Episodic growth of the Kodiak convergent margin

Convergent plate boundaries have long been recognized as zones where deep-sea sediments become accreted to plate margins, causing the margin to grow with time¹. However, our understanding of the evolution of these margins is limited because accreted rocks are often too poorly exposed to unravel the complex history theyrecord. Recent results from field, deep-sea drilling and high-resolution seismic-reflection studies indicate that various processes can occur in time along a specific margin². For example, both the middle America and Japan trenches are believed to record a history of strike-slip faulting and/or tectonic erosion before the periods of subduction accretion which presently characterize these margins^3,4. Here, we propose that growth of the Kodiak continental margin in south-west Alaska, one of the largest accretionary prisms in the world, has been dominated by two relatively short episodes of accretion; the first in the late Cretaceous and the second in the early Eocene. These two periods of growth appear to account for >70% of the margin growth during the past 75-100 Myr.