PAKT 4.] 
Wynne : Geology of Mount Tilla, Punjab. 
85 
It will perhaps be observed that—though, as has been said, the lofty portion of the 
ridge of Mount Tilla coincides with a fractured anticlinal curvature of the strata which 
might bo expected to assume approximate horizontality on the axis of the ridge—the height 
of the hill is given at over 3,200 feet, while the total amount of the thicknesses of groups in 
the sectional table only reaches about 1,000 feet, excluding the tertiary Si valik rocks 
which mainly lie in tho plain below and on the northern slopes of the hill. To explain 
this seeming discrepancy, it may bo stated, 1 st, that the height of 3,200 feet is attained 
by the mountain just at the point where the beds commence to turnover: 2 nd, that the 
axis of the contortion rises towards the summit of the hill: 3rd, that 800 or perhaps 900 
feet must he allowed for the height of tho general southern base (the outcrop side) of the 
mountain, and that a considerable sloping talus above this is formed of slipped masses 
and debris at the top of which the section of the vertical cliffs begins to become visible. 
Added to these there are three, if not four, step-faults along the south-eastern side of the 
highest part of the hill, each of which repeats some portion of the strata, as seen in the 
accompanying sketch section :— 
Mount Till a 
5242 . 
1000 {eel V't.rhaal. 
One Milt — Gor ox onhxd 
Section across Mount Tilla, looking south-west. 
1. Purple sandstone. 4. Red, shaly, and flaggy zone. 
2. Black, shaly zone. 5. Nummulitic limestone. 
3. Pseudo-limestone and compact sandstone. 0. Tertiary (Sivalik) beds. 
With regard to the physical structure of the remainder of the hill, the upper portion of 
the anticlinal curve expands to the west, beyond two deep coombs or glens, one of which opens 
broadly to the south, but enters into the very heart of the mountain ; this expansion of the 
arch being accompanied by so slight a southerly dip that the lower members of the series 
present,_ even to the lowest of all (the red marl), appear at tho base of the hill along a line 
which sinks gently to the west-south-west. 
Along the Boonhar fault in this neighbourhood, some difference in the section is per¬ 
ceptible, the group No. 2 of the above figure having apparently thinned out both on the Tilla 
and the opposite side of the gorge : the purple band beneath seems to he also thinner; but the 
ground is much obscured by local slips, small faults, and large detritus from the pseudo-lime¬ 
stone group which, with many undulations, sheets the hilly ground or plateau about Chova. 
Beyond tills plateau and above it. a somewhat tortuous cliff-line extends along the brow 
of the hill, broadly edged by the nearly horizontally rolling beds of the red, flaggy, and shaly 
band; while the tertiary strata of the plain beneath rise at a steep angle on the northern 
slopes, and, like the crest of a wave, overlap the ridge, forming most of the lol'tv ground 
westward of the summit. 
Tim extreme western termination of tho hill is very abrupt, and some complicated faulting 
occurs just at Pind So yield, the last of tho high ground being formed of the red, flaggy, nnd 
the underlying group, either vertical along a west-north-west line (coinciding with” that of 
the Chambal scarp), or dipping with the steep ground at high angles to the westward, hut 
