Speleothem

A speleothem (/ˈspiːliəθɛm/; from Ancient Greek σπήλαιον (spḗlaion) 'cave' and θέμα (théma) 'deposit') is a geological formation made by mineral deposits that accumulate over time in natural caves.

Most cave chemistry involves calcium carbonate (CaCO3) containing rocks such as limestone or dolomite, composed of calcite or aragonite minerals.

[5] Oxygen (δ18O) and carbon (δ13C) stable isotopes are used to track variation in rainfall temperature, precipitation, and vegetation changes over the past ~500,000 years.

[6][7] The Mg/Ca proxy has likewise been used as a moisture indicator, although its reliability as a palaeohygrometer can be affected by cave ventilation during dry seasons.

[9] Exceptionally, climate proxy data from the early Permian period have been retrieved from speleothems dated to 289 million years ago sourced from infilled caves exposed by quarrying at the Richards Spur locality in Oklahoma.