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The stratigraphy of the limeport member of the Allentown Formation: An Upper Cambrian carbonate within the Kittatinny supergroup

Conference · · Geological Society of America, Abstracts with Programs; (United States)
OSTI ID:5587745
 [1]
  1. Hunter Coll. of the City Univ. of New York, NY (United States). Dept. of Geology and Geography
The Limeport Member occurs as thin to thickly bedded cycles of peritidal dolomite. A complete cycle includes a shallow subtidal dolarenite overlain by domal algal stromatolites, along with graded sequences of pisoids, oncoids, and oolitic facies. The upper portions of the cycle include fine grained beds of micritic, algal laminated dolomite, whose upper surfaces bear rip up clasts and edgewise conglomerates. The top of a complete sequence is capped by a dark gray, shaly, rubbly dolomite that gives way to a thinly bedded, black calcareous shale. Petrographic thin sections of the shaly units reveal silt-size angular quartz fragments, which may have an aeolian origin. More than 40 unconformity-bounded sequences have been measured along outcrops within the Hamburg Quadrangle in Sussex County, New Jersey. Chert occurs in distinct oolitic facies and also as a selective replacement of algal stromatolites and occasionally along stylolite surfaces associated with sulfides. Three silicification events are illustrated in the chert-rich facies. Thin section analysis of oncoid-rich facies has yielded evidence for silicification early in the diagenesis of the dolomite in the form of preservation of chert-replaced, early diagenetic epitaxial cements. Scanning electron microscopy (SEM) also reveals chert-replaced algal filament within oncolites. The selective replacement of algal stromatolites by chert may represent the second silicification event. Chert occurring along pressure solution surfaces is free of detrital clays and represents a later silicification event associated with the development of stylolites. Geological mapping within the Limeport Member has revealed the presence of several large prehistoric chert quarries, whose prospect pits are developed within the oolitic facies.
OSTI ID:
5587745
Report Number(s):
CONF-9303211--
Conference Information:
Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:2
Country of Publication:
United States
Language:
English