ABSTRACT: A 1200-year record of paleoceaongraphic and paleoclimatic variability from the Seymour-Belize Inlet Complex, central coastal mountains region of British Columbia.

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Abstract

Foraminiferal biofacies and trace elements distribution patterns were utilized to investigate variation in regional paleoceanography and paleoclimate through the last ~1200 years, as archived in a freeze core (VEC0A13) from Mereworth Sound (MSFC) in the Seymour-Belize Inlet Complex (SBIC). Ocean circulation patterns in the SBIC are strongly linked to precipitation, which is closely linked to the relative strength and position of the Center of Action (COA) of the Aleutian Low (AL) and North Pacific High. The MSFC was comprised of monotonous massive mud and silt sediments interspersed with minor sandy intervals. The fossiliferous upper portion (after ~1300 A.D. AD) was found to be sandier than the poorly fossiliferous lowermost section (~820-1300 AD). A down core increase and higher concentrations of aluminosilicate related elements (e.g., Al, Ca, Ti, K and Mg) particularly prior to ~1300 AD, are consistent with the predominance of mud sediments in the basal portion of the core (~820-1300 AD). Cluster analysis of the quantified foraminiferal results identified four biofacies: Haplophragmoides bradyi-Eggerella advena-Stainforthia feylingi, Buccella frigida, Buccella frigida-Cribroelphidium excavatum, and Buccella frigida-Haplophragmoides bradyi Biofacies, which characterized subtly different depositional environments in sediments deposited after ~1300 A.D. It can be generally stated though that the dominance of marine calcareous foraminifera indicate that higher oxygen and cooler temperature prevailed for a significant proportion of the core deposited after ~1300 years A.D. The high concentrations of redox sensitive elements and general absence of foraminifera in the basal portion of the core ~820-1300 AD suggests that deposition of this part of the MSFC occurred under warm, low-oxygen bottom water conditions. This basal core interval likely corresponds to the Medieval Warm Period (MWP). The reduced oxygen conditions likely came about as a result of diminished precipitation in the SBIC catchment as the COA of the AL progressively moved westward over time, resulting in significantly reduced estuarine circulation and only infrequent incursions of oxygenated open water into the SBIC basin. The overlying fossiliferous ~1300-1500 AD interval corresponds to the onset of the Little Ice Age (LIA). During this time the COA of the AL migrated further to the East, which in the SBIC resulted in higher levels of precipitation, which greatly enhanced estuarine circulation and frequent incursions of cold, well oxygenated ocean currents into the bottom waters and development of a diverse calcareous foraminiferal fauna.

Bibliography of Canadian Geomorphology