Since the discovery of radiocarbon dating in 1949, science has leapt onto the concept of using atomic behavior to date objects, and a plethora of new methods was created. Here are descriptions of a few of the many new methods.
Potassium-ArgonThe potassium-argon dating method, like radiocarbon dating, relies on measuring radioactive emissions. The Potassium-Argon method dates volcanic materials and is useful for sites dated between 50,000 and 2 billion years ago. It was first used at Olduvai Gorge. A recent modification is Argon-Argon dating, used recently at Pompeii.
Fission TrackFission track dating was developed in the mid 1960s by three American physicists, who noticed that micrometer-sized damage tracks are created in minerals and glasses that have minimal amounts of uranium. These tracks accumulate at a fixed rate, and are good for dates between 20,000 and a couple of billion years ago. (This description is from the Geochronology unit at Rice University.) Fission-track dating was used at Zhoukoudian. A more sensitive type of fission track dating is called alpha-recoil.
Obsidian hydration uses the rate of rind growth on volcanic glass to determine dates; after a new fracture, a rind covering the new break grows at a constant rate. Dating limitations are physical ones; it takes several centuries for a detectable rind to be created, and rinds over 50 microns tend to crumble. The Obsidian Hydration Laboratory at the University of Auckland, New Zealand describes the method in some detail. Obsidian hydration is regularly used in Mesoamerican sites, such as Copan.
Thermoluminescence datingThermoluminescence (called TL) dating was invented around 1960 by physicists, and is based on the fact that electrons in all minerals emit light (luminesce) after being heated. It is good for between about 300 to about 100,000 years ago, and is a natural for dating ceramic vessels. TL dates have recently been the center of the controversy over dating the first human colonization of Australia. There are several other forms of luminescence dating as well, but they are not as frequently used to date as TL.
Archaeo- and Paleo-magnetismArchaeomagnetic and paleomagnetic dating techniques rely on the fact that the earth's magnetic field varies over time. The original databanks were created by geologists interested in the movement of the planetary poles, and they were first used by archaeologists during the 1960s. Jeffrey Eighmy's Archaeometrics Laboratory at Colorado State provides details of the method and its specific use in the American southwest.
Oxidized Carbon RatiosThis newly developed method is a chemical procedure that uses a dynamical systems formula to establish the effects of the environmental context (systems theory), and was developed by Douglas Frink and the Archaeological Consulting Team. OCR has been used recently to date the construction of Watson Brake.
Racemization DatingRacemization dating is a process which uses the measurement of the decay rate of carbon protein amino acids to date once-living organic tissue. All living organisms have protein; protein is made up of amino acids. All but one of these amino acids (glycine) has two different chiral forms (mirror images of each other). While an organism lives, their proteins are composed of only 'left-handed' (laevo, or L) amino acids, but once the organism dies the left-handed amino acids slowly turn into right-handed (dextro or D) amino acids. Once formed, the D amino acids themselves slowly turn back to L forms at the same rate. In brief, racemization dating uses the pace of this chemical reaction to estimate the length of time that has elapsed since an organism's death. For more details, see racemization dating
Racemization can be used to date objects between 5,000 and 1,000,000 years old, and was used recently to date the age of sediments at Pakefield, the earliest record of human occupation in northwest Europe.