What is Speleothem Science?

Geologists and paleoclimatologists use mineral deposits called “speleothems” found deep in caves to understand how the climate has changed in the past. Caves that contain these mineral structures are found in regions around the world where the bedrock contains limestone. The process by which speleothems form starts with rainwater, which filters down into the ground and becomes slightly acidic. Even a small change in the acidity of infiltrating water allows it to dissolve the soft limestone below the soil layer and hollow out underground chambers that form into complex cave systems. Over time, water continues to drip into these caves and carries with it carbon from the soil, and oxygen in the water molecules. These two elements form calcium carbonate minerals inside droplets and build up into various types of layered structures. The most important of these structures for paleoclimatology is called a stalagmite.  

The variations of the climate system control the amount of rainfall that is able to drip into a cave, and thus controls the chemical and physical properties of the layers within a cave structure. By interpreting changes in the mineral layers and their chemistry, scientists learn about the variability of past environmental conditions. 

How do we learn about climate from speleothems? 

Scientists use a variety of proxies from speleothems and caves to study past climate. The layers of calcium carbonate that build up over time in speleothems are layers of history. The changes in layer chemical composition can be analyzed to develop a time series that records changes in local, regional, or global water cycles. In addition to these basic minerals, small amounts of other elements such as metals that become trapped in the main mineral structure can also be used to create a time series of chemical changes that can be linked to environmental changes. Finally, past flooding events can be reconstructed from analyzing both layers of mud in speleothems and combining dendrochronological techniques to analyze dead trees that have been washed into caves. Speleothem studies have been able to reconstruct the past climate history of a region spanning time periods that range from just a few decades to hundreds of thousands of years. If a speleothem grows really slowly, it can often be used to reconstruct climate over a long period of time, but usually at a lower temporal resolution of maybe a few decades to a hundred years at best. Very fast-growing speleothems, on the other hand, usually do not cover more than a few hundred to a few thousand years of time, but they can often be analyzed at yearly resolution.

PIRE CREATE research

In the PIRE-CREATE project, scientists are using speleothems from across South America to reconstruct hydroclimate variability and understand past environmental changes. The proxy records developed from these caves are key sources of information for studying tropical and subtropical climate, with the potential to record climate extending back thousands of years. Much of this research explores changes in the South American Summer Monsoon, which is the main source of precipitation in the tropical part of the continent. The project findings show how rainfall patterns changed in space and intensity as a response to periods of increased or decreased global temperature. Speleothem proxy records are also studied in combination with mathematical models of the climate to examine how changes in global climate influence local precipitation and atmospheric circulation.

PIRE CREATE project in the news:

Research shows how the Little Ice Age affected South American climate. For the first time, PIRE-CREATE scientists reconstructed the rainfall distribution in Brazil during the climate changes that marked the Medieval Period using isotopic records from caves. Read the article>

The project “Lights in the Darkness” arose from the idea of ​​bringing some of the greatest cave photographers in the world, together with great Brazilian photographers, to record unpublished images of some of the most beautiful caves in Brazil. Read more>

SISAL - Speleothem Isotopes Synthesis and AnaLysis. Read more>

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