SURFACE FORMATIONS OF SOUTHERN NEW JERSEY. 485 



The oni2;inal nortluvard extension of the formation is unknown, but it would 

 seem that it must have reached at least as far north as the Watchunt; mountains. 

 There is some reason to believe that it extended even farther in this direction. 



AGE OF TUB FORMATIOS 



It has long been insisted* that this member of the " yellow gravel" series was 

 much older than the Pleistocene. On the basis of certain identifications which 

 have been made by Professor Clark in the vicinity of Freehold, the various isolated 

 remnants of sand and gravel in the positions specified are regarded as JMio(;ene. 

 The argument is simply this: If Professor Clark's identification of Miocene beds 

 near Freehold be correct, all the dissevered remnants here referred to are also 

 Miocene. l*rofessor Clark thinks that tiiese beds are to be connected with forma- 

 tions farther south, which carry fossils by means of which their Miocene age can 

 be fixed. 



OROGEXIC AXD EROSIVE CIIAXGES 



The distril)ation of the formation is such as to show that after it was deposited 

 there was a very considerable uplift, accompanied by a very considerable deforma- 

 tion, both of the Beacon Hill and the Cretaceous beds, and that a long i)eriod of 

 erosion followed. This was more effective to the north, where the formation was 

 high, and was less effective to the south, where the formation was low. 



During this erosion interval the northern part of the present Cretaceous area of 

 the state was cut down nearly to a plain. High hills remained at a few points 

 only. After the surfiice was reduced to a peneplain it would appear that valleys 

 were cut in it down nearly to the present level of the sea. Tiiis condition of 

 things would seem to suggest a bifold elevation. After the first the peneplain 

 was developed, and after the elevation of the peneplain valleys were cut in the 

 same. Before they became wide, subsidence set in, and the lower part of the pene- 

 plained surface was again brought below the level of the sea. 



Pensauken Formation 



IJISTRUn'TIOX 



On this surface wa.s accumulated the second member of the " yellow gravel " 

 series. This is known as the Pensauken formation, from the locality near the 

 mouth of Pensauken creek, just below Palmyra, where the formation is well ex- 

 posed. It is also well exposed in the high iiills in South Andjoy, in the lower part 

 of the railway cuts near Jamesburg, and at numerous points in the vicinity of 

 Hight«town and Newtown. 



COMPOS/TIO.V 



This formation has among its constituents all sorts of materials which the Mio- 

 cene beds ccjntain, including Miocene conglomerate. It also contains materials 

 from the Cretaceous beds which underlie the Miocene, and whicii had been ex- 

 pose<l by the erosion which followed deposition of the Miocene and which i)re- 

 ceded the deposition (jf the Pensauken. The PiMisauken als(j contains fragments 

 of shale and sandstone from the Triassi(; formation, as well as fragments of trap, 

 gabbro, gnei.sH, granite, ilicrt, Medina and Oneida sandstone and conglomerate, 

 and probably fragments from the Green Pond Mountain conglomerate. Tiiis last 



•Sep Annual Uf|>ort.s of tho Stjilo (icoloL'ist of Now Jcr.sfy for IX'il, p. Ion ; I8!t2, p. It.fi- XH'Xi pp. 



