T252 Advances in Cave and Karst (Posters): A Tribute to the Distinguished Career of E. Calvin Alexander Jr.

Tuesday, 27 September 2016
9:00 AM - 6:30 PM
Exhibit Hall E/F

VARIATION OF δ18O IN THE METEORIC PRECIPITATION, DRIP WATER, AND CALCITE DEPOSIT IN MIAODONG CAVE, LIAONING PROVINCE AND ITS IMPLICATION FOR PALAEOCLIMATIC RECONSTRUCTION

Paper number: T252-10
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

  • Binggui CAI Presenting Author
    College of Geographical Sciences, Fujian Normal University, Fuzhou
  • Binggui CAI Presenting Author
    Fujian Normal University, Fuzhou
  • Binggui CAI Presenting Author
    University of Texas at San Antonio, San Antonio, TX
  • Fang Wang
    College of Geographical Sciences, Fujian Normal University, Fuzhou
  • Fang Wang
    Fujian Normal University, Fuzhou
  • Yongli Gao
    University of Texas at San Antonio, San Antonio, TX
  • Xiuming Liu
    Fujian Normal University, Fuzhou
  • Xiuming Liu
    College of Geographical Sciences, Fujian Normal University, Fuzhou
  • Xiuming Liu
    Macquarie University, North Ryde

Abstract

Miaodong Cave is located in northeastern China, a northern margin region of the East Asian Summer Monsoon (EASM). Sub-monthly in-situ monitoring of δ18O of meteoric precipitation, drip-water, and calcite deposition were carried out at Miaodong Cave, Liaoning province, through two hydrological years (from January 2012 to December 2013) to determine seasonal variability and mechanisms of oxygen isotope transfer in Miaodong Cave.

Oxygen isotope ratio in precipitation (δ18Op, VSMOW) exhibits significant seasonal trend, with most negative values in winter snow (~-13.5‰), less negative values in summer rainfall (~-9.6‰), and highest values in spring and autumn rainfall. Annually weighted average value of δ18Op is about -9.8‰. The local Meteoric Water Line (LMWL) has smaller slope, which is different from Global Meteoric Water Line (GMWL). This trend is similar to Shihua Cave in northern China but different from caves in southern China.

δ18O in drip water (δ18Od, VSMOW) at three drip sites (MD1, MD3 and MD4) shows extremely constant values at both seasonal and spatial scales with a mean value of -9.6‰ and minor inter-annual variability (about 0.2 ‰ negative in 2013 than in 2012). δ18Od ranges between annually weighted average of precipitation and weighted average of rainfall (from April to October). The δD-δ18Od in drip water is plotted in a medium position of the linear regression line of rainfall δ18Od, which is different from that of snowfall. This implies that drip water δ18Od corresponds well with rainfall δ18Op and snowfall contributes much less to the drip water.

The variability of δ18O in calcite deposit of drip water (δ18Oc) exhibits site-dependent values. At a site with moderate drip rate (MD1), the δ18Oc is relatively constant, similar to those of feeding drip water. On the contrary, the δ18Oc shows seasonal trend at drip site MD3, with slower drip rate (less than 2 drops per minute). δ18Oc at site MD3 is ~0.4‰ heavier in dry season than that in rainy reason. In addition, δ18Oc of MD3 is slightly (~0.3‰) heavier than that of MD1. This discrepant δ18Oc values between the two drip sites maybe caused by dynamic fractionations due to much different drip rates.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-286032

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