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A palaeomagnetic pole position, derived from a precisely dated primary remanence, with minimal uncertainties due to secular variation and structural correction, has been obtained for China’s largest dyke swarm, which trends for about 1000 km in a NNW direction across the North China craton. Positive palaeomagnetic contact tests on two dykes signify that the remanent magnetization is primary and formed during initial cooling of the intrusions. The age of one of these dykes, based on U–Pb dating of primary zircon, is 1769.1 ± 2.5 Ma. The mean palaeomagnetic direction for 19 dykes, after structural correction, is D = 36°, I = − 5°, k = 63, α95 = 4°, yielding a palaeomagnetic pole at Plat=36°N, Plong=247°E, dp = 2°, dm = 4° and a palaeolatitude of 2.6°S. Comparison of this pole position with others of similar age from the Canadian Shield allows a continental reconstruction that is compatible with a more or less unchanged configuration of Laurentia, Siberia and the North China craton since about 1800 Ma

The Gunflint Formation, a Paleoproterozoic chemical–clastic sedimentary assemblage outcropping to the immediate northwest of Lake Superior, became famous in 1954 as containing the oldest fossil assemblage known at that time. Older microfossils have since been discovered, but the Gunflint procaryotes remain one of the most diverse Precambrian fossil communities. The finding of possible multicellular organisms in correlative lithic units in Michigan has recently added to the need for an exact age of the Formation. Zircons were extracted from rainout and storm reworked volcanoclastic beds in the upper portion of the Gunflint Formation. A euhedral zircon population has yielded a 1878.3 ± 1.3 million years BP U–Pb age, believed to be nearly synchronous with the depositional age. This not only provides a precise age for the community of organisms, but also strongly supports a back-arc extensional setting for the Animikie Basin, rather than a foreland trough.

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