Figure 2. Locality map showing the distribution of the Marlstone Rock Bed west of Banbury, and the Hornton Quarries at Edge Hill near the village of Ratley.
Three samples of fossil wood were collected from the south wall of Hornton Quarries, one from immediately adjacent to the belemnite fossil (Figure 5) during the first visit, and two from locations nearby during the second visit. All the fossil wood samples were from short broken lengths of what were probably branches of trees fossilised in situ. The woody internal structure was clearly evident, thus the samples were not the remains of roots that had grown into this weathered rock from trees on the present land surface. When sampled, the fossil wood readily splintered, diagnostic of it still being woody in spite of its impregnation with iron minerals during fossilisation.
Pieces of all three samples were sent for radiocarbon ( 14 C) analyses to Geochron Laboratories in Cambridge, Boston (USA), while as a cross-check, a piece of the first sample was also sent to the Antares Mass Spectrometry Laboratory at the Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights near Sydney (Australia). Both laboratories are reputable and internationally recognised, the former a commercial laboratory and the latter a major research laboratory.
The staff at these laboratories were not told exactly where the samples came from, or their supposed evolutionary age, to ensure that there would be no resultant bias.
Both laboratories used the more sensitive accelerator mass spectrometry (AMS) technique for radiocarbon analyses, recognised as producing reliable results even on samples with minute quantities of carbon.
Figure 3(a) General view of the south wall of the Hornton Quarries at Edge Hill near Ratley, north-west of Banbury.
(b) Closer view of the quarry face of the south wall showing the oxidized limestone of the top of the Marlstone Rock Bed which is quarried as Hornton Brown building stone.
The results
The radiocarbon ( 14 C) results are listed in Table 1 . Obviously, there was detectable radiocarbon in all the fossil wood samples, the calculated 14 C ages ranging from 20,700 ± 1,200 to 28,820 ± 350 years BP (Before Present).
For sample UK-HB-1, collected from on top of the belemnite index fossil (Figure 5), the results from the two laboratories are reasonably close to one another within the error margins, and when averaged yield a 14 C age almost identical (within the error margins) to the 22,730 ± 170 years BP of sample UK-HB-2.
Alternatively, if all four results on the three samples are averaged, the 14 C age is almost identical (within the error margins) to the Geochron result for UK-HB-1 of 24,005 ± 600 years BP. This suggests that a reasonable estimate for the 14 C age of this fossil wood would be 23,00023,500 years BP.