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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.
1

The geology of the Wenlock shales around Builth Wells

Harris, J. H. January 1987 (has links)
Detailed field mapping and palaeontological collecting have revealed a complete sequence of Wenlock graptolite biozones around Builth. Bio-stratigraphical work has greatly improved the correlation with other British and European successions. The <i>flexilis</i> Zone, of wider international value, replaces the <i>linnarssoni</i> Zone, and eight subzones are suggested. The earliest Wenlock records the diachronous transgression across the Ordovician inlier. The <i>centrifugus</i> Zone, well developed in the W, thins to the E to a condensed horizon - the Acidaspis Bed- on the inlier. Calcareous mudstone slide deposits occur at four levels: in the <i>rigidus</i>; <i>flexilis</i>; <i>ellesae</i>; and <i>nassa-ludensis</i> zones. The Builth Mudstone Formation (formerly the Wenlock shales) comprises dark, laminated, silty mudstones deposited by hemipelagic processes under largely anoxic bottom conditions. The slide deposits reflected slope failure, possibly generated by fault-related seismic events. The Wenlock strata were greatly folded and then cut by a series of NE-SW trending faults forming the eastern boundary to the Pontesford Lineament. Some faults probably had a strike-slip displacement, others are possibly reactivated basement structures. Deformation and metamorphism are weak, and cleavage is localised to fault zones. Graptolite reflectivity indicates the zeolite- diagenetic grade. The intensity of cleavage and metamorphism increases northwestwards into the Pontesford Lineament. A review of early Palaeozoic and Wenlock palaeo- geography, - climatology, -oceanography, and -biogeography was undertaken. The causes of anoxia in the Wenlock Welsh basin were examined in the light of new Caledonian plate tectonic models. A correlation between graptolite occurrence and inferred sites of upwelling was shown. Three poorly defined graptolite subprovinces were established, which were probably caused by oceanographic and climatic effects. Systematic palaeontological studies have clarified the <i>Monograptus flemingii</i> and <i>Monoclimacis vomerina</i> subspecies, the <i>Monograptus antennularius-retroflexus</i> species, the genus <i>Cyrtograptus</i>, and the retoilitid group. The genus <i>Plectograptus</i> was divided, with a new genus <i>Maculagraptus</i> proposed.
2

EVENT AND SUBSURFACE STRATIGRAPHY OF THE WENLOCK SERIES (SILURIAN) MIDLAND PLATFORM , UK

Ray, David Christopher 11 October 2001 (has links)
No description available.
3

Dynamic linkages between stratigraphy, climate, oceanography, and biotic events in the middle Silurian of eastern Laurentia

Thomka, James R. January 2015 (has links)
No description available.
4

Analysis of the Song Cycle “On Wenlock Edge” by Ralph Vaughan Williams

Pummill, John Douglas 01 1900 (has links)
This examination of Ralph Vaughan Williams' song cycle to poetry of Alfred Edward Housman, "On Wenlock Edge," will follow primarily two avenues of approach. First, following a brief biographical sketch of Vaughan Williams' career prior to the composition of "On Wenlock Edge," will be a discussion of Vaughan Williams' and Housman's respective aesthetic philosophies. In order to lay the background for certain salient characteristics of this cycle, parallels as well as differences in their artistic thinking will be explained. Secondly, a poetic analysis will precede the musical analysis of each song in order to differentiate between the original intent of the poet and the interpretation of the poetry by Vaughan Williams.
5

Diversity and Life Habits of Silurian Strophomenide Brachiopods of Gotland / Siluriska strophomenider (Brachiopoda) från Gotland: artsrikedom och levnadssett

Hoel, Ole Andreas January 2005 (has links)
<p>The Superfamily Strophomenoidea is a very diverse group of brachiopods in the Early Palaeozoic. In the Silurian succession on Gotland, they are among the most easily identifiable, and commonly found fossils. However, there are few detailed studies of this group from Gotland, and no new strophomenide taxa have been described from this area since 1869. The life habits of strophomenides are also poorly understood, partly because their morphology differs greatly from that of living brachiopods. </p><p>The succession on Gotland yielded 27 species belonging to the Strophomenoidea, of which two species and two subspecies are new. The remaining species have been described earlier from Gotland or Great Britain. The most important group is the Leptaeninae, which occurs commonly throughout the entire succession on Gotland. Five species (one new), two new subspecies and two taxa treated under open nomenclature were found. <i>Leptaena rhomboidalis</i> and <i>Lepidoleptaena poulseni</i> were specialized for life in shallow water environments, retaining a large apical pedicle; the remaining leptaenines were ambitopic. The Furcitellininae is represented by three genera comprising six species, of which only one persisted into the Ludlow. All were ambitopic, except <i>Pentlandina loveni</i>, which was specialized for high-energy environments. Six species of “strophodontids” from Gotland, belonging to the Leptostrophidae, the Strophodontidae and the Shaleriidae, share a shallow-bodied, variably concavo-convex shell with costellate ornament. <i>Mesoleptostrophia</i> and <i>Brachyprion</i> (<i>Brachyprion</i>) were long-ranged and ecologically tolerant, while <i>B.</i> (<i>Erinostrophia</i>), <i>Strophodonta</i> and <i>Shaleria</i> had short ranges and were ecologically specialized. The two earliest known cementing strophomenides occur on Gotland, and their hitherto unknown dorsal valves have been identified: <i>Liljevallia </i>was found to belong to the Douvillinidae. The cementing <i>Leptaenoidea silurica</i> was found to be conspecific with the ambitopic <i>Scamnomena rugata</i>; it was able to live ambitopically if removed from the substrate. The thickened dorsal valves allow reconstruction of its lophophore.</p>
6

Diversity and Life Habits of Silurian Strophomenide Brachiopods of Gotland / Siluriska strophomenider (Brachiopoda) från Gotland: artsrikedom och levnadssett

Hoel, Ole Andreas January 2005 (has links)
The Superfamily Strophomenoidea is a very diverse group of brachiopods in the Early Palaeozoic. In the Silurian succession on Gotland, they are among the most easily identifiable, and commonly found fossils. However, there are few detailed studies of this group from Gotland, and no new strophomenide taxa have been described from this area since 1869. The life habits of strophomenides are also poorly understood, partly because their morphology differs greatly from that of living brachiopods. The succession on Gotland yielded 27 species belonging to the Strophomenoidea, of which two species and two subspecies are new. The remaining species have been described earlier from Gotland or Great Britain. The most important group is the Leptaeninae, which occurs commonly throughout the entire succession on Gotland. Five species (one new), two new subspecies and two taxa treated under open nomenclature were found. Leptaena rhomboidalis and Lepidoleptaena poulseni were specialized for life in shallow water environments, retaining a large apical pedicle; the remaining leptaenines were ambitopic. The Furcitellininae is represented by three genera comprising six species, of which only one persisted into the Ludlow. All were ambitopic, except Pentlandina loveni, which was specialized for high-energy environments. Six species of “strophodontids” from Gotland, belonging to the Leptostrophidae, the Strophodontidae and the Shaleriidae, share a shallow-bodied, variably concavo-convex shell with costellate ornament. Mesoleptostrophia and Brachyprion (Brachyprion) were long-ranged and ecologically tolerant, while B. (Erinostrophia), Strophodonta and Shaleria had short ranges and were ecologically specialized. The two earliest known cementing strophomenides occur on Gotland, and their hitherto unknown dorsal valves have been identified: Liljevallia was found to belong to the Douvillinidae. The cementing Leptaenoidea silurica was found to be conspecific with the ambitopic Scamnomena rugata; it was able to live ambitopically if removed from the substrate. The thickened dorsal valves allow reconstruction of its lophophore.
7

Conodont Biostratigraphy and δ¹³C Chemostratigraphy of the Salina Group (Silurian) in Western Ohio and Eastern Indiana

Swift, Robert James Anthony 20 October 2011 (has links)
No description available.

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