Seismic-refraction measurements in the Magellan Straits

The results of 22 seismic-refraction profiles in the Magellan Straits are presented, together with the correlation between seismic layers and the onshore surface geology of Isla Riesco and Península Brunswick and one well in the Manantiales oil field. Five seismic layers were measured: A, 1.78–2.52 km/sec; B, 2.78–3.00 km/sec; C, 3.24–3.51 km/sec; D, 4.02–4.59 km/sec; and E, 5.18–5.87 km/sec. Layer A is identified as Quaternary-Pliocene; B, Miocene-Eocene; C, Cretaceous; D, Cretaceous and Jurassic; and E, basement. The results indicate zero sediment thickness at Península Brecknock (southern end of Canal Magdalena) to 6600 meters of Cenozoic and Mesozoic sediments measured at Bahia Whitsand. A 200-km-long profile recorded between Cabo Cono in the Second Narrows and Península Brecknock measured a sub-basement layer, velocity 6.70 km/sec, at an average depth of 17 km. The M discontinuity, velocity 7.95 km/sec, was measured at a depth of 29.6 km at Cabo Cono and 34.8 km at Península Brecknock.