Albany County Bedrock Units

Dhmo - HAMILTON GROUP: Upper Non-Marine Facies

Gray thin to thick bedded sandstone with interbedded red and green shales.
Total thickness = >2000'

Dhpl - HAMILTON GROUP: transitional

Thick bedded to flaggy green and gray crossbedded sandstones and gray, arenaceous shales.

Dhm - HAMILTON GROUP: Lower Marine Facies

Fine, argillaceous sandstones and silty dark gray to fissile black shales.

Dou - ONONDAGA LIMESTONE

Light to dark bluish gray, massively bedded limestone, containing beds and lenses of chert.
Total thickness <150'.
Lower portion of mapped unit contains the Schoharie Formation and the Esopus shale of the
TRISTATES GROUP

• Schoharie Formation - Dark, blue gray, laminated mudstones and and argillaceous limestone.
  Total thickness = 25'.
• Esopus Shale - Dark gray to black, sandy shales, which weather readily to a dark brown gravel.
  Total thickness =~ 175'.

Do - TRISTATES GROUP: Oriskany Sandstone

Calcareous quartz sandstone, grading eastward to siliceous limestone of the Glenerie Formation.
Total thickness >10'.

Dgl - TRISTATES GROUP: Glenerie Formation

Cherty, arenaceous limestone.

Dhg - HELDERBERG GROUP

The Helderberg Group consists of six units in Albany County as follows:

• Becraft Limestone - Light to medium gray, to pinkish, coarsely crystalline, massively bedded, fossiliferous limestone. Total thickness = 15' to 50'.
• New Scotland Formation - Medium to dark gray, fine grained, shaley, fossiliferous limestones and interbedded dark gray, calcareous mudstones. Total thickness =~ 100'.
• Kalkberg Formation - Bluish gray, fine grained, argillaceous, thin to medium bedded, siliceous, fossiliferous limestones with seams of shale. The lower portion of unit has beds and lenses of chert. Total thickness =~60'.
• Coeymans Formation - Light, coarsey crystalline, massively bedded, fossiliferous limestone.
  Total thickness = 20'- 35'.
• Manlius Limestone -Dark gray, fine grained,, interbedded ribbon-thin to medium bedded limestones and massive, biostromal (blanket-type reefs) limestones. Total thickness =~55'.
• Rondout Formation - Olive gray, fine grained dolostone, with occasional interbedded shales. Unit is rarely exposed in county. Total thickness = 0'-3'.

Osc - TRENTON GROUP: Schenectady Formation

Medium to dark gray, brown weathering,thin to thick bedded sandstones and subgraywackes interbedded with gray-black silty shales. Toal thickness =>2000'.

On - TRENTON GROUP: Snake Hill Shale

Medium to dark gray, silty, micaceous, pyritic shales, with occasional thin interbeds of siltstone, calcareous mudstone and fine grained sandstone. The unit is intensely folded and well cleaved. It includes conglomerate of various kinds and sizes of rock (melange) derived from emplacement of thrust blocks of Austin Glen graywacke into Snake Hill mud. Total thickness = >4000'.

Oag - NORMANSKILL GROUP: Austin Glen Formation

Tan-bluish-gray, medium to thick bedded, brown weathering, coarse grained graywackes, subgraywackes, and calcareous siltstones, alternating with silty, micaceous, gray shale. Locally, bedded cherts occur. The Austin Glen is intensely folded and in thrust-faulted contact with the underlying, younger Snake Hill Beds. Total thickness =>2000'.

Note: These brief bedrock descriptions have been compiled from several sources. For a more detailed map and description of Albany County geology, see:

• Fickies, R.H., (1982). Generalized Bedrock Geology of Albany County, NY.
  NY State Museum/Geological Survey Education Leaflet 25.