Riesselman, Christina R. and Dunbar, Robert B. (2013): Diatom evidence for the onset of Pliocene cooling from AND-1B, McMurdo Sound, Antarctica

Leg/Site/Hole:
IODP 306
ODP 177
IODP 306 U1313
ODP 177 1090
Identifier:
2013-025118
georefid

10.1016/j.palaeo.2012.10.014
doi

Creator:
Riesselman, Christina R.
Stanford University, Department of Geological and Environmental Sciences, Stanford, CA, United States
author

Dunbar, Robert B.
author

Identification:
Diatom evidence for the onset of Pliocene cooling from AND-1B, McMurdo Sound, Antarctica
2013
Palaeogeography, Palaeoclimatology, Palaeoecology
Elsevier, Amsterdam, Netherlands
369
136-153
The late Pliocene, approximately 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 degrees 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 approximately 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.
English
Serial
Coverage:Geographic coordinates:
North:-77.5324
West:167.0524East: 167.0524
South:-77.5324

Isotope geochemistry; Stratigraphy; adaptive radiation; algae; AND-1B; ANDRILL; ANtarctic geological DRILLing Program; Antarctica; assemblages; Atlantic Ocean; biogenic processes; biostratigraphy; boreholes; Cenozoic; climate change; cooling; cores; cyclostratigraphy; diatoms; Expedition 306; Expeditions 303/306; floral list; geochronology; Integrated Ocean Drilling Program; IODP Site U1313; isotope ratios; isotopes; Leg 177; lithostratigraphy; magnetostratigraphy; marine sediments; McMurdo Sound; microfossils; Mid-Atlantic Ridge; Neogene; North Atlantic; O-18/O-16; Ocean Drilling Program; ODP Site 1090; oxygen; paleoclimatology; Plantae; Pliocene; range; Ross Sea; sediments; silica; South Atlantic; Southern Ocean; stable isotopes; statistical analysis; cluster analysis; Tertiary; upper Pliocene;

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