Transactions . felsite, occurring in this order. In places,by reason of deformation of the granite, gneisses and schistsalso are found. This granitic area occurs north of Johannes-burg, where the width of its outcrop is about 17 miles. It liesbelow, and is coextensive with the Witwatersrand syncline,presently to be described. Probably it forms, as Truscott sug-gests, a complete envelope over the synclines under considera-tion, though in many places it is obscured by later overlyingformations. There are at places intrusions from this envelopinggranitic mass into the younger formations. Immediat
Transactions . felsite, occurring in this order. In places,by reason of deformation of the granite, gneisses and schistsalso are found. This granitic area occurs north of Johannes-burg, where the width of its outcrop is about 17 miles. It liesbelow, and is coextensive with the Witwatersrand syncline,presently to be described. Probably it forms, as Truscott sug-gests, a complete envelope over the synclines under considera-tion, though in many places it is obscured by later overlyingformations. There are at places intrusions from this envelopinggranitic mass into the younger formations. Immediately overlying the granite area and to the south iswhat is known as the Quartzite-Shale group. The total horizon-tal thickness of this group north of Johannesburg is about 16,000ft. In dip it varies considerably along its strike. This groupextends around the Witwatersrand and the Heidelberg syn-clines. Auriferous conglomerates occur in this series, which, OOLD-MINING in iiii i i: \\~\ \ u S01 , ,, u ,.,, ,A<. x a v 5s IE 6 3 •£ £ 2 -3 „ a 3 jj m - 5 a T3 *J u *i 832 GOLD-MINING [N THE TRANSVAAL, SOUTH AFRICA. though persistent in strike, have been more or less patchy incharacter, and usually subject to considerable Dupreez Reef series lies within this group. Next in order come the Witwatersrand beds of quartzites, Conglomerates and sandstones, lying between tbe quartzite-shale and the amygdaloidal diabase, and conformable in strati-fication with the underlying quartzite-shale group, to whichthey geologically belong. The width of outcrop of the Wit-watersrand beds in the section through Johannesburg is about26,000 ft., making a total thickness of the stratified rocks onthe N. and S. section through Johannesburg of about 42,000 ft. At a distance of 36,000 ft. from Johannesburg occurs theamygdaloidal diabase above mentioned, which overlies thestratified rocks, and has a thickness of about 19,000 ft. meas-ured on the surface along this section. Overlying t
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
