STUDIES FOR STUDENTS 171 



trating sediments. It is generally interstitial, in contrast with the 

 preponderant matrix of raft breccias, but about the margins blocks 

 projected farthest may be found sporadic. 



Talus and landslide breccias may be discriminated from each 

 other by their characteristic profiles — the even and smooth slope 

 talus and the hummocky surface of the landslide — by the longer 

 extension of the landslide from the parent cliffs, and, in the follow- 

 ing example, by the landslide ' tearing up the sediments of the sea- 

 floor over which it moves and mingling them with its own debris. 



The very interesting Jurassic breccia of the Ord, on Moray 

 Firth, Scotland, is pretty certainly due to a landslide fallen into the 

 sea. 1 The strata among which the breccias are imbedded consist 

 of finely laminated shales with occasional thin seams of limestone. 

 Hence the water in which they were laid was quiet, unvexed by 

 powerful waves or currents. The littoral fossils — ammonites, 

 corals, etc. — show that the deposits are marine and indicate the 

 close proximity of the shore. This is confirmed by numerous 

 remains of cycads, ferns, and conifers apparently drifted in by rivers. 

 Both fauna and flora prove the warmth of the climate and forbid 

 the assumption of an ice raft as the means of transportation. The 

 breccia is contemporaneous with the Jurassic beds in which it lies, 

 but it is not intraformational, since its fragmental material is 

 derived from the Old Red Sandstone which occurs in the immediate 

 vicinity. The fragments vary in size from chipstone to blocks 10 

 feet in diameter. The majority are sharply angular, some show 

 signs of attrition on the edges, and not a few, especially those of 

 smaller size, are completely rounded. They are heaped together 

 in the wildest confusion. The upper surface of the breccia beds is 

 irregular, and the strata deposited upon it show the influence of 

 its projections. The breccias vary in thickness from a foot or two 

 to 50 feet. The matrix is fossiliferous with contemporaneous 

 Jurassic fossils in a more or less comminuted condition. In places 

 are found numerous masses of Jurassic reef -building coral torn from 

 their bases and heaped in all positions among the debris. 



1 J. W. Judd, "The Secondary Rocks of Scotland," Quar. Jour. Geol. Soc. London, 

 XXIX (1873), 187-95; J. F. Blake, "On a Remarkable Inlier among the Jurassic 

 Rocks of Sutherland," ibid., LVIII (1902), 290-310. 



