Geologic and petrologic evidence indicates that the Ashland pluton and the Wooley Creek batholith, two major plutons of the Klamath Mountain province, have been significantly tilted subsequent to emplacement. Late Cretaceous sandstone depositionally overlies the Ashland pluton and dips approximately 25 ø toward the ENE. Contact metamorphic assemblages in diverse wall rocks surrounding the Wooley Creek batholith suggest at least 30 ø of tilt toward the WSW. Subsequent erosion has exposed at least 12 km of structural relief in the Wooley Creek batholith. Tilting was accomplished, at least in part, by thrusting of the plutons and their host rocks over low-density rocks of the western Jurassic belt, followed by regional doming of deeply buried rocks of the underthrust terrane (Condrey Mountain Schist). Diagrammatic reconstruction of the plutons to pretilt positions suggests inward chemical fractionation of the Ashland pluton but upward fractionation of the Wooley Creek batholith and comagmatic Slinkard pluton. The results of this study indicate that rootless plutons in accretionary margins can undergo significant tilting, facilitating petrologic interpretations. In addition, the study suggests that for Klamath plutons, the effects of tilting must be taken into account before meaningful paleomagnetic interpretations can be made. , 1960, 1966, 1981]. These are, from west to east in ascending structural order, the western Jurassic belt, the western Paleozoic and Triassic belt, the Central Metamorphic belt, and the eastern Klamath belt [Irwin, 1981] (Figure 1). The western Paleozoic and Triassic belt has been further subdivided [Irwin, 1972] into three terranes, each bounded by eastward dipping thrust faults. These terranes are, from west to east in ascending structural order, the Rattlesnake Creek terrane, the Hayfork terrane, and the North Fork terrane (Figure 2). The Wooley Creek batholith and Ashland pluton were intruded into rocks of the western Paleozoic and Triassic belt. The Wooley Creek batholith has yielded Pb-U ages from zircon of approximately 161 Ma [Allen et al., 1982; Barnes et al., this issue]. K-Ar dates on hornblende and biotite from the Ashland pluton range from 133 to 166 Ma and cluster near 6059
SETTING
The Klamath Mountain province of northern California and southern Oregon has been divided into four major lithostratigraphic belts [Irwin
