Regolith hand specimen atlas
Guide for explorers and teaching aid.
The recently published Regolith hand specimen atlas for South Australia provides a broad overview of the wide variety of in situ and transported regolith across the state featuring a collection of 212 samples.
The five main types of regolith materials are described – transported, in situ and indurated regolith, lag materials and soils – as well as rock-derived, extraneous and biogenic components and reworked regolith materials. Composition, fabric, structure and stratigraphy of dominantly in situ regolith are displayed, as well as cases of regolith with mixed origin and/or complex overprinting.
The regolith samples were collected over the last 30 years by Geological Survey of South Australia staff and members of the Cooperative Research Centre for Landscape Environments and Mineral Exploration (CRC LEME). The collection is stored at the South Australia Drill Core Reference Library and can be viewed upon request. It has already been used for teaching during the last two National Exploration Undercover Schools (NExUS) and was on display at the Geological Survey of South Australia Discovery Day 2017.
Regolith formation in South Australia
The formation of regolith is closely related to weathering, driven dominantly by changes in climate. This resulted in the widespread occurrence of extensively weathered rocks throughout South Australia, commonly reaching depths of 10 to greater than 100 m.
Extensive deep weathering occurred prior to the Middle Eocene and may be as old as early Mesozoic. Deep weathering after the Late Eocene-Early Oligocene appears to be dominantly related to the formation of duricrusts and paleodrainage and ancient coastal barrier systems.
Duricrusts formed semi-continuously from the Late Cretaceous to Pleistocene and cap a variety of paleosurfaces of different ages and origins. Major silcrete and minor ferricrete formation occurred in the Paleocene to Early Eocene, Late Eocene and Late Miocene to Early Pliocene.
Increased aridity and persistent strong winds during the Pleistocene caused the development of extensive dunefields like the Simpson and Great Victoria deserts. During this period, a variable influx of aeolian carbonate dust, sourced from the exposed continental shelf during sea level low stands, led to extensive calcrete and soil formation throughout South Australia.
Download the atlas (PDF 18 MB)
– Carmen Krapf, August 2018