University af Nevada Reno TECTONXC GEOMORPHOLOGY AID NZOTECTONXC8 OP .THE SAN LUXS RANGE@ SAN LUXS OBXSPO COUNTY'ALXFORHXA A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geology by Steve P. Nitchman Nay 1988 8808190i89 8308i2 PDR ADOCK 05000275 P PDC 1 't The thesis oz e~ Thesis Advisor Dejfartment Chair Dean, Graduate School University of Nevada Reno May, 1988 -5 I' Y 1 ACKNOWLEDGMENTS This thesis presents the conclusions of a three year study which was supervised by Drs. D. Burton Slemmons and Richard Schweickert of the University of Nevada, Reno. The study was funded by a grant from the U.S. Nuclear Regulatory Commission (NRC) as part a licensing review study of the Diablo Canyon Nuclear Power Plant. This thesis has benefited from concurrent and parallel studies which were performed in the area. by Pacific Gas and Electric (PG&E) and its consultants Geomatrix and Earth Sciences Associates (ESA). Special thanks go to N. Timothy Hall of ESA, and Kathy Hanson and Bill Lettis of Geomatrix for their wi'llingness to share information and discuss issues. Special appreciation is extended to John H. Wiese and Timothy S. Cleath, two San Luis Obispo Geologists who shared their extensive knowledge of the geological wonders of the area, and who also extended their hospitality during the author s numerous trips;to;the area. Tiziano Vittori of ENEA-,DZSP in Roma, XtalyIinthoduced the author,'to the finer v I points of mesostructural ynalysis. Kudos to numerous UNR faculty and grad students, particularly < Doug, Clark, Tom I Sawyer, and Bob Whitney'ho "discussed and contributedt to some of the ideas 'presented herewithin. A medal of valor t should be awarded to Hichael "Spam" Ellis,'ho withstood a withering onslaught of half-baked tectonic models during the composition of the final chapters, and whose influence has been substantial. I I , 0 I ~ ~ I I II l II I g ~ l I I I I I: l ABSTRACT Th's thesis . documents the neotectonic setting of the San Luis Range, in San Luis Obispo County, California. The N60W-trending San Luis Range is bound by reverse faults which have uplifted the range. The Los Osos fault, forms the northern boundary, and is composed of three segments. The southern boundary .consists of several„reverse faults; the Wilmar Avenue fault forms the eastern paxt of the southern boundary, and is composed of two segments. Both the Los Osos and Wilmar Avenue faults show evidence of late Quaternary displacement. The San Luis Range is the northernmost range ~ within the Santa Maria Fold and Thrust Belt, a structural province , characterized by late Quaternaxy compressional tectonics. l.V TABLE OP CONTESTS PAGE ACKNOWLEDGMENTS ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ii ABSTRACT ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ a ~ a ~ ~ o E ' TABLE OF CONTENTS ~ ~ e ~ ~ ~ ~ ~ a ~ ~ ~ ~ a ~ ~ o o o ~ ~ ~ ~ o a e ~ o ~ o ~ ~ o ~ ~ ~ ~ iV LIST OF FIGURES ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o a o ~ ~ ~ ~ o ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ o oVii LIST OF TABLES...... ~ ~ ~ ~ ~ ~ .. ~ ~ ~ ~ ~ ~ .. ~ .. .. oXii INTRODUCTIONoooeoo ~ o.o ~ .ooo ~ ~ o.ao ~ o ~ ~ a ~ ~ ~ o ~ ~ a.o.oooo..oo 1 REGIONAL SETTINGoooooe.e.oo.... ~ oo.o ...o.......o 1 ' PREVIOUS'ORKo ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 4 DEFINITIONS.. ~ ....." ~ ..... .. .............. ~ ~ .. 4 I STRATIGRAPHYoo.ooooeo.aoooooo.oooooo.a.o 6 C GENERAL STATEMENT ~ ~ ~ ~ ~ 6 l MESOZOIC ROCKS, ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ' ~ ~ ~ e ~ ~ o o ~ ~ ~ o ~ ~ e e o e ~ ~ ~ ~ 6 CENOZOIC ROCKS ~ ~ oo ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 8 PALEOGENE ROCKS ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ . ~ ~ ~ ~ ~ ~ ..o ~ 8 NEOGENE ROCKS ~ ~ ~ ~ o ~ o ~ o ~ o o ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ e o ~ ~ ~ ~ ~ ~ ~ ~ 8 DETAILED STRATIGRAPHY ~ .. ~ ~ ~ ~ ~ ~... ~........ 9 UPPER PLIOCENE o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 9 SQUIRE MEMBER OF THE PISMO FORMATION. ~ ~ ~ ~ ~ ~ 9 QUATERNARY UNITSoooo oooo'.ohio.o ~ a..oooo .. ....13 GENERAL STATEMENT. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 13 PLEISTOCENE PASO ROBLES FORMATION.. ~ . ~ ~ . ~ ~ ~ ~ ~ ~ 13 ADDXTIONALQUATERNARY UNITS...................18 ' PALEOGEOGRAPHY o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ e e ~ ~ 2 1 LATE PLIOCENE PALEOGEOGRAPHY ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 21 'ID PLEISTOCENE PALEOGEOGRAPHY. ~ ~ ~ ~ ~ ~ '...24 I S TRUCTURE ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ ~ 2 5 GENERAL STATEMENT.. ~............. ~ . ~....... ~ . 25 ' PISMO SYNCLINEo ~ ~ ~ ~ ~ ~ ~ oo ~ ~ ~ ~ o ~ ~ ~ ~ o ~ ~ ~ ~ o ~ o ~ ~ o ~ 25 SAN LUIS RANGE TECTONIC BLOCK. ~ ~ ~ ~ ~ - ~ ~ ~ ~ o....30 FAULTS ~ ~ ~ ~ e ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ o ~ o ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ e ~ 3 1 FAULT NOMENCLATURE......... ~ ~ ~ ~ ~ ~ ~ ~.... 31 SAN LUXS RANGE TECTONIC BLOCK BOUNDARY FAULTS.. ~ .32 .HOSGRX FAULT. ~ ~ ~ .. ~ ' ~ ~ ~ ~ ~ ~ ~ ",. ~ ... ~ 32 It 't „'ASTERN BOUNDARY~ ~ ~ ~ ~ ~ ~,o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 'o ~ ~ ~ ~ ~ ~ ~ 33 I t I CLOS OSOS FAULT ZONE..... o ~ ~ ~ o ~ ~ f ~ o ~ ~ ~ ~ eto ~ ~ ~ ~ ~ ~ 34 WESTERN SEGMENTo ~ ~ o ~ ~ ~ ~ oo ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ o, ~ ~ ~ ~ ~ ~ ~ 34 MXDDLE SEGMENTe ~ ~ ~ ~ ~ ~ ~ oeo ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ....39 ~ EASTERN SEGMENT ~ ~ ~ e 40 I WXLMAR AVENUE FAULT...... ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ o ~ ~ ~ o ~ ~ ~ ~ ~ 45 WESTERN SEGMENTeo ~ oe ~ oo ~ o ~ ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ oo ~ 47 EASTERN SEGK5To ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ oe ~ o ~ oo ~ 55 ADDXTXONAL LATE QUATERNARY STRUC'PJ'S...... ~ ~.... 59 ORCUTT ROAD ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ e ~ ~ ~ ~ ~ 59 FAULTS WXTHIN THE SAN LUXS RANGEo ~ ~ ~ ~ ~ e o ~ ~ o ~ ~ ~ ~ ~ ~ 64 EDNA FAULTo ~ ~ ~ ~ ~ ~ ~ e ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 6 4 SAN MIGUELITO FAULT. ~ ~ ~ ~.... ~... ~ . ~ ~ .. ~ . 66 INDIAN KNOB FAULT.. ~ ~ .. ~ ..... .......,.. ~ ~ ....67 SKB9fARY OF FAULT ACTIVITY... ~ ~ ~ ~ o ~ . o ~ ~ . ~ . ~ ~ .68 CROSS SECTXONS ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ a ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ a ~ o ~ ~ a ~ ~ 69 EASTERN SAN 'LUXS RANGE o ~ ~ ~ ~ a ~ ~ ~ ~ ~ ~ a ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 6 9 WESTERN 'SAN LUXS RANGE o o o o o ~ o ~ a o o ~ o o ~ o ~ e o o ~ ~ ~ ~ 73 TECTONXC GEOMORPHOLOGY OF THE, SAN LUXS RANGE ~ ~ ~ ~ o ~ ~ ~ ~ 77 GENERAL STATEMENT ~, ~ ~ ~ ~ ~ ~ o ~ a o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 7 7 TOPOGRAPHIC ZONES ~ ~ ~ ~ ~ a ~ ~ ~ ~ o o a ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 78 ANTECEDENT STREAMS ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 80 "ARROYO GRANDE FLUVIAL TERRACES ~ ~ ~ ~ ~ ~ ~ ~ . ~ .. ~ ~ . 81 ' FORMATION .OF 'ARROYO GRANDE TERRACES ~ ~ ~ ~ ~ ~ o ~ ~ 83 LOS OSOS~EDNA VALLEY SYSTEM.. ~ e' ~ ~ ~ ~ 8 7 PASO ROBLES FAN PIEDMONT ~ ~ ~ . ~ ~ ~ ~ ~ .. ~ ~ 88 REGIONAL NEOTECTONXC SETTING ~ . ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ .. ~ ~ 91 STRUCTURAL HISTORY.. .. ~ . .... .'.... ..91 I DIVERGENT REGIME. ~.............. ~ ~ ....... ~ .. 92 CONVERGENT REGIMEa ~ ~ ~ ~ ~ e ~ a ~ ~ ~ ~ a ~ ~ ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 9 5 STRUCTRL DOMAINS ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 9 6 SANTA MARIA FOLD AND THRUST BELT..............96 'OFFSHORE SANTA MARIA BASXN.......'.....;....100 SOUTHERN COAST RANGES ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 100 WESTERN TRANSVERSE RANGES ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 1 0 1 SIMILARITIES BETWEEN TRANSVERSE RANGES AND S MFTBe ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 102 VLL PLIO-QUATERNARY DEVELOPMENT OF THE SMFTB.. ~ .'... ~ 103 KINEMATIC FRA16iWORK« ~ ~ ~ ~ o ~ ~ ~ ~ ~ « ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 103 SALINIAN BLOCK.RATES'~ ......... ~ ...".. ~ .... ~ . ~ .. ~ 103 DEFORMATION ...,' ~ ~ .......... ~ ~ . .... ~ ~ .105 HOSGRI FAULT« ~ ~ ~ ~ ~ ~ ~ ~ ~ « ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ . ~ ~ ~ ~ ~ ~ o ~ ~ o 107 ' ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ APPENDIX A g GLOSSARY ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 1 09 ' 'e REFERENCES ~ ~ ~ ~ « ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ «« ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 1 11 viii LIST OP FIGURES FIGURE PAGE 1 GENERALIZED LOCATION MAP. ~ ~ . ~ ~ .o . .... .o. ... 2 2 REGIONAL STRATZGRAPHXC COLUMN. ~ ~ ~ ~oooo.os ~ ~ ~ ~ ~ ~ ... o 7 3 BEDROCK DISTRIBUTION MAP. ~ ~ o ~ ... ~ .o. 9 4 DISTRIBUTION OF'SQUXRE SUBMEMBERS ' . ~ ~ ~ .o.. ~ ~ .10 5 DZSTRZBUTZON OF QUATERNARY UNITSo ~ ~ . ~ ~ ~ 14 6 LATE PLXOCENE PMZOGEOGRAPHY' ~ ~ ~ . ~ ... ~ ~ . ~ 23 ~l. 7 MID PLEISTOCENE PALEOGEOGRAPHY.................... 24 8 'ENERALIZED STRUCTUE&L MAP OF THE SAN LUIS RANGE. ~ 26 9 SCHEMATIC DIAGRAM OF'TRUCTURAL CULMINATIONS AND DEPRESSIONS'ITHIN THE PISMO SYNCLZNE. ~ ~ .. ' .'.28 '0 MZD TO LATE QUATERNARY FAULTS AND FOLDS ~...... ~ ~ ..31 11 PHOTOGRAPH OF UPLXFTED AIR GAP ALONG LOS OSOS '0 FAULT ZONE o ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 3 5 12 STRIP MAP OF WESTERN SEGMENT'OF THE LOS OSOS o' FAULT~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~, ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~, ~ ~ ~ ~ ~ ~ ~ 3 7 STRIP MAP OF THE MXDDLE AND EXTERN SEGMENTS OF LOS'OSOS FAULT. ~ ~ ~ ~ ~ ~ . ~ ~ ~ ~ . ~ ~ ... ~ .. ~ ~ ........ ~ ~ ~ ..37 14 SCHEMATIC TRENCH LOG.. ~ .. ~ ~ ~ . ~ ~ ~ . ~ ~ ~ ~ ..'....... 38 15 PHOTOGRAPH OF A THRUST FAULT SCARP ...............39 16 CROSS SECTION OF EASTERN SEGMENT OF THE LOS OSOS FAULTo ~ ~ eo ~ ~ ~ ~ o ~ ~ ~ oe ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ e ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ o ~ 43 17 SCHEMATIC TRENCH LOG OF EASTERN SEGMENT OF THE LOS OSOS FAULTo ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ . ~ ~ ~ 44 18 STRIP MAP OF THE ONLAND WILMAR AVENUE FAULT.......46 19 CROSS SECTION