Radiometric method
This section explains how the radiometric method, including radiocarbon
dating, was used in the Bosumtwi impact crater. Baratoux et al.(2019b ) used a radiometric survey combined with detailed
topographic analysis, including roughness mapping, to map near-surface
K, Th, and U concentrations and field observations. The Geological
Survey of Ghana provided two airborne radiometric surveys for this
investigation. One of them (Aerodat) was taken with a
200 m gridded line spacing. It
was properly calibrated and delivered absolute readings for K (weight
percent), Th (ppm), and U surface concentrations (ppm). Unfortunately,
only half of the Bosumtwi impact crater was covered by this survey. The
second survey covers the full impact structure and has a grid line
spacing of 400 m, although it was
not calibrated. The two airborne surveys were combined to create a
gridded data collection of K, Th, and U concentrations with a 50 m/pixel
resolution. The authors obtained evidence that the moat and outer ring
are features inherited from the impact event and represent the partially
eroded ejecta layer of the Bosumtwi impact structure.
Peck et al. (2004 ) used the results from the Accelerator
Mass Spectrometer (AMS) radiocarbon dating process and produced an age
model from a suite of 30 AMS 14C dates from cores 12P, 15P, and 19P.
While a distinct downcore trend of older sediment ages exists in these
data, there is a significant amount of scattering below
700 cm standardised depth. The
calibrated age range is between 3321 years for the sample taken at
90.0 cm depth and 24,355 years
for the sample taken at 844.1 cm
depth.