1. Paleomagnetic constraints on the emplacement and temperature of select volcaniclastic debris flows of the Pliocene Tuscan Formation in Northern California Presented by: Roy Hull Advisor: Dr. Rachel Teasdale California State University – Chico

2. Why this Research? We want to know more about the emplacement process of the debris flows Magmatic Meteoric and/or volcanic event Identify new characterization attributes for Tuscan Formation – correlation aid Validate that paleomagnetic techniques can be used on volcanic related debris flows

3. Similar Research Paleomagnetic techniques have been used in the past. ◦Pyroclastic flows i.e. Japan, Italy ◦Volcanic debris avalanche flows i.e. Mexico ◦Lava deposits worldwide Why not debris flows?

5. 2008 Proof of concept ◦Big Chico Creek Ecological Reserve USGS CSU – Chico CSU – Sac

6. Proof of concept - 2008 Upper Flow  Plots were widely scattered – Cold emplacement Medial Flow  Plots were inconclusive either way Base Flow  Type 3 vector that indicated a reheating to 450- 500˚C, but slightly scattered Possible brief interval between lower and upper units Emplaced around 3Ma Distance from source might be a factor (45Km)

7. Was the debris flow hot or cold when emplaced? ◦If hot, can the actual temperature of reheating be determined ◦If hot, can the genesis be interpreted, i.e. volcanic episode Can a geomagnetic reversal be detected? Can a depositional age be assigned to a specific debris flow? Research Questions

8. Geomagnetic Reversals Tuscan Debris flows were deposited during a time interval when numerous reversals occurred

9. Site Logistics Sample collection ◦Interbedded lava ◦Proximal, midway and distal from Mt Yana

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15. Sample Processing Progressive Thermal Demagnetization ◦Heating and Cooling cycle Cryogenic Magnetometer (USGS – Menlo Park) ◦3 axis magnetic moment (x, y, z)  Total magnetic moment, H  Inclination, I (vertical component)  Declination, D (horizontal component)

17. Rocks do not age well ◦Lightening and Chemical ◦Viscous Remanent Magnetism  Minimum Temperatures Hematite > 300°C Magnetite > 190°C Titanomagnetite < 200°C

18. Progressive Thermal Demagnetization Points 0 – 3 younger magnetic Points 4 – 6 original magnetic

19. Type 1 ◦Vector  Similar inclination  Similar declination ◦Highest temperature  Unknown ◦What is this?  Lava

20. Type 2 Vector ◦Different vector directions between clasts  Widely scattered plots Example – Cold flow and conglomerates

21. Type 3 Vector ◦Two component vectors Why two? ◦Clasts reheated, but not enough to completely over-write older imprints Lower vector – Consistent direction Higher vector – Random direction

22. Current Analysis Proximal (small sample lots size)  Site 2: ◦ Lava flows are all normal polarity, NE declinations and different inclinations  Site 3: ◦ Very similar inclination and declination  Site 2 and 3 debris flows: ◦ “Somewhat scattered and general indication of normal polarity” Site 1 (Medial), 4 (Distal)  Not processed

23. What is left? More sample collection ◦Proximal sites ◦Find another medial site Trip(s) to Menlo Park ◦Sample processing and document results Write thesis

24. References Butler, Robert, “Paleomagnetism: Magnetic Domains to Geologic Terranes”, University of Portland, Electronic Edition, September 2004 Clement, B.M., Conner, C.B. and Graper, G, “Paleomagnetic estimate of the emplacement temperature of the long-runout Nevado de Colima volcanic debris avalanche deposit, Mexico”, Earth and Planetary Sciences Letters, 120, pp499-510,1993 Lydon, Philip, “Geology and Lahars of the Tuscan Formation, Northern California”, GSA Memoir 116, 1969 (Former Chico Prof) Dr. Duane Champion – USGS Volcano Hazards Team (Paleomagnetic Expert) Google Earth