Glacial-interglacial variations in Quaternary production of marine organic matter at DSDP Site 594, Chatham Rise, southeastern New Zealand margin

CaCO3 and total organic carbon concentrations, organic matter C/N and carbon isotope ratios, and sediment accumulation rates in late Quaternary sediments from DSDP Site 594 provide information about glacial-interglacial variations in the delivery of organic matter to the Chatham Rise offshore of southeastern New Zealand. Low C/N ratios and nearly constant organic delta(13)C values of -23 parts per thousand indicate that marine production dominates organic matter supply in both glacial and interglacial times during oxygen isotope stages 1 through 6 (0-140 ka) and 17 through 19 (660-790 ka). Increased organic carbon mass accumulation rates in isotope stages 2, 4, 6, and 18 record enhanced marine productivity during glacial maxima. Excursions of organic delta(13)C values to ca. -29 parts per thousand in portions of isotope stage 2 suggest that the local concentration of dissolved CO2 was occasionally elevated during the last glacial maximum, probably as a result of short periods of lowered sea-surface temperature. Dilution of carbonates by elastic continental sediment generally increases at this location during glacial maxima, but enhanced delivery of land-derived organic matter does not accompany the increased accumulation of elastic sediments. (C) 1997 Elsevier Science B.V.