Differential interferometric synthetic aperture radar (DInSAR) is a recognized remote sensing method for measuring the land motion occurring between two satellite radar acquisitions. Advanced DInSAR techniques such as persistent scatterers (PS) and small baseline methods are excellent over urban and rocky environments but generally poor over more rural and natural terrain where the signal can be intermittently good and bad. Here, we describe the ISBAS (Intermittent Small Baseline Subset) method, which appears to improve results over natural, woodland and agricultural terrain. This technique uses a multilooked, low-resolution approach, which is particularly suitable for deriving the linear components of subsidence for large-scale deformations. Application of the ISBAS method over a coal mining area in the UK indicates that it is able to significantly improve upon a standard small baseline approach.

SUMMARY During the Permo-Triassic the Sellafield area formed part of the eastern margin to the East Irish Sea Basin. Basin-margin alluvial fan, shallow marine and coastal mudflat sedimentation created a locally thick Permian succession. Triassic sediments are represented by the Sherwood Sandstone Group, which comprises the St Bees, Calder and Ormskirk sandstone formations. The basal few metres of the St Bees Sandstone are characterized by sheetflood sandstones, interbedded with playa-mudflat deposits. These pass upwards into thick, multistorey fluvial sandbodies, formed on sandy braidplain. Rare aeolian units are interbedded with the channel facies. The top of the St Bees Sandstone is sharply defined and represents the regional abandonment of the fluvial system. The overlying Calder Sandstone Formation is coarser grained and dominated by aeolian sediments, with dune and interdune facies recognized. These sands were blown into the area from the east. Minor episodes of fluvial reworking punctuated aeolian deposition and the top of the Calder Sandstone is represented by a fluvially deposited unit. The lower part of the overlying Ormskirk Sandstone is of aeolian facies and can be distinguished from the Calder Sandstone by its finer grain size. The two formations can also be differentiated using geophysical logs, as aeolian and fluvial sandstones have diagnostic geophysical log characteristics allowing recognition of different sedimentary facies associations.

SUMMARY The subdivisions of the Sherwood Sandstone Group, previously recognized on geophysical and lithological criteria in boreholes offshore in the East Irish Sea Basin, can be identified in the onshore exposures and boreholes of west Cumbria. The term St Bees Sandstone Formation is here restricted to the lower, fluvial, fine-grained sandstone, with claystone and siltstone partings, exposed around St Bees. This formation is sharply overlain by softer and coarser grained, aeolian and subordinate fluvial sandstone, which contains abundant, well-rounded aeolian sand grains, referred to the newly defined Calder Sandstone Formation. Higher sandstone has been separated from the Calder Sandstone Formation by its finer grain size and by geophysical log signatures. This is referred to the Ormskirk Sandstone and is dominantly aeolian in origin. Similar divisions of the Sherwood Sandstone Group can be recognized in the Carlisle Basin, and may also be present in other onshore areas, but await formal definition.

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