Geology of the Central and Northern Parts of the Western Cascade Range in Oregon
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Geology of the Central and Northern Parts of the Western Cascade Range in Oregon GEOLOGICAL SURVEY PROFESSIONAL PAPER 449 Prepared in cooperation with the State of Oregon, Departtnent of Geology and Mineral Industries Geology of the Central and Northern Parts of the Western Cascade Range in Oregon By DALLAS L. PECK, ALLAN B. GRIGGS, HERBERT G: SCHLICKER, FRANCIS G. WELLS, and HOLLIS M. DOLE ·~ GEOLOGICAL SURVEY PROFESSIONAL PAPER 449 Prepared in cooperation with the State of Oregon, Department of Geology and Mineral Industries ,... UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director . -~ The U.S. Geological Survey Library catalog card for this publication appears after page 56. For sale by the Superintendent of Documents,. U.S. Government Printing Office · · ·. Washington, D.C. 20402 CONTENTS Page Page Stratigraphy-Continued 1 Abstract------------------------------------------- Sardine Formation-Continued Introduction ______ --------------------------------- 2 Lithology and petrography-Continued Scope of investigation ______ - ___ - __ -------------- 2 Location, accessibility, and culture __ -------------- 2 Pyroclastic rocks __________ -- __ ---------'-- 33 Physical features ______ --_---_-_- ___ -----_------- 3 Age and correlation ____ - _--- __ -------------- 34 Climate and vegetation ___ --- ___ - ___ -----_------- 4 Troutdale Formation _____ ------------------------ 35 Fieldwork and reliability of the geologic map ______ _ 4 Boring Lava and volcanic rocks of the High Cascade Acknowledgments _____ --_--- __ -- ___ -----_------- 5 Range--------------------------------------- 36 Rock nomenclature and petrographic techniques_--- 5 General features------------------------~-- 36 StratigraphY--------------------------------------- 7 Lithology and petrography---------_---------- 36 Pre-Tertiary rocks ____ -- _____ - - - _ -- - - - - - - - - - - - - - 9 Age and correlation ___ --_-- ___ - ___ ---------- 38 Eocene marine formations __________________ -- __ -- 9 Quaternary all u vi urn ___________ - ______ ---- ___ - - _ 38 Colestin Formation _________________ - __ -- __ --_--- 10 Intrusive rocks of the Western Cascade Range- _____ --- 39 General features---------------------------- 10 Medium-grained intrusive rocks_- __ - ___ ---------- 39 Lithology and petrography--- ___ ------------- 10 Age of the medium-grained intrusive rocks __ --_ 39 Age and correlation ________ - ___ -----_------- 11 Fine-grained intrusive rocks ____ - ___ - __ ----------- 40 Little .Butte Volcanic Series _____________________ _ 11 Alteration----------------------------------------- 40 General features--------------------------- 11 Zeolitic alteration ________ -- __ ---_-- __ ----------- 40 Lithology and petrography------------------- 12 Propylitic alteration _____ ------------------------ 41 Areal distribution __________ - ______ --_--- 12 Contact metamorphism ________ - ____ --------_---- 42 Pyroclastic rocks ____________ -_--- __ ------ 15 Structure------------------------------------------ 42 Basaltic and andesitic flows and breccia__ ~_ 17 Gross structural features of the Cascade Range in Dacitic and rhyodacitic flows and domes __ _ 20 42 Distribution of volcanic vents ________________ _ FoldsOregon--------------------------------------_________________________________________ _ 21 42 Age and correlution ____________ - ______ -- ___ _ 22 Faults----------------------------------------- 43 Marine tuff and sandstone __________ - ______ -- ___ _ 25 Petrologic Data ______ -- __ -------------------- -- ---- 46 Columbia River Basalt--------------------------- 26 46 General features ___________________________ _ 26 Var~ation in chemical composition_----_----------- Volume and average composition ________________ _ 48 Lithology and petrography------ _________ - ___ _ 28 Variation in mineralogical composition _________ --_ 48 Age and correlation ________________________ _ 30 Variation in composition with time _____________ --_ 50 Sardine Formation ______________________________ _ 30 Location of volcanic vents ________ -- ___ -_---_---- 50 Generrufeatures ___________________________ _ 30 Lithology and petrography------ _____________ _ 31 Speculation on the origin of the volcanic rocks ____ - __ --- 51 Flows- _____ ---------------------------- 32, References cited _________ -··-_- ____ ----- __ -------_--- · 53 ILLUSTRATIONS Page PLATE 1. Reconnaissance geologic rna p and sections of the Western Cascade Range north o·f la t 43 ° _______________ In pocket FIGURE 1. Index maps showing location of Cascade Range and map area in the Pacific Northwest and physical divisions of central and western Oregon____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 2. Oblique aerial photograph of a part of the crest and western slope of the Cascade Range____________________ 3 ::\. Classification of clastic volcanic rocks_________________________________________________________________ 7 4. Comparison of silica content and refractive index of fused bead for 13 chemically analyzed samples of volcanic ~ rocks------------------------------------------------------------------------------------------- 7 5. Correlation chart of Cenozoic formations in parts of western Oregon______________________________________ 9 ~ 6. Location of some upper Eocene plant localities in t.he Colestin Formation and equivalent strata______________ 12 7. Generalized columnar section of the Little Butte Volcanic .Series along the Little River and the North Umpqua ~ River between Glide and Illahee Rock, Oregon_______________________________________________________ 13 III ..... IV CONTENTS Page FIGURE 8. Photomicrograph of an altered pumice lapillus in tuff in the Little Butte Volcanic Series ____ - ______________ _ 15 9. Photomicrograph of curved hairlike crystallitE's (trichites) in welded tuff in the Lit tie Butte Volcavic Series ___ _ 16 10. Comparison of silica content of volcanic rocks of the Western Cascade Range in Oregon and the anorthite content of their plagioclase __________________________________ - ____ -- ___ ----_--------------_--- __ - _________ _ 16 ll. Comparison of composition and angular spacing of 28(131) -28(131) of plagioclase from Tertiary volcanic rocks_ 17 12. Comparison of specific gravity (bulk) and silica content of chemically analyzed samples of basalt and andesite_ 18 13. Comparison of specific gravity (bulk) and modal color index of basalt and andesite ________________________ _ 18 14. Photomicrograph of olivine basalt iu the Little Butte Volcanic Series ________ - ___ - ________________________ _ 18 15. Location of known volcanic vents of the Little Butte Volcanic Series of Oligocene and early Miocene age ______ _ 21 16. Location of Oligocene and lower Miocene plant localities in the Little Butte Volcanic Series _________________ _ 23 17. Inferred location of middle Oligocene and early Miocene marine shorelines in the area of the present Cascade Range, Oreg----~-------------------------------------------------------------------------------- 25 18. Outcrop areas and inferred original extent of Columbia River Basalt and volcanic rocks of the Astoria Formation in northwestern Oregon and parts of southwestern Washington ________________ - _______________________ _ 27 19. Photomicrograph of hyalo-ophitic basalt in the Columbia River Basalt ____________________________________ _ 28 20. Photomicrograph of skeletal magnetite crystals in Columbia River Basalt _________________________________ _ 29 21. Location of known volcanic vents of the Sardine Formation of middle and late Miocene age _________________ _ 31 22. Photomicrograph of hypersthene andesite in the Sardine Formation ______________________________________ _ 32 23. Location of middle and late Miocene plant localities in the Sardine Formation _____________________ ~ _______ _ 34 24. Photomicrograph of porous-textured basaltic andesite in the volcanic rocks of the High Cascade Range _______ _ 37 25. Photomicrograph of olivine basalt from plug at Snow Peak _____________________________________________ _ 38 26. Location of diorite, quartz diorite, granodiorite, and quartz monzonite intrusives, areas of propylitically altered rocks, and mines and prospects north of lat 43 ____________________________________ _: __________________ _ 41 27. Inferred contours on top of rocks of Eocene age _______________________________________________________ _ 42 28. Silica-variation diagrams of rocks from the Cascade Range and some other regions _________________________ _ 47 29. Composition rliagram of normative feldspar of chemically analyzed rocks _________________________________ _ 48 30. Triangular diagram of normative quartz, plagioclase, and orthoclase of chemically analyzed rocks ____________ _ 48 31. Approximate relative abundance of volcanic rocks of different composition ________________________________ _ 49 32. Phenocrysts in volcanic rocks ______________________________________________________________ ..; ________ _ 49 33. Sequence of crystallization in an olivine basalt and a hypersthene andesite ___________________________________ _ 50 34. Triangular FMA diagram of chemically analyzed rocks________ .; _________________________________________ _ 50 35. _Summary of the sequence in composition of the Cenozoic volcanic rocks of the Cascade Range in Oregon _____ _ 51 36. Center lines of belts of vents of Cenozoic volcanic rocks