New insight into Saanich Inlet varved sediments (British Columbia, Canada) from micro-scale analysis of sedimentary facies and micro-XRF core scanning analyses

Abstract

The late Pleistocene and Holocene laminated marine sediments deposited in Saanich Inlet, British Columbia, contain a well-known annually resolved record of environmental change. In this paper, these sediments were analyzed for the first time with an Itrax micro-X-ray fluorescence core scanner with a resolution of 100 μm. These analyses were complemented by image analysis of backscattered scanning electron images, coupled with energy dispersive spectrometry analysis using a scanning electron microscope. Using this new information, nine sedimentary facies were identified based on distinct geochemical, sedimentological and morphological characteristics at both the macro and the microscopic scale:Facies 1: massive deposit during Termination 1 (T1),Facies 2: T1 varved sediment,Facies 3: early Holocene varved sediment,Facies 4: volcanic ash-rich sediment,Facies 5: mid-Holocene varved sediment,Facies 6: disturbed sediment,Facies 7: massive sediment,Facies 8: clay-rich layer,Facies 9: fecal pellet-rich sediment.We determined how these analyses reinforced or refined previous interpretations about the sedimentary processes responsible for their deposition, their sedimentary environments and/or their provenance with seasonal to sub-seasonal resolution. Each lithofacies has distinctive chemical and sedimentological signatures, which can be used to establish sediment provenance with seasonal to sub-seasonal resolution, and to help understand paleoclimatic variations.