The Jenolan Caves Limestone is probably the best known (or ‘known about’) limestone in the State, on account of it containing the Jenolan Caves which are a major tourist destination and are which are now being widely referred to as the oldest passageable caves in the world. Although the limestone is widely known about, it’s petrography, palaeontology and depositional environments (related to palaeogeography) still has not been systematically studied.
How little the geology of Jenolan Caves vicinity is known, or agreed upon, will be evident upon reading the literature. Various accounts of the geology may be quite irreconcilable. For example Lishmund et al. (1986, p. 17) wrote “West of (stratigraphically below) the limestone belt, the sediments are thought to be of Silurian age because of their similarity to Silurian sediments elsewhere within the zone, notably those of the Kildrummie Formation. These rocks are overlain, possibly unconformably, by the Jenolan Caves Limestone which is in turn overlain (probably conformably) by a sequence of sediments which probably range to Early Devonian in age”. What Lishmund et al. meant by “elsewhere within the zone” should be clear enough, as they divided the State’s limestone deposits into zones, putting the Jenolan Caves Limestone within the “Captains Flat-Goulburn Synclinorial Zone”. The Kildrummie Formation referred to includes the Abercrombie Caves Limestone. However, regional metamorphism is so advanced in most Kildrummie it is hard to imagine what ‘similarity’ of features anyone could have been thinking of for such a comparison to have been suggested. Unfortunately insufficient detail is given for knowing that, and also exactly who it was that ever ‘thought’ the sediments below the Jenolan Caves Limestone to be of Silurian age is not made clear either (the publication is by three authors – none of whom are known to have studied Jenolan and so they were probably quoting somebody else but did not record who). Possibly they are quoting from Leonie Chalker (1971) (this is still to be checked). Earlier writers (e.g. see geological map by C. A. Sussmilch) all considered that the rocks west of the Jenolan Caves Limestone are Ordovician. Some sort of marked break between those and the Jenolan Caves Limestone was thought to be present by early observers. Some thought an angular unconformity is likely present; others thought the junction might be a fault or overthust (the western folded Ordovician rocks thrust east over the Jenolan Caves Limestone which itself is overturned slightly and dips steeply west. In the radiolarian cherts mapped by Sussmilch one of us (JB) has found radiolarians years ago west of the upper parking area, and so has never doubted the identification of rocks west of the limestone as being Ordovician.
The Parastriatopora bed that is the focus of this webpage was discovered by Ted Matthews. Ted is a senior caves guide at Jenolan and over the years has made a lot of educational materials available on Jenolan and on karst more generally. For Ted’s contact details, and an outline of materials available from him please see:
The present webpage is put together by John Graham Byrnes (contact john.mail “@” ozemail.com.au ; LachlanHunter Associates, P.O. Box 121, BURWOOD, NSW 1805).
This small project was commenced in 2009, after Ted exhibited at the ‘Castlereagh talks’ (held in September 2009 at the Wesleyan church conference room in Upper Castlereagh) some very fine specimens of Parastriatopora from just off the end of a branch of Burma Road at Jenolan Caves. One piece from the bed is as shown below:
The first seen Ted Matthew’s specimen from the Parastriatopora find at the end of Burma Road, Jenolan Caves, as Ted brought and displayed at some talks on the past at Upper Castlereagh.. There
look to be extensive laminar overgrowths around some of the branches seen here.
Photograph at outcrop at the end of Burmah Road site, showing a fragment that appears to be two branches or stems of a corallum that were later subject to encroaching sheet overgrowth extending from elsewhere in the corallum.
This Castlereagh talks had been organised by John Byrnes who long ago (1960s-70s) had worked some on Silurian corals in New South Wales, including at Jenolan Caves. John recognised the material as being almost certainly a Parastriatopora thicket base boundstone. This is a facies long known from a number of other places in NSW, such as in the Narragal Limestone. In 2010 a specimen from the Burma Road bed of Parastriatopora was taken to another student of fossil corals, Gary Dargan. Gary made thin sections which immediately confirmed that the bed is a boundstone.
Parastriatopora is the commonest Silurian branching coral in the NSW Silurian. It is thought at present to constitute just one species which was very abundant. It is the Silurian growth-form analogue of the abundant branching corals seen in modern seas – Acropora – as below:
A fine thicket of staghorn coral. Maybe Parastriatopora thickets looked a little modern Acropora thickets?
( Photo: National Oceanic and Atmospheric Administration, USA )
Closer branching Acropora. Formosa Staghorn Coral Colony (Acropora formosa) growing on a coral reef in the Banda Sea. (Photo: Paul Osmond)
BACKGROUND TO PARASTRIATOPORA INTERESTS
Parastriatopora is widespread and abundant in NSW Silurian limestone. It commonly occurs as packstones of broken fragments:
One of us (JB) in the late 1960s to early 1970s did a study of Palaeozoic limestones, particularly those flanking the Hill End Trough on both sides. This was to survey what could be easily seen of their biotic and paleaenvironmental aspects (Byrnes, 1972). During those years numerous Parastriatopora packstones were observed (carbonate beds with loosely packed framework or near-framework abundance of one dominant skeletal element – the presumably transported or rolled fragments of the coral Parastriatopora). Also observed were much fewer small occurrences of limestone beds also dominated by or rich in paratriatopora which were of a different nature and mght be the in situ preserved bases of small patch reefs of this coral. The current Jenolan focus of attention was thought to be one of this second mentioned and less abudant type of Parastriatopora bed. Such beds ought to be of boundstone fabric under this micropscope. This was confirmed in 2010 when Gary Dargan cut thin sections from the bed.
Distribution in New South Wales – Throughout the NSW Silurian limestones occurrences of Parastriatopora that have been noted in limestones of six broad regions (areas “A” to “F”) as grouped in Byrnes (1972). These occurrences known in 1972 were:
Area A – Ironstone Creek Beds
Area B – Jenolan Limestone, Tuglow Formation, Bungonia Limestone
Area C – Mount Fairy Beds
Area D – Wylinga Formation, Narragal Limestone, Barnyby Hills Shale (limestone lenses), Molong Limestone, Nandillyan Limestone,
Borenore Limestone, Sounder Marble, Dripstone Group (north of Wellington near Bodangora)
Area E – Hume Limestone, Yass Series, Yass Basin, Glenbower Beds, Cooleman Limestone, Yarrangobilly Limestone
Area F – Sugarloaf Hill Limestone, and near Dangelong Homestead (formation name unknown).
Observations of 1972 – The Parastriatopora packstones were recognised as an abundant and widespread facies of NSW Silurian limestones. Such beds are often six inches to a foot in thickness. Few would exceed 30 cm in thickness. At some places these packstones are seen to occur in regular repetition over intervals of up to 20m in limestones.
Although the genus continues into the Devonian in NSW no Devonian packstones of Parastriatopora were noted. Either there was something particular to our Silurian conditions that favoured packstone accumulations of this coral, or else the apparent lack of it forming packstones in the Devonian is just a reflection of diminishing abundance of the genus in NSW over time?
The 1972 conclusion about the near-monospecific packstones in the Silurian limestones (mainly Parastriatopora but other species also form packstones to a lesser degree) was that they had accumulated in shallow and likely storm-affected waters. Many cases were observed where sizeable colonies of other corals in these packstones (like Pycnostylus, Syringopora, etc.) had internal ‘matrix’ between that corallites which contrasts quite strongly with the general matrix of the packstone bed. This suggested that such corals were transported as clasts, along with the abundant fragments of Parastriatopora, from other lime-mud area. Similar conclusion was made for such colonies with internal lime-mud that now sit in shale – these being imagined to have been swept into still deeper and likely quieter water than the packstone beds accumulated in. In such shales some ‘pockets’ of Parastriatopora fragments were sometimes observed. In the most distinctive cases the ‘pocket’ of Parastriatopora fragments, a metre of so across, was the only place where Parastriatopora might be found at a shale locality. Such occurrences (where there are also transported smaller coralla in shale) were thought to be cases where an entire Parastriatopora colony, or large part of it, was somehow swept into deeper quiet water – but with no idea as to why such a branching corallum, transported entire, might later disintegrate into fragments before final burial. If this interpretation were correct it gives some vague picture or impression of what may have been the size that a Parastriatopra colony could reach – rather large, perhaps extending through half a cubic metre.
That the abundant-Parastriatopora beds of the Silurian limestones in NSW are better termed packstones than wackestones was suggested by a number of observations. It was observed that in almost all localities with well exposed thin beds of abundant Parastriatopora one could see preserved cases of fractured branch fragments in which the resultant halves remain close together in the surrounding matrix. Such breakage must be post the transport of the fragments, and it suggests that the accumulations of branch fragments were at least in places close enough to a self-supported rubble of clasts (relatively low in matrix) that later superincumbent weight could crush and break fragments, or less likely some impacts of larger storm-thrown clasts against the rubble pile of coral fragments might have caused some of such observable breakages. Compared to somewhat similar dense or fossil-‘crowded’ wackestones in the same limestones it was a very broad overall impression that the Parastriatopora packstones carried more dolomite in the matrix than did the crowded wackestones, perhaps a consequence of different early porosity.
Considerably more common than the observations of what look like further late stage post depositional breakage of branch fragments is a ‘stripping of the coenostereozone (outer dense zone)’ phenomenon. This is very commonly observed and perhaps it originated in a variety of different ways(?).
Coenostereozone stripping might even have happened somehow whilst the colonies still remained alive. Or perhaps it mainly occurred as ongoing pre-burial disintegration once corallum fragments had become detritus. Such stripping was often looked for at outcrops and was usually able to be found wherever looked for. However nothing was ever seen that allowed any firm concept of how the process occurred. Annuli of coenostereozone were often removed, it seems, by flaking along sparsely thickened zones of the branches. But just as frequently the stripping off or parting occurred at the main junction at the base of a distinct coenosterezone, sometimes along a zone of croweded tabulae. The coenosterozone development varies a good deal from coral branch to branch and the influence of coenostereozone on the breakup of the corallum into fragments seems to be purely a factor of physical structure and relative strength.
It was observed that In some outcrops the apparent “peeling off” of coenostereozone is suggested by the presence of curved segments of coenostererozone that are still lying ‘concave outwards’ with respect to nearby branch fragments that appear denuded of coenostereozone.
It was wondered if the apparent in situ peeling off of coenostereozone could have been the result of differential strain set up by continued or periodic exposure to alternate heating and cooling – repeated dessication and re-soaking.
No conclusive proof for the speculation that Parastriatopora packstone beds could be of very shallow water origin like this was even found, despite being carefully looked for with such possibility in mind. At one place, the Nandillyan Limestone east of Molong some accretionary lapilli were found in the sequence (though not close to any particular Parastriatopora bed) and this in a general way supports that these well layered limestones may have experienced some very shallow water conditions during their formation. Also a facies called ‘narragalite’ in Byrnes (1972) can be common in sequences containing the Parastriatopora packstones; and consideration of narragalite has favoured a very shallow water or intermittently exposed origin for this facies.
Attempts were made to try and trace individual Parastriatopora packstone beds laterally. Owing to the presence of numerous minor faults, in addition to presence of multiple packstone beds in vertical sequence (so that identity of any particular bed is easily lost across faulting) such attempts were generally of litte success. The furthest a Parastriatopora packstone was ever traced for in the 1972 study was only ca. 200 feet, within the Narragal Limestone south of Wellington.
Although occasion patch reef bases, as imagined for the assumed masses of staghorn coral growth that would have shed all the fragments for Parastriatopora packstone, were found pre-1972 these were never investigated in any detail. It is also now thought that the Jenolan example is likely the best of all such known to date, and hence very worthy of some further investigation. Other similar examples seen, as in the Narragal Limestone, were previously examined to see if any had any proximity to packstones, or could even be in direct lateral continuity. However, nothing that ‘direct’, as could support inferences that transported branch fragments came off dense fields of branching coral colonies similar in general aspect as those of today, could ever be found.
Parastriatopora of the Silurian times was probably nothing near as impressive and ‘graceful’ as many of the ‘fields’ of modern staghorn or branching coral (mostly Acropora). Thickets of Parastriatopora were probably smaller and of more ‘stubby’ growth form. However the actual form and maximum possible size (height) of the Silurian Parastriatopora entire colony has not yet been reconstructed. To reconstruct a corallum of the species would probably require finding pieces of an isolated corallum in shale, extracting them and piecing back together. This is potentially feasible yet unlikely.
Below are two photos of branching tabulate coralla of Devonian age at Falls of the Ohio which appear to have been buried and preserved substantially intact. For some reason our branching Parastriatopora in the NSW Silurian has never been seen preserved substantially intact despite the vast amount of this species which have been buried and preserved to form a substantial part of the Silurian limestones of the State.
“Thamnopora limitaris”, Devonian, Falls of the Ohio -“Intact colonies like this are widespread on the fossil beds.”
“Emmonsia ramosa”, a giant branching favositid. This “forms colonies over 50 ft (15m) across”. Falls of the Ohio.
(Photos: The Falls of the Ohio State Park)
Although abundant, and a major contributor to the building of our Silurian limestones, Parastriatopora in NSW is dominantly found in fragmental and possibly transported form. Fragments of it are preserved usually in horizontal orientation, and often so abundantly as to be the principal or almost sole skeletal component of packstones. Such packstones may be up to a foot thick and they may continue for considerable distances. By contrast, Parastriatopora boundstone facies is rare and no occurrence of it has ever been seen to continue any appreciable distance. These observations lead previously, in the 1970s, to the conclusion that Parastriatopora typically formed small patch reef thickets; and that periodic storm destruction of these spread Parastriatopora branch fragment far and wide between the thickets.
Unlike in the Parastriatopora packstones, the coral fragments in Parastriatopora boundstone facies do not lie in any dominant orientation. Also, many fragments in boundstone facies show overgrowths of the same species or maybe even the same corallum – something generally not seen in Parastriatopora packstones. This supports the idea that Parastriatopora boundstone represents the preserved bases of thickets.
Typical Parastriatopora branch fragments from elsewhere, showing greater alignment. This is perhaps a wackestone fabric. Note the darker coloured peripheral zones on the branches. These are ‘stereozone’ as explained below. From the Fukuji Formation of Japan (“Yoshiki-gun, Gifu Kamitakara Fukuchi farm village. Late Silurian”
(Source: Watacchi specimen FK005)
Another typical but horribly preserved Parastriatopora packstone in Japan.
( http://www006.upp.so-net.ne.jp/kaseki/1/2/21.htm )
Narragal Limestone packstone specimen, showing how common breakages may be – four pointed out here.
Breakages are often seen in Parastriatopora packstones. The reason is uncertain but it may in indicate that the jumble of branch fragments were in sufficient contact througout the mass to direclty transmit accumulating load pressure after burial.
The next step for the Burma Road project will be field observation, to try and determine the stratigraphic position of the limestone with respect to Ordovician strata which are expected to lie close-by to the west, the along-strike lateral extent of the bed, and to note anything intermal to the bed which can tell us anything of the conditions of deposition and coral life.
SLOW PROGRESS WITH PROJECT PARASTRIATOPORA AND/OR UNDERSTANDING OF THE JENOLAN CAVES LIMESTONE
I spent some time during 1965 doing geology in the area; and living at “Upper Farm” clearing near Budthingeroo Creek on the Kanangra Walls Road, south of Jenolan Caves. Also in the 60s/70s I visited some of the caves with a university cavers group – Mammoth Cave being the most memorable for me. In one of the years just pre-1972 I made I made examinations over the limestone extending north from the Grand Arch and up McKeowan’s valley. At that time I noted some rare indications of very shallow (or emergent) palaeoenvironments in the limestone, especially what I thought was some small pockets of very early internal sediment (later thrown perhaps into some doubt by Armstrong Osborne’s work on ‘caymanite’ there), some undulating growth of a flat Coenites which I thought looked like that may have been upon a disturbed/burrowed lagoonal floor; and some intraclasts which I thought looked like they might have been storm-thrown, suggesting very shallow water. By and large though, such things I found to be very rare and not representative of the great bulk of the limestone – whose depositional environment remained highly opaque to me no matter how much I looked at it in those years. At that time (60s-70s) a larger amount of shallow water features had been observed by me in the limestone at Tuglow Caves and my thinking was whether or not some sort of facies pattern might be findable between Tuglow and Jenolan Caves akin to what exists between limestone at Molong and the Narragal Limestone further north (where a whole variation, and assumed lateral sequence, from penecontemporaneously eroded hard-rock-reefal limestone to oncolitic sands (pelsparites) to bedded/dolomitic lagonal biomicrite limestone (Narragal facies) were known. However, the time was never found to explore any of the country intervening between Tuglow and Jenolan Caves.
My next renewal of some connection with Jenolan Caves was when caves guide Ted Matthews phoned me and said he had read section of my 1972 work on limestone palaeoenvironments – and that he was particularly interested in the Narragal facies and questions of dolomitisation etc. Amongst Ted’s own writings and photos I then came upon his photo of piece of the Burma Road Parastriatopora bed and immediately suspected such as being from an in situ excellent remant of one of the long postulated patch reefs with this species – the postulated source of the abundant species of this coral as seen in the packstone beds such as in the Narragal Limestone. Ted later on displayed a chunk of the bed at a discussion day at Upper Castlereagh and transferred a piece of it to me at that time (this being the piece I organised for Gary Dargan to thin section).
To commence trying to promote some interest in the occurrence, the material was next taken to the Australian Museum (although at the time the then palaeontology, Bob Jones, was about to retire and he was not able to suggest anyone known to be interested in or working on tabulate corals). During that visit the museum collections were looked through. There was quite an assortment of small pieces of Parastriatopora which had already been collected from Jenolan Caves in the past. None of them, however, had localilty details or were of any particular note. They were by and large small isolated pieces, and none seeming to be from packstone/boundstone beds.
Gary Dargan at the Deparment of Mines Londonderry facility made some excellent LARGE thin sections from the Parastriatopora bed limestone piece that Ted Matthews had collected. The thin sections fully confirmed the expected coralgal nature of the rock, and that the bases of a Parastriatopora were miost likely to be here preserved in situ. This was the first recognision of in situ preservation in NSW of this very abundant species that is seen in so many of our Silurian limestone ( Parastriatopora certainly also ranges into the Devonian but has never yet been seen as the principal component of beds in the Devonian limestones of NSW – the Silurian was its time of epic proportions it would appear ). Shortly after Gary made the thin sections he went overseas and was lost touch with. Some meagre efforts later on to find his new address were not successful.
Following the making of the thin sections, some suitable base map for plotting the bed at the end of Burma Road upon was next sought. Little progress could be made with that. The first batch of enquiries looking for persons who might be interested in describing the material also failed to bear any fruit at all. This was impeded by the fact that Nomen nudum had apparently ceased being produced (a very valuable directory to ongoing palaeontological work in Australia). Also the entire website where ALL former issues of NN had been downloadable from vanished. This had been connected with a formerly very vigorous palaeontological centre at Macquarie University. For all that could be gleaned remotely it was as if that had vanished too and it looked rather like a mini dark ages for palaeontology in Australia(?).
One of the next things to be done was to try and catch up on later work on the Jenolan Caves Limestone, as embodied in theses at University of NSW, Kensington (where I’d done my own thesis in 1965 on an areas south of Jenolan). Back in 1965 all geology thesis were instantly accessible at UNSW, on rows at the back of the geology library. But “now”, upon my return after very many years — the geology librarian was no more, the geology library had long since vanished, and it was in fact proving very difficult to find/see theses.
The project languished till 2012 when it was learned by chance that Nomen nudum had been resurrected and I managed to get copy of recent issues sent from the Geological Survey in Queensland.
Following my renewal of interest in seeking Parastiatopora information in 2012, the next significant thing to be learned was about preserved in situ colonies of such had been reported in Silurian strata at southwest Ireland near Dunquin (Ferriter’s Cove) at the Western tip of the Dingle Peninsula. Three places (one a newspaper) reporting on these colonies (up to a metre across) were written to.
ASSISTANCE AND MISCELLANEOUS INFORMATION RECEIVED
Assistance is acknowledged with gratitude to those who have given discussion on this matter or sent information, especally Dr Shuji Niko, (Department of Environmental Studies, Hiroshima University, Japan); and Doctora Esperanza Fern�ndez-Mart�nez (Palaeontology, Biology and Environmental Sciences, Vegazana campus, University of Leon, Spain). Since 1991, Esperanza Fern�ndez-Mart�nez has together with others studied species of Parastriatopora from Argentina, Bolivia and Spain.
Dra. Esperanza Fern�ndez-Mart�nez, Universidad de Le�n – a leading publisher on Parastriatopora.
According to information mainly received from Fern�ndez-Mart�nez, it is currently thought that the genus Parastriatopora may have arisen in the Upper Ordovician of Northern China, slightly preceeded by Kolymopora which is regarded as its most likely ancestor.
Parastriatopora persisted in North China into the Lower Silurian, at which point it spread throughout southeast Asia, Siberia, the Urals and the Baltic region.
Later in the Silurian it reached Australia, Iran, and possibly Alaslka. The time when its most widespread distribution was achieved was during the Lower Devonian. In addition to the previously mentioned regions it then spread to the Carnic Alps, the Armorican Massif, Sprain, Morocco and Algeria. Shortly after this it disappeared, prior to the Eifelian.
Lines of investigation by Professor of Palaeontology Esperanza Fern�ndez-Mart�nez are at http://www3.unileon.es/personal/wwdimefm/web/textos/investigacion/lineas.htm , and they include the following:
� Estudio sistem�tico y paleoecol�gico de diversos g�neros de corales tabulados ramificados no constructores de grandes edificaciones, presentes en el Dev�nico Inferior de la Pen�nsula Ib�rica:
| – G�nero Parastriatopora (Cordillera Cant�brica, Cordillera Ib�rica, Ossa Morena). – G�nero Saouraepora (Cordillera Cant�brica). – G�nero Yacutiopora (Cordillera Ib�rica). – G�nero Crenulipora (Cordillera Cant�brica).
� Paleobiogeograf�a del g�nero Parastriatopora. Su inter�s en la reconstrucci�n de Am�rica del Sur durante el Paleozoico Inferior y Medio.
dimefm “@” unileon.es
Most of the Siluro-Devonian time was at the world’s warmest known average global temperature. Note that strong change in environmental conditions appears to have been rapid at the beginning of the Silurian. After that, however, conditions were rather stable continuing into the Devonian. At Jenolan Caves the situation well matches that. Below the Silurian limestone there is a marked contrast with the Ordovician strata/conditions; but upwards from there things are gradational and it is possible that the limestone might continue slightly into Devonian time.
The warm shallow warm water conditions in the Silurian gave rise to an abundance of limestone formation. Tabulate corals are prolific in most of these limestones. In a biostratigraphic review of the Silurian tabulate corals and chaetetids of Australia, Munson et al. (2001) concluded:
The biostratigraphic distribution of the Silurian Tabulata and Chaetetida of Australia can informally be described in terms of four successive coral assemblages. The earliest Bridge Creek Assemblage (Rhuddanian-Aeronian) contains abundant halysitids and is not geographically widespread. Species of this assemblage tend to be holdovers from Late Ordovician faunas. A major radiation event occurred at the time of the Quarry Creek Assemblage (Telychian-early Sheinwoodian), involving favositids, heliolitids, halysitids, and other groups. This may indicate the onset of conditions favourable to corals over widespread areas of eastern Australia. The late Sheinwoodian-earliest Gorstian Dripstone Assemblage is characterised by a continued expansion in the number of species of favositids, the appearance of auloporids, and a contraction in the number of species of sarcinulids, multisoleniids, and halysitids. Favositids continued to dominate the youngest Hatton’s Corner Assemblage (Gorstian-Pridoli), but halysitids almost became extinct by the end of the Ludlow. Faunas of Pridoli age are neither abundant nor well studied, but appear to be reduced continuations of earlier faunas. A number of tabulate taxa are identified as possibly useful biostratigraphic indicators in Silurian sequences.
No halysitids have ever been seen in the Jenolan Caves Limestone but south of Jenolan they do occur in red limestone at Tuglow Caves. This is reminescent of the Molong (or Molong-Borenore) area on the opposite side of the Hill End Trough. There, the very thick Molong Limestone is devoid of halysitids except for a thin interval of red limestone (similar to the Borenore Limestone) irregularly preserved at its base. These red halysitid bearing limestone at all localities (Molong, Borenore, Tuglow Caves) show fabric evidence of emergence or erosion. This might represent a regional event (?tectonic) or else emergence might be a function of particular palaeogeographic aspect of the depositional environment.
THE GENUS PARASTRIATOPORA
Para means something like, e.g. paramedic. So Parastriatopora is something like the earlier named Striatopora.
“Striatopora linnaeana” from Lower Devonian near Louisville.
On the above branch fragment of a Striatoropora species it can be seen that the corallites ascend obliquely to the branch surface and their calyces are ribbed with short thick prominent septa.
Parastriatopora differs in that the corallites before reaching branch surface curve to meet branch surface orthogonally. Also the septa are much more strongly developed, sometime almost completely clogging the corallite below where the polyps dwelt at the branch surface. This great thickening gives a dense outer annulus to the skeleton, called a ‘stereozone’.
Thus two basic features characterise the concept of the genus Parastriatopora as it has generally been recognised – the form of the corallum as cylindrical branching growths, and the presence of a well differentiated marginal zone of skeletal thickening (stereozone, or sometimes called coenostereozone).
Contributing to the formation of a distinctly demarcated stereozone may be the turning of the course of corallite growth (so that corallites met the surface of the cylinder perpendicularly rather than obliquely as in the above image of Striatopora), thickening and/or increased frequency of tabulae, thickening of septal ridges, or all these factors combined. Various authors have also considered if microstructure might be a characteristic feature.
Within the broad idea of just two basic features, cyclindrical form and distinct stereozone, as concept of the genus Parastriatopora there may indeed be room for sub-genera or more than one genus. This has been proposed but perhaps is not entirely unanimous. In particular, Niko (2004) introduced a new genus, Hitoeganella, with very thickened tabulae in the stereozone, which if accepted as valid by other workers might end up a better taxonomic placement for the NSW Silurian species. For the moment the separate genus Hitoeganella is ignored here. Another similar genus, Argentinella Fernadez-Martinez, Plusquellec, Tourner, from the Lower Devonian of Argentina, does seem reliably separtated from Parastriatopora. It does not have such clear demarcation of stereozone and is highly septate throughout.
The type species of Parastriatopora is P. rhizoides Sokolov 1949 from the Llandoverian of the Siberian Platform. Garcia-L�pez and Fernandez-Martinez (1995) wrote that this species is probably synonymous with Striatopora mutabilis Tchernychev 1937 from the Upper Silurian in the north of Zembla. If so, that species lasting throughout the Silurian accords with the suspected likelihood of the NSW Silurian Parastriatopora being a single long range form. The Silurian form does not appear to extend into the Devonian in NSW and perhaps there will eventually be a hiatus discerned in NSW for Parastriatopora-like corals, with the Silurian form dying out and other representative/s of the genus having migrated in from elsewhere during the the Devonian.
Thin section appearance of branching favositids with marked peripheral stereozone, kindly supplied by
Esperanza Ferdin�ndez-Mart�nez in “Parastriatopora, La Vid”
Close-ups of polished hand specimen with Parastriatopora from the Fukuji Formation of Japan,
showing stereozones. (Source: Watacchi specimen FK005)
Parastriatopora commutabilis Klaamann, 1962
( Upper Silurian Tabulata of Estonia – In Russian, Trudy Instituta geologii AN ESSR, vol. 9, pp. 25-70 )
From the Estonian Silurian there have been a number of species of Parastriatopora described. P. commutabilis has very strongly developed stereozone and the other two species much less so. Such variation is not noted in the Silurian material in NSW, which seemingly shows continuous variation and could be of just one species.
Silurian ‘Striatopora’ from Grogarnshuvud, Gotland, Sweden. ( Photo: Heidi Freidhoff )
“More Parastriatopora” – http://www.flickr.com/photos/32063424@N05/5696908504 By Linda Mary Fowler in Dunquin, Kerry, Ireland. “Ferriters Cove has exposures of Lower Silurian Dunquin Group: we worked our way up through a parasequence from offshore calcareous siltstones through bioturbated shoreface sandstones, a barrier island deposit, volcanics, a tidal flat and lagoonal facies”. She states that Parastriatopora is adapted to lagoonal facies (“P1040480 – Parastriatopora – coral adapted to the lagoon niche”), and Parastriatopora packstones abundant in the Narragal Limestone (and similar facies elsewhere) in the Silurian in NSW is also regarded as lagoonal.
Parastriatopora from elsewhere within the Jenolan Caves Limestone. A common occurrence of the coral there is in red-brown highly dolomitic matrix. (Photo: Ted Matthews)
The occurrence of Parastriatopora at Dunquin, Kerry, Ireland was first learned of via the Flickr photo “More Parastriatopora” above by Linda Mary Fowler.
Following up on that located brief mentions of it in a book “Sedimentation, Tectonics, and Eustasy” Special Publication 12 of the International Association of Sedimentologists, edited by David I. M. Macdonald ( John Wiley & Sons, 15/04/2009 – 368 pages ). And specifically within “Volcano-tectonic control of offshore to tidal-flat regressive cycles from the Dunquin Group (Silurian) of southwest Ireland” by R.J. Sloan and B.P.J. Williams (pp. 105-122).
(Sloan – Department of Geology, Bristol University ; Williams – Department of Geology and Petroleum Geology, Aberdeen University. )
What is said by Sloan and Williams about Parastriatopora is not lengthy but is interesting. On page 114 it is stated:
Fig. 9E of Sloan and Williams (2009) – “Lagoonal facies: branching coral Parastriatopora in rare growth position. Individual colonies are up to 1m across”.
The colonies shown above are currently the only intact colonies of the genus known to this writer. The Dunquin Group is Late Wenlockian to early Ludlovian.
Years previously the typical Narragal Limestone facies of alternating mottled micritic and dolomitic layers, with monospecific packstones, lead to interpretation of subtital lagoon for this facies. The Narragal Limestone represents a very large lagoon with many stromatoporoid-coral patch reefs, it was concluded. However no in situ portions of Parastriatopora colonies were ever recognised at such patch reefs prior to the find at Jenolan Caves.
“Underlying the spectacular, rugged beauty of Corca Dhuibhne, the Dingle Peninsula, a stony core of rock records a fascinating saga of earth history going back at least 410 million years to the Silurian Period. The earliest chapters in this story reveal the presence of a shallow sea where small colonial corals, brachiopods and trilobites lived on a soft bottom of fine sand and mud. Nearby, active volcanoes made life difficult for this early marine life by periodically blanketing the region in fine deposits of volcanic ash and an occasional lava flow ……. In 79 AD, Mt. Vesuvius awoke from a fitful slumber to devastate the silence and bury alive the residents of Pompeii within a time-encapsulating tomb of fiery ash and cinders. It happened at Clogher Head, too, but this time it was only the likes of trilobites and brachiopods which were left to scream in silence as the molten ash and cinders boiled their juices and clogged the shallow seaways of their watery home.”
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THE PREVIOUS (SILURIAN) LOCATION
The Burma Road Parastriatopora bed predates New South Wales and predates Australia. Australia would not separate from Gondwanaland till long after the Silurian. On the below map ‘Australia’ is not easy to recognise as the eastern part of it was shallow seaway (Tasman Geosyncline). This lay north of the equator and shallow sea is shown near-continuous to North/South China regions, regarded as once joined with Australia as part of the Gondwanaland supercontinent. The closest similarities to our Parastriatopora are known from locations in the SE Asian region.
The Silurian World, adapted from the Paleogeographic Globes of Prof. Ron Blakey of Northern Arizona University
Polar view of Gondwana supercontinent part of the world in the Silurian, using modern landmass outlines
to show the then equatorial position of ‘Australia’ and the south pole then in Africa.
THE PRESENT LOCATION AND PHYSIOGRAPHY
The region around Jenolan Caves is now a deeply dissected tableland. The following two views are from south and north of Jenolan Caves:
Looking over the relatively gently undulating top of the tableland at Kanangra Walls, south of Jenolan Caves, showing encroaching arms of deep erosion along creeks draining to the Cox River. The rocks at this point are inclined (folded) Late Devonian quartzites (Lambie Group) overlain by flat-lying Permian strata (with the white scar patches). [Photo: David Skeoch]
On a fine day – the view from Mt Inspiration lookout, on the Jenolan Road north of Jenolan Caves, showing how the district is a deeply dissected tableland. (Photo: Jason Waddell)
Same view with mist rising from the valleys – a common sight also in the Blue Mountains.
The geological compilation surrounding Jenolan Caves is in much need of further work. The area map portion at right, has had less detailed work or little advancement since the 1960s. That part is from Brunker & Rose (1967). The area at left has been more recently revised; by Raymond, Pogson et al. (1998). Width of this whole area depicted is about 45 km. Tv – Tertiary volcanics (basalt, dolerite, microsyenite, trachyte and tinguaite). Cg – Carboniferous granite and granodiorite, Cwg – Carboniferous, Kanangra Granite (pale pink, medium grained hornblende granite), Dlg – Devonian, Gibbons Creek Sandstone of Lambie Group (thickly to thinly bedded quartz sandstone, siltstone, mudstone), Dul – Devonian, Lambie Group conglomerate, sandstone and shale. Duv – Devonian, undifferentiated volcanics (Bindook Porphyry), Dcd – Devonian, Dunchurch Formation of Crudine Group, Skc – Silurian, Kildrummie Group. Ss – Silurian, undifferentiated sediments, volcanics and limestone. Smc – Silurian, Campbells Formation of Mumbil Group (East), Smh – Silurian, Hollanders Formation of Mumbil Group (East), Smi – Silurian, Karawina Formation of Mumbil Group (East), Qcr – Ordovician, Rockley Volcanics of Cabonne Group, Qkt – Ordovician, Triangle formation of Kenilworth Group, Qa – Ordovician, Adaminaby Group. [This combination by Jill Rowling in 2004.] (NB: The SW-trending linear “tail” from the Cg intrusion to the east of Jenolan is not granite. It is a coarse mafic intrusive known as the Budthingeroo Amphibolite.]
Below are examples of some of the maps/imagery available for Jenolan. An air photo enlargement is perhaps the best option for attempted mapping. The online “State topographic data”, either via the Lands Department “SIX server” or the 1:25,000 topographic map (8930-III-N) may be of auxilliary interest but is probably not adequate for any detailed recording.
Overlooking Jenolan from the southwest. The road down on the east is called the “five mile” bends and the rise on the west towards Oberon is termed the “two mile” rise. This shows the stream (McKeown’s Creek) that cuts through the on-end limestone formation at Jenolan Caves and the flatter country to the west after rising up the “two mile” rise. The higher land on the Oberon side has been extensively cleared for Pinus radiata forest.
The site of interest with the suspected Parastriatopra thicket preserved more or less in situ, at the end of Burmah Road, is at the eastern end of the house seen immediately west of the “7” (here termed “Devils Coach House Lookdown”. This has been the best map found to date of Jenolan Caves vicinity. (Source: Lands Department, Land and Property Information section, 2006). The two chunky promintories east of point “7” (Devil’s Coach House Lookdown) look to be bedding-joint controlled (possibly erosional re-entrants along shaley or thin-bedded units in the limestone – airphoto interpretation only).
Driving through the limestone from the east (the Grand Arch), showing the ‘massive’ bedded nature of much of the limestone. A complexity of joints and water stainings along cracks may combine to defeat the eager seeker after “where’s the bedding”, but essentially the limestone is about-vertical (if that helps pick the bedding planes). [Contact Ted Matthews re places where bedding is exposed within the caves.]
Parastriatopora bed outcrop beyond Cottage 2, Burma Road, is near the base of the Jenolan Caves Limestone as on this map compiled by C.A. Sussmilch (Sussmilch and Stone, 1916).
Jenolan Caves vicinity as depicted on the 1:25,000 topographic map, 8930-III-N
Jenolan Caves on State topographic data ( per SIX server, http://lite.maps.nsw.gov.au ). Burma Road is the road seen north of Caves House, running off the main ‘Oberon road’. Burma Road first runs WNW and has several cottages, then turns to run NE where there are further cottage sites. The “Caves House” is situated at the western edge of the Jenolan Limestone that runs approximately N-S. Follow the northerly grid line and it would appear that the base of the limestone should pass close by the easternmost cottage at the northern end of Burma Road. Just east of there is the Parastriatopora bed as shown below.
Caves House, and showing topography surrounding the valley which the caves are down in. The Burma Road is on high ground north of Caves House (to the right in above photo).
Same area and same source (SIX server) with 25% topo lines mixed to aerial photography. The bare area seen between Burma Road and Caves House is the “upper” or “Carlotta” parking area. Not very clear, and better maps sought.
Google Earth – upper parking area to Burma Road cottages.
Broader view of the area with Burma Road pin-pointed. About pin’s length NW of the pin point here is seen the cottage clearing on the final NE trending stretch of Burma Road. If the line of the NS creek whose mouth is just west of Caves House (at base of limestone) is projected north it can be seen that it passes just east of that cottage. (….see larger view below) that is near the end of Burma Road. [per SIX server]
Thought to possibly be where the base of the limestone might run to the north and where Parastriatopora might also extend to – but the label is premature as this has not yet been checked. The limestone rapidly falls away to the east as cliffs as shown.
Search for a map of Jenolan in Google generally produces only versions of this, which comes from GoogleMaps. It is of minimal detail yet virtually all tourist agents operating online use this map and seem to have nothing better.
Same data in Google Earth, lit from the east. The steep limestone rise west of McKeowns Creek (a.k.a. Jenolan River) runs north from the Grand Arch area to where it bends to run NW, north of the Burma Road cottages. The reason for this is that the creek here cuts across the limestone from the east side to its western flank (where Burma Road zig-zags down to cross it.).
Currently, any other good strongly detailed maps of Jenolan Caves are being sought. University theses are yet to be read and will doubtless prove fruitful in containing some products of mapping at Jenolan Caves.
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Fernández-Martínez, E., Plusquellec, Y., Ttourneur, F. & Herrera, Z., 1999. Parastriatopora sanjuanina, nueva especie de tabulado del Devónico Inferior de Argentina. Revista Espagnola de Paleontologia, 14 (1), pp. 37-57.
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