Stratigraphy and components of annually laminated (varved) sediments

Annually laminated (varved) sediment sequences are regarded as one of the most important paleoenvironmental archives because they offer: - accurate „internal" age information in calendar years combined with - exceptional high temporal resolution down to a subannual timescale. This online varve image library shows different varve types, their seasonal sublaminae and successions as well as their components. This site is intended to summarize and distribute existing image information about varves, allow a better start of students and scientists to get acquainted with finely laminated sediment structures. Thin section preparation: There are two main techniques for impregnation of soft sediments: (1) acetone-water-resin exchange and (2) shock-freeze and freeze-dry technique. Each technique has certain advantages and disadvantages. Unless otherwise noted, all thin section presented were prepared using the shock-freeze and freeze-dry method adapted and modified from Lotter & Lemcke (1999). An expoy resin (Araldite2020) is used to impregnate the sediments. Standard techniques are then used to fabricate thin sections from the impregnated sediment slab applying rocksaw and grinding maschines, although some adaptation might be necessary of large-format thin sections (10 cm length). Imaging techniques: For macroscopic images we use a commercially available flatbed scanner with transparency unit and two sheets of polarizing foil. This foil can be bought on the internet (check e**y) or in stores supplying material for classroom experiments in physics. Microscopic images are taken by a Nikon D100 SLR camera mounted on an Olympus B50 microscope