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92 Erdkunde Band XVIII schungskorrosion, die beim Vermischen verschie den temperierter Wasser auftritt. Beim Abkiihlen wird weiterhin C02 frei,was zur Korrosion fiihrt: Durch diese vier Korrosi Abkuhlungskorrosion. wird der ganze verkarstungs onsmoglichkeiten in Karbonatgesteinen in seinem fahige Raum zu einer Ganzheit Werden zusammengeschlossen. Literatur ? A.: Probleme der Karrenbildung. Bogli, Geographica H. 3, 1951. Helvetica, ? ?: Re Der Chemismus im Karst. der Losungsprozesse in Karst Phenomena, port of the Commission IGU, New 1956. York, ? ?: im Muotatal. Untersuchungen Karsthydrographische 1960. Basel Regio Basiliensis, ? ?: fiir Geo Zeitschrift und Karrenbildung. Kalklosung 1960 Bd. 2: Karstmorphologie, Suppl. morphologie, ? ?: Leben und Umwelt H. Das Holloch imMuotatal. 19, 1963. ? von Karsthohlen. Die Hohle, Beitrag zur Entstehung 1963. Wien 3, ? Inst, des etu de l'Europe. Corbel, J.: Les Karst du NE des rhodaniennes, Memoires 12, Lyon 1957. ?: en terrain calcaire. ? de Geographie, Annales Erosion H. 366. ?: H. Gmelins der anorganischen 8. Auflage. Handbuch Chemie, ? W. R.: Changing of Speleogenesis. Halliday, Concepts Bulletin Vol. of the National 22, Society, Speleological 1960, USA. Tabellen. Landolt-Bornstein: Physikalisch-chemische ? Karstwasser. H.: kubanischer Chemismus Lehmann, Briefl. Mitt. ? O.: Hydrographie der des Karstes. Lehmann, Enzykl. 1932. Erdkunde, Wien to the Origin G. W.: of Limestone Introduction Moore, ? Caves. of the National Bulletin Society, Speleological Vol. 22, 1960. USA. von Karstgewassern. H.: Karbonatharte ?Stalac Oertli, tite" 1953. Kal des kohlensauren iiber die Loslichkeit Pia, J.: Theorien ? 1953. kes. Mitt. Geol. Ges. Wien, H.: der Bestim Theoretische SchmasSmann, Grundlagen in naturlichen Gewas mung von agressiver Kohlensaure sern. und f. angewandte Wissenschaft Schweiz. Archiv 1947. Technik, Jg. 13?14, von Wasser und chemische Untersuchung Tillmans, J.: Die ? 1932. W. Knapp, Halle, Abwasser. ? 1952. F.: Traite de Speleologie. Paris, Trombe, B.: Terminations of Passages in Appalachian W. White, ? as Evidence Bul Phreatic Origin. for a Shallow Caves letin of the NSS, Vol. 22, 1960, USA. Freie Kohlensaure Zehender-Stumm-Fischer: und pH von und Wasserfachman Wasser. ? Schweiz. Ver. von Gasnern, H. 11, 1956. SOME FACTORS IN THE ABSOLUTE DENUDATION OF LIMESTONE TERRAINS With 1 photo and 6 figures M. M. Sweeting Such values are therefore probably only a rough for bringing our We are indebted to Corbel attention to themean rates of erosion of limestone guide to the range of intensity of chemical denuda tion. It is also difficult to be sure that the mean areas and particularly for stressing the variations is It differences (1). figures give a realistic picture of chemical denu dependent upon temperature dation in a limestone area. There is therefore a quite clear however that solution rates in lime need for the systematic observation and analysis stones are dependent upon many factors, of which of limestone waters and springs in order to isolate one. Hence Corbel's is figures temperature only rates to the factors which may be causing the variations. the real though useful are not a true guide of solution which may be occurring in a given area. With this aim inmind a series of observations of This contribution seeks to point out some of the springs and waters in many parts of the British results Isles has been started. The preliminary factors. other show that in a small region such as the British Isles, If the rates for themean, maximum and minimum rates of chemical erosion for various rivers are quite significant variations in solution rates may are be observed. examined it will be seen that these figures In N. W. England, the area best known to the extremely variable. Tarn writer, the figures given for the Malham are the limestone for 1 waters in Table fairly typical fig. (Figures supplied by I. Douglas, Ballioc College, Oxford [2]) solubility of the springs and waters of the district. Rates of chemical denudation ms/km2/year The calcium content in general varies inversely with the discharge. The average calcium content Minimum Maximum Mean River of waters varies from about 140-180 p. p. m. The Thames (Teddington) 288,0 12,87 104,0 on to the curves of Trombe, figures when plotted Derwent 65,92 197,4 (Matlock Bath) are more or less in equi waters the show that 3,44 297,0 63,75 Kentucky (U. S. A.) Lee (Essex) libriumor only slightlyaggressive(fig. 2). The 23,05 63,36 155,0 Kissimmee 26,94 (Florida) values for a dry period and for the summer months 63,04_15,90 M. M. Some Sweeting: factors in the absolute denudation of limestone terrains 93 Oct. Nov. Dec. Jan. Feb. March June Sept. July Aug. April __r_rn?, May 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 1824 31 6 15 22 29 6 13 20 28 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? 200i-1-\-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1 190_ -Water 180- ?. Water Tarn flowing into Malham Tarn a flowing out of Malham Aire Head -?p\ Springs \ V -^-c-\-y1 - 120110- / ^ \ Nv 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_ 10J 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 June Oct. Nov. April Dec. July May Aug. Sept. Fig. 20 inn. i i 60. i r~i 80.. i lu/ui . H i f?. 9,5 content -1-1 z 80 -V--4iE 80-^^^^- aggressiv I_-?30 "^^^^5^^2o e_ 30 6,5^-40 6,5-1-AQ 1* 6/0 50 100 150 200 _I_I_I_I 0 5 10 15 20 Fig. 2: Malham 250 I 25 300 I 30 Tarn 350 I 35 System 400 _| I 40 . 450 m9 CaC?3/L 0 45?fH Fig. 6'? aggressiv I 2+ 50 I 5 I 3: 1 2 3 4 are relatively saturated, those for a wet period and for winter being more aggressive (fig. 3). of the calcium content of pools and Examination 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) 180 200 saturated ^ ~-1-1-9-??%- ccl_I 160 -V-1-1 saturated ^ 90 -V Tarn waters of the Malham Du rngC02/L semi-comb. mg C02/l semi-comb. 120 uo 160 180 200 i 20 40 60 80 120 UP 100 i i n 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 100 -V-1-1-9/5 1: Calcium to thedissolvedCaC03, and shows that this is a straight-forward connection. 3o "^^^^5^31 4. 100 I 10 150 I 15 200 ' I 20 250 I 25 300 I 30 350 I 35 400 I 40 . 450m9 I CaC03/l 45?fH N. W. England Limestone waters in summer Limestone waters in winter Inflow to Malham Tarn (N. W. Yorks.) Great Close Springe (N. W. Yorks.) 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 inN .W.Yorkshire fit in very well with this type of calculation (photo), and support the idea of a general lowering of this amount inNorthern 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 / / ' 50 100 50 Fig. 4: Malham 1x 2 250 200 Total Hardness p.p.m. 150 Area (N. W. Yorks.) in South West England also The Mendip Hills form limestone terrain and many thousands of measurements of the calcium content of thewaters 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 as due to the great concentra by Smith and Mead 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 the depth of penetration of those waters; greatest concentrations of calcium seem to occur in those springs and waters which have been in con tact longestwith 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 below: in the British Isles are given Cambrian Limestones, Durness, N. Scotland Carboniferous Limestones, S.Wales Carboniferous Limestones, Clare, W. Ireland Jurassic Limestones, 290 Cotswolds Chalk of Southern England Photo 1: Pedestal of the Norber inN. W. Yorkshire boulders similar limestone localities inNorthern England 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 lime the Quaternary (4). In N.W.England stone was glaciated during the period of theNewer 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 ismade up of bare pavements, while that in the Southern area is grass covered. This fact may inpart explain themuch higher figures for the amount of calcium in thewaters 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). Calcium 60- content 80 p. p. m. 80-100 120-134 p.p.m. p. p. m. p. p. m. 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 toCorbel's graphs inhis 1959 paper, seem that they refer to potential agres itwould 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 can be shown to exist. such as suggested by Corbel This can be seen from the following figures: 280-300 Calcium 214 Cockpit Country, Jamaica 139-200 Africa North Cyrenaica, 140-150 Dinaric Coast Yugoslavia, 200 N. W. Australia, Fitzroy Area These obtained content p. p. m. p. p. m. p. p. m. p. p. m. figures should be compared with those from areas in the British Isles. Figure 6, compares the results of two districts in southern this shows that Australia, (New South Wales), while the aggressivity of thewaters may be greater in the cooler region, the rate of actual limestone solution is greater in the warmer region. Bauer: Fridtjof Kalkahtragungsmessungen mg C02A semi-comb. 60 120 UP 160 180 200 100 20 40 80 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 ^ ? 9,0 1 6'? 0 mg CO2/L semi-comb. 120 UP 160 180 200 80 100 40 20 60 10,01-1-n?1-n?1-i?p-1?n?nr?1-1-1?1-rj?1-i?p-1? u V saturated saturated 9/0 m * aggressiv # ^^^^^^^Slo-. 30 aggressiv "^^^r^^2p--30 6,5-AO 1* 2 + 2 * 50 I 5 Fig. 95 Kalkhochalpen (drip from stalactite) \v^V 6,5-AO in den osterreichischen 100 I 10 5: 150 I 15 1 Mendips: 2 Central 200 I 20 _[[[I 250 I 25 400 300 350 I_I_I_I 30 35 40 450 m9 CaC?3/l 45?fH streams and risings Runding S. Pennines Peak District, 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 thismaximum chemical denudation ismost likely to occur at or near maximum discharge, due to the large volumes of water involved. Recent work factors (litho suggests that non-climatic 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 KALKABTRAGUNGSMESSUNGEN 6'? 5P I_I 5 0 Fig. 1PP 10 15P I 15 200 I 20 250 I 25 300 I 30 350 I 35 400 I 40 . 450 m9 I CaC?3/L 45?fH 6: New South Wales (Australia) 1 Coolaman Plain (1330 m. above S. L., 1200 mm mean C. annual temp.) 12? rainfall, 2 Jenolan S. L., 800 mm rainfall, (800 m. above 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 en Terrain Ann. "Erosion Calcaire", J. 68e annee, pp. 97?116. Geogr., 2. Douglas, I. 1962. "An Evaluation of some Techniques used in the Study of landforms with special reference to Limestone Areas". of Oxford. Unpublished thesis, Univ. 3. Kendall, P. F. and Wroot, H. E. 1924. "The Geology of Yorkshire", page 943. 4. Piggott, on "Denudation D. 1963. Symposium in Lime stone Regions"; Soc. Unpublished. Royal Geog. 5. Ingle Smith, D. and Mead, D. G. 1962. "The solution of with special reference toMendip. Proc. Uni Limestone", Soc. Vol. 9, No. versity of Bristol Spelaeological 3, pp. 188?211. 1. Corbel, 1959. IN DEN OSTERREICHISCHEN KALKHOCHALPEN Mit 4 Abbildungen und 2 Tabellen Fridtjof Eines der wesentlichsten Merkmale eines Karst seiner gebietes ist die dauernde Umgestaltung Oberflache durch die karbonatlosende Wirkung Diese kontinu C02-haltiger Niederschlagswasser. vor sich ge ierliche, auch unter Bodenbedeckung hende Veranderung der Gesteinsoberflache schafft Bauer 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 des Karbonatgesteinsabtrages Geschwindigkeit mufi daher im Rahmen eines Karstforschungspro