New scientific direction of the bacterial paleontology in Mongolia : an essence of investigation

We review the initial development of Bacterial Paleontology in Mongolia and present some electron microscopic images of fossil bacteria in different stages of preservation in sedimentary rocks. Indeed bacterial paleontology is one the youngest branches of paleontology. It has began in the end of 20 century and has developed rapidly in recent years. The main tasks of bacterial paleontology are detailed investigation of fossil microorganisms, in particular their morphology and sizes, conditions of burial and products of habitation that are reflected in lithological and geochemical features of rocks. Bacterial paleontology deals with fossil materials and is useful in analysis of the genesis of sedimentary rocks, and sedimentary mineral resources including oil and gas. The traditional paleontology is especially significant for evolution theory, biostratigraphy, biogeography and paleoecology; however bacterial paleontology is an essential first of all for sedimentology and for theories sedimentary ore genesis or biometallogeny


INTRODUCTION
Bacteria or microbes preserved well as fossils in various rocks, especially in sedimentary rocks alike natural substances. Major types of sedimentary rocks form in the photic zone of epicontinental basins of the past, originated under influence of microorganisms. Photic zone, surface layer of the ocean receives sunlight. The uppermost 80 m or more of the ocean, which is sufficiently illuminated to permit photosynthesis by phytoplankton and plants, is called the euphotic zone? Within these oceanic expances, all the microorganisms had lived and propagated without breakdowns. Bacterial paleontological data accompanied by the data on the first origin of eukariotes, metazoan, etc. The essential role of bacteria and other microbes in the geological and biological processes was proposed long ago. Many specialists of the 19 th century claimed that there is a tremendous role of bacteria in the formation of the sedimentary mineral resources, like phosphorite, bauxite, iron ores, oil, hydrocarbon, petroleum gas, gold, sulfide, sulfur and sulfate, etc. The most significant break-

Review paper
Mongolian Geoscientist through was made after the introduction of electron microscopy to the study of microbial remains. Mongolian bacterial fossils from Precambrian and Cambrian sedimentary rocks and bedded phosphorite were examined using a Zeiss EVO50 SEM with an Oxford INCA microanalyzer (Energy 350) at the Paleontological Institute of the Russian Academy of Sciences were published repeatedly (Zhegallo et al., 2000). According to A.Yu.Rozanov a start of forming of the bacterial paleontology was kick-off research of the Mongolian phosphorite (Rozanov, 2016). New scientific technology revealed that almost all sedimentary rocks contain micro-scale bacteria. The main task for bacterial paleontology is to study the fossil microbes. The traditional paleontology deals with remains of ancient organisms. As known the main "users" of paleontology are the evolutionary theory, the history of organic world and the biostratigraphy. Bacterial paleontology or geomicrobiology is limited in its input data by the simplicity of the objects' morphology and specificity in systematization of the bacterial material. So, the bacterial paleontology is very important for sedimentology, and consequently for detailed study of the geneses of sedimentary mineral resources, including oil, gas, iron, phosphate, and gold. Geomicrobiology is a scientific field at the intersection of geology and microbiology (Dorjnamjaa et al., 2018(Dorjnamjaa et al., , 2019. It concerns the effect of microbes on geological and geochemical processes and vice versa. Such interactions occur in the geosphere (rocks, minerals, soils, and sediments), the atmosphere and the hydrosphere. All kinds of microbes, including prokaryotes and eukaryotes and their symbiotic associations with each other and higher organisms, can contribute actively to geological phenomena, and central to many such geomicrobial processes are transformations of metals and minerals. Indeed a diverse Proterozoic-Phanerozoic sedimentary stratigraphic rocks in Mongolia record and faunal, floral, and also bacterial localities (Mitrofanov et al., 1981;Bat-Ireedui, 1991, Bosak et al., 2011a, b;Barsbold and Byamba, 2012;Byamba, 2012;Dorjnamjaa, 2016;Dorjnamjaa et al., 2016;Dorjnamjaa, 2017;Anderson et al., 2017aAnderson et al., , b, 2018. In Mongolia the oldest microorganisms from the Paleoproterozoic were found in the iron-bearing quartzite. In 1981, B.V.Timofeev (Russian palynologist of Leningrad Institute of the Precambrian geology and geochronology, RAS, who pioneered the study of Precambrian an Early Paleozoic acritarchs) described and published several new genera and species of acritarchs (Protosphaeridium sp., Gloeocapsomorpha priscata Tim., Trematosphaeridium sp., etc). These bacterial microfossils of the "bodaibin" type were extracted from Khangiltsig metacomplex (Khankhukhei block). Also T.N.German together with B.V.Timofeev have described number of bacterial fossils (Spheromorphides, Filamentous algae, etc.) from Meso-Neoproterozoic sedimentary and metaargillaceous rocks of the Tseel, Baidrag and Tarvagatai blocks (Mitrofanov et al., 1981). The presence of cyanobacteria in all mentioned rocks could be considered as a reliable fact. Also it has importance for paleogeography and paleoecology in the study of epicontinental basins as Khuvsgul and Zavkhan shallow basins in Mongolia (Ragozina et al., 2010;Serezhnikova et al., 2014). The Khuvsgul and Zavkhan basins host economic-grade phosphorite deposits (Ilyin, 1973;Dorjnamjaa and Soyolmaa, 2001). The high preservation potential of organic microfossils in phosphorites makes Mongolia an obvious target for new Lagerstatten, which might inform the debate about the phylogenetic affinities of these early organisms (Anderson et al., 2018). Just Anderson et al., (2018) have recently presented systematic palaeontology of the recently discovered Kheseen Lagerstatten, which includes Doushantuo-Pertatataka-type acanthomorphs and other microfossils, including animal embryo-like forms, and discussed its biostratigraphical and palaeobiological significance. A Lagerstatten (German:from storage, place) is a sedimentary deposit that exhibits extraordinarily preserved fossils with exceptional preservation, which sometimes include preserved soft tissues. These formations may have resulted from carcass like burial in an anoxic environment with minimal bacteria, thus delaying the decomposition of both gross and fine biological features until long after a durable impression was created in the surrounding matrix. We are fully conscious of the fact that microfossil assemblages of the acritarchs, known from Proterozoic-Lower Cambrian strata are commonly found in shale and chert, as well as carbonaceous lithologies that are sufficiently phosphatized (Zhegallo et al., 2000;Pruss et al., 2017;Anderson et al., 2018;Dorjnamjaa et al., 2018) (Goldring et al., 1996), stromatolite (thrombolites), soft-bodied fossils (Spatangopsis mongolica, Paracharnia, Oldhamia radiata), medusoid (jellyfish) and small shelly fossils: protoconodonts, anabaritids, cap-shaped fossils, Salanacus, hyolithelminthes, coeloscleritophorans, tommotiids, orthothecimorphs, molluscs and calcareous brachiopods (Zhegallo et al., 2000;Dorjnamjaa et al., 2016;Anderson et al., 2018). Trilobites and Archaeochyathids are confined to the Salaanygol Formation in Zavkhan area, Salaanygol section and Erkhelnuur Formation (Kheseengol, Ongoliggol and Urandush sections) in western Coast of Khuvsgul Lake and Egiingol Formation (Myaras ovoo section, Blue Montain section, Chuulgant mountain section near the East Khargana river), Khoridulin, Jamatulingol and Ujiggol formations in western and southern Khuvsgul area (Dorjnamjaa et al., 1982).

RESULTS
The highest significance of bacterial paleontological data is obvious for study of biosphere evolution, especially in the Precambrian and the early Paleozoic. And finally, bacterial paleontology is one of the principle aspects for the astromaterials' study (Dorjnamjaa et al., 2012). The recent electronmicroscopic studies of rocks varying both in chemical composition and age prove that fossilized microorganisms can be practically found in almost all sedimentary rock. Bacterial fossils are the remains of animals or plants that are preserved in rocks, that bacteria   (Dorjnamjaa et al., 2018). Precisely these rocks contain fantastic preservation of diverse cyanobacteria and other microorganisms (Figs. 1-10).
On the whole, bacterium applies to an ordinary microscopic organism that consists of a single cell without noticeable nucleus, but possesses of colossal biochemical energy. Moreover, bacteria Tasmanites sp., specimen PIN 5492/8; 3-Octoedryxiumtruncatum Rud., 1989, specimen PIN 5492/3; 4-Problematicum Navifusa sp., specimen PIN 5492/9; 5-Tanarium sp., specimen PIN 5492/4; 6-Tanarium sp., specimen PIN 5492/10; 7-8-Tallophycoides sp., fragments of lamellae, specimen PIN 5492/11-12 (after Serezhnikova et al., 2014)      were accepted an active participation in process of decomposition and oxidation of organic matter. Here it should be emphasized that by the process of mineralization primary matter of skeleton and cyanobacterial mats are substituted with other mineral matter or pseudomorphism. The most prevailing bacteriogenic mineral matters are calcium, mineral carbon, mineral oil, magnesium carbonate, phosphate, sulphide (pyrite), oxides and hydroxyls (silica in different  modification), and indigenous limonite. So the ancient phosphorites have become the classic object for such studies (Dorjnamjaa, 2016). All kinds of bacteria can be an active contribution to geological phenomena, and centre of many such geomicrobial and biometallogenical processes and transformation or bioremediation of metals and minerals. The deposits of sedimentary mineral resources give clearly show another perfect paradigm of the tremendous bacterial role in the ancient geological event. The ancient phosphorites have become the classic object for such studies. Thirty years ago, we were aware of twenty minerals that could originate with the microbial activity. In recent times, the number of such minerals grew significantly, and nowadays it is more than a hundred. Using new methodology and factual data we would like to introduce some sedimentary mineral resources (biogenic phosphorites, gold-forming black shale, uranium and oil-gas deposits) those could be formed with the significant assistance of bacterial microfossils. In addition to above mentioned phosphorites, iron ores, graphite, and rare metal ores, bauxites, sulfides, gold, etc. are noteworthy (Dorjnamjaa et al., 2018).

CONCLUSION
1. Summing up all that has been said, in conclusion of our paper using new methodology and factual information we would like to note that some sedimentary mineral resources (biogenic phosphorites, iron -bearing quartzites, gold-forming black shales, diaspore bauxite, supposed "coal-andoil-gas-bearing Sabkha Formation"-salt domes) could be formed by significant assistance of bacterial microfossils (Dorjnamjaa et al., 2018(Dorjnamjaa et al., , 2019. In general a major role for bacterial-paleontological investigation lies in consideration of problems of the Biosphere evolution, especially in the Precambrian and Early Paleozoic as well as in Astrobiology (Hoover et al., 1998(Hoover et al., , 2003a(Hoover et al., , b, 2004Dorjnamjaa et al., 2012). 2. In fact biogenic phosphorites are concrete evidence and object for an academic research of bacterial paleontology. Bacteria were the beginning of an life. The "Khuvsgul" and "Zavkhan" biota were mostly cyanobacterial. The cyanobacterial mat community was preserved in phosphorites in the form of a stromatolite, microphytolite, blue-green algal remain, and micronodul side by side with trace and small shelly fossils (SSFs), also spiculate sponges. The micronodules are clearly predominant in our observations. The micronodule sizes usually vary from tens to several hundreds of microns (Archaeooides, Tasmanites, Obruchevella, Siphonophycus, Lagerstatten, so on). Soft-bodied animals resemble organisms such as coelenterates and annelids and may be early forms of these groups. In all probability, all the fossils are closely connected and intercommunicated by one's genesis and accumulation in the ancient phosphatic basins. This is a target for future investigation.