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chamber in Thampanna Cave. As the deposit accumulated, stalactites hanging from the ceiling were incorporated. Broken fragments of others were observed in the section. A 1 m thick sequence of calcite pool deposits exposed by collapse in the wall of a low-roofed
Source publication
Activity ratios of 234U/238U, 230Th/234U, and 230Th/232Th have been determined for calcite, gypsum and halite speleothems from caves of the Nullarbor Plain, mostly in the area N and NW of Mundrabilla Station, for the purpose of U-series dating. All calcite speleothems contain adequate amounts of uranium for dating, but some show an excess of 230Th....
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Context 1
... Carbonate deposition has not been abundant in Thampanna Cave, but a 1 m thick sequence of calcium carbonate pool deposits was found exposed in the roof and walls in one chamber. In section, it was observed that stalactites growing from the ceiling had become incorporated in the deposit and several others were found lying horizontally within it (Fig. 2). Accumulation of the calcium carbonate speleothems, that are clearly relict and not being actively deposited at present, would have required a lengthy period, or a number of periods, when effective surface precipitation was significantly greater than today, so that vadose percolation was ...
Context 2
... gypsum stalactite lying on the floor of the chamber. Two samples of calcite pool deposits collected from the base of a 1 m vertical section exposed by rockfall in the ceiling and walls of a low-roofed chamber. The deposit had accumulated to incorporate several stalactites while broken fragments of others were found lying horizontally within it (Fig. 2). A few gypsum speleotherns have grown from the ceiling exposure of the pool ...
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Citations
... Gypsum and halite speleothems can also be dated, even though halite contains low levels of uranium. On the Nullarbor, the abundance of salt and gypsum reflects the current arid climate; dating of gypsum and salt speleothems gave ages of *185,000 years and less than 40,000 years, respectively (Goede et al. 1990(Goede et al. , 1992, indicating that aridity on the Nullarbor has been in existence for a long time. ...
Australian caves have an astonishing variety of cave minerals and a breathtaking range of world-class speleothems. Altogether 71 cave minerals are recorded here; of these eight were first described from Australian caves. By far the most abundant cave mineral is calcite, followed by aragonite and gypsum, and, on the Nullarbor, halite. There are 44 minerals found in Australian caves that only occur associated with guano. Australian cave minerals have been studied since the late nineteenth century, and new minerals are still being found. Calcite speleothems in Australian caves occur as four basic categories: those deposited by seeping and/or flowing water, still water, capillary water and condensation water. To interpret past climate and environmental data from calcite speleothems, the sequentially deposited layers must be dated; three main dating techniques are available, of which one, U/Pb, was developed in Australia.
... The abundance of halite and gypsum speleothems in many caves reflects the current arid climate. Dating of a gypsum and two halite speleothems gave ages of *185,000 years and less than 40,000 years, respectively (Goede et al. 1990(Goede et al. , 1992, consistent with evidence elsewhere that the climate reached its present level of aridity about 1 million years ago (Chen and Barton 1991;Fujioka and Chappell 2010). ...
The Nullarbor Plain, the largest karst area in Australia (~190,000 km2), slopes very gently seawards, terminating abruptly in an 820 km long continuous cliff line. The semi-arid to very arid climate means the vast majority of the plain is treeless. The surface is covered by low parallel bedrock ridges believed to be the etched footprints of an extensive linear dune system. Some of the ~50 deep caves in the Nullarbor reach the water table and contain lakes of clear, salty, blue-green water, from which lead flooded collapse passages. Shallow caves are much more abundant (there may be perhaps 20,000), and are mostly narrow, smooth-walled vertical tubes called blowholes, because air blows in and out of them as the caves respond to changes in atmospheric pressure. Some of the larger shallow caves contain abundant dark brown to black calcite stalactites. Initial development of the deep caves probably occurred during the Oligocene; the blowholes are younger flank margin caves that formed along the mid-Miocene shoreline on the low gradient limestone platform.
... The long exposure of the limestone plain to the subaerial environment has resulted in karst features with collapse dolines, blowholes, dayas, pocket valleys and caves (Burnett et al., 2013;Gillieson and Spate, 1992;Goede et al., 1990;Goudie, 2010;Jennings, 1962;Lipar and Ferk, 2015;Lipar et al., 2019;Lowry, 1968;Sexton and Tech, 1965;Webb and James, 2006;Woodhead et al., 2019). In addition, the geomorphology of the Nullarbor Plain includes relict fluvial river channels (Benbow et al., 1995b), relict aeolian dune morphology (Burnett et al., 2020), and small neotectonic escarpments (Hillis et al., 2008;O'Leary et al., 2015). ...
The Nullarbor Plain is a ~200,000 km ² planar karst surface in southern Australia, underlain by Cenozoic shallow‐water limestones. During the Miocene the area was uplifted, and although the plain is generally considered extremely flat, locally, the geomorphology of the Nullarbor Plain retains evidence of earth surface processes across a long, middle Miocene‐to‐present time span. The accessibility of the recent 0.4 arc‐second TanDEM‐X digital elevation model (DEM) by the German Aerospace Centre motivated the search for other possible fine‐scale landforms that would previously have been unresolvable. The analysis of DEM images revealed an enigmatic annular landform with an outer diameter between 1200 m and 1300 m. It consists of a circular elevated rim and a central dome. Its morphology is distinct from other landforms observed on the plain, and cannot be readily explained as a part of known active or inferred/expected processes on the plain (e.g., fluvial, aeolian, karst, tectonic or extra‐terrestrial impact processes).
More recent karst processes (dayas formation) overprinting the landform indicates the presence of the annular structure prior to dayas formation. A unique microbial boundstone facies sampled from the bed‐rock of the annular structure supports an interpretation of long‐lived, at least partial retention of a primary depositional structure. Differential carbonate deposition, especially bioherm growth, was a likely origin of the annular topographical expression of the present‐day landform and is comparable to biogenic structures in the modern day deeper Great Barrier Reef.
... The age of the enigmatic caves formed beneath the Nullarbor Plain has long been a mystery, in the absence of suitable chronometers (e.g. ref. 14 ). The area is currently arid, receiving ~200-250 mm rainfall per year, with potential evapotranspiration of c. 1250 mm/year (ref. ...
... 15 ) greatly exceeding precipitation, and, with the exception of a thin coastal strip, the region is largely treeless -giving rise to its name. The negative moisture balance, sparse vegetation and lack of a well-developed soil profile on the karst surface inhibit modern speleothem formation and the predominantly shallow caves are dry and dusty, except where they intersect the local water table (Fig. 2, and Supplementary videos) Rare, evaporitic calcite, gypsum and halite 16 speleothems grow episodically beneath occasional drip points and are of Holocene to Late Pleistocene age, but the majority of the formations lie beyond the range of the U-Th geochronometer and thus were, until recently, of unknown age 14 . Our initial exploratory studies, using the U-Pb method to date three speleothems 17,18 , revealed that at least some of the materials from the region were of considerable antiquity -several million years in age. ...
Speleothems represent important archives of terrestrial climate variation that host a variety of proxy signals and are also highly amenable to radiometric age determination. Although speleothems have been forming on Earth for at least 400 million years, most studies rely upon the U-Th chronometer which extends only to the mid Pleistocene, leaving important questions over their longer-term preservation potential. To date, older records, exploiting the advantages of the U-Pb chronometer, remain fragmentary ‘snapshots in time’. Here we demonstrate the viability of speleothems as deep time climate archives by showing that a vast system of shallow caves beneath the arid Nullarbor plain of southern Australia, the world’s largest exposed karst terrain, formed largely within the Pliocene epoch, with a median age of 4.2 Ma, and that, in these caves, even the most delicate formations date from this time. The long-term preservation of regional-scale cave networks such as this demonstrates that abundant speleothem archives do survive to permit the reconstruction of climates and environments for much older parts of Earth history than the ~600 ka period to which most previous studies have been limited.
... Gypsum is a common mineral in caves (White, 1976;Hill & Forti, 1997;Onac, 2012) and has been reported from Australian caves such as Jenolan and Wombeyan Caves in eastern Australia and Exit Cave and Mole Creek Caves in Tasmania (Mingaye, 1899;Pogson et al., 2011). Gypsum from the caves on the Nullarbor Plain has been previously described by Caldwell et al. (1982), Goede et al. (1990) and James (1991), and new caves with abundant gypsum are still being discovered (Jackson, 2018). Gypsum may precipitate from supersaturated drip water or during water evaporation, with sulfur variously derived from meteogenic sources (from sea spray or precipitation), decomposition of organic matter in soil or in caves (e.g., guano), biotic or abiotic oxidative recycling of sulfide from the aquifer, or pyrite in nearby strata (Swezey et al., 2002(Swezey et al., , 2017Onac, 2012;Onac et al., 2011;Pogson et al., 2011, White, 2015. ...
... The only published age from gypsum of the Nullarbor Plain is a ~185 ka U/Th date obtained by Goede et al. (1990) from Thampanna Cave (Fig. 1). This relatively recent age (Late Quaternary) from the gypsum contrasts with much older (Pliocene) ages of calcite deposition (Woodhead et al., 2006;Blyth et al., 2010), and is consistent with the occurrence of substantial speleothems of gypsum superimposed on carbonate speleothems (Goede et al., 1990). ...
... The only published age from gypsum of the Nullarbor Plain is a ~185 ka U/Th date obtained by Goede et al. (1990) from Thampanna Cave (Fig. 1). This relatively recent age (Late Quaternary) from the gypsum contrasts with much older (Pliocene) ages of calcite deposition (Woodhead et al., 2006;Blyth et al., 2010), and is consistent with the occurrence of substantial speleothems of gypsum superimposed on carbonate speleothems (Goede et al., 1990). Consequently, these ages suggest that the gypsum, found in the caves of the Nullarbor Plain today, may post-date the cave formation and consequently may not be a recorder of speleogenesis. ...
Large deep caves with little relation to surface topography are distinctive karst features on the Nullarbor Plain of Australia. The presence of gypsum deposits and chemoautotrophic bacteria within the caves have been suggested as evidence for cave formation and (or) enlargement via sulfuric acid speleogenesis. To test this hypothesis, the stable sulfur isotope compositions (δ 34 S) of both cave gypsum and surface gypsum were measured. Analyses yielded relatively high, positive δ 34 S values from both cave gypsum and surface gypsum, arguing against gypsum genesis via microbial chemoautotrophy, and more broadly, sulfuric acid speleogenesis. Instead, the gypsum is interpreted as forming via evaporation of seawater during the Quaternary.
... Rainfall (often as intense storms) is the main recharge of the aquifer (Gillieson and Spate, 1992; Gillieson et al., 1994). Surface and subsurface karst features developed during changeable environmental conditions after the uplift of the Eucla Basin in the middle Miocene (Jennings, 1962; Grodzicki, 1985; Goede et al., 1990; Gillieson and Spate, 1992; Benbow et al., 1995a; James et al., 2006; Webb and James, 2006; Woodhead et al., 2006). Despite the relatively flat surface, the remarkable karst features are caves (Sexton and Tech, 1965; Hunt, 1970), often divided into shallow (generally less than 30 m below the surface) and deep (generally 50–150 m below the surface, and often intersecting the watertable) caves (Jennings, 1962Jennings, , 1963 Grodzicki, 1985; Gillieson and Spate, 1992; Webb and James, 2006; Burnett et al., 2013), blowholes (Lowry, 1968; Doerr et al., 2012; Burnett et al., 2013), collapse dolines (Jennings, 1962; Gillieson and Spate, 1992; Webb and James, 2006 ) and dryland solutional depressions — dayas (Jennings, 1962; Gillieson and Spate, 1992; Goudie, 2010). ...
... In addition , calcrete clasts within the alluvial fans simultaneously indicate the increasing overall aridity and seasonality (calcretes are characteristic of semiarid climates with limited and/or seasonal precipitation; Goudie, 1983; Alonso-Zarza and Wright, 2010). The onset of aridity in southern Australia, occurring in the late Pliocene to Pleistocene, was also reported by Goede et al. (1990), Sesiano and Hedley (1996), Woodhead et al. (2006), and McLaren and Wallace (2010). The semiarid conditions of the late Pleistocene–Holocene are indicated by formation of calcrete layers on exposed surfaces of the pocket valleys, representing the latest event as they cover both the flowstone and colluvial deposits. ...
... The Nullarbor's caves provide significant information on palaeontology, landscape evolution, and palaeoclimates (e.g. Goede et al., 1990;Prideaux and Warburton, 2009;Blyth et al., 2010;Burnett et al., 2013). The Nullarbor Plain is notable for its aridity and the sparsity of its vegetation (Webb and James, 2006); its aesthetic qualities are iconic. ...
Geological heritage is insufficiently recognised in Australia; it should be considered in its own right, not as an addendum to other heritage values. The lack of a suitable robust and repeatable methodology has seriously constrained the assessment of geological sites suitable for the National Heritage List (NHL). A desktop assessment of Australian desert landscapes required intrinsic natural values of a diverse group of sites, spread over a vast area, to be assessed against NHL criteria. The Earth Sciences Comparative Matrix (ESCoM) was developed for this study. In the ESCoM, sites are grouped in process themes. Each is assessed against NHL criteria then compared with other similar places, according to degree of unusualness, integrity, and authenticity. A site scoring well across multiple themes has increased heritage significance. The overall values of a site are quantified, leading to a qualitative judgement on whether it achieves the threshold of outstanding heritage value. Examples of assessment using this method are given. In this methodology, significance determination is based on rigorous comparisons of specific values. It is semi-quantitative, repeatable, and robust. It differs from other geoheritage assessment methods in its combination of process-based groupings (facilitating the separation of site type from heritage criteria), matrix structure (minimising complexities of scale or diversity), and use of numerical rankings as an aid in decision-making. While the study for which ESCoM was developed was focused on landforms, it can be used for other types of geoheritage (e.g. fossils, tectonic processes), with modification of matrix theme headings.
... Rare features include salt blisters and rims associated with aerosol deposition (De Waele and Forti, 2010). Dating of salt speleothems by the U-Th method was attempted by Goede et al. (1990), demonstrating Holocene salt deposition in the Nullarbor limestone caves. ...
Halite is the most soluble common mineral. Salt karst is concerned with extremely soluble and erodible rock- salt geomorphology, which demonstrates a dynamic end-member to karst processes. Salt outcrops are rare, due to the high solubility, and common total dissolution underground, but subsurface salt is common, and often associated with environmental problems. These are associated with salt hazards, often due to anthropogenic modification of hydrological systems, causing aggressive water to attack salt rock. Most salt outcrops appear under desert conditions, where the salt mass escapes total dissolution. In such outcrops, runoff produces well-developed karst terrains, with features including karren, sinkholes, and vadose caves. Existing salt relief is probably not older than Pliocene, but the known well-developed salt karst systems are of Quaternary age. Up to now, radiocarbon dated accessible caves that have been radiocarbon dated are of Holocene age, indicating rapid formation of new caves and destruction of old ones. The largest cave is the 6.7 km long Malham Cave, Mt. Sedom (Israel). Such caves are dendritic vadose caves with shafts and canyons, whose downstream part joins smoothly the base level or ends within the salt body.
... As this is based largely on sites from the Atherton Tableland that, because of topographical variation, experiences a steep rainfall gradient, the amplitude of change in moisture between the drier glacial and wetter Holocene is likely to have been less over the much more subdued landscape around Chillagoe. Gypsum forms as an evaporative layer in limestone caves during arid environmental conditions (Bull, 1983; Goede et al., 1990). It is soluble in water and can be redissolved during wetter conditions. ...
... It is soluble in water and can be redissolved during wetter conditions. As such, it is considered an indicator of more recent dry geological episodes (Bull, 1983; Goede et al., 1990; Sancho et al., 2004). In this instance the most recent dry period described above is the last 4000 years. ...
Raman spectroscopy and FT-IR imaging analyses of cave wall pigment samples from north Queensland (Australia) indicate that some hand stencils were undertaken during a dry environmental phase indicating late Holocene age. Other, earlier painting episodes also took place during dry environmental periods of the terminal Pleistocene and/or early Holocene. These results represent a rare opportunity to attain chronological information for rock art in conditions where insufficient carbon is present for radiocarbon dating.
... Large, organic-rich speleothems interpreted as having formed beneath forest and/or swamp vegetation are widespread in caves beneath the plain, and until now have only been shown to be older than the ca. 350 ka maximum age limit of alpha spectrometric U-Th dating (Goede et al., 1990). MC-ICPMS U-Th analyses from our laboratory (Hellstrom, unpublished data) have found some limited calcite deposition in the period 350 to $500 ka, but confirmed that the majority of Nullarbor speleothems are within measurement uncertainty of secular equilibrium and thus beyond the limit of mass spectrometric U-Th dating. ...
... 3.6. Regional implications, Nullarbor Goede et al. (1990) investigated speleothems from a number of caves in the Mundrabilla region using U-series methods and concluded that there had been no significant deposition of carbonate in the area for more than 400 ka. Subsequently, Sesiano and Hedley (1996) determined that a black calcite stalagmite from Koomooloobooka Cave was reversely magnetised and thus at least older than 780 ka. ...
Building upon the work of Richards et al. [1998. U-Pb dating of a speleothem of Quaternary age. Geochimica et Cosmochimica Acta 62, 3683-3688], we have developed a method for precise dating of speleothems beyond the range of the U-Th technique using the U-Pb decay scheme. By coupling low-blank sample preparation procedures and multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) analytical methodologies developed for low-level Pb-isotope analysis, we find that, under ideal circumstances (radiogenic speleothems with very low common Pb), U-Pb dating of speleothems is not only possible, but also produces excellent age resolution-often comparable to or better than U-Th studies. Corrections for initial isotopic disequilibrium are necessary and exert a strong control on the achievable age uncertainty. The technique will be of immediate benefit in extending speleothem-based climate proxy records beyond ∼500 ka and will also find other uses, such as the dating of associated sub-fossil remains, and providing constraints on rates of landscape evolution and neo-tectonic processes. Here we present initial results for speleothems from the Nullarbor Plain, Western Australia, and the Alpi Apuane, Italy. The Nullarbor samples provide important new constraints on the development of aridity in Australia during the late Tertiary/early Quaternary, while the Apuane samples offer insights into the landscape history and uplift of that region.
