Precambrian Palaeosols: A View from the Canadian Shield

  1. Médard Thiry and
  2. Régine Simon-Coinçon
  1. Q. Gall

Published Online: 14 APR 2009

DOI: 10.1002/9781444304190.ch8

Palaeoweathering, Palaeosurfaces and Related Continental Deposits

Palaeoweathering, Palaeosurfaces and Related Continental Deposits

How to Cite

Gall, Q. (1995) Precambrian Palaeosols: A View from the Canadian Shield, in Palaeoweathering, Palaeosurfaces and Related Continental Deposits (eds M. Thiry and R. Simon-Coinçon), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304190.ch8

Author Information

  1. 1–1190 Richmond Road, Ottawa, Ontario, Canada K2B 8J3

Publication History

  1. Published Online: 14 APR 2009
  2. Published Print: 26 MAY 1995

ISBN Information

Print ISBN: 9780632053117

Online ISBN: 9781444304190

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Keywords:

  • South African Waterval Onder palaeosol and Canadian Steep Rock, examples of Precambrian palae;
  • Precambrian palaeosols, including karst features, duricrusts and corestones;
  • physical and chemical criteria, in identifying Precambrian palaeosol;
  • Destratification, prevalent in Precambrian palaeosols;
  • Flin Flon and Sheigra palaeosols in Scotland - disrupted protolith;
  • microstructural cutans and peds in in palaeosol identification

Summary

Diligent research over the last two decades has found that records of palaeoweathering (palaeosols) and palaeosurfaces can be identified from rocks of Precambrian age in many shield terranes around the world. In the Canadian Shield, for example, approximately 40 palaeosols have been identified despite the camouflage effects of diagenesis, metamorphism and structural overprinting. Both physical and chemical criteria have proven useful in identifying Precambrian palaeosols; and include:

1 stratigraphical position along unconformities;

2 ascending protolith disruption;

3 the presence of macrostructures (e.g. karstification, corestones);

4 the presence of microstructures (e.g. peds and cutans);

5 mineralogy and colour contrast with adjacent lithologies; and

6 ascending element depletion with concomitant change in chemical weathering indices.

There appear to be difficulties in applying modern soil classifications to Precambrian palaeosols owing to the general paucity of horizonation; suggesting that drab-coloured saproliths may be the normal end result of weathering during the Precambrian. In Precambrian terranes, physical and chemical overprinting by burial diagenesis or metamorphism also appear to be common, and tend to mask original pedogenic features. Difficulties in accurately determining the age and duration of palaeoweathering are also common place in Precambrian terranes.

Despite these difficulties in studying Precambrian palaeosols, once identified, they may be useful in: (i) reinforcing old, or suggesting new, regional stratigraphical correlations and, hence, in identifying regional to world-wide episodes of palaeoweathering, and (ii) in helping to track unconformity-related mineralization.