Micropaleontological data have been analyzed through mathematical and statistical procedures, in order to: (1) establish the distribution pattern of radiolarian assemblages in the surface sediments, (2) establish the relationship of these assemblages with oceanographic variables, (3) determine the faunal composition down-core with respect to the faunal surface pattern, and (4) estimate water temperatures and 1OO M PO₄ within the geological past. This, together with the analysis of opal and quartz content of the sediments, has permitted the inference of the paleo-oceanography of the subtropical southeastern Pacific during the last 75,000 years. Factor analysis shows that five major radiolarian assemblages (factors), accounting for 93.6% of the variance, reflect the mixed layer circulation and its associated water masses. According to their position in the area, these factors are called: (1) the Subtropical factor, (2) the Equatorial factor, (3) the Peru (current) factor, (4) the Chile (current) factor, and (5) the Backwater factor. The subtropical factor is correlated with "warm" water temperatures, the Equatorial factor with opal production, the Peru factor with coastal upwelling, the Chile factor with "cool" water temperatures, and the Backwater factor with mixing of water masses. The distribution pattern of quartz reflects the position of the southeast trade winds which largely control the oceanographic conditions of the subtropical southeastern Pacific. The opal distribution resembles the patterns of surface primary productivity. Opal content is "high" below the Equatorial Undercurrent. However, it is "low" along the South American coast probably due to dilution by terrigenous input. Cores RC11-230 (8°48'S-110°48'W), V19-29 (3°35'S-83°56'W), and Y71-6-12 (16°26'S-77°23'W) were used in the stratigraphic study. Their stratigraphic control (correlation) is made through their δ ¹⁸O records. The changes of quartz, opal and radiolarian assemblages contents down-core are considered to be the result of shifts or changes in intensity of the atmospheric and oceanic circulation. Oceanographic changes have occurred in the subtropical southeastern Pacific during the last 75,000 years, but they are not manifested at each location in the same form. These changes have not been synchronous with changes of global ice volume; rather, during pronounced climatic changes, a sequence which is initiated by changes in the wind circulation is observed. The oxygen isotope stage 4 is characterized by mixing of water masses, "deep" thermocline and low concentration of nutrients. The lower interval of isotope stage 3 is characterized by weakened wind-driven circulation and "high" water temperatures. The middle of isotope stage 3 is a time in which wind-driven conditions become dominant in the region. Oxygen isotope stage 2 is "cool" and has strong wind-driven conditions. The shift to the present oceanographic conditions in the subtropical southeastern Pacific occurred 11,000 years ago. / Graduation date: 1976

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No description available.

The Thompson Valley between Spences Bridge and Lytton, where it joins the Fraser, merits attention because of the abundance of clear sections of late glacial and postglacial deposits in road and rail cuts, and its position as an important transition zone between the glacial lake deposition of the southern Interior and the dominantly fluvial aggradation of the Fraser. Most attention was paid to the stratigraphy of road and rail cuts, as the only morphological features preserved in the steep and narrow valley are terraces, fans, landslides and talus slopes. Quaternary deposits yield little evidence of the depositional environment prior to the last major advance of ice, but there is a good record of conditions during and following deglaciation. The last ice sheet, which wasted away by down-melting, left a thin mantle of till over the uplands and till deposits up to 50 ft. thick in the valley. The Lower Thompson Valley, close to the glacier sources of the Coast Mountains, was one of the last areas to be free of ice. Consequently major lakes developed in the Thompson and Nicola Valleys and were forced to drain into the Okanagan Valley. When the ice plug south of Spences Bridge failed, some time before 9,000 B.P., drainage was resumed down the Thompson Valley to the Fraser. During deglaciation, up to 300 ft, of silts and deltaic gravels were deposited in the l,230 ft. stage of Lake Deadman, which was dammed by ice south of Spences Bridge. Between Skoonka Creek and Seddall, respectively 4 and 7 miles south of Spences Bridge, are deposits of collapsed silt and flow till and it is suggested that an ice plug remained here separating lacustrine deposition north of Skoonka Creeks from fluvial aggradation south of Seddall, where the valley was by then largely ice-free. Aggradation, which was due to the large supply of material from lateral sources resulting from recent glaciation and weathering, was extremely rapid; more than 500 ft. of cross-bedded and horizontal gravel and sand were deposited in probably little more than 1,000 years. Aggradation ceased well before 7,530 B.P. With amelioration of the climate and stabilization of the slopes, the load of the river was considerably reduced and it degraded its former valley fill creating a series of terraces, with a veneer of imbricate cobbles, from 500 ft. down to 30 ft. above present river level. Most terraces are non-cyclic, but paired terraces, approximately l4O ft. above the river, mark a period of relative stability prior to 7,530 B.P. The river was probably within 50 ft. of its present level by 6,600 B.P., and since then downcutting appears to have proceeded relatively slowly. At least three phases of alluvial fan formation occurred during this period of dominant degradation, the terraces acting as temporary base levels for the mudflows. Mazama ash, deposited on the terraces and fans approximately 6,600 years ago, provides a useful marker horizon. Apart from slow down-cutting by the river and some alluvial fan formation, the dominant processes affecting the topography since 6,600 B.P have been landsliding and slumping. The largest slide, the Drynoch Earthflow, has been active for at least 3,175 years and slumping due to seepage and river erosion has occurred intermittently along the river banks. / Arts, Faculty of / Geography, Department of / Graduate

No description available.

No description available.

published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Earth Sciences / Doctoral / Doctor of Philosophy

This study utilizes a multidisciplinary research approach integrating the sciences of archaeology, geology, pedology and paleoclimatology. Deeply stratified and radiocarbon dated sedimentary sequences spanning the last 10,000 yr B.P. are reported for the Cremer site (24SW264), south-central Montana. Previous investigations at the site revealed an archaeological assemblage with Early Plains Archaic through Late Prehistoric period affiliations. Expanded testing of the site integrates the existing cultural record with new data pertaining to Holocene environmental changes at this northwestern Great Plains locality. Detailed pedological descriptions were made along three trenches excavated at the site. The combined soil-stratigraphic record indicates that distinct intervals of relative landscape stability and soil development occurred at the site at ca. 10,000 yr B.P., 7,500 yr B.P. and intermittently throughout the last ca. 6,000 yr B.P. Periods of significant landscape instability (upland erosion and valley deposition) occurred immediately following each of the early Holocene soil forming intervals identified above, and episodically throughout the middle to late Holocene. The impetus for early Holocene environmental instability is attributed to generally increased aridity on the northwestern Great Plains. Comparative analyses of site data with both regional environmental proxy records and numerical models of past climates (General Circulation and Archaeoclimatic models) are made to test the findings from the Cremer site. The collective paleoenvironmental evidence indicates that the period of maximum post-glacial warming and aridity occurred at the Cremer site during the early Holocene period (prior to ca. 6,000 yr B.P.). These data also indicate that the existing archaeological assemblage from the site is younger than ca. 6,000 yr B.P., although future excavations may reveal cultural sequences associated with the earliest dated soils at the site. This geoarchaeological study of the Cremer site should contribute to a much needed research base in this sparsely studied region. / Graduation date: 1999