The integration of data from high-resolution heavy mineral and palaeomagnetic analyses of samples from nine East Irish Sea wells, and from onshore sections at St Bees Head and the North Cheshire Basin, has generated a temporally-constrained heavy mineral stratigraphy and regional correlation within the Triassic Sherwood Sandstone Group. These results have shown that the combined application of these two techniques offers an effective tool for extending the zonation and correlation of barren strata into uncored wells. The lateral persistence of the heavy mineral zones, and the significant differences in the distributions of the heavy mineral varieties between individual zones, may reflect tectonic events and, to a lesser extent, climatic variations.

Palaeomagnetic results indicate that the original magnetisation of the analysed samples was acquired as a detrital remanent magnetisation and that the characteristic remanent magnetisation in the red beds was acquired during and shortly after deposition. Magnetopolarities have been interpolated using the available data from which a composite reference section has been constructed.

All well sequences exhibit a regionally persistent three fold zonation (Zones A, B and C, locally with subzones), defined by systematic changes in characteristic heavy mineral

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suites. Using a common sample set, the independently erected heavy mineral stratigraphy was tied to specific magnetostratigraphic Chrons. Heavy mineral Zone A coincides with a period of dominantly normal polarity, fixed by a 244 Ma Chron of Middle Scythian age. A change in polarity from normal to reversed at >243 Ma coincides with the boundary of Zones AIR Zone B is Middle to Upper Scythian and shows a dominantly reversed polarity. A well-defined Chron of 242.7 Ma has been detected close to the boundary of Zones BIC. Zone C is Anisian in age and is characterised by a dominantly normal polarity.