KARST MORPHOGENESIS AND SPELEOGENESIS (DEVON),
and Karst Evolutionary Development.
This aspect of the Society's karst research activities in Devon is instrinsically linked with the Karst Geomorphological Mapping Programme and in particular, with the Karst Rock-head Profiling Programme,.which is directed by the developments and results of our core Karst Morphogenetical Research. This work is one of the Society's more important areas of karst research.
Before we consider karst morphogenesis in some detail, it is necessary to review some definitions. We begin with the "Concept of Karst" .......
|THE CONCEPT OF KARST :||
1.1. THE CONCEPT OF KARST :
1.1.1...Karst is a stage in the natural development or evolution of dominantly limestone (carbonate) landmasses and which, together with a characteristic appearance, is the result of the corrosion of such a landmass by a series of natural chemical reactions culminating in its aqueous hydrogen-carbonate dissolution.
This is the prime, fundamental aspect of the karst process.
1.1.2...The ordinary base process of simple aqueous solution of the carbonate landmass in itself does not represent the karst process but is obviously an intrinsic part of that process.
It is necessary to state that there continues to be an unhealthy trend in the application of the word "karst" to any solutional environment. The Karst Process is clearly limited to the corrosional or chemical evolution of carbonate landmasses via the complex process of aqueous hydrogen-carbonate dissolution.
The active process is referred to as karstification.
Karstification of the carbonate deposits can take place at any time, including during (or soon after) the process of deposition. This is known as syngenetic karst.
1.1.3...The aqueous hydrogen-carbonate dissolutional process is both assisted by, or may be the direct result of a dynamic interplay between various chemical, physical, biological, hydrological, geological, geographical, climatological and other authigenic environmental processes on and throughout the 3-dimensional volume or body of the carbonate landmass, resulting in a characteristic (dissolutional) surface landscape (exokarst) and an attendant characteristic underground landscape (endokarst).
The complex reactions and inter-reactions, together with the multitudinous effects of the environmental variants mentioned above, separately and collectively in their infinite varying contributive proportions and combinations with each other, on and throughout the entire 3-dimensional volume of the karstic landmass, can seriously influence the dynamism of karstification.
In this respect, it would be generally true to state that the variation, fluctuation, or alteration, however caused, in any one of the prevailing component processes of karstification, would lead to an appropriate variation etc. in at least some of the other component processes. As all these processes are of the natural environment, they are changing, varying or fluctuating minute by minute, year in and year out continuously through time - the fourth dimension.
It should be noted that the evolution or development of both the exokarst and endokarst landscapes are subject to the parallel physical processes of abrasion and corrasion. This can often enhance the appearance of the original dissolutional effects and the dynamism of karst evolution as a whole.
However, when the karst environment is subject to the additional influences or input of allogenic variants from adjacent non-karst environments, the increase in the dynamism of karst evolution can be staggering.
1.1.4...Karst landscapes are usually characterised by being devoid of integrated surface drainage systems. Allogenic surface water crossing into a karstic environment would usually soon disappear into the karst underground or endokarst. Atmospheric precipitation would also usually be absorbed directly into the karst.
1.1.5...All carbonate landmasses are karstifiable, ie. have the potential to become karstified, if the environmental conditions support this development. However, it should be noted that not all carbonate landmasses have become karst environments. Carbonates represent approximately 80% of all known "soluble" rock types and represent about 10% of the Earth's crust.
Under similar effects and conditions, carbonate landmasses composed of CHALK and DOLOMITE will also undergo karstification, as outlined above, although for different reasons in each case, less so than for LIMESTONE, DOLOMITIC LIMESTONE and MAGNESIAN LIMESTONE.
[Furthermore, landscapes composed of GYPSUM, ANHYDRITE, ROCK SALT or HALITE and certain SILICATES will also undergo a certain amount of solutional development. However, such solutional development in most of these cases is mainly due to simple aqueous solution and is not due to hydrogen-carbonate dissolution. Where such non-carbonate solutional environments occur, they are referred to as pseudo-karsts.in the literature. However, the Society does not accept these as being pseudo-karsts but rather as totally non-karst environments.]
1.1.6...There are other significant chemical corrosion processes which can contribute to apparent karstification. In particular is the generation of sulphuric and other mineral acids by microbial and bacterial ecosystems within or adjacent to carbonate landmasses and which are responsible for excreting or producing waste products including hydrogen sulphide. Such microbes and bacteria often attack specific minerals within the carbonate mass, such as the iron or manganese constituents leading to the production of sulphuric and other mineral acids which then corrosively dissolve the carbonate landmass producing caves. There are specific examples of these bio-mineral ecosystems in the Guadelope Mountains of New Mexico, USA. and in Mexico and Romania. Such cave development often results in the massive deposition of crystalline gypsum within the caves.
It should be remembered that these processes are not the karst process but are what the Society accepts as being true pseudo-karst processes; ie. the corrosion of carbonate strata by chemical / bio-chemical processes which are not of the form given in para 1.1.1. above.
are various types of karst environment, classified according to the system
used, eg. Morphological Classification, Climatological Classification etc.
as well as various sub-types. Even within a specific karst environment,
there are further classification systems defining specified 3-dimensional
spatial zones, such as epikarst,
the various karst hydrological zones etc.
It is an observed fact that the more spectacular an environment is in appearance, the more dynamic are the processes that created it.
A DEFINITION OF
The term "Karst" is not an easy one to define in simple terms in one sentence. Much qualification is needed of other terms used in the course of the prime definition.
landscapes are usually more rocky than those of other rock types. Often,
this difference is pronounced at the margins of the karst near or at the
physical contact with the adjacent non-karst strata. In Slovenia, the name
"Kras" as a Proper Noun or Toponym, has contemporary use in those areas
where the Dinaric Karst Plateaux protrude most visibly near the non-karst
areas in the Region which is now almost universally known as the [Slovene]
Classical Karst and the Trieste Karst.
The extension in the use of the word from that of an ordinary noun to being an international term of physical geography was probably via the route of its use as an adjective.
The term "Karst Morphogenetics" is the result of a formal conceptual joining of the component terms karst, morphology and genesis and means the science of the origin of karst forms. It is a part of Karst Geomorphology, the science of karst landforms and, in a wider sense, of Physical Geography.
1.4. DEFINITION OF SPELEOGENESIS :
The term "Speleogenesis" is a formal conceptual joining of the component terms speleology and genesis and means the science of the origin of caves. It is a part of Speleology, the multi-disciplinary science of caves. The science can only be understood and applied within the wider context of Karst Morphogenetics, of which it is an intrinsic part.
The application of Karst
Morphogenetic Theories enables the observer of the karst landscape to predict
specific environmental scenarios in given locations, a practise in which
the Society has become particularly adept. The application of this compound-science
has been of extraordinary use in identifying specific types of concealed
karstic limestone landscapes in Devon which, for the most part, are buried
and masked to greater or lesser degrees beneath younger sediments.
(CLASSIFICATION OF KARST EVOLUTIONARY DEVELOPMENT) :
Many attempts have been made
over the course of the last five or six decades to systematically describe
and classify the various karst environmental situations that occur across
our Planet. Attempts have also been made to determine the precise mechanisms
of, and the resultant phenomena associated with the Karst Process. The
importance of recognizing the different contributions made by authigenic
and allogenic water sources upon karstification has been described by Pitty
in "An Approach to the Study of Karst Water". However, there has
been little international recognition of the remarkable efforts of the
late Hungarian Academic, Professor Dr László
Jakucs, who, in the course of his detailed study entitled "Morphogenetics
of Karst Regions - Variants of Karst Evolution", made the first serious
and very successful attempt to analyse the whole spectrum of environmental
causes for and variants of karstification; then to link these variously
with the resultant observed karst phenomena. From many years of personal
study of karst scenarios in his native Hungary and throughout Eastern Europe,
he brought his experiences and observations together in a book "Morphogenetics
of Karst Regions - Variants of Karst Evolution".
The present mode of
karstification or karst evolution [ie. either Allogenic (B-Type)
by definition normally found associated at or with contact karst
areas, or Authigenic (A-Type)] of any karst landscape can be accurately
determined by identifying the topographic, hydrologic and orogenic relationships
between the karst and adjacent non-karst landmasses.
Authigenic [A-Type] Mode of Karstification or Karst Evolution ....
Allogenic [B-Type] Mode of Karstification or Karst Evolution ....
IDENTIFICATION AND LOCATION OF HYDROLOGICALLY-ACTIVE PONOR ZONES OCCURRING
THE IDENTIFICATION AND LOCATION OF HYDROLOGICALLY-ACTIVE PONOR ZONES OCCURRING AS BURIED KARST DOLINE FIELDS IN SOUTH DEVON.
Our most successful practical application of the theories of karst morphogenesis has been in identifying the location of hydrologically-active ponor zones, which occur as "Buried Karst Doline Fields" in many karstic locations in South Devon and then determining their evolutionary history. Individually, these "Buried Karst Doline Fields" represent the largest, in areal extent, of all the karst geomorphological features in Devon's karst.
Buried Karst Doline Fields must be considered as being Karst Geohazard Zones as they present areas at high risk of catastrophic (sudden) collapse, general subsidence and other ground movement. They are thus classified as mature karst areas containing many of the classic karst landforms. They are usually drained underground by a master karst conduit-aquifer into which intermittently active or permanently active ponors (swallow holes) and their cave-stream passages feed their individual water flows.
general problem in South Devon is that the exokarst has become buried in
the post-glacial period, masking and partly filling many of the classic
karst features. One of the most problematic type of karst geohazards in
these areas is that of buried karst shafts. Example areas 1., 2., 4. and
7. below exemplify such problems. Examples 4. and 7. have been particularly
impacted by limestone quarrying in their vicinity.
1. The Shute Buried Karst Doline Field / Ponor Zone (BKDF-01), Denbury, S. Devon.The above list is not exhaustive.
Most of these areas include specific geomorphological features strongly suggestive of their origin, ie. morphogenesis. An understanding of the morphogenesis and subsequent landform development can lead to a better understanding of the extant karst geohazards and in being able to predict where they may occur in the future.
[Note: The present considerable delay in our activating the above Links has been due to the problem of presenting information without causing unecessary problems for the respective land-owners. When gaining access to private land in the past in order to carry out karst research, assurances have been given in good faith by the Society to many property owners, whereby the specific identity and location of "at risk" properties (houses & other buildings) would never be revealed. As a consequence, we are having some difficulty in finding a form in which to present the information without compromising these assurances. However, we are working on the problem and the above Links will be activated to present some very interesting karst-environmental information.]
|BIBLIOGRAPHY AND FURTHER READING.||
[ * signifies a stock item in the Society's Reference Library.]
Jakucs, L. (1977) *....."Morphogenetics of Karst Regions - Variants of Karst Evolution".
..................................Published in separate English Language Editions by Adam Hilger (Bristol) & Akadémiai Kiadó (Budapest). 284.pp.
Pitty, A. (1966) *........."An Approach to the Study of Karst Water".
..................................Published by University of Hull, UK. 70.pp.
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