Palaeo-flux records from electron microscope studies of Holocene laminatedsediments, Saanich Inlet, British Columbia

Holocene varved sediments recovered from Saanich Inlet, ODP Leg 169S, have been analysed using high-resolution scanning electron microscope techniques . The individual centimetre-scale varves form couplets, comprising diatom o oze/diatomaceous mud deposited during spring to autumn and silty clay depos ited during winter. Each individual varve may contain up to 19 laminae, rec ording sub-seasonal to seasonal-scale processes. These intra-annual laminae contain a range of components, including pelagic faecal pellets and aggreg ates of diatomaceous material. The combination of these individual componen ts in varying proportions with a heterogeneous sediment, leads to a range o f laminae fabrics. These include intact monospecific Skeletonema costatum a nd Thalassiosira pacifica diatom oozes and highly fragmented, aggregate- an d faecal pellet-dominated diatom oozes which are typically Chaetoceros spp, -dominated. Additional laminae fabrics include diatomaceous mud, stringer t ype diatomaceous mud which contains discrete diatom aggregates, homogeneous and pelleted silty clay. The varved diatom succession typically commences in early spring with Thalassiosira spp./Chaetoceros spp., followed by Chaet oceros spp. in late spring. During late spring/early summer blooms of S. co statum may be recorded, and summer to autumn production is characterised by one to several Chaetoceros spp.-dominated blooms. Inter-annual variability in diatom flux typically comprises the presence/absence of Thalassiosira s pp, and S. costatum. In addition, resting spores of Chaetoceros spp., Thala ssiosira nordenskioeldii and Leptocylindricus danicus are intermittently re corded. There is a major change in varve thickness from thinner varves prio r to approximately 2100 yr BP to thicker varves after this date, which is a ttributed to increased terrigenous input throughout the varve. The identifi cation of laminae fabrics. diatom successions and a unique massive interval has enabled an inter-site correlation between sites 1033B and 1033B. (C) 2 001 Elsevier Science B.V. All rights reserved.