Landscape Development in the Western Transverse Ranges, California: Insights from Mapping, Geochronology, and Modeling Item Type text; Electronic Dissertation Authors DeLong, Stephen 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 29/09/2021 06:14:07 Link to Item http://hdl.handle.net/10150/195640 LANDSCAPE DEVELOPMENT IN THE WESTERN TRANSVERSE RANGES, CALIFORNIA: INSIGHTS FROM MAPPING, GEOCHRONOLOGY, AND MODELING by Stephen Berend DeLong ______________________ A Dissertation Submitted to the Faculty of the DEPARTMENT OF GEOSCIENCES In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA 2006 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Dissertation Committee, we certify that we have read the dissertation prepared by Stephen B DeLong entitled “Landscape Development in the Western Transverse Ranges, California: Insights from Mapping, Geochronology, and Modeling” and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy _______________________________________________________________________ Date: 4/03/06 Jon D Pelletier _______________________________________________________________________ Date: 4/03/06 Jay Quade _______________________________________________________________________ Date: 4/03/06 Clem Chase _______________________________________________________________________ Date: 4/03/06 Phil Pearthree Final approval and acceptance of this dissertation is contingent upon the candidate’s submission of the final copies of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement. ________________________________________________ Date: 4/03/06 Dissertation Director: Jon D Pelletier STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment 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 dissertation are allowable without special permission, provided that accurate acknowledgement 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 or her 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: Stephen B DeLong TABLE OF CONTENTS ABSTRACT……………………………………………………………..………….5 INTRODUCTION……………………………………………………………….…7 PRESENT STUDY……………………………………………………….……….13 REFERENCES………………………………………………………………….…17 APPENDIX A: DATING ALLUVIAL DEPOSITS WITH OPTICALLLY STIMULATED LUMINESCENCE, AMS 14C AND COSMOGENIC TECHNIQUES, WESTERN TRANSVERSE RANGES, CALIFORNIA, USA………………………………………………………………………….…….20 APPENDIX B: COUPLED ALLUVIAL FAN AND AXIAL CHANNEL DEVELOPMENT IN CUYAMA VALLEY, CALIFORNIA…………………….50 APPENDIX C: GEOMORPHIC FATE OF LATE CENOZOIC BASINS IN SOUTHERN CALIFORNIA: AN EXAMPLE FROM THE UPPER CUYAMA VALLEY……………………………………………………….……..66 APPENDIX D: BEDROCK LANDSCAPE DEVELOPMENT MODELING: CALIBRATION USING FIELD STUDY, GEOCHRONOLOGY AND DEM ANALYSIS……………………………………………………………………..…96 5 ABSTRACT Understanding how climate and tectonics have interacted to shape current landscape configuration requires application of the latest geomorphological techniques. This dissertation presents results from a combination of field mapping, geochronology, and numerical landscape development modeling. The papers contained here focus on studies from Cuyama Valley, California, at the junction of the Coast Ranges and Western Transverse Ranges in southern California. Combining field observation with three geochronological techniques has led to a detailed understanding of the late Quaternary alluvial history of Cuyama Valley. The alluvial history, in turn, allows for a better understanding of important events in the history of landscape development. In the western Cuyama Valley, the timing and morphology of alluvial fans record both climatic forcing in the form of variable sediment supply from drainage basins, and tectonic forcing from ongoing tectonically driven incision of the axial Cuyama River. Fan-terrace surfaces are subparallel (older surfaces are slightly steeper) and offset systematically in relation to their ages, suggesting response to ongoing base-level incision and fluctuation in sediment supply. The fans aggraded during relatively cool and wet climate of the last glacial period, which is out-of- phase with the regional model developed in nearby desert regions. In the upper Cuyama Valley, deposition in the Cuyama sedimentary basin ceased in the mid-Pleistocene, after which basin fill was uplifted, deformed, and beveled, forming a low-relief erosion surface on which the alluvium of San Emigdio Mesa was 6 deposited. Subsequent fluvial drainage network development formed the Cuyama badlands by incising into the deformed Cuyama basin sediments. The history of the upper Cuyama Valley was used to calibrate a numerical landscape development model. Uplift rate U, bedrock erodibility K, and landslide threshold-slope Sc are related to steady-state relief, hypsometry, and drainage density for a wide range of synthetic topographies produced by a stream-power-based landscape development model. A combination of fluvial channels and threshold-slopes occurs for only a relatively narrow range of U/K between 10 and 5000 m·kyr/kyr. Using measured values for hypsometric integral, drainage density and relief, the U/K value can be further constrained, enabling K to be determined if U is known. 7 INTRODUCTION This dissertation addresses fundamental questions that relate climate and tectonics to landscape development. Though the dissertation is a compilation of manuscripts with coauthors, the research design and execution is largely that of the first author. Appendix A presents results of an intercomparison of geochronological techniques as applied to alluvial deposits. Accurate age-determination of alluvial deposits in arid and semi-arid climates is possible using a number of techniques; each with its own limitations. Most widely applied are radiocarbon dating, cosmogenic radionuclide surface-exposure dating, and optically-stimulated luminescence dating. Radiocarbon (14C) dating relies on the presence of organic material in an interpretable context within the alluvial deposit, which is rare in dry environments. Cosmogenic radionuclide (CRN) techniques require determination of the effects of pre-depositionally inherited radionuclides and post-depositional erosion of the target deposit, and proper calibration of isotope production rates. Optically-stimulated luminescence (OSL) dating shows great promise, but is still regarded as developmental in its application to fluvial deposits. I present results of a “blind” comparison of all three techniques (with emphasis on direct comparison of radiocarbon and OSL dating by two independent laboratories) applied to late-Pleistocene to late-Holocene axial-fluvial and alluvial-fan deposits in Cuyama Valley, in the western Transverse Ranges, California, USA. This study serves to highlight both limitations and successful applications of these techniques within a detailed case-study. This is not intend to be a comprehensive review of details of each dating technique; for a complete review of methodology and application of each 8 technique the reader is directed to publications such as Gosse and Phillips (2001) for CRN techniques, Wallinga (2002) and Aitken (1998) for OSL dating, and Faure (1986) for radiocarbon dating. This paper also does not detail the geologic interpretations made within the wider scope of the study, but instead focuses on the comparison of the geochronologic data. Appendix B presents geological interpretations made from the some of the results presented in Appendix A as well as additional field mapping and topographic analysis of alluvial fans in Cuyama Valley, California. Suites of inset alluvial fan surfaces found on mountain piedmonts in arid regions record episodic alluvial episodes caused by changes in upstream sediment and water flux. These episodes of increased piedmont sedimentation (and intervening times of fluvial entrenchment and lateral erosion) are widely thought of as caused by cyclic climate change. In regions where past climates have acted on distinct catchments in similar ways, these flights of terraces are often assumed to be age-equivalent. The causes of these alluvial episodes can be diverse. In desert regions (Wells, et al., 1987; Bull, 1991; Reheis et al., 1996; Harvey, et al., 1999; Ritter, et al., 2000; McDonald et al., 2003) and in at least one semi-arid to subhumid region (Weldon, 1986), changing hillslope vegetation and precipitation regime (increased storm intensity) during and after cool/wet to warm/dry climate transitions are most often cited as causing alluviation. In glaciated regions, drainage basin erosion by valley glaciers led to piedmont alluviation during