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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. Evaluating ground‐penetrating radar antenna performance for investigating Mississippian mound construction compared with data from solid‐earth cores and magnetometry

   https://doi.org/10.1002/arp.1772  

   Schurr, Mark R. ; Monaghan, G. William ; Herrmann, Edward W. ; Pike, Matthew ; Wilson, Jeremy J. ( March 2020 , Archaeological Prospection)

   Mississippian mounds in the south‐eastern and mid‐continental United States often contain multiple construction stages and a diverse array of features. Investigating mound construction with excavation is expensive, logistically challenging, and sometimes politically impossible. Three mounds at the Angel site (12VG1), a Mississippian village (caad1100–1450) in the lower Ohio River Valley, were investigated with non‐invasive geophysical and minimally invasive geoarchaeological methods. We compare the efficacy of two different ground‐penetrating radar (GPR) antenna frequencies (250 and 500 MHz) for detecting elements of mound construction previously identified with solid‐earth cores, magnetometry, and electrical resistance tomography. Solid‐earth cores provide stratigraphic information about mound layers and construction soils and materials with low horizontal spatial resolution. Surface magnetometry provides information on shallow features, such as buried building walls and floors at high resolution, but little information about depth. Radar profiles taken with 500 MHz and 250 MHz antennae were evaluated to determine which antenna frequencies are most suitable for detecting features and strata that had been documented using the other methods. Utilizing the solid‐earth cores for velocity correlations, the 500 MHz antenna provided the most useful information about prehistoric structures near the mound surface, but was limited by its relatively shallow penetration depth. The 250 MHz antenna was not able to resolve shallow features as clearly as the 500 MHz antenna. However, it was able to detect possible interior mound platforms and features, although without providing many details about possible buried structures. In combination, GPR, solid‐earth cores, and magnetometry provided new information about the construction of mounds at the Angel site.

    

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3. ImpDAR: an open-source impulse radar processor

   https://doi.org/10.1017/aog.2020.44  

   Lilien, David A. ; Hills, Benjamin H. ; Driscol, Joshua ; Jacobel, Robert ; Christianson, Knut ( October 2020 , Annals of Glaciology)

   Abstract Despite widespread use of radio-echo sounding (RES) in glaciology and broad distribution of processed radar products, the glaciological community has no standard software for processing impulse RES data. Dependable, fast and collection-system/platform-independent processing flows could facilitate comparison between datasets and allow full utilization of large impulse RES data archives and new data. Here, we present ImpDAR, an open-source, cross-platform, impulse radar processor and interpreter, written primarily in Python. The utility of this software lies in its collection of established tools into a single, open-source framework. ImpDAR aims to provide a versatile standard that is accessible to radar-processing novices and useful to specialists. It can read data from common commercial ground-penetrating radars (GPRs) and some custom-built RES systems. It performs all the standard processing steps, including bandpass and horizontal filtering, time correction for antenna spacing, geolocation and migration. After processing data, ImpDAR's interpreter includes several plotting functions, digitization of reflecting horizons, calculation of reflector strength and export of interpreted layers. We demonstrate these capabilities on two datasets: deep (~3000 m depth) data collected with a custom (3 MHz) system in northeast Greenland and shallow (<100 m depth, 500 MHz) data collected with a commercial GPR on South Cascade Glacier in Washington. 

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4. 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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5. Active Seismic Refraction, Reflection, and Surface‐Wave Surveys in Thick Debris‐Covered Glacial Environments

   https://doi.org/10.1029/2023JF007304  

   Kuehn, Tyler ; Holt, John W. ; Johnson, Roy ; Meng, Tyler ( January 2024 , Journal of Geophysical Research: Earth Surface)

   Debris‐covered glaciers (DCG) and rock glaciers have been increasingly studied in recent years because of the role they play within local watersheds, glacial ablation models due to climate change, and as analogs for buried ice features on planetary bodies such as Mars. Characterizing the supraglacial debris layer is a large part of these efforts. Geophysical exploration of DCG has mostly excluded active seismic methods, with the exception of refraction studies, due to the attenuating properties of the debris cover and field survey efficiency. We evaluate the accuracy, field efficiency, and effectiveness of seismic refraction, reflection, and surface‐wave surveys for determining the elastic properties of the debris layer and any underlying layers on DCG using the Sourdough Rock Glacier in Southcentral Alaska as a test site. We provide evidence for imaging an ultra‐shallow seismic reflection from the bottom of the loose debris layer using ultra‐dense receiver arrays and compare it to ground‐penetrating radar (GPR) images taken along the same profiles. We also detail how reliable dispersion curve images can be extracted from the surface wave package of the seismic data using the multi‐channel analysis of surface waves technique, which allows for the (s)‐wave profile to be inverted for. We find this could be a valuable addition to the toolbox of future geophysical investigations on DCG.

    

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