Australia: The Land Where Time Began

A biography of the Australian continent 

Exhumed Surfaces and Forms

Exhumed surfaces are exposed unconformities or landscapes that have been resurrected or disinterred. Surfaces that have long, complex chronologies that are as yet undetermined are typically found in shield lands, area that have been appropriately termed 'oldlands' (Wilson, 1903; Hills, 1955; Twidale, 1995). They are difficult to interpret as in many areas the ages and extent of marine transgressions have still to be documented.

Bracketing can readily be used to date many exhumed surfaces, the surface being younger than the youngest rocks it transects, but older than the basal member of the sequence covering it. According to the author¹ in practice an enormous interval of time may be indicated. Therefore, in the case of the west coast of the Eyre Peninsula a regolith that developed on granite from the Middle Proterozoic, gneiss and sandstone is preserved widely beneath dune calcarenite from the Middle-Late Pleistocene, a time interval of about 1.6 Gy. It is suggested by common sense, long-distance correlation and general argument that it immediately precedes the calcarenite, being of Pliocene or even Early Pleistocene age (Molina Ballesteros et al., 1995). In general, surfaces, and any preserved regolith, can be taken to immediately predate the oldest cover deposit.

Sources & Further reading

1. Smith, Mike, 2013, The Archaeology of Australia's Deserts, Cambridge World Archaeology Series, Cambridge University Press