Further evidence for the age of the Sofala volcanics

Abstract

A small assemblage of conodonts, corals, and algae recovered from an agglomerate within the Sofala Volcanics indicates a mid-Gisbornian to Early Eastonian age for this part of the formation. The Sofala Volcanics crop out to the north of Bathurst, in a north - south trending zone between Mudgee in the north and Paling Yards in the south (figure 1). To the east they are faulted against quartz-rich Late Devonian sediments of the Larabie Group; on the west they are unconformably overlain by the probably Late Llandoverian Tanwarra Shale, or separated from the Bells Creek Volcanics by a zone of shearing, the Wiagdon Fault Zone. The Sofala Volcanics are the oldest known formation in the area, and represent basement for sediments on the eastern side of the Hill End Trough and on the Capertee Rise

Stratigraphic and structural evidence, and distribution of metamorphic zones defined by biotite, andalusite, and sillimanite, suggest that the north western part of the Willyama Complex is dominated by the variably plunging, variably oriented, regional D1 Kantappa - Lakes Nob Syncline. Formation of meta morphic zones generally parallel to bedding in a pre S1 event leads to a depth control on metamorphism and to the recognition of tectonic levels in this area. Although this depth relationship was destroyed by F1 folding, the folded distribution of these metamorphic zones controlled the meta morphic grade and style of structures formed in the D1 event.