Gravity Survey of the Randalia Magnetic Anomaly Fayette County, Iowa

Supplementary gravity data on an anomaly delineated from an aeromagnetic survey of northeastern Iowa is presented in this report. The gravity survey included 240 observation stations located at section corners from central to western Fayette County. Analysis of the simple Bouguer map, residual gravity maps, and gravity profiles suggests that the observed gravity anomalies probably derive primarily from large fault blocks within the Precambrian crystalline complex and related variations in the thickness of superjacent clastic deposits. Interpretations based on magnetic susceptibility indicate that rocksof the basement complex lie at a depth of 2,000 feet (610 m) to 2,700 feet (823 m) below the surface within the study area and vary laterally in composition from basic to acidic. Two areas that exhibit high gravity and magnetic values may warrant exploration for potential mineralization.