The organic-matter content of
sediment was estimated by the method described by Dean
(1974). The particle-size analysis was done by the sieving
method described by Suguio (1973) and classified according
to Folk & Ward (1957), with the values expressed on the
phi scale (Φ), the base 2 negative logarithm of the size in
mm. The statistical parameters of particle size were
calculated using the program SYSGRAN 2.0. The index of
constancy was used to classify the frequency of occurrence
of species in the samples (Dajoz 1971).