Fine-grained sediments are thought of as barriers to subsurface fluid flow, but non-marine mudstones in the early Mesozoic Newark Supergroup of eastern North America contain an abundance of coarsely crystalline authigenic minerals. These mudstones also display depositional cycles on several scales that reflect paleoclimatic fluctuations and provide the means for very precise stratigraphic correlation. This is a detailed petrographic study of the authigenic minerals in the Newark mudstones on a regional scale to determine how they vary as a function of stratigraphic position, as well as other important factors such as geographic location, depositional environment, and proximity to igneous intrusions. By working closely with a number of other specialists, particularly Dr. Joseph Smoot of the U.S.G.S. Branch of Sedimentary Processes, we will be able to use a number of different analytical techniques to attack this problem. The results will shed light either on 1) how groundwater varies in the shallow subsurface as a function of long-term climatic fluctuation, or 2) how and why mudstones can served as conduits for late diagenetic fluid flow. Either way, they should provide important new insights in a variety of areas, e.g. the formation of sediment- hosted ore deposits.
