West Basin Research Articles

Lower Jurassic calcareous nannofossil taxonomy revisited according to the Neuquén Basin (Argentina) record

Abstract. Standard Early Jurassic biostratigraphic studies were performed in the boreal and Tethys realms (western Europe and northern Africa), and biozonations from these areas are the most accurate of the world. Comparatively, investigations in the Pacific realm are scarce, and, in Argentina, they are limited to contributions based on oil-industry subsurface and outcrop reports for the Los Molles Formation. A focused systematic analysis was not previously addressed in the area. The Neuquén Basin in west–central Argentina offers a unique opportunity to study the Early Jurassic calcareous nannofossil history in the south-eastern Pacific Ocean. Calcareous nannofossil assemblages from El Matuasto I section (Los Molles Formation) represent one of the earliest records for the Early Jurassic in the Neuquén Basin and one of the few for the eastern Pacific realm. A detailed systematic analysis allowed the recognition of major bioevents and a comparison with worldwide associations and biostratigraphic schemes. A thorough taxonomic discussion of the Early Jurassic nannofossil species of the Neuquén Basin is presented for the first time. Herein, the taxonomic features of coccoliths recorded in the Neuquén Basin are settled. The age of the calcareous nannofossil assemblages recorded in El Matuasto I is early–late Pliensbachian, covering the NJT4a to NJT4c subzones. Similarities between the Neuquén Basin and localities from the proto-Atlantic region suggest an effective connection between the Pacific and Tethyan basins during the Pliensbachian.

Unrecognized post-rifting deposition and uplift history of the Erlian Basin, Northern China: Evidence from seismic reflection data and apatite fission-track thermochronology

Early Cretaceous rift basins in Northeast Asia typically experienced varying degrees of post-rifting thermal subsidence and compressional deformation. However, previous workers believed that only a thin post-rifting sequence was developed in basins west of the Great Xing'an Range, making a proper understanding of the post-rift tectonic history in this part of Northeast Asia difficult. In this study, newly acquired shallow seismic reflection data were utilized to unravel the shallow deformation of the Erlian Basin, which to the west of the Great Xing'an Range contains a thin post-rifting sequence. Furthermore, we used apatite fission-track thermochronology to analyze the post-rifting deposition and uplift processes in the Erlian Basin, for which there are limited stratigraphic records. Our results show that the Erlian Basin experienced a typical post-rifting stage whose sequence from the Albian to the Campanian was not controlled by normal faults. The corresponding sedimentary thickness was up to 2 km, which contradicts the previously reported little or no post-rifting thermal subsidence. The current thin post-rifting sequence is the remaining stratum after 1.4–1.8 km of denudation at the end of the Erlian period. In addition, by further comparing the sedimentary thickness and time-lag in the onset of post-rifting to those of other basins in Northeast Asia, we found two driving mechanisms of rifting in Northeast Asia, which occurred simultaneously: the gravitational collapse and back-arc extension. Moreover, the basins in Northeast Asia experienced a gradual weakening in the compressional deformation from east to west during the Cenomanian to the Coniacian, and an intense compressional deformation in the east of Northeast Asia and large-scale vertical uplift in the west during the Late Cretaceous Campanian to the Eocene.

Organic aerosol source apportionment by using rolling positive matrix factorization: Application to a Mediterranean coastal city

We investigated the contributions and the evolution of organic aerosol (OA) sources at the Marseille-Longchamp supersite (MRS-LCP, France) based on Time-of-flight Aerosol Chemical Speciation Monitor (ToF-ACSM) measurements of non-refractory PM 1 over a fourteen-month period (1 February – 3 April 2018). The OA source apportionment was performed by positive matrix factorization (PMF) using the novel “rolling window” approach implemented in the Source Finder Professional (SoFi Pro). Here, PMF is performed over a 14-days window moving over the entire OA dataset, in order to account for the temporal variability of the source profiles. Six factors were resolved, including hydrocarbon-like organic aerosol (HOA) which is related to traffic exhausts, cooking-like organic aerosol (COA), biomass burning aerosol (BBOA), less oxidized organic aerosol (LOOA), more oxidized organic aerosol (MOOA) and a new defined source related to the mix between shipping and industrial plumes (Sh-IndOA). While HOA and COA consistently contribute to the total OA with on average 11.2% (ranging between 9.2 and 12.1% over the seasons) and 11.5% (11–12.1%), respectively, BBOA (11.7% on average) shows a larger seasonal variability with 18% in winter and no contribution in summer. BBOA profiles during winter were attributed to fresh biomass burning emissions from domestic heating, and more oxygenated profiles were assigned to regional land and agricultural waste burning for spring and early autumn. Sh-IndOA fraction is estimated to 4.5% (3.7–6.1%) and contributes to the total OA mass concentrations to a minor extent. The secondary organic aerosol (SOA) fraction includes both LOOA with 21.5% (18.8–27.2%) and MOOA with 39.6% (36.8–42.6%). Based on the f44/f43 analysis these sources appeared to be more linked to biogenic influences in summer, whereas the concentrations were associated with oxidized anthropogenic sources (biomass burning and road traffic) for the rest of the year. The investigation of MOOA geographical origins suggests some influence of air masses transported from the Rhône Valley and the west basin of the Mediterranean Sea. • OA source apportionment over 14 months at an urban background site. • Positive matrix factorization using the novel rolling window approach. • A new defined source of OA related to shipping and industrial plumes. • Highest contribution of SOA during every season.

Crustal and uppermost mantle structure of the Porcupine Basin west of Ireland from seismic and gravity methods

The Porcupine basin is a failed rift that formed during the opening of the North Atlantic Ocean. Here, we provide additional insights into the crustal structure of the northern Porcupine Basin and assess the degree of crustal extension from long streamer seismic data and free-air gravity modelling. Recent re-processing of the 2013/2014 streamer data involved de-multiple and de-noise processing with pre-stack-depth migration using velocity models derived from reflection travel time tomography and full waveform inversion. Forward modelling of satellite gravity data was used to constrain the velocity and mass density of the basement and lower crust, where the seismic constraints are limited. Prior knowledge, from previous geophysical and geological studies, was included to guide the modelling and reconcile the gravity data with the seismic sections. It also served to minimize the non-uniqueness inherent in the forward problem. Crustal thinning occurs across the basin axis and increases southwards. We infer maximum stretching factor (β) at the basin axis, increasing from ∼4 to 6 in the North Porcupine at 52.5°N to >10 at ∼51°N in the Central Porcupine. The gravity modelling supports the presence of mantle serpentinisation, and the high β implies that crustal break up and mantle exhumation may have locally occurred in the Central Porcupine Basin, in agreement with previous seismic tomographic studies. Basaltic melt generation in the centre of the basin where the maximum bulk stretching factor exceeds10 in the hyper-extended crust may have led to localized sea-floor-spreading.

A Note of a Unique Inland, Saline Water Fishery: Brine Flies (Diptera: Ephydridae) of Lake Cuitzeo, Mexico

Fisheries in Cuitzeo, the second largest Mexican lake, used to take place on the permanent freshwater East and Central Basins as opposed to the temporal, saline, and initially thought barren West Basin. The 1980 fisheries collapse forced fishers to look for non-conventional fishing products elsewhere in the lake. The West Basin’s temporal, saline-alkaline, and shallow water provides exceptional habitat for ephydrids to flourish. Locally known as “pupa”, ephydrids are collected in large numbers. Although consumed since pre-Hispanic times, no other commercial fisheries of ephydrids are known worldwide. This study records the species composition and abundance of the “pupa” throughout an annual cycle in the West Basin, where fisheries occur. Two species were found: Ephydra hians and Lamproscatella muria. Ephydrids co-occurred in June and July at the end of the dry season when salinity was highest. L. muria was more abundant (954 ± 2385 ind m−2) than E. hians (94 ± 38 ind m−2). The relatively low salinity of the West Basin favoured L. muria over E. hians, which prefers higher salinities. This “pupa” fishery is still unpredictable due to the astatic nature of the lake, and hence limited economic importance to the local fishers.

Physical and Biogeochemical Influences on Nutrients Through the Canadian Arctic Archipelago: Insights From Nitrate Isotope Ratios

AbstractThe Canadian Arctic Archipelago (CAA) provides a gateway for the flow of nutrients from the North Pacific to the North Atlantic. The transport and biogeochemical cycling of nutrients throughout the CAA, however, are sparsely documented. Here, we report water column nitrogen and oxygen isotope ratios of nitrate (δ15NNO3 and δ18ONO3) collected in a throughflow of the CAA into Baffin Bay, providing insights on inherent nutrient dynamics. The nitracline shoaled eastward into the CAA, wherein large subsurface chlorophyll maxima and coincident increases in δ15NNO3 and δ18ONO3 indicated enhanced nitrate assimilation relative to the oligotrophic Canada Basin. High δ15NNO3 values characteristic of Pacific Winter Water (PWW) pervaded the Archipelago and Baffin Bay, decreasing eastward due to mixing with underlying Atlantic water (AW)—from the Canada Basin west of Barrow Strait, and from Baffin Bay east thereof. Nearly 25% of nutrients in the central CAA were of Atlantic origin, a substantially larger fraction than surmised previously. Nutrient properties in the CAA were notably not influenced by benthic denitrification. Those in underlying AW in the western CAA, however, were modified by remineralization of Pacific‐sourced nutrients, manifested from increases in δ15NNO3 relative to the Canada Basin. Properties in the eastern CAA exposed the complex hydrography of Baffin Bay, characterized by lateral intrusions of nutrient‐poor winter waters into PWW and of cold mode waters in underlying AW. High δ15NNO3 values in AW revealed the presence of a substantial fraction of N from remineralization, stemming from the high productivity in Baffin Bay fueled by Pacific nutrients.

Spatiotemporal assessment of the environmental quality of bottom waters through the study of benthic foraminifera in a semi-enclosed gulf

The evolution of the bottom water in Amvrakikos Gulf in Ionian Sea at western Greece for a 50-year timespan was assessed by benthic foraminifera assemblages. The degradation of the bottom water of Amvrakikos has been a catalyst for the surface water degradation. The east basin has shown permanent low environmental quality in bottom waters since 1980, while the west basin has been under seasonal hypoxic regime since 2000. The most adverse environmental conditions occurred in 1990–2000 and 2005–2010 coinciding with the recorded fish mortality events. The major cause of the environmental quality improvement of the bottom water is the intrusion of seawater. In western areas of the gulf, where the influence of the seawater is high, the decreased temperature improves the environmental conditions, while in the areas influenced by river discharges (east and northern), the environmental conditions are depended on multiple causes like organic matter input and surface salinity.

Meander reshaping – the formation process of a wintering riverbed depression of fish

The study of the spatiotemporal distribution of fish is an important and poorly studied aspect of the ecology of aquatic organisms. The research work was performed using the modern hydroacoustic method and geographic information systems. A section in the lower reaches of the Irtysh, a large transboundary Siberian river (in Western Siberia, Russian Federation), was studied. It has a strong development of meandering. The merging (i.e., reshaping of closely spaced meanders and erosion-accumulating channel processes) results in development of wintering riverbed depression, which is a critical “temporal bottleneck” during the winter period of the fish life cycle. The average density of fish in the study area in summer and autumn was 8,031 and 9,194 individuals per ha, respectively. Analysis of the distribution of fish showed that the distribution in the horizontal aspect had a more aggregated character in the autumn. In the vertical aspect, it had a more surface (pelagic) character. The ichthyofauna in the water area of the riverbed depression is mainly represented by cyprinids. The loop-shaped evolution of the channel formed a section of the river with multidirectional, circulating, and counter-current flows. It also created zones with depths exceeding 20 m and aggregations of fish. These features characterize the studied water area as a wintering riverbed depression of the fish of the Lower Irtysh. This section of the river should be included in the list of protected wintering biotopes of fish in the West Siberian fishery basin, which will ensure the conservation of fish at the critical stage of the life cycle.

Meander reshaping – the formation process of a wintering riverbed depression of fish

The study of the spatiotemporal distribution of fish is an important and poorly studied aspect of the ecology of aquatic organisms. The research work was performed using the modern hydroacoustic method and geographic information systems. A section in the lower reaches of the Irtysh, a large transboundary Siberian river (in Western Siberia, Russian Federation), was studied. It has a strong development of meandering. The merging (i.e., reshaping of closely spaced meanders and erosion-accumulating channel processes) results in development of wintering riverbed depression, which is a critical “temporal bottleneck” during the winter period of the fish life cycle. The average density of fish in the study area in summer and autumn was 8,031 and 9,194 individuals per ha, respectively. Analysis of the distribution of fish showed that the distribution in the horizontal aspect had a more aggregated character in the autumn. In the vertical aspect, it had a more surface (pelagic) character. The ichthyofauna in the water area of the riverbed depression is mainly represented by cyprinids. The loop-shaped evolution of the channel formed a section of the river with multidirectional, circulating, and counter-current flows. It also created zones with depths exceeding 20 m and aggregations of fish. These features characterize the studied water area as a wintering riverbed depression of the fish of the Lower Irtysh. This section of the river should be included in the list of protected wintering biotopes of fish in the West Siberian fishery basin, which will ensure the conservation of fish at the critical stage of the life cycle.

Use of Revised Universal Soil Loss Equation (RUSLE) Model to Estimate Soil Erosion in Jibab Wadi Basin West of Iraq

The study dealt with one of the most important environmental problems that leads to soil deterioration, increase in the degree of desertification and the loss of large areas of lands that suffer from dry and semi-arid areas. This study aims to calculate the amount of soil transported using the revised universal equation model of erosion RUSLE, and five representative surface samples were obtained. For all the watershed of the valley, analyses were carried out for the general equation of erosion, and the climatic data of the Anah meteorological station were used, whose values ranged between (0.0554-0.4923), as well as the values of normalized difference vegetation index (NDVI) between its high and low values (0.10084-0.645161). Maps were created from the general equation factors (RUSLE) and their units were classified according to water erosion rates to investigate the susceptibility of soil to erosion and the risk of soil erosion.

Information control and competence: participant experience of public participation in EIA for proposed mining projects in Queensland

ABSTRACT Public participation is embedded within requirements for Environmental Impact Assessment (EIA) in Australia and many other countries. Although the widespread requirements for public participation have been criticised as rhetorical, it is deemed to have significant symbolic significance. The use of public participation to gather multiple perspectives expresses an intent to improve environmental decision-making and respond to increasing demand for a role in decisions that affect people’s homes, livelihoods, and communities. This research examines participant experience of public participation in the EIA processes undertaken for four proposed coal mining developments close to the small, remote cattle grazing community of Alpha, in Queensland’s Galilee Basin in the central west of the state. Participant experience is examined through the lens of competence in environmental decision-making, which asserts that, for public participation to be competent, participants need access to information and its interpretations. Participants in 25 semi-structured interviews described two major flaws in public participation in relation to the proposed projects: proponent control of project information, and the government’s ‘hands-off’ approach.

Integrated geological and gravity modelling to improve 3-D model harmonization—Methods and benefits for the Saxony-Anhalt/Brandenburg cross-border region (North German Basin)

SUMMARYAs 3-D geological models become more numerous and widely available, the opportunity arises to combine them into large regional compilations. One of the biggest challenges facing these compilations is the connection and alignment of individual models, especially in less explored areas or across political borders. In this regard, gravity modelling is suitable for revealing additional subsurface information that can support a harmonization of structural models. Here, we present an integrated geological and gravity modelling approach to support the harmonization process of two geological 3-D models of the North German Basin in the cross-border region between the federal states of Saxony-Anhalt and Brandenburg. Gravity gradient calculation, filtering and Euler deconvolution are utilized to reveal new insights into the local fault system and gravity anomaly sources. The independent models are merged and harmonized during 3-D forward and inverse gravity modelling. Herein, density gradients for individual layers are incorporated in the framework of model parametrization. The resulting geological 3-D model consists of harmonized interfaces and is consistent with the observed gravity field. To demonstrate the plausibility of the derived model, we discuss the new geophysical findings on the sedimentary and crustal structures of the cross-border region in the context of the regional geological setting. The cross-border region is dominated by an NW–SE oriented fault system that coincides with the Elbe Fault System. We interpret a low-density zone within the basement of the Mid-German Crystalline Rise as a northward continuation of the Pretzsch–Prettin Crystalline Complex into the basement of the North German Basin. Additionally, we observe two types of anticlines within the basin, which we link to provinces of contrasting basement rigidity. Our gravity modelling implies that the Zechstein salt has mostly migrated into the deeper parts of the basin west of the Seyda Fault. Finally, we identify a pronounced syncline that accommodates a narrow and up to 800 m deep Cenozoic basin.

Record and provenance of Pleistocene volcaniclastic turbidites from the central Lesser Antilles (IODP Expedition 340, Site U1398B)

Pleistocene volcaniclastic turbidites drilled during IODP 340 (U1398B, ≤ 170 mbsf) in the Grenada basin west of Martinique (central Lesser Antilles) have been investigated for sediment provenance. U/Pb ages by ion microprobe from 323 detrital zircon grains at three U1398B levels reveal youngest population maximum ages which are interpreted to represent major eruption periods. Systematic age progression with depth defines a ~ 20 cm/ka depositional rate and provides a robust chronostratigraphic frame for the ≤167.5 mbsf (≤ 856 ± 10 ka) interval of U1398B, and confirms on-board paleomagnetic constraints for a possible late Matuyama age for the lowermost sampled parts of U1398B. The achieved chronostratigraphic frame yields sedimentation rates for carbonate ooze and of volcaniclastic sands and gravels of 8.2 and 7.6 cm/ky, respectively. Depth plots of cumulative thickness of these lithologies allow for a differentiation into periods of enhanced and reduced volcanic activity.Porphyritic lava and mineral fragments include plagioclase, diopside, augite and enstatite, as well as magnesio-hornblende and ferri-tschermakite. Geothermobarometry based on clinopyroxene and amphibole reveal the dominant role of upper crustal magma reservoirs. Ferri-tschermakite from 93 and 167.5 mbsf (~410 and 856 ka, respectively) records contributions from lower crustal, hot magma reservoirs. These temperature estimates are supported by Ti-in-zircon data. O-isotope ratios and trace elements in zircon reflect magmatic activity typical for an evolved island arc system.The bathymetry of the Grenada basin, the composition of lava clasts and minerals, scarcity of altered lava fragments, the narrow maximum age population of detrital zircon, and the O-isotope and trace element data on zircon suggest that the majority of U1398B volcaniclastic turbidites originated from the island of Dominica. The thick volcaniclastic units are most likely related to major eruption periods of andesitic magma that ascended from crustal reservoirs. Debris avalanche-related processes seem to be less important in U1398B at ≤170 mbsf.Mineral chemistry and O-isotope data obtained from plagioclase, pyroxene, amphibole, zircon and glass, separated from deep marine volcaniclastic turbidites, provide a chronostratigraphic frame for the sedimentary succession, and helps to genetically fingerprint the volcanic and magmatic evolution of the neighboring volcanic islands. While this is documented here for the well-constrained Pleistocene history of the central Lesser Antilles, the applied methods may also be used to characterize ancient marine volcaniclastic mass flow deposits and to reconstruct their volcanic source areas.

Structural architecture of the Middle Niger Basin, Nigeria based on aeromagnetic data: An example of a non-volcanic basin

The Middle Niger Basin is located within the west-central half of Nigeria, as a NW-SE trending Campano-Maastrichtian depo-centre which extends from the southern end of the Sokoto Basin west of Kainji reservoir southwestwards to the convergence of the Benue and Niger Rivers at Lokoja. The aeromagnetic anomaly data of the Middle Niger Basin was interpreted to characterize the structural architecture and depth to the magnetic basement of the basin. This is to expand the current knowledge of the region. The analysis of the data has been facilitated by the application of derivative and source parameter imaging techniques. The results from the application of total gradient to the aeromagnetic data provided here signify a rift origin of the basin and NW-SE trending fault systems in the surrounding basement complex terrain. The absence of magnetic highs on the first vertical derivative of the reduced-to-pole aeromagnetic data reveals lack of volcanic rocks within the sedimentary layers of the basin. Additionally, the consistent NW-SE trending source parameter imaging depth solutions within the basin confirm the internal geometry and NW-SE orientation of the basin with sediments not more than 1100 m thick.

Ecosystem change as a driver of fish recruitment dynamics: A case study of two Lake Erie yellow perch populations

Abstract Although previous research has identified ways in which environmental conditions influence population processes in many ecosystems, these relationships often weaken or break down with the inclusion of additional years of data, for reasons that remain unclear. To better understand if and how the relationships between historically important environmental drivers of yellow perch (Perca flavescens) recruitment varied during 1969–2018 in two Lake Erie basins characterised by contrasting productivity, we used dynamic linear modelling, which allows for nonstationary relationships between predictor and response variables to be quantified. Our analyses revealed that abiotic conditions during egg and larval development (i.e. winter temperature, springtime river inflows, and thermal conditions) were important in the productive west basin, whereas a combination of abiotic (i.e. winter temperature and river inflows) and biotic (i.e. small‐bodied and large‐bodied predators) conditions were important in the less‐productive central basin. While the importance of most environmental factors to yellow perch recruitment remained static through time, the importance of river inflows changed through time in the west and central basins. Large‐bodied predators (i.e. walleye, Sander vitreus) also varied in their importance through time in the central basin. These changes in recruitment drivers were independent of temporal changes to the environmental conditions themselves, coinciding instead with the timing of major shifts in Lake Erie's nutrient status. Our results demonstrate that ecosystem change can cause the relationships between environmental conditions and population processes (e.g. recruitment) of aquatic organisms to vary through time and space. They also highlight the value of periodically revisiting their applicability, especially if these relationships are used to help manage or sustain populations in ecosystems experiencing human‐driven environmental change.

New finds of the turtle Plesiochelys in the Upper Jurassic of Portugal and evaluation of its diversity in the Iberian Peninsula

ABSTRACT Two unpublished shells of thalassochelydian turtles from Tithonian (Late Jurassic) outcrops of the Lusitanian Basin (west central Portugal) are studied here. They are recognised as attributable to the plesiochelyid littoral genus Plesiochelys. They show characters unknown for the so far available Portuguese record of Plesiochelys, exclusively based on a partial shell, also from the Tithonian. The comparison between all these specimens and the only remains of Plesiochelys from the Spanish Tithonian record allow us to recognise several differences, compatible with the intraspecific variability reported for the genus. One of the oldest references to Thalassochelydia for the global record corresponds to that of the enigmatic taxon ‘Hispaniachelys prebetica’, from the Oxfordian of Jaén (Spain), hitherto recognised as a nomen dubium. Its holotype is identified here as belonging to the oldest member of Plesiochelys, the new combination Plesiochelys prebetica being proposed. Thus, the presence of at least two forms of Plesiochelys is recognised for the Iberian record, one of them corresponding to the only one identified at levels older than the middle Kimmeridgian, and the other being younger than the two species of which the shell was known (i.e. Plesiochelys etalloni and Plesiochelys bigleri).

The influence of multiple salt layers on rift‐basin development; The Slyne and Erris basins, offshore NW Ireland

AbstractIn contrast to much of the European Atlantic margin, the influence of salt on basin evolution has received little attention to date in the basins west of Ireland, despite salt being proven in several boreholes. Using an extensive seismic reflection database coupled with data from exploration wells and shallow boreholes, this study maps the distribution and composition of salt layers and investigates their role in the structural evolution of the Slyne and Erris basins offshore west of Ireland. Two salt‐prone intervals have been proven. The Upper Permian Zechstein Group is present throughout the Slyne and Erris basins, whereas the Upper Triassic Uilleann Halite Member is only developed in the Northern Slyne and Southern Erris sub‐basins. Both sedimentary units mechanically detach pre‐, post‐ and intra‐salt stratigraphy. Both salt layers underwent halokinesis during basin development, creating a variety of salt‐related structures. Salt pillows and salt rollers formed in the Zechstein Group, causing folding and rafting in the overlying Mesozoic section, driven by active faulting within the pre‐salt basement. Halokinesis in the Uilleann Halite Member caused thin‐skinned crestal collapse of the overlying Jurassic section above anticlines cored by Zechstein salt. Where both Triassic and Permian salt are present, unique structural geometries are formed when two stratigraphically discrete but kinematically linked halokinetic structures develop. The most common structural configuration consists of a Zechstein salt pillow and an Uilleann Halite salt wall separated by Lower Triassic sandstones. The fold axis of the salt pillow trends parallel to the strike of the salt wall. The results of this study provide a framework for the evolution of halokinetic structures in other basins on the Irish Atlantic margin, give a greater insight into the Permian and Triassic palaeogeography of the region and have more general implications for the evolution of salt‐related structures in rift basins with multiple stratigraphically discrete salt layers.

Results of Modeling of Generation and Accumulation Hydrocarbon Systems in the Sedimentary Basins of the Sea of Okhotsk

The paper presents the results of modeling of generation and accumulation hydrocarbon systems in the sedimentary basins of the sea of Okhotsk. The results of modeling HC migration showed that the most likely zones of hydrocarbon accumulation are the side parts of sedimentary basins. The anticline zones located on the border of two or more basins have the most favorable conditions. These areas, in general, are among the most promising in terms of hydrocarbon prospecting. However, such zones are characterized by complex conditions for the formation and preservation of deposits due to the non-synchronous evolution of adjacent sedimentary basins. This leads to uncertainties when assessing their prospects at the regional research level, for example, when predicting the type of fluid in deposits. For example, Vostochno-Shmidtovsk (East Schmidt) anticline zone is located on the border of two large centers of oil and gas generation: Severo-Sakhalinsky (North-Sakhalin) and Deryugin basin. The results of numerical modeling of the regional level allowed us to establish that HC migration towards the anticline zone occurs from the East (from the Deryugin basin) and the West (from the Severo-Sakhalinsky (North-Sakhalin) basin). The type of fluid in the predicted clusters is controlled by the type and maturity of the organic matter of the generation centers.

Distribution and intensity of High-Temperature Low-Pressure metamorphism across the Pyrenean-Cantabrian belt: constraints on the thermal record of the pre-orogenic hyperextension rifting

Whereas a straightforward link between crustal thinning and geothermal gradients during rifting is now well established, the thermal structure of sedimentary basins within hyperextended domains remains poorly documented. For this purpose, we investigate the spatial distribution of rift-related High-Temperature Low-Pressure (HT/LP) metamorphism recorded in the preserved hyperextended rift basins inverted and integrated in the Pyrenean-Cantabrian belt. Based on Vitrinite Reflectance (Ro) data measured in 169 boreholes and more than 200 peak-metamorphic temperatures (Tmax) data obtained by Raman Spectroscopy of Carbonaceous Material (RSCM) added to ∼425 previously publishedTmaxdata, we propose a new map depicting the spatial distribution of the HT/LPmetamorphism of the Pyrenean-Cantabrian belt. We also provide three regional-scale geological cross-sections associated with RoandTmaxdata to constrain the distribution of paleo-isograds at depth. Based on these results, we show that the impact of rift-related metamorphism is restricted to the pre- and syn-rift sequence suggested by the depth profiles of Rovalues measured in different tectonostratigraphic intervals (pre-, syn- and post-rift and syn-convergence sediments). However, a small strip of early orogenic sediments (Santonian in age) appears also affected by high temperatures along the North Pyrenean Frontal Thrust and above the Grand Rieu ridge, which we attribute to the percolation of hot hydrothermal fluids sourced from the dehydration of underthrust basement and/or sedimentary rocks at depth during the early orogenic stage. The map shows that the HT/LPmetamorphism (reaching ∼500 °C) is recorded with similar intensity along the Pyrenean-Cantabrian belt from the west in the Basque-Cantabrian Basin to the east in the Boucheville and Bas-Agly basins, for similar burial and rift-related structural settings. This thermal peak is also recorded underneath the northern border of the Mauléon Basin (calibrated by wells). It suggests that the high temperatures were recorded at the basement-sediment interface underneath the most distal part of the hyperextended domain. At basin-scale, we observe in the Basque-Cantabrian, Mauléon-Arzacq and Tarascon rift segments an asymmetry of the thermal structure revealed by different horizontal thermal gradients, supporting an asymmetry of the former hyperextended rift system. Using our results, we compare the Pyrénées to the Alps that also recorded hyperextension but no HT/LPmetamorphic event and suggest that the high-temperature record within the basins depends on high sedimentation rate promoting a thermal blanketing effect and circulation of hydrothermal fluids.

ЛОКАЛИТЕТ ФОРМИРУЮЩЕЙСЯ ЗИМОВАЛЬНОЙ ЯМЫ В РЕКЕ ИРТЫШ

The article describes a new locality of the formed wintering riverbed depression discovered in the erosion zone of the isthmus of conjugate meanders of the Irtysh river for the rational use and effective protection of aquatic biological resources in places of their concentration in the Irtysh river basin (Western Siberia, the Russian Federation. The morphology of the riverbed depression was mapped (relief and bathymetric maps). The maximum depths in the channel depression exceeded 27 m. The channel depression and 4 control river sections were studied. The analysis 
 of hydroacoustic surveys showed that in the wintering riverbed depression there is, according to the statistical data, higher fish density compared to the control areas: in the water area of the riverbed depression the average fish density made 4 524 species/ha, in the control sections 245-2091 sp./ha. The cluster analysis based on the fish density and the size-taxonomic composition of the ichthyofauna has revealed that the riverbed depression is being separated into a cluster, but at the same time goes to the control section No. 4, which is located downstream, where further erosion of the river channel is registered. In this regard, the minimum protection zone of the wintering channel depression should include the water area of the channel depression and the water area of control section No. 4. In the water areas of the riverbed depression and control sections in the spring period, cyprinids dominate - up to 65% of the total number of fish, percids are represented to a lesser extent - 36.76%, coregonids and pikes - up to 18.18, sturgeons - up to 9.31%. The given locality of the wintering riverbed depression must be included in the list of protected river sections of the Fishing Rules for the West Siberian fishery basin for developing the effective strategy for the protection, restoration and rational use of aquatic biological resources, including rare and endangered fish species of the Irtysh River and the whole Ob-Irtysh basin