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An Antarctic Stratigraphic Record of Stepwise Ice Growth Through the Eocene-Oligocene Transition

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An Antarctic Stratigraphic Record of Stepwise Ice Growth Through the Eocene-Oligocene Transition Montclair State University Montclair State University Digital Commons Department of Earth and Environmental Studies Faculty Scholarship and Creative Works Department of Earth and Environmental Studies 3-1-2017 An Antarctic stratigraphic record of stepwise ice growth through the Eocene-Oligocene transition Sandra Passchier Montclair State University, [email protected] Daniel J. Ciarletta Montclair State University Triantafilo E. Miriagos Montclair State University Peter K. Bijl Utrecht University Steven M. Bohaty University of Southampton Follow this and additional works at: https://digitalcommons.montclair.edu/earth-environ-studies-facpubs Part of the Geology Commons MSU Digital Commons Citation Passchier, Sandra; Ciarletta, Daniel J.; Miriagos, Triantafilo E.; Bijl, eterP K.; and Bohaty, Steven M., "An Antarctic stratigraphic record of stepwise ice growth through the Eocene-Oligocene transition" (2017). Department of Earth and Environmental Studies Faculty Scholarship and Creative Works. 27. https://digitalcommons.montclair.edu/earth-environ-studies-facpubs/27 This Article is brought to you for free and open access by the Department of Earth and Environmental Studies at Montclair State University Digital Commons. It has been accepted for inclusion in Department of Earth and Environmental Studies Faculty Scholarship and Creative Works by an authorized administrator of Montclair State University Digital Commons. For more information, please contact [email protected]. An Antarctic stratigraphic record of stepwise ice growth through the Eocene- Oligocene transition Sandra Passchier1, Daniel J. Ciarletta1, Triantafilo E. Miriagos1, Peter K. Bijl2, Steven M. Bohaty3 1Department of Earth and Environmental Studies, Montclair State University, 1 Normal Ave, Montclair NJ, 07043, U.S.A., [email protected] 2Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Heidelberglaan 2, 3584CS Utrecht, The Netherlands 3Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, 20 European Way, Southampton SO14 3ZH, UK ABSTRACT Ma, associated with the EOT-1 δ18O Maximum glaciation appears to have excursion, glaciers advanced into been a climatic overshoot as benthic Earth’s current icehouse phase began Prydz Bay, coincident with a decline δ18O values gradually rebounded ~34 million years ago with the onset in chemical weathering and (decreased) following the Oi-1 of major Antarctic glaciation at the temperature. We conclude that excursion (Zachos and Kump, 2005). Eocene-Oligocene Transition (EOT). Antarctic continental ice growth Although the magnitude of the Oi-1 Changes in ocean circulation and a commenced with the EOT-1 benthic stable oxygen isotope shift is decline in atmospheric greenhouse gas “precursor” glaciation, during a time consistent through the ocean basins, levels were associated with step-wise of Subantarctic surface ocean cooling there is uncertainty regarding the cooling and ice growth at southern and a decline in atmospheric pCO2. degree, timing, and spatial variability high latitudes. The Antarctic These results call for dynamic high- of deep-water temperature change, cryosphere plays a critical role in the latitude feedbacks that are currently which translates into uncertainties in ocean-atmosphere system, but its early poorly represented in Earth system ice volume estimates (e.g., Bohaty et evolution is still poorly known. With a models and emphasize the need for al., 2012). Furthermore, ice sheets are near-field record from Prydz Bay, additional near-field glacio- currently not fully coupled in Earth Antarctica, we demonstrate that sedimentological, high-latitude SST, system models, which limits the Antarctic ice growth was stepwise and and pCO2 records across the EOT. understanding of Antarctic ice sheet – had an earlier onset than previously atmosphere – ocean feedbacks at the suggested. Prydz Bay lies downstream INTRODUCTION onset of the icehouse phase (DeConto of a major East Antarctic ice-sheet and Pollard, 2003; Zachos and Kump, drainage system and its sedimentary The Eocene-Oligocene transition 2005; Miller et al., 2009; Goldner et records uniquely constrain the timing (EOT) at ~34 Ma marks the onset of al., 2014; Ladant et al., 2014). of ice-sheet advance onto the continental-scale Antarctic glaciation, continental shelf. We investigate a but questions remain about the exact Despite the importance of the EOT detrital record extracted from three mechanisms involving ice sheet interval, detailed insights into the Ocean Drilling Program drill holes formation and the dynamics of ice timing and paleoenvironmental within a new depositional and growth during this time. Based on implications of ice growth close to the chronological framework spanning the deep-sea proxy evidence, the onset of locus of ice formation on Antarctica late Eocene to early Oligocene (~36- Antarctic glaciation most likely are sparse (e.g., Galeotti et al., 2016). 33 Ma). The chemical index of occurred in steps (Coxall et al., 2005; Recent improvements of age control alteration (CIA) and the S-index, Coxall and Wilson, 2011). Benthic and collection of new calculated from the major element foraminiferal oxygen isotope (δ18O) sedimentological and geochemical geochemistry of bulk samples, yield records coupled with sea level and data allow us to characterize the onset estimates of chemical weathering paleotemperature proxies suggest that and extent of ice growth on the intensities and mean annual a first 0.5‰ δ18O step at the EOT was Antarctic margin in unprecedented temperature (MAT) on the East primarily an effect of cooling, with a detail within a ca. 400 m thick Antarctic continent. We document small ice-volume component, whereas sequence drilled by the Ocean Drilling evidence for late Eocene mountain the second, larger δ18O step (Oi-1) was Program (ODP) in Prydz Bay (Figures glaciation along with transient warm predominantly an ice volume signal 1 and 2). Here, we interpret a record events at 35.8-34.8 Ma. From 34.4 (Lear et al., 2008; Katz et al., 2008). of detrital sediment delivery to the Accepted version of GSA Bulletin 2017; v. 129; no. 3/4; p. 318-330; doi: 10.1130/B31482.1 The onset of Antarctic glaciation Antarctic continental shelf that carries Young, 1982) to characterize paleo- calculated according to Nesbitt and the signature of late Eocene-to-early weathering conditions and the S-index Young (1982) as 100x the molar ratio Oligocene high-latitude climate and (Sheldon et al., 2002) to reconstruct of Al2O3 to Na2O, CaO*, K2O and ice sheet variability. continental surface temperatures. Our Al2O3, where CaO* designates CaO in new data and stratigraphic framework detrital silicate minerals only. Calcium Prydz Bay lies on the passive margin along with recently published detrital carbonate percentages of the of East Antarctica downstream of the geochemical data for the same and sediments analyzed in Holes 739C and Lambert Graben that carries the nearby cores (Cox et al., 2010; Scher 742A were < 2 % (Barron et al., 1989) largest ice stream in East Antarctica. et al., 2011; Tochilin et al., 2012; and no corrections were applied. CIA The Gamburtsev Mountains, upstream Thomson et al., 2013) allow us to analyses are reproducible within one from the Lambert Graben, are reconstruct late Eocene–earliest CIA unit. The temperature regarded as one of the first nucleation Oligocene climate variability and climofunction applied is based on the points of East Antarctic glaciation stepwise glaciation of East Antarctica. S-index from Sheldon et al. (2002), (DeConto and Pollard, 2003; Rose et which is defined as the molar ratio of al., 2013). Glaciation of the METHODS Na2O and K2O to Al2O3. The Mean Gamburtsev Mountains commenced Annual Temperature (MAT) with ephemeral cirque glaciers (Bo et Materials and analytical methods calibration of the S-index has a 1-σ al., 2009). Following the cirque uncertainty of 3.6°C (Sheldon et al., glaciation, alpine glaciers eroded New sedimentological logging and 2002). All instrumental analyses were overdeepenings into the Gamburtsev descriptions of the ODP 739C, 742A, carried out at Montclair State Province likely over a short period of and 1166A drillholes were carried out University. 0.3-3.0 Myr prior to development of a on the archive halves at the persistent cold-based ice cover at high International Ocean Discovery Application of the CIA and S-index elevation (Rose et al., 2013). The Program (IODP) Gulf Coast as weathering proxies timing of the landscape and ice sheet Repository in 2013. Previous evolution, however, is poorly descriptions carried out during The CIA was developed as a constrained with regional shipboard core characterization in continental weathering proxy applied paleoenvironmental data. 1988 and 2000 did not apply the same to mudrocks sourced from glaciated classification schemes. Our lithofacies drainage basins (Nesbitt and Young, Three ODP drill holes at Sites 739, designations were based on the 1982) and can be applied to basins that 742 and 1166 were drilled in 400-500 classifications of Mazullo and Graham are weathering-limited, with high m water depth in Prydz Bay and, (1988) and Moncrieff (1989). Particle erosion and sediment transport rates together, provide a detailed record of size distributions were collected on the and short-term floodplain storage the Eocene-Oligocene transition in matrix (< 2 mm) of 253 samples from (Passchier et al., 2013). Under these East Antarctica. The timing and Holes 739C, 742A
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