Seasonal Sediment and Diatom Record from Late Holocene Laminated Sediments, Effingham Inlet, British Columbia, Canada

Abstract

Abstract Laminated diatomaceous sediments from Effingham Inlet, British Columbia, are described and classified in this study. Analyses were made from ten 15-cm long sediment slabs, spanning the last 5500 years, and 52 thin sections from which 408 sedimentary couplets were identified. Microfossil analysis and radiocarbon dating of the sediments reveal that the laminae are annually deposited (i.e., varves), with couplets containing a terrigenous and diatomaceous lamina pair. Terrigenous laminae, averaging 0.56 mm in thickness, consist of silt, organic debris, and robust diatoms, and are deposited during the winter months. Diatomaceous laminae, with a mean thickness of 1.85 mm, can be divided into three component laminae of differing compositions that reflect changing seasonal conditions during the spring, summer, and autumn months. This seasonal succession is seen in 76% of the couplets examined, recurring year after year with variations in couplet thickness and species occurrence. Couplets lacking the succ...