Geochronology

A wide variety of geochronological tools or methods can be employed to estimate quantitative and qualitative dating of rocks and sediments. Techniques exist to date all geological materials, from billions of years to historical records. U-series dating is the most reliable method for dating Quaternary (the last 2 million years) sedimentary carbonate, silica, and fossil material. Quaternary dating provides a record of climate change and geologically recent changes in environment. U-Pb geochronology of zircon, baddelyite, and monazite is used for determining the age of emplacement of igneous rocks of all compositions, ranging in age from Tertiary (last 65 million years) to Early Archean (3.8 billion years). U-Pb ages of metamorphic minerals, such as zircon, sphene and monazite are used to date thermal events, including terrestrial meteoritic impacts, and to determine thermochronologic histories of terranes. U-Pb ages of zircon in sediments are used to determine the provenance of the sediments. Strontium-isotope stratigraphy is a method that uses extremely precise Sr-isotope measurements of marine fossils in conjunction with the known Sr isotopic composition of sea water through time to provide an age for the fossil. This technique can also be used to determine ages for other geologic processes, such as dolomitization. 40Ar/39Ar provides isotopic ages ranging from 10,000 years to billions of age with 0.1-0.5% precision.. Tephrochronology dates volcanic ash and tuff, with a range of the last 15 million years. 14C dates material with organic carbon, and has a maximum range of 100,000 years. Thermoluminescence provides ages within a range of 100-800,000 years. 210Pb has a short half-life, and dates material from the past 150-200 years.

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U-Th-Pb SYSTEM Technique Equipment Contacts Rb-Sr SYSTEM Technique Equipment Contacts Sm-Nd SYSTEM Technique Equipment Contacts Lu-Hf SYSTEM Technique Equipment Contacts ARGON 40/39 Technique Equipment Contacts TEPHROCHRONOLOGY Technique Equipment Contacts Pb 210 Technique Equipment Contacts

FISSION TRACKS Technique Equipment Contacts CARBON 14 Technique Equipment Contacts THERMOLUMINESCENCE Technique Equipment Contacts 3He/4He Technique Equipment Contacts He/Ne Technique Equipment Contacts BERYLLIUM 10 Technique Equipment Contacts

| Capabilities | | Geochronology, Geochemistry, and Tracer Studies  |

URL http://geology.cr.usgs.gov/capabilities/gronemtrac/geochron/geochron.html