How old are the rocks of Barrington Tops?
The oldest rocks in Barrington Tops are Devonian-Carboniferous Period sedimentary rocks (410-290 million years old) of various lithologies (siltsones, mudstones, minor conglomerates and limestones), with the Bowman Beds of the north-east being the most ancient. Together these old rocks outcrop extensively in the valleys.
During the Permian Period (290-250 million years ago), granitic magma was intruded into the sediments resulting in a relatively low relief with a number of granite hills rising above.
During the Tertiary Period (44-55 million years ago) there was volcanic activity at Mount Barrington and Mount Royal. The steep-sided straight valleys that are up to 1000 metres deep, with narrow ridges and marked scarps and benching along the Barrington Massif resulted from erosion following this volcanic activity.
Associated with the Barrington shield volcano was the formation of gemstones (ruby, sapphire and zircon) which occur in alluvial deposits. Barrington Tops contains the largest commercial ruby deposit in Australia.
The Barrington Tops basalts contain the only location for the mineral barringtonite, and the only recorded locality in NSW for the rare zeolite, cowlesite. However, the main mineralisation in the area was gold, particularly in the Upper Hunter and Copeland-Barrington areas.
Regular tours of the Mountain Maid Gold Mine are conducted by the NSW National Parks and Wildlife Service. It lies hidden in a rainforest within Copeland State Conservation Area near Gloucester.
(Source: “Barrington Tops National Park, Mount Royal National Park, and Barrington Tops State Conservation Area Plan of Management”, p18. Published by NSW National Parks and Wildlife Service, September 2010.)
(Fossil photo courtesy of Callicoma Hill Eco-cabins near Mount Royal)