Место издания: Florence , Год издания: 2004

Upper Jurassic Georgiev Formation of the West Siberian geosyneclise the main part of which corresponds to the Kimmeridgian Stage is the typical condensed ones. Its thickness in most cases not exceeds five to seven meters. At the same time the Formation is widespread on the area more than one million square kilometers. The Formation consists mainly of argillites and occasionaly aleurolites and sandstones. Glauconite is constant component of Georgiev Formation and found virtually in all samples. Scattered phosphorite nodules are found almost in all places of the Formation distribution, however more rarely than glauconite. The manganese carbonates occur in the western and partly in central parts of the West Siberian Geosyneclise. Microbial forms are found in all these authigenic materials. Phosphorites contain mainly tubular forms. There are curved ones among them varying in size in cross section; rather thin bridges (5 mm) connect much lager bulges to 15 mm across. Some pipes contain inside two smaller tubular forms. Sometimes small phosphate grains are found in the pipes. The thickness of the pipe walls is 2 mm. We regard the tubular forms as cyanobacterial filaments. Along with tubular forms posphorite contains phosphatized capcules of 2-4 mm in size of undoubtedly biogenic origin and showing more or less regular sphere in shape. In our opinion r they present the initial stage of formation of the cyanobacterial threads. Microbial-like forms found in glauconite are mainly also tubular. They are presented by threads of 50 mm length with 10 mm in outer diameter and 3,5-8 mm in inner ones, which are hollow inside. Only in one case we have found in glauconite the spherical cocco-like very regular forms 3,5-7 mm in size. In manganese carbonate rocks we have found two microbiological forms, both tubular and spherical. In one case we can observe both of them, in another only spherical forms. Evidently the most common microbical forms in studied glauconites, phosphorites and manganese carbonates are tubular ones. Determining them as capsules of cyanobacterial threads, we don't exclude that in phosphorites some of these forms can be true fungi. The spherical forms are observed not so often as tubular ones. They can be determined as cocco-like type. It should be said in the conclusion, that tubular and spherical forms were not often observed jointly, forming the isolated communities.