Microfacies and depositional environments of selected Pennsylvanian calcareous algal deposits from southern U.S.A., and application of information technology for sedimentary petrology teaching and research
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Pennsylvanian calcareous algal bioherms dominated by Donezella, Beresellid, and Cuneiphycus could potentially form prolific hydrocarbon reservoirs. Understanding the biological makeup and depositional settings of these carbonate buildups is imperative. To provide an understanding of the geological and biological processes controlling the formation of these buildups, three localities in the southern United States were studied by integrating field sampling, microfacies analysis, and microstratigraphic analysis. A Lower Pennsylvanian Donezella- and siliceous sponge-dominated carbonate buildup from the Wapanucka Formation, Oklahoma is composed of irregular pockets of boundstone dominated by Donezella, worm tubes, microbial peloids and micrite, siliceous sponge spicule, and peloidal wackestone with other bioclasts. The most significant finding of this study is the recognition of delicate a Donezella framework or colony of thalli enclosing and forming constructional pores. viii Upper Pennsylvanian Beresellid algal colonies from the Holder Formation, New Mexico, are the product of an in situ growth fabric and constituents of Beresellid algal colonies. The Beresellid boundstone fabric was created by bundles of tangled algal thalli growing at an angle or parallel with the bedding surface, in association with phylloid algae, foraminifera, Tubiphytes, and rare brachiopods and crinoid fragments. The Lower Pennsylvanian Cuneiphycus-dominated buildups from the Marble Falls Formation, Texas are composed of irregular pockets of boundstone dominated by Cuneiphycus, Donezella boundstone, and peloidal wackestone with other bioclasts. The first account of the red alga Cuneiphycus building a delicate framework of thalli and building a small-scale framework is documented. In order to effectively handle large numbers of digital images of thin sections used in this study, a new method for creating and authoring virtual carbonate thin sections in PDF format was devised that it is a highly flexible, and platform independent image digitization and content creation method. The significance of this approach is that an image of the thin section is preserved/created and as well as preserves a variety of valuable information about a specimen that can be directly linked to the image of the specimen itself. Another method of building a digital petrography image archive was devised to supplement the labor-intensive nature of teaching optical petrography. The architecture, process, and lessons learned from developing an interactive multimedia CD-ROM tutorial in sandstone petrology for undergraduates is documented. This approach provides possible models for similar development in other fields of petrography or in any other field that utilizes large quantities of visual material, such as seismic or remote-sensing image interpretation.