Figure F4. Leg 205 Costa Rica drilling area (box) and isochrons derived from seafloor magnetic anomalies (Barckhausen et al., 2001). Numbers indicate crustal age in millions of years. Tectonic boundaries, convergence direction and rate (arrow) (DeMets et al., 1990), and arc volcanoes (triangles) are shown. QSC = Quesada Sharp Contortion. Dashed ellipse encloses proposed region of sill intrusion from Silver et al. (2004). Note transition from rough to smooth incoming crust, following Hey (1977), and "seamount" region (from Morris, Villinger, Klaus, et al., 2003).

Figure F4. Leg 205 Costa Rica drilling area (box) and isochrons derived from seafloor magnetic anomalies (Barckhausen et al., 2001). Numbers indicate crustal age in millions of years. Tectonic boundaries, convergence direction and rate (arrow) (DeMets et al., 1990), and arc volcanoes (triangles) are shown. QSC = Quesada Sharp Contortion. Dashed ellipse encloses proposed region of sill intrusion from Silver et al. (2004). Note transition from rough to smooth incoming crust, following Hey (1977), and "seamount" region (from Morris, Villinger, Klaus, et al., 2003).