Deciphering an annually resolved climate signal invarved sediments using image analysis. Abstract Varved sediments are valuable paleoclimatic records, because data retrievedfrom such laminated sequences can be temporally constrained. Varvesthemselves contain climatic information, but up to now, varve thickness wasthe only available climatic indicator.
Imaging techniques allow the retrieval of additional data.
X-raydensitometry images retrieved from hardened sediment slabs can also be processed to infer rapid downcore relativedensity variations. Measurements of the size, shape, orientation and packing of the particles forming the varves areobtained. Lamination thickness does not correlate with mean summer temperatureover the same period. Coarse subannual sandy layers due to summer rain events aretracked by the 90th percentile of the grain-size of each lamina. This comparison is necessary for the quantification of the climatic control onsediment fluxes to the lake and for the construction of a model linking sediment to climate.