80 CRETACEOUS ROCKS OF S. INDIA. [PaRT II. § 1. 



case whore the Ootatoor beds re-appcar close to the gneiss of Scraganoor. A little gully, 



about half a mile North of the Tillage, after cutting through some coarse conglomerates and 



sands of the Trichinopoly group in the upper part of its course, exposes, a few yards lower down, 



^ , „ the fine flakev clays of the Ootatoor rocks (the bedding of which 



Fault at Seraganoor. _ . v o 



is rendered very distinct by some of their intercalati-d arenaceous 



bands,) dipping at angles of 80° and 90° and at one spot reversed.* The whole extent of beds 



exposed in this little nullah does not exceed a few j^ards, and the disturbance, however intense 



at this spot, is probably very local. The gneiss occurs in situ a few yards to the South of the 



nullah, and there can be no doubt that the Ootatoor beds are faulted against it, but on following 



the boundary to the East of the Trichiuopoly road, no traces of dislocation are discoverable, and 



Character of boundary to ^ many places the Ootatoor beds evidently rest undisturbed on the 

 E ast of Seraganoor. ^eiss. At two other points only on this boundary ; (first, to the 



East of the little Trichinopoly outlier of Muddam, the second, in a small nullah about a 

 mile to the North-west of Peria Koorkay,) were there any indications of fractiure in 

 the Ootatoor beds; and both of these were quite insignificant in amount, while in the 

 intervals, beds undoubtedly at the base of the Ootatoor Group, are seen restiag on the gneiss . 

 In the numerous little sections of Ootatoor beds exposed in the banks of the nullah that drain 

 the high ground round Muddam and Agaram, amid frequent iiTegularities of dip, I have never 

 observed any case of undoubted fracture or indication of violent disturbance, I am inclined, 

 therefore, to believe that the Southern boundary of the Cretaceous rocks between Seraganoor 

 and Paroovalapoor is formed by several little faults with intervals, in which the Ootatoor beds 

 rest undisturbed on the gneiss. The Trichinopoly beds, which will be described further on, 

 are in all cases quite undisturbed. 



To the East of Seraganoor the ridge along which the new Madras road runs, is thickly 

 covered vsdth cotton soil, beneath which the Cretaceous rocks are concealed. To the east 

 of this a large area of broken ground, stretchiag away to Agaram and Paroovalapoor, exposes 

 the Ootatoor beds very clearly, with irregular patches of the Trichinopoly beds as before, 

 along their Southern boundary. 



On the Northern boimdary the junction of the gneiss and Ootatoor beds is exposed in several 



Beds to East of Madras little nullahs which cut deeply into the Cretaceous rocks. 

 ^o^^- The latter rest on a highly inclined gneiss cliff, in accordance 



with which the lowest beds dip, so as to present much of the appearance of faulting. There 

 is, however, no evidence of any disturbance, and the bedding follows the irregularities of the 

 gneiss in such a manner as to prove that its high dip is that of original deposition. At a 

 few yards distance the dip diminishes generally to 2 or 3 degrees, but about half a mile to 

 the South the high dip again obtains, in an opposite direction, or towards North-west and away 

 from the Southern boundary. At the "Western extremity of the Trichinopoly outlier of Mud- 

 dam, the junction of the gneiss and Ootatoor beds is exposed in a little nullah, but the 

 section is not veiy clear. The latter beds are fine brownish laminated clay, dipping where 

 close to the gneiss, at an angle of only 4° or 5° a dip, which increases to 15° at a few yards 

 distance ; close by they are capped with masses of fossiliferous conglomerate belonging to the 



* These clays are intersected with irregular lines of a soft white mineral resembling chalk, 

 which crushes readily between the fingers, and proves, on examination, to consist of almost pure 

 carbonate of lime. "We shall meet with it again in great abundance in the clays of Ootatoor, 

 where I shall describe it more fully. 



