Abstract
Recent studies have proposed the existence of several major ancient rift zones in the midcontinent region of North America. Although the dating of some of these rifts (and even the rift interpretations) are subject to question, an analysis of these “paleo-rifts” reveals three major episodes of rifting: Keweenawan (~ 1.1 b.y. B.P.), Eocambrian (~ 600 m.y. B.P.), and early Mesozoic (~ 200 m.y. B.P.). The extent of these events documents that rifting has played a major role in the tectonic development of the midcontinent region. This role goes well beyond the initial rifting event because these features display a strong correlation with Paleozoic basins and a strong propensity for reactivation. For example, the Eocambrian Reelfoot rift was reactivated in the Mesozoic to form the Mississippi embayment and is the site of modern seismicity which suggests reactivation in a contemporary stress field of ENE compression. Even though the importance of rifting can be established, recognition of rifts and delineation of their complexities remain a major problem which requires more study.
Published Version
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