Title:

The Palaeomagnetism of Precambrian Igneous and Sedimentary Rocks of the Orange River Belt in South Africa and South West Africa

Author(s):
Publication Year:
1975
Abstract:

Palaeomagnetic results are presented for a variety of Precambrian rocks from south‐western Africa. Oldest rocks studied are the Orange River Lavas (> 1850 My) from which the three least altered sites give a VGP at 254° E, 19° N near the polar wander curve for Africa at c.2100 My. Five sites from basic intrusions believed to be about 1200 My in age at O'okiep, Namaqualand, give a pole at 155° E, 15° S. Nineteen sites in lavas of the Barby Formation (Sinclair Group, < 1200 My) in South West Africa yield a significant direction after cleaning with five sites reversed with respect to the remainder; grouping is improved after correction for folding (> 1020 My). Palaeomagnetic results are also given for lavas of the overlying Guperas Formation (< 1020 My), sediments of the succeeding Auborus Formation, basic dykes at Klein Karas (878±41 My), and six dolerite dykes from Namaqualand (probable age of 653±70 My). Nine sites from the Fish River Formation (probable Lower Cambrian age) give pole positions correlating with a late Precambrian to Ordovician polar shift recognized from other Gondwanaland data. The Doornpoort Formation of Central South West Africa gives a direction of magnetization which a fold test dates as originating from the Damaran folding (550–500 My). The results define a loop in the polar wander curve for Africa between 1200 and 1000 My which can be matched in size, shape and age to a loop in the North American curve implying that the two regions were in juxtaposition at this time.

Publication Title:

Geophysical Journal of the Royal Astronomical Society

Volume:
40
Issue:
3
Pages:
313-344
Item Type:
Journal Article
Language:
en

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