No description available.

<p> The objective of this project was to construct pollen-climate transfer functions for the Western Interior of Canada and to apply these to dated fossil pollen records to obtain estimates of past climates.</p> <p> Climate curves from the calibration functions were constructed for summer precipitation and temperature, fall precipitation and temperature, winter temperature, and spring temperature.</p> <p> The palaeotemperature estimates suggest winter and fall temperatures were warmer during the mid-Holocene whereas the summer and spring temperatures suggest there was no significant difference in temperature between this time and the present. Results are not in accordance with the Milankovitch estimates of Holocene insolation variation or the conclusions of previous palaeoclimatic studies in the region.</p> <p> The palaeoprecipitation estimates constructed indicate decreased precipitation during the mid-Holocene. Increased aridity in the mid-Holocene is consistent with both the Milankovitch theory and the results of previous palaeoclimatic reconstructions from the study area. However, it is not clear if the high aridity reflects decreased precipitation or increased evapotranspiration.</p> <p> The theoretical and practical limitations of the pollen-climate transfer function approach to this approach to the estimation of paleoclimates are discussed.</p> / Thesis / Candidate in Philosophy

No description available.

Marine palynomorph assemblages from the Campanian-Maastrichtian Bearpaw Formation, consisting of 34 genera and 69 species of dinoflagellate cysts and 8 forms of acritarchs, were recovered from a composite section in the Cypress Hills and the Research Council of Alberta Castor borehole in southern Alberta, Canada. Correlation of the sections with magnetostratigraphy and radiometric dates of bentonites within the Bearpaw Formation provided a chronostratigraphic control that enabled correlation between the two sections and the Campanian-Maastrichtian Boundary Global Stratotype Section and Point at Tercis les Bains, France. Correlation of first and last occurrence data of key taxa in the boundary section at Tercis with the same taxa in the studied sections support the placement of the Campanian-Maastrichtian Boundary at the transition between magnetochrons 32n.1n and 31r within the <i>Baculites baculus</i> ammonoid range zone of the Western Interior of North America.<p>Semi-quantitative analyses of the assemblages record the transgressive-regressive episodes of the Bearpaw cyclothem. Increases in the relative abundances of gonyaulacacean cysts, numbers of dinocysts compared to terrestrial palynomorphs and assemblage diversity correlate with transgressive episodes, with the richest assemblages occurring during periods of open, offshore to neritic conditions correlated with the cyclothems transgressive peak.<p>Two new species of dinoflagellate cyst are described. The first, Dinoflagellate sp. 1, is a novel taxon, while the second, Downiesphaeridium sp. A, is a chorate cyst similar to Mesozoic forms previously ascribed to <i>Cleistosphaerdium diversispinosum</i> Davey et al. emend. Eaton et al.

Marine palynomorph assemblages from the Campanian-Maastrichtian Bearpaw Formation, consisting of 34 genera and 69 species of dinoflagellate cysts and 8 forms of acritarchs, were recovered from a composite section in the Cypress Hills and the Research Council of Alberta Castor borehole in southern Alberta, Canada. Correlation of the sections with magnetostratigraphy and radiometric dates of bentonites within the Bearpaw Formation provided a chronostratigraphic control that enabled correlation between the two sections and the Campanian-Maastrichtian Boundary Global Stratotype Section and Point at Tercis les Bains, France. Correlation of first and last occurrence data of key taxa in the boundary section at Tercis with the same taxa in the studied sections support the placement of the Campanian-Maastrichtian Boundary at the transition between magnetochrons 32n.1n and 31r within the <i>Baculites baculus</i> ammonoid range zone of the Western Interior of North America.<p>Semi-quantitative analyses of the assemblages record the transgressive-regressive episodes of the Bearpaw cyclothem. Increases in the relative abundances of gonyaulacacean cysts, numbers of dinocysts compared to terrestrial palynomorphs and assemblage diversity correlate with transgressive episodes, with the richest assemblages occurring during periods of open, offshore to neritic conditions correlated with the cyclothems transgressive peak.<p>Two new species of dinoflagellate cyst are described. The first, Dinoflagellate sp. 1, is a novel taxon, while the second, Downiesphaeridium sp. A, is a chorate cyst similar to Mesozoic forms previously ascribed to <i>Cleistosphaerdium diversispinosum</i> Davey et al. emend. Eaton et al.

The Kremmling Paleontological Resource Area (KPRA) contains one of the most fossiliferous units within the Late Cretaceous Western Interior Seaway of North America. It was deposited during the late Campanian Baculites compressus/cuneatus ammonite biozones ((\approx) 72.5 Ma) and records slightly less than one million years of depositional history. Examination of the fauna, its dominant preservational mode and taphonomy as well as the lithologic evidence from measured stratigraphic sections strongly suggests that the depositional environment of the KPRA was a shallow, relatively nearshore environment. A detailed taxonomic examination of the molluscan fauna was undertaken in order to re-evaluate past work as well as to more thoroughly document the fauna. Samples were collected from 79 locations within the (\approx) 1 km² study area. The molluscan fauna from the KPRA consists of 47 bivalve, 22 gastropod, and 13 cephalopod species; ten of these species are new. In addition, two inarticulate brachiopods and one serpulid are described. This highly diverse assemblage points to an increase in nearshore diversity as compared to faunas described from earlier intervals with similar environmental settings. The timing of this increase in species richness remains elusive, but may have initiated in the late Campanian and continued into the early Maastrichtian.

No description available.

No description available.

The Upper Cretaceous Tropic Shale of southern Utah captures critical oceanographic changes that occurred during Oceanic Anoxic Event 2 (OAE 2) and the transgression of the Greenhorn Sea. We investigated the response of planktic and benthic foraminifera in a shallow (<100 >m) marine environment stressed by the onset of OAE 2 during the Cenomanian-Turonian boundary (CTB; 93.9 Ma) to determine the oceanographic mechanisms controlling the observed turnovers in the foraminiferal record. This study is based on high-resolution quantitative foraminifera counts and isotope paleoecology (d18O and d13C) from a 40-m outcrop. The OAE 2 interval is identified by a distinctive d13Corg signature and by correlation of bentonites and limestones across the seaway. Results of assemblage analyses indicate discrete intervals of environmental perturbations across the CTB interval. At the onset of OAE 2, surface waters were dominated by planktic Guembelitra cenomana with minor species of Heterohelix. Benthic abundances increase and were initially dominated by oxygen tolerant infaunal Neobulimina albertensis. Epifaunal Gavelinella dakotaensis briefly proliferated during the core of the OAE 2 and coinciding with the planktic “Heterohelix shift” and increasing accumulation of organic matter. The peak of OAE 2 at ~17 m is marked by a rapid shift to infaunal Neobulimina dominance. We suspect incursion of oxygen-poor Tethyan intermediate waters with peak transgression during the early Turonian, coupled with high productivity in surface waters resulted in the rapid depletion of benthic oxygen. The foraminiferal record reveals strong cyclicity in planktic/benthic ratio resembling parasequences that correlate to the GSSP in central Colorado.

Mosasauria is a clade of essentially Late Cretaceous marine reptiles. Although well known by several nicely preserved specimens, phylogenetic relationships of mosasaurians within Squamata are still a matter of intense debate. Most of the works discussing the relationships of mosasaurians in global contexts of squamates were based mainly on more derived taxa, including only few basal forms. Here the anatomy, phylogeny, ontogeny and taxonomy of the basalmost mosasaurian radiation, the commonly known \"dolichosaurs\", is reviewed, mostly on the light of new and exquisitely preserved coniasaur remains from Texas. New remains described here encompass dozens of specimens, including a new species represented by a gravid female and several embryos. A revision of the genus Coniasaurus suggest it as encompassing four species: C. crassidens, C. longicollis (former Dolichosaurus longicollis), C. gracilodens and the new taxon described here. Contrary to what is observed in more derived forms, the patterns of tooth attachment in coniasaurs are very similar to those of varanoids, suggesting similarities between tooth attachment and implantation in snakes and derived mosasaurs to be the result of homoplasies. The evolution of the dolichosaurian postcranial anatomy is assessed, finding new diagnostic characters for several distinct lineages. A phylogenetic analysis of Mosasauria in a global matrix of squamates, including the largest sample of basal forms ever tested, consistently found the group to be closely related to Varanoidea, rejecting the hypotheses of the group being closely related either to snakes or lying in a more basal position among squamates. Results gathered by this thesis are expected to greatly contribute to the knowledge of this astonishing group / Mosasauria é um clado formado essencialmente por répteis marinhos do Cretáceo Superior. Embora bem conhecido por diversos espécimes, as relações filogenéticas do grupo dentro de Squamata formam um tópico de intenso debate. A maior parte dos trabalhos discutindo o tema em análises globais de Squamata foram baseadas em táxons mais derivados, incluindo apenas poucas formas basais. Aqui, a anatomia, filogenia, ontogenia e taxonomia da irradiação mais basal do grupo, os \"dolicossauros\", foi revista, principalmente à luz de novos restos fósseis de coniassauros do Texas. Os novos fósseis descritos aqui englobam dezenas de espécimes, incluindo uma nova espécie representada por uma fêmea gravida e diversos embriões. Uma revisão do gênero Coniasaurus sugere que o mesmo engloba quatro espécies: C. crassidens, C. longicollis (antes Dolichosaurus longicollis), C. gracilodens e o novo táxon descrito aqui. Ao contrário do observado em formas mais derivadas, os padrões de fixação dentária nos coniassauros é muito similar àqueles dos varanóides, sugerindo que as similaridades observadas nestes padrões entre serpentes e mosassauros derivados resulta da ocorrência de homoplasias. A evolução do esqueleto pós-craniano dos dolicossauros foi avaliada, encontrando novos caracteres diagnósticos para diferentes linhagens. Uma análise filogenética de Mosasauria em uma matriz global de Squamata, incluindo a maior amostragem de formas basais já testada, consistentemente encontrou o grupo como proximamente relacionado ao clado Varanoidea, rejeitando hipóteses de proximidade com serpentes ou numa posição mais basal dentro de Squamata. Espera-se que os resultados provenientes desta tese contribuam consideravelmente para o conhecimento deste incrível grupo