Engineers Australia

Coastal Limestones

Ray Gordon

Abstract

The carbonate rocks that have been deposited in the coastal environment of western and southern Australia consist of two main types. Firstly and the most conspicuous are eolianites, which are wind blown limesands that have been cemented in place by calcium carbonate under subaerial conditions. The second group are the beachrocks, which consist of beach sand and gravel cemented in place. As beaches and sand dunes are often contiguous in the coastal environment, so eolianites and beachrocks are associated in present and past coastal environments, and along with shallow marine deposits, tufa, marls, travertines and coral reefs, make up the carbonate rocks that are known collectively as the coastal limestones. These rocks occupy over one quarter of the coastline of Western Australia over some 4000 km. They thus form a major part of the environment where most West Australians live. The limestones underlie the numerous development projects that are transforming the coastal region. The geology and properties of these rocks are however not well documented.