A post-glacial isotope record of primary production and accumulation in the organic sediments of Saanich Inlet, ODP Leg 169S

Abstract

Changes in palaeoproduction in Saanich Inlet, British Columbia, were examined from sediments using total organic carbon contents and stable carbon isotope ratios. Sediments were obtained from Holes 1033B and 1034B of Ocean Drilling Program Leg 169S. These cores contain two distinct zones: (1) carbon poor (%C org <0.5 wt.%) glaciomarine muds from the upper Pleistocene, and (2) carbon rich (%C org 1–3 wt.%), well-laminated sediments from the Holocene. A slight monotonic rise in %C org and δ 13 C org throughout the Holocene suggests that primary production in the inlet has been steadily increasing. Some influence of changes in local land vegetation is also evident. Sharp decreases in %C org and δ 13 C org in the early Holocene probably represent material deposited from a major flood. Differences in organic δ 13 C org between light and dark laminae are related to seasonal variations in species composition temperature and nutrient conditions.