ABSTRACT
This paper concerns deals with biogeologic accumulation
and their peculiarities, lithological unites of the phosphorite-bearing
formations of these basins and an evolution of the old biota. Old bedded
phosphorites are believed to be connected with specific biogeological events
happening in the Neoproterozoic glaciation, which was followed by rapid
deglaciation, Ediacaran bioradiation and the “great” postglacial
transgression bearing phosphorites at its initial phase. The Mongolian
phosphate basins give evidence of this phenomenon. Khubsugul basin is located
in the northern Mongolia. The Neoproterozoic-Cambrian phosphorite-bearing
khubsugul group is subdivided into 3 formations as ongolik, kheseen and
erkhelnuur which are rich in organic fossils (a group of cyanobacterial mats,
archaeocyaths, trilobites) in the ascending order. The Zavkhan basin lies in
the western Mongolia. The Ediacaran-lower Cambrian sediments are divided into
five formations: Maikhanuul (diamictites), Tsagaanolom (phosphorite-bearing
carbonate), Bayangol, Salaanygol and Khairkhan. All the formations contain the
paleontological fossils (algae, sponges, cyanobacterial mats, ichnocoenosis,
soft-bodied fauna, archaeocyaths, etc.). Bedded phosphorites are the object for
comprehensive research of bacterial paleontology. It is shown at example of the
Mongolian Khubsugul and Zavkhan sea shelf phosphate basins. The expounded
actual material clearly shows that the heterogeneous biologic activity,
suitable geologic (transgressive systems tracts) and paleogeographic
(glaciations, warm climate, etc.) conditions played an important role in the
formation and accumulation of the biogenic bedded phosphorites.