Boston Meeting of the Geological Society. 211 
small slippings rather than a few large ones. Most of the faults ob- 
served are of the normal variety, with the hade from 15° to -±5°. Illus- 
trations are given of the different types of faults observed. 
31. A geological study of lake Mohorikand lake Minnewaska, N. Y. 
William H. Niljes, Boston, Mass. The paper gave the results of the 
study of the origin of these mountain tarns. It necessarily included 
the structure of the Shawangunk range, upon the crest of which the 
lakes are located in rock basins. The relation of the geological struc- 
ture to the occurrence of the lakes was the leading question under dis- 
cussion. 
32. Geologic relations in the belt from Green pond, New Jersey, to 
Skunnemunk mountain, New York. N. H. Darton, Washington, D. C. 
This paper related to a narrow belt of Paleozoic rocks, which occupy a 
narrow trough in the Archean highlands of New Jersey,and extend north- 
ward in Orange county, New York. These rocks comprise limestones, 
shales, conglomerates, quartzites, and flags, ranging in horizon from 
the middle Cambrian to middle Devonian. In greater part they are 
far distant from the main mass of the formations in the region west- 
ward. The principal ridges to which the harder members give rise are 
Bowling Green, Green Pond, Copperas, Kanouse, Bearport, Bellvale, 
and Skunnemunk mountains. Greenwood lake lies in one of the prin- 
cipal valleys. 
Various ages have been assigned to the rocks and much uncertainty 
has always prevailed regarding their horizons and relations. Mather 
considered all the conglomerates Oneida in age, the slates Hudson 
River, and the limestones Lower Silurian. The New Jersey 
Survey considered the conglomerates and flags Potsdam, the slates 
Hudson River, and the limestones Lower Silurian. In 1884 Mr. Darton 
began observations in the region and his discovery of Lower Helder- 
berg fossils in some of the limestones afforded evidence that the asso- 
ciated conglomerates are Oneida in age. These observations were ex- 
tended by Merrill and Britton, who showed that certain areas of slates 
about Newfoundland are Devonian and apparently Hamilton in posi- 
tion. In 1871 Prof. D. S. Martin had found Devonian plants in the flags 
at the south end of Skunnemunk mountain. In 1887 Smock studied 
the relations in that region, and showed that the conglomerate capping 
this mountain overlies the flags. 
Recently Mr. Walcott has found Olenellus in the basal limestones at 
one point, and Foerste and others have shown the wide extension of 
middle Cambrian limestones in the northern New Jersey region. 
The results of Mr. Darton's studies were shown by a map and a series 
of cross-sections. It was stated that there is conclusive evidence of a 
great fault extending along the western side of the belt, and that there 
are several other faults of greater or less importance. The general 
structure of the region is synclinal, but there are various minor folds, 
notably in the region south of Newfoundland. 
The rocks were classified in a table, of which the following list is an 
abstract: 
Name. Approximate Age. 
Skunnemunk conglomerate. Middle Devonian. 
Bellvale flagstones. Upper Hamilton (group). 
Monroe shales. Lower Hamilton (group). 
Oriskany quartzite and conglom- Oriskany, etc. 
" erate. 
Helderberg limestone. "Lower" Helderberg. 
Longwood red shales. Clinton to Medina. 
Green Pond conglomerate and 
quartzite. Oneida. 
Hudson shales and sandstones. Hudson "River." 
Great unconformiti/. Karly Ordovician to ( anihiian. 
Limestone. Middle Cambrian. 
Quartzite and conglomerate. do. do.? 
Crystalline rocks, Archean. 
