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Benthic foraminifera as paleo-sea-ice indicators in the western Arctic Ocean

Lazar, Kelly Best
http://rave.ohiolink.edu/etdc/view?acc_num=osu1417617424

Abstract Details

2014, Doctor of Philosophy, Ohio State University, Geological Sciences.
As global climate continues to warm, the Arctic Ocean is becoming increasingly vulnerable, largely due to a fast retreat of sea ice. Knowledge of paleo-sea-ice conditions is essential for comprehending the changing Arctic system. This study combines micropaleontological (foraminiferal) data with existing litho- and chronostratigraphic results to construct a more resolved stratigraphic record and history of sea-ice change during the Quaternary in the western Arctic Ocean. Benthic foraminiferal assemblages were investigated in four sediment cores from the Northwind, Mendeleev, and Lomonosov Ridges (western Arctic Ocean). A uniquely-preserved sediment core from the Northwind Ridge was found to contain the longest calcareous foraminiferal record in the Arctic Ocean, estimated to extend to the early Pleistocene, ca. 1.5 Ma. This record was divided into two assemblage zones, representing distinct changes in foraminiferal composition with respect to ecological groups (polar vs. phytodetrital species) and extinct taxa. The distribution of polar and phytodetrital species yields significant information related to sea ice (perennial vs. seasonal) and associated climatic conditions. A principal faunal and sedimentary turnover occurred near the early-middle Pleistocene boundary (estimated ca 0.7-0.8 Ma), indicating an advance of perennial sea ice along with an increase in glacial inputs from the Laurentide ice sheet at the end of the Mid-Pleistocene Transition (MPT). Foraminiferal groups identified in the Northwind Ridge record were then translated to other western Arctic cores in order to better understand sea-ice change over the entire region. Foraminiferal abundances and assemblage composition show stratigraphically consistent changes, with major transitions estimated at the end of the MPT (ca. 0.7-0.8 Ma) and later near the bottom of Marine Isotope Stage 7 (ca. 0.25 Ma). These foraminiferal records, interpreted in terms of sea-ice conditions, indicate an overall expansion of year-round Arctic ice cover during the Pleistocene. The Holocene part of the record is not yet adequately resolved due to mostly insufficient sedimentation rates. To evaluate the stratigraphic significance of the morphological change between foraminifers Cassidulina teretis and C. neoteretis, suggested by an earlier study for the North Atlantic region, their tests were investigated in two sediment cores from the Northwind Ridge. Unlike the North Atlantic, where a clear, although time-transgressive transition between these test types is present in the early Pleistocene, they coexist throughout most of the western Arctic record, except for its youngest (late Pleistocene) part. This pattern suggests that these morphologies respond to changing ecological conditions, possibly related to sea-ice history, over a considerable period of time. Therefore, the use of C. teretis/C. neoteretis transition as a biostratigraphic marker should be applied with caution at specific localities and cannot be used over the entirety of the Arctic and sub-Arctic.
William Ausich (Advisor)
Leonid Polyak (Committee Member)
Lawrence Krissek (Committee Member)
Matthew Saltzman (Committee Member)
235 p.
Paleoclimate Science; Paleoecology
Arctic Ocean; foraminifera; sea ice; Quaternary; Northwind Ridge

Recommended Citations

Citations

  • Lazar, K. B. (2014). Benthic foraminifera as paleo-sea-ice indicators in the western Arctic Ocean [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417617424

    APA Style (7th edition)

  • Lazar, Kelly. Benthic foraminifera as paleo-sea-ice indicators in the western Arctic Ocean. 2014. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1417617424.

    MLA Style (8th edition)

  • Lazar, Kelly. "Benthic foraminifera as paleo-sea-ice indicators in the western Arctic Ocean." Doctoral dissertation, Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417617424

    Chicago Manual of Style (17th edition)

osu1417617424
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This open access ETD is published by The Ohio State University and OhioLINK.