Study guide to tectonics and terranes of the Pacific Northwest


This Dynamic Earth, Bob Tilling

This Dynamic Planet, Smithsonian



Map Scales   (types: bar, verbal, fraction; implications for area covered and detail?)

Projections  (ex: conic, plane, cylindrical, interrupted, Mercator; equivalence vs. conformality)

Isolines and contour maps  (contour interval, index contour; rule of v’s; how made—historically vs. today?, magnetic north vs. true north and declination)

Remote sensing: aerial photos, orthophotos, georeferencing, color/infrared, microwave, multispectral (LANDSAT), LIDAR; radar interfereometry)

Global Positioning Systems (GPS)

Geophysical imaging: gravity, seismic, magnetics

GIS—Geographic Information Systems


Jack Powell’s 11-stage overview of Washington Geology

1)      Rodinia and Belt Supergroup (1.5–1 Ga)

2)      Rifting of Rodinia (750 Ma)

3)      Kootenai coastal sediments (750–200 Ma)  (Snowball Earth in NW?)

4)      Pangaea  (300–200 Ma)

5)      Docking of Intermontane Superterrane—rocks of Okanagan Highlands: (What is terrane?   superterrane?   see next lecture (180–170 Ma); new volcanic arc forms

6)      Docking of Insular Superterrane (rocks of North Cascades (100–60 Ma)

7)      Eocene-to-Miocene Sandstones and volcanics (55–20 Ma)

8)      Docking of Olympia Peninsula (50–30 Ma)

9)      Eruption of Columbia River Basalts (17–6 Ma)

10)  Ice Ages (1.6 Ma–11,500 yr B.P.)

11)  Modern Cascades Volanoes, 2 Ma to today


Ancient Rocks of the Pacific Northwest

Geologic Time Scale    USGS revised geologic time scale 2007

Age of Earth

First life  3.8–3.5 Ga? (Prokaryotes)

Oxygen revolution ~2.4 Ga  Stromatolite fossils, cyanobacteria, Prokaryotes vs. Eukaryotes; Snowball Earth #1;

Eukaryotes? 2.1–1.5 Ga?,

Precambrian rocks—where? Craton, basement rocks? How to study basement rocks? Rb87-Sr87

Parent vs. daughter product> 0.706 line for Sr87.

How to study basement?  (windows, cores, inclusions, geophysics).

Thickness of Belt rocks (15–20 km)

Belt rock types (Ss, Sltstn, Ls, Sh);  Structures (ripple marks, raindrop imprints; fossils (stromatolites)

Environment of deposition?


 Terranes of the Pacific NW

How to grow a continent?  Sedimentation, subduction, collision??

What are terranes?     superterranes?

Types of terrane? hot spot, island arc, small continent, oceanic spreading ridges, microcontinents. (types of rocks for each?)

Where did terrane originate?  rock types, microcontinents, fossils, sediment provenance, and paleomagnetics

      Paleomagnetics (inclination vs. declination)

Major terranes of WA

North Cascades rocks: Terrane groupings! 95 Ma. Some were “exotic terranes”; melange