To explain:
The site out of x, y, and z, which would be added to refine the boundary, between Silurian period and Ordovician period on the map given below.
Given:
Table 1 given below shows the ratio between the 206Pb and 238U and the estimated age of the sites given.
Introduction:
According to the data given in tables and radioactive isotope dating, the sites formed during the Ordovician and Silurian periods of the geological timescale are given as below:
Site 1, 2, 4, 5, 8, 9, and 10 were formed during the Ordovician period of the Palaeozoic era having estimated age from 443.7 to 488.3 million years ago
Site 3 and 6 were formed during the Silurian period of the Palaeozoic era having estimated age from 416 to 443 million years ago.
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