Crag Farm

Sudbourne, Suffolk (TM 42805232 and 42985235)

This quarry, just to the west of Crag Farm, has long been a popular locality for field parties due to its large size, accessibility, and the spectacular cross-bedding developed in the Sudbourne Member. About 5.6m of leached sediments are exposed, a borehole showing a total thickness of 6.3m of the Sudbourne Member overlying 5.9m of the Ramsholt Member beneath the quarry floor, with the surface of the London Clay at approximately 10.4m below Ordnance Datum (OD). Fissures penetrating the Coralline Crag may be infilled with shelly sediments (?Pleistocene) or white micritic calcite.

The Sudbourne Member here comprises relatively pure skeletal calcarenites containing less than 5% mud. Cross-beds have set thicknesses of 0.5-2.0m with concave foresets dipping at up to 25°. Occasional thin silty laminae are seen, mostly within the bottomsets. The fauna of the Coralline Crag here consists mainly of transported, abraded fragments of calcitic molluscs and bryozoans but more intact bryozoan colonies (e.g. Pentapora) do occur, suggesting that they lived on or between the sandwaves and were deposited more or less in-situ.

Adapted from Daley and Balson, 1999.

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Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith