An overview of the geology of the Sydney Region

Abstract

This Chapter introduces the geology of the Sydney region. The Sydney region consists dominantly of gently-deformed Triassic sandstones and shales, with minor occurrences of Irregularly distributed Cainozoic sediments. Igneous rooks consist of breccia necks and dolerite dykes, varying in age from Jurassic to Tertiary. The rooks of the Sydney region are dominantly of sedimentary origin, having been deposited within a broad zone of subsidence known as the Sydney Basin. The groundwater in the Triassic rooks is of only minor significance in the study region it is economically important in a few local areas to the north mangrove mountain, west mount Mt. wilson and south mittagong, moss vale. It Is also economically significant in the Quaternary and Tertiary sediments of the Sydney region, particularly in the Botany Bay and Nepean-Hawkesbury valley. Three types of sediment and sedimentary rook are: fine clays, sands and peats of lacustrine and fluvial origin; river and estuarine sands and gravels, and beach and sand dunes.