Modifying the Coast Transform Motion

Our Story So Far… Animated Cordillera Animated Cordillera - James Sears

Question still in debate… Where did the Insular Terrane actually accrete to North America? Intermontaine ST Insular ST N. Cascades Present Day WA State

Two Hypotheses Intermontaine ST Insular ST & N. Cascades Hypothesis A at 90 Myrs Hypothesis B at 90 Myrs WA State Baja BC Hypothesis

Baja BC 85 Myrs

Baja BC 80 Myrs

Baja BC 70 Myrs

Baja BC 60 Myrs

Main Evidence for Baja BC Paleomagnetics of Mt. Stuart Batholith Mt. Stuart 90 Myrs 30° inclination Eocene Volc. Rocks <55 Myrs 45° inclination (Modern lat.)

Other Evidence: Sediment Provenance Inconclusive - needs more study Source A Source B What do the overlapping sedimentary rocks tell us?

Other Evidence: Fossils What do the fossils tell us? New study - not yet published Supports Baja BC

Other Evidence: Plate Tectonic Reconstructions Supports Baja BC

However - there are problems… 1.No major faults discovered 2.Sedimentary rocks around the batholith are tilted…could it be tilted, too? The Question Remains Unanswered…

Post-Insular Plate Tectonics Graphics by Steve Dutch - U of Wisconsin D-2

80Myr: Formation of the Kula Plate D-2

55 Myrs D-2

40 Myrs D-2

30 Myrs D-2

20 Myrs D-2

Present D-2

Major Events of the Cenozoic Age (Myrs) Straight Creek Transform Fault Western Cascade Arc Challis Arc High Cascade Arc Columbia River Basalts Formation of Olympic Rocks Accretion of Olympic Rocks Major Sedimentary Basins VolcanismTectonicsOlympicsSedimentary Events Ice Ages