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Highlights

  • Seismic events trigger aragonite growth in speleothems from Mawmluh Cave
  • 230Th/U dating identifies a recent calcite-to-aragonite shift between 1859 and 1950 CE
  • Earthquakes reactivate fractures, increasing dripwater Mg/Ca ratios through dissolution of dolomite host rock
  • Recent aragonite "caps" are widespread across stalagmites in Mawmluh Cave
  • Anthropogenic activity may sustain conditions favorablefor aragonite precipitation

Abstract

Mawmluh Cave, north-east India, is located in a seismically very active region within the Himalayas with frequent earthquakes of varying magnitude. So far, speleothems from the cave have mainly been used to reconstruct past monsoon variability. The potential effect of seismic events on speleothem formation in Mawmluh Cave, however, has not been studied in detail yet. We investigated three stalagmites from Mawmluh Cave, each predominantly consisting of calcite overlain by substantially younger aragonite at the top (i.e., an aragonite ‘cap’). 230Th/U-dating shows that the initiation of aragonite growth occurred between 1859 and 1950 CE in agreement with previous studies. The underlying calcite is between 2,000 and 62,000 years older. Detailed speleothem petrography, Raman spectroscopy, and trace element concentrations enabled us to identify aragonite and calcite sections in the three speleothems. This revealed a further aragonite growth phase in an older section of one of the speleothems, in addition to the recent aragonite ‘caps’. We compiled all earthquakes with a minimum shaking intensity of IV (ESI-07) at Mawmluh Cave since 1845 CE. These frequent seismic events had the potential to reactivate fractures and to produce fine-grained dolomite and dolomitic limestone from the host rock. Dissolution of the dolomite will result in increased Mg/Ca molar ratios of the drip water, a prerequisite for precipitation of aragonite speleothems. Thus, we suggest that the initiation of growth of aragonitic speleothems at Mawmluh Cave was triggered by seismic events in this tectonically active region. Anthropogenic processes, such as blasting in the nearby quarry, atmospheric pollution from the nearby cement plant, and removal of soil and vegetation cover, may have sustained or even amplified the conditions favorable for aragonite precipitation, which would explain the frequent observation of the young aragonite ‘caps’.

DOI

https://doi.org/10.5038/1827-806X.ijs2612

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