THE TECTONIC SIGNIFICANCE OF UNCONFORMABLE CONTACTS AT THE BASE OF EARLY PERMIAN SEQUENCES, SOUTHERN NEW-ENGLAND FOLD BELT

In the upper Barnard River district in the southern New England Fold Belt, unconformable contacts separate Early Permian clastic sedimentary rocks from Devonian spilites to the west of the Peel Fault and from chert and siliceous argillite of probable Middle Palaeozoic age to the east of the Peel Fault. In the Comboyne district, 110 km to the east, a similar contact between Early Permian and older rocks occurs. At each locality several thousand metres of pre-Permian erosion is indicated, with uplift, possibly a product of back thrusting, immediately west of the Peel Fault and subduction accretion farther east. Uplift may not everywhere have been synchronous, and the unconformities need not relate to a discrete episode of deformation. Early Permian rocks from either side of the Peel Fault in the upper Barnard River have a common provenance and contain compositionally distinctive detrital augite which is indistinguishable from that in the Devonian spilites, indicating limited post-Carboniferous movement only on the fault. Although the fault separates depositional realms of contrasting character in the Devonian and Early Carboniferous, it does not mark a major Early Permian facies boundary. © Taylor & Francis Ltd.