Maps of Pleistocene sea levels in Southeast Asia: shorelines, river systems and time durations

Aim Glaciation and deglaciation and the accompanying lowering and rising of sea levels during the late Pleistocene are known to have greatly affected land mass configurations in Southeast Asia. The objective of this report is to provide a series of maps that estimate the areas of exposed land in the Indo-Australian region during periods of the Pleistocene When sea levels were below present day levels. Location The maps presented here cover tropical Southeast Asia and Austral-Asia. The east-west coverage extends 8000 km from Australia to Sri Lanka. The north-south coverage extends 5000 km from Taiwan to Australia. Methods Present-day bathymetric depth contours were used to estimate past shore lines and the locations of the major drowned river systems of the Sunda and Sahul shelves. The timing of sea level changes associated with glaciation over the past 250,000 years was taken from multiple sources that, in some cases, account for tectonic uplift and subsidence during the period in question. Results This report provides a series of maps that estimate the areas of exposed land in the Indo-Australian region during periods of 17,000, 150,000 and 250,000 years before present. The ancient shorelines are based on present day depth contours of 10, 20, 30, 40, 50, 75, 100 and 120 m. On the maps depicting shorelines at 75, 100 and 120 m below present levels the major Pleistocene river systems of the Sunda and Sahul shelves are depicted. Estimates of the number of major sea level fluctuation events and the duration of time that sea levels were at or below the illustrated level are provided. Main conclusions Previous reconstructions of sea-level change during the Pleistocene have emphasized the maximum lows. The perspective provided here emphasizes that sea levels were at their maximum lows for relatively short periods of time but were at or below intermediate levels (e.g. at or below 40 m below present-day levels) for more than half of each of the time periods considered.