Detailed crustal thickness variations beneath the Illinois Basin area: Implications for crustal evolution of the midcontinent

作者：Yang Xiaotao^*; Pavlis Gary L; Hamburger Michael W; Marshak Stephen; Gilbert Hersh; Rupp John; Larson Timothy H; Chen Chen; Carpenter N Seth

来源：JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 2017, 122(8): 6323-6345.

DOI：10.1002/2017JB014150

We present high-resolution imaging results of crustal and upper mantle velocity discontinuities across the Illinois Basin area using both common conversion point stacking and plane wave migration methods applied to P wave receiver functions from the EarthScope Ozark, Illinois, Indiana, and Kentucky experiment. The images reveal unusually thick crust (up to 62km) throughout the central and southeastern Illinois Basin area. A significant Moho gradient underlies the NW trending Ste. Genevieve Fault Zone, which delineates the boundary between the Illinois Basin and Ozark Dome. Relatively thinner crust (<45km) underlies most of the Precambrian highlands surrounding the Illinois Basin and beneath the rift-related structures of the Reelfoot Rift and the Rough Creek Graben. We consider four hypotheses to explain the presence of thick crust under the central and southeastern Illinois Basin. Crustal thickening may have been produced (1) prior to its accretion to North America around 1.55Ga and is an inherited characteristic of this crustal province; (2) by underthrusting or shortening during Proterozoic convergent margin tectonics around 1.55-1.35Ga; (3) by Late Precambrian magmatic underplating at the base of older crust, associated with the creation of the Eastern Granite-Rhyolite Province around 1.3Ga; and (4) through crustal relamination during an episode of Proterozoic flat-slab subduction beneath the Illinois Basin, possibly associated with the Grenville Orogeny.

• 出版日期2017-8