GEOCHEMICAL EVIDENCE FOR LATE HOLOCENE MULTIDECADAL-CENTENNIAL PALEOCLIMATIC AND PALEOCEANOGRAPHIC VARIABILITY IN AN ANOXIC BASIN, COASTAL BRITISH COLUMBIA

Geochemical proxies were utilized to investigate a 2500-year (~3500-1000 years BP) Late Holocene record of fluctuating paleoclimatic and paleoceanographic conditions archived in a piston core from glacier-carved Alison Sound fjord within the Seymour-Belize Inlet Complex, British Columbia coast.The core is primarily comprised of organic-rich annually laminated mud and silt sediments punctuated by some intervals made up of massive slumps and turbidites.

The C_org/N_total ratios observed through the core were high (15.9-50.56) indicating that the organic matter was terrestrially derived. The enrichments of δ¹³C (-25.74‰ mean) δ¹⁵N (~2.74‰ mean) isotopes corroborate the hypothesis that organic matter deposited in the inlet is terrestrially derived.

Geochemical proxy data indicates that both the laminated and homogeneous core intervals were deposited under similar suboxic to anoxic bottom water conditions.- Although the above crustal limit concentrations of some redox related trace elements (e.g. Cd, Cu, Mo, Pb, U, V, and Zn) found through the core could indicate either diagenetic enrichments or prevalence of suboxic to anoxic condition the distribution of redox indices such as U/Th, Th/U, Ni/Co, V/Cr, V/(V+Ni),V/Sc, (Cu+Mo)/Zn and U_authigenic as well as the extremely low values of manganese provides corroborating evidence that suboxic to anoxic bottom water conditions prevailed during deposition. Based on δ¹³C and δ¹⁵N distributional patterns evidence of five distinct climate intervals were identified through the 2500 year record, which alternated between periods of relative warm/cool and dry/ cooler conditions. .

Time series analysis of the organic matter and elemental data utilizing spectral and wavelet techniques revealed the presence of stationary cycles; particularly a PDO-like (34-67 year) cyle, as well as theGleissberg (80-~100 year) and Suess (~150-250 year) solar cycles. These cycles have previously been identified as influencing the positioning and strength of Aleutian Low and North Pacific High atmospheric circulation systems, which have strongly influences the regional climate of the northeast Pacific throughout the Late Holocene.