Organic geochemical comparisons of Fortune Bay and Bay d'Espoir

Abstract

Fortune-Bay and Bay D'Espoir are two fjords in close proximity, yet with contrasting internal properties and processes. Samples from six cores from Bay D'Espoir and five cores from Fortune Bay were analysed for organic carbon and nitrogen content, δ¹³C, δ¹⁵N, and total and individual amino acids. The δ¹³C values for Bay D'Espoir samples were relatively lower than those for Fortune Bay, indicating a stronger influence of a terrigenous source in Bay D'Espoir. The δ¹⁵N values were constant (7-8°/oo) for all cores except for cores BDE-1643 and BDE-1657, which were strongly depleted in ¹³C and ¹⁵N. The δ¹⁵N and the amino acid signatures delineate a predominantly macrophytic source of organics within both bays. Productivity levels were reflected in the percent organic carbon and total amino acid abundances which were higher in Fortune Bay samples than those in Bay D'Espoir samples. There is a general decrease in percent organic carbon and total amino acids with depth. The magnitude of this trend varies with each core. In cores FO-840404 and FO-840405 the trend may be related to a change from modern marine sedimentation to glaclomarine sedimentation. The change in sedimentation pattern is also reflected in the fraction greater than 63µ, foraminiferal count and ¹⁸O abundances of the foraminiferal carbonate tests. Finally, the D[AILE] / L[ILE] indicated higher sedimentation rates in Bay D'Espoir than in Fortune Bay.