THE SURFACE GEOLOGY OF THE KALAHARI

REFERENCES

• Passarge , S. 1904 . “ chapters xxxiv, xxxvi, xxxvii ” . In “Die Kalahari”
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• Maufe , H. B. 1919 . Report of the Director of the Geological Survey of Southern Rhodesia for 1915 4 and “Recent Advances in Rhodesian Geology”, Proc. Geol. Soc. S.A., p. xxii
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• Haughton , S. H. 1915 . “On some Dinosaur Remains from Bushmanland” . Trans. Roy. Soc. S.A. , v : 259 A. W. Rogers, “The Occurrence of Dinosaurs in Bushmanland,” ibid., A. L. Dutoit, “The Geology of South Africa, p. 341
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• 1929 . “The Geology of the Zambezi Basin” . Q.J.G.S. , lxiii : 182 G. W. LAMPLUGH1907 B.LIGHTFOOT, “Geology of the Central Part of the Wankie Coalfield”, Geol. Surv. Southern Rhodesia, Bulletin 15,p. 43
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• In addition to the basalt struck in the Thatchwe bore-hole it has been found in the Khari hole, from which Dr. du Toit sent me samples. The volcanic rocks are not known to have extended over the eastern, southern, and western Transvaal, though the occurrence of agates in the Ermelo district and in some of the diamond gravels of the western Transvaal may point to the former presence of the Karroo basalts in those areas
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• Though the southern ranges lie far from the Kalahari their region affords evidence that in early Cretaceous times the great synclinal valleys were filled with material derived from the mountains which came into existence at some date between the deposition of the Ecca beds and that of the Stormberg beds. The date of the mountains may be more closely fixed in future if the necessity should arise of deep boring in the Springbokvlakte area in Steytlerville. (Sheet 150 and Cape Sheet 9, and Explanations by S. H. Haughton.) The outlier of Stormberg sediments and volcanic rocks south of Zuurberg, taken together with their uncleaved condition in contrast to the disturbed state of the Dwyka series in the same area, points to an unconformity at some horizon in or below the Cave Sandstone there and supports the earlier surmise that the boulders in the Molteno beds came from the southern ranges
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• Du Toit , A. L. 1927 . 88 – 101 . “Report on the Kalahari Reconnaissance of 1925”, 1926; and “The Kalahari and some of its Problems”, S.A. Journ. Science
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• 1904 . 754 – 59 . The fossil shells recorded by Passarge from the northern region (“Die Kalahari”,) are: Succinia, arborea, Mousson. Succinia Moussoni, v. Martens. Buliminus (Leucocochloides) minusculus, Mousson. Buliminus Damarensis? var. expectatus, Mousson. Planorbis salinarum, Morlet. Physa parietalis, Mousson. Ampullaria occidentalis, Mousson. Lanistes ovum, Peters. Vivipara Passargei, v. Martens. Cochlicella opposita, Mousson. Melania tuberculata, Muller. Unio Kunenensis, Mousson. Corbicula africana, Krauss. None of these species was mentioned by Boettger in his list of the shells from Witkop in Gordonia in L. Schultze's “Aus Namaland und Kalahari”, Jena, 1907,pp. 706–8; see also Ann. Rep. Geol. Comm. for 1907,pp. 107–8. The collection of land and fresh-water snails made by members of the Vernay-Lang Kalahari Expedition in 1930 has not yet been reported upon: Major Connolly kindly identified some shells from limestones which I took to him, including Lanistes, Viviparus Passargei, and Melania tuberculata from the Linyanti and Ngami limestones, and Burnupia trapezoides (an Ancylus of Boettger's list) from Matapa Pan besides probable identifications of Bulinus tropicus and Planorbis gibbonsi Nelson, from the Okwa, Ghanzi, and Matapa limestones. The fossils are often difficult to get out and a more thorough examination must await the report on the recent shells. It should be noted that in my collection no bivalves occur, and that the conspicuous northern genera Lanistes, Ampullaria, Melania, and Viviparus are not found in the rocks from Ghanzi, Quale, Okwa, Matapa, and other places south of Ngami and the Okavango region
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• 349 – 55 . In his paper “Crustal Movements as a Factor in the Geographical Evolution of South Africa”, S.A. Geog. Journ., xvi, December 1933, Dr. du Toit suggests that the Basuto Highlands used to stand much higher relatively to the surrounding country than they now do, chiefly to satisfy isostasy. There is difficulty in accepting this view because on it one would expect a much greater development of river gravels due to the reduction of river grade involved in the rising of the surrounding country. It also introduces difficulty in explaining the Kaap-Storm-berg peneplain, which Dr. du Toit first recognised (“The Evolution of the River System of Griqualand West”, Trans. Roy. Soc. S.A., i,) and which he thought was produced when the continent stood at a much lower level than it now does, even suggesting greater uplift of the Drakensberg region than of the rest of the country, a view that seems to be in better agreement with what we know of the rivers and the relative rates of denudation of a mountain region and the surrounding lower country
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• Lamplugh , G. W. “Note on the Geological History of the Victoria Falls” . Geol. Mag., December 1905, and Q.J.G.S. , lxiii 167 – 8 .
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• Maufe , H. B. 1927 . “Some Problems in Rhodesian Physical Geography” . S.A. Journ. Science , xxiv
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• Du Toit , A. L. 1933 . “Crustal Movements as a Factor in the Geographical Evolution of South Africa” . S.A. Geog. Journ. , xvi : 9 gives the name Griqualand-Transvaal Axis to this structure and attributes to it the increase in grade of the Orange River at Buchuberg and that of the Hartebeest River between Verneuk Pan and Kenhardt; these increased grades, however, coincide in position with outcrops of harder rock than usual—Matsap beds of the Langeberg-Ezel Rand at Buchuberg and the granite floor below the Karroo beds on the Hartebeest River— which must have checked downward erosion, and therefore lowered the grade, in the valleys above them. It was to this circumstance that I attributed the position of Verneuk Pan (Trans. Roy. Soc. S.A., ii, 1911,p. 82), and it seems.a more likely explanation than the presence of an anticline, for the form of the outcrop of the almost flat Dwyka series in that part of the country does not seem to be that of a broad or narrow anticline. I think that Dr. du Toit's earlier opinion given in the paper quoted above (Trans. Roy. Soc. S.A., i, p. 349) that there has been no warping of the Karroo beds over the area embraced by the Kaap-Stormberg peneplain in Kenhardt and Prieska is nearer the truth than his later view
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• Range , P. 1912 . T.G.S.S.A. , xv : 63 – 73 . “Topography and Geology of the German Kalahari”, and in Beitr. z. geol. Erforsch. d. Deutschen Schutzgebiete, Hft. 11, 1915, for details of bore-holes in the region. H. F. FROMMURZE, “Bore-holes in Rehoboth, Gibeon, and Gobabis, S.W.A.”, T.G.S.S.A., xxxiv, p. 124
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• Rogers , A. W. Ann. Rep. Geol. Comm. for 1907 , 96 S. H. HAUGHTON, Trans. Roy. Soc. S.A., xiv, 1927 p. 228
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• Du Toit , A. L. 1905 . Ann. Rep. Geol. Comm. for , : 255 (a) p.
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• 1906 . Ann. Rep. Geol. Comm. for , : 61 and for 1907,p. 188
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• 1906 . Ann. Rep. Geol. Comm. for , : 76 – 78 .
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• Macgregor , A. M. 1932 . 45 in Report by Mr. Jeffares on the Rhodesia-Walvis Bay Recon-naissance Survey
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• The results of sieving some sands were as follows for samples:— 1. from 196 miles on road from Gaberones to Ghanzi. 2. “ 200 miles on same road. 3. “ Kaotwe, surface. 4. “ Kaotwe, 3½ feet below the surface. 5. “ 2 miles N.W. of van Zyl's Cutting. 6. “ 2½ miles N. of Gemsbok Pan. 7. “ 12 miles S.W. of Quagganai. 8. “ River bed at Toten, from a well. 9. “ Well on northern edge of Ngami at Tololamoro. 10. “ Bolibing pit, 4 feet down. S.W. end of Ngami. 11. “ White sand in Mopani bush near Mababe Flat. 12. “ Red sand near Victoria Falls. 13. “ White sand from Witsands in southern Kalahari. For comparison the following sands from other places were sieved:— 14.from Red sand, Intermediate Pumping Station, Kimberley Water Works (A.L.d.T.). 15. “ Red sand, Klokfontein Siding, Kimberley. (A.L.d.T.). 16. “ Glencairn beach, Simonstown. 17. “ Kaffir Kuil River Mouth (Dr. Muir). 18. “ Nordkappers Kop. (Dr. Muir)
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• The sands which have come to be called “millet-seed” are perhaps larger in grain than the Kalahari sands; those known to me are: Penrith and St. Bee's sandstones, Lickey quartzite, Taquara sandstone (a Brazilian rock corresponding to our Cave Sandstone or Red Beds, of which a specimen was given me by Dr. du Toit), and the spherical grains of the “sago” quartzites of the Witwatersrand and Black Reef formations. M. L. Cayeux, in “Roches Siliceuses,” 1929, p. 75, says in reference to the sphericity of desert sands: “I was much surprised when, turning from the literature and looking at the facts, I found that the exception had generally been made the rule.” My experience agrees with that of M. Cayeux.
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• 1854 . 144 These variously shaped bodies of opaline silica, chiefly spade-shaped or knobbly rods, are profusely illustrated in G. C. Ehrehberg's “Mikrogeologie”, (a copy is in the library of the South African Museum) under the general name of “Phyto-litharien”, but without description or explanation; I had difficulty in finding what organisms they came from, but a reference in Früh and Schröter's “Moore der Schweiz”, 1908,p., states that they are the siliceous skeletons of grass, and examination of the residue from bits of grass boiled in Schultze's solution confirmed that statement. Reichelt, in “Die Kalahari”,p. 761, refers to them, a statement that I had missed. Kalkowsky, writing of the salt mud collected by Passarge (“Die Verkieselung der Gesteine in der nordlichen Kalhari”, Abh. d. naturwis. Gesellschschaft. “Isis” in Dresden, 1901,p. 66–67)says: “The reeds die off; they contain silica in their tissues which reach the basin in very fine flocks and particles associated with organic matter. I have not been able to discover from books on botany the fate of the silica in dead plants; it must in any case either remain or be removed in the solid state or in solution. We only know the siliceous remains of diatoms.“
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• 1931 . 336 – 40 . Professor H. B. FANTHAM kindly examined twelve samples of Kalahari sands for protozoa; the results are included in a paper by him on “Soil Protozoa found in certain South African Soils, X”, in the South African Journal of Science, In a letter to me he wrote that occasionally in his work on other sandy soils diatoms overran the cultures made under bacteriologically sterilc conditions; this was in answer to an enquiry of mine after I had seen living diatoms in some of my samples, for I did not know they lived in soils
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• The quickest way to find the diatoms and the grass skeletons in dry sand is to place the sand on a dry glass slip and let it fall off gently by tilting the slip; some dusty material will remain on the slide, and a drop of clove oil or balsam and a cover-glass on it will let the siliceous bodies be found easily
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• Reichelt , H. “Die Kalahari” . 783 in, p., expresses the opinion that redepositon of silica from diatoms was an important process in the formation of the silicified rocks of the Kalahari; that it took part in the making of these rocks is certain, but the quantity of diatoms is insufficient for the purpose, except in the diatom earths, and these are the one type of deposit in which silicification, on a macroscopic scale at least, has not been noticed
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• 1933 . 10 – 11 . The distribution of the sand-pans will be well known only when a map of the country has been made from the air. The observations of travellers such as Chapman, Andersson, Woosnam, and Passarge furnish evidence that these pans are both frequent and distributed at random north of the Molopo; they certainly seem to be so between the Molopo and Orange Rivers. Professor Fritz Jaeger (“Kalkpfannen des östliches Südwestafrikas”, in the Report of the XVIth International Geological Congress, Washington, reprint dated 1936,) thinks that the limestone pans of S.W.A. chiefly lie along the courses of former rivers, and the elongated form of pans like Kuke and Gomodimo, which hardly come under that class of pan, though they contain much carbonate of lime, give the traveller the same impression
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• Du Toit , A. L. 1907 . 151 Ann. Rep. Geol. Comm. forp., and “Geology of South Africa”,p. 369. A. W. ROGERS, Ann. Rep. Geol. Comm. for 1907,p. 106
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• The barytes in these marls was found after that mineral had been determined from the Ngami limestone described on a later page
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• 370 “Geology of South Africa”
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• 1906 . 72 Ann. Rep. Geol. Comm. forp.
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• 1906 . Ann. Rep. Geol. Comm. for , : 74 – 76 . for 1907,p. 147
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• “Die Kalahari”, pp. 120, 516, 358
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• Maufe , H. B. 1922 . Rep. Dir. Geol. Survey of S. Rhodesia for 1915 pp. 4–5, and “The Karroo and Kalahari Rocks of the Gwampa Valley” . Proc. Rhod. Sci. Association , xx : 5 J. C. Ferqusson, Short Report, No. 29 (Geol. Surv. 8. Rhod.), p. 5.
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• Michaelsen , HEINZ . 1910 . “Die Kalkphannen des östlichen Damaralandes” 32 Mitt. a. d. deutsch. Schutzgebieten, Hft. No. 3,p. of reprint, points out the importance of plants in causing the deposition of carbonate of lime in the pan waters
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• Reichelt , H. “Die Kalahari” . 783 in, p., after quoting Frenzel and Marsson on the solution of diatom shells by water alone or by water containing bicarbonate of lime, attributes the effect in the Kalahari to water, warmth, and lime, but he adds that the process is not understood. He thought that the poverty in species in some limestones was due to the destruction of thin-shelled kinds; but this does not agree with the presence of thin-shelled species in such limestones as those of the Okwa and Quale, nor with the occurrence of only thin-shelled species in many of of the limestones
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• Schultze , L. 1907 . “Aus Namaland und Kalahari” 706 – 8 . and Ann. Rep. Geol. Comm. for 1907 p. 107
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• I did not visit Matapa Pan; the limestone from it was given me by Mr. Vernay. It contains Burnupia, Planorbis, and Bulinus. Mr. Vernay thought the place looked more like part of a laagte than an isolated pan
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• These shells are of different groups; see note (7)
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• Young , R. B. 1906 . in “The Calcareous Rocks of Griqualand West” ( . Trans. Geol. Soc. S.A. , ix : 58 ),quotes three analyses of surface limestones from the Kaap Plateau giving 1–57, 2–8, and 18–57 per cent, of magnesium carbonate. S. Passarge quotes three, a pan sandstone from Nakais, and Kalktuffs from Lotlakani and Kalkfontein with no magnesium carbonate; in six others of his specimens 0–8 to 10-0 per cent. were found (“Die Kalahari”, p. 753). W. Wybergh's samples of surface limestones from Bechuanaland within the Union had from 1½ to 25 per cent, of magnesium carbonate (“Limestone Resources of the Union”, 1918 vol. i, ch. xi)
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• The refractive index of the aluminous material is about that ascribed to allophane in Larsen and Barman's Tables (Bull. 848 of U.S. Geol. Survey), but allophane is a very soft mineral
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• The mineral was separated from the insoluble residue of the Motlhatlogo limestone and found to be a sulphate; I took it to be celestine on account of its shape, but could not get a reaction for strontium; Mr. Partridge kindly examined it in the laboratory of the Geological Survey, Pretoria, and proved the presence of barium together with very little calcium and strontium by the spectroscope
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• Partridge , Mr. found iron and magnesia by the spectroscope and by microchemical tests, but no alumina; I found alumina after fusion with soda, but the sample was not pure. The refractive indices are about 1–61
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• 1897 . 68 – 112 . Ann. Rep. Geol. Comm. forp.; for 1898,p. 51; for 1901,p. 66; for 1903,p. 164; for 1904,p. 44; for 1906, pp. 74, 81; for 1907,pp. 96-, 149–55; for 1911,pp. 78–81
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• 69 Explanation of the Heidelberg (Tvl) Sheet
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• 192 Trans. Geol. Soc., Second Series, vii
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• Kalkowsky , E. 1901 . “Die Verkieselung der Gesteine in der nördlichen Kalahari”, Ah. d. naturwis. Gesellschaft. “Isis” in Dresden
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• Storz , MAX . 1926 . “Die Diamantwuste Südwestafrikas” , ii ch. xxv, and “Die Sekundare authigene Kieselsaure …” Berlin, 1928, 478 pp., 25 plates, and 202 text-figures
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• Kaiser , E. and Beetz , W. 1926 . “Die Diamantwuste Sudafrikas”
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• 1905 . 296 Ann. Rep. Geol. Comm. forp.
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• 1934 . Annals of the South African Museum , xxxi : 67 – 96 . The silcretes of Fort Grey lie on decomposed dolerite and are chalcedonic rocks; an examination of the slices which Professor Adamson had cut shows that little opal is in them now, and no carbonates
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• 70 Samples of the silcrete lying on the surface of the eastern part of the Makarikari were brought to me by Mr. Douthwaite. They are of two kinds—one is dull green and has many obvious grains of sand in it, and its surface is rough; the other is white, with a conchoidal fracture like that of fine porcelain but smoother. On examining the crushed rocks the green silcrete is seen to be opal, enclosing great numbers of irregularly shaped, minute particles of carbonate, about 0.002 mm. wide, which can be removed by acid, flakes of the green mica-like mineral referred to onp. and in note (35), fragments of diatoms and of grass skeletons, which can be seen after removal of the carbonate. The opal does not appear to have replaced carbonates but to have been deposited round whatever lay there. The white rock is made of chalcedony, and no grains of sand or plant skeletons were seen in it; very few particles of carbonate were seen in it
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• 345 “Die Kalahari”
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• which will be printed in the forthcoming volume of the South African Geographical Journal , xviii 760 – 84 . “Die Kalahari”, Postscript.—Just before this address was completed I received from Mr. Maufe the typescript of an important paper “Some Factors of the Geographical Evolution of Southern Rhodesia and Neighbouring Countries”,. Mr. Maufe's paper is not concerned with details of the Kalahari deposits but with the origin of the floor on which they rest, the Pre-Kalahari Peneplain, and its probable identity with the Kaap-Stormberg pencplain referred to in notes (8) and (11)
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