Geology and Ground- Water Features of Shasta Valley, Siskiyou County California By SEYMOUR MACK GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1484 Prepared in cooperation with the California Division of Heater Resources Property of GROUND WATER BRANCH UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : I960 UNITED STATES DEPARTMENT OF THE INTERIOR FRED A. SEATON, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director The U.S. Geological Survey Library has cataloged this publication as follows: Mack, Seymour, 1922 Geology and ground-water features of Shasta Valley, Siskiyou County, Calif. Washington, U.S. Govt. Print. Off., 1959. V, 115 p. illus., maps (2 fold, in pocket) diagrs., tables. 24 cm. (U.S. Geological Survey. Water-supply paper 1484) Prepared in cooperation with the California Division of Water Resources. Bibliography: p. 110-111. 1. Geology California Siskiyou Co. 2. Water, Under­ ground California Siskiyou Co. 3. Water Supply California Siskiyou Co. I. California. Dept. of Water Resources. II. Title: Shasta Valley, Siskiyou County, Calif. (Series) For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. CONTENTS Page Abstract. _ ________________________________________________________ 1 Introduction-_____________________________________________________ 3 Purpose and scope of the investigation-__________________________ 3 Location of the area____-_---___________--__----___-_--________ 3 Methods of investigation._________-_-_____-_----___-___________ 5 Previous investigations.________________________________________ 5 Acknowledgments. ____________________________________________ 6 Well-numbering system._______________________________________ 6 Geography.___________________________________ ___________________ 7 Topography and drainage-_____________________________________ 7 Climate-__---_--_____-_-___-______-_____-_-___-------___---_- 11 Transportation._______________________________________________ 15 Population____ _ _______________________________________________ 15 Agriculture._____-___-____-___-__--_-__---_---___-_---_-____-- 16 Mineral resources.______.___________________-_-_--_-__-___-___- 16 Geology-------_-_________-_-___-____-_______---_-_---__-___-----_ 17 General character and age of the rocks_ _________-_----_-_________ 17 Hydrologic properties of aquifers___________-_-_-__-_-_--___--_-_ 23 Geologic units and their water-bearing properties._________________ 24 Rocks of pre-Late Cretaceous age____----------_-------__--_- 24 Consolidated sedimentary rocks of Cretaceous and Eocene age_ _ 26 Chico formation (Upper Cretaceous)________---_-_____--_ 26 Umpqua formation (Eocene)__-_----------_-------__-__- 29 Volcanic rocks of Tertiary and Quaternary age________________ 31 Volcanic rocks of the western Cascades (Eocene to Miocene)- 31 Volcanic rocks of the high Cascades (Pliocene to Recent) _ . _ 38 Plutos Cave basalt (Recent)____________________________ 41 Unconsolidated deposits of Quaternary age.________--_---__-_ 43 Terrace deposits (Pleistocene)___________________________ 43 Morainal and fluvioglacial deposits (Pleistocene and Recent) _ 44 Older alluvium (Pleistocene and Recent)_____-_______---_ 45 Younger alluvium (Recent)_____________________________ 47 Structure. _-_-_-_________________-___--______-__-___---_--_--- 49 Geologic history.______________________________________________ 50 Ground water_----______-______________________--_-__-_--_-__-_--- 54 Occurrence and movement._-______-.__________--_--_--_-___---_ 54 Springs__ _ ____________________________________________________ 57 Fluctuations of water levels._______-_-_______-__-_--_--__----_-- 60 Recharge.____________________________________________________ 62 Discharge._--_________--____________--______-_-------_--__--_ 63 Water utilization. _--___-_--_____________-____-_______-_-_________- 66 Quality of water.__________________________________________________ 67 Relation to use____-___--___--________---_-___-_-___---_____--- 68 Relation to geology.-__________________----__-_-___-_--___----- 71 References cited.__________________________________________________ 110 Index______________________________________________________________ 113 IV CONTENTS ILLUSTRATIONS [Plates in pocket] PLATE 1. Geologic map of Shasta Valley, Calif., showing location of wells and springs. 2. Map of Shasta Valley, Calif., showing location of wells and water-level contours, spring 1954. Page FIGURE 1. Map of Siskiyou County, Calif., showing location of valleys investigated for Upper Klamath project.________________ 4 2. Annual discharge of Shasta River near Yreka and precipita­ tion at Yreka_ _______________________________________ 12 3. Geologic section A-A' across Shasta Valley________________ 19 4. Tuff-breccia in the volcanic rocks of the western Cascades on the southwest side of Sheep Rock_____________________ 34 5. Owls Head, a jointed rhyolitic lava dome in the volcanic rocks of the western Cascades.______________________________ 35 6. Mount Shasta, looking southeast from vicinity of Montague; low hillock in foreground underlain by volcanic rocks of western Cascades; and older alluvium in middle distance-- 40 7. Collapsed lava tube in Plutos Cave basalt near Pluto Cave__ 41 8. Diagrammatic sections B-B' and C-C" across Shasta Valley illustrating geologic structure._________________________ 51 9. Hydrographs of wells 44/5-34C1, 45/5-28D1, and 44/6-20Al_ _ 60 10. Hydrographs of wells 43/6-21J1 and 43/6-21J2, ____________ 61 11. Cation relationships of Shasta River water at five sampling localities in Shasta Valley-__________________--__-----_ 72 12. Graphical presentation of analyses of selected samples of ground water in Shasta Valley..________________________ 78 CONTENTS TABLES Page TABLE 1. Measured discharge in acre-feet, of Shasta and Little Shasta Rivers and Parks Creek at gaging stations near the entrance to Shasta Valley______ _____--_______________________ 10 2. Annual precipitation, in inches, at Yreka, Montague, and Edgewood, Calif____________________________________ 13 3. Average monthly precipitation at Yreka, Calif., 1872-1954-- 15 4. Average monthly temperature at Yreka, Calif., 1903-55____- 15 5. Summary of yield characteristics of wells tapping the volcanic rocks of the western Cascades in Shasta Valley___________ 36 6. Summary of yield characteristics of wells tapping Plutos Cave basalt in Shasta Valley__________________________ 42 7. Summary of yield characteristics of wells tapping morainal and fluvioglacial deposits in Shasta Valley_______________ 45 8. Summary of yield characteristics of wells tapping the younger alluvium in Shasta Valley.______________-_-__--_--_-__ 49 9. Flow at Cold Spring from January to May 1954____________ 58 10. Gaged and estimated surface-water inflow to Shasta Valley in the year ending September 30, 1953___________--___-_-_ 64 11. Principal water-service agencies in Shasta Valley in 1953____ 66 12. Chemical features of water draining the serpentine___ _______ 71 13. Chemical features of water draining known limestone beds___ 73 14. Chemical features of water draining the Chico formation.- __ 74 15. Chemical features of water from springs near Table Rock and well 46/5-8P2..._-____-_-_----_--_---_--_------------ 75 16. Chemical features of water from the Umpqua formation..--- 75 17. Chemical features of water from wells tapping the Plutos Cave basalt__________________________--_----_---_-- 76 18. Chemical features of water from wells tapping the volcanic rocks of the western Cascades..___-___________--__----_ 77 19. Description of water wells______-___-___-----___--_------ 79 20. Weekly water-level measurements-_______________________ 87 21. Selected drillers' logs of wells in Shasta Valley.________-_-- 95 22. Chemical analyses of ground water.___________--_____-_-- 100 23. Chemical analyses of surface water. ___-_-_--------_---_-- 108 GEOLOGY AND GROUND-WATER FEATURES OF SHASTA VALLEY, SISKIYOU COUNTY, CALIFORNIA By SEYMOUR MACK ABSTRACT Shasta Valley is in the central part of Siskiyou County, Calif., and about 12 miles south of the Oregon border. It lies between the Klamath Mountains on the west and the Cascade Range 011 the east. The valley has an area of about 250 square miles; the north-south length is about 30 miles and the maxi­ mum width is about 15 miles. The average precipitation from July 1 to June 30 at Yreka and Montague is about 17 and 12 inches, respectively, and the av­ erage annual temperature at Yreka is 51.5°F. The area has a population of about 12,000, most of whom are employed in farming, cattle raising, and lum­ bering. The farm income is derived chiefly from livestock, principally beef cattle, hogs, and sheep. Alfalfa, wheat, barley, oats, and rye are the main crops grown in the valley. The Klamath Mountains are underlain by metamorphic and sedimentary rocks of Paleozoic age and by intrusive rocks of Mesozoic age that form the basement complex. Near Yreka the Chico formation of Late Cretaceous age, which is composed of shale, sandstone, and some conglomerate, overlies the older rocks with profound unconformity. The Chico formation in turn is overlain disconformably by the Umpqua formation of Eocene age, which con­ sists mainly of black shale. These rocks are covered by a thin veneer of older alluvium which floors much of the northern part of the valley. Volcanic rocks make up much of the valley floor from Montague southward to Edgewood. The southeastern, flatter part of the valley is occupied by the Plutos Cave basalt, which is a relatively large single flow erupted