Identification of Holocene Sedimentary Processes in the Doce River Delta (Brazil) via Multiple Factor Analysis-clustering

Sediment cores collected at the Doce River adjacent continental shelf, Espírito Santo State (Brazil), were analyzed to distinguish the record of sedimentary processes more influenced by the riverine system or marine dynamics and identify possible anthropogenic interferences. The study was based on applying the multiple factor analysis combined with clustering (MFA-Clustering), which included grain size and chemical elements variables. Thereby, it was considered clay, silt, very fine sand-fine sand (VFS-FS), and medium sand-very coarse sand (MS-VCS) percentages and the content of the following metals: Mg, Al, Cr, Mn, Fe, Ni, Ba and Pb. The aluminum content was used to normalize the metals. The results pointed out four clusters that describe different sedimentary processes. Cluster 1, influenced by clay and silt, was interpreted as an indicator of typical riverine mud deposition to the south and in front of the mouth. Cluster 2, highlighted only by the presence of VFS-FS, seems to indicate the transport of sand sediments by the action of coastal currents. This group, as well as Cluster 1, indicated greater depletion of the metals evaluated at locations closer to the coast. Cluster 3, influenced by Ba, VFS-FS, and MS-VCS, showed a trend towards sediments transport northward associated with moments of greater energy. The samples included in this group tended to occur in deeper strata, that is perhaps a reflection of anthropogenic interference in watershed. Cluster 4, highlighted by Ni, Mn, Cr, Fe, Pb and sand content, suggests reworking terrigenous materials towards deeper zones promoted by waves/tidal action.