Arc to craton provenance switching in a Late Palaeozoic subduction complex, Wandilla and Shoalwater terranes, New England Fold Belt, eastern Australia

Abstract

The Wandilla and Shoalwater terranes of the northern New England Fold Belt are accretionary subduction complexes formed during the Carboniferous at the convergent plate boundary that extended along the eastern edge of Palaeozoic Gondwana. Sandstones from the Wandilla terrane are quartz-poor and quartz-intermediate lithic or feldspathic volcanic sandstones that were derived principally from the associated magmatic arc, whereas those of the Shoalwater terrane are quartzrich and were sourced from a cratonic region dominated by low-grade metamorphic and granitic rocks. The location of the Shoalwater source cannot be determined unambiguously but probably was situated to the north with detritus supplied longitudinally to the convergent plate boundary. At that time arc-derived sediment was confined to the forearc basin behind an outer arc ridge, the physiographic manifestation of the accreted rocks of the Wandilla terrane. The tectonic situation may have been similar to that of the present-day Lesser Antilles subduction system where quartzose sediment carried down the Orinoco River is transported northward and incorporated into the Barbados Ridge subduction complex