Portland State University PDXScholar Dissertations and Theses Dissertations and Theses 1982 Structure and influence of the Tillamook Uplift on the stratigraphy of the Mist area, Oregon Moinoddin Murtuzamiya Kadri Portland State University Follow this and additional works at: https://pdxscholar.edu/open_access_etds Part of the Geochemistry Commons, and the Stratigraphy Commons Let us know how access to this document benefits you. Recommended Citation Kadri, Moinoddin Murtuzamiya, "Structure and influence of the Tillamook Uplift on the stratigraphy of the Mist area, Oregon" (1982). Dissertations and Theses.3216 This Thesis is brought to you for free and open access. It has been accepted for inclusion in Dissertations and Theses by an authorized administrator of PDXScholar.
Please contact us if we can make this document more accessible: pdxscholar@pdx. AN ABSTRACT OF THE THESIS OF Moinoddin Murtuzamiya Kadri for the Master of Science in Geology presented October 6, 1982. Title: Structure and influence of the Tillamook uplift on the stratigraphy of the Mist area, Oregon. APPROVED BY MEMBERS OF THE THESIS COMMITTEE: Chairman obi farvin H.
B€eson Around the hamlet of Mist, in Columbia County, north- western Oregon, four formations ranging in age from late Eocene to middle Miocene are exposed. The late Eocene Keasey Formation consists of gray, tuffaceous, concretionary mudstone, siltstone and minor sandstone. The unstable and complex environment of deposition is indicated by lutokinesis and wide, shallow submarine channels. Deltaic deposits of the Pittsburg Bluff Formation 2 unconformably overlie the Keasey Formation.
The lower laminated member (informal) of the Pittsburg Bluff Formation consists of finely laminated mudstone, and interlayered, arkosic sandstone. The upper siltstone member (informal) consists of bioturbated, carbonaceous siltstone and sandstone. It crops out in an arcuate belt generally paralleling the Nehalem River, and thins rapidly towards the west. The middle Miocene Astoria Formation unconformably overlies the Pittsburg Bluff and Keasey Formations, and consists of poorly consolidated, lithic arkosic to quartzose sandstone and siltstone.
Primary structure is well developed in the Astoria Formation; micro cross- bedding and trough cross-bedding are common in the sandstone. The Columbia River Basalt Group is represented by the Grande Ronde and Frenchman Springs geochemical types. Some of the basalt clasts in the conglomerates in the Astoria Formation were derived from Columbia River basalt flows. Fifty three sedimentary samples were analyzed for their minor and trace element concentrations utilizing instrumental neutron activation analysis.
Concentrations of Na, K, La, Sm and Sc, and their ratios appear to establish significant trends. The data suggest a major break from a granitic-metamorphic provenance and a volcanic component dominated provenance between the 3 Cowlitz and Keasey Formations respectively. The provenance of the Astoria Formation indicates the presence of flood basalts. Complex faulting along northeast-southwest, and younger northwest-southeast trends primarily involves vertical movements.
Exposed faults have steep dips, narrow shear zones, very little drag and form horsts and grabens.diagrams of the Keasey, Pittsburg Bluff and Scappoose Formations indicate near horizontal to northerly or northeasterly dips. Northeast-trending, horizontal Beta axes in the Pittsburg Bluff (siltstone member) and Scappoose Formations parallel the axis of the Tillamook arch. The northwest-trending Beta axis of the Scappoose Formation probably reflects the latest structural grain of the area. Near horizontal dips of the strata, especially those of the post-Cowlitz age, the high angle faults, and the horizontal Beta axes probably preclude uplift involving extensive compression and thrusting.
The post- Keasey uplift produced an unconformity and restricted the deposition of coarser lithofacies of the Pittsburg Bluff Formation to the east and around the nose of the plunging axis of the Tillamook arch. Post-Keasey but pre-Astoria uplift along the axis of Tillamook arch and Willapa Hills upwarp produced the east-west trending Columbia River synclinal trough. The Astoria Formation and the Columbia River basalt flows are depositionally confined to this 4 structural downwarp. Continuity in the outcrop pattern of the middle Tertiary units perhaps precludes any large scale strike-slip offset.
STRUCTURE AND INFLUENCE OF THE TILLAMOOK UPLIFT ON THE STRATIGRAPHY OF THE MIST AREA, OREGON by MOINODDIN MURTUZAMIYA KADRI A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in GEOLOGY Portland State University 1982 TO THE OFFICE OF GRADUATE STUDIES AND RESEARCH: The members of the committe approve the thesis of Moinoddin Murtuzamiya Kadri presented October 6, 1982. Robert Van Atta APPROVED: Benson, Head, Department of Earth Sciences of Graduate Studies and Research ACKNOWLEDGMENTS The writer is deeply indebted to the faculty of the Earth Sciences Department, Portland State University, especially to Dr. Benson who supervised the research, to Dr. Van Atta who initiateo the Mist project of which this thesis is part, and to Dr.
Beeson for suggesting a 'new approach' in solving the 'unorthodox' geology of the area. Along with Dr. Johnson, all three critically rea~ the thesis. Financial support by Diamond Shamrock Corp., Oregon Natural Gas Development Corp., and Reichhold Energy Corp.
Appreciation is due Wesley G. Bruer for reviewing the thesis, and making valuable suggestions. Discussions with Kevin Kelty, Betty Ordway and Dale Timmons during the course of the Mist project aided in refining the ideas. Discussions with Mike Alger, Dr.
Alan Niem and Michael Jackson were helpful. Gullixon provided assistance with the computer work, and Mike Pollock assisted with chemical analysis. Assistance of Gene Pierson during the course of the study is appreciated. Kirn Elliott critically read the rough draft of the thesis, and accompanied the author on a rafting trip down the Nehalem River on a iv 'rainiest' day in Oregon ! Deepest and most sincere gratitude and appreciation is due Sal and Betty Kadri for their generous support which 0 helped considerably in completing this thesis.
Lastly, my parents perseverance, understanding and support is deeply appreciated. TABLE OF CONTENTS PAGE ACKNOWLEDGEMENT •. iii LIST OF TABLES vii LIST OF FIGURES. viii INTRODUCTION 1 Location • • •.
1 Purposes of Investigation 1 Methods of Investigation • • • 1 REGIONAL GEOLOGY • • • • • • • • • • 5 Stratigraphic Units. 5 Structure 8 STRATIGRAPHY 11 Keasey Formation ••. 11 Pittsburg Bluff Formation 23 Laminated Member • • 24 Siltstone Member • • • • 26 Astoria Formation. 27 Columbia River Basalt Group • • • • • • • 31 GEOCHEMISTRY • • • • • • • • • • • • • • • • 35 STRUCTURE 49 Pi and Beta Diagrams • 51 Faults • • • • • • • • 66 vi PAGE Lineaments • • •.
84 DISCUSSION AND CONCLUSION 89 REFERENCES. 97 APPENDIX A SAMPLE LOCATIONS • • • • • • • • • • • • 103 LIST OF TABLES TABLE PAGE I Major-Oxide chemical analyses of basalt samples • 36. II Trace and minor element concentration of analyzed samples. 38 LIST OF FIGURES FIGURE PAGE 1.
Location map of the Mist area 2 2. Regional stratigraphic correlation chart • • 7 3. Outcrop pattern of the Tertiary formations • • • • 9 4. Stratigraphic correlation chart for the study area •.
Aligned burrows and discontinuous silt. Prominent bluff south of Mist. Wide, shallow submarine channel. Northeast-trending elastic dike.
Typical outcrop of the laminated member 25 12. Astoria Formation in the Mist field. Basalt clast conglomerate underlying the Grande Ronde flow. Ti0 2 versus P 2o5 diagram of basalt samples.
Concentrations of Na, K, Sc and La/Sm ratio plotted against the formations •. 42 ix FIGURE PAGE 16. Sodium versus potassium plot. Lanthanum to samarium ratio versus potassium plot • • • • • • 45 18.
Lanthanum to samarium ratio versus scandium plot 47 19. Bouguer gravity anomaly of northwestern Oregon and southwestern Washington 50 20. Pi diagram of the Keasey Formation 53 21. Pi diagram of the laminated member.
Pi diagram of the siltstone member 55 23. Pi diagram of the Scappoose Formation • • 56 24. Superimposed maximum countours of the Keasey and Pittsburg Bluff Formations •• 57 25. Beta diagram of the Keasey Formation • • •.
Beta diagram of laminated member of the Pittsburg Bluff Formation • • • • • 60 27. Beta diagram of siltstone member of the Pittsburg Bluff Formation 62 28. Beta diagram of the Scappoose Formation • • • 64 29. Map of faults in the area • • • • • • • • 67 30.
Exposed faults along the Clatskanie Tie road. Lineaments drawn from SLAR • • • • • • • • • 73 32. Distribution of shelf type of lithofacies on the Oligocene shelf • • • • • • • • • • • 78 x FIGURE PAGE 33. Sketch diagram of probable stratigraphic relationships between the Keasey and laminated and siltstone members of the Pittsburg Bluff Formation 80 34.
Sketch diagram of middle Miocene embayment that restricted the deposition of the Astoria Formation and the Columbia River Basalt Group •. Log of Texaco 'Clark and Wilson' well. Subsurface correlation of three wells in the Mist field. Hypothetical sketch illustrating some features of the Keasey basin •.
92 INTRODUCTION Location The thesis area is located in Columbia County, northwestern Oregon, around the hamlet of Mist. The area covers approximately 110 square kilometers, and includes parts of T. The location of the area is shown in Figure 1. Oregon Highways 47 and 202 provide the primary access to the area; the interior is accessible by logging-roads.
Purposes of Investigation The objective of this study were (1) to construct a detailed geologic map of the study area, (2) to develop the pattern of the structure through field observations with emphasis on bedding attitudes, (3) an analysis of structural data utilizing equal-area plots to determine geometry and possibly, the sequence of tectonic events, and (4) determination of lineaments drawn from side looking airborn radar imagery (SLAR), high altitude aerial photographs, infra-red photographs and topographic maps. Methods of Investigation Field work was conducted during the months of 2 T. Location map of the Mist area. 3 August and September, and intermittently through the Fall of 1980.
Mapping utilized high altitude aerial photo- graphs at a scale of 1:78,000, and the Cathlamet, Clatskanie, Vernonia, and Birkenfeld u. Geological Survey 15 minute quadrangle maps enlarged to a scale of 1:31,250. Lithology of outcrops, bedding attitudes, and orientation of linear features were noted on the topographic map. Formation contacts were later drawn in part on synthesis of mapped lithology and analysis of cross-sections.
A total of 12 samples from the Keasey Formation were analyzed for microfossils. The samples were disaggregated with kerosene and/or quaternary-0, and sieved using a 200 mesh screen. The analysis of structural data included the construction of pi and beta diagrams utilizing a Honeywell 66/20 computer and programs PIPLOT and BETACAL. The computer-generated pi and beta density plots were hand contoured and reduced to a usable scale.
Bedding attitudes from the unpublished geologic map of T., Columbia County, Oregon (Kadri and others, 1980} were incorporated along with the bedding attitudes from the study area in the construction of pi and beta diagrams. Whole-rock major-element chemical analyses of basalt samples were made by Peter R. Hooper, Washington State 4 University. Whole-rock and 200 mesh fraction of 53 sedimentary samples and three basalt samples were analyzed by the author (at Portland State University) for minor and trace element concentrations utilizing instrumental neutron activation analysis (INAA) • Limited subsurface data were obtained from the Oregon Department of Geology and Mineral Industries, Diamond Shamrock Corporation, Oregon Natural Gas Development Corporation , Reichhold Energy Corporation, and American Quasar Petroleum Company.
REGIONAL GEOLOGY Stratigraphic Units Early to middle Eocene oceanic crust is the basement of the Oregon Coast Range geologic province upon which 7000 meters of volcanic and sedimentary rocks have accumulated (Snavely and others, 1980). Tholeiitic pillow basalts and submarine breccias with minor interbedded tuffaceous siltstone and basaltic sandstone of early to middle Eocene Tillamook Volcanics are the oldest rocks exposed in northwestern Oregon (Snavely and Wagner, 1964).