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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 69 (1985)

Issue: 9. (September)

First Page: 1433

Last Page: 1433

Title: Anchizone Metamorphism in Triassic Sedimentary Rocks of the Newark Basin, Pennsylvania-New Jersey: ABSTRACT

Author(s): Diana Bermingham

Article Type: Meeting abstract


The degree of crystallinity of authigenic illite was determined, by x-ray Previous HitdiffractionNext Hit, for samples Previous HitfromNext Hit the Lockatong Formation (Triassic) of the Newark basin of southeastern Pennsylvania and adjacent New Jersey. Sixteen samples Previous HitfromNext Hit approximately 30 m of section in the lowermost Lockatong near Trooper, Pennsylvania, were analyzed.

Preliminary results ranging Previous HitfromNext Hit 22° to 41° ^Dgr2^Thgr, indicate a range of metamorphism extending through the anchizone to the boundary with the greenschist facies, and indicate that the rocks were subjected to temperatures of ~ 300°C for a period of time.

An episode of elevated temperature might have resulted Previous HitfromNext Hit proximity to an intrusive rock body, Previous HitfromNext Hit burial a short distance beneath a lava flow, or Previous HitfromNext Hit burial beneath ~ 8-10 km of overlying rock. None of these proposed mechanisms is consistent with the geologic evidence; another explanation for such a high temperature must be sought.

Four other samples Previous HitfromNext Hit widely distributed localities within the Newark basin also fall within this range of illite crystallinity. Samples Previous HitfromTop the Gettysburg basin and the Connecticut basin are less well crystallized, suggesting that the thermal event hypothesized here was restricted to the Newark basin.

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