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Potential lacustrine source rocks have been recognised in several Cretaceous syn-rift basins including the producing Taranaki Basin, but have not been officially recognised from drill core and seismic data. The late-Cretaceous Paparoa Coal Measures contain three lacustrine mudstone formations which outcrop in several localities and have been extensively drilled for coal mining. These formations are considered to be an easily accessible analogue for late-Cretaceous lacustrine source rocks in New Zealand and also provide valuable information regarding syn-depositional tectonics and basin formation during the late-Cretaceous. Stratigraphic columns and isopach maps were constructed from field work and drill hole descriptions and results showed variations in lithofacies across the basin. The western side of the basin is characterised by sandy lithofacies, abundant proximal turbidites and debris flows. The transition to a sub-aerial environment is marked by thick conglomerate and meter wide rip-up clasts. The central and eastern sections of the basin show massive mudstone, distal turbidites, low energy fluvial sandstones and thin, discontinuous coal. Isopach maps constructed from drill hole data identified three NNE – SSW oriented lakes with lacustrine sediment of up to 180m thick truncated by the eastern Roa – Mt Buckley Fault Zone. It was determined fault control during deposition was to the west and the basin extended further than its current location. Revisions to isopach models highlighted a lack of change in basin orientation during deposition of the Paparoa sediments. Plate reconstructions combined with direct evidence from the basin indicate formation of the Paparoa Coal Measures could have occurred in either a rift or transtensional basin. The mudstones were geochemically assessed for hydrocarbon potential using a Source Rock Analyser (SRA). Preliminary analysis of the three mudstones has shown TOC values ranging from 1.0 to 4.5 wt.%, HI values ranging from 68 to 552 mHC/gTOC and Tmax results show the mudstones to range in maturity from immature to late – mature. A sample from the Waiomo Formation has excellent potential for oil generation and the low maturity results for the Goldlight Formation make it a potential shale gas resource. These results have shown the potential for hydrocarbon bearing lacustrine source rocks to exist in the Greymouth Coalfield. In addition, revisions have been made to basin formation which should be considered. Due to the availability of data from the Paparoa lacustrine source rocks, they should be used as an accessible analogue for Taranaki and other Late Cretaceous basins.

Channing Lake Basin, located west and northwest of Channing, in the Texas Panhandle, is of substantial area and presumably includes lake beds of Pliocene and Pleistocene ages within the Rita Blanca Formation, a member of the Ogallala Group. The foci of this study were a micritic ooid layer and a directly overlying stromatolite layer, which crop out in a canyon approximately 10 kilometers west of Channing. Research was conducted primarily using petrographic and scanning electron microscopy. Significant conclusions include: organic matter was preserved in ooids as filaments and nanoscale spheroids, which served to capture ostracode carapaces within ~10% of micritic cortices; and stromatolites were deposited within an evolving alkaline lacustrine environment producing discernible zones. Potential significance includes improving the understanding the role of organic matter in calcium carbonate precipitation, which has plausible applications in medical, industrial, and academic realms.

<p> The forms of phosphorus in sediments of acid and non-acid shield lakes were determined in order to assess the effects of lake acidification on the mobility of sediment phosphorus. Sediment phosphorus is conveniently classified into three categories: non-apatite inorganic phosphorus (NAI-P), apatite-P and organic P. The distribution of P between different categories was found to be dependent on the lithology of the lake basin, the pH in the water column, and the redox conditions.</p> <p> More than 90% of inorganic P in shield lake sediments was in the NAI-P category, associated presumably with hydrated Fe and Al oxides. Organic P accounted for more than 40% of total P in sediments of acid lakes, which is proportionally higher than that found in sediments of neutral lakes. Bioavailable P, a measure of the fraction of sediment inorganic P readily available for biological utilization, amounted to ~70% of NAI-P, similar to that found in hard water lakes.</p> <p> A series of experiments was designed to investigate the immobilization of P from solution. The uptake of P by solid phase was explained by an adsorption mechanism. The quantitative estimates of phosphate sorption parameters for sediments of acid and non-acid lakes show that mineralogical and chemical characteristics of sediments are more important than the pH of water in determining their efficiency of P removal. Therefore, acidification of lakes does not significantly influence the uptake of P by sediments.</p> / Thesis / Master of Science (MSc)

The Virginia Solite Quarry assemblage of Tanytrachelos ahynis, with its exceptionally abundant and uniquely preserved specimens, offers an opportunity to quantify multiple aspects of vertebrate taphonomy. The presence or absence of 128 skeletal elements (i.e., bones) as well as the presence or absence of 136 skeletal variables (i.e., morphometric dimensions) were recorded for 100 specimens collected from two distinct layers within the quarry (lake cycles 2 and 16). Anatomical specimen completeness (or the percent of bones/variables present in a specimen) is low (the median specimen preserves 14.5% of bones and 11.8% of measured variables) in spite of protection from high energy currents, predators, and scavengers afforded by anoxic bottom waters. Specimen size, as approximated by femur length, does not significantly impact specimen completeness. Also, post-exhumation weathering, duration of exposure before burial, and morphotype groupings do not appear to have significantly affected anatomical specimen completeness or articulation. Presence or absence of the enigmatic heterotopic bones represents a true biological signal as indicated by the lack of significant difference in anatomical specimen completeness between the two morphotypes as well as qualitative taphonomic evidence. When anatomical specimen completeness has been corrected for post-depositional faulting, lake cycles 2 and 16 differ from one another significantly in terms of articulation and anatomical completeness of specimens. Specimens with soft-bodied preservation are significantly more articulated, but not significantly more complete, than specimens without preserved soft tissues. Preservation frequency of bones/variables (or the percent of specimens in which a bone/variable is present) varies greatly, but is generally low (an average skeletal element is present in 19% of specimens and an average variable can be measured in 12% of specimens), with significant preferential removal of smaller skeletal elements. Hind limbs, specifically femora, are most commonly preserved. Low anatomical specimen completeness and positive correlation between bone size and frequency of preservation both indicate specimen disturbance by minor hydraulic currents. These taphonomic patterns suggest a moderate-depth depositional environment (slightly shallower than previously proposed). / Master of Science

Recent sedimentary records have indicated that climate in low latitude, continental environments have varied significantly throughout the mid to late Holocene. In subtropical North America, major climatic phenomena such as the migration of the Intertropical Convergence Zone (ITCZ) and the Bermuda High have been shown to play a major role in this variability. Specifically, the northward migration of the ITCZ and the eastward position of the Bermuda High during summer months leads to warmer and wetter conditions over subtropical North America, and vice versa. A quantitative approach to understanding hydrologic dynamics (i.e. atmospheric circulation patterns, relative humidity) associated with these and other phenomena is necessary to accurately reconstruct the behavior of these hydrologic parameters in the past. Previous studies have shown that the hydrogen isotopic composition of algal material is a direct reflection of source waters, and that hydrogen isotopic enrichment in terrestrial material relative to aquatic biomass is a function of evaporative processes associated with the level of relative humidity in a given environment. This study utilizes a lacustrine system to provide a modern calibration that will attempt to develop a new climatic proxy for relative humidity and further examine varability in the behavior of environmental waters. This calibration was then applied to a sedimentary record to examine hydrologic variability in the geologic past.

Mercury concentrations in freshwater and marine biota are an ongoing concern, even in areas remote from local point sources, such as in the Canadian Arctic and sub-Arctic. Anadromous Arctic charr, which feed in the marine environment, have lower mercury concentrations than non-anadromous Arctic charr, which feed strictly in freshwater, but the two life-history forms have rarely been studied together, and the mechanisms driving the difference are unclear. Here, data from nine pairs of closely-located anadromous and non-anadromous Arctic charr populations were used to explore the impact of biological and life-history factors on individual total mercury concentration ([THg]) across a range of latitudes (49 – 81° N) in eastern Canada. From six of these sampling locations, additional samples of lower trophic level biota (i.e., algae, invertebrates, and forage fishes) were obtained in order to investigate patterns of total mercury (THg) and methylmercury (MeHg) biomagnification in the marine and lacustrine foodwebs supporting Arctic charr. Arctic charr mean [THg] ranged from 20 to 114 ng/g wet weight (ww) in anadromous populations, and was significantly higher in non-anadromous populations (all p < 0.01), ranging from 111 to 227 ng/g ww. Within-population variations in Arctic charr [THg] were best explained by fish age, and were also positively related to fork-length and δ15N-inferred trophic level. Across all sampling sites, the relationship between Arctic charr [THg] and fish age was significant and statistically similar in both life-history types, but only the non-anadromous fish demonstrated a significant relationship with trophic level. Fork-length and site latitude did not explain significant additional variation in Arctic charr [THg] across sampling locations. Trophic magnification factors were 1.98 – 5.19 for THg and 3.02 – 6.69 for MeHg in lacustrine foodwebs, and 1.59 – 2.82 for THg and 2.72 – 5.70 for MeHg in marine foodwebs, and did not differ significantly between the two feeding habitats for either THg or MeHg. The biomagnification rate of MeHg exceeded that of THg in both habitats. Mercury concentrations at the base of the foodweb were higher in the lacustrine environment (estimated at 17 – 139 ng/g dw for THg and 5 – 42 ng/g dw for MeHg) than in the marine environment (8 – 39 ng/g dw for THg and 1 – 11 ng/g dw for MeHg). The proportion of mercury in the methylated form was related to trophic level, and the relationship was statistically similar in the lacustrine and marine habitats. There was no effect of site latitude on mercury concentrations in marine or lacustrine biota, thus the difference between feeding habitats was consistent across a range of latitudes (56 – 72°N) in eastern Canada. We conclude that a difference in prey mercury concentration, driven by differential mercury concentrations at of the base of the lacustrine and marine foodwebs, is important for explaining the difference in mercury concentration between anadromous and non-anadromous in Arctic charr.

Nitrification became the dominant nitrogen transformation in a number of lakes which accumulated ammonium, in hypolimnetic water, under aerobic conditions. The timing and duration of this activity varied between lakes but was characterized by decreasing ammonium, and increasing nitrate, concentrations. In Grasmere lake this phase was found to be due to the activity of planktonic chemolithotrophic nitrifying bacteria. The observed nitrate concentration increased during this phase and accounted for up to 15% of the total oxygen deficit of the hypolimnion. At similar in situ temperatures nitrification rates and nitrifying bacterial populations were greater in oxidised sediments than in the water column. Littoral sediments were more important than profundal sediments as sites of nitrification due to higher temperatures and the persistance of oxidising conditions to greater depths into these deposits. Within the littoral zone the physical characteristics of the sediment were important with organic rich deposits sustaining greater rates of nitrification than sandy sediments. Nitrate reduction was the primary determining factor of nitrate concentrations in sediment interstitial waters. Some observations on the culture of chemolithotrophic nitrifying bacteria from lakewater were discussed. Reviews of the methodology for nitrification research and nitrification in the lacustrine environment are presented.

Lake basins contain depositional systems whose stratigraphy and sedimentology are highly influenced by allogenic and authigenic processes. Identifying the relative roles of these controls is complicated in settings where both tectonic and climate influences control sediment inputs and accommodation availability. In order to identify how these controls may interact in carbonate lake basins the lacustrine Mayrán Formation, northeast México was investigated. The Mayrán Formation is well exposed and the strata geometries are well preserved. The necessary data needed to unravel these complexities was obtained using field based techniques (geological and structural mapping, sedimentary logging and sampling), combined with optical and electron optical microscopy, mineralogical (XRD), and geochemical (oxygen and carbon stable isotopes, total organic carbon [TOC], organic carbon isotopes, and U-Pb carbonate dating) techniques, to characterise the lake basins. These data reveal that the Mayrán Formation was deposited in four, northerly, down-stepping, broadly coeval, hydrologically linked, carbonate-dominated lake subbasins (the Mayrán Basin system), that formed at different elevations spanning ~500 m. Subbasin geomorphology was controlled by the inherited topography of the exhumed and eroded Parras foreland fold-and-thrust belt, as a result, the subbasins are compartmentalized by prominent sandstone ridges that form sills between subbasins. Sedimentary infill of the subbasins consists of a fluvio-lacustrine succession (carbonate and clastic) that overly an angular unconformity truncating the folded and faulted Cretaceous bedrock. Clastic sediments were preferentially trapped in the most proximal subbasin in the south, adjacent to the mountain front. In more distal settings to the north, carbonate production resulted in deposition of horizontally bedded lacustrine limestones with subordinated siliciclastics and evaporite minerals. Carbonate deposition occurred during overfilled to balance filled conditions. Prominent aggradational to progradational tufa clinoforms form at the spillover points between the subbasins, and interfinger up- and down-dip with the horizontally bedded lacustrine limestones. The tufas consist of steeply dipping clinoforms that prograde northwards. They formed by inorganic and biogenically mediated calcite precipitation as waters from the topographically upper lake overflowed the sill. U-Pb dating of speleothem cements formed in the tufas yield a Pliocene age (3.06 ± 0.2 Ma). The horizontally bedded limestones that predominantly fill the subbasins are composed of nine lithofacies. These are: ostracode mudstone-wackestone, clotted boundstone, gastropod wackestone-packstone, oncoid wackestone-packstone, stromatolite, charophyte wackestone-packstone, marlstones, crystalline carbonate and evaporite minerals. These lithofacies contain variable proportions of production-derived components, with subordinated detrital and diagenetic components. They overall contain inorganic and organic calcite (average 91%), organic matter (average 12.6 % TOC) and subordinated detrital quartz, feldspar and clay. Stable isotope conditions from stromatolite laminations (δ13C -6.3‰ and δ18O -8.0‰), and micritic matrix from samples in all the subbasins (δ13C -5.7‰ and δ18O -8.4‰), indicate that overall calcite deposition occurred in freshwater lakes, under predominantly oxic conditions. Carbonate particles deposited mainly by in situ disaggregation and by settling. Significant preservation of the organic matter likely occurred because of the fine grained carbonate matrix, and because of moderate rates of both carbonate sediment and organic matter production. Stacking patterns in the lake successions show an overall shallowing upward cyclicity. It is considered, that the effects of inherited basin geomorphology and climate, ultimately controlled facies variability and strata geometries in these subbasins.