Lead-210 dating

FIGURE 14.26 Decay pathways and products of radium-226 and lead-210. 

FIGURE 14.27 Schematic showing the vertical distribution of lead-210 activity (supported and unsupported Pb) in sediments. 

Supported is based on the average measurement of °Pb activity determined by measuring the activity of a °Pb as a decay product such as Pb in the lowest section of the sediment profile where °Pb activity is constant. Sedimentation or accretion rates are estimated from the excess (unsupported) °Pb profiles in the sediment profile using the constant initial concentration method (Goldberg et al., 1977). Linear regression analysis is used to solve for (X/s) in the log-transformed equation for radioactive decay  

The slope of the regression in the °Pb profiles is equal to (-X/s). More negative slope indicates lower accretion rates. 

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The study demonstrates the geochemical characteristics of phosphorus, combined with the lead-210 dating for interpreting the environmental changes of Jiaozhou Bay. 

Hilgers, E., H. Thies W. Kalbfus, 1993. A lead-210 dated sediment record on heavy metals, polycyclic aromatic hydrocarbons and soot sphemles for a dystrophic mountain lake. Verb. Internal. Verein. Eimnol. 25 1091-1094. 

Tolonen, K., R. Haapalahti J. Suksi, 1990. Comparison ofvarve dated soot ball chronology and lead-210 dating in Finland. In Saamisto, M. A. Kahra (eds.) Laminated Sediments. Geological Survey of Finland, Special Paper 14 65-75. 

Our planet was probably transformed to a ball of magma 4.45 billion years ago by an impact with a small planet-like body the resulting debris formed the Moon. Yet uranium-lead dating shows us how quickly this magma ocean must have cooled, since it reveals that the oldest zircons, found in Western Australia, crystallized about 4.4 billion years ago. What is more, these ancient zircons show signs of having been formed in contact with water, implying that even in that distant era the world had... 

McNaughton, N.J., Rasmussen B. Fletcher I.R. (1999) SHRIMP uranium-lead dating of diagenetic xenotime in siliciclastic sedimentary rocks. Science 285, 78-80. 

French, P. W., J. R. L. Allen, and P. G. Appleby. 1994. 210-Lead dating of a modern period saltmarsh deposit from the Severn Estuary (Southwest Britain), and its implications. Mar. Geol. 118 327-334. 

One of the most common applications for these two metalloids is for use when strengthening alloys, or mbrtures of elements, especially lead. Lead is a relatively soft, dense metal, so to make lead harder for applications such as bullets, either metalloid can be added to help make the resulting product stronger. This practice of alloying arsenic and antimony with lead dates back to the Bronze Age. 

Figure 1 A statuette of lead date circa 3800 BC. (Reproduced by kind permission of the Trustees of the British Museum.)...

EXAMPLE 19.6 Using Uranium/Lead Dating to Estimate the Age of a Rock... 

The kinetics of radioactive decay is used to date objects and artifacts. The age of materials that were once part of living organisms is measured by carbon-14 dating. The age of ancient rocks and even Earth itself is determined by uranium/lead dating. 

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