Early carbonate diagenesis in slope sequences and at their boundaries, Cenozoic, offshore New Jersey (ODP Leg 150)
Abstract This paper reports the genetic links among the depth distribution, mineralogy, and stable isotopic composition of diagenetic carbonates with sedimentation rates and types and preservation of organic matter in the terrigenous and biogenic sediments of Oligocene and Miocene age on the New Jersey slope. Calcites formed close to the sediment surface at sequence boundaries and maximum flooding surfaces, when the profile of early-diagenetic reactions was stabilized in the sediment column for extended periods. Dolomites precipitated in the sulfate reduction zone when diagenetic profiles stabilized during truncation, sequence boundary formation, and the deposition of lowstand sediments that overlie the sequence boundaries. Most dolomites occur in distal slope sediments that were deposited before the shelf had prograded into the study area. Siderites formed during a later stage of burial in the methanogenic zone; they are not directly genetically related to the sequence stratigraphy of the New Jersey slope. The diagene-tic dolomites and siderites occur in widely separated depth intervals below the present sea floor. The distribution of the diagenetic carbonates and their preferential occurrence in separated depth intervals resulted from different combinations of sedimentation rates and organic matter types and preservation.