Late Quaternary marine terraces in the Mediterranean coastal area of Syria: Geochronology and neotectonics

In order to provide new data on the neotectonics and geodynamic properties of western Syria, studies of marine terraces have been carried out. The most attention was paid to the lower terraces in the range of 3–5 to 30–35 m above sea level, because they have more complete distributions along the shore. The lower terraces were examined along the coastal area from Tartus to Latakia, and along the carbonate cliff on Arwad Island. Seven ²³⁰Th/U dates for these terraces are in the range of 85–130 ka, suggesting the age interval of the last interglacial (MIS 5). New dates on the lower terraces provide a basis for stratigraphical and geomorphological interpretation as well as neotectonic reconstruction. According to the geomorphological data and lithological composition of those terraces, two main uplifted blocks can be established. One coincides with the Latakia block, and another corresponds to the western margin of the Banias volcanic plateau. These blocks are divided by a subsided structure corresponding to the Nahr el Kebir graben. The amplitude of neotectonic uplifting in the Latakia and Banias blocks reaches 15–20 m for the Late Pleistocene.     

Influence of hydrothermal-metasomatic processes on the formation of present-day sulfide ores in carbonate bottom sediments of the mid-Atlantic Ridge (19°–20° N)

Based on materials obtained in Cruises 33 and 34 of the R/V Professor Logachev, the paper addresses formation conditions, morphology, structures, mineral composition of the present-day oceanic sulfide ores, and their relationships with the host (biogenic carbonate) bottom sediments in the 19°–20° N MAR (Zenith-Victoria and Petersburg hydrothermal fields) region. The grain size distribution, mineral composition of the carbonate (background) and ore-hosting sediments, as well as physicochemical parameters of their interstitial waters, are examined. The results suggest a significant role of hydrothermal-metasomatic processes in the formation of ores and ore-bearing sediments. A model is proposed for the formation of sulfide mineralization in oceanic sediments at the geochemical barrier in the zone of their interaction with the acid hydrothermal (diffuse-type) ore-bearing solutions delivered from rocks of the ocean floor.     

Lithostratigraphic and tectonic features of the formation of hydrocarbon pools on the shelf of the Russian eastern Arctic

Chronostratigraphic, geologic, and tectonic preconditions of the formation of hydrocarbon pools on the shelf of the Russian eastern Arctic are considered. Based on study of the Upper Cretaceous section at Cape Derevyannye Gory (Novaya Sibir Island), it is shown that the Arctic shelf comprises thick deltaic sequences that can accommodate solid and liquid hydrocarbons.     

Mineral Composition and Geochemical Zoning of Bottom Sediments in the Pobeda Hydrothermal Cluster (17°07.45′ N–17°08.7′ N Mid-Atlantic Ridge)

Lithology and Mineral Resources - The paper presents the mineral and chemical compositions of carbonate, metalliferous, and ore-bearing sediments developed within the Pobeda ore cluster based on...     

Fossil Coals (Gagates) from Pleistocene Sediments in Black Sea Terraces,Southeastern Crimea

Lithology and Mineral Resources - The marine Quaternary (Chaudian) terrace V in the outskirts of Sudak accommodates layers saturated with lenses and fragments of fossil coal scrutinized by the...     

Hydrothermal metasomatic alteration of carbonate bottom sediments in the Ashadze-1 field (13° N Mid-Atlantic Ridge)

We have performed the first detailed study of hydrothermal alteration of the Holocene-upper Pleistocene sediments in the recent Ashadze-1 hydrothermal field sampled during the 26th cruise of R/V Professor Logachev in 2005. It has been established that alterations in mineralogy and geochemistry are caused by the dissolution of calcite shells in bottom sediments and their metasomatic replacement with sulfides and other hydrothermal minerals. A zone of sediments enriched in magnesian hydrothermal minerals has been revealed in the sediments of the MAR for the first time. It is suggested that metasomatism is related to diffuse percolation of hydrothermal fluids through sediments.     

Clay minerals in recent sediments of the World Ocean and their relation to types of lithogenesis

Problem of the distribution of clay minerals in water areas of the World Ocean and their relation to different (humid, arid, and volcanosedimentary) types of lithogenesis is considered. It is shown that layer silicates can be used as index minerals for distinguishing types of lithogenesis under conditions of marine sedimentation. Humid marine lithogenesis is represented by sediments of the White, Baltic, Black, and Mediterranean seas. Genetic link of marine clay formation with soil-climatic zones is clearly manifested in recent sediments of the World Ocean. Accumulation of statistic data on the mineral composition of clays allowed us to distinguish two modes of spatial-latitudinal distribution of clay minerals: maximal concentrations of illites and chlorites are confined to high latitudes, whereas kaolinite and smectite accumulate in the equatorial zone. In the arid lithogenesis, the dependence of clay formation on drainage areas is practically absent. The whole process is realized in surficial sediments and bottom waters: under conditions of intense evaporation, especially in closed water basins, the concentration of elements in the medium is enough for the synthesis of layer silicates, such as palygorskite and sepiolite. The processes were studied based on the Paleogene Fergana Bay and bottom sediments of the Sea of Aral, as well as DSDP core materials from the Atlantic (near the western coast of Africa) and Indian (the Arabian Peninsula area) oceans. The investigation of processes of volcanosedimentary lithogenesis was carried out within the East Pacific Rise (on the basis of core materials obtained during cruises of R/V Dmitry Mendeleev and Akademik Kurchatov). The results obtained made it possible to establish authigenic (primarily celadonite) K-Fe mineralization in the most active geothermal zones. The formation of clay minerals has specific features in each of the studied (humid, arid, and volcanosedimentary) types of lithogenesis. This should be taken into consideration during the lithological investigations and the study of clay mineralogy of past geological epochs. Clay minerals (particularly, unstable mixed-layered phases) are actively used as index minerals for paleogeographic and climatologic reconstructions.     

In memory of M. A. Rateev

Chronicle

In memory of M. A. Rateev     

Hydrothermal alterations of modern organic sediments at the Ashadze-1 hydrothermal field,Mid-Atlantic Ridge, 13° N

For the first time detailed investigations of hydrothermal alterations on microbiota of ore-bearing sediments of the Ashadze-1 field (13° N, Mid-Atlantic Ridge) were carried out and local mineral-geochemical zoning was established. For the first time for the region, enriching of Mg sediments related with hydrothermal activity was revealed. It was concluded that hydrotherms affecting sediments are characterized with a high Mg content.