Geochemical mapping of carbonate sediments in the Makgadikgadi basin, Botswana using moderate resolution remote sensing data

Abstract

This paper maps the carbonate geochemistry of the Makgadikgadi Pans region of northern Botswana from moderate resolution (500 m pixels) remotely sensed data, to assess the impact of various geomorphological processes on surficial carbonate distribution. Previous palaeoenvironmental studies have demonstrated that the pans have experienced several highstands during the Quaternary, forming calcretes around shoreline embayments. The pans are also a significant regional source of dust, and some workers have suggested that surficial carbonate distributions may be controlled, in part, by wind regime. Field studies of carbonate deposits in the region have also highlighted the importance of fluvial and groundwater processes in calcrete formation. However, due to the large area involved and problems of accessibility, the carbonate distribution across the entire Makgadikgadi basin remains poorly understood. The MODIS instrument permits mapping of carbonate distribution over large areas; comparison with estimates from Landsat Thematic Mapper data show reasonable agreement, and there is good agreement with estimates from laboratory analysis of field samples. The results suggest that palaeo-lake highstands, reconstructed here using the SRTM 3 arc-second digital elevation model, have left behind surficial carbonate deposits, which can be mapped by the MODIS instrument.

Analyses of Recent Sediment Surface Dynamic of a Namibian Kalahari Salt Pan Based on Multitemporal Landsat and Hyperspectral Hyperion Data

“…Over the last decades a limited number of studies have applied remote sensing techniques to study salt pan evaporite minerals and were able to provide spatial information on pan surfaces in terms of evaporite mineral discrimination supported by field observations. Most of them rely on traditional optical multi-spectral satellite sensors [1,13,[16][17][18][19]] that often do not provide the necessary spectral resolution to cover the spectral complexity of evaporite mineral assemblages on salt pan surfaces [20] and only provide a mono-temporal assessment. In comparison, analysis based on advanced hyperspectral imagery, also named imaging spectroscopy, are more sensitive for the identification and quantification of a wider range of evaporite minerals [13,21], and usually achieve higher modeling results [20].…”

Pans, Playas and Salt Lakes

“…These data have facilitated the application of a range of remote sensing approaches to both evaporite mineral mapping and facies mapping to a limited number of playas (e.g. Bryant, 1996;Castañeda, Herrero and Casterad, 2005a;White and Eckardt, 2006). Crowley and Hook (1996) and Katra and Lancaster (2008) have also utilised multispectral thermal infrared data to map mineral phases and surface types (Figure 15.13).…”

Going the distance: Mapping mobility in the Kalahari Desert during the Middle Stone Age through multi-site geochemical provenancing of silcrete artefacts

“…12), for example, allows the position of potential quarries to be compared against the palaeolake record for the MSA. During the four millennial-scale mega-lake phases centred on 105, 92, 65, and 39 ka (thousands of years ago), when up to 66,000 km 2 of present-day Botswana was flooded, water levels in the Ngami basin would have exceeded 945 m asl (White and Eckardt, 2006) and only the highest elevation silcrete outcrops on the southern lake rim (i.e., BOT11/1 and 11/3) would have remained exposed. Three of these mega-lake phases (centred on 105, 92, and 39 ka) are concordant with periods of speleothem growth at Gcwihaba Cave (e.g., Brook et al, 1998), suggesting widespread wetter conditions.…”