<p> Fluvial suspended sediment is a master variable affecting a wide range of fluvial and coastal environmental processes, and dominating the terrestrial mass flux to the oceans. Although it has long been recognized that relationships between suspended sediment concentration and discharge are not stationary in small, mountainous rivers over time scales from hours to decades, most studies continue to assume stationarity. This collection of studies directly addresses the issue of non-stationarity in the suspended sediment &ndash;discharge relationship of the Salinas River, central California, and examines the progression of abandoned channel fill sequences in the Eel River Estuary of northern California. </p><p> Preceding these studies is a methodological analysis of the pretreatment of fluvial and marsh sediments for particle size analysis. Pretreatment of sediment with hydrogen peroxide to remove organic constituents and aid deflocculation is a common component of particle size analyses of terrestrial and marine sediments. The first chapter presents the quantitatively determined effect of a range of treatment levels on particle size distribution among four sediment types representing a range of mineral/organic particle size distributions, organic content and particle characterization (charcoal or detrital plant material). </p><p> The following three chapters examine the effects of antecedent basin conditions on the suspended sediment &ndash; discharge relationship in the Salinas River. In chapter two, forty-five years of suspended sediment data from the lower Salinas and 80 years of hydrologic data were used to construct hydrologic descriptors of basin preconditioning and test the effects of these preconditions on suspended sediment behavior. Fine (diameter (<i>D</i>) &lt; 63 &mu;m) and sand sized (<i>D</i> > 63 &mu;m) sediment were found to respond differently to antecedent hydrologic conditions. Fine sediment was most sensitive to flushing flows of moderate discharge (10 &ndash; 20x mean discharge (<i>Q_mean</i>) that led to lower subsequent fine sediment concentrations, while sand concentrations were generally decreased by periods of drought and longer elapsed time since a wide range of discharges acting as maintenance flows. </p><p> Chapter three examines the interannual to decadal scale persistence of suspended sediment &ndash; discharge relationship states in the lower Salinas River, assesses the role of antecedent hydrologic conditions in controlling these patterns, and addresses their relationship to El Ni&ntilde;o Southern Oscillation (ENSO) climatic states. The decadal scale variability in suspended sediment behavior was influenced by interannual to decadal scale fluctuations in hydrologic characteristics, including: elapsed time since small (&sim; 0.1x Qmean), and moderate (&sim; 10x Qmean) threshold discharge values, the number of preceding days that low/no flow occurred, and annual water yield. El Ni&ntilde;o climatic activity was found to have little effect on decadal-scale fluctuations in the fine suspended sediment &ndash; discharge relationship due to low or no effect on the frequency of moderate to low discharge magnitudes, annual precipitation, and water yield. However, sand concentrations generally increased in El Ni&ntilde;o years due to the increased frequency of moderate to high magnitude discharge events, which generally increase sand supply. </p><p> Chapter four brings to bear the decadal scale persistence of suspended sediment - discharge behavior, the effects of antecedent hydrologic conditions, and ENSO influences on the estimation of inter-decadal scale sediment flux from the Salinas River. The longer sampling records employed in this study and incorporation of decadal scale behavior or antecedent hydrologic conditions resulted in average annual load estimates of 2.1 or 2.4 Mt, in comparison to earlier estimates of &sim; 3.3 Mt by previous researchers. El Ni&ntilde;o years dominated the sediment budget by producing on average ten times more sediment than non-El Ni&ntilde;o years. </p><p> Chapter five proposes a modification of the current generic model for abandoned channel fill stratigraphy produced in unidirectional flow river reaches to incorporate seasonal tidal deposition. This work was based on evidence from two consecutive abandoned channel fill sequences in Ropers Slough of the lower Eel River Estuary. Planform geomorphic characteristics derived from these images were used in conjunction with sub-cm resolution stratigraphic analyses to describe the depositional environment processes and their resultant sedimentary deposits. The abandoned channel fill sequences appeared to differ due to the topographic steering of bed sediment transport and deposition previously identified in rivers experiencing only unidirectional flow, while also expressing the seasonal dichotomy of fluvial and tidal deposits.</p>

<p> Up until recently research on Paleoindian archaeology has focused on Clovis hunters and the demise of 35 genera of megafauna at the end of the Pleistocene. However, with increasing evidence of Pre-Clovis settlement many megafaunal sites older than Clovis are now under scrutiny. In this endeavor, geoarchaeology plays a key role, particularly with assessing the stratigraphic and geomorphological aspects of sites suspected of being Pre-Clovis. This Thesis looks at, and analyzes three mammoth sites in western Oklahoma; Helena, Grandfield, and Foss. These sites were analyzed on a geologic, geomorphologic, hydrologic, anthropologic, and soil pedogenic basis. Understanding of soils and their developmental processes can help give us a better understanding of the landscape and the environment in which they were formed. These sites were then compared to known sites Domebo, Hajny, and Burnham, all of which have had both an absolute date and an in depth soil analysis. The purpose of the comparison is to try and apply relative dating to a site when absolute dating is not obtainable, either due to funding, or technical issues that prevent obtaining a reliable date. It has been hypothesized that older mammoth finds should be found in higher terraces, while those of younger age, possibly with archaeological significance, should be found in lower terraces near flood plains. The three mammoth sites studied through this research are associated with lower terraces regardless of age. This example shows how complex the relationship is between site age and site distribution in the landscape. This research shows also how important is to evaluate soil development for estimating relative ages. This approach in turn is important for assessing late Pleistocene paleontological sites with potential association with Pre-Clovis human populations. </p>

<p> New stratigraphic and geomorphic data from the Santa Maria Basin, California, suggests that the major basin-bounding Little Pine fault system has been acting in a primarily reverse offset fashion since the late Pleistocene. A series of stratigraphic columns in the Plio-Pleistocene Paso Robles Formation measured along the Little Pine fault indicate that there was episodic uplift during the latest Pleistocene. A 20-40% increase in the percent composition of resistive, Franciscan Complex-derived cherts within active drainages indicate that uplift of the San Rafael Mountain front increased rapidly since the deposition of older sediments. The shape of stream profiles created along the Little Pine fault suggest ongoing uplift associated with the central and southeastern segments of the fault, with a lesser amount of uplift occurring further northwest along the Little Pine fault. A number of ridgeline profiles were also created which exhibit significant jumps in topography near, or just northeast of the Little Pine fault, suggesting that recent uplift is responsible. The ridgeline profiles also suggest an increased rate of uplift adjacent to the central and southeastern segments of the Little Pine fault zone, in agreement with the along-strike variations in uplift suggested by the stream profiles. Stream traces were also examined for deflections as they flowed across the Little Pine fault, but most show no significant lateral offset.</p>

<p>Features observed on a seismic horizon at or near the Cretaceous-Paleogene boundary in a roughly 200 square km (77 square miles) 3D seismic survey from northern Louisiana resemble large subaqueous dunes or &ldquo;mega-ripples.&rdquo; It is hypothesized that these features may represent subaqueous dunes emplaced by tsunami waves generated by the end-Cretaceous Chicxulub Impact event on the Yucat&aacute;n Peninsula. Seismic data are scrutinized to determine whether or not features observed in the data represent true subsurface geometries. Other hypotheses are tested including the possibility that these features may represent seismic data acquisition footprints, a portion of a slump deposit, or a portion of an aeolian dune field. Results indicate that it is very unlikely that these features represent an acquisition footprint, a slump deposit, or an aeolian dune field. Well-logs are interpreted and seismic velocities are calculated to determine a range of possible lithologies within the Upper Cretaceous interval but the results of the two methods are inconsistent with each other. </p>

<p> Geomorphologic methods document poorly exposed tectonically active structures in the first study to determine quantified ages for Quaternary Age fluvial terraces at Santa Cruz Creek. GPS surveys of three flights of terrace surfaces and a stream gradient profile reveal deformation at the Baseline/Los Alamos fault zone and Little Pine fault. Optically Stimulated Luminescence (OSL) dating was employed to determine ages for the terraces. The formation age of Terrace 1 is 19.3 ka with an incision rate of 1.63 to 1.82 mm/yr, Terrace 2 was dated at 32.9 ka with incision rate of2.02 to 1.82 mm/yr. Based on incision rates an estimated age of 44.0-47.0 ka was calculated for Terrace 3. Offsets in T-2 and T-3 were used to calculate a short term faulting rates of .91 mm/yr and a long term faulting rate of 0.67 to 0. 73 mm/yr for the Baseline/Los Alamos fault.</p>

<p>This aim of this dissertation is to investigate "pedogenesis" (soil formation and change over multi-millennial timescales with minimal human impact) and "anthropedogenesis" (centurial and decadal soil formation and change through the Holocene with increased human influence) in the highly weathered, upland soils of the Southern Piedmont physiographic region in the southeastern United States. I start by combining an analysis of the cosmogenic nuclide meteoric beryllium-10 (10Be) with a mass balance analysis of pedogenic 9Be loss to estimate how long the Southern Piedmont Ultisol have been residing at Earth's surface. This coupled analysis indicates that pedogenesis has been operating in these highly weathered Ultisols for much, if not all, of the Quaternary; considerably longer than previously thought. Next, I utilize traditional soil analyses alongside iron stable isotope measurements to investigate how one century of reforestation after agricultural land abandonment impacts the coupled carbon -iron cycle in these ancient subsoils. This project suggests that widespread patterns of anthropogenic land use change in the Southern Piedmont have caused significant subsoil changes that impact carbon storage and the distribution of iron deep below ground. Finally, I analyze over 50 years or repeated soil and forest ecosystem observations from the Calhoun Experimental Forest to investigate the relationship between soil macronutrient contents aboveground forest ecosystem development in the region. These long term observations suggest that decadal patterns of secondary forest growth and decline fundamentally alters the role that soils plays in individual ecosystem nutrient cycles and that the potential for ecosystem nutrient loss is highly nutrient dependent, despite well-established ecological theory.</p> / Dissertation

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Bird Island is a former flood tide delta occurring in the mouth of the River Murray, Encounter Bay, South Australia. The island has experienced a rapid development history; in around 60 years the formerly ephemeral deltaic deposits have rapidly become stabilised, forming a permanent island approximately 1 km in diameter. / It has been possible to place tight time restraints on the progressive development of Bird Island over this 60 year period. Its sand dunes and marshes of different ages can be distinguished clearly from an analysis of successive aerial photographs. Evidence suggests they represent different phases in the growth and development of the island, resulting from an interplay of factors including the position and migration of the Murray Mouth relative to the island as well as the availability of sediment and conditions conducive to aeolian sand transport. / The landforms of Bird Island present a unique opportunity for the assessment and study of progressive plant colonisation and succession on a pristine landscape in a coastal/estuarine setting. Bird Island comprises 19 different dune and marsh vegetation types. Research has identified several trends suggesting that the environmental gradients associated with the marsh-dune landforms has influenced some characteristics of species distribution. It also appears that in a general way, species distributions may represent succession on the sand dunes, but this was not as clearly demonstrated across the marshes of different ages on Bird Island. / Research suggests that the construction of the lower River Murray barrages in 1940, which has reduced the median annual flow to the estuary by nearly 75%, and has reduced the tidal prism by up to 90%; has facilitated the development of Bird Island. Bird Island contributed to the closure of the mouth of the River Murray in 1981; inlet behaviour not demonstrated in the 100 years prior to barrage construction according to the results of this research. / The continuing development of Bird Island suggests considerable potential for more blockages in the future. The continuing sedimentation in the Murray Mouth reflects the inability of the current flow regime and marine processes in maintaining the mouth as they did prior to the construction of regulatory works on the Lower River Murray. / Thesis (MApSc(EnvironmentRecreationMg))--University of South Australia, 2004