The confrontation of structural styles and the evolution of a foreland basin in central SW England

Abstract

Detailed mapping of the rocks to the north and south of Plymouth reveals a sedimentary sequence deformed by a series of folds and thrusts. Two structural zones exist each with a different style of deformation. In the Lower to Upper Devonian rocks of the southern zone, slip vectors, vergence and facing of D1 folds indicate that the transport direction is to the north-west. An associated first phase cleavage dips to the south-east. The northern zone, of Upper Devonian and Lower Carboniferous strata, extends into central Devon and east Cornwall and the geometry and facing of the early folds in these rocks indicate a transport direction to the south or south-east. D1 folds generally verge north but are downward facing towards the south. A flat-lying, penetrative slaty cleavage occurs in the mudrocks and also indicates southward facing. Generally the Carboniferous rocks in this area are inverted. The two structural zones confront each other at an E-W-trending line which passes through Cargreen, 8 km north of Plymouth.Here the deformation is more intense as the cleavage, common to the southern zone, overprints that

Geochemistry of the Start Complex greenschists: Rhenohercynian MORB?

“…The actual age of the complex is not known, although it is often assumed to be the highly deformed equivalent of the Lower Devonian sequence that outcrops just to the north (Dineley, 1986). However, they share a common deformation history with the Devonian strata, except that the early metamorphic segregation fabric in the Start Complex rocks predates the first phase of folds common to both units (Seago & Chapman, 1988). However, they share a common deformation history with the Devonian strata, except that the early metamorphic segregation fabric in the Start Complex rocks predates the first phase of folds common to both units (Seago & Chapman, 1988).…”