Hasil untuk "Stratigraphy"

C. Kooymans, C. W. Magee Jr., K. Waltenberg et al.

<p>This study assesses the effect of chemical abrasion on in situ mass spectrometric isotopic and elemental analyses in zircon. Chemical abrasion improves the U–Pb systematics of SIMS (secondary ion mass spectrometry) analyses of reference zircons, while leaving other isotopic systems largely unchanged. SIMS <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi/><mn mathvariant="normal">206</mn></msup><mi mathvariant="normal">Pb</mi><msup><mo>/</mo><mn mathvariant="normal">238</mn></msup><mi mathvariant="normal">U</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="57pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="0e7f0274f6f359dc8ea519812ebbfe44"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-337-2024-ie00001.svg" width="57pt" height="15pt" src="gchron-6-337-2024-ie00001.png"/></svg:svg></span></span> ages of chemically abraded reference materials TEMORA-2, 91500, QGNG, and OG1 are precise to within 0.25 % to 0.4 % and are within uncertainty of chemically abraded TIMS (thermal ionization mass spectrometry) reference ages, while SIMS <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi/><mn mathvariant="normal">206</mn></msup><mi mathvariant="normal">Pb</mi><msup><mo>/</mo><mn mathvariant="normal">238</mn></msup><mi mathvariant="normal">U</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="57pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="f357d854cd57aae1f270b2d3c0090b15"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-337-2024-ie00002.svg" width="57pt" height="15pt" src="gchron-6-337-2024-ie00002.png"/></svg:svg></span></span> ages of untreated zircons are within uncertainty of TIMS reference ages where chemical abrasion was not used. Chemically abraded and untreated zircons appear to cross-calibrate within uncertainty using all but one possible permutation of reference materials, provided that the corresponding chemically abraded or untreated reference age is used for the appropriate material. In the case of reference zircons QGNG and OG1, which are slightly discordant, the SIMS U–Pb ages of chemically abraded and untreated material differ beyond their respective 95 % confidence intervals.</p> <p>SIMS U–Pb analysis of chemically abraded zircon with multiple growth stages is more difficult to interpret. Treated igneous rims on zircon crystals from the S-type Mount Painter Volcanics are much lower in common Pb than the rims on untreated zircon grains. However, the analyses of chemically abraded material show excess scatter. Chemical abrasion also changes the relative abundance of the ages of zircon cores inherited from the sedimentary protolith, presumably due to some populations being more likely to survive the chemical abrasion process than others. We consider these results from inherited S-type zircon cores to be indicative of results for detrital zircon grains from unmelted sediments.</p> <p><span id="page338"/>Trace element, <span class="inline-formula"><i>δ</i>¹⁸</span>O, and <span class="inline-formula"><i>ε</i></span>Hf analyses were also performed on these zircons. None of these systems showed substantial changes as a result of chemical abrasion. The most discordant reference material, OG1, showed a loss of OH as a result of chemical abrasion, presumably due to dissolution of hydrous metamict domains or thermal dehydration during the annealing step of chemical abrasion. In no case did zircon gain fluorine due to exchange of lattice-bound substituted OH or other anions with fluorine during the HF partial dissolution phase of the chemical abrasion process. As the OG1, QGNG, and TEMORA-2 zircon samples are known to be compositionally inhomogeneous in trace element composition, spot-to-spot differences dominated the trace element results. Even the 91500 megacrystic zircon pieces exhibited substantial chip-to-chip variation. The light rare earth elements (LREEs) in chemically abraded OG1 and TEMORA-2 were lower than in the untreated samples. Ti concentration and phosphorus saturation ((<span class="inline-formula"><i>Y</i></span> <span class="inline-formula">+</span> REE) <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="fb147fccdcf98a9911cf3d26a8f6dc33"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-337-2024-ie00003.svg" width="8pt" height="14pt" src="gchron-6-337-2024-ie00003.png"/></svg:svg></span></span> P) were generally unchanged in all samples.</p>

O. V. Yakubovich, O. V. Yakubovich, N. P. Konstantinova et al.

<p>We propose an analytical approach for (U–Th) <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e653eaf840568ee76bb20ba3bf368ae0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-653-2024-ie00004.svg" width="8pt" height="14pt" src="gchron-6-653-2024-ie00004.png"/></svg:svg></span></span> He dating of Fe-(oxyhydr)oxides that includes sealing samples in quartz ampoules and demonstrates its suitability as a reliable tool for the investigation of geological processes. The (U–Th) <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="57ee8123d9c9aefcf23d9c7f6463c158"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-653-2024-ie00005.svg" width="8pt" height="14pt" src="gchron-6-653-2024-ie00005.png"/></svg:svg></span></span> He ages of goethite clasts and veins from Fe- and Mn-oxide cemented rocks recovered from the slope of the Chukchi Borderland in the Amerasia Basin demonstrate reproducibility, yielding a weighted mean age of 8.6 <span class="inline-formula">±</span> 0.3 Ma (<span class="inline-formula"><i>n</i>=4</span>) and 4.8 <span class="inline-formula">±</span> 0.4 Ma (<span class="inline-formula"><i>n</i>=2</span>), respectively, providing insights into the Neogene mineralization history of the region. This study also focuses on the sample preparation technique, which might influence the (U–Th) <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="880d1b22cfae9b4167ff115d05c6894c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-653-2024-ie00006.svg" width="8pt" height="14pt" src="gchron-6-653-2024-ie00006.png"/></svg:svg></span></span> He ages. Our data indicate that some of U can be leached from the goethite during sonication by distilled water, which might result in erroneous (U–Th) <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="3af55808dad7e355d8e0b0b2a0272ce7"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-653-2024-ie00007.svg" width="8pt" height="14pt" src="gchron-6-653-2024-ie00007.png"/></svg:svg></span></span> He ages of multi-mineral grains. However, the analyzed goethite samples were formed in a specific underwater environment; so far it is not clear whether the same behavior of U would be observed in a terrestrial supergene goethite.</p>

C. Glotzbach, T. A. Ehlers, T. A. Ehlers

<p>Recent applications of the in situ (U–Th–Sm) <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e653eaf840568ee76bb20ba3bf368ae0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-697-2024-ie00004.svg" width="8pt" height="14pt" src="gchron-6-697-2024-ie00004.png"/></svg:svg></span></span> He thermochronometry technique demonstrate its potential to address some of the analytical challenges associated with the whole-grain technique. In this study, we adapted state-of-the-art apatite and zircon production–ejection–diffusion models for application to in situ dating methods, aiming to enhance the applicability of this technique to a broad range of geologic samples and applications. Our modifications to thermal history models include accommodation of the full range of stopping distances for alpha particles and cylindrical grain geometries. This investigation focuses on several key aspects of in situ data interpretation: (i) exploring the relationship between in situ dates and the position of ablation spots across individual grains, (ii) assessing differences and similarities between whole-grain and in situ dates, (iii) determining optimal strategies and performance for reconstructing cooling histories from in situ (U–Th–Sm) <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="57ee8123d9c9aefcf23d9c7f6463c158"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-697-2024-ie00005.svg" width="8pt" height="14pt" src="gchron-6-697-2024-ie00005.png"/></svg:svg></span></span> He data, and (iv) reporting the effects of radionuclide zoning on (U–Th–Sm) <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="93e47eb16cb371fe6916d3191efc4f1d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-697-2024-ie00006.svg" width="8pt" height="14pt" src="gchron-6-697-2024-ie00006.png"/></svg:svg></span></span> He thermochronology. Results indicate that the measured in situ helium distribution is a function of grain size, ablation spot position and size, and cooling history. Together, these analytical and natural factors result in systematic variations in in situ dates with distance from the grain rim. Therefore, similar to whole-grain analyses, robust interpretation requires determining grain geometry and the distance of the laser spot from the nearest prismatic face. In most cases, resulting in situ dates are approximately 30 % older than corresponding alpha-ejection-corrected whole-grain dates, irrespective of the cooling rate and grain size. Whole-grain and in situ dates are similar solely for gem-sized samples or samples exhibiting negligible diffusional helium loss and thus spent more time at surface temperatures compared to their transit time through the partial retention zone. Reconstruction of cooling histories using in situ (U–Th–Sm) <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="073414a2b77546d8d5847ae97897d626"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-697-2024-ie00007.svg" width="8pt" height="14pt" src="gchron-6-697-2024-ie00007.png"/></svg:svg></span></span> He data can be achieved through single measurements in several grains with varying grain size and/or effective uranium content or within a single grain with measurements taken at different distances from the grain rim. In addition, statistical analysis of a large compilation of measured radionuclide variations in apatite and zircon grains reveals that radionuclide zoning strongly impacts whole-grain analyses but can be directly measured with the in situ method. Overall, our results suggest that in situ measurements for (U–Th–Sm) <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mo>/</mo></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="36bd7baae116a5efc17e692d563c2b51"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-697-2024-ie00008.svg" width="8pt" height="14pt" src="gchron-6-697-2024-ie00008.png"/></svg:svg></span></span> He date determination offer a means to extract meaningful cooling signals from samples with poor reproducibility from traditional whole-grain techniques.</p>

Narges Nabizadeh Chamazcoti, Gholam Hossein Karami, Azizollah Taheri et al.

AbstractThe Nekarood basin is located in the north of Iran and has an area of 2275 km2. In the Nekarood Basin, the majority of limestones include thick bedded and massive limestones of Lar and Cretaceous limestones, and there is also a lesser amount of Elika, Dalichai and Ruteh limestones. Various features such as the amount of outcrop, thickness and lithological characteristics of karst rocks and their relationship to other lithologies on a regional scale are the geological controls on karst development. Among these factors, the thickness and lithology of the existing formations in the studied area are of great importance, in such a way that if the outcropping limestone is thick bedded and massive, the karstification process is very high. The stratigraphy of the region and the spread of The Lar limestones in the region are among the reasons for the dominance of the conduit flow system in this basin. Stratigraphy has an effective role in the development of karst and the spatial distribution of the amount of recharge in the formations of the studied area, and by considering the effect of factors affecting recharge using GIS and remote sensing, the status of the hydrogeological budget of karst in the region is investigated. Estimating the amount of recharge is also one of the most important parameters in hydrogeological studies for calculating the budget. The recharge potential map was prepared using several layers of information, including lithology, slope, aspect, density of streams, precipitation, density of fractures and epikarst, after weighting by expert method and integrating information in the Geographic Information System (GIS) environment. According to the obtained results, the desired area is divided into five sections with 12, 20, 28, 36 and 48% recharge potential, and the corresponding area of each section is 50, 360, 877,817, and 5 km2, respectively. The average recharge in the whole range was estimated to be about 29%. Based on the amount of recharge and average annual precipitation (430 mm), the total amount of recharge in the Nekarood karst basin is estimated to be about 261 million cubic meters (MCM), of which about 64 MCMis discharged by springs and wells in the karst basin, so the annual discharge volume in this area is more than the annual discharge volume of about 197 MCM. Considering the location of the Nekarood karst basin near the Caspian Sea and the existence of faults in this area, it can be stated that, most likely, part of the water recharge in this basin is discharged to the sea.Keywords: Karst, Stratigraphy, Recharge potential, Discharge to the sea  IntroductionAccording to the definition of Ford and Williams, karst is a basin with a specific hydrology and morphology, which was created by high dissolution of rock and high development of secondary porosity (Williams & Ford 2007). Karst groundwater is one of the most important sources of groundwater worldwide. Due to the expansion and diversity of carbonate formations, more than 25% of the world's population gets their drinking water from karst underground aquifers (Williams & Ford 2007; Liu et al. 2019; Hao et al. 2021).  As a coastal karst aquifer, the Nekarood karst basin can drain its water into the Caspian Sea through alluvium, faults and deep dissolution channels. Due to the climatic conditions (high rainfall) and stratigraphy in this region, no estimation of the amount of recharge in this basin has been done so far. The main purpose of this research is to investigate the role of stratigraphy in the development of karst and the spatial expansion of the amount of recharge in the formations of the region, with considering the effect of factors affecting recharge by using GIS and remote sensing, to investigate the karst hydrogeological balance in this area and the amount of recharge. Materials & MethodsIn order to investigate the role of stratigraphy on the development of karst in the Nekarood Basin, firstly, field studies were conducted regarding the stratigraphy and formations of the area. Then hydrogeological studies were conducted in this basin. Important layers of information affecting recharge, including lithology, amount of slope, aspect, density of streams, precipitation, density of fractures and epikarst have been prepared. According to the nature of each factor, their role in the amount of recharge has been determined. After weighing, these information layers were prepared using an integrated GIS and map of recharge potential. Then the water balance of the karst basin was estimated according to the amount of feeding, precipitation and discharge. Discussion of Results & ConclusionsIn the Nekarood Basin, the majority of limestone includes thick bedded and massive limestones of Lar and Cretaceous limestones, and there are also dolomitic limestones, Elika, Delichai and Ruteh limestones in a smaller amount. There are about 716 springs in this basin, of which four springs (Sanbi, Espeh O, Jezi and Kaocheshmeh) have a flow of more than 10 liters per second and are located in the Lar Formation in this basin. The Lar limestone formation in this basin consists of thick bedded to massive limestones and hydrogeologically has a high potential of karstification. Also, there are a lot of dissolution features as well as caves in these limestones. The existence of three important faults in this basin, namely the Caspian Fault, the North Alborz Fault and the Nekarood Fault, has also been one of the important factors in the development of karst in this basin. The flow system in the Lar Formation, which is dominated by lithology, is a conduit system type. Examining the temporal changes of physical (such as discharge) and chemical (electrical conductivity) characteristics also shows that the variability of these parameters is high for the mentioned springs, which indicates the dominant conduit system in this basin and the development of the karst phenomenon in this area. To determine the recharge potential in the study area, factors affecting recharge were classified, and based on expert judgment, points from 2 to 8 were considered for them. Based on this classification, wherever the factor has a score of 8, it has the greatest impact on recharge, and wherever the score is 2, it has the least impact on recharge. Based on the effective factors, the average recharge percentage in this basin is estimated at 29 percent.Based on the investigations conducted in the Nekarood karst area, it can be seen that in some parts of this karst basin, the degree of karst development is more evident, and the dominant system is conduit flow. Therefore, the main factor of karst development and the dominance of conduit flow system in parts of this basin is thick bedded and massive limestone. In order to estimate the percentage of annual recharge potential in hydrogeological balance studies, in addition to stratigraphy, the influential factors of density of faults and fractures, rainfall, amount of slope, direction of slope, karst effects, density of waterways and soil cover have also been used. Using the GIS, the influencing factors in the recharge potential have been evaluated and weighed, and finally, the recharge potential map has been prepared. According to the recharge potential map, the highest amount of recharge is related to the thick limestones of the Lar and Cretaceous layers, which include about 36 to 45% of the recharge potential. The annual recharge in this area was about 261 MCM. The total annual discharge volume of springs and wells was about 64 MCM, and the difference between recharge and discharge is about 197 MCM. Considering that the groundwater tends to move towards the base level of erosion and due to the shape of the basin as well as the presence of large faults and bedrock in the region, it is likely that a part of the recharge water is discharged to the alluvium and the Caspian Sea. However, the estimation of the amount of recharge due to the factors affecting the recharge is associated with uncertainty, which can be reduced by using isotopic and hydrogeochemical samples in the area of water exit from the basin and achieving a favorable result.

Rebecca J. Sanderson, Neil Ross, Kate Winter et al.

An array of information about the Antarctic ice sheet can be extracted from ice-sheet internal architecture imaged by airborne ice-penetrating radar surveys. We identify, trace and date three key internal reflection horizons (IRHs) across multiple radar surveys from South Pole to Dome A, East Antarctica. Ages of ~38 ± 2.2, ~90 ± 3.6 and ~162 ± 6.7 ka are assigned to the three IRHs, with verification of the upper IRH age from the South Pole ice core. The resultant englacial stratigraphy is used to identify the locations of the oldest ice, specifically in the upper Byrd Glacier catchment and the Gamburtsev Subglacial Mountains. The distinct glaciological conditions of the Gamburtsev Mountains, including slower ice flow, low geothermal heat flux and frozen base, make it the more likely to host the oldest ice. We also observe a distinct drawdown of IRH geometry around South Pole, indicative of melting from enhanced geothermal heat flux or the removal of deeper, older ice under a previous faster ice flow regime. Our traced IRHs underpin the wider objective to develop a continental-scale database of IRHs which will constrain and validate future ice-sheet modelling and the history of the Antarctic ice sheet.

Kai Wang, Hong-He Xu, Bing-Cai Liu et al.

Summary: Testate amoebae, a polyphyletic protist group inhabiting a wide variety of extant ecosystems, have evolved as far back as early Neoproterozoic. However, their fossil record is discontinuous and biased toward empty shells. Here, we report an arcellinid testate amoeba species, Cangwuella ampulliformis gen. nov., sp. nov., from a shallow-marine community in the Early Devonian of Guangxi, southwestern China. With the aid of scanning electron microscopy and X-ray micro-tomography, we find that the shell of our testate amoeba contains some acetabuliform structures. Although such configuration does not match exactly with the known internal structures in extant testate amoebae, our fossils highlight the potential of exploring the ecological relationships between fossil testate amoebae and their associated organisms, and increase our knowledge on the diversity of testate amoebae in Early Devonian environments.

Ya-Lei Yin, Cheng Ji, Min Zhou

The palatal anatomy of ichthyosauriforms remains largely unknown. Here, the complete palate of the early-branching ichthyosauriform Chaohusaurus brevifemoralis is reconstructed and described for the first time with the assistance of high-resolution X-ray computed tomography (CT) scanning on the basis of the three-dimensionally preserved skull of its paratype (GMPKU-P-3086) from the Lower Triassic of South China. The reconstruction reveals new palatal features of C. brevifemoralis. The palatine contacts the jugal directly, which is observed in ichthyosauriforms for the first time. A single row of denticles is present on each side of the palate. The vomer exceeds the anterior and posterior margins of the internal naris. The pterygoid is posterior to the internal naris. The epipterygoid is present and the ectopterygoid is absent.

Xuefang Wei, Rodrigo Vargas Pêgas, Caizhi Shen et al.

Anurognathids are an elusive group of diminutive, potentially arboreal pterosaurs. Even though their monophyly has been well-supported, their intrarelationships have been obscure, and their phylogenetic placement even more. In the present work, we present a new genus and species from the Middle-Late Jurassic Tiaojishan Formation, the third nominal anurognathid species from the Jurassic of China. The new species provides new information concerning morphological diversity for the group. Furthermore, we provide a new phylogenetic analysis incorporating into a single data set characters from diverging phylogenetic proposals. Our results place them as the sister-group of Darwinoptera + Pterodactyloidea, as basal members of the Monofenestrata.

Yuryi L. Rebetsky

In the article by N.A. Sycheva and L.M. Bogomolov, the authors proposed to combine the interrelated data on the stress drop in the earthquake sources, ∆σ, and reduced seismic energy, ePR, to analyze the dependence of these parameters on earthquake scale along with expansion of the measurement statistics (assessments). The dependence of these parameters of a source on the seismic moment or on the earthquake magnitude within 2.2 ≤ М ≤ 4.0 magnitude range has been determined using the example of the Northern Tien Shan (Bishkek geodynamic polygon with the KNET network). The author of the letter to the editor notes the article conclusions to be limited, because such relationship is only manifested within the more or less narrow range of the magnitudes. Attention is also drawn to the semantic difference between the ∆σ and ePR parameters. It is the reduced seismic energy that reflects the mean strain in the source area, and its appliance to the analysis of scale dependences of earthquake sources is more informative.

Qingshan LI, Shaobin GUO, Zesheng HOU et al.

The Qaidam Basin is a large transpressional Mesozoic to Cenozoic basin in the Tibet Plateau, West China. Since the Indosinian Movement, it has been in the subsidence stage and more than 3 trillion cubic meters of natural gas accumulated at the same time. The palaeoclimate evolution during the Pliocene Shizigou stage not only controlled sequence stratigraphy development and evolution, but also worked as a key restraining factor for the largest biogas resource in the world. A case study was made in the well Qijia 1, which is the longest cored well in the Qaidam Basin. The palaeoclimate evolution during the Shizigou stage was reconstructed by using geochemistry methods, including the contents of chloride ion, trace elements and TOC, combined with core data, well logging, paleontology data and sequence stratigraphy. The contents of Sr/Ba and Sr/Ca have a positive correlation with chloride ion, which means that the values of Sr/Ba and Sr/Ca are high in an arid environment. But the contents of Rb/Sr and TOC have a negative correlation with chloride ion, which means that the values of Rb/Sr and TOC are low in an arid environment. The palaeoclimate during the Shizigou stage came through an arid-humid-arid evolution and the water body is brackish water. Based on sequence stratigraphy, five sub-palaeoclimate cycles were recognized for the first time. The palaeoclimate evolution and sequence evolution have the same cyclicity, which shows the controlling function of palaeoclimate.

S. Mock, C. von Hagke, C. von Hagke et al.

<p>In this paper, we present new exhumation ages for the imbricated proximal molasse, i.e. Subalpine Molasse, of the northern Central Alps. Based on apatite <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>-</mo><mi mathvariant="normal">Sm</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="82pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="85cd7cfabec0782a4966b7435f363872"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="se-11-1823-2020-ie00001.svg" width="82pt" height="14pt" src="se-11-1823-2020-ie00001.png"/></svg:svg></span></span> thermochronometry, we constrain thrust-driven exhumation in the Subalpine Molasse between 12 and 4&thinsp;Ma. This occurs synchronously to the main deformation in the adjacent Jura fold-and-thrust belt farther north and to the late stage of thrust-related exhumation of the basement massifs (i.e. external crystalline massifs) in the hinterland. Our results agree with other findings along the north Alpine foreland. While site-specific variations in the mechanical stratigraphy of the molasse deposits influence the pattern of thrusting at the local scale, we observe that late-Miocene thrusting is a long-wavelength feature occurring along the north Alpine foreland roughly between Lake Geneva and Salzburg. The extent of this thrusting signal as well as the timing suggests that late-Miocene thrusting in the north Alpine foreland coincides with the geometries and dynamics of the attached Central Alpine slab at depth. Interestingly, this implies that the slab geometry at depth does not coincide with the boundary between the Eastern and Central Alps as observed in the surface geology. Using this observation, we propose that thrusting in the Subalpine Molasse and consequently also the late stage of thrust-related exhumation of the external crystalline massifs, as well as the main deformation in the Jura fold-and-thrust belt are at least partly linked to changes in slab dynamics.</p>

Dmytro Haskevych, Eiko Endo, Dai Kunikita et al.

Ideas about the origin of the Buh-Dnister Culture under the influence of the Danube Early Neolithic were questioned by series of radiocarbon dates falling into the second half of the 7th millennium BC measured on bones at the Kyiv laboratory in 1998–2004. To start addressing this problem, 11 AMS dates on organic inclusions in the ceramic paste and charred residues on the surface of vessels were obtained at the Tokyo University laboratory. Apart from two heavily overestimated values, measured on samples with very low carbon content, they fall into the range of the 60th–46th century BC that correspond better to the primary views of this chronology. However, the issues of the time and direction of spreading of the first pottery in the region need further research.

W. Helland‐Hansen, J. Gjelberg

M.A. Soboleva, D.B. Sobolev

The main features of the Upper Devonian sediments on the right side of the Ostantsovy Creek (the left tributary of the Malaya Usa River) in the eastern part of the Bielsko-Eletskaya structural formational belt on the western slope of the Polar Urals have been considered. The late Frasnian age of these sediments has been determined on the basis of conodonts (the linguiformis zone of the standard conodont scale). The transition from clastic and organic limestones with massive stromatoporoid forms to limestones with fused (reservoir) stromatoporoid forms and Palmatolepis biofacies is indicative of the transgressive shift of the linguiformis phase. This transgressive level is an indirect expression of the Upper Kellwasser global event.

P. Koch, J. Zachos, D. Dettman

Virgínio Henrique Neumann, Dunaldson E. G. A. Rocha

L. Akhmetshina, A. Kan

O. VIDAL-ROYO, J.A. MUÑOZ, S. HARDY et al.

This paper reports on the integration of different modelling techniques to construct a unified conceptual model of structural evolution of the Pico del Águila anticline (External Sierras, southern Pyrenees, Spain). The structure is a well-known example of a detachment fold, which exhibits a N-S structural trend, perpendicular to the general structural trend of the southern Pyrenees (mainly E-W). Based on field observations of an unevenly distributed Triassic décollement, analogue modelling shows how to generate orogen-perpendicular structures which may result in transverse anticlines. The models show how contrasts between high and low friction patches in the basal décollement led to the formation of structures at high angle, centered over the high friction areas. Numerical models investigate the effect of a complex mechanical stratigraphy, characterized by an interlayering of competent and incompetent layers, plus syn-kinematic sedimentation in the fold growth. Based on field data and seismic interpretations, a 3D reconstruction and sequential geomechanical restoration of the Pico del Águila anticline suggests the coexistence of multiple folding mechanisms occurring simultaneously in different units and structural domains of the fold, leading to a complex strain pattern that can not be assessed by simplistic kinematic 2D approaches. By integrating the models with previous data in the region, the benefits and drawbacks of each modelling technique are discussed and an integrated model of structural evolution for the Pico del Águila anticline is presented. This enables a better comprehension of the structure as well as of the processes that drove the evolution of the N-S detachment anticlines in the External Sierras of the southern Pyrenees.