Late Wisconsinan to present sedimentation of organic matter off northern Newfoundland in response to climatological events

Carbon and nitrogen isotopic and elemental analyses were conducted on sediments from piston cores collected from the inner to mid-continental shelf of northern Newfoundland. These data provide a basis to evaluate shifts in the relative contributions of sources of organic matter as a result of changes in productivity or climatological events. Five Units were recognized as representing the sedimentation record from the Late Wisconsinan to present. Unit 5 (the lowermost) consists of glacial till which has average δ 15 N, δ 13 C and C/N values of 4.3‰, −25.3‰ and 6.0, respectively. These values suggest that the till was initially deposited in a lacustrine setting prior to subsequent transport and redeposition on the shelf by a Late Wisconsinan ice sheet. The isotopic compositions of Unit 4 indicates a glacial origin with a minor marine influence. The presence of diatom laminations and depletions in 13C and 15N in Unit 3 could have resulted from low productivity in cold, nutrient rich waters. A marine origin is assigned to Unit 2, although the variation in isotope values is large: 5.5–9.2‰ for δ 15 N and −24.4 to −21.8‰ for δ 13 C. These shifts are reflective of changes in productivity and the relative contributions of macroalgae and phytoplankton. Holocene sedimentation dominates in Unit 1 and is indicated by deposition of a mixture of phytoplankton and macroalgae.