Aeromagnetic Anomaly Map of Iowa

modified from Zietz and others (1976)

Although its linear trend from north-central to southwest Iowa is evident, the intensities of the aeromagnetic anomaly associated with the MRS in Iowa are only slightly above background levels. Comparisons with MRS rocks in the outcrop belt and magnetic modeling suggest that the volcanic rocks on the Iowa Horst include a thick sequence of early reversely-polarized lavas, overlain by a thinner sequence of normally-polarized basalts. The two sequences effectively cancel one another, leaving a minimal net magnetic anomaly.

- Reds and yellows signify positive anomalies.
- Blues and purples identify negative anomalies.