Continental shelf

154

Continental Slope; Debris flow deposit; Dark bluish gray gravel; Embedded, small slide size, cobbles sourced pebble to cobble sized; Oligocene CUTS17 Thin cover slip, trimmed to size, K- from magmatic 367 U1499 B 39 R 1 W 30 1014.25 IXC gravel lithology is coarse (and pre- 312512 Section feldspar and Plagioclase arc or recycled to very coarse sand sized Oligocene) staining, no orientation. orogen possibly gravelly sandstone coming from Continental shelf

Continental Slope; Debris flow deposit; Very dark gray gravel; Embedded, small slide size, cobbles sourced pebble to cobble sized; Oligocene CUTS17 Thin cover slip, trimmed to size, K- from magmatic 367 U1499 B 40 R 1 W 43 1024.07 IXC gravel lithology is (and pre- 312542 Section feldspar and Plagioclase arc or recycled medium-coarse grained Oligocene) staining, no orientation. orogen possibly sandstone coming from Continental shelf

155

Appendix B. Sample Description Table for Site U1500

Top Bottom IODP Core Sect. Type of Notes during processing (sieving or Depositional Exp Site Hole Core Sect. Offset Offset Sample LSU Sample Description Ages Type Half analysis from Spectrum Petrographics) Environment (cm) (cm) ID

Sieved; acid bath & resieved half of sample; looks great lots of siliciclastics; needs more material; Thin bed of dark WDGE1 Grain late Distal turbidite 367 U1500 A 20 R CC W 8 10 Dissolved the other half of the sample III greenish gray coarse- 7012432 Mount Miocene sequence to add to the amount. Double grained sandstone; embedded and stained for plagioclase and K-feldspar.

Thin bed of dark Second batch, originally going to be greenish gray WDGE1 Thin sieved but too lithified to break apart. medium to coarse- late Distal turbidite 367 U1500 A 25 R 6 W 26 28 III 7012902 Section Double embedded and stained for grained sandstone; Miocene sequence plagioclase and K-feldspar. fining upward sequence

Medium bed of dark Embedded, small slide size, cover WDGE1 Thin greenish gray late Distal turbidite 367 U1500 A 29 R 1 W 5 7 slip, trimmed to size, K-feldspar and III 7013542 Section medium-grained Miocene sequence Plagioclase staining, no orientation. sandstone

156

Thin bed of dark Embedded, small slide size, cover WDGE1 Thin greenish gray late Distal turbidite 367 U1500 A 29 R 1 W 73 75 slip, trimmed to size, K-feldspar and III 7013902 Section medium-grained Miocene sequence Plagioclase staining, no orientation. sandstone

Medium bed of very Embedded, small slide size, cover WDGE1 Thin dark greenish gray late Distal turbidite 367 U1500 A 32 R 1 W 15 17 slip, K-feldspar and Plagioclase III 7014222 Section medium to coarse- Miocene sequence staining, no orientation. grained sandstone

Second batch, originally going to be Thin bed of very dark sieved but too lithified to break apart; greenish gray fine to WDGE1 Thin need to make a mosaic of all of the medium-grained late Distal turbidite 367 U1500 A 34 R 1 W 5 7 III 7014602 Section broken pieces. Double embedded and sandstone; intraclast Miocene sequence stained for plagioclase and K- sedimentary feldspar. structures

Medium bed of very Embedded, small slide size, cover dark greenish gray WDGE1 Thin late Distal turbidite 367 U1500 B 7 R 1 W 119 121 slip, K-feldspar and Plagioclase IV fine to very coarse- 7015392 Section Miocene sequence staining, no orientation. grained sandstone; poorly sorted

Medium bed of very Embedded, small slide size, cover dark greenish gray WDGE1 Thin late Distal turbidite 367 U1500 B 8 R 1 W 94 96 slip, K-feldspar and Plagioclase IV fine to very coarse- 7015492 Section Miocene sequence staining, no orientation. grained sandstone; poorly sorted

Medium bed of dark Second batch, originally going to be greenish gray coarse WDGE1 Thin sieved but too lithified to break apart. late Distal turbidite 367 U1500 B 23 R 1 W 58 60 IV to very coarse- 7016002 Section Double embedded and stained for Miocene sequence grained sandstone plagioclase and K-feldspar. with gravel

Medium bed of dark Embedded, small slide size, cover WDGE1 Thin gray medium to late Distal turbidite 367 U1500 B 28 R 1 W 26 28 slip, K-feldspar and Plagioclase IV 7016622 Section granule sized Miocene sequence staining, no orientation. sandstone

157

Thin bed of very dark Embedded, small slide size, cover greenish gray WDGE1 Thin late Distal turbidite 367 U1500 B 29 R 1 W 81 83 slip, K-feldspar and Plagioclase IV medium to very 7016912 Section Miocene sequence staining, no orientation. coarse-grained sandstone

Thin bed of very dark Embedded, small slide size, cover greenish gray WDGE1 Thin late Distal turbidite 367 U1500 B 34 R 1 W 4 6 slip, K-feldspar and Plagioclase IV medium to very 7017132 Section Miocene sequence staining, no orientation. coarse-grained sandstone Thick bed of dark greenish gray Embedded, small slide size, cover WDGE1 Thin medium to very late Distal turbidite 367 U1500 B 40 R 1 W 15 17 slip, K-feldspar and Plagioclase IV 7017502 Section coarse-grained Miocene sequence staining, no orientation. sandstone; poorly sorted

Thick bed of dark Turbidite Embedded, small slide size, cover greenish gray sequence that WDGE1 Thin Oligoce 367 U1500 B 54 R 1 W 25 27 slip, K-feldspar and Plagioclase VI medium to very has undergone 7025762 Section ne staining, no orientation. coarse-grained hydrothermal sandstone alteration

Thick bed of dark Turbidite Embedded, small slide size, cover greenish gray sequence that WDGE1 Thin Oligoce 367 U1500 B 54 R 1 W 41 43 slip, K-feldspar and Plagioclase VI medium to very has undergone 7025802 Section ne staining, no orientation. coarse-grained hydrothermal sandstone alteration

Medium bed of dark Turbidite Embedded, small slide size, cover greenish gray sequence that WDGE1 Thin Oligoce 367 U1500 B 55 R 1 W 8 10 slip, K-feldspar and Plagioclase VI medium to very has undergone 7025822 Section ne staining, no orientation. coarse-grained hydrothermal sandstone alteration

158

Very thick bed of Turbidite Embedded, small slide size, cover very dark greenish sequence that WDGE1 Thin Oligoce 367 U1500 B 56 R 1 W 12 14 slip, K-feldspar and Plagioclase VI gray medium to very has undergone 7026282 Section ne staining, no orientation. coarse-grained hydrothermal sandstone alteration

Very thick bed of Turbidite Embedded, small slide size, cover very dark greenish sequence that WDGE1 Thin Oligoce 367 U1500 B 56 R 1 W 51 53 slip, K-feldspar and Plagioclase VI gray medium to very has undergone 7026382 Section ne staining, no orientation. coarse-grained hydrothermal sandstone alteration

Very thick bed of Turbidite Embedded, small slide size, cover very dark greenish sequence that WDGE1 Thin Oligoce 367 U1500 B 56 R 1 W 107 109 slip, K-feldspar and Plagioclase VI gray medium to very has undergone 7026432 Section ne staining, no orientation. coarse-grained hydrothermal sandstone alteration

159

Appendix C. Raw Data from Point Counting at Sites U1499 and U1500. See Table 4 in Chapter 3 for definition of parameter abbreviations.

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

367-U1499A

<63-125: 1.3% 125-250: 21.1% 4H-6W, 35.04 250-500: 70.5% 12 166 73 42 7 0 0 0 0 0 0 1 0 0 5 1 0 307 104-106 >500: 7.1% max: 644

125-250: 7.7% 4H-7W, 250-500: 58.5% 36.15 11 160 29 12 2 0 3 8 2 1 0 0 0 47 14 21 0 310 65-67 >500: 33.8% max: 900

<63-125: 0.63% 125-250: 8.3% 5H-5W, 42.49 250-500: 83.2% 25 201 45 25 5 0 5 1 4 0 1 0 0 1 3 0 0 316 49-51 >500: 7.9% max: 644

160

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 6.1% 5H-6W, 125-250: 37.1% 122-124 44.72 250-500: 53.4% 7 185 52 23 7 0 11 1 1 0 1 0 0 14 3 8 0 313 B8T-004 >500: 3.5% max: 630

<63-125: 4.5% 5H-6W, 125-250: 36.6% 122-124 44.72 250-500: 57.0% 13 194 54 13 6 0 5 1 1 0 3 1 2 14 1 5 1 314 B8T-005 >500: 1.9% max: 630

<63-125: 27.2% 5H-7W, 125-250: 69.9% 45.56 11 137 107 20 6 0 2 0 0 0 5 1 0 17 2 3 1 312 56-58 (125) 250-500: 2.9% max: 350

5H-7W, 45.56 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 56-58 (250)

<63-125: 0.96% 125-250: 33.4% 6H-1W, 45.78 250-500: 64.6% 12 153 104 18 4 1 6 0 2 0 3 3 0 5 3 0 0 314 8-10 >500: 0.96% max: 560

161

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 1.3% 125-250: 35.0% 6H-2W, 47.82 250-500: 61.7% 15 157 92 28 6 0 4 0 1 0 5 1 0 1 0 1 0 311 82-84 >500: 1.9% max: 560

<63-125: 2.8% 8H-4W, 125-250: 45.6% 137-139 70.37 250-500: 51.3% 16 195 84 8 3 0 2 0 3 0 0 1 1 3 0 0 0 316 B8T-009 >500: 0.31% max: 560

<63-125: 4.7% 8H-4W, 125-250: 52.0% 137-139 70.37 11 169 89 7 14 0 4 0 1 0 1 0 1 0 1 0 2 300 250-500: 43.2% B8T-010 max: 490

<63-125: 4.5% 29X-1W, 125-250: 74.4% 259.93 18 134 106 27 6 0 4 2 0 0 3 1 5 1 0 1 0 308 53-55 250-500: 21.1% max: 420

125-250: 11.0% 29X-1W, 250-500: 84.4% 259.93 6 125 106 50 10 0 2 1 0 0 0 1 4 3 0 0 0 308 53-55 >500: 4.5% max: 798

162

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 1.3% 125-250: 17.2% 29X-1W, 260.15 250-500: 78.0% 9 147 101 28 5 0 2 4 0 0 0 4 5 3 0 1 0 309 75-77 >500: 3.6% max: 770

<63-125: 1.7% 125-250: 15.9% 39X-CCW, 357.48 250-500: 81.4% 11 183 66 13 8 0 6 5 1 0 2 1 0 4 0 1 0 301 39-41 >500: 1.0% max: 588

<63-125: 0.32% 125-250: 12.2% 54X-CCW, 502.05 250-500: 78.1% 14 175 61 23 5 0 6 4 1 0 0 0 0 11 0 9 0 309 15-17 >500: 9.3% max: 840

<63-125: 1.9% 125-250: 26.4% 56X-CCW, 521.49 250-500: 70.7% 10 172 79 24 2 0 1 4 1 0 0 2 5 10 0 1 0 311 19-21 >500: 0.96% max: 700

163

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 0.66% 125-250: 12.6% 57X-CC, 532.05 250-500: 78.5% 0 11 9 5 1 0 0 14 0 0 45 97 0 36 20 64 0 302 31-33 >500: 8.3% max: 840

125-250: 65.1% 67X-1W, 629.19 250-500: 34.9% 16 166 46 64 4 0 4 2 1 0 0 2 5 0 0 5 0 315 119-121 max: 420

<63: 0.97% 69X-CC, 125-250: 76.4% 648.46 8 116 118 36 8 0 3 8 0 0 0 1 2 0 4 6 1 311 36-38 250-500: 22.7% max: 490

367-U1499B

<63-125: 0.96% 125-250: 15.7% 3R-3W, 668.08 250-500: 80.4% 25 116 89 34 13 1 10 2 1 0 6 11 0 2 1 1 0 312 59-61 >500: 2.9% max: 560

<63-125: 23.6% 125-250: 57.3% 4R-CCW, 674.45 250-500: 16.2% 15 142 78 37 2 0 4 2 1 0 1 8 5 5 4 2 3 309 5-7 >500: 2.9% max: 1050

164

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 0.96% 125-250: 15.3% 9R-1W, 723.64 250-500: 79.2% 25 85 123 15 8 0 9 2 1 0 7 21 0 0 9 8 0 313 74-77 >500: 4.5% max: 700

<63-125: 0.32% 9R-1W, 125-250: 16.5% 107-109 723.97 250-500: 78.5% 27 127 82 38 9 0 13 5 0 0 1 6 0 0 1 4 0 313 B8T-021 >500: 4.7% max: 840

<63-125: 1.6% 9R-1W, 125-250: 19.5% 107-109 723.97 250-500: 74.4% 34 105 97 23 14 0 11 6 1 0 6 11 0 0 3 2 0 313 B8T-022 >500: 4.5% max: 630

<63-125: 0.99% 125-250: 10.9% 10R-3W, 734.78 250-500: 75.8% 2 4 15 2 0 0 0 0 0 0 7 142 0 1 92 35 2 302 11-13 >500: 12.3% max: 980

<63-125: 1.9% 125-250: 18.8% 12R-1W, 752.34 250-500: 76.7% 12 64 42 32 8 1 10 60 1 0 4 19 0 13 7 35 1 309 34-36 >500: 2.6% max: 690 13R-4W, 766.36 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 94-96 30R-2W, 928.54 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA 55-59 165

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 21.4% 125-250: 49.3% 30R-2W, 929.03 250-500: 27.6% 0 12 94 19 0 1 2 4 0 0 1 4 9 130 0 26 2 304 104-107 >500: 1.6% max: 700

<63-125: 35.9% 125-250: 49.7% 30R-2W, 929.27 250-500: 13.5% 1 15 110 21 0 0 1 0 0 0 3 6 6 116 2 21 2 304 128-132 >500: 0.99% max: 1120

<63-125: 44.9% 125-250: 40.9% 30R-3W, 929.31 250-500: 12.5% 1 52 125 31 2 0 0 5 0 0 3 3 1 64 2 12 2 303 0-5 >500: 1.7% max: 1290

<63-125: 27.0% 125-250: 47.0% 30R-3W, 929.69 250-500: 23.7% 1 22 92 34 1 3 1 1 0 0 4 3 2 135 0 5 0 304 38-43 >500: 2.3% max: 1680

<63-125: 47.5% 125-250: 45.2% 30R-4W, 931.18 250-500: 6.6% 9 73 145 14 1 0 8 5 0 0 9 17 0 4 0 16 2 303 77-82 >500: 0.66% max: 900

<63-125: 38.2% 125-250: 36.5% 30R-5W, 931.93 250-500: 22.4% 1 28 128 23 4 9 3 5 1 0 7 6 0 66 0 17 6 304 23-29 >500: 3.0% max: 1200

166

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 34.1% 125-250: 46.0% 30R-5W, 932.61 250-500: 18.9% 10 53 180 17 4 3 6 0 2 0 10 10 0 1 3 2 1 302 91-96 >500: 0.99% max: 750

<63-125: 3.6% 125-250: 30.4% 32R-1W, 946.03 250-500: 53.1% 14 43 187 26 6 11 7 2 2 0 2 1 0 0 2 0 1 304 3-5 >500: 12.9% max: 1050

32R-1W, 80-320 946.58 19 24 146 29 13 0 6 9 5 0 6 0 0 0 3 0 0 260 58-62 max: 400

32R-1W, 946.88 60-160 25 23 153 83 2 0 0 0 10 0 6 1 0 1 3 0 0 307 88-91

<63-125: 24.8% 33R-1W, 125-250: 63.7% 955.89 20 21 183 31 3 8 7 6 10 0 3 0 0 0 13 0 0 305 19-27 250-500: 11.5% max: 392

<63-125: 20.7% 33R-2W, 125-250: 62.6% 956.92 13 31 166 50 12 5 3 7 2 0 6 2 0 1 3 1 1 303 7-12 250-500: 16.8% max: 490

167

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 15.8% 125-250: 36.5% 33R-2W, 957.12 250-500: 31.5% 42 51 151 19 13 8 3 5 10 0 0 0 0 0 0 0 0 302 27-33 >500: 16.2% max: 1650

<63-125: 10.8% 125-250: 37.8% 34R-1W, 965.4 250-500: 28.1% 18 42 157 39 5 13 2 5 19 0 3 0 0 0 1 0 0 304 0-6 >500: 23.3% max: 1560

<63-125: 19.8% 125-250: 64.2% 34R-1W, 965.9 250-500: 13.2% 7 26 199 58 4 1 1 1 5 0 1 0 0 0 0 0 0 303 50-55 >500: 2.8% max: 840

<63-125: 10.4% 125-250: 38.5% 34R-1W, 966.27 250-500: 29.5% 21 35 207 26 3 0 1 2 6 0 2 0 0 1 2 0 0 306 87-91 >500: 21.5% max: 2720

<63-125: 6.8% 125-250: 13.2% 34R-2W, 966.93 250-500: 38.2% 14 42 160 46 6 15 4 0 10 0 2 0 0 1 4 0 0 304 11-17 >500: 41.8% max: 1290

<63-125: 9.6% 125-250: 30.7% 36R-1W, 985.31 250-500: 36.1% 14 37 153 72 1 11 2 0 2 0 2 0 0 0 9 0 1 304 51-55 >500: 23.6% max: 1290

168

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 7.2% 125-250: 36.6% 36R-1W, 985.69 250-500: 36.2% 12 30 167 65 0 15 4 2 5 0 1 0 0 1 3 0 0 305 89-93 >500: 19.9% max: 1320

<63-125: 52.0% 36R-1W, 125-250: 42.7% 985.8 10 44 137 94 1 1 2 1 0 0 5 0 0 1 9 0 1 306 100-104 250-500: 5.4% max: 350

<63-125: 40.2% 125-250: 47.4% 37R-1W, 995.55 250-500: 11.0% 6 38 165 71 2 0 3 0 0 0 12 0 0 0 8 0 0 305 105-112 >500: 1.4% max: 660

<63-125: 6.8% 125-250: 13.2% 39R-1W, 1014.2 250-500: 24.0% 23 27 131 57 5 31 14 3 8 0 2 0 0 0 2 0 1 304 30-35 >500: 56.1% max: 3040

<63-125: 15.9% 125-250: 31.6% 40R-1W, 1024.03 250-500: 29.2% 18 47 158 45 1 8 9 1 2 0 5 0 0 0 15 0 2 311 43-47 >500: 23.3% max: 1500

367-U1500A

<63-125: 0.32% 125-250: 17.9% 20R-CCW, 689.78 250-500: 79.9% 24 135 80 36 7 0 4 13 3 0 5 0 1 1 1 1 2 313 8-10 >500: 1.9% max: 672

169

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 34.0% 125-250: 49.2% 25R-6W, 745.12 250-500: 16.5% 12 129 104 31 1 0 5 1 0 0 9 13 5 1 0 3 1 315 26-28 >500: 0.32% max: 600

<63-125: 32.4% 125-250: 50.2% 29R-1W, 777.05 250-500: 15.4% 9 150 34 42 1 0 3 1 0 12 3 11 15 14 3 3 3 304 5-7 >500: 2.0% max: 798

<63-125: 50.8% 125-250: 38.0% 29R-1W, 777.725 250-500: 10.5% 6 138 57 31 0 0 3 0 0 2 6 22 14 21 4 3 3 310 73-75 >500: 0.66% max: 570

<63-125: 44.6% 125-250: 42.0% 32R-1W, 806.25 250-500: 12.1% 11 124 70 51 0 0 4 7 1 7 5 12 6 5 2 2 2 309 15-17 >500: 1.3% max: 742

<63-125: 44.1% 125-250: 34.3% 34R-1W, 825.55 250-500: 19.6% 9 109 106 29 4 0 1 0 0 0 8 7 0 30 2 1 0 306 5-7 >500: 2.0% max: 700

367-U1500B

<63-125: 38.4% 125-250: 36.7% 7R-1W, 895 250-500: 21.6% 18 115 59 63 1 1 3 4 2 5 5 6 13 2 2 6 3 308 119-121 >500: 3.3% max: 1760

170

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 26.7% 125-250: 51.8% 8R-1W, 904.44 250-500: 18.2% 19 130 53 60 1 0 5 1 3 3 7 10 8 1 2 2 2 307 94-98 >500: 3.3% max: 700

<63-125: 44.8% 125-250: 41.0% 23R-1W, 1049.58 250-500: 11.9% 18 108 113 36 2 0 2 4 0 0 11 6 0 7 0 3 0 310 58-60 >500: 2.3% max: 7000

<63-125: 53.8% 125-250: 34.1% 28R-1W, 1097.76 250-500: 5.4% 13 127 93 39 5 0 1 0 0 0 5 4 17 6 2 1 1 314 26-28 >500: 6.7% max: 2800

<63-125: 28.9% 125-250: 56.5% 29R-1W, 1108.01 250-500: 13.0% 10 130 82 35 5 0 9 4 0 0 5 10 20 1 1 0 3 315 81-83 >500: 1.6% max: 1020

<63-125: 5.1% 125-250: 24.5% 34R-1W, 1155.74 250-500: 57.3% 31 128 55 46 9 0 13 1 2 0 4 2 16 2 1 0 4 314 4-6 >500: 13.1% max: 1140

<63-125: 13.3% 125-250: 51.9% 40R-1W, 1214.05 250-500: 32.1% 22 108 79 44 7 0 8 4 1 0 5 6 16 4 0 2 1 307 15-17 >500: 2.6% max: 1020

171

Core, Total section, Depth Average grain Dense Qp Qm P K Lp Lv Lm Lsi Lsch Lsc Mus Biot Glau Bio Opaques Carb Grains interval (mbsf) size (µm) Minerals Counted (cm)

<63-125: 18.8% 125-250: 56.2% 54R-1W, 1349.96 250-500: 23.3% 22 133 67 34 4 1 8 1 2 0 4 7 24 4 1 1 0 313 25-27 >500: 1.6% max: 900

<63-125: 21.8% 125-250: 55.4% 54R-1W, 1350.11 250-500: 21.2% 19 140 68 23 10 0 9 0 0 0 7 9 24 2 1 0 0 312 41-43 >500: 1.6% max: 810

<63-125: 21.5% 125-250: 55.8% 55R-1W, 1359.48 250-500: 20.8% 13 127 73 47 6 0 4 4 1 0 1 7 23 4 0 1 1 312 8-10 >500: 1.9% max: 1078

<63-125: 20.3% 125-250: 57.2% 56R-1W, 1369.22 250-500: 20.6% 22 135 70 34 7 0 8 1 0 0 6 5 15 5 2 1 0 311 12-14 >500: 1.9% max: 630

<63-125: 21.2% 125-250: 54.8% 56R-1W, 1369.605 250-500: 22.4% 19 135 71 40 5 1 2 1 0 0 3 7 21 4 1 2 0 312 51-53 >500: 1.6% max: 780

<63-125: 24.5% 125-250: 53.2% 56R-1W, 1370.17 250-500: 21.0% 30 104 92 38 5 0 7 1 0 0 5 5 17 3 1 2 0 310 107-109 >500: 1.3% max: 700

172

Appendix D. Comments from thin section descriptions

367-U1499A-4H-6W (104-106) Medium sand is the dominant size of grains in this thin section; Monocrystalline quartz subangular to subrounded, some overgrowth, many inclusions including tourmaline and oxides, fractures; some oxides create a rim around some of the grains; polycrystalline grains subrounded; plagioclase and K-feldspar identified based on stain, twinning pattern, and shape/orientation of oxides/cleavage plains; some grains have yellow and pink stain making an orange color - the mineral identified in that case was whichever stain was stronger; many oxide grains, several plutonic rock fragments and one spotted volcanic rock fragment with plagioclase laths; plutonic rock fragments include mica, quartz, feldspar minerals; chlorite was counted and recorded in the biotite box. Overall lacking mica, rock fragments and dominated by quartz.

367-U1499A-4H-7W (65-67) Medium sand is the dominant size of grains in this thin section; Monocrystalline quartz is subangular to angular with a few more rounded grains, very strained, a lot of fractures, oxide/tourmaline/mica inclusions and very large (making up most of the >500 micron grains); mica or carbonate rim is found around most quartz grains, some secondary growth of quartz within another quartz grain is visible; polycrystalline quartz subrounded to subangular, rimmed with carbonate overgrowth; several rock fragments were observed such as 8 siltstone/sandstone grains consisting of carbonate cement, subangular quartz and feldspar minerals and glauconite; chert lithic fragments, metamorphic rock fragments with elongated quartz and oriented mica minerals and plutonic rock fragments of mica, feldspar and quartz, were counted and more were observed in the field of view; Carbonate material very abundant in this thin section with 47 counted calcareous bioclasts and 21 carbonate minerals.

367-U1499A-5H-5W (49-51) Medium sand is the dominant size of grains in this thin section; Monocrystalline quartz angular - subrounded, several grains with quartz overgrowth, very heavily strained, mica and heavy mineral inclusions common and oxide inclusions common, small needle-like inclusions are also common (may be tourmaline and/or rutile); vacuoles common in quartz grains, fractures common (one fracture filled with plagioclase/mica); rounded to subangular polycrystalline grains with vacuoles and oxides, some more strained than others; some plagioclase and K-feldspar grains altered to clay but most show parallel twinning or tartan twinning and are stained with pink/yellow/orange which helps to distinguish between quartz and feldspar grains; oxides abundant in feldspar grains along with mica inclusions; sandstone rock fragment included glauconite, feldspar, quartz, and iron cement; the chemical rock fragments counted includes mainly chert however chalcedony was spotted in thin section; many metamorphic grains spotted and counted with elongated quartz and usually mica grains; plutonic rock fragments include quartz, feldspar and mica grains typically; mud blobs were counted as matrix.

367-U1499A-5H-6W (122-124) – B8T-004 Medium to fine-grained sand sized grains; Subangular to subrounded monocrystalline quartz grains, iron oxide coating around grains, abundant fractures (some filled with iron) some oxide, tourmaline, heavy mineral inclusions, and some needle-like mineral inclusions that could be tourmaline or rutile; polycrystalline quartz rounded to subrounded, mineral inclusions; blocky, somewhat weathered plagioclase and K-feldspar identified mostly based on cleavage, stain color, twinning patterns, and oxide inclusion 173 alignment along cleavage plains, there was an abundance of oxide inclusions in feldspar grains; Many metamorphic rock fragments that contain aligned mica minerals and aligned oxide/dark minerals and elongated quartz minerals; several plutonic rock fragments were also counted and observed containing quartz, and feldspar; One sedimentary sandstone rock fragment contained feldspar and glauconite; abundant calcareous microfossils including forams, some filled with glauconite or oxide minerals, some were recalcified forams meaning that there would have been a lot more carbonate in the past compared to what is observed in thin section today; There were also several carbonate grains that did not appear to have a biogenic orogen but it could have been recalcified; some mud blobs were identified as matrix that wasn’t well sieved.

367-U1499A-5H-6W (122-124) – B8T-005 Medium to fine-grained sand sized grains; angular to rounded monocrystalline quartz grains, iron oxide coating around grains, abundant fractures filled with oxides, stain, and sometimes mica, inclusions of oxides, tourmaline, heavy minerals, and needle-like minerals (that could be tourmaline or rutile), some overgrowth of quartz filled with mica and sometimes glauconite; polycrystalline quartz angular to subrounded with oxides and blue tourmaline inclusions; some plagioclase grains show total alteration to clay, both plagioclase and K-feldspar are blocky and show cleavage, both contain inclusions of heavy minerals and tourmaline, oxide alignment and occasionally parallel twinning and tartan twinning are visible; rock fragments include mainly metamorphic rock fragments of elongated quartz and mica minerals and plutonic rock fragments that include quartz and feldspar grains; muscovite and some chlorite grains were visible; one chert rock fragment and one sandstone rock fragment composed of feldspar, quartz and calcite cement was counted; several calcareous microfossils were observed in grain mount and also several carbonate minerals; a few dense minerals that were pleochroic green to blue in ppl and bright pink in xpl were also observed and counted, these could have been amphibole grains; mud blobs were counted as matrix.

367-U1499A-5H-7W (56-58) – 125 µm Fine sand is the dominant size of grains in this thin section; Monocrystalline quartz is mostly angular to subrounded, contains iron oxide rims and iron oxide inclusions, vacuoles, dense mineral and tourmaline inclusions, mica alteration around the edge of some quartz grains, fractures; polycrystalline quartz grains also fairly angular although not abundant; plagioclase and potassium feldspar grains much more altered to clay and weathered than previous samples and identified based on stain color, blocky shape, and cleavage; two metamorphic rock fragments counted with elongated quartz grains and oriented mica grain; 6 plutonic rock fragment grains containing quartz and feldspar minerals; several mica grains counted and some containing a rim of calcite; calcareous microfossils abundant filled with glauconite and mud in some cases; several carbonate grains were also counted; although hornblende was observed it was not counted, one unidentified dense mineral that was green in ppl and xpl was also counted.

367-U1499A-5H-7W (56-58) – 250 µm Can’t use – more than 80% calcareous microfossils.

367-U1499A-6H-1W (8-10) Medium to fine-grained sand sized grains; subangular to subrounded monocrystalline quartz grains, iron oxide coating around grains, vacuoles, abundant fractures (some filled with iron) some oxide, tourmaline, heavy mineral inclusions, and some needle-like mineral inclusions that could be tourmaline or rutile, some surrounded by mica/sericite; polycrystalline quartz grains subrounded to subangular, oxides and vacuoles; plagioclase and K-feldspar grains weathered and some grains completely altered to clay (kaolinite/sericite), with many inclusions and oxides; chert rock fragments, several metamorphic rock fragments consisting of elongated quartz and oriented layers of oxides/dark minerals; 4 plutonic rock fragments consisting of quartz and feldspar minerals; mica common throughout thin section especially chlorite; some microfossil grains counted that were blocky in shape; mud blobs were counted as matrix.

174

367-U1499A-6H-2W (82-84) Medium to fine-grained sand sized grains; subrounded to angular monocrystalline quartz grains, iron oxide coating around grains, vacuoles and fractures abundant, oxide, tourmaline, heavy mineral inclusions and some needle-like mineral inclusions that could be tourmaline or rutile, some overgrowth of megaquartz and quartz, and mica/sericite rims around grains; polycrystalline quartz grains subrounded to subangular with oxide inclusions and vacuoles; plagioclase and K-feldspar have a lot of oxide inclusions, very weathered and altered to clay in some cases, filled with glauconite and clay inclusions (alterations), angular to subangular, identified based on staining, cleavage, and twinning pattern; one chalcedony rock fragment was observed, four metamorphic rock fragments with elongated quartz and mica were observed, several plutonic rock fragments consisting of quartz and feldspar minerals were also counted; several mic minerals observed; not many microfossils as compared to other samples; zircon mineral spotted but not counted.

367-U1499A-8H-4W (137-139) – B8T-009 Medium to fine-grained sand sized grains; subrounded to rounded monocrystalline quartz grains, strained, tourmaline, oxide and needle-like mineral inclusions with iron oxide rims around some of the grains and overgrowths of quartz and mica surrounding the grains; polycrystalline quartz grains subrounded to angular with inclusions and vacuoles; plagioclase and potassium feldspar mostly angular and blocky with some weathering and alteration to kaolinite and sericite, mostly identified based on cleavage pattern, twinning, and staining (orange staining called plagioclase according to Spectrum Petrographics correspondent); chert rock fragments (some slightly metamorphosed), metamorphic rock fragments of mica and elongated quartz and plutonic rock fragments of quartz and feldspar minerals were observed; few calcareous microfossils counted; glauconite fills microfossils as well as being present alone in grain mount; some mica minerals observed including chlorite recorded under the biotite column.

367-U1499A-8H-4W (137-139) – B8T-010 Fine to medium sand is the dominant size of grains in this thin section; Monocrystalline quartz is rounded and subrounded to subangular, inclusions of tourmaline, oxides, needle-like minerals, abundant vacuoles, some overgrowth, rims of sericite and iron oxide, strained, fractured; polycrystalline quartz is subrounded to subangular, strained, inclusions of oxides, sericite and tourmaline; plagioclase and potassium feldspar grains have a lot of oxides, blocky angular shape, cleavage visible, identified by stain, K-feldspar not abundantly observed; one chert rock fragment grain, some metamorphic rock fragment grains of oriented micas and elongated quartz, many plutonic rock fragments were observed which consisted of quartz and feldspar minerals and mica; few glauconite and muscovite grains observed; 2 dense minerals observed of hornblende; two mud blobs were counted as matrix.

367-U1499A-29X-1W (53-55) – 125 µm Fine sand is the dominant size of grains in this thin section; monocrystalline quartz irregular to subrounded (overall more rounded than previous samples), abundant vacuoles, fractures common, some feldspar and quartz overgrowth, several grains surrounded with green chlorite or clay or glauconite, tourmaline, iron oxide and heavy mineral inclusions present; polycrystalline quartz rounded to very well rounded with iron oxide inclusions within grains and forming a rim around grains; plagioclase and K-feldspar surrounded by glauconite/clay, one grain contained a vein of quartz within the plagioclase, weathered and identified based on stain and cleavage; sandstone rock fragments in a clay matrix; several plutonic grains of quartz and feldspar minerals; one chlorite grain counted but many spotted (recorded under biotite); glauconite common especially in the shape of microfossils filling in dissolved pores; several hornblende grains spotted but not counted.

367-U1499A-29X-1W (53-55) – 250 µm Medium sand is the dominant size of grains in this thin section; Monocrystalline quartz subangular to subrounded, some overgrowth of megaquartz and mica, many inclusions including tourmaline and oxide inclusions, fractures, some oxides create a rim around some of the grains; polycrystalline grains subrounded to subangular; plagioclase and K-feldspar identified by stain and twinning pattern, shape and 175 orientation of oxides and cleavage plains; not as weathered as samples down core, not nearly as much alteration to clay; some grains have yellow and pink stain making an orange color - the mineral identified in that case was whichever stain was stronger; medium grained sandstone rock fragment identified, two MRFs identified with elongated quartz and mica, and several plutonic rock fragments with quartz, feldspar, and mica; several glauconite grains however lacking mica grains except for one counted chlorite grain recorded under biotite; many other mica grains were spotted in the field of view but not counted; amphibole was also spotted but not counted; a few calcareous microfossils (forams) were counted.

367-U1499A-29X-1W (75-77) Medium sand is the dominant grain size; Monocrystalline quartz is mostly subangular to angular in shape with some more subrounded grains, abundant fractures, surrounded by glauconite, sericite, and clay, rimmed by iron oxide with tourmaline, needle-like minerals, and oxide inclusions, some grains contain abundant vacuoles, all grains strained with undulatory extinction; polycrystalline quartz grains angular to subrounded, containing several vacuoles, outlined by clay/sericite; plagioclase and K-feldspar occupied by glauconite, weathered and altered to kaolinite and sericite although some grains have strong twinning visible, abundant inclusions in some of the grains, vary in shape (some more blocky and some more angular); several sandstone/siltstone rock fragments counted with iron oxide cement, few metamorphic rock fragments with oriented mica minerals, several plutonic rock fragments that contain quartz, feldspar and mica minerals; Biotite and glauconite common, chlorite abundant and counted in the biotite column; few calcareous bioclasts (most filled with glauconite and sometimes counted in glauconite column); some mud blobs counted as matrix.

367-U1499A-39X-CCW (39-41) Medium sand is the dominant grain size; Monocrystalline quartz is mostly subangular to subrounded in shape with some more angular grains, abundant fractures, sometimes rimmed by iron oxide and sericite, with tourmaline, needle-like minerals, oxide, and dense mineral/clay mineral inclusions, abundant vacuoles, very strained; polycrystalline quartz grains subrounded with inclusions and abundant vacuoles, strained (sometimes counted as MRF due to high level of strain and elongation); plagioclase and K-feldspar altered to kaolinite and sericite although some grains have little weathering and abundant inclusions of dense minerals and mica and show twinning; several sandstone/siltstone rock fragments with calcite/clay cement and one counted chert rock fragment; several metamorphic rock fragments consisting of elongated quartz minerals and oriented mica minerals (or sometimes just one or the other); many plutonic grains were counted that consist of quartz and feldspar minerals in one grain (only counted when diagenesis isn't suspected as the root cause of quartz within the grain filling in weathered plagioclase); some mica minerals were counted, some with carbonate outlining the grain; several calcareous bioclasts were counted and observed.

367-U1499A-54X-CCW (15-17) Medium sand is the dominant grain size; Monocrystalline quartz grains are subangular to angular in shape, very strained, abundant vacuoles and fractures, inclusions of oxides, tourmaline and dense minerals common although not overwhelming within any grain (2 or 3 commonly), sometimes vacuoles appear aligned but not on a cleavage plane (slight metamorphism?); polycrystalline quartz grains appear strained, subangular in shape (with irregularly shaped quartz minerals), many counted as MRFs due to their strained and elongated nature, vacuoles and mica inclusions common; plagioclase and K-feldspar weathered and altered to kaolinite and sericite, some grains containing both plagioclase and K-feldspar due to some alteration between the two, sometimes filled with glauconite and/or clay; identified based on twinning, cleavage, and stain color, blocky to angular shape; four sandstone rock fragments, one with iron cement and little pore space and 3 with more calcite and/or clay matrix/cement, all with quartz minerals; one chalcedony rock fragment was identified but not spotted elsewhere; several metamorphic rock fragments identified with elongated quartz minerals and oriented mica minerals; several plutonic grains were identified with quartz and feldspar minerals; calcareous microfossils and carbonate minerals were both very common throughout this thin section as an acid bath was not applied to this sample prior to making the grain mount. 176

367-U1499A-56X-CCW (19-21) Medium sand is the dominant grain size; Monocrystalline quartz grains are subangular, abundant fractures and oxide, dense mineral inclusions, and vacuoles, iron oxide forms a rim around some of the grains making grain boundaries very well defined; polycrystalline quartz grains are subrounded; Plagioclase and K-feldspar are weathered and altered to kaolinite and sericite in some grains and twinning is very visible in others, they are identified by twinning, cleavage, and stain color, some plagioclase grains show alteration to albite and some feldspar grains have a different composition in the rim than in the core of the grain; several sandstone rock fragments were counted, two having a calcite matrix and consisting of subrounded- subangular quartz grains, one surrounding by clay matrix/cement, and the other surrounded by iron oxide cement; one chert rock fragment was identified; metamorphic rock fragment included elongated quartz minerals; two plutonic rock fragments consisted of quartz and feldspar minerals; much more glauconite than previous sample and one chlorite grain that was recorded in the biotite column; calcareous microfossils common and some mud blobs were counted as matrix.

367-U1499A-57X-CC (31-33) Medium sand is the dominant grain size; this grain mount is dominated by mica grains and carbonate/calcareous microfossil grains with few framework grains (with Q,F, and L representing only 13.2% of the total grains; Monocrystalline quartz grains are subrounded in shape with some vacuoles and occasional fractures, few inclusions and evidence of overgrowth, clay or iron oxide sometimes cover the grain and provide a rim around the grain, straining very abundant; polycrystalline quartz spotted in the field of view with a subrounded shape although not counted (at least two were spotted); plagioclase and K- feldspar were mostly identified based on stain, both were weathered and tattered and altered to sericite and kaolinite; sandstone and siltstone rock fragments were extremely abundant, some of these rock fragments contained quartz, feldspar, and dense minerals with light colored calcite cement and other sedimentary rock fragments contained iron oxide cement and clay matrix and quartz minerals; one plutonic rock fragment was identified with quartz and K-feldspar minerals; Mica was extremely abundant, dominating the grain mount and making up 47% of the total grains, muscovite was very common but biotite was the most abundant with 69 counted grains and chlorite was counted 28 times and recorded with biotite, biotite often appeared to be altering to chlorite with both minerals often being identified together in the same grain, when this was identified the grain was most often recorded as biotite; calcareous microfossils were very abundant as were carbonate minerals that didn't seem to have a biogenic orogen but could have been fragments of shells; opaque grains and oxide strands were very common throughout the grain mount, some containing a reddish hue on the edge of the grains indicating hematite; several iron stained or clay blobs were counted as matrix.

367-U1499A-67X-1W (119-121) Fine sand is the dominant grain size; Monocrystalline quartz grains are angular to subangular, very strained, some overgrowth, some contain oxide rims outlining grain boundaries, some inclusions although not many, abundant fractures and vacuoles; polycrystalline quartz grains subangular-subrounded with vacuoles; K-feldspar more abundant than plagioclase in this sample as evidenced by yellow staining and microcline twinning; sandstone/siltstone rock fragments consist of iron cement, calcite, glauconite, and quartz minerals; one chert rock fragment counted; several metamorphic rock fragments counted with elongated quartz and oriented mica minerals; several plutonic grains counted of quartz and feldspar; overall subequal lithic abundances among the three different types of rock; some biotite observed and counted; glauconite abundant; carbonate minerals also abundant; some clay blobs counted as matrix; Counted every grain within half of the field of view and moved to another layer 500 microns apart instead of 1 mm due to small number of grains.

367-U1499A-69X-CC (36-38) Fine sand is the dominant grain size; Monocrystalline quartz grains are angular to subrounded, strained, with abundant vacuoles and oxide inclusions, as well as dense mineral inclusions, marks/lines on quartz grains look like further evidence of strain, some grains surrounded by glauconite and other clay minerals; 177 polycrystalline quartz grains are angular to subangular with a couple well rounded grains they contain biotite, oxide, and heavy mineral inclusions; all quartz grains contain fractures though not as abundantly as previous samples; plagioclase and potassium mostly recognizable by stain color as much of the plagioclase has been filled with quartz grains after weathering, some grains contain both plagioclase and K-feldspar due to alteration, most grains irregular or blocky in shape, cleavage and twinning also help identify these minerals; several siliciclastic rock fragments of sandstone/siltstone were observed containing mostly a clay matrix and in a few grains little matrix and thin iron oxide cement separating quartz and feldspar grains; several metamorphic rock fragments containing elongated crenulated quartz minerals were observed; several plutonic grains of feldspar and quartz were also counted; chlorite was counted and muscovite was observed although not counted; glauconite was also fairly common; Some irregular shaped oxide minerals were counted; several carbonate minerals counted although they could have been mud blobs with bright birefringence; one dense mineral was counted and identified as zircon; plagioclase was so weathered in some grains that it was difficult to differentiate between an SRF with all of the quartz grains or if it was a weathered plagioclase filled in by quartz.

367-U1499B-3R-3W (59-61) Medium sand is the dominant size of the grains in this thin section; Monocrystalline quartz subangular to angular, very strained, some very large grains, many inclusions including tourmaline and oxide inclusions, vacuoles common, fractures, some iron oxide creates rim around grains; Polycrystalline grains subangular to angular, variety of quartz sizes in each grain, very strained, oxide and tourmaline inclusions; some plagioclase and K-feldspar grains weathered and altered to clay but not in all grains; feldspar grains mostly identified by stain, twinning pattern, shape and orientation of oxides, and cleavage plains; this sample had many more lithic fragments than shallower samples, such as 13 plutonic rock fragments with quartz, feldspar and mica minerals usually, 10 metamorphic rock fragments with elongated quartz minerals and oriented mica minerals; muscovite and biotite also common with three chlorite grains recorded under biotite; Some mud blobs were observed and counted as matrix; some calcareous microfossil fragments observed and counted.

367-U1499B-4R-CCW (5-7) Fine sand is the dominant grain size in this thin section; Monocrystalline quartz grains are subangular to subrounded, some very strained others have straight unit extinction, contain abundant fractures and vacuoles as well as mica, oxide, clay and dense mineral inclusions, some of the quartz grains are very large and fall in the >500 micron range; polycrystalline quartz grains are subangular to irregular and blocky in shape with inclusions of oxides and mica minerals and abundant vacuoles; Plagioclase and K-feldspar are weathered and altered to sericite and kaolinite, they show cleavage and are best identified by stain color, shape, cleavage, and twinning, plagioclase grains contain some albitization and some grains contain alteration from plagioclase to K-feldspar and vice versa (shown by both pink and yellow stains); two siltstone siliciclastic rock fragment grains were counted and have a clay matrix with quartz and oxide minerals, one chert grain was counted; several metamorphic rock fragments were counted and identified with crenulated and elongated quartz minerals and mica minerals; two plutonic rock fragments were counted containing feldspar, quartz, mica, and dense minerals; mica minerals were very common in this thin section especially biotite and chlorite (five chlorite minerals were counted and recorded under the biotite category; several glauconite grains were observed and counted; calcareous bioclasts common throughout the thin section; few oxides were counted and identified (much less than previous samples in U1499A; several dense minerals were observed and counted such as hornblende and zircon; matrix dominated by calcite cement, several mud blobs and few sericite minerals; quartz grains fill in gaps most likely created by diagenesis.

367-U1499B-9R-1W (74-77) Medium sand is the dominant grain size; Monocrystalline quartz grains are angular to subangular, some overgrowth in the form of polycrystalline quartz (megaquartz), abundant vacuoles and fractures as well as oxide, dense mineral, clay mineral, and mica inclusions, mostly strained grains; polycrystalline quartz grains mostly subangular to angular with vacuoles and oxide and mica and clay inclusions, mostly strained 178

(some categorized as MRF grains due to elongation and straining); plagioclase and K-feldspar grains very weathered and altered to kaolinite and sericite, some albitization, much more weathering than previous samples, blocky and irregular in shape, mostly identified by stain, all feldspar grains appear very different some have many inclusions and some are completely stained dark red - varying degrees of Ca composition, some grains surrounded by glauconite; two siltstone/sandstone rock fragments counted with oxide cement; one chert grain counted; many metamorphic rock fragments counted containing elongated, crenulated quartz minerals and oriented oxide and mica minerals; there were also many plutonic rock fragments that contained quartz and feldspar minerals; biotite and muscovite were also extremely common in this thin section unlike previous samples (two chlorite grains counted and recorded under biotite); no glauconite observed; several opaque oxide strands; several carbonate minerals were counted (identified as white in XPL with a yellow vertical line in the middle and hardly visible in PPL); several clay blobs counted as matrix.

367-U1499B-9R-1W (107-109) – B8T-021 Medium sand is the dominant grain size; Monocrystalline quartz grains are subrounded to subangular with many inclusions such as oxides, needle-like inclusions that could be rutile or tourmaline, dense minerals, mica, and clay minerals, abundant vacuoles filled with water inclusions, some iron oxide coating present around grains, some overgrowth noted in the form of small megaquartz, abundant fractures and mostly strained rather than unit extinction; polycrystalline quartz varies in shape from angular to rounded with abundant vacuoles and inclusions (same as monocrystalline quartz grains), most grains are strained and some are significantly strained and therefore recorded under MRF; Plagioclase and K-feldspar have been weathered and altered to kaolinite and sericite and contain inclusions of oxides, they are blocky and irregular and shape (most likely due to weathering), they are often surrounded by glauconite and iron oxide, some evidence of albitization, some alteration from one feldspar to another observed, best identified based on stain color, cleavage, and twinning; several siltstone/very fine sandstone rock fragments were identified with iron oxide cement and little matrix; metamorphic rock fragments were extremely common in this thin section with several counted and even more observed in the field of view containing elongated quartz minerals and oriented mica minerals including chlorite; plutonic rock fragments were also very common containing quartz and feldspar minerals; biotite and chlorite were common (two chlorite grains counted and recorded under biotite) and muscovite was also common in the field of view although not counted many times; hornblende spotted although not counted; few clay blobs were counted as matrix.

367-U1499B-9R-1W (107-109) – B8T-022 Medium sand is the dominant grain size; Monocrystalline quartz grains are subangular to angular in shape, very strained, abundant vacuoles and fractures, inclusions of oxides, needle-like minerals such as rutile or tourmaline, mica, clay and dense minerals common, often surrounded by glauconite or mica; polycrystalline quartz grains are angular to subrounded and very abundant, they are strained and contain oxide inclusions as well as other inclusions and abundant vacuoles; plagioclase and K-feldspar heavily weathered and altered to kaolinite and sericite and filled in with quartz minerals due to diagenesis (difficult to discern between plutonic rock fragments and diagenetic alteration), blocky and irregular in shape and best identified by stain, cleavage and twinning, feldspar grains commonly have a lot of unidentifiable small inclusions; several sandstone and siltstone sized siliciclastic rock fragments were identified with oxide cement and clay matrix surrounding quartz, feldspar and oxide minerals; one chert grain was also identified, several metamorphic grains were counted and many others were observed in the field of view containing elongated quartz and oriented mica and oxide minerals; several plutonic rock fragments were also counted containing quartz and feldspar minerals; mica is very abundant in this thin section with several grains of muscovite and biotite (one grain of chlorite was identified and recorded under the biotite column); clay blobs were counted as matrix.

367-U1499B-10R-3W (11-13) Medium sand is the dominant grain size; this grain mount is dominated by mica, opaque grains, and carbonate grains with few framework grains (with Q,F, and L representing only 7.6% of the total grains); Monocrystalline quartz grains are subangular with abundant vacuoles and fractures, other quartz grains 179 were identified in the field of view but very few were landed on, grains surrounded by clay and oxides, very strained with few inclusions; polycrystalline grains subangular; plagioclase and K-feldspar weathered and altered to sericite and kaolinite, identified by stain color; one very fine grained sandstone rock fragment spotted in the field of view with a clay and iron oxide cement but not counted; mica was extremely common with 81 biotite grains, some altering to chlorite, and 61 counted chlorite grains (recorded with biotite), only seven muscovite grains were counted however many more were observed in the field of view; opaque grains were common especially strands of oxides throughout the grain mount; several carbonate grains were identified in the field of view; several clay blobs and iron oxide strands were counted as matrix/cement.

367-U1499B-12R-1W (34-36) Medium sand is the dominant grain size; Monocrystalline quartz grains are subrounded to subangular with few to no inclusions, abundant vacuoles, some fractures, strong evidence of straining among all grains, some overgrowth, and some clay and oxides filling in fractures and forming a rim around some grains; Polycrystalline quartz grains are subrounded to subangular; plagioclase and K-feldspar heavily weathered and tattered and altered to sericite and kaolinite with evidence of albitization, some plagioclase grains contain several inclusions of clay and dense minerals; sandstone and siltstone rock fragments were extremely abundant (more abundant than in any other sample) and this could be a result of poor disaggregation while sieving or it could just represent an abundance of sedimentary rock fragments, most contain quartz and feldspar minerals and iron oxide cement with clay matrix and others contain a calcite matrix with quartz and feldspar minerals, one chert grain was identified; several metamorphic rock fragments were identified with elongated quartz and oriented mica minerals and quartzite grains; several plutonic rock fragments were identified containing quartz and feldspar minerals and one volcanic rock fragment was identified with an opaque mineral and fine grained matrix; mica was again fairly common with 14 identified biotite grains and five identified chlorite grains recorded with biotite; calcareous microfossils were abundant as were carbonate minerals; oxide strands and minerals were abundant but not as abundant as previous samples.

367-U1499B-13R-4W (94-96) Can't use - more than 80% calcareous microfossils and grains too small

367-U1499B-30R-2W (55-59) Can't use - more than 80% calcareous microfossils and grains too small

367-U1499B-30R-2W (104-107) Fine sand is the dominant grain size; Monocrystalline quartz grains are subrounded to rounded in shape with vacuoles and few fractures, some contain clay, needle-like minerals, mica and/or dense mineral inclusions, quartz grains infrequently counted throughout the thin section; plagioclase and K-feldspar grains are heavily weathered, tattered, and altered to sericite and kaolinite with clay and mica inclusions, identified best based on stain and cleavage planes, blocky in shape; several siltstone rock fragments were identified with feldspar, carbonate, and quartz minerals and clay matrix and calcite cement; two metamorphic rock fragments, one identified with a quartz mineral inside strained mica minerals creating a mylonitic texture; one volcanic rock fragment with laths of plagioclase; mica common in this thin section with 2 biotite minerals identified and 2 chlorite minerals identified and recorded with biotite and several more muscovite grains observed in the field of view; glauconite is common in this thin section; calcareous microfossils dominate this thin section and carbonate minerals are also quite abundant; Matrix represents the majority of this thin section and grains were difficult to come by even with a 1 mm vertical spacing between rows; Matrix dominated by clay, and sericite and calcite cement; iron oxide strands most likely present although difficult to identify and distinguish between reddish brown colored clay and sericite.

367-U1499B-30R-2W (128-132) Fine sand and very fine sand are the dominant grain sizes; Monocrystalline quartz grains are subrounded in shape with some (although not a lot) inclusions of dense minerals, clay, mica, oxide, and needle-like 180 minerals, abundant vacuoles and fractures, one very large quartz grain; polycrystalline quartz grains not abundant; plagioclase and K-feldspar grains heavily weathered and altered to kaolinite and sericite, tattered in appearance with mica inclusions, blocky in shape; one metamorphic rock fragment of elongated quartz minerals and mica; mica common with several muscovite and biotite spotted in the field of view and counted occasionally, one chlorite mineral identified and recorded with biotite; glauconite common filling in void space; calcareous microfossils dominate the thin section, making up the majority of the grains; iron oxide strands and opaque grains were scattered throughout the thin section; carbonate minerals also common; matrix represents the majority of this thin sections and grains were difficult to come by even with a 1 mm vertical spacing between rows; Matrix dominated by clay and sericite and calcite cement; opaque iron oxide strands present although sometimes difficult to identify and distinguish between reddish brown colored clay and sericite and red stain.

367-U1499B-30R-3W (0-5) Very fine sand and fine sand are the dominant grain sizes counted however most grains in this thin section as a whole are silt or clay sized; Monocrystalline quartz grains are subangular to angular in shape with inclusions of needle-like minerals (could be rutile or tourmaline) and oxide minerals and abundant vacuoles and fractures, strong evidence of straining within all of the minerals counted in this thin section; polycrystalline quartz grains are angular; Plagioclase and K-feldspar grains are heavily weathered, tattered, and altered to kaolinite and sericite, identified based on stain and cleavage, many grains have some spots of red which could indicate stain or oxide inclusions, therefore grains were mostly identified by cleavage and weathered appearance; several siltstone rock fragments were identified some with clay matrix and angular feldspar minerals and some with clay matrix and quartz and feldspar minerals; plutonic rock fragments were also observed with plagioclase and quartz minerals; one metamorphic rock fragment was spotted in the field of view but not counted with oriented oxide and mica minerals; mica and biotite were observed in this section; calcareous microfossils and carbonate minerals were both very abundant in this thin section; oxides were also observed; thin section dominated by matrix and very fine grain size therefore grains were difficult to come by even with a 1 mm vertical spacing between rows; Matrix dominated by clay and iron oxide and calcite cement; opaque iron oxide strands present although sometimes difficult to identify and distinguish between reddish brown colored clay and red stain; half of the slide is taken up by a darker colored, oxide-rich nodule or circular deformation surrounding megaquartz which probably formed as a result of diagenesis as was therefore not counted as a grain.

367-U1499B-30R-3W (38-43) Fine sand is the dominant grain size; Monocrystalline quartz grains are on average subrounded in shape but are occasionally more angular, fractures and vacuoles abundant as well as needle-like and oxide inclusions, evidence of straining is common in quartz grains as well as in all other grains in this thin section; polycrystalline quartz grains are subangular in shape; Plagioclase and K-feldspar grains are heavily weathered, tattered and altered to sericite and kaolinite, best identified based on stain and cleavage, blocky in shape; one siltstone rock fragment was identified with an abundance of calcite cement and quartz minerals; one metamorphic rock fragment was identified with stretched, elongated quartz minerals; several igneous rock fragments were identified including one plutonic rock fragment of quartz and feldspar minerals and three volcanic rock fragments, one of which was dark and very fine grained, such as maybe a basalt fragment, another contained feldspar laths both big and small; A large plutonic rock fragment was identified but because it was coarse-sand sized it was counted as the mineral that I landed on, muscovite; mica common in this thin section with several muscovite minerals identified and pleochroic biotite (sometimes altering to chlorite); Calcareous microfossils once again dominated the thin section making up the majority of the counted grains; due to the small grain size and abundant matrix, grains were difficult to come by even with a 1 mm vertical spacing between rows; Matrix dominated by clay and a lot of calcite cement; few opaque iron oxide strands present although sometimes difficult to identify and distinguish between reddish brown colored clay and red stain; some megaquartz present probably as the result of diagenesis.

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367-U1499B-30R-4W (77-82) Very fine and fine sand are the dominant grain sizes in this thin section; Monocrystalline quartz grains are subangular to rounded with some overgrowth, abundant vacuoles, some needle-like mineral inclusions, and some fractures although not very abundant; tried not to count secondary quartz minerals but difficult to distinguish with the small grain size; plagioclase and K-feldspar heavily weathered and altered to kaolinite and sericite, common inclusions of clay, sericite, and dense minerals, often identified based on stain and cleavage; all grains surrounded by clay and sericite and biotite making grain boundaries difficult to recognize; siltstone rock fragments were common with clay matrix and iron cement and one with little matrix and quartz, feldspar, and calcite minerals; several metamorphic rock fragments were identified with a mica mineral dissecting a quartz mineral or elongated quartz minerals and some interspersed mica minerals and opaque minerals; mica was very abundant with nine muscovite grains and 17 biotite grains (many more were identified in the field of view but not counted; calcareous microfossils were abundant as well as perfectly rhombohedral carbonate minerals. Matrix dominated this thin section and it was difficult to find grains to count; Matrix dominated by clay, sericite and kaolinite, some megaquartz cement common and quartz grains filling in pore space probably as the result of diagenesis; iron oxide also most likely abundant although difficult to identify and distinguish between reddish brown colored clay and sericite.

367-U1499B-30R-5W (23-29) Very fine and fine sand are the dominant grain sizes in this thin section; Monocrystalline quartz grains are subrounded with abundant vacuoles and fractures, some inclusions of dense minerals or clay, some quartz grains counted within larger rock fragment grains, straining abundant; Plagioclase and K-feldspar weathered, tattered and altered to sericite and kaolinite with some inclusions and straining, and a blocky shape, also counted often as part of a larger rock fragment; several siltstone and sandstone rock fragments were identified, some with calcite matrix and quartz and feldspar minerals and some with calcite/clay matrix and biotite and feldspar minerals; one chert rock fragment was identified; several metamorphic rock fragments were identified with strained, stretched and elongated quartz minerals and one quartz mineral surrounded by stretched mica (similar to a mylonitic strain); plutonic and volcanic rock fragments were identified (often as part of a larger rock fragment that was counted on the mineral it landed on which were usually smaller volcanic pieces within a larger grain), volcanic rock fragments consisted of plagioclase laths and small angular quartz minerals, plutonic consisted of feldspar and quartz minerals; mica abundant with several muscovite and biotite grains and one chlorite grain recorded with biotite; calcareous microfossils were abundant throughout the thin section along with carbonate minerals; several dense minerals counted and some identified as zircon; very poorly sorted, large rock fragments in a very fine sand composition dominated by matrix, used a 1 mm vertical spacing between rows; Matrix dominated by clay matrix and calcite cement, some megaquartz cement common and quartz grains filling in pore space probably as the result of diagenesis; iron oxide strands also most likely abundant although difficult to identify and distinguish between reddish brown colored clay and red stain.

367-U1499B-30R-5W (91-96) Fine sand and very fine sand are the dominant grain sizes; Monocrystalline quartz grains are subrounded to rounded with abundant evidence of strain and inclusions including a brown colored translucent mineral, dense minerals/clay minerals, and needle-like inclusions, abundant vacuoles and fractures, some overgrowth; polycrystalline quartz grains are subrounded in shape with vacuoles and some mica/clay mineral inclusions; Plagioclase and K-feldspar grains are heavily weathered, tattered and altered to sericite and kaolinite (some altered almost entirely), containing mica/clay/dense mineral inclusions, blocky in shape, identified best by cleavage and stain; chert rock fragments identified; several metamorphic rock fragments identified with elongated quartz minerals and one of a quartz mineral with strained mylonitic mica surrounding the quartz; plutonic and volcanic rock fragments were also abundantly identified with plagioclase laths; mica also abundant in the field of view and often counted with 5 chlorite minerals recorded with biotite; few carbonate minerals/microfossils identified; grains for this point count were counted within two very large grains on the thin section, the rest of the thin section was dominated by stain and matrix and few to no grains; a 1 mm vertical spacing was used and a 200 micron horizontal spacing was used; Matrix dominated by clay, sericite and kaolinite matrix, some megaquartz cement common and 182 quartz grains filling in pore space probably as the result of diagenesis; iron oxide strands also most likely abundant although difficult to identify and distinguish between reddish brown colored clay and red stain.

367-U1499B-32R-1W (3-5) Medium to fine-grained sand grains; monocrystalline quartz angular to subangular and sometimes irregular, iron oxide rims and inclusions, also tourmaline inclusions common, vacuoles abundant, inclusion heavy, strained, fractured, some overgrowth; polycrystalline quartz rounded to angular (vary in shape), inclusions of tourmaline, oxides, strained and fractured; plagioclase and potassium feldspar grains have feldspar overgrowths and even some evidence of faulting, some grains are very blocky in shape, tourmaline inclusions common, some grains are completely weathered and altered to kaolinite and sericite and some are not all that weathered and twinning is still very visible; two sedimentary rock fragments were counted, one with clay matrix and very fine quartz minerals and one with calcite cement and feldspar and quartz minerals; two chert grains were observed and many metamorphic grains of elongated quartz and oriented mica minerals were also observed; several igneous rock fragments were observed in the form of volcanic laths and larger quartz and feldspar minerals in one grain; one dense mineral was counted and several zircon minerals were spotted; Kaolinite/clay matrix; radial megaquartz cement and megaquartz veins common; iron oxide abundant coating grains and in strands throughout thin section.

367-U1499B-32R-1W (58-62) Polycrystalline quartz well rounded; very weathered plagioclase almost completely serecitized; zircons spotted; siltstone and chert primary SRFs; Kaolinite/clay matrix; radial megaquartz cement; sericitic cement.

367-U1499B-32R-1W (88-91) Polycrystalline quartz well rounded; monocrystalline quartz had inclusions (tourmaline/apatite); extremely weathered plagioclase and K-feldspar, almost completely sericitized; zircons spotted; chert primary SRFs; iron oxide strands common; Kaolinite/clay matrix; megaquartz vein; sericitic cement.

367-U1499B-33R-1W (19-27) Undulatory monocrystalline and polycrystalline quartz with several inclusions especially tourmaline; some well-rounded polycrystalline grains with several oxides and strained undulatory extinction; feldspars very strained with some visible twinning; plagioclase extremely weathered and altering to sericite and kaolinite with inclusions; metamorphic rock fragments extremely strained; iron oxide strands present and zircons spotted but not counted; chert primary SRF; Kaolinite/clay matrix; megaquartz vein; sericitic cement.

367-U1499B-33R-2W (7-12) Monocrystalline quartz subrounded to angular and strained; plagioclase extremely weathered to kaolinite and sericite, very strained with inclusions of tourmaline and maybe apatite; K-feldspar strained and smaller in size in general; zircons spotted; Kaolinite/clay matrix; megaquartz veins; sericitic cement; iron oxide strands and clumps.

367-U1499B-33R-2W (27-33) Monocrystalline quartz subangular to angular with small inclusions and oxides (some oriented in layers) with overgrowth on many of the grains and straining abundant; tourmaline and rutile inclusions in weathered polycrystalline quartz grains; plagioclase extremely weathered to kaolinite and sericite, strained with iron oxide staining and small oxide inclusions, some twinning visible on several grains; chert primary SRF; plutonic and volcanic rock fragments abundant; muscovite spotted but not counted; Zircons spotted but not counted. Grains much larger than previous samples; Iron oxide coating grains; megaquartz vein and megaquartz rims around grains; limonite cement; some clay/kaolinite matrix but significantly less than previous samples.

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367-U1499B-34R-1W (0-6) Monocrystalline quartz strained with no overgrowth but with alteration around the edge of the grain, a lot of grains very large and subangular to subrounded; polycrystalline quartz very strained and rounded; Quartz grains have many inclusions of tourmaline and possibly apatite; plagioclase strained and extremely weathered to sericite and kaolinite leaving holes in many of the grains and a stringy appearance; some twinning visible on several grains not as heavily weathered; chert very large, rounded and the primary SRF although this sample had several noticeable Sandstone/siltstone rock fragments with small quartz grains; Zircons spotted; grains much larger than previous samples; many volcanic rock fragments with feldspar laths; Iron oxide coating grains; iron oxide cement/inclusions within grains and in matrix especially in quartz; sericite matrix abundant; much less kaolinite and clay matrix than in previous samples; megaquartz rim around grains and megaquartz veins present.

367-U1499B-34R-1W (50-55) Monocrystalline quartz strained with no overgrowth but with alteration around the edge of the grain, subangular to angular with tourmaline and oxide inclusions; Polycrystalline quartz subrounded to well- rounded but uncommon; plagioclase heavily altered to sericite and kaolinite, hard to recognize grain boundaries and distinguish between K-feldspar and Plagioclase, most grains strained; chert most common SRF but contains iron coating around grain; Several muscovite grains spotted but not counted; several zircon minerals spotted but not counted; grains significantly smaller in this sample than in previous samples; Iron oxide coating grains; iron oxide cement/inclusions within grains and in matrix; sericite and kaolinite matrix very abundant (much more than previous sample).

367-U1499B-34R-1W (87-91) Monocrystalline quartz strained and altered (appear fragmented) with inclusions of oxides in layers and tourmaline/apatite inclusions; monocrystalline quartz is subrounded to angular with more angular subangular grains; few polycrystalline grains; plagioclase heavily altered and weathered to kaolinite and sericite; subrounded to angular (many blocky pieces); degree of alteration varies among plagioclase grains which may represent more than one source for feldspar; plagioclase and k-feldspar grains contain iron oxide inclusions and many have an oxide rim (distinguishing between pink stain and limonite cement/iron oxide cement is difficult in this sample); potassium feldspar grains very large; plutonic grains large but contain quartz and feldspar grains; chert most common SRF; no zircons spotted; Iron oxide coating grains and forming a rim around grains; iron oxide cement/inclusions within grains and in matrix; sericite and kaolinite matrix very abundant (especially the kaolinite); small megaquartz abundantly form a rim around grains and fill in pores (maybe as a secondary process filling in gaps created by diagenesis); some clay matrix.

367-U1499B-34R-2W (11-17) Monocrystalline quartz strained and altered (appear fragmented and containing embayment), some overgrowth, angular to subangular with inclusions of tourmaline and fractures visible; polycrystalline quartz strained and tattered; plagioclase blocky and angular with inclusions of oxides, tourmaline, and possible rutile or magnetite; plagioclase and K-feldspar extremely weathered and altered to sericite and kaolinite; degree of alteration varies among plagioclase grains which may represent more than one source for feldspar; chlorite spotted in volcanic rock fragment and as a single mineral; zircon spotted several times but not counted; chert most common SRF; very abundant volcanic rock fragments with laths of feldspar and other needle shaped minerals; Quartz rich, abundantly form a rim around grains and fill in pores (maybe as a secondary process filling in gaps created by diagenesis), also quartz veins common; some clay matrix; iron oxide cement and inclusions within grains and in matrix (but significantly less iron oxide than previous samples); Sericite and kaolinite matrix abundant.

367-U1499B-36R-1W (51-55) Monocrystalline quartz subangular to subrounded, many small oxide inclusions on the majority of quartz grains, undulatory extinction showed evidence of strain as well as the elongated shape of grains; polycrystalline quartz strained and rounded to subrounded with tourmaline and mica inclusions; Plagioclase 184 highly weathered and altered to sericite and kaolinite, shape subangular to angular with oxides (such as magnetite) and tourmaline or rutile inclusions, most grains blocky; degree of alteration varies among plagioclase and K-feldspar grains; Many more K-feldspar grains in this thin section than observed in previous samples (Identified by yellow stain); chert less abundant than previous samples; many volcanic rock fragments counted and spotted without counting; zircon spotted; Quartz rich, abundantly form a rim around grains and fill in pores (maybe as a secondary process filling in gaps created by diagenesis); iron oxide cement and inclusions within grains and in matrix common; Sericite and kaolinite matrix very abundant and dominates thin section.

367-U1499B-36R-1W (89-93) Monocrystalline quartz subangular to subrounded, very big fractured grains with many small oxide inclusions on the majority of quartz grains, undulatory extinction showed evidence of strain as well as the elongated shape of grains, some quartz grains also contain tourmaline inclusions; polycrystalline quartz strained and rounded (often documented as metamorphic rock fragments due to abundance of straining and mica), subrounded, containing tourmaline, oxide, and mica inclusion; plagioclase highly weathered and altered to sericite and kaolinite, shape blocky and angular with oxides, and tourmaline inclusions, small quartz and megaquartz grains fill in the holes in feldspar grains after diagenesis; Some K-feldspar grains almost totally altered to clay/quartz, identified by small oxide grains aligned with cleavage planes; Degree of alteration varies feldspar grains; majority of lithic grains are volcanic rock fragments that contain feldspar laths; zircons spotted but not counted; pink stain is observed throughout the thin section although grain boundaries were difficult to distinguish; Quartz grains and megaquartz grains fill in pores (maybe as a secondary process filling in gaps created by diagenesis); iron oxide cement and inclusions within grains and in matrix common (hard to delineate between stain and iron oxide); Sericite and kaolinite matrix very abundant and dominates thin section. sericite forms a rim around some grains.

367-U1499B-36R-1W (100-104) Grains for this thin section extremely small, majority of grains are in the <63-125 micrometer size range, therefore identification is difficult; monocrystalline quartz angular to subangular, many inclusions and oxides present as well as undulatory extinction which is evidence of straining; small polycrystalline quartz grains are well rounded while some are more altered and include more inclusions; plagioclase and K- feldspar mostly identified based on staining colors due to heavily altered and weathered nature of grains and small grain size; muscovite more abundant in this sample; oxides common; zircons spotted but not counted. The thin section is dominated by kaolinite and sericite matrix. Sericite forms a rim around some grains; iron oxide cement and inclusions within grains and in matrix common; big crack through thin section of just epoxy; thin section overwhelmed by clay.

367-U1499B-37R-1W (105-112) Grains for this thin section are very small with majority of the grains counted in the <63 to 250 micrometer size range, therefore identification is difficult; monocrystalline quartz not very abundant, subangular to subrounded, inclusions of tourmaline and oxides; some overgrowths observed; very few polycrystalline quartz some rounded polycrystalline quartz spotted but not counted, most subangular with inclusions and mica; plagioclase and K-feldspar extremely weathered and altered to sericite and kaolinite, very blocky in shape with oxide inclusions aligned with cleavage planes, feldspars mostly identified based on staining colors but difficult to distinguish between plagioclase and K-feldspar due to weathering and small grain size; muscovite very abundant; very few rock fragments due to small grain size; zircon grains spotted but not counted; dark clay or black to dark oxide strands dominate the thin section in parallel laminations limiting the amount of grains in thin section that can be identified, the organized orientation of these layers does not appear to have a metamorphic origin due to a lack of strained grains and a lack of any particular orientation of minerals within the thin section; Kaolinite and sericite matrix very abundant and dominates thin section. Sericite forms a rim around some grains; iron oxide cement and inclusions within grains and in matrix common, also iron oxides coat grain rims defining grain boundaries; thin section overwhelmed with dark laminated clay that could also be dark iron oxide strands.

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367-U1499B-39R-1W (30-35) Grains much larger in this thin section than in other previous samples with the majority of the grains falling in the >500 micrometer grain size; Monocrystalline quartz strained and subangular to angular in shape with minimal overgrowth; polycrystalline quartz more common and large sometimes with inclusions of mica and tourmaline; several metamorphic rock fragments with oriented grains of mica and elongated quartz; many volcanic rock fragments, some with granophyric texture in feldspar and feldspar laths; several zircon grains spotted but not counted; variety of alteration in plagioclase and K-feldspar grains with some almost entirely altered to sericite and kaolinite and some with preserved twinning; overall significantly less matrix in this thin section compared to previous thin sections; Kaolinite/clay rich matrix however little to no sericite matrix or cement; iron oxides coat grain rims defining grain boundaries, iron oxide cement and inclusions within grains and in matrix; quartz grains and megaquartz grains fill in pores (maybe as a secondary process filling in gaps created by diagenesis); one or two quartz veins counted as part of cement/matrix.

367-U1499B-40R-1W (43-47) Monocrystalline quartz angular to subangular, strained with minimal to no overgrowth, oxide inclusions and alteration in some grains; Majority of the grains observed fall in the 125-250 micrometer grain size range; polycrystalline quartz grains not very common but subangular and strained; Plagioclase grains weathered and altered to sericite and kaolinite with granophyric and myrmekite texture, with many oxide inclusions and fragmented edges; potassium grains heavily weathered and altered and difficult to distinguish from plagioclase without yellow stain; metamorphic rock fragments show evidence of straining, elongation, and the orientation of grains, usually with muscovite; volcanic rock fragments contain plagioclase laths; zircon grains spotted; several cracks in thin section contain no grains or matrix/cement; Kaolinite/clay rich matrix however little to no sericite matrix or cement observed in previous samples by high birefringence; iron oxide cement and inclusions within grains and in matrix; also iron oxides coat grain rims defining grain boundaries; quartz grains and megaquartz grains dominate thin section and fill in pores (maybe as a secondary process filling in gaps created by diagenesis); many quartz veins observed counted as part of cement/matrix.

367-U1500A-20R-CCW (8-10) Medium sand is the dominant grain size; Monocrystalline quartz grains are on average subrounded to rounded although some are more angular in shape, vacuoles and fractures are abundant, strong evidence of straining, some quartz overgrowth, inclusions common and include mica, needle-like minerals (rutile/tourmaline), blue-green minerals identified as tourmaline, iron oxide rims form around grain boundaries, clay fills in fractures; polycrystalline quartz grains are subrounded to angular although there were some well-rounded grains, vacuoles and mica/sericite inclusions abundant; plagioclase shows evidence of albitization, some grains have some green and black minerals covering the grain which could be from oxides or weathering or clay, clay fills in cleavage planes and encompasses grains, heavily weathered grains; several sandstone and siltstone rock fragments were identified with a clay matrix and iron oxide cement and quartz and feldspar minerals; three chert grains were identified, some with clay filled fractures; four metamorphic rock fragments were identified, one with plagioclase and chlorite and others with quartz and mica minerals; several plutonic rock fragments were identified, one with plagioclase, zircon, and a large unidentified heavy mineral that is clear in ppl and blue in xpl with high relief and an elongated shape, other plutonic rock fragments contain quartz and feldspar minerals; muscovite was the only common mica mineral; several clay blobs were counted as matrix and discounted.

367-U1500A-25R-6W (26-28) Fine sand is the dominant grain size although very fine sand is also very abundant; Monocrystalline quartz grains are subangular to angular, abundant vacuoles and fractures, strong evidence of straining through undulatory extinction, inclusions not common, clay fills in fractures; polycrystalline quartz grains are subrounded to rounded; plagioclase shows evidence of albitization, plagioclase and K-feldspar grains are heavily weathered and altered to kaolinite and sericite, with inclusions of mica, clay, and dense minerals, clay fills in fractures and cleavage planes; one siltstone /sandstone rock fragment was identified with clay 186 matrix and sericite cement; several metamorphic rock fragments were identified with elongated quartz minerals and mica minerals; one plutonic rock fragment was identified with quartz and feldspar minerals; mica grains were very abundant with several muscovite grains and biotite grains and three counted chlorite grains recorded with biotite; several mud blobs were identified and counted as matrix; Dominated with clay matrix and sericite, iron oxide, and calcite cement; many small silt sized grains of quartz, some could have been formed by diagenesis; iron oxides coat grain rims defining grain boundaries and clay matrix fills in fractures in quartz grains and in cleavage plains in feldspar.

367-U1500A-29R-1W (5-7) Monocrystalline quartz strained and altered, subrounded to subangular, some overgrowths, some grains surrounded entirely by glauconite or carbonate material; polycrystalline quartz rounded; plagioclase less abundant than previous samples and less weathered than the gravel lithologic unit at the bottom of site U1499; more K-feldspar than plagioclase in this thin section; many micrite sedimentary rock fragments; biotite and chlorite very abundant (chlorite counted with biotite); glauconite very abundant in this thin section; calcareous bioclasts (foram remnants) very abundant; many dense minerals observed and some counted, mostly grains of amphibole identified due to pleochroism in plane light; Dominated with carbonate cement; quartz grains fill in gaps most likely created by diagenesis; iron oxides coat grain rims defining grain boundaries; iron oxide inclusions within grains and in matrix.

367-U1500A-29R-1W (73-75) Very fine sand is the dominant size of grains in this thin section; thin section dominated by carbonate cement; monocrystalline quartz grains subangular to angular with iron oxide and tourmaline inclusions, some rounded grains and some other heavy mineral inclusions and fractures; some quartz grains surrounded by glauconite that formed as a thick rim around the grain; few polycrystalline quartz grains counted although many rounded polycrystalline quartz grains spotted in the field of view; plagioclase and potassium feldspar show some weathering and alteration to clay but are mostly identified from quartz due to stain color and shape of the grain; few micrite grains and metamorphic rock fragments summing to very few lithic grains; there is an abundance of mica grains in this thin section with 7 biotite grains counted, 15 chlorite grains counted, 6 muscovite grains counted, and 14 glauconite grains counted; an abundance of calcareous microfossils were counted such as fragments of forams and sponge spicules; a few diatoms were spotted as well; hornblende was fairly common and spotted in the field of view but not counted often; zircon was also spotted but not counted often; Dominated with carbonate cement; quartz grains fill in gaps most likely created by diagenesis; some iron oxide inclusions within grains and in matrix.

367-U1500A-32R-1W (15-17) Very fine to fine sand is the dominant size of grains in this thin section; this thin section is dominated by carbonate cement; monocrystalline quartz grains subrounded-angular, strained with heavy mineral inclusions, oxide inclusions and tourmaline inclusions, some fragmented and fractured; polycrystalline grains subangular (not as rounded as previous samples); plagioclase and K-feldspar show some weathering and alteration to clay but are mostly identified from quartz due to stain color and blocky shape of the grain; several sedimentary rock fragments of sandstone and micrite grains and 4 metamorphic rock fragments one of which composed of chlorite, muscovite, and quartz; several mica grains were counted and several more were spotted including 5 chlorite grains that were recorded in the biotite category; glauconite very abundant in thin section and commonly forms a thick rim around quartz grains; many calcareous microfossils were spotted and counted as fragments of forams; zircon and hornblende were commonly observed in the field of view; Dominated with carbonate cement; quartz grains fill in gaps most likely created by diagenesis; some iron oxide inclusions within grains and in matrix.

367-U1500A-34R-1W (5-7) Very fine sand and fine sand are the dominant grain sizes however overall most grains are silt or clay sized; Monocrystalline quartz grains are subrounded to angular in shape with inclusions of needle-like minerals (could be rutile or tourmaline) and blue-green colored minerals which also can indicate tourmaline, grain sizes are very small and extinction is difficult to distinguish but some show evidence of straining 187

(especially larger grains and some have straight unit extinction, vacuoles abundant with fractures abundant in larger grains; polycrystalline quartz grains are subrounded to rounded, a couple of the counted poly quartz grains are the largest grains counted; plagioclase and K-feldspar are heavily weathered and are only distinguishable based on stain and cleavage (little twinning was observed); one metamorphic rock fragment was identified of elongated mica and quartz minerals although several more were identified in the field of view; a few plutonic rock fragments were identified containing quartz and feldspar minerals; mica was fairly common with 8 muscovite grains, 5 biotite grains and 2 chlorite grains (recorded with biotite); glauconite was spotted however it was not counted; calcareous microfossils were extremely abundant throughout the thin section; Iron oxide strands were common throughout the thin section along with opaque oxide minerals; Overall much more matrix than grains; Dominated with clay matrix and calcite cement; iron oxide strands common; moderately lithified as shown by areas of the thin section lacking matrix and covered with epoxy, most grains extremely small.

367-U1500B-7R-1W (119-121) Very fine to fine sand is the dominant size of grains in this thin section; this thin section is dominated by carbonate cement; monocrystalline quartz grains angular-subrounded, strained, tourmaline and oxide inclusions, fractured, some massive grains (most of the 500+ micron sized grains were big quartz grains); polycrystalline grains subrounded- rounded, strained, containing some matrix or yellow stain surrounding pieces of quartz (sometimes identified as sedimentary rock fragments); plagioclase and potassium feldspar weathered and altered to clay, mostly identified from quartz due to stain color and blocky shape of the feldspar grains; Rock fragments include sandstone SRFs, chert grains, micrite biochemical rock fragments, metamorphic rock fragments (including one with elongated quartz grains and bright blue crystals, maybe tourmaline), 2 VRFs with some laths and many unaligned different minerals within one grain; abundant glauconite grains; glauconite sometimes forms thick rims around some quartz and feldspar grains; abundant mica grains including 4 chlorite grains recorded in the biotite category; zircon and hornblende were spotted and counted occasionally along with other unidentified heavy minerals; microfossils common although not typically recorded; Dominated with carbonate cement; quartz grains fill in some pore space most likely created by diagenesis; some iron oxide inclusions within grains and in matrix; some grain rims coated with sericite and/or iron oxide.

367-U1500B-8R-1W (94-98) Fine sand is the dominant size of grains in this thin section; this thin section is dominated by carbonate cement; monocrystalline quartz grains subangular to subrounded, strained, tourmaline and oxide inclusions, fractured, some massive grains (most of the 500+ micron sized grains); polycrystalline grains angular- subangular, strained, containing some yellow stain surrounding pieces of quartz; plagioclase and K-feldspar altered and weathered to clay, identified by stain color and shape/orientation of oxides in cleavage planes; rock fragments include chert grains and micrite grains as well as several metamorphic grains consisting of elongated quartz and aligned micas; abundant glauconite grains; glauconite forms thick rims around some quartz and feldspar grains; abundant mica grains including 6 chlorite grains recorded in the biotite column; several calcareous bioclasts spotted but not often counted; hornblende as well as other dense minerals were spotted and sometimes counted; no zircon minerals were spotted or counted; Dominated with carbonate cement; quartz grains fill in some pore space most likely created by diagenesis; some iron oxide inclusions within grains and in matrix; some grain rims coated with sericite and/or iron oxide.

367-U1500B-23R-1W (58-60) Very fine and fine sand is the dominant grain size although there were several (3+) gravel to pebble sized sedimentary (siltstone) rock fragments or mudclasts scattered in the thin section (moderately sorted); Monocrystalline quartz grains are subangular to angular, vacuoles abundant, some fractures, no noticeable overgrowth, most quartz grains show evidence of straining, not many inclusions however some strands of sericite are noticeable on some grains along with clay filled fractures, some of the grains were too small to identify (silt sized grains) but many appeared to be quartz; polycrystalline quartz grains were rounded to subangular and appeared elongated in some grains; Some of the plagioclase and K-feldspar grains were heavily weathered and altered to sericite and kaolinite although some grains looked more preserved, 188 identified best through staining and cleavage; several medium sand to pebble sized siltstone rock fragments were identified with clay matrix and iron oxide cement and small silt-sized quartz minerals, some of the larger pebbles were angular in shape indicating a close proximity to the sediment source; two metamorphic rock fragments were identified, one was a meta-sandstone with clay matrix and stretched quartz minerals, other included mica minerals and stretched quartz minerals; two plutonic rock fragments were also identified consisting of feldspar and quartz minerals; mica was common in this thin section especially muscovite and chlorite which was counted 4 times and recorded with biotite; calcareous microfossils were abundantly observed in the field of view; carbonate minerals were common; matrix dominated this thin section and grains were difficult to identify; Dominated with sericite and clay matrix and iron oxide cement; some carbonate cement surrounding grains throughout the thin section but overall not dominated by carbonate cement like other 1500 samples (looks very different from all other 1500B samples; some quartz grains fill in some pore space (but overall size is very small so hard to distinguish between silt sized grains and diagenesis; Some grain boundaries coated with sericite or iron oxide.

367-U1500B-28R-1W (26-28) Very fine and fine sand is the dominant grain size although there were several (8+) very coarse and gravel sized grains of quartz, feldspar, and rock fragments scattered in the thin section (poorly sorted sample); Monocrystalline quartz grains are subangular to subrounded and sometimes angular in shape, some grains are surrounded by oxides, glauconite, and sericite, inclusions include oxides, mica, clay, dense minerals, tourmaline and/or rutile (needle like minerals), some contain evidence of strain and others have straight extinction (most grains so small it is hard to tell), vacuoles very abundant, fractures abundant, a lot of the very coarse sand grains are large monocrystalline or polycrystalline quartz grains; polycrystalline quartz grains are subrounded to subangular and not very abundant; plagioclase and K-feldspar grains are heavily weathered and altered to sericite and kaolinite with inclusions of mica and other unidentifiable clay and dense minerals, identified mostly based on stain color, cleavage, and twinning pattern, often surrounded by glauconite or filled in with quartz minerals after weathering; very few lithic grains were counted including one metamorphic grain of crenulated and strained quartz and five plutonic grains (a few of the very large gravel sized grains were plutonic grains but using Dickinson's method of point counting only the grains landed on were counted) most contain quartz and feldspar minerals; glauconite was extremely abundant and was observed in the field of view more times than it was counted; mica was also common, two chlorite grains were counted and recorded under the biotite category; There were several calcareous microfossils counted and observed especially making up the cement in fragments; one dense mineral was counted but not identified; Dominated with carbonate cement; quartz grains fill in some pore spaces most likely created by diagenesis; some iron oxide inclusions within grains and in matrix and forming a rim around some grains; several clay blobs.

367-U1500B-29R-1W (81-83) Fine sand is the dominant grain size although very fine sand is also very abundant; Monocrystalline quartz grains are subrounded to subangular, abundant vacuoles, some straining although some grains have straight unit extinction rather than undulatory, overgrowth of megaquartz common, most grains have an iron oxide rim around the grain boundary; inclusions include oxides, mica, clay, dense minerals, tourmaline and/or rutile (needle-like minerals), abundant fractures, some grains surrounded by sericite or glauconite; polycrystalline quartz grains were irregular to subangular and not very abundant; plagioclase showed evidence of albitization and both plagioclase and K-feldspar were heavily weathered and altered to kaolinite and sericite, blocky and irregular in shape and best identified by cleavage and stain color; several sandstone rock fragments with iron oxide cement and clay matrix were counted; abundant metamorphic rock fragments counted with a lot of mica and crenulated quartz minerals; plutonic rock fragments commonly with quartz minerals and feldspar minerals; glauconite is extremely abundant in this thin section; mica also very abundant, especially muscovite although it wasn't often counted it was commonly observed in the field of view, biotite was also common along with chlorite which was counted six times and was recorded under the biotite tab; calcareous microfossils were sometimes observed in the matrix and identified as foram fragments; several dense minerals were observed and counted including pyroxene (maybe hornblende - it was green to blue pleochroic in ppl and yellow in xpl with two planes of cleavage) 189 and zircon minerals; Dominated with carbonate cement; small quartz grains fill in some pore spaces most likely created by diagenesis; some iron oxide inclusions within grains and in matrix and forming a rim around some grains; several clay blobs.

367-U1500B-34R-1W (4-6) Medium sand is the dominant grain size although there is a wide range in grain size; Monocrystalline quartz grains are rounded to subrounded in shape, very strained, abundant vacuoles and fractures, most grains have an iron oxide rim around the grain boundaries; inclusions include oxides, mica, clay minerals, dense minerals; polycrystalline quartz grains were irregular to rounded in shape and more abundant than previous samples; plagioclase showed evidence of albitization and both plagioclase and K-feldspar were weathered and altered to kaolinite and sericite, blocky and irregular in shape and best identified by cleavage, twinning and stain color; one sandstone rock fragment was identified with iron oxide cement and clay matrix; two chert rock fragments were identified; several metamorphic rock fragments were identified, mostly with elongated quartz minerals and some oriented mica minerals; plutonic rock fragments of quartz and feldspar minerals were also common; although there were only a few muscovite minerals counted, many more were spotted in the field of view; chlorite was identified twice and recorded under the biotite category; glauconite was very abundant; a few calcareous microfossil fragments were identified within the calcium carbonate matrix; four dense minerals were identified as either hornblende or pyroxene; Dominated with carbonate cement; small quartz grains fill in some pore spaces most likely created by diagenesis; some iron oxide inclusions within grains and in matrix and forming a rim around some grains; some or clay blobs.

367-U1500B-40R-1W (15-17) Fine sand is the dominant grain size although medium sand is also very abundant; Monocrystalline quartz grains are subrounded to subangular, heavily strained, some fractures and vacuoles although not as many as previous samples, often covered in clay or surrounded by glauconite with oxides and clay filling in fractures, not as many inclusions but some inclusions of oxides, mica, dense minerals/clay minerals; polycrystalline quartz grains rounded to subrounded with mica and clay inclusions and vacuoles; plagioclase showed evidence of albitization and both feldspars were weathered and altered to kaolinite and sericite, blocky to irregular in shape, minerals surrounded by glauconite, best identified by stain color and cleavage; several sandstone/siltstone rock fragments were identified (one with small rounded quartz grains with a clay matrix and one with bigger sized subrounded to subangular quartz grains and a clay matrix, and two with iron oxide cement and some clay matrix); one chalcedony rock fragment was identified; several metamorphic rock fragments were identified with elongated quartz minerals and oriented mica minerals; plutonic rock fragments were also common with quartz and feldspar minerals; mica was also very common in this thin section with several muscovite and biotite identified (two chlorite grains were counted and recorded under the biotite category); glauconite was very abundant; calcareous microfossils were identified within the carbonate matrix; Dominated with carbonate cement; small quartz grains fill in some pore spaces most likely created by diagenesis; some iron oxide inclusions within grains and in matrix and forming a rim around some grains; some clay blobs; clay/oxides often infiltrating/covering grains.

367-U1500B-54R-1W (25-27) Fine sand is the dominant grain size although very fine sand and medium sand are also very abundant; Monocrystalline quartz grains are subrounded to subangular, sometimes strained sometimes show straight unit extinction, some fractures and vacuoles although not as many as previous samples, often covered in clay or surrounded by glauconite, some inclusions of oxides, mica, dense minerals, and clay minerals; polycrystalline quartz grains are rounded to subrounded with some mica inclusions and vacuoles; plagioclase and K-feldspar are both very weathered and altered to sericite and kaolinite, blocky to irregular in shape with several inclusions of clay minerals, dense minerals, and mica, best identified using stain color, twinning and cleavage (this thin section has a lot of areas of just epoxy which makes it difficult to tell between extremely weathered plagioclase and epoxy since both can contain stain); one sandstone rock fragment with clay matrix and one chert rock fragment counted; several metamorphic rock fragments identified of mostly elongated strained quartz and oriented mica minerals; several plutonic rock fragments 190 of quartz and feldspar were counted as well as one volcanic rock fragment containing volcanic laths; muscovite and biotite were very abundant in the field of view although only counted a few times (chlorite was very abundant with a total of 6 counts and was recorded under the biotite category); glauconite was very abundant and pretty large (medium sized sand); fragments of calcareous microfossils were identified within the carbonate matrix; Dominated with carbonate cement; small quartz grains fill in some pore spaces most likely created by diagenesis; some iron oxide inclusions within grains and in matrix and forming a rim around some grains; some clay blobs; clay/oxides often infiltrating/covering grains.

367-U1500B-54R-1W (41-43) Fine sand is the dominant grain size although very fine sand and medium sand are also very abundant; Monocrystalline quartz grains are well rounded to subangular (shape dependent on size - some perfectly well rounded grains and some more angular), abundant vacuoles and fractures, some overgrowth in the form of megaquartz and straight quartz, inclusions of blue green minerals (maybe tourmaline), oxides, and needle-like minerals, often covered in clay or surrounded by glauconite, most grains strained but some grains contain unit or straight extinction; Polycrystalline quartz grains subrounded to subangular with inclusions of mica and clay minerals; plagioclase and potassium feldspar grains are both heavily weathered and altered to sericite with quartz grains filling in weathered parts of the grain, blue-green inclusions observed within some of the grains, cleavage filled in with brown clay, blocky to irregular shape; metamorphic rock fragments very abundant in the field of view with muscovite, chlorite and quartz minerals; plutonic rock fragments also very abundant with a variety of minerals such as quartz and feldspar minerals; mica was also very common, muscovite was even more abundant in the field of view then what was counted in the 300 grains, biotite also common as well as chlorite which was counted 7 times and recorded with biotite; glauconite was extremely abundant, similar to the previous samples; calcareous microfossils were observed in the carbonate matrix; Dominated with carbonate cement; small quartz grains fill in some pore spaces most likely created by diagenesis; some iron oxide inclusions within grains and in matrix and forming a rim around some grains; some clay blobs; clay/oxides often infiltrating/covering grains.

367-U1500B-55R-1W (8-10) Fine sand is the dominant grain size although very fine sand and medium sand are also very abundant; Monocrystalline quartz grains are subrounded to subangular, sometimes strained sometimes show straight unit extinction (dependent on size), fractures and vacuoles abundant, iron oxides form a rim around some grains, some include inclusions of oxides and needle-like minerals and blue-green minerals (could be tourmaline and/or rutile), dense minerals; clay minerals and mica minerals, often surrounded by clay, sericite, or glauconite; polycrystalline quartz grains rounded to subrounded with tourmaline and other dense mineral inclusions (overall most quartz grains rounder than previous samples); plagioclase and K-feldspar both heavily altered and weathered to sericite and kaolinite, blocky to irregular in shape; siltstone and sandstone rock fragments contain a clay matrix and iron oxide cement with rounded to angular quartz and feldspar minerals, one rock fragment contained a lot of glauconite in the matrix; one chert rock fragment was identified; several metamorphic rock fragments observed in the field of view and counted with oriented mica minerals and elongated quartz minerals; several plutonic rock fragments were also counted containing quartz and feldspar minerals; mica was very common with five chlorite minerals counted and recorded with biotite and several mica grains observed in the field of view but not counted; glauconite was very abundant which is similar to the previous samples; calcareous microfossils were abundant within the carbonate matrix; Dominated with carbonate cement; small quartz grains fill in some pore spaces most likely created by diagenesis; some iron oxide inclusions within grains and in matrix and forming a rim around some grains; some clay blobs; clay/oxides often infiltrating/covering grains; glauconite also forming a rim around some grains.

367-U1500B-56R-1W (12-14) Fine sand is the dominant grain size although very fine sand and medium sand are also very abundant; Monocrystalline quartz grains are subangular to angular with clay and glauconite surrounding them and infiltrating into fractures, abundant vacuoles and fractures and some inclusions of oxides, mica, and dense 191 minerals although inclusions not abundant; polycrystalline quartz grains are subangular to subrounded with clay infiltrating fractures and mica and dense mineral inclusions, more in the field of view than were counted in point counting; plagioclase and K-feldspar were heavily weathered and altered to sericite and kaolinite and blocky to irregular in shape, sometimes surrounded by glauconite; one sandstone rock fragment counted with clay matrix and oxide cement and subangular quartz minerals; several metamorphic rock fragments counted, several with chlorite and stretched polycrystalline quartz; plutonic rock fragments of feldspar and quartz minerals were also common; mica was also abundant with 5 chlorite grains recorded with biotite; glauconite was very abundant, similar to previous thin sections in this lithologic unit; calcareous microfossils were abundant within the carbonate matrix; Dominated with carbonate cement; small quartz grains fill in some pore spaces most likely created by diagenesis; some iron oxide inclusions within grains and in matrix and forming a rim around some grains; some clay blobs; clay/oxides often infiltrating/covering grains; glauconite also forming a rim around some grains.

367-U1500B-56R-1W (51-53) Fine sand is the dominant grain size although very fine sand and medium sand are also very abundant (similar to the previous samples); Monocrystalline quartz grains are mostly rounded to subrounded in shape with some angular grains, inclusions of clay minerals and dense minerals within some grains but most grains do not contain many inclusions, vacuoles abundant and fractures common, some inclusions of oxides, some grains surrounded by clay, sericite and glauconite; polycrystalline quartz grains are subrounded to subangular with some well-rounded grains, some mica and dense mineral inclusions within poly quartz and also some filled with vacuoles; plagioclase and K-feldspar were weathered and altered to sericite and kaolinite and were blocky to irregular in shape, best identified by stain color, twinning and cleavage; one sandstone rock fragment with glauconite and iron cement and quartz and feldspar minerals; a few metamorphic rock fragments were identified with oriented mica (chlorite) and small quartz minerals; several plutonic rock fragments were identified with muscovite and plagioclase or with quartz and feldspar minerals and one volcanic rock fragment was identified with plagioclase laths (overall not many lithic grains); mica was abundant in the field of view and was counted several times with 6 chlorite grains counted and recorded with biotite; glauconite was extremely abundant; some calcareous microfossils were identified within the carbonate matrix along with some carbonate minerals; Dominated with carbonate cement; small quartz grains fill in some pore spaces most likely created by diagenesis; some iron oxide inclusions within grains and in matrix and forming a rim around some grains; some clay blobs; clay/oxides often infiltrating/covering grains and filling in fractures; glauconite also forming a rim around some grains.

367-U1500B-56R-1W (107-109) Fine sand is the dominant grain size although very fine sand and medium sand are also very abundant (similar to the previous samples); Monocrystalline quartz grains are subangular to subrounded in shape, inclusions of dense minerals, clay minerals, mica and oxides, vacuoles abundant, some fractures, straining abundant, some overgrowth of mega quartz/polycrystalline quartz minerals, surrounded by mica/sericite and glauconite; Polycrystalline quartz grains are round in shape with abundant vacuoles; plagioclase and K- feldspar both heavily weathered and altered to sericite and kaolinite, filled in with quartz where weathered away and cleavage filled in with clay, surrounded by clay and glauconite; one sandstone rock fragment with iron oxide and quartz cement and quartz minerals; several metamorphic rock fragments were identified with chlorite and elongated quartz and oriented mica minerals; several plutonic rock fragments were also identified with quartz and feldspar minerals; mica was abundant in the field of view and was counted several times with four counted chlorite minerals recorded under biotite; glauconite was very abundant (similar to previous samples); calcareous microfossils were identified within the carbonate matrix along with carbonate minerals; some mud blobs counted as matrix; Dominated with carbonate cement; small quartz grains fill in some pore spaces most likely created by diagenesis; some iron oxide inclusions within grains and in matrix and forming a rim around some grains; some clay blobs; clay/oxides often infiltrating/covering grains and filling in fractures; glauconite also forming a rim around some grains.

192

Appendix E. Calculated parameters for each sample at Site U1499. See Table 4 in Chapter 3 for definition of parameter abbreviations.

Core, section, Depth QFL QFL QFL LmLvLs LmLvLs LmLvLs QmKP QmKP QmKP LSU %M Qp/Q P/F Lp/Lvt % Glau interval (cm) (mbsf) %Q %F %L %Lm %Lvt %Lst %Qm %K %P

U1499A-4H-6W 35.04 I 59.3 38.3 2.3 0.0 100.0 0.0 59.1 14.9 26.0 0.3 0.1 0.6 1.0 0.0 104-106

U1499A-4H-7W 36.15 I 75.0 18.0 7.0 18.8 12.5 68.8 79.6 6.0 14.4 0.0 0.1 0.7 1.0 0.0 65-67

U1499A-5H-5W 42.49 I 72.7 22.5 4.8 33.3 33.3 33.3 74.2 9.2 16.6 0.3 0.1 0.6 1.0 0.0 49-51

U1499A-5H-6W 44.72 I 66.9 26.1 7.0 55.0 35.0 10.0 71.2 8.8 20.0 0.3 0.0 0.7 1.0 0.0 122-124 B8T-004

U1499A-5H-6W 44.72 I 72.1 23.3 4.5 38.5 46.2 15.4 74.3 5.0 20.7 1.3 0.1 0.8 1.0 0.6 122-124 B8T-005

U1499A-5H-7W 45.56 I 52.3 44.9 2.8 25.0 75.0 0.0 51.9 7.6 40.5 1.9 0.1 0.8 1.0 0.0 56-58 (125)

U1499A-6H-1W 45.78 I 55.0 40.7 4.3 46.2 38.5 15.4 55.6 6.5 37.8 1.9 0.1 0.9 0.8 0.0 8-10

U1499A-6H-2W 47.82 I 56.8 39.6 3.6 36.4 54.5 9.1 56.7 10.1 33.2 1.9 0.1 0.8 1.0 0.0 82-84

193

Core, section, Depth QFL QFL QFL LmLvLs LmLvLs LmLvLs QmKP QmKP QmKP LSU %M Qp/Q P/F Lp/Lvt % Glau interval (cm) (mbsf) %Q %F %L %Lm %Lvt %Lst %Qm %K %P

U1499A-8H-4W 70.37 II 67.8 29.6 2.6 25.0 37.5 37.5 67.9 2.8 29.3 0.3 0.1 0.9 1.0 0.3 137-139 B8T-009

U1499A-8H-4W 70.37 II 61.0 32.5 6.4 21.1 73.7 5.3 63.8 2.6 33.6 0.3 0.1 0.9 1.0 0.3 137-139 B8T-010

U1499A-29X-1W 259.93 IIIB 51.2 44.8 4.0 33.3 50.0 16.7 50.2 10.1 39.7 1.3 0.1 0.8 1.0 1.6 53-55 (125)

U1499A-29X-1W 259.93 IIIB 43.7 52.0 4.3 15.4 76.9 7.7 44.5 17.8 37.7 0.3 0.0 0.7 1.0 1.3 53-55 (250)

U1499A-29X-1W 260.15 IIIB 52.7 43.6 3.7 18.2 45.5 36.4 53.3 10.1 36.6 1.3 0.1 0.8 1.0 1.6 75-77

U1499A-39X-CCW 357.48 IV 66.2 27.0 6.8 30.0 40.0 30.0 69.8 5.0 25.2 1.0 0.1 0.8 1.0 0.0 39-41

U1499A-54X-CCW 502.05 VI 65.4 29.1 5.5 37.5 31.3 31.3 67.6 8.9 23.6 0.0 0.1 0.7 1.0 0.0 15-17

U1499A-56X-CCW 521.49 VI 62.1 35.2 2.7 12.5 25.0 62.5 62.5 8.7 28.7 0.6 0.1 0.8 1.0 1.6 19-21

U1499A-57X-CC 532.05 VI 27.5 35.0 37.5 0.0 6.7 93.3 44.0 20.0 36.0 47.0 0.0 0.6 1.0 0.0 31-33

U1499A-67X-1W 629.19 VII 60.1 36.3 3.6 36.4 36.4 27.3 60.1 23.2 16.7 0.6 0.1 0.4 1.0 1.6 119-121

U1499A-69X-CC 648.46 VII 41.8 51.9 6.4 15.8 42.1 42.1 43.0 13.3 43.7 0.3 0.1 0.8 1.0 0.6 36-38

U1499B-3R-3W 668.08 VII 48.5 42.3 9.3 37.0 51.9 11.1 48.5 14.2 37.2 5.4 0.2 0.7 0.9 0.0 59-61

194

Core, section, Depth QFL QFL QFL LmLvLs LmLvLs LmLvLs QmKP QmKP QmKP LSU %M Qp/Q P/F Lp/Lvt % Glau interval (cm) (mbsf) %Q %F %L %Lm %Lvt %Lst %Qm %K %P

U1499B-4R-CCW 674.45 VII 55.9 40.9 3.2 44.4 22.2 33.3 55.3 14.4 30.4 2.9 0.1 0.7 1.0 1.6 5-7

U1499B-9R-1W 723.64 VII 41.0 51.5 7.5 45.0 40.0 15.0 38.1 6.7 55.2 8.9 0.2 0.9 1.0 0.0 74-77

U1499B-9R-1W 723.97 VII 51.2 39.9 9.0 48.1 33.3 18.5 51.4 15.4 33.2 2.2 0.2 0.7 1.0 0.0 107-109 B8T-021

U1499B-9R-1W 723.97 VII 47.8 41.2 11.0 34.4 43.8 21.9 46.7 10.2 43.1 5.4 0.2 0.8 1.0 0.0 107-109 B8T-022

U1499B-10R-3W 734.78 VII 26.1 73.9 0.0 0.0 0.0 0.0 19.0 9.5 71.4 49.3 0.3 0.9 0.0 0.0 11-13

U1499B-12R-1W 752.34 VII 33.0 32.2 34.8 12.5 11.3 76.3 46.4 23.2 30.4 7.4 0.2 0.6 0.9 0.0 34-36

U1499B-30R-2W 929.03 IXA 9.1 85.6 5.3 28.6 14.3 57.1 9.6 15.2 75.2 1.6 0.0 0.8 0.0 3.0 104-107

U1499B-30R-2W 929.27 IXA 10.8 88.5 0.7 100.0 0.0 0.0 10.3 14.4 75.3 3.0 0.1 0.8 0.0 2.0 128-132

U1499B-30R-3W 929.31 IXA 24.5 72.2 3.2 0.0 28.6 71.4 25.0 14.9 60.1 2.0 0.0 0.8 1.0 0.3 0-5

U1499B-30R-3W 929.69 IXA 14.8 81.3 3.9 16.7 66.7 16.7 14.9 23.0 62.2 2.3 0.0 0.7 0.3 0.7 38-43

U1499B-30R-4W 931.18 IXA 32.2 62.4 5.5 57.1 7.1 35.7 31.5 6.0 62.5 8.6 0.1 0.9 1.0 0.0 77-82

U1499B-30R-5W 931.93 IXA 14.4 74.8 10.9 13.6 59.1 27.3 15.6 12.8 71.5 4.3 0.0 0.8 0.3 0.0 23-29

195

Core, section, Depth QFL QFL QFL LmLvLs LmLvLs LmLvLs QmKP QmKP QmKP LSU %M Qp/Q P/F Lp/Lvt % Glau interval (cm) (mbsf) %Q %F %L %Lm %Lvt %Lst %Qm %K %P

U1499B-30R-5W 932.61 IXA 22.9 71.6 5.5 40.0 46.7 13.3 21.2 6.8 72.0 6.6 0.2 0.9 0.6 0.0 91-96

U1499B-32R-1W 946.03 IXC 19.1 71.5 9.4 25.0 60.7 14.3 16.8 10.2 73.0 1.0 0.2 0.9 0.4 0.0 3-5

U1499B-32R-1W 946.58 IXC 17.1 69.7 13.1 18.2 39.4 42.4 12.1 14.6 73.4 2.3 0.4 0.8 1.0 0.0 58-62

U1499B-32R-1W 946.88 IXC 16.2 79.7 4.1 0.0 16.7 83.3 8.9 32.0 59.1 2.3 0.5 0.6 1.0 0.0 88-91

U1499B-33R-1W 955.89 IXC 14.2 74.0 11.8 20.6 32.4 47.1 8.9 13.2 77.9 1.0 0.5 0.9 0.3 0.0 19-27

U1499B-33R-2W 956.92 IXC 15.2 74.7 10.0 10.3 58.6 31.0 12.6 20.2 67.2 2.6 0.3 0.8 0.7 0.0 7-12

U1499B-33R-2W 957.12 IXC 30.8 56.3 12.9 7.7 53.8 38.5 23.1 8.6 68.3 0.0 0.5 0.9 0.6 0.0 27-33

U1499B-34R-1W 965.4 IXC 20.0 65.3 14.7 4.5 40.9 54.5 17.6 16.4 66.0 1.0 0.3 0.8 0.3 0.0 0-6

U1499B-34R-1W 965.9 IXC 10.9 85.1 4.0 8.3 41.7 50.0 9.2 20.5 70.3 0.3 0.2 0.8 0.8 0.0 50-55

U1499B-34R-1W 966.27 IXC 18.6 77.4 4.0 8.3 25.0 66.7 13.1 9.7 77.2 0.7 0.4 0.9 1.0 0.0 87-91

U1499B-34R-2W 966.93 IXC 18.9 69.4 11.8 11.4 60.0 28.6 16.9 18.5 64.5 0.7 0.3 0.8 0.3 0.0 11-17

U1499B-36R-1W 985.31 IXC 17.5 77.1 5.5 12.5 75.0 12.5 14.1 27.5 58.4 0.7 0.3 0.7 0.1 0.0 51-55

196

Core, section, Depth QFL QFL QFL LmLvLs LmLvLs LmLvLs QmKP QmKP QmKP LSU %M Qp/Q P/F Lp/Lvt % Glau interval (cm) (mbsf) %Q %F %L %Lm %Lvt %Lst %Qm %K %P

U1499B-36R-1W 985.69 IXC 14.0 77.3 8.7 15.4 57.7 26.9 11.5 24.8 63.7 0.3 0.3 0.7 0.0 0.0 89-93

U1499B-36R-1W 985.8 IXC 18.6 79.7 1.7 40.0 40.0 20.0 16.0 34.2 49.8 1.6 0.2 0.6 0.5 0.0 100-104

U1499B-37R-1W 995.55 IXC 15.4 82.8 1.8 60.0 40.0 0.0 13.9 25.9 60.2 3.9 0.1 0.7 1.0 0.0 105-112

U1499B-39R-1W 1014.2 IXC 16.7 62.9 20.4 23.0 59.0 18.0 12.6 26.5 60.9 0.7 0.5 0.7 0.1 0.0 30-35

U1499B-40R-1W 1024 IXC 22.5 70.2 7.3 42.9 42.9 14.3 18.8 18.0 63.2 1.6 0.3 0.8 0.1 0.0 43-47

197

Appendix F. Calculated parameters for each sample at Site U1500. See Table 4 in Chapter 3 for definition of parameter abbreviations.

Core, section, Depth QFL QFL QFL LmL vLs LmLvLs LmLvLs QmKP QmKP QmKP LSU %M Qp/Q P/F Lp/Lvt % Glau interval (cm) (mbsf) %Q %F %L %Lm %Lvt %Lst %Qm %K %P

U1500A-20R-CCW 689.78 III 52.6 38.4 8.9 14.8 25.9 59.3 53.8 14.3 31.9 1.6 0.2 0.7 1.0 0.3 8-10

U1500A-25R-6W 745.12 III 49.8 47.7 2.5 71.4 14.3 14.3 48.9 11.7 39.4 7.0 0.1 0.8 1.0 1.6 26-28

U1500A-29R-1W 777.05 III 63.1 30.2 6.7 17.6 5.9 76.5 66.4 18.6 15.0 4.6 0.1 0.4 1.0 4.9 5-7

U1500A-29R-1W 777.73 III 60.8 37.1 2.1 60.0 0.0 40.0 61.1 13.7 25.2 9.0 0.0 0.6 0.0 4.5 73-75

U1500A-32R-1W 806.25 III 49.1 44.0 6.9 21.1 0.0 78.9 50.6 20.8 28.6 5.5 0.1 0.6 0.0 1.9 15-17

U1500A-34R-1W 825.55 III 45.7 52.3 1.9 20.0 80.0 0.0 44.7 11.9 43.4 4.9 0.1 0.8 1.0 0.0 5-7

198

Core, section, Depth QFL QFL QFL LmL vLs LmLvLs LmLvLs QmKP QmKP QmKP LSU %M Qp/Q P/F Lp/Lvt % Glau interval (cm) (mbsf) %Q %F %L %Lm %Lvt %Lst %Qm %K %P

U1500B-7R-1W 895 IV 49.1 45.0 5.9 18.8 12.5 68.8 48.5 26.6 24.9 3.6 0.1 0.5 0.5 4.2 119-121

U1500B-8R-1W 904.44 IV 54.2 41.1 4.7 38.5 7.7 53.8 53.5 24.7 21.8 5.5 0.1 0.5 1.0 2.6 94-98

U1500B-23R-1W 1049.6 IV 44.5 52.7 2.8 25.0 25.0 50.0 42.0 14.0 44.0 5.5 0.1 0.8 1.0 0.0 58-60

U1500B-28R-1W 1097.8 IV 50.4 47.5 2.2 16.7 83.3 0.0 49.0 15.1 35.9 2.9 0.1 0.7 1.0 5.4 26-28

U1500B-29R-1W 1108 IV 50.9 42.5 6.5 50.0 27.8 22.2 52.6 14.2 33.2 4.8 0.1 0.7 1.0 6.3 81-83

U1500B-34R-1W 1155.7 IV 55.8 35.4 8.8 52.0 36.0 12.0 55.9 20.1 24.0 1.9 0.2 0.5 1.0 5.1 4-6

U1500B-40R-1W 1214.1 IV 47.6 45.1 7.3 40.0 35.0 25.0 46.8 19.0 34.2 3.6 0.2 0.6 1.0 5.2 15-17

U1500B-54R-1W 1350 VI 57.0 37.1 5.9 50.0 31.3 18.8 56.8 14.5 28.6 3.5 0.1 0.7 0.8 7.7 25-27

U1500B-54R-1W 1350.1 VI 59.1 33.8 7.1 47.4 52.6 0.0 60.6 10.0 29.4 5.1 0.1 0.7 1.0 7.7 41-43

199

Core, section, Depth QFL QFL QFL LmL vLs LmLvLs LmLvLs QmKP QmKP QmKP LSU %M Qp/Q P/F Lp/Lvt % Glau interval (cm) (mbsf) %Q %F %L %Lm %Lvt %Lst %Qm %K %P

U1500B-55R-1W 1359.5 VI 50.9 43.6 5.5 26.7 40.0 33.3 51.4 19.0 29.6 2.6 0.1 0.6 1.0 7.4 8-10

U1500B-56R-1W 1369.2 VI 56.7 37.5 5.8 50.0 43.8 6.3 56.5 14.2 29.3 3.5 0.1 0.7 1.0 4.8 12-14

U1500B-56R-1W 1369.6 VI 56.2 40.5 3.3 22.2 66.7 11.1 54.9 16.3 28.9 3.2 0.1 0.6 0.8 6.7 51-53

U1500B-56R-1W 1370.2 VI 48.4 46.9 4.7 53.8 38.5 7.7 44.4 16.2 39.3 3.2 0.2 0.7 1.0 5.5 107-109

200