Abstract Background The Chenghai-Binchuan fault zone in northwestern Yunnan Province, China, is a tectonically active structure with frequent paleo-landslides, largely controlled by normal faulting and left-lateral strike-slip motion. Methods To systematically investigate their formation mechanisms, and chronological evolution, To examine their formation and chronology, 284 landslides across representative zones were analyzed, with selected cases field-investigated to characterize morphology and classify failure mechanisms. Field investigations combined with OSL and ESR dating were used to estimate the timing of the major landslide events. Results Field observations show that paleo-landslides are strongly concentrated along active fault traces, and that some of them exhibit large, coherent accumulations with well-preserved stratigraphy, long horizontal runouts with limited vertical displacement, whereas others display pronounced creep deformation characteristics, together with steep rear scarps and well-developed tensile fractures. Their kinematic features include bedding-controlled creep, tensile-fracture sliding, ejection, and widely distributed shallow instability or collapse. Chronological analyses reveal that large paleo-landslides occurred between 485 ± 32 ka and 13.0 ± 0.7 ka, accompanied by long-lived landslide-dammed lakes. The integrated evidence indicates that strong fault–slope coupling, expressed through long-term creep weakening and abrupt seismic acceleration, exerts the primary control on the initiation, evolution, and spatial clustering of major paleo-landslides. Conclusion These findings provide new insights into the mechanisms and temporal evolution of fault-controlled paleo-landslides and their implications for landscape development in seismically active regions.
Jianhao Liang, Yaning Wang, Shangfeng Zhang
et al.
This study has determined the period of sedimentation of the Lingshui Formation as the Oligocene (Rupelian-Chattian) through biostratigraphic data, including planktonic foraminifera zonation. The astronomical timescale framework for the Lingshui Formation was accurately constructed by integrating geophysical logging data and employing a multidisciplinary approach that includes time series analysis, cyclostratigraphy, astronomical dating, and Power Ratio Accumulation (PRA) methods. Sensitivity analysis of PRA has shown that natural gamma (GR) is the optimal paleoclimatic proxy, laying the foundation for subsequent analyses. The optimal sedimentation rate for the Lingshui Formation, determined by combining the coefficient of correlation (COCO) method with PRA analysis, is 5–5.4 cm/kyr. The duration of the Lingshui Formation was established at 5.02 Ma (28.52 Ma–23.5 Ma) based on time series analysis and astronomical tuning. The sediment noise model has revealed that the ~1.2 Myr obliquity modulation period has a significant impact on sea-level changes, further confirming the stratigraphic control of astronomical forcing on the sedimentation rate of the Lingshui Formation. This study establishes a high-precision astronomical timescale framework for the Lingshui Formation and provides a robust methodology, offering scientific basis for the research in astronomical chronostratigraphy and cycle stratigraphy, which has significant potential implications.
T. M. Weitkamp, T. M. Weitkamp, M. J. Razmjooei
et al.
<p>Deep Sea Drilling Project (DSDP) Site 407, located near the Reykjanes Ridge (southwest of Iceland) offers a rare and extensive record of Late Cenozoic planktonic foraminifera evolution spanning the Neogene and Quaternary periods. This ca. 300 m sequence provides a nearly continuous record of planktonic foraminifera with mostly good preservation quality, aiding the study of pelagic diversity changes over the past 25 million years as the modern North Atlantic Ocean system evolved. Initially investigated in 1979 by Poore, this study presents a taxonomic reassessment of upper Oligocene to Pleistocene planktonic foraminifera at Site 407, including species range documentation, assemblage analysis, biostratigraphic zonation, and age modelling based on planktonic foraminifera, calcareous nannofossils, and scanning electron microscopy. This study employs modern taxonomic perspectives that integrate morphological and stratophenetic frameworks for fossil species with genetic data for taxa having living representatives. Systematic species counts enable quantitative diversity analysis, with a particular focus on the genus <i>Neogloboquadrina</i>, which becomes increasingly prevalent at Site 407 from the late Neogene to Quaternary. The planktonic foraminifera assemblages at Site 407 exhibit a contraction in diversity and a shift in species dominance, notably around 160 m b.s.f. (metres below seafloor) (ca. 8.9–16.5 Ma) and 56 m b.s.f. (ca. 2–3.4 Ma). The upper Oligocene and lower Miocene include species belonging to the genera <i>Catapsydrax</i>, <i>Globoturborotalita</i>, <i>Dentoglobigerina</i>, and <i>Paragloborotalia</i>. An acme of “<i>Ciperoella</i>” <i>pseudociperoensis</i> (lower and middle Miocene), still of uncertain generic affiliation, may have biostratigraphic use. Well-preserved <i>Turborotalita quinqueloba</i> are relatively common throughout the sequence. In Oligocene and Miocene material, <i>T. quinqueloba</i> is accompanied by <i>Tenuitella</i> spp. From the upper Miocene onwards, neogloboquadrinids including <i>Neogloboquadrina praeatlantica</i>, <i>N. atlantica</i>, <i>N. incompta</i>, and <i>N. pachyderma</i> become increasingly common and dominate Pliocene assemblages, together with <i>Globigerina bulloides</i>. Assemblages with an increasingly high-latitude nature, i.e. where <i>N. pachyderma</i> dominates, take over in the lower Pleistocene. Multiple hiatuses are recorded, of which the largest is ca. 8 million years long, separating the middle and upper Miocene (8.9–16.5 Ma; 158.56–160.06 m b.s.f.). Continuous biozonation at Site 407 is challenged by limited species diversity and the absence of standard low-latitude biozone markers, rendering standard schemes ineffective. Recognizable biozones include the low-latitude O7 and M1 Zones in the late Oligocene and early Miocene, respectively; the high-latitude <i>Neogloboquadrina atlantica</i> sinistral Zone in the late Miocene and Pliocene; the <i>Globoconella inflata</i> Zone in the late Pliocene; and the <i>Neogloboquadrina pachyderma</i> Zone in the Pleistocene. The nannofossil biozonation faces similar challenges. A revised biostratigraphic age model integrates calibrated planktonic foraminifera and nannofossil events, incorporating abundant species like “<i>C.</i>” <i>pseudociperoensis</i>, <i>N. atlantica</i> dextral and sinistral, <i>Globoconella puncticulata</i>, <i>G. inflata</i>, and <i>N. pachyderma</i>. These findings are expected to contribute to the Neogene–Quaternary Middle Atlas of planktonic foraminifera and potentially improve the use of neogloboquadrinids in palaeoceanography and biostratigraphy.</p>
Karen Fontijn, Benjamin Bernard, Drew Downs
et al.
Volcano-geologic mapping and stratigraphic reconstructions provide important information toward understanding patterns of edifice construction and destruction of volcanic systems, their eruptive histories and recurrence rates, and magmatic evolution and plumbing systems, all of which are required to make informed hazard assessments. Geologic mapping of volcanic terrains also provides context in the search for and identification of natural resources, including geothermal reservoirs and magmatic-related ore deposits, and can provide useful background for communication and outreach. Most volcano-geologic maps and chrono-stratigraphic frameworks are based on a systematic lithostratigraphic approach and are constructed using an iterative process whereby field observations and mapping alternate with acquisition of rock compositional and geochronological data. Modern technological and analytical tools have greatly advanced geochemical and geochronological data acquisition and accuracy, while some technologies have provided new useful tools for fieldwork, including in poorly accessible environments.
The rates of incision and aggradation in the channels in the Terek River basin (North Caucasus) for the last 50–85 years were estimated at 18 gauging stations. The stage–discharge method (annual low water stages at the same discharges) was applied. The stability of the Terek River channel was recorded on the tectonically subsiding Tersko–Kuma Lowland. On the subsiding Kabardian Plain, channel aggradation up to 14 mm a<sup>−1</sup> was registered. The rapid (~32 mm a<sup>−1</sup>) incision of the Terek River occurs within the antecedent valley of the rising Sunzha Ridge, causing regressive erosion and incision (~25 mm a<sup>−1</sup>) of rivers on the Ossetian Plain, despite its tectonic subsiding. The rivers in the uplifting mountains of the North Caucasus transport the sediments delivered from slopes as climatically controlled debris flows. Aggradation and incision here alternate without a visible overall trend. The rates of modern channel bed deformations are 10 to 100 times higher than the mean rates of tectonic movements. The main effect of tectonics is the changes in river channel slopes, which cause changes in the bed load transport budget and channel bed deformation. Human-made constructions induce rapid deformations in the channels but have a local effect.
The purpose of this research is to establish the relationship between the gold grades and the various pebble sizes from a mine. This objective was reached by choosing parameters of interest from the logging and sampling data, lithological data and assay data from the mine. These parameters were further processed using Microsoft Excel to plot graph of pebble size against gold grade. In order to build a concrete ground for the analysis, an average gold grade for the various samples used was calculated and compared to the cut-off grade at the Mine which is 0.45g/t. Upon further analysis, it was observed that, gold grade which are considered economically feasible at the mine is associated with the coarse pebbles, which has a diameter range of (5mm-30mm) and those which are considered as waste are associated with the fine pebbles (less than 5mm diameter). Some of these coarser pebbles are not economically feasible, since their average gold grade when calculated falls below the cut-off grade at the mine. The mode of deposition as well as the topography of the medium at the time of deposition of gold determine the gold grade of a reef. The degree of roundness and sorting of the conglomerates associated with mineralization as well as ore dilution within the depositional medium by the pebbly quartzite and quartzite waste account for the fall in gold grade of the reef.
Attic black-glazed pottery takes a special place among the many artifacts found during archaeological excavations. Its chronology, done based on mass finds at reference sites, especially in Athens, is a reliable basis for dating such ceramics in all state formations of the Northern Black Sea region, which gives it the importance of a chronoindicator. The dating of certain types of tableware, in particular bowls and salt cellars, together with studies of the stratigraphy of the sites, makes it possible to analyze the composition of Attic black-glazed pottery and to ascertain its quantitative indicators for a certain period. This, in turn, contributes to the study of a much wider range of issues related to the development of trade and economic relations of a particular center and the region as a whole with the ancient Mediterranean.
Bowls of various shapes and sizes belong to the category of mass ceramic material not only from Olbia and Berezan but also from all, without exception, ancient cities and settlements. They, including the black-glazed items, were popular during all periods. It is interesting that despite a large amount of similar tableware of local production and the production of neighboring centers, the number of black-glazed imported produced items in Olbia did not decrease. Peaks of the popularity of some types of shapes are traced, however, in all studied periods black-glazed bowls of Attic production are present almost in equal quantity. That is why this issue is relevant for the study of all sites of the Early Iron Age, because Attic ceremonial tableware is found on the whole territory of Ukraine, not only at ancient sites.
Detailed dating of bowls can favor in setting the dates of entire complexes and sites. In the course of the study, a selection of 402 bowls and salt shakers of various types from Olbia (acropolis and necropolis of the city) was made. According to the results of its quantitative and qualitative analysis, we can trace the dynamics of the delivery of different types of tableware to Olbia market from Attica in the period from 500 to 310 BCE. Such an analysis allows revealing the chronological context of the development of certain types of bowls and salt cellars as well as certain trends in the incoming delivery of their different types from Attica to Olbia.
<p>Assessing the size of a former ocean of which only remnants are found in mountain belts is challenging but crucial to understanding subduction and exhumation processes. Here we present new constraints on the opening and width of the Piemont–Liguria (PL) Ocean, known as the Alpine Tethys together with the Valais Basin. We use a regional tectonic reconstruction of the Western Mediterranean–Alpine area, implemented into a global plate motion model with lithospheric deformation, and 2D thermo-mechanical modeling of the rifting phase to test our kinematic reconstructions for geodynamic consistency. Our model fits well with independent datasets (i.e., ages of syn-rift sediments, rift-related fault activity, and mafic rocks) and shows that, between Europe and northern Adria, the PL Basin opened in four stages: (1) rifting of the proximal continental margin in the Early Jurassic (200–180 Ma), (2) hyper-extension of the distal margin in the Early to Middle Jurassic (180–165 Ma), (3) ocean–continent transition (OCT) formation with mantle exhumation and MORB-type magmatism in the Middle–Late Jurassic (165–154 Ma), and (4) breakup and mature oceanic spreading mostly in the Late Jurassic (154–145 Ma). Spreading was slow to ultra-slow (max. 22 <span class="inline-formula">mm yr<sup>−1</sup></span>, full rate) and decreased to <span class="inline-formula">∼5</span>1 <span class="inline-formula">mm yr<sup>−1</sup></span> after 145 Ma while completely ceasing at about 130 Ma due to the motion of Iberia relative to Europe during the opening of the North Atlantic. The final width of the PL mature (“true”) oceanic crust reached a maximum of 250 km along a NW–SE transect between Europe and northwestern Adria. Plate convergence along that same transect has reached 680 km since 84 Ma (420 km between 84–35 Ma, 260 km between 35–0 Ma), which greatly exceeds the width of the ocean. We suggest that at least 63 % of the subducted and accreted material was highly thinned continental lithosphere and most of the Alpine Tethys units exhumed today derived from OCT zones. Our work highlights the significant proportion of distal rifted continental margins involved in subduction and exhumation processes and provides quantitative estimates for future geodynamic modeling and a better understanding of the Alpine Orogeny.</p>
The Ebeko volcano located in the northern part of Paramushir Island (Northern Kuril Islands) is currently the most active volcano of the Kuril Island arc: since 2016, next explosive eruption has continued, proceeding in the form of regular ash-gas explosions of moderate force. In the period from January 2018 to October of 2020 a total of at least 1834 emissions were recorded (during daylight hours and under good weather conditions). In May–July 2020, the intensification of the eruptive activity of the volcano was observed, that manifested in a sharp increase of the emissions frequency and height. During this period, 296 emissions were recorded, 90 of which were at an altitude of 3 km or more.
Majstorska Cesta is a historical road along Velebit Mt., NW of Sveti Rok, preserved in its original state since opening in 1832 and therefore added to the cultural heritage list of the Republic of Croatia in 2007. The road passes through sedimentary rocks ranging in age from Upper Carboniferous to Upper Paleogene, i.e. from 315 Ma until approx. 25 Ma old rocks (a time span of 290 Ma). These are mostly well exposed limestones and dolomites, sporadically clastics. Such rocks build up not only Velebit Mt., but also the entire Karst Dinarides. As such, they represent a unique natural museum important not only for the Croatian landscape, but also for all countries with shallow marine carbonates in the Mediterranean Region and wider, i.e. areas of Mexico, the Caribbean, along mountains like the Atlas, the Pyreneans, the Alps, the Carpathians, the Dinarides, the Helenides, the Pontides, the Taurides, the Iranides and the Himalayas. The most important geological feature is a section from Mali Alan Saddle to Tulove Grede Ridge. It is a continuous section along the Jurassic carbonates, typical for the Karst Dinarides, of stratigraphic period from Hettangian to Middle Tithonian (201.3-148 Ma), comprising the typical (index) fossils and complete geological rock sections, including contact between Jurassic and Triassic rocks. The authors have researched Velebit Mt. since 1962 until recent times, and thus recognize the necessity to preserve the described Jurassic rock outcrops. They describe the geology of Majstorska Cesta from Sv. Rok to Obrovac.
Abstract Marked along‐strike changes in stratigraphy, mountain belt morphology, basement exhumation, and deformation styles characterize the Andean retroarc; these changes have previously been related to spatiotemporal variations in the subduction angle. We modeled new apatite fission track and apatite (U‐Th‐Sm)/He data from nine ranges located between 26°S and 28°S. Using new and previously published data, we constructed a Cretaceous to Pliocene paleogeographic model that delineates a four‐stage tectonic evolution: extensional tectonics during the Cretaceous (120–75 Ma), the formation of a broken foreland basin between 55 and 30 Ma, reheating due to burial beneath sedimentary rocks (18–13 Ma), and deformation, exhumation, and surface uplift during the Late Miocene and the Pliocene (13–3 Ma). Our model highlights how preexisting upper plate structures control the deformation patterns of broken foreland basins. Because retroarc deformation predates flat‐slab subduction, we propose that slab anchoring may have been the precursor of Eocene–Oligocene compression in the Andean retroarc. Our model challenges models which consider broken foreland basins and retroarc deformation in the NW Argentinian Andes to be directly related to Miocene flat subduction.
F. A. Stamm, M. de la Varga, M. de la Varga
et al.
<p>Uncertainties are common in geological models and have a considerable impact on model interpretations and subsequent decision-making. This is of particular significance for high-risk, high-reward sectors. Recent advances allows us to view geological modeling as a statistical problem that we can address with probabilistic methods. Using stochastic simulations and Bayesian inference, uncertainties can be quantified and reduced by incorporating additional geological information. In this work, we propose custom loss functions as a decision-making tool that builds upon such probabilistic approaches.</p>
<p>As an example, we devise a case in which the decision problem is one of estimating the uncertain economic value of a potential fluid reservoir. For subsequent true value estimation, we design a case-specific loss function to reflect not only the decision-making environment, but also the preferences of differently risk-inclined decision makers. Based on this function, optimizing for expected loss returns an actor's best estimate to base decision-making on, given a probability distribution for the uncertain parameter of interest. We apply the customized loss function in the context of a case study featuring a synthetic 3-D structural geological model. A set of probability distributions for the maximum trap volume as the parameter of interest is generated via stochastic simulations. These represent different information scenarios to test the loss function approach for decision-making.</p>
<p>Our results show that the optimizing estimators shift according to the characteristics of the underlying distribution. While overall variation leads to separation, risk-averse and risk-friendly decisions converge in the decision space and decrease in expected loss given narrower distributions. We thus consider the degree of decision convergence to be a measure for the state of knowledge and its inherent uncertainty at the moment of decision-making. This decisive uncertainty does not change in alignment with model uncertainty but depends on alterations of critical parameters and respective interdependencies, in particular relating to seal reliability. Additionally, actors are affected differently by adding new information to the model, depending on their risk affinity. It is therefore important to identify the model parameters that are most influential for the final decision in order to optimize the decision-making process.</p>
G. J.-M. C. Leysinger Vieli, C. Martín, R. C. A. Hindmarsh
et al.
Subsurface ice-sheet radar images reveal large plume-shaped bodies rising from the base, with their origin not yet understood. Here, the authors show that freeze-on of water at the ice-sheet base combined with ice-flux explains the vertical extent, shape and structure of the observed plumes.
Laurențiu ȚUȚUIANU, Alfred VESPREMEANU–STROE, Florin PENDEA
et al.
This study proposes a local paleo–landscape reconstruction of the Danube floodplain based on a stratigraphic sequence retrieved from Brateș Lake which, by its emplacement near the confluence of Danube – Prut rivers, was fully receptive to changes associated to hydrological, geomorphological or anthropogenic driven events. Due to its intermediate position within the Lower Danube valley Brateș Lake is a proxy for the evolution of Cotul Dunării area (the region of Danube valley turning from S–N to W–E direction) and provide valuable information about the timing of Danube river advancement to the Black Sea after its reconnection to World Ocean. The sediments were analysed to get the history of their deposition by means of accelerator mass spectrometry (AMS) 14C dating, grain–size parameters, organic matter and carbonate content, magnetic susceptibility together with paleo–fauna and pollen content which altogether led to the identification of main stages: i) delta front advance into Danube estuary (before 8000 BP), ii) shoreline foreshore deposits which describe shoreline position (8000–7900 yrs BP), iii) river floodplain development (7900–5300/5000 yrs BP), iv) lake formation (5300/5000 yrs BP – present).
Gianluca Cornamusini, Paolo Conti, Filippo Bonciani
et al.
A detailed geological map at 1:50,000 scale of the Marecchia Valley and adjoining areas (Northern Apennines, NA, Italy) is presented here. The Marecchia Valley represents a geological ‘unicum’ for the NA and it has been the focus of scientific debate for a long time, due to the occurrence in the area of the ‘Coltre della Val Marecchia (CVM)’, a complex stack of allochthonous and semi-allochthonous units emplaced in a foredeep basin during the Late Miocene to Early Pliocene. In order to clarify the geological evolution for this area, the lithostratigraphic relationships and the tectonic framework have been studied, allowing better understanding of the complex relationships between tectonics and sedimentation. The main result has been a new evolutionary framework for this sector of the orogen during the Late Miocene-Early Pliocene. Several new findings about the geological-structural setting and stratigraphy, result from the geological map presented here. These are overall supported by stratigraphic and tectonic evidence, which suggest time and modes of the CVM allochthonous emplacement within the Messinian-early Pliocene foredeep successions. Relationships between the allochthonous and autochthonous formations allowed recognition of two different bodies in the CVM, gravitationally emplaced following different trajectories and timing.
V Savdski Arabiji je bilo raziskanih in izmerjenih več velikih vulkanskih jam v različnih poljih lave. Ena največjih je Ghar Al Hibashi na polju lave Harrat Buqum-Nawasif. To je v glavnem raven rov (400 m dolg in 15 m širok), dostopen skozi majhno brezno, ki se odpira v stranskem rovu. Jama je dolgo služila za skrivališče netopirjem, hijenam, volkovom in lisicam. Zaradi tega je dno jame, deloma iz debelih plasti nesprijetega peska, prekrito s številnimi kostmi in koproliti ter razmeroma velikimi kupi gvana. Nekateri so se bili vneli, zaradi česar so deloma zgorele tudi na njih ležeče kosti. Edine prave kapnike predstavlja nekaj majhnih, rumenih in prosojnih stalaktitov. Tekom treh odprav 2003 je bilo iz jame vzetih nekaj sekundarnih kemičnih odkladnin za mineraloške preiskave. Kljub majhnemu številu vzorcev je bilo do sedaj zaznanih vsaj 19 različnih mineralov, največ takih, ki so povezani z biogeno mineralizacijo kosti in gvana. Trije od teh, pyrocoproite, pyrophosphite in arnhemite, so izredno redke organske spojine, izključno vezane na goreči gvano. Do danes so bili ti minerali znani le iz nekaj jam v Afriki. Zahvaljujoč tem odkritjem ni jama Hibashi le najpomembnejša vulkanska jama v Savdski Arabiji, ampak tudi tamkajšnje daleč najbogatejše mineraloško nahajališče. Zato te raziskave, ki še zdaleč niso končane, potrjujejo novejše domneve, da so v jamskem okolju prav vulkanske jame najprimernejše za razvoj različnih mineralogenih mehanizmov.
Several large lava tubes have been explored and mapped in different lava fields around the Saudi Arabia. One of the largest is Ghar Al Hibashi, located in the Harrat Buqum-Nawasif lava field. It mainly consists of a huge rectilinear gallery (over 400 m long and 15 m wide) the access to which is through a small vertical pit reaching a side corridor. The cave was long used as a shelter for bats, hyenas, wolves and foxes. Therefore the entire cave floor, consisting of locally thick uncemented sand, is scattered with a great amount of bones and coprolites, while some rather large guano deposits are also found. Some of these guano deposits caught fire, which partially burnt the bones overlaying them as well. The only true speleothems consist of a few small yellow translucent stalactites. During three expeditions in 2003, a few samples of secondary chemical deposits were collected inside this lava tube to be analysed from the mineralogical point of view. Despite the scarcity of these samples, at least 19 different minerals have already been detected, most of which are related to the biogenic mineralization of bones and guano deposits. Three of them, pyrocoproite, pyrophosphite and arnhemite are extremely rare organic compounds strictly related to the guano combustion, which have been observed until now only in a few caves in Africa. Thanks to these findings Hibashi lava tube is not only the most important volcanic cave of Saudi Arabia but also by far the richest mineralogical shelter of the country. Therefore this research, which is far from coming to an end, confirms the recently advanced opinion that amongst the different cave environments, volcanic cavities are very favourable for the development of different minerogenetic mechanisms.