Passaic Formation gray bed

Upper Triassic gray lake deposits (Trpg) consist of gray to black silty mudstone, gray and greenish- to purplish-gray argillaceous siltstone, black shale, and medium- to dark-gray, argillaceous, fine-grained sandstone and are abundant in the lower half of the Passaic Formation. Gray lakebeds occur in groups of two to five cycles although they also occur as single cycles in some parts of the formation. Several lakebed sequences consisting of one or two thick groups of drab-colored beds as much as 30 m (98 ft) thick or more can be traced over tens of kilometers. Many gray-bed sequences are locally correlated within fault blocks; some can be correlated across major faults or intrusive rock units. Thickness of the (entire Passaic) formation between Sourland Mountain and Sand Brook syncline is about 3,500 m (11,483 ft).
State New Jersey
Name Passaic Formation gray bed
Geologic age Lower Jurassic and Upper Triassic
Lithologic constituents
Sedimentary > Clastic > Mixed-clastic > Siltstone-mudstone (Bed)gray and greenish- to purplish-gray argillaceous siltstone
Sedimentary > Clastic > Sandstone (Bed)medium- to dark-gray, argillaceous, fine-grained sandstone
Sedimentary > Clastic > Mudstone > Shale > Black-shale (Bed)
Comments Part of the Brunswick Group. This unit's description is combined with JTRp (Passaic Formation) on the printed map. However, it is mapped seperately, so the description has been separated into two records. Also, this unit is called the 'gray bed' because that is what is used in the digital map.

Dalton, R.F., Herman, G.C., Monteverde, D.H., Pristas, R.S., Sugarman, P.J., and Volkert, R.A., 1999, New Jersey Department of Environmental Protection, Bedrock Geology and Topographic Base Maps of New Jersey: New Jersey Geological Survey CD Series CD 00-1; ARC/INFO (v. 7.1), scale 1:100,000.

Owens, James P., Sugarman, Peter J., Sohl, Norman F., Parker, Ronald A., Houghton, Hugh F., Volkert, Richard A., Drake, Avery A., Jr., and Orndorff, Randall C., 1998, Bedrock Geologic Map of Central and Southern New Jersey: U.S. Geological Survey Miscellaneous Investigations Series Map I-2540-B, 8 cross sections, 4 sheets, each size 58x41, scale 1:100,000.

NGMDB product
Counties Hunterdon - Mercer - Middlesex - Somerset