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COLLABORATIVE RESEARCH: Mapping the Relationship between Subaerial Chemical Weathering, Landscape Evolution, and Climate throughout the Transantarctic Mountains

1.0 Introduction An evolving geologic surface will uniquely preserve evidence of the interaction with its

environment through chemical weathering. The resultant weathering products depend on both their age and the climate under which they formed (e.g., Campbell and Claridge, 1987; Bockheim, 1990). Our goal is to constrain both of these variables and to quantitatively relate them to measures of chemical weathering throughout the Transantarctic Mountains (TAM) to understand the age and evolution of these unique landscapes. We will regionally map weathering products and establish quantitative relationships between landscape age and stability derived from cosmogenic nuclide measurements and weathering intensity derived from laboratory and spectral observations. Remote sensing will enable the study of landscape age and stability over greater spatial extents than previously possible, and will provide a baseline for investigations into the TAM response to modern and future climate change.

Our interdisciplinary and collaborative investigation will (1) verify the relationship between spectral signatures and landscape age and stability, (2) map this association throughout the TAM, and (3) determine the relationship between the observed associations and macro- and micro-climatic processes.

Recent investigations have shown that the chemical alteration of surfaces dominated by the Ferrar Dolerite in the McMurdo Dry Valleys (MDV) can be characterized using orbital multispectral datasets (Salvatore et al., 2013a). By coupling this characterization of chemical alteration with surface exposure ages and landscape erosion/accumulation rates as derived by cosmogenic 3He and 10Be analyses, respectively, we will develop quantitative relationships to extrapolate surface ages and landscape histories using remotely sensed data. While previous studies have suggested a link between remote spectroscopy and relative surface ages (e.g., Kahle et al., 1988; Abbott et al., 2013), this combined analysis will enable large-scale, contiguous analyses of surface and landscape evolution throughout the TAM, which has never before been possible.

On what temporal and spatial scales do these polar landscapes respond to changes in climate? The geographic distribution of our study regions will help to determine whether the observed surface properties throughout the TAM are related to long-term “legacy” climatic properties (e.g., macro-climate), or short-term “modern” propert ies (e.g., micro-climate). By collecting samples, performing detailed laboratory assessments, and deriving relationships between the measured variables and latitude, we will further understand the relationship of these surface and landscape processes to the influence of macro- and micro-climatic properties. We hypothesize that latitude-dependent relationships between spectral, geochemical, and cosmogenic nuclide measurements would indicate the dominance of macro-climatic influences, while the absence of such relationships (in addition to considerable local variability) would indicate the dominance of micro-climatic influences. These predictions will indicate the sensitivity of these polar landscapes to changes in climate and the timescales of communication between the surface and the environment. This forward approach towards understanding polar climate change will help to direct future scientific investigations to regions under immediate climatic distress.

This proposal focuses on landscapes dominated by the Ferrar Dolerite and Kirkpatrick Basalt because of (1) their widespread distribution across more than 20º of polar latitudes (Elliot et al., 1999; Elliot and Fleming, 2004), (2) their well-documented chemical makeup (Fleming et al., 1995, 1997), (3) their high susceptibility to subaerial chemical weathering (Glasby et al., 1981; Salvatore et al., 2013b), and (4) their ease of detection using remote spectroscopic datasets (Salvatore et al., 2013a). In tandem, these unique properties make landscape-scale studies throughout the TAM possible.

Through a combination of orbital analyses, spectral ground truthing and verification, laboratory analyses of surface compositions, and a truly statistical sampling and analysis of cosmogenic nuclides from a variety of geologic landscapes, this proposed work will elucidate the relationships between landscape dynamics, chemical alteration, spectral signatures, and climatic processes at a variety of scales. This multifaceted investigation will enhance our ability to determine surface age and landscape evolution using high resolution remote datasets that are available throughout the TAM.

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2.0 Motivation and Background This proposed work is rooted in previous fundamental studies that suggest a relationship between

landscape evolution, the climate under which they formed, and new remote techniques that are capable of measuring the products of chemical and physical weathering over large geographic areas. Here, we summarize some of these earlier studies and their significant findings, and we describe how modern advancements in analytical techniques can resolve some of the fundamental outstanding questions that remain.

The ice-free landscapes of the TAM uniquely preserve evidence of surface-climate interactions. Some of these surfaces have been devoid of ice and vegetation for ~106 years, and represent the oldest non-lithified landscapes on Earth (Bockheim, 1990, 2013; Marchant et al., 1994, 1996). In particular, soil stratigraphies and their associated weathering products have been shown to correlate with age throughout the TAM (Bockheim, 1990). The antiquity of these surfaces was further corroborated by measuring the accumulation of cosmogenic nuclides in rocks and soil horizons in the TAM (e.g., Brook et al., 1993; Summerfield et al., 1999; Putkonen et al., 2008; Morgan et al., 2010). These investigations have revolutionized our understanding of surface and landscape stability throughout Antarctica, and have shown that geologic landscapes act as local recorders of the complex relationship between the surface and the environment.

The traditional techniques of data collection and analyses required to characterize surface and landscape evolution – extensive field work, sample collection and documentation, sample preparation, mineral separation, detailed laboratory analyses, etc. – are spatially, temporally, logistically, and financially intensive, and present significant challenges to conducting such studies across extensive geographic regions. However, it is clear that a systematic characterization of landscape stability and the influences of modern and legacy climate properties is necessary, especially as the currently observed warming associated with the Anthropocene is overprinting the preserved ancient climate signatures preserved in these landscapes (Bockheim, 2013).

We propose to associate detailed laboratory and cosmogenic nuclide dating analyses to surface weathering signatures derived from remote multispectral datasets using recent and ongoing calibration techniques. Previous studies have shown that dolerites and basalts are particularly susceptible to subaerial chemical weathering and modification under the cold and dry Antarctic environment, and that these surface clasts are generally representative of the age and stability of the landscape (Claridge and Campbell, 1968; Talkington et al., 1976; Bockheim, 1979; Glasby et al., 1981; Allen and Conca, 1991; Bockheim and Ackert, 2007; Bockheim, 2009, 2010; Salvatore et al., 2013b). While the current spatial resolution of orbital assets is not capable of accurately assessing the morphological features associated with surface alteration (e.g., surface pitting, ventifaction, desert pavement development), surface compositions and their resultant spectral signatures can be observed and quantified (Salvatore et al., 2013a). Salvatore et al. (2013b) performed detailed laboratory analyses on alteration rinds formed on dolerites in Beacon Valley of the MDV (Fig. 1) and showed that rind development is driven by anhydrous oxidation of Fe-bearing species at rock surfaces.

Salvatore et al. (2013a) also showed that oxidative weathering of dolerites can be observed remotely using orbital visible/near-infrared (VNIR) spectroscopic datasets from signatures derived from the uppermost ~100 micrometers of the surface. VNIR spectroscopy has since been applied to mapping relative spectral variability throughout the central TAM using the WorldView-2 dataset, which images the surface at an average resolution of ~2 m pix-1 over eight multispectral channels between 427 nm and 908 nm (SpecMap, 2014). This wavelength range is dominated by electronic absorption associated with Fe2+ and Fe3+ in crystalline and nanocrystalline materials (Clark et al., 1990), and Salvatore et al. (2013a) show that basaltic and mafic lithologies (i.e., dolerites and basalts) can be spectrally discriminated in this wavelength region. Furthermore, the presence and thickness of weathering rinds can be correlated with the spectral properties of these mafic lithologies (Fig. 2). The advantageous distribution and spectral distinctiveness of the Ferrar Dolerite and the Kirkpatrick Basalt permit landscape-scale surface investigations of weathering extent to be conducted using remote multispectral datasets. With measurements of surface age and the relationship to the observed spectral signatures, the link between

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these signatures and surface processes could be effectively constrained and used to extrapolate surface ages from doleritic and basaltic landscapes across the TAM.

We propose to use resources and methodologies now available to determine whether quantitative relationships exist between the extent of chemical alteration of dolerites/basalts and the age and evolution of the landscape throughout the TAM. Our proposed work will investigate these relationships, improve our understanding of paleoenvironmental influences on surface stability and chemical weathering, and examine whether long-term “legacy” or short-term “modern” climates play larger roles in landscape evolution. 3.0 Relevance to NSF PLR Antarctic Earth Science Program Goals

The proposed work is highly relevant to the goals of the NSF Polar Programs Antarctic Earth Sciences Program for several reasons. We seek to associate the age and stability of geologic landscapes with the spectral features derived from their uppermost surfaces. Establishing the ability to assess these properties remotely will provide regional context for previous investigations, and will alleviate significant logistical and financial burden in studying weathering and landscape evolution by using currently available resources and data. Multispectral imagery is already archived and currently available through the Polar Geospatial Center (PGC, Award No. 1043681, see Letter of Support - Morin), and the techniques and methodologies developed in this proposed work will be made available to the scientific community via publication and via the PGC. The characterization of the ancient Antarctic landscapes will help to elucidate the preserved paleoenvironmental record while furthering our understanding of the unique processes of chemical alteration and landscape evolution under such extreme climatic and geographic scenarios.

This interdisciplinary research also unites three separate branches of Antarctic sciences: remote sensing, geochemistry, and cosmogenic nuclide techniques. The union of these fields will highlight their relationship to one another and result in novel overlapping datasets. For example, geochemical signatures of altered doleritic and basaltic surfaces will be compared to surface exposure ages and landscape erosion histories, which will help to understand the magnitude and significance of these relationships.

Figure 1. (a) A broken dolerite clast in Beacon Valley, MDV, exhibiting a well-developed alteration rind and an unoxidized interior. (b) A thin section micrograph of the alteration rind, showing a highly oxidized surface and a diffuse gradient into the unaltered interior.

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Figure 2. Laboratory spectra of Ferrar Dolerite (Beacon Valley, MDV) and Kirkpatrick Basalt (Grosvenor Mountains, TAM) surfaces and interiors, showing their unique spectral signatures. Major absorption features are labelled. Spectral resolution was degraded to WorldView-2 bandpasses. Beacon Valley samples are from Salvatore et al. (2013b), and Grosvenor Mountain samples are on loan from the Byrd Polar Research Center Polar Rock Repository.

4.0 Research Summary and Tasks The proposed research

requires a combination of remote spectral analyses, detailed field investigations and sample collection, and subsequent laboratory analyses and data processing. Two field seasons are required in the Antarctic to collect rock and regolith samples, and to ground truth orbital spectral datasets using in situ spectroscopic verification. Year 1 (2015-2016) will make use of the proposed Shackleton Glacier deep field logistics hub to study remote interior locations that are difficult to access and that represent a high-latitude continental climate (e.g., Dalrymple, 1966). Year 2 (2016-2017) will focus on Victoria Land and the Hillary Coast to study the more northern locations that receive climatic influences from both the Antarctic interior and the coast (Dalrymple, 1966). Investigation of multiple sites throughout the TAM is required to accurately assess the effects of climate on the spectral, compositional, and evolutionary history of these ice-free landscapes. The individual sampling locations within each geographic region are also required to understand the role of micro-climatic influences, which have been shown to have significant effects on landscape processes in the MDV (e.g., Marchant and Head, 2007). To accomplish this proposed work, we will undertake six specific research tasks to derive important relationships, investigate the role of macro- and micro-climate variability, and provide a means with which to map landscape age and evolution throughout the TAM: Task 1: Derive spectral index maps of the areas of proposed field work to identify and map compositional diversity due to weathering. Field locations include the Shackleton Glacier region, McMurdo Dry Valleys, Darwin Mountains, and Mesa Range. Task 2: Collect spectral grids at the field locations for ground truthing of spectral properties; collect surface doleritic and basaltic rock samples, and subsurface regolith samples. Task 3: Characterize the surface weathering products associated with the dolerite and basaltic clasts via bulk mineralogy and chemical analysis of rinds. Task 4: Measure surface exposure ages for select doleritic and basaltic samples and derive landscape erosion rates from regolith samples. Task 5: Parameterize the derived analytical datasets to determine the relationship between (a) compositional and spectral signatures of subaerial weathering products, (b) the observed spectral signatures and surface exposure ages, and (c) the observed spectral signatures and regolith erosion rates. Task 6: Create “landscape evolutionary history” maps of (a) the areas investigated during both field seasons utilizing the relationships determined in Task 5, and (b) Arena Valley, MDV, where the regolith erosion history has been independently derived in several previous investigations. Below, we describe the methods that will be employed to complete each task:

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4.1 Task 1: Spectral index maps of field sites. As previously mentioned, doleritic and basaltic surfaces exhibit unique spectral signatures in the VNIR wavelength range that are indicative of both the primary igneous composition as well as secondary weathering processes (Salvatore et al., 2013a,b). Because this wavelength range is dominated by the electronic behavior of Fe2+ and Fe3+ in the material, and because the Ferrar Dolerite and Kirkpatrick basalt contain significantly more iron than the granitic basement rocks (Borg, 1983; Elliot et al, 1999), the observed spectral signatures in dolerite- and basalt-dominated landscapes contain only minor spectral contributions from other lithologies (an assumption that will be further investigated through field and laboratory spectral analyses).

Based on currently available geologic maps (McGregor and Wade, 1969; Grindley and Laird, 1969; Siders and Elliot, 1985; Elliot et al., 1999; Cox et al., 2012), published research, and preliminary spectral index mapping (SpecMap, 2014), we have selected ground truthing sites in landscapes dominated by the Ferrar Dolerite or Kirkpatrick Basalt. The four selected regions for ground truthing include the Shackleton Glacier region, the McMurdo Dry Valleys, the Darwin Mountains, and the Mesa Range (Fig. 3, see Logistical Requirements and Field Plan). These regions span a wide range of Antarctic macro-climate zones (e.g., Dalrymple, 1966). Within each region, multiple sampling locations will be identified that represent a range of geologic and micro-climatic environments, evolutionary histories, and unique spectral signatures. For example, areas including patterned ground, glacial moraines, and scree slopes likely vary in age and geologic histories, and are expected to exhibit different spectral signatures. Specific sampling locations have already been identified in the Shackleton Glacier region and the McMurdo Dry Valleys, and additional spectral interpretation will be required to identify individual locations within the Darwin Mountains and Mesa Range. All remote spectral interpretations will be made using the WorldView-2 (WV2) instrument, which was built and is operated by DigitalGlobe, Inc. WV2 has already been shown effective at discriminating between major lithologies as well as identifying areas of spectral heterogeneity within individual geologic units (SpecMap, 2014, and unpublished data) (Fig. 3). Full-resolution (up to ~ 2 m pix-1) multispectral (eight channels between 427 nm and 908 nm) data are currently available for all of the proposed field sites, and additional data will be targeted for the 2014-2015 austral summer to supplement any gaps throughout the entirety of the TAM. As the lead investigator in the development of the SpecMap product, PI Salvatore will lead the efforts of Task 1. These efforts require identifying surfaces dominated by dolerite and/or basalt. Regions that exhibit highly oxidized signatures in addition to a broad long-wavelength absorption feature due to the presence of pyroxene have been shown to uniquely represent surfaces dominated by dolerite and basalt (Salvatore et al., 2013a; SpecMap, 2014). Once these locations are spectrally mapped, smaller areas of interest can be identified that exhibit spectral heterogeneity in locations thought to be compositionally homogeneous. Glacial moraine complexes will be specifically targeted as locations where orbital investigations, subsequent ground truthing, and cosmogenic nuclide measurements can elucidate the local history of the nearby ice sheet and glaciers. Several glacial moraine complexes have already been targeted for the Shackleton Glacier region (Fig. 3). Atmospheric correction of WV2 data for these regions will be performed using a modified dark object subtraction - regression (DOS-R) method derived for remote polar locations (Salvatore et al., 2013a). This procedure will allow for subsequent laboratory analyses to be directly comparable to these orbital data. Preliminary analyses confirm that spectral trends observed in laboratory measurements are comparable to those observed in atmospherically corrected WV2 data (Fig. 4). 4.2 Task 2: Collect spectral grids, rocks, and regolith in the field. Under the guidance of the orbital spectral mapping products, individual locations will be identified at each field site for detailed ground truthing. When possible, doleritic and basaltic clasts of sufficient size will be collected to permit spectral, geochemical, and cosmogenic nuclide measurements to be performed on the same clasts. PI Salvatore will lead the whole rock and regolith sample collection efforts, with the objective of identifying lithologies and samples that can help to explain the full range of spectral variability observed from orbit. Whole rock samples (~10-25) and surface regolith samples (~5-10) will be collected from

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several sampling locations in each sub-region. These sample collection efforts will also be conducted with spectral verification and surface exposure efforts in mind, as each sample can be of use to numerous scientific investigations. Co-I Ehlmann will lead the spectral gridding and ground truthing efforts to understand pixel-to-pixel and subpixel spectral signatures and variability. Ehlmann will be providing a FieldSpec3 hyperspectral field spectrometer for both field seasons so as to obtain high-quality, calibrated reflectance

Figure 3. (a) Proposed field locations for Year 1 (2015-2016, green circles) and Year 2 (2016-2017, red circles), with the locations of McMurdo Station (red star) and the proposed Shackleton Glacier camp (green star). (b) High resolution spectral index map of a portion of Otway Massif, derived using WorldView-2 data and identical methods to those used in SpecMap (2014). Areas in red, pink, or purple indicate the presence of mafic minerals (e.g., pyroxene) that indicate the presence of doleritic or basaltic compositions. Landforms of interest are identified, as well as a proposed camp location. (c) High resolution spectral index map of Mt. Heekin with the same spectral stretch applied.

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Figure 4. (a) A plot of spectral parameters that show the transition from unaltered dolerite (grey dots) to altered dolerite (red dots) in laboratory spectra (samples from Beacon Valley, MDV, and Salvatore et al. (2013b)). Blue squares represent atmospherically corrected WorldView-2 data for a doleritic region in Wright Valley, MDV, which exhibits the same spectral trend. (b) A dolerite from Beacon Valley, MDV, exhibiting more (left) and less (right) oxidized surfaces. Image is ~1 m in width.

spectra between 350 nm and 2500 nm. These data directly overlap with the WV2 spectral range and will be used to supplement and/or refine the atmospheric correction routine currently in place for remote Antarctic locations (Salvatore et al., 2013a). At each targeted sampling location, 1-5 spectral gridding campaigns will be conducted under the guidance of the orbital spectral mapping product. Each campaign consists of marking off a 400 m2 grid (10 x 10 WV2 pixels) with spectra collected at 1.0 m intervals and calibration conducted after every 20 measurements. Spectra within a grid can be averaged to “truth” the satellite data or separated to assess sub-pixel variability. These data will also be utilized to confirm the dominance of the doleritic and basaltic signatures over other lithologies. Additional spectral measurements will be obtained over each cosmogenic nuclide sampling location. These spectral measurements will also encompass their own separate dataset with which to investigate a range of possible scientific questions, including the extent of aqueous alteration in hypo-thermal and hyper-arid environments throughout the TAM.

Co-I Morgan will lead the cosmogenic nuclide sampling efforts in the field. These analyses will be performed to investigate both surface exposure ages of individual clasts (3He) as well as landscape erosion rates through the collection of regolith samples (10Be). Regolith samples will be collected in vertical profiles from hand-dug soil pits to determine the rates of geomorphic processes active on these surfaces to examine landscape stability. To determine the link between the spectral signature of a surface and its exposure age, we will employ exposure dating techniques with cosmogenic nuclides. Because we are focusing on surfaces dominated by dolerite and basalt, which contain significant amounts of pyroxene, we will utilize cosmogenic 3He produced in pyroxene. 3He is ideal for this investigation because pyroxene minerals are easy to separate from whole rocks, 3He can be readily extracted from pyroxene grains using mass spectrometry, and 3He has been extensively applied to studies of the Ferrar Dolerite and Kirkpatrick Basalt in the past (e.g., Brook et al., 1993; Margerison et al., 2005). The ease of separation and measurement of 3He will also allow for rapid measurements of many samples. At each targeted location, we will collect 15-20 doleritic and/or basaltic clasts for 3He analysis. Depending on the surface, these clasts will either consist of small sections that we extract from a large boulder, or a single clast in its entirety. Because the relationship between local surface exposure ages and spectral signatures at a broader scale has never before been investigated, our field techniques, sampling protocol, and subsequent data interpretation must remain flexible to ensure that we are able to accurately extrapolate beyond the scale of each individual clast. To further explore the relationship between the exposure age of a surface, its spectral signature, and the history of the clasts currently exposed at the surface, we must also understand the rate of landscape evolution (e.g., erosion, burial, accumulation). To determine landscape evolution rates, we will

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measure cosmogenic nuclide concentrations from regolith collected in a vertical profile from hand-dug soil pits. This method has been successfully used to quantify rates of erosion, sublimation of ground ice, mixing, and landscape stability in Antarctica (Putkonen et al., 2008; Morgan et al., 2010; Morgan et al., 2011). For best results, a mineral target must be selected for sampling that is abundant and uniformly disseminated in the subsurface. Quartz is typically present in the regolith at significant quantities, making it an ideal target mineral for such cosmogenic nuclide studies. Thus, we will utilize cosmogenic 10Be measured in quartz from regolith samples to quantify rates of geomorphic processes acting on the landscape. At each targeted location, we will identify a single area for subsurface analysis. We will collect 4-5 samples in a vertical profile from each regolith pit. Over the course of two proposed field seasons, we will collect regolith samples from ~10 pits to analyze for 10Be. Because of the limited number of vertical profiles, we must be particularly mindful of sampling biases and extrapolation to the scale of orbital measurements during our field investigations. 4.3 Task 3: Characterization of weathering products. Chemical, mineralogical, and spectral analyses of the returned samples will be performed following each field season. These assessments will provide a thorough understanding of the evolution of doleritic and basaltic surfaces during chemical alteration. Remote multispectral data observe a snapshot of this landscape evolution; laboratory analyses provide context for these remote spectral measurements to quantitatively determine the nature and duration of the alteration process that produced the observed spectral signatures.

Detailed spectral analyses (visible/near-infrared and Mossbauer) will be performed by a graduate student under the supervision of Co-I Ehlmann, while other mineralogical and chemical analyses (X-ray diffraction, thermal emission spectroscopy, and flux fusion/inductively coupled plasma-atomic emission spectroscopy) will be performed by PI Salvatore and undergraduate students under the supervision of PI Salvatore. Sample preparation will also be performed at Arizona State University by undergraduate students and PI Salvatore. Visible/Near-infrared (VNIR) spectra of whole rock samples, subsampled fragments, and regolith samples will be measured under laboratory settings at the California Institute of Technology (Caltech) using the same FieldSpec3 instrument utilized during field operations. The FieldSpec3 instrument’s spectral range (350 nm - 2500 nm) overlaps with that of the WorldView-2 orbital data. The VNIR spectral range is highly sensitive to vibrational absorptions associated with the presence of adsorbed or structurally bound H2O and OH- molecules, as well as electronic absorptions resulting from the presence of Fe2+ and/or Fe3+ present in defined lattice structures (Clark et al., 1990). These samples will also be measured in the thermal infrared (TIR) at the Arizona State University (ASU) SpecLab facility. TIR wavelengths are sensitive to the molecular vibrations of most geologic mineral species, including silicates, oxides, sulfates, and carbonates. Homogeneous and fine-grained (< 60 micron) powders will be created for additional chemical and mineralogical analyses. Rock surfaces and interiors will be powdered using the methodologies detailed in Salvatore et al. (2013b), whereby a diamond-tipped rotary drill is used to shave the uppermost rock surfaces as to sample the oxidized alteration rind with limited inclusion of underlying unaltered materials. Rock interiors will be powdered in the same fashion to eliminate any possible sampling biases. We estimate that a total of ~40 rock samples (both interior and surfaces) will be processed in this fashion, with an additional ~40 regolith samples. The mineralogy of dolerites and basalts, particularly how the rock surfaces differ from their “unaltered” interiors, is directly related to their respective spectral signatures. Additionally, the mineralogy of regolith samples will provide information as to the modes of alteration occurring throughout the TAM, and how these sediments are related to both the surrounding clasts and the observed spectral signatures from the field and from orbit. X-ray diffraction (XRD) will be performed at the ASU LeRoy Eyring Center for Solid State Science (see Letter of Support - Sharp, and Facilities, Equipment, and Other Resources). XRD analyses will quantify the mineralogical effects of chemical weathering, including the production of secondary phases, the removal of primary igneous phases, and the formation

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of amorphous and micro-crystalline alteration products (Salvatore et al., 2013b). We anticipate ~20 rock surfaces to be analyzed in addition to ~60 powdered samples. Mossbauer (MB) spectroscopy is able to quantitatively assess the distribution of iron among its oxidation states as well as provides information regarding the nature and structure of iron-bearing phases (Klingelhofer et al., 2003). Regolith samples, in addition to powdered rock surfaces and interiors, will be measured to quantitatively determine the extent of iron oxidation and the relative contributions of iron-bearing phases that may contribute to the observed spectral signatures. MB spectra are plotted as relative absorption intensity versus velocity, where velocity indicates the Doppler shift of gamma rays as they interact with a sample (Klingelhofer et al., 2003). MB spectroscopy will be performed at Caltech under the supervision of Co-I Ehlmann, utilizing the laboratory facilities in the Division of Chemistry and Chemical Engineering (see Letter of Support – Peters). This particular spectrometer utilizes a 57Co source at an operational temperature of 273 K. We anticipate analyzing ~30 powdered samples using MB spectroscopy. Bulk chemistry will be determined for rock surfaces, rock interiors, and regolith samples through inductively coupled plasma-atomic emission spectroscopy via the flux fusion technique (Murray et al., 2000) (FF/ICP-AES). These measurements will provide additional clues as to the nature of the chemical alteration process throughout the TAM, particularly the role of liquid water. This technique was previously utilized to show that dolerite surfaces from Beacon Valley are depleted in Ca and Mg and enriched in Na and K relative to their unaltered interiors (Salvatore et al., 2013b). This observation strongly suggests that liquid water plays very little role in the chemical alteration of dolerite surfaces in Beacon Valley. The relationship between the alteration process in Beacon Valley and those observed elsewhere in the TAM has yet to be determined, and this relationship will shed important light on the climatic influences on chemical alteration. FF/ICP-AES will be performed at the Brown University Environmental Chemistry Facility by PI Salvatore (see Letter of Support - Murray and Facilities, Equipment, and Other Resources). 4.4 Task 4: Cosmogenic nuclide measurements and interpretation. As discussed earlier, cosmogenic nuclide measurements will be used to determine the surface exposure ages of individual clasts as well as the geologic history of landscapes throughout the TAM. The accuracy of these measurements and our ability to interpret the results are pivotal in understanding the progression of chemical weathering and spectral signatures as a function of time. Surface exposure dating methods based on cosmic ray-produced nuclides in Earth materials are well established (e.g., Gosse and Phillips, 2001; Granger et al., 2013). The concentration of cosmogenic nuclides in a rock or soil sample depends on three parameters: (1) any prior exposure that the sample had before deposition (often called inheritance), (2) the length of time that sample has been in the upper few meters of Earth’s surface, and (3) the rate of geomorphic activity that changes the depth of the sample over time, such as erosion, accumulation, sublimation, or mixing (Lal, 1991; Lal and Chen, 2005, 2006; Ng et al., 2005).

In order to successfully associate individual measurements with meter-scale orbital observations, we must determine surface exposure ages from a statistically significant population of surface clasts. We choose to analyze cosmogenic 3He for this statistical analysis. 3He is produced in pyroxene grains, which are common in dolerites and basalts, and the production rate of cosmogenic 3He in pyroxene is well understood (Goehring et al., 2010). The separation and purification of pyroxene from whole rock samples is straightforward (Bromley et al., 2009), requiring only simple acids, heavy liquids, magnetic separation, and hand-picking of pyroxene grains. Less than one gram of clean pyroxene is required for 3He measurements and requires average preparation times that are much shorter than for other mineral separates. As such, we will aim to analyze ~200 doleritic and basaltic samples over the two proposed field seasons, giving us the ability to analyze a statistically significant number of samples from each geologic surface that is characterized with spectral analyses. Separation of pyroxenes will be undertaken at Vanderbilt University by undergraduate students who will be trained in these laboratory techniques under the supervision of Co-I Morgan. The concentration of 3He in the pyroxene samples will be measured at the Berkeley Geochronology Center (BGC) under the supervision of Co-I Balco. An undergraduate

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student from Vanderbilt will travel to the BGC for two to four weeks to assist with the measurements and to learn how to run the mass spectrometer. Co-I Balco was the recent recipient of a National Science Foundation Instrumentation and Facilities grant (Award No. EAR-1054079) to construct the analytical system that will be utilized in this award and is designed to analyze large sample suites. To interpret the dolerite and basalt exposure age results, assumptions must be made regarding any prior exposure or erosion history of the clasts being analyzed. Inheritance can create difficulties in Antarctica where many glaciers are cold-based, nuclide production rates are high, and many deposits are millions of years old (Brook et al., 1995), but some authors have reported that samples emerging from ice have little inherited nuclides (Staiger et al., 2006) and that inheritance issues can be avoided with careful sample collection (Joy et al., 2014). The erosion rate of these samples can be estimated from bedrock erosion rates (Summerfield et al., 1999), and we will also sample doleritic and basaltic bedrock wherever possible to determine average erosion rates from our study areas. Numerous other studies have successfully dated glacial deposits with cosmogenic exposure ages in Antarctica, lending additional credence to the proposed activities (e.g., Brook et al., 1993; Brook and Kurz, 1993; Stone et al., 2003; Mackintosh et al., 2007; Todd et al., 2010; Bromley et al., 2010; Joy et al., 2014). These considerations are directly applicable to understanding the chemical weathering of rock surfaces, as chemical weathering is subject to the same preservation and inheritance issues as the accumulation of cosmogenic nuclides. Measuring the concentration of cosmogenic nuclides collected from vertical regolith profiles will determine the geologic histories of these landscapes and relate them to the derived surface ages and measured spectral signatures. The principles behind determining surface erosion rates are rooted in the fact that the production of cosmogenic nuclides decreases exponentially with depth in soil profiles. Because different geomorphic processes result in variations in the depth and rate of soil burial/exhumation, measured cosmogenic nuclide patterns in vertical soil profiles are indicative of different processes (erosion, accumulation, sublimation, and mixing), and their concentrations determine the rates of these processes (Fig. 5). This method has been successfully applied in Antarctica to determine regolith erosion rates of 0.2 - 4 m/Myr and sublimation rates of 0.7 - 12 m/Myr (Putkonen et al., 2008; Morgan et al., 2010, 2011).

Quartz is one of the most abundant minerals in Antarctic soils (e.g., Campbell and Claridge, 1987), and so we choose to measure the abundance of cosmogenic 10Be in quartz grains to derive the rate and mechanisms of landscape evolution throughout the TAM. The production rate of 10Be in quartz is well understood and the laboratory methods for quartz purification are well documented (e.g., Balco et al., 2008; Balco, 2011). Quartz will be separated and purified at Vanderbilt University by undergraduate students under the supervision of Co-I Morgan. Extraction of Beryllium and conversion to BeO in preparation for analysis by accelerator mass spectrometry will be performed at the Purdue Rare Isotope Measurement (PRIME) Laboratory at Purdue University (see Letter of Support - Caffee). An undergraduate student from Vanderbilt University will travel to the PRIME Laboratory for two to three weeks to perform these additional preparations for analysis under the supervision of Greg Chmiel (Staff, PRIME Laboratory).

4.5 Task 5: Parameterize analytical datasets. Determining quantitative relationships between the measured spectral, compositional, and cosmogenic nuclide analyses is essential to understand the environmental influences on the weathering process. As mentioned earlier, the products of chemical alteration (including the observed spectral signatures), relative to their unaltered parental lithology, are due to a combination of their age and the climate under which they formed. By analytically determining the products of chemical alteration and the age of the surfaces under investigation, we are able to uniquely constrain the climatic environments responsible for their formation. The relationship between spectral signatures, alteration product composition, surface exposure ages, and the rates and modes of landscape evolution will all be evaluated. Potential relationships of interest are discussed below:

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Figure 5. (a) Model predictions of cosmogenic nuclide concentrations with depth given different landscape evolution histories. (b) 10Be nuclide measurements with depth in the Koenig Colluvium in Wright Valley, MDV, with a best-fit curve that represents an erosion rate of 1.6 m/Myr. (c) Sample soil pit in the Koenig Colluvium showing a dolerite-rich desert pavement capping the deposit.

Co-I Ehlmann will supervise the Caltech graduate student in associating the spectral signatures measured in the laboratory (e.g., absorption depths, spectral slope intensity parameters) with surface exposure ages derived under the supervision of Co-I Morgan. As VNIR spectroscopy is one of the most sensitive analytical techniques to surface oxidation (Salvatore et al., 2013b), we expect the relationship between these spectral signatures and the exposure age of the rock surface will provide a robust estimate for the rate of development of oxidative weathering rinds. PI Salvatore will then utilize these established relationships to parameterize the WV2 orbital dataset and to derive remote parameters to estimate surface exposure ages from orbit. Sampled glacial moraine complexes will be critical in testing the relationship between observed spectral signatures and surface exposure ages. Glaciers deposit a combination of sediment and clasts as they stagnate and retreat following their advancement onto ice-free landscapes. Previous age determinations of these moraine complexes relied upon in situ field investigations, typically utilizing cosmogenic nuclide dating techniques (e.g., Brook et al., 1993; Brook and Kurz, 1993; Stone et al., 2003; Mackintosh et al., 2007; Todd et al., 2010; Bromley et al., 2010; Joy et al., 2014). The ability to estimate the relative age and stratigraphy of moraine complexes using remote multispectral datasets will provide an additional tool to constrain the timing and magnitude of ice sheet and glacier dynamics throughout the TAM. Quantifying these relationships over a range of latitudes and climate zones will also indicate the degree to which local-, regional-, and continental-scale climate properties influence the behavior of the cryosphere throughout Antarctica.

Similar relationships will be investigated between spectral signatures and landscape erosion rates. These relationships will be used to determine whether the clasts present at the surface are truly representative of the stability of the immediate subsurface. If our original hypothesis is correct, heavily oxidized and altered doleritic and basaltic clasts on the surface will be representative of landscapes that exhibit slow erosion rates. Conversely, less weathered surface clasts should be associated with either geologically young landscapes or landscapes with extremely rapid erosion rates. If the null hypothesis is correct, then the extent of dolerite or basalt weathering observed at the surface will have no relationship to the measured erosion rates from vertical regolith pits, which is an equally intriguing result.

Similar to the investigation of glacial moraine complexes, evaluating the relationship between landscape evolution and spectral properties over a range of macro- and micro-climates will be used to produce geographically dependent calibration factors to be used when relating orbital spectral signatures to surface and subsurface properties. The similarity (or disparity) of these calibration factors will provide information regarding the role that climate plays on surface alteration and the evolution of ice-free landscapes throughout the TAM. If systematic variations exist between the Shackleton Glacier region and the Mesa Range, one may assume that macro-climatic (legacy) variations driven largely by latitude play the most significant role in landscape modification. Alternatively, if non-linear trends exist, particularly

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within a given geographic location, micro-climatic (modern) influences are the likely result, which would indicate that the communication between the surface and modern climatic properties occurs on geologically rapid timescales.

4.6 Task 6: Create “landscape evolutionary history” maps. The previously accomplished tasks

will allow us to assess the landscape evolutionary history in the regions where we collected samples. The goal of Task 6 is, therefore, to produce spectral mapping products of landscape evolutionary history for (a) the landscapes visited during our field seasons, and (b) for an independent test location in Arena Valley of the MDV. This task will be led by PI Salvatore.

Orbital datasets obtained from the Polar Geospatial Center (see Letter of Support - Morin) will be atmospherically corrected as described in Task 1 and will used ground truthing spectral measurements obtained in Task 2 to verify and update these techniques. Once the orbital data have been corrected to surface reflectance, the relationships determined in Task 5 will be applied to these data using image processing software. These raster files will then be imported into a geographic information system software package (ArcGIS) for mapping purposes and to create vector overlays. Individual vector files will be created for each derived surface and landscape unit. All data will be made available following publication.

The second goal for Task 6 is to determine how robust the association between spectral signatures and landscape evolutionary history is in a region that was not investigated in the field during this analysis. We choose to test our capabilities in Arena Valley, where doleritic clasts dominate the surface and previous studies (Denton et al., 1989; Bockheim, 1977, 1982; Brook et al., 1993; Brook and Kurz, 1993; Marchant et al., 1994; Swanger and Marchant, 2007; Putkonen et al., 2008; Morgan et al., 2010) have independently assessed landscape stability and erosion rates. Using the same remote sensing techniques applied to our field sites, and after assuming the macro- and micro-climatic influences that best relate to Arena Valley (as determined in Task 5), we will independently map the landscape evolutionary history in Arena Valley as determined from orbit. This mapping product will be compared to previous cosmogenic nuclide and surface analyses to independently determine the utility of this technique. Of particular interest is whether the history of the glacial moraine complex can be effectively characterized.

The use of remote spectroscopic datasets to create geospatial datasets of landscape evolutionary history is a unique and innovative application of these widely available datasets. Following the publication of our methods and geographic/climatic calibration factors, other investigators will be able to replicate our techniques to derive landscape evolutionary history maps throughout the TAM. These calibration factors will also be made available through the Polar Geospatial Center. 5.0 Summary

Relating remote spectroscopic observations to the geochemical and evolutionary history of different landscapes throughout the TAM will revolutionize the way that geologic investigations are performed in the Antarctic. The tools developed in this study will provide a better understanding of the climatic influences on the evolution of the Antarctic landscape in the past, while providing a means of assessing the current and future effects of a changing climate during the Anthropocene epoch. The integration of orbital assets into the previously established fields of chemical weathering, landscape evolution, and cosmogenic nuclide analyses presents a means of rapidly, remotely, and efficiently assessing such properties, and will place previous studies into regional geographic context. 6.0 Impact of the Proposed Work on the State of Knowledge in the Field

The ability to remotely assess surface stability and landscape evolution will provide the scientific community with a new ability to reconcile remote, field, and laboratory analytical techniques. This proposed work will develop new applications and produce new calibrations for orbital datasets that are currently available to the Antarctic research community. In particular, the availability, resolution, and coverage of the WorldView-2 instrument will allow for similar remote investigations to be conducted throughout the TAM, and will identify areas of interest for continued monitoring and/or more detailed in

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situ investigations. Continuous monitoring will help us to better understand how these important windows into the continent’s geology are adapting to the changing climate of the Anthropocene epoch (Bockheim, 2013). The application of this technique to assess moraine complexes will also strengthen future glaciology and paleoclimatology studies in the TAM, which would benefit from accurate estimations of moraine ages and modification history.

During the International Workshop on Antarctic Permafrost and Soils in 2004 (Bockheim, 2005), the scientific community identified eight future research needs and priorities. These future research needs include understanding landscape dynamics and evolution, the impacts of climate change, physical and chemical weathering, and surficial processes along environmental gradients. The proposed research will address all of these future research topics. Lastly, the “application of technology and new research methods” in researching Antarctic soils was emphasized as a priority for the future, and our proposed work is an exemplary example of how new technologies can complement current research methodologies. 7.0 Broader Impacts of the Proposed Work

The proposed work has several broader impacts that will benefit the scientific community. First, we will be utilizing and enhancing the current capabilities of data that are currently available to the Antarctic scientific community. These techniques, in addition to the landscape evolutionary history maps produced during this project, will be made available to the scientific community via publication and via the Polar Geospatial Center (see Letter of Support - Morin). Second, we will be donating all collected samples to the Polar Rock Repository at the Byrd Polar Research Center when analyses are complete (see Letter of Support – Grunow). These samples will be the first donated sample suite collected specifically for the verification of remote spectral datasets. Third, we will be providing support for seven undergraduate student research opportunities and one graduate student. The graduate student (supported through Caltech) will focus on field and laboratory spectral measurements under the guidance of Co-I Ehlmann. The undergraduate students will have the opportunity to be actively involved in the research experience, including field work, sample collection, sample preparation, data acquisition, analysis, and the presentation of results. Those undergraduate students visiting the BGC will be educated on mass spectrometry and will have the opportunity to interact with the Berkeley Earth science research community. Five undergraduate students will be supported through Vanderbilt University and two undergraduate students will be supported through Arizona State University. Fourth, PI Salvatore is an early career scientist with close ties to the planetary science community. The methods and results of this proposed research will have significant implications for the remote spectroscopic datasets currently available for Mars, where orbital datasets are abundant but the means of ground truthing are limited. Lastly, PI Salvatore has partnered with Science Arizona, a non-profit and volunteer-run organization that aims to promote science literacy in Arizona, to educate the broader community about Antarctic research and the potential impacts of future climate change (see Letter of Support – Kane). Possible venues to highlight this research include giving talks at local science cafes and virtual lectures and question/answer sessions with local K-12 students. 8.0 Duration, Work Plan, and Deliverables

A timeline of the proposed work is provided in Table 1. While the exact dates of this investigation are subject to change, we have anticipated the duration of funding to be from 01 August 2015 to 31 July 2018. For details regarding the proposed field investigations, please refer to the Logistical Requirements and Field Plan.

Year 1 (01 August 2015 - 31 July 2016) will consist of completing Task 1 for at least the Shackleton Glacier region. This area has already been spectrally mapped as a portion of the SpecMap project (SpecMap, 2014), but the detailed characterization of doleritic- and basaltic-dominated landscapes as well as atmospheric correction has yet to be performed. The first field season (2015-2016) to the Shackleton Glacier region will also accomplish some of Task 2, while Task 3 and Task 4 will begin following the arrival of samples from the Antarctic.

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Table 1. Proposed timeline of major events associated with this proposed work. More detailed information regarding field sites and field logistics can be found in Logistical Requirements and Field Plan.

Year 2 (01 August 2016 - 31 July 2017) will consist of spectral mapping of the MDV, the Darwin Mountains, and the Mesa Range (Task 1), continued sample preparations and analyses (Tasks 3 and 4), and sample collection during the 2016-2017 field season (Task 2). Once all samples have returned from the field, Task 3 and Task 4 will continue on the 2016-2017 sample suite.

Year 3 (01 August 2017 - 31 July 2018) will see the completion of Task 3 and Task 4, data quantification (Task 5), and the generation of landscape evolutionary maps (Task 6). 8.1 Deliverables. Deliverables associated with this proposed work include (1) refinements to spectral calibration techniques, (2) the quantification of numerous spectral and compositional variables, in addition to quantitative links between surface exposure, landscape evolution, and spectral signatures, (3) maps of landscape evolutionary history for the regions investigated in this study, as well as the tools necessary to produce landscape evolutionary history maps elsewhere throughout the TAM, and (4) a rock and regolith sample suite (to be donated to the Polar Rock Repository) with accompanying high quality geographical, spectral, and compositional data. 9.0 Personnel Contributions

Dr. Mark Salvatore is the PI of this proposed work and will be leading pre-field mapping and planning efforts, sample collection, compositional analyses, and the creation of landscape evolutionary mapping products. He has extensive experience with sample collection in the Antarctic, chemical and mineralogical laboratory analyses, remote and laboratory spectroscopic measurements, and remote spectroscopic investigations of ice-free regions of the Antarctic. He has consulted with the Polar Geospatial Center to identify the geologic utility of the WorldView-2 dataset, and is currently funded through the NSF to spectrally map the central Transantarctic Mountains using remote data. He will be advising two undergraduate research assistants in sample preparation and analysis techniques. Salvatore is an early career scientist, having received his Ph.D. in 2013.

Salvatore is a Postdoctoral Research Scholar at Arizona State University under Dr. Philip Christensen, who will serve as the unfunded internal institutional investigator for this project.

Dr. Bethany Ehlmann is a Co-I of this proposed work and will lead the field and laboratory spectral collection and analyses tasks with the assistance of a part-time graduate student. Ehlmann is an Assistant Professor of Planetary Science at Caltech and a research scientist at the Jet Propulsion Laboratory. She is experienced in the analysis of ground truthing remotely acquired reflectance data, multiple laboratory techniques, and the application and testing of quantitative VNIR unmixing models. She has worked on several martian missions and has led numerous collaborative research projects.

Dr. Daniel Morgan is a Co-I of this proposed work and a Senior Lecturer at Vanderbilt University. Morgan will lead the collection of rock and regolith samples for cosmogenic nuclide analyses, in addition to sample preparation, mineral separation, and sample analysis. He is a geomorphologist with experience utilizing cosmogenic nuclides to determine ages and rates of geomorphic surface processes in Antarctica, Peru, California, and the Pacific Northwest. Morgan has field experience in the McMurdo Dry

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Valleys and the Miller Range of the TAM. He was a participant in the deep field central TAM camp at the Bowden Névé during the 2010-2011 field season. At Vanderbilt University, Morgan has advised several honors undergraduate theses and field projects, and is currently the Director of Undergraduate Studies for the Department of Earth and Environmental Sciences at Vanderbilt University.

Dr. Greg Balco is a Co-I of this proposed work. He is a researcher at the Berkeley Geochronology Center with wide experience in Earth science applications of cosmogenic nuclide geochemistry. Although he has worked extensively in Antarctica, including two field seasons with Co-I Morgan, he will not participate in the proposed field work. His role in this project is to facilitate cosmogenic 3He measurements by training and supervising Co-I Morgan and his students in use of the Berkeley Geochronology Center’s noble gas mass spectrometers.

Dr. Joseph Levy is a Collaborator on this proposed work and is a Research Associate at the University of Texas Institute for Geophysics. Levy is the PI of an NSF Antarctic Integrated System Science (AISS) proposal (submitted in April, 2014) that will utilize airborne spectrometers to assess geochemical cycling throughout the MDV at high spatial and spectral resolutions. The scientific intersection of this grant with work proposed here is an expected source of fruitful collaboration. 10.0 Results from Prior NSF Support 10.1 Salvatore. PLR-1414378, “EAGER: Surface Variability and Spectral Analyses of the Central Transantarctic Mountains, Antarctica,” Award Amount: $168,586, Period of Support: 01/01/2014 – 12/31/2015. Intellectual Merit: WorldView-2 data are currently being utilized for spectral characterization of the central Transantarctic Mountains. This work is designed to supplement currently available geologic maps of the region with high-resolution compositional data to support research at the proposed 2015-2016 Shackleton Glacier camp. Since the start of funding, more than 90 satellite images have been processed to show “relative spectral variability,” and atmospheric correction is currently underway. As promised, this “SpecMap” data product was made publicly available as of 01 March 2014 via the Polar Geospatial Center website at http://pgc.umn.edu/about/research/specmap. Broader Impacts: Since its launch, SpecMap has received 202 page visits from unique IP addresses, indicating that this product is of great interest to the scientific community. In addition, Salvatore has been contacted directly by four researchers with interests in collaboration. This research has proven the utility of the WorldView-2 dataset as a geologic and geochemical tool, and standardized calibration and correction practices are currently under development and will be shared with the scientific community. 10.2 Ehlmann. AST-1313461, “The Nature of Europa’s Surface and Ocean from New Infrared Spectroscopy,” PI: Michael Brown, Award Amount: 335,570, Period of Support: 06/01/2013 – 05/31/2016. Intellectual Merit: Determining the composition of ices on Europa dictates the depth to the inferred liquid ocean and the geochemistry of waters. Keck NIRSPEC data recently acquired provide the best spectral resolution of the Europan surface. Broader Impacts: A first-year graduate student has begun training on this project and will begin dissemination of results at conferences in the fall. 10.3 Morgan. No current or prior NSF funding as Principal Investigator. 10.4 Balco (with Morgan as non-PI collaborator). PLR-0838968, “Collaborative Research: Systematic Analysis of Landscape Evolution and Surface Ages in the Transantarctic Mountains,” PIs: Putkonen, Balco, Shuster, Award Amount: $366,712, Period of Support: 09/01/2009 – 08/31/2013. Intellectual Merit: This project applied geomorphic observations and cosmogenic nuclide measurements to quantify rates of erosion, sediment transport, and landscape evolution in ice-free areas of the central Transantarctic Mountains. Analytical work is ongoing and contributions include quantifying the age of glacial tills, sublimation rates of subsurface ice, and bedrock and surface erosion rates. A focus of this work is to exploit the relative speed and efficiency of cosmogenic noble gas measurements to collect spatially dense data; more than 150 cosmogenic 21Ne analyses have been made to date. Broader Impacts: Impacts are focused in graduate and undergraduate education. Balco and Morgan co-trained one graduate student in cosmogenic nuclide geochemistry, and Morgan trained five undergraduate students in sample preparation and the interpretation of data and results. All students were co-authors on recent conference presentation, and the results from this project have been presented in five total abstracts.

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