Usefulness of stream order to detect stream sediment geochemical anomalies

Abstract

Unlike drainage basin area, stream order has not been quantitatively integrated in analysis of stream sediment geochemical data. It is hypothesized here that stream order is a useful surrogate for drainage basin area in ‘correcting’ for sediment dilution in order to detect stream sediment geochemical anomalies. Geochemical residuals, derived from catchment-based background corrections, are multiplied with respective sample site stream order to obtain stream-order-‘corrected’ residuals, which are compared and contrasted with corresponding values of productivity of a drainage basin. The validity of the hypothesis is tested and demonstrated in a drainage basin in the Aroroy gold district in the Philippines. There are strong and statistically significant correlations between stream-order-‘corrected’ residuals and values of productivity. Anomalous areas based on uni-element stream-order-‘corrected’ residuals are spatially identical or strongly spatially similar to anomalous areas based on uni-element values of productivity. Multi-element associations extracted from stream-order-‘corrected’ residuals are identical or highly similar to multi-element geochemical associations that can be extracted from values of productivity. The results of the study demonstrate that routine calculations of stream-order-‘corrected’ residuals would be particularly useful for interpretation of reconnaissance stream sediment geochemical data derived by sampling low-order streams.