The existence of deep marine hypersaline anoxic basins (DHAB) has been well-documented starting with the MedRiff Project in the Eastern Mediterranean. We suppose that there is analogy between the recent and ancient DHABs. This premise allows us to hypothesize that some methane accumulations in geological reservoirs may have been generated by historical euryhaline bacteria. The extreme life conditions of the bacteria and the facieses, as found in currently existing supersaturated salt brines DHABs, may have also existed in the geological past. Since salt basins overlap some of the most productive gas provinces, this article aims to introduce a new approach to salt and methane generation. It highlights the need to reconsider the classical approach to salt and methane generation due to new observations. Hereby we describe a new mechanism for DHAB generation due to membrane polarization. These phenomena generate a surface on which seawater of normal salinity meets the underneath brine of high salinity, and there is no diffusion between them. Hence we presume that non-crystalized, over-pressured, salty brine is the appropriate material to trap and host methane. Following overburden by deposited basin sediments, this viscous, gas-saturated brine can be an engine for diapir formation, which is prior to the crystalline phase. This new idea redefines our search for salt and methane deposits yet it requires further research and consideration, along with the new approach of salt diapir formation in specific salt basins.
Abstract:The study of the evolution of the river network in the Great Hungarian Plain has been based on sedimentological, neotectonical, morphological investigations, heavy mineral analysis and complementary OSL dating. The study area extends from the Körös sub-basin into the Ér and Berettyó river valleys which are situated northeast from the subsiding basin and northwest from the uplifting Apuseni Mountains. The OSL ages provide evidence that a large river run in the Ér-valley at least from 46±4 to 39±4 ka. It deposited garnet and magnetite-ilmenite-rich sediments, similar to the recent Berettyó, Ér and SebesKörös rivers and less intensive the modern Tisza river. These sediments originated from the nearly located metamorphic and Neogene volcanic rocks and contain some reworked older clastic sedimentary rocks from the northern part of the Apuseni Mountains. These OSL ages fit the active tectonic phase of the Érmellék depression. Loess is 49-47, 44, 39 and 25 ka old and aeolian sands 10 to 9 ka were dated. Their heavy mineral composition and that of fluvial sands is similar.
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