Geology

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Africa Groundwater Atlas >> Additional resources >> Geology

Geology of Africa

A new geology map of Africa was developed for this Atlas. It is based on the USGS 1:5 million scale map of geology, oil and gas fields and geologic provinces of Africa (Persits et al., 2002). The USGS map is itself based on the 1:5 million scale geological map published in 1964 by UNESCO. The USGS map (Persits et al. 2002) is made available through the USGS and can be accessed via the USGS Energy Data Finder.

The new geology map of Africa presented here was modified by the British Geological Survey in order to highlight significant hydrogeological features. Some of the geological units in the original USGS map have been grouped or subdivided; and some areas where unconsolidated sediments are mapped have been re-categorised to highlight important underlying bedrock aquifers geology (MacDonald et al., 2012). The following key modifications have been made:

Precambrian rocks In the original USGS map, Precambrian rocks are undivided. In the new map presented here, Precambrian rocks have been subdivided into three groups:

  1. metasedimentary
  2. orogenic/mobile belt – crystalline metamorphic and igneous rocks within linear, mostly Proterozoic, orogenic belts
  3. craton – Archaean and Palaeoproterozoic rocks which have not been affected by Proterozoic and younger orogenic events

Sedimentary rocks These rocks have, where relevant, been grouped by the major groundwater sedimentary basins to which they belong: for example, the Taoudeni, Chad and Iullemeden basins.

Unconsolidated sedimentary deposits These are distinguished in the new map where they cover a large area and/or where they overlie less permeable rocks. However, they are not generally shown where they have small outcrops (for example, alluvial outcrops in small river valleys) or where they overlie sedimentary basins of greater hydrogeological significance.

  • Geology of Africa, 1:5 million scale. From USGS (Persits et al. 2002).
  • Legend for geology map of Africa, 1:5 million scale. From USGS (Persits et al. 2002)

If you reproduce any of the geology maps from this Atlas, please cite both the Africa Groundwater Atlas and the USGS (Persits et al., 2002).

Citations

Persits, F, Ahlbrandt, T, Tuttle, M, Charpentier, R, Brownfield, M, and Takahashi, K. 2002. | Map showing geology, oil and gas fields and geologic provinces of Africa, Ver 2.0. USGS Open File report 97-470 A.

MacDonald, A M, Bonsor, H C, Ó Dochartaigh, B É, and Taylor, R G. 2012. | Quantitative maps of groundwater resources in Africa. Environmental Research Letters 7(2). doi: 10.1088/1748-9326/7/2/024009

UNESCO/Association for African Geological Surveys. 1964. Geological Map of Africa. Prepared by UNESCO and the Association for African Geological Surveys. UNESCO, Paris, 1964.

Country geology maps

The new, modified geology map of Africa was used as the basis for producing a geology map for each country in Africa, which are shown on the country pages. For some countries, the country map was extracted from the Africa-wide map with no further modifications. For some other countries, further modifications have been made to represent more accurately the geology at a country scale. These modifications were made in collaboration with the co-authors of the relevant country pages, who are experts in the hydrogeology and geology of the respective countries.

If you reproduce any of the geology maps from this Atlas, please cite both the Africa Groundwater Atlas and the USGS (Persits et al., 2002).

OneGeology: another source of geological information

Many countries across Africa (27 in total) are members of OneGeology, an international initiative to make worldwide geological data and maps available at a scale of at least 1:1 million. Further information can be found via the OneGeology website and data can be accessed via the OneGeology portal.


Africa Groundwater Atlas >> Additional resources >> Geology