In five summer cruises during the period 2000-2004, seventy-four box cores were collected from eleven locations from the Mississippi Canyon (480- 2750m, northern Gulf of Mexico), and an adjacent transect (336-2920) to understand the community structure and trophic function of amphipods and for measuring the bioaccumulation of polycyclic aromatic hydrocarbons, (PAHs). Amphipods were discovered to be an important component of the macrofauna of the Mississippi Canyon (40 % of the total faunal abundance). Seventy two species, belonging to nineteen families, were collected from the study area with 61 species from the canyon and only 38 species from the non-Canyon transect. The head of the canyon (480m) was dominated by dense mats (15,880 ind/m2) of a new amphipod (Ampelisca mississippiana). The logarithm of the amphipod abundance decreased linearly with depth. The species diversity (H`) exhibited a parabolic pattern with a maximum at 1100m. The differences in amphipod abundances and biodiversities were correlated with the variation in the amount of available organic matter. The depression in diversity in the canyon head is thought to be competitive exclusion resulting from the dominance by A.mississippiana, but the high species richness is presumed to be a function of the structural complexity of the canyon. Annual secondary production of A. mississippiana was 6.93 g dry wt m-2, based on size-frequency method and corresponding to an estimated univoltine generation from a regression model. The production/biomass ratio (P/B) was 3.11. Production of this magnitude is comparable to shallow marine ampeliscids but are high for the depauperate northern Gulf of Mexico. The effect of the organic contaminants and the bioavailability to the amphipods was determined through measuring the bioaccumulation of the PAHs. The distribution of PAHs in sediments was different from the distribution in the organisms suggesting preferential uptake/depuration or uptake from pore or bottom waters. The average bioaccumulation factor (4.36 ± 2.55) and the biota sediment accumulation factor (0.24±0.13) for the total PAHs by the ampeliscids were within the range reported for other benthic invertebrates. The average bioaccumulation factors were highest for dibenzothiophenes (up to 132) and alkylated PAHs and lowest for parent high molecular weight PAHs.

Presented here are the results of a study of geological hazards conducted in Canyon Lake Gorge of Central Texas. Canyon Lake Gorge formed in 2002 when the emergency spillway of Canyon Lake was overtopped. Since that time, the gorge has been opened to public tours, and the organization governing the gorge has expressed concern regarding visitor safety. The surveys in this study gathered data through field observations and supplemented those data with non-destructive tests from an impact test hammer. The goal of this study was to gather original field data on potential hazards of the gorge with the hope that insight from these data could be used to enhance visitor safety in the gorge. The field observations made in this study identified the presence of undercut rock ledges that could present varying degrees of risk to visitors. Easily eroded clayey wackestone facilitated formation of these potential hazards. Lithologies such as packstone and grainstone serve to form ledges atop the wackestone. Preexisting fractures and joints in the ledge forming rock, which compound the danger of the unstable masses of undercut ledges, provide failure planes. This study identified current areas of unstable masses by location and differentiates the degree of risk present at each location, using simplified classes of low, medium, and high risk. Level of risk was determined primarily by the potential injuries incurred. Often, the height was dependent upon the thickness of an easily eroded wackestone bed that undercuts ledge forming rock. Canyon Lake Gorge is a young and dynamic geomorphological environment seeking equilibrium through gravity facilitated erosional events. In time, natural formation of riser beds will mitigate the potential hazards of some undercut ledges. Based on the potential hazards identified in Canyon Lake Gorge, four safety recommendations are proposed: - Visitors should always be guided by trained personnel. This practice is in place. - Visitors should be educated on the dangers of Canyon Lake Gorge before entering. - Unavoidable hazards should be evaluated for ways to mitigate risk. - The gorge should be continually monitored to insure safety of the visiting public.

A study was made of rocks outcropping along a road section in the vicinity of Hell's Gate, some 12 miles south of Boston Bar, British Columbia. Biotite schists belonging to the Hozameen group (Carboniferous or Permian in age), were the oldest rocks found. The Custer granodiorite, a heterogeneous igneous body having the average composition of a hornblende granodiorite, intrudes the biotite schists. The age of the Caster granodiorite is believed to be Upper Jurassic. Large numbers of pegmatite and aplite dykes intrude the Custer granodiorite. Two types of pegmatites, magmatic and metasomatic were distinguished. The Hell's date granodiorite, a uniform igneous body of trondjhemitic composition, intrudes the Custer granodiorite and also post dates the pegmatite and aplite dykes. The age of the Hell's Qate granodiorite is believed to be Upper Jurassic or possibly Lower Cretaceous. Sight plagioclase porphyry dykes, classified into one of three groups, (staple, multiple, and protoclastic types) were found. The plagioclase porphyry dykes are believed to be genetically related to the Hell's Gate granodiorite. Six dykes having an andesitic composition were found; the dykes have been classified into light colored and dark colored andesites. The rocks along the road section have been intensively fractured. Faulting has taken place close to the southern contact between the two granodiorites. The narrow N-S trending outcrop of Custer granodiorite in the area could possibly have been produced by faulting, and its shape suggests a horst structure, A study, using a method suggested by Gorai, was made of the plagioclase twins occurring in the Hell's Gate rocks. The conclusions drawn from this work largely confirms the conclusions drawn from the field evidence. / Arts, Faculty of / Geography, Department of / Graduate

Graduation date: 1983 / Best scan available for p.26, 111. Original is a copy of a copy. / For master (tiff) digital images of maps contained in this document contact scholarsarchive@oregonstate.edu

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Call number: LD2668 .R4 1966 G3

The purposes of this study are to evaluate and elucidate distribution patterns, speciation and pollution status of As and Hg in coastal sediments. The study focuses on coastal zones off southwestern Taiwan including the Kaoping River estuary, the Kaoping Canyon, Chiku and Tapong lagoons. Experimental results show that As and Hg in surface sediments from the Kaoping River estuary are mainly associated with mud (clay+silt) and TOC. They may also co-precipitate with Fe-Mn oxides/ hydroxides in sediments. Consequently, the seasonal variability of As and Hg distributions in estuarine sediments is likely attributed to the variations of particles size and TOC contents. Distributions of As in surface sediments from the Kaoping Canyon are also related closely to mud, Fe-Mn oxides and TOC contents. The spatial variation of surface enrichment of As, however, is insignificant along the Kaoping Canyon. Concentrations of Hg in surface sediments are elevated around the river mouth and decrease seaward in the Kaoping Canyon. According to As and Hg distributions and accumulation rates in the Kaoping Canyon, pollution appears to increase significantly around 1970 corresponding to the period of economic boom in Taiwan. With the exception of locations near the Chiku River and Daliao Creek, spatial distributions of As and Hg are largely determined by particle size, organic and Fe-Mn contents. In the Tapong Bay, concentrations and enrichments of As and Hg are generally higher in the inner bay than in the outer bay, primarily affected by distributions of particle size, organic and Fe-Mn contents. The enrichment of Hg in the inner bay appears to be enhanced by waste-water discharge, TOC accumulation and sulphide formation. The magnitudes of EF are larger in the Tapong Bay than in the Chiku Lagoon and the Kaoping River estuary for both As and Hg, indicating a higher pollution status in the Tapong Bay than in other areas. Sequential extractions separate As and Hg into five fractions that can be roughly divided into mobile phase and non-mobile phase (residual fraction). The sum of mobile-like fractions is significantly correlated with the content extracted with 0.1M HCl. Arsenic and mercury speciation of sediments are quite similar in the Kaoping River estuary, the Chiku Lagoon and Tapong Bay. Both As and Hg are mostly concentrated in the residual fraction, and secondly located in Fe-Mn oxides for As, and in organic matter for Hg. Arsenic and mercury speciation in sediments are apparently not controlled by the variability of salinity in the estuary.