140 
GEOLOGY OF THE FOURTH DISTRICT. 
Section at Morganville, Genesee county. 
1. Onondaga limestone, with fossils; in several courses,...... 
2. Oriskany sandstone, very distinct,. 
3. Hydraulic limestone in thin courses,........ 
4. Hydraulic limestone in thick strata—one being 6 to 8 feet thick—siliceous in character, and embracing numerous 
irregular cavities,._........... 
5. Hydraulic limestone in thin grey layers, with seams of blue marl,.......... 
6. Bluish marl, crumbling into irregular, angular fragments,........ 
7. Grey and greenish marl, with some portions very compact, 10 or 12 feet of the lower part filled with small cavi¬ 
ties or pores like those in the rock covering the gypsum,. 
3 feet. 
4 in. 
4 feet. 
22 “ 
12 “ 
5 “ 
19 “ 
This section not only presents the contact of the two groups, but exhibits the gradual 
changes in the upper part of the salt group where it passes from its usual marly and shaly 
character to the impure limestone which terminates the whole. 
At Black-Rock, the junction of the two groups is plainly visible, the salt group terminat¬ 
ing with a drab limestone containing numerous irregular cavities, and succeeded by the On¬ 
ondaga limestone, there being no representative of the Oriskany sandstone. 
About three miles east of Black-Rock there is a quarry where the junction of the two 
groups is plainly visible. The limestone below the Onondaga is channelled or grooved into 
trenches of six or eight inches deep, and as much in diameter, in which the latter appears 
to have been deposited. 
In the eastern part of the State there are several formations succeeding the Onondaga salt 
group, which at the west are only meagrely developed, or are entirely wanting. Some of 
these have apparently existed, and were swept off by denudation previous to the deposition 
of the higher masses. Others have probably never extended far westward, one or two of 
them scarcely appearing beyond Schoharie county, where those limestones forming the Hel* 
derberg division are better developed than elsewhere in the State. 
These rocks and groups will be enumerated in their proper order. 
