COBISS: 1.01 THE wORLD’S OLDEST CAVES: - HOw DID THEy SURVIVE AND wHAT CAN THEy TELL US? NAJSTAREJŠE JAME NA SVETU: KAKO SO SE OHRANILE IN KAJ NAM LAHKO POVEDO? R. Armstrong L. OSBORNE1 Abstract UDC 551.44(091) R. Armstrong L. Osborne: Te world’s oldest caves: - how did they survive and what can they tell us? Parts of an open cave system we can walk around in today are more than three hundred million years old. Common sense tells even enthusiasts like me that open caves this old should not still exist, but they do! Teir survival can be partly explained by ex-tremely slow rates of surface lowering, but this is not sufcient by itself. Isolation by burial and relative vertical displacement by faults are probably also required. Now one very old set of caves have been found, are there more of them? what can they tell us? Key words: speleology, oldest cave, survival of old caves. Izvleček UDK 551.44(091) R.A.L. Osborne: Najstarejše jame na svetu: kako so se ohranile in kaj nam lahko povedo? Deli odprtega jamskega sistema, po katerem se lahko danes sprehajamo, so stari več kot 300 milijonov let. Zdrav razum celo takemu navdušencu, kot sem jaz, pove, da tako stare odprte jame ne morejo obstajati, a vendar so! Da so se ohranile, je lahko deloma vzrok v izredno počasnem zniževanju površja, toda to samo po sebi ni dovolj. Jama je morala biti najbrž tudi zasuta in s tem odrezana od sveta, potreben pa je bil tudi relativen navpičen premik ob prelomih. Zaenkrat je bil najden en sam niz zelo starih jam, ali jih je morda še več? Kaj nam lahko povedo? Ključne besede: speleologija, najstarejša jama, ohranitev starih jam. INTRODUCTION In June 2004, when I last spoke here at Postojna about dating ancient caves and karst I found it difcult to not to reveal the exciting discovery which this paper follows (see Osborne, 2005). My collaborators and I had been convinced since mid 2001 that sections of Jenolan Caves in eastern Australia had formed 340 million years ago. we had to ensure that our story was published and that we could convince others. Te issue was not whether the dates themselves were correct, but did the evidence really mean that the caves containing the clays were of such a great age. Tis took four years of intensive work on the clays and additional dating. Now afer the publication of the results (Osborne et al, 2006), and the following media interest; it seems appro-priate to refect on the signifcance and implications of the survival of Early Carboniferous open caves. 1 R.A.L. Osborne, Faculty of Education and Social work, A35, University of Sydney, NSw 2006, Australia; e-mail: a.osborne@edfac.usyd.edu.au Received/Prejeto: 27.11.2006 TIME in KARST, POSTOJNA 2007, 133–142 R. ARMSTRONG L. OSBORNE THE POTENTIAL FOR CAVES/SECTIONS OF CAVE TO HAVE A GREAT AGE Despite many years of working on palaeokarst, I initially found the Early Carboniferous (340 Ma) K-Ar dates for unlithifed clays in Jenolan Caves incredible (Figure 1). Fig. 1: Plastic illite–bearing clay, mustard yellow, in the River Cave, jenolan Caves, NSW Australia. Te < 2µm fraction of this clay was K-Ar dated by Osborne et al., (2006) at 357.30 ± 7.06 ma. As I pointed out in 2004 (Osborne, 2005), some Permian landforms do survive relatively intact in Australia. Even a Late Carboniferous age would not have been too sur-prising, as a Late Carboniferous landsurface has been ex-humed at Jenolan from below the overlying Permo-Trias-sic Sydney Basin. An Early Carboniferous age seemed challenging for two main reasons: 1 Te 340 Ma age sits in the middle of the accepted tim-ing for the last folding event in the area (350-330 Ma). Not only the caves, but also the relatively undeformed and well-lithifed caymanite deposits they intersected had to be younger than this event. Te clay dates upset the accepted chronology for the area and suggested that the last folding was older than previously thought. 2 Te 340 Ma age is older than the accepted emplace-ment age for the adjacent Carboniferous granites (320 Ma). Te plateau surface adjacent to the caves inter-sects granite plutons. why didn’t the process that exposed the plutons wipe out the ancient caves? My opponents believed that while other landforms in Australia were old, the caves were not. Tey argued that there was no demonstrably old sediment in the caves. I have already discussed this argument elsewhere (Osborne, 1993a, 2002, 2005). Te Early Carboniferous clays from Jenolan are the frst evidence for ancient sediments in Australian caves accessible to humans, but they make the problem of the survival of ancient caves even more difcult, because they are so very old. If we think about the geological history of karstif-cation at Jenolan then the formation of caves in the Car-boniferous should not be surprising. Te best dates for the Jenolan Caves Limestone put it in the Latest Silurian (Pridoli, 410-414 Ma)(Pickett, 1982). As well as telling us about the 340 Ma event, the KAr clay dating indicated that the limestone underwent a pre-tectonic period of cave development in the Early Devonian before 390 Ma when the caves were flled with the unconformably overlying volcaniclastics. Tere was also a post-tectonic period of ancient speleogenesis be-fore a marine transgression flled the second generation of caves with lime-mud and crinoidal debris. I suspect if we had announced a third-phase of lithifed palaeokarst some 340 million years old at Jenolan, there would have been little reaction, although the problem of its survival and the problem with the timing of folding would have been the same as the problems with our relict sediments. It would not be surprising for limestone anywhere in the world to have undergone speleogenesis some 70 Ma afer its deposition. Te development of a modern cave in Late Cretaceous limestone is hardly unusual. So, what is the problem? I suspect that while geo-morphologists think surface lowering will destroy old caves, many geologists expect that: 1 open caves fail relatively quickly by breakdown (by analogy with mines and quarries) 2 palaeokarst caves only survive because they are flled with rock; the rock supports the roof preventing de-struction due to breakdown. 3 cave sediments become lithifed quickly, so old unlithi-fed relic sediments cannot exist Tese ideas are refuted by the fndings of palaeo-karst workers, surface cavers and the oil industry so I will not expand on them here, rather I will concentrate on geomorphological challenges to the survival of 340 million year old caves. 134 TIME in KARST – 2007 THE wORLD’S OLDEST CAVES: - HOw DID THEy SURVIVE AND wHAT CAN THEy TELL US? HOw COULD THEy SURVIVE? wHy CAVES MAy SURVIVE LONGER THAN SURFACE LANDFORMS Landforms are always under threat from the processes of weathering, incision and surface lowering. weath-ering in the normal sense of the word is irrelevant in karst since, except in the case of Nadja’s incomplete so-lution (Zupan-Hajna, 2003), carbonate weathering re-sults in almost total removal of the rock mass. Incision may re-activate or expose ancient caves, but will rarely afect enough of the rock mass to lead to the destruc-tion of ancient caves. It is surface lowering that is the greatest threat to ancient caves and the main process that leads to their late stage modifcation into unroofed caves. what processes may protect caves from surface lowering? Protection by the rock mass Since caves form below the surface, there is a thickness of rock between them and the zone where surface lowering is progressively removing the surface of the Earth. Tis means that caves have a head start in survival compared with surface landforms of the same age. Caves unroofed at the surface are always substantially older than the sur-face in which they are exposed. Isolation and “karst resistance” Not a lot happens once a cave space enters the vadose zone, there may be breakdown or speleothem deposition, but many cave openings just sit there, inactive while the water is directed through active conduits at a lower level. Te “god” that protects cave walls Apart from speleothem and lithifed sediments that may outlive all of the cave they formed in (Figure 2), it is the walls of a cave that survive the longest, right up to the very last stage of an unroofed cave (Figure 3). why don’t the cave walls fail and simply fall into the void beside them and why don’t they allow the whole cave to fll with speleothem during its siesta in the vadose zone? Some process must protect cave walls from failure and penetration by potentially lethal vadose fow. I am indebted to Andrej Mihevc for the concept of a ‘”god” that protects cave walls’. I am sure this god is a useful addition to the karst panoply. Tree factors are probably important for the survival of cave walls, particularly in teleogenic karsts: - • rock strength • Slow and gentle cave excavation, leading to gradual stress release (caves are not mines or tunnels) Degassing and precipitation from seeping water makes cave walls self-sealing • Fig. 2: Speleothem, exposed on surface above dip Cave, Wee jasper, NSW, Australia. Cave entrance can be seen top of photo. Tis speleothem has outlived all of the cave it formed in. Some cave walls do fail for a variety of reasons. we can observe this in many breakdown chambers and it is possible to recognise the sources of the weakness in the walls that resulted in their failure. Lack of substantial entrances Some caves, e.g. cryptokarst caves of thermal /hydrother-mal origin, may have no entrances or very poor connec-tion to the surface. If there is no entrance or surface con-nection then surface processes cannot get in and modify the cave. Entrance Blockages It is very easy for cave entrances to become blocked. Pro-grading entrance facies talus cones reaching the ceiling, talus from the surface or breakdown, growth of fow-stone masses, logs, vegetation and biogenic deposits such as guano piles can all easily block cave entrances. with a small amount of vadose cementation, these blockages can become efectively permanent and the cave can be-come isolated. TIME in KARST – 2007 135 R. ARMSTRONG L. OSBORNE Fig. 3: Looking towards the surviving cave wall from the foor of an Carso, Italy. Protection by flling If a cave is flled with easily removed material, it is pos-sible for the cave to remain “fossilized” for a geologically signifcant time and then become exhumed. If the fll is impermeable to vadose seepage, it will not become ce-mented. Even if it is cemented, if the fll contains minerals that are unstable when exposed to oxygen-rich vadose water it can be removed from the cave with little efect on the enclosing walls. Protection by cover/burial Cover by sediments, volcaniclastics or lava fows can protect not only the caves, but also surface karst land-forms. For the process to be efective, the cover must be removed without a great efect on the underlying older karst. It helps if the cover consists of relatively weak rock or of rock that is easily weathered. An outstanding ex-ample of this process is the burial by Permian basalt and later exhumation of the Shinlin karst in southern China. DENUDATION RATES Both biblical prophets and geomorphological pioneers predicted a fat future, the “rough places a plain” of Isaiah 40:4 and the peneplanation of w. M. Davis. while peneplanation may be out of favour, surface lowering is a real phenomenon. Te problem for survival of old caves is that even with the slowest rates of surface lowering most Mesozoic and all Palaeozoic caves should have been destroyed, except those that have been deeply buried and later exhumed following tectonic movements. In some parts of Australia, extremely low denudation rates apply. wilford (1991) reported rates as low as 0.5 metres per million years in the Ofcer Basin of western Australia over the last hundred million years. 136 TIME in KARST – 2007 Surface lowering rates in the eastern Australian highlands, where Jenolan Caves are located, are said to range between 1-10 metres per million years (Bishop 1998). If this is so, then the limestone exposed at the surface today in these areas was between 65 and 650 metres below the surface at the end of the Meso-zoic. while these rates are slow by world standards, they are not slow enough to account for the survival of extremely old features. Surface lowering and early incision may be slower than we think Studies of past erosion rates in the unroofed cave, trieste Shoalhaven Catchment in eastern Australia by Nott et al., (1996) show that we must approach incision and denudation with some care. Teir relevant fndings are that: • summit lowering and scarp retreat were insignifcant when compared to the process of gorge extension • the rate of summit lowering was 250 times less and the rate of scarp retreat was 15 times less than the rate of headward advancement of gorges • stream incision in the plateau upstream of the erosion head is very slow compared to the rate of gorge extension there was “insignifcant lowering of the interfuves throughout the Cainozoic” (Nott et al., 1996, p 230) • “Over the long term, the highlands…will become con-siderably more dissected well before they decrease sub-stantially in height or are narrowed” (Nott et al., 1996, p 224) Te stream incision rate is important when we con-sider the age of relict caves. If incision rates early in the history of the landscape are much slower than at later stages, present incision rates will lead us to seriously un-derestimate the age of relict caves located high in the sides of valleys. If lowering of interfuves, i.e. surface lowering, is much slower than incision, scarp retreat and nick-point recession then plateau karst, high level caves and surface caves exposed on hilltops could be very much older than we have previously thought. In dissected terrains the caves will not just be as old as the hills, but considerably older. TECTONIC PROCESSES ARE NECESSARy FOR ExTREME SURVIVAL Low denudation rates, low relief and low rainfall, the Australian trifecta, can only go so far to preserve old • THE wORLD’S OLDEST CAVES: - HOw DID THEy SURVIVE AND wHAT CAN THEy TELL US? landforms. Stephen Gale recognised this point: “Al-though low rates of denudation are an important fac-tor in ensuring the survival of ancient landscapes, this alone is inadequate as an explanation of the maintenance of landforms over ten and even hundreds of millions of years” (Gale, 1992, p 337). Gale went on to discuss how denudation needed to be localized if old landsurfaces were to survive. One way the landsurface can be isolated from surface lowering is through the relative adjustment of adjacent blocks by faulting. Te Fault-Block Shufe Te problem at Jenolan is the elevation of the old caves relative to the adjacent plateau surface. Te plateau sur-face to the south of Jenolan Caves exposes and intersects post-tectonic Carboniferous granites, thought to be 320 million years old. Figure 4 is a cartoon drawn to explain in simple terms how the caves may have survived. Te caves must have been relatively close to the sur-face when the cupolas formed and the volcanic ash that formed our old clays entered them (Step 1 in Figure 4). Fig. 4: Cartoon of postulated events at jenolan Caves to explain the survival of caves with Carboniferous clays 1 Cave excavated by thermal processes following folding of limestone 2 volcano erupts; tephra falls to ground and enters caves. 3 Fine tephra begins to fll caves and reacts with water in caves to produce clay minerals. Tese clays have been dated at 340 million years. 4 volcano stops and begins to be eroded. Te caves are full of clay. Granite intrudes the rock near the caves (? 320 ma). 5 Te rock mass containing the granite moves up along the fault, while the rock mass containing the caves moves down. 6 Late Carboniferous: At least 8 kilometres thickness of rock is eroded away, probably partly by glaciation. Tis cuts of the top of the granite and brings the cave back close to the surface. 7 Late mesozoic: valleys erode into the surface and a new stream cave forms below the level of the flled cave. Te clays, still sof, are undermined. Tey fall down and are carried way by the stream. 8 today: Almost all of the 340 million year old clay has now been removed from the caves, small remnants are found and dated. TIME in KARST – 2007 137 R. ARMSTRONG L. OSBORNE Even if the granites did form close to the surface, something between hundreds of metres and a few kilome-tres of rock must have been removed from the plateau sur-face to expose the granite. Tis amount of surface lowering should have removed any older caves, particularly those shallow enough to fll with surface-derived sediment. For the caves to survive there must have been a relative change in elevation between the mass of rock intrud-ed by the granite and the mass of rock hosting the caves (Step 5 in Figure 4) before signifcant regional denudation took place. For the sake of simplicity and because the history is not well understood, several steps have been lef out when speaking here in 2004 (Osborne, 2005) I suggested a number of characteristics of localities where one might expect to fnd very old caves, interestingly Jenolan has only some of these. So how might we recognize “funny old caves” and ancient cave sediments? “ABNORMAL CAVES” AND “ABNORMAL” SECTIONS OF “NORMAL” CAVES My work on palaeokarst in caves and on non-fuvial cave morphology frequently takes me to caves that others regard as unusual. Te Carboniferous clays from Jenolan are found in cupolas and other non-fuvial sections of the caves. Interestingly, these same sections of cave also in-tersect caymanite palaeokarst. Fieldwork on non-fuvial morphology in Europe during 2005 took me to Belianska Cave in Slovakia and Račiška pečina in Slovenia. Co-incidentally, (or not) these are the same localities where Pavel Bosak and co-workers have found the oldest relict cave sediments in Europe (see Bella et al., 2005 & Bosák et al., 2005). Non-fuvial caves, the per ascensum caves of Ford (1995), are characterised by being isolated from or poor-ly integrated with the modern hydrological system. Some have no natural entrances, while others have poor con-nection or secondary breakdown entrances. Tis gives them a head start in the survival stakes when compared with fuvial caves. Generally odd caves may survive longer than normal ones. THE OLDEST CAVES ARE NOT ALwAyS AT THE TOP when I frst discovered the caymanite deposits in Jenolan Caves in the 1980s, I could not understand why they were intersected by cave passages at low levels in the limestone mass, not by (older) high-level passages. I did not realize in Figure 4 between Step 6 and Step 7. In the Late Car-boniferous, the upper sections of the present valleys were incised and fuvial caves formed. Tese flled with gla-ciofuvial sediment and the whole landscape was buried under the Sydney Basin. In the late Mesozoic, the Sydney Basin was stripped back and the valleys re-juvenated. New fuvial caves formed below the level of the old flled ones (Step 7 in Figure 4). Underhand stoping has now removed most of the old clay and only tiny remnants of clay remain in the caves. then that while level in the landscape is a good indicator of the age of fuvial caves, it has little to do with the age Fig. 5: Palaeokarst sandstone flling spar-lined tube intersected by more recent cave in the entrance area of Lucas Cave, jenolan Caves, NSW, Australia. Te strongly cemented sandstone is younger than the plastic clay shown in Figure 1. wHERE ARE THE OTHER OLD CAVES? 138 TIME in KARST – 2007 THE wORLD’S OLDEST CAVES: - HOw DID THEy SURVIVE AND wHAT CAN THEy TELL US? of non-fuvial caves. In fuvial caves you look to the top for the old sections of cave, but in non-fuvial caves, you must look high and low. RECOGNISING OLD SEDIMENTS How can we recognise very old relict sediments in caves? Te old clays at Jenolan were not found by looking for old material, we were originally looking for unusual minerals. Te clays that looked diferent contained larg-er than normal amounts of illite and so we were able to date them. Afer the frst old date, samples were chosen strategically, to get the maximum amount of chronologi-cal information from the minimum number of samples. Tis was only possible because there were existing pal-aeokarst and cave morphology stratigraphies to test (Os-borne, 1999). Unconsolidated Relict Sediments May Be Older than Lithifed Palaeokarst Deposits In my last presentation here, I raised the idea of the lithi-fcation trap: the idea that strongly lithifed cave deposits and palaeokarsts may be younger than some unconsoli-dated or uncemented cave sediments (Osborne, 1995). Tis makes sense if we think about fowstone growing over mud and recognise that cementation, rather than compaction is the main agent of lithifcation in caves. Above ground geologists ofen fnd this idea conceptu-ally challenging. At Jenolan Caves, a crystal-lined cave passage is flled with strongly cemented sandstone (Figure 5). we have no problem with the sandstone being younger than the crys-tal, but stratigraphy suggests that this sandstone is younger than the unconsolidated clay shown in Figure 1. wHAT CAN THEy TELL US? GEOLOGICAL HISTORy OF THE CAVES During the 1980s and 1990s, the aim of my research on palaeokarst was to show that speleogenesis and karstif-cation in eastern Australia had a geological history (Os-borne 1984, 1986, 1991b, 1993 a & b, 1995, 1999). Tat is, palaeokarst deposits intersected by “modern” accessible (open) caves indicate repeated periods of cave development at the same locality over periods of hundreds of millions of years. Cavities flled with strongly lithifed palaeokarst deposits represented the older periods of cave development. Te discovery of 340 million year old clays in open accessible caves at Jenolan (Osborne et al., 2006) demon-strated something signifcantly diferent. Te open caves themselves, not just cavernous karsts, can have develop-mental histories extending over geologically signifcant periods of time (i.e. hundreds of million years). Not much happens during the life of an old cave; they just snooze like an old pet cat. Sometimes dramatic events above, below or beside the cave may wake it from its slumber and leave their mark for us to fnd in the fu-ture. GEOLOGICAL HISTORy FROM THE CAVES Much has been said about the potential of the strati-graphic, geomorphic and climatic record in caves. Even the most generous previous estimates for the age of caves (not palaeokarst) suggested that such evidence would be limited largely to the younger end of the Cainozoic, and might perhaps in places like eastern Australia with old landscapes extend to the late Mesozoic. Te survival of Palaeozoic open caves presents a new vista of using caves as a source of geological information. Both ancient caves and palaeokarst deposits could contain records of “miss-ing sequences” for which there is no other record. while there has been signifcant progress in reading the ancient record of palaeokarst, lack of suitable dating techniques and a lack of expectation make geological history from the caves an open and uncultivated feld. Evidence for Global Events Cave sediment research, particularly in the UK and Aus-tralia, began with a focus on a geological problem of global signifcance. Today we call it the Pleistocene ex-tinction. Te protagonists at the time saw it in terms of the “deluge” and the extinction or not of “antediluvian” faunas (see Osborne 1991a). Caves were an obvious focus for this research as Pleistocene vertebrate fossils occur in great abundance in the red earths of caves throughout the globe. If the surface of some interfuves dates back to the Mesozoic, then ancient caves have the potential to con-tain evidence of the K-T boundary. what signal should we expect to fnd in the caves from the K-T event and how would we recognise it? Commentators have sug-gested that the K-T event involved dramatic changes in the pH of meteoric water, with strongly acidic rain falling from the sky. If this were sustained it should have lef an imprint of extreme surface karstifcation and enhanced vadose and fuvial speleogenesis. Given how efectively caves have trapped Pleistocene loess, we might also ex-pect to fnd iridium-rich silt in caves that were open at the K-T boundary. I don’t know if anyone has looked, but perhaps they should. TIME in KARST – 2007 139 R. ARMSTRONG L. OSBORNE Caymanites & unknown transgressions Lazlo Korpas has been able to make great progress in understanding the evolution of the karst of Hungary by dating caymanites, because these contain fossils and they correlate with magnetostratigraphy (Korpas, 1998, Korpas et al., 1999). Caymanites provide very useful evidence for marine transgressions (Korpas, 2002). Caves intersect caymanites in at least six karst areas in eastern Australia. None of the caymanites have been directly dated. Te 340 Ma old caves at Jenolan intersect caymanites, indicating a minimum age. Te eastern Aus-tralian caymanites indicate one or more marine trans-gressions, probably in the Early Carboniferous for which there is no other geological evidence. Volcaniclastic cave sediments/palaeokarst Given the close physical relationship between stratovol-canoes and carbonate terrains in island arcs and active margins, volcaniclastic cave sediments and palaeokarst deposits should be common in both modern and ancient island arcs and active margins. Tere seems, however, to we still know very little about extremely ancient caves. Tere are good prospects for making new geological dis-coveries in very old caves. All we have to do is identify funny old sediments in funny old caves, ascertain their meaning and fnd ways to date them. Tis sounds easy, but it is not. Te Jenolan team consisted of a karst geologist, a dating guru (essential so there is no argument about the technical aspects of the dates) and two mineralogists. It be scant reference to such deposits in the literature. Per-haps this is due to the concentration of karstological ef-fort on Tethyan karsts. Volcaniclastic cave sediments and palaeokarst de-posits should be expected to occur around the Pacifc rim, particularly in volcanically active island arcs e.g. Indonesia, Philippines, Malaysia, Japan, New Zealand and in southern Europe (Mts Etna and Vesuvius). Tey should also be expected where I work in the early Palaeo-zoic island arc environments of the Tasman Fold Belt of eastern Australia. while andesitic and silicic stratovolca-noes are likely to be the most common sources of tephra for volcaniclastic deposits in caves and karst depressions, basaltic tephra can also fll caves. Five volcaniclastic palaeokarsts and volcaniclastic relict sediment deposits, including the 340 million year old clays, have now been recognised in eastern Australia (Table 1). It seems likely that more will be recognised, given that many of the cavernous Palaeozoic limestones are overlain by volcaniclastics. took six frustrating years and a sponsor with deep pock-ets to get the work completed and published. A new world of geology of and from ancient caves awaits those with a stout heart, a thick skin, a good sponsor and eyes for caves and sediments that don’t seem quite right; something like the qualifcations for Antarc-tic explorers. tab. 1: volcaniclastic Palaeokarst and Relict Cave Sediments in eastern Australia Type Likely Age Karst Area Chemistry Reference Pk ? Tertiary Crawney Pass Basaltic observed by author Pk Mid Devonian Jenolan Silicic Osborne et al. 2006 R Early Carboniferous Jenolan Silicic Osborne et al. 2006 Pk Mid Devonian Wombeyan Silicic Osborne, 1993 Pk ? Wellington Silicic Osborne in prep Pk = palaeokarst R= relict cave sediment SPECULATION 140 TIME in KARST – 2007 THE wORLD’S OLDEST CAVES: - HOw DID THEy SURVIVE AND wHAT CAN THEy TELL US? ACKNOwLEDGEMENTS Tis paper was presented at the Time in Karst symposium at the Karst Research Institute, Postojna, Slovenia in March 2007. Te University of Sydney Overseas Travel Grant Scheme and Top-Up funding for the Faculty of Education and Social work supported attendance at the symposium. Tis paper arises from the dating of clays at Jenolan Caves (Osborne et al., 2006). Many thanks are due to my co-workers, Horst Zwingmann, Ross Pogson and David Colchester. Final corrections to the Jenolan Clay paper were made in Europe in the second half of 2005. I wish to thank colleagues in the Czech Republic, Hungary, Slova-kia and Slovenia for their assistance and support. work on Belianska Cave with Pavel Bella, Peter Gazik, Jozef Psotka and Stanislav Pavlarčik assisted in developing the ideas presented here. Other inspiration came when Karel Žác showed me the caves of the Bohemian Karst and Lazlo Korpas showed me his caymanite sequences and well-dated unconsolidated old sediment. Andrej Mihevc engaged in lively discussions about surface lowering, the “god that protects cave walls” and the origins and survival of Račiška pečina. Penney Osborne read the drafs. REFERENCES Bella, P., P. Bosák, P. , J. Glazek, D. Hercman, T. Kiciniska, & S. Pavlarcik., 2005: Te antiquity of the famous Belianska Cave (Slovakia). Abstracts, 40th International Speleological Congress, Athens-Kalamos 21-28 August 2005: 144-145. Bishop, P. , 1998: Te eastern highlands of Australia: the evolution of an intraplate highland belt. 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