Geological Map Of The Colony Of The Cape Of Good Hope Sheet 4: Paternoster – Langebaan – Darling – Malmesbury

Cartographer: Rogers, A. W, Schwarz, E. H. L & Du Toit, A. L
Publisher: The Geological Commission
Price: £175 (post-free in the UK)
Publication Date: 1906
Edition: 1st edition thus
Format: Lithograph
Condition: In very good condition
Sheet Size: 96.7cm x 56cm

Condition:

Lithograph. Sheet Size: 96.7cm x 56cm. 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: 002852

Geology Of The Western Cape Region: An Historical Overview

Introduction

The Western Cape, situated at the south-western edge of South Africa, possesses one of the most diverse and ancient geological landscapes on the African continent. This complex region showcases a variety of rock types, tectonic structures, and geomorphological features that span over 1 billion years of Earth history. Its geological foundations underpin the region’s topography, water systems, soils, and even the globally significant Cape Floristic Region.

The geology of the Western Cape is best understood through the interaction of three major elements:

• The basement rocks (Malmesbury Group and Cape Granite Suite)
• The Cape Supergroup (notably the Table Mountain Group)
• The effects of Mesozoic and Cenozoic tectonic activity and erosion

1. The Basement Complex: Malmesbury Group and Cape Granite Suite

Malmesbury Group (Pre-Cambrian)

The oldest rocks in the Western Cape belong to the Malmesbury Group, formed during the Neoproterozoic era, over 550 million years ago. These are low-grade metamorphic rocks—predominantly greywackes, shales, and siltstones—deposited in deep marine environments associated with ancient oceanic subduction zones.

These sediments were later deformed and metamorphosed during the Saldanian Orogeny, a mountain-building event that affected much of southern Gondwana’s margin. The result is a folded and faulted assemblage of rocks that underlie much of the south-western Cape, especially around Cape Town, Paarl, and Stellenbosch.

Cape Granite Suite

Intruding into the Malmesbury rocks are massive bodies of granite plutons, collectively referred to as the Cape Granite Suite. These formed during the Pan-African tectonic cycle, approximately 540–500 million years ago, as the ancient crust was compressed and heated by tectonic convergence.

Prominent outcrops include:

• The Paarl Rock granite dome
• Granite cliffs around Sea Point and Simon’s Town
• Subsurface granite that supports much of the Cape Peninsula

These granites are coarse-grained, crystalline, and often exfoliated, forming rounded hills and tors—features that dominate the topography of many inland areas.

2. The Cape Supergroup: Sedimentation and Folding

Following the stabilisation of the basement complex, the region experienced a long period of marine transgression and sedimentation, giving rise to the Cape Supergroup. This series of sedimentary rocks was deposited between approximately 485 and 300 million years ago, from the Ordovician to the Carboniferous period.

The Cape Supergroup is composed of three main units in the Western Cape:

1. a) Table Mountain Group

The oldest and most prominent unit, the Table Mountain Group is made up of:

• Graafwater Formation: reddish mudstones and sandstones, representing tidal flats and shallow marine conditions.
• Peninsula Formation: thick, white to grey quartzitic sandstones, resistant to erosion and forming the core of Table Mountain, the Hottentots-Holland Mountains, and the Cederberg range.

These quartzites provide the scenic high cliffs and rugged peaks of the Cape and are famous for preserving trace fossils and ancient glacial features.

1. b) Bokkeveld Group

Lying above the Table Mountain Group, the Bokkeveld Group consists of mudstones, siltstones, and fossil-rich shales deposited in deeper marine settings. These rocks, found predominantly in the Cape Fold valleys, are softer and more fertile, supporting agriculture, particularly vineyards and fruit orchards in areas such as Ceres and Worcester.

1. c) Witteberg Group

Representing the youngest Cape Supergroup rocks, the Witteberg Group is composed of fine sandstones and quartzites deposited in deltaic to nearshore environments. It forms ridges and hills in more inland parts of the province.

3. The Cape Fold Belt: Tectonics and Orogeny

The dramatic folding of the Cape Supergroup was the result of a major tectonic event, known as the Cape Orogeny, occurring between 270 and 230 million years ago. During this time, compressional forces generated by the collision of the Gondwana supercontinent margins created the Cape Fold Belt, a series of:

• East-west trending anticlines and synclines
• High-angle thrust faults
• Closely spaced fold limbs

The Cederberg, Hex River, Langeberg, and Outeniqua mountains are expressions of these structural folds. Erosion over tens of millions of years has exhumed the most resistant formations (notably the Peninsula quartzites), resulting in the high-relief terrain seen today.

4. Mesozoic to Cenozoic: Rifting, Erosion, and Coastal Development

With the break-up of Gondwana in the Jurassic (~180 million years ago), the southern margin of Africa was subjected to rifting, leading to the development of the South Atlantic Ocean. This marked the onset of post-orogenic erosion, during which the Cape Fold Belt was extensively worn down.

Key features of this era include:

• Formation of fault-bound coastal basins, such as the Bredasdorp Basin and Mossel Bay Basin
• Deposition of marine and terrestrial sediments, now hosting groundwater and gas reserves
• Uplift of the Great Escarpment, enhancing river incision and sediment transport

Throughout the Tertiary and Quaternary periods, climate fluctuations, sea-level changes, and fluvial erosion further shaped the Cape’s valleys, estuaries, and dune fields.

5. Modern Landscapes and Geology’s Influence on Ecology and Human Use

Today, the geology of the Western Cape plays a vital role in:

• Soil development: Quartzite-derived soils are acidic and nutrient-poor, favouring fynbos vegetation, while shales and granites support renosterveld and agricultural land
• Water resources: Groundwater aquifers and mountain catchments are tied to geological fractures and formations
• Natural hazards: Rockfalls and slope instability occur along folded sandstone ridges
• Cultural heritage: Caves, overhangs, and stone outcrops contain archaeological evidence of Middle Stone Age habitation

The geodiversity of the Western Cape also underpins its status as a global biodiversity hotspot, where ancient soils and complex microclimates have led to the evolution of unique plant species and endemic ecosystems.

Conclusion

The geology of the Western Cape is a tapestry of ancient oceanic sediments, granite intrusions, mountain-building, and post-tectonic erosion, resulting in one of the most varied and scenic landscapes in Africa. These geological foundations not only shape the physical environment, but also influence human settlement, agriculture, biodiversity, and cultural heritage.

From the dramatic folds of the Cape Fold Belt to the flat summits of Table Mountain, the rocks of the Western Cape record a history both profoundly ancient and immediately visible—a testament to the dynamic forces that continue to shape the Earth’s surface.

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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