Wrangellia terrane

[2] There are two conflicting hypotheses about whether the Wrangellia Superterrane originated at polar or equatorial latitudes: Geological evidences indicate that the Caledonide closure of the Iapetus and Rheic Oceans along the Laurentian westcoast (modern coordinates) also opened an ocean between the northern margin of Laurentia and Baltica on one side and Siberia on the other.

[4] Rocks of Wrangellia (the individual terrane, not the composite terrane) were originally created in the Pennsylvanian to the Jurassic somewhere, but probably near the equator, in the Panthalassic Ocean off the west coast of Laurentia (North American craton) as island arcs, oceanic plateaus, and rock assemblages of the associated tectonic settings.

It is composed of many rocks types, of various composition, age, and tectonic affinity, but the Late Triassic flood basalts are the defining unit of Wrangellia.

These basalts, extruded onto land over 5 million years about 230 million years ago, on top of an extinct Pennsylvanian and Permian island arc, constitute a large igneous province, currently exposed in a 2,500 km (1,553 mi) long belt.

Over time, plate tectonics moved this amalgamation of crust generally northeastward into contact with the North American continental margin.