Late Pliocene deglaciation of southern Greenland

Author(s): Walczak, M. H.; Carlson, A. E.; Stoner, J. S.; Hatfield, R. G.; Wolhowe, M. D.; Mathias, A.
Author Affiliation(s): Primary:
Australian National University, Canberra, A. C. T., Australia
Oregon State University, United States
COAS, United States
Volume Title: AGU 2015 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2015; American Geophysical Union 2015 fall meeting, San Francisco, CA, Dec. 14-18, 2015. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Predicting the response of the remaining Antarctic and Greenland ice sheets to increasing atmospheric greenhouse gas concentrations is an important goal of climate science. The late Pliocene (3.3-3.0 Ma; formerly the middle Pliocene) may offer a natural quasi-analogue to climate in the upcoming centuries: CO2 levels were ≈400 PPM, global surface temperatures were 2-3 degrees higher, and sea level was likely at least 6 m higher than today. Yet little is currently known about the history of the pre-Quaternary Greenland ice sheet. IODP Expedition 303 site U1307 at 2575 m depth on the Eirik Ridge extends back to 3.4 Ma, capturing the late-Pliocene warm period adjacent to the southern Greenland ice sheet. Ice-rafted debris records, interpreted on a paleomagnetic reversal age model, suggest roughly 40 ka cyclicity of between ≈5% and ≈40% sand. Between ≈3.3 and 3.2 Ma there is a significant change in lithology characterized by an abrupt reduction in magnetic susceptibility, during which time the sand fraction remains below 10%. Assuming a magnetite mineralogy, hysteresis ratios support a much finer magnetic assemblage of unique provenance in this interval; Mrs/Ms values of the silt fraction range from ≈0.2-0.25, compared to ≈0.1 in the sediments above and below. The origin this material will be discussed, although this observation is unambiguously consistent with the disappearance of silt transported from the southern Greenland ice sheet. The lack of Greenlandic source material observed in this interval is unique in the last 3.4 Ma at this location, and may indicate full deglaciation of southern Greenland in the late Pliocene.
Year of Publication: 2015
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Arctic region; Atlantic Ocean; Cenozoic; Climate change; Deglaciation; Expedition 303; Expeditions 303/306; Greenland; IODP Site U1307; Integrated Ocean Drilling Program; Neogene; North Atlantic; Northwest Atlantic; Paleoclimatology; Pliocene; South Greenland; Tertiary; Upper Pliocene
Coordinates: N583000 N583000 W0462400 W0462400
Record ID: 2016064642
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