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The Pakhuis Ice Sheet — When the Cape Was Covered in Ice 440 Million Years Ago
Long before the Cape was wine country, it was buried under ice. The Pakhuis Formation in the Table Mountain Group preserves evidence of a major ice sheet that covered the Western Cape in the Late Ordovician (~440 million years ago).
The evidence:
- Striated and faceted pebbles — rocks scratched and polished by glacial movement
- Glacial pavements at Pakhuis Pass (near Clanwilliam) — bedrock surfaces polished and grooved by ice
- Infraglacial folding — where the ice ploughed into soft underlying sands and buckled them
- Plate 11 in Trusswell shows a photograph of a glaciated pavement below the Pakhuis Formation near Wuppertal, with 'scribing tools at the end of the grooves, indicating the sense of movement'
- Transport directions shown in Fig. 48 indicate ice movement generally southeastward
The Pakhuis Formation is only about 60 meters thick in the Western Cape (combined with the overlying Cederberg Formation) — but its significance for soil formation is enormous.
Why glacial history matters for growers:
- Glaciers are nature's rock crushers — they pulverize bedrock into mineral-rich 'rock flour'
- Glacial grinding releases trace elements that would otherwise remain locked in solid rock
- The Pakhuis ice sheet ground up Cape Granite, Malmesbury shale, and quartzite — mixing minerals that became your soil parent material
- Periglacial material (sediment deposited after the ice retreated) has been recorded as far east as Port Elizabeth
The ice sheet extent is shown in Fig. 50 — it covered much of the southwestern Cape, with a shallow sea to the east.
Every time you water your cannabis, you are working with soil that was ground into existence by an ice sheet older than the dinosaurs.
Source: Trusswell, Chapter 6. Rust (1973), Visser (1974).