A multi-proxy holocene record of environmental change fromthe sediments of Skinny Lake, Iskut region, northern British Columbia,Canada

Abstract

A stratigraphic record from a lake in the Central Plateau Regionof northern British Columbia reveals changes in environment and inferredclimate during the Holocene. Upon deglaciation (ca. 11500 BP), Skinny Lakebecame an embayment of an ice-dammed lake. High clastic sedimentationrates, an unstable landscape, and cool, possibly wet conditions likelypersisted until the early Holocene (ca. 9000 BP). From ca. 9000–8300 BPdeclining lake levels coupled with warm and dry conditions resulted in theformation of a prominent marl bed. A colonizing shrub and herb assemblagepersisted from 9000 BP until about 8300 BP when it was replaced by a spruce(Picea) and subalpine fir (Abieslasiocarpa) forest under slightly cooler and moister conditions. Themiddle Holocene was warmer-than-present, however, decreasingtemperature and increasing precipitation trends characterize the period fromca. 6000 BP–3000 BP. The transition to modern climate at 3000 BP isevident primarily in the lithostratigraphic record and corresponds with theinitiation of the Tiedemann glacial advance (ca. 3300 BP) in thesouth-coastal mountains of British Columbia. A significant change infossil pollen occurs at ca. 2400 BP and is characterised by an increase in pinepollen accompanied by decreases in alder (Alnus), spruceand fir. This also coincides with an increase in west-sourced exoticwestern hemlock (Tsuga heterophylla) and cedar type(Cupressaceae) pollen possibly transported by regional changes in air masscirculation patterns associated with Aleutian Low dynamics. This studydemonstrates that both lithostratigraphic and biotic proxies are helpful inreconstructing the timing and nature of climate change and that each may havevarying sensitivities to a particular type of change.