Research Article DOI: 10.2110/jsr.2008.057 DIAGENETIC CYCLING OF NUTRIENTS IN SEAFLOOR SEDIMENTS AND THE CARBONATE–SILICA BALANCE IN A PALEOZOIC COOL-WATER CARBONATE SYSTEM, SVERDRUP BASIN, CANADIAN ARCTIC ARCHIPELAGO

ABSTRACT: Seafloor processes are often destructive of biogenic remains, while at the same time promoting growth of authigenic minerals such as hematite, fluorapatite, glauconite, and chalcedony. Middle to Late Permian sedimentary rocks in the Sverdrup Basin are cool-water marine sandstones, shales, limestones, and cherts, rich in carbonate and siliceous biotic components. The authigenic minerals hematite, fluorapatite, glauconite, and chalcedony are abundant, from the interactions of nutrient elements (silica, phosphorus, and iron), with carbonate and siliceous biotas in ramp environments of variable energy and sediment accumulation rate. These authigenic phases represent, in part, faunas that are no longer preserved, and should not be viewed simply as diagenetic products. Early middle Permian siliciclastic rocks (the Assistance Formation) contain carbonate heterozoan biotas with widespread siderite and hematite, and local void-filling phosphate, deposited under moderate sediment accumulation rates. Sponge spicules were dissolved unless encased in hematite or siderite, and incorporated in silica cement. In contrast, more slowly deposited younger middle Permian inboard cherty limestones (the lower Trold Fiord Formation) underwent frequent physical and biological reworking, resulting in dissolution of biogenic silica and precipitation of glauconite, and carbonate fluorapatite. Sediment reworking also excavated and produced rounded glauconite and phosphate clasts; much of the glauconite was then oxidized to hematite on the seafloor. Again, unless encased in phosphate, sponge spicules were dissolved and the silica precipitated as glauconite or chalcedony. Coeval deeper-water phosphatic cherty limestones (the Degerböls Formation) do