Similar seasonal patterns also occur in ice cores and in varves (layers of sediment deposition in a lake, river, or sea bed). The deposition pattern in the core will vary for a frozen-over lake versus an ice-free lake, and with the fineness of the sediment. Sclerochronology is the study of algae deposits. Some columnar cacti also exhibit similar seasonal patterns in the isotopes of carbon and oxygen in their spines (acanthochronology). These are used for dating in a manner similar to dendrochronology, and such techniques are used in combination with dendrochronology, to plug gaps and to extend the range of the seasonal data available to archaeologists and paleoclimatologists. A similar technique is used to estimate the age of fish stocks through the analysis of growth rings in the otolith bones. See also Dendrology International Tree-Ring Data Bank Post excavation Timeline of dendrochronology timestamp events References External links Nottingham Tree-Ring Dating Laboratory Video & commentary on medullary rays, heart wood, and tree rings. Video & commentary on Tree Rings – Formation and Purpose Oxford Tree-Ring Laboratory Bibliography of Dendrochronology Multilingual Glossary of Dendrochronology Digital Collaboratory for Cultural Dendrochronology (DCCD) International Tree-Ring Data Bank Ultimate Tree-Ring Web Pages Laboratory of Tree-Ring Research University of Arizona "Tree Ring Science", the academic site of Prof. Henri D. Grissino-Mayer, Department of Geography, The University of Tennessee, and the Laboratory of Tree-Ring Science American inventions Art history Conservation and restoration of cultural heritage Dating methods Dendrology Incremental dating Paleoecology