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Allentown Dolomite

Allentown Dolomite (Wherry, 1909) - Very thin to very thick bedded dolomite containing minor orthoquartzite and shale. Upper part is medium-light- to medium-dark-gray, fine- to medium-grained, locally coarse-grained, medium- to very thick bedded dolomite. Floating quartz sand grains and two sequences of medium-light- to very light gray, thin-bedded quartzite and discontinuous, dark-gray chert lenses occur directly below upper contact. Rhythmically bedded lower dolomite beds alternate between light and dark gray weathering, medium and very light gray, fine and medium grained, and thin and medium bedded, which are interbedded with shaly dolomite. Ripple marks, crossbeds, edgewise conglomerate, mud cracks, oolites, and algal stromatolites occur throughout unit, but more typically in lower part. Shaly dolomite increases downward toward lower conformable contact with the Leithsville Formation. Oldest beds contain trilobite fauna of early Late Cambrian age; younger beds contain latest Cambrian fauna (Howell, 1945; Howell and others, 1950). Thickness about 580 m (1,900 ft).
StateNew Jersey
NameAllentown Dolomite
Geologic ageLower Ordovician and Upper Cambrian
Original map labelOCa
CommentsKittatinny Supergroup (Lower Ordovician and Cambrian) (Drake and Lyttle, 1980)
Primary rock typedolostone (dolomite)
Secondary rock typeorthoquartzite
Other rock typesshale; chert
Lithologic constituents
Major
Sedimentary > Carbonate > Dolostone (Bed)Upper part is medium-light- to medium-dark-gray, fine- to medium-grained, locally coarse-grained, medium- to very thick bedded dolomite. Rhythmically bedded lower dolomite beds alternate between light and dark gray weathering, medium and very light gray, fine and medium grained, and thin and medium bedded, which are interbedded with shaly dolomite.
Minor
Sedimentary > Clastic > Mudstone > Shale (Bed)Very thin to very thick bedded dolomite containing minor orthoquartzite and shale. Shaly dolomite.
Incidental
Metamorphic > Metasedimentary > Metaclastic > Quartzite (Bed)orthoquartzite; floating quartz sand grains and two sequences of medium-light- to very light gray, thin-bedded quartzite
Sedimentary > Chemical > Chert (Bed)discontinuous, dark-gray chert lenses occur directly below upper contact.
Map references
Dalton, R. F., Herman, G. C., Monteverde, D. H., Pristas, R. S., Sugarman, P. J., 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) export file: geology.e00, scale 1:100,000, unit description files: cslegend.pdf and nlegend.pdf, metadata: metast.pdf.
Unit references
Dalton, R. F., Herman, G. C., Monteverde, D. H., Pristas, R. S., Sugarman, P. J., 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) export file: geology.e00, scale 1:100,000, unit description files: cslegend.pdf and nlegend.pdf, metadata: metast.pdf.
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, scale 1 to 100,000, 4 cross sections, 2 sheets, size 56x40; 58x41.
Wherry, E.T., 1909, The early Paleozoic of the Lehigh Valley district, Pennsylvania: Science, new series, v. 30, p. 416.
Drake, A.A., Jr., and Lyttle, P.T., 1980, Alleghanian thrust faults in the Kittatinny Valley, New Jersey, in Manspeizer, Warren, ed., Field studies of New Jersey geology and guide to field trips; 52nd annual meeting of the New York State Geological Association: Newark, N.J., Rutgers University Press, p. 92-114.
Howell, B.F., 1945, Revision of the Upper Cambrian faunas of New Jersey: Geological Society of America Memoir 12, 46 p.
Howell, B.F., Roberts, H.B., and Willard, Bradford, 1950, Subdivision and dating of the Cambrian of eastern Pennsylvania: Geological Society of America Bulletin, v. 61, no.12, p. 1355-1367.

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