Heterogeneous Basement Research Articles

Late Palaeozoic and Mesozoic evolution of the Amu Darya Basin (Turkmenistan, Uzbekistan)

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.

Groundwater potential mapping using remote sensing techniques and weights of evidence GIS model: a case study from Wadi Yalamlam basin, Makkah Province, Western Saudi Arabia

In the present study, remote sensing techniques, GIS models and field measurements are integrated to identify and map groundwater potential zones at Wadi Yalamlam (Sa’diyah) basin, Makkah Province, Western Saudi Arabia. The study area is located in the Arabian Shield heterogeneous basement terrain. It is characterized by insignificant primary porosity and permeability and is mainly covered by massive and altered gneissose granites, diorite, and gabbro and metamorphosed basalts. Lithology, rainfall, lineament density, drainage density, slope steepness and landuse/landcover are the main hydrogeological parameters defined to be related to the groundwater storage in the study area. They are prepared using the processed satellite data and integrated using weights of evidence and index overlay GIS models to generate groundwater potential zones map. Within the GIS model, those parameters are assigned values of 30, 20, 15, 15, 10 and 10, respectively, as score values. The resulting groundwater potential zone map for Wadi Yalamlam basin is categorized into three main classes (high, moderate and low groundwater potential zones) based on pixel values. The results of this study indicate that the lower parts of the Wadi Yalamlam basin is the most promising area for groundwater occurrences and contains both high and moderate potential zones. High groundwater potential zones are located to the north of the main dyke area around Abu Helal farm. They are characterized by loose wadi deposits, flat areas, gentle slope (ranges between 0 and 5 degrees), low drainage density (<100 D/30 km2) and shallow water table (water table is 7 m from the ground surface). The present study proved: (1) the usefulness of the processed remote sensing satellite imageries for generating several indirect groundwater parameters; (2) the usefulness of weights of evidence and index overlay GIS models for the integration process and the production of groundwater potential zone map along the study area.

Seismic model of the crust and upper mantle in the Scythian Platform: the DOBRE-5 profile across the north western Black Sea and the Crimean Peninsula

The Scythian Platform (ScP) with a heterogeneous basement of Baikalian–Variscan–Cimmerian age is located between the East European Craton (EEC) on the north and the Crimean–Caucasus orogenic belt and the Black Sea (BS) Basin on the south. In order to get new constrains on the basin architecture and crustal structure of the ScP and a better understanding of the tectonic processes and evolution of the southern margin of the EEC during Mesozoic and Cenozoic time, a 630-km-long seismic wide-angle refraction and reflection (WARR) profile DOBRE-5 was acquired in 2011 October. It crosses in a W–E direction the Fore-Dobrudja Trough, the Odessa Shelf of the BS and the Crimean Plain. The field acquisition included eight chemical shot points located every 50 km and recorded by 215 stations placed every ∼2.0 km on the land. In addition, the offshore data from existing profile 26, placed in the Odessa Shelf, were used. The obtained seismic model shows clear lateral segmentation of the crust within the study region on four domains: the Fore-Dobrudja Domain (km 20–160), an offshore domain of the Karkinit Trough at the Odessa Shelf of the BS (km 160–360), an onshore domain of the Central Crimean Uplift (Crimean Plain, km 360–520) and the Indolo-Kuban Trough at the Kerch Peninsula (km 520–620) that is the easternmost part of the Crimea. Two contrasting domains of the ScP within the central part of the DOBRE-5 profile, the Karkinit Trough and the Central Crimean Uplift, may represent different stages of the ScP formation. A deep Karkinit Trough with an underlying high-velocity (>7.16 km s−1) lower crust body suggests its rifting-related origin during Early Cretaceous time. The Central Crimean Uplift represents a thick (up to 47 km) crustal domain consisting of three layers with velocities 5.8–6.4, 6.5–6.6 and 6.7–7.0 km s−1, which could be evidence of this part of the ScP originating on the crust of Precambrian craton (EEC). The thick heterogeneous basement of the Central Crimean Uplift shows inclusions of granitic bodies associated with magmatic activity related with Variscan orogeny within the ScP. General bending and crustal scale buckling of the Central Crimean Uplift with a wavelength of 230 km could be an effect of the Alpine compressional tectonics in the adjacent Crimean Mountains. The extended/rifted continental margin of the ScP (EEC) at the Odessa Shelf and buckling/uplifted domain of the Central Crimean Uplift affected by compressional tectonics, are separated by the N–S oriented Western Crimean Fault. The crust of the southern margin of the EEC is separated from the ScP, which originated on the EEC crust tectonised and reworked during the Palaeozoic–Mesozoic, by the crustal fault of ∼W–E orientation, which corresponds with the Golitsyn Fault observed at the surface between the EEC and the ScP. The Fore-Dobrudja Domain with a thick (>10 km) heterogeneous basement and two subhorizontal layers in the crystalline crust (with velocities 6.2–6.3 and 6.4–6.65 km s−1) differs from the ScP crust and its origin could be very similar to that of the Trans-European Suture Zone and Palaeozoic West European Platform.

Early Palaeoproterozoic volcanism of the Karelian Craton: age, sources, and geodynamic setting

A combined study of major and trace elements, Nd isotopes, and U-Pb systematics has been conducted for the early Palaeoproterozoic (Sumian) volcanic rocks and granites localized in different portions of the Karelian Craton. SHRIMP dating of zircons from the Sumian basalts indicates an emplacement age of 2423 ± 31 Ma, which constrains the lower age boundary of the early Palaeoproterozoic sequence at the Karelian Craton. The early Palaeoproterozoic mafic volcanic rocks of the Karelian Craton show practically no lateral geochemical and isotope-geochemical variations. The rocks bear signs of crustal contamination, in particular Nb and Ti negative anomalies, light rare earth element (LREE) enrichment, and nonradiogenic Nd isotope composition. However, some correlations between incompatible element ratios suggest that the crustal signatures were mainly inherited from mantle sources metasomatized during a previous subduction event. En route to the surface, melts presumably experienced only insignificant contamination by crustal material. Felsic rocks do not define common trends with mafic rocks and were formed independently. They exhibit higher REE contents, large-ion lithophile element (LILE) enrichment, and extremely wide variations in Nd isotope composition, which clearly demonstrates a considerable contribution of heterogeneous basement to their formation. Geochemically, the felsic rocks of the Karelian Craton correspond to A2-type granites and were formed by melting of crustal rocks in an anorogenic setting. Their possible sources are Archaean sanukitoid-type granitoids and Archaean granite gneisses. The high Yb content and pronounced Eu anomaly imply that they were generated from a garnet-free pyroxene – plagioclase source at shallow depths. By the Palaeoproterozoic, the older Vodlozero block was colder than the Central Domain, which facilitated the development of the brittle deformations and faulting and, correspondingly, rapid magma ascent to the surface without melting of crustal rocks. This resulted in the absence of felsic rocks and the formation of more primitive basalts in this area.

Tectonic zoning of the sedimentary cover of the Sea of Okhotsk based on lithophysical, structural and structural-lithophysical indicators

In terms of tectonics, the Sea of Okhotsk (Fig.1) is the epi-Mesozoic Okhotsk plate comprising the heterogeneous basement that is mainly pre-Cenozoic (the lower structural stage) and the sedimentary cover that is mainly represented by the Paleogenic-Neogenic-Quaternary deposits with the Upper Cretaceous sedimentary rocks observed locally without a visible hiatus (the upper structural stage). Results of tectonic zoning of the sedimentary cover based on lithophysical indicators (Fig. 2) are represented in the format of maps showing lithophysical complexes (LC) within the limits of four regional seismo-stratigraphic complexes/structural layers (RSSC I-IV) corresponding to the following time intervals: the pre-Oligocene К 2 -P 1-2 (RSSC I), the Oligocene – Lower Miocene P 3 -N 1 1 (RSSC II), the Lower-Mid Miocene N 1 1-2 (RSSC III), and the Upper Miocene – Pliocene N 1 3 -N 2 (RSSC IV). Diverse lithological-facies associations composing the RSSCs are grouped into the following lithophysical complexes (LC): 1 - coal-bearing silty-clayey-sandy terrigenous, 2 - sandy-silty-clayey terrigenous, 3 - silty-clayey-siliceous, and 4 - sandy-silty-clayey volcanic [Sergeyev, 2006]. Tectonic zoning of the sedimentary cover based on structural indicators is carried out with reference to the sediment-thickness map [Sergeyev, 2006], including a significantly revised segment showing the area of the Deryugin basin [Semakin, Kochergin, 2013]. Results of such zoning are represented in the format of a structural-tectonic map (Fig. 3) showing orientations and morphology of the structural elements of the sedimentary cover, the thickness of the sedimentary cover, and amplitudes of relative uplifts and troughs. With reference to the structural-tectonic map (see Fig 3), the structural elements of different orders are grouped by their sizes, spatial positions and orientations and thus comprise tectonic sistems (Fig. 4), structural zones (Fig. 5) that unclude relative uplifts and troughs that are considered as structural elements of smaller sizes (Fig. 6) Tectonic zoning of the sedimentary cover based on the structural-lithophysical indicators (Fig. 7-10) is carried out with reference to the maps of the lithophysical complexes of the four regional seismo-stratigraphic complexes/structural layers (see Fig. 2) and the map of high-order structural elements in the sedimentary cover (see Fig. 6).

Heat flow data from the southeast of South Australia: distribution and implications for the relationship between current heat flow and the Newer Volcanics Province

This paper presents the results of 34 new heat flow estimates taken in 2004 from 16 water bores and 18 petroleum exploration wells in the western Otway Basin. The average estimated heat flow measured across the study area is 65.6 ± 9.4 mW/m2, with a range of 42–90 mW/m2. There are three recognisable sectors within the study area where heat flow is slightly elevated relative to the background levels. These sectors can be broadly classified as Mount Schank (73.5 ± 0.5 mW/m2), Mount Burr (71.2 ± 7.6 mW/m2) and Beachport (78.3 ± 10.4 mW/m2). Thermal conductivity values for each unit involved in heat flow estimation were determined from laboratory measurements on representative core using a divided bar apparatus. Borehole thermal conductivity profiles were then developed in this study by assigning a constant value of conductivity to each geological formation. The process of collecting temperature data involved measuring temperature profiles for 16 water bores using a cable, winch and thermistor, and compiling well completion temperature data from 18 petroleum wells. The precision of temperature data was higher in the water bores (continuous logs) than in the petroleum wells (largely bottom-of-hole temperature estimates). Inversion heat flow modelling suggests heterogeneous heat flow at 6000 m depth, with two zones where vertical heat flow might exceed 90 mW/m2, and several zones where vertical heat flow might be as low as 40 mW/m2. Therefore, while slightly higher surface heat flow does coincide with some of the volcanic centres, heterogeneous basement heat production is a more likely explanation, as there are no heat flow anomalies greater than 5–10 mW/m2 associated with the Pleistocene–Recent Newer Volcanics Province. The distribution of heat flow in south-east South Australia is most simply explained by non-volcanic phenomena.

Tectonic zoning of the sedimentary cover in the Deryugin basin of the Sea of Okhotsk based on structural-material (lithophysical) indicators

In terms of tectonics, the Deryugin basin (Fig. 1) is a part of the epi-Mesozoic Okhotsk plate comprising the heterogeneous basement that is mainly pre-Cenozoic (the lower structural stage) and the sedimentary cover that is mainly represented by the Paleogenic-Neogenic-Quaternary deposits with the Upper Cretaceous sedimentary rocks observed locally without a visible hiatus (the upper structural stage). The acoustic basement (AB) is composed of the metamorphosed Upper Cretaceous-Paleogenic silty-clayey-siliceous deposits (the western part of the region), amphibolites, gneisses, crystalline schists, weakly metamorphosed sandstones, siltstones, and mudstones (often siliceous), as well as intrusive and effusive rocks of basic, intermediate, and rarely persilic composition (the eastern part of the region). AB is generally dated as Mesozoic–Paleozoic. Results of tectonic zoning of the sedimentary cover based on material (lithophysical) indicators (Fig. 2) are represented in the format of maps showing lithophysical complexes (LC) within the limits of four regional seismo-stratigraphic complexes/structural layers (RSSC I-IV) corresponding to the following time intervals: the pre-Oligocene К2–P1-2 (RSSC I), the Oligocene – Lower Miocene P3–N11 (RSSC II), the Lower – Mid Miocene N11–2 (RSSC III), and the Upper Miocene – Pliocene N13–N2 (RSSC IV). Diverse lithological-facies associations composing the RSSCs are grouped into the following lithophysical complexes (LC): 1 - coal-bearing silty-clayey-sandy terrigenous, 2 - sandy-silty-clayey terrigenous, 3 - silty-clayey-siliceous, and 4 - sandy-silty-clayey volcanic [Sergeyev, 2006]. In the studied area (Fig. 2), the deposits of the pre-Oligocene RSSC are identified in limited areas within its northern, northwestern, and southwestern parts; they are represented by coal-bearing silty-clayey-sandy terrigenous and silty-clayey-siliceous LCs. Other RSSCs (II, III, and IV) in this area represented mostly by sandy-silty-clayey terrigenous and silty-clayey-siliceous LCs, and only the extreme southwestern part along the eastern Sakhalin coast contains narrow bands of the coal-bearing silty-clayey-sandy LC. The sandy-silty-clayey volcanic LC is absent in the Deryugin basin. Tectonic zoning of the sedimentary cover based on structural indicators is carried out with reference to the sediment-thickness map [Sergeyev, 2006] that was significantly revised in its segment showing the area of the Deryugin basin. Results of such zoning are represented in the format of a structural-tectonic map (Fig. 3) showing orientations and morphology of the structural elements of the sedimentary cover, the thickness of the sedimentary cover, and amplitudes of relative uplifts and troughs. With reference to the structural-tectonic map (see Fig. 3), the structural elements of different orders are grouped by their sizes, spatial positions and orientations and thus comprise structural zones (Fig. 4) that include relative uplifts and troughs that are considered as structural elements of smaller sizes (Fig. 5). Tectonic zoning of the sedimentary cover based on structural-material (lithophysical) indicators (Fig. 7–10) is carried out with reference to the maps of the lithophysical complexes of the four regional seismo-stratigraphic complexes/structural layers (see Fig. 2) and the map of high-order structural elements in the sedimentary cover (see Fig. 5).

East Sakhalin island arc paleosystem of the Sea of Okhotsk region

It has been established that volcanic rocks of the Schmidt, Rymnik, and Terpeniya terranes are fragments of the compound Early to Late Cretaceous-Paleogene East Sakhalin island arc system of the Sea of Okhotsk region. This island arc paleosystem was composed of back-arc volcano-plutonic belt, frontal volcanic island arc, fore-arc, inter-arc, and back-arc basins, and the Sakhalin marginal paleobasin. The continental volcanic rocks dominate in the back-arc volcano-plutonic belt and frontal volcanic island arc. The petrochemical composition of basalts, basaltic andesites, andesites, and trachytes from the frontal island arc formed in submarine conditions are typical of oceanic island arc or marginal sea rocks (IAB). The petrochemical composition of volcanic rocks from the island arc structures indicates its formation on the heterogeneous basement including the continental and oceanic blocks.

Structure, age substantiation and tectonic setting of the Lower-Middle Ordovician volcanic-sedimentary and plutonic complexes of the western part of the Kyrgyz Range (Northern Tien Shan)

Among the Caledonides exposed in the western part of the Kyrgyz Range the Lower Ordovician volcanogenic-sedimentary, plutonic, and tuffaceous-terrigenous complexes were distinguished. Volcanogenic-sedimentary sequences are the Kentash Formation, composed of volcanic rocks, tuffs and subvolcanic bodies of dacitic, andesitic and basaltic composition, sandstones and tuffites with interlayers and lenses of limestone. On the basis of conodonts and U-Pb dating of zircon grains the age of this Formation is in the age interval between Late Tremadocian Stage and Early Darriwilian Stage. Differentiated volcanites are associated with ultramafic-gabbro massifs of the Kokkiya Complex of the Late Darriwilian age (U-Pb zirconology). Features of the chemical composition of rocks of the Kentash Formation and the Kokkiya Complex indicate that they formed in suprasubduction settings within the island arc with a thick heterogeneous basement. Tuffaceous-terrigenous deposits are presented by the olistostrome formation, and coarse-grained deposits of the Taldybulak and Kyzylkainar Formations. The formation of olistostrome formation is associated with the over-thrusting of Cambrian melanocratic complexes on terrigenous-carbonate and shale strata of the Upper Precambrian-Cambrian age. Deposits of the Taldybulak and Kyzylkainar Formations accumulated in the back-arc basin and on the island arc slope, made of rocks of the Kentash Formation.

Reconstruction of the Sakhalin marginal paleobasin by geological and petrochemical data

The structural and compositional volcanosedimentary complexes and igneous rocks of the Sakhalin marginal paleobasin as well as the geodynamic setting were described. The Sakhalin marginal paleobasin was formed in Sakhalin Island and the adjacent water areas at the end of the Early Cretaceous-start of the Late Cretaceous. The paleobasin was a part of the Kula Plate separated from the ocean along with spreading zones and oceanic volcanic islands by the Sea of Okhotsk microcontinent and the Jurassic-Early Cretaceous Sheltinga volcanic island arc. The petrochemical features and geodynamic setting of the igneous rock formation testify to the fact that magma-generating tectonomagmatic structures of the epioceanic Sakhalin marginal paleobasin continued functioning after its isolation under intensive terrigenous sedimentation. The Sakhalin marginal paleobasin had a heterogeneous basement composed of oceanic and continental crust blocks of the Earth. The paleobasin completed its development in the Paleogene.

The structure of the heterogeneous basement of the Krasnoleninsky arch and adjacent territories (West Siberia) according to the analysis of gravitational and magnetic fields

In this work a scheme of the gravitational and magnetic fields is represented that allows us to distinguish blocks in the basement of the studied region that are homogeneously manifested in the potential fields. Two approaches are considered: the qualitative (contact) approach and the regionalization approach using a classification algorithm. Both approaches give similar results. The association of hydrocarbon fields opened in the Pre-Jurassic sediments to the boundaries of the tectonic blocks we distinguished is noted.

Tectonic evolution of Early Paleozoic island-arc systems and continental crust formation in the Caledonides of Kazakhstan and the North Tien Shan

The extended Saryarka and Shyngyz-North Tien Shan volcanic belts that underwent secondary deformation are traced in the Caledonides of Kazakhstan and the North Tien Shan. These belts are composed of igneous rocks pertaining to Early Paleozoic island-arc systems of various types and the conjugated basins with oceanic crust. The Saryarka volcanic belt has a complex fold-nappe structure formed in the middle Arenigian-middle Llanvirnian as a result of the tectonic juxtaposition of Early-Middle Cambrian and Late Cambrian-Early Ordovician complexes of ensimatic island arcs and basins with oceanic crust. The Shyngyz-North Tien Shan volcanic belt is characterized by a rather simple fold structure and consists of Middle-Late Ordovician volcanic and plutonic associations of ensialic island arcs developing on heterogeneous basement, which is composed of complexes belonging to the Saryarka belt and Precambrian sialic massifs. The structure and isotopic composition of the Paleozoic igneous complexes provide evidence for the heterogeneous structure of the continental crust in various segments of the Kazakh Caledonides. The upper crust of the Shyngyz segment consists of Early Paleozoic island-arc complexes and basins with oceanic crust related to the Saryarka and Shyngyz-North Tien Shan volcanic belts in combination with Middle and Late Paleozoic continental igneous rocks. The deep crustal units of this segment are dominated by mafic rocks of Early Paleozoic suprasubduction complexes. The upper continental crust of the Stepnyak segment is composed of Middle-Late Ordovician island-arc complexes of the Shyngyz-North Tien Shan volcanic belt and Early Ordovician rift-related volcanics. The middle crustal units are composed of Riphean, Paleoproterozoic, and probably Archean sialic rocks, whereas the lower crustal units are composed of Neoproterozoic mafic rocks.

Geochemistry and petrogenesis of volcanic rocks in the Kuril island arc

Newly obtained precise analytical data on trace elements and radiogenic Sr, Nd, and Pb isotopes testify to anomalous geochemical characteristics of mafic and intermediate Quaternary lavas in Paramushir (in the north of the Kuril arc), Kunashir and Iturup (in the south) islands, which are the largest three islands of the Kuril island arc. The high K and LREE concentrations in the volcanic products in Paramushir Island resulted from the southward expansion of the mantle thermal anomaly of the Kamchatka Peninsula and the involvement of melts related to the melting of oceanic sediments in magma generation. The depleted characteristics of the mafic volcanics are explained by the relatively young tectono-magmatic events during the opening of the Kuril backarc basin. The Kuril island-arc system developed on a heterogeneous basement. The northern islands are a continuation of the volcanic structures of southern Kamchatka, which were formed above an isotopically depleted and hot lithospheric mantle domain of composition close to that of the Pacific MORB type. The southern islands were produced above an isotopically enriched and cold lithospheric domain of the Indian-Ocean MORB type, which was modified in relation to relatively young backarc tectono-magmatic processes. Although issues related to the genesis of the transverse geochemical zoning were beyond the originally formulated scope of our research, the homogeneous enough isotopic composition of the rear-arc lavas in the absence of any mineralogical and geochemical lines of evidence of crustal contamination suggests an independent magmatic source.

New data on the composition and age of basement rocks of the Tagil paleo-island arc system

The Tagil paleo-island arc terrane is composed of Late Ordovician-Devonian intrusive, volcanic, and volcano-sedimentary complexes. The western margin of the terrane is comprised of dunite-clinopyroxenite-gabbro massifs of the Ural platinum-bearing belt, which are fringed by rock strata of widely different metamorphic grades. Work on isotope systematics of olivine gabbros enabled us to infer a Vendian age (550–540 Ma) of homogenization of the Sm-Nd isotopic system of the Kytlym and Knyaspa massifs within the Ural platinum-bearing belt. The Sm-Nd ages for metamorphic rocks of the Belaya Gora complex surrounding the studied massifs also agree with a Vendian age (573–574 Ma). Our results suggest that metamorphites of the Belaya Gora complex (amphibolites, plagiogneisses, two-mica and biotite gneisses, schists containing garnet, cordierite, staurolite, gedrite, and sillimanite) and dunite-clinopyroxenite-gabbro intrusions of the proto-platinum-bearing belt may have been formed in a convergence setting above a mantle plume, most likely in a back-arc (?) extension region. Reactivation of this plume during the late Precambrian resulted in the opening of the Ural paleo-ocean. The Late Ordovician-Early Devonian times were marked by metamorphic reworking and tectonic transport of pre-Paleozoic complexes into an accretionary prism setting of the Tagil paleo-arc that was accompanied by generation of gabbroid and granitoid magmas. Based on the obtained results, the Tagil terrane can be now considered as part of the Paleozoic paleo-island arc system developed on a heterogeneous Proterozoic basement.

Subsurface structure and tectonic style of the NE Outer Carpathians (Poland) on the basis of integrated 2D interpretation of geological and geophysical images

Subsurface structure and tectonic style of the NE Outer Carpathians (Poland) on the basis of integrated 2D interpretation of geological and geophysical imagesIntegration of the information from surface and subsurface geological exploration (maps and well sections) and results of geological reinterpretation of more than ten archival seismic sections and several dozen magnetotelluric soundings (MT; published and archival) implies a new structural picture of the Carpathian tectogene, interpreted to depths exceeding 10 km. The tectonics of nappes and their basement is illustrated by four regional cross-sections (derived from geological and petroleum-exploration traverses) and examples of detailed interpretation of zones with complicated structure, as well as results of testing the initial structural models with application of the balanced cross-section method and gravimetric modelling. In the tectonics, a complicated system of overthrusts and detachments of sedimentary covers (from their heterogeneous basement) represents a predominant feature. It induced, within particular nappes and tectonically altered structural-facies units, specific systems of narrow folds with diversified geometries. Broad folds of the intermediate structural stage, which are gently sloping in the hinterland of the nappes, were interpreted on the basis of geophysics as paraautochthonous elements. They cover deep-seated faults with large throws, which obliquely or subvertically dip to the SW and were distinguished in the basement on the grounds of extreme contrasts at the resistivity boundaries. Zones of dramatically low resistivities, which separate blocks of the uplifted basement, were interpreted as tectonic sutures with geometry rebuilt in the stage of the Neogene lithosphere subduction. Therefore, the structural layout of the sedimentary cover is characterized by more gently dipping nappe overthrusts of the sequential type and secondary, out-of-sequence thrust slices, most frequently imbricate ones. The flysch covers resting over the tectonic sutures, particularly in margins of inherited structural depressions, are characterized by more diversified tectonic style in comparison with peripheral, gently-sloping covers thrust over the flexural platform slope, and with steep slices and imbricate thrusts having consequent NE vergence. A specific type of dislocation is represented by flat inversional detachments (seismically documented) which are accompanied by disharmonic folding of "thin-skinned" structural elements. In the eastern part of the foreland of the Dukla overthrust, they form a developed system of backthrusts on the slope of a triangular structure superposed on a "shallower" tectonic suture of the basement; the system replaces sets of fault-propagation folds developed in the eastern part of this zone.

10.1007/s11491-008-1013-7

For the first time, the structure of the sedimentary basins of the Late Proterozoic rift system in the White Sea is characterized based on a set of new marine geological geophysical data such as the results of the common depth point seismic method, gravity and magnetic data, and seismoacoustics. The main tectonic structures in the topography of the heterogeneous basement within the basin of the White Sea are distinguished and described. A structural tectonic scheme of the basement surface is presented. The thicknesses of the sediments are estimated and the stratigraphic confinement of the seismic units recognized is done.

Tectonic reconstruction of Uda-Murgal arc and the Late Jurassic and Early Cretaceous convergent margin of Northeast Asia–Northwest Pacific

Abstract. A long tectonic zone composed of Upper Jurassic to Lower Cretaceous volcanic and sedimentary rocks is recognized along the Asian continent margin from the Mongol-Okhotsk fold and thrust belt on the south to the Chukotka Peninsula on the north. This belt represents the Uda-Murgal arc, which was developed along the convergent margin between Northeast Asia and Northwest Meso-Pacific. Several segments are identified in this arc based upon the volcanic and sedimentary rock assemblages, their respective compositions and basement structures. The southern and central parts of the Uda-Murgal arc were a continental margin belt with heterogeneous basement represented by metamorphic rocks of the Siberian craton, the Verkhoyansk terrigenous complex of Siberian passive margin and the Koni-Taigonos Late Paleozoic to Early Mesozoic island arc with accreted oceanic terranes. At the present day latitude of the Pekulney and Chukotka segments there was an ensimatic island arc with relicts of the South Anyui oceanic basin in a backarc basin. Accretionary prisms of the Uda-Murgal arc and accreted terranes contain fragments of Permian, Triassic to Jurassic and Jurassic to Cretaceous (Tithonian–Valanginian) oceanic crust and Jurassic ensimatic island arcs. Paleomagnetic and faunal data show significant displacement of these oceanic complexes and the terranes of the Taigonos Peninsula were originally parts of the Izanagi oceanic plate.

Capel and Faust basins—integrated geoscientific assessment of Australia's remote offshore eastern frontier

The paper discusses the results from the GA–302 2D seismic survey and GA–2436 (RV Tangaroa) marine reconnaissance survey over the Capel and Faust basins in the northern Tasman Sea. The integration of seismic, potential field and bathymetric data sets in 3D space at an early stage in the project workflow has assisted in the visualisation of the basin architecture, the interpolation of data between the seismic lines and the iterative refinement of interpretations. The data sets confirm the presence of multiple depocentres previously interpreted from satellite gravity data with a maximum sediment thickness of 5–7 km. Preliminary interpretation of the seismic data has identified two predominantly Cretaceous syn-rift and two Upper Cretaceous to Neogene sag megasequences overlying a heterogeneous pre-rift basement. The comparison of seismic facies and tectonostratigraphic history with offshore New Zealand and eastern Australian basins suggests the presence of possible Jurassic to Upper Cretaceous coaly and lacustrine source rocks in the pre-rift and syn-rift, and fluvio-deltaic to shallow marine reservoir rocks in the syn-rift to early post-rift successions. Preliminary 1D basin modelling suggests that the deeper depocentres of the Capel and Faust basins are within the oil and gas windows. Large potential stratigraphic and structural traps are also present.

Gravity anomalies and orthogonal box fold development on heterogeneous basement in the Neogene Ronda Depression (Western Betic Cordillera)

The Ronda Depression constitutes a Neogene intramontane basin located in the external zones of the Western Betic Cordillera. Major deformation structures affect only the southwestern part of its sedimentary infill and consist of NNE–SSW and WNW–ESE box folds that developed simultaneously. New gravity data reveal two negative NNE–SSW elongated Bouguer anomalies, unrelated to basin depocenters, but corresponding to the accumulation of low-density ductile Triassic basement rocks in the core of antiforms or directly under the northwestern undeformed sedimentary infill. The Subbetic basement is also deformed by early-Burdigalian to Serravallian NNE–SSW folds and thrusts, although there is no clear continuity with those affecting the late-Miocene sedimentary infill. The aim of this contribution is to describe in detail the late-Miocene folds that deform the Ronda Depression, as well as to discuss the role of the basement nature on their reactivation. The reactivation of the pre-Tortonian folds, due to the heterogeneous distribution of evaporitic Triassic rocks in the basement as well as the presence of rigid limestones on the southwestern basin boundary, determined the simultaneous orthogonal fold development that only evidence local deformation.

Structure of the basins of the White Sea rift systems

For the first time, the structure of the sedimentary basins of the Late Proterozoic rift system in the White Sea is characterized based on a set of new marine geological geophysical data such as the results of the common depth point seismic method, gravity and magnetic data, and seismoacoustics. The main tectonic structures in the topography of the heterogeneous basement within the basin of the White Sea are distinguished and described. A structural tectonic scheme of the basement surface is presented. The thicknesses of the sediments are estimated and the stratigraphic confinement of the seismic units recognized is done.