One of the intractable problems in provenance analysis is the hydraulic sorting effect and resultant mineralogical heterogeneity in coarse- and fine-grained sediments which conceals provenance characteristics. The present study uses factor analysis to address geochemical responses to the sorting effect and provenance of Late Mesozoic sediments in the Nagato Basin, SW Japan. Factor analysis has proven useful for comprehending geochemical gradients between coarse- and fine-grained sediments. In the present example, compositional differences are based on varying proportions of quartz, plagioclase, chrome spinel, authigenic minerals and phyllosilicates. The contrasting behaviors of these minerals during the depositional stage resulted in the systematic fractionation of SiO2/Al2O3, Na2O/K2O and Cr/Ba. Sandstones and mudstones exhibit an array of compositions in SiO2/Al2O3-Na2O/K 2O and SiO2/Al2O3-Cr/Ba diagrams, the ranges of which reflect compositional variations due to the sorting effect. Sediments of different provenance exhibit distinctive mineral arrays and can be discriminated simply by reading the gradients of the continua. Therefore, this kind of data management concurrently quantifies the sorting effect and allows an estimation of the original source material. The SiO2/Al2O3 -Na2O/K2O diagram is particularly useful for scrutinizing igneous and mature continental provenances, while the SiO2/Al2O3-Cr/Ba diagram ascertains contributions from mafic sources. This investigative approach delineates a systematic provenance transition within the Nagato Basin: a serpentinite melange provenance in the early Early Jurassic, a magmatic arc in the late Early to middle Middle Jurassic and a continental interior in the latest Jurassic to earliest Cretaceous. The provenance changed by the direct input of mature continental material into the Nagato Basin, which resulted from dissection of the volcanic arc.
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