Janece McDonald conducting research
Speleothem research.
Image: Janece McDonald

The word speleothem is Greek for “cave deposit”.  A speleothem, more commonly known as a cave formation, is a mineral deposit  formed in limestone or dolostone caves found around Australia.

Speleothems (cave stalagmites, stalactites) develop from the accumulation of calcite precipitated from water that drips through the ceilings of caves.

Water seeping through cracks in a cave’s surrounding bedrock may dissolve certain compounds, usually calcite and aragonite (both calcium carbonate), or gypsum (calcium sulfate).

Speleothem research
Image: Janece McDonald

Many factors impact the shape and color of speleothem formations including the rate and direction of water seepage, the amount of acid in the water, the temperature and humidity content of a cave, air currents, the above ground climate, the amount of annual rainfall and the density of the plant cover.

Speleothems have the capacity to preserve records of rainfall variability extending from modern times back tens of thousands of years.

Currently a number of Australian researchers are developing rainfall records extending back for several centuries from two key water resource regions in south-eastern Australia: Wombeyan Karst Conservation Reserve on eastern margin of the Murray–Darling Basin, and Yarrangobilly Caves in headwaters of the Murray River.

These records will provide critical baseline climatic data to better quantify the long-term context of south-eastern Australia’s recent rainfall decline.