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Quaternary Science Reviews 164 (2017) 1e24 Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev Invited review Analysis of Antarctic glacigenic sediment provenance through geochemical and petrologic applications * Kathy J. Licht a, , Sidney R. Hemming b a Department of Earth Sciences, Indiana University Purdue University Indianapolis, Indianapolis, IN, USA b Department of Earth and Environmental Sciences, Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY, USA article info abstract Article history: The number of provenance studies of glacigenic sediments in Antarctica has increased dramatically over Received 2 October 2016 the past decade, providing an enhanced understanding of ice sheet history and dynamics, along with the Received in revised form broader geologic history. Such data have been used to assess glacial erosion patterns at the catchment 10 February 2017 scale, flow path reconstructions over a wide range of scales, and ice sheet fluctuations indicated by Accepted 6 March 2017 iceberg rafted debris in circumantarctic glacial marine sediments. It is notable that even though most of the bedrock of the continent is ice covered and inaccessible, provenance data can provide such valuable information about Antarctic ice and can even be used to infer buried rock types along with their geo- and Keywords: Glacial geology thermochronologic history. Glacigenic sediments provide a broader array of provenance analysis op- Bedrock geology portunities than any other sediment type because of their wide range of grain sizes, and in this paper we Till review methods and examples from all size fractions that have been applied to the Antarctic glacigenic Ice-rafted debris sedimentary record. Interpretations of these records must take careful consideration of the choice of Sediment transport analytical methods, uneven patterns of erosion, and spatial variability in sediment transport and rock Petrography types, which all may lead to a preferential identification of different elements of sources in the prove- Geochronology nance analyses. Because of this, we advocate a multi-proxy approach and highlight studies that Radiogenic isotopes demonstrate the value of selecting complementary provenance methods. Thermochronology © 2017 Elsevier Ltd. All rights reserved. 1. Introduction bedrock geology. Bedrock geology influences erosion rates and ice flow (e.g., Jamieson et al., 2010; Golledge et al., 2013), and the The persistence of the Antarctic ice sheet through warm inter- lithological and geochemical/geochronological expressions of the glacial periods sets it apart from most continental-scale northern geologic history of sediment sources provide important tools for hemisphere ice sheets. While Antarctica provides important op- tracing the transport pathways of sediment (e.g., Licht and Palmer, portunities to directly study modern ice dynamics and geomorphic 2013; Pierce et al., 2014) and for probing erosion rates and thus processes, we cannot rely as readily on the glacial geomorphology inferring landform evolution of hidden sources (e.g., Thomson to reconstruct its past configuration as pioneering naturalists et al., 2013). Schimper, Charpentier, Agassiz, Chamberlain and others used in the On glacial-interglacial timescales, changes in Antarctic ice sheet 1800's to begin to understand the history and influence of glacier volume have resulted in eustatic sea level changes causing major ice on the landscape. Although tremendous progress has been changes locally to the geomorphology and deposition on conti- made in understanding Antarctic ice with multibeam swath nental shelves around Antarctica, but also, globally as coastlines bathymetric data that provided paradigm-shifting images of the shifted, altering ocean currents and fluvial gradients. This link to continental shelf geomorphology (e.g., Shipp et al., 1999), targeted global sea level changes strongly motivates ongoing study of sampling of glacial landforms, comparable to terrestrial glacial Antarctica ice sheets to inform models that can more reliably es- studies, has been difficult to achieve. Glacial geologists working in timate the potential for future sea level rise, an area of substantial the Antarctic also lack the ‘luxury’ of having direct access to the uncertainty (Church et al., 2013). Many of the first-order questions of Antarctic ice sheet history (i.e., ice sheet extent), particularly for the last glacial maximum (LGM), have been addressed (e.g., RAISED * Corresponding author. consortium, 2014) and data-driven numerical models have been E-mail address: [email protected] (K.J. Licht). developed that attempt to optimize model outputs with existing http://dx.doi.org/10.1016/j.quascirev.2017.03.009 0277-3791/© 2017 Elsevier Ltd. All rights reserved. 2 K.J. Licht, S.R. Hemming / Quaternary Science Reviews 164 (2017) 1e24 geologic data on ice extent and flow pathways (e.g., Golledge et al., (origin and transport). 2013)(Fig. 1). However, many fundamental questions about ice In this review we use the term “sediment provenance” or sheet extent and configuration remain even for the last deglacia- “provenance analysis” in the most general sense: it is the recon- tion, and there is a particularly sparse record for pre-LGM times. struction of the origin of sediment, that is the sources and processes The limited exposure of pre-LGM deposits onshore, and limited on the landscape from which the sediment was derived. Prove- access to offshore deposits means that relatively few samples have nance analysis has been widely used in glaciated areas of the been analyzed. Thus reconstructions mainly rely on indirect northern hemisphere for both academic studies of ice sheet history geophysical datasets such as marine seismics and airborne radar. and applied science such as mineral exploration, but has only However, physical samples provide information essential to ice begun to be widely used in Antarctica in the past decade. Early sheet reconstructions, including analysis of sediment provenance work in the Ross Sea by Stetson and Upson (1937), using cores Fig. 1. (A) Locations named in text shown on the BEDMAP 2 subglacial topography from Fretwell et al. (2013) with a semi-transparent overlay of the Landsat Image Mosaic created with GeoMapApp. Red lines show ice divides, black dashed lines are ice streams, blue arrow show generalized surface currents. AL ¼ Adelie Land, BG¼Byrd Glacier, DV ¼ Dry Valleys, EM ¼ Ellsworth Mountains, GVL ¼ George V Land, MA ¼ Mt. Achernar and Law Glacier, NG¼Nimrod Glacier, NVL ¼ north Victoria Land, R-F ¼ Ronne-Filchner, and RG ¼ Reedy Glacier, SCIS¼Siple Coast ice streams, yellow dot marks Skelton-Mulock Glaciers. (B) Model reconstruction of Antarctic ice flow lines for the Last Glacial Maximum (Golledge et al., 2013) compared to modern grounded ice extent shown on base image (grey shading). K.J. Licht, S.R. Hemming / Quaternary Science Reviews 164 (2017) 1e24 3 collected during the second Byrd Antarctic Expedition, appears to single provenance method is applied. This concept is summarized be the first to analyze till composition and infer its provenance. with simplistic scenarios (Fig. 2) showing how pairing petrographic Their sand petrographic analysis showed spatial variation across and geochronologic analysis may allow differentiating geologic the Ross Sea, which they speculated meant there were different terranes. Finally, we have selected examples that show how prov- source terranes upstream. Since that time, efforts have broadened enance analysis of Antarctic glacigenic sediments has advanced our to include a source-to-sink approach that evaluates the provenance knowledge of Antarctica's glacial and geologic history from the of terrestrial tills from inland nunataks and follows their contri- continent to the catchment scale and across a broad range of butions to offshore deposits (Licht and Palmer, 2013). We have temporal scales. learned through this strategy that it is possible to obtain sediment eroded from the entirely ice-covered continental interior by col- 2. Background lecting till at the most upstream limits of outlet glaciers before ice crosses through and incorporates sediment eroded from the 2.1. What is the geology of Antarctica that makes this possible? Transantarctic Mountains (Palmer et al., 2012). A diverse suite of provenance tools and multi proxy approaches, ranging from Many of the topics typically addressed with glacigenic sediment traditional sand petrography to isotopic and geochronological provenance studies, such as ice flowline reconstructions and origin methods, have been applied to Antarctic provenance questions and of ice-rafted detritus (IRD), require that the bedrock types and ages will be discussed in the paper. have some spatial variability. The scale of that variability and the Glacigenic sediments provide a broader array of sediment processes by which sediment is eroded and transported affect what provenance analysis opportunities than any other sediment type provenance signatures are resolvable in the geologic record. because of the wide range of grain sizes that characterize them. The Antarctica poses a special challenge because so little bedrock of the provenance tools that have been well tested for sandstones, continent is exposed and the catchment areas for outlet glaciers can mudrocks and conglomerates can be applied in combination to be more than 106 km2. Whereas both the source terranes and gla- glacigenic sediments. The challenge (and opportunity)
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