| Abstract: | Initially horizontal sheet intrusions of Middle Proterozoic diabase are abundant in a region 650 by 300 km across in Arizona and California. The diabase forms discordant sheets in basement granite and gneiss and sills in overlying shelf sedimentary sequences. Massive granite is the most common basement host for the sheets, probably because it fractured more easily than foliated hosts during sheet emplacement. Steep feeder dikes are rare compared to the sheets. The diabase in many places is exposed in fault blocks that were tilted during Tertiary tectonic extension. Structure sections restored from the map patterns of upended blocks shows that the sheets were intruded at levels throughout the upper crust, therefore it is concluded that the crust was under tectonic compression or in an isotropic state of stress at the time of diabase intrusion about 1.1 Ga. -from Author |
| Genre: | Article |
| ProdID: | 70016410 |
| Citation Author: | Howard, K. A. |
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| Citation Issue: | B7 |
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| Citation Language: | English |
| Citation Larger Work Title: | Journal of Geophysical Research |
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| Citation Search Results Text: | Intrusion of horizontal dikes: tectonic significance of Middle Proterozoic diabase sheets widespread in the upper crust of the southwestern United States; 1991; Article; Journal; Journal of Geophysical Research; Howard, K. A. |
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| Citation Volume: | 96 |
| Citation Year: | 1991 |
| Type: | citation/reference |
| Text: | Intrusion of horizontal dikes: tectonic significance of Middle Proterozoic diabase sheets widespread in the upper crust of the southwestern United States; 1991; Article; Journal; Journal of Geophysical Research; Howard, K. A. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Tue, 1 Jan 1991 00:00 -0600 |
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