Stylolites in twelve stratigraphic sections of the Salem Limestone, distributed throughout the Illinois Basin, provide clues to their origin and development. Chemical and X-ray diffraction analyses reveal that stylolite seam material contains organic matter and clay minerals too sparse or absent in the host limestone to be considered solely as insoluble residue. Stylolite distribution in various lithofacies suggests that stylolites develop along thin sedimentary layers rich in organic matter and clay minerals. Stylolite density (vertical distribution) mimics the distribution of organic-rich sedimentary layers: sparse but thick in grainstone, and abundant but thin in packstone and wackestone. Many stylolites grade laterally into organic-rich layers, or hummocky seams. Thicknesses of stylolite caps and hummocky seams are approximately equal in the same host rock, but hummocky seams tend to be more laterally continuous. Stylolite density in packstone increases with burial depth, whereas hummocky seam density decreases. Hummocky seam thickness does not change with depth. Stylolite column height in grainstone, which is sparse in hummocky seams, increases with depth, whereas stylolite density does not increase. This list of observations supports the hypothesis that stylolites develop along pre-existing, organic-rich layers, or hummocky seams, rather than nucleating in pure host rock and creating organic-rich seams as accumulations of insoluble residue. Volumetric calculations indicate that the contribution of stylolites to pore-filling cement is 5 to 25 percent throughout the Illinois Basin.
Alkylammonium ion exchange, x-ray powder diffraction (XRD), x-ray fluorescence spectroscopy (XRF), and high resolution transmission electron microscopy (HRTEM) have been used to study the chemistry and the physical properties of illite/smectite (I/S) clays from Paleozoic K-bentonites. The data have been used to evaluate current models of I/S interstratification and the mechanism of formation of illite during bentonite diagenesis.
The depositional style, biostratigraphy and burial history of the Late Early Pliocene, Moruga Group were studied in outcrop and the subsurface, along the south coast of Trinidad to determine its depositional environments, sediment sources, geologic age, and diagenetic history.
Rare occurences of coeval late Wisconsin glacigenic diamictons and ice-proximal sediments with a diverse faunal assemblage provided an opportunity to test the viability of the glacigenic sediments as proxy paleoclimate indicators.
The Middle Proterozoic Jacobsville Sandstone, located on the upper peninsula, Michigan, is the youngest rift- related sedimentary unit in the 1.1 Ga Midcontinent rift. Although outcrops of the Jacobsville Sandstone along the Lake Superior shoreline and in river gorges are well studied, these outcrops represent stratigraphically only the upper 300-400 feet of the estimated 9,000 feet thick Jacobsville Sandstone. I used drill cores and newly-studied outcrop samples; 1) to characterize stratigraphically continuous sections; 2) to compare the Jacobsville Sandstone in subsurface with the Jacobsville Sandstone in outcrop; 3) to identify lateral and vertical variations in texture and petrographic composition within the Jacobsville Sandstone; and 4) to determine petrographic provenance of the Jacobsville Sandstone.