Out of the Silence by Erle Cox

All Alan Dundas wanted, when he started digging into the ancient clay river bed on his land, was a watering hole for his stock. In 1900s Australia, the land without a history, the last thing he expected to find was a dome of golden metal beneath his land. Or a series of traps barring his entrance, each deadlier than the last, which drove him in single-minded determination to get to the bottom of the mystery, heedless of what he might find, or what threats he might bring to life out of the silence of the past.