Rockhall Wood

Sutton, Suffolk (TM 304440)

This site, consisting of several small quarries lying around Rockhall Wood, was described by Charles Lyell in 1839 and later contributed to the subdivision of the Coralline Crag into ‘zones’ by Prestwich (1871). Rockhall Wood represents an outlier of Coralline Crag that forms a slight yet perceptible hill.

Quarries in the cemented, aragonite-leached upper part of the Coralline Crag have provided blocks for building use, as in the farm buildings at Pettistree Hall to the north. The famous ‘bullockyard pit’ is on the east side of the hill; Lyell recognised a buried cliff in this pit, with Red Crag being banked up against vertical and overhanging ‘cliffs’ of Coralline Crag. Under the general name ‘Sutton’, Rockhall Wood has featured prominently in almost every study concerning Coralline Crag fossils, including Busk’s (1859) monograph on bryozoans and Wood’s molluscan monographs.

A maximum of just under 12m of Coralline Crag is preserved resting unconformably on an undulating surface of London Clay. Red Crag surrounds the hill and rests either directly on the London Clay or on, or against, the Coralline Crag.

At the base of the Coralline Crag is a conglomerate containing vertebrates and boxstones. Above are silty carbonate sands of the Ramsholt Member containing a rich benthic fauna. At the top of the section is the lateral equivalent of the Sudbourne Member seen in the main Coralline Crag outcrop to the north. Strong tidal currents produced a sandwave facies, with trough cross-stratification. The contact between the two members appears sharper than at sites such as Gedgrave Cliff and Broom Pit.

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