treatise on geomorphology || 6.9 preservation and burial of ancient karst

6.9 Preservation and Burial of Ancient KarstRAL 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
Os

Sh

Ge

Ge

Tre

GlossaryBreakdown 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.

borne, R.A.L., 2013. Preservation and burial of ancient karst. In:

roder, J. (Editor in Chief), Frumkin, A. (Ed.), Treatise on

omorphology. Academic Press, San Diego, CA, vol. 6, Karst

omorphology, pp. 95–103.

atise on Geomorphology, Volume 6 http://dx.doi.org/10.1016/B978-0-12-3747

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.

39-6.00132-9 95

96 Preservation and Burial of Ancient Karst

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, andrelict 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 havesurvived 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 karstlandscapes 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 andstalagmites can be the longest surviving karst features.

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.

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

Preservation and Burial of Ancient Karst 97

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.

Figure 2 Volcaniclastic paleokarst dyke, Wombeyan Caves, NSW,Australia, protruding above surface of surrounding marble bedrock.

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

CaCO3 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 (Bosak, 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 3 Unroofed cave, karst plateau above Trieste, Italy. Note lackof 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.


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 Satork +opuszta Cave in Hungary

(Figure 4) and caves without floors and walls occuring in the

sides of limestone monadocks in the Krakow-Czestochowa

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


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

Figure 6 Caymanite filling ancient cave now intersected by the wallof River Cave, Jenolan Caves NSW, Australia. A¼ steeply dippingSilurian limestone bedrock, B¼ unconformity, trace of wall ofpaleokarst cave, and C¼ gently dipping caymanite palaeokarst fillingancient cave.


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 7 Exhumed void left after pyrite-bearing caymanite hasweathered away – Bungonia Caves, NSW, Australia. A¼ pyrite-bearing caymanite, B and C¼massive Silurian limestone formingwalls of paleokarst void.


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, Burial, andExhumation

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

Demanovska 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 8 Stalagmite base, all that is remaining of a cave from whichthe roof and walls have been removed by denudation, WellingtonCaves, NSW, Australia. Photo courtesy Christine Robinson.


established from a combination of crosscutting relationships

between cavities and dating of sediments where possible.

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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 research, 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.

treatise on geomorphology || 6.9 preservation and burial of ancient karst

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