114 



CRETACEOUS ROCKS OF S. INDIA. [pART II. § 1. 



lithologicalljs except that in the latter AVere intercalated thin plates of Gypsum which were 

 absent in the former. This explanation once clearly established, was of much importance, as 

 Importance of the indicai ion it proved how unreliable is the most regular and persistent apparent 

 Diereby afforded. stratification in these beds, and gave me a clue which proved of 



much service in elucidating similar anomalies in the mass of the group to the Eastward. The 

 section will be rendered more clear by the accompanying diagram, which represents an imagi- 

 naiy section across the Trichinopoly group, a little to the West of Paroovalapoor. 



Fig. 12. Sketch Section of the TKiCHiNoroLY Group. 



JL mile- 



Beds East of Paroovalapoor. 



g. Gneiss; o. Ootatoor beds,- t. Trichinopoly beds. 

 Crossing the nvdlah to the East of Paroovalapoor, the Trichinopoly beds spread out in 

 all dii-ections. To the South and East they fill a bay-shaped 

 depression in the gneiss, (4 miles across) and the same distance 

 m depth ; the beds resting on gneiss on the "Western boundary and on the coral-limestone of 

 Cullygoody to the Eastward, while their Southern exti-emity is concealed beneath the alluvial 

 deposits of the Cauvery vallej^, which lap roxmd the extremity of the Thutchuncoorchy 

 granite ridge. 



The beds exposed between Paroovalapoor and Seeroovoyalore are sands and sandy shales, 



„ with conglomerate, omewhat irregularly stratified, but with a 



Beds around Thapaye. o > o j o ■■ 



general low dip to the North-east, or away from the gneiss. South 



of this village little is seen of the lowest beds, owing to the increasiag thickness of the super- 

 ficial alluvium : the ■\dllage of Thapaye stands a mile to the Eastward, on a bed of granitic gravel, 

 and both to the North and South of it are accumulations of quartz, granitic, and gneiss 

 pebbles, in-egularly iatercalated in the bedded rocks. To the East and South-east again 

 follows a great mass of fine argUlaceous shale, sometimes gypseous, and sometimes full 

 of kunkiu', and closely resembling the mass of the Ootatoor beds. Bands of a calcareous 

 conglomerate and blue Limestone are occasionally iatercalated -with these, but fossils are 

 scarce. Almost the only species met -svith is a Natica, closely resembling the Kaiica 

 Pagoda of the Valudayur group. AH these deposits dip at low angles, and on the whole 

 to the North-east, as far as the Palambaddy millah ; beyond which the dip is in the opposite 

 direction, and generally low. 



The mass of the beds with an Easterly dip is much greater than that with a dip in an 

 Prevalent Easterly dip of opposite dii'ection, and ia some places the Easterly dip continues to 

 ^ ™^' within a short distance of the Eastern boundary, thus repeating 



on a larger scale the phenomena exhibited by the beds North-west of Pai'oovalapoor. Irregula- 

 i-iaties of bedding, accompanied by sudden changes of mineral character, are frequently met with 

 in this part of the group, and I cannot doubt that the incUnation of the beds is due to original 

 drifting of the sediment, that from the "Westward predominating ia amount. 



