Influences Of Temperature And The Meteoric Water Delta O-18 Value On A Stalagmite Record In The Last Deglacial To Middle Holocene Period From Southwestern Japan

Our understanding of stalagmite delta O-18 paleoclimate records would be significantly improved by determining the relative influence of the two factors, temperature and water delta O-18 Here we apply carbonate clumped isotope thermometry to a well-dated (18.1-4.5 ka) stalagmite, Hiro-1 from Maboroshi Cave in Hiroshima Prefecture, southwestern Japan. The Delta(47) values from 50 stalagmite layers, calibrated using Delta(47) -temperature relationships observed in modern stream tufa from Japan (Kato et al., 2019) yield estimates of paleo-temperature and water delta O-18 variability. Several layers affected by significant prior calcite precipitation under a dry climate display strong kinetic isotope influences: positive delta O-18 and negative Delta(47) deviations. Except for these layers, Hiro-Delta(47) records temperature changes that are broadly consistent with climatic stages after the last glacial maximum (LGM) to the mid-Holocene, although the significant Bolling-Allerod warming does not appear in Delta(47) values. The estimated temperature difference between the period after the LGM (18.0-16.0 ka) and mid-Holocene (7.7-4.9 ka) was 8.3 degrees C. Using Delta(47) temperature, stalagmite delta O-18 values, and change in seawater delta O-18(SW), the comprehensive isotopic depletion from vapor source (seawater) to meteoric water was reconstructed. We obtained larger 18(O)-depletion (-9.5 to -10.0 parts per thousand) in the pre-Holocene section than in the middle Holocene section (around -8.5 parts per thousand). The larger 18O(-)depletion of the pre-Holocene period was ascribed to a larger fractionation during vapor generation under a lower temperature, change in seasonality of precipitation, or a longer vapor trajectory due to the subaerially exposed Seto Inland Sea. Unlike Chinese stalagmites, delta O-18 record of Hiro-1 stalagmite appear largely unaffected by rainfall amount. (C) 2020 The Author(s). Published by Elsevier Ltd.