134 



SCIEXC E-GOSSIP. 



G-EOLOG-R'AL NOTES IX THE ORANGE RIVEB COLONY 



By Major B. M. Skinner. R.A.M.C. 



(Continued from pagt 106.) 



WORKING downwards from the buff sandstone 

 at southern foot of New Fort Kop. the country 

 slopes gently eastward for some distance, showing 

 at the upper part of the slope sandstones, becoming 

 more muddy at the lower part, and succeeded by 

 shales. These outcrops soon disappear, to be found 

 again in the bed and banks of a donga running 

 between New Fort Kop and Naval Hill, where 

 there is first exposed about 4 feet of grey sand- 

 stone, with rounded grey sandstone pebbles : 

 second, a blue-grey shale, very sandy, 2 feet: 

 third, grey thin-bedded sandstone. 1 foot 9 inches, 

 of which two layers were ripple-marked, and others 

 contained worm-tracks; fourth, blue-grey shale 

 varying in shade in different layers, extending 

 downwards some 10 feet, the bottom not being 

 visible. This series gave 45 feet to the top of the 

 buff sandstone. 



Proceeding westward from the same level (the 

 buff sandstone) nearly a mile of doleritic debris is 

 crossed, sloping gently west till the " drift " of the 

 Bloemspruit. where the Kimberley road cross - 

 its bed, is reached. This bed consists of soft sand- 

 stone with imbedded sandstones at some levels, 

 and is at this spot fifty feet below the above 

 datum ; this sandstone extends some distance up- 

 stream, being cut across by a dyke, until buried in 

 alluvial sand. It extends a short distance down- 

 stream, where it is soon succeeded by shales, 

 which are fairly constant down to the town, occa- 

 sionally showing a thin sandstone layer, the same 

 condition being visible in the spruit or donga on 

 the Jacobsdal road. Crossing the Kimberley road 

 drift and turning a little south of west, a gentle slope 

 is ascended, grass-covered, without outcrops, almost 

 at the top of which is a small sandstone quarry, 

 5 or 6 feet deep : at one part large boulders like 

 those at Bustfontein are seen. The top layer of 

 this quarry is sandy shale : the highest point of 

 these strata is 50 feet above the drift. 



Berurning to the Kimberley road, there is a 

 gentle slope upwards towards the west ; at first the 

 road passe.- across sandy debris, then the red debris 

 of volcanic rock, which is continuous to north of 

 road, but is mi x ed with aUuvial sand on the 

 south ; for the ground takes here an extra upward 

 curve, and, after crossing a dolerite dyke, outcrops 

 of grit and sandstone are met with, the first grit 

 being 140 feet above the buff sandstone, and the 

 highest sandstone in the quarry at the top of the 

 ascent 50 feet higher. Here the grits are very 

 marked. This series to the south-west is cut across 

 by dolerite, continuous through Spitz Kop with the 

 western extension from New Fort Kop. Spitz Kop 



is evidently the remains of one of the local up- 

 bursts which overflowed the neighbouring strata, 

 as may be seen on a hill to its south-west, where 

 sandstone and grit are capped by dolerite. The 

 same condition is seen at Haldon Hill, where 

 a denuded surface of grit, curved at the top. 

 has been covered by dolerite. The grits ob- 

 served are occasionally very coarse, entirely 

 formed of quartz ; above or below some layers 

 is frequently a thin layer of sand with largish 

 fragments of angular quartz. To the north of 

 Spitz Kop are two exposures of stratified rock, both 

 showing a denuded surface of standstone which 

 has been overflowed and baked by the dolerite 

 sheet extending to the north and east, referred to 

 above, and which, when denudation has cut away 

 deep enough, generally shows subjacent stratified 

 rocks which furnish evidence by their denuded 

 condition of having formed a land surface before 

 the upbursts of dolerite, as seen at Spitz Kop. 

 Naval Hill, and elsewhere, occurred. Besides these 

 overflows of dolerite there are, in the lower strata 

 exposed in the dongas, dykes which may or may 

 not have extended upwards to the surface of the 

 then existing land. There are also bosses of the 

 same material causing small local dislocations of 

 the strata from the horizontal, evidently showing 

 that the intrusive material had not sufficient energy 

 to push itself further than the level of some of the 

 lower strata. 



On the south of Naval Hill is a succession of 

 alternating shales and sandstones similar to those 

 seen extending upwards from the donga between 

 this bill and New Fort Kop, up to the shale al 

 the white sandstone on the latter hill. The lowest 

 sandstones here show marked current-bedding, 

 with lenticular patches of black shale, sometimes 

 very small sometimes forming a layer 2 or 3 inches 

 thick and 3 or 4 feet long, but failing to give any 

 evidence of structure. A similar, but less marked, 

 condition is seen in one of the sandstones in the 

 small quarry west of New Fort Kop. This sand- 

 stone would be the same as the buff sandstone so 

 often referred to, but the latter shows no sign of 

 current-bedding at its upper part, though it does 

 below ; while the corresponding sandstone in the 

 quarry shows in its lower part some boulders. 



A short distance north of Deale's Farm is an 

 extensive exposure of sandstones and shales- 

 beginning with shales in a donga, passing up to 

 sandstones, the top one of which shows boulders. 

 One layer shows annelid burrows. These strata 

 extend upwards 160 feet, the lowest corresponding 

 with the shale in the donga east of New Fort Kop. 



