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Low thermal diffusivity of peat and soils overlying parts of the oil and gas province of the eastern Magellan basin has resulted in several unusually shallow (< 2 m deep) relative heat-flow determinations. The values are in agreement with the single published heat-flow value for Tierra del Fuego of 2.3 HFU and with deep bottom-hole temperature measurements located in coincidence with the shallow determinations. They are furthermore consistent with local surface air temperature measurements obtained for a period of one year prior to the field work. Compared with that for similar tectonic provinces (post-Precambrian, non-orogenic) the heat flow in eastern Tierra del Fuego appears to be about 0.5 HFU greater than might be expected. Maturation level estimates based on buri l history of sediments in the area suggest considerable lateral migration (> 100 km) of hydrocarbons from deeper in the Magellan basin. A model is explored whereby the same mechanism for transport of the hydrocarbons, namely, deep ground-water movement can also explain the heat-flow results. The dramatic 10 HFU decrease in relative surface heat flow observed across the southwestern edge of the San Sebastian oil and gas field is of similar magnitude as other thermal anomalies reported to be in close association with hydrocarbon accumulations.
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