Basin modeling of temperature and heat flow distributions and permafrost evolution, Urengoy and Kuyumbinskaya areas, Siberiaстатья
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Дата последнего поиска статьи во внешних источниках: 5 февраля 2014 г.
Аннотация:Thermal history and permafrost evolution in sedimentary basin during the Pliocene-Quaternary were reconstructed numerically using the software package FROST that is a part of the Basin Modeling system GALO. Computations are carried out for two sedimentary sections: Urengoy area in the West Siberia Basin and Kuyumbinskaya area in the East Siberia Platform. Calculations suggest a significant role of variations in rock composition with depth in permafrost evolution. Numerical assessments point to a decrease of rock temperatures by 15-20oC within the upper 1500 m of sedimentary section resulted from climate cooling in the Pliocene-Holocene. The effect of cooling is more considerable in the Kuyumbinskaya area with thinner sedimentary cover than in more northern Urengoy area. The model allows an estimation of depth of permafrost zone and stability zone of methane gas hydrate. An increase in salt content in porous water from 1 to 30 g/l decreases a ice melting temperature just by 2ºС and decrease of permafrost thickness almost by 100 m. Consideration of change in shape of the unfrozen water curve, W(T), depending upon lithological composition of sedimentary rocks, can correct considerably the numerical estimations of permafrost depth. The modeling demonstrates that permafrost thickness, the temperature and heat flow distributions with depth in the present-day sedimentary section of the basin, calculated with climate variations of the last 50,000 years, will differ significantly from the values obtained with consideration of the climate variations during last 200,000 or 3,400,000 years