West Pymble Bicentennial Park Walk
Visitors will see the remains of an old, abandoned quarry and hear a geologist's explanation of the basalt dyke formation.
This short walk will be led by geologist Dr John Martyn, author of Sydney’s Natural World, Field Guide to the Bushland of the Lane Cove Valley and Rocks and Trees (published by STEP environment group). John is also the co-ordinator and compiler of STEP’s published series of bushwalking maps. John will lead a short walk through Bicentennial Park and explain how its old, abandoned quarry reveals a basalt dyke that is one of a large number of igneous rock occurrences in the Ku-ring-gai GeoRegion. The West Pymble site is an excellent example of the thermal effects of super-hot intruded basalt magma on Hawkesbury Sandstone, which has been visibly baked and recrystallised to a hard, white quartzite, once sought after and quarried for heavy duty tasks like road base and railway ballast. Work is underway with Ku-ring-gai Council to produce a permanent information sign for the site, and to clean out the weed growth that partially obscures the heavily weathered dyke.