Deep seismic reflection profiling and the growth of the continental crust

Abstract

Deep seismic reflection profiling provides evidence for the style and magnitude of Phanerozoic crustal growth by both lateral and vertical accretion. Profiles across convergent zones have been interpreted as showing tectonic underplating of the continental crust by fragmented oceanic lithosphere. Profiling across extensional zones provides evidence for magmatic underplating of the crust. In addition to studies over active areas, deep reflection profiling over large areas of western Europe, North America and Australia shows that the lower crust is strongly reflective and seismically distinct from the upper crust and upper mantle. The layering is detected beneath many different terranes of varying crustal type and basement age, from Archaean to Cenozoic, and is often apparently younger than the tectonic or metamorphic age of the exposed upper crust. Thus continental growth curves estimated from upper crustal measurements alone may underestimate Phanerozoic crustal additions, and mean crustal ages similarly estimated may be too high.