WESTERN PACIFIC PALEOCEANOGRAPHY ACROSS THE EARLY–MIDDLE PLEISTOCENE BOUNDARY (~773 KA, MARINE ISOTOPE STAGE 19): DINOFLAGELLATE CYSTS OF THE CHIBA COMPOSITE SECTION, JAPAN Eseroghene Jedidiah Balota Department of Earth Sciences A thesis submitted in partial fulfilment of the requirements for the degree of M.Sc. in Earth Sciences Faculty of Mathematics and Science, Brock University St. Catharines, Ontario ©2018 DEDICATION This thesis is dedicated to God almighty, my fiancée, Ife, my parents and siblings. i ABSTRACT The Chiba composite section, central Boso Peninsular, Japan, is a candidate Global Boundary Stratotype Section and Point for the Early–Middle Pleistocene Subseries boundary. This well-exposed, continuous and expanded marine silty sedimentary succession has a detailed paleomagnetic record and an ultra-high-resolution oxygen isotope stratigraphy supported by U-Pb zircon dating of the Byk-E tephra bed which occurs ~1 m below the Matuyama– Brunhes boundary. A detailed dinoflagellate cyst (dinocyst) study from late Marine Isotope Stage (MIS) 20 to late MIS 19 provides information on paleoceanographic changes in the Western Pacific Ocean between 791 and 770 ka. During Termination IX, a decrease in heterotrophic species (e.g. Brigantidinium spp., Selenopemphix nephroides) and corresponding increase in warm-water autotrophs (e.g. Spiniferites hyperacanthus/mirabilis, Spiniferites sp. 2) indicate a progressive decline in productivity corresponding to deglaciation and a transition from cold nutrient-rich waters of MIS 20 to warm conditions in MIS 19. This gradual warming is interrupted by a sudden but brief cooling at 790 ka which is also reflected in the MAT-based dinocyst sea-surface temperature (SST) for February and August. The dinocyst record shows a gradational response to the onset of MIS 19c. Abundant warm-water autotrophic dinocysts during MIS 19c reflects warm conditions and a northward shift of the warm Kuroshio current from 786 to 773 ka. The end of MIS 19c is marked by a sharp decrease in species richness and evenness, an abrupt and sustained rise to dominance of Protoceratium reticulatum, and a corresponding increase in dinocyst concentrations, indicating an increase in productivity and presaging the onset of the MIS 18 glaciation. Pollen and spore concentrations show a strong terrestrial influence during MIS 19. During the peak of MIS 19, Tsuga has low abundance while angiosperm pollen (deciduous broadleaved trees) increase significantly, which is similar to vegetation presently dominant in the northeastern part of the Japanese archipelago. ii ACKNOWLEDGEMENTS Many thanks to God almighty who enabled me to start and complete this work. I am immensely grateful to Prof. Martin J. Head, my supervisor, for guiding me through this work. He introduced me to this research on the Chiba section and provided all the resources for its successful completion. I really appreciate his mentorship and relentless sharing of knowledge with me. I thank Prof. Makoto Okada for his great support and for providing all the samples analysed in this research. I appreciate the efforts of the Chiba research members for their ongoing work on the Chiba section, which gave me great insight and knowledge in writing this thesis. I thank Prof. Francine McCarthy and Prof. Rick Cheel for their kind support and for providing more insight to this thesis. I appreciate my wonderful colleagues, Mukudzei Dube, Saif Silwadi and Walid Abomriga, who were also very helpful in sharing their knowledge with me on dinoflagellate cysts. I gratefully acknowledge research funding from a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant to Prof. Martin J. Head, Brock University graduate funding, and the Dean of Graduate Studies Spring 2016 Research Scholarship from the Faculty of Graduate Studies, Brock University. Words alone cannot express my appreciation for my fiancée, Ifelayo, for her unconditional love for me. She was always beside me throughout this research offering words of encouragement and motivation. I am indebted to my wonderful parents for their huge support, prayers, words of advice and frequent calls. I also thank my siblings; Evwophia, Egaverere and Eguolo for their support, Emma Totor for his financial support, Pastor Ifeanyi and Obiageli Uzoka for their material and financial support, and all DLCM members in Canada for helping me in one way or another during my MSc program. I thank you all. iii TABLE OF CONTENT CHAPTER ONE 1.1 Introduction……………………………………………………………………………1 1.2 Purpose of study…………………………………………………………………….....3 CHAPTER TWO 2.0 THE STUDY LOCATION……………………………………………………………5 2.1 The Chiba composite section……………………………………………………….....5 2.1.1 The Chiba section……………………………………………………………...6 2.2 Modern oceanographic setting of the Western Pacific Ocean and climate of the Japanese archipelago…………………………………………………………………..6 CHAPTER THREE 3.0 LITERATURE REVIEW…………………………………………………………….10 3.1 Kanto Tectonic Basin………………………………………………………………...10 3.2 Kazusa Group and Kokumoto Formation……………………………………………11 3.3 Sedimentary processes of the Chiba section…………………………………………15 3.4 Depositional environment of the Chiba composite section…………………………..18 3.5 Matuyama–Brunhes polarity boundary………………………………………………18 3.6 Oxygen isotope stratigraphy………………………………………………………….19 3.7 Ontake–Byakubi (Byk-E) Tephra bed………………………………………………..20 3.8 Biostratigraphy of the Chiba composite section……………………………………...21 3.9 Paleoenvironmental reconstructions of the Chiba composite section………………..21 3.10 Application of dinoflagellate cysts in paleoceanography…………………………….24 CHAPTER FOUR 4.0 MATERIALS AND METHODS…………………………………………………….26 4.1 Age model for the Chiba composite section…………………………………………26 4.2 Sample selection……………………………………………………………………...29 4.3 Palynological processing and analysis……………………………………………….32 4.4 Taxonomy and nomenclature………………………………………………………...34 4.5 Statistical analysis……………………………………………………………………34 4.5.1 Modern analogue technique………………………………………………….34 iv 4.5.2 Constrained cluster analysis………………………………………………….38 4.5.3 Species richness………………………………………………………………39 4.5.4 Species evenness……………………………………………………………..39 CHAPTER FIVE 5.0 RESULTS…………………………………………………………………………….41 5.1 Dinoflagellate cyst assemblages……………………………………………………...41 5.1.1 Dinoflagellate cyst concentrations…………………………………………...43 5.1.2 Heterotrophic dinoflagellate cysts……………………………………………43 5.1.3 Autotrophic dinoflagellate cysts……………………………………………...44 5.2 Other palynomorphs………………………………………………………………….48 5.2.1 Terrestrial palynomorphs…………………………………………………….48 5.2.2 Acritarchs and foraminiferal linings…………………………………………50 5.2.3 Reworked dinocysts………………………………………………………….51 5.3 Statistical analysis……………………………………………………………………51 5.3.1 SST and SSS reconstruction using Modern Analogue Technique (MAT)…..51 5.3.2 Species richness and evenness……………………………………………….55 5.3.3 Cluster analysis and dinocyst assemblage biozonation………………………56 CHAPTER SIX 6.0 DISCUSSION………………………………………………………………………..62 6.1 Paleoceanographic and paleoclimatic history of the Chiba section………………….62 6.2 Taphonomy…………………………………………………………………………...69 6.3 Lead-lag relationships and duration of full interglacial conditions in the Chiba section………………………………………………………………………………………...73 6.4 Northern Hemisphere climatic drivers and teleconnections during MIS 19…………75 6.5 Hypothetical timing for the next glacial inception of the present interglacial……….78 Conclusions…………………………………………………………………………………..81 References……………………………………………………………………………………83 Appendix 1: Descriptions of selected dinocysts and acritarch taxa………………………..99 Appendix 2: Plates………………………………………………………………………..111 v Appendix 3: 3.1 Palynological processing……………………………………………110 3.2 Palynological analysis and data collection………………………….112 Appendix 4: Raw counts of palynomorphs……………………………………………….114 LIST OF FIGURES Fig. 1: Location and geographic setting of the Chiba composite section, central Boso Peninsula, Japan………………………………………………………………...8 Fig. 2: Sedimentary succession across the Early–Middle Pleistocene boundary in the Chiba section……………………………………………………………………9 Fig. 3: Schematic map of the Kanto tectonic basin. Inset map shows the location of the study area……………………………………………………………………11 Fig. 4: Simplified geologic map of the Boso Peninsula……………………………...13 Fig. 5: Lithostratigraphic profile of the Kazusa Group showing all formations……..15 Fig. 6: Detailed stratigraphic log and grain-sizes of silty beds in the Chiba section...............................................................................................................17 Fig. 7: The Kokumoto Formation showing magnetostratigraphy with the position of the M–B polarity boundary...……………………………………………...20 Fig. 8: Age model based on the high-resolution δ18O stratigraphy from the Chiba composite section…………………………………………………………….28 Fig. 9: Part of the Chiba composite section, comprising the Yoro River section and the Yoro–Tabuchi section ..………………………………………………….30 Fig. 10: Detailed stratigraphic correlations of the Chiba composite section between the Yanagawa, Yoro River, Yoro-Tabuchi, and Kokusabata sections…………...31 Fig. 11: Sedimentation rates for the study interval in the Chiba composite section…..32 Fig. 12: Northern Hemisphere data set of modern dinoflagellate cyst assemblages….38 Fig. 13: Stratigraphic distribution and relative abundances of all important dinocyst taxa recorded from the Chiba composite section plotted against depth……...42 Fig. 14: Relative abundances of the main dinoflagellate cyst taxa and dinoflagellate cyst concentrations, including