The Midcontinent Rift System in Iowa
The Midcontinent Rift System (MRS) is a billion year old rip in the continental crust that formed during an episode of crustal stress that nearly ended in the complete severing of the southeastern part of North America and the formation of a new ocean about a billion years ago. Like a giant scar, the MRS stretches for over 900 miles from eastern Lake Superior to southern Kansas, with a possibly related eastern arm extending southeastward across Michigan and into Ohio. Rocks produced during the formation of the MRS are exposed in the Lake Superior area, along the lake shore from Duluth north into Canada and east into Michigan, including Wisconsin's Bayfield and Michigan's Keweenaw peninsulas. These rocks are dominated by basalt lavas (and related intrusive rocks) and reddish sedimentary rocks (sandstones, siltstones and shales). These same rocks continue southward beneath a cover of younger rocks. In Iowa, the rocks of the MRS are buried by 1,200 to 5,500 feet of younger sedimentary rocks and glacial-related unconsolidated materials. The very dense basaltic lavas and very light sedimentary rocks associated with the MRS produces a series of linear gravity anomalies that form the most dramatic gravity anomaly in North America. Because it lies so deeply buried, much of what is known about the MRS in Iowa has come from interpretations and modeling of its gravity anomaly in conjunction with magnetic anomaly maps, seismic data, and by examination of the very limited number of drill samples.
Abstracts:
Geochemistry of Buried Midcontinent Rift Volcanic Rocks in Iowa: Data from Well Samples (Abstract)
Keweenawan Supergroup Clastic Rocks in the Midcontinent Rift of Iowa (Abstract)
Evidence of Recurring Phanerozoic Structural Movements Along the Trend of the Middle Proterozoic Midcontinent Rift System in Iowa (Abstract)
Clastic Rocks Associated With the Midcontinent Rift System in Iowa, Midcontinent U.S.A. (Abstract)
Keweenawan Supergroup Clastic Rocks of the Midcontinent Rift System in Iowa (Abstract)
New Interpretations of Clastic Sedimentary Rocks Associated with the Middle Proterozoic Midcontinent Rift System in Iowa (Abstract)
Clastic Sedimentary Rocks of the Middle Proterozoic Midcontinent Rift System in Iowa (Abstract)
Overview of Petroleum Potential of Proterozoic Clastic Rocks of the Midcontinent Rift System in Iowa (Abstract)
Review of the Precambrian Geological History of the Central United States and the Midcontinent Rift System (Abstract)