Seismic refraction measurements within the Peninsular terrane, south central Alaska

摘要: We present an interpretation of crustal seismic refraction data from the Peninsular terrane, one many exotic terranes that have been accreted to continental margin southern Alaska in past 200 m.y. A line was collected along Glenn Highway Copper River Basin south central 1984 and 1985, as part U.S. Geological Survey Trans-Alaska Crustal Transect (TACT) program. P wave velocities 2.7–3.5 km/s thicknesses 1–2 km characterize post-Lower Jurassic sedimentary rocks underlie most line. An average velocity structure includes following five divisions. Beneath lie 4.0–4.6 materials, correlating with andesitic volcaniclastic lava flows Lower Talkeetna Formation. Below these rocks, increases rapidly, 5.0 6.1 km/s, 2–3 km. At 7–8 depth, jumps 6.3 increments 6.6 by 10–12 depth. Velocities increase 6.8 7.0 between 12 20 about 22 a jump 7.4 is inferred but poorly resolved. Depth Moho discontinuity could not be determined our data. The absence clear PmP reflections may indicate deeper than 40 Data two offset shotpoints northeast within Wrangellia terrane constrain deep transition terranes. 6.3–6.6 material thickens northeast, toward suture terranes, southwest its mapped trace at West Fork fault. appears dissimilar interiors. It similar structures for island arc fragments California, such basement Great Valley Klamath Mountains.