Geoelectric Method-based Survey on the Existence of Iron Sand Layers at Jolosutro Beach, Blitar Regency, East Java Province, Indonesia

This study was conducted at Jolosutro Coastal Coast, Blitar, Indonesia. It aimed to find out the presence of a thickness layer of iron sand. Data acquisition was performed using geoelectric resistivity method with dipole-dipole navigation on a trajectory length of 200 meters and a distance between points of 10 meters. Measurement was made in three areas along the coast consisting of two passes for each. The resistivity value at the research area was around 7-357 Ωm with the following details: 1) The resistivity value of 7-60 Ωm was assumed to be an iron sand layer; 2) The resistivity value of 157 Ωm was assumed to be sand mixed with clay; and 3) The resistivity value of 210-357 Ωm was assumed to be bedrock. The visual observation shows that the first area on line one and two had brownish sand, line three and four had brownish-black sand, and line five and six had grayish-black sand, but they turned to be solid black when the condition was moist. Based on the interpretation of geoelectric data and the results of visual observation, it shows that there were iron sand layers w