Sclerochronology
Encyclopedia
The term sclerochronology dates from the early 1970s, and was coined in 1974 following pioneering work on nuclear test atolls by Knutson and Buddemeier. Sclerochronology is the study of physical and chemical variations in the accretionary hard tissues of invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

s and coralline red algae, and the temporal context in which they formed. The term comes from the three Greek words scleros – hard, chronos – time and logos – science, and refers to the science of ordering events in time. Sclerochronology focuses primarily upon growth patterns reflecting annual, monthly, fortnightly, tidal, daily, and sub-daily (ultradian) increment
Increment
An increment is an increase of some amount, either fixed or variable. For example one's salary may have a fixed annual increment or one based on a percentage of its current value...

s of time. The regular time increments are controlled by biological clock
Biological clock
Biological clock may refer to:* Circadian rhythm, living organisms' adaptations to solar related rhythms* Age, as a general factor of female infertility...

s which - in turn - are entrained by environmental and astronomical pacemakers.

Familiar examples include annual bandings in reef coral
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...

 skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...

s or annual, fortnightly, daily and ultradian growth increments in mollusk shells as well as annual bandings fish otoliths. Sclerochronology is analogous to dendrochronology
Dendrochronology
Dendrochronology or tree-ring dating is the scientific method of dating based on the analysis of patterns of tree-rings. Dendrochronology can date the time at which tree rings were formed, in many types of wood, to the exact calendar year...

, the study of annual rings in trees, and equally seeks to deduce organismal life history
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...

traits as well as to reconstruct records of environmental and climatic change through space and time.

The science of sclerochronology as applied to hard parts of various organism groups is now routinely used for paleoceanographic and paleoclimate reconstructions.

Improvements in imaging techniques have now realised the potential to decipher coral banding at daily resolution, although biological 'vital' effects may blur the climate signal at such a high resolution.
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