There are two fundamental requirements for the development of laminated sediment sequences:
(1) Variation in input/chemical conditions/ biological activity that will result in compositional changes in the sediment.
(2) Environmental conditions that will preserve the laminated sediment fabric from bio-turbation. In lakes, strong seasonal signals are dominant while preservation is effected by bottom-water anoxia resulting from stratification, and high sedimentation rates.
Varves are defined as laminae or group of laminae interpreted to represent one year's deposition. Lamination can be formed by changes in terrigenous sediment grain-size, differences in biogenic influx and/or production, seasonal diatom production cycles, chemical variations, and water-column precipitation.
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