Within the Arckaringa Basin the Stuart Range Formation is characterised as a confining layers, and the Mount Toondina Formation and Boorthanna Formation as aquifers. A lack of confining layer between the Mount Toondina Formation and the overlying aquifers of the GAB suggests that there is potential for extensive connectivity between the GAB aquifer and aquifer units within the Mount Toondina Formation within the Arckaringa subregion (Ransley et al., 2012). That being said, the paucity of information concerning intra-formational variability with respect to lithology, spatial distribution and the impact of digenetic changes such as fracture development or mineral dissolution renders only a general interpretation possible.
There is insufficient information to define boundary conditions around the Arckaringa Basin, so the potential for lateral inter-basin connectivity along the western margin and south-eastern corner is considered possible. Discharge from the Arckaringa Basin into the Stuart Shelf has been conceptualised as an important hydrogeological flow feature (Figure 26).
The following is a summary of the main hydrostratigraphic units found within the Arckaringa subregion. Discussions concerning minor units such as the Cenozoic, Officer and Warburton Basins will be limited to what has previously been discussed for brevity and/or due to a lack of relevant data on the subject.
Rolling Downs Group
The Oodnadatta Formation, Bulldog Shale and lateral equivalents are the main units that confine the GAB aquifer. While the Bulldog Shale outcrops extensively through the subregion, outcrop of the Oodnadatta Formation is restricted to the northern and north-eastern portions of SA. Little information concerning the water quality or aquifer properties of this aquitard is known. Measured vertical hydraulic conductivity values range from 3.46 x10-9 to 1.04 x 10‑8 m/day (Love et al., 2013b), suggesting that intergranular cross-formational flow through the aquitard is much less than previously recognised and inferring that the majority of cross-formational flow must therefore occur via preferential flow paths such as faults.
As previously discussed, the GAB aquifer at a regional scale is used to describe the Cadna-owie Formation and Algebuckina Sandstone as a single aquifer unit, although local variations to this may occur (Berry and Armstrong, 1995). In the Arckaringa subregion, the JK aquifer reaches a maximum thickness of approximately 220 m. Examples of hydrogeological properties pertinent to the Arckaringa subregion are provided in Table 6. Detailed discussion may be found in Keppel et al. (2013), Love et al. (2013a), Love et al. (2013b) and Smerdon et al. (2013).
Upper and lower Mount Toondina Formation
Sandstone units in the Mount Toondina Formation encountered during petroleum exploration work have been described as having porosities from as low as 4% (Wopfner and Allchurch, 1967) to as high as 36.6% (Linc Energy, 2010b), while shale and siltstone units have been interpreted as potential seals for petroleum (Cotton et al., 2006; Tucker, 1997). Although no direct comparative work has been undertaken to examine why there is such variance in porosity, possible reasons include lithological heterogeneity, diagenetic processes that may either enhance of reduce porosity or differences in measurement techniques. Six packer permeability tests conducted on coal seam and coal seam interbeds in the Wintinna Coal Field by Coffey and Partners (1983) found coal seams to be of low to moderate hydraulic conductivity, while interbedded sediments were found to have a very low to low hydraulic conductivity; the greater permeability in the coal seams was attributed to observed fracturing (fissility), which can be well developed (Coffey and Partners, 1983; Dames and Moore, 1986). Tucker (1997) notes that feldspar found in sandstone units within the Mount Toondina Formation can appear to be partially dissolved, indicating the development of secondary porosity that may enhance primary porosity. Published hydrogeological properties for the Mount Toondina Formation are provided in Table 6 and Table 7.
The definition of the lower Mount Toondina Formation used for this study is relatively new (Menpes et al., 2012). Previously, Hibburt (1995) noted that the lower units of the Mount Toondina Formation were composed predominantly of marine shales. However, recent reviews of seismic data by Menpes (2012), Menpes and Sansome (2012), Menpes et al., (2012) and this study have identified a maximum flooding surface (mfs) as the base of the Mount Toondina Formation. Above this mfs are prograding deltaic sedimentary rocks, which may correlate with the middle Mount Toondina Formation unit of Hibburt (1995), which was described as consisting of prograding deltaic sandstone and siltstone. Similarly, Hibburt (1995) suggested that the lower Mount Toondina Formation units were recorded in two drill-holes, whereas the most recent interpretation presented here does not specify a distribution. Given these uncertainties regarding the distribution and lithological composition of the Lower Mount Toondina Formation, little can be implied regarding the hydrogeological characteristics.
Table 6 Basic hydrogeological parameters for the JK aquifer within the western margin of the GAB
Source: Keppel et al. (2013)
Note: Current figure has been developed by authors for this contextual statement.
Stuart Range Formation
No aquifers of any significance are known to occur in the Stuart Range Formation. Additionally, there is very little measured data with respect to the hydrogeological properties of the Stuart Range Formation, although a vertical conductivity of 1x10-4 m/day being one example (Table 7). Ransley et al. (2012) suggested that minor sandstones within the south-western portion of the Stuart Range Formation may act as partial aquifers, However reviews of seismic, drill-hole and other geophysical datasets conducted for the purposes of this report have reclassified much of this rock as Boorthanna Formation. In most cases, descriptions of the hydrogeological properties of the Stuart Range Formation are qualitative. Kellett et al. (1999), Belperio (2005), SKM (2009) and Aquaterra (2009) suggest that the Stuart Range Formation is a leaky aquitard, while Aquaterra REM (2005a) and SKM (2009) used head differences between groundwater in the Boorthanna Formation and the overlying watertable to suggest that the Stuart Range Formation acts as an effective barrier to downward leakage. Published hydrogeological properties for the Stuart Range Formation are provided in Table 7.
Most information concerning the hydrogeological characteristics of the Boorthanna Formation is sourced from the south-eastern Arckaringa Basin, where several studies have been undertaken (Kellett et al., 1999; Rogers and Zang, 2006; Belperio, 2005; Howe et al., 2008; Lyons et al., 2010; Enesar, 2006; SKM, 2009). The aquifer characteristics of the Boorthanna Formation are interpreted to be heterogeneous at a regional scale and highly dependent on intra-formational characteristics and secondary porosity development. This heterogeneity is reflected by the range of lateral hydraulic conductivities, which vary from 0.02 to 5 m/day. In addition, a literature review by Wohling et al. (2013) found that sandstone units in the Boorthanna Formation can have relatively high porosity of up to 25%. Published hydrogeological properties for the Boorthanna Formation are provided in Table 7.
Table 7 Reported porosity and permeability for the Arckaringa Basin
Source: Wohling et al. (2013) a) Calculated from density; b) Determined in a laboratory using helium and a porosimeter; c) Determined in a laboratory using a permeameter.
Table 8 Reported hydrogeological properties for the Arckaringa Basin
Source: Wohling et al. (2013) a) Three discrete aquifers identified in Mount Toondina Formation: these were called the P (Permian sediments), S (S coal seam) and T (T coal seam) aquifers; b) Results are thought to be affected by slumping of P aquifer and partial blockage of underlying S and T aquifers
Cambrian and Precambrian basement (fractured rock and karstic aquifers)
Whereas the Andamooka Limestone has developed karstic features, the hydrogeological characteristics within the Arcoona Quartzite and Corraberra Sandstone are largely structurally controlled. Kinhill (1997) calculated that hydraulic conductivity values for a combined Arcoona Quartzite and Corraberra Sandstone hydrogeological unit may vary between 1x10-3 m/day in the upper part of the section to 1 m/day in the basal fractured section. Additionally, air-lift yields from monitoring bores at Olympic Dam range from less than 1 to greater than 10 L/second in the more highly fractured sections.
Based on hydrogeological studies completed within the south-east, the possibility that the Arckaringa Basin is partitioned into a series of semi-discrete sub-basinal areas exists. It is also assumed that a regional groundwater flow regime exists.
Groundwater flow in the south-east Arckaringa Basin is generally eastward toward the Stuart Shelf and a number of salt pan and saline environments near the basin margin (Kellett et al., 1999; Aquaterra REM, 2005a; Howe et al., 2008; SKM, 2009; Lyons et al., 2010). Additionally, a deep groundwater flow path from the Boorthanna Trough to the south has been inferred (Aquaterra REM, 2005a).
With respect to other sub-basinal groundwater flow systems based on limited head data, groundwater within the western Arckaringa Basin is speculated to flow in an easterly direction from the basin margin abutting the Officer Basin towards the Stuart Range. Also, headward erosion contributing to the development of the Stuart Range and the subsequent development of the Lake Eyre (hydrological) Basin may be associated with a zone of recharge for the eastern Arckaringa Basin. Subsequent flow associated with this conjectural zone of recharge is interpreted to be eastward toward the Boorthanna Trough.
Great Artesian Basin and other overlying aquifers
Outcropping aquifer units along the western GAB are important recharge zones that contribute to the groundwater resource and provide water to the many GAB spring environments located in SA. Consequently, groundwater within the GAB in the vicinity of the Arckaringa subregion is typically interpreted to flow from the western basin margin to the east and south-east, where discharge at least partially occurs at a series of springs located along the Torrens Hinge Zone (Figure 27).
As previously mentioned, Cenozoic aquifers are scattered throughout the landscape and are conseptualised as a number of discontinuous local groundwater systems. However, the phreatic surface presented in Figure 24 may be used to provide a general indication regarding groundwater flow. The phreatic surface reflects the regional topography, displaying elevevated groundwater near the Musgrave Ranges and the Central Australian Plateau to the north-west and west respectively and low groundwater elevation near Kati Thanda – Lake Eyre and Lake Torrens, located to the east and south-east respectively. Consequently a general groundwater flow of north-west to south-east may be implied.
Little is known about the flow dynamics of groundwater within the Officer Basin, however using a regionally scaled, simplistic approach, Alexander and Dodds (1997) and Read (1990) suggested a general north to south groundwater migration from the southern Everard Ranges to discharge points associated with salt lakes along the southern margin of the basin, while recharge via paleochannels may form localised groundwater flow paths.
Cambrian and Precambrian basement (fractured rock and karstic aquifers)
The most well-known fractured rock and karstic aquifers in the Arckaringa subregion are in the south-east. Here, such aquifers may be found in a number of stratigraphic formations, inclusive of the Andamooka Limestone, the Arcoona Quartzite and the Corraberra Sandstone (Kellett et al., 1999). Kellett et al. (1999) interpreted flow lines within Precambrian fractured rock to be short (approximately 20 km), radial and essentially following surface drainage lines centred toward the numerous number of salt lakes in the region. Kellett et al. (1999) stated that such a flow pattern highlighted the importance of structural control on the hydrodynamics of the fractured rock aquifers in this region.
A similar interpretation was made with respect to fractured rock aquifer hydrodynamics within the Peake and Denison Inlier, located near the eastern margin of the Arckaringa Basin (Love et al., 2013a), with localised flow away from areas of Precambrian outcrop within the uplifted ranges toward basinal areas in the nearby surrounds.
Kellett et al. (1999) proposed that recharge in the south-east corner of the Arckaringa Basin occurs via diffuse discharge from the JK aquifer. Howe et al. (2008) suggested possible direct recharge to the Boorthanna Formation near the southern basin margin and north of the Boorthanna Fault. Other suggested recharge zones include freshwater stream and wetland environments located near the south-eastern margin of the basin. An average groundwater velocity of 1.4 m/year and a residence time up to 200,000 years was estimated by Kellett et al. (1999) for Boorthanna Formation groundwater. Beyond the south-east corner of the Arckaringa Basin, the use of very limited head data suggests that recharge occurs along the western margin of the Arckaringa Basin, near the Musgrave and Everard ranges and Central Australian Plateau (Figure 26).
An estimate for diffuse recharge to the Permian aquifers in the south-east corner of the Arckaringa Basin using a chloride mass balance approach ranged between 0.05 and 0.22 mm/year, with an average rate of 0.09 mm/year (Wohling et al., 2013). Kellett et al. (1999) used a similar chloride mass balance approach to obtain a recharge rate of 0.5 mm/year through a combined GAB/Boorthanna Formation for the south-eastern corner of the Arckaringa Basin. Both results indicated that diffuse recharge at the well locations assessed is small.
Discharge from the south-east corner of the Arckaringa Basin occurs into the Andamooka Limestone of the Stuart Shelf (Kellett et al., 1999; Howe et al., 2008; Lyons et al., 2010); while Aquaterra REM (2005a) and SKM (2009) also indicate that upward leakage from the Boorthanna Formation aquifer into the overlying GAB, salt pan and saline environments along the western margin of the Billa Kalina Fault is possible on the basis of hydraulic gradient data. Beyond this, discharge from the Arckaringa Basin is poorly understood, although conditions similar to those described for the south-east corner of the Arckaringa Basin occur to the west of the Peake and Denison Inlier (Figure 26).
Overlying aquifers (Cenozoic and Great Artesian Basin)
Current research suggests diffuse recharge to the GAB along the western margin is currently minimal with major recharge events linked to wetter periods of paleoclimatic history. Consequently the GAB groundwater system is now viewed as being in a state of transience (Love et al., 2013a).
Of potentially more importance to the current day system is ephemeral river recharge (ERR), which has been identified as an important contributor to recharge to the GAB in the vicinity of the Finke River, southern NT. ERR describes the process of focused recharge to aquifers resulting from episodic flow events in arid zone rivers (Love et al., 2013a). Recharge rates of between 380 and 850 mm/year were estimated using carbon-14 derived groundwater velocities; while recharge from a single flow event in 2010 was estimated at 1275 mm based on hydraulic head measurements. The volumetric contribution of this recharge event across the recharge zone was estimated at 17,000 ML (Love et al., 2013a). Although ERR has not been recognised in the Arckaringa subregion to date, this is due to a lack of research. As there are a number of river catchments located within the Arckaringa sub-basin, the possibility that ERR may be contributing to recharge requires consideration. Discharge from the GAB occurs via direct discharge from springs, creek beds or other groundwater-dependent environments or via diffuse discharge through confining layers such as the Bulldog Shale. That being said, diffuse discharge is likely to only be meaningful where the confining layers have been deformed by faulting, as the vertical hydraulic conductivity ranges of 3.46 x10-9 to 1.04 x 10‑8 m/day for the Bulldog Shale would necessarily preclude this as a major discharge mechanism (Love et al., 2013b).
With respect to younger aquifers, the source of groundwater to these systems is hypothesised to occur via diffuse or focused recharge following large rainfall events and upward leakage, typically from the underlying GAB aquifer through the Bulldog Shale and Oodnadatta Formation.
Alexander and Dodds (1997) suggested that recharge was primarily being achieved via Paleogene and Neogene paleochannels that extend southward from the Musgrave Block over the extent of the Officer Basin, as well as via points of localised recharge. Additionally, Read (1990) suggested that recharge to the Officer Basin aquifers was likely to be occurring along the southern margin of the Everard Ranges and that salt lakes along the basin’s southern margin provided the only evidence for discharge from the basin.
Cambrian and Precambrian basement (fractured rock and karstic aquifers)
Typically, groundwater recharged into fractured rock aquifer systems within the subregion is interpreted to be either by direct infiltration or via drainage channels to crystalline Precambrian basement rocks. The radial flow patterns mapped by Kellett et al. (1999) indicate that salt lakes located near basement outcrops are the likely points of discharge for such groundwater.
Areas of potential intra-basinal aquifer connectivity at a regional scale are influenced by the extent and characteristics of the Stuart Range Formation. In particular, in areas where the removal of the Stuart Range Formation prior to the deposition of younger sedimentary units occurred interconnectivity between the Boorthanna Formation and overlying aquifer units in the Mount Toondina Formation is possible. An issue concerning the extent and characteristics of the Stuart Range Formation is not only a lack of quantitative information regarding hydrogeological characteristics, but also identification. Much of the Stuart Range Formation located in the south-west portion of the Arckaringa discussed by Ransley et al. (2012) as potentially containing partial aquifers has been reclassified during the compilation of this report as Boorthanna Formation.
Additionally, pre-depositional erosion by glaciation and possibly syn- and post-depositional faulting are interpreted to have resulted in a highly variable thickness of the Permo-Carboniferous formations, as well as potentially demarcating the wider Arckaringa Basin into sub-basinal areas. Faulting may also be actively contributing to changes in regional hydrodynamics and hydrogeological properties, such as porosity and permeability and therefore providing a means of inter-aquifer connectivity.
Lateral interconnectivity between the Arckaringa Basin aquifers and those on the margins may occur. Aquaterra REM (2005a) proposed interconnectivity between the Boorthanna Formation aquifer and fractured rock aquifer on the south-east margin of the Arckaringa Basin. Additionally, based on an understanding of lithology and regional groundwater flows, there is a possibility that groundwater throughflow from the Officer Basin into the Arckaringa Basin along the north-western margin may occur, however there is no groundwater related data to support such a theory.
Currently, a large and important use of groundwater resources within the Arckaringa Basin is mining-related abstraction from the south-east corner of the Arckaringa Basin associated, with mining operations at Prominent Hill. To date, groundwater monitoring has not suggested any adverse impacts to either the overlying GAB aquifer or the Arckaringa aquifer system on a regional scale. However, due to the nature of development in the region, there is currently no long term data to determine impacts to either neighbouring aquifer systems or groundwater related ecosystems within the general vicinity, nor is there any monitoring of groundwater levels within the Stuart Range Formation, which provides the primary confining layer within the area.
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- 1.1.1 Bioregion
- 1.1.2 Geography
- 1.1.3 Geology
- 1.1.4 Hydrogeology and groundwater quality
- 1.1.5 Surface water hydrology and surface water quality
- 1.1.6 Surface water – groundwater interactions
- 1.1.7 Ecology
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