Abstract

Middle Pennsylvanian bryozoan reefs and Pennsylvanian to Lower Permian shelf-edge carbonates exposed on Ellesmere Island record a complex sequence of submarine to postburial diagenetic events. Submarine phenomena include (1)cementation in primary pore systems by magnesian calcite preserved as fibrous calcite enriched in Mg and C13; (2) fracturing followed by cementation of fracture surfaces by micritic and fibrous magnesian calcite preserved as micritic and fibrous calcite enriched in Mg and C13; and (3) precipitation in fracture and primary pores of botryoidal aragonite preserved as botryoidal calcite enriched in Sr (7,500 ppm) and C13 and replacive growths of aragonite in the host sediment preserved as spherulitic calcite.

Analogues for these diagenetic fabrics may be found in modern coralgal reefs. Both ancient and modern submarine cements develop preferentially in the seaward fronts of reefs and barriers (shelf edges).

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