No description available.

No description available.

A major change in sedimentary and structural style occurs in Eocene strata exposed along the southern margin of the Oregon Coast Range. Lithofacies of the early Tertiary Umpqua Group have been described, mapped and assigned to likely depositional environments. Submarine fan and slope facies (upper Roseburg Formation) overlie Paleocene basaltic basement rocks to the north, whereas fluvial, deltaic and shallow marine facies (Lookingglass Formation) overlie Franciscan-equivalent strata to the south along the flank of the Klamath Mountains. These two depositional systems are gradational into one another, and were prograding northwestward until about 52 Ma. Means of clast compositions from sandstones and conglomerates from both the Roseburg and Lookingglass Formations suggest derivation from identical recycled orogen or arc-continent collision sources in the Klamath Mountains. Change from Klamath-parallel to more north-south structural trends is well displayed within early Eocene strata of the Umpqua Group. Five major fault systems involve lower Umpqua (Roseburg and Lookingglass) strata, and were active while deposition was taking place. All these faults ceased to be active at about 52-50 Ma, and are overlapped by the middle Eocene Tyee Formation. Regional strain analysis indicates more than 20 percent shortening by right-lateral convergence during early Eocene time. The structural style and syn-tectonic deformation of marine slope facies suggest deposition in an active subduction complex until about 52 Ma. Structural trends in the southern Oregon Coast Range parallel those in the adjacent Klamath Mountains until the end of the early Eocene. At 52-50 Ma, subduction apparently ceased as incoming seamounts clogged the trench, and may have jumped to an outboard position near the present day coastline. In middle Eocene time, the newly developed forearc region rapidly filled with sediments from a much sandier depositional system. Paleomagnetic studies of relatively undeformed Tyee forearc strata indicate as much clockwise rotation as the much more deformed, underlying volcanic basement of the Oregon Coast Range. Rotation of the Oregon Coast Range as a single crustal block must have occurred after, rather than during seamount accretion to the continental margin, which was essentially complete by 52 Ma.

Abstract not available

Includes one folded map in pocket in back cover. / Includes bibliographical references. / iv, 214, [46] leaves, [10] leaves of plates : ill. (some col.), col. maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1994

"February 2001" / Bibliography: p. 335-349. / xxix, 394 p. : ill. (some col.), maps (some col.), plates (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, National Centre for Petroleum Geology and Geophysics, 2004

A 3D seismic volume was acquired summer 2000 over the southern end of Hydrate Ridge (FIR), an anomalously shallow ridge 100 km offshore Newport, Oregon. The survey followed a succession of scientific expeditions aimed at studying the gas hydrates present in the shallow subsurface that gave the name to the ridge. This thesis consists of a seismic sequence analysis of the high-resolution (125 Hz) 3D survey. Identification of seismic units and interpretation of depositional sequences observed on the seismic sections is presented. The sequence analysis is compared with the results from nine sites cored during ODP Leg 204 during summer 2002. The first objective is to document in detail the stratigraphy of the ridge so that we can compare it with the gas hydrate distribution. The second is to reconstruct the structural evolution through time of this complex anticline as inferred from the depositional history. The result is a time series of structural evolutionary cross-sections as well as a series of paleo-bathymetric maps revealing the development of and interplay between the structures now buried in the subsurface of southern HR. The structural evolutionary diagrams show the existence of three anticlines, interpreted as thrust-related folds. They formed at the deformation front and controlled the distribution and deformation of the sediments during the Pleistocene. The current southern HR started its uplift less than 0.5 Ma. A seismic relict in the form of a double BSR is a witness to the evolution of the gas hydrate system of HR. It confirms the recent uplift of the ridge and consequent shallowing of the base of the gas hydrate stability zone (GHSZ). Further detailed studies of the stratigraphy reveal stratigraphic controls on the fluid flow, which in turn control the distribution of gas hydrates. Analysis of the amplitude map of the bottom-simulating reflector (BSR), which is a proxy for the free gas distribution, shows a relationship between anticlinal features within the older strata (older than 1.6 Ma) and strong amplitude anomalies of the BSR, which confirm previous observations suggesting a very low permeability for the young slope-basin sediments and an accumulation of gas within the older sediments underneath. / Graduation date: 2004

Graduation date: 1952

Graduation date: 1999

Thesis (M.Sc.)--Memorial University of Newfoundland, 2004. / Bibliography: leaves 311-318. Also available online.