Late-Holocene buried forests on the Oregon coast

摘要

Deposits of late-Holocene beach sand buried conifer forests episodically emerge on beaches of the Oregon coast. Simultaneously, sand dunes buried late-Holocene forests growing on marine terraces landward of the beaches. Dune ramps, up to 60 m in elevation, connected the beach and dune deposits. The average age of wood samples from stumps rooted on the shore platforms is 3.07 +/- 1.45 ka. The average age of wood and charcoal samples embedded in forest soil on the marine terraces is 3.27 +/- 1.46 ka. Between 1994 and 2006, winter storm waves exposed more than 4.5 km(2) of late-Holocene forest soil on shore platforms at 19 localities. Rooted stumps without soil were uncovered at an additional 14 localities. Once exposed, wave action eroded the soil rapidly (one to two years). The intact forest soil and roots on the shore platforms must have been nearly continuously buried, protected and preserved prior to recent exposure. The late-Holocene buried forest provides the basis for a conceptual model of coastal evolution. A three stage reversal of erosion and sand supply must have occurred: (1) wave erosion switched to seaward advancement of forests, (2) forest growth and soil development switched to burial beneath beach and dune sand and (3) burial and preservation switched to wave erosion, truncation of dune ramps and landward retreat of sea cliffs. Copyright (c) 2006 John Wiley & Sons, Ltd.