AN ABSTRACT OF THE THESIS OF Elizabeth C. Geiger, for the Master's degree in Geology, presented on August 28, 2008, at Southern Illinois University Carbondale. TITLE: PALEOECOLOGY OF PLEISTOCENE GASTROPODS IN GLACIAL LAKE DEPOSITS IN SOUTHERN ILLINOIS/MISSOURI MAJOR PROFESSOR: Dr. Scott Ishman During the Pleistocene Epoch in the central Midwest United States multiple glaciations and interglaciations occurred in response to the advance and retreat of glaciers. This study focused on the Illinoian and Wisconsinan glaciations, which are separated by the Yarmouthian and Sangamonian interglacials. The advance of glaciers during glacial stages caused major rivers and their tributaries to aggrade creating slackwater lakes in many tributary valleys to the Mississippi River. Gastropod assemblages, found in glacial lake deposits, were used to interpret paleoecology during major glacial advances. Gastropods were collected from four sites in southern Illinois and Missouri to compare the Illinoian and Wisconsinan glaciations to one another, as well as to compare similar aged glacial lake deposits. This study identified forty-eight gastropod species, which were analyzed using statistical procedures. Hierarchical cluster analyses resulted in the identification of gastropod assemblages that were interpreted using habitat classifications. The results indicate specific similarities and differences between the Illinoian and Wisconsinan glaciations regarding environmental and climatic conditions.

Most approaches to interpreting alluvial records in drylands fall into one of two categories: (1) The "arroyo problem," wherein workers study cycles of streambed aggradation and degradation in broad, unconstricted alluvial valleys; and (2) paleoflood hydrology, where alluvial sequences in constricted bedrock canyons are interpreted as paleoflood deposits from streams with stable channel grade and geometry. Both approaches can be valid in their end-member settings, but there is confusion about how the two record types relate in a single drainage. We address this disconnect in Buckskin Wash, an ephemeral stream that consists of a broad alluvial reach draining into a tightly constricted slot canyon. By employing detailed sedimentology, stratigraphy, and geochronology in both the alluvial and constricted reaches of the watershed, we test the hypothesis that the slot canyon deposits are anticorrelated to valley-fill deposits upstream, implying that arroyo cutting is driven by episodic flooding. Alluvial reach deposits are characterized by stratal packages representing incremental, long-term aggradation bound by erosion surfaces representing channel entrenchment. At least four packages younger than ~3 ka are present, the youngest spanning ~0.7 - 0.15 ka. Each is composed of interfingering imbricated gravels, laminated sands, and massive silty clays. Constricted reach deposits consist of five discrete packages, each composed of tabular beds of laminated silty sand that were deposited relatively rapidly. The oldest package dates to ~1.9 - 1.1 ka, whereas the rest of the deposits are younger than ~0.15 ka. Traditional paleoflood techniques would suggest that the constricted reach deposits record a ~1000-year absence of paleofloods followed by ~100 years of frequent, high-magnitude flooding that indeed correlate to arroyo cutting upstream. We argue instead that the constricted reach deposits record an episode of higher preservation potential. Transport of sediment from the alluvial reaches during historic arroyo cutting likely led to a pulse of sediment storage and changed stage-discharge relations in the slot canyon downstream, allowing even moderate floods to overtop existing deposits and be preserved. This new interpretation suggests that, because preservation may be a function of episodic sediment loading from upstream, constricted-reach deposits may not accurately record the paleoflood history of a stream.

Lai, Yuk Fo. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 169-191). / Abstracts in English and Chinese. / Abstract --- p.i / Abstract (in Chinese) --- p.iv / Dedication --- p.v / Acknowledgement --- p.vi / Table of contents --- p.viii / List of tables --- p.xii / List of figures --- p.xiii / List of plates --- p.xv / List of symbols and abbreviations --- p.xvi / Chapter Chapter One --- Introduction / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Research background --- p.1 / Chapter 1.2.1 --- Wetlands and water quality --- p.1 / Chapter 1.2.2 --- The role of sediments in eutrophication control --- p.3 / Chapter 1.2.3 --- Wetlands in ecological mitigation --- p.4 / Chapter 1.2.4 --- Previous studies of wetland pollution in Hong Kong --- p.6 / Chapter 1.3 --- Conceptual framework --- p.8 / Chapter 1.4 --- Objectives of the study --- p.12 / Chapter 1.5 --- Significance of study --- p.13 / Chapter 1.6 --- Organization of the thesis --- p.14 / Chapter Chapter Two --- Literature Review / Chapter 2.1 --- Introduction --- p.15 / Chapter 2.2 --- Quantification of phosphorus retention in wetlands --- p.16 / Chapter 2.2.1 --- Input-output concentration approach --- p.16 / Chapter 2.2.2 --- Mass balance approach --- p.18 / Chapter 2.2.3 --- Phosphorus removal efficiency --- p.19 / Chapter 2.3 --- Phosphorus sorption by wetland sediments --- p.20 / Chapter 2.3.1 --- Sorption and its significance --- p.20 / Chapter 2.3.2 --- Phosphorus sorption maxima --- p.22 / Chapter 2.3.3 --- Adsorption-desorption equilibrium --- p.23 / Chapter 2.3.4 --- Phosphorus sorption kinetics --- p.24 / Chapter 2.4 --- Phosphorus exchange across the sediment-water interface --- p.24 / Chapter 2.4.1 --- Phosphorus mobilization and transport mechanisms --- p.25 / Chapter 2.4.2 --- Phosphorus flux from aquatic sediments --- p.26 / Chapter 2.5 --- Phosphorus fractionation in wetland sediments --- p.29 / Chapter 2.5.1 --- Major sediment phosphorus fractions --- p.29 / Chapter 2.5.2 --- Phosphorus fractionation methods --- p.30 / Chapter 2.5.3 --- Relationships between phosphorus fractions and bioavailability . --- p.32 / Chapter 2.6 --- Factors affecting sediment-water phosphorus exchange --- p.33 / Chapter 2.6.1 --- pH --- p.34 / Chapter 2.6.2 --- Redox potential --- p.34 / Chapter 2.6.3 --- Temperature --- p.35 / Chapter 2.6.4 --- Salinity --- p.35 / Chapter 2.6.5 --- Sediment properties --- p.36 / Chapter Chapter Three --- Methodology / Chapter 3.1 --- Overall study approach --- p.38 / Chapter 3.2 --- Geographical setting of Hong Kong --- p.41 / Chapter 3.2.1 --- Climate --- p.42 / Chapter 3.2.2 --- Geology and landform --- p.44 / Chapter 3.2.3 --- Soil --- p.45 / Chapter 3.2.4 --- Vegetation --- p.45 / Chapter 3.3 --- Study sites --- p.46 / Chapter 3.3.1 --- Site selection --- p.46 / Chapter 3.3.2 --- Site description --- p.48 / Chapter 3.3.2.1 --- The Hong Kong Wetland Park --- p.48 / Chapter 3.3.2.2 --- Mai Po Marshes Nature Reserve --- p.50 / Chapter 3.4 --- Sampling strategy --- p.53 / Chapter 3.4.1 --- Sampling locations --- p.53 / Chapter 3.4.2 --- Sampling dates --- p.57 / Chapter 3.4.3 --- Sample collection and treatment --- p.58 / Chapter 3.5 --- Sample analysis --- p.60 / Chapter 3.5.1 --- Analysis of sediment samples --- p.61 / Chapter 3.5.1.1 --- Sediment texture --- p.61 / Chapter 3.5.1.2 --- Sediment pH --- p.61 / Chapter 3.5.1.3 --- Redox potential --- p.61 / Chapter 3.5.1.4 --- Sediment moisture --- p.62 / Chapter 3.5.1.5 --- Organic matter --- p.62 / Chapter 3.5.1.6 --- Total Kjeldahl nitrogen --- p.63 / Chapter 3.5.1.7 --- "Total Fe, Al, and P" --- p.63 / Chapter 3.5.1.8 --- "Oxalate-extractable Fe, Al, and P" --- p.63 / Chapter 3.5.2 --- Analysis of water samples --- p.64 / Chapter 3.5.2.1 --- "Water pH, conductivity, salinity, turbidity, temperature and DO" --- p.64 / Chapter 3.5.2.2 --- Orthophosphate --- p.64 / Chapter 3.5.2.3 --- Total nitrogen and phosphorus --- p.65 / Chapter 3.5.3 --- Determination of phosphorus exchange characteristics --- p.65 / Chapter 3.6 --- Statistical analysis --- p.65 / Chapter Chapter Four --- Phosphorus Fractionation in Wetland Sediments in Hong Kong / Chapter 4.1 --- Introduction --- p.67 / Chapter 4.2 --- Methodology --- p.68 / Chapter 4.2.1 --- Sample collection and analysis --- p.68 / Chapter 4.2.2 --- Phosphorus fractionation --- p.69 / Chapter 4.2.3 --- Statistical analysis --- p.72 / Chapter 4.3 --- Results and discussion --- p.72 / Chapter 4.3.1 --- Physico-chemical properties of sediments --- p.72 / Chapter 4.3.2 --- Physico-chemical properties of overlying water --- p.78 / Chapter 4.3.3 --- Phosphorus fractionation in sediments --- p.82 / Chapter 4.3.3.1 --- Phosphorus fractions in sediments of the Hong Kong Wetland Park --- p.82 / Chapter 4.3.3.2 --- Phosphorus fractions in sediments of the Mai Po Marshes --- p.89 / Chapter 4.3.3.3 --- Phosphorus fractions in relation to mobility and bioavailability --- p.96 / Chapter 4.4 --- Conclusions --- p.100 / Chapter Chapter Five --- Phosphorus Sorption by Wetland Sediments in Hong Kong / Chapter 5.1 --- Introduction --- p.103 / Chapter 5.2 --- Methodology --- p.104 / Chapter 5.2.1 --- Sample collection and analysis --- p.104 / Chapter 5.2.2 --- Batch incubation experiments --- p.105 / Chapter 5.2.3 --- Sorption kinetics --- p.106 / Chapter 5.2.4 --- Effects of selected environmental factors on phosphorus sorption --- p.106 / Chapter 5.2.5 --- Estimation of sorption parameters --- p.107 / Chapter 5.2.6 --- Statistical analysis --- p.109 / Chapter 5.3 --- Results and discussion --- p.109 / Chapter 5.3.1 --- Phosphorus sorption parameters of wetland sediments --- p.109 / Chapter 5.3.1.1 --- Phosphorus adsorption isotherms --- p.109 / Chapter 5.3.1.2 --- The role of sediments in phosphate buffering --- p.116 / Chapter 5.3.1.3 --- Relationships between phosphorus sorption parameters and physico-chemical properties of sediments --- p.121 / Chapter 5.3.2 --- Kinetics of phosphorus adsorption --- p.124 / Chapter 5.3.3 --- Effects of environmental factors on phosphorus sorption --- p.128 / Chapter 5.3.3.1 --- Effects of pH --- p.128 / Chapter 5.3.3.2 --- Effects of salinity --- p.131 / Chapter 5.3.3.3 --- Effects of temperature --- p.133 / Chapter 5.4 --- Conclusions --- p.136 / Chapter Chapter Six --- Phosphorus Flux from Wetland Sediments in Hong Kong / Chapter 6.1 --- Introduction --- p.139 / Chapter 6.2 --- Methodology --- p.140 / Chapter 6.2.1 --- Sample collection and analysis --- p.140 / Chapter 6.2.2 --- Core incubation experiments --- p.141 / Chapter 6.2.3 --- Estimation of phosphorus flux --- p.142 / Chapter 6.2.4 --- Statistical analysis --- p.142 / Chapter 6.3 --- Results and discussion --- p.143 / Chapter 6.3.1 --- Phosphorus flux from wetland sediments --- p.143 / Chapter 6.3.1.1 --- Phosphorus flux from sediments in the Hong Kong Wetland Park --- p.143 / Chapter 6.3.1.2 --- Phosphorus flux from sediments in the Mai Po Marshes --- p.147 / Chapter 6.3.2 --- Effects of redox conditions on sediment phosphorus flux --- p.152 / Chapter 6.4 --- Conclusions --- p.156 / Chapter Chapter Seven --- Conclusion / Chapter 7.1 --- Introduction --- p.159 / Chapter 7.2 --- Summary of major findings --- p.159 / Chapter 7.3 --- Limitations of study --- p.166 / Chapter 7.4 --- Suggestions for future study --- p.166 / References --- p.169

Thesis (M.S.)--University of North Carolina Wilmington, 2008. / Title from PDF title page (viewed September 22, 2008) Includes bibliographical references (p. 60-62)

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