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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 69 (1985)

Issue: 9. (September)

First Page: 1448

Last Page: 1448

Title: Petrology of Basal Conglomerate of Triassic Pekin Formation, Sanford Subbasin, North Carolina: ABSTRACT

Author(s): Julie W. Stagg, Daniel A. Textoris, Walter H. Wheeler

Article Type: Meeting abstract

Abstract:

This conglomerate, locally known as the "millstone grit," is exposed in a narrow strip along the western border of the Sanford subbasin of the Deep River basin. The grit is composed of interbedded fine to coarse rudite and medium to coarse arenite. The most common grains are schistose metamorphic quartz, metaquartzite, and quartz-mica schist.

Ten microfacies are identified. These include four arenites in decreasing abundance--hematitic sublitharenite, litharenite, sublitharenite, and feldspar-bearing litharenite--and six rudites in decreasing abundance--sublithic rudite, lithic rudite, hematitic lithic rudite, hematitic sublithic rudite, feldspar-bearing lithic rudite, and feldspar-bearing sublithic rudite.

Diagenetic events include compaction and alteration of less stable mineral grains in the eogenetic stage. Pressure solution, the precipitation of silica as syntaxial overgrowths and microquartz, and the precipitation of pore-filling kaolinite occurred in the mesogenetic stage. The telogenetic stage consists of hematite cement and alteration of other less stable grains.

The grit was deposited in the midfan area of a wet or stream-dominated alluvial fan. Sedimentation may have been initiated by movement on a western fault, evidence of which has been eroded. Source of the sediment was the metasediments and volcaniclastics of the Carolina slate belt of the Piedmont directly west of the Sanford subbasin. When the microfacies are plotted on the QFL diagram of Dickinson et al, they do not fall in the zone of the transitional continental (arkose), but are located in the recycled orogenic tectonic regime.

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