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The evolution of end-member continental waters: The origin
of acidity in southern Western Australia

Kathleen C. Benison, Dept. of Geology and Geography, West interactions. These environments present evidence of new brine
Virginia University, Morgantown, West Virginia 26506-6300, USA, evolution pathways and suggest the potential for future intense
kathleen.benison@mail.wvu.edu; and Brenda B. Bowen, Dept. of acid brine environments.
Geology and Geophysics, Global Change and Sustainability
Center, University of Utah, Salt Lake City, Utah 84112, USA INTRODUCTION

ABSTRACT The “wheat belt” and “gold fields” of southern Western
Australia are associated with a regional acid saline groundwater
The Yilgarn Craton of Western Australia hosts a regional acid system. Groundwaters have pH as low as 2.4 and salinities as high
saline groundwater system and hundreds of ephemeral saline as 28% total dissolved solids (TDS) and have greatly affected
lakes characterized by complex acid brines. These acid saline lakes bedrock and subsurface sediments. The surface expressions of
and groundwaters have pH as low as 1.4 and salinities as high as these acid brine groundwaters are the hundreds of shallow,
32% total dissolved solids. The low pH formed by a combination ephemeral acid saline lakes with pH as low as 1.4 and salinities as
of processes dependent upon the host rock lithology and miner- high as 32% TDS (Fig. 1) (Benison et al., 2007; Bowen and
alogy, climate, weathering, organisms, and time. Although these Benison, 2009). These acid lake and groundwaters are chemically
modern acid saline environments are relatively rare, they have complex. They are rich in Na-Cl-Mg-SO4, poor in HCO3, and have
both ancient terrestrial and extraterrestrial counterparts. unusually high and highly variable concentrations of Al, Si, Fe, Br,
Understanding acidification processes provides enhanced under- and some other metals (Bowen and Benison, 2009; Gray, 2001). The
standing of hydrosphere-lithosphere-atmosphere-biosphere

GSA TODAY | JUNE 2015 Figure 1. Yilgarn Craton in southern Western Australia. (A) Map of southern portion of Yilgarn Craton. Approximate locations and general pH range of 60
lakes studied in detail since 2001. (B) Image of “wheat belt” landscape near “gold fields,” located southwest of Salmon Gums. Note the many lakes with
different colors.

GSA Today, v. 25, no. 6, doi: 10.1130/GSATG231A.1

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