594 JOURNAL, BOMBAY NATURAL HLST. SOCIETY, Vol. XXVII. 



would indicate that Worli Hill formed at this period the shallow bank of the 

 lake. There is no means for the present of deciding as to what was the sub- 

 soil on which this lake stood, but the probability is that it consisted of trap. 

 Trap must have been pre-existing for there are large pebbles of volcanic origin 

 found embedded in these beds and the crystalline nature of the material of the 

 shales shows the, detritus to be of volcanic origin. The lakes were most 

 probably caused by the unequal weathering and denudation of the surface of 

 the original rock or by different lava flows crossing each other and thereby 

 causing hollows. So far no dykes have been met with in the sedimentary 

 beds and in their absence the second hypothesis must be considered as the less 

 probable. 



As previously stated the lowest sedimentary beds have been greatly altered 

 by the effusion of the lower trap and it would be idle to speculate as to whether 

 they were deposited by floods or by gentle waters. But coming to the lowest 

 frog bearing bands it is clear that they were deposited in a very fine sediment 

 in quiet water. The first band is about 4 inches thick and is full of frog impres- 

 sions. It is a dark coloiired shale and splits into very thin laminae. Soon after 

 there seems to have occurred a period of floods which caused a layer about 9 

 inches thick of a coarse grained ashy grey sediment. Then recurred a further 

 period of calm days which caused the second band of frog bearing shale 

 which is in all respects similar to the former one but the layers are in a very 

 much weathered state. Some soil seems to have been formed on the surface. 

 It would appear that after this layer was deposited there was a considerable 

 change in the level of the lake due probably to secular upheaval which caused 

 this layer to be exposed to atmospheric influences. Then a reverse movement 

 seems to have set in and what was dry land became a raging torrent. 

 Heavy floods passed over it resulting into very thick deposits of coarse light 

 coloured shales which contain not only gravel and pebbles but even bits of 

 charcoal washed down from distant forests set on fire by thunderstorms. 

 Even some of the pre-existing aqueous beds seem to have been broken and 

 carried away as large angular pieces of the shale are found embedded in the 

 grey shales. The extent and the violence of the floods seem to suggest that 

 there occurred a breach in the banks of the lake thereby converting it into a 

 tumultuous river. 



These floods brought down large quantities of vegetable matter from the 

 aforesaid forests judging from the fact that it arrived at Worli in a highly bruised 

 condition. Were it not so there would have been found at least occasionally 

 some distinguishable impressions of leaves, etc., in these highly carbonaceous 

 shales. The vegetable detritus came to rest in the coves in the marghi of the 

 lake so that the carbonaceous shales are found in fairly thick isolated deposits 

 practical^ forming pockets in the grey shales ; they are never continuous. Large 

 pebbles of igneous origin are invariably associated with these deposits. The 

 frogs seem to have survived through these cataclysms but in very much smaller 

 numbers ; they must have been washed away to the ocean. On what these 

 frogs were feeding is not easy to say. 



Subsequent to this period there occurred floods of lesser violence which have 

 caused alternating layers of dark and light coloured shales. Some of these layers 

 are very thin indeed, and it is a question as to what were the determining causes 

 of these rapidly alternating layers of such minute thickness. It may be that 

 one grey and one dark band is the result of one flood, the grey material being 

 heavier and settling earlier than the darker sediment. These dark bands give 

 a very interesting appearance to the section of the quarry. Towards the 

 close of this period some logs of wood drifted to this place and are now found 

 as fine anthracitic coal embedded in the grey shales. There are no positive 

 indications that there were any trees , shrubs or aquatic plants growing on the 

 margins of this lake or river. Nor are we in a position to say deflnitely whether 



