Paleomagnetic contributions to the Klamath Mountains terrane puzzle-A new piece from the Ironside Mountain batholith, northern California

- The 170-Ma Ironside Mountain batholith is the base of the Western Hayfork terrane.
- Paleomagnetic data were corrected using tilt of the coeval Hayfork Bally Meta-andesite.
- A clockwise rotation of 73.5° ± 11.8° and no latitudinal displacement are indicated.
- Nearly 1/2 of the rotation occurred before accretion to the province at ~ 168 Ma.
- How two inboard terranes and their exotic elements are related remains unclear.

We obtained paleomagnetic samples from six sites within the Middle Jurassic Ironside Mountain batholith (~ 170 Ma), which constitutes the structurally lowest part of the Western Hayfork terrane, in the Klamath Mountains province of northern California and southern Oregon. Structural attitudes measured in the coeval Hayfork Bally Meta-andesite were used to correct paleomagnetic data from the batholith. Comparing the corrected paleomagnetic pole with a 170-Ma reference pole for North America indicates 73.5° ± 10.6° of clockwise rotation relative to the craton. Nearly one-half of this rotation may have occurred before the terrane accreted to the composite Klamath province at ~ 168 Ma. No latitudinal displacement of the batholith was detected.