1840.] 



On the Geology of Cutch. 



Alternation of Basalt with Travertin. — A very good example of suc- 

 cessive eruptions of basalt occurs near the small village of Wurrowsow^, 

 on the south-western flanks of the Charwar range. This point must at 

 one period have been a lake, it being now a dead flat, about 4| miles 

 in diameter, and surrounded by low but steep hills, whose surfaces 

 are covered with small fragments of basalt ; its general level is about 20 

 feet above the ground to the east of it. The soil consists of alluvial 

 matter and fine gravel, totally different from ihe sandy plain by which 

 it is bounded ; but its most interesting feature is the basalt at the eas- 

 tern outlet or break in the low surrounding hills. This mass of trap 

 consists of perfectly polygonal columns about 25 feet in height, but 

 broken into lengths, forming a series of regular steps, cut into a horse- 

 shoe shape by a small stream, which discharges itself during the rainy 

 season. The hills that flank it on each side are composed of a base of 

 coarse sandstone capped by an earthy basalt, a dyke of which, 8 or 9 

 inches wide, has, in one spot, penetrated the subjacent sandstone. 



The friable basalt forms the base of the fall. Above the columns 

 the bed of the small stream consists of a loose, calcareous calc-tuff. 



This section presents several interesting facts ; as, from the alterna- 

 tion of basalt with the limestone or travertin, it is evident, that a consi- 

 derable time must have elapsed between the igneous eruptions. The 

 variety in the texture of the limestone or travertin may be accounted 

 for by supposing, that the waters under which it was deposited were 

 sometimes perturbed, or rendered muddy by a flood ; but at other sea- 

 sons clear, when a pure calcareous precipitate would take place. The 

 basalt forming the columns is very hard, compact, of a dark blue colour, 

 and smooth surface ; and it may be traced to some small hills northward 

 of the spot. 



Near this place the surface has been affected in a manner worthy of 

 observation. Every here and there, a small spot, varying in size from 

 3 to 20 yards in diameter, has been raised into a convex form ; th« 

 pavement, that covers it, consisting of tabular plates of slaty sandstone, 

 broken into small masses ; and the fractured lines generally radiating, 

 though in an irregular manner, from a centre. In some places the tops 

 of these little globular elevations have been removed, leaving a regular 

 circle of stones, whose bounding lines are disposed like the stones of an 

 arch. In other instances they assume a more conical shape, resembling 

 small hillocks, from the upper part of which the outer coating or tabular 

 masses have generally fallen away. When they are of a larger character, 

 the whole presents a heap of broken masses of rock. 



