Davis — Quarries in the Lava Beds at Meriden. 7 



changes of dip, these changes always departing from the rule 

 of the monocline in such a way as to indicate a dragging pull 

 from the neighboring fault : finally, it is upon these lines that 

 occasional "dikes" of brecciated structure are found, agreeing 

 in strike and dip with the expected attitude of normal fault 

 planes. All these features occur so repeatedly and systemati- 

 cally that the faulting cannot be doubted for a moment when 

 the facts become familiar. One after another of the ridges of 

 lava, sandstone, or conglomerate that continue without inter- 

 ruption across a block will submissively end as they reach the 

 invisible oblique line of a fault. Examples of this submission 

 are so numerous and so systematic that the faulting of the 

 blocks may be considered as conclusively proved as the extru- 

 sion of the lava beds.* 



For those to whom it seems questionable to use lava beds as 

 if they were sedimentary strata, a reassuring confirmation of 

 the occurrence of faults may be found in the repetition of two 

 beds of fossiliferous black shale, one in the anterior and the 

 other in the posterior valley adjoining the ridges of the main lava 

 sheet. Here the more customary stratigraphic argument for 

 faulting, re-enforced by paleontological support, leads to the 

 same conclusion as that already reached, but less definitely to 

 my mind, for the beds of black shale are topographically weak, 

 and are so seldom exposed that they prove only the occurrence 

 but not the location of the faults by which they are dislocated, t 



It is only when the facts and conclusions here briefly out- 

 lined are familiar that the Meriden quarries gain their full 

 value. They are then seen to be not only serviceable as excel- 



* Details concerning the faults m the Meriden district may be found in " The 

 Faults in the Triassic Formation near Meriden, Connecticut/' Bull. Mus. Comp. 

 Zool., xvi, 1889, 61-86. 



f Further details on this subject are given in ;: Two belts of fossiliferous 

 black shale in the Triassic Formation of Connecticut,'' Uavis and Loper, Bull. 

 Geol. Soc. Amer., h\ 1891, 415-430. 



It is well known that observations which are convincing to one geologist may 

 not appeal forcibly to another. This was illustrated by an incident during the 

 excursion made by many members of the International Geological Congress of 

 1891 from Washington to the West. On reaching Salt Lake, a recent fault along 

 the base of the Wasatch mountains was argued from the visible topographic dis- 

 location of the alluvial fans and glacial moraines at the foot of the range ; but 

 the European geologists of the party were so unaccustomed to arguments based 

 on topographic form that with hardly an exception they refused to credit the con- 

 clusion as to recent faulting that had been reached by the geologists of our 

 western surveys. It was only after repeated examples of faulted fans and moraines 

 had been seen during two days of local excursions that a limited acceptance was 

 allowed for what seemed to many of us as a very clear case. With this m mind, 

 the evidence of faulting in the Connecticut Trias, as supplied by the ordinary 

 stratigraphic and paleontological arguments from the black shales, has been a 

 welcome addition to the evidence derived from the lava beds: not, however, so 

 much for its effect on my own belief — for the argument based on the lava beds 

 seems to me conclusive alone — as for the effect it might have on others to whom 

 the lava beds may not seem to be altogether orthodox members of the sedimentary 

 series. 



