Jurassic and Cretaceous Glendonites of the Novoyakimovskaya-1 Borehole (Western Taimyr): Age, Morphology, Depositional Settings and Alterations of Mineral Composition

According to biostratigraphic data, Bathonian and Callovian (Malyshevka and Tochinskoe Formations), Oxfordian (Sigovoe Formation), Volgian and Ryazanian (Yanov Stan Formation), Valanginian and Hauterivian (Sukhaya Dudinka Formation) stages were recognized in the core of Novoyakimovskaya-1 well. Characteristic species of mollusks from the Bathonian–Hauterivian are figured. For the first time, members previously established in the Bazhenovo Formation and the Lower Tutleim Subformation were traced into the Yanov Stan Formation. All studied formations except for Malyshevka Formation contain glendonites. Glendonites are pseudomorphs after cold-water mineral ikaite and can be used as indicators of cold water paleoenvironments. The size of glendonites varies from a few to 9–10 cm. Glendonites are morphologically diverse, however, no patterns in the distribution of glendonites of different shapes across the section are noted. Glendonites are abundant in the lower part of the section (Bathonian and Callovian stages), but their number decreases up the section. The stratigraphic distribution of glendonites is compared with the stages of climate cooling in the Arctic region. All studied glendonites are composed of two types of calcite; this feature is stable for glendonites of different ages and can be used for microscopic identification of glendonites.