Environmental magnetic variations in sediments from contrasting mangrove environments along coastal Karnataka, India

Abstract Environmental magnetic properties of surficial sediments from two contrasting mangrove systems along the Udupi coast, Karnataka (Saligrama and Thonse West), were investigated to evaluate sediment dynamics and potential anthropogenic influence. Saligrama, representing a low-energy backwater setting, exhibits lower magnetic concentration (χlf, SIRM) and higher grain-size sensitive parameters (χfd%, χARM/χlf), indicating the dominance of fine superparamagnetic (SP) to Stable Single Domain (SSD) particles formed through authigenic and diagenetic processes. In contrast, Thonse West, a high-energy estuarine system, shows significantly higher magnetic concentration and coarser ferrimagnetic grains, reflecting detrital influx and likely anthropogenic inputs as evident from the field observations. Inter-parametric relationships and thermomagnetic behaviour confirm magnetite as the dominant magnetic mineral in both systems; however, the Saligrama mangrove contains a mixture of hard magnetic components such as goethite and hematite. The enhanced ferrimagnetic enrichment in Thonse West suggests the possibility of pollution-associated metal accumulation highlighting potential ecological degradation along with natural detrital influx.