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Evolution of Earth's Global Climate

2010; Elsevier BV; Linguagem: Inglês

10.1016/b978-0-444-53757-7.00014-3

2352-281X

O. G. Sorokhtin, George V. Chilingar, Н. О. Сорохтин,

Geological Studies and Exploration

This chapter discusses the evolution of Earth's global climate. The most important definitive factor of the Earth's climatic conditions is its surface temperature. Temperatures during the past epochs may be deduced from the oxygen isotopic shifts, for instance, in the marine Flintstones, which usually form in equilibrium with the surrounding water. It is known from isotope geochemistry that the δ18O value in marine Flintstones substantially depends on the temperature of the water, where the siliceous sediments were deposited. Based on such determinations, it is usually assumed that a high atmospheric temperature occurred already in Archaean about 3.4 BY ago. By mid-Archaean, the oceanic water temperature reached +70 °С. It is not clear to this day, however, to what extent the δ18O values in ancient Flintstones reflect their origin and, most important, the temperatures of the water where these Flintstones formed: the isotope ratio in the Flintstones may have been affected also by the same ratio in the oceanic water. It is possible that the observed regular decline of the δ18O values in the Flintstones is not only due to the oceanicwater temperature change but also due to other reasons causing regular δ18O value decline in the Archaean oceanic waters.