314 Geology of 



upon the lower end of which the town of Timara is situated, is the largest 

 remnant. The best section to be obtained of the relations between 

 the dolerites and calcareous rocks, also forming here the uppermost 

 beds of the Oamaru formation, is in Mount Horrible, about 12 miles 

 from Timaru, rising 113S feet above the sea-level. From here to the 

 sea, the coulees of dolerite can be traced almost without intermission, 

 showing first; that they gradually get thinner as we advance towards 

 the coast, and also that their fall is very slight, being for the last seven 

 miles only about 90 feet in the mile, or 1 foot in 58, the inclination 

 indeed being almost imperceptible. Thus one of the streams, which on 

 Mount Horrible, where they appear almost horizontal, is about 50 feet 

 thick, dwindles down to four feet near Timaru. The streams consist of 

 a basic rock (Anamesite), porous, and resembling the uppermost beds 

 in the Malvern Hills. Upon the calcareous greensand, forming the 

 upper bed of the Oamaru formation, and which is often so rich in 

 carbonate of lime that it can be used for the limekiln, a bed of volcanic 

 tufa reposes, sometimes changing into an agglomerate, after which the 

 first lava-stream appears. Then follow a number of tufaceous beds 

 with some smaller lava streams between them, till the uppermost 

 coulee is reached, having like the lowest one also a thickness of about 

 50 feet. This anamesiric rock is extensively quarried near Timaru, and 

 forms a valuable building stone for that town. A similar coulee occurs 

 at the "Waihi Bush, between the Eiver Waihi and Hae-Hae te Moana 

 creek, both affluents of the Opihi. There also it covers strata of a 

 calcareous nature, belonging to the Oamaru formation. More to the 

 south, no volcanic rocks of any kind are to be observed, but in the 

 greensands underlying the calcareous beds, lapilli of basic lava are 

 not unfrequent. They might have some connection with the volcanic 

 eruptions during which the lava-streams near the Otepopo river in 

 Otago were ejected, and which are found in a similar position. There 

 is thus sufficient evidence that submarine volcanic eruptions were of 

 not unfrequent occurrence in our tertiary seas. 



Age kst> Thickness. 



From the nature of the lowest beds of this formation, we must con- 

 clude that they were only deposited after the strata forming the 

 "Waipara or cretaceo-tertiary series had undergone considerable changes, 

 and a large amount of denudation. Moreover, it is clear that these 

 older marine beds, in many instances, were uplifted from the ocean, 

 and that the newer beds were deposited upon them, either as littoral 



