The Richmond Group (Late Ordovician) in the tristate region of southwestern Ohio, north-central Kentucky, and southeastern Indiana consists of a succession of clastic and carbonate sediments deposited on a prograding intracratonic ramp and distal clastic fan. Six regional depositional facies have been delineated during a detailed examination of cores, outcrops, and geophysical logs across a 325 by 350 km study area. The facies, informally designated Facies A through F, are assigned to depositional environments consisting of: a shale-dominated shale distal intracratonic ramp; mixed carbonate and shale proximal intracratonic ramp; shallow subtidal to supratidal intracratonic ramp, and shallow-water, distal clastic wedge; based on their sedimentologic and paleontologic characteristics. Regional cross sections of these facies indicate that the distal clastic wedge prograded from the east and that the intracratonic ramp prograded from the south. In addition, isopach maps indicate that the depocenter of the basin was located southeastern Indiana and southwestern Ohio.
The Coalinga, California region contains massive amounts of diapirically emplaced deposits of serpentinite. The largest deposit, the New Idria Formation, forms the core of the Joaquin Ridge Anticline and outcrops over an elliptically-shaped 48-square mile area in a mountainous area 17 miles northwest of Coalinga and 15 miles west of the California Aqueduct constructed along the western margin of the San Joaquin Valley. The serpentinite deposit is in faulted diapiric contact with Cretaceous-aged sandstones and shales and became emergent approximately 17 to 20 million years ago in the Miocene era. Eroded asbestos-bearing sediment from this ultramafic deposit has been incorporated in late-Miocene and younger sedimentary formations in the central San Joaquin Valley region.
The Miamitown shale has been considered an enigmatic unit in the upper part of an Edenian-Maysvillian sequence. A new look at Cincinnatian sequences reveals that this unit is actually an integral part of a complex sequence architecture. Three fourth-order sequences at the base of the Upper Ordovician in the Cincinnati area are formally named in stratigraphic order: (1) the Brent Sequence, comprising the Edenian Kope Formation; (2) the Riedlin Sequence comprising the Maysvillian Fairview, Miamitown and Bellevue formations; and (3) the Stonelick Sequence comprising the Maysvillian Corryville and Mt Auburn formations. A detailed study of the Riedlin Sequence in outcrops, cores and well logs between Cincinnati, Ohio, Ft Wayne, Indiana, and Indianapolis, Indiana, (13,000 km$\sp2$), reveals stacking patterns within the Riedlin Sequence that are comparable to those of a type-2 sequence. This interpretation contrasts with previous interpretations wherein Cincinnatian third- and fourth-order cycles are dominated by highstand systems tracts with thin or absent lowstand and transgressive deposits, or where these cycles are interpreted as parasequences or parasequence sets rather than sequences. The Miamitown Shale provides a testing ground for a new integrated cyclic, lithologic, and quantitative faunal method of correlating meter-scale fifth-order cycles. This has been accomplished within the 12 m interval surrounding the Miamitown Shale in the upper part of the Riedlin Sequence. First, using lithologic criteria alone, six shale-to-limestone cycles bounded by flooding surfaces were delineated and correlated between seven 12 m outcrop sections within a 30 km radius. Unusual fossil occurrences constrained correlations of cycles 3 & 4, and the presence of a dalmanellid, Heterorthina fairmountensis, showed that the flooding surface above cycle 3 lay 10 cm below the lithologic contact. Quantitatively-defined faunal clusters constrained correlations between all cycles, and revealed a major transition at the top of cycle 2, again below the lithologic contact. Finally, depth gradient fluctuations interpreted from ordination of faunal data suggest that the major transition at the top of cycle 2 is a transgressive surface, and that the middle part of cycle 3 includes the interval of maximum depth.
Stratigraphic, sedimentologic and petrographic studies of the Lower and Upper Cretaceous in northwest Sonora show that deposition of the Bisbee Group occurred at the northern margin of a back-arc marine basin, and of the El Chanate Group and El Charro volcanic complex in a closed continental foreland basin. This study also finds that the Proterozoic-Paleozoic formations in northwest Sonora (Caborca terrane) were not part of the Cretaceous landscape, thus raising doubts about the existence of the Mojave-Sonora megashear.
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.
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.
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.
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.
In this dissertation I present a tectonic, geochemical, and thermal history for the Witwatersrand basin, located on the Archean Kaapvaal craton, South Africa. The foreland basin tectonic setting of the Central Rand Group controls both the chemical and the thermal evolution of the basin, and unifies the basin evolution model presented here.