Passaic Formation

(Olsen, 1980) - Reddish-brown to brownish-purple and grayish-red siltstone and shale (JTrp) maximum thickness 3,600 m (11,810 ft). At places contains mapped sandy mudstone (JTrpms), sandstone (JTrps), conglomeratic sandstone (JTrpsc) and conglomerate containing clasts of quartzite (JTrpcq), or limestone (JTrpcl). Formation coarsens up section and to the southwest. Quartzite conglomerate unit (JTrpcq) is reddish-brown pebble conglomerate, pebbly sandstone, and sandstone, in upward-fining sequences 1 to 2 m (3-6 ft) thick. Clasts are subangular to subrounded, quartz and quartzite in sandstone matrix. Sandstone is medium to coarse grained, feldspathic (up to 20 percent feldspar), and locally contains pebble and cobble layers. Conglomerate thickness exceeds 850 m (2,790 ft). Limestone conglomerate unit (JTrpcl) is medium-bedded to massive, pebble to boulder conglomerate. Clasts are subangular dolomitic limestone in matrix of brownish- to purplish-red sandstone to mudstone; matrix weathers light-gray to white near faults. Maximum thickness unknown. Conglomeratic sandstone (JTrpsc) is brownish-red pebble conglomerate, medium- to coarse-grained, feldspathic sandstone and micaceous siltstone; unit is planar to low-angle trough cross laminated, burrowed, and contains local pebble layers. Unit forms upward-fining sequences 0.5 to 2.5 m (1.6-8 ft) thick. Conglomeratic sandstone thickness exceeds 800 m (2,625 ft). Sandstone (JTrps) is interbedded grayish-red to brownish-red, medium- to fine-grained, medium- to thick-bedded sandstone and brownish-to purplish-red coarse-grained siltstone; unit is planar to ripple cross-laminated, fissile, locally calcareous, containing desiccation cracks and root casts. Upward-fining cycles are 1.8 to 4.6 m (6-15 ft) thick. Sandstone beds are coarser and thicker near conglomerate units (JTrpcq, JTrpcl). Maximum thickness about 1,100 m (3,610 ft). Sandy mudstone (JTrpms) is reddish-brown to brownish-red, massive, silty to sandy mudstone and siltstone, which are bioturbated, ripple cross-laminated and interbedded with lenticular sandstone. To southwest where similar lithologic units also occur, they have not been mapped separately, but have been included in undivided unit JTrp. Rhythmic cycles 2 to 7 m (7-23 ft) of thick gray-bed sequences (Trpg), termed Van Houten cycles by Olsen (1985), contain basal thin-bedded to finely laminated shale to siltstone, which grade upward through laminated to microlaminated, locally calcareous mudstone to siltstone and finally into massive silty mudstone. Lowest part of cycle has some desiccation features and local fossils; middle part has highest organic content and the most fossils; highest part contains mudcracks, burrows, and root casts. Gray-bed cycles are abundant in lower half of Passaic Formation and less common in upper half. Rocks of the Passaic Formation have been locally thermally metamorphosed to hornfels where in contact with the Orange Mountain Basalt, diabase dikes, and sheetlike intrusions. Total thickness of formation ranges from 3500 to 3600 m (11480-11810 ft).
State New Jersey
Name Passaic Formation
Geologic age Lower Jurassic and Upper Triassic
Lithologic constituents
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed)
Comments Newark Supergroup, Brunswick Group (Lyttle and Epstein, 1987). The Passaic Formation unit description on the map encompasses multiple units (JTRp, JTRpms, JTRps, JTRpsc, JTRpcq, JTRpcl, and TRpg). The Passaic Formation was split into individual units according to the digital map and the appropriate descriptions were used for each. The entire description was used for this unit (JTRp).

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.

Drake, Avery A. Jr.,Volkert, Richard, A., Monteverde, Donald H., Herman, Gregory C., Houghton,Hugh F., Parker, Ronald A., and Dalton, Richard F., 1996, Bedrock Geologic Map of Northern New Jersey: U.S. Geological Survey Miscellanenous Investigations Map I-2540-A, 4 cross sections, 2 sheets, size 56x40; 58x41, scale 1:100.000.

Olsen, P.E., 1980, The latest Triassic and Early Jurassic formations of the Newark basin (eastern North America, Newark Supergroup); stratigraphy, structure, and correlation: New Jersey Academy of Science Bulletin, v. 25, no. 2, p. 25-51.

Lyttle, P.T., and Epstein, J.B., 1987, Geologic map of the Newark 1 x 2 degree quadrangle, New Jersey, Pennsylvania, and New York: U.S. Geological Survey Miscellaneous Investigations Series Map I-1715, scale 1:250,00.

Olsen, P.E., 1985, Distribution of organic-matter-rich lacustrine rocks in the early Mesozoic Newark Supergroup, in Robinson, G.R., Jr., and Froelich, A.J., eds., Proceedings of the second U.S. Geological Survey workshop on the early Mesozoic basins of the Eastern United States: U.S. Geological Survey Circular 946, p. 61-64.

NGMDB product
Counties Essex - Hudson - Hunterdon - Mercer - Middlesex - Somerset - Union