A 14.5-million-year record of East Antarctic Ice Sheet fluctuations from the central Transantarctic Mountains, constrained with cosmogenic <sup>3</sup>He, <sup>10</sup>Be, <sup>21</sup>Ne, and <sup>26</sup>Al

Abstract

Abstract. The distribution of moraines in the Transantarctic Mountains affords direct constraint of past ice-marginal positions of the East Antarctic Ice Sheet (EAIS). Here, we describe glacial geologic observations and cosmogenic-nuclide exposure ages from Roberts Massif, an ice-free area in the central Transantarctic Mountains. We measured cosmogenic 3He, 10Be, 21Ne, and 26Al in 168 dolerite and sandstone boulders collected from 24 distinct deposits. Our data show that a cold-based EAIS was present, in a configuration similar to today, for many periods over the last ∼14.5 Myr, including the mid-Miocene, late Pliocene, and early to Middle Pleistocene. Moraine ages at Roberts Massif increase with distance from, and elevation above, the modern ice margin, which is consistent with a persistent EAIS extent during glacial maxima and slow, isostatic uplift of the massif itself in response to trough incision by outlet glaciers. We also employ the exceptionally high cosmogenic-nuclide concentrations in several boulders, along with multi-isotope measurements in sandstone boulders, to infer extremely low erosion rates (≪5 cm Myr−1) over the period covered by our record. Although our data are not a direct measure of ice volume, the Roberts Massif glacial record indicates that the EAIS was present and similar to its current configuration during at least some periods when the global temperature was believed to be warmer and/or atmospheric CO2 concentrations were likely higher than today.

Early and middle Miocene ice sheet dynamics in the Ross Sea: Results from integrated core-log-seismic interpretation

“…14 Ma, termed the middle Miocene climate transition (MMCT), one of the three major climate transitions of the Cenozoic, which was accompanied by significant Southern Ocean cooling and inferred expansion of ice sheets in Antarctica (Shackleton and Kennett, 1975;Flower and Kennett, 1994;Zachos et al, 2001;Shevenell et al, 2004Shevenell et al, , 2008Miller et al, 2020). Geological studies support intensification of high latitude cooling and ice sheet expansion during the MMCT, with geomorphic, geological, and paleo-ecological evidence for the transition to a cold, hyper-arid polar landscape in the Transantarctic Mountains (Brook et al, 1995;Summerfield et al, 1999;Sugden and Denton, 2004;Lewis et al, 2006Lewis et al, , 2008Warny et al, 2009;Gulick et al, 2017;Balter-Kennedy et al, 2020). The ∼1‰ far-field deep-sea δ 18 O isotopic increase was originally associated with the development of a permanent East Antarctic Ice Sheet (EAIS) and the first major marine-based expansion of the West Antarctic Ice Sheet (WAIS), also supported by terrestrial evidence from Antarctica (Shackleton and Kennett, 1975;Kennett, 1977;Sugden et al, 1993;Sugden and Denton, 2004;Lewis et al, 2006).…”

Cosmogenic nuclide exposure age scatter records glacial history and processes in McMurdo Sound, Antarctica

“…Cosmogenic nuclide scatter in glacial environments is likely due to clasts or surfaces that contain nuclides that accumulated during periods of prior exposure but were not subsequently removed by non-erosive, cold-based glacial ice (Briner et al, 2006;Corbett et al, 2019;Koester et al, 2020). Cold-based glaciation occurs where ice thickness and/or basal ice temperatures are insufficient to produce meltwater and basal sliding, both of which facilitate subglacial erosion and therefore removal of inherited nuclides in formerly exposed surfaces (Bennett and Glasser, 1996). The basal thermal regime below ice can be highly heterogeneous, resulting in selective erosion of the landscape (Briner et al, 2006;Jamieson et al, 2010;Sugden et al, 2005).…”

Geochemical zones and environmental gradients for soils from the central Transantarctic Mountains, Antarctica

“…In the McMurdo Dry Valleys (MDV), organic matter and salt concentrations influence soil communities, where soils with higher amounts of organic carbon, lower water-soluble N : P ratios, and lower total water-soluble salt concentrations generally harbor the greatest biomass and biodiversity (Barrett et al, 2006;Bottos et al, 2020;Caruso et al, 2019;Magalhães et al, 2012). These Antarctic ecosystems are relatively simple and are among the few known soil systems where nematodes and microarthropods (Collembola, Acari) are at the top of the food chain (Freckman and Virginia, 1998;Hogg and Wall, 2012).…”

“…Biological processes in Antarctic soils are largely dependent on the availability, duration, and proximity of soils to liquid water (Barrett et al, 2006). Due to the seasonality of thawing events, liquid water acts as a pulse to the ecosystem, providing water for organisms but also wetting surface soils and dissolving soluble salts (Webster-Brown et al, 2010;Zeglin et al, 2009).…”

“…With this study, we determined and evaluated geochemical patterns and gradients of water-soluble ions in soils collected from 11 ice-free areas along the Shackleton Glacier, central Transantarctic Mountains (CTAM). Particular attention was given to total water-soluble salt concentrations, N : P ratios, and ClO − 4 and ClO − 3 concentrations based on their influence on biodiversity as determined in previous studies (e.g., Ball et al, 2018;Barrett et al, 2006;Courtright et al, 2001;Dragone et al, 2020;Nkem et al, 2006). The geochemical data were compared to geographic parameters to understand how the physical environment influences the observed geochemical variability.…”