Geological Map Of The Colony Of The Cape Of Good Hope Sheet 52 – Mafeking

Cartographer: Du Toit, A. L
Publisher: The Geological Commission
Price: £125 (post-free in the UK)
Publication Date: 1908
Edition: 1st edition thus
Format: Lithograph
Condition: In very good condition
Sheet Size: 87.4cm x 57.4cm

Condition:

Lithograph. Sheet Size: 87.4cm x 57.4cm. Neat ink number to lower right margin. Old fold lines. Closed tears to a couple of fold lines to the margins. Creased, marked, dusty and rubbed. Colouration very bright and clean. A very good copy. Very scarce.

Location: Pocket RSAGEOL: SR: 002855

Geology Of The Mafeking Area: An Historical Overview

1. Introduction and Geographical Setting

The Mafeking region, located in the North West Province of South Africa near the Botswana border, lies at the intersection of the Kalahari Basin and the Kaapvaal Craton—two major geological domains that define the southern African interior. While the topography is largely flat and dominated by bushveld and savanna vegetation, the subsurface geology reveals a complex history of ancient basement rocks, overlying sedimentary sequences, and younger Quaternary deposits.

Mahikeng’s geological setting has important implications for hydrogeology, agriculture, construction, and regional tectonic understanding.

2. Basement Geology: The Kaapvaal Craton

Beneath the Mafeking region lies part of the Kaapvaal Craton, one of the oldest and most stable pieces of continental crust on Earth. This Archaean craton, which formed between 3.6 and 2.5 billion years ago, consists of a deeply buried core of gneisses, granites, and greenstone belts. Though largely obscured by younger cover, its influence on tectonic stability and crustal rigidity remains profound.

The exposed Archaean rocks are minimal in the immediate Mafeking area but lie not far to the east, near the Ventersdorp and Klerksdorp goldfields. Their presence underlies the region’s long-term tectonic stability and low seismicity.

3. Transvaal Supergroup and Post-Archaean Sequences

The Transvaal Supergroup, deposited between 2.5 and 2.0 billion years ago, represents the sedimentary and volcanic sequences that overlie the Kaapvaal basement in much of the North West Province. Although not well exposed near Mahikeng, these formations—including dolomites, banded iron formations, and quartzites—are regionally extensive to the south-east.

Where present, these rocks are often associated with:

• Karst development in dolomitic terrains, which can influence water supply and ground stability
• Historic iron ore and manganese mineralisation, mostly explored elsewhere in the province

To the north and west of Mafeking, these older rocks are generally buried beneath younger Kalahari sediments and unconsolidated cover.

4. Kalahari Group Cover and Surface Geology

The dominant surface geology of the Mafeking region is that of the Kalahari Group, comprising late Cretaceous to Quaternary sands, calcretes, and silcretes. These unconsolidated to weakly cemented deposits were laid down over the last 70 million years and are part of the broader Kalahari Basin, which stretches across Botswana, Namibia, Angola, and into South Africa.

Key features of the Kalahari deposits in this region include:

• Red aeolian sands, forming dunes and low ridges
• Pans and clayey depressions, often seasonally waterlogged
• Duricrust horizons, especially calcrete (calcium carbonate cemented soils) that form hard, shallow surface layers
• Localised silcrete caps, resulting from silica-rich groundwater evaporation

These sediments are relatively young but mask a much older geological substrate, making subsurface exploration and mapping challenging.

5. Structural Geology and Tectonic Context

The Mafeking region lies on the western margin of the Kaapvaal Craton, near the Kheis tectonic belt, a poorly exposed yet significant zone of Proterozoic deformation. Although the area is now tectonically quiescent, its ancient structural history includes:

• Crustal shortening, shearing, and low-grade metamorphism
• Regional-scale faulting that may control modern drainage and groundwater movement
• Influences on basement topography, which in turn affect surface sedimentation and soil development

Modern seismic activity is rare, and the region is considered tectonically stable compared to more mobile belts to the east and north.

6. Hydrogeology and Groundwater Resources

Due to the semi-arid climate and lack of perennial rivers, the geology of the Mafeking region plays a critical role in water supply. Groundwater is the primary source of domestic and agricultural use.

• Kalahari sands and underlying weathered basement host limited but important fractured aquifers
• Calcretes and clay lenses can form perched water tables, though recharge is slow and variable
• Borehole yields are generally low to moderate, and water quality may be affected by high salinity and hardness

Groundwater management is thus closely tied to the geological structure and porosity of the buried layers, with careful monitoring required to ensure sustainable use.

7. Economic Geology and Land Use

The Mafeking region is not a major mining district, but its geology supports certain localised resources and activities:

• Brick-making and sand quarrying from surface Kalahari deposits
• Potential for groundwater-dependent agriculture
• Historical interest in base metals and diamonds in surrounding areas, though no major deposits have been developed locally

The lack of significant mineral wealth has limited industrial development, but this has preserved much of the region’s natural landscape and heritage value.

8. Geomorphological and Environmental Considerations

The landscape of the Mafeking area is shaped by long-term weathering, fluvial erosion, and aeolian activity. Its features include:

• Flat plains with occasional pans and seasonal drainage lines (vleis)
• Sparse vegetation cover, highly sensitive to overgrazing and land degradation
• Soils derived from Kalahari sands, typically sandy and low in nutrients, requiring careful management for agriculture

The geology also plays a role in environmental planning, particularly in:

• Waste disposal site selection
• Infrastructure foundation design
• Protection of wetlands and groundwater recharge zones

Conclusion

The geology of the Mafeking region is a story of ancient foundations masked by youthful sediments. From the deep-time stability of the Kaapvaal Craton to the more recent Kalahari sand cover, the area embodies a complex interplay of Archaean stability, Proterozoic tectonics, and Quaternary surface processes.

Though less mineral-rich than other regions, Mafeking’s geological character remains vital for groundwater supply, ecological resilience, and long-term land use planning. Understanding this hidden geological framework provides the key to responsible development in one of South Africa’s historically and culturally significant regions.

A. L. Du Toit: A Short Biography

Early Life and Education

Alexander Logie du Toit was born on 14 March 1878 in Newlands, Cape Town, within the then Cape Colony of South Africa. He was raised in a cultured and academically inclined household of Scots descent, and from an early age demonstrated a marked interest in the natural world.

Du Toit received his schooling at the South African College School and later enrolled at the South African College (now the University of Cape Town), where he pursued studies in geology, chemistry, and physics. He continued his education in Britain, studying mining engineering at the Royal Technical College in Glasgow and gaining practical experience in geological fieldwork and mapping.

Early Career and Geological Survey Work

Upon returning to South Africa in the early 1900s, du Toit joined the Geological Commission of the Cape of Good Hope, later absorbed into the Geological Survey of the Union of South Africa. His initial assignments took him to the Karoo Basin, where he began conducting detailed fieldwork and geological mapping, especially in the semi-arid interior of the country.

His early work included:

• Mapping of coal-bearing strata in the Karoo Supergroup
• Detailed studies of stratigraphy and sedimentology
• Investigations into the economic potential of South Africa’s coal and mineral resources

Du Toit rapidly distinguished himself through his meticulous field observations, clear cartographic skills, and interpretive insights. He played a major role in the development of South Africa’s first comprehensive geological maps of key economic regions.

Pioneering Work on Continental Drift

Du Toit’s greatest contribution to science lay in his early and robust support for the then-controversial theory of continental drift. Building upon the ideas of Alfred Wegener, the German meteorologist and geophysicist who proposed that continents had once formed a single landmass (Pangaea), du Toit became one of the theory’s most articulate and respected advocates.

In 1923, he undertook an ambitious geological expedition to South America, specifically to Argentina and Brazil, to compare geological formations with those in southern Africa. His comparative analysis of:

• Fossil flora (notably Glossopteris)
• Stratigraphic sequences
• Glacial deposits
• Petrological similarities

provided compelling evidence for the idea that Africa and South America had once been joined as part of the southern supercontinent Gondwana.

This work culminated in the publication of his landmark book, “Our Wandering Continents” (1937), in which he elaborated on the geological, palaeontological, and climatological data supporting continental drift theory. Although controversial at the time, the book would later be seen as a foundational text in support of what would evolve into the theory of plate tectonics.

Scientific Recognition and International Engagement

Despite initial scepticism from many geologists, particularly in North America and Britain, du Toit’s work earned widespread respect for its rigour, clarity, and global vision. He was known not only for the detail of his fieldwork but also for his ability to synthesise large bodies of data across continents—an approach that was well ahead of its time.

He received numerous honours and appointments, including:

• Fellowship of the Royal Society of South Africa
• Membership in the Geological Society of London
• Honorary doctorates from South African and international universities

Du Toit remained a modest and disciplined scholar, focused on the scientific method and the global implications of geological phenomena. His dedication to field-based observation and intercontinental comparison made him a model of methodological integrity.

Later Life and Legacy

Alexander du Toit retired from official survey work in the 1940s but continued to publish, correspond, and advise until his death in Cape Town in 1948. At the time of his passing, the theory of continental drift remained controversial, yet within two decades it would be revitalised and universally accepted under the framework of plate tectonics—a scientific revolution to which du Toit had made a crucial early contribution.

Today, du Toit is recognised as one of South Africa’s most distinguished geologists, and one of the key transitional figures in the history of Earth science. His legacy includes:

• The Du Toit Nunataks in Antarctica, named in his honour
• His enduring role in Gondwana studies and palaeogeographic reconstruction
• The development of modern geological mapping and stratigraphic correlation in southern Africa

Conclusion

L. du Toit was a geologist of remarkable vision, discipline, and intellectual courage. At a time when the idea of drifting continents was ridiculed, he pursued a global, integrative approach to geological science, based on painstaking fieldwork and comparative analysis.

His work not only advanced understanding of South Africa’s geological foundations, but also helped lay the groundwork for the most significant paradigm shift in Earth sciences in the 20th century. Du Toit’s life exemplifies the qualities of curiosity, persistence, and scientific integrity, making him a figure of enduring importance in both national and international geological history.

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