January 26, 1900.] 



SCIENCE. 



141 



etc. M. E. Campbell remarked the possi- 

 ble diagonaling of sandstone and shales, 

 and the pinching out of some. J. J. Stev- 

 enson corroborated I. C. White's state- 

 ments to the letter, and insisted that the 

 difference was a botanical and not a strati- 

 graphic one. H. S. Williams supported 

 David White by analogies drawn from the 

 Catskill problem. I. C.White, in reply, again 

 described the continuity of the Upper Free- 

 port with the Stockton. He also stated 

 that the marine forms contradicted the 

 plants ; that an abundant marine fauna be- 

 neath the Eagle coal corresponded with that 

 of the ferriferous limestone. H. S. Wil- 

 liams- and then I. C. White spoke again, 

 but it was evident that there was a dead- 

 lock between the paleobotanists and the 

 field geologists. The difference was so pro- 

 nounced that all the rest of the Society 

 hoped the two Messrs. White would go to- 

 gether over the field from one end to the 

 other and report at a later meeting. 



NEWARK FORMATION OP THE POMPERAUG 

 VALLEY, CONNECTICUT. 



William Herbert Hobbs, Madison, Wis. 



The ISTewark formation of the Pomperaug 

 Valley rests unconformably upon and is 

 entirely surrounded by Cambrian and pre- 

 Cambrian gneisses. Its sedimentary beds 

 consist mainly of material of other than 

 local derivation, associated with which are 

 sheets of basalt which were once poured out 

 at the surface. Subsequent to their forma- 

 tion the rocks of the area were elevated, 

 tilted to the southeastward at a low angle, 

 and while in this inclined position depressed 

 an amount not less than 2000 feet. This 

 depression of the area was accomplished 

 through an elaborate system of dislocations 

 (gravity faults) involving hundreds of in- 

 dividual fault planes. Of these more than 

 200 have been mapped. 



The fault planes as mapped are quite 

 regularly spaced. The area is thus cut up 



into blocks of regular shape, and these 

 blocks are in some cases found to be further 

 subdivided by parallel faults of small 

 displacement until the faulting passes 

 ultimately into prismatic jointing. The 

 directions of the fault planes, which have 

 almost a vertical hade, bear N. 54 J° E., IST. 

 5^° W., N. 16° E., and K 34° W., with less 

 common faults in other directions. Wher- 

 ever large displacements have resulted from 

 faulting, they are found to be distributed 

 over a number of parallel planes, so as to 

 produce a regular step, or rampart structure. 



The crystalline gneisses and schists sur- 

 rounding the basin of the Pomperaug 

 Valley have been deformed by faulting in 

 the same manner as the Newark rocks 

 themselves, thus making it clear that the 

 theory of " lateral compression and differ- 

 ential faulting by accommodation of beds 

 within the gneiss formation " cannot ex- 

 plain the faulting of the Newark formation, 

 as has been claimed. 



The peculiar block faulting discovered 

 within the area has brought about a num- 

 ber of topographic forms of relief that have 

 not before been recognized. The drainage 

 of the entire area is found to conform to 

 the deformation, so that both major and 

 minor streams run in courses like eaves- 

 gutters — broken lines with sharp elbows, 

 the elements in the course corresponding 

 in directions with the fault directions named 

 above. The stream channels are generally 

 square in cross section, with a level floor of 

 nearly uniform width, similar to that of an 

 artificial canal. The Pomperaug River, 

 which drains the area, is an illustration of 

 reversal of drainage brought about by the 

 ' discovery ' of an upfaulted block of 

 gneiss in its bed. This has resulted in 

 producing a new base level with the forma- 

 tion of a lake above it, which in a later 

 stage has been drained by the pushing back 

 of the divide of one of the principal tribu- 

 taries, so as to capture the headwaters. 



