Shales --- the final frontier of sedimentary geology. This statement, adapted from the opening sequence of STAR TREK is may be an exaggeration, but I consider it not too far from the truth. Shales contain the lions share of earth history that is recorded in sedimentary rocks. Understanding their deposition is key to the reconstruction of past oceans, landscapes, climates, and climatic cycles. Yet, whereas students of sandstones and carbonates have been able to learn a great deal about the deposition of these rocks from studying bedforms and sedimentary structures in the context of experimental data and direct observations in modern environments, the situation is not as fortunate when we examine our current knowledge concerning shales and mudstones. To "boldly go where no one has looked before" (to paraphrase another line from STAR TREK), has been a very rewarding approach to my studies of shales. Basically I think that shales are fascinating rocks, and that there is much we can learn from them about earth history and geologic processes.
My research is characterized by a facies approach to shales, and consists of an integration of field studies and lab studies (thin sections, electron mincroscopy, geochemistry) in order to understand the various factors that are involved in the deposition of shales. Shales that I had an opportunity to study with this approach range in age from Proterozoic to Eocene and come from the Proterozoic Belt Supergroup of Montana, the Cambrian Wheeler Shale of Utah, the Ordovician Athens Shale of Alabama, the Devonian Chattanooga Shale of Tennessee, the Triassic Moenkopi Formation of Utah, the Posidonia Shale of Germany, the Mancos Shale of Utah, and the Green River Formation of Wyoming. In addition to my broad interest in shales, I am also curious about the formation of sedimentary mineral deposits and the diagenesis of sediments.
Currently I pursue two major research projects. (1) A study of sequence boundaries and a reexamination of the depositional history of the Chattanooga Shale in Tennessee and adjacent areas (Kentucky, Indiana). This research into the origin of black shales has been continually funded by the Petroleum Research Fund since 1994. (2) A textural-geochemical study of pyrite ooids and their possible origins is beeing funded by NSF. You can see some pictures of sequence boundaries in black shales on picture page 5, and of pyrite ooids on picture page 1. The sequence stratigraphic study in the Chattanooga Shale is a combination of outcrop studies, gamma ray surveys, and conodont stratigraphy (in cooperation with Jim Barrick and Jeff Over), and should lead to a much more refined picture of sea level variations, basin tectonics, and black shale genesis for the eastern Appalachian Basin. The study of pyrite ooids involves examination and comparison of examples from several locations and geologic time periods, and includes geochmical characterization by electron microprobe and laser ablation mass spectrometry (sulfur isotopes). Because pyrite ooids are often associated with black shales, this study may also contribute to a better understanding of black shale formation.
To wish is little: We must long
with utmost eagerness to gain our end.
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© Jürgen Schieber, UTA Department of Geology
Last updated: August 29, 2000.