Simplified Geological Map of Cornwall

Millook Cliffs

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To the North East of Cornwall lie the Carboniferous rocks known as Culm. The majority consist of shale’s and thin sandstones, slate limestone and chert.  The 12 mile section of cliffs and coastal habitats between Boscastle and Widemouth are classic geological exposures of Namurian rocks and Variscan structures.   High Cliff is the highest sheer-drop cliff in Cornwall at 735 ft (224m). Biological interest includes the unique Dizzard Oak Woodland, maritime heaths and intertidal zones.

Simplified map showing the granite batholiths

and mafic igneous rocks of Cornwall

                                Rough Tor on Bodmin Moor                                                                                                                                                                                       

LOCAL GUIDE BOOKS

A GEOLOGY GUIDE TO NORTH CORNWALL. J.MACADAM PUBLISHED BY NORTH CORNWALL COAST AND COUNTRYSIDE SERVICE

BOSMIN NIIE 400 MILLION YEARS IN THE MAKING.  J.MACADAM. PUBLISHED BY CARADIN COUNTRYSIDE SERVICE

NORTH COAST OF CORNWALL BUDE TO TINTAGEL. GEOLOGISTS ASSOCIATION GUIDE NO 10 1970

THEMATIC TRAILS

NORTH CORNWALL GEOLOGY GUIDE HEUD LYN LEWIS

This stout glossy book has water resistant pages with easy to open wire binding designed for outside use.  150 illustrations with identification of local rocks and minerals, geological history  and mention of the mining and quarrying in the area.

CRACKINGTON GEOLOGY TRAIL.  NORTH CORNWALL DISTRICT COUNCIL.

10 page pocket size pamphlet with clear maps of trails and associated geology

    In the Crackington formation, the presence of rare goniatites has been vital in unravelling the complicated local stratigraphy.  This area shows an excellent display of sedimentary features associated with shallow water turbidites, an outstanding site for the study of paleogeography sedimentation and tectonics. Near Boscastle exposures of carboniferous slates, siltstones and sandstones of the Crackington Formation, show an excellent exposure of the refolded folds at Penally Point.  This area has good accessibility which is ideal for field trips (see Tremoutha and Sea Haven for accommodtion). In the Widemouth to Saltson Strand there are exposures of folded and faulted sandstones of the Bucle Formation (in the north) and shale’s and sandstones of the Crackington Formation (in the south)

South Coast

    This is a more sheltered area with broad estuaries which have been formed when the valleys or rias were flooded by rising sea levels.  Here are safe anchorages such as Falmouth and Fowey.  The beaches here made up of  coarser sand and shingle interspersed with rocky sections of wave-cut platform.

Interior

    The interior is made up of the rather infertile and exposed upland consisting of granite intrusions such as Bodmin Moor.  This is a roughly east–west spine intrusion. These uplands are surrounded by more fertile areas used for farming, mainly grazing.  Nearer the south are found the wooded valleys consisting of mainly Devonian sandstone and slates.

The granite interior intruding into the sedimentary rocks has given rise to metamorphism and mineralization.  This in turn has led to Cornwall being rich in tin ore (cassiterite), copper, zinc, lead and silver.  Also china clay (kaolinite) in the areas around St Austell.

The Lizard peninsula is a complete example of an ophiolite.  Red and dark green rock called serpentinite forms the cliffs at Kynance Cove.  Ultramafic rocks forms the infertile soil which cover the heaths of the Goonhilly

Folded shales.  Crackington Haven.