Genetically different organogenic buildups in isotope values D13C and D18O

The isotopic composition of carbon and oxygen of 165 samples of carbonate rocks of genetically different organogenic structures: the Upper Ordovician Bol'shaya Kos'yu reef, the Upper Devonian Shar'yu microbial mound, the Kozhym skeletal mound, the Upper Miocene Kazantip bioherm complex and deep-water organogenic-carbonate structures of the north of the Mid-Atlantic Ridge was studied. The reef and microbial mound are characterized by d13CPDB values within the limits close to normal-sedimentary marine carbonates (-0.33-3.13 ‰) and (0.8-3.0 ‰), but with significant variations in d18OSMOW - (22.24-30.0 ‰) and (20.4-26.3 ‰), respectively. The most isotopically-heavy carbon composition (5.1-7.3 ‰) in combination with varying d18OSMOW values (22.4-30.0 ‰) is characteristic of limestones and brachiopods of the skeletal mound. Fluctuations of d13CPDB and d18OSMOW values in carbonate rocks of the Kazantip bioherm complex are the most expressive (-2.76-7.17 ‰) and (24.20-33.1 ‰), respectively. Deep-water organogenic structures from the bottom of the axial zone with active volcanism, in contrast to others, showed stable d13CPDB values (-0.98-0.83 ‰) within the area of normal-sedimentary marine carbonates, whereas for oxygen the values are istopic-heavy (32.27-39.75 ‰). As a result, the specificity of the development of the objects under study, established by lithological-paleoecological and chemical-physical methods, found its substantiation in isotopic values, paleosalinity and paleotemperatures caused by paleogeographic and climatic conditions.