92 Erdkunde Band XVIII
schungskorrosion, die beim Vermischen verschie den temperierter Wasser auftritt. Beim Abkiihlen wird weiterhin C02 frei, was zur Korrosion fiihrt:
Abkuhlungskorrosion. Durch diese vier Korrosi onsmoglichkeiten wird der ganze verkarstungs fahige Raum in Karbonatgesteinen in seinem Werden zu einer Ganzheit zusammengeschlossen.
Literatur
Bogli, A.: Probleme der Karrenbildung. ?
Geographica Helvetica, H. 3, 1951.
?: Der Chemismus der Losungsprozesse im Karst. ? Re port of the Commission in Karst Phenomena, IGU, New York, 1956.
?: Karsthydrographische Untersuchungen im Muotatal. ? Regio Basiliensis, Basel 1960.
?: Kalklosung und Karrenbildung. ? Zeitschrift fiir Geo morphologie, Suppl. Bd. 2: Karstmorphologie, 1960
?: Das Holloch im Muotatal. ? Leben und Umwelt H. 19, 1963.
?: Beitrag zur Entstehung von Karsthohlen. ? Die Hohle, H. 3, Wien 1963.
Corbel, J.: Les Karst du NE de l'Europe. ? Inst, des etu des rhodaniennes, Memoires 12, Lyon 1957.
?: Erosion en terrain calcaire. ? Annales de Geographie, H. 366.
Gmelins Handbuch der anorganischen Chemie, 8. Auflage.
Halliday, W. R.: Changing Concepts of Speleogenesis. ? Bulletin of the National Speleological Society, Vol. 22,
1960, USA.
Landolt-Bornstein: Physikalisch-chemische Tabellen.
Lehmann, H.: Chemismus kubanischer Karstwasser. ? Briefl. Mitt.
Lehmann, O.: Hydrographie des Karstes. ? Enzykl. der Erdkunde, Wien 1932.
Moore, G. W.: Introduction to the Origin of Limestone Caves. ? Bulletin of the National Speleological Society, Vol. 22, 1960. USA.
Oertli, H.: Karbonatharte von Karstgewassern. ?Stalac tite" 1953.
Pia, J.: Theorien iiber die Loslichkeit des kohlensauren Kal kes. ? Mitt. Geol. Ges. Wien, 1953.
SchmasSmann, H.: Theoretische Grundlagen der Bestim mung von agressiver Kohlensaure in naturlichen Gewas
sern. - Schweiz. Archiv f. angewandte Wissenschaft und Technik, Jg. 13?14, 1947.
Tillmans, J.: Die chemische Untersuchung von Wasser und Abwasser. ? W. Knapp, Halle, 1932.
Trombe, F.: Traite de Speleologie. ?
Paris, 1952.
White, W. B.: Terminations of Passages in Appalachian Caves as Evidence for a Shallow Phreatic Origin. ? Bul
letin of the NSS, Vol. 22, 1960, USA.
Zehender-Stumm-Fischer: Freie Kohlensaure und pH von Wasser. ? Schweiz. Ver. von Gas- und Wasserfachman
nern, H. 11, 1956.
SOME FACTORS IN THE ABSOLUTE DENUDATION OF LIMESTONE TERRAINS
With 1 photo and 6 figures M. M. Sweeting We are indebted to Corbel for bringing our
attention to the mean rates of erosion of limestone areas and particularly for stressing the variations dependent upon temperature differences (1). It is quite clear however that solution rates in lime
stones are dependent upon many factors, of which temperature is only one. Hence Corbel's figures though useful are not a true guide to the real rates of solution which may be occurring in a given area.
This contribution seeks to point out some of the
other factors.
If the rates for the mean, maximum and minimum rates of chemical erosion for various rivers are examined it will be seen that these figures are extremely variable.
Table (Figures supplied by I. Douglas,
Ballioc College, Oxford [2])
Rates of chemical denudation ms/km2/year
River Mean Maximum Minimum
Thames (Teddington) 104,0 288,0 12,87
Derwent (Matlock Bath) 197,4 65,92
Kentucky (U. S. A.) 63,75 297,0 3,44
Lee (Essex) 63,36 155,0 23,05
Kissimmee (Florida) 26,94 63,04_15,90
Such values are therefore probably only a rough guide to the range of intensity of chemical denuda
tion. It is also difficult to be sure that the mean figures give a realistic picture of chemical denu dation in a limestone area. There is therefore a need for the systematic observation and analysis of limestone waters and springs in order to isolate
the factors which may be causing the variations.
With this aim in mind a series of observations of springs and waters in many parts of the British Isles has been started. The preliminary results show that in a small region such as the British Isles, quite significant variations in solution rates may be observed.
In N. W. England, the area best known to the writer, the figures given for the Malham Tarn waters in fig. 1 are fairly typical for the limestone
solubility of the springs and waters of the district.
The calcium content in general varies inversely with the discharge. The average calcium content of waters varies from about 140-180 p. p. m. The
figures when plotted on to the curves of Trombe, show that the waters are more or less in equi
librium or only slightly aggressive (fig. 2). The
values for a dry period and for the summer months
M. M. Sweeting: Some factors in the absolute denudation of limestone terrains 93
__r_rn?, Jan. 9 3 10 17 24 31 7 14 21 28 7 14 21 28 5 12 19 26 3 10 17 24 31 7 14 21 28 5 12 19 26 2 9 16 23 30 6 13 20 27 4 11 18 24 31 6 15 22 29 6 13 20 28 200i-1-\-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1 Feb. March April May June i |-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1? July Aug. Sept. Oct. Nov. Dec.
190 _ -
Water flowing into Malham Tarn -Water flowing out of Malham Tarn a 180- ?. Aire Head Springs -?p\
V \ / \ ^
120- - - -^-c-\-y1
110- Nv
10J I l_I_I_I_I_I_I_I_I_I_I_I_I_I_I_I_I_I-1-1_I-1-1_I_I-1_I-1_I_I-1_I_I_I_I_I_I_I_I_I_I_I_I_I_I_I_I_I_I_I_ 3 10 17 24 31 7 14 21 28 7 14 21 28 5 12 19 26 3 10 17 24 31 7 14 21 28 5 12 19 26 2 9 16 23 30 6 13 20 27 4 11 18 24 31 6 15 22 29 6 13 20 28
Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec.
Fig. 1: Calcium content of the Malham Tarn waters
Du rng C02/L semi-comb. mg C02/l semi-comb.
inn. . 20 lu/ui H i i i i r~i i f?. 60. 80.. 100 120 uo n i 160 180 200 I i | i n?i-1?pi-1?i lU/Ui-1-n?i-n?i-1?r~i-1?p?~~i-1-i-1?i-n?i-rrn-1?i 20 40 60 80 100 120 UP 160 180 200
9,5 -V-1-1-9/5 -V-1-1
^ saturated
saturated ^
~-1-1-9-??%- 90 -1-1
-V z -V--4iE
80-^^^^-
80
aggressiv "^^^^5^^2o aggressiv "^^^^5^31
ccl_I I_-?30 e_ 30 I
6,5-1-AQ 6,5^-40
1* 2+ 3o 4.
6/0 50 100 150 200 250 300 350 400 450 m9 . 6'? 50 100 150 200 250 300 350 400 450m9 .
_I_I_I_I I I I _| I CaC?3/L I I I I I '
I I I I I CaC03/l
0 5 10 15 20 25 30 35 40 45?fH 0 5 10 15 20 25 30 35 40 45?fH
Fig. 2: Malham Tarn System Fig. 3: N. W. England
1 Limestone waters in summer 2 Limestone waters in winter
3 Inflow to Malham Tarn (N. W. Yorks.) 4 Great Close Springe (N. W. Yorks.)
are relatively saturated, those for a wet period and for winter being more aggressive (fig. 3).
Examination of the calcium content of pools and pans at selected periods after rain shows that the
calcium is taken up relatively quickly after rain:
the waters contain 120-140 p.p.m. after a short interval of time or after having flowed for only a few metres upon the bare rock. Subsequently rela tively little calcium is picked up. Figure 4 shows the relationship of dissolved total hardness
(MgC03 + CaC03) to the dissolved CaC03, and
shows that this is a straight-forward connection.
If these figures for N. W. England are used in conjunction with Corbel's formula, then the average lowering of the surface by chemical denu dation per kilometre square is of the order of 0.04 mm. per year (1). The amount of lowering since the end of the last phase of the Quaternary Ice Age should then be of the order of 40-50 cm.
The pedestals of the well-known Norber boulders in N .W. Yorkshire fit in very well with this type of calculation (photo), and support the idea of a general lowering of this amount in Northern Eng
land, since the Quaternary (3). In several other
94 Erdkunde Band XVIII
E 250i-1-1-1-1 d d
<n i/>
o c T3
i /
E 200 -/
I <'
* /
150-A^r xx\*
/*?
.3?
100 /
/ ' 1 x
2 50 50
100 150 250 200
Total Hardness p.p.m.
Fig. 4: Malham Area (N. W. Yorks.)
Photo 1: Pedestal of the Norber boulders in N. W. Yorkshire
localities in Northern England similar limestone pedestals can be found. Locally, solution rates, may be relatively greater, particularly where favourable
conditions occur.
In the Southern Pennines, only a 100 kilometres or so south of the areas just considered, Piggott has produced evidence for a very similar rate of
lowering of the limestone surface since the end of the Quaternary (4). In N.W.England the lime stone was glaciated during the period of the Newer Drift, whereas the limestone of the Southern Penni nes is believed to have remained ice free. As a result much of the limestone of N. W. England is made
up of bare pavements, while that in the Southern area is grass covered. This fact may in part explain the much higher figures for the amount of calcium in the waters of the Southern Pennines, about 230 250 p.p.m.; such figures if plotted on Trombe's curves show that the waters are saturated (fig. 5).
The Mendip Hills in South West England also form limestone terrain and many thousands of measurements of the calcium content of the waters
have been made by members of Bristol University (5). The figures for the springs in the Mendip area are in general very consistent, averaging about 220-240 p. p. m. These results are explained by Smith and Mead as due to the great concentra
tion of soil C02 consequent upon a complete grass cover. A further point made by these two authors concerns the importance of the length of time the
limestone has been in contact with the waters and the depth of penetration of those waters; the greatest concentrations of calcium seem to occur in those springs and waters which have been in con tact longest with thelimestones (5). Hence the lower and deeper the percolation, the greater the solution and the actual chemical denudation, a result which might be inverse to the rates of mechanical denu
dation.
Other observations in the British Isles are given below:
Calcium content Cambrian Limestones,
Durness, N. Scotland 60- 80 p. p. m.
Carboniferous Limestones,
S.Wales 80-100 p.p.m.
Carboniferous Limestones,
Clare, W. Ireland 120-134 p. p. m.
Jurassic Limestones,
Cotswolds 290 p. p. m.
Chalk of Southern England 280-300 p.p.m.
These results thus indicate that amounts of calcium picked up by percolating waters are not dependent upon temperature variations and that lithology and nature of the vegetation must also be taken into account.
Returning to Corbel's graphs in his 1959 paper, it would seem that they refer to potential agres sivity and saturation of the waters rather than to actual solution rates. Individual variations in the calcium content of waters occur from place to place but no systematic variation on a world scale
such as suggested by Corbel can be shown to exist.
This can be seen from the following figures:
Calcium content Cockpit Country, Jamaica 214 p. p. m.
Cyrenaica, North Africa 139-200 p. p. m.
Yugoslavia, Dinaric Coast 140-150 p. p. m.
N. W. Australia, Fitzroy Area 200 p. p. m.
These figures should be compared with those obtained from areas in the British Isles. Figure 6, compares the results of two districts in southern Australia, (New South Wales), this shows that while the aggressivity of the waters may be greater
in the cooler region, the rate of actual limestone solution is greater in the warmer region.
Fridtjof Bauer: Kalkahtragungsmessungen in den osterreichischen Kalkhochalpen 95
mg C02A semi-comb.
20 40 60 80 100 120 UP 160 180 200 10,0]-1-n?i-n?i-r?p-1?p?lt?i-1-1?i-rj?i-r-p-1?|
9,5 -V-1
^ saturated
9,0 ?
\v^V (drip from stalactite)
aggressiv # *
^^^^^^^Slo
-. 306,5-AO 1 2 *
_[[[I
6'? 50 100 150 200 250 300 350 400 450 m9
I I I I I I_I_I_I CaC?3/l
0 5 10 15 20 25 30 35 40 45?fH
Fig. 5: 1 Mendips: Runding streams and risings 2 Central Peak District, S. Pennines
Thus a brief review of the results now coming to light suggest that temperature is not a major factor in the dissolution of limestones. There is almost invariably a correlation between the log. of
the discharge and the calcium hardness of waters;
despite this maximum chemical denudation is most likely to occur at or near maximum discharge, due to the large volumes of water involved. Recent work suggests that non-climatic factors (litho logy and structure of the limestones, depth and length of time of percolation) more than compen sate for any variation due to temperature. Further more, the importance of soil C02 as a result of a
vegetation cover has been completely ignored in hypotheses based solely on temperature variations.
Such a situation has been for many years recog nized by geographers and geologists ?
long before
u mg CO2/L semi-comb.
20 40 60 80 100 120 UP 160 180 200 10,01-1-n?1-n?1-i?p-1?n?nr?1-1-1?1-rj?1-i?p-1?
V saturated
9/0 m
aggressiv "^^^r^^2p --30
6,5-AO 1* 2 +
6'? 5P 1PP 15P 200 250 300 350 400 450 m9 .
I_I I I I I I I I CaC?3/L
0 5 10 15 20 25 30 35 40 45?fH
Fig. 6: New South Wales (Australia)
1 Coolaman Plain (1330 m. above S. L., 1200 mm rainfall, 12? C. mean annual temp.)
2 Jenolan (800 m. above S. L., 800 mm rainfall, 16? C. mean annual temp.)
(from observations by J. N. Jennings)
the somewhat misleading attempts which have been made recently to over-simplify a very com plex problem. It also illustrated the need to tackle
the problem in a completely different manner.
References
1. Corbel, J. 1959. "Erosion en Terrain Calcaire", Ann.
Geogr., 68e annee, pp. 97?116.
2. Douglas, I. 1962. "An Evaluation of some Techniques used in the Study of landforms with special reference to Limestone Areas". Unpublished thesis, Univ. of Oxford.
3. Kendall, P. F. and Wroot, H. E. 1924. "The Geology of Yorkshire", page 943.
4. Piggott, D. 1963. Symposium on "Denudation in Lime stone Regions"; Royal Geog. Soc. Unpublished.
5. Ingle Smith, D. and Mead, D. G. 1962. "The solution of Limestone", with special reference to Mendip. Proc. Uni versity of Bristol Spelaeological Soc. Vol. 9, No. 3, pp.
188?211.
KALKABTRAGUNGSMESSUNGEN IN DEN OSTERREICHISCHEN KALKHOCHALPEN
Mit 4 Abbildungen und 2 Tabellen Fridtjof Bauer
Eines der wesentlichsten Merkmale eines Karst gebietes ist die dauernde Umgestaltung seiner Oberflache durch die karbonatlosende Wirkung C02-haltiger Niederschlagswasser. Diese kontinu ierliche, auch unter Bodenbedeckung vor sich ge hende Veranderung der Gesteinsoberflache schafft
laufend neue Voraussetzungen fiir die Entwick lung der iiberlagernden Boden und der Struktur der Vegetation, wie auch fiir Mikroklima und Oberflachenwasserhaushalt. Die Frage nach der Geschwindigkeit des Karbonatgesteinsabtrages mufi daher im Rahmen eines Karstforschungspro
