Biostratigraphic analysis of the lower part (Oxfordian-Kimmeridgian) of the Upper Jurassic Humber Group in the Outer Moray Firth of the North Sea and coeval onshore Scottish sections has resolved a long-standing controversy regarding the stratigraphic range of key dinoflagellate cyst (‘dinocyst’) taxa. The biostratigraphic ranges of these key species can now be shown to be comparable for Scotland, the North Sea and the classic Upper Jurassic English sections, indicating that the former North Sea Dome did not represent a barrier to faunal migration in Kimmeridgian times. Causes behind previously reported biostratigraphic anomalies can now be demonstrated to result from a combination of erroneous identification of cored material, inconsistent taxonomy and past failures to adhere to the codes of taxonomic nomenclature. The resolution of these reported biostratigraphic anomalies enables a new, robust, chronostratigraphically calibrated dinocyst biozonation to be proposed for the Regulare to Mutabilus Standard Ammonite Zones of Scotland and the North Sea. The application of the unified biostratigraphic scheme enables a revision of the lithostratigraphy, and therefore depositional history, of the Piper and Kimmeridge Clay Formations of the Humber Group in the Outer Moray Firth. The results from the Ivanhoe, Rob Roy and Hamish fields of United Kingdom Continental Shelf (U.K.C.S.) block 15/21 indicate that the Mid Shale Member, a component part of the Piper Formation, was deposited from Oxfordian, Rosenkrantzi Zone times to basal Kimmeridgian, Baylei Zone times. This conclusively demonstrates its strategraphic equivalence to the I-shale Member of the Piper field for the first time, thus necessitating redefinition but simplification of the lithostratigraphic terms used in the basin. Deposition of the Supra Piper Sands was terminated by a transgressive event which was initiated in Mutabilis Zone times, with Kimmeridge Clay Formation mudstone deposition occurring in response to a major transgression which reached its maximum extent in the Eudoxus Zone.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:652390 |
| Date | January 2002 |
| Creators | Hesketh, Richard A. P. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/15016 |
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