Environmental Engineering Reference
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Figure 11.1 Reconstruction of the supercontinent Pangaea
during the Permo-Triassic c. 250 Ma ago. Note the
Caledonian collision orogen, formed on closure of the
Iapetus Ocean as Pangaea coalesced, and the concentration
of coal and evaporite deposits along the equator. Petroleum
deposits were also formed there later, in the Cretaceous.
Source: Partly after Kearey and Vine (1996).
collision with Eurasia. The Tethys connected briefly with the developing Atlantic to form
a narrow, equatorial Cretaceous ocean before closing like a zip. Biogenic sediments in its
marginal basins and epicontinental seas now form the world's principal oil reserves. The
'zip' did not close smoothly, and early Euro-African collision in the west less than 140
Ma ago allowed younger rifts in East Africa and the Red Sea-Gulf of Aden-Persian Gulf
region to develop in the east (Figure 11.3). The Red Sea and Gulf of Aden are flooded
rifts but, so far, without sea-floor spreading.
India and Australia broke away to the north-east, opening up the Indian Ocean behind
and closing the eastern Tethys ahead, culminating in the Cenozoic India- Asia collision
40 Ma ago. Continuing indentation of India into Asia nudges south-east Asia and China
eastward to aid the consumption of the north-west Panthalassic Ocean. The Pacific Ocean
is its diminutive successor, almost completely refloored since break-up. The oldest
surviving early Jurassic floor is now subducting in the Marianas trench, compared with
younger Cenozoic crust beneath
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