Determining the post-glacial evolution of a northeast Pacific coastal fjord using a multiproxy geochemical approachThis article is one of a series of papers published in this Special Issue on the theme Polar Climate Stability Network

• 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: 01.11.2008
• 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, sea-level 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-1a, the dominance of local crustal rise over eustatic sea-level 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 δ 18 O 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 (×10 4 ) and 1-3.4 (×10 4 ), 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.