Study on the Influence Factors of Modern Speleothem Hiatus: A case from Jiguan Cave, Henan

Key words: 
• karst cave /
• modern speleothem hiatus /
• water-rock effect /
• NO₃^-anomaly /
• Jiguan Cave of Henan Province

Abstract: Stalagmite has increasingly become an important part of global change research due to its exclusive advantages of precise dating and high-resolution records. The study of carbonate sedimentary mechanism is significant of understanding the stalagmite sedimentation rate, crystal morphology and precisely interpreting climate proxies, and reasonable protection of modern cave. Jiguan Cave in Henan Province is selected as the example in Asian monsoon-sensitive area in the north-south China intersection, we have monitored the drips and carbonate deposition for 6 consecutive hydrological years from 2010 to 2015, and found:(1)The hydrochemical indices of drips have the similar pattern compared with deposition rate. The biological activity and soil CO₂ are strengthened in wet season due to the increase of precipitation and air temperature, as a result, the dripping rate, Ca²⁺, HCO₃^-, EC and deposition rate of drips also increase, dry season shows opposite pattern. The inhibition of cave CO₂ to calcite deposition is masked by drip saturation. (2)The water-rock effect goes weak for the impact of precipitation markedly decreasing from 2012-2013, and saturation of drips became minimum in 2014 when calcite hiatus also occurred. The deposition was collected again in Nov.2014 becausing increasing rain in the latter half of the year. (3)The cave was washed by artificial leaching and NO₃^- of drips rised more than 10 times. Simulation result shows that~60% CaCO₃ can be more dissolved than before, which suggests the inhibition of NO₃^- to calcite deposition. This may be the reason why the calcite hiatus happened during the drip was with high degree of saturation in some months. It is suggested that the water quality should be taken into consideration in the process of water supply.