Deformation of the Eastern Franciscan Belt, northern California

The late Jurassic and Cretaceous Eastern Franciscan belt of the northern California Coast Range consists of two multiply deformed, blueschist-facies terranes; the Pickett Peak and Yolla Bolly terranes. Four deformations have been recognized in the Pickett Peak terrane, and three in the Yolla Bolly terrane. The earliest recognized penetrative fabric, D₁, occurs only in the Pickett Peak terrane. The later penetrative fabrics, D₂ and D₃, occur in both the Yolla Bolly and Pickett Peak terranes. D₁ and D₂ apparently represent fabrics that formed during subduction and accretion of the terranes. Fabrics from both D₁ and D₂ are consistent with SW-NE movement directions with respect to their present geographic positions. D₃ postdates blueschist-facies metamorphism of the terranes and may be related to emplacement of the terranes to higher structural levels. A broad regional warping, D₄, is evident from the map pattern and folding of large metamorphosed thrust sheets. D₄ folds may be related to deformation associated with oblique convergence along the continental margin in late Cretaceous and (or) early Tertiary time.