Geological Epochs Research Articles

Palaeontological evidence for defining the Anthropocene

Abstract Palaeontology formed the basis for defining most of the geological eras, periods, epochs and ages that are commonly recognized. By the same token, the Anthropocene can be defined by diverse palaeontological criteria, in accordance with commonly accepted biostratigraphic practice. The most useful Anthropocene biostratigraphic zones will be assemblage and abundance zones based on mixes of native and non-native species in both the marine and terrestrial realms, although lineage zones based on evolution of crop plants may also have utility. Also useful are human-produced trace fossils, which have resulted in prominent biohorizons that can mark the onset of the Anthropocene, especially the paved road system, widespread through terrestrial regions, and microplastics, ubiquitous in near-shore and deep-water marine sediments. Most of these palaeontological criteria support placing the Holocene–Anthropocene boundary near 1950. Continuation of current extinction rates would produce an extinction biohorizon on the scale of the Big Five mass extinctions within a few centuries, but enhanced conservation measures could prevent making mass extinction an Anthropocene signature. A grand challenge for palaeontologists now is to define Anthropocene biostratigraphic zones rigorously, not only as a necessary precursor to formalizing the epoch, but also to more fully understand how humans have restructured the biosphere.

Recent geodynamics of the faults and paradoxes of the rates of deformation

The results of analyzing the long (20–50 years) time series of geodetic observations carried out in the regions with enhanced seismotectonic activity (Kopet Dag, Kamchatka, and California) are presented. It is established that recent vertical and horizontal displacements in the fault zones estimated by instrumental geodetic observations with increased spatiotemporal resolution indicate that the deformations in the fault zones paradoxically deviate from the movements inherited from the previous geological epochs.

Reconstruction of the Holocene climate of Transbaikalia: Evidence from the oxygen isotope analysis of fossil diatoms from Kotokel Lake

Fossil diatoms or Bacillariophyta are microscopicunicellular organisms with siliceous cell–frustule consisting of two separate valves that play an importantrole in marine and lake sedimentation. The data ofdiatom analysis provide reliable spatial and temporalreconstructions of the natural environment and theclimate of past geological epochs [1].The possibility of investigation of fossil Bacillariophyta by the oxygen isotope method in order to obtainpaleoinformation was originally demonstrated by L.Labeyrie [2]. The plotted isotope curves indicate variations in the temperature and isotope composition ofwater (δ

The digital global geologic map of Mars: Chronostratigraphic ages, topographic and crater morphologic characteristics, and updated resurfacing history

A new global geologic map of Mars has been completed in a digital, geographic information system (GIS) format using geospatially controlled altimetry and image data sets. The map reconstructs the geologic history of Mars, which includes many new findings collated in the quarter century since the previous, Viking-based global maps were published, as well as other discoveries that were made during the course of the mapping using new data sets. The technical approach enabled consistent and regulated mapping that is appropriate not only for the map's 1:20,000,000 scale but also for its widespread use by diverse audiences. Each geologic unit outcrop includes basic attributes regarding identity, location, area, crater densities, and chronostratigraphic age. In turn, units are grouped by geographic and lithologic types, which provide synoptic global views of material ages and resurfacing character for the Noachian, Hesperian, and Amazonian periods. As a consequence of more precise and better quality topographic and morphologic data and more complete crater-density dating, our statistical comparisons identify significant refinements for how Martian geologic terrains are characterized. Unit groups show trends in mean elevation and slope that relate to geographic occurrence and geologic origin. In comparison with the previous global geologic map series based on Viking data, the new mapping consists of half the number of units due to simpler, more conservative and globally based approaches to discriminating units. In particular, Noachian highland surfaces overall have high percentages of their areas now dated as an epoch older than in the Viking mapping. Minimally eroded (i.e., pristine) impact craters ≥3km in diameter occur in greater proportion on Hesperian surfaces. This observation contrasts with a deficit of similarly sized craters on heavily cratered and otherwise degraded Noachian terrain as well as on young Amazonian surfaces. We interpret these as reflecting the relatively stronger, lava-rich, yet less-impacted materials making up much of the younger units. Reconstructions of resurfacing of Mars by its eight geologic epochs using the Hartmann and Neukum chronology models indicate high rates of highland resurfacing during the Noachian (peaking at 0.3km2/yr during the Middle Noachian), modest rates of volcanism and transition zone and lowland resurfacing during the Hesperian (∼0.1km2/yr), and low rates of mainly volcanic and polar resurfacing (∼0.01km2/yr) for most of the Amazonian. Apparent resurfacing increased in the Late Amazonian (∼0.03km2/yr), perhaps due to better preservation of this latest record.

Selected geotourist attractions of Death Valley, USA

Death Valley National Park located in the U.S. states of California and Nevada is one of many units within the National Park Service established because of their exceptional natural and geological values. Death Valley National Park is renownedworldwide for its perfectly exposed, complex, unique and diverse geological resources. Within the park visitors encounter representatives of many geological epochs, from Precambrian metamorphic rocks exposed in the Black Mountains to recent desert sediments. This paper presents the geology of Death Valley and some of the most interesting geosites: Zabriskie Point, Badwater Basin, Devil’s Golf Course, Harmony Borax Works and Ubehebe Craters.

Solar irradiance modulation of Equator-to-Pole (Arctic) temperature gradients: Empirical evidence for climate variation on multi-decadal timescales

Using thermometer-based air temperature records for the period 1850–2010, we present empirical evidence for a direct relationship between total solar irradiance (TSI) and the Equator-to-Pole (Arctic) surface temperature gradient (EPTG). Modulation of the EPTG by TSI is also shown to exist, in variable ways, for each of the four seasons. Interpretation of the positive relationship between the TSI and EPTG indices suggests that solar-forced changes in the EPTG may represent a hemispheric-scale relaxation response of the system to a reduced Equator-to-Pole temperature gradient, which occurs in response to an increasing gradient of incoming solar insolation. Physical bases for the TSI-EPTG relationship are discussed with respect to their connections with large-scale climate dynamics, especially a critical relationship with the total meridional poleward energy transport. Overall, evidence suggests that a net increase in the TSI, or in the projected solar insolation gradient which reflects any net increase in solar radiation, has caused an increase in both oceanic and atmospheric heat transport to the Arctic in the warm period since the 1970s, resulting in a reduced temperature gradient between the Equator and the Arctic. We suggest that this new interpretative framework, which involves the extrinsic modulation of the total meridional energy flux beyond the implicit assumptions of the Bjerknes Compensation rule, may lead to a better understanding of how global and regional climate has varied through the Holocene and even the Quaternary (the most recent 2.6 million years of Earth's history). Similarly, a reassessment is now required of the underlying mechanisms that may have governed the equable climate dynamics of the Eocene (35–55 million years ago) and late Cretaceous (65–100 million years ago), both of which were warm geological epochs. This newly discovered relationship between TSI and the EPTG represents the “missing link” that was implicit in the empirical relationship that Soon (2009) recently demonstrated to exist between multi-decadal TSI and Arctic and North Atlantic climatic change.

Multistability with a Metastable Mixed State

Complex dynamical systems often show multiple metastable states. In macroevolution, such behavior is suggested by punctuated equilibrium and discrete geological epochs. In molecular biology, bistability is found in epigenetics and in the many mutually exclusive states that a human cell can take. Sociopolitical systems can be single-party regimes or a pluralism of balancing political fractions. To introduce multistability, we suggest a model system of D mutually exclusive microstates that battle for dominance in a large system. Assuming one common intermediate state, we obtain D+1 metastable macrostates for the system, one of which is a self-reinforced mixture of all D+1 microstates. Robustness of this metastable mixed state increases with diversity D.

Italian freshwater biodiversity: status, threats and hints for its conservation

Freshwater makes up 3% of the planet's water, 67% of which is ‘trapped’ in glaciers and polar caps. Lakes, ponds, streams, etc. (excluding subterranean waters) constitute approximately 6.5% of freshwater, which is less than 0.2% of the earth water and 0.8% of its surface. Nevertheless, beyond supporting the livelihood of billions of people, especially in poor countries, according to the different estimates 100,000/126,000 animal species are known for inland waters, from 6 to 9.5% of the total animal described. As far as Italy is concerned, there are 5496 freshwater animal species out of 55,732 total; that is, around 10% of its fauna (terrestrial species are 41,923, while marine are 8330, several eurialine species being considered as present in both marine and freshwater environments). This fauna is highly specific: we can estimate a percentage of Italian freshwater endemics that could exceed 10%. Unfortunately, freshwater species are extinct or at risk with loss rates which could be of the same extent of those of previous transitions between geological epochs like the Pleistocene-to-Holocene. In Italy it is difficult to evaluate the conservation status and trends of aquatic faunas due to the lack of previous studies. The analysis of selected taxa seems to depict a critical situation. Besides, inland waters only recently have been addressed by conservation politics and only a reduced part of their fauna is involved in preservation measures. As regards protection politics in Italy, we can safely say that those regarding freshwater animals are badly addressed: out of 841 protected species only 100 are from inland waters, and only 15 of them are invertebrates. Proposals and priorities for conservation and management of Italian freshwaters are discussed.

Subduction geodynamics in Archean and formation of diamond-bearing lithospheric keels and early continental crust of cratons

The diamond-bearing mantle keels underlying Archean cratons are a unique phenomenon of Early Precambrian geology. The common stable assemblage of the Archean TTG early continental crust and underlying subcontinental lithospheric mantle clearly shows their coupled tectogenesis, which was not repeated in younger geological epochs. One of the least studied aspects of this phenomenon is concerned with the eclogitic xenoliths carried up by kimberlite pipes together with mantle-derived nodules. The eclogitic xenoliths reveal evidence for their subduction-related origin, but the Archean crustal counterparts of such xenoliths remained unknown for a long time, and the question of their crustal source and relationships to the formation of early continental crust remained open. The Archean crustal eclogites recently found in the Belomorian Belt of the Baltic Shield are compared in this paper with eclogitic xenoliths from kimberlites in the context of the formation of both Archean subcontinental lithospheric mantle (SCLM) and early continental crust. The crustal eclogites from the Belomorian Belt are identical in mineral and chemical compositions to the eclogite nodules (group B), including their diamond-bearing varieties. The eclogite protoliths are comparable in composition with the primary melts of the Meso- and Neoarchean oceanic crust, which was formed at a potential temperature of the upper mantle which exceeded its present-day temperature by 150–250 K. The reconstructed pathways of the Archean oceanic crust plunging in the upper mantle suggest that the Archean mantle was hotter than in the modern convergence settings. The proposed geodynamic model assumes coupled formation of the Archean diamond-bearing SCLM and growth of early continental crust as a phenomenon related to the specific geodynamics of that time controlled by a higher terrestrial heat flow.

Rotation parameters of the Siberian domain and its eastern surrounding structures during different geological epochs

The motion of lithospheric blocks was analyzed in the junction zone between the Eurasian Plate and its surrounding structures. Its present-day stage was considered using GPS and seismologic data. Models of the movement of a rigid plate are considered for Eurasia. A model of Eurasia (northern part of Asia) was used to determine the rotation parameters of its southern periphery (Amur Plate) based on GPS data for the Far East (Sikhote Alin profile), and Transbaikal regions are shown as an example. A model of the Amur Plate was used to illustrate the behavior of the extension zone on its western boundary represented by the Lake Baikal depression during the Kultuk earthquake (M = 6.3, August, 27, 2008). Paleomagnetic data made it possible to determine the rotation pole of the Siberian Craton relative to its surrounding folded structures during the Mesozoic and to estimate its kinematic parameters. The permanent position of the rotation pole in the relative coordinate system since the terminal Paleozoic until the Recent indicates a constant rotation velocity of the Siberian domain within the Eurasian Plate structure.

A Cell-Molecular Approach Predicts Vertebrate Evolution

In contrast to the conventional use of genes to determine the evolution of phenotypes, we have functionally integrated epithelial-mesenchymal interactions that have facilitated lung phylogeny and ontogeny in response to major geologic epochs. As such, this model reveals the underlying principles of lung physiology based on the evolutionary interactions between internal and external selection pressures, providing a novel understanding of lung biology. As a result, it predicts how cell-molecular changes in this process can cause disease and offers counterintuitive insights to diagnosis and treatment based on evolutionary principles.

On the issue of time speed

On the basis of almost constant ratio between duration of consecutive geological epoch, which is approximately equal to two, and on the basis of assumptions that change of a level of development of the organic world on the Earth for each epoch is the same, the author makes a conclusion that speed of development of organic matter on the Earth for the last two billion years can be described with indicative (or exponential curve) dependence. This exponent can be used for the description of not only geological epochs, but also for shorter time intervals, in particular, for dividing of Quaternary into stone, bronze and iron periods.

Father Damian Kreichgauer SVD (1859-1940) and Father Erich Wasmann SJ (1859-1931): geology, earth history and evolution in two German lives between science and faith

The physicist Damian Kreichgauer entered the German Missionary Order Societas Verbi Divini (SVD) in 1892. From 1895 onwards, he taught natural sciences to future missionaries at the Order's seminary St Gabriel (Austria). In 1902, he published a book called Die Äquatorfrage in der Geologie (The Question of the Equator in Geology) with the Order's publishing outlet, in which he advocated the idea of a mobilistic Earth, where the Earth's crust as a whole moved with respect to the fluid core and the Earth's rotational axis. The main evidence for this idea he found in the changing of climate zones during geological epochs. Due to a small database, which was basically restricted to European plate localities, Kreichgauer did not notice discrepancies between polar wander on different continents. Nevertheless, the book was later cited and discussed as one of his precursors by Alfred Wegener in his book on the origin of continents and oceans. Kreichgauer also introduced his ideas to parallel the events of the biblical Genesis with geological epochs. He later expanded this ‘concordance theory’ in a separate book Das Sechstagewerk (The Work of the Six Days). He eventually abandoned scientific work, possibly due to censorship wielded by the Superior of his Order, unlike his contemporary, the Jesuit Erich Wasmann, a respected entomologist, who defended evolutionary ideas despite adverse Church politics and censorship.

Secondary chaotic terrain formation in the higher outflow channels of southern circum-Chryse, Mars

Higher outflow channel dissection in the martian region of southern circum-Chryse appears to have extended from the Late Hesperian to the Middle Amazonian Epoch. These outflow channels were excavated within the upper 1 km of the cryolithosphere, where no liquid water is expected to have existed during these geologic epochs. In accordance with previous work, our examination of outflow channel floor morphologies suggests the upper crust excavated by the studied outflow channels consisted of a thin (a few tens of meters) layer of dry geologic materials overlying an indurated zone that extends to the bases of the investigated outflow channels (1 km in depth). We find that the floors of these outflow channels contain widespread secondary chaotic terrains (i.e., chaotic terrains produced by the destruction of channel-floor materials). These chaotic terrains occur within the full range of outflow channel dissection and tend to form clusters. Our examination of the geology of these chaotic terrains suggests that their formation did not result in the generation of floods. Nevertheless, despite their much smaller dimensions, these chaotic terrains are comprised of the same basic morphologic elements (e.g., mesas, knobs, and smooth deposits within scarp-bound depressions) as those located in the initiation zones of the outflow channels, which suggests that their formation must have involved the release of ground volatiles. We propose that these chaotic terrains developed not catastrophically but gradually and during multiple episodes of nested surface collapse. In order to explain the formation of secondary chaotic terrains within zones of outflow channel dissection, we propose that the regional Martian cryolithosphere contained widespread lenses of volatiles in liquid form. In this model, channel floor collapse and secondary chaotic terrain formation would have taken place as a consequence of instabilities arising during their exhumation by outflow channel dissection. Within relatively warm upper crustal materials in volcanic settings, or within highly saline crustal materials where cryopegs developed, lenses of volatiles in liquid form within the cryolithosphere could have formed, and/or remained stable. In addition, our numerical simulations suggest that low thermal conductivity, dry fine-grained porous geologic materials just a few tens of meters in thickness (e.g., dunes, sand sheets, some types of regolith materials), could have produced high thermal anomalies resulting in subsurface melting. The existence of a global layer of dry geologic materials overlying the cryolithosphere would suggest that widespread lenses of fluids existed (and may still exist) at shallow depths wherever these materials are fine-grained and porous. The surface ages of the investigated outflow channels and chaotic terrains span a full 500 to 700 Myr. Chaotic terrains similar in dimensions and morphology to secondary chaotic terrains are not observed conspicuously throughout the surface of Mars, suggesting that intra-cryolithospheric fluid lenses may form relatively stable systems. The existence of widespread groundwater lenses at shallow depths of burial has tremendous implications for exobiological studies and future human exploration. We find that the clear geomorphologic anomaly that the chaotic terrains and outflow channels of southern Chryse form within the Martian landscape could have been a consequence of large-scale resurfacing resulting from anomalously extensive subsurface melt in this region of the planet produced by high concentrations of salts within the regional upper crust. Crater count statistics reveal that secondary chaotic terrains and the outflow channels within which they occur have overlapping ages, suggesting that the instabilities leading to their formation rapidly dissipated, perhaps as the thickness of the cryolithosphere was reset following the disruption of the upper crustal thermal structure produced during outflow channel excavation.

Relationship between the alpha diversity of communities and the appearance rates of new genera in the evolution of phanerozoic marine biota

The influence of the alpha diversity of communities on the appearance rates of new species may be either positive (due to coevolution and niche construction) or negative (due to community saturation). The development of global paleontological databases allows the extrapolation of the analysis of these effects to past geological epochs. To assess the effect of alpha diversity on the rates of generic formation in the evolution of the Phanerozoic marine biota, the correlation of the parameters D (mean generic diversity of paleontological collections containing representatives of a large taxon) and B (relative rate of the appearance of new genera in the given large taxon) was analyzed. The majority of large taxa, and the Phanerozoic biota in general, characteristically show predominance of periods of positive correlation (synchronous changes) of B and D, separated by shorter periods of negative correlation (opposite phase changes). These can be interpreted as periods of positive and negative influence of alpha diversity on diversification, although positive correlation can be generated by other factors, including taphonomic ones. Apparently, in the evolution of the Phanerozoic marine biota, the coevolution and “niche construction” played a more significant role than the effect of “saturation” of communities.

Some Comments on Possible Processes in the Earth's Mantle

Many participants of the Symposium in their papers have discussed the possibilities of movements within the material of the Earth’s mantle which have the character of convection currents. As is well known, a number of researchers consider these movements to be the cause of horizontal displacements of continents. Unfortunately, the theoretical models of this type seldom take into account the limitations set by geological data. For instance, several models, rather popular at present, suggest that the distribution and size of the convective cells in the mantle are determined by the distribution on the Earth’s surface of mid-oceanic ridges and rift valleys connected Qith them. It is usually assumed that under the mid-oceanic ridges the rising currents are active, while the descending currents are in-between. The latter usually correlate with geosynclinal folded zones. The spaces between the mid-oceanic ridges and folded zones are considered as whole blocks experiencing only horizontal shifts. On continents the platforms are located outside the folded zones. The relative areas of both types of structures do not remain one and the same, but change with time: in more ancient geological epochs the area of folded zones was greater and the platforms covered correspondingly less space than in later epochs. However, we shall not dwell on this and refer to that pattern of folded zones and platforms which characterise the youngest tectonic cycle, the Alpine, because the constructions of the ‘ convectionists ’ always use this particular latest distribution of folded zones. The geological data provide undoubted indications that the platforms lying outside the limits of folded zones of the Alpine age cannot be considered as monolithic rigid blocks. Uneven distribution of the sedimentary cover on platforms testify to the division of the latter into areas of prolonged sinking and of prolonged rising. These areas have different sizes and we can distinguish among them structures of different order. The largest areas of subsidence and uplifting, correspondingly called syneclises and anteclises, are several hundreds of kilometres across. Moreover, the syneclises usually have irregular rounded contours, while the anteclises fill in the areas between them. Separate syneclises and anteclises exist for extremely long periods in the geological time scale. For instance, the Moscow syneclise as the subsidence region lasts at least from the end of the Proterozoic, i.e. more than 600 million years. It does not mean that the form of the syneclises and anteclises and their distribution remain unchanged during such long periods of time: separate syneclises extend and reduce with time and also move slightly in this or that direction on the surface. From time to time new syneclises and anteclises originate, and some of the old ones cease to exist. But all these changes are of a secondary character and on the whole the complex of syneclises and anteclises on the platforms is rather stable. The rates of vertical movements within both these structures are very small. If we average for hundreds of millions of years these rates will be of the order of mm /year, while the average From the geological point of’ view the scheme is very far-fetched.

10.1007/s11491-008-1009-3

Based on the study of the scleractinian azooxantellate corals sampled during many marine expeditions of Russian research vessels in the Pacific, Indian, and Atlantic oceans, habitat temperature ranges of their species were first estimated with compiling of temperature series according to the growing thermophility. The temperature series compiled for these oceanic basins consist of 35, 17 and 10 species, respectively. The confinement of scleractinian species to particular water masses is revealed. These data are thought to be useful for reconstructing ecological and oceanological characteristics in the past geological epochs, since coral species exist for millions years. For example, the temperature series established for scleractinian species may be used for reconstructing water temperatures in Cenozoic oceans and, probably, for determining geological ages for some coral species.

Biological mineralization of organic matter in the modern virgin and plowed chernozems, buried chernozems, and fossil chernozems

The phenomenon of mineralization (biological mineralization) of organic matter in chernozems has been studied. A decrease in the content of Corg with time can be considered an index of the organic matter mineralization. It is suggested that the humus horizons of modern chernozems contain the pools of organic matter of different ages: easily decomposable organic matter, labile biologically active humus, stable biologically active humus, and relatively inert humus. The composition and mean residence times of these pools and their contribution to the total organic matter content have been estimated. The particular types of the biological mineralization have been determined on the basis of the comparison between the velocities of mineralization (M) and humification (H) processes: total unidirectional mineralization (M ≫ H), equilibrium mineralization (M ∼ H), nonequilibrium mineralization (M> <H), and zero mineralization. The separation of subtypes is based on data on the relative rates (%) of the organic matter mineralization. On the basis of available experimental data on chernozems buried under kurgans and in loess sediments (with the age of up to 800 ka), the quantitative relationship of the humus content in the buried soils on their age has been found; it has an exponential shape. During the first 100 ka after the soil burial, the soil humus content gradually (with a slowing intensity) decreases from 100–75 to 6.5% of its content in the virgin chernozems. Then, 100–1000 ka after the soil burial, the soil humus content remains approximately constant (6.5% of the initial level, or 0.3% of the soil mass). The rates of mineralization have been estimated. It is shown that the elemental composition (C, H, N, O) of humic acids remains relatively stable for a long time due to the regeneration of the chemical structure of humus (matric restoration of humus). It is suggested that several different forms of humus related to pedogenesis should be distinguished in the biosphere. The renewable humus in the equilibrium state with the environment is typical of the open biospheric (soil) systems. The fossil humus, whose content decreases with time, and whose composition remains stable, is typical of the semiclosed and closed systems. With time, it transforms into residual humus, whose content and composition remain stable. The fossilized organic matter in the fossil soils and sediments of the past geological epochs (Mesozoic and Paleozoic) considerably differs from the renewable, fossil, and residual humus.

Deep-seated structure and metallogenic dynamics of the Ailaoshan polymetallic mineralization concentration area, Yunnan Province, China

The Ailaoshan poly-metallic mineralization concentrated area (MCA) consists of the well known Ailaoshan metallogenic belt and adjacent mineral districts and/or deposits. Located in an area of several complex and intersecting tectonic units, the Ailaoshan poly-metallic MCA is controlled by deep crustal and mantle tectonism. Through interpretation of remote sensing images, we identified a largering structure system that surrounds the MCA. This ring structure encloses regional deep-crustal faults, ductile shear zones, geothermal anomalies, magmatic rocks, and the major mineral deposits, all of which are the reflections of deep tectonic geodynamics that have been long active in this area. Geophysical data indicate that the crust is comprised of relatively stable two or three layers, with some irregular lower-velocity belts. The Moho in the ring sutures occurs as an area of local uplift. There exists an obvious transitional zone between the crust and mantle boundaries. Asthenopheric mantle shows multi-layer upwelling, which indicates multiple events during different geological epochs. It is believed that these mantle events or pulses were responsible for the formation of the regional shear zones, magmatic rocks, and polymetallic orebodies. Furthermore, an integrated metallogenic dynamics model related to the asthenopheric upwelling pulses in the MCA is established, defining events as old as Late Paleozoic.

Genesis of oil: A fundamental problem of geology (the current state of the problem)

The current state of the problem of oil genesis is discussed. The biogenic (sedimentary-migration theory) of oil genesis is shown to be valid based on the analysis of present-day data on the composition and properties of oil, the composition and distribution of organic matter (OM) in sedimentary rocks, and numerous calculations of the balance of oil-and-gas generation at different stages of catagenetic evolution. The confinement of oil and gas fields to sedimentary basins, as well as the relation of oil and/or gas reserves to volumes of oil-and-gas source rocks, which occur (or occurred) in the generation center, and/or to extremely high potential of oil source formations also indicate of the relationship between oil-and-gas fields and the “life” of former geological epochs.