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Friday 6th January 2006

The Sticklepath Fault: aspects of the Petrockstow Basin
Field trip led by: Martin Milne and Chris Cornford

The post-conference field trip on Friday 6th January will follow the multiple phases of movement of the Sticklepath Fault and pick up on the “Variscan” theme. In the morning we plan to visit the Oligocene Ballclay pits of the wrench-related Petrockstow Basin (Watts, Blake, Bearn Clay Ball Clay Pit - Grid Ref SS503124) and in the afternoon view the nearby Portledge/Peppercombe section of Permian redbeds overlying the Carboniferous Culm sandstones and shales (i.e. the Variscan unconformity) where Sticklepath-associated faults cut the coast cliff section (Grid Ref SS384232). High tide: 10.32 (5.16 metres).

9.00: Meet at Tantons Hotel

The more productive clay pits of the northern Petrockstow Basin show quiet water fluvial – lacustrine clays interbedded with carbargillites and lignites (brown coals) and sands. These relatively young beds are locally folded and tilted by late stage movement on the Sticklepath fault. Periglacial ice disturbance of the near surface beds may also be seen. Historic and modern mining methods are illustrated together with quality control and processing procedures leading to the high quality product exported from Bideford Quay.

12.30 – 14.00: Pub lunch at Coach & Horses, (NGR: SS384232), Tel:01237 451214

At Peppercombe, shallowly dipping coarse red conglomeratic and marly sandstone unconformably overlie the folded Bude Formation (Culm) sandstones. You can walk on the Variscan desert floor. These ‘Permian’ redbeds are preserved in two 'half grabens', the controlling fault being a splay of the nearby Sticklepath fault. Excellent coastal exposure with rapid erosion allows a detailed inspection of the 800m section. A range of flash flood and playa lake deposits can be seen together with unusually well preserved soil horizons (calcretes, silcretes) and cemented rootsystems. Return is via the Coastal Path running along the top of the cliff.

 

 


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