Geology: Difference between revisions
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=== Country-scale geological maps === | === Country-scale geological maps === |
Revision as of 14:41, 21 March 2016
Africa Groundwater Atlas >> Additional resources >> Geology
Dataset description
The geology map of Africa shown here is based on the USGS/UNESCO 1:5 million scale map of geology, oil and gas fields and geologic provinces of Africa (Persits et al., 2002), which itself was based on the 1:5 million scale geological map published in 1964 by UNESCO. This base map has been modified by the British Geological Survey to group or subdivide selected geological units, or to reveal bedrock geology below unconsolidated deposits, in order to better reflect significant hydrogeological differences (MacDonald et al., 2012). The following key modifications have been made:
Precambrian rocks have in most cases been subdivided into three:
- metasedimentary
- orogenic/mobile belt – crystalline metamorphic and igneous rocks within linear, mostly Proterozoic, orogenic belts
- craton – Archaean and Palaeoproterozoic rocks which have not been affected by Proterozoic and younger orogenic events
Sedimentary 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 have been distinguished where they have a significant outcrop and, generally, where they overlie less permeable rocks. They are not generally shown where they are minor (for example, alluvial outcrops in small river valleys) or where they overlie sedimentary basins of greater hydrogeological significance.
Country-scale geological maps
This modified geological map of Africa was used as the basis to develop country-scale geological maps for this Atlas. For some countries, further modifications have been made to reflect more accurately the geology at a more detailed, national scale. These modifications were done in discussion with experts in the hydrogeology and geology of the respective countries.
Links to external data
The 1:5 million scale map of geology, oil and gas fields and geologic provinces of Africa (Persits et al., 2002) is made available through the USGS. It can be accessed via the USGS Energy Data Finder.
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. https://pubs.usgs.gov/of/1997/ofr-97-470/OF97-470A/
MacDonald, AM, Bonsor, HC, Ó Dochartaigh, BÉ and Taylor, RG. 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.
Other sources of geological information
OneGeology
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