Polgari（aの頭に´）,M., Hein,J.R., Toth（oの頭に´）,A.L., Pal（aの頭に´）-Molnar（aの頭に´）,E., Vigh,T., Biro,（iの頭は´、oの頭に´）L. and Fintor,K.(2012): Microbial action formed Jurassic Mn-carbonate ore deposit in only a few hundred years(Urkut（Uとuの頭に´）, Hungary). Geology, 40(10), 903-906.

『たった数百年間に微生物の作用により形成されたジュラ紀のマンガン炭酸塩鉱床（ハンガリーのウルクツ）』

『Abstract
　The Urkut（Uとuの頭に´） (Hungary) manganese (Mn) ore, hosted by Jurassic black shale, was studied using high-resolution mineralogical, microtextural, and chemical methods. Two independent superimposed biostructures were identified consisting of rhythmic laminations that provide important proxies for paleoenvironments and duration of ore formation. Millimeter-scale laminae reflect a depositional series of Fe-rich biomats, mineralized microbially produced sedimentary structures. These biomats formed at the sediment-water interface under dysoxic and neutral pH conditions by enzymatic Fe2+ oxidizing processes that may have developed on a daily to weekly growth cycle. The early diagenetic sedimentary ore is composed of Ca rhodochrosite, celadonite, and smectite, and also shows a 100-μm-scale element oscillation that produces Mn (Ca)-rich and Si(Fe clay)-rich microlaminae. This microlamination may reflect a 10 h to daily rhythmicity produced by the growth of microbial communities. If true, then the giant Urkut（Uとuの頭に´） ore deposit may have formed over hundreds of years, rather than hundreds of thousands of years as previously thought.』

Introduction
Study area and ore description
Samples
Results
Discussion
　Millimeter- and micrometer-scale rhythmicities
　Duration of ore formation based on millimeter-scale laminae
　Duration of ore formation based on micrometer-scale oscillations
　Combination of cycles
　Paleoenvironmental considerations
Conclusion
Acknowledgments
References cited

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