The pits appear to have been refilled with the freshly excavated chalk rubble soon after being dug as no weathering has been noted on the chalk sides of the pits. They may also have been dug out and refilled numerous times. The holes are in an accurate, 271.6m circumference circle, distributed around the edge of the area enclosed by Stonehenge's earth bank, with a standard deviation in their positioning of 0.4m. The circle they describe is around 5m inside the monument's bank. Twenty-one of the holes remain unexcavated and no reliable dating material has been recovered from the other thirty-five. The only available carbon date from the holes comes from charcoal in one of the later cremations. It gives the broad range of 2919–1519 cal BC. That sarsen stone chips have only been found in the upper fills of the excavated pits implies that the digging of the holes predates the megalithic phases of Stonehenge. From this stratigraphic evidence it is therefore likely that the holes were dug during the first phase of the monument, Stonehenge 1 (around 3100 BC) and were then reused for burials during Stonehenge 2 in successive centuries. By the time the standing stones of Stonehenge 3 were erected (around 2600 BC), the holes had fallen out of use.