The Midcontinent Rift system and surrounding Precambrian rocks are known to host highly significant mineral resources. Our project objectives are to increase understanding of this system through the integration of new and legacy geophysical data with geochemical and borehole data, map the lithology and structure of PreCambrian rocks, and develop an integrated 3D geologic model of the region.
Science Issue and Relevance
The Midcontinent Rift system and surrounding Precambrian rocks are known to host highly significant mineral resources. However, more than 90% of the Midcontinent Rift system is covered by Phanerozoic sedimentary rocks and sediments, and many regions lack drilling, meaning much of the region’s geology and mineral potential is poorly constrained and that geophysical methods are critical.
The USGS is uniquely qualified to carry out this important geologic framework research on behalf of the American public. No other government agency has our geological and geophysical expertise and capacity, academia does not do this type of work, and potentially relevant research by private exploration companies is not available in the public domain. Moreover, our Federal role allows us the best position from which to conduct this research, because the Midcontinent Rift system extends across multiple state lines.
Our objectives are the following:
- To map the lithology and structure of concealed and poorly understood Precambrian rocks. This part of the rift is almost completely unknown, and work here will help provide a basis for expanding the understanding of the extent and nature of the entire Midcontinent Rift system.
- To develop an integrated 3D geology model of the midcontinent rift in the western Lake Superior region from legacy geophysical data, new EarthScope and magnetotelluric data, borehole information, and geologic mapping.
- To acquire high-resolution ground and/or airborne electromagnetic data in several target regions and to interpret these data together with geophysical, geochemical, and borehole data to define their structural framework.
Methodology to Address Issue
We will be conducting the following activities to help characterize and increase understanding of the mineral resource potential of the region:
- Geologic Characterization of the Northeast Iowa Intrusive Complex
Objective: to map the lithology and structure of concealed and poorly understood Precambrian rocks through the collection of aeromagnetic data, ground gravity data and borehole data.
- 3D Modeling in the Western Lake Superior Region
Objective: to develop an integrated 3D geology model of the mid-continent rift in the western Lake Superior region from legacy geophysical data, new EarthScope and magnetotelluric data, borehole information, and geologic mapping.
- Regional and Local Electromagnetic Modeling
Objective: to acquire high-resolution ground and/or airborne electromagnetic data in several target regions and to interpret these data together with geophysical, geochemical, and borehole data to define their structural framework.
- Mapping Concealed Precambrian Geology, Central Upper Peninsula, Michigan
Objective: to map the lithology and structure of concealed and poorly understood Precambrian rocks by securing aeromagnetic data along with ground gravity data.
- Scientific Borehole in Northeast Iowa
Objective: to test geophysical interpretations of the Proterozoic geology in northeastern Iowa by: 1) drilling a scientific borehole through Paleozoic cover to Proterzoic basement, 2) recover core from the Proterozoic basement sufficient for petrologic and radiometric analyses, and 3) obtain data on the overlying Paleozoic section to improve understanding of the Proterozoic-Paleozoic unconformity.

Below are other science projects associated with this project.
Synthesis of the Tectonic, Magmatic, and Metallogenic Evolution of the Midcontinent Rift System
Below are data releases associated with this project.
Updated aeromagnetic and gravity anomaly compilations and elevation-bathymetry models over Lake Superior
Exposed Precambrian Bedrock in Part of Dickinson County, Michigan, and Marinette and Florence Counties, Wisconsin
Airborne Magnetic Total-Field Survey, Manchester Region, Iowa, USA
Below are publications associated with this project.
Geophysical insights into Paleoproterozoic tectonics along the southern margin of the Superior Province, central Upper Peninsula, Michigan, USA
Integrated geophysical analysis provides an alternate interpretation of the northern margin of the North American Midcontinent Rift System, Central Lake Superior
Evidence for a concealed Midcontinent Rift-related northeast Iowa intrusive complex
The first 3D conductivity model of the contiguous US: Reflections on geologic structure and application to induction hazards
Making it and breaking it in the Midwest: Continental assembly and rifting from modeling of EarthScope magnetotelluric data
Below are news stories associated with this project.
Below are partners associated with this project.
- Overview
The Midcontinent Rift system and surrounding Precambrian rocks are known to host highly significant mineral resources. Our project objectives are to increase understanding of this system through the integration of new and legacy geophysical data with geochemical and borehole data, map the lithology and structure of PreCambrian rocks, and develop an integrated 3D geologic model of the region.
Science Issue and Relevance
The Midcontinent Rift system and surrounding Precambrian rocks are known to host highly significant mineral resources. However, more than 90% of the Midcontinent Rift system is covered by Phanerozoic sedimentary rocks and sediments, and many regions lack drilling, meaning much of the region’s geology and mineral potential is poorly constrained and that geophysical methods are critical.
The USGS is uniquely qualified to carry out this important geologic framework research on behalf of the American public. No other government agency has our geological and geophysical expertise and capacity, academia does not do this type of work, and potentially relevant research by private exploration companies is not available in the public domain. Moreover, our Federal role allows us the best position from which to conduct this research, because the Midcontinent Rift system extends across multiple state lines.
Our objectives are the following:
- To map the lithology and structure of concealed and poorly understood Precambrian rocks. This part of the rift is almost completely unknown, and work here will help provide a basis for expanding the understanding of the extent and nature of the entire Midcontinent Rift system.
- To develop an integrated 3D geology model of the midcontinent rift in the western Lake Superior region from legacy geophysical data, new EarthScope and magnetotelluric data, borehole information, and geologic mapping.
- To acquire high-resolution ground and/or airborne electromagnetic data in several target regions and to interpret these data together with geophysical, geochemical, and borehole data to define their structural framework.
Methodology to Address Issue
We will be conducting the following activities to help characterize and increase understanding of the mineral resource potential of the region:
- Geologic Characterization of the Northeast Iowa Intrusive Complex
Objective: to map the lithology and structure of concealed and poorly understood Precambrian rocks through the collection of aeromagnetic data, ground gravity data and borehole data.
- 3D Modeling in the Western Lake Superior Region
Objective: to develop an integrated 3D geology model of the mid-continent rift in the western Lake Superior region from legacy geophysical data, new EarthScope and magnetotelluric data, borehole information, and geologic mapping.
- Regional and Local Electromagnetic Modeling
Objective: to acquire high-resolution ground and/or airborne electromagnetic data in several target regions and to interpret these data together with geophysical, geochemical, and borehole data to define their structural framework.
- Mapping Concealed Precambrian Geology, Central Upper Peninsula, Michigan
Objective: to map the lithology and structure of concealed and poorly understood Precambrian rocks by securing aeromagnetic data along with ground gravity data.
- Scientific Borehole in Northeast Iowa
Objective: to test geophysical interpretations of the Proterozoic geology in northeastern Iowa by: 1) drilling a scientific borehole through Paleozoic cover to Proterzoic basement, 2) recover core from the Proterozoic basement sufficient for petrologic and radiometric analyses, and 3) obtain data on the overlying Paleozoic section to improve understanding of the Proterozoic-Paleozoic unconformity.
Sources/Usage: Public Domain. Visit Media to see details.Geophysical anomalies over Decorah Complex, Iowa. From Drenth and others, 2015, doi:10.1139/cjes-2014-0178. - Science
Below are other science projects associated with this project.
Synthesis of the Tectonic, Magmatic, and Metallogenic Evolution of the Midcontinent Rift System
The overall project objective is to develop a comprehensive synthesis of the tectonic, magmatic, and metallogenic evolution of the Midcontinent Rift System (MRS) through time by integrating geophysical, magmatic, and geochemical data and to create 3-D models of the rift over its evolution. - Data
Below are data releases associated with this project.
Updated aeromagnetic and gravity anomaly compilations and elevation-bathymetry models over Lake Superior
New gravity and magnetic compilations and elevation-bathymetry models have been compiled for the Lake Superior region. These data provide continuous sets of observations for geologic interpretations spanning political boundaries such as US States and the US-Canada border where bedrock geology is largely concealed beneath glacial deposits and surface water. These data are providing constraints forExposed Precambrian Bedrock in Part of Dickinson County, Michigan, and Marinette and Florence Counties, Wisconsin
The U.S. Geological Survey conducted a program of bedrock geologic mapping in much of the central and western upper peninsula of Michigan and parts of Wisconsin from the 1940s until the late 1990s. Geologic studies in this region are hampered by a scarcity of bedrock exposures because of a nearly continuous blanket of unconsolidated sediments resulting from glaciation of the region during the PleiAirborne Magnetic Total-Field Survey, Manchester Region, Iowa, USA
This data release includes the airborne magnetic survey data collected from the Manchester region of Iowa. The Mineral Resources Program of the U.S. Geological Survey is tasked with understanding the nation's mineral resources. Precambrian rocks concealed under Paleozoic sedimentary rocks in northeast Iowa are poorly mapped and understood. Detailed high-resolution airborne magnetic surveys, ground - Publications
Below are publications associated with this project.
Geophysical insights into Paleoproterozoic tectonics along the southern margin of the Superior Province, central Upper Peninsula, Michigan, USA
The southern margin of the Archean Superior Province in the central Upper Peninsula of Michigan was a nexus for key Paleoproterozoic tectonic events involved in the ~2.1 Ga rifting of proposed Archean supercraton Superia and subsequent assembly of Laurentia. Interpretations of the region’s tectonic history have historically been hampered by extensive Pleistocene glacial and Paleozoic sedimentary cAuthorsBenjamin J. Drenth, William F. Cannon, Klaus J. Schulz, Robert A. AyusoIntegrated geophysical analysis provides an alternate interpretation of the northern margin of the North American Midcontinent Rift System, Central Lake Superior
The Midcontinent Rift System (MRS) is a 1.1 Ga sequence of voluminous basaltic eruptions and multiple intrusions followed by widespread sedimentation that extends across the Midcontinent and northern Great Lakes region of North America. Previous workers have commonly used seismic-reflection data (Great Lakes International Multidisciplinary Program on Crustal Evolution [GLIMPCE] line A) to demonstrAuthorsV. J. Grauch, Eric D. Anderson, Samuel J. Heller, Esther K. Stewart, Laurel G. WoodruffEvidence for a concealed Midcontinent Rift-related northeast Iowa intrusive complex
Large amplitude aeromagnetic and gravity anomalies over a ~9500 km2 area of northeast Iowa and southeast Minnesota have been interpreted to reflect the northeast Iowa intrusive complex (NEIIC), a buried intrusive igneous complex composed of mafic/ultramafic rocks in the Yavapai Province (1.8–1.7 Ga). Hundreds of meters of Paleozoic sedimentary cover and a paucity of basement drilling have preventeAuthorsBenjamin J. Drenth, A. Kate Souders, Klaus J. Schulz, Joshua M. Feinberg, Raymond R. Anderson, Val W. Chandler, William F. Cannon, Ryan ClarkThe first 3D conductivity model of the contiguous US: Reflections on geologic structure and application to induction hazards
Estimation of ground level geoelectric fields has been identified by the National Space Weather Action Plan as a key component of assessment and mitigation of space weather impacts on critical infrastructure. Estimates of spatially and temporally variable electric fields are used to generate statistically based hazard maps and show promise toward monitoring and responding to geomagnetic disturbancAuthorsAnna Kelbert, Paul A. Bedrosian, Benjamin S. MurphyMaking it and breaking it in the Midwest: Continental assembly and rifting from modeling of EarthScope magnetotelluric data
A three-dimensional lithospheric-scale resistivity model of the North American mid-continent has been estimated based upon EarthScope magnetotelluric data. Details of the resistivity model are discussed in relation to lithospheric sutures, defined primarily from aeromagnetic and geochronologic data, which record the southward growth of the Laurentian margin in the Proterozoic. The resistivity signAuthorsPaul A. Bedrosian - News
Below are news stories associated with this project.
- Partners
Below are partners associated with this project.