•  
  •  
 

Document Type

Research

Keywords

gravity map, gravity profile, basement structure

Abstract

A gravity survey was conducted over approximately 4600 square km of northeast Iowa. It was undertaken to provide detailed gravity coverage at approximately 1.6 km intervals and to model the source of several significant gravity and magnetic anomalies. 1,460 gravity stations were occupied in the survey area. Bouguer gravity and residual gravity anomaly maps were prepared, the latter using band-pass filter and trend-surface analysis techniques. The residual maps reveal that the large oval Bouguer gravity anomaly centered beneath Decorah can be traced to the southern border of the survey. Profiles crossing this feature were prepared from the Bouguer map and a total intensity magnetic anomaly map. These profiles, combined with drill hole information, support the interpretation of a mafic (troctolite) intrusive extending over 90 km from the northwest corner of Winneshiek County to near the southern boundary of Fayette County. The western portion is dominated by a shallow elastic basin while the eastern portion appears to be dominantly felsic in nature. The gravity interpretation did not provide conclusive evidence for faulting near Decorah although faulting cannot be ruled out.

Publication Date

December 1998

Journal Title

Journal of the Iowa Academy of Science

Volume

105

Issue

4

First Page

145

Last Page

151

Copyright

© Copyright 1998 by the Iowa Academy of Science, Inc.

Language

EN

File Format

application/pdf