Determining the post-glacial evolution of a Northeast Pacific coastal fjord using a multiproxy geochemical approach

• Published in: Canadian journal of earth sciences Vol. 45; no. 11; pp. 1331 - 1344
• Main Authors: Ivanochko, Tara S, Calvert, Stephen E, Southon, John R, Enkin, Randolph J, Baker, Judith, Dallimore, Audrey, Pedersen, Thomas F
• Format: Journal Article
• Language: English
• Published: Ottawa National Research Council of Canada 01.11.2008; Canadian Science Publishing NRC Research Press
• Subjects: absolute age; aluminum; anaerobic environment; British Columbia; C-14; Canada; carbon; Cenozoic; chemical ratios; climate change; coastal environment; cores; correlation; dates; Deglaciation; East Pacific; Effingham Inlet; Environmental changes; experimental studies; fjords; framework silicates; Freshwater; Freshwater lakes; Geochemistry; Geological time; glacial features; Holocene; Ice; isotopes; laminations; Marine; marine environment; marine sediments; Meltwater; metals; molybdenum; North Pacific; Northeast Pacific; Ocean circulation; Oceanography; opal; Organic carbon; Pacific Ocean; paleo-oceanography; paleocirculation; paleoclimatology; paleoecology; planar bedding structures; Pleistocene; postglacial environment; productivity; Quaternary; Quaternary geology; radioactive isotopes; regression analysis; rock, sediment, soil; Sea level; sea-level changes; Sediment composition; Sedimentary geology; sedimentary structures; sedimentation; sedimentation rates; Sediments; SEM data; shore features; silica minerals; silicates; statistical analysis; Studies; textures; Transitions; upper Pleistocene; upper Weichselian; Vancouver Island; Water circulation; Weichselian; Western Canada; Younger Dryas; Vancouver Island; Effingham Inlet; INE, Pacific; INE, Canada, British Columbia, Vancouver I; INE, Canada, British Columbia, Vancouver I., Effingham Inlet; AN, Greenland
• ISSN: 0008-4077; 1480-3313
• DOI: 10.1139/E08-030

A 40.32 m piston core recovered from Effingham Inlet, on the west coast of Vancouver Island, provides the basis for a high-resolution geochemical study of the last deglaciation and the Holocene. Glacial retreat, basin isolation, sealevel rise, and productivity variations are determined using proxies for sediment composition (K/Al, Fe/Al, Mg/Al), grain size (Ti/Al, Zr/Al), sedimentary redox conditions (Mo/Al, U/Al), and productivity (wt.% organic carbon, wt.% opal). As local ice retreated and marine waters inundated the basin, coarse-grained glacimarine sediments were replaced by finer grained, laminated, opal-rich sediments. During meltwater pulse-la, the dominance of local crustal rise over eustatic sealevel rise resulted in the progressive restriction of ocean circulation in Effingham Inlet and the formation of a temporary freshwater lake. The transition into stable Holocene conditions was initiated at ∼12 700 BP, which corresponds to the onset of the Younger Dryas, as identified by the Greenland Ice core Project (GRIP) ice core δ18O record and was completed by 10 700 BP, ∼800 years after the GRIP ice core record stabilized. Holocene Mo/Al and U/Al ratios range between 12-35 (×104) and 1-3.4 (×104), respectively, indicating that although large-amplitude, high-frequency fluctuations occur, the sediments of Effingham Inlet inner basin have remained organic rich and oxygen depleted for the entire Holocene period. The combination of anoxic bottom waters and a Holocene sedimentation rate of 217 cm/ka have preserved a high resolution record of environmental change in the northeast Pacific over the last 11 000 years.