Paleocurrent analysis of the Upper Miocene formations, Los Angeles Basin, California Item Type text; Thesis-Reproduction (electronic); maps Authors Bennett, John Newton, 1943- Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 02/10/2021 00:27:25 Link to Item http://hdl.handle.net/10150/554033 PALEOCURRENT ANALYSIS OF THE UPPER MIOCENE FORMATIONS, LOS ANGELES BASIN, CALIFORNIA by John Newton Bennett, Jr. A Thesis Submitted to the Faculty of the DEPARTMENT OF GEOLOGY In Partial Fulfillment of the Requirements .For the Degree of MASTER OF SCIENCE In the Graduate College THE UNIVERSITY OF ARIZONA 19 6 7 STATEMENT BY AUTHOR This thesis has been submitted in partial fulfill­ ment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate acknowl­ edgement of source is made• Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED: J Z , APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below: . /f. Date / ACKNOWLEDGMENTS . I wish to thank Drs. J. J. Wright, thesis director, W. D. Pye, and J. W. Harshbarger for their helpful advice and review of this manuscript, and Dr. J. F. Schreiber, Jr. for his assistance with the heavy mineral analysis. Thanks is also extended to the Mobil Oil Corpora­ tion for permitting the use of data collected by the author during the summer of 1966 while employed by the company. iii TABLE OF CONTENTS Page LIST OF FIGURES....................................... vi ABSTRACT..................................... viii INTRODUCTION..... .................................... 1 Location and Accessibility...................... 1 Purpose of the Investigation.................... 1 Previous Work................................... 3 Methods of Investigation........................ Ij. GENERAL GEOLOGY............. 6 EVIDENCE OF TURBIDITY CURRENTS....................... 8 Oriented Features....................... 9 Non-oriented Features.............................. 17 BASEMENT ROCKS.. ........................................ 19 Western Complex.................................... 19 Eastern Complex............................ 20 PUENTE FORMATION........................................ 22 La Vida Member.................. Puente Hills................ Peralta. Hills............... Soquel Member................... Channels.................... Elysian and Repetto Hills, Puente Hills.... San Jose Hills.......... Peralta Hills........... Yorba Member..................... Elysian and Repetto Hills...., San Jose and Puente Hills.... Peralta Hills...... .......... Sycamore Canyon Member.......... Peralta Hills............... iv V TABLE OP CONTENTS— Continued Page MONTEREY FORMATION.......................... lj.8 San Joaquin Hills » • ................. I4.8 Palos Verdes. Hills..**.......................... 5l CAPISTRANO FORMATION.................................. 5^ HEAVY MINERALS. ....................................... 58 CONCLUSIONS. ................................. 62 BIBLIOGRAPHY............................. 66 APPENDIX A— Measurements of Directional S t r u c t u r e s . • 69 APPENDIX B— Heavy Mineral Distribution. ...... 81 LIST OF FIGURES Figures Page 1* Index map of the Los Angeles basin............ 2 2<> Small-scale cross-stratification, shown . below pencil, exhibited by fine grained sandstone bed l|r inches thick— typical of the Yorba Member in the Elysian Hills. Current is from left to right, parallel to pencil....................................... 13 3* Load casts parallel to current at base of a . sandstone bed of the Sequel Member in the Elysian Hills. Current as determined from nearby cross-bedding is from left to right, parallel to the linear sole features......... llf. Ij-. Flute cast bordering on a load cast is lo- cated just above putty knife, bulbous end being just above handle. Current is from right to left, parallel to the putty knife... li|. 5* Cross-section of a load cast showing very common flame structure (shown by arrow). Current is from right to left.. ............ lf> 6. Current directions in the La Vida Member of the Puente Formation— Puente Hills.......... 25 7. Current directions in the Soquel Member of the Puente Formation— Elysian and Repetto Hills................. 29 8« Current directions in the Soquel Member of the Puente Formation— Puente Hills . ........ 33 9. Current directions in the Soquel Member of / the Puente Formation— Northern Santa Ana Mountains........ 36 X 10# Current directions in the Yorba Member of the Puente Formation— Elysian and Repetto Hills..., 4-0 vi LIST OF FIGURES— Continued Figure Page 11* Current directions in the Yorba Member of the Puente Formation— Puente Hills........... 1|2 12. Current directions in the Sycamore Canyon Member of the Puente Formation— Puente Hills and Northern Santa Ana. Mountains............. I4.5 13* Current directions in the Monterey Formation— San Joaquin and Western Santa Ana. Mountains...... ............................ llj.* Current directions in the Capistrano Formation— San Joaquin Hills....................... .. 15• Paleocurrent directions in Upper Miocene Formations and Geology of the Los Angeles basin................ .................... .in pocket l6. Map showing the location of source areas that contributed sediment to the Los Angeles basin during Late Miocene time.1...in pocket ABSTRACT Almost all sandstone beds occurring in the Upper Miocene formations of the Los Angeles basin were deposited by turbidity currents. Primary textures and structures in­ dicative of turbidites occur in fair abundance throughout all three Upper Miocene formations. All accessible outcrops of the Puente, Modelo, and Upper Miocene portions of the Monterey and Capistrano For­ mations were scrutinized for sandstone beds containing primary sedimentary structures. Through study of these structures, the direction of current movement was deter­ mined. The pattern of current movement displayed reveals that sediment was being transported into the Los Angeles basin from all sides. Current directions and mineralogic studies indi­ cate that essentially three source areas were supplying sediment into the basin. These source areas are 1) the San Gabriel Mountains, 2) an area to the east of the Santa Ana Mountains, and 3) a ridge of metamorphic rock parallel­ ing the present coast line. The majority of sediment was derived from an area in the San Gabriel Mountains located northeast of the basin. This is evidenced by the fact that the thickness, grain size, and total sand content of the Up­ per Miocene units decrease southwestward across the basin. viii INTRODUCTION Location and Accessibility The Los Angeles basin is a northwest-trending allu­ viated lowland plain about $0 miles long and 20 miles wide on the coast of southern California. It lies approximately between lat. 33°30' and 3^0N. and long. 1 1 7 ° and 118°30'W (Fig. 1). This thesis deals predominantly with Upper Mio­ cene formations exposed in the hills rimming the basin. The formations studied include the Modelo Formation ex­ posed on the south flank of the Santa Monica Mountains, the Puente Formation, and portions of the Capistrano and Monte­ rey Formations. Except for a few coastal areas, all of the land un­ der investigation is privately owned. Obtaining entrance to land in the Puente Hills and Santa Ana Mountains was particularly difficult. Portions of the Santa Ana Moun­ tains and San Joaquin Hills remain unstudied due to the un­ cooperative nature of the Irvine Company. Purpose of the Investigation It has been known for several years that the majori­ ty of sediments filling the Los Angeles basin were emplaced by turbidity currents. Sediments deposited by turbidity 1 2 I 11*1$' t i • * o a < ||7 * 4 * ' San ~ Gabriel Santa Monica Mts ' I Repetto i ,/v 6 Pomona Hills Long Beach Santa Ana . P A C I C C E A N FIG- I INDEX MAP OF THE LOS ANGELES BASIN 3 currents characteristically contain textures and structures oriented with respect to the current at the time of deposi­ tion. It is the primary objective of this report to deter­ mine the directions of sediment transport into the basin through study of current oriented features. Source areas can be delineated by means of paleocurrent directions, but in order to work out a more detailed paleogeography, miner- alogic data is also required. Therefore, the secondary ob­ jective of this investigation is to determine rock types that were present at source areas through petrographic work. Because of the tight security placed on data con­ cerning the Upper Miocene formations by the oil companies, any detailed subsurface work was impossible. Stratigraphic details and relationships such as changes in grain size and thicknesses observed in the outcrop were only noted casual­ ly, since previous investigators have already covered