Geophysical Expedition Research Articles

The crustal structure of the western Amundsen Basin, Arctic Ocean, derived from seismic refraction/wide-angle reflection data

SUMMARY Two geophysical expeditions (LOMROG II and III) were carried out in 2009 and 2012 to acquire seismic data in the western Amundsen Basin in the Arctic Ocean, a basin formed by ultraslow seafloor spreading at the Gakkel Ridge. Previous studies show alternating magmatic and amagmatic segments at the ridge but it is unclear if such segmentation persisted throughout the entire opening history of the basin. The seismic refraction data were used to develop P-wave velocity models down to the uppermost mantle using forward modelling of traveltimes. The coincident seismic reflection data were used to constrain the geometry of the sedimentary layers and for characterizing the acoustic basement. 2-D gravity modelling was used to determine the Moho depth in areas when data quality was insufficient to resolve a Moho reflection. The models distinguish three different basement types: oceanic crust with layers 2 and 3, oceanic crust that is lacking a layer 3 and exhumed and serpentinized mantle. The maximum observed crustal thickness is 6 km. Areas with thin crust (<3 km) may be underlain by partially serpentinized mantle. Where exhumed mantle is observed, a serpentinization front separates highly serpentinized mantle at the top from partially serpentinized mantle below. The presence of oceanic crust off-axis of the presently amagmatic sector of the Gakkel Ridge indicates that there is both a spatial and temporal variation of crustal accretion processes at the ridge.

Improved predictive modelling of coralligenous formations in the Greek Seas incorporating large-scale, presence–absence, hydroacoustic data and oceanographic variables

Our understanding of the distribution of coralligenous formations, throughout but mostly on the Eastern Mediterranean seafloor, is still poor and mostly relies on presence-only opportunistic trawling and fishermen reports. Previous efforts to gather this information created relevant geodatabases that led to a first draft predictive spatial distribution of coralligenous formations in the Mediterranean Sea using habitat suitability modelling techniques. In the last few decades, the use of hydroacoustics to map the seafloor for various geotechnical and habitat mapping projects accumulated high amounts of detailed spatial information about these formations, which remains majorly unexploited. Repurposing these datasets towards mapping key habitats is a valuable stepping stone to implementing the EU Habitat Directive. In Greece, a unique volume of seafloor mapping data has been gathered by the Laboratory of Marine Geology and Physical Oceanography, Geology Department, University of Patras. It accounts for more than 33 marine geophysical expeditions during the last three decades, having collected hydroacoustic data for a total seafloor area of 3,197.68 km2. In the present work, this information has been curated, re-evaluated, and archived to create the most complete, until now, atlas of coralligenous formations in the Greek Seas and the only integrating presence–absence data. This atlas has been used to train and validate a predictive distribution model, incorporating environmental variables derived from open data repositories, whose importance has been assessed and discussed. The final output is an improved probability map of coralligenous formation occurrence in the Greek Seas, which shall be the basis for effective spatial planning, gap detection, and design of future mapping and monitoring activities on this priority habitat.

Results of geophysical research on the Zmiyinyy island

The article presents the results of geophysical observations by the Dnepropetrovsk geophysical expedition «Dneprogeofizika» on Zmiyinyy Island, which performed a full cycle of work from prospecting and surveying studies to providing the island with drinking water.
 In structural and tectonic conditions, the island is considered as the Zmiyinyy insular block of the Danubian horst megablock. The geodynamics of the region is determined by the position and inclination of the collision sutures within the zone of interaction between the Eurasian and African lithospheric plates. Comprehensive geological and geophysical studies included magnetic prospecting, gravity prospecting and electric sounding (Dipole-axial sounding induced polarization DAS-IP) with geological routes along all rock outcrops on the Zmiyinyy island. Detailed integrated geophysical studies were: gravimetric observations over a network of 20×10 m, magnetometric — 10×5 m and electrometric (DAS-IP) — 40×5 m. For the first time on the island, gravimetric stations were set up, which will later become a support for gravimetric surveys. According to the results of magnetic field survey and DAZ-OP electrical exploration observations, an anomalous area was identified, which is perspective for archaeological research. Based on a comprehensive interpretation of geological and geophysical materials, a well was drilled to a depth of 120 m, which confirmed the constructed predictive stratigraphic section of about. Zmiyinyy. Based on the results of the search for sources of drinking water, three wells were drilled, with a fresh water flow rate of up to 10 m3 per day (each). Subsequently, fresh water with minor purification is used as drinking water.

3D model of the Selenga depression of the Baikal rift zone

The article presents the results of the interpretation of unique archival data of vertical electrical soundings obtained in the Selenga basin of the Baikal rift zone in the 50s of the last century by the detachment of the Baikal geophysical expedition of the PGO "Irkutskgeofizika", using modern computer technologies. The purpose of this work is to refine the geoelectric characteristics of the sections according to the measurement profiles, as well as the structure of such seismically active structures as the Delta and Fofanovsky faults, the Proval Bay, the Tvorogovo-Istok uplift using a 2–3D inversion program with visual data visualization.

Комплексные геолого-геофизические исследования по обоснованию внешней границы континентального шельфа России в Охотском и Восточно-Сибирском морях (2006–2009 гг.): обзор

The paper discusses the results of complex geological and geophysical studies of the deep structure of the seabed along the profiles “Magadan – Southern Kurils” (2-DV-M), “Shantar Islands – Northern Kurils” (1-OM) and “Cape Billings – Outer Continental Shelf Limits” (5-AR), carried out in 2006–2009 within the framework of the State program of expeditionary works on substantiation of national sovereignty over the continental shelf in the Sea of Okhotsk and East Siberian Sea. The main executors were the staff of the V.I. Il’ichev Pacific Oceanological Institute of FEB RAS and Federal State Unitary Scientific and Production Company (FSUSPC) Sevmorgeo. A special role was assigned to gas-geochemical studies with the purpose to establish regional background and anomalous gas fields to assess prospects for oil, gas and gas hydrates. As a result of complex geological and geophysical expeditions led by A.A. Merezhko (Sevmorgeo) in the Sea of Okhotsk, it was established that the enclave outside the 200-mile zone in the central part of the water area does not differ in geological structure from the adjacent parts and is a natural continuation of the framing geological structures of the basement. The evidence obtained was sufficient to successfully justify the application to the UN. On March 11, 2014, after careful consideration of the application and draft recommendations, the enclave of international waters in the Sea of Okhotsk was legally assigned to the Russian Federation. Studies in the East Siberian Sea have provided a huge amount of data on lithology, geochemistry and gas potential of bottom sediments in this area.

Editor's Note

Editor's Note

Microscopic impactor debris at Kamil Crater (Egypt): The origin of the Fe-Ni oxide spherules

Kamil crater (Egypt) is a natural laboratory for the study of processes and products associated with the impacts of small iron projectiles on the Earth’s crust. In particular, because of the distinctive composition of the impactor (an ungrouped Ni-rich ataxite) and the target (Cretaceous sandstones and minor wackes) it offers a unique opportunity to study impactor–target physical–chemical interactions. Continuing the study of impact melt ejecta, we investigated the mineralogy and geochemistry of 25 Fe-Ni spherules - representative of a suite of 135 - recovered from the soil around the crater. Samples were collected during our 2010 geophysical expedition and investigated by combining scanning electron microscope imaging, electron probe microanalyzer and Raman spectroscopy analyses. Spherules range in size from 100 to 500 µm and show a variety of dendritic textures and mineral compositions dominated by Fe-Ni oxides of the wüstite – bunsenite and magnetite – trevorite series or Fe-Ni metal. All these features indicate quenching of high temperature (1600–1500 °C) oxide or metal liquid droplets under varying oxidizing conditions. A geochemical affinity with the iron impactor recorded by the Fe, Co, Ni ratios in the constituent phases (average Ni/Co element ratio of 25.1 ± 7.6; average Ni/(Ni + Fe) molar ratio of 0.21 ± 0.13), combined with target contamination (i.e., the ubiquitous occurrence of Si and Al from trace to minor amounts), document their origin as impact melt spherules formed through the physical and chemical interaction between metal projectile and silicate target melts and air. We propose a petrogenetic model that envisions formation as liquid droplet residues of immiscible projectile in a mixed silicate melt and their subsequent separation as individual spherules by stripping during hypervelocity ejection. We also argue that this model applies to all impact events produced by small iron projectiles and that such individual Fe-Ni oxide and metal spherules should be common impact products, despite little documentation in the literature. Our detailed mineralogical and geochemical characterization will facilitate their distinction from other, similar spherules of different origin (cosmic spherules, ablation spherules) often encountered in the geologic record.

Ice gouging on the arctic shelf of Russia

The results of recent geological and geophysical expeditions indicate the activation of hazardous natural phenomena associated with ice gouging and represent geohazard for almost all activities, including operation of the Northern Sea Route. Within the Barents Sea and the western part of the Kara Sea, the modern ice gouging is mainly associated with icebergs which are formed as a result of the destruction of the glaciers of Novaya Zemlya, the Spitsbergen archipelago and Franz Josef Land, while on the eastern shelf it is caused by the destruction of seasonal or perennial ice fields. Fixed furrows can be divided into modern coastal gouges or deep water ploughmarks. All deep water gouges within the periglacial and glacial shelf are of paleogeographical origin, but with different mechanisms of action on the seabed. These furrows were formed by floating ice on the periglacial shelf. On the glacial shelf deep water ploughmarks were formed by large icebergs, which could carry out the gouging even on the continental slope and deep-sea ridges of the Arctic Ocean.

The integrated geological and geophysical expedition aboard the R/V Akademik Oparin to the Tatar Strait, Sea of Japan (cruise No. 54, 2017)

According to the Plan of Integrated Scientific Research of the World Ocean for 2017–2022, the Il’ichev Pacific Oceanological Institute, Far Eastern Branch of the Russian Academy of Sciences (POI FEB RAS) began a comprehensive study of the northern part of the Sea of Japan and the Tatar Strait, having developed a three-year plan for expeditionary research in the area. The first expedition from the three-year expeditionary research cycle was carried out from September 21 to October 31, 2017 on the R/V “Akademik Oparin” (cruise № 54). The main goal of the expedition was to study the geological structure, conditions and mechanisms for the formation of the Tatar Strait, to study the correlation of the distribution of gas-fluid flows with a network of tectonic disturbances of different ranks in one of the seismic areas of Sakhalin Island, as well as the reaction of the Sea of Japan to climate change and increasing anthropogenic impacts.

Ice Gouging on Russia’s Arctic Shelf

Abstract—The results of recent geological and geophysical expeditions indicate the activation of hazardous natural phenomena associated with ice gouging and representing a geohazard for almost all activities, including operation of the Northern Sea Route. The underwater parts of ice formations plow up the seabed. Within the Barents Sea and the western part of the Kara Sea, modern ice gouging is mainly associated with icebergs formed as a result of the breakup of glaciers of Novaya Zemlya and the Svalbard and Franz Josef Land archipelagos, while on the eastern shelf it is caused by the destruction of seasonal or perennial ice fields. Fixed furrows can be divided into modern coastal gouges or deep water plowmarks. All deep water gouges within the periglacial and glacial shelf are of paleogeographical origin, but with different mechanisms of action on the seabed. These furrows were formed by floating ice on the periglacial shelf; on the glacial shelf, deep-water plowmarks were formed by large icebergs, which were able to cause gouging even on the continental slope and deep-sea ridges of the Arctic Ocean.

Integrated Geological and Geophysical Expedition aboard the R/V Akademik Oparin to the Tatar Strait, Sea of Japan (Cruise 54, 2017)

According to the Plan of Integrated Scientific Research of the World Ocean for 2017–2022, the Il’ichev Pacific Oceanological Institute, Far Eastern Branch of the Russian Academy of Sciences (POI FEB RAS) began a comprehensive study of the northern part of the Sea of Japan and the Tatar Strait, having developed a three-year plan for expeditionary research in the area. The first expedition from the three-year expeditionary research cycle was carried out from September 21 to October 31, 2017 on the R/V “Akademik Oparin” (cruise № 54). The main goal of the expedition was to study the geological structure, conditions and mechanisms for the formation of the Tatar Strait, to study the correlation of the distribution of gas-fluid flows with a network of tectonic disturbances of different ranks in one of the seismic areas of Sakhalin Island, as well as the reaction of the Sea of Japan to climate change and increasing anthropogenic impacts.

The magmatic system beneath the Tristan da Cunha Island: Insights from thermobarometry, melting models and geophysics

This study provides new insights on the conditions of melt generation and of magma transport and storage beneath Tristan da Cunha Island in the South Atlantic. Situated at the seaward end of the Walvis Ridge-guyot hotspot track, this island is related to the evolving magmatic system of the Tristan plume. Much is known about the geochemical and isotopic composition of the alkaline lavas on Tristan, but the pressure–temperature conditions of the hotspot magmas are under-explored. This contribution reports new data from a suite of 10 samples collected during a geologic–geophysical expedition in 2012. The focus of this study is on the least-evolved, phenocryst-rich basanite lavas but we also included a sample of trachyandesite lava erupted in 1961. Mineral-melt equilibrium thermobarometry uses the composition of olivine, clinopyroxene and plagioclase phenocrysts. In addition to bulk-rock data we also analysed olivine-hosted melt inclusions for the P–T calculations. The results for olivine-melt and clinopyroxene-melt calculations suggest crystallization conditions of around 1200–1250°C and 0.8–1.3GPa for the least-evolved magmas (ankaramitic basanites). Combined with seismological evidence for a Moho depth of about 19km, these results imply magma storage and partial crystallization of Tristan magmas in the uppermost mantle and at Moho level. The trachyandesite yielded values of about 1000°C and 0.2–0.3GPa (6 to 10km depth), indicating further crystallization within the crust.Constraints on the depth and degree of melting at the source of Tristan basanites were derived from REE inverse modelling using our new trace element data. The model predicts 5% melt generation from a melting column with its base at 80–100km and a top at 60km, which is consistent with the lithospheric thickness resulting from cooling models and seismological observations. The thermobarometry and melting models combined suggest a mantle potential temperature of about 1360°C for the Tristan hotspot.

New geological interpretation of multi-channel seismic profiles from the Pacific Margin of the Antarctic Peninsula

AbstractThe Polish Geophysical Expedition to West Antarctica in 1979–1980 was carried out by the Institute of Geophysics, Polish Academy of Sciences. Beside deep seismic soundings, 12 multi-channel seismic profiles, with a total length ofca1000 km have been recorded north and east of the South Shetland Islands and in the Bransfield Strait, but they have never before been completely interpreted and published. All profiles have been processed with modern processing flow including time migration. Profiles crossing the South Shetland Trench revealed distinct reflector inside continental slope, which has been interpreted as border between buried accretionary prism and overlying slope sediments of glacial-marine origin. Profiles in the Bransfield Strait show traces of the Last Glacial Maximum (LGM) in the form of glacial foreground valleys, with some of them used as weak spots for young age volcanic intrusions. This paper is the first comprehensive geological interpretation of collected dataset and differences between results from other expeditions are discussed.

Microscopic impactor debris in the soil around Kamil crater (Egypt): Inventory, distribution, total mass, and implications for the impact scenario

AbstractWe report on the microscopic impactor debris around Kamil crater (45 m in diameter, Egypt) collected during our 2010 geophysical expedition. The hypervelocity impact of Gebel Kamil (Ni‐rich ataxite) on a sandstone target produced a downrange ejecta curtain of microscopic impactor debris due SE–SW of the crater (extending ~300,000 m2, up to ~400 m from the crater), in agreement with previous determination of the impactor trajectory. The microscopic impactor debris include vesicular masses, spherules, and coatings of dark impact melt glass which is a mixture of impactor and target materials (Si‐, Fe‐, and Al‐rich glass), plus Fe‐Ni oxide spherules and mini shrapnel, documenting that these products can be found in craters as small as few tens of meters in diameter. The estimated mass of the microscopic impactor debris (<290 kg) derived from Ni concentrations in the soil is a small fraction of the total impactor mass (~10 t) in the form of macroscopic shrapnel. That Kamil crater was generated by a relatively small impactor is consistent with literature estimates of its pre‐atmospheric mass (>20 t, likely 50–60 t).

The deep seismic structure of the Earth's crust along the Antarctic Peninsula—A summary of the results from Polish geodynamical expeditions

A summary of the results of four Polish geophysical expeditions, which constituted an extensive programme of seismic wide-angle refraction experiments in the northern Antarctic Peninsula region between 1979 and 1991, is analysed here. The results include the interpretation of 20 deep seismic sounding profiles located along the western coast of the Antarctic Peninsula. Additionally, a few shallow seismic profiles in the Deception Island area and a total of 10 reflection profiles from the Bransfield Strait and Drake Passage area were carried out. Crustal velocity models extending across the Antarctic Peninsula continental shelf between the Adelaide Island and the Bransfield Strait show a typical continental crustal structure, with crustal thicknesses of 36–42km near the coast that decreases to 25–28km beneath the outer continental shelf. Farther north in the Bransfield Strait region, the models document a southeastward dip of the Moho discontinuity from a depth of 12km beneath the South Shetland Trench to 40km under the northern tip of the Antarctic Peninsula. Beneath the trough of the Bransfield Strait, a high-velocity body with P-wave velocities exceeding 7.0km/s was detected in a depth range of 6–32km.

ROSING Promotes Russian R&D, Education, and Training

Society Spotlight Editor's note: SPE seeks to develop strong relationships with other oil and gas societies worldwide. Many of these societies partner with SPE and other organizations on conferences, workshops, and other programs, at both the local and international levels. This series offers an overview of some of these societies. This second installment in the series spotlights the nongovernmental organization Russian Society of Petroleum and Gas Engineers, commonly known as ROSING. The Russian Society of Petroleum and Gas Engineers (ROSING) was founded on 7 December, 2001 by the ROSING Congress after a production enhancement conference organized by a Lukoil subsidiary. The Congress set up the central executive board, selected the president and the audits commission, and approved the charter of association. Since the day ROSING was created, its president has been Vyacheslav Manyrin, who is also a member of the country's Supreme Engineering Council. During its short existence, the organization has earned great respect among Russian oil and gas professionals. The organization's primary goal is to integrate, coordinate, and implement the creative capacity of oil industry researchers, engineers, and experts in Russia and abroad to benefit the industry. ROSING outlines its mission as one ofCreating a favorable environment for a free exchange of knowledge, ideas, and scientific and practical results of intellectual activityDisseminating R&D data using all modern methods and meansPromoting, publishing, and educating, including providing education and training to oil and related industry professionals ROSING boasts more than 10,000 members in 48 regions of Russia. It conducts various conferences, exhibitions, and seminars, including its major conference, the well-known Conference on Oil & Gas Recovery and Reservoir Stimulation, which has grown steadily in size and stature among Russian technical professionals. It also publishes the ROSING newsletter and the Interval Innovations journal. The organization has been a member of the Russian Trade and Industry Chamber since 2003. Its president chairs the Engineering and Technology Subcommittee of the Committee for Fuel and Energy Complex Strategy and Development. The subcommittee was involved in drafting Russia's Public Concept of Rational Oil Reserve Utilization Management. In 2002, ROSING established the Golden ROSING Award to recognize outstanding performance in engineering, education, or research. The award has been given to some of the country's most renowned oil and gas engineers. Recent recipients include professor Igor Gutman, director and founder of the Institute of Design and Scientific Expertise of the Field of Geology Department at Gubkin Russian State University of Oil and Gas; Vladimir Chirskov, a member of the Russian Academy of Natural Sciences; Anatoly Usmanov, general director of the Northwestern Oil Trunk Pipelines Company; Gennady Pozdnyshev, the author of numerous publications on new production techniques and environmental practices at field sites; and Alexei Kashik, general director of the Central Geophysical Expedition Company. In the future, the organization said it plans to open offices throughout Russia as well as develop cooperation initiatives with professional associations both in and outside of Russia.

Fifty years of detailed seismological investigations: The Kuril-Kamchatka arc

Kamchatka and the Kuril Islands (the Kuril-Kamchatka arc) make up the region of highest seismicity in Russia. About 80% of Russian earthquakes occur there, but a mere handful of three seismographic stations had been in operation until the autumn of 1957. On September 2, 1957, the Seismological Team of the Pacific Multidisciplinary Geologic and Geophysical Expedition, Institute of Physics of the Earth, USSR Acad. Sci. set foot on Iturup I, South Kuril Is. to do research for the International Geophysical Year program during 1957–1959, and began detailed seismological investigations in the Kuril-Kamchatka arc. During the subsequent 50 years, six organizations of the USSR/Russian Academy of Sciences conducted and developed this research in the Kuril Is. and Kamchatka. We review previous seismic expeditionary studies, which were carried out in other regions of the USSR from 1949 to 1957. The beginning of the detailed seismological investigations for the Kuril-Kamchatka arc is described, providing brief information on how this research was organized, as well as on the researchers involved, their lines of research, and the development of the extensive and comprehensive studies carried out in 1957–2007, along with some of their leading results. These results include the study of seismicity, its patterns, geodynamics, deep structure, upper mantle properties, the relationships between seismicity and volcanism, and successful long-term earthquake forecasts, among other subjects.

Ground penetrating radar study of iron age tombs in Southeastern Kazakhstan

AbstractAn international archaeological and geophysical expedition was carried out to study Iron Age tombs of the Saka culture in southeastern Kazakhstan. Single‐fold and multifold ground‐penetrating radar (GPR) surveys, in two and two and a half dimensions, focused on the identification of burial chambers beneath the mound‐shaped Saka tumuli, named kourgans. Primary objectives of the geophysical study were the testing and optimization of GPR techniques for studying this type of tomb and the reconstruction of subsurface images of use for the design of archaeological excavations. Single‐fold GPR grids with line spacing ranging between 50 and 200 cm were obtained at each of the 13 sites selected. After identification of the sectors of major potential interest from data processing performed directly in the field and interpretation of the single‐fold grids, multifold profiles with average 1200 per cent fold were designed and performed. Processing of the data focused on velocity analyses, pre‐stack coherent noise attenuation by means of FK and KL filters, stacking and analysis of the instantaneous attributes of the complex radar trace. Multifold GPR data processing techniques achieved a substantial increment in the signal to noise ratio at most sites, allowed accurate depth conversions of the stacked profiles (average deviation of estimated target location from the actual target was less than 5% of total depth) and provided indications to identify the characteristic response from the target of interest through the joint interpretation of pre‐stack gathers, velocity analysis and amplitude versus offset analysis. Interpretation of stacked sections and three‐dimensional models obtained from the single‐fold/multifold grid allowed the identification of a burial chamber located at an estimated depth of 140–150 cm, which was excavated successfully by the archaeological team. Further reflectors with similar characteristics are shown from other sites, which will be excavated by the next archaeological expeditions to the area. Copyright © 2001 John Wiley & Sons, Ltd.

Stephan Mueller (1930”1997)

Stephan Mueller, professor emeritus at the Institute of Geophysics at the Swiss Federal Institute of Technology (ETH) in Zurich and highly respected leader of international geoscience, died February 17, 1997. His untimely death, due to pneumonia following intestinal surgery, came just 18 months after his retirement from the ETH Chair of Geophysics and Directorship of the Swiss Seismological Service. He is survived by his wife, Doris, two sons, and six grandchildren.Mueller received a diploma in physics at the University of Stuttgart in 1957 and an M.S. in electrical engineering from Columbia University in New York in 1959. As an undergraduate at Stuttgart, he was influenced by seismologist Wilhelm Hillerand geophysics quickly became his major academic and career objective. After receiving a 1954–1955 German Academic Interchange Scholarship at Columbia, Mueller sought out Maurice Ewing and his group at Lamont Geological Observatory, where Mueller's enthusiasm for geophysics was strongly encouraged. While at Lamont, he participated in the first U.S. deep‐sea geophysical expedition in the Mediterranean Sea during the summer of 1956 aboard the RV Vema.

Researchers investigate submarine faults north of Puerto Rico

A 23‐day marine geophysical expedition in the summer of 1996 revealed a previously unidentified strike‐slip fault zone within 60–100 km of the densely populated northern coast of Puerto Rico. The purpose of the expedition, which was held aboard the U.S. research vessel Maurice Ewing, was to map the northeastern portion of the North America Caribbean plate boundary.The 3000‐km‐long North America‐Caribbean plate boundary stretches from Guatemala to the Lesser Antilles arc. The dominantly left‐lateral strike‐slip boundary accommodates slow (1–2.6 cm/yr) eastward motion of the Caribbean plate relative to North America. Distributed interplate motion in the region generates large earthquakes (Figure 1, inset). In 1976, an M 7.5 left‐lateral, strike‐slip earthquake in Guatemala killed approximately 23,000 people and left a quarter of the nation's population homeless.