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Paleokarst

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Osborne R.A.L. (2013) Preservation and Burial of Ancient Karst. In: John F. Shroder (ed.) Treatise on
Geomorphology, Volume 6, pp. 95-103. San Diego: Academic Press.
© 2013 Elsevier Inc. All rights reserved.
6.9 Preservation and Burial of Ancient Karst
RAL Osborne, The University of Sydney, Sydney, NSW, Australia
r 2013 Elsevier Inc. All rights reserved.
6.9.1 Introduction 96
6.9.2 The End of Karstification 97
6.9.3 Examples of Extreme Preservation 97
6.9.3.1 Ancient Paleokarst 97
6.9.3.2 Positive Paleokarst Forms 97
6.9.3.3 Ancient Relict Surface Karst 97
6.9.3.4 Ancient Relict Caves 97
6.9.3.5 Caves without Roofs 97
6.9.3.6 Ancient Active Surface Karst 98
6.9.3.7 Ancient Active Subsurface Karst 98
6.9.4 Conditions and Mechanisms for Survival 99
6.9.4.1 Location 99
6.9.4.2 Isolation 99
6.9.4.3 Low Rates of Denudation 99
6.9.4.4 Sequential Vertical Motion on Faults 99
6.9.5 Filling and Burial 99
6.9.5.1 Filling 99
6.9.5.2 Burial 99
6.9.6 Exhumation 100
6.9.6.1 Vadose Fluvial Exhumation 100
6.9.6.2 Exhumation by Stoping 100
6.9.6.3 Exhumation by Vadose Weathering 100
6.9.6.4 Exhumation by Removal of the Host Rock 100
6.9.7 Difficulties with Recognizing Exhumation 100
6.9.8 Implications of Preservation, Burial, and Exhumation 101
6.9.8.1 Cave–Landscape Relationships 101
6.9.8.2 The Surprising Fate of Stalagmites and Flowstone 101
6.9.8.3 Complex Caves 101
References 102
Glossary
Breakdown The process of failure of cave voids,
particularly their walls and ceilings, and the debris
produced by this process.
Caymanites Marine turbidite palaeokarst deposits (graded
bedded laminated limestones) formed when marine
sediment flows into caves flooded during a marine
transgression, first described from the Cayman Islands.
Ceiling The upper inner surface of a cave void.
Cupola A cave void with a dome-shaped ceiling and a
circular to elliptical plan with a diameter or long axis in
plan greater than 1.5 m.
Endokarst Karst features formed deep within the rock
mass, antonym of epikarst.
Gossan Weathered surface exposure of an ore deposit.
Hypogene Processes, or formed by processes, originating
from inside the Earth.
Morphostratigraphy The order of formation of
morphological features. In caves the order of formation of
voids and speleogens.
Overhand stoping The physical removal of Earth material
from the bottom-up.
Roof The rock mass between the cave ceiling and the
surface.
Undercapture The capture of water flow from a higher-
level passage into a lower-level passage in fluvial caves.
Osborne, R.A.L., 2013. Preservation and burial of ancient karst. In:
Shroder, J. (Editor in Chief), Frumkin, A. ( Ed.), Treatise on
Geomorphology. Academic Press, San Diego, CA, vol. 6, Karst
Geomorphology, pp. 95–103.
Treatise on Geomorphology, Volume 6 http://dx.doi.org/10.1016/B978-0-12-374739-6.00132-9 95
Author's personal copy
Abstract
Ancient karst features can be preserved by burial, filling, or by occurring in areas with extremely slow denudation. Although
the terms ‘paleokarst’,‘relict karst’,‘buried karst’, and ‘fossil karst’ have caused much confusion, paleokarst, buried karst, and
relict karst can be defined in terms useful to karst geomorphologists and cave scientists. The term ‘fossil karst’ is best
abandoned. Burial and paleokarstification are not necessarily the end of karst. Ancient features may be exhumed and
reactivated. Karst ends with denudation at the Earth’s surface. Unroofed caves are a particular feature of karst denudation.
Most ancient karst features may be preserved by filling, burial, and exhumation. In unusual conditions, karst features have
survived at the surface since the Mesozoic. Burial, exhumation, and slow denudation may not be sufficient for extreme
survival; relative vertical movement may be required. As caves and many other karst landforms are negative features, they
are prone to filling by a range of materials, making cave sediments and paleokarst deposits quite diverse. Whole karst
landscapes can be buried and evidence of burial can be recorded in the diagenesis of sediments. Although filled and
unfilled caves can survive shallow burial, deep burial can crush caves, forming crackle breccia. Exhumation can occur from
the surface following uplift or from below following hypogene speleogenesis. Preservation, burial, and exhumation of
ancient karst have two unexpected consequences. Caves can be older than the landscapes in which they occur and
stalagmites can be the longest surviving karst features.
6.9.1 Introduction
Karst has existed since soluble rocks first appeared on the
Earth. If we restrict our consideration to carbonates, that
means largely since the Proterozoic, but it is not too difficult
to imagine surface and underground landscapes forming in
noncarbonate rocks under the range of atmospheric and
hypogene chemistries that existed in earlier times.
When we consider the problem of ancient landforms, it is
possible to recognize three general types, paleo landforms that
are now preserved in the rock record, relict landforms that are
the product of processes in the distant past and are now in-
active, and ancient landforms where the processes that formed
them are still active whereas the landforms have survived due
to the extremely low rate of these processes. For example, a
cross-bed might be a paleo-dune or ripple preserved in the
rock record, glacial valleys in the Alps are relict landforms, as
the glaciation that formed them has ceased, whereas valleys
incising plateaus in stable cratons can be ancient active land-
forms with downcutting acting at the same locality for a
hundred million years or more.
A great deal has been written, and there is much confusion
about the definition of paleokarst (
Osborne, 2000). If we
apply the above ideas to karst, then paleokarst must be evi-
dence of karst processes from the past, which is now part of
the rock record. Put another way, if a karst feature is filled by
or buried under strongly lithified rock, such that the fill and
the host rock behave as a single unit then it is paleokarst
(
Figure 1). Paleokarst by this definition does not have to be
particularly old. Caves containing well-lithified fill, perhaps
only 1000 years old, occur in raised coral reefs in the Hawaiian
Islands.
A vast literature on paleokarst exists, but much of this refers
to ‘paleokarst facies’, small-scale features produced during
brief periods of exposure and buried rapidly by the next de-
positional episode. Although this is of great interest to
geologists, particularly those in the petroleum industry, it is
unlikely to excite karst geomorphologists or speleologists.
Paleokarstificaion is not always a permanent condition and
given the right chain of events the paleokarst of today could
become the relict karst of the future.
If a karst feature is neither paleokarst, nor a product of
currently active processes, then it is either relict or buried.
Relict karst includes abandoned stream cave passages and in-
active hypogene caves. Karst features, including caves and
dolines, filled by unlithified sediment, which are capable of
being exhumed are considered buried karst here. Like paleo-
karst, relict and buried karst features do not necessarily have to
be old, just isolated from the processes that formed them. All
dry, air-filled fluvial cave passages are by this definition relict.
Ancient active karst features could include seasonally dry
valleys, surface karst features in areas with low relief and
rainfall, and some karst towers. Undercapture and develop-
ment of new conduits at progressively lower levels make an-
cient active fluvial cave passages less likely, but it will not be
surprising if some are discovered in unexpected places, with
increasing work being undertaken in both dating and meas-
uring the rates of processes.
The terms ‘fossil karst’, ‘fossil cave’, and ‘fossil passage’ are
probably best avoided as they have been applied to paleokarst,
relict karst, and to caves containing fossil-bearing sediments.
Since karst landforms, including most hypogene caves,
form at, or relatively close to, the Earth’s surface, one might
expect that it would be quite rare for relict or ancient active
Figure 1 Paleokarst flowstone (center right) and bedrock limestone
(left, above and below flowstone) forming the wall of Main Cave,
Timor, NSW, Australia. Note how wall niche cuts across bedrock-
flowstone boundary without a significant change in morphology.
96 Preservation and Burial of Ancient Karst
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karst to survive over geologically significant periods of time.
Ancient land surfaces, however, are commonly preserved in
the geological record as unconformities. Paleokarst features
can be exposed when unconformity surfaces are re-exposed at
the Earth’s surface and when rocks containing endokarstic
paleokarst (i.e., former caves filled with now solid rock) are
exposed or incised. Sometimes, buried and filled paleokarst
features are exhumed to produce relict karst.
6.9.2 The End of Karstification
Before considering the survival of ancient karst features, it is
important to have an understanding of their demise. Until
about 25 years ago, it was generally agreed that karst features,
and in particular caves, were quite young (
Osborne, 2010).
Although geomorphologists such as
Jennings (1982) con-
sidered that ‘‘y the probability is that most caves developed
during the course of the Quaternary,’’ many geologists thought
that caves were somewhat older but were pessimistic about
their survival: ‘‘y every large cave is probably at least half a
million years old’’, ‘‘All important limestone caves in the world
are less than 10 million years old’’,‘‘Geologically, caves are very
short-lived (see
Anonymous, 1968). Only a few million years
can intervene between the initiation of a cave and its de-
struction by roof collapse.’’
There is now so much literature on multiphase karst and
exhumed karst for it to be clear that burial is not necessarily the
end of the karst history of a body of soluble rock. As
Osborne
(2004)
pointed out, caves are difficult to destroy and ‘‘the only
reliable way to destroy cave voids is to emulate the natural
process and remove the enclosing rock from around them.’’
From this viewpoint, the cessation of karst occurs at one of
its most active points, the rock/air interface. Here, endokarst
features and the karst rock mass itself meet their demise as
CaCO
3
returns to its origins in the air and waters.
6.9.3 Examples of Extreme Preservation
6.9.3.1 Ancient Paleokarst
If rocks from the distant past can survive in the geological re-
cord, then paleokarst from the distant past should survive also.
Reports of early Proterozoic paleokarst from the Transvaal by
Martini (1981) have been followed by numerous reports of
Proterozoic palaeokarsts from Northwest Canada (
Pelechaty
et al., 1991
) and North Greenland (Smith et al., 1999).
6.9.3.2 Positive Paleokarst Forms
Most paleokarst exposures are usually level with or are nega-
tive features in the landscape. If the material filling ancient
caves or dolines is strong enough, paleokarst features can be
preserved as positive features protruding above the general
level of the land surface. An example of this is the pyroclastic
dyke at Wombeyan, NSW, Australia described by
Osborne
(1993)
(Figure 2).
It is likely that many so-called ‘false gossans’ reported by
mineral prospectors from limestone areas are in fact positive
paleokarst forms, representing paleokarst ore bodies from
which the original carbonate host rock has been removed by
solution.
6.9.3.3 Ancient Relict Surface Karst
Limestone towers and pinnacles in Tibet (Cui et al., 1997) and
northern Australia (Robinson, 1978, Grimes, 2009) have
been interpreted as exhumed relic karst features that origin-
ated in Permian or Cretaceous times. The origin of the shinlin
(stone forests) in China appears to be more complex and
may involve a combination of subcutaneous development and
exhumation.
6.9.3.4 Ancient Relict Caves
Caves have one major advantage over surface features; they
form underground and so are separated from surface processes
by their overlying rock mass. Hypogene caves have the extra
advantage of being originally isolated from the surface and
thus its destructive influence.
Until relatively recently, there were no dated examples of
naturally open caves that were older than the Pliocene. By
2006, only five karst areas were reported to contain open relict
caves older than 65 Ma: the Bohemian Karst of the Czech
Republic 67–70 Ma (
Bosa
´
k, 1998), the Guadalupe Mountains
of New Mexico 92 Ma (
Lundberg et al., 2001), the Black Hills
of South Dakota 310–320 Ma (
Palmer and Palmer, 2000),
Jenolan Caves, NSW, Australia 339–345 Ma (
Osborne et al.,
2006
), and possible Silurian Caves from West Ohio (Kahle,
1988
). Although all of these caves are in Palaeozoic rocks, and
some are in old landscapes, none are in very ancient land-
scapes or in Proterozoic rocks. Burial and exhumation have
probably played an important role in the survival of ancient
caves in the Black Hills and at Jenolan, but this and slow
landscape processes are probably not enough to explain the
survival of early Carboniferous caves at Jenolan.
6.9.3.5 Caves without Roofs
Caves without roofs are a special type of relict cave as they
represent the last remnant of karst, prior to its annihilation.
Figure 2 Volcaniclastic paleokarst dyke, Wombeyan Caves, NSW,
Australia, protruding above surface of surrounding marble bedrock.
Preservation and Burial of Ancient Karst 97
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Caves without roofs have been reported in eastern Australia
since 1870 with the recognition of flowstone, stalagmite bases,
and vertebrate fossils at the Earth’s surface (Thomson, 1870;
Broom, 1896). Due to the isolation of Australian scientists
from mainstream karst research, these unroofed caves were
considered unexceptional features, resulting from normal
surface processes.
Although unroofed caves were recognized in Europe by
Dawkins (1874) (see Mais, 1999), the recognition of unroofed
caves in southern Europe in the 1990s (
Mihevc et al., 1998)
was noteworthy and at the time controversial. Inspired by the
karst cycle of
Cvijic
´
(1918), a tradition had developed that
interpreted unconsolidated sediments on karst plateaux as
pre-karst fluvial deposits. New evidence from the expressway
excavations in Slovenia showed that these sediment masses
filled unroofed caves and that unroofed caves were quite
common features of karst plateaus. Studies of unroofed caves
revealed something quite surprising; they contained little or
no breakdown debris (
Figure 3). This suggested that rather
than being produced by catastrophic underground ceiling
failure, caves are unroofed mostly by the gradual removal by
solution of the cave roof, that is, the rock mass between the
cave ceiling and the surface. The walls of unroofed caves also
generally remained intact as the surrounding surface was
lowered, gradually bringing it level with the floor of the un-
roofed cave.
Most unroofed caves are elongate trenches, but more
complex forms occur when the surface above and beside
hypogene caves is denuded. These forms include multiple thin
arches formed by the unroofing of cupolas such as those
forming the Angel Gate above Sa
´
tork
+
opuszta Cave in Hungary
(
Figure 4) and caves without floors and walls occuring in the
sides of limestone monadocks in the Krakow-Cz˛estochowa
upland of Poland (
Figure 5).
6.9.3.6 Ancient Active Surface Karst
In areas where the land surface in general is known to be
ancient, surface karst features are also likely to be ancient. In
plateau surfaces in eastern Australia where there has been
insignificant lowering during the Cenozoic (
Nott et al., 1996),
karren on the plateau surfaces and limestone gorges incised
into them are likely, as with the rest of the landscape, to have
been active since the Mesozoic. Surface karst forms developed
on Cambrian and Proterozoic carbonates of the arid and
seasonally wet tropical cratons in the Gondwana fragments
may have been active for even longer periods of time and
should be investigated with this in mind.
6.9.3.7 Ancient Active Subsurface Karst
It is more difficult for subsurface karst forms to be active over
significant time periods than for surface forms. If we consider
Figure 3 Unroofed cave, karst plateau above Trieste, Italy. Note lack
of breakdown in cave floor.
Figure 4 The Angel Gate above Sarkartopuszta Cave, Hungary,
a system of denuded cupolas.
Figure 5 Cave without wall, Podzancze, Poland.
98 Preservation and Burial of Ancient Karst
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a fluvial cave passage, it is more likely that it will be replaced
by or undercaptured into a new passage at a lower level, than
survive as an active form over tens of millions years or more.
Although hypogene caves may be active over long periods of
time, this activity appears to occur in phases, so old hypogene
cavities and speleogens will be relict features, overprinted by
new generations of forms from subsequent periods of activity.
6.9.4 Conditions and Mechanisms for Survival
6.9.4.1 Location
Ancient landforms, both relict and active, are best preserved in
situations where the host rock is old, the relief is low, average
rainfall is low, and the last deformation or uplift occurred in
the distant past. Thus, ancient landforms are more likely to be
preserved in ancient cratons than in active alpine foldbelts.
This would suggest that Proterozoic and Cambrian carbonates
in the cratonic regions of Africa, Australia, and South America
would be highly likely to host ancient relic karst and ancient
active karst. The lack of reports from these locations is prob-
ably due to a lack of research, in these areas. There are
promising indications from work now underway in the cra-
tonic areas of Brazil.
6.9.4.2 Isolation
Since the final destruction of karst features is a result of surface
processes, isolation plays an important role in their preser-
vation. Caves are particularly well suited for long-term survival
as they form underground and so are separated from the
surface by the overlying rock mass. Once the active stream has
left a fluvial cave or the fluids cease rising in a hypogene cave,
things slow down. There might be some breakdown here, or
speleothem growth there, but the cave wall itself commonly
largely remains intact, or is even strengthened by precipitation
of carbonate in cracks.
Because they generally lack significant connection with the
surface, hypogene caves may have a greater likelihood of sur-
vival than their fluvial counterparts. Besides downcutting,
uplift may result in caves becoming isolated from geomorphic
activity. Some complex caves began life at depth as hypogene
features, were uplifted into the dynamic phreatic zone, and
then completely isolated from all but vadose seepage by fur-
ther uplift.
6.9.4.3 Low Rates of Denudation
Low rates of denudation are essential for very old relict karst
and caves to survive but they are probably not enough. Areas
where ancient landforms survive tend to have low denudation
rates, low relief, and low rainfall.
Low denudation rates, low relief and low rainfall, can only
go so far to preserve very old landforms. As
Gale (1992) rec-
ognized: ‘‘Although low rates of denudation are an important
factor in ensuring the survival of ancient landscapes, this alone
is inadequate as an explanation of the maintenance of land-
forms over ten and even hundreds of millions of years’’ (
Gale,
1992
, p. 337). Gale proposed that denudation needed to be
localized if old land surfaces were to survive.
6.9.4.4 Sequential Vertical Motion on Faults
The survival of 340-million-year-old relict caves at Jenolan
Caves cannot be explained by a combination of isolation, low
denudation, or burial and exhumation. The vertical relation-
ships between the old caves and the planated surfaces that
intersect batholiths younger than the caves suggest that sur-
vival is only possible if vertical relationships between the rock
mass containing the caves and the adjoining rocks have
changed over time.
Osborne (2007a) called this process the
Fault-Block Shuffle and envisaged that the block containing
the caves was downfaluted when the planation took place. In
fold belts with many faults, this type of process may be re-
sponsible for the localization of denudation proposed by
Gale
(1992)
.
6.9.5 Filling and Burial
It is important to distinguish between filling and burial of
karst features. Filling affects negative karst forms such as caves,
grikes, and dolines. Filling may be partial or complete. Com-
plete filling results in the whole of the feature being filled to
the level of the surface. Burial occurs when the whole land-
scape is covered by material above the level of the karst sur-
face. Burial generally, but not always, results in complete
filling of underlying negative karst features.
A large range of geological materials can fill and/or bury
karst features, including terrestrial, marine, and aeolian sedi-
ments; lava and pyroclastics; internal karst sediments; ore
bodies and biogeochemical deposits.
6.9.5.1 Filling
Filling is most common in boundary karsts and impounded
karsts because they have an immediate source of clastic sedi-
ments available. Ponor caves in boundary and impounded
karsts can become blocked by debris, leading to flooding of
upstream blind valleys and the subsequent filling of both the
cave and the valley with sediment. This can raise the water
table in the karst, leading to paragenesis in the caves. In some
small impounded karsts, caves may undergo a sequence of
filling and emptying events. Loess, slope sediments, and
tephra can fill surface karst depressions and caves with dry
entrances.
6.9.5.2 Burial
Burial occurs where a whole karst landscape is covered by
sediment as a result of geological processes such as marine
transgression, basinal subsidence, down faulting, or volcanic
eruption.
Burial may lead to the preservation of both surface and
subterranean karst features if the burial is not too deep.
Loucks
(2007)
described the destruction of cave systems and their
Preservation and Burial of Ancient Karst 99
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conversion into breccia zones by overburden pressure when
they were buried at depths of more than 3000 m.
Although burial will fill cave entrances, it need not result in
the whole cave being filled with sediment. Burial can block
cave entrances, with the result that inner spaces of the cave
may fill with fluids, including petroleum, but not clastics.
Where clastics do enter caves during a marine transgression,
they may take the form of fine turbidite deposits, as occurs
with caymanites (marine turbidite paleokarst deposits;
Figure 6).
Burial should also affect cave sediments. If the burial is
sufficient, then speleothem should recrystallize and diagenesis
should be evident in the matrices and cements of clastic
sediments. There has been little study of the diagenesis of cave
deposits.
Osborne et al. (2006) dated hairy illite regrowth on
large illite crystals at Jenolan Caves, NSW, Australia to the late
Permian and attributed this regrowth to diagenesis caused by
burial under the Sydney Basin.
6.9.6 Exhumation
Exhumation refers to the reversal of either burial or filling.
Exhumation may be localized or widespread, resulting in a
whole buried landscape being exposed from cover. Incision
and/or stripping, usually associated with uplift, are often in-
volved in exhumation; however, hypogene speleogenesis can
also exhume filled or buried caves.
Whole landscapes, including surface karst and caves, can
be exhumed at the margins of uplifted sedimentary basins
where the underlying unconformity surface becomes re-
exposed. Where incision cuts below the buried land surface or
into the beds of exhumed valleys, new fluvial caves can form
below old filled caves, leading to their exhumation.
In broadly folded sequences, unconformity surfaces are
most likely to be exposed and buried karst exhumed along the
axes of anticlines. In this situation, surviving ancient features
will retain their original vertical orientation.
Impounded karst, particularly long, narrow impounded
karsts in steeply dipping limestone are ideal situations for
filled caves to be intersected and exhumed because the num-
ber of structural paths available for water, fluvial or hypogene,
to pass through is limited. In these situations, new caves
are likely to intersect or undercut filled ones, leading to
exhumation.
6.9.6.1 Vadose Fluvial Exhumation
If caves are filled with permeable material, then surface water
can penetrate through the fill after uplift or incision and
simply wash the fill out. This process can involve either high-
energy work by sinking streams or the slow, low-energy action
of rain-wash or seepage entering through entrances and cracks.
6.9.6.2 Exhumation by Stoping
Overhand stoping is one of the most important processes for
the removal of unconsolidated and unstable internally wea-
thered fills. This occurs when a new cave system develops
below and partly intersects a higher-level filled system. The fill,
now hanging in space, falls away aided by lubrication from
seepage water. This process can exhume very large, filled
chambers.
6.9.6.3 Exhumation by Vadose Weathering
Caves filled by strongly lithified deposits may be intersected
and exposed on the walls of more recent hypogene caves, but
are rarely exhumed in the process. The exception is where the
lithified fill contains minerals that are unstable under vadose
conditions. If these minerals are more abundant in the fill
than in the bedrock, then the fill can weather out, exhuming
the ancient cavity. This process has been observed where
caymanite and quartz sandstone fills contain pyrite and there
is little or no pyrite in the enclosing limestone (
Figure 7 ).
6.9.6.4 Exhumation by Removal of the Host Rock
Although we generally think of exhumation as referring to the
removal of material overlying or inserted within a cave or
doline, the gradual denudation of the karst surface pro-
gressively exhumes and then destroys caves and other endo-
karst forms. Thus, the production and destruction of unroofed
caves is a special form of exhumation.
6.9.7 Difficulties with Recognizing Exhumation
It is not always easy to distinguish between exhumed karst and
some other types of karst features. The most difficult issues
involve distinguishing between exhumed karst and epikarst
Figure 6 Caymanite filling ancient cave now intersected by the wall
of River Cave, Jenolan Caves NSW, Australia. A ¼ steeply dipping
Silurian limestone bedrock, B ¼ unconformity, trace of wall of
paleokarst cave, and C ¼ gently dipping caymanite palaeokarst filling
ancient cave.
100 Preservation and Burial of Ancient Karst
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and distinguishing between exhumed small-scale endokarst
forms and epikarst.
One significant issue with the identification of exhumed
ancient surface karst is distinguishing between it and exhumed
subcutaneous karst. Subsoil landform development has long
been recognized as a significant process in both noncarbonate
and carbonate rocks (
Twidale and Mueller, 1988). Slabe and
Lui (2009) provided a contemporary summary of subsoil karst
forms.
Both subsoil forms and buried paleokarst forms can be
exhumed by contemporary processes. Distinguishing between
the two is not always straightforward. Subsoil channels as in
Slabe and Lui (2009, figures 2 and 3) are difficult to dis-
tinguish from exhumed and modified subsurface forms,
whereas subsoil half bells in figure 13 of
Slabe and Lui (2009)
look very much like exhumed and penetrated cave cupolas.
Definitional problems also arise with exhumed subsoil and
subjacent karst forms. One model for the origin of shinlin
(stone forests) in China interprets them as exhumed subjacent
karst features, resulting from processes that were initiated in the
early Permian (Knez and Slabe, 2009, Song and Liang, 2009).
In many karst areas, particularly those with hypogene
caves, features in the epikarst are a combination of true epi-
karst forms, small-scale exhumed endokarst forms (tube
fragments, small cavities, etc.), and exhumed endokarst forms
that have been modified by epikarst processes. It is commonly
not easy to distinguish between the two.
6.9.8 Implications of Preservation, Buri al, and
Exhumation
6.9.8.1 Cave–Landscape Relationships
The traditional view of the relationship between caves and the
landscape was that caves were either the same age or younger
than the landscape in which they occur. As
Sussmilch (1923,
p. 15)
commented about Jenolan Caves (NSW, Australia):
‘‘y the caves themselves cannot be older than the valley in
which they occur.’’ In the case of Bungonia Caves (NSW,
Australia), where a series of relatively deep caves occur ad-
jacent to a limestone gorge,
James et al. (1978) concluded
that: ‘‘y most of the caves could be considerably younger
than the rejuvenation which formed the gorge’’ (
James et al.,
1978
, p. 61).
A clear link between landscape and cave evolution was the
basis for some of the most influential work on cave chron-
ology, for example,
Droppa (1966) on the caves of the
Dema¨novska
´
Valley, Slovakia, which correlated levels in the
caves with river terraces in the surrounding landscape. Emer-
ging views about hypogene speleogenesis (
Klimchouk, 2007)
make the reverse assumption that many hypogene caves are
older than the present land surface and are later intersected by
surface processes such as valley erosion.
6.9.8.2 The Surprising Fate of Stalagmites and Flowstone
Old geography books and even some university websites refer
to the vulnerability and short survival time of speleothems in
general and stalagmites and flowstone in particular. Cavers
and cave managers also relate how vulnerable these features
are to damage by careless humans and removal by vandals and
climate scientists.
Observations of unroofed caves and denuded karst surfaces
have shown that rather than being the most vulnerable of
karst features, stalagmites and flowstone frequently survive
after the roof and walls of the cave in which they were
deposited have been completely removed by denudation
(
Figure 8).
6.9.8.3 Complex Caves
Taken together, the combination of preservation and inter-
section of paleokarst, exhumation of paleokarst and filled
relict cavities, and preservation of ancient open cavities results
in the production of complex caves. Such caves may intersect
several generations of paleokarst, incorporate exhumed cav-
ities, and their unfilled sections may be the product of mul-
tiple phases of different types of speleogenesis.
Jenolan Caves intersect at least three generations of
paleokarst and consist of interlinked hypogene, paragenetic,
and fluvial cavities dating back to the Carboniferous
(Osborne, 1999; Osborne et al., 2006), whereas Cathedral
Cave at Wellington, NSW, Australia, intersects at least four
generations of paleokarst resulting from the overprinting of at
least five phases of hypogene speleogenesis (
Osborne, 2007b).
In complex multiphase and multiphase/multiprocess
caves, there is no simple answer to the question ‘‘how old is
the cave and how did it form?’’ A morphostratigraphy must be
Figure 7 Exhumed void left after pyrite-bearing caymanite has
weathered away Bungonia Caves, NSW, Australia. A ¼ pyrite-
bearing caymanite, B and C ¼ massive Silurian limestone forming
walls of paleokarst void.
Preservation and Burial of Ancient Karst 101
Author's personal copy
established from a combination of crosscutting relationships
between cavities and dating of sediments where possible.
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102 Preservation and Burial of Ancient Karst
Author's personal copy
Biographical Sketch
Armstrong Osborne has been investigating caves, karst, and paleokarst in the complex impounded karsts of
eastern Australia for the last 35 years. A geologist by training, his original focus was on the stratigraphy and
petrology of cave sediments and paleokarst deposits. During the 1990s he realized that while the sediments and
paleokarst in eastern Australian caves made sense, the caves themselves did not, so his interests expanded to
include cave morphology and hypogene speleogenesis. Over the last 14 years, he has been involved in col-
laborative studies of cave minerals, palaeokarst, and hypogene caves with colleagues in central Europe and more
recently on gneiss caves in Sri Lanka.
Armstrong has been actively involved in karst and geodiversity conservation through advisory committees,
consultancies, contract researc h, cave guide training, and as an expert witness in court cases. He is a visiting fellow
of the Karst Research Institute, Postojna Slovenia, a research associate of the Australian Museum, and serves on
editorial and advisory boards for journals related to caves and karst. As Associate Professor, science education at
the University of Sydney, he coordinates and teaches science units for primary education students along with earth
science and ‘science as a human endeavor’ units for secondary education students.
Preservation and Burial of Ancient Karst 103
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Article
Full-text available
Jenolan Caves are Australia's premier show caves. It has proved difficult to explain the origin and development of these caves. A new synthesis and framework chronology is proposed involving at least ten distinct phases of development beginning in the Carboniferous and extending until recent times. Key elements of this new synthesis are Carboniferous and Permian palaeokarst, exhumation of palaeokarst, hydrothermal speleogenesis, the influence of steeply dipping limestone on morphology, complex hydrology, sediment blockages and paragenesis. Many significant features of the caves are not the products of solution by meteoric water. This new synthesis and framework chronology challenges not only the accepted scientific view of the caves, but also the way in which they are conserved, managed and interpreted.
Chapter
The Lockport Dolomite in northwestern and west- central Ohio and the stratigraphically equivalent Peebles Dolomite in southwestern Ohio collectively display a variety of previously unrecognized subsurface and surface paleokarst features. The former include molds, vugs, in situ breccia with corroded clasts, collapsed strata, solution-enlarged joints, internal sediment derived partly from soil, boxwork, and caves. Surface paleokarst features at the top of these units are represented by locally developed pa- leosol and sinks. Erosional relief at the top of the Lockport/Peebles ranges from fractions of an inch (typical) up to 9 feet (2.7 m) (rare). The contact between the Lockport/Peebles and the overlying Greenfield Dolomite is typically a paraconformity in the form of a paleokarst planar erosion surface. As such, the contact can be difficult to recognize, but it is not a fades contact nor is it gradational.