Compound-Specific Isotope Records of Dust Provenance and Hydroclimate in the North Pacific and Marginal Seas of East Asia: Integrating n-Alkane δ13C and δD with Standardized Analytical Frameworks

Author

Julian W. Traphagan, Louisiana State University and Agricultural and Mechanical CollegeFollow

Degree

Doctor of Philosophy (PhD)

Department

Geology and Geophysics

Document Type

Dissertation

Abstract

This dissertation presents advancements in compound-specific isotope analysis (CSIA) through methodological innovation and paleoclimate reconstruction in Central and East Asia. Utilizing plant wax n-alkanes from International Ocean Discovery Program (IODP) and Ocean Drilling Program (ODP) sediment cores, this research reconstructs atmospheric circulation shifts responding to tectonic evolution and climate transitions since the Late Miocene.

Chapter 1 investigates hydrogen isotope compositions (δD_wax) from IODP U1430 (Sea of Japan), ODP 886, and ODP 1208 (North Pacific) to trace dust provenance and hydroclimate changes since ~13 Ma. Results reveal persistently segmented source-to-sink systems: the Sea of Japan dominated by westerly input from northern Tibetan Plateau, Gobi Desert, and Eastern China, while the North Pacific integrates broader Asian interior material. Three phases emerge: Late Miocene deuterium depletion (13–6.2 Ma), Mio-Pliocene transition with increased δD_wax (6.2–3.8 Ma), and Plio-Pleistocene decline corresponding to Northern Hemisphere glaciation.

Chapter 2 combines carbon isotope analysis (δ¹³C_wax) with published Sr-Nd provenance tracers to identify atmospheric organic matter sources. The δ¹³C_wax values show consistent shifts toward more negative values, demonstrating increasing C3-dominated arid interior contributions from the Gobi Desert, Hexi Corridor, Taklimakan Desert, and Qaidam Basin. Arid interior C3 signatures dominated despite localized C4 expansion in humid lowlands, reflecting atmospheric circulation reorganization during global cooling.

Chapter 3 introduces Chroma, a MATLAB package streamlining gas chromatograph flame ionization detector analysis for hydrocarbon indices (CPI, ACL, P_aq). The tool enables automated peak identification and integration, reducing subjectivity and enhancing reproducibility, demonstrated through Qaidam Basin n-alkane data.

Chapter 4 presents SINC (Standardized Isotope Normalization for CSIA), a MATLAB toolkit for GC-IRMS data processing with improved drift correction, scale normalization, and uncertainty propagation. SINC enhances data comparability and interpretability for robust paleoenvironmental reconstructions.

These geochemical records provide new insights into vegetation dynamics, hydrological variability, and sediment provenance. The computational advances create a scalable platform for future CSIA work, improving inter-laboratory consistency and enabling sophisticated paleoclimate proxy applications through enhanced resolution and reliability of compound-specific isotope records.

Date

8-31-2025

Recommended Citation

Traphagan, Julian W., "Compound-Specific Isotope Records of Dust Provenance and Hydroclimate in the North Pacific and Marginal Seas of East Asia: Integrating n-Alkane δ13C and δD with Standardized Analytical Frameworks" (2025). LSU Doctoral Dissertations. 6908.
https://repository.lsu.edu/gradschool_dissertations/6908

Committee Chair

Guangsheng Zhuang