High-resolution ∼55 ka paleomagnetic record of Bien Ho maar lake sediment from Vietnam in relation to detailed 14C and 137Cs geochronologies

Vietnam's Central Highlands in Pleiku feature numerous volcanic craters (i.e. maars) formed over 0.2 Ma ago that contain continuous high-resolution lacustrine sediment records extending from the Late Pleistocene through the Holocene. Their evolution and sedimentary proxies are potentially powerful archives for interpretation of East-Asian monsoon variability across Vietnam, as well as for local to regional changes in landcover. The focus of this study is to develop a reliable chronology for the Bien Ho 25-m-long lake sediment sequence in Vietnam's Central Highlands. We present a combined sediment chronology extending back to 55 ka cal BP that is based on Cs-137 surface sediment chronology, paleomagnetic dating, and 47 C-14 dates distributed evenly throughout the sequence. Based on sedimentary facies analysis and a smooth age-depth model based on Cs-137 and C-14 data, we infer a long-term stable rate of sedimentation in Bien Ho lake without unconformities or erosional hiatuses, except for the uppermost section (ca. 100 years) where human activities increase the rate of sedimentation significantly. The Bien Ho sequence thus provides a complete and uninterrupted record of the lake's depositional history. The present contribution is a geochronologic opening salvo for future contributions from Bien Ho lake featuring multi-disciplinary evidence for longer-term paleoclimate and environmental changes.

Automated summary

Vietnam's Central Highlands in Pleiku contain volcanic craters with high-resolution lacustrine sediment records that offer important insights into East-Asian monsoon variability and landcover changes. This study focuses on developing a reliable chronology for the Bien Ho lake sediment sequence, using Cs-137 surface sediment chronology, paleomagnetic dating, and 47 C-14 dates. The findings show a stable sedimentation rate in Bien Ho lake with the exception of the uppermost section influenced by human activities.