Geological Map Of The Colony Of The Cape Of Good Hope Sheet 41 – Griqua Town

Cartographer: Du Toit, A. L & Rogers, A. W.
Publisher: The Geological Commission
Price: £125 (post-free in the UK)
Publication Date: 1909
Edition: 1st edition thus
Format: Lithograph
Condition: In very good condition
Sheet Size: 73.5cm x 56cm

Condition:

Lithograph. Sheet Size: 73.5cm x 56cm. Institutional stamp tp upper margin. Neat ink number to lower right margin. Old fold lines. Slightly creased, marked, dusty and rubbed. Colouration very bright and clean. A very good copy. Very scarce.

Location: Pocket RSAGEOL: SR: 002861

Geology Of The Griqua Town Region: An Historical Overview

1. Introduction and Geographic Context

Griquatown, historically known as Griqua Town, is located in the Northern Cape Province of South Africa, situated between Prieska and Kuruman. Geologically, it lies within the Griqualand West Basin, a major Proterozoic sedimentary and volcanic basin that forms part of the larger Transvaal Supergroup. This region is particularly noted for its banded iron formations (BIFs), dolomitic platforms, and early sedimentary successions that preserve a deep-time record of early Earth’s tectonic and biological evolution.

The Griquatown area is thus of considerable interest both for its economic mineral potential and for the insight it offers into Palaeoproterozoic environmental conditions, including the Great Oxygenation Event.

2. Geological Foundations: The Kaapvaal Craton

The basement of the Griquatown region lies within the Kaapvaal Craton, a stable continental crustal block formed over 3 billion years ago. This ancient core provided a tectonically stable platform upon which the extensive sedimentary sequences of the Transvaal Supergroup were deposited.

Although not widely exposed at the surface in the immediate area, the craton’s rigidity controlled basin formation, subsidence rates, and the overall stratigraphic architecture of the region.

3. The Transvaal Supergroup and the Griqualand West Basin

The Griqualand West Basin is a western extension of the Transvaal Supergroup and comprises a thick sequence of chemical and clastic sedimentary rocks, punctuated by volcanic layers. The geological succession in the Griquatown region is dominated by three main groups:

1. Ghaap Group

This group includes:

• Dolomites and limestones of the Campbell Rand Subgroup
• Cherts and stromatolitic carbonates, deposited in shallow, warm marine environments

These formations represent one of the oldest carbonate platforms on Earth and include fossil evidence of early microbial mats.

1. Asbestos Hills Subgroup

Overlying the dolomites, this unit consists of:

• Cherts, ferruginous shales, and early iron-rich sediments
• Important transition beds that mark changing ocean chemistry prior to widespread oxygenation

1. Kuruman Formation (part of the Mapedi Formation in this area)

This is the most famous geological unit in the region and includes:

• Banded Iron Formations (BIFs): Alternating layers of iron oxide (hematite and magnetite) and silica (chert)
• These deposits are geochemically linked to the onset of oxygenic photosynthesis and are a key marker of the Great Oxygenation Event (~2.3 billion years ago)

These iron formations are of both scientific significance and economic interest, having been mined historically for iron and manganese.

4. Tectonic Setting and Basin Evolution

The Griquatown region developed as part of a passive-margin style basin along the western edge of the Kaapvaal Craton. Tectonic activity was relatively subdued during deposition, although synsedimentary faulting and subsidence occurred along basin margins.

Later regional deformation, including:

• Folding and faulting
• Low-grade metamorphism
• Subtle tilting of stratigraphic units

…occurred during the Kheis orogenic event, approximately 1.8–2.0 billion years ago. This event caused gentle warping and fracturing but did not significantly disrupt the overall stratigraphy.

5. Economic Geology and Mineral Resources

The Griquatown region is historically important in South Africa’s mining history, especially for:

• Iron ore: Derived from BIFs of the Kuruman Formation
• Manganese: Associated with supergene enrichment in shallow weathered zones
• Asbestos: Formerly extracted from serpentinised ultramafic rocks (now abandoned due to health risks)

Small-scale mining and prospecting were active from the late 19th to mid-20th century. Today, the focus has shifted to conservation, heritage, and research, though potential for renewed mineral exploration remains.

6. Surface Cover and Recent Deposits

Much of the Griquatown area is lightly mantled by:

• Kalahari Group sediments: Wind-blown sands and clayey soils of Cenozoic age, deposited over the last 60 million years
• Calcretes and silcretes: Formed through soil formation in arid conditions
• Alluvium and pan deposits: In low-lying seasonal drainage basins

These cover deposits, while geologically recent, play a crucial role in modern land use, soil fertility, and groundwater recharge.

7. Hydrogeology and Water Resources

The geological structure of the region supports moderate groundwater development, with aquifers hosted in:

• Fractured dolomites and cherts of the Campbell Rand Subgroup
• Weathered and faulted BIFs
• Unconsolidated cover sediments in ephemeral drainage channels

Springs and boreholes often yield usable groundwater, though salinity and hardness may be elevated in some zones, particularly where iron- or manganese-rich rocks influence the chemistry.

8. Scientific and Heritage Value

The Griquatown region has long been of interest to geologists and palaeontologists. Its significance includes:

• Being one of the oldest preserved sedimentary successions on Earth
• Hosting clear markers of the early biosphere and atmospheric evolution
• Providing study material for geobiology, ore genesis, and Precambrian stratigraphy

In recognition of its value, the area contributes to geoconservation efforts and is sometimes included in field excursions by universities and research institutions.

Conclusion

The geology of the Griquatown region captures a chapter of Earth’s history that is both profound and globally significant. With its dolomitic platforms, iron formations, and signs of early microbial life, the area offers a well-preserved record of Palaeoproterozoic environmental change, tectonic stability, and economic mineralisation.

Though its mining legacy has faded, Griquatown remains a vital reference site for understanding the early development of Earth’s oceans, atmosphere, and continental crust. It continues to support scientific inquiry, heritage appreciation, and careful environmental stewardship in South Africa’s arid interior.

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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