CLIMATE CYCLICITY IN LATE HOLOCENE ANOXIC MARINE SEDIMENTS FROM THE SEYMOUR-BELIZE INLET COMPLEX, BRITISH COLUMBIA

Abstract

An 8.72 m late Holocene sediment core (VEC02A07) obtained from Alison Sound in the Belize–Seymour Inlet Complex of central British Columbia, Canada was deposited between ∼ 3500–1000 yr BP under primarily anoxic marine conditions. This core contains a detailed cyclic record of land–sea interactions as evidenced by significant fluctuations in marine primary productivity and changes in the supply of terrigenous material that can be related to long term variation in the relative influence of the Aleutian Low (AL) and North Pacific High (NPH). Sedimentologically, the core is characterized by alternating intervals of fine-grained massive intervals (70%), laminated intervals (23%), turbidites (5%) and graded silt–clay layers (2%). The laminated intervals are comprised of couplets that vary between light-coloured, diatom-rich layers, deposited primarily during the summer months, and dark-coloured, mineral-rich layers deposited during winter. Laminated couplets are most common in portions of the core deposited between ∼3150 and 2700 yr BP, which corresponds to an episode of regional neoglaciation. Time-series analysis was carried out on high-resolution particle size measurements obtained from core sub-samples and on sediment grey-scale colour variability derived from X-ray scans of the core. Non-linear time-series analyses revealed that the succession of massive and laminated sedimentation displayed characteristics of self-organization following a power law relationship for core length segments of b 13 cm (b ∼ 50 years of deposition). Wavelet and spectral time-series analysis indicated that core length segments of N 13 cm (N ∼ 50 years of deposition) contained evidence of sedimentary depositional cycles of ∼ 70– 96, 135–155 and 250–330 years that reflect changes in AL and NPH mediated regional precipitation patterns that can in turn be related to larger-scale climate drivers such as the Pacific Decadal Oscillation (PDO) or solar irradiance cyclicity.