ABSTRACT. In order to estimate the modern reservoir age of the seawater (R) and the corresponding local offset from the global marine radiocarbon calibration curve (∆R) for coastal sites of Senegal and Mauritania, we analyzed pre-bomb mollusk shells collected between AD 1837 and 1945. In total, 27 shell samples were measured, including 19 from Senegal and 8 from Mauritania. The results for Senegal for the weighted mean of R is 511 ± 50 BP and ∆R is 176 ± 15 BP; for Mauritania, R is 421 ± 15 BP and ∆R is 71 ± 13 BP. While these values indicate a significant difference from the global mean value of R for Senegal, the R value for coastal Mauritania is close to the average ocean value R of ~400 yr (Stuiver and Braziunas 1993).

In this study, the activity concentrations of 226 Ra, 232 Th and 40 K in twenty cement samples of four types (CEM, CEM II, CEM III, and CEM IV) collected from building material suppliers in Senegal were measured using a low-background digital gamma-ray spectrometer equipped with broad energy germanium detector. The activity concentrations of 226 Ra, 232 Th and 40 K varied from 7.1-150.3 Bq kg −1 , 3.7-16.1 Bq kg −1 , and 48.7-133.9 Bq kg −1 , respectively. Also, possible radiological risks from the usage of these materials were assessed by estimating external and internal index, indoor absorbed gamma dose rate and the corresponding annual effective dose, effective dose rate to different body organs and tissus, and excess lifetime cancer risk. The estimated radiological hazard indices were revised in light of the relevant national and international legislation and guidance. The values of the radiological hazard indices were found to be within relevant all limit values for structural building materials.

Radiocarbon (14C) in atmospheric CO2 for the Dakar (Senegal) urban area was measured using tree leaves collected by botanists from 1900 to 2003. The aim of our study was to compare the local Suess effect in Dakar to the global one during the 20th century. The ∆14C of atmospheric CO2 in this region decreased from 1900 to 1958 during the pre-bomb era (–2±5‰ to –22±4‰). From 1958 to 1964, nuclear bomb tests injected a large amount of artificial 14C into the atmosphere, reflected in the rise of ∆14C values. In the Dakar region, the atmospheric ∆14C reached 773±8‰ in 1964, but subsequently decreased to 80±5‰ by 2003, which is consistent with the global exponential decreasing trend. The ∆14C record presented here remains slightly lower than the global record. This result is attributed to the input of anthropogenic fossil carbon into the atmosphere. The amount of carbon input can be evaluated by comparing urban areas to those of clean air sites. The calculation of anthropogenic fossil carbon is deduced from a simple mathematical model.

Following the passing of Prof Cheikh Anta Diop in 1986, the radiocarbon laboratory (LC14) he created 20 yr earlier at the Institut Francophone d'Afrique Noire (IFAN), Dakar, Senegal, fell into a long hibernation. It took nearly 3 yr to renovate the laboratory and reinstall new equipment in order to return LC14 to full functionality and resume its activity. A new dating system has been implemented around a super low-level liquid scintillation spectrometer from Packard, the Tri-Carb 3170TR/LS, located in an underground room.In this paper, we assess the performance of the dating setup (background level and figure of merit) using known samples from Paris 6 and international standards from the International Atomic Energy Agency (IAEA). After the calibration, the setup was used to study bolé seashells from the Khant area in the northern part of Senegal (West Africa). The aim is to present evidence of the correlation between the transgression of the Nouakchottan (5500 BP) and a few industries in the Khant area. The corresponding ages are difficult to assess and the dates available for this cultural site are randomly distributed, ranging from 4500 to 1500 BP, i.e., a chronological period spanning from the Neolithic to the Iron Age.

ABSTRACT.Results obtained from a liquid scintillation counter using BGO (Bi 4 Ge 3 0 12 ) tubes have produced more precise radiocarbon dates in our laboratory. Duplicate analyses confirm the electronic stability of the counter with a background of 0.1 cpm. Our 14 C dates agree well with those from another laboratory (Paris 6-LOCEAN). Most of the 14 C dates in this study were obtained on samples taken from different archaeological sites. Calibration of the various dates with the appropriate software (CALIB 5.0 in our case) allows better interpretation of the results and their importance in this understudied region. In this paper, we investigate the performance of the counter by analyzing samples from archaeological and marine sites in Senegal and Mauritania, and report the results in our first laboratory date list.