ISSN:
1365-246X
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geosciences
Notes:
Palaeomagnetic studies on bore core or on tectonically disturbed localities often lose declination information, but the inclination still offers important palaeogeographic information. While the arithmetic mean of inclinations, 〈inlineGraphic alt="inline image" href="urn:x-wiley:0956540X:GJI495:GJI_495_mu1" location="equation/GJI_495_mu1.gif"/〉, is a biased estimator, the bias is negligible with shallow data. Using co-inclination 〈inlineGraphic alt="inline image" href="urn:x-wiley:0956540X:GJI495:GJI_495_mu2" location="equation/GJI_495_mu2.gif"/〉 and precision K*= 1/variance, we find that the arithmetic mean and associated 95 per cent confidence interval are acceptable estimates when 〈inlineGraphic alt="inline image" href="urn:x-wiley:0956540X:GJI495:GJI_495_mu3" location="equation/GJI_495_mu3.gif"/〉. When inclination is steep and or precision low, numerical methods must be applied. We develop the likelihood function for θ and K and offer an efficient method to find its maximum, (〈inlineGraphic alt="inline image" href="urn:x-wiley:0956540X:GJI495:GJI_495_mu4" location="equation/GJI_495_mu4.gif"/〉), and to calculate the confidence interval. When 〈inlineGraphic alt="inline image" href="urn:x-wiley:0956540X:GJI495:GJI_495_mu5" location="equation/GJI_495_mu5.gif"/〉, the confidence interval is asymmetric about the mean. When sites are collected from several rigid blocks, the relative declinations within each block can be useful. Using ‘block-rotation Fisher analysis’, better inclination estimates with tighter confidence intervals can be made, even on very steep data. We describe how to apply these methods to an inclination-only fold test. The techniques are illustrated on real data and are tested extensively using numerical simulations.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-246X.1996.tb05305.x
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