Speight. — The Tertiary Beds of the Trelissick Basin. 333 



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difficult to say whether or not this is a slip from solid outcrop in the vicinity. 

 It resembles in character the lower layers of the limestone in position above 

 it, but this is not conclusive proof that it is a slip. 



In Whitewater Creek the sequence is as follows, in descending order 

 (fig. 3) .— 



Limestone, a hard flaky rock, breaking in the upper part into quad- 

 rangular blocks ; thickness, 40 ft. 

 Calcareous tuff, composed of limestone and fragments of volcanic 

 rock, exactly similar to that in the analogous position in Home 

 Creek and Broken River; from 2ft. to 3ft. thick; passing 

 down into 

 Volcanic tuff, 100 ft. thick. 



Limestone, thickness about 25 ft. : this may be a part of the upper 

 portion of the limestone beds. 

 These beds strike N. 60° E., and dip in a westerly direction at an angle 

 of 20°. 



In Volcanic Creek the beds have the same dip and strike, and are as 

 follows : — 



Limestone, the lower portion having a definite jointing into quad- 

 rangular blocks ; the upper portion like the ordinary upper 

 limestone in general appearance, but corals were absent in the 

 specimens examined. There was a distinct separation into two 

 facies, but no unconformable junction, and no tuff beds between 

 them. Total thickness, 80 ft. 

 Calcareous volcanic tuff : This is well bedded and clearly exposed 

 under the limestone, and similar in lithological character to those 

 beds in the same position elsewhere. 

 Volcanic tuff, of uncertain thickness. 

 There is no appearance of a lower band of limestone on the banks of 

 this creek, but it may be covered up by surface accumulations ; some 

 indication of its presence should, however, be apparent. This absence 

 increases the probability that the lower band of limestone in Whitewater 

 Creek is only slip from the one bed which is in position, and that there 

 are not two limestones. 



Traced towards Coleridge Creek the limestones appear to thin out and 

 lose their distinctive character, especially in the lower part of the creek, 

 where the volcanic tuffs are so well developed. The band of limestone 

 dips to the west, but it is bent round in the form of a syncline and, passing 

 close to the sheepyards, meets the creek again higher up and crosses it to 

 the northern side. 



The succession here is as follows : — 

 Limestone. 



Volcanic calcareous tuff, full of fossils. 

 Volcanic tuff. 



Limestone, 100 ft. to 150 ft. thick. 

 These beds are bent round on leaving the creek lower down, but at the 

 upper crossing they have a north-easterly strike and a dip to the north- 

 west at very high angles. 



On the western side of the basin there are numerous isolated blocks of 

 limestone, detached from the main mass probably by a fault running north 

 near the base of the Craigieburn Range, which is probably distinct from the 

 main fault movement which bounded the area to the west. These blocks 



