Radioactive dating in massachusetts

Gondwanaland straddled the equator at 540 Ma, lay wholly in the Southern Hemisphere by 350 Ma, and then rotated clockwise so that at 250 Ma Australia reached the S pole and Africa the equator.

By initial breakup of Pangea at 185 Ma, Gondwanaland had moved northward such that North Africa reached 35°N.

The interior was crossed by the Prydz–Leeuwin and Mozambique Orogenic Belts.

Outliers of basalt throughout western Siberia, and extensive subcrops within the West Siberian Basin, are often associated with the 250 Ma Siberian Traps volcanism.

Borehole samples located south of the city of Chelyabinsk gave ages of 243.3 ± 0.6 Ma and 242.2 ± 0.6 Ma clearly demonstrating that volcanism to the southeast of the Urals is ~7 Ma younger than the main activity on the Siberian craton and within the WSB (Reichow et al. Sills with Triassic ages were also reported (Ivanov et al., 2005) in the Kansk-Taseevskaya basin along the southern border of the Siberian craton and for extrusive rocks in the Semeitau area, Kazakhstan (Lyons et al., 2002).

Ar measurements of biotite from intrusive rocks tend to give slightly older ages, possibly related to the presence of excess argon. (1997); Putorana region - Renne and Basu (1991); Maymecha-Kotuy region -Basu et al. (1995), age of ash Bed 25 (Renne et al., 1995) with error bars in grey delineates the peak of the end-Permian extinction at its base.

Zircons and baddeleyites from intrusions at Noril'sk, together with perovskite, zircon and baddeleyite from Maymecha-Kotuy, give U/Pb concordia ages that are slightly but significantly older than the dates: West Siberian Basin (WSB) - Reichow et al. (1995); Noril'sk region - Renne and Basu (1991), Dalrymple et al. All Ar-Ar dates are given relative to FC at 28.02 Ma (Renne et al., 1998).

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In the mid-Carboniferous, Laurussia and Gondwanaland merged in the composite called Pangea by definitive right-lateral contact along the Variscan suture, with collisional stress and subsequent uplift felt as far afield as Australia.

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