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.

Keywords::

• varves
• facies analysis
• scanning electron microscope-energy dispersive spectrometry
• late Pleistocene to Holocene environmental change

Acknowledgements

We are especially thankful to the IMAGES VIII (International Marine Past Global Changes Study) program which provided access to the sediment core, and Tom Pedersen who facilitated this study. This research was funded by the Institut Paul-Emile Victor (IPEV), Plouzané, France; Rotary Foundation; Geological Society of America; Drilling, Observation and Sampling of the Earths Continental Crust; the Canadian Foundation for Innovation; the Natural Science and Technologies Research Council of Canada and the Department of Geosciences of the University of Massachusetts, Amherst. Kinuyo Kanamaru is grateful to Steven Petsch for his helpful revisions to the earlier version of this manuscript, Andrée Blais-Stevens who provided data associated with ODP Leg 169S cores and Maxime Debret who also provided data associated with the chronological method. Authors thank Arndt Schimmelmann, John Ridge and an anonymous reviewer for their significant input.