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Change in the bottom water composition and lithological sediment provenance of the Bering Sea during the Pleistocene : Insights from neodymium isotopes and NGR-based K, Th and U concentrations : 네오디뮴 동위원소 및 NGR 기반 K, Th, U 농도를 이용한 플라이스토세 기간 베링해 중층수/심층수 조성 및 퇴적물 기원지 변화 추적 연구

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dc.contributor.advisor허영숙-
dc.contributor.author장광철-
dc.date.accessioned2017-10-27T17:14:05Z-
dc.date.available2017-10-27T17:14:05Z-
dc.date.issued2017-08-
dc.identifier.other000000145599-
dc.identifier.urihttps://hdl.handle.net/10371/137168-
dc.description학위논문 (박사)-- 서울대학교 대학원 자연과학대학 지구환경과학부, 2017. 8. 허영숙.-
dc.description.abstractThe Bering Sea is an important location to understand global climate system because of its high sensitivity to advance/retreat of sea ice and continental ice sheet. Enhanced sea ice formation may induce the formation of the North Pacific Intermediate/Deep Water (NPIW/NPDW) in the Bering Sea, and the development of continental ice sheet in Alaska can potentially determine the provenance of the Bering Sea sediments. To examine the relationships between NPIW/NPDW formation, lithological sediment provenance and ice dynamics responding to glacial/interglacial cycles, here I present authigenic and detrital neodymium (Nd) isotopes and NGR-based K, Th and U concentration of marine sediments in the Bering Sea obtained during the Integrated Ocean Drilling Program (IODP) Expedition 323. Authigenic Nd isotopes is a quasi-conservative water mass tracer, and detrital Nd isotopes and NGR-based K, Th and U concentrations can be used as indicators of lithological sediment provenance. To acquire reliable authigenic Nd isotopes without contamination from labile volcanic components in sediments, Nd isotopes and elemental concentrations of six different authigenic fractions are compared each other.
Reconstructed authigenic Nd isotopes (ɛNd,AUTH) at site U1345 on the Bering Slope over ~520 kyr showed average value of -3.3 ± 0.9 (1σ, n = 98) with large temporal fluctuations, which can be interpreted either as episodic occurrences of the NPIW formation or boundary exchange between seawater and sediments. Likewise, ɛNd,AUTH records at site U1343 over ~2.4 Myr showed average value of -3.0 ± 1.1 (1σ, n = 155) with large temporal variation. Only one NPDW formation is attributed to this variation, and boundary exchange between seawater and sediments is the most likely reason for ɛNd,AUTH variation. The detrital Nd isotopes (ɛNd,DET) at site U1343 showed average of -6.6 ± 1.5 (1σ, n = 70) with temporal variation, indicating change in lithological sediment provenance. Overall, Alaska is a dominant source over the Aleutian Arc at site U1343, and outstanding unradiogenic ɛNd,DET peaks can result from meltwater discharge from Alaska. Considering the repetitive occurrence of unradiogenic ɛNd,DET peaks after 2.4 Ma, extensive glaciation have probably developed in Alaska since at least 2.4 Myr ago. Spatial and temporal variation in terrigenous sediment provenance of the Bering Sea sediment are partly shown in NGR-based K/Th, K/U and Th/U ratios at sites U1341 and U1342 on the Bowers Ridge and sites U1343 and U1345 on the Bering Slope. The Bowers Ridge sediments showed distinct K/Th, K/U and Th/U ratios from the Bering Slope sediments. However, heavy mineral sorting and/or change in paleo-oceanic redox conditions can disturb primary signals from parent rocks, and therefore K/Th, K/U and Th/U ratios are only used as a preliminary result to trace lithological sediment provenance in the Bering Sea.		-
dc.description.tableofcontentsChapter 1. Introduction 1
References 6
Chapter 2. The chemical treatment method for authigenic Nd isotopes to acquire reliable seawater signal 12
2.1. Introduction 12
2.2. Neodymium isotopes 12
2.3. Methods 15
2.3.1. Separation of authigenic and detrital fractions 15
2.3.1.1. Authigenic Fe-Mn oxyhydroxide fraction 15
2.3.1.2. Carbonate fraction and second authigenic fraction 17
2.3.1.3. Detrital fraction 18
2.3.2. Purification and instrumental analysis 18
2.3.2.1. Elemental concentrations of the different fractions 18
2.3.2.2. Column separation 19
2.3.2.3. Nd isotope composition 19
2.3.3. The Nd comparison between Wilson Authigenic and Rutberg Authigenic 19
2.4. Results and discussion: the most suitable extraction method 20
2.4.1. Nd and elemental composition results at site U1345 20
2.4.2. Nd results at site U1343 22
2.4.3. Leaching protocol for Bering Sea sediments 23
References 26
Chapter 3. Authigenic Nd isotope record of North Pacific Intermediate Water formation and boundary exchange on the Bering Slope 39
Abstract 39
3.1. Introduction 40
3.2. Materials 45
3.2.1. Sampling location 45
3.2.2. Core description 45
3.3. Method 47
3.4. Results and Discussion 47
3.4.1. Temporal variation of εNd over 520 kyr 47
3.4.1.1. Authigenic εNd record 47
3.4.1.2. Detrital εNd record 48
3.4.2. Mechanisms for authigenic εNd variation on the Bering Slope 49
3.4.3. NPIW formation 53
3.4.3.1. Periods of radiogenic Nd input 55
3.4.3.2. Periods of unradiogenic Nd input 58
3.4.4. Relationship between NPIW and NADW 60
3.5. Conclusion 62
Acknowledgements 63
References 64
Chapter 4. Early-Pleistocene glaciation of Alaska and its influence on deep-water Nd isotopic composition in the Bering Sea across the mid-Pleistocene transition 83
Abstract 83
4.1. Introduction 84
4.2. Materials 87
4.2.1. Site information 87
4.2.2. Core description 88
4.3. Method 88
4.3.1. Authigenic and detrital Nd isotopes 88
4.3.2. Spectral analysis on authigenic Nd 89
4.4. Results and discussion 89
4.4.1. The seawater-derived Nd isotopes 89
4.4.2. The possibility of NPDW formation 91
4.4.3. Sediment-water interaction controlling εNd in the Bering Sea 94
4.4.4. Sediment binary mixing system between Alaska and the Aleutian Arc 98
4.4.5. Cross spectrum analysis across the MPT 100
4.5. Conclusion 102
References 104
Chapter 5. K, Th and U concentrations derived from shipboard natural gamma radiation spectra of Bering Sea sediments and their utility as tracers of lithological sediment provenance and paleo-oceanic redox conditions 122
Abstract 122
5.1. Introduction 124
5.2. Background information 129
5.2.1. Sampling sites 129
5.2.2. Quantification of K, Th and U contents from NGR spectra 131
5.2.3. K, Th and U concentrations of the Aleutian Arc and Alaska 131
5.3. Results 132
5.3.1. Bering Sea sediment cores 132
5.3.2. The Aleutian Arc and Alaska bed rocks 133
5.4. Discussions 135
5.4.1. Simple sediment mixing model 135
5.4.2. Lithological provenance tracer 137
5.4.3. Paleo-oceanic redox tracer 141
5.5. Summary 143
References 145
Chapter 6. Conclusion 165
Appendix: Publication list 167
A1. Journal Articles 167
A1.1. International Journals 167
A1.2. Domestic Journals (Korean) 167
A2. Conference Abstracts 168
A2.1. International Conferences 168
A2.2. Domestic Conferences 169
국문초록 170		-
dc.formatapplication/pdf-
dc.format.extent5573477 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectBering Sea-
dc.subjectNeodymium Isotopes-
dc.subjectNorth Pacific Intermediate Water formation-
dc.subjectBoundary exchange-
dc.subjectNGR counts-
dc.subjectIODP Expedition-
dc.subject.ddc550-
dc.titleChange in the bottom water composition and lithological sediment provenance of the Bering Sea during the Pleistocene : Insights from neodymium isotopes and NGR-based K, Th and U concentrations-
dc.title.alternative네오디뮴 동위원소 및 NGR 기반 K, Th, U 농도를 이용한 플라이스토세 기간 베링해 중층수/심층수 조성 및 퇴적물 기원지 변화 추적 연구-
dc.typeThesis-
dc.contributor.AlternativeAuthorKwangchul Jang-
dc.description.degreeDoctor-
dc.contributor.affiliation자연과학대학 지구환경과학부-
dc.date.awarded2017-08-
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