Abstract

Glacial and probably fluvioglacial rocks are present in the Currabubula Formation, an 8500-foot unit of Carboniferous age (Westphalian) exposed in the Werrie Basin of the New England geosyncline, New South Wales, Australia. Approximately 70 per cent of the formation is conglomerate and coarse conglomeratic sandstone, approximately 10 per cent is mudstone and fine sandstone, and approximately 20 per cent is tuff. The Rosedale Member, about 60 feet thick at the type locality, occurs in the middle of the Currabubula Formation and consists largely of varved mudstone with abundant ice-rafted pebbles. The best evidence for Carboniferous glaciation in eastern Australia is from the Rosedale Member and similar units exposed in other areas of northeastern New South Wales.

The most common rock types in the Currabubula Formation are poorly sorted pebble conglomerates and lithic wackes composed largely of mineral grains and lithic fragments from flows and tuffs. Nearly all such rocks are stratified to some degree, and were probably deposited by streams, perhaps as glacial outwash. Rhyolitic and andesitic tuffs were deposited subaerially, in shallow lakes, and as ignimbrites.

The Currabubula Formation was probably deposited near a mountain range undergoing glaciation. Much of the clastic material is volcanic, and includes pyroclastic fragments similar in composition to the contemporaneously deposited tuffs. This suggests that the clastic sediments were locally derived, and supports the idea that glaciation was restricted to the alpine variety. It is not necessary to infer either widespread Carboniferous climatic cooling or a relationship with the more widely occurring Permian glacial rocks in other parts of Australia.

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