| Abstract: | Previous geological and geophysical investigations have suggested that the Mississippi Embayment is the site of a Late Precambrian continental rift that was reactivated in the Mesozoic. New information on the deep structure of the northern Mississippi Embayment, gained through an extensive seismic refraction survey, supports a rifting hypothesis. The data indicate that the crust of the Mississippi Embayment may be characterized by six primary layers that correspond geologically to unconsolidated Mesozoic and Tertiary sediments (1.8 km/s), Paleozoic carbonate and clastic sedimentary rocks (5.9 km/s), a low-velocity layer of Early Paleozoic sediments (4.9 km/s), crystalline upper crust (6.2 km/s), lower crust (6.6 km/s), modified lower crust (7.3 km/s), and mantle. Average crustal thickness is approximately 41 km. The presence and configuration of the low-velocity layer provide new evidence for rifting in the Mississippi Embayment. The layer lies within the northeast-trending upper-crustal graben reported by Kane et al. (1981), and probably represents marine shales deposited in the graben after rifting. The confirmation and delineation of a 7.3 km/s layer, identified in previous studies, implies that the lower crust has been altered by injection of mantle material. Our results indicate that this layer reaches a maximum thickness in the north-central Embayment and thins gradually to the southeast and northwest, and more rapidly to the southwest along the axis of the graben. The apparent doming of the 7.3 km/s layer in the north-central Embayment suggests that rifting may be the result of a triple junction located in the Reelfoot Basin area. The crustal structure of the Mississippi Embayment is compared to other continental rifts: the Rhinegraben, Limagnegraben, Rio Grande Rift, Gregory Rift, and the Salton Trough. This comparison suggests that alteration of the lower crust is a ubiquitous feature of continental rifts. ?? 1983. |
| Genre: | Article |
| ProdID: | 70011584 |
| Citation Author: | Mooney, W. D.; Andrews, M. C.; Ginzburg, A.; Peters, D. A.; Hamilton, R. M. |
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| Citation End Page: | 348 |
| Citation Issue: | 1-4 |
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| Citation Language: | English |
| Citation Larger Work Title: | Tectonophysics |
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| Citation Number Of Pages: | 22 |
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| Citation Search Results Text: | Crustal structure of the northern mississippi embayment and a comparison with other continental rift zones; 1983; Article; Journal; Tectonophysics; Mooney, W. D.; Andrews, M. C.; Ginzburg, A.; Peters, D. A.; Hamilton, R. M. |
| Citation Start Page: | 327 |
| Citation Volume: | 94 |
| Citation Year: | 1983 |
| Type: | citation/reference |
| Text: | Crustal structure of the northern mississippi embayment and a comparison with other continental rift zones; 1983; Article; Journal; Tectonophysics; Mooney, W. D.; Andrews, M. C.; Ginzburg, A.; Peters, D. A.; Hamilton, R. M. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Sat, 1 Jan 1983 00:00 -0600 |
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