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1. Ground Penetrating Radar Investigation of Late Pleistocene Shorelines of Pluvial Lake Clover, Elko County, Nevada, USA

   https://doi.org/10.3390/quat3010009  

   Munroe, Jeffrey S. (March 2020, Quaternary)

   Beach ridges constructed by pluvial Lake Clover in Elko County, Nevada during the Late Pleistocene were investigated with ground-penetrating radar (GPR). The primary objective was to document the internal architecture of these shorelines and to evaluate whether they were constructed during lake rise or fall. GPR data were collected with a ground-coupled 400-Mhz antenna and SIR-3000 controller. To constrain the morphology of the ridges, detailed topographic surveys were collected with a Topcon GTS-235W total station referenced to a second class 0 vertical survey point. GPR transects crossed the beach ridge built by Lake Clover at its highstand of 1725 m, along with seven other ridges down to the lowest beach at 1712 m. An average dielectric permittivity of 5.0, typical for dry sand and gravel, was calculated from GPR surveys in the vicinity of hand-excavations that encountered prominent stratigraphic discontinuities at known depths. Assuming this value, consistent radar signals were returned to a depth of ~3 m. Beach ridges are resolvable as ~90 to 150-cm thick stratified packages of gravelly sand overlying a prominent lakeward-dipping reflector, interpreted as the pre-lake land surface. Many ridges contain a package of sediment resembling a buried berm at their core, typically offset in a landward direction from the geomorphic crest of the beach ridge. Sequences of lakeward-dipping reflectors are resolvable beneath the beach face of all ridges. No evidence was observed to indicate that beach ridges were submerged by higher water levels after their formation. Instead, the GPR data are consistent with a model of sequential ridge formation during a monotonic lake regression. 

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2. I-165-M GPR Field Report 2019-2020

   https://doi.org/10.15784/601669  

   Brook, Edward; Nesbitt, Ian (January 2023, U.S. Antarctic Program (USAP) Data Center)

   This document details the ground-penetrating radar (GPR) collection activities carried out by I. Nesbitt in the Allan Hills during the 2019-2020 field season. This document is intended as an informal catalogue of the fild work and post-processing activities performed at the Allan Hills and later at McMurdo and elsewhere. It contains preliminary post-processing and analysis only. Any interpretation made and presented in this report based on the data herein is subject to change pending further examination. GPR was used to examine sub-ice bedrock topography and the stratigraphic relationship between two shallow ice core drill sites (CMC1 and CMC2), as well as to explore potential future drill sites. In accordance with. the project's objective to drill and analyze ancient ice at relatively shallow depths, the two main features of interest in this study are 1) bedrock topographic features in which ancient ice could be trapped, and 2) englacial stratigraphic layers, especially those which may represent large age discontinuities. 

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3. Mapping a Subsurface Water Channel with X-Band and C-Band Synthetic Aperture Radar at the Iron Age Archaeological Site of ‘Uqdat al-Bakrah (Safah), Oman

   https://doi.org/10.3390/geosciences8090334  

   Wiig, Frances; Harrower, Michael; Braun, Alexander; Nathan, Smiti; Lehner, Joseph; Simon, Katie; Sturm, Jennie; Trinder, John; Dumitru, Ioana; Hensley, Scott; et al (September 2018, Geosciences)

   Subsurface imaging in arid regions is a well-known application of satellite Synthetic Aperture Radar (SAR). Archaeological prospection has often focused on L-band SAR sensors, given the ability of longer wavelengths to penetrate more deeply into sand. In contrast, this study demonstrates capabilities of shorter-wavelength, but higher spatial resolution, C-band and X-band SAR sensors in archaeological subsurface imaging at the site of ‘Uqdat al-Bakrah (Safah), Oman. Despite having varying parameters and acquisitions, both the X-band and C-band images analyzed were able to identify a subsurface paleo-channel that is not visible on the ground surface. This feature was first identified through Ground Penetrating Radar (GPR) survey, then recognized in the SAR imagery and further verified by test excavations. Both the GPR and the excavations reveal the base of the paleo-channel at a depth of 0.6 m–0.7 m. Hence, both X-band and C-band wavelengths are appropriate for subsurface archaeological prospection in suitable (dry silt and sand) conditions with specific acquisition parameters. Moreover, these results offer important new insights into the paleo-environmental context of ancient metal-working at ‘Uqdat al-Bakrah and demonstrate surface water flow roughly contemporary with the site’s occupation. 

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4. Comprehensive multi frequency airborne mapping of the southern flank of Dome A: results of the COLDEX airborne program.

   https://doi.org/10.5194/egusphere-egu24-12995  

   Young, Duncan; Paden, John; Kerr, Megan; Singh, Shivangini; Kaundinya, Shravan; Yan, Shuai; Vega_González, Alejandra; Greenbaum, Jamin; Buhl, Dillon; Ng, Gregory; et al (March 2024, Copernicus EGUsphere)

   The Center for Oldest Ice Exploration (COLDEX) is a US initiative funded to search for climate records over the last 5 million years, including locating sites for an accessible continuous ice core going back 1.5 million years. As part of this effort, COLDEX has mapped the southern flank of Dome A, East Antarctica using an instrumented Basler, including dual frequency radar observations of the ice sheet and ice bed, as well as potential fields measurements (see presentation by Kerr in EGU session G4.3) across two field seasons from Amundsen-Scott South Pole Station. The aerogeophysical system included both the UTIG VHF MARFA radar system operating at 52.5-67.5 MHz, as well as a new large high resolution UHF array from CReSIS operating at 670-750 MHz operating simultaneously. A goal of this project was to obtain airborne repeat interferometry for segments of the survey, as well as directly feed ice sheet models using englacial isochrons (see Singh presentation in EGU session CR5.6). These goals lead to a survey explicitly designed around ice sheet flow lines. While prior work had sampled the region at lithospheric scales, the COLDEX survey had two components - the first was to map the region at crustal scales (line spacing of 15 km), and the second was to map subareas at ice sheet scales (line spacing of 3 km). Immediate observations include an extensive basal unit and strong discontinuity in englacial stratigraphy that runs across the survey area and appears correlated with changes in bed interface properties. The airborne campaign will be used to inform follow up ground campaigns to understand processes relevant for old ice preservation. 

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5. Formation and evolution of an extensive blue ice moraine in central Transantarctic Mountains, Antarctica

   https://doi.org/10.1017/jog.2019.83  

   Kassab, Christine M.; Licht, Kathy J.; Petersson, Rickard; Lindbäck, Katrin; Graly, Joseph A.; Kaplan, Michael R. (February 2020, Journal of Glaciology)

   null (Ed.)

   Abstract Mount Achernar moraine is a terrestrial sediment archive that preserves a record of ice-sheet dynamics and climate over multiple glacial cycles. Similar records exist in other blue ice moraines elsewhere on the continent, but an understanding of how these moraines form is limited. We propose a model to explain the formation of extensive, coherent blue ice moraine sequences based on the integration of ground-penetrating radar (GPR) data with ice velocity and surface exposure ages. GPR transects (100 and 25 MHz) both perpendicular and parallel to moraine ridges at Mount Achernar reveal an internal structure defined by alternating relatively clean ice and steeply dipping debris bands extending to depth, and where visible, to the underlying bedrock surface. Sediment is carried to the surface from depth along these debris bands, and sublimates out of the ice, accumulating over time (>300 ka). The internal pattern of dipping reflectors, combined with increasing surface exposure ages, suggest sequential exposure of the sediment where ice and debris accretes laterally to form the moraine. Subsurface structure varies across the moraine and can be linked to changes in basal entrainment conditions. We speculate that higher concentrations of debris may have been entrained in the ice during colder glacial periods or entrained more proximal to the moraine sequence. 

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