Proceedings of the Integrated Ocean Drilling Program Vol. 341: Expedition reports Southern Alaska margin

Abstract

A remarkable expedition discovery is the substantial sediment volume accumulating on the shelf, slope, and deep sea fan since the early Pleistocene intensification of Northern Hemisphere glaciation and more significantly since the mid-Pleistocene transition. The Expedition 341 cross-margin transect discovered transitions in sediment accumulation rates from >100 m/m.y. in the distal fan to >800 m/m.y. in the proximal fan to >1000 m/m.y. on the slope and continental shelf that provide a telescoping view of strata formation from the Miocene to the Holocene. All five sites sampled Middle Pleistocene to recent sediment and demonstrate exceptional accumulation rates. The 709 m of sediment recovered at Site U1417 records Miocene to recent deposition in the distal Surveyor Fan, including the onset of glaciation at the Pliocene/Pleistocene boundary when sedimentation rates doubled to ~100 m/m.y. Site U1418 contains an expanded Middle to Late Pleistocene sedimentary record that also includes significant increases in sedimentation from ~400 m/m.y. in the Middle Pleistocene to >1200 m/m.y. in the Late Pleistocene. Slope Site U1421 and shelf Site U1420, both proximal to the Bering Glacier during glaciations, provide cores penetrating thick sequences of poorly sorted glacigenic sediments ranging from mud to boulders, accumulating at a rate of at least 1 km/m.y. Slope Site U1419 is slightly west of the Bering Trough mouth and also has exceptional Late Pleistocene sedimentation rates (~3 km/m.y.). The complete report is available at: http://publications.iodp.org/proceedings/341/341toc.htm