Pore Throats to Plate Margins: An Integrated Approach to Basin Analysis: ABSTRACT

The basin analysis approach to modeling sedimentary basins affords the opportunity to view ore deposits or accumulations of fossil fuels in the context of the evolution of the entire basin. Integration of data from diverse specialties is now widely practiced, and the multidisciplinary approach to the study of basins has greatly enhanced our ability to understand and to predict the occurrence and distribution of economically important commodities. A significant outgrowth of the basin analysis technique is a more rigorous testing of scientific paradigms. Feedback from diverse specialties provides numerous constraints so that no conclusion can be drawn about one aspect of a basin's history without affecting the interpretation of other aspects. Thus, when a conclusion from one line of evidence is at variance with a conclusion drawn from several other lines of evidence, it is necessary to challenge the assumptions that led to the different conclusions. Challenging such assumptions usually involves examining cherished theories or paradigms. Our general reluctance to discard prevailing theories reflects our heavy reliance on useful rules of thumb; without them we could not begin to interpret the geologic past. This reluctance to reli quish useful theories is more easily overcome when several lines of evidence point us toward new concepts that have exciting implications of their own. Basin analysis, by its very nature, pushes us toward new perspectives and thus serves to promote new discoveries in geoscience. A case study in the San Juan basin of New Mexico serves as an example of the basin analysis approach to a geologic problem and serves to illustrate that sometimes answers to questions that were never posed are the most significant (and surprising) outcome of the basin-analysis approach. The original goal of the San Juan basin study was to develop a genetic model for sandstone-type uranium deposits in the Jurassic Morrison Formation. Tectonic, geophysical, sedimentologic, petrographic, End_Page 1523------------------------------ hydrologic, and geochemical (organic and inorganic) studies were drawn together so that mineralization could be evaluated as one diagenetic event in the context of the entire depositional, structural, and diagenetic framework. The result was not only a model for uranium mineralization but also the development of several new concepts, many of them unrelated to the original problem. Spin-offs from the original study include significant advances in fields as diverse as hydrology, coal geology, saline, alkaline-lake geochemistry, and clay mineralogy. It was possible to document, for instance, that authigenic illite formed at near-surface conditions in the absence of the elevated temperatures commonly thought to be required. This finding limits the use of illite as a geothermometer and mak s it of considerable interest in petroleum geology. The integrative nature of the basin analysis approach allows a synoptic rather than a myopic view of specific geology problems. The approach can be applied to any geologic problem and will continue to lead us away from current paradigms as multiple lines of evidence force us to question our most cherished beliefs. Most certainly we will continue to learn surprising answers to questions we forgot to ask. End_of_Article - Last_Page 1524------------