<p> Cryoconite holes are vertical columns of meltwater within the shallow subsurface of glaciers. In the McMurdo Dry Valleys (MDV) of Antarctica cryoconite holes are a source of meltwater and harbor microbial communities in an otherwise arid environment with low biologic activity. The holes form as sediments on the ice surface, which are darker than the surrounding ice, are preferentially heated by solar radiation. The warm sediments melt the underlying ice and migrate downwards. An ice lid forms, isolating them from the below-freezing atmosphere enabling them to remain thawed. In this study, field observations, laboratory experiments, and numerical modeling are used to characterize the fundamental variables controlling cryoconite hole development. </p><p> Field and laboratory results show that solar radiation drives cryoconite hole melting by controlling the energy available to the cryoconite and to warm the surrounding ice. Holes deepen further in warmer ice. Laboratory results show that at temperatures of &ndash;10 &deg;C at least 405 (W m^&ndash;2) are needed to warm the cryoconite sufficiently to melt surrounding ice. Numerical modeling shows that increased radiation flux into the subsurface and warmer air temperatures cause cryoconite to descend deeper and the meltwater-filled holes to enlarge, while increased surface ablation decreases their average depth. Cryoconite holes thaw sooner and refreeze later when the optical properties of the ice facilitate greater radiation transmission. Cryoconite warms the ice significantly more than ice without cryoconite. Within the melt-filled hole, the heat capacity of the water keeps the surrounding ice warm for several weeks after the cryoconite-free ice has cooled. The cryoconite itself is last to completely freeze.</p><p>

<p> The upper Wilcox group in the Tullos-Urania oilfield has not been imaged with enough resolution for interpretation. Prior seismic data collected in the area was designed for formations much deeper than the Wilcox Group. The purpose of this investigation was to produce an image of the subsurface and identify formations of interest for production of oil and gas by applying different processing methods. With an optimal processing workflow and use of limited well logs, an interpretation of the data was provided to the oil company. </p><p> The advantage of using an accelerated weight-drop source is the shallow horizons, ranging from 1,500 to 3,000 feet in-depth, become distinct with higher resolution. The acquisition achieved a dominant frequency averaging around 45&ndash;65 Hz compared to a nearby pre-existing 3D survey volume with a dominant frequency range of 15&ndash;35 Hz. Refracted waves dominated the unprocessed shot records from this data. Consequently, the field records had a significantly low signal-noise ratio. Therefore, the most critical processing steps focused on signal processing and velocity analysis. Without enough ground roll and noise suppression, the velocity analysis would not have been coherent. Some obstacles faced with processing the data included a sparse horizontal sampling and a lack of velocity logs along the seismic line. </p><p> The results of this study included a set of stacked lines, velocity models, and an optimal processing workflow for future high-frequency shallow seismic exploration surveys in the vicinity of LaSalle, LA. These results have concluded seismic surveying with an accelerated weight-drop source is a cost-effective method to produce a high- resolution cross-section of the high and low-velocity sand and shale channels of the fluvial Wilcox strata of Northern Louisiana. Further research should look to build on these results and gather a 3D survey to image the structure of the Tullos-Urania oilfield and identify hydrocarbons-in-place. </p><p>

<p>Features observed on a seismic horizon at or near the Cretaceous-Paleogene boundary in a roughly 200 square km (77 square miles) 3D seismic survey from northern Louisiana resemble large subaqueous dunes or &ldquo;mega-ripples.&rdquo; It is hypothesized that these features may represent subaqueous dunes emplaced by tsunami waves generated by the end-Cretaceous Chicxulub Impact event on the Yucat&aacute;n Peninsula. Seismic data are scrutinized to determine whether or not features observed in the data represent true subsurface geometries. Other hypotheses are tested including the possibility that these features may represent seismic data acquisition footprints, a portion of a slump deposit, or a portion of an aeolian dune field. Results indicate that it is very unlikely that these features represent an acquisition footprint, a slump deposit, or an aeolian dune field. Well-logs are interpreted and seismic velocities are calculated to determine a range of possible lithologies within the Upper Cretaceous interval but the results of the two methods are inconsistent with each other. </p>