12 Davis — Quarries in the Lava Beds at Meriden. 



of the filling is of trap fragments ; but the space between the 

 angular blocks of trap is generally filled with a matrix of sand- 

 stone or sandy shale ; not fragments of bedded sandstone and 

 shale, but a recomposed mass, presumably derived in the form 

 of sandy or muddy powder from the grinding of overlying 

 sandstones and shales at the time of faulting. All the ordinary 

 features of fault structure may here be studied to good advan- 

 tage.* 



The amount of movement on the fault lines reaches fifteen 

 or twenty feet in the best examples now exposed ; this being 

 on the little hill of rock left standing between the two northern 

 quarries, where the vesicular surface of the lower lava bed is 

 dropped by nearly twenty feet on the northwest side of the 

 fault. This dislocation is very clearly exhibited at present. 

 Several smaller examples of measurable throw occur in various 

 parts of the quarries. The trend of the fractures varies 

 from about north-northeast to northeast, the latter direc- 

 tion being that of a little swampy water course that ob- 

 liquely terminates the quarry ridge on the south. The 

 rock exposures nearest to this little valley are the weath- 

 ered breccias on the margin of the southern quarry, and 

 there is every reason to think that the valley itself is nothing 

 but the topographic expression of a broad band of fractured 

 rock, produced by a strong fault. The distribution of ledges 

 and ridges in the neighborhood gives full support to this idea. 

 Just across the little valley is the northern end of a ridge of 

 conglomeratic sandstone, whose strike would carry its strata 

 directly into the lava beds. Although the lavas were poured 

 out previous to the deposition of the overlying fragmental 

 beds and although the pebbles of the conglomeratic beds give 

 evidence of rather active currents, no trap fragments are to be 

 found among the pebbles ; and this increases the presumption 

 that the two masses — the lava beds and the conglomeratic 

 sandstones — do not lie in their original relative positions, but 

 have been brought into their present relation by faulting. 

 Adopting provisionally the general course of the little valley as 

 the trend of the dislocation separating the two dissimilar ridges, 

 and walking northeast or southwest, abundant confirmation of 

 this idea is found. The sandstone ridges, coming northward 

 towards the line of the supposed fault, end on reaching it in 

 the submissive manner already described ; and at a distance of 

 several miles to the northeast, the northern eads of the anterior, 

 main and posterior sheets of the Lamentation block are simi- 

 larly truncated. The uplift of the fault is then seen to be on 

 the eastern side, and its movement approaches two thousand 



* Details are given in the article on "The Faults in the Triassic Formation near 

 Meriden," already referred to. 



