Diatom evidence for the onset of Pliocene cooling from AND-1B, McMurdo Sound, Antarctica

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doi: 10.1016/j.palaeo.2012.10.014
Author(s): Riesselman, Christina R.; Dunbar, Robert B.
Author Affiliation(s): Primary:
Stanford University, Department of Geological and Environmental Sciences, Stanford, CA, United States
Volume Title: Palaeogeography, Palaeoclimatology, Palaeoecology
Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Vol.369, p.136-153. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-0182 CODEN: PPPYAB
Note: In English. 21 refs.; illus., incl. 2 tables, sketch map
Summary: The late Pliocene, ∼3.3-3.0Ma, is the most recent interval of sustained global warmth in the geologic past. This window is the focus of climate reconstruction efforts by the U.S. Geological Survey's Pliocene Research, Interpretation, and Synoptic Mapping (PRISM) Data/Model Cooperative, and may provide a useful climate analog for the coming century. Reconstructions of past surface ocean conditions proximal to the Antarctic continent are essential to understanding the sensitivity of the cryosphere to this key interval in Earth's climate evolution. An exceptional marine sediment core collected from the southwestern Ross Sea (78° S), Antarctica, during ANDRILL's McMurdo Ice Shelf Project preserves evidence of dramatic fluctuations between grounded ice and productive, open ocean conditions during the late Pliocene, reflecting orbitally-paced glacial/interglacial cycling. In this near-shore record, diatom-rich sediments are recovered from interglacial intervals; two of these diatomites, from ∼3.2Ma and 3.03Ma, are within the PRISM chronologic window. The diatom assemblages identified in PRISM-age late Pliocene diatom-rich sediments are distinct from those in mid-Pliocene and later Pliocene/Pleistocene intervals recovered from AND-1B, and comprise both extant taxa with well-constrained ecological preferences and a diverse extinct flora, some members of which are previously undescribed from Antarctic sediments. Both units are dominated by Chaetoceros resting spores, an indicator of high productivity and stratification that is present at much lower abundance in materials both older and younger than the PRISM-age sediments. Newly described species of the genus Fragilariopsis, which first appear in the AND-1B record at 3.2Ma, are the most abundant extinct members of the PRISM-age assemblages. Other extant species with established environmental affinities, such as Fragilariopsis sublinearis, F. curta, Stellarima microtrias, and Thalassiothrix antarctica, are present at lower abundances. Environmental inferences drawn from extant diatom assemblages are in good agreement with those from Chaetoceros resting spores and the Fragilariopsis radiation. All three lines of evidence indicate the onset of late Pliocene cooling in the Ross Sea near-shore environment at 3.2Ma, with intensification and possible regional persistence of summer sea ice by 3.03Ma. An important implication of this research is the indication that the Ross Ice Shelf fluctuated dramatically on orbital timescales at a time when nearshore Antarctic conditions were only modestly warmer than present. Abstract Copyright (2013) Elsevier, B.V.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; AND-1B; ANDRILL; ANtarctic geological DRILLing Program; Adaptive radiation; Algae; Antarctica; Assemblages; Atlantic Ocean; Biogenic processes; Biostratigraphy; Boreholes; Cenozoic; Climate change; Cluster analysis; Cooling; Cores; Cyclostratigraphy; Diatoms; Expedition 306; Expeditions 303/306; Floral list; Geochronology; IODP Site U1313; Integrated Ocean Drilling Program; Isotope ratios; Isotopes; Leg 177; Lithostratigraphy; Magnetostratigraphy; Marine sediments; McMurdo Sound; Microfossils; Mid-Atlantic Ridge; Neogene; North Atlantic; O-18/O-16; ODP Site 1090; Ocean Drilling Program; Oxygen; Paleoclimatology; Plantae; Pliocene; Range; Ross Sea; Sediments; Silica; South Atlantic; Southern Ocean; Stable isotopes; Statistical analysis; Tertiary; Upper Pliocene
Coordinates: S775324 S775324 E1670524 E1670524
Record ID: 2013025118
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands