Abstract We examine three questions concerning the post-glacial geological history of the eastern Gulf of Finland: (1) the amplitude of the Holocene sea-level regressions; (2) the time and mechanism of the development of large sand accretion forms (bars and spits), including dunes; and (3) the sea-level changes and coastal development over the last 4 kyr. Recent on-land geoarchaeological studies, as well as detailed marine geological research of the Gulf of Finland nearshore bottom, have provided new data for developing a hypothesis about the palaeogeographical development of the area. Geoarchaeological studies carried out around Sestroretsky Artificial Lake and within Okhta Cape, as well as analyses of previous studies of the Neolithic–Early Metal settlements, have shed new light on some aspects of coastal system development. Geographical information system (GIS)-based modelling of Holocene shorelines for the different time periods can be useful for future archaeological research. A series of submarine terraces was found at the bottom of the Gulf (sea depths from 10 to 2 m). The analysis of marine geological data (submarine terraces) and distribution of archaeological sites can be explained by a possible rise in relative sea level in the Gulf of Finland at 5 ka BP and a regression around 3 ka BP.

Abstract Within the Rayner Province in the Lambert Glacier area, two Proterozoic lithotectonic zones are distinguished, which differ in age and lithology. In the Fisher Zone, a significant juvenile component (ɛ Nd (t)=+2 to +4) is represented by mafic, intermediate and felsic plutonic and volcanic rocks; the tectonomagmatic processes were concentrated at c. 1400–1200 Ma. In the Beaver Zone, orthogneisses record multiple emplacement, metamorphism and ductile deformation at c. 1150–930 Ma. New U–Pb SHRIMP-II zircon ages (c. 1140 Ma and 1095 Ma – protolith emplacement; c. 950–850 and c. 540 Ma – metamorphism), chemical and Sm–Nd isotopic data indicate that both zones have their continuations in the eastern Amery Ice shelf coast. The Rayner Province has some geological features in common with the Albany-Fraser Orogen in Western Australia, suggesting that these regions evolved in similar tectonic environments at c. 1400–1300 Ma, followed by steady closure, from east to west, of the ocean that separated the Mawson Continent from Western Australia. Supplementary material: Chemical compositions of rocks, a summary of trace element ratios, a summary of published U–Pb dates, field photo views, new U–Pb analyses by SIMS SHRIMP-II and new Sm–Nd data are available at http://www.geolsoc.org.uk/SUP18621

Abstract An area of focused fluid venting off NE Sakhalin, Sea of Okhotsk, was investigated in 2003 during the 31st and 32nd international expeditions of R/V Akademik M. A. Lavrentyev within the framework of the CHAOS Project. More than 40 structures related to seafloor gas venting were discovered and gas hydrates were sampled from three of these: CHAOS, Hieroglyph and Kitami. Geochemical analyses were used to define the mechanisms of gas hydrate accumulation and the sources of fluids involved. Chemical and isotopic analyses of the interstitial and hydrate waters suggest that hydrates were formed from seawater (or in-situ pore water) and an ascending fluid enriched in salts. Hydrate formation occurs at locations of the most intensive saline water upflow, and this is probably a function of the gas solubility in water in equilibrium with hydrate. The water involved in gas hydrate formation consists of about 70% pore water derived from the host sediment and 30% from the ascending fluid. The overall isotopic composition of the ‘fluid’ taking part in hydrate formation was calculated as δ 2 H≈−11‰ and δ 18 O≈−1.5‰.

Abstract: Over the past decade several restorations of the hypothetical Mesoproterozoic to Neoproterozoic supercontinent have been suggested. In this paper, we summarize the most recent data on Mesoproterozoic to Neoproterozoic geology of the Siberian craton to test different restorations. U-Pb zircon ages of the Siberian craton basement are typically older than 2300 Ma or have Paleoproterozoic ages between 2050 Ma and 1700 Ma, whereas Sm-Nd model ages (T DM ) are typically older than 2100 Ma. A similar radiometric age profile has been reported from basement of crystalline massifs exposed to the east of the Siberian craton. An important feature for paleocontinental correlation is a widespread anorogenic magmatic belt (ca. 1740-1700 Ma) that links the Aldan shield, the Okhotsk massif, and the Prikolyma terrane. Mesoproterozoic magmatic events are represented by mafic dike swarms with chemistry typical of continental flood basalts. Most of the dated examples come from the Anabar shield and yield ages of ca. 1500 Ma, 1410-1380 Ma, and 1320 Ma. In contrast, two Neoproterozoic magmatic events (1000-930 Ma and 760-720 Ma) are typical of the eastern and southern margin of the craton. These areas contain significant portion of MORB-like basalts, implying extensive rift events. The most complete Mesoproterozoic to Neoproterozoic type section is located in the Sette-Daban Range of southeast Siberia and contains several hiatuses. The largest is between the Vendian Yudoma Group (younger than 620 Ma) and the Uy Group (older than ca. 930 Ma). Sedimentary successions on the western and southern margins of the craton contain rock units younger than ca. 720 Ma (Baikalian Complex) that are absent in the type section. On the margins of the Anabar shield below the Yudoma group, only rock units older than ca. 1380 Ma have been reported. The Mesoproterozoic to Neoproterozoic sedimentary cover of the Okhotsk and Omolon massifs correlates well with successions on the eastern margin of the Siberian craton. The Yudoma Group typically unconformably overlies underlying sedimentary rock units and locally rests on the crystalline basement. The data show inconsistency between Mesoproterozoic to Neoproterozoic sedimentary and magmatic evolution with paleocontinental restorations that plot Siberia as a single continent within the World Ocean without connection to other continental masses. Reconstructions that juxtapose southern Siberia to northern Laurentia (cf. Rainbird et al., 1998 ) or eastern Siberia to western Laurentia (cf. Sears and Price, 2003 ) show better fit with geological data, but more isotopic studies are necessary for a final assessment.

Abstract This paper provides a brief overview of the long history of the A.P. Karpinsky Geological Committee and Russian Geological Research Institute (VSEGEI) in the development of the Geological Survey and reinforcement of the mineral resource base of Russia. The status of state geological mapping in the country is highlighted. The issues, challenges and future prospects for state geological mapping in Russia are outlined.

Abstract Several existing schemes for Carboniferous stratigraphy officially adopted in regions of the Russian Federation are summarized and discussed. These regions with different geological histories and distinct depositional settings include the Moscow Basin, the Urals, North Timan, Siberia, the Kuznetsk Basin and the Mongol–Okhotsk, Verkhoyansk–Okhotsk and Kolyma–Omolon regions. Broad correlations based on macro- and microfossils are possible between the regions, while all regional schemes are correlated to the official Russian General Stratigraphic Scheme for the Carboniferous, using zonations based on orthostratigraphic fossils. The Russian General Stratigraphic Scheme is correlated to the International Stratigraphic Scale using ammonoids, conodonts, foraminifers and palynomorphs.

Abstract Muruntau in the Central Kyzylkum desert of the South Tien Shan, western Uzbekistan, with past production of ~3,000 metric tons (t) Au since 1967, present annual production of ~60 t Au, and large remaining resources, is the world’s largest epigenetic Au deposit. The host rocks are the mainly Cambrian-Ordovician siliciclastic flysch of the Besapan sequence. The rocks were deformed into a broadly east-west fold-and-thrust belt prior to ca. 300 Ma during ocean closure along the South Tien Shan suture. A subsequent tectonic transition was characterized by left-lateral motion on regional splays from the suture and by a massive thermal event documented by widespread 300 to 275 Ma magmatism. The Besapan rocks were subjected to middle to upper greenschist-facies regional metamorphism, an overprinting more local thermal metamorphism to produce a large hornfels aureole, and then Au-related hydrothermal activity all during early parts of the thermal event. The giant Muruntau Au deposit formed in the low-strain hornfels rocks at ca. 288 Ma at the intersection of one of the east-west splays, the Sangruntau-Tamdytau shear zone, with a NE-trending regional fault zone, the Muruntau-Daugyztau fault, which likely formed as a cross fault during the onset of left-lateral translation on the regional splays. Interaction between the two faults opened a large dilational zone along a plunging anticlinorium fold nose that served as a major site for hydrothermal fluid focusing. The Au ores are dominantly present as a series of moderately to steeply dipping quartz ± K-feldspar stockwork systems surrounding uncommon central veins and with widespread lower Au-grade metasomatites (i.e., disseminated ores). Pervasive alteration is biotite-K-feldspar, although locally albitization is dominant. Sulfides are mainly arsenopyrite, pyrite, and lesser pyrrhotite, and scheelite may be present both in preore ductile veins and in the more brittle auriferous stockwork systems. The low-salinity, aqueous-carbonic ore-forming fluids probably deposited the bulk of the ore at 400 ° ± 50 ° C and 6-to 10-km paleodepth. The genesis of the deposit remains controversial with metamorphic, thermal aureole gold (TAG), and models related to mantle upwelling all having been suggested in recent years. More importantly, the question as to why there was such a focusing of so much Au and fluid into this one location, forming an ore system an order of magnitude larger than other giant Au deposits in metamorphic terranes, remains unresolved.

Abstract The Amu Darya Basin (ADB) has been studied primarily for its important hydrocarbon reserves and to a lesser extent for its geodynamic evolution. The ADB is located on the SE portion of the Turan Platform, between the sutures of the Turkestan and Palaeo-Tethys oceans, which closed during the Late Palaeozoic and Early Mesozoic, respectively. Blocks and island arcs accreted to Eurasia during the Palaeozoic form a poorly defined, heterogeneous basement underlying the ADB. They played an important role in shaping its composite structure into variously orientated sub-basins and highs. In this paper, depth–structure and isopach maps, and regional cross-sections, are analysed to unravel the location and origin of the main structural elements and to characterize the subsidence evolution of the ADB. The main tectonic events leading to the formation and evolution of the ADB took place: (1) in the Late Palaeozoic–Early Triassic (back-arc, rollback and extension/strike-slip); (2) from the Middle Triassic to the Triassic–Jurassic boundary (Eo-Cimmerian collision of Gondwana-derived continental blocks with Eurasia); and (3) during the Early–Middle Jurassic (post-collision extensional event). The last part of this evolution reflects shortening and flexure due to Cenozoic collisions to the south. Palaeotectonic maps are used to relate these events to the geodynamics of the Tethyan domain.

Abstract The Thala Hills area occupies a key position in Gondwanaland reconstructions near the India–Sri Lanka–Antarctica junction. We present U–Pb zircon isotopic age determinations from SHRIMP II obtained on four granite gneiss samples. Three high-temperature tectonomagmatic episodes may be distinguished in the study area at c . 980–970, c . 780–720 and c . 545–530 Ma. The c . 980–970 Ma event corresponds to the Rayner Structural Episode that affected East Antarctica, including the Sør Rondane Mountains to the west and Kemp Land to the east. The c . 780–720 Ma episode included two events at approximately 780 Ma (high-grade anatexis) and 720 Ma (syntectonic granitoid emplacement), and was roughly coeval with tectonomagmatic events in Dronning Maud Land of East Antarctica, as well as in other Gondwanaland regions, such as Madagascar, Sri Lanka and eastern Africa. The c . 780–720 Ma episode may be correlated with the East African Orogeny. These correlations argue for a similar geological evolution and conjugate position for Dronning Maud Land and Enderby Land despite a postulated Cambrian Lützow–Holm Bay suture separating them. The Cambrian (c . 545–530 Ma) episode was manifested by high-grade anatexis that confirms previously identified late Neoproterozoic–Cambrian tectonothermal activities in the study area. Supplementary material: Trace element compositions of zircons and whole-rock chemical compositions obtained by previous studies are available at https://doi.org/10.6084/m9.figshare.c.3738332