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This study aims to document the dinoflagellate cyst biostratigraphy and paleoenvironmental record of the Maastrichtian Neylandville and Corsicana Formations and the lower part of the Danian Kincaid Formation from the Brazos River, Texas. Rock samples are exposed to standard palynological methods for biostratigraphic interpretations. The quantitative data collected from palynological samples are combined with δ13C and δ18O stable isotope geochemistry and TEX86 and BIT Index organic geochemistry data for paleoenvironmental interpretations. Biostratigraphically important species of dinoflagellates divide the section into three intervals. Interval 1 occurs within the Neylandville Formation, and the presence of Alterbidinium acutulum, Xenascus ceratioides and Isabelidinium cooksoniae indicate that this interval is not younger than early Maastrichtian. Interval 2 represents the Corsicana Formation. The presence of the late Maastrichtian species Disphaerogena carposphaeropsis, Palynodinium grallator and Deflandrea galeata at the base of the Corsicana Formation indicate that this interval is of late Maastrichtian age. Interval 3 occurs within the Kincaid Formation. The presence of Carpetalla cornuta and Damassadinium californicum at the base of the Kincaid Formation indicates that this interval is of Danian age. Previously published Gulf of Mexico palynology studies, as well as planktonic foraminifera and nannoplankton data confirm the age assignments of the studied interval. Dinoflagellate species assemblages increase in diversity upwards from Interval 1 to Interval 2, and then show a small decrease above the K-Pg boundary within Interval 3, indicating that the K-Pg event was not catastrophic for the dinoflagellates. The Cerodinium spp. and Spiniferites spp. complex comprise a large proportion of the species within the section. High abundance peaks of Glaphyrocysta spp., Cribroperidinium spp., and Yolkinigymnium lanceolatum occur within Interval 2. Two intervals in the section are dominated by peridinioid dinoflagellates, measured by the Peridinioid/Gonyaulacoid (P/G) ratio. The first one occurs within Interval 2 and contains peaks of the P/G ratio that correlate with increases in δ13C, suggestive of an increase in paleoproductivity. Two more peaks occur within Interval 3. Bottom water δ18O temperatures determined from benthic foraminifera and sea surface temperatures determined from TEX86 organic geochemistry show an overall cooling trend from Early Maastrichtian to the K-Pg boundary.

The Brazos River, located predominantly within the state of Texas, has the highest water and sediment discharge of all rivers in the state, and ranks second behind the Mississippi River in terms of sediment load delivered to the Gulf of Mexico. This river is the only Texas river that consistently drains directly into the Gulf of Mexico forming a wave-dominated delta. The delta has experienced dramatic and rapid changes over the last 100-plus years. These changes have resulted from both natural and anthropogenic alterations to the coastal zone proximal to the river mouth and within the rivers watershed. By utilizing high-resolution geophysical data, sediment cores, water column data, and historic shoreline data this study investigated the mechanisms in which sediment is transported to the coastal ocean, the fate of that sediment as it becomes preserved in the modern geological record, and the evolution of a modern delta. Results from this study show that during for a majority of the time a salt-water intrusion in the lower river traps sediment, preventing export to the coastal ocean. The trapped sediment forms an ephemeral mud layer in the lower river that may be remobilized during increased river discharges. When river discharges increase above an observed threshold of 300 m^3/s the salt wedge is pushed seaward of the river mouth and sediment is exported via a buoyant plume. As export of sediment is episodic, accumulation of sediment on the subaqueous delta characterized as non steady-state, and resembles typical foreset delta attributes. These include physical stratification of sediment layers, episodic but relatively high rates of accumulation, and little bioturbation. Currently sediment is primarily accumulating west of the river mouth, and the majority of sediment is bypassing the system. Over the history of the delta, changes both anthropogenic and natural have shifted the relative balance of fluvial sediment supply and marine sediment dispersal. These changes have resulted in dramatic changes in the shoreline, and phases of activation and abandonment of deltaic lobes, which can be seen through historical data and imagery, and is preserved in the recent sedimentary record.

The Cataraqui River, which drains 930 square km of watershed before emptying into the inner harbour of Kingston, Ontario (pop: 113,000), has a long history of anthropogenic use. More than 40 industries have existed within the inner harbour over the last century, and while many of these industries are no longer present, the properties that they operated on remain to the present day as potential sources of persistent contamination. This study examined total mercury (THg) concentrations in depth profiles of 21 sediment cores within the inner harbour. THg in pore waters was measured in some selected cores along with methylmercury (MeHg), and total organic carbon measured as % Organic Matter (OM). Results show that the spatial distribution of THg in the surface sediment is not homogenous; concentrations in surface sediment along the southwestern shoreline, adjacent to the former industrial properties, are significantly greater than the rest of the inner harbour, and above the severe effect limit (2000 μg/kg) guideline for sediment. MeHg was detected in some sediment cores, and was found to have a significant, positive correlation with [THg] in surface sediment. THg in pore water was below detection limits in most cores, indicating possible strong associations with sediments, however OM only showed significant, positive correlations with THg in one core sampled. To determine the sources of Hg to sediments, soils, runoff and storm sewer discharges near high concentration sediments were measured for THg. Hg was not detected in storm sewers, but was detected in terrestrial soil near the Kingston Rowing Club at a concentration of more than 4000 μg/kg. Significant [THg] was detected in runoff draining shoreline soils, indicating that erosion from terrestrial sources may be an ongoing source of Hg to sediment. Since [THg] was correlated to the [MeHg] in surface sediment, reducing the amount of Hg entering the river from terrestrial sources may reduce the amount of bioavailable Hg in sediments of the inner harbour. / Thesis (Master, Biology) -- Queen's University, 2007-11-01 19:12:24.364

Benthic uptake of mercury (Hg) governs bioavailability to fish yet there are still large gaps in our knowledge of what mediates this process. Without this information it is difficult to ascertain where Hg accumulation in the foodweb will be greatest. In the St. Lawrence River Area of Concern (AOC) at Cornwall, one contaminated zone (Zone 1) shows elevated Hg in yellow perch (Perca flavescens) and their prey items compared to those from other zones in the AOC. Greater availability of Hg to benthos due to unique physical features (large deposition of woodfibre deposits) of Zone 1 is hypothesized to account for this observation. In this study, amphipods (Gammarus fasciatus) and (Echinogammarus ischnus) were collected in Zone 1 using artificial substrates between June-September 2007, and Hg concentrations compared to those obtained in sediments and porewaters of surficial sediments, as well as methane gas evasion rates. Methylmercury (MeHg) concentrations in amphipods were significantly related to porewater total Hg (THg) and MeHg concentrations. No parallel relationship was found for sediment Hg concentrations or methane bubbling rates from sediments. Spatial and temporal trends in Hg bioavailability were evident from significant relationships with water column depth and temperature. Water column depth was associated with higher MeHg concentrations in amphipods and porewaters. Concentrations of porewater MeHg were above the detection limit in all of the June samples, the month which also coincided with highest amphipod MeHg concentrations. Finally, sediment organic matter may be influencing patterns of MeHg availability in Zone 1, and displayed a negative relationship to amphipod MeHg. Although bubbling from contaminated sediments did not directly correlate with amphipod Hg uptake, future studies should look at the influence of bubbling on the redistribution of contaminated sediment particles within the zone. / Thesis (Master, Biology) -- Queen's University, 2008-12-30 23:34:20.287

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