A NEW LIMESTONE UNIT FROM THE UPPER CRETACEOUS PEEDEE FORMATION (MAASTRICTIAN) FROM PITT COUNTY, NORTH CAROLINA

An approximately 7 meter thick section of Upper Cretaceous to Pleistocene sediments is exposed along the Tar River at Greenville, Pitt County, North Carolina. The Cretaceous section is represented by the Peedee Formation of Maastrictian age. Within the Peedee Fm. exposure is a 0.45-0.6 m thick limestone unit representing a shallow, open shelf facies. The Peedee Fm. in this area is composed dominantly of shelfal sands and well developed limestones are rare.

The limestone occurs as a gray to tan, well indurated, fossiliferous, arenaceous, wackestone-packstone limestone at the base that grades upward into a moldic, arenaceous, wackestone-packstone limestone at the top. This unit started out as lag infilling of probable burrows within the underlying shelfal sands creating hanging protrusions along the lower contact. The matrix was micritic lime mud at the time of deposition, but has aggraded to microspar throughout. Aragonitic shells have been removed through dissolution and equant to blocky calcite spar cement added with full to partial replacement of shell fragments as you go up section (moldic at top).

Insoluble residues average 35.36% and are composed of 0.42% gravel, 93.89% sand, and 5.68% mud. The mean grain size is 0.24 mm. The sand fraction is largely quartz with minor glauconite throughout. The quartz is sub-angular to well rounded and is dominated by single grains with slightly undulose extinction. The glauconite is well rounded, unaltered in the lower portion and gets progressively altered up section. The top contact appears to be planar and erosional creating another discontinuity surface. This surface has been subjected to subaqueous/subaerial exposure leading to dissolution of aragonitic shells, leaving a moldic fabric at the top. The limestone is overlain by an unconsolidated to carbonate cemented, gravelly, quartz sand sequence.