ALBERT

Description: Wavelengths of hummocky cross-stratified (HCS) beds (a common sedimentary feature of storm-dominated shorefaces) are documented for the first time using measurements in three-dimensional (3-D) ground-penetrating radar (GPR) data for a well-developed Upper Cretaceous lower-shoreface succession at Dry Wash in the Ferron Sandstone Member, Utah. The shallow-marine sequence consists of upward-thickening HCS sand beds alternating with interstorm deposits. The thickness variation of the storm beds indicates locally steadily growing storm intensity with at least four cycles. Weakly coarsening-upward (mud to very fine-grained sand) fair-weather background deposits suggest a slow progradation of deposition with no significant change in environment. The GPR interpretation mapped three conformable, high-continuity, high-amplitude reflections throughout the 3-D GPR data volume. The interpreted radar surfaces (RSs) are well correlated with tops of HCS sand beds (and thus paleotopographic surfaces); the associated radar units (RUs) have a uniform thickness (on average ∼0.8 m [∼2.6 ft]). The RUs and the adjacent outcrop observations suggest that the shoreface sandstone at the Dry Wash site has a simple layered internal architecture. The hummocky-swaley surfaces generally dip westerly, as a product of postdepositional structural alterations that are mostly in the shoreline direction, and contain variable-size, structurally undulating rounded features. A 2-D continuous wavelet transform analysis is applied to the detrended RSs, producing a multiresolution image decomposition of the GPR surfaces. Surface features with a wavelength range of 1–7 m (3–23 ft) are in good agreement with the observations on modern hummocky shallow-marine seabeds. Quantitative measurements indicate that the hummocky surfaces at the Dry Wash site are dominated by uniformly distributed circular to elongate bed forms with maximum correlation at 1.5–3.5-m (4.9–11.4 ft) wavelength and that the deltaic sedimentary layers were simultaneously deformed by the middle Campanian compressional stress of the Sevier orogeny transmitted from the northwest. Quantitative information on the subseismic-scale surface geometry of the HCS beds is expected to result in more refined reservoir models. In addition, the connectivity of units indicated by the scale of the morphology can be an indirect indicator of unit correlation and permeability paths. 2nd revised manuscript received August 31, 2008 Keumsuk Lee received his B.Sc. degree in mathematics (1994) and his M.Sc. degree in geological oceanography (1999) from Kunsan National University, Kunsan, Korea, and his Ph.D. in geophysics from the University of Texas at Dallas in 2005. He worked for the Bureau of Economic Geology at the University of Texas at Austin before joining the Korea National Oil Corporation, Anyang, Korea, as a senior geoscientist. His main research interests are basin analysis based on seismic sequence stratigraphy, reservoir characterization using 2-D/3-D ground-penetrating radar data, and multiresolution wavelet analysis. Robert Szerbiak received his B.Sc. degree (1971) in geoscience from Michigan State University, M.Sc. degree (1981) in geophysics from Texas A&M University, and Ph.D. (2002) in geoscience from the University of Texas at Dallas. He has worked as a geophysicist with Petty-Ray Geophysical Company, Phillips Petroleum Company, British Petroleum Exploration, and recently as a research associate at Boise State University. His specialization includes stochastic modeling, reservoir characterization, petrophysical parameter simulation, and ground-penetrating radar and seismic modeling and imaging. His outside interests include near-surface geophysical scaling studies, wavelet decomposition methods, and fluid flow and transport. George McMechan received his B.Sc. in geological engineering from the University of British Columbia in 1970 and his M.Sc. in geophysics from the University of Toronto in 1971. He is the Ida Green Professor of Geosciences at the University of Texas at Dallas. He has published approximately 230 technical articles, and in 1997, he received the Virgil Kauffman gold medal from the SEG. His main research interests are wavefield imaging, reservoir characterization, and ground-penetrating radar. He is a member of Society of Exploration Geophysicists (SEG), American Geophysical Union (AGU), Seismological Society of America (SSA), Environmental and Engineering Geophysical Society (EEGS), and Association of Professional Engineers and Geoscientists of British Columbia (APEGBC). Namsoon Hwang obtained her B.Sc. (1994) and M.Sc. (1998) degrees in oceanography from Kunsan National University, Kunsan, Korea. Her main research interest is the application of heavy mineral analysis and sequence stratigraphy to various geological and environmental problems.