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Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 182-218). Also available via the Internet.

Thesis (M. Sc.), Memorial University of Newfoundland, 1998. / Bibliography: leaves 195-212. Also available online.

Over the past decade, the study of organismal or systematic paleobiology has been progressing into a new age of digital paleobiology, in which advanced instrumentation is utilized for primary data collection and analyses. Having been progressing throughout this field of study, advanced instruments–commonly electron- and ion- microbeam equipment–have been employed for numerous fossils over the entire range of geologic time, from microfossils to macrofossils and from the Archean (beginning at 3800 Ma) to the Cenozoic (ending at the recent). These techniques, predominantly used for geochemical, morphological, and ultra-/micro-structural analyses, have unlocked an incredible amount of detail contributing to our understanding of fossil organisms, their modes of life, and their biological affinities. But further, as these techniques continue to grow and become popularized in various fields of paleobiological study, they are certain to significantly progress our comprehension and knowledge of the evolution of life through time. While the chapters presented in this dissertation may not have a unifying theme in terms of a distinct fossil organism or specific time in Earth's history, furthering the use of electron- and ion- microbeam instrumentation and expanding the paleo-genres to which digital paleobiological approaches may be applied encompasses the fundamental intention of my research. Two of the chapters reported here focus on the geochemical, ultrastructural, and microstructural investigation of organic-walled microfossils, or acritarchs, from the Paleoproterozoic (2500–1600 Ma) and Mesoproterozoic (1600–1000 Ma), using a range of advanced instrumentation including field emission scanning electron microscopy, transmission electron microscopy, laser Raman spectroscopy, electron microprobe, secondary ion mass spectroscopy, and focused ion beam electron microscopy. Moving into the Neoproterozoic (1000–542 Ma), the third primary research chapter utilizes field emission scanning electron microscopy for high-resolution, high magnification imaging and quantitative evaluation of an entire fossil assemblage–from acritarchs and algal fossils to the earliest metazoan embryos. This study was conducted in an effort to examine and describe the phosphatization taphonomic window of the Doushantuo Formation of South China, which is a prime example of exceptional preservation. Finally, the fourth primary research chapter reported here uses field emission scanning electron microscopy and environmental scanning electron microscopy in a field of paleobiology in which advanced instrumentation has been highly underutilized – predatory-prey interactions. This research examines microstructural characteristics of predatory drill holes in both modern and fossil organisms in an attempt to mitigate the identification of predation traces in the fossil record. / Ph. D.

<p>The only direct evidence of past life is provided by fossils. Fossils tell us about the evolution of life on Earth and they give us clues concerning ancient environments. The Ediacaran Period (roughly 635-542 million years ago) is characterised by the appearance and diversification of various microbiota and also the diversification of metazoans. Well-preserved organic-walled microfossils referred to as acritarchs occur abundantly in Ediacaran sedimentary successions in the Officer Basin in South Australia. Acritarch assemblages from the Giles 1 and Murnaroo 1 drillcores show a wide morphological disparity and are taxonomically diverse. Assemblages change over short stratigraphic intervals which enables the recognition of different biozones. The presence of taxa common between Australia, Siberia, Baltica and China provides a means for global correlation of the Ediacaran System. Examination of the wall ultrastructure of several acritarch specimens by use of transmission electron microscopy reveals a complexity in the cell wall that is not seen in prokaryotes but is indicative in some cases of particular clades of microalgae. Wall ultrastructures range from single-layered to three- and four-layered and from homogeneous to porous. The wall ultrastructure can be used to assess biological affinities and the affinities of the studied taxa in relation to green algae, dinoflagellates and metazoans are discussed. However, before taxonomic interpretations can be made with confidence, an understanding of taphonomic degradation of microorganisms is required. With focus on illustrated specimens, one part of this thesis explains what happens to an acritarch as it undergoes various types of degradation and why an understanding of these processes is important for taxonomic identification. A meteorite impact in South Australia spread an ejecta layer over a 550 km radius area. This ejecta layer is recognised in subsurface drillcores and provides an independent stratigraphic marker horizon that supports an acritarch-based correlation.</p>

The only direct evidence of past life is provided by fossils. Fossils tell us about the evolution of life on Earth and they give us clues concerning ancient environments. The Ediacaran Period (roughly 635-542 million years ago) is characterised by the appearance and diversification of various microbiota and also the diversification of metazoans. Well-preserved organic-walled microfossils referred to as acritarchs occur abundantly in Ediacaran sedimentary successions in the Officer Basin in South Australia. Acritarch assemblages from the Giles 1 and Murnaroo 1 drillcores show a wide morphological disparity and are taxonomically diverse. Assemblages change over short stratigraphic intervals which enables the recognition of different biozones. The presence of taxa common between Australia, Siberia, Baltica and China provides a means for global correlation of the Ediacaran System. Examination of the wall ultrastructure of several acritarch specimens by use of transmission electron microscopy reveals a complexity in the cell wall that is not seen in prokaryotes but is indicative in some cases of particular clades of microalgae. Wall ultrastructures range from single-layered to three- and four-layered and from homogeneous to porous. The wall ultrastructure can be used to assess biological affinities and the affinities of the studied taxa in relation to green algae, dinoflagellates and metazoans are discussed. However, before taxonomic interpretations can be made with confidence, an understanding of taphonomic degradation of microorganisms is required. With focus on illustrated specimens, one part of this thesis explains what happens to an acritarch as it undergoes various types of degradation and why an understanding of these processes is important for taxonomic identification. A meteorite impact in South Australia spread an ejecta layer over a 550 km radius area. This ejecta layer is recognised in subsurface drillcores and provides an independent stratigraphic marker horizon that supports an acritarch-based correlation.

Diverse, well preserved organic-walled phytoplankton assemblages were recovered from the Tertiary section of the Oak Grove core drilled on the Virginia Coastal Plain. Strata penetrated include the Aquia, Marlboro Clay, and Nanjemoy Formations (Paleocene to Eocene) of the Pamunkey Group and the Calvert and Choptank Formations (Miocene) of the Chesapeake Group. The assemblages are composed of 176 dinoflagellate species and subspecies (82 genera), of which 20 species and subspecies and one combination are new; five acritarch species (two genera) and five chlorophyte species (three genera) are also reported. The biostratigraphic distribution of the 186 species provides information concerning the ages of the formations and the nature of their lithologic contacts. The organic-walled phytoplankton assemblages corroborate the Paleocene (Thanetian) age indicated by the calcareous nannofossils, Foraminifera, ostracodes, and pollen and spores for the Aquia strata; certain dinoflagellate and pollen species in the lowermost 11.5 m (37.9 ft), however, suggest this basal interval, devoid of other microfossils, could be Paleocene (Danian) in age. An Eocene (Ypresian) age is assigned to the Nanjemoy strata based on the organic-walled phytoplankton, as well as the pollen and spores, calcareous nannofossils, ostracodes, and mollusks. The intervening Marlboro Clay appears to straddle the Paleocene-Eocene boundary based on its dinoflagellate and pollen species. Dinoflagellate species suggest a general Early to Middle Miocene age for the Calvert and Choptank section in the core; diatom samples in the Calvert indicate a late Early to early Middle Miocene age and in the Choptank a middle Middle Miocene age. Lithologic and biostratigraphic evidence suggests the upper and possibly the lower Marlboro Clay contacts represent minor disconformities, in addition to the major disconformity at the Nanjemoy-Calvert boundary; the Calvert-Choptank contact appears conformable. The ten provisional dinoflagellate zones proposed for the Aquia, Marlboro Clay, and Nanjemoy strata of the core permit correlation with other previously studied Paleocene and Eocene sections of the Virginia and Maryland Coastal Plain. These Lower Tertiary strata are also generally biostratigraphically correlated with numerous coeval European sections, and a composite offshore eastern Canada section. The dinoflagellate, acritarch, and chlorophyte assemblages are statistically analyzed for paleoenvironmental implications using species diversity indicators (richness, Shannon-Wiener index, evenness) and analyses patterned after previous palynological studies suggesting correlation of various assemblage parameters and characteristics with particular depositional environments. Results are consistent with sedimentological and foraminiferal-based paleoenvironmental assessments of generally inner shelf marine settings for the Aquia, Nanjemoy, Calvert, and Choptank Formations, and a lagoonal or estuarine setting for the Marlboro Clay. Cluster, principal coordinates, and rank-abundance analyses help to objectively define and characterize six major and 12 smaller clusters of samples related by their species associations through time. / Ph. D.

Light microscopy studies of collections of late Cambrian/Early Ordovician organic-walled microfossils, informally called acritarchs, provide the observations on phenotypic traits that are comparable to Modern microalgae and make possible recognition of various developmental stages in their complex life cycle. The exceptionally preserved Saharidia fragilis microfossils show the internal body within the vesicle and the formation of the fringe and pylome, the opening for releasing of the daughter cells from the phycoma-like cyst. All the reproductive stages are distinguished and the hypothetical reconstruction of the complex life cycle is proposed. Various morphotypes are recognized to be a part of the class Prasinophyceae and some microfossils of the genus Leiosphaeridia are thought to represent the develop-mental stage of Saharidia fragilis life cycle. The morphological similarity suggests that those micro-fossils from the Cambrian-Ordovician transitional time interval are the ancestral representatives and early lineages of the Modern class Prasinophyceae. / Alger är idag viktiga producenter av fritt syre i atmosfären. I denna avhandling presenteras nya studier av encelliga organiska mikrofossil från den ryska ön Kolguev. Fossilens form och struktur (där många visar på en karaktäristisk rund öppning, så kallad pylome) ger en grund för att rekonstruera en komplex livscykel hos vissa av dessa kambrisk-ordoviciska taxa och tolka dem som alger. Studier med hjälp av ljusmikroskop utfördes i syfte att fastställa mikrofossilens funktionsmorfologi och fenotypiska drag. Dessa studier är viktiga för att klargöra biologiska släktskap och livscykeln av de studerade arterna.

The thermal maturity of sediments from the upper Cambrian to lower Ordovician Mila and Ilbeyk  formations in the Zagros Basin in southwestern Iran is evaluated in this thesis. A number of low-cost,  fast, optical evaluation methods are utilised to assess their effectiveness for providing accurate, well  constrained thermal maturity results. Palynomorph colours under transmitted light are measured using  two optical evaluation methods (Palynomorph Darkness Index , PDI- Goodhue &amp; Clayton 2010;  Acritarch Alteration Index, AAI- Legall et al., 1981) to study 540 acritarchs of three acritarch  morphotype-groups: acanthomorphs, Cristallinium-type and veryhachides. Correlation of the PDI and  AAI results collected in this study with UV fluorescence and rock-eval pyrolysis data taken from  previous studies suggests that the studied sediments are within the wet gas thermal maturity window.  Furthermore, investigating the PDI results of acritarchs allowed for the identification of reworked or  recycled acritarchs. Investigation of the stratigraphy of strata containing abundant reworked or recycled  acritarchs allowed for the identification of a ravinement surface in a transgressive shallow water  depositional environment in the studied strata.

Marine organic-walled microplankton biostratigraphy of the Maastrichian Prairie Bluff Chalk is documented. A total of 69 dinoflagellate species were identified in the Prairie Bluff Chalk. Samples were studied from three sites in central and western Alabama (Tombigbee River, Millers Ferry, and Braggs). Also included were several samples of the overlying Clayton Formation, and the underlying Ripley Formation. The species and their stratigraphic ranges were compared with other coeval sections in the U. S. and Europe. Dinoflagellate Zones Va and Vb of Wilson (1974) are recognized in the Prairie Bluff Chalk. This suggests the age of the Prairie Bluff Chalk is restricted to late Maastrichtian. The Prairie Bluff Chalk correlates to the upper Providence Formation of Georgia (Firth 1984); the lower Providence being early Maastrichtian. The basal Clayton Formation may be latest Maastrichtian in age / Master of Science