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Calcrete Mapping and Palaeo-Environments in the Qangwa Area, Northwest Botswana

Ludo Gobagoba, Thoralf Meyer, Susan Ringrose, Ali Basira Kampunzu and Stephan Coetzee
Botswana Notes and Records
Vol. 37, Special Edition on Human Interactions and Natural Resource Dynamics in the Okavango Delta and Ngamiland (2005), pp. 264-279
Published by: Botswana Society
Stable URL: http://www.jstor.org/stable/40980419
Page Count: 16
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Calcrete Mapping and Palaeo-Environments in the Qangwa Area, Northwest Botswana
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Abstract

Calcrete deposits of the Qangwa area, northwestern Botswana are evaluated on the basis of satellite imagery and sedimentological analysis. Enhanced Thematic Mapper imagery interpretation combined with field evidence has led to identification of the calcrete. This project aims at making a detailed surficial geology map accompanied by a report as a step in expanding the knowledge of calcretes. It also attempts to develop an understanding of the relationship in the timing of the late Quaternary wetter and drier phases. A digital map using GIS and remote sensing applications was developed from both analysed data and fieldwork. Data analysis revealed five types of calcretes and a calcareous soil. Hardpan calcrete along with brecciated and conglomeratic calcrete dominate the interfluves and are believed to predate the formation of nodular and honeycomb calcrete which occupy the valleys. The older hardpan associated types may have developed following regional wet/warm periods the last of which has been dated elsewhere as occurring c. 120,000. The younger valley calcretes show different mechanisms of formation, and are believed to have been developed following incision and palaeo-lake establishment, c. 25,000 years ago.

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