8 Paleoclimatology/Paleoceanography I

Monday, 5 November 2001
8:00 AM - 12:00 PM

POSSIBLE RELATIONSHIPS TO LATE HOLOCENE PALEOPRODUCTIVITY IN THE NORTHEASTERN PACIFIC; BENTHIC FORAMINIFERAL ASSEMBLAGES FROM AN ANOXIC/DYSOXIC FJORD OF WESTERN VANCOUVER ISLAND, BRITISH COLUMBIA

Paper number: 8-13
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

The publicized collapse of the Pacific salmon and Atlantic cod fisheries has spurred a greater interest in the understanding of long-term relationships between the ocean-climate system and pelagic fish stocks. Effingham Inlet, where the present study is situated, is located at the bifurcation point of the Subarctic Current and the West Wind Drift. The north-south shifting of this point determines whether the Californian or the Alaskan Current will dominate the regional ocean climate, and the laminated sediments in Effingham Inlet preserve a record of some of these shifts.

Sedimentological interpretation of an 11m core from the Inner Basin suggests three distinct intervals over the last 4500 years. Intervals 1 (0-2500a) and 3 (3500 -?) suggest present-day climatic conditions - warm and dry; whereas Interval 2 (from 2500-3500a) is inferred to be cooler and wetter than today. The average sedimentation rate of the Outer Basin, is twice that of the Inner Basin, 5.5 mm/y and 2.2 mm/y respectively.

Paleoclimatic and paleoceanographic interpretations are based on foraminiferal assemblages from a series of cores from Effingham Inlet. In both basins, there was a relatively constant presence of Reophax scottii and Trochammina ochracea, indicating organic-rich estuarine conditions. However, several discrete pulses of Buccella frigida, Cibicides spp. suggest occasional incursions of offshore waters, which may indicate an upwelling event. Buliminella elegantissma, a dysoxic indicator species and Fursenkoina fusiformis, a dysoxic to anoxically favoured benthic foraminifera, also appear sporadically throughout the core just after the marine incursions, and suggest a connection to increased productivity as a result of upwelling. Changes in diatom production (Chaetoceros and Skeletonema spp.) tend to foreshadow changes in foraminiferal abundance while fish scale counts also appear to mirror these trends.