Үңгірдегі минералдық шөгінділер мен палеоклимат деректері

Structure formed in a cave by the deposition of minerals from water
secondary deposits, derived from concrete, lime, or mortar, outside the cave environment

A speleothem ('/s//p//iː//l//i//ə//θ//ɛ//m/; ) is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on their depositional history and environment. Their chemical composition, gradual growth, and preservation in caves make them useful paleoclimatic proxies.

Speleothem transects can provide paleoclimate records similar to those from ice cores or tree rings. Slow geometrical growth and incorporation of radioactive elements enables speleothems to be accurately and precisely dated over much of the late Quaternary by radiocarbon dating and uranium thorium dating, as long as the cave is a closed system and the speleothem has not undergone recrystallization. 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. 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. Variations in precipitation alter the width of speleothem rings: closed rings indicates little rainfall, wider spacing indicates heavier rainfall, and denser rings indicate higher moisture. Drip rate counting and trace element analysis of the water drops record short term climate variations, such as El Niño–Southern Oscillation (ENSO) climate events. 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.

The usual definition of speleothem excludes secondary mineral deposits derived from concrete, lime, mortar, or other calcareous material (e. g. limestone and dolomite) outside the cave environment or in artificial caves (e. g. mines, tunnels), which can have similar shapes and forms as speleothems. Such secondary deposits in man made structures are termed calthemites. Calthemites are often associated with concrete degradation, or due to leaching of lime, mortar, or other calcareous material.