Sedimentary Units Research Articles

Geomorphic evolution of the craton-derived Sone megafan in the southern Ganga plain, India: A tectono-climatic interplay

The Ganga plain neotectonics has been studied from surface and sub-surface faults, frequent geomorphic readjustment, changing sedimentation pattern, piedmont progradation, pedological variation, and frequent earthquake occurrences. However, being neotectonically stable, the peninsular region’s geomorphic changes are governed by climatic fluctuations, contributing to the Ganga plain’s sedimentation. Therefore, peripheral craton sourced marginal alluvial deposits in the Ganga basin are appropriate features to study the control of both the Himalayan tectonics and climate of core peninsular region away from their respective source areas. This study uses a process-response approach model to describe the geomorphic development of the Sone megafan, located at the marginal part of the Ganga plain to the south of the Ganga River, bordering the Indian craton.Geomorphological mapping, field investigation of the depositional features, soil profiles, and Optical Stimulated Luminescence (OSL) chronology suggest four phases of geomorphic evolution, i.e., in 22–8 Ka, 8.0 Ka–7.3 Ka, 7.3 Ka–2.4 Ka, and 2.4 Ka–0.5 Ka on the Sone megafan. The different evolutionary phases are marked by channel and floodplain abandonment and soil profile development. The megafan surface is divided into four distinct geomorphic units (OdSP – Oldest Sone Plain, OSP – Old Sone Plain, YSP – Young Sone Plain, and AFP – Active Floodplain) based on OSL ages and soil properties. Geomorphology and soil suggest a mixed climate in the source and sink area. The arid climate in the catchment contributed to the sediment production, and the humid climate promoted its transport, which resulted in the largest depositional unit of the megafan, even during the arid period in the Ganga basin. Contrast to the north of the Ganga River, no surface faults are found on the Sone megafan. However, the tectonic activity of the bounded basement faults, i.e., the East and the West Patna faults, are well pronounced in the sediment distribution and fluvial response. Tilting and twisting the fault-bounded block controls the sediment remobilization in space and time. Thus, the climatic fluctuation in the source, the sink, and the activity of the basement faults, propelled by the Himalayan tectonics, contributed to the Sone megafan’s geomorphic evolution. Two events of the Ganga River’s encroachment at the distal part of the Sone megafan were recorded (2.4 ± 0.14 and 1.3 ± 0.16 ka). The correlation between OSL ages of megafan units, climatic fluctuations in the Sone River’s catchment, and established time windows of tectonic episodes in the Ganga basin has also been investigated. As the Sone and the Gandak megafans rest on the same tectonic blocks, their tectono-geomorphic responses to the Himalayan neotectonics are similar.

New constraints for the western Paleotethys paleogeography-paleotectonics derived from detrital signatures: Malaguide Carboniferous Culm Cycle (Betic Cordillera, S Spain)

Carboniferous sandstone within the Paleo-Mesomediterranean Domain (Malaguide Subdomain), in southern Spain, represents a key detrital mode within the sedimentary budget of convergent plate boundaries during the Variscan s.s. to Paleotethysian orogenic time span (≈420–300 Ma). This Carboniferous detritus corresponds with Culm lithostratigraphic depositional unit, and it covers an important gap of information (paleogeographic, paleotectonic, source areas) to the area located between the Iberian-French massifs and the African Paleo-Atlas, in the western Paleotethys. Sandstone composition is quartzolithic and records an important high-to-medium-low grade metamorphic content. The source area was a lithic and transitional recycled orogen with a signature of volcanic and ophiolitic detritus (≈330 Ma and/or older). These supplies seem to be derived from a mid-crustal deformed and thrusted pre-late Ordovician to Early Carboniferous terrane, involved in the plate convergence (the southern Europe Iberian-French massifs overriding the north African area) southeatwards of the Variscan s.s. orogenic system, rapidly exhumed and uplifted at mid-Late Carboniferoous time. Consequently, in the overriding hinterland (southern Europe: Iberian-French massifs), metamorphic basement should be already structured during middle Carboniferous when thrusting took place and deposition of Culm facies started in the Malaguide Complex, suggesting Proterozoic-Early Carboniferous (most probably, ≈420 to 330 Ma) metamorphic highlands. The presence of serpentinite-like detritus (≈330 Ma and/or older) seems to indicate a metamorphosed oceanic crust being dismantled at that time. Thus, sources from ophiolitic suture (most probably developed at ≈420–330 Ma) zones are tentatively proposed in other northern Gondwana of southwestern Europe. The occurrence of a synsedimentary volcanic activity (andesitic) should be related to a lost magmatic arc (most probably developed at ≈360–330 Ma), reinforcing the idea of a nearby subduction area. Therefore, the thick terrigenous Culm deposits (≈330–300 Ma) from the Malaguide Subdomain could be deposited in a complex foreland system basin connected northward with carbonate platforms and with a crystalline highland uplifted domain from the southern Europe Iberian-French massifs and southward with the African Paleo-Atlas Domain. The studied mid- to late Carboniferous sandstone petrofacies deeply contributes to paleogeographic reconstructions since block fragmentation and spreading, during the Paleotethysian and Alpine orogenies, rearranged the Paleozoic paleogeography now part of the Cenozoic Perimediterranean Chains. After the correlation with the Carboniferous from other western Paleotethys domains, new paleogeographic-paleotectonic constraints are proposed for the transitional area between the Iberian-French massifs and the African Paleo-Atlas Domain.

A revised Proterozoic tectono-stratigraphy of the South Nicholson region, Northern Territory, Australia—insights from SHRIMP U–Pb detrital zircon geochronology

New SHRIMP U–Pb detrital zircon geochronology on Mesoproterozoic and Paleoproterozoic siliciclastic rocks from the South Nicholson region, in concert with recently acquired complementary regional geophysical datasets, have enabled comprehensive revision of the regional Proterozoic tectono-stratigraphy. The identification of analogous detrital zircon spectra of units deposited in half-graben hanging walls of major east-northeast-trending extensional faults, offers compelling evidence for regional tectono-stratigraphic correlation. This study sampled units from the hanging walls of the Benmara, Bauhinia, and Maloney-Mitchiebo (east-northeast-trending) faults, which identified immature proximal lithofacies hosting a small yet persistent population of ca 1660–1640 Ma aged zircon and lack Mesoproterozoic detritus. The timing of this event is consistent with deposition coincident with crustal extension during the extensional River Event at ca 1640 Ma, an event previously identified from the Lawn Hill Platform in western Queensland. This finding suggests the hanging wall sequences are chrono-stratigraphically equivalent to the highly prospective sedimentary rocks of the Isa Superbasin, host to world-class sediment-hosted base metals deposits across western Queensland and northeastern Northern Territory. Subsequent inversion of the extensional faults resulted in development of south-verging thrusts, and exhumation of late Paleoproterozoic hanging wall siliciclastic rocks through overlying Mesoproterozoic South Nicholson Group rocks as fault propagated roll-over anticlines. These geochronology data and interpretations necessitate revision of the existing stratigraphy and the renaming of a number of stratigraphic units in the South Nicholson region. Accordingly, the distribution of the highly prospective late Paleoproterozoic units of the McArthur Basin, Lawn Hill Platform and Mount Isa Province is greatly expanded across the South Nicholson region. These findings imply that the underexplored South Nicholson region is a highly prospective greenfield area for energy and mineral resources. KEY POINTS SHRIMP U–Pb detrital zircon geochronology provides a basis for revision of the Proterozoic stratigraphy in the South Nicholson region. Correlation of sedimentary units across the region is based on closely matching zircon age spectra, lithofacies and tectono-sedimentary setting. Revision of the Proterozoic stratigraphy increases the prospectivity for sediment-hosted base metal resources across the South Nicholson region.

Unravelling the hydration history of an inverted passive continental margin using epidote U[sbnd]Pb geochronology and Pb–Sr–O–H isotope geochemistry

Inverted passive continental margins permit to comprehensively characterize fluid circulation in the continental crust in orogens from rifting to tectonic inversion. Since granitic rocks have low primary water contents and dominate the continental crust, their hydration exerts important control on metamorphism and deformation of the continental crust during orogeny. It is therefore of great interest to determine whether the granitic continental crust is hydrated during rifting phases or after tectonic inversion. Because fluid circulation may occur at both stages, a comprehensive picture of hydration of the continental crust in inverted passive continental margins can be obtained by the combination of different geochronometers and geochemical methods.In this study, we combine UPb geochronology and Pb–Sr–O–H isotope geochemistry of epidote in hydrothermal veins in the Albula Pass area (eastern Swiss Alps) as powerful tools to trace hydration events in the continental crust in orogens. The Albula Pass area is part of the inverted Adriatic passive continental margin, which was extensively affected by seawater infiltration during continental rifting in Jurassic times. Epidote geochronology elucidates the fluid circulation history in this rifted crustal section by revealing two hydration events that are not recorded by other datable minerals: (1) 85.2 ± 9.7 Ma and (2) 59.9 ± 2.7 Ma, showing that fluid circulation in the Adriatic passive continental margin continued after Late Cretaceous tectonic inversion. Epidote Pb–Sr–O–H isotope geochemistry characterizes pathways and fluid sources of the epidote forming fluids, which differ between the Late Cretaceous and the Paleocene fluid circulation events. The Late Cretaceous epidote-forming fluids were produced by compaction of sedimentary units beneath the Err nappe and release of modified seawater (i.e., formation/connate water) from marine sediments, while Paleocene veining was mainly mediated by syn-kinematically infiltrated meteoric water. The present geochronological and isotope data argue for multi-stage hydration of the continental crust in the inverted Adriatic passive continental margin. This work promotes the importance of the interplay of newly introduced and recycled fluid components in the hydrothermal alteration of the continental crust, and it highlights epidote as a powerful hygrochronometer and isotope tracer.

The Manhattan project: Isotope geochemistry and detrital zircon geochronology of schists in New York City, USA

The geology of New York City (USA) consists primarily of metasedimentary rocks that were deformed during the series of orogenies between ca. 470 Ma and ca. 300 Ma that culminated in the amalgamation of Pangea. The rocks in New York City play a key role in understanding the tectonic history of these orogenies because they lie at a critical location at the boundary between the Northern and Southern Appalachian Mountains. The primary question addressed here is where these metasedimentary rocks originated prior to the assembly of Pangea. Through detrital zircon and whole-rock Nd isotope analyses, we show that all the metasedimentary rocks of New York City, mapped as the Manhattan Schist and the Hartland Group, are primarily derived from Laurentia as indicated by detrital zircon populations dominated by 1200−900 Ma grains and εNd values between −7 and −13. The results presented here do not necessitate an exclusively Laurentian source for the detrital material found in New York City, but the data strongly suggests protoliths represent sedimentary units that are primarily derived from the Laurentian margin. Another important result from this study is the limited contributions from any rift volcanics and/or Gondwanan material(s). There is some subtle variability across our zircon sample suite, but there is no convincing evidence for major changes in bulk provenance signal that would be consistent with derivation from vastly different continental sources for these rocks. The shared provenance signal observed here is counter to the previous suggestions that a major terrane boundary, often called Cameron’s Line, exists in New York City, separating Laurentian rocks from those of a Gondwanan affinity.

Magnetic surveying as a proxy for defining cyclicity in thick sedimentary fillings: Application to the Cretaceous Cameros Basin (N Spain)

This work proposes the application of magnetic surveying to the study of cyclicity in sedimentary basins. This application is favoured by the particular bed attitude/topography relationships found in the eastern sector of the Cretaceous Cameros Basin, N Spain. Both the measured total magnetic field (after diurnal correction) and the vertical magnetic gradient, provide a profile (14 cm separation between measurements, in average) of the short-wavelength magnetic anomalies associated with the sedimentary sequence. These anomalies depend on the magnetic susceptibility (dominant for low Koenigsberger ratios, a common scenario in sedimentary rocks), and the magnetic remanence (whose orientation is fairly constant in remagnetised basins) of the different sedimentary units. The comparison with direct measurements of magnetic susceptibility (in the field and in the laboratory) provided a successful double-check. The cyclostratigraphic analysis of magnetic profiles of this 6 km-thick series indicates the existence of cycles of 405 kyr (long eccentricity) and 100–125 kyr (short eccentricity), as well as other lower and higher frequency cycles. Cycles with similar, but slightly different, periodicities are the result of different sedimentation rates (mean of ∼0.2 mm/yr, with values ranging between ∼0.1 and ∼0.36 mm/yr). These results provide and indirect method for dating the basin fill, between the Tithonian–Berriasian boundary and the basalmost Albian (∼143.2–∼112.6 Ma), and impose new constraints for basin evolution. The results obtained open a promising field for quick and reliable determination of magnetic properties and cyclicity in thick sedimentary sequences.

Kahi mélange complex in Kurram and Waziristan, NW Pakistan: An integrated approach for tectonic implications to India–Afghan suturing

The Kahi mélange complex in the Waziristan and Kurram sector (N–W Pakistan) is one of the several Neotethyan ophiolite–mélange complexes exposed along the westernmost margin of the Indian plate, preserving significant information on pre, syn and post–collision tectono–stratigraphic evolution of collision tectonics between the Indian plate and the Afghan block. It consists of highly dismembered ophiolitic and sedimentary units. Petrographic and field observations of mafic and ultramafic rocks within the ophiolitic unit, reveal a complete, but dismembered ophiolite suite similar to the Waziristan Ophiolite (WO) to its southwest. The sedimentary units consist of syn–orogenic deposits, turbidites and slope sediments of Campanian age as constrained by the Late Cretaceous radiolarians (Stichomitra communis Squinabol) and planktonic foraminifera (Rodotruncana Calcarata). From the structural point of view, the dismembered ophiolitic units represents the highest tectonic edifice. It’s overthrusting onto the Campanian sedimentary unit constraints the onset of the collision between the Indian plate and Afghan block to the Late Cretaceous. The subsequent obduction of combined ophiolite–sedimentary units over the brecciated Late Paleocene Lockhart Formation of Indian plate margin constraints the time of the end of the collisional stage. The unconfirmable deposition of the marine Patala Formation, Late Paleocene–Early Eocene in age, above the Kahi mélange complex documents the closure of Neotethys in the Early Eocene. In conclusion, our findings document that the Kahi mélange complex represents a typical polygenetic mélange formed by the superposition of two different dismembered units (the ophiolitic and the sedimentary units) coupled as a result of at least two tectonic events in a subduction–accretion setting related to the collision between the Indian plate and the Afghan block.

U–Pb ages and paleoenvironmental evolution of the guanchín formation (neogene fiambalá foreland basin), Central Andes, Argentina

The Guanchín Formation is a sedimentary unit that was deposited during the Andean orogeny and is preserved in the Fiambalá Basin in NW Argentina. It records an advanced stage of the broken-foreland evolution in a transitional zone between the morphotectonic domains of the Precordillera, the Sistema de Famatina, the Western Sierras Pampeanas, and the southern Puna. Furthermore, it preserves a record of Late Miocene explosive volcanism that is common in all the foreland basins in this Andean segment. The Guanchín Formation was studied at Cuesta Loro Huasi and Guanchíncito sections, where seven facies associations (FA) were recognized. These represent ephemeral sandy braided fluvial systems with thin mud floodplains (FA1), sheetflow-dominated sandy-tuffaceous alluvial plain (FA2), perennial sandy braided fluvial system (FA3), fine-grained alluvial plain built up by unconfined flows and less terminal splays (FA4), sheetflow-dominated sandy alluvial plain (FA5), and sandy-gravelly (FA6) and sandy-dominated (FA7) braided fluvial system, arranged in chronological order from oldest to youngest. To date the formation, zircon U/Pb ages from tephras were obtained from the Cuesta Loro Huasi section, which yielded depositional ages of 6.10 ± 0.07, 5.89 ± 0.09, 5.60 ± 0.06, and 5.20 ± 0.05 Ma, while a fifth sample from the Guanchíncito section yielded an age of 3.26 ± 0.05 Ma. Additionally, detrital zircon analyses were performed to infer sediment provenance and constrain the maximum depositional age of sedimentary units. These data combined with paleoenvironmental analysis and clast compositions in conglomerates suggest that the Western Sierras Pampeanas had been uplifted around ∼6 Ma. By this time the drainage was dissipated as a distributary fluvial system (DFS) under semiarid climatic conditions, which received sediments from northern, eastern, and to a lesser extent from western sources. Around ∼3 Ma the basin started to receive coarse-grained sediments of braided fluvial systems (FA6 and 7) indicating a closer proximity to the Pampean sources areas. The Guanchín Formation records an overall progradational trend manifested through two minor progradational cycles, each one controlled by changes in the equilibrium profile and accommodation space of the basin. This trend is likely associated with a basinward increase in the subsidence rate or enhanced water availability in the headwaters, potentially linked to tectonic uplift in the eastern and/or northern ranges, including the final uplift of the southern Puna. Since previous works placed the deposition of the overlying Rodado de la Puna Formation deposition began at 4 Ma, these news ages suggest the top of the Guanchin Formation is younger than previously thought.

Sedimentary evolution of the western North Yellow Sea mud patch: A Holocene perspective

The western North Yellow Sea mud patch has a unique location, abundant sediment supply and a complex sedimentary environment. Reconstructing its sedimentary evolution is crucial for a comprehensive understanding of source to sink process in the North Yellow Sea. Using core W03 collected from the mud patch, this study unravels its Holocene history through analysis of sedimentology, mineralogy and micropalaeontology. The results indicate that core W03 can be divided into three depositional units (DU). DU3 (538-461 cm) is composed of earthy yellow clayey silt and characterized by a hard layer. It was formed in the near-coast environment between 10.3 and 9.8 cal kyr BP, a hiatus period between Melt Water Pulse 1B and 1C events. DU2 (460-341 cm) was formed during the period of 9.8–6.5 cal kyr BP. As sea level rose, the westward retreat of the Yellow River mouth caused the transportation of Yellow River-derived sediment over longer distances, leading to an increase in flaky minerals. The rising sea level also induced a shift towards a reducing environment in the western North Yellow Sea. DU1 (340-0 cm) was formed after 6.5 cal kyr BP. During this period, the study area remained in a shelf shallow sea environment characterized by relatively strong chemical hydrolysis and reducing conditions. The intensification of the Yellow Sea Warm Current and an increase in Yellow River sediment transported to the sea led to an obvious increase in sedimentation rate after 2.3 cal kyr BP.

Tracing past extreme floods on an alluvial fan using geophysical surveying

SummarySedimentary units in alluvial fans may record gradual transport and deposition during multiple floods or sediment‐laden flows or, conversely, during few catastrophic events. While outcrops are a valuable source of direct information to constrain past geomorphic and hydrologic processes, such exposures are scarce, especially along aggrading rivers or those that have been subject to recent catastrophic sedimentation. In this context, near‐surface geophysical techniques can constrain the dimensions, internal architecture, composition, and petrophysical properties of different sedimentary units. We consider the Grimmbach alluvial fan in the cuesta landscape of southwestern Germany, which was heavily impacted by sediment and wood loads during a flash flood in 2016; published radiocarbon dates indicate that at least three floods similar to the one in 2016 may have occurred since the 17th century. To test whether and to which detail near‐surface geophysics might reveal the sedimentary legacy of these floods, we survey the Grimmbach alluvial fan using detailed topographic data and geophysical imaging based on electromagnetic induction, electrical resistivity tomography (ERT), and ground‐penetrating radar. Our geophysical results indicate former channel courses and two coarse bar deposits up to 3 m below the surface, which are comparable with the more extensive bar deposits of the 2016 flood. From the ERT models, we interpret coarse, up to 5 m thick, gravel lag overlying bedrock at a maximum depth of 10 m. Our geophysical results also highlight patches of finer materials derived from gradual sedimentation and soil development. Overall, our results show that the Grimmbach alluvial fan may have formed and reshaped during catastrophic flows, which likely caused channel avulsions. Our findings point to the need to reconsider flash flood and debris‐flow hazards in similar headwaters and fans of this seemingly quiescent cuesta landscape in southern Germany.

Geochemical Evaluation of the Lower Senonian Ogugu Shale, Southern Benue Trough, Nigeria: Implication for Source Richness, Quality and Petroleum Potential

The Lower Senonian Ogugu Shale is the topmost layer of the Coniancian-Santonian depositional unit in the Southern Benue Trough. Sediments of this unit have been suggested to have huge potential for hydrocarbon generation. However, detailed geochemical studies on the organic matter source, thermal maturity and the hydrocarbon potential Ogugu Shale are still missing. For the present study, a total of 16 cuttings and 3 core samples of the Ogugu Shale from Amasiodo-1 well were subjected to total organic carbon (TOC), Rock-Eval pyrolysis and gas chromatography mass spectrometry (GC-MS) analyses in order to characterize the organic matter richness, kerogen type and liquid hydrocarbon-generative potential in the samples. The TOC values (0.70 to 1.20 wt. %) and Rock-Eval pyrolysis data S2 (0.26-0.73 mg HC/g rock) as well as its calculated parameters Hydrogen Index (HI; 23-72 mg HC/g rock) and Generative Potential (GP; 0.33-0.84 mg HC/g rock) suggest poor to fair organic rich rock containing dominantly terrestrially derived Type III kerogen. The biomarkers as well as the source-indicating aromatic hydrocarbons in the samples suggest contributions from mixed aquatic and vascular organic matter deposited under oxic-dyoxic conditions of deltaic paleoenvironment. The Rock-Eval pyrolysis Tmax (434-4560 C) including the derived vitrinite reflectance (Rc; 0.65-1.05%) indicate thermally matured source rocks. The thermal maturity status of Ogugu Shale is further supported by molecular thermal parameters from the saturate and aromatic compounds. This study therefore conclude that that the Senonian Ogugu Shale of the Southern Benue Trough contain thermally matured fair quantity of organic matter with poor hydrocarbon potential.

Facies, diagenesis, and palaeo-environment significances of the Plio-Quaternary fluvio-lacustrine deposits of Ain Cheggag region, Sais foreland basin, Morocco

Fluvio-lacustrine deposits are promising archives that afford to decipher climate and tectonic signatures, typically when evidence of changes in the depositional settings therein is remarkable. As such, the present work coveys a case study whose fluvio-lacustrine deposits may serve to provide insights into climate and tectonic controls on palaeoenvironmental settings. The study area lies in the northwestern portion of Ain Cheggag, southeastern the Sais foreland basin (northern Morocco). The lithostratigraphical analysis of Plio-Quaternary fluvio-lacustrine deposits in the area has enabled the identification of nine facies. The depositional systems are organized into three deposit units, each of which reflects a typical depositional environment. The first (lower) unit consists of detrital facies implying deposition in alluvial-dominated settings. The alternation of detrital and carbonate facies giving way to the second (middle) unit suggests sedimentation in a fluvio-lacustrine environment. Whilst being carbonate-rich, the third (upper) unit reflects a shift into lacustrine-dominated settings. Accordingly, the vertical succession of the sedimentary pile delivers remarkable insights into a general palaeo-environmental shift from alluvial settings, with enhanced pedogenesis processes, towards carbonate-dominated lacustrine conditions where early- and late-stage diagenesis processes would have prevailed. This broad shift in depositional systems is likely to be the response of palaeohydrological changes that are modulated both by the neotectonic subsidence background and, specifically, the general palaeoclimate evolution towards more humid conditions. Bioturbation, desiccation, and void-filling with internal sediments are key features of early-stage diagenesis processes, whereas cementation, micritization, recrystallization, dissolution, and iron and manganese oxidation are the main features of late-stage diagenesis altering the primary structures of the studied deposits. Finally, we highlight the significance of fluviolacustrine deposits in deciphering palaeoclimatic signatures and tectonic implications.

A new isochron for stratigraphic correlation in the Permian Delaware Basin and beyond

Altered volcanic ash, preserved as bentonite clay within sedimentary depositional units, can facilitate regional stratigraphic correlation. While many bentonite ash beds have been documented in core extracted over decades of hydrocarbon exploration in the Delaware Basin, a particular ∼1 cm-thick bentonite has been identified at a distinct stratigraphic position, at a sedimentary facies transition from thin-bedded calciclastic turbidites to thick-bedded siliciclastic turbidites, in the compositionally-mixed upper Wolfcamp formation. A comparison of geochemical analyses of the ash from two cores and petrophysical correlations across eight wells was conducted to test the regional correlation of the ash. Despite diagenetic alteration since seafloor deposition ∼280 Ma, nearly identical geochemical trends between incompatible elemental subsets, including light and heavy rare earth elements, large ion lithophiles, and high field strength elements, suggest that these two ash deposits originated from the same volcanic center. Detailed sedimentologic analyses and lithostratigraphic correlations across three cores spaced tens of km apart confirm that the ash bed is bound by correlative quiescent deepwater strata. Based on the chemical composition, probable timing of deposition, and proximity, we speculate that the Las Delicias Arc produced this ash, and it was transported by wind and deposited as a hemipelagite into the Delaware Basin deep marine environment. This discovery implies the existence of the ash marker in other cores within Late Paleozoic western equatorial Pangea, e.g. in compositionally-mixed deep marine deposits of the Midland Basin and outcropping deposits around the Greater Permian Basin and beyond, which would facilitate regional chronostratigraphic correlation for a critical time in Earth's history.

The classical Cuevas River section revisited: an update to the style and timing of deformation of the Aconcagua region based on new geological, structural and geochronological data (32°50′S)

The Aconcagua region constitutes a classical site to study the growth of the Andes, being host of the highest mountain of South America and focus of numerous investigations since its first description by Charles Darwin almost 200 years ago. The last detailed works in this area characterized it as a typical thin-skinned fold-thrust belt with a basal detachment located in the lower evaporitic units of the Mesozoic sequences. Previous authors in this area correlated the different thrust sheets on the basis of their marine fossils, sedimentological characteristics and structural relations. Although these criteria were useful for the identification of the marine and evaporitic units, the resemblance between the nonmarine red beds and among the different volcanic units has difficulted their unequivocal assignment. Moreover, the inaccessibility of the outcrops and the lack of an adequate geochronological control has led to underestimate the importance of the Aconcagua fold-thrust belt in the last couple of years, being characterized as a secondary feature in Andean orogenesis. A series of new field observations, sedimentological studies and geochronological analyses were performed to update the geological map of this area and build a schematic cross section along the Río Cuevas at 32°50’S in west-central Argentina. These studies allowed the identification of important variations on the thickness of the Upper Jurassic nonmarine sequences associated with the activity of normal faults and the development of structural highs. Many of these normal faults are presently inverted, which suggests that tectonic inversion played an important role in the structuration of this region, leading to a deformational style that varies from a thick-skinned inner domain towards a thin-skinned frontal sector. A series of sedimentological profiles aided by four new U-Pb detrital zircon analyses and its integration with new geochronological databases allowed the documentation of previously unrecognized Paleogene deposits, the age reassignation of several volcanic and sedimentary units and the modification of the stratigraphy. Finally, at least three contractional events with different structural mechanisms were identified along this transect, revealing a dynamic tectonic evolution that underscores the role of structural inheritance and the relevance of the Aconcagua fold-thrust belt in the Andean orogeny.

Qualitative evaluation of thaw settlement potential in permafrost regions of Canada

Permafrost thaw negatively impacts the built environment in circumpolar regions. Thaw-induced settlement causes various engineering problems such as differential settlement, sinkholes, culvert failures, and pipeline deformations. Large-scale pre-construction evaluation reduces the risk of building infrastructure in thaw settlement-prone areas. This evaluation enables the comparison and screening of multiple route/location alternatives, the identification of vulnerable sections of a route, and the development of more effective site investigation plans. This study presents a systematic approach for evaluating thaw settlement potential in various regions across Canadian permafrost. In developing the approach, we considered three main factors: ground ice content, surficial deposit unit, and bedrock type. These factors were prioritized based on their relative importance in defining settlement behaviour, and a weighting factor was determined for each. In this study, the weighting factors of 0.78, 0.15, and 0.07 were suggested for ground ice content, surficial deposit type and bedrock type, respectively. We subsequently developed a Thaw Settlement Potential Index (TSPI), which can be calculated for any given location using publicly available Canada-wide resources. We calculated TSPI for several reported cases of thaw settlement issues across Canada and compared the results with site observations. A comparison was also made with a more detailed assessment conducted on the Northern Alaska Highway using a different approach. While the TSPI assessment required minimal time, effort, and resources, the obtained results generally matched those of finer-scale assessments with more detailed information. Thus, our methodology simplifies early identification of thaw-unstable regions in projects with large footprints and helps allocate resources more efficiently for subsequent site investigations.

Neotectonics and paleoseismology of the North Tabriz Fault, Azerbaijan Region, Northwest Iran

Structural characteristics and seismic parameters were investigated to reevaluate seismic hazards along the North Tabriz Fault (NTF). Field surveys and paleoseismology on the central segment of the fault, combined with dating of sedimentary units, document multiple surface-rupturing paleoearthquakes during the past 3.5 ka. The calculated moment magnitudes (Mw) for the identified paleoearthquakes range from 6.3 to 7.5, causing surface ruptures of ca. 50 km with a maximum slip per event of 5.7 ± 0.2 m. Kinematic GPS surveys on displaced geomorphic features, combined with the dating results indicate that the central segment of the NTF slips at a rate of 6.4 ± 0.5 mm.yr-1 over the past 7.5 ka. Fault orientations and scattered volcanic vents in Sahand Volcanic Complex (SVC) suggest that its configuration and evolution have been affected by the regional transpression.

Kinematic analysis of the mesozoic - Early Cenozoic deformation in the paipote basin (27°10′S)

An integrated structural and kinematic study focused on the characterization of an Andean Mesozoic basin was carried out in the upper stream of the Paipote Creek, in the western limit of the Southern Puna, Fault slip data analysis (n = 80) and structural observations at different scales were collected from Triassic to Upper Cretaceous volcanic and sedimentary units to constrain the structural architecture and the kinematic evolution of the area. Regional observations provide evidence for syntectonic extensional deposition during the Triassic - Jurassic and positive tectonic inversion from at least the Late Jurassic. Extensional features such as growth strata, harpoon structures and roll-over anticlines, helped to infer two main depocenters controlled by west dipping listric faults. E-W extension directions have been recognized in Triassic - Jurassic units, linked to an extensional basin architecture, and mixed contraction directions were related to compressional and strike-slip deformation in the area. A forward model is proposed based on the interpreted architecture in depth of the basin, defining two major depocenters that, together, define the Paipote basin. A shortening estimate of 21% (5,44 km) was calculated for the basin, wich corresponds to the lowest shortening values reported for the Triassic-Jurassic basins in the Atacama region. The strike-slip deformation can be associated previously with recognized NW-SE strike-slip faults, and aids in proposing the Paipote basin as a transitional zone between the Lautaro basin to the south and the Potrerillos basin to the north.

A database of detrital zircon U–Pb ages and Hf isotopic compositions from the Tarim, West Kunlun, Pamir, Tajik and Tianshuihai terranes

AbstractWith the development of detrital zircon U–Pb ages and Hf isotope analysis as conventional sedimentological research methods, a large number of studies have been conducted in the Tarim, West Kunlun, Tajik, Pamir and Tianshuihai regions and abundant data have been accumulated. Summarizing these data to characterize sedimentary units and source regions is more important than local studies of specific geological epochs; therefore, we compiled a database of detrital zircon U–Pb ages and Hf isotope analyses from the Tarim, West Kunlun, Pamir, Tajik and Tianshuihai terranes. The database contains data from 90 papers, including 35,281 individual U–Pb ages and 4,181 Hf isotope analyses. The database records the literature source, petrologic sample information, regional geological information, geographic coordinates and analytical parameters for each data point in as much detail as possible to allow readers to review, process, analyse and use the data. The database relies on the Deep‐time Digital Earth (DDE) platform and uses an open database update system to enable sharing and collaborative building. We encourage other researchers to contribute relevant published data to facilitate wider use.

Flow depth estimates and avulsion behaviour in alluvial stratigraphy (Willwood Formation, Bighorn Basin, Wyoming, USA)

AbstractThe size and geometry of river channels play a central role in sediment transport and the character of deposition within alluvial basins across spatiotemporal scales spanning the initiation of grain movement to the filling of accommodation generated by subsidence. This study compares several different approaches to estimating palaeoflow depths from fluvial deposits in the early Palaeogene Willwood Formation of north‐west Wyoming, USA. Fluvial story heights (n = 60) and mud plug thicknesses (n = 13) are statistically indistinguishable from one another and yield palaeoflow depth estimates of 4 to 6 m. The vertical relief on bar clinoforms (n = 112) yields smaller flow depths, by a factor of ca 0.3, with the exception that the largest bar clinoforms match story heights and mud plug estimates. This observation is consistent with modern river data sets that indicate unit bar clinoforms do not capture the reach‐mean bank‐full flow depths except in rare circumstances. Future studies should use story heights (i.e. compound bar deposits) and mud plugs to estimate bank‐full flow depths in alluvial strata. Additionally, the thickness of multi‐storied fluvial sandbodies (n = 102) and overbank cycles composed of paired crevasse splay and palaeosol deposits (n = 45) were compared. The two depositional units display statistically indistinguishable mean and median values. Building upon previous depositional models, these observations suggest basin rivers aggraded approximately one flow depth prior to major avulsion. This avulsion process generated widespread crevasse splay deposition across the floodplain. Once the main river channel stem was reestablished, overbank flooding and palaeosol development dominated floodplain settings. The depositional model implies river aggradation autogenically generated topography in the basin that was effectively filled during the subsequent avulsion. This constitutes a meso‐timescale (103–104 years) compensational pattern driven by morphodynamics that may account for the high completeness of fossil and palaeoclimate records recovered from the basin.

Subaqueous volcanic eruptive facies, facies model and its reservoir significance in a continental lacustrine basin: A case from the Cretaceous in Chaganhua area of southern Songliao Basin, NE China

The conventional lithofacies and facies model of subaerial and marine pyroclastic rocks cannot reflect the characteristics of subaqueous volcanic edifice in lacustrine basins. In order to solve this problem, the lithofacies of subaqueous eruptive pyroclastic rocks is discussed and the facies model is established by taking the tuff cone of Cretaceous Huoshiling Formation in the Chaganhua area of the Changling fault depression, Songliao Basin as the research object. The results indicate that the subaqueous eruptive pyroclastic rocks in the Songliao Basin can be divided into two facies and four subfacies. The two facies are the subaqueous explosive facies and the volcanic sedimentary facies that is formed during the eruption interval. The subaqueous explosive facies can be further divided into three subfacies: gas-supported hot pyroclastic flow subfacies, water-laid density current subfacies and subaqueous fallout subfacies. The volcanic sedimentary facies consists of pyroclastic sedimentary rocks containing terrigenous clast subfacies. A typical facies model of the tuff cone that is formed by subaqueous eruptions in the Songliao Basin was established. The tuff cone is generally composed of multiple subaqueous eruption depositional units and can be divided into two facies associations: near-source facies association and far-source facies association. The complete vertical succession of one depositional unit of the near-source facies association is composed of pyroclastic sedimentary rocks containing terrigenous clast subfacies, gas-supported hot pyroclastic flow subfacies, water-laid density current subfacies and subaqueous fallout subfacies from bottom to top. The depositional unit of the far-source facies association is dominated by the subaqueous fallout subfacies and contains several thin interlayered deposits of the water-laid density current subfacies. The gas-supported hot pyroclastic flow subfacies and the pyroclastic sedimentary rocks containing terrigenous clast subfacies are favorable subaqueous eruptive facies for reservoirs in continental lacustrine basins.