Abstract

Breccias exposed north of the Lizard boundary in east Meneage have hitherto been regarded as tectonic in origin, and the area occupied by them has been called the Meneage crush zone.

The characters and relations of the rocks of this zone are most clearly seen in the coast section between Nare Point and Porthallow. Unstratified clastic sedimentary rocks that make up the bulk of this section consist of four divisions: siltstone breccia, slate with phacoids of greywacke, conglomeratic pebbly slate, and conglomerate. Somewhat similar rocks are poorly exposed inland and are also found at one locality on the west coast of the peninsula.

The rocks have been deformed tectonically but it is concluded that their lack of stratification is due to a process that operated soon after deposition, most probably subaqueous slumping. There is no evidence to support the hypothesis of large-scale northward thrusting of the Lizard series.