APPENDIX. 43 



Narbada Valley, showing laterite underlying and interstratified with beds contain- 

 ing nummulites. At Wagulkhore 1 he found the following section (in ascending 



order) :— 



Laterite. 

 Yellow clay. 

 Pipe clay. 

 e Sands passing up into 

 Ferruginous ^ Limestone with nummulites, gasteropods, &c. 

 Sandstone. 



Laterite containing, in places, pebbles. 

 In one place the fossiliferous stratum is hardly distinguishable from laterite. 

 Other sections show laterite beneath a set of sedimentary beds and near Tur- 

 kesur 2 a bed of laterite appears to lie between two beds of Nummulitic Limestone. 

 Somewhat similar cases are described by Mr. Wynne 3 in Kach. Laterite 

 occurs regularly interbedded with the tertiary nummulitic beds, and there is also a 

 subtertiary laterite. He figures an interesting case 4 (at Chaper) of a bed of late- 

 rite overlying a white unctuous rock and sending down stalactite-like processes into 

 it, which are evidently due to infiltration. 



Mr. Foote, 5 in his Geology of Madras, shows clearly that the laterite of that 

 part of the country is of sedimentary origin. It frequently contains pebbles. The 

 highest laterite lies about 500 to 600 feet above the sea. Palaeolithic implements were 

 found in situ in the laterite, showing that the rock was in process of formation after 

 the appearance of man upon the earth. Mr. Foote considers the laterite to have 

 been formed in the sea, and suggests that the iron may be derived from magnetic 

 iron sand. The greater the proportion of magnetic iron mixed with the other sand, 

 the more ferruginous would be the laterite formed. At the present day large areas 

 on the Coromandel Coast are black in colour, the colour being due to magnetic 

 iron sand. 



Mr. Theobald, 6 in his Geology of Pegu, appears to consider the laterite of 

 Pegu as due to the lateritisation, or, as he proposes to term it, the laterosis,oi allu- 

 vial clays. He looks upon the laterite bordering the Poungloung range as the 

 marginal deposit of a basin which has since been filled with alluvial clay. 



In the South Mahratta country Mr. Foote 7 separates the laterite of the Ghats 

 from that of the low country of the Konkan, and adopts Voysey's name— iron-clay — 

 for the former. He considers the iron clay to have been formed by decompo- 

 sition in situ of the trap rocks. There are numerous sections showing the passage 

 of the basalt into a brownish earthy mass containing nuclei of the original rock. 

 In the upper parts of the section the nuclei have disappeared and " a process of 

 concretional solidification from the infiltration of surface waters holding iron in 

 solution" has converted the rock into laterite. In only one case (viz., at Chapoli, 

 where quartz pebbles were found in the rock) was there any evidence of sediment- 



1 Mem. G. S. I., VI, 362. 



2 Loc. cit., p. 367. 



3 Mem. G. S. I., IX, 1. 



4 Loc. cit., p. 69. 

 »Mem.G.S. I., X, 27. 

 6 Mem. G. S. I., X, 244. 



' Mem. G. S. I., XII, 200. 



( 243 ) 



