Intense Folding Research Articles

Emissions from surrounding strata in coalbeds: Guaduas formation (Colombia)

During underground coal mining operations, greenhouse gas emissions are produced, mainly methane. These emissions originated not only from coal, but also from the subsidence of the surrounding rocks. Until now, emissions from surrounding rocks have been calculated from international tables, but it is proposed that they be calculated from gas measurements on coal-adjacent rocks in coalbed methane exploration in which drillings and canisters desorption systems were used in the provinces of Boyacá and Cundinamarca. The gas contents of the surrounding rocks, and thus the emissions, are less than those found in the coal at the same depth. The areas with the highest gas content values in the surrounding rocks are Samacá and Chinavita with contents between 40 and 50 feet3/ton. These values equate to one-third or a quarter of those obtained from the coalbeds close to such samples. The highest gas content did not correspond to the highest coal rank (Socotá) which would be explained by the intense folding and faulting in that area. The gas contents found in the shales (clays) of the Guaduas formation can also be used as a proxy indicator for older and deeper formations that could have good shale gas potential.

THE KARST IN ANO VLASSIA ACHAIA (GREECE) AND THE CONTRIBUTION OF OLONOS -PINDOS GEOTECTONIC UNIT ON ITS FORMATION

The study area includes the Selinous river hydrologie basin on East Erimanthos (Olonos) Mountain, to close to Ano Vlassia village (N. Péloponnèse - Greece). It is formed at an altitude between 700 - 2.169 m and occ 'Dies an area 30 Km2. It belongs to the Olonos - Pindos geotectonic unit, which characterized by lithostratigraphic unevenness, intense folds, successive thrusts with NE - SW directions and transverse faults. Lithostratigraphic and tectonic conditions are accountable for a directed karst development with many karstic basic planes. The above research includes systematic survey in all karstic formations that were observed. Karrens, kluft karrens, shallow dolines and dry karst valleys are developed on the surface. Furthermore, an underground formation was found and composed by caves, gulfs and an underground karstic river. Above 25 karstic fountainheads were observed which gush from the limestones with a 100 m3/h (summer) maximum supply. The imperfect development of surface karst, the good development of underground karst, karstic fountainheads, hydnlogical network and vert, allow for the studied area to be classified to the Transitional type of karst Dy Cvijic (1926) or to Halbkarst by Grund (1903).

Enigmatic gravity-flow deposits at Ujście (western Poland), triggered by earthquakes (as evidenced by seismites) caused by Saalian glacioisostatic crustal rebound

Two breccia layers occur directly stacked upon each other in a silty/sandy Saalian glaciolacustrine succession near Ujście (western Poland). This complex is exceptional because of two aspects: the two breccia layers consist of distinctly more fine-grained material (mainly silt) than the rest of the succession, and they contain numerous soft-sediment clasts of sandy silt with irregular shapes. The silty clasts are interpreted to represent fragments of eroded sediment from the more marginal (proximal) bottom of the lake. The fine-grained character of the breccia matrix excludes that the process responsible for their deposition had a sufficiently high erosional capability to erode the embedded clasts. The only feasible explanation is that this enigmatic breccia consists of a mixture of sediments: the silty matrix must first have been deposited on the bottom of a lake and afterward have been eroded and redeposited by gravity flows that initially had sufficient power to erode the lake margin over which they ran down. The source of the gravity-flow silt remains enigmatic because no sediments with similar lithology are currently present nearby at a higher topographic level. We must therefore deduce that such sediments existed previously but were entirely eroded away, probably by the Weichselian ice mass that had reached this area during the next glaciation.The probable trigger of the gravity flows is evidenced by the presence of soft-sediment deformation structures in two levels around 4.5 m below the breccias. These two levels show intense folding, collapse, and load structures indicative of liquefaction and fluidization. The deformation is ascribed to shocks, most probably resulting from earthquakes that were induced by glacioisostatic rebound during the Saalian deglaciation. Similar seismic shocks are likely to have triggered the mass flows that resulted in the breccia layers.

Inversion of the Erlian Basin (NE China) in the early Late Cretaceous: Implications for the collision of the Okhotomorsk Block with East Asia

A significant transition in tectonic regime from extension to compression occurred throughout East Asia during the mid-Cretaceous and has stimulated much attention. However, the timing and driving mechanisms of the transition remain disputed. The Erlian Basin, a giant late Mesozoic intracontinental petroliferous basin located in the Inner Mongolia, Northeast China, contains important sedimentary and structural records related to the mid-Cretaceous compressional event. The stratigraphical, sedimentological and structural analyses reveal that a NW–SE compressional inversion occurred in the Erlian Basin between the depositions of the Lower Cretaceous Saihan and Upper Cretaceous Erlian formations, causing intense folding of the Saihan Formation and underlying strata, and the northwestward migration of the depocenters of the Erlian Formation. Based on the newly obtained detrital zircon U-Pb data and previously published paleomagnetism- and fossil-based ages, the Saihan and Erlian formations are suggested as latest Aptian–Albian and post-early Cenomanian in age, respectively, implying that the inversion in the Erlian Basin occurred in the early Late Cretaceous (Cenomanian time). Apatite fission-track thermochronological data record an early Late Cretaceous cooling/exhuming event in the basin, corresponding well with the aforementioned sedimentary, structural and chronological analyses. Combining with the tectono-sedimentary evolutions of the neighboring basins of the Erlian Basin, we suggest that the early Late Cretaceous inversional event in the Erlian Basin and the large scale tectonic transition in East Asia shared the common driving mechanism, probably resulting from the Okhotomorsk Block–East Asia collisional event at about 100–89 Ma.

Riesgo geológico que afectará al poblado Tapacocha (Recuay ‐ Ancash)

Las construcciones civiles edificadas sobre suelos inestables son vulnerables a los procesos naturales como la geodinámica interna, externa y el cambio climático. El poblado de Tapacocha que está asentado sobre suelo deslizado es sensible a los procesos naturales. El terremoto de mayo de 1970 ocasionó fracturamiento de la planicie, destrucción de sus construcciones; las intensas lluvias de los años 1942 y 1997 ocasionaron huaycos que destruyeron algunas de sus edificaciones y terrenos de cultivo. La geodinámica interna modeló el basamento con un intenso plegamiento y fracturamiento de las rocas sedimentarias; la geodinámica externa por geoformas modeladas por los movimientos rotacionales, deslizamientos, erosión diferencial. En la actualidad el efecto del cambio climático se manifiestan por las inusuales torrenciales lluvias que erosionan periódicamente y ponen en peligro las edificaciones civiles y la agricultura. Con el presente estudio se propone alertar a las autoridades y sus pobladores para prevenir y mitigar los efectos naturales destructivos.

Heat Shock Protein Genes Undergo Dynamic Alteration in Their Three-Dimensional Structure and Genome Organization in Response to Thermal Stress.

Three-dimensional (3D) chromatin organization is important for proper gene regulation, yet how the genome is remodeled in response to stress is largely unknown. Here, we use a highly sensitive version of chromosome conformation capture in combination with fluorescence microscopy to investigate Heat Shock Protein (HSP) gene conformation and 3D nuclear organization in budding yeast. In response to acute thermal stress, HSP genes undergo intense intragenic folding interactions that go well beyond 5'-3' gene looping previously described for RNA polymerase II genes. These interactions include looping between upstream activation sequence (UAS) and promoter elements, promoter and terminator regions, and regulatory and coding regions (gene "crumpling"). They are also dynamic, being prominent within 60 s, peaking within 2.5 min, and attenuating within 30 min, and correlate with HSP gene transcriptional activity. With similarly striking kinetics, activated HSP genes, both chromosomally linked and unlinked, coalesce into discrete intranuclear foci. Constitutively transcribed genes also loop and crumple yet fail to coalesce. Notably, a missense mutation in transcription factor TFIIB suppresses gene looping, yet neither crumpling nor HSP gene coalescence is affected. An inactivating promoter mutation, in contrast, obviates all three. Our results provide evidence for widespread, transcription-associated gene crumpling and demonstrate the de novo assembly and disassembly of HSP gene foci.

Unusual enhancement in tropospheric and surface ozone due to orography induced gravity waves

In this study, we investigate the causative processes responsible for the observed enhancement in the tropospheric and surface ozone during December 09–11, 2008 orography induced gravity wave event over Himalayan region. The analysis is done using surface ozone measurements and satellite datasets from Atmospheric Infrared Sounder/Advanced Microwave Sounding Unit-A (AIRS/AMSU-A), COSMIC, TES and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). Observations depict a two fold increase in surface and tropospheric ozone during the event as compared to normal days in both AIRS and TES ozone measurements. COSMIC temperature perturbations show generation of shorter vertical wavelengths efficient for the sub-tropical tropopause folding due to orography induced gravity waves. Moreover, the intense tropopause folding as evidenced by upward-downward vertical velocities couplet could trigger the intrusion of stratospheric ozone rich air into upper tropospheric ozone poor air as also confirmed by high values of potential vorticity during the observational period. Hence, present study reemphasizes the importance of wave induced atmospheric dynamics on atmospheric constituents' especially tropospheric ozone over Himalayan region.

Sedimentary and tectonic evolution of the southern Qiangtang basin: Implications for the Lhasa‐Qiangtang collision timing

AbstractThe Mesozoic stratigraphic record of the southern Qiangtang basin in central Tibet records the evolution and closure of the Bangong‐Nujiang ocean to the south. The Jurassic succession includes Toarcian‐Aalenian shallow‐marine limestones (Quse Formation), Aalenian‐Bajocian feldspatho‐litho‐quartzose to feldspatho‐quartzo‐lithic sandstones (shallow‐marine Sewa Formation and deep‐sea Gaaco Formation), and Bathonian outer platform to shoal limestones (Buqu Formation). This succession is truncated by an angular unconformity, overlain by upper Bathonian to lower Callovian fan‐delta conglomerates and litho‐quartzose to quartzo‐lithic sandstones (Biluoco Formation) and Callovian shoal to outer platform limestones (Suowa Formation). Sandstone petrography coupled with detrital‐zircon U‐Pb and Hf isotope analysis indicate that the Sewa and Gaaco formations contain intermediate to felsic volcanic detritus and youngest detrital zircons (183–170 Ma) with εHf(t) ranging widely from +13 to −25, pointing to continental‐arc provenance from igneous rocks with mixed mantle and continental‐crust contributions. An arc‐trench system thus developed toward the end of the Early Jurassic, with the southern Qiangtang basin representing the fore‐arc basin. Above the angular unconformity, the Biluoco Formation documents a change to dominant sedimentary detritus including old detrital zircons (mainly >500 Ma ages in the lower part of the unit) with age spectra similar to those from Paleozoic strata in the central Qiangtang area. A major tectonic event with intense folding and thrusting thus took place in late Bathonian time (166 ± 1 Ma), when the Qiangtang block collided with another microcontinental block possibly the Lhasa block.

15d-PGJ2 as an endoplasmic reticulum stress manipulator in multiple myeloma in vitro and in vivo

Multiple myeloma (MM) is characterised by intense protein folding and, consequently endoplasmic reticulum (ER) stress. The prostaglandin 15d-PGJ2 is able to raise oxidative stress levels within the cell and potentially trigger cell death. The aim of this study was to evaluate the antineoplastic effect of 15d-PGJ2 on MM in vitro and in vivo via ER and oxidative stress pathways. MM.1R and MM.1S cell lines were treated with 15d-PGJ2 at 1–10μM and evaluated with regard to proliferation, mRNA expression of PRDX1, PRDX4, GRP78, GRP94, CHOP, BCL-2 and BAX. Stress data was validated via oxidized glutathione assays. MM.1R cells were inoculated into NOD/SCID mice, which were subsequently treated daily with 15d-PGJ2 at 4mg/kg or vehicle (control), with tumour volume being monitored for 14days. 15d-PGJ2 reduced cell proliferation, induced cell death and apoptosis at 5μM and 10μM and Stress-related genes were upregulated at the same doses. Oxidized glutathione levels were also increased. 15d-PGJ2 at 4mg/kg in vivo halted tumour growth. In conclusion, 15d-PGJ2 induced myeloma cell death via ER stress in vitro. 15d-PGJ2 in vivo also inhibited tumour growth.

Constraining quantitatively the timing and process of continent-continent collision using magmatic record: Method and examples

Based on the main driving force of plate motion (the slab pull force generated by the descent of the oceanic plate in subduction zones) and the three primary mechanisms for magma generation (adding fluid, increasing temperature, and decreasing pressure), the continent-continent collisional process has been divided into three stages, including initial collision, ongoing collision, and tectonic transition. These stages are characterized by normal calc-alkaline andesitic magma (dehydration of the oceanic crust to release fluids), the migration of calc-alkaline magma toward the trench (dehydration of the oceanic crust or an increase in temperature) or small-scale crust-derived peraluminous magma (heat from intra-crustal shearing), and extensive magmatism with compositional diversity induced by slab break-off (increasing temperature and decreasing pressure), respectively. On the basis of the obtained age of slab break-off, the timing of the initial continent-continent collision can be quantitatively back-dated using the convergence rate, depth of slab break-off, and subduction angle. The spatio-temporal migration of the magmatic activity of the Gangdese Batholith, the onset of magmatic flare-up, and the increase of magma temperature at 52–51 Ma documented by the volcanic rocks of the Linzizong Pana Formation were most likely the result of the break-off of the Yarlung-Zangbo Neo-Tethyan oceanic lithosphere at approximately 53 Ma. This proposed age of slab break-off suggests that the initial India-Asia collision likely occurred at approximately 55–54 Ma, which is consistent with the collision ages constrained by other abundant geological data (60–55 Ma). This magmatic method has been applied to the Bitlis orogenic belt in southern Turkey in the Arabia-Eurasia continental collision zone, yielding an age range of approximately 29–22 Ma for the initial Arabia-Asia continental collision that is close to the collision ages recently obtained by apatite fission-track dating (approximately 20 Ma) and regional tectonic shortening (approximately 27 Ma). The intense folding of the Upper Cretaceous and the angular unconformity between the overlying Linzizong volcanic rocks in the southern Lhasa Terrane (90−69 Ma) are not related to the initial continental collision between India and Asia, but can be interpreted as the consequences of the strong coupling between the hot and young subducting oceanic crust immediately south of the spreading ridge and the overriding lithosphere or the subduction of the Neo-Tethys oceanic plateaux or seamounts. The tectonic event documented by the angular unconformity between the Linzizong Dianzhong Formation and the Nianbo Formation lasted approximately 3 Ma and likely marks the initial India-Asia collision. The significant deceleration of the Indian continent at approximately 51 Ma can be attributed to the disappearance of the slab pull force in the subduction zone due to the break-off of the Yarlung-Zangbo Neo-Tethyan oceanic lithosphere. The descent of the eclogitized lower crust of the northern Indian continent provides the main driving force for the current northward motion of Indian plate. The weak deformation of the lithospheric plate in the overriding plate of the India-Asia collisional zone between 60 and 40 Ma can be attributed to the high-angle subduction related to the rollback of the Yarlung-Zangbo Neo-Tethyan oceanic lithosphere after the initial India-Asia continental collision, the presence of the thick crust and high elevation on the southern margin of the Lhasa Terrane, and the decoupling between the mid-upper and lower crust and between the lower crust and lithospheric mantle of the Indian continent.

Iranshahr blueschist: subduction of the inner Makran oceanic crust

AbstractThe Makran accretionary prism in SE Iran and SW Pakistan is one of the most extensive subduction accretions on Earth. It is characterized by intense folding, thrust faulting and dislocation of the Cenozoic units that consist of sedimentary, igneous and metamorphic rocks. Rock units forming the northern Makran ophiolites are amalgamated as a mélange. Metamorphic rocks, including greenschist, amphibolite and blueschist, resulted from metamorphism of mafic rocks and serpentinites. In spite of the geodynamic significance of blueschist in this area, it has been rarely studied. Peak metamorphic phases of the northern Makran mafic blueschist in the Iranshahr area are glaucophane, phengite, quartz±omphacite+epidote. Post peak minerals are chlorite, albite and calcic amphibole. Blueschist facies metasedimentary rocks contain garnet, phengite, albite and epidote in the matrix and as inclusions in glaucophane. The calculated P–T pseudosection for a representative metabasic glaucophane schist yields peak pressure and temperature of 11.5–15 kbar at 400–510 °C. These rocks experienced retrograde metamorphism from blueschist to greenschist facies (350–450 °C and 7–8 kbar) during exhumation. A back arc basin was formed due to northward subduction of Neotethys under Eurasia (Lut block). Exhumation of the high‐pressure metamorphic rocks in northern Makran occurred contemporarily with subduction. Several reverse faults played an important role in exhumation of the ophiolitic and HP‐LT rocks. The presence of serpentinite shows the possible role of a serpentinite diapir for exhumation of the blueschist. A tectonic model is proposed here for metamorphism and exhumation of oceanic crust and accretionary sedimentary rocks of the Makran area. Vast accretion of subducted materials caused southward migration of the shore.

An incomplete correlation between pre-salt topography, top reservoir erosion, and salt deformation in deep-water Santos Basin (SE Brazil)

In deep-water Santos Basin, SE Brazil, hypersaline conditions during the Aptian resulted in the accumulation of halite and carnallite over which stratified evaporites, carbonates and shales were folded, translated downslope and thrusted above syn-rift structures. As a result, high-quality 3D seismic data reveal an incomplete relationship between pre-salt topography and the development of folds and thrusts in Aptian salt and younger units. In the study area, three characteristics contrast with known postulates on passive margins’ fold-and-thrust belts: a) the largest thrusts do not necessarily occur where the salt is thicker, b) synthetic-to-antithetic fault ratios are atypically high on the distal margin, and c) regions of intense folding do not necessarily coincide with the position of the larger syn-rift horsts and ramps below the salt. Regions marked by important erosion and truncation of pre-salt strata, uplifted and exposed sub-aerially before the deposition of Aptian salt, can form structural lows at present or be part of horsts uplifted after the Aptian. This is an observation that suggests significant intra-salt shear drag above pre-salt structural highs during Aptian-Late Cretaceous gravitational gliding, but not on younger horsts and ramps reactivated after the main phase of salt movement. Either formed by drag or sub-aerial erosion, strata truncation below the Aptian salt does not correlate with the present-day pre-salt structure in terms of its magnitude and distribution. In addition, there is a marked increase in deformation towards the distal margin, where low-angle thrusts are ubiquitous on seismic data. The geometry and large synthetic-to-antithetic fault ratios of post-salt strata on the distal margin lead us to consider a combination of gravitational gliding of salt from the northwest and ridge push from the east as responsible for the observed styles of salt deformation.

3D Graphene Hollow Nanospheres@Palladium‐Networks as an Efficient Electrocatalyst for Formic Acid Oxidation

Graphene has served widely as a support material for noble metal nanoparticle electrocatalysts in fuel cells. During the synthesis of electrocatalysts, however, the intense stacking and folding of graphene nanosheets decreases the utilization and activity of electrocatalysts, owing to the following aspects: i) the noble metal wrapped by the winding graphene cannot be fully utilized; ii) the structural destruction of graphene decreases the specific surface area and increases electrical resistance; and iii) the hydrophobicity and wrinkles of graphene greatly increase the mass transfer resistance of fuel molecules and electrolytes. In this work, 3D graphene oxide hollow nanospheres are designed to minimize wrinkles, maximize specific surface area, and realize the regular clipping of 2D graphene oxide. The 3D‐reduced graphene oxide hollow nanosphere supported Pd‐network nanohybrids (3D‐RGO/Pd‐NWs) are then obtained using 3D graphene oxide hollow nanospheres as a reaction precursor. The skeleton of 3D‐RGO not only acts as an exclusive inner conducting shell to promote electron and ion kinetics but is also crucial for enhancing the permeation of fuel molecules and electrolytes. Therefore, 3D‐RGO/Pd‐NWs exhibit enhanced electrocatalytic activity and durability for the formic oxidation reaction in an acidic medium compared to 2D graphene supported Pd nanoparticles and commercial Pd/C electrocatalysts.

Late Paleozoic evolution of the South Tien Shan: Insights from P–T estimates and allanite geochronology on retrogressed eclogites (Chatkal range, Kyrgyzstan)

In the South Tien Shan range (Kyrgyzstan), the Late Paleozoic geodynamic evolution remains debated especially to the west of the Talas-Fergana fault (TFF) fault where suture-related high-pressure (HP) rocks are scarce. We provide new petrological and geochronological data on garnet amphibolites from the Chatkal range, to the west of the TFF, northwest of the South Tien Shan suture. These rocks are retrogressed eclogites. We used a micro-mapping approach combined with forward modeling and empirical thermobarometry to decipher the P–T path of these amphibolitized eclogites. The metamorphic peak conditions culminated at 490±50°C and 18.5±2kbar and were followed by higher temperature retrogression (∼560°C at 11–7kbar). In order to constrain the age of the HP stage, we dated allanite crystals texturally coeval to the HP mineral assemblage. Allanite grains dated in situ with a U–Pb LA-ICPMS methodology yield an age of 301±15Ma. Compared with previously published data for the east of the TFF, these P–T constraints allow improving the understanding of the Late Paleozoic geodynamic evolution of the South Tien Shan. To the east of TFF, the Turkestan Ocean closed around 320Ma with the collision of the Tarim Craton with the Kazakh microcontinent. To the west of TFF, the Turkestan Ocean closed around 300Ma, when the Alai block collided with the Kazakh microcontinent. This later collision involved nappe-stacking and intense subvertical folding in the western South Tien Shan. This complex folding explains the S-shape of the suture to the west of the TFF that cannot be observed in the eastern part. These new data allow us to propose a distinct tectonic evolution of the two sides of the TFF, which suggests that this fault was a major transform fault before being a strike-slip intra-continental fault.

임진강대의 중부 고생대층: 임진계

1962년 북한 연구자들은 휴전선 이북에 분포된 임진강 유역의 상부고생대 평안계 지층에서 데본기의 것으로 추정되는 완족동물과 극피동물 화석을 찾아 이 화석들을 포함하는 지층을 평안계로부터 분리하여 '임진계'로 설정하였다. 이후 임진계의 여러 분포지에서 발견된 중기 데본기의 차축조(車軸藻, 윤조(輪藻)와 동의어)화석은 그 지질시대를 확정하는 결정적 요소가 되었다. 평남분지와 경기육괴 사이에 분포하는 임진계는 강원도 철원군, 황해북도 금천군, 판문군 및 토산군에 걸치는 동부와, 황해남도 강령군과 옹진군 일원의 서부지역에 대상으로 분포하며, 경기도 북부의 연천층군(변성암복합체)을 포함한다. 해성 무척추 동물화석만 산출되는 하부 고생대층과는 달리 임진계는 다양한 육상 식물화석을 포함한다. 임진계에서 흔히 산출되는 완족동물화석은 남중국대지 데본기 지층에서 알려진 것과 종의 구성에서 유사할 뿐 아니라 남중국대지의 풍토종을 포함하고 있어 두 지역 사이의 고지리적 근연관계를 지시한다. 임진계의 지질시대는 연구자에 따라 견해차는 있으나, 데본기 중-후기로 보는 견해가 지배적이며, 일부 연구자는 데본기 중기-석탄기로 추정하기도 한다. 북한의 연구자들은 데본기에 남중국의 바다가 한반도까지 확장된 '임진해'가 존재하였으며, 따라서 임진계가 현 위치에서 퇴적된 것으로 해석하였다. 임진계는 분포 지역에 따라 심한 층서적 편차를 보이며 국지적으로 두꺼운 층후를 보인다. 최근 북한의 임진계 분포지 도처에서 충상에 의한 지층의 역전과 반복이 보고되었으며, 남한에 분포한 임진계의 연장부인 연천층군의 퇴적기원 변성암 또한 고도의 압축변형작용에 기인한 것으로 알려져, 임진계 분포지 전반에 걸쳐 광범위한 습곡-충상단층대가 형성되었음을 시사한다. 연천층군이 임진강대의 북부로 가면서 점진적으로 고변성대에서 저변성대로 바뀌는 사실로 미루어볼 때, 경기육괴의 북부지역 및 임진강대는 다비-술루(Dabie-Sulu) 벨트의 연장부로 남중국대지와 한중대지의 충돌대였으며, 임진계는 남중국대지의 연장선상에 있었던 경기육괴에서 발달한 퇴적층으로, 남중국대지와 한중대지가 충돌하면서 첨합(accretion)된 잔재로 해석된다. 향후 한반도와 동아시아의 고생대 고지리의 복원과 지각진화사를 심도 있게 이해하기 위하여 임진계의 층서, 퇴적 및 조구조적 진화에 대하여 남북한 관련분야 연구자들이 함께 참여하는 후속연구가 필요하다. 【The 'Imjin System' (or Rimjin System) was established in 1962 as a new stratigraphic unit separated from the Upper Paleozoic Pyeongan System based on the discovery of brachiopods and echinoderms of possible Devonian age. Subsequent discoveries of the Middle Devonian charophytes confirmed the Devonian age of the system. The System is distributed in the Imjingang Belt between the Pyongnam Basin and the Gyeonggi Massif, spans from the eastern areas including Cholwon-gun of the Gangwon Province, Gumchon-gun, Phanmun-gun, and Tosan-gun of the Hwanghaebuk Province, to the western areas of Gangryong-gun and Ongjin-gun of the Hwanghaenam Province, and includes the Yeoncheon Group (metamorphic complex) to the south. Unlike the lower Paleozoic strata in the Pyongnam Basin which solely produce marine invertebrate fossils, the System yields diverse non-marine plant and algal fossils. Brachiopods of the system are similar to those from the Devonian of the South China Block and include taxa endemic to the platform, implying a close paleogeographic affinity to the South China Block. The System is generally considered as of Middle to Late Devonian in age, although there have been suggestions that the system is of the Middle Devonian to Carboniferous in age. North Korean workers postulated that the System was deposited in the current geographic position, where the Imjin Sea (an extension of the South China Platform) was located during the Devonian. The System displays strong local variations in stratigraphy and its thickness. It has recently been reported that the strata are repeated and overturned by thrust faults in many exposures. The Yeoncheon Group a southward extension of the System, also experienced intense tight folding and contractional deformation. Northward decrease in metamorphic grade within the system suggests that the northern part of the Gyeonggi Massif and the Imjingang Belt are probably an extension of the Dabie-Sulu Belt between the South China and Sino-Korean blocks, and the System is an remnant of accretion resulted from the collision between the two blocks. In order to understand tectonic evolution and Paleozoic paleogeography of eastern Asia, further studies on stratigraphic, sedimentologic and tectonic evolution of the System involving scientists from the two Koreas are urgently needed.】

The Structural and Preservation Conditions for Shale Gas Enrichment and High Productivity in the Wufeng—Longmaxi Formation, Southeastern Sichuan Basin

We have analysed the Wufeng–Longmaxi shale gas field (gas pool) in the Southeastern Sichuan Basin in the light of previous studies on the main constraints of shale gas field enrichment in North America. We have demonstrated that, unlike the relatively simple tectonic evolutionary history of its North American counterparts, South China, represented by the Sichuan Basin and its peripheral areas, has undergone multiple uplifting events and intense folding and thrusting processes. After the distribution of high-quality shale formations has been identified, the structural and preservation conditions are important determinants of the level of shale gas enrichment and productivity. For a complex structural area that has experienced high thermal evolution to become enriched in shale gas and highly productive, the following prerequisites are indispensable: (1) normal structures, i.e. uplifts and anticlines, the latter being the most favourable structural type for shale gas enrichment; (2) hyperpressure, which is not only an important identifier of the presence of a regionally closed environment, but also, an important signature of natural gas pool enrichment; (3) late regional strike-slipping processes and good roof and floor conditions—the existence of structural conditions for forming and maintaining a compressional-shearing environment and a roof and floor that provide good closure are critical indicators of shale gas enrichment in complex structural areas; (4) distance to any regional aqueous layers and avoidance of faults channelling these aqueous layers.

Late Cretaceous extension and Palaeogene rotation-related contraction in Central Anatolia recorded in the Ayhan-Büyükkışla basin

The configuration and evolution of subduction zones in the Eastern Mediterranean region in Cretaceous time accommodating Africa–Europe convergence remain poorly quantitatively reconstructed, owing to a lack of kinematic constraints. A recent palaeomagnetic study suggested that the triangular Central Anatolian Crystalline Complex (CACC) consists of three blocks that once formed an ~N–S elongated continental body, underthrusted below ophiolites in Late Cretaceous time. After extensional exhumation and upon Palaeogene collision of the CACC with the Pontides of the southern Eurasian margin, the CACC broke into three fragments that rotated and converged relative to each other. Here, we date the extension and contraction history of the boundary between two of the rotating massifs of the CACC by studying the Upper Cretaceous–Palaeogene Ayhan–Büyükkışla basin. We report an 40Ar/39Ar age of an andesite at the base of the sequence to show that the deposition started in an E–W extensional basin around 72.11 ± 1.46. The basin developed contemporaneously with regional exhumation of the CACC metamorphics. The lower basin sedimentary rocks were unconformably covered by mid-Eocene limestones and redbeds, followed by intense folding and thrust faulting. Two balanced cross-sections in the study area yield a minimum of 17–27 km of post-mid-Eocene ~N–S shortening. We thus demonstrate the Cenozoic compressional nature of the Kırşehir–Niğde-Hırkadağ block boundary and show that the extensional exhumation of the CACC predates collision-related contraction. A plate kinematic scenario is required to explain these observations that involves two Late Cretaceous–Palaeogene subduction zones to the north and south of the CACC, for which we show a possible plate boundary configuration.

Sedimentological evidence of Pleistocene earthquakes in NW Poland induced by glacio-isostatic rebound

Soft-sediment deformation structures are abundantly present in two levels within Warthanian/Eemian lacustrine sediments at Siekierki, near the Polish/German border. The two ‘event horizons’ show intense folding, collapse, sag and load structures, indicative of liquidization and fluidization. The structures must have been caused by sudden shocks, most probably resulting from earthquakes that were induced by glacio-isostatic rebound, probably after the Warthanian deglaciation. Such seismites have not been previously recognized in Polish Quaternary sediments. They provide supporting evidence for glacio-isostatic movements that were interpreted up till now based on drilling, lithostratigraphic, geophysical and geodetic data. The recognition of seismites in NW Poland may help recognize other deformed ‘event horizons’ in Pleistocene sediments as glacio-isostatic or neotectonic seismites.

Ržanovo metamorphosed lateritic Fe-Ni deposit, Republic of Macedonia

The Ržanovo deposit is a unique example of metamorphosed lateritic Fe-Ni deposits in the wellknown Vardar ophiolitic belt of the Balkans, where Fe-Ni mineralization is a product of the Early Cretaceous lateritic weathering mantle after Jurassic ultramafic rocks subsequently redeposited into the Cretaceous shallow-water marine basin. As a result, a layer of Fe-Ni ore 30–50 m thick with an average Ni grade of ∼1% was formed at the Ržanovo deposit; this layer is traced for more than 4 km along the strike and 500 m down the dip. At the end of the Late Cretaceous, intense Alpine tectonic faulting and folding resulted in overturning of the initially horizontal ore layer, which is now nearly vertical. The most abundant fissile hematite ore contains 0.70–1.27% Ni, whereas the economically most important massive hematite ore with 0.93–1.49% Ni occurs locally. The major Ni-bearing minerals are magnetite, hematite, chromite, sulfides, talc, chlorite, amphibole, and stilpnomelane.

Internal crustal deformation in the northern part of Shan-Thai Block: New evidence from paleomagnetic results of Cretaceous and Paleogene redbeds

In order to describe the internal deformation of the northeast part of the Shan-Thai Block resulting from the penetration of the Indian plate into Asia, a paleomagnetic study was carried out on the Cretaceous and Paleogene strata in the southern part of the Simao Terrane. High-temperature magnetic components with unblocking temperatures around 680 °C were isolated and positive fold test shows its primary nature of magnetization. The tilt corrected site-mean directions of the Lower Cretaceous and Upper Cretaceous from the Menglun area are Ds = 46.2°, Is = 45.9°, k = 11.0, α95 = 10.6° and Ds = 33.2°, Is = 30.9°, k = 68.4, α95 = 8.2°, respectively. The site-mean directions of the Upper Cretaceous and Lower Paleogene for the Mengban area are Ds = 50.5°, Is = 31.0°, k = 207.6, α95 = 6.4° and Ds = 43.5°, Is = 23.0°, k = 26.1, a95 = 13.4°, respectively. The results of the Lower Cretaceous and Upper Paleogene from the Mengla area are Ds = 46.9°, Is = 42.2°, k = 27.3, α95 = 7.7° and Ds = 41.8°, Is = 23.8°, k = 38.9°, a95 = 5.8°, respectively. In comparison with previous paleomagnetic data of the Simao Terrane, the rotational deformation can be divided into four stages. The Cretaceous and Paleocene sediments of the Simao Terrane experienced intensive folding before the early Oligocene. During the early Oligocene to early Miocene, the Shan-Thai and Indochina Blocks experienced southeastward extrusion with ~ 20° clockwise rotation relative to the South China Block. During the middle to late Miocene, the Shan-Thai Blocks experienced more 15° clockwise rotation. Since the late Miocene, the activity of strike-slip faults surrounding the Simao Terrane enhanced the internal differential rotations of the Terrane. These deformation processes finally resulted in a complex internal deformation of the Simao Terrane.