40 FOOTE : GEOLOGY OF MADURA AND TINNEVELLY DISTRICTS. 



To the east, and especially to the south-east of Mana-Madura, is a 

 Mana-Madura sec- large show of grits of white or yellowish or mottled 

 ^^°^^- colours. Though a large surface of the grits is 



exposed, the sections are very shallow ones, and afford little information 

 about the formation. The beds dip east at very low angles or roll about 

 gently. Near Pikulam (Pecolum) the overlying lateritic beds have 

 escaped denudation, and they pass below the alluvium, thus masking the 

 grits which are however seen in one or two places in irrigation channel 

 sections south of Vunneygoody, the most southerly exposures of the 

 Cuddalore rocks in Madura district. 



The gritty sandstones which occur at intervals along and near 

 to the coast of the Ramnad zemindari are all of unequivocally marine 

 origin, as shown by the numerous marine organisms they include, 

 and no connection is known to exist between them and the sub-lateritic 

 series in this quarter, though there is in many cases very great petrolo- 

 gical resemblance between the whitish or greyish varieties of both series. 



Section determining ^^ *^® ^^^' south, however, one section was met with 



the age of the Cuddalore in the right bank of the Yellava Odai, a tributary 

 sandstones as sub-recent. . - . . 



of the Nambi- Ar in which a very decided connection 



exists between one of the sub-recent marine beds abounding in fossils and 

 a very typical whitish grit having the strongest possible resemblance 

 to the grit beds at Mana-Madura, and in many sections of the Shahkotai 

 patch. If the petrological similarity between the typical Cuddalore grits 

 and these South Tinnevelly grits be accepted as sufficient evidence to 

 identify them, then the age of the Cuddalore and Rajahmundry beds is 

 established to be not tertiary but recent. This section will be described a 

 little further on. 



The most northerly occurrences of beds supposed to be of Cuddalore 

 Sections in Tinnevelly ^S^ ^cen in Tinuevelly district occur in the south- 

 district at PettakulDin. western part of the Tenkarai taluqs to the north- 

 east, east, and south-east of Pettakulam (Vaulacolum of map.) The 

 grits are exposed only in well-sections, the general surface of the country 

 being thickly covered by blown sands or by local alluvia. The grits 

 ( 40 ) 



