Skip to Main Content

Abstract:

The Yilgarn River, predecessor of the Swan River, was a major river during the Tertiary before uplift of the Yilgarn Craton and the Darling Range. Tectonic activity and climatic change associated with movement of the Australian Plate caused this river system to dry up, with the formation of riverine playa lakes in its abandoned channel. Study of: (1) saline lake sediments, (2) paleochannel deposits, and (3) older sedimentary formations, reveal the history of this change. The palynologic record within the river system shows that the most recent sediments were deposited in the present lake basins during the Quaternary. During Pliocene time, siliciclastic sediments and peat were deposited in the paleochannel system in the central part of the catchment. Other sediments vary in age from Pliocene to Miocene. The oldest sediments (Eocene) are preserved in crevices in uplifted areas of the Darling Range and at the base of paleochannels.

Saline lakes in the eastern part of the catchment are larger and contain more salt. Lake areas decrease westward and the amount of halite contained in these lakes decreases substantially. The surface of Lake Deborah is covered by a thick halite crust underlain by stratified lacustrine deposits of poorly consolidated salt, clay and sand with intercalated salt and gypsum. In Lake Deborah, prolonged arid periods occurred when no salt was added to the lake. For most of its history, the lake has remained a NaCl repository. Sodium chloride and other solutes are introduced by groundwater and surface inflow. Brine migration from the lake is minimal due to the presence of thick mudstone layers at the bottom of the sedimentary sequence and the build up of sand dunes during arid periods. This may explain why Lake Deborah is the most saline of the eastern lakes.

You do not currently have access to this chapter.

Figures & Tables

Contents

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal