Diatoms

Author(s): Harwood, David M.
Author Affiliation(s): Primary:
Ohio State Univ., Dep. Geol. and Mineral., Columbus, OH, United States
Volume Title: Antarctic Cenozoic history from the MSSTS-1 drillhole, McMurdo Sound
Volume Author(s): Barrett, P. J., editor
Source: Antarctic Cenozoic history from the MSSTS-1 drillhole, McMurdo Sound, edited by P. J. Barrett. DSIR Bulletin, Vol.237, p.69-107. Publisher: Department of Scientific and Industrial Research (DSIR), Wellington, New Zealand. ISSN: 0077-961X. ISBN: 0-477-06785-9 CODEN: NEZSAC
Note: In English. 114 refs.; illus. incl. 2 tables, 8 plates, sketch map
Summary: This paper describes the upper Miocene-lower Pliocene and upper Oligocene to lower Miocene marine diatom floras recovered from the 227 m glacial-marine MSSTS-1 (McMurdo Sound Sediment and Tectonic Studies) drill core. These represent the southernmost occurrence known to date. Over one hundred and thirty siliceous microfossil taxa are described and/or illustrated. A provisional upper Oligocene to lower Miocene diatom biostratigraphic zonation based primarily on MSSTS-1 diatom data with supporting information from Southern Ocean DSDP Site 513A is proposed for the Ross Sea region. Recalibration of existing MSSTS-1 magnetostratigraphy, guided by diatom data, yields an age of 31 Ma at the bottom of the hole to 24.5 Ma at 115 m. The magnetostratigraphy enables determination of an average rate of sediment accumulation of 20 m/m.y. which shows minor variation. Extrapolation of this rate to 51 m yields an age of 21 m.y., consistent with the diatom data. The linear nature of the accumulation rate curve suggests no major breaks in the lower MSSTS-1 sequence, and little tectonic activity on the adjacent Transantarctic Mountain block during the late Oligocene. Micropaleontologic and sedimentologic data, however indicate at least six episodes of ice-grounding over this period. Diatom assemblage diversity and composition fluctuate between benthic-dominated shallow and planktonic-dominated deep water assemblages and probably reflect glacially induced eustatic changes. Between ≈ 216 m and 214 m a dramatic drop in diatom diversity uphole and an increase in the benthic to planktonic diatom ratio suggests an abrupt shallowing. This event is centered at ≈ 30 Ma (paleomagnetic data) and corresponds to the largest regression of the Cenozoic which has been attributed to a major increase in the volume of Antarctic ice. Fifteen meters of glacial-marine sediments with dropstones below the record of this ≈ 30 Ma climatic event in MSSTS-1 indicate that ice was present at sea level in the western margins of the Ross Sea region more than 31 million years ago.
Year of Publication: 1986
Research Program: DSDP Deep Sea Drilling Project
Key Words: 09 Paleontology, Paleobotany; Algae; Antarctic Ocean; Antarctica; Cenozoic; Diatoms; McMurdo Sound; Microfossils; Paleobotany; Plantae; Ross Sea; Southern Ocean; Thallophytes
Record ID: 1987059421
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data supplied by Institute of Geological and Nuclear Sciences Limited (GNS Science), Lower Hutt, New Zealand

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