Luminescence chronology of the Bama Beach Ridge, Chad Basin, north eastern Nigeria

摘要

The Mega Lake Chad palaeo-beach ridge is covered by aeolian deposits. The elevation (320, 335 and 338 m.a.s.l) is the rim to the southwestern shores of Mega Lake Chad and the initial deposits of this palaeo-beach are believed to have been guided by a neotectonic fault line trending NNW-SSE. Luminescence dating was conducted on quartz grains extracted from sedimentary layers of the ridge section. Samples from the highest point on the ridge have revealed that aeolian deposits covering the ridge date from 3.3 ± 0.31 ka at 2 m to 6.6 ± 0.64 ka at about 5 m. A water laid deposit of fine to medium sands from 5 m to 8 m depth has ages of 6.1 ± 0.54 to 9.6 ± 0.7 ka, and fine, medium to coarse sand from 10 to 17 m depth have ages from 18.4 ± 1.5 to 26.4 ± 9.3 ka.