SEDIMENTOLOGY

This page summarizes the sedimentology, mineralogy and petrology of the lake systems. Subenvironments in and around the lakes were mapped, including sediment composition, sedimentary textures and sedimentary structures. Any rock types at and near the lakes were also mapped.

Interior of sand dune

Ephemeral channel

Acid and neutral saline lakes are surrounded by sand dunes, sand flats, ephemeral stream channels, desert soils, and outcrops of Archean rocks. These saline lakes undergo repeated flooding, evaporation, and desiccation. They are considered as "semi-closed basins" because, although there is no surface outflow (except evaporation), the low topographic relief, high winds, and slow-moving groundwater flow allow for sediment and solutes (as aerosols) to be transported from lake to lake.

Lake Brown

Flooding stage

Evaporation stage

Desiccation stage

from Benison et al., 2007

Cross-sectional view of shallow core showing gypsum crystals and hematite mud-Lake Aerodrome

Most host sediments are reworked quartz and gypsum sand grains, many coated by hematite. Winds rework the grains during evapoconcentration and desiccation stages. Thin, discontinuous beds of lignites form as eucalyptus debris, carried into lakes and sandflats by flooding, decays. An unusual assemblage of minerals precipitates in these lakes and from the shallow acid groundwaters. These minerals include halite, gypsum, hematite, goethite, kaolinite, jarosite, alunite, and rare opaline silica. This results in bedded and early diagenetic chemical precipitates, including evaporite beds, displacive crystals, cements, and hematite concretions. The acid saline lake systems are making sandstones, siltstones, and bedded and displacive evaporites.

"Hairy Blob" microbial remains in halite fluid inclusions

Halite Crust

Sand flat sediment, (gypsum, quartz and hematite) -
Lake Aerodrome; scale bar = 1 mm

Mudcracks - Lake Brown

Cross section of sand flat.- Lake Aerodrome