Lithification of Deep Sea Sediments by Pyrite

Abstract

UNIQUE pyrite-cemented silty sand layers have been found in three piston cores taken from the North Carolina lower continental rise at depths from 4,770 to 4,950 m (Fig. 1). The layers are approximately 0.5 cm thick and consist mainly of terrigenous grains in a cement identified as pyrite by X-ray diffraction analysis. None of the precursor iron sulphides commonly associated with sedimentary pyrite¹ were found. Single layers at core depths of 530 and 870 cm were noted in cores B and C respectively (Fig. 1). In core A, two pyritized silty sand layers occur at depths in the sediment of 540 and 560 cm. Fig. 2 is a photograph of a fragment of one of the lithified sand layers. The rock has approximately the same 6 cm diameter as the piston core cutter, suggesting strongly that the rock was punched out of a pyritized sheet of unknown lateral extent by the core tube.