Magnetic properties of sediments in cores from the Mandovi estuary, western India: Inferences on provenance and pollution

•Anti-ferromagnetic minerals and very high Fe and Mn in the upper/middle estuary.•Ferri-magnetic minerals and low Fe and Mn in the lower estuary/bay.•Ore material-dominated sediments in the upper/middle estuary.•Very strong to significant pollution of Fe and Mn in sediments of the upper/middle estuary. Magnetic properties of sediments were investigated in 7 gravity cores recovered along a transect of the Mandovi estuary, western India to understand their provenance and pollution. The maximum magnetic susceptibility of sediments was at least 6 times higher in the upper/middle estuary than in lower estuary/bay. The χfd% and χARM/SIRM of sediments indicated coarse, multi-domain and pseudo-single domain magnetic grains, resembling ore material in the upper/middle estuary and coarse stable single domain (SSD) to fine SSD grains in the lower estuary/bay. Mineralogy parameters indicated hematite and goethite-dominated sediments in the upper/middle estuary and magnetite-dominated sediments in the lower estuary/bay. Two sediment types were discernible because of deposition of abundant ore material in the upper/middle estuary and detrital sediment in the lower estuary/bay. The enrichment factor and Index of geo-accumulation of metals indicated significant to strong pollution with respect to Fe and Mn in sediments from the upper/middle estuary.