Master of Science / Department of Geology / Abdelmoneam Raef / Matthew W. Totten / This study examines an ovoid drainage feature southwest of Topeka, Kansas, whose discovery sparked a flurry of activity. Geomicrobial and surface gamma ray surveys indicated possible vertical migration of hydrocarbons, and a ground magnetic survey produced anomalies that resemble the profile of a crater. The area was dubbed the Echo Cliff structure and considered analogous to the Ames structure in Oklahoma, an Ordovician impact structure remarkable for significant hydrocarbon recovery. However, four wells drilled in the area were dry and abandoned. The Echo Cliff structure did yield further indications of its origins by the discovery of possible shocked quartz in drill cuttings from the Ordovician Simpson Group. Our study integrated well log analysis, geophysical modeling, and petrographic analysis to verify or refute the proposed identity of the Echo Cliff structure. Well logs from the area were used to create a structural and stratigraphic cross-section in Petrel® 2016. A gravity survey was conducted in the study area and combined with an aeromagnetic survey, donated by Applied Geophyics, Inc., to use as the basis for geophysical modeling within GM-SYS®. Finally, drill cuttings from the Simpson Group of two wells in the study area were mounted for thin sectioning. These thin sections were examined for planar deformation features, which are indicative of an impact event. The structural and stratigraphic cross sections indicated minimal variation in the subsurface, which is uncharacteristic of an impact event. The GM-SYS® geophysical models seem to indicate that variations in the topography of the Precambrian basement and faulting from the Bolivar-Mansfield Tectonic Zone are responsible for the geophysical anomalies and possibly the current drainage pattern of the study area. Finally, no planar deformation features were observed in any of the examined thin sections. Therefore, there is currently no evidence in support of the claim that the Echo Cliff structure is an impact structure.

In the northern part of Swedish Caledonides, north of Lake Torneträsk is a 7 km long exposure of a breccia layer. The layer thins westwards and eastwards from the central part where it is up to 27 m thick. It is called the Vakkejokk Breccia after the type section. The breccia has been described in literature since about a century, but its origin is enigmatic. The breccia layer is since the summer of 2012 investigated by three geologists specialized in impact craters, Paleozoic sediments, and the Caledonian orogeny. They put forward evidence for the breccia being formed by a hypervelocity impact during the Lower Cambrian at approximately 520 Ma (Ormö et al. 2017). At that time the target area was a shallow epicontinental sea that surrounded the mainly peneplanized continent Baltica. An impact into the sea is known to generate tsunami waves as well as resurge deposits when the water brings ejected and rip-up material back into the crater. Ormö et al. (2017) suggest the top part of the Vakkejokk Breccia to include such resurge deposits. The depositional marine environment is also known to rapidly protect an impact crater from further erosion. It is possible that only the topographic rim of the Vakkejokk crater was eroded during the millions of years it may have taken before the crater was covered by younger sediments. About 100 m.y. after the formation, it was completely covered by overthrust nappes during the Caledonian orogeny, when Baltica and Laurentia collided. The crater itself is not exposed today, merely parts of what is thought to be the ejecta layer and resurge deposits. This Bachelor of Science project aimed to investigate the putative resurge deposits to learn more about the process of formation and the provenance in the target of the clasts in the deposits. This was carried out by three short drillcores through the resurge deposit part of the Vakkejokk Breccia layer. The place to drill the boreholes was chosen at an outcrop which is proximal to the putative hidden crater. The retrieved drillcores were cut longitudinally, then polished and photographed in high resolution. Each core was then analyzed in an image analysis software with respect to clast granulometry and lithology. To the results are presented as graphs showing clast size, size sorting, clast shape, of the relative amounts of different lithologies and the matrix content. The results are discussed with respect to well-documented analogue marine-target craters

As one of the most common minerals in crustal rocks, quartz has been widely used as an indicator for shock metamorphism. Shocked quartz is found in the Chicxulub impact crater, an impact crater that has been linked to the Cretaceous-Tertiary extinction ~66 million years ago. The microstructural deformation features found in the shocked quartz do not form randomly, and their orientation provides a better understanding of the impact cratering process. At present, there are no studies of EBSD data analysis of shocked quartz from Chicxulub. We investigated six thin sections from two samples from the M0077A borehole in the lower peak ring of the Chicxulub impact crater, using the Scanning Electron Microscopy (SEM)-EBSD technique. Both samples consist of shocked granite, with a significant amount of quartz.  Therefore, this study investigates the crystallographic preferred orientation (CPO) of shocked quartz and predicts the seismic velocities and anisotropy, based on the EBSD data. We carried out the analysis of EBSD data by using the MATLAB-based MTEX toolbox that can perform CPO analysis from pole figure plots and the prediction of seismic properties of minerals based on the Voigt-Reuss-Hill effective medium method. Although acquiring the EBSD data from these samples is challenging, leading to the lack of data measured, we found out that the prediction of P wave seismic velocity is in good agreement with other recent studies conducted in the same area. The range of predicted P wave velocities is 5.5-6.5 km/s with anisotropy of 8-15%. The actual observed laboratory measurements and in-situ seismic measurements are considerably smaller than this velocity range because our calculations do not incorporate pores or take microcracks into account.  A likely explanation for the large variability of anisotropy in shocked quartz is the relatively few mapped grains with EBSD, which would influence the CPO and lead to high predicted seismic anisotropy. Considering a greaternumber of grains in the CPO analysis, the CPO is reduced, and seismic anisotropy becomes smaller.