Stratigraphic Units Research Articles

Relationships between brachiopod fauna (Lochkovian–Frasnian) from northwest Gondwana (Amazonas Basin) and environmental changes during the Devonian

The Devonian marked a significant phase in the evolutionary history of the Brachiopoda. During this period, the Phylum achieved its peak diversity (Emsian) and suffered one of its greatest declines (Frasnian–Famennian), ranking second only to the mass extinction event at the Late Permian period. In Brazil, the Amazonas Basin has a rich record of Devonian brachiopods distributed in four stratigraphic units: i) Manacapuru (Lochkovian), ii) Maecuru (early Eifelian), iii) Ererê (late Eifelian), and iv) Barreirinha (early Frasnian) formations. This article aims to survey the occurrences of brachiopods during the Devonian in the Amazonas Basin and to discuss the possible factors that influenced their diversity. Environmental changes may explain the variation of brachiopod diversity throughout the Devonian in the Amazonas Basin. We noted that the diversity variation of Devonian brachiopods in the Amazonas Basin unfolded in three distinct stages. The peak of brachiopod diversity occurred in the early Eifelian (Maecuru Formation), when the Amazonas Basin was between the subtropical latitudes 30°S and 60°S, under shallow marine and cold conditions, justified by the absence of carbonates, evaporites, and reefs in the region (Stage 1). The first diversity decline is recorded in the Ererê Formation (late Eifelian), attributed to a warmer climate and deeper water than in the Maecuru Formation (Stage 2). During the Frasnian, there was a second diversity decline of brachiopods in the Amazonas Basin (Barreirinha Formation). A major global transgression occurred in the Late Devonian. In this period, the Amazonas basin experienced the deepest marine conditions in its history. The brachiopods of the Barreirinha Formation occur in layers of black shale (offshore), attributed to an anoxic or dysoxic environment of high stress, which explains the low diversity of brachiopods in this unit (Stage 3).

Stress state estimation – new data and variability assessment of model results

Abstract. The upper crust of the Earth is used more and more to transport and extract raw materials and energy. It is also used for the final disposal of radioactive waste in deep geological repositories with a particularly crucial requirement for long-term safety over 1×106 years. An accurate knowledge of the hosting rock and surrounding formation coupled with comprehensive modelling is fundamental to demonstrate the geological site has the required properties for safe and long-term underground storage. Besides other criteria, geomechanics play an important role. Even if the determination of rock properties is already a challenge, the estimation of the contemporary stress state in the upper crust is even more challenging. To predict the stress state 3-D geomechanical–numerical models are used, but high-quality underground structure, rock properties and in situ stress data for model calibration are needed. In particular, data of maximum and minimum horizontal stress magnitudes (SHmax and Shmin) are required to find suitable lateral displacement boundary conditions to produce a best-fit model. During the recent exploration phase for a deep geological repository for radioactive waste in Switzerland, a unique dataset of stress magnitude data has been acquired from eight cored boreholes. Rock mechanical properties were constrained from geophysical logging and laboratory testing. The empirically correlated rock properties were not simply averaged, but a probability distribution was provided. The stress field was explored by conducting more than 120 micro-hydraulic fracturing (MHF) and dry sleeve re-opening (SR) tests in different stratigraphic units, to estimate the magnitudes of Shmin and SHmax. We present the results of a 3-D geomechanical–numerical model that shows the best fit with respect to the measured stress magnitudes. Considering the uncertainties of the MHF/SR tests and the ones resulting from rock property variability, the model can reproduce most of the measurements. However, we do show not only the best-fit result but also a bandwidth of individual stress components within a P05–P95 probability range. We also show that there are still outliers for this bandwidth, but we will show that these can be explained by scaling effects.

A note on the duration of claystone exploration programs

Abstract. In a recent report, the German Federal Company for Radioactive Waste Disposal (BGE) estimated the probable duration of exploration activities within potential siting regions (BGE, 2022). Based on many years of expertise regarding the exploration of the subsurface, we outline in this contribution that the BGE (2022) likely underestimates the time necessary to characterize claystones within potential siting regions. Our latest experience originates from two research projects that developed sequence stratigraphic frameworks for the largely homogenous claystone successions of the Lower Cretaceous in northern Germany (Thöle et al., 2020) and the Middle Jurassic in southern Germany, respectively. Although the specific study areas are not considered in the site selection procedure, both stratigraphic units are reviewed to potentially host a nuclear waste repository. Accordingly, our hands-on experience might constitute a highly relevant contribution to the ongoing debate. Within each study area, drill cores were extracted from four boreholes with a total length of ∼660 m (northern Germany) and ∼930 m (southern Germany). After the drilling campaigns, each having taken approx. 5–6 weeks, the cores were split, photographed in high resolution, lithologically described, scanned with an X-Ray fluorescence (XRF) core scanner (10 mm scan interval) to determine the elemental distribution, and sampled for lithological, mineralogical and geochemical analyses at a resolution of 1 m, which took approx. 12 months. However, the most time-consuming steps were the analysis and interpretation of the stratigraphy and particularly the mineralogical investigations. With a sampling resolution of 1 m, an analysis time of approx. 6 months per 250 core meters is a robust reference. We reckoned a total duration of 5 years for the workload in each of the abovementioned research projects. Obviously, the duration of claystone exploration will vary, depending on the number and length of the core drillings per siting region, in addition to the sampling resolution. However, if BGE aims to characterize claystones with a degree of detail comparable to our projects, the estimated 42 months (see Table 3 in BGE, 2022) will likely be insufficient.

Seismic stratigraphy of the southern Eratosthenes High, eastern Mediterranean Sea: growth, demise and deformation of three superposed carbonate platforms (Mesozoic–Cenozoic)

Interpretation of seismic data over the southeastern flank of the Eratosthenes High shows nine principal seismic stratigraphic units overlying probable faulted basement. Among these are three superposed carbonate platforms that build a stratigraphy exceeding 3000 m. Regional comparisons suggest these range in age from Jurassic to Miocene.The Jurassic carbonate platform exhibits a layered stratigraphy and aggradational deposition style over the whole study area. A Lower Cretaceous platform subsequently developed as a linear, aggrading bank and prograded as multiple high-frequency sequences for more than 40 km into the Eratosthenes High interior, isolating an intrashelf basin that remained connected to the Levant Basin by a narrow seaway. The Jurassic platform margin was a fault-controlled, scalloped escarpment, while the mid-Cretaceous platform was strongly influenced by linear, NW–SE-orientated, fault-controlled sags.The Miocene platform, a shoaling, ‘catch-up’ neritic shelf, was established after a hiatus during which the flat top of the Cretaceous platform lay below the photic zone. The Miocene platform surface was subsequently incised by Messinian erosional channels that fed offlapping and downstepping regressive carbonate or evaporitic shorelines which tracked Messinian sea-level fall. Updoming and segmentation of the Eratosthenes High occurred during the early Messinian prior to the emplacement of Messinian salt onto its flanks.

Pre- and postsettlement depositional processes and environments of the 3rd- to 5th-order White Clay Creek watershed, Piedmont Province, Pennsylvania and Delaware, USA

We extend two hypotheses based on studies of 1st- to 3rd-order Piedmont watersheds of southeastern Pennsylvania, USA, by collecting data in a larger 3rd- to 5th-order watershed nearby. One hypothesis posits that presettlement river corridors were dominated by wetlands, and the other suggests that river valleys were filled by millpond sedimentation following European settlement. Both hypotheses support new river restoration practices, so their generality is important to assess. Ten lithofacies indicate depositional environments, while pedostratigraphic criteria and 14C dating define presettlement and postsettlement stratigraphic units. Basal gravels similar to modern stream bed sediments represent presettlement channels with active bedload transport. Wedge-shaped gravel deposits resembling modern bars further document presettlement bedload transport by channelized flows. Extensive presettlement and postsettlement units of massive, organic-poor, fine-grained sediment formed when overbank flows inundated floodplains. Peat deposits, exposed at a single site (but absent elsewhere), represent a presettlement wetland. Decimeter-thick, discontinuous, massive carbonaceous fine-grained sediments occasionally overlie basal gravels; these may represent localized wetlands adjacent to presettlement channels or hydraulic backwater environments. Laminated sand and mud accumulated behind one 3-m-high mill dam, but these millpond deposits are absent at other sites. Instead of being dominated by wetlands, presettlement river corridors are better described as a complex mosaic of riparian environments including older colluvial landforms, floodplains (some of which may have been seasonally inundated wetlands), primary (and possibly secondary) channels, and depending on geomorphic setting, either localized or valley-spanning wetlands. After European settlement, millponds were important locally, but their deposits represent a minor component of the stratigraphic record.

Strength and durability status of the Fagfog Quarzite from the Lower Nawakot Group, central Nepal Lesser Himalaya

Railways have played vital role in the development of many countries worldwide. Government of Nepal has already planned to establish various national and international railway networks within the nation. A substantial quantity of durable rock ballasts is required for building a sustainable railway network. Quartzites from central Nepal Lesser Himalaya can be a promising source to fulfill this requirement. Therefore, the quartzites from the stratigraphic unit Fagfog Quartzites of the Lower Nawakot Group located in Dhading District along the Kalu Pandey Highway have been assessed to determine physical, strength and durability characteristics of the ballasts. All quartzite ballasts obtained from the bedrocks were of Precambrian, medium-grained, bladed to prolate shaped, white to brownish white, crushed quartzites. Dry density and water absorption were respectively 2336-2641 kg/m3 and 0-2.5%. The bulk density varies from 1204 and 1387 kg/m3. Point load strength index varies from 2.04 to 11.55 MPa (medium strong to extremely strong). Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV) ranges from 14.85 to 22.77% and 15.51 to 22.17% respectively. Some 7% results of AIV and 20% of ACV results exceeded the established limiting value of 22%. The slake durability index (Id5) ranges from 95.19 and 99.11%, whereas Id2 ranged between 96.94 and 100%, which shows that 80% of the samples have very high slake durability whereas remaining 20% exhibit high slake durability. There was no significant change in slake durability index from the second to the fifth cycles. Los Angeles Abrasion Value (LAAV) varies from 12.07 to 31.34% and Sulphate Soundness Value (SSV) varies within a limited range of 0.20 and 4.59%. Conclusively, the comprehensive evaluation suggests that the quartzite ballast from the Fagfog Quartzite source display favourable qualities in terms of point load, crushing and impact strengths and durable against abrasion, slaking and frosting. Thus, the quartzites from Fagfog Quartzite hold significant potential as a suitable rock type for railway track ballasts.

Application of audio-frequency magnetotelluric data to cover characterisation – validation against borehole petrophysics in the East Tennant region, Northern Australia

The characterisation of the thickness and geology of cover sequences significantly improves targeting for mineral exploration in buried terrains. Audio-frequency Magnetotelluric (AMT) data is applicable to characterise cover sequences, where their conductivity (inverse resistivity) can be differentiated. We present a regional study from the under-cover East Tennant region in the Northern Territory (Australia) where we have applied deterministic and probabilistic inversion methods to derive 2D and 1D resistivity models. We integrated these models with information of co-located basement penetrating boreholes (lithological and geophysical logs) to ground-truth and validate the models and to improve geophysical interpretations. In the East Tennant region, borehole lithology and wireline logging demonstrate that the modelled AMT response is largely controlled by the mineralogy of the cover and basement rocks. The bulk conductivity is due primarily to bulk mineralogy and the success of using the AMT models to predict cover thickness is shown to be dependent on whether the bulk mineralogy of cover and basement rocks are sufficiently different to provide a detectable conductivity contrast. Our investigation of a range of geological scenarios that differ in thickness, complexity and geology of the cover and basement rocks suggests that in areas where there is sufficient difference in bulk mineralogy and where the stratigraphy is relatively simple, AMT models predict the cover thickness with high certainty. In more complex scenarios interpretation of AMT models may be more ambiguous and requires integration with other data (e.g. drilling, wireline logging, potential field modelling). Overall, we conclude that the application of the method has been validated and the results compare favourably with borehole stratigraphy logs once geological (i.e. bulk mineralogical) complexity is understood. This demonstrates that the method is capable of identifying major litho-stratigraphic units with resistivity contrasts. Our results have assisted with the planning of regional drilling programs and have helped to reduce the uncertainty and risk associated with intersecting targeted stratigraphic units in covered terrains.

Eocene to Miocene palynology of the Amagá Basin (Cauca Valley, Colombia) compared to the Caribbean Region

The Cenozoic sedimentary basins of northwestern Colombia contain clues to understanding the evolution of past ecosystems and their possible relationship to regional events, such as the uplift of the northern Andes and the collision of the Panama-Chocó Block with the South American continent. However, these basins have not been thoroughly investigated. This work aims to fill this knowledge gap by performing a comprehensive palynological analysis of the Amagá Basin (Valle del Cauca). Three outcrops were studied to determine their depositional ages, paleoenvironments, and overall floral composition over time. To contextualize our analyses, a comparison was made with two drill holes (ANH-SSJ-Nueva Esperanza-1X and ANH-San Jacinto-1) in the Sinú-San Jacinto Basin in the Colombian Caribbean. The application of the palynological zonation from the Llanos Basin in eastern Colombia was also used to evaluate its suitability in the Amagá Basin. The age of deposition was determined by using several traditional palynostratigraphic markers, including Perisyncolporites pokornyi, Foveotriporites hammeni, Retibrevitricolporites speciosus, Magnastriatites grandiosus, Concavissimisporites fossulatus, Clavainaperturites microclavatus, and Polypodiaceoisporites pseudopsilatus. This assemblage indicates a Middle to Late Eocene, Oligocene, and Miocene age spanning from ~40 to 18 Ma (~22 Myr). However, there are also some differences with respect to the Llanos zonation, such as the absence of Cicatricosisporites dorogensis. Based on this age model, we question whether it is correct to include all these deposits in a single lithostratigraphic unit under the rank of a formation. In the Caribbean, stratigraphic units of similar age exhibit a greater number of key taxa than in the Llanos zonation. In addition, the presence of calcareous microfossils allows for a more detailed determination of the sedimentation age. Furthermore, the discovery of new pollen and spore species could improve the resolution of the biostratigraphy in western Colombia. In the Amagá Basin, only terrestrial palynomorphs were found, which, together with the sedimentary facies, suggest a humid lowland tropical vegetation in fluvial and lacustrine environments.

Stratigraphic context of Oligocene to Pliocene mammal-bearing deposits in Linxia Basin, Gansu Province, China: a historical review and a discussion of ongoing controversies

In this paper, we critically review the half-century (1962–2022) history of study of Oligocene to Pliocene mammal-bearing successions in the eastern Linxia Basin, Gansu Province, China. Despite great strides in our understanding of the regional geology and the discovery of a large quantity of mammal fossils, there remains major discrepancies concerning the definition and age assignment of the formations that comprise the Linxia Group. This has resulted in the development of two competing schemes for its subdivision: the first scheme was proposed by geologists of the Lanzhou University and the Institute of Tibetan Plateau Research, and the second scheme is associated with paleontologists of the Institute of Vertebrate Paleontology and Paleoanthropology. In an attempt to solve these discrepancies, a five year project was initiated in 2017, and herein we report the main findings as follows: (1) The Jiaozigou Formation does not extend into the Miocene, with its top calibrated at about 23 Ma; (2) The Liushu Formation, as defined in the Maogou section, should be considered as the penecontemporaneous shallow water facies of the coarse-grained Hujialiang Formation of Middle Miocene age; (3) The widespread Hipparion-bearing deposits along the Guangtong River, which have been also referred to the “Liushu” Formation represent a different stratigraphic unit and should be given another name to eliminate confusion following further stratigraphic analysis.

Link Mo isotopes to the sources of the Paleoproterozoic Mo mineralization in the Qinling orogen

Longmendian and the Zhaiwa are the two oldest Mo deposits in the Qinling orogenic belt, China, which is one of the most important Mo provinces in the world with numerous and diverse types of Mo deposits that experienced multistaged mineralization. Here we investigated Mo isotope compositions in molybdenite and rocks from the Longmendian and the Zhaiwa Paleoproterozoic Mo deposits to link Mo isotopes to the sources of Mo metal. The significant Mo isotope variation in the Longmendian and the Zhaiwa Mo deposits (δ98Mo = −0.51‰ to + 1.01‰ and −0.37‰ to +0.53‰, respectively, relative to NIST-3134) may be controlled by Rayleigh and equilibrium fractionation. The different distributions of Mo isotope compositions of molybdenite in the two deposits may be caused by the physiochemical differences in ore-forming systems. The high Mo content of the Taihua Supergroup and the Xiong’er Group, combined mean values of Mo isotopes between molybdenite and whole rocks suggested that the two stratigraphic units would be the main contributor of Mo for the Paleoproterozoic Mo mineralization that mixed with small proportions of isotopically lower values of the mantle.

Petrogenesis of metavolcanics and detrital zircon geochronology of the Mesoarchean western Iron Ore Group supracrustals, Singhbhum Craton (India): Evidence for an intracontinental extension setting

The Singhbhum Craton of eastern India, consisting of well-preserved Paleo- to Mesoarchean granitoids, volcanic and sedimentary rocks, is an excellent archive of early earth processes. In this contribution, we investigated the geological evolution of the Noamundi-Jamda-Koira IOG Basin (WIOG) using detrital zircon U-Pb ages, whole rock geochemical and Nd isotopic data on metavolcanic rocks from this belt including the Jagannathpur volcanics. The metavolcanics of the WIOG and Jagannathpur are compositionally basaltic andesites with enriched LREE and negative anomalies of Nb-Ta and Ti. The ratios of crustal contamination sensitive elements such as La/Sm, Sm/Nd, Nb/La, Th/Yb and Nb/Yb are close to that of bulk continental crust. The Nd isotopic composition of these basaltic andesites are broadly chondritic (εNdt = +0.93 to −1.20). The geochemical and isotopic signatures are consistent with significant assimilation of Paleoarchean granitoids of the Singhbhum Craton. The overlapping geochemical and isotopic compositions support the view that Jagannathpur volcanics is an eastward extension of the ∼3.04 Ga WIOG metavolcanics and shouldn’t be considered as a separate stratigraphic unit. The presence of pillowed structures, vesicularity, absence of volcanic breccia, and their association with clastic sediments clearly indicate a subaqueous and shallow marine eruption for the WIOG basaltic andesites. The deposition of clastic sediments before basaltic magmatism points towards lithospheric thinning and basin opening. The detrital zircon ages from the WIOG ranges from 3.51 to 2.96 Ga and the detritus was mainly sourced from the adjacent Singhbhum granite and Bonai granite. The petrogenesis of the WIOG metavolcanics can be attributed to assimilation-fractional crystallisation of a depleted mantle derived tholeiitic mafic-ultramafic magma in an intracontinental extension setting.

Understanding the initial upper plate architecture and shortening distribution in subduction-related orogens: Insights from the Central Andean forearc

The Central Andean Forearc (26°S) structure has been debated for decades. Extension, contraction, and strike-slip deformation are commonly proposed mechanisms to explain the main tectonic elements exposed in the Domeyko Cordillera, Salar de Pedernales Basin, and others partially exposed in the Coastal Cordillera and Central Depression. Although pre-Andean tectonic inheritance seems to have influenced the style and mechanisms of mountain uplift in this region, its current architecture and the way it controlled the shortening distribution during orogen evolution are highly speculative, mainly because some of the tectonic provinces in this segment consist of covered areas (e.g., the Central Depression). To address this question, we present the first balanced cross-section and pre-shortening restoration of the Andean forearc at 26°S. We integrated new field data from the Coastal and Domeyko cordilleras with well data and re-interpreted 2D seismic profiles from the Salar de Pedernales Basin to construct a regional-scale cross-section of 210 km length from the Coastal Cordillera to the current Volcanic Arc, thus showing a two-dimensional (2D tectonic model to help understand the tectonic evolution of the western Central Andes. The results indicate a pre-shortening architecture dominated by Late Permian–Jurassic half-graben structures related to continental rifting. West- and east-dipping basement-rooted normal faults controlled rift-related basins, along which kilometric-scale marine and continental syn-rift sequences accumulated. During early Andean orogenesis, the normal faults were partially inverted, and large anticlines developed at the hanging wall faults, which Upper Cretaceous progressively covered to Paleocene synorogenic units. This suggests that the initial topographic relief in the region resulted from a basin inversion. During the more advanced stages of orogenesis (mid-Cenozoic), new reverse and thrust faults (or shortcut faults) were created, which connected upward with incompetent stratigraphic units and facilitated the propagation of localized fold-and-thrust belts in the eastern Domeyko Cordillera and Salar de Pedernales basins. A minimum of 16.3 km of W-E shortening was reported; however, nearly 11 km was accommodated by the newly created thrusts, indicating that these were most relevant to mountain building.

Quaternary stratigraphy of Poland – current status

A critical verification of the previous stratigraphic Quaternary subdivisions has updated the setting of the stratigraphic units in Poland. Inconsequently applied classification and terminology in the Polish Quaternary stratigraphy has been accompanied by arbitrary correlation with marine isotope stages. This has resulted in the creation of several stratigraphic units, occasionally with ambiguous stratigraphic setting and chronology, and usually devoid of the type sections. A record of most of the Early and Middle Pleistocene is full of sedimentary hiatuses. The detailed stratigraphic setting of 5 glaciations (Nidanian, Sanian 1, Sanian 2, Odranian and Vistulian) and 4 interglacials (Podlasian, Ferdynandovian, Mazovian and Eemian) has been established in the Pleistocene of Poland. The palaeomagnetic Brunhes/Matuyama boundary was determined within the Podlasian Interglacial and therefore, the oldest glaciation (Nidanian) has no equivalent anywhere in Europe. The stratigraphic units distinguished are correlated with those in Western Europe and with the marine isotope stages. The Quaternary stratigraphy in Poland is faced with the necessity of how to define regional stratotypes of the main stratigraphic units and boundaries. A crucial issue is to change the approach from a qualitative description of the stratigraphic units to one based also on selected quantitative criteria.

Convective Versus Conductive Heat Flow in The Central Alberta Part Of The Western Canada Sedimentary Basin

Alberta, Canada, T6H 5X2. A detailed study of the hydrogeological and geothermal regimes in the Phanerozoic sequence of the Western Canada Sedimentary Basin was carried out for the Swan Hills and Cold Lake areas in central Alberta. The study was based on the examination, processing and interpretation of information from 6276 wells distributed over a total area of 39,500 km². The information processed refers to stratigraphic picks, chemistry of formation waters, drill stem tests and bottom hole temperatures. As a result, every stratigraphic unit is defined in terms of geometry and lithology, and characterized by appropriate hydraulic and thermal parameters. A sequence of eight major aquifer groups separated by eight aquitards and two aquicludes was identified. The fluid flow in the Paleozoic aquifers is mainly horizontal and regional in nature, being driven by the difference in hydraulic potential between the high areas in the foothills and the lowland areas in the prairies. The fluid flow in the Cretaceous aquifers is of regional to intermediate type, with a significant downward component. The fluid flow in the aquitards is vertical. The very low permeability of the strata is reflected in flow velocities on the order of magnitude of 1 cm/a and less. Dimensional analysis of heat transport processes in each hydrostratigraphic unit shows that convective heat transfer is negligible with respect to conductive heat transfer. The respective values of the Peclet number for heat flow in porous media areas are less than 10-2. In the Swan Hills and Cold Lakes areas the flow of the terrestrial heat flux from the crystalline Precambrian basement of the sedimentary basin to the atmosphere is controlled by the geometry and the changes in the thermal properties of the formations in the basin. The geothermal gradients for individual layers vary from 17 mK/m for sandstone units to 42 mK/m for shales. The integral geothermal gradient of the entire sedimentary column varies between 22 mK/m and 36 mK/m. The areal distribution of the integral geothermal gradient shows a strong correlation with stratigraphy and lithology.

Controls on sedimentation in a deep‐water foredeep: Central Pindos foreland basin, western Greece

AbstractThis study provides a sedimentological, stratigraphic and palaeocurrent investigation of Upper Eocene to Lower Oligocene deep‐sea fan deposits found in the central part of the Pindos foreland basin in western Greece. According to facies analysis, the examined succession at Amfilochia area has 13 sedimentary facies and 10 facies and sub‐facies associations. Depositional elements include abyssal plain pelagics, outer fan, inner fan, and slope deposits. Outer fan sediments are classified as lobe‐axis, lobe‐off‐axis, lobe‐fringe, and distant lobe‐fringe deposits, while inner fan sediments are classified as channel‐fill, crevasse‐splay, internal and external levee deposits. The stratigraphic study shows an upward shift from abyssal plain pelagics to outer, inner fan, and finally slope deposits, implying submarine fan system progradation and progressive infilling of a deep‐water sediment depocentre. The sediments were deposited in the foredeep of the Pindos foreland system and correspond to the system's underfilled stage, when sedimentation was unable to exceed the accommodation provided by lithospheric flexure. They point to deposition near the onset of the Pindos orogen, after the closure of the Pindos basin because of the collision of the Apulian with the Pelagonian microplate during the Cretaceous‐Palaeogene period. Palaeocurrent data from sole marks show bipolar directions associated with two distinct spreading sub‐marine fan deposits. As a result, the study region was split into Upper (major SE‐direction flow) and Lower (major NW‐direction flow) parts, indicating that axial flows were predominant during sediment deposition. However, as the deposition of the elements continued, the progradation of both systems constrained the space accommodation because of the increased basin sediment supply and forced an increase in the degree of basin confinement that changed the compensational to aggradational stacking pattern. The goals of this research are to develop an updated facies model for these deep‐sea fans as well as a robust correlation framework for the various stratigraphic units in the central Pindos foreland basin. This research also connects the stratigraphic development of deep‐sea fan deposits to the evolutionary phases of the Pindos foreland system, providing fresh insights into the palaeogeographic circumstances in the Pindos foreland basin.

Tectono-stratigraphic framework and evolution of the northwestern Arabian plate, Central Jordan

The northwestern Arabian plate has been long influenced by various processes, including late Precambrian crustal extension, Paleozoic rifting and ice-sheet loading/unloading, and inversion during the Late Cretaceous–Late Eocene times. It has been experiencing extension in a N-S direction since the Oligocene, N-S-trending strike-slip faulting along the Dead Sea Transform Fault accompanied by the N-S extension of its surroundings, as well as shortening from E to W since the Miocene. The primary objective of this research is to examine the tectono-stratigraphic development of the Central Jordan Region (CJR), located in the northwestern Arabian plate, by employing data from seismic surveys and well logs. The CJR hosts five significant fault systems: Feinan-Zekimat AlHasa, Salwan, Karak-Wadi Al Fayha, Dana, and Hasa faults. Despite the surface expressions of these faults highlighting the tectonic impacts during the Late Cretaceous-recent period, there is a lack of comprehensive research investigating how previous tectonics influenced their structural evolution. Seismic data and well-log integration provide a unique opportunity to fill this knowledge gap. Here we identified six major stratigraphic units: upper Precambrian, Cambrian, Ordovician, Silurian, Lower Cretaceous, and Upper Cretaceous. Using time-structure maps, we also identified several phases of fault growth, with evidence suggesting that faulting primarily occurred during the late Precambrian as part of the Najd Fault System. The reactivation of these faults can be attributed to the combined effects of the Late Ordovician ice-sheet loading and the uplift during the late Paleozoic to Early Cretaceous periods. The growth of all pre-existing faults was contemporaneous with a change in the regional stress field from the Late Cretaceous to the recent. The vertical correlation between the latest Cretaceous faulting of the CJR and the previously published topographic lineaments map suggests a tectonic control on the evolution of the surface structures.

Bayesian fusion of MT and AEM probabilistic models with geological data: examples from the eastern Gawler Craton, South Australia

When building 3D models of the subsurface, reconciling several geological and geophysical data of diverse nature, resolutions, coverage, or sensitivity, is challenging, both numerically and petrophysically. In this work, we propose a workflow for mapping selected geological features and characterise their uncertainty using a Bayesian Estimate Fusion algorithm. Different datasets such as 1D probabilistic models derived from geophysical data, drillholes and geological data are combined to produce probabilistic maps of selected geological boundaries, relying on petrophysical and geological assumptions. Leveraging large, high-quality geophysical datasets acquired in the eastern Gawler Craton in South Australia, we demonstrate the applicability of our approach with two examples: (1) we map in 3D the top of a stratigraphic unit in the cover, the Tregolana Shale, using 1D magnetotelluric (MT) and 1D Airborne Electromagnetic (AEM) probabilistic models, drill holes and surface geology; (2) we map the depth to basement using 1D probabilistic MT models, drill holes and interpreted structural information. Our results show that the different resolution, data sampling, depth of investigation and reliability of the utilised datasets can be combined in a complementary fashion, overcoming their respective limitations, to find solutions/models that satisfy all the datasets. We show that probabilistic workflows permit characterisation and reduce uncertainty when mapping the location of features of interest, but also permit the testing of geological hypotheses against other geophysical and geological data. These types of models are valuable to better characterise, interpret, and conceptualise the subsurface, enabling better exploration targeting and supporting efforts to discover new mineral deposits.

Sedimentation since 140 ka in Te Tai-o-Aorere Tasman Bay, Aotearoa New Zealand

ABSTRACT Late Pleistocene and Holocene sedimentation records changes in glacio-eustatic cycles, oceanography, active tectonics, and sediment supply. Here, we use high-resolution seismic-reflection profiles in Te Tai-o-Aorere Tasman Bay to investigate sedimentary deposit distributions associated with sea-level cyclicity over ∼140 ka. We identify nine seismic stratigraphic units below the inner continental shelf, interpret their character based on stratal relationships and acoustic properties, and infer ages using global sea level. The sequence includes stacked deposits and unconformities associated with the shifting shoreline over glacial cycles. Prominent erosional features include a lowstand ravinement surface and two transgressive surfaces formed during sea-level rise following the last two glacial maxima of ∼20 ka and ∼140 ka. The youngest surface marks the base of post-glacial sediment accumulated since ∼12 ka in the study area. Post-glacial sediment includes five seismically mappable units, covering an area of ∼1400 km2 and deposit volume of ∼9 km3. Time-averaged sediment accumulation rates are estimated to range from a maximum of ∼1.6–2.8 m/kyr to ∼0.5–0.9 m/kyr. Sequence stratigraphy interpreted in Te Tai-o-Aorere Tasman Bay is representative of accumulation in a relatively wide-shelf, sheltered inner bay setting supplied by mountainous catchments, and provides stratigraphic context necessary for future stratigraphic and tectonics studies.

Rapid geomorphological evolution in the Mediterranean Basilicata region (southern Italy) during Little Ice Age

There is a general consensus that the increased frequency of extreme climatic events will quickly change the morphology of the landscapes in the Mediterranean area. Knowing and understanding the expected changes becomes crucial for defining future adaptive strategies. This paper deals with the very rapid geomorphological evolution in an emblematic Mediterranean area, the Basilicata region of southern Italy, during the last 300 years. The results show that the landscape evolution was mainly controlled by the extreme sensitivity of surface processes to climate change. Landslides, a new cycle of the formation of badland landforms such as calanchi and biancane, and an aggradation/incision phase in the main river valleys have completely reshaped the landscape of the Bradanic Trough, whereas fresh eroded material was moved to the coast. New data on valley-fill alluvium in the Basento River and one of its main left tributaries, the Vella stream, show ages ranging from 1700 to 1850. This deposition phase coincides with the Little Ice Age, an epoch of global climate variability. Previous literature showed that the alluvium of this age consists of a mappable stratigraphic unit outcropping in all the large alluvial valleys of the Basilicata and Mediterranean regions. Palaeoclimate and high-resolution palaeoflood data indicate that valley-fill alluviation occurred during a long humid period. Valley aggradation ended in approximately 1850 with the beginning of a new phase of historic arroyo cutting, mainly due to high magnitude-low frequency rainy events within prolonged drought periods. The stream incision drew the terminal dissection of the clayey slopes into biancana rounded morphologies. These data seem to be confirmed by the comparable heights of about 3 m, both of the biancane and of the fluvial terraces.

Trace fossils from Furnas formation (Paraná Basin) reveal a marine depositional environment

Trace fossils are important biogenic signatures in sedimentary environments because they indicate the paleoecologic controls during deposition. In some cases, trace fossils are the unique preserved biologic evidence, allowing to infer paleoenvironments in controversial stratigraphic units. This is the case of Furnas Formation from Paraná Basin, Brazil. This unit was widely interpreted as fluvial-generated up to 1990's, but facies association analysis and the ichnologic data have been used as tools to suggest a marine origin for the unit. However, some recent studies have been ignored that information and continuous to interpret Furnas Formation as a fluvial-generated unit. In this study we analyzed some outcrops at northeast of the Ponta Grossa Arch aiming to infer depositional processes and paleoenvironments for basal and intermediated units of Furnas Formation (Lower Silurian). Nine ichnotaxa (Cruziana, Didymaulichnus lyelli, Didymauliponomos rowei, Heimdallia chatwini, Palaeophycus tubularis, Rusophycus, Skolithos, Taenidium dieslingi, and Thalassinoides) expressing proximal and depauperate Cruziana ichnofacies were reported for the studied outcrops, corroborating the shallow marine paleoenvironment inferred for the unit.