Compare methods

	Amino Acid Racemization	Single-Aliquot Regenerative-Dose (SAR) Protocol
Field	Archaeology	Archaeology
Family	Regression model	Process / pipeline
Year of origin	1997	2000
Originator	Reviewed for archaeology by Beverly Johnson and Gifford Miller	Andrew Murray and Ann Wintle
Type	Chemical kinetic dating clock based on the racemization of amino acids in biogenic materials	Measurement protocol for estimating the equivalent dose in optically stimulated luminescence dating
Seminal source	Johnson, B. J., & Miller, G. H. (1997). Archaeological Applications of Amino Acid Racemization. Archaeometry, 39(2), 265-287.	Murray, A. S., & Wintle, A. G. (2000). Luminescence Dating of Quartz Using an Improved Single-Aliquot Regenerative-Dose Protocol. Radiation Measurements, 32(1), 57-73.
Aliases	AAR Dating, Amino Acid Geochronology, Amino Acid Epimerization, D/L Ratio Dating	SAR Protocol, Single-Aliquot Regenerative-Dose OSL, SAR Equivalent-Dose Estimation, Quartz SAR Luminescence
Related	3	3
Summary	Amino acid racemization (AAR) dating estimates the age of biogenic materials such as mollusc shell, ostrich eggshell, bone, and teeth from the slow chemical conversion of amino acids from one mirror-image form to the other after an organism dies. Living tissue builds proteins almost entirely from left-handed (L) amino acids, but after death these gradually interconvert toward an equilibrium mixture of left- and right-handed (D) forms, so the measured ratio of D to L rises predictably with time. Because the reaction is a temperature-dependent chemical process rather than a radioactive decay, AAR is fundamentally a kinetic clock that must be calibrated against an independently dated reference and corrected for the sample's thermal history. Reviewed for archaeology by Johnson and Miller and covered as a standard chronometric tool in Renfrew and Bahn's textbook, it offers a rapid, inexpensive way to date or correlate deposits across the Quaternary, well beyond the radiocarbon range.	The single-aliquot regenerative-dose (SAR) protocol is the measurement methodology that underlies modern optically stimulated luminescence (OSL) dating, providing the recipe by which the equivalent dose of a sediment sample is estimated from a single sub-sample. Its central problem is that exposing a mineral grain to light and radiation in the laboratory changes how brightly it luminesces, so a naive comparison of natural and laboratory signals is biased. Murray and Wintle's protocol solves this by measuring, after every luminescence readout, the response to a fixed small 'test dose' and using it to normalize for sensitivity change, so that natural and regenerated signals can be compared on a common footing. The aliquot's natural signal is then interpolated onto a regeneration growth curve to read off the equivalent dose, and a suite of internal checks — recycling, recuperation, and dose recovery — verifies that the procedure behaved correctly. Because the entire measurement is done on one aliquot, the protocol is efficient, reproducible, and the de facto standard for quartz OSL.