OSL is a method for dating when minerals, in this case the quartz in the chalk, were last exposed to sunlight. Trenches were dug at various points to obtain early samples of the giant. Authors Dr Thomas Morcom, postdoctoral fellow at the University of Oslo and Dr Helen Gittos, associate professor in Medieval History at the University of Oxford, say the hillside carving was potentially used as a mustering site for West Saxon armies.
They discovered that the giant has been largely kept visible through scouring, except for two major rechalkings. Dr Morcom said: "OSL cannot precisely date when the figure was cut, but rather when the silt began to accumulate within his outlines and when the hillwash built up downslope of them.
"The dates indicate that the outlines of the giant were silting up in the period 700-1110 AD, with a midpoint date of 905 (this date comes from his right elbow). This is confirmed by a second sample, from the silt in the bottom of the trench in his right foot, which gave dates of 650-1310 AD, with a midpoint date of 980.
"These early medieval dates are confirmed by two other samples from higher up in the stratigraphy which both have a midpoint date of the mid-thirteenth century. They are also supported by the analysis of snail shells in the soils, which reveals that the early levels contain snails first introduced into Britain in the Middle Ages.
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"It is therefore most likely that the giant was cut in the early Middle Ages rather than earlier or later, although it could have happened anytime within the period of c. 7001100. The dates also suggest that he was not much cleaned after having been initially cut but that he was then substantially rechalked."