290 



THE CARBONIFEROUS ROCKS AT RUSH. [May I906. 



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(/) The Cyathaxonia-Be&s. 



These beds, which extend northward from 

 the Bathing-Place, on the north side of Rush 

 Bay, past Giant's Hill and Brook's End (where 

 the section, so far as the present paper is con- 

 cerned, finishes), are characterized by con- 

 taining a highly-specialized coral-fanna in 

 which species of Cyathacconia are dominant, 

 and they form a special phase of the Upper 

 Dibunophyllum-Zone which Dr. Vanghan pro- 

 poses to call the Cyat7iaxonia-s\\bzoi\e. The 

 beds consist in part of evenly-bedded lime- 

 stones with partings of shale, and in part of 

 thin limestones, usually earthy-looking, and 

 arranged in beds only 1 to 3 inches thick, 

 though several such beds are often welded 

 together to form one thick bed. Many of these 

 thin limestones have a peculiar nodular- 

 looking structure, which gives them an 

 1 augen '-appearance that easily serves to dis- 

 tinguish them from any of the beds hitherto 

 seen in the Eush coast-section. Interstra- 

 tified with them are frequent partings and 

 beds of shale or shaly limestone, seams of 

 chert, and occasional thicker pure limestone- 

 bands, not of the ' augen '-type, which, how- 

 ever, do not often exceed 7 or 8 inches in 

 width. 



The stratigraphical arrangement of the beds 

 is interesting. Their strike is a little to the 

 north of east, their dip is often high, and 

 the beds are folded and sometimes inverted. 

 Where they are first seen at the Bathing-Place 

 they emerge from the shore in several small 

 folds, of which one anticline is well exposed. 

 In the little cliff at the Bathing Place, there 

 is a northerly dip at 80° and over, and two 

 small thrusts are seen, intersecting at the 

 foot of the cliff (fig. 9, p. 291). Some quite 

 thin limestone-bands between the two thrusts 

 are much contorted and shattered ; and some 

 imperfect cleavage in the shales is noticeable, 

 the cleavage dipping to the south. The beds 

 pass up, in a few feet, into highly-contorted, 

 decomposed shah' beds with included seams 

 of chert. It will be shown presently that 

 these are decalcified beds. They form a 

 syncline beyond which the limestones again 

 emerge, dipping southward at an angle of 40° 

 to 50°, while two or three adjacent beds form 

 the long cliff-slope that bounds the south side 



