A new computer program for strain visualization has been written. Given an upper triangular deformation tensor, which corresponds to homogeneous deformations where no shearing occurs in the z-direction (assuming a right-handed reference system), the program calculates and displays the strain ellipsoid. In addition, it can show the orientations and magnitudes of the finite strain axes, paths of particle motion, instantaneous strain axes, vorticity vector, and flow apophyses. The strain visualization program has been applied to the wrench-dominated transconvergence of the Pacific-Sierra Nevada plate boundary. I find that, within the uncertainties, the two end-members of accommodation of fault-normal contraction can produce finite strain axes matching the orientation of the mean fold-axis azimuth of the California Coast Range. Furthermore, I find that modeling the regional geology as though it were experiencing coaxial deformation is not an invalid oversimplification.

Temperature distribution in subduction zones is a key factor in understanding magma generation, earthquake occurrence, metamorphic reactions, and geochemical element recycling. In this thesis, I have developed a new numerical method to model subduction zone thermal structures with real slab geometries. The new method couples the finite-difference method with the finite-element method to solve the conduction-convection heat transfer system involved in a subduction zone. The mantle and wedge convection is simulated with the finite-element method with the incoming slab convergence rate imposed as a boundary condition at the slab surface. The heat transfer problem is solved with the finite-difference method. It uses a staggered-grid discretization approach so that the effect of the mantle and wedge convection on the thermal model can be accurately taken into account. With material averaging, the simulation method can easily handle a curved slab with a simple, structured grid. The thermal structures that I have calculated for the east Aleutian subduction zone show that a two-segment slab model can overestimate the slab surface temperature at 100 km by up to 90°C for a 75-km thick overriding lithosphere. The thermal structures of ten subduction zones around the Pacific Rim have been generated including the east Aleutians, the Cascades, the Central and South America, the northeast Japan, and Mariana subduction zones. I have shown that the predicted slab surface temperature at 100 km is correlated with B/Zr ratio. As the slab surface temperature increases, the B/Zr ratio decreases systematically for two different levels of B-enrichment (5 ppm and 10 ppm). The results show that the slab tip temperatures have little correlation with the slab lengths and depths.

The Yucatan Platform bisects the NW-SE Sierra de Chiapas fold belt of SE Mexico at right angles. The outcropping Sierra de Chiapas involves Mesozoic platform carbonates, but its northwestern subsurface continuation involves mostly Mesozoic basinal and slope facies sediments in the Villahermosa folds and their offshore continuation, the Sonda de Campeche folds. The main decollement level for the folds is a middle Jurassic evaporite sequence. The pre-salt "basement" of the area is poorly defined but estimated to dip from about a depth of 6 km to the north (Campeche offshore) to 13 km in the south (Sierra de Chiapas). The fold belt was formed during upper Miocene time and is characterized by bivergent NW-SE striking folds. The amount of shortening is estimated to be in the order of 45 km to 65 km. In the onshore and offshore subsurface the folded belt is orthogonally superposed by a late Neogene growth fault system which soles out near the base of the Neogene. This growth fault system developed on the continental slope and intercepted salt diapirs that probably emanated from the core of deep-seated folds. Much of the salt accumulated farther north in the large allochthonous mass of the Campeche salt domes.

This sequence stratigraphic analysis examines an Oligocene to Miocene carbonate platform from the Northwest Shelf of Australia. Five Oligocene sequences, eleven Miocene sequences and one Pliocene sequence are identified with the aid of seismic, well logs, and biostratigraphy. To test the global nature of these sequences, their ages are compared to Europe, New Jersey, and the Bahamas. Most sequences correspond well, within a few hundred thousand years, with the exception of five sequences 32.0 Ma, 29.4 Ma, 20.5 Ma, 19.5 Ma, and 17.3 Ma (listed with European ages) that are not found in Australia. The global correlations and oxygen isotopes from an industry well suggest that eustasy is the primary control on the genesis of Oligocene to mid-Miocene sequences. Sequence boundaries correlate to heavy delta18O peaks while maximum flooding surfaces coincide with light delta18 O peaks.

Apatite fission track data show a gradual decrease in age (∼30 Ma to ∼15 Ma) from north to the south in the eastern SerranIa del Interior, northeastern Venezuela. Based on a previous study, a model for the tectonic evolution of the eastern SerranIa is proposed in which two stages of deformation occurred. Stage 1 (45 Ma--20 Ma) involves the internal deformation of fault blocks. Stage 2 (20 Ma--12 Ma) involves envelopment thrusting, doubling the thickness of the thrust sheet. Shortening within the SerranIa del Interior ceased at 12 Ma. In stage 1, cooling and exhumation rates were 5.8°C/km and 0.26 km/my, respectively, and in stage 2, cooling and exhumation rates were 4.25°C/km and 0.2 km/my, respectively. The deformation of the SerranIa prior to the collision of the Caribbean plate with South America is probably related to the convergence of the North and South American plates.

Observations of submersible dives across Mauna Loa's submarine western flank suggest the flank has been influenced by a number of interacting processes, including large-scale sector collapses, deep volcanic spreading, and hydrothermal alteration. Subaerially derived pillow lavas observed draping the upper flank are in strong contrast to the volcaniclastic debris discovered at the toe of the flank. The distribution of rock types, deformation structures, and alteration phases within the volcaniclastic rocks suggest the mid-slope bench is constructed of a series of thrust sheets formed by seaward sliding of the western flank. Volcaniclastic sediments within the bench have been locally altered by circulation of hot hydrothermal fluids along the faults. The remnant landslide scar, from which much of the clastic debris within the bench derived, has largely been concealed by a flood of new lava flows, many of which crossed the shoreline and were deposited on the upper flank as pillow basalts.

A detailed investigation of the Nueces incised valley of central Texas focused on three problems: (1) the sea-level history of the region over the last 18 ka, (2) how coastal systems responded to sea level and other forcing mechanisms, and (3) the facies architecture of the valley as compared to other Gulf of Mexico valleys and existing incised-valley facies models. A difference in sea-level histories between the Gulf of Mexico and equatorial regions of up to 30 m over the last 18 ka is attributed to the effects of glacio-hydro-isostasy, the gravitational and flexural deformation of the earth in response to the melting of the last great ice sheets. Numerical modeling of glacio-hydro-isostasy suggests that ice sheet reconstructions with a Laurentide source for meltwater pulse 1-A best fit sea-level observations with predictions within the Gulf of Mexico. The coastal systems preserved within the Nueces incised valley record two fundamentally different responses to essentially the same sea-level and climatic changes over the last 10 ka. Mustang Island aggraded over the last 9.5 ky. Corpus Christi Bay experienced no less than four periods of abrupt reorganization marked by the backstepping of estuarine environments around 9.6, 8.0, 4.8, and 2.5 ka. A possible rapid increase in the rate of sea-level rise, climatic changes, and the flooding of relict fluvial terraces contributed to these backstepping events within Corpus Christi Bay. The Nueces incised valley represents one end member in a continuum of incised-valley types. The Nueces valley contains a thin layer of fluvial deposits at its base, estuarine deposits in the middle, and marine deposits at the top. The valley is marked by a terraced morphology and is located in the same location as other valleys cut by the Nueces River during older glacio-eustatic cycles. This contrasts with other incised valleys such as the Brazos River valley which is almost completely filled with fluvial deposits with a thin cap of transgressive deltaic deposits. Instead of forming fluvial terraces, the Brazos cut multiple highstand valleys and transgressive channels and did not incise in the same location through multiple glacio-eustatic cycles.

No description available.

No description available.

No description available.