Papers by Yuri O Gavrilov
The Geochemistry of Sapropelic Interbeds in Paleogene of the Central Caucasus
Lithology and Mineral Resources
These beds are enriched in a series of elements: S, Ni, Co, Mo, Cu, Pb, Cr, and sometimes Fe and ... more These beds are enriched in a series of elements: S, Ni, Co, Mo, Cu, Pb, Cr, and sometimes Fe and P, with a simultaneous reduction in CaCO3, Mn and Ti. The level of concentration of elements within the beds, together with their distribution, were controlled by various factors, the most important of which were diagenetic processes. A similarity is noted between the geochemistry of the Palaeocene-Eocene sapropelic beds and similar Quaternary formations in the Black Sea and the eastern Mediterranean. -from Journal summary
Isotopic Composition (δ13C, δ18O) of Carbonate Concretions from Terrigenous Deposits in the Northern Caucasus
Lithology and Mineral Resources - LITHOL MINER RESOUR, 2001
The isotopic composition of carbon and oxygen was studied in carbonate concentrations with differ... more The isotopic composition of carbon and oxygen was studied in carbonate concentrations with different compositions (calcite, dolomite, and siderite) from Jurassic, Cretaceous, and Tertiary terrigenous deposits of the Northern Caucasus. Wide variations in the isotopic composition (from 41.4 to 18.1‰ for d13C and from 11.7 to 33.5‰ for d18O) point to different formation conditions in the early diagenesis zone and the later catagenesis zone.
Lithology and Mineral Resources, 2007
Results of the comprehensive study of structural, lithological, mineralogical, and isotopic chara... more Results of the comprehensive study of structural, lithological, mineralogical, and isotopic characteristics of Lower Jurassic rocks exposed in the Belaya River valley (Adygeya) in meganticlinorium of the Greater Caucasus are presented. Deformation microstructures were studied. Lithological and textural-structural changes in sequences related to intense secondary transformations should affect the state of isotopic systems of rocks. To reveal basic trends in the evolution of isotopic systems, investigation using the K-Ar method was carried out. Clay fraction (less than 1 µ m) separated from rocks and bulk samples were analyzed. Cleavage development, approximate value of rock contraction, and isotopic characteristics are compared with the available data on alteration of clay mineral assemblages. Relationship between the degree of rock deformation at the microlevel and calculated K-Ar ages has been established. K-Ar systems of clayey rocks indicate the age of cleavage formation and correspond to the Bajocian-Bathonian contraction period.
Environment of Upper Paleocene as revealed by an isotope and biomarker study
EGU General Assembly Conference Abstracts, May 1, 2010
, +7(495)9510443) A series of global events related to wide occurrence of anoxic environment are ... more , +7(495)9510443) A series of global events related to wide occurrence of anoxic environment are detected in sedimentary record of epeiric basins of northeastern Peri-Tethys. The most pronounced among them are latest Cenomanian OAE 2 and Paleocene-Eocene Thermal Maximum (PETM). The repercussions of OAE 2 were studied in seven sections of different paleogeographic settings in Crimea and Caucasus, and PETM manifestations were found and analyzed in 13 distant sections in huge area (about 3,000 km WE) from Crimea to Central Asia. Both events are characterized by wide accumulation of sediments rich in TOC. In OAE2 sediments TOC values vary from 5 to 10% in the eastern Caucasus, reach up to 20% in the western Caucasus and consist 6-10% in Crimean sections. TOC values in PETM sediments range 1-10% in Caucasus and reach up to 25% in Central Asia. Sedimentary records of both events display pronounced cyclicity in TOC distribution. Each band (0.1-0.25 m) is composed of dark TOC-rich lower layer and pale more calcareous upper layer and their contrasting can be very distinct. The band number in the OAE 2 and PETM records is different: the first event incorporates up to ten cycles, while second event comprises not more than four cycles. If this sedimentary cyclicity is caused by precession cycles, the duration of TOC-rich sediment accumulation during OAE 2 (∼ 200 k. y.) appears to be much longer than the episode of TOC accumulation during PETM (∼ 40-50 k. y.). Within each band, pyrolysis revealed the domination of basinal organic matter in the dark layers and higher amount of terrestrial organic matter in the pale layers. Both events were preceded by significant sea-level falls marked by occurrence of relatively shallow-water sediments or hiatuses and TOC-rich sediments in both cases accumulated during rapid large-scale transgressions. At the same time, a propagation of sea-level rise had slip-stick character that caused variations in terrestrial runoff and microplankton productivity enabled cyclic pattern of TOC-rich sediment formation. 2 and PETM are featured by large oxygen isotope excursions reflecting dramatic climatic warming. Simultaneously, d13C displays positive excursion corresponding OAE2 and negative excursion during PETM. A response of nannoplankton to climatic and hydrological reorganizations during both events was essentially different in both cases: sediments correlated to OAE 2 include oligotaxonic nannofossil assemblage composed of long-lived euritopic Watznaueria spp., while PETM is characterized by wide occurrence of short-lived highly specified Rhomboaster spp. and asymmetric discoasters. Significant variations in TOC concentrations throughout the NE Peri-Tethys and cyclic character of sedimentary records of both events enable reasonable assumption of variable level of oxygen depletion through time and space changing from anoxic to suboxic environments in different parts of basin and in different stages of OAE 2 and PETM evolution. Restricted area of TOC-rich sediment accumulation during PETM comparing to OAE 2 was likely caused by changes in ocean morphology and circulation.
Volgian black-shale sediments of the Ivkino section, northern Russian Platform: sedimentary structure, geochemical and biotic record
Oxigen depletion events in the Paleogene of northeastern Peri-Tethys
At the different stratigraphic intervals of Phanerozoic sedimentary record of many areas, there a... more At the different stratigraphic intervals of Phanerozoic sedimentary record of many areas, there are levels enriched by chemical elements, specifically iridium. The most interesting and intricate problem is the occurrence of Ir-anomaly at the K/T boundary. As it is widely known, this and Ir-anomalies at some other stratigraphic levels are mostly considered as a result of meteorite impact. Difficulty of its nature revelation is caused by low iridium concentrations in both embedded sediments and Ir-rich layer. We consider here possible causes of the formation of geochemical anomalies by the example of more large-scale processes where maturation of Ir-anomalies is a particular case. In the Phanerozoic sedimentary record, there are prominent boundaries between TOC-rich sediments, most commonly clayey, and sediments lack in TOC, mainly sandstones, limestones, cherty rocks. In many cases, sulfide-rich beds correspond to these interfaces. Their thickness ranges from few cm to few dm and spa...
A variety of PETM record in different setting, northeastern Peri-Tethys
The K–Ar and Rb–Sr Isotopic Systems in Rocks from the Jurassic Terrigenous Complex of the Greater Caucasus
The behavior of K–Ar and Rb–Sr isotopic systems in clayey rocks from the Jurassic terrigenouis co... more The behavior of K–Ar and Rb–Sr isotopic systems in clayey rocks from the Jurassic terrigenouis complex of the Greater Caucasus sampled along the Terek River is discussed. It is shown that the rocks experienced intense postdiagenetic alterations accompanied by substantial changes in mineral composition and K–Ar and Rb–Sr isotopic systems. Lateral stress is the leading factor responsible for secondary mineral
Rare biogenic structures, after which diagenetic minerals are developed, are described from Paleo... more Rare biogenic structures, after which diagenetic minerals are developed, are described from Paleogene rocks of southern Dagestan. It is shown that these minerals form tabular mica-like and colloform aggregates confined to fucoids. In terms of composition, they represent the glauconite group minerals. Tabular and colloform minerals are compared with globular glauconite occurring in host sandy rocks. It is demonstrated that the globular variety is characterized by higher K and Fe contents, whereas the tabular variety has a higher SiO 2 content. The probable mechanism of the formation of tabular and colloform minerals in biogenic structures is discussed.
Lithology and Mineral Resources, 2007
Lithology and Mineral Resources, 2012
The paper discusses changes in both mineral composition and structural textural characteristics o... more The paper discusses changes in both mineral composition and structural textural characteristics of the Jurassic terrigenous complex along the Avar Koisu River (Dagestan) profile that intersects rocks with significantly various types of deformation. The profile extends from the monoclinal zone to the intense defor mation and cleavage development zone. The alterations are manifested in the change of clay mineral assem blages, polytype modifications of micaceous minerals and their crystallinity index, rock density, reflectance of vit rinite, and other properties. Growth of the degree of secondary alterations (primarily, cleavage intensity) is accom panied by an appreciable decrease in K-Ar age of rocks and simultaneous increase of their stratigraphic age.
The Late Paleocene Anoxic Event in epicontinental seas of Peri-Tethys and formation of the sapropelite unit: sedimentology and geochemistry
… RESOURCES C/C OF …, 1997
... organic matter. These sediments are characterized by increased concentra tions of V, Ni, Cu, ... more ... organic matter. These sediments are characterized by increased concentra tions of V, Ni, Cu, Pb, Cr, Zn, Mo, Se, Ag, Au, etc., decreased contents of CaCO 3 and Mn, and passive behavior of Ti, Zr, Nb, Sc, Hf, Y, and REE. The ...
Lithology and Mineral Resources, 2008
The second half of the Late Jurassic Period was characterized by the development of conditions fa... more The second half of the Late Jurassic Period was characterized by the development of conditions favorable for the accumulation of high-carbonaceous (frequently, oil-generating) sediments in different regions of the Northern Hemisphere (West Europe, Russian Plate, Barents Sea, West Siberia, and others). In the East European Platform, organic-rich sediments of the Volgian Stage (oil shales) are developed over a spacious area. Researchers have proposed different concepts for the accumulation of high-carbonaceous sediments. However, formation mechanisms of such sediments remain unclear so far. Development of their genetic models requires data on sections from different parts of the spacious Volgian Basin, which would make it possible to understand general regularities in its evolution and determine the influence of local factors on sedimentation processes. Data on the typical shale-bearing sections with the most complete record of their sedimentation history are also essential.
Lithological and geochemical characteristics of recent and Quaternary sedimentation in the Arctic Ocean
Geochemistry International, 2012
This paper addresses some problems concerning the geologic activity of sea ice and icebergs, as w... more This paper addresses some problems concerning the geologic activity of sea ice and icebergs, as well as the influence of continental and shelf glaciations on the sedimentation in the Arctic Ocean during Recent and Quaternary times. Seasonal and circumcontinental zoning is clearly manifested in the sedimentation. The role of glacial material in the modern and older sediments was estimated. Mathematical statistical methods were employed for the reliable stratigraphic subdivision of Quaternary sequences and determination of main factors controlling their chemical composition. Silica content was proposed as an optimal parameter for the lithochemostratigraphic subdivision of Quaternary sediments.
Lithology and Mineral Resources
Eocene and Lower Oligocene rocks in the northeastern Caucasus were examined in the most represent... more Eocene and Lower Oligocene rocks in the northeastern Caucasus were examined in the most representative Chirkei section (Sulak River basin). Sharp lithogeochemical distinctions between them were revealed. The results of the study of nannoplankton demonstrated that the Eocene/Oligocene interface occurs slightly below the boundary between the Belaya Glina and Khadum formations. The studied section revealed a series of nannoplankton bioevents facilitating its stratigraphic subdivision. It has been established that organic matter (OM) in rocks of the Khadum Formation is characterized by a relatively high degree of maturity. Probably, the material of mainly marine genesis contains a terrigenous OM admixture. Positive oxygen isotope anomaly in the upper part of the Belaya Glina Formation reflects global climate changes (cooling) near the Eocene/Oligocene interface. Limitation of the anomaly by the upper boundary of the Belaya Glina Formation is likely related to changes in water salinity variations in the Early Oligocene basin and intense early diagenetic processes in rocks therein. Lithological, geochemical, and paleoecological data suggest that the Khadum paleobasin was depleted in oxygen. Such environment was unstable with periodic intensification or attenuation. Paleoecology in the Belaya Glina basin was typical of normally aerated basins.
Architecture of the Southern Marginal Zone of the Upper Jurassic–Valanginian Carbonate Platform of the Northeastern Caucasus (Dagestan, Shakhdag Massif)
Lithology and Mineral Resources
The structure of the southern marginal zone of the Upper Jurassic–Valanginian carbonate platform,... more The structure of the southern marginal zone of the Upper Jurassic–Valanginian carbonate platform, Northeastern Caucasus, is considered with the Dagestan sector of the Shakhdag Massif as example. The massif consists of several large genetically diverse sedimentary complexes: (1) Upper Jurassic basal complex represented by the shallow-water terrigenous and carbonate sediments, which were formed under unstable sedimentation conditions; (2) reef complex ascribed to the barrier reef system; and (3) sedimentary sequence with the typical clinoform structure and the southwestward dip, toward the Dibrar trough. The formation of the marginal zone of the carbonate platform was mainly determined by (1) climatic conditions (transition from the humid climate in the Early and Middle Jurassic to the arid climate in the Late Jurassic) and (2) differences in the tectonic evolution of different structural-facies zones (weak subsidence of the Northeastern Caucasus, where carbonate platform was formed, and intense subsidence to the south in the flysch trough area). The formation of the internal structure of the Shakhdag Massif was mainly defined by the eustatic sea-level fluctuations.
The mineralogical, isotope (K–Ar), structural, and textural features of the Jurassic siliciclastic complex in various tectonic environments (Greater Caucasus, Chechnya, and Georgia)
Moscow University Geology Bulletin
The variations in the structural, textural, mineralogical, and geochemical (isotope) features of ... more The variations in the structural, textural, mineralogical, and geochemical (isotope) features of Lower to Middle Jurassic siliciclastic sediments along the Chanty-Argun River in Mountainous Chechnya and Georgia are discussed. This profile transects areas with various types of deformed sediments, from the northern comparatively weakly deformed and altered zone, to the southern zone of intense deformation and cleavage. Southward along the profile, these alterations are accompanied by the evolution of clay mineral assemblages, as well as polytypic modifications of micas and their crystallinity index. Increasing intensity of rock alteration and cleavage leads to a change of the K–Ar system, which results in a substantially rejuvenated isotope age of the sediments with a simultaneous increase of their stratigraphic age.
Lithology and Mineral Resources
Abstract⎯Numerous traces of paleoseismic events (seismites) were established in Mesozoic-Cenozoic... more Abstract⎯Numerous traces of paleoseismic events (seismites) were established in Mesozoic-Cenozoic marine sedimentary sequences of the northern Caucasus. These traces are most prominent in the terrigenous Middle Miocene sandy-clayey sediments. Impact of seismic shocks upon the relatively weakly lithified sediments provoked distortion of the primary sedimentary structure, liquefaction of the sandy material, and injections of different morphologies (neptunic dikes and sills). The formation of jointing in sediments fostered their vertical permeability and promoted the migration of diagenetic solutions into the adjacent horizons, which stimulated the formation of subvertical carbonate bodies. The amount and intensity of seismic events varied at different stages of the accumulation of sequences and in different areas of the paleobasin. In the eastern sector of the northern Caucasus, seismic activity similar to the present-day general pattern was likely developed as early as the Middle Miocene: maximum activity in the Dagestan and its westward attenuation. Traces of seismic activity are also recorded in the Maikopian (Oligocene-Lower Miocene) and Lower-Middle Jurassic rocks.
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Papers by Yuri O Gavrilov