An Antarctic stratigraphic record of stepwise ice growth thr

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TitleAn Antarctic stratigraphic record of stepwise ice growth through the Eocene-Oligocene transitionAbstractEarth's current icehouse phase began ~34 m.y. ago with the onset of major Antarctic glaciation at the Eocene-Oligocene transition. Changes in ocean circulation and a decline in atmospheric greenhouse gas levels were associated with stepwise cooling and ice growth at southern high latitudes. The Antarctic cryosphere plays a critical role in the ocean-atmosphere system, but its early evolution is still poorly known. With a near-field record from Prydz Bay, Antarctica, we demonstrate that Antarctic ice growth was stepwise and had an earlier onset than previously suggested. Prydz Bay lies downstream of a major East Antarctic Ice Sheet drainage system, and its sedimentary records uniquely constrain the timing of ice-sheet advance onto the continental shelf. We investigated a detrital record extracted from three Ocean Drilling Program drill holes within a new depositional and chronological framework spanning the late Eocene to early Oligocene (ca. 36-33 Ma). The chemical index of alteration (CIA) and the S index, calculated from the major-element geochemistry of bulk samples, yielded estimates of chemical weathering intensities and mean annual temperature on the East Antarctic continent. We document evidence for late Eocene mountain glaciation along with transient warm events at 35.8-34.8 Ma. From 34.4 Ma, associated with the Eocene-Oligocene transition precursor δ18O excursion, glaciers advanced into Prydz Bay, coincident with a decline in chemical weathering and temperature. We conclude that Antarctic continental ice growth commenced with the Eocene-Oligocene transition "precursor glaciation", during a time of Subantarctic surface ocean cooling and a decline in atmospheric pCO2. These results call for dynamic high-latitude feedbacks that are currently poorly represented in Earth system models and emphasize the need for additional near-field glacio-sedimentological, high-latitude sea-surface temperature and pCO2 records across the Eocene-Oligocene transition. AcknowledgementsThis research used samples provided by the International Ocean Discovery Program. Funding for this research came from the U.S. National Science Foundation (award ANT-1245283) to S. Passchier. P.K. Bijl thanks NWO-VENI for grant 863.13.002. This research also benefited from a Global Education Grant from Montclair State University. Phil Rumford and his staff are thanked for assistance during work at the Gulf Coast Core Repository in College Station, Texas. Nick Tadrick is thanked for carrying out some of the sample preparations, and Xiaona Li is thanked for assistance with the inductively coupled plasma--atomic emission spectroscopy measurements at Montclair State University. Constructive feedback from Paul Wilson and an anonymous reviewer significantly improved the manuscript.Funding DetailsANT-1245283, NSF, National Science Foundation

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1st AuthorPasschier, S.AuthorPasschier, S.Ciarletta, D.Miriagos, T.Bijl, P.Bohaty, S.Year2017JournalBulletin of the Geological Society of AmericaVolume129Number3/04/2017Pages318-330DOI10.1130/B31482.1URLhttps://www.scopus.com/inward/recor.....d7b7a09882a6103cc9dbf9cafKeywordsAtmospheric chemistryAtmospheric temperatureGeochemistryGlacial geologyGlaciersGreenhouse gasesOceanographyStratigraphySurface watersWeathering, Atmospheric greenhouseChemical index of alterationsEast antarctic ice sheetsMean annual temperaturesOcean drilling programsOcean-atmosphere systemSea surface temperature (SST)Stratigraphic records, Ice

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TypeArticleCitationPasschier, S., Ciarletta, D., Miriagos, T., Bijl, P. and Bohaty, S. (2017). An Antarctic stratigraphic record of stepwise ice growth through the Eocene-Oligocene transition. Bulletin of the Geological Society of America, 129(3-4): 318-330 IdentifierPasschier2017Antarctica NZ supported?NoNZARI?No