Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


Dipre_Dissertation_2019.pdf (8.66 MB)

ETD Abstract Container

Abstract Header

Plio-Pleistocene Environments In The Western Arctic Ocean Based On Sediment Records From The Northwind Ridge

Dipre, Geoffrey R
http://rave.ohiolink.edu/etdc/view?acc_num=osu1566134560384948

Abstract Details

2019, Doctor of Philosophy, Ohio State University, Earth Sciences.
The Arctic is warming at increasingly rapid rates as a consequence of current global climate change. Temperature increases are amplified at these high latitudes and have resulted in major environmental changes, especially pronounced in the continual decline of sea ice at the surface of the Arctic Ocean. Through atmospheric and oceanic connections, these effects have been linked to many of the climatic changes taking place around the world. In addition, sea ice loss has major societal impacts, as it allows for increased human activity in the Arctic Ocean region. Therefore, it is necessary to improve our understanding of the changing Arctic system, which requires a profound knowledge on its history on various time scales, from decades to millions of years. This dissertation investigates multiple sedimentological proxies from the western Arctic Ocean, with a focus on reconstructing paleoenvironmental conditions during the Pliocene and early Pleistocene (Plio-Pleistocene; ~5-0.8 Ma). This time period preceded the expansion of major Northern Hemisphere glaciations (~0.8 Ma) and potentially represents one of the most useful paleo-analogs for the changes currently taking place in the Arctic Ocean. Two sediment cores from the Northwind Ridge north of Alaska were analyzed in detail, as they recovered material dating back to the Pliocene and exhibit uniquely good preservation of calcareous microfossils, primarily benthic foraminifera. These microfossils aided in constructing a better resolved Plio-Pleistocene stratigraphy for the Arctic Ocean, and they provided a proxy for reconstructing paleo-sea ice conditions by relating the distribution of specific ecological groups to sea-ice extent. Other proxies, such as sediment texture (grain size) and elemental composition (X-ray Fluorescence) were used to interpret paleo-circulation and sediment transport processes. Together, these proxy records indicate that the Pliocene and early Pleistocene environments had little effect from glaciations, were seasonally ice-free, and had increased current activity on the ridge top. To further understand the sedimentation processes that affected the study region during the Plio-Pleistocene, detailed grain size analysis of fine (<63 µm) sediments was conducted using a laser particle analyzer. Two other cores from the ridge were added for comparison between the glacially-dominated environments of the late-middle Pleistocene and the reduced-ice preglacial environments (Pliocene-early Pleistocene). The grain size distributions of all four cores indicate that sea ice and bottom currents represent the primary transport mechanisms controlling sedimentation on the ridge. Variations in deposition from sea ice controlled sedimentation distribution during the late Pleistocene, while bottom currents were strongest during the Plio-Pleistocene. They also played a significant role during major interglacial intervals in the late Pleistocene. Finally, sediment proxies were used to investigate the dominant long-term orbital cyclicities that affected the Arctic during the early Pleistocene. Several cyclicities were identified across sediment textural (sand content), geochemical (manganese), and paleobiological (benthic foraminiferal carbon and oxygen stable isotopes) proxies, with an especially consistent, low-frequency signal likely related to long-eccentricity (~400 kyr) cycles. Pulses of intensified circulation related to sea level fluctuations could have driven this signal, which is strongest in the δ13C and Mn records. These cycles may provide a useful chronostratigraphic tool for the early Pleistocene and potentially older sediments in Arctic paleoceanographic records. Additionally, these cycles provide evidence for connections between the Arctic Ocean and the global climatic system during the Plio-Pleistocene, as they have also been identified in paleoceanographic records from other oceans.
Andrea Grottoli (Advisor)
Leonid Polyak (Advisor)
Lawrence Krissek (Committee Member)
Cinnamon Carlarne (Committee Member)
255 p.
Oceanography; Paleoclimate Science; Sedimentary Geology
Arctic Ocean; Paleoceanography; Sediment Cores; Pliocene; Pleistocene; Sea Ice

Recommended Citations

Citations

  • Dipre, G. R. (2019). Plio-Pleistocene Environments In The Western Arctic Ocean Based On Sediment Records From The Northwind Ridge [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1566134560384948

    APA Style (7th edition)

  • Dipre, Geoffrey. Plio-Pleistocene Environments In The Western Arctic Ocean Based On Sediment Records From The Northwind Ridge. 2019. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1566134560384948.

    MLA Style (8th edition)

  • Dipre, Geoffrey. "Plio-Pleistocene Environments In The Western Arctic Ocean Based On Sediment Records From The Northwind Ridge." Doctoral dissertation, Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1566134560384948

    Chicago Manual of Style (17th edition)

osu1566134560384948
96
© 2019, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.