Filling in the Gaps: Paleosols as Regional Recorders of Hydroclimatic Change in Northeast China at the Cretaceous – Paleogene

Bobik, Theodore

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Year:: 2024
Contributor:: Bobik, Theodore (creator); Ibarra, Daniel (Advisor); Russell, James (Reader); Saal, Alberto (Reader); Brown University. Department of Earth, Environmental, and Planetary Sciences (sponsor)
Genre:: theses
Subject:: Geochemistry; Paleoclimatology; Stable isotopes; Cretaceous-Paleogene boundary; Paleopedology; Clumped isotopes
Extent:: vii, 76 p.

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Abstract:: The Songliao Basin in Northeast China contains one of the most complete terrestrial sedimentary records of the Cretaceous and represents an important terrestrial paleoclimate archive. This study analyzes paleosols formed across the Cretaceous-Paleogene Boundary (K-Pg) between 66.24 and 65.52 Ma for the stable isotopic composition of soil carbonates, nodules and matrix, and the bulk elemental concentration of soil matrix. By analyzing both carbonate nodules and disseminated matrix carbonate we increase the temporal resolution of the K-Pg, producing 82 new δ18O and δ13C measurements, and 38 new carbonate clumped isotope measurements. The Δ47 temperatures indicate that the latest Cretaceous was hotter than previously interpreted (>30℃). Discrete spikes in temperature correlate to well-defined pulses of increased Deccan Traps volcanic activity and global (and local) increases in Hg. Temperatures are coherent with global and regional trends. In sum, these data points support the Late Maastrichtian Warming event as a volcanically forced global phenomena. Paleosol geochemistry indicates increased pedogenesis during such warm periods, however, we detail concerns regarding the CIW proxy as biased by provenance and sediment reworking. We calculate the δ18O of soil porewater (δ18Opw) and highlight the potential impact of evaporation. As a result, we reevaluate the efficacy of previous comparisons between δ18Opw and the δ18O of modern seasonally influenced precipitation. Lastly, we advance efforts to model soil respiration (SR) from Songliao Basin paleosols by increasing the number of in situ measurements (Δ47, δ13Corg). We find these additions increase previously published SR by an average of 500 gCm-2yr-1, more accurately reflecting an ecosystem under elevated Cretaceous pCO2atm. Overall, we conclude that during the K-Pg the Songliao Basin paleosols record a much warmer and highly productive lower latitude environment analogous to modern subtropical conditions with soil respiration rates comparable to modern tropical environments (~1200 gCm-2yr-1).
Notes:: Thesis (Sc. M.)--Brown University, 2024

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Bobik, Theodore, "Filling in the Gaps: Paleosols as Regional Recorders of Hydroclimatic Change in Northeast China at the Cretaceous – Paleogene" (2024). Earth, Environmental and Planetary Sciences Theses and Dissertations. Brown Digital Repository. Brown University Library. https://repository.library.brown.edu/studio/item/bdr:au2ytdxf/

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Earth, Environmental and Planetary Sciences Theses and Dissertations

Theses and Dissertations for the Earth, Environmental and Planetary Sciences department.
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