Mound Spring Complexes in Central Australia: an Analog for Martian Groundwater Fed Outflow Channels?

Introduction: The arid inland of Australia contains a diversity of landscapes and landscape processes, often of great antiquity, extending back to the Mesozoic and Paleozoic. The potential of this landscape as a source of Mars analogs has, however, been little explored. The few examples studied so far include radiation-tolerant microbes in thermal springs [1] and hematite-silica hydrothermal alteration near Arkaroola in the Finders Ranges [2], and aeolian landforms at Gurra Gurra water hole the north east of Arkaroola [3]. Further Australian Mars analog studies were provided by the studies of Bourke and Zimbelman [5, 6] of the paleoflood record of the Todd and Hale Rivers in central Australia. To facilitate study of such analogues, Mars Society Australia has embarked on a project to construct a Mars Analog Research Station near Arkaroola [4]. The international scientific community will soon have the opportunity to participate in Mars analog studies in central Australia utilizing this facility. An area of considerable Mars analog potential is the mound spring complexes that occur at the margins of the Great Artesian Basin (GAB) [7] which underlies 22% of the Australian continent and covers 1.7 million km 2. The mound springs are formed when ground water flows to a topographic low, and subsurface strata dips up causing a hydrological head at the surface. Minerals precipitated at the spring discharge zone form low mesas or "mounds", the height of which are controlled by the hydrological head. This paper describes the Dalhousie Mound Spring Complex (DMC) in the northern part of South Australia (Figure 1), and its potential as a Mars analog. Hydrogeology: The DMC consists of a cluster of more than 60 active springs formed by natural discharge from the GAB) [7]. Total measured discharge from the GAB is 1.74 GL per day, estimated unfocussed natural leakage through the aquaclude is thought be approximately equal to this figure. Some 54 ML per day are currently discharged by the DMC, 3% of the measured total. The discharged artesian waters [8] are of low to moderate salinity (700-9400 ppm), near neutral pH (6.8-7.3) and warm (20-46 o C). The elevated temperatures are due to passage of the groundwater through deeply buried (up to 3 km) aquifers in an region of high heat flow, rather than magmatic heating. The waters also contain high levels of dissolved iron and H2S and <1 ppm dissolved oxygen. The water is carried in the Late Jurassic …