The Chad Formation is of Quaternary age. In northeast Nigeria it contains two principal confined aquifers (middle and lower zones) from which samples have been examined for palaeohydrological evidence. Radiocarbon contents range from 2.6-6.3 pmC in the middle zone aquifer (and up to 8.3 pmC in the lower zone). This represents a very narrow range of ages, some 4 ka, and using the ~(13)C results (mean value - 14per thousand) to construct a model for evolution of the TDIC, this age span is most likely from 24.0 to 19.9 ka BP, which implies a linear groundwater velocity of 40 m/a during this period.
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机译：乍得形成是第四纪时龄。在东北尼日利亚，它包含两个主要受限含水层（中下部区域），从中检测样品对古草学证据。辐射碳内含物的范围从中间区含水层的2.6-6.3 PMC（下部区域上最多8.3 PMC）。这代表了一个非常窄的年龄，约4ka，并使用〜（13）C结果（平均值 - 14per千）来构建TDIC演化的模型，这个年龄段很可能是24.0到19.9 ka BP，这意味着在此期间的线性地下水速度为40米/ a。
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