Boulders, cobbles, pebbles and gravel in layers of otherwise fine sedimentary rocks are all glacial erratics or drop stones picked up in valleys by moving glacial ice to the south. The glacial ice broke up at the coast to form icebergs which carried the load of rocks and rock fragments north. As the ice melted the rocks dropped into the silty seafloor.
Drop stones include metamorphic rocks such as schist, phyllite, slate, hornfels, meta-chert and quartzite; igneous rocks such as rhyolite, ignimbrite, syenite, dolerite, and granite with occasional sedimentary rocks such as clongomerate and brecia. The drop stones are of Cambrian, Ordivician or Devonian origin, much older than the Permian sediments along the coast.
MapsMurramarang National Park Morton National Park South Pacific Heathland Reserve
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