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The Trabuco and Baker Conglomerates of the Santa Ana Mountains

Popenoe, W. P. (1941) The Trabuco and Baker Conglomerates of the Santa Ana Mountains. Journal of Geology, 49 (7). pp. 738-752. ISSN 0022-1376. doi:10.1086/625004.

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A thick conglomerate series unconformably overlies Triassic metamorphics and Jura-Cretaceous intrusives and probably conformably underlies marine early Upper Cretaceous sandstones. The lower 300-400 feet of this series are deeply weathered, red, soft, massive; the upper 100 feet are fresh, greenish-gray to brown, resistant, thick bedded, and probably marine. The red lower part, named the "Trabuco formation" by E. L. Packard, was interpreted as a continental deposit older than the overlying gray conglomerate, and by Bernard Moore as a marine deposit continuous with and genetically inseparable from the gray conglomerate but weathered to its present condition by circulating iron-bearing meteoric waters after the deposition of the entire conglomerate series. Field studies of the conglomerates and pebble counts show that the upper and lower conglomerates are probably conformable and have no constant differences in composition, size, or rounding of the included pebbles. The marked and constant differences in color, consolidation, and topographic expression are believed due to differences in weathering. The Trabuco conglomerate is interpreted as a flood-plain deposit weathered deeply in place before deposition of the gray marine conglomerate overlying. The Trabuco conglomerate is thus recognized as a valid formation, confirming Packard's original interpretation.

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Additional Information:© 1941 University of Chicago Press. This study was carried forward under the supervision of Dr. Ian Campbell, of the California Institute of Technology, who has helped me greatly with advice and criticism. Dr. G. H. Anderson, of the Texas Power and Light Company, has been in the field with me on a number of occasions, has helped in determining some of the puzzling rock types found in the conglomerates, and has advised me on broader features of the problem. Mr. J. M. Holloway, of the California Institute, drafted the sketch maps and figures. I am glad to acknowledge the help I have had from these friends.
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Balch Graduate School of the Geological Sciences325
Issue or Number:7
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Official Citation:The Trabuco and Baker Conglomerates of the Santa Ana Mountains. W. P. Popenoe. The Journal of Geology 1941 49:7, 738-752; DOI: 10.1086/625004
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110592
Deposited By: Tony Diaz
Deposited On:27 Aug 2021 16:21
Last Modified:16 Nov 2021 19:41

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