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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Evolution of the Lower Cretaceous Chifeng Half-Graben Basins, Inner Mongolia, China

Friedman, Scott Joshua 01 May 2009 (has links)
As a result of complex extensional tectonics in northeast China and southern portions of Mongolia, some workers have interpreted the Cretaceous Maanshan Uplift and associated Chifeng basins as metamorphic core complex. Previous work has relied solely upon kinematic indicators to determine the structural origin of these basins. To fully understand the creation of these basins, the sedimentiological record was analyzed in this study. The early Cretaceous sedimentary fill of these basins was analyzed to determine if it is synextensional in nature, and if so what manner of extension was in progress during that deposition. The Chifeng basins are filled with four distinct facies associations and are floored by Late Jurassic and Early Cretaceous volcanics of intermediate and felsic composition. The facies associations observed are interpreted as lacustrine/fluvial deposits, alluvial fan conglomerates, distal fan deposits with fluvial deposits, and hanging wall derived fluvial deposits. These facies are composed of sediment shed from the footwall and hanging wall of the master faults and volcanic deposits. Paleocurrent indicators, primarily in the form of imbrication, along with clast count data show provenance directly off the structure separating the two basins and from the eastern margin of the southeast basin. The distribution of facies, as well as paleocurrent data, provenance data, and structural geometry, implies that these basins are of half-graben origin and that no sedimentological evidence exists of an Early Cretaceous metamorphic core complex near Chifeng.
42

Cretaceous Diptera From Orapa, Botswana.

Waters, Saskia January 1990 (has links)
A DISSERTATION SUBMITTED TO THE FACULTY OF SClENCE, UNIVERSITY OF THE WITWATERSRAND, JOHANNESBURG, FOR THE DEGREE OF DOCTOR OF PHILOSOPHY. / An assemblage of Cretaceous, Diptera, recovered from the sediments of the Orapa Diamond mine, Botswana, is described. The fossil Diptera are placed In the following families: Tipulidae, Empididae, Hybotidae, Bibionidae, and possibly the Mycetophilidae, Rhagionidae and Anisopodidae. A new pulid species, Helius botswanensis (Tipulidae, subfamily Limoniinae), is described; it is the oldest representative of the subfamily. (Abbreviation abstract) / Andrew Chakane 2019
43

SYSTEMATICS, PALEOBIOGEOGRAPHY, AND PALEOECOLOGY OF CRETACEOUS DECAPOD FAUNAS FROM NORTHEAST TEXAS

Frantescu, Ovidiu D. 10 July 2013 (has links)
No description available.
44

Chronostratigraphy and Paleontology of the Mid-Cretaceous Wayan Formation of Eastern Idaho, with a Description of the First Oryctodromeus Specimens from Idaho

Krumenacker, Laurel J. 05 August 2010 (has links) (PDF)
The mid-Cretaceous Wayan Formation of Idaho consists of floodplain-deposited siltstones and mudstones, with subordinate fluvial sandstones and conglomerates. Deposition occurred in a tectonic foredeep at the toe of the Sevier thrust complex. Measurement of two incomplete and one complete section indicates a thickness of roughly 1,344 meters in the study area. No laterally extensive marker beds are present but the lower Wayan contains distinct chert pebble conglomerates, and the middle Wayan may contain a higher relative abundance of fluvial sandstone. Known fossil localities are limited to the lower and middle portions of the formation. The Wayan Formation, as currently defined, has a flora consisting of the ferns Gleichenia and Anemia, conifers, and angiosperms. This flora compares best with the Cenomanian aged Dakota Sandstone flora of Westwater, Utah. The vertebrate fauna is overwhelmingly dominated by the small burrowing ornithopod Oryctodromeus with other vertebrates being rare, consisting of a small dromaeosaurid theropod, iguanodontid grade ornithopods, and a large crocodilian similar to Deinosuchus. The fauna is most similar to the Cenomanian Blackleaf Formation of Montana. Prior to this report, only fragmentary dinosaurian remains had been reported from Idaho. The recovery of 10+ individuals of Oryctodromeus, some reasonably complete and partially articulated, provide significant insights into this genus, including an elongate femoral head projecting at roughly 40° from the femoral shaft, elongate cervical and dorsal centra, and abundant ossified tendons in the dorsal and caudal columns. Taphonomic evidence supports previous suggestions of adult/juvenile social groups and burrowing behavior in this taxon. New detrital zircon U-Pb dates and palynological analyses support a latest Albian to Cenomanian age for the Wayan Formation, but provide little additional age resolution. The tightest age resolution is provided by faunal correlation using Oryctodromeus, a taxon previously known only from the Cenomanian-age Blackleaf Formation of southwestern Montana. Similar tectonic settings, ages, lithologies, and the presence of Oryctodromeus in both faunas suggest synonymy of the Wayan and Blackleaf Formation, with the Wayan having precedence.
45

Late Cretaceous Sponge Borings - Indicators of Salinity and Sedimentation Drumheller, Alberta

Birchard, Mark Christopher 04 1900 (has links)
<p> A detailed study of sponge boring morphotypes within the molluscan fauna of Upper Cretaceous estuarine sediments near Drumheller, Alberta provides information relevant to the depositional environment. Problems with regard to utilizing Entobia as a paleoenvironmental indicator and as an indicator of salinity do not appear to be insurmountable.</p> <p> Distributions and characteristics of associated marine organisms (phoronid worms, gastropods and encrusting bryozoa) suggest that sponge colonies were affected by salinity and sedimentation. Boring networks in Ostrea glabra suggest that more than one species of sponge were present. Sponge distribution patterns, changes in papilla and chamber sizes and preferential occurrence of sponge borings on certain shell thicknesses provide good evidence for responses to salinity and sedimentation.</p> / Thesis / Bachelor of Science (BSc)
46

Sedimentology, Ichnology and High-Resolution Allostratigraphy of the Lower Cretaceous Viking Fonnation, Central Alberta, Canada

Burton, James 05 1900 (has links)
<p> The Lower Cretaceous (Upper Albian) Viking Formation of central Alberta contains numerous linear sandbodies and fewer large irregularly-shaped sandbodies. Most studies to date have focused on individual sandbodies, leaving their interrelationships largely unknown. Developing a high-resolution allostratigraphy for the Viking of central Alberta allows mapping of regional bounding discontinuities and the definition of distinct allomembers. Placement of the Viking hydrocarbon fields within this framework permits an understanding of the exact stratigraphic relationships of the various fields. </p> <p> Examination of 120 cores and numerous well log correlations suggests the existence of four regionally mappable bounding discontinuities (BDl-4) which separate five distinct allomembers (I-V). Sandbodies within these allomembers were deposited in a variety of sedimentologically distinct environments. These include 'regional Viking' offshore to shoreface sandstones, prograding highstand shoreface sediments, transgressive incised shoreface sediments, and forced regressive, onlapping shoreface 'tongues'. The series of linear trending hydrocarbon fields from Joffre to Chain are also stratigraphically distinct. The sandbodies exist at five separate stratigraphic horizons and therefore are not all part of the same incised shoreface deposits. </p> <p> The four regional bounding discontinuities are interpreted as transgressive surfaces of erosion formed by four separate drops and subsequent rises of relative sea level. These fluctuations were greater than 30m and each complete cycle occurred over roughly 375,000 years. </p> / Thesis / Master of Science (MSc)
47

Pillars and Buttes: A Petrologic Comparison of Modern and Ancient Hydrocarbon Seep Rock

Morelli, Erica C. 28 July 2015 (has links)
No description available.
48

Are 'exceptionally' preserved skeletal fossils necessarily exceptional chemically and cytologically?

Korneisel, Dana Elaine 19 September 2019 (has links)
At the macroscopic scale, vertebrate fossils are considered exceptional when non-biomineralized (soft) tissues are preserved. Histologically, high quality is defined by trueness to original shape of a bone, preservation of fine details (e.g. canaliculi), and presence or absence of matrix material in void spaces. Some fossils are hypothesized to preserve cells and durable organelles. Traditionally, cytological details and biomolecular remains have been sought in exceptional fossils. Durable cytological features such as melanosomes do appear to follow feather preservation, but traditionally exceptional fossils are not necessarily exceptional on a microscopic scale. Here, we analyze a feathered dinosaur specimen from the Jehol Lagerstätte to assess claims of blood cell preservation and the state of potential biomolecular preservation. Beipiaosaurus inexpectus is a fairly complete specimen with preserved feathers. Though crushed, fine details in thin section are prevalent. Using Raman spectroscopy, Energy Dispersive X-ray Spectrometry, and Time-of-Flight Secondary Ion Mass Spectroscopy we found no evidence of exceptional molecular preservation. Instead, we found evidence that the vasculature, once hypothesized to contain preserved red blood cells, is filled with clay minerals, with the purported cells chemically indistinguishable from materials of other shapes infilling the vessels. Despite yielding exceptional fossils, the preservational environment of the Jehol biota does not necessarily preserve exceptional details cytologically or biomolecularly. Consequently, we conclude that a systematic approach to biomolecular and cytological preservation studies should rely on traits other than classic exceptional preservation. / Master of Science / What makes a fossil particularly excellent? Traditionally, fossils from animals with skeletons were considered high quality when many or most of the bones from an animal are preserved. If these bones line up with one another like they would in the animal when it was alive (i.e. are articulated) the fossil is even better. To be exceptional, though, soft tissues, or parts of the animal that were not hardened with minerals while the animal lived (e.g. feathers, skin) need to be preserved. All of these traits can be observed with the naked eye. With the use of a microscope, we can see how much a skeleton has been crushed and whether the spaces in the bone for blood vessels and cells have been well preserved. Additionally, we may be able to observe preserved cells, which would be exceptional. On an even smaller scale, the molecules present in a bone might be well or poorly preserved. How much the minerals that make up the bone have changed chemically from when the animal was alive is one indicator of quality. Another might be preservation of molecules that come from the animal such as DNA and the proteins present in bone. In this study, we chose an exceptional fossil based on the traits visible to the naked eye (many of the bones are present and it has feathers) and looked for evidence of cell and unique molecule preservation. On the microscope, we saw beautiful details of the structures in the bone that held bone cells and blood vessels. We also observed red spheres which have been described by other researchers as possible blood cells in the spaces for blood vessels. Using three types of machine which can identify minerals, elements, and molecules in the bone and vessels, we did not find any evidence that the spheres represent preserved blood cells. Nor did we find any evidence of exceptional molecules. However, we did find evidence that the bone itself is not highly changed from when the animal lived, though we see elements and molecules in the vessels that probably did not come from the animal. We started this study knowing that the fossil we chose is exceptional in some ways, but what we found shows that it has a mix of excellent and poor traits visible on the microscope and it does not have any excellent traits in terms of its molecules besides the minerals in the bone itself. We conclude that fossils that are exceptional in the traditional sense are not necessarily exceptional in other ways. / What makes a fossil particularly excellent? Traditionally, fossils from animals with skeletons were considered high quality when many or most of the bones from an animal are preserved. If these bones line up with one another like they would in the animal when it was alive (i.e. are articulated) the fossil is even better. To be exceptional, though, soft tissues, or parts of the animal that were not hardened with minerals while the animal lived (e.g. feathers, skin) need to be preserved. All of these traits can be observed with the naked eye. With the use of a microscope, we can see how much a skeleton has been crushed and whether the spaces in the bone for blood vessels and cells have been well preserved. Additionally, we may be able to observe preserved cells, which would be exceptional. On an even smaller scale, the molecules present in a bone might be well or poorly preserved. How much the minerals that make up the bone have changed chemically from when the animal was alive is one indicator of quality. Another might be preservation of molecules that come from the animal such as DNA and the proteins present in bone. In this study, we chose an exceptional fossil based on the traits visible to the naked eye (many of the bones are present and it has feathers) and looked for evidence of cell and unique molecule preservation. On the microscope, we saw beautiful details of the structures in the bone that held bone cells and blood vessels. We also observed red spheres which have been described by other researchers as possible blood cells in the spaces for blood vessels. Using three types of machine which can identify minerals, elements, and molecules in the bone and vessels, we did not find any evidence that the spheres represent preserved blood cells. Nor did we find any evidence of exceptional molecules. However, we did find evidence that the bone itself is not highly changed from when the animal lived, though we see elements and molecules in the vessels that probably did not come from the animal. We started this study knowing that the fossil we chose is exceptional in some ways, but what we found shows that it has a mix of excellent and poor traits visible on the microscope and it does not have any excellent traits in terms of its molecules besides the minerals in the bone itself. We conclude that fossils that are exceptional in the traditional sense are not necessarily exceptional in other ways.
49

Brachiopoda a polychaeta v tafocenózách české křídové pánve / Brachiopoda and polychaeta in Taphocenoses of the Bohemian Cretaceous Basis

Sklenář, Jan January 2013 (has links)
The sesile suspension feeders of Brachiopoda and Polychaeta phyla are relatively well represented in the Bohemian Cretaceous Basin (BCB), and show significant diversity. All three subphyla of Brachiopoda (Linguliformea, Craniiformea and Rhynchonelliformea) are present in the fossil record of the sedimentary basin infill; from Polychaeta, there has hith- erto been evidence of only the Canalipalpata subclass members that created solid, usually carbonatic tubes. In both abundancy and diversity, the most richest associations of fossil brachiopods and polychaets occure in near-shore facies of the Cenomanian to the Lower Turonian, and hemipelagic facies of the Late Turonian age. Prior research, as shows the literature survey given by the author, has been focused mainly on representatives of both groups of near-shore facies origin. The aim of this thesis is to fill in the existing gaps in our understanding of these groups within the BCB. This objective is accomplished in the form of a series of studies (Sklenář & Simon 2009, Vodrážka & al. 2009, Sklenář & al., in press) elaborating the following topics in detail: (A) taxonomy, distribution, morphology, variabil- ity, evolutionary relationships and stratigraphic significance of cancellothyrid brachiopod Gyrosoria abundant in the Middle and particularly in...
50

Paleoekologie turonskych ostrakodů (Ostracoda) lokality Úpohlavy / Paleoecology of the Turonian Ostracoda from the Úpohlavy section

Houdková, Markéta January 2016 (has links)
This thesis deals with the class Ostracoda from the Úpohlavy quarry, which is an important paleontological site of the Turonian in the Czech Cretaceous Basin with abundant and well- preserved fauna. Twenty samples from marls and limestones of Jizera and Teplice formation were colected in which 36 marine middle and upper Turonian ostracods species were identified. Ostracods of the studied profile are characterized by gradual increase of species richness and decline of dominance of Cytherella cf. ovata (Roemer, 1840). The lowest diversity is in the Jizera formation and the highest diversity in the Teplice formation. The order Platycopida prevails on the order Podocopida in the Jizera formation, in which percentages of Platycopida is in the range 67-89%, while its percentage in the Teplice formatiion is lower in the range 25-59 %. Using the Platycopida Signal Hypothesis in a sense of Whatley et al. (2003), which compares percentages of Platycopida and Podocopida, a low O2 content in Jizera formation and in the Coprolite bed (monotonous dark marls) of Teplice formation is supposed. This is in accordance with low number of species (5-11 per sample) and with higher TOC content (0.34-0.74 %). With the beginning of limestone and marl sedimentation of the Teplice formation a number of species increases...

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