 Barrington Tops is a plateau between two of the large peaks in the range, The park is believed to be an extinct volcano and the mountain ranges are made up of a mixture of sedimentary rocks with a granite top.Erosion has weathered the granite and rounded granite boulders can be seen in some areas of the park.Estimates put the age of the rock at 300 to 400 million years, well before Australia separated from Gondwana.