Geologic setting and lithologic column of the Cajon Pass Deep Drillhole
- Creators
- Silver, Leon T.
- James, Eric W.
Abstract
The Cajon Pass Deep Drillhole penetrates a late Tertiary basin developed on crystalline basement in the SW Mojave Desert, 4 km from the San Andreas fault. Cores, continuous cuttings and geophysical logs from phase I show great diversity in rock types, structure, and alteration. The hole encountered Cajon formation arkoses; granodiorite/tonalite; unusual megacrystic granite and augen gneiss; granitic and pelitic gneisses with quartzite; quartzofeldspathic orthogneiss cut by sheets of hornblende gabbro; and interlayered mafic and quartzofeldspathic orthogneisses with rare calcsilicate intervals. Foliation and compositional layering have low dips throughout the column and layered gneisses contain 10-cm-scale recumbent folds. Faults and alteration zones bound several rock units with low apparent dips. Basement cores are typically cut by steep fractures, <1 mm wide, that contain zeolites±calcite or chlorite-epidote. Fractures and faults decrease in abundance with depth.
Additional Information
© 1988 by the American Geophysical Union. Received April 6, 1988; revised July 14, 1988; accepted July 14, 1988. Synthesis of the column involved major Contributions from Epoch, Inc, especially D. Milham and R. Behl. Assistance by the U.S.G.S. curatorial facility staff, especially W. Campbell, F. Raup, D. Volturno, and W. Linenburger was invaluable. Meticulous reviews by K. Meisling and R. Weldon are appreciated. This work supported by the National Science Foundation and DOSECC. Contribution No. 4635 of the Division of Geological and Planetary Sciences, California Institute of Technology.Attached Files
Published - grl4044.pdf
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Additional details
- Eprint ID
- 39281
- Resolver ID
- CaltechAUTHORS:20130710-095829427
- NSF
- DOSECC
- Created
-
2013-07-10Created from EPrint's datestamp field
- Updated
-
2021-11-09Created from EPrint's last_modified field
- Other Numbering System Name
- Caltech Division of Geological and Planetary Sciences
- Other Numbering System Identifier
- 4635