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Mid Jurassic to earliest Cretaceous (Callovian-Ryazanian) radiolaria of the North Sea Basin

Kavouras, Charalampos N; (1994) Mid Jurassic to earliest Cretaceous (Callovian-Ryazanian) radiolaria of the North Sea Basin. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

The North Sea is a series of interconnecting sedimentary basins, located on the northwest margin of the Eurasian tectonic plate. The complex geological setting and sedimentation patterns of the North Sea Basin have been reviewed as an introduction to this study. Eleven wells/exposures from this area, spanning the Mid Jurassic (Callovian) to Earliest Cretaceous (Ryazanian) time interval, have been examined for radiolaria. The inclusion of 2 more wells from the Norwegian and Barents Seas has been used for comparative purposes and contributed to the taxonomic understanding of the less well-preserved North Sea radiolarians. Previous work on radiolarians from around the world for the studied interval has been recorded and a database/list has been produced. The state of preservation of the radiolarian assemblages has been discussed and Electron Microprobe analyses have been performed. In some instances the siliceous radiolarian skeletons have been replaced by other minerals, most commonly calcite or pyrite. A total of 129 species/morphotypes from 392 samples has been described and illustrated with scanning electron and light microscope micrographs. The occurrence of these taxa in previous studies in the literature is reviewed to aid interpretation of the North Sea assemblages, which exhibit some affinity with other Boreal assemblages. By employing careful processing techniques and taking into account the commonly poor preservation of radiolarians, their biostratigraphic value has been demonstrated by means of the Unitary Associations method. The ranges of 52 taxa have been used for computer treatment with the BioGraph program, from which 18 Unitary Associations have been established. These were grouped into 5 zones which were correlated to the standard ammonite zones: Biozone 1. early Callovian to mid Kimmeridgian; 2: mid Kimmeridgian to Early Volgian. 3: Early Volgian to Mid Volgian. 4: Mid Volgian to latest Mid Volgian. 5: latest Mid Volgian to Late Ryazanian. The application of radiolaria to stratigraphic problems in the North Sea Basin is reviewed and suggestions made for future work.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Mid Jurassic to earliest Cretaceous (Callovian-Ryazanian) radiolaria of the North Sea Basin
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10108860
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