Development of Middle Triassic red-bed plays is commonly hampered by a lack of understanding of the stratigraphic relationships between reservoir sandstones. This inadequacy reflects poor palynological recoveries and a general deficiency in understanding the controls on palynological preservation. The sedimentology and palynology of Triassic red-bed facies, from the UK North Sea and onshore analogues, are studied to determine the sedimentary controls on palynological preservation and to investigate whether palynology is useful in these facies, where other stratigraphic techniques do not always provide unique solutions. The Skagerrak Formation (Quadrants 22, 29 and 30) typically comprises ephemeral channel and sheet-flood deposits in the north, but includes sediments deposited in perennially wet, alluvial plain and lacustrine settings in the south. Further north (Quadrant 210), the Cormorant Formation comprises dry alluvial deposits. Onshore, the Bromsgrove Sandstone Formation is characterised by ephemeral channel deposits that pass progressively upwards into tidally-influenced, fluvial and estuarine deposits; these are partly comparable with sediments in the Tarporley Siltstone Formation. Palynological analysis reveals that, in the absence of palynomorphs, palynodebris and absolute organic concentration can distinguish between preservational regimes, and thus environment. Palynological preservation demonstrates a correlation with facies deposited in perennially wet, alluvial plain, lacustrine and tidally influenced settings. Organic assemblages distinguish between members in the Bromsgrove Sandstone Formation, and can subdivide members on palaeoenvironmental criteria, which is of local value in correlation. Palynological assemblages are mostly lacking where ephemeral depositional processes were dominant. The assemblages demonstrate a close relationship with sedimentary facies, their associations, and sediment colour, but the oxidation potential of pore fluids, during and soon after deposition, is an overriding control on organic preservation. These relationships are all beneficial for targeting sediments for further palynological analysis.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:301192 |
| Date | January 1999 |
| Creators | Farris, Matthew A. |
| Publisher | Keele University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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