The tectonics of Costa Rica are more complicated because the Cocos Plate subdivided into two blocks separated by the Costa Rica Fracture Zone (running northeast onto land), with the northern block being subducted. Submarine canyons have been used to infer the path of the Panama Fracture Zone running along the coast creating wrench faults. On the Osa Peninsula, the Nicoya Complex preserves oceanic crust with basaltic lava, dolerite, gabbro, limestone, chert and argillite, obducted onto land before the Oligocene and then rearranged by Miocene wrench faults.[3]