Outcrop Area Research Articles

Rock outcrops as interglacial refugia for plants: Ecological evidence from the forest‐steppe transition of Patagonia

AbstractIn the forest‐steppe transition of Patagonia from Argentina, the intense physical variability promotes the occurrence of contrasting vegetation units, among which is the saxicolous meadow developed on rock outcrops. In temperate and tropical regions, these geoforms of highly variable climate and topography, and poor soil development play an ecological and evolutionary role disproportionate to their reduced area. In Aguas Frías (38°46′S, 70°54′W), the range, diversity, density and adaptation of vascular plant species growing in the saxicolous meadow were compared to those of the surrounding steppe, forest and hygrophilous meadow. We hypothesize that rock outcrops exhibit a compositionally and functionally divergent, cold‐adapted flora of a previously more widespread distribution, allowing them to be categorized as refugia for species whose range retreated during the current interglacial. In comparison to the other units, the saxicolous meadow exhibited a small area, low plant cover, high total, native and rare species richness, high density and diversity of species, high richness of unique families and species and an exclusive presence of (rock) ferns. It also presented a high richness of endemic species with more extreme latitudinal and altitudinal distribution, particularly >46° S and >3000 m a.s.l. The similarity of species between the saxicolous meadow and the other units was low. Chamaephytes and nanophanerophytes were dominants, hemicryptophytes and geophytes were infrequent and mesophanerophytes and therophytes were absent. Equivalent results in terms of area of rock outcrops, and origin, strategy, composition, diversity and range of species were found in different regions. The biological and physical attributes would allow these outcrops to be characterized as reduced habitats of high diversity which could be acting as refugia for cold‐adapted plants. Conservation actions must prevent and mitigate the effects of fire, biological invasion and cattle grazing that represent the current threats to this ecosystem.

Palynological variability within the Permian (Changhsingian) Umm Irna Formation (Jordan): implications for biostratigraphy and fluid-flow character in alluvial formations

The Permian (Changhsingian) Umm Irna Formation (Jordan) yields important plant fossils that have influenced our understanding of the early evolution of plants that later dominated the vegetation of the Mesozoic. The formation was deposited in a fluvial regime characterised by the co-occurrence of stacked small-scale braided channels and of larger, higher-sinuosity channels with deposition on point bars, all intercalated into a heterogeneous background sedimentation of finer-grained floodplain deposits, including stacked crevasse-splay deposits, interspersed abandoned-channel and oxbow-lake fills, and lenses of peaty back-swamp deposits. Here, we document the remarkable compositional variability expressed in 124 palynomorph assemblages that were recovered from different argillaceous deposits in the Umm Irna Formation within a ∼2 km2 outcrop area around a major meandering channel. Our results reveal lateral and vertical variation within individual argillaceous units, as well as lateral variation between different argillaceous units in the same sedimentary complex at similar stratigraphic levels. When combined with plant macrofossil data, the results show that variability in the palynological content may be influenced mainly by two factors. The first is connectedness to the major channel; the drainage system carried a mixture of palynomorphs from across the floodplain but also from a large hinterland of tributaries draining higher parts of the floodplain and uplands beyond to the south and east. The second is the influence of local vegetation communities on the floodplain which would likely be more marked in less connected parts of the floodplain. These findings have implications for the palynological study of alluvial sequences of the Palaeozoic and Mesozoic, and for understanding the ability to identify mudstone units via palynological fingerprinting. Such individual units are of great importance as baffles to fluid flow in reservoirs that might be used for oil and gas, low-temperature geothermal energy storage, carbon capture and storage, and hydrogen storage in alluvial successions.

How much rainwater contributes to a spring discharge in the Guarani Aquifer System: insights from stable isotopes and a mass balance model

ABSTRACT Outcrops play an important role in groundwater recharge. Understanding groundwater origins, dynamics and its correlation with different water sources is essential for effective water resources management and planning in terms of quantity and quality. In the case of the Guarani Aquifer System (GAS) outcrop areas are particularly vulnerable to groundwater pollution due to direct recharge processes. This study focuses on the Alto Jacaré-Pepira sub-basin, a watershed near Brotas, a city in the central region of the state of São Paulo, Brazil, where groundwater is vital for supporting tourism, agriculture, urban water supply, creeks, river and wetlands. The area has a humid tropical climate with periods of both intense rainfall and drought, and the rivers remain perennial throughout the year. Therefore, the aim of this study is to investigate the interconnections between a spring and its potential sources of contribution, namely rain and groundwater, in order to elucidate the relationships between the different water sources. To achieve this, on-site monitoring of groundwater depth, rainfall amount, and stable isotope ratios (deuterium (2H) and oxygen-18 (18O)) from rain, spring discharge, and a monitoring well was carried out from 2013 to 2021. The results indicate that the mean and standard deviations for δ18O in rainwater exhibit higher variability, resulting in −4.49 ± 3.18 ‰ VSMOW, while δ18O values from the well show minor variations, similar to those of the spring, recording −7.25 ± 0.32 ‰ and −6.94 ± 0.28 ‰ VSMOW, respectively. The mixing model’s outcomes reveal seasonal variations in water sources contribution and indicate that groundwater accounts for approximately 80 % of spring discharge throughout the year. Incorporating stable isotopes into hydrological monitoring provides valuable data for complementing watershed analysis. The values obtained support the significance of the aquifer as a primary source, thereby offering critical insights into stream dynamics of the region.

Geology and characteristics of petrographic rocks in the region of Trepça, Kosovo

Purpose. The purpose of this paper is to accomplish a thorough identification of rock types occurring within the Mitrovica region by describing in detail all encountered varieties. The authors aim to determine the discontinuity or continuity of all inter-formational boundaries, crucial for accurate delineation on the ground and complete reflection on a 1:25000 scale map. Additionally, the objective is to identify the nature of contact between rock types and provide a detailed their description. Methods. Field exploration in the Mitrovica region was conducted for several months. Rock identification involved detailed sampling and petrographic analysis, including thin section preparation of magmatic rocks. The method included sample preparation, polarized light source interactions with minerals and observation of optical properties. Key properties observed are birefringence, interference colors, extinction angles, identification and analysis. Findings. Based on the study of stratigraphic units and geological descriptions of mineral outcrop areas, various types of rocks through petrographic microscope preparation, as well as chemical and geochemical analyses, have been differentiated. The Mitrovica area encompasses the following lithostratigraphic units: harzburgite, gabbro, diabase, metasandstone, sandstone, quartzite and grainstone with calcium (Aeolisaccus sp.; Bioclastic grainstone with dacycladal algae and small milliolides; Salpin-goporella sp.). Originality. The originality of the research lies in employing an optical microscope for the precise identification of rocks. Through the re-search carried out in the study area, we obtained a comprehensive petrographic description of mineral composition, texture, and mineralization, facilitating the assessment of the area exploitation potential. Practical implications. The petrographic exploration yielded the conclusion that the Pb-Zn mineralization is present in the study area, which is a sig-nificant finding for the advancement of the mining sector and the local community, provided that environmental preservation measures are upheld and responsible methods of area exploitation are implemented.

Detrital zircon ages and proposed provenance of the Koegas Subgroup of the Ghaap Group, and overlying Makganyene Formation, of the Postmasburg Group, Transvaal Supergroup

Abstract The late Archaean to early Palaeoproterozoic strata of the Transvaal Supergroup of southern Africa is renowned for hosting geological units that preserve some the Earth’s most significant geological events. The glaciogenic Makganyene Formation is one such significant unit, given that it has been associated with the Snowball Earth Event. The maximum age of deposition of this formation, and subsequent timing of this event, has come into question, mostly because of concordant detrital zircon ages as young as ~2.2 Ga reported by Beukes et al. (2013). These ages are younger than the recently revised ca. 2.43 Ga baddeleyite age inferred for the overlying Ongeluk Formation and subsequently led to a significant revision of a long-held correlation between the upper Postmasburg- and Pretoria groups of the respective sub-basins of the Transvaal Supergroup. The primary objective of this study is to investigate the mode of occurrence of the ~2.2 Ga zircons in the Makganyene Formation as well as selected formations of the underlying Koegas Subgroup. Here, we report a total of 183 near concordant U-Pb zircon ages for the Koegas Subgroup (Pannetjie- and Naragas formations) and 967 such ages for the Makganyene Formation, extracted from seventeen samples from across the outcrop area for these units. Sensitive High Resolution Ion MicroProbe (SHRIMP) as well as three different Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) techniques were used for U-Pb age measurements. We assessed the quality of the respective data sets and possible shortcomings of the techniques to constrain the maximum age of deposition of the units and to infer possible source areas for the detritus. In contrast to zircon ages determined for the Koegas Subgroup, zircons younger than ~2.4 Ga are a prominent feature of the Makganyene Formation. Upon careful consideration of each data set, we concluded that these so-called young grains have likely suffered significant Pb-loss and that a possible overcorrection for common Pb during data reduction could not be ruled out. Although the age distribution generated using the respective techniques were comparable, none of the four techniques were successful in shedding light on the reliability of the ~2.2 Ga ages. The maximum age of deposition of the Makganyene Formation could not be constrained with confidence and therefore the revised correlation between the Postmasburg- and Pretoria groups is not contested. The detrital zircon age distribution of the Koegas-Makganyene succession was however found to be remarkably similar, with a major ~2.5 Ga age fraction and subordinate fractions at ~2.65 to ~2.9 Ga and older than ~3.0 Ga. The major ~2.5 Ga zircon age fraction points towards a prominent, likely orogenic source of detritus. We assign the origin of the major ~2.5 Ga and older zircon age fractions to a Rae-type craton, which we proposed to have been attached to the north of the Vaalbara Craton at time of deposition of these units and consider a tectono-magmatic event characteristically associated with this family of cratons as the possible cause of alteration and Pb-loss in zircon grains dated at ~2.2 Ga.

Impact of landslide on geoheritage: Opportunities through integration, geomorphological classification and machine learning

Landslides are widely understood to cause damage to the geological features and the surrounding environment. Our study focuses on the northern region of the Karangsambung-Karangbolong Geopark (KKNG), characterized by diverse lithology and multi-phase tectonics. This study aims to explore (i) landslide susceptibility assessment, (ii) geomorphological characteristics and distribution of landslide susceptibility, and (iii) identification of landslide impacts on geosites. We mapped morphogenesis, morphology, materials, and processes to understand the geomorphological context, identifying three primary landforms: structural, pediments, and fluvial. For landslide susceptibility mapping, we used the XGBoost algorithm with cross-validation and utilized the area under the receiver operating characteristic curve (AUROC) for model validation. The XGBoost model revealed a high susceptibility classification for 10 geosite points. Landslides have negative impacts, such as Olistoliths of coral limestones, Exotic-blocks of chert, and calcareous red claystone that change landforms and damage outcrops. Nevertheless, some landslides have positive impacts on the geosite, such as Exotic-blocks of phyllites, and Exotic-blocks of pillow lava and radiolarian chert, because landslides can reveal fresher outcrops and rock structures, and the outcrop area becomes larger. Landslide mapping has successfully identified geosites that are highly vulnerable and have adverse impacts, especially those with certain lithological characteristics. This research on viewing disaster as a harmful process has evolved into a more holistic view of the disaster. This view includes various positive aspects that involve understanding the complex interactions between geology and geomorphology towards the geosite. By understanding the relationship between geomorphologic features (morphology, material, process, morpho-arrangement) and landslide occurrence, effective management strategies can be implemented to develop geological heritage further.

Exploring the formation of Tangará sill: A single-pulse intrusion feeding CAMP lava flows in Parecis Basin, Brazil

The Central Atlantic Magmatic Province (CAMP) stands out as a distinctive large igneous province on the Earth. Due to the extensive outcrop area of CAMP and its complex geological setting, the links between the extrusive and intrusive units are not fully understood. In the intracratonic Parecis Basin located in Central Brazil, the CAMP rocks are represented by mafic lava flows at its south (Tapirapuã Formation) and western edges (Anari Formation). Despite the availability of substantial geophysical, petrological and geochronological data, the understanding of CAMP feeder system in this region remains unclear. In this study, our focus is on investigating the Tangará sill, a dolerite intruded into Triassic sedimentary rocks in the South region of the Parecis Basin. Our aim is to contribute to a better understanding of the plumbing system in this area by investigating the Tangará sill and its potential links to the lava flows at the surface. The sill is identified as a tabular feature in seismic data, with a discernible base and top that extend for about 100 km from northeast to southwest. The Tangará sill was drilled by the 6-ANP-MT-02 stratigraphic well, revealing a continuous igneous intrusion with a thickness of 180 m (at depths ranging from 470 to 650 m). The dolerite intrusion is composed by plagioclase, clinopyroxene, opaque minerals and mesostasis (quartz + feldspar intergrowth and apatite). It can be divided into five segments: the upper and basal margins consist of fine-grained dolerite, the central portion comprises coarse-grained gabbro, which includes pegmatoid zones. The central portion is separated from the margins by two sections of medium-grained dolerite. The dolerite is tholeiitic, with low TiO2 content (<2 wt% TiO2) and low La/Yb ratio (average of 4.4). Geochemical and petrographic data indicate that the intrusion was formed by a single magma pulse and underwent differentiation through plagioclase and pyroxene dominated crystal fractionation. Two samples dated by 40Ar/39Ar geochronology using laser step-heating technique, yield plateau ages ranging from 204.0 ± 0.4 Ma to 202.0 ± 0.5 Ma. Sr-Nd-Pb isotopic data suggest a lithospheric mantle source with possible crustal contamination. Our findings suggest an emplacement model in which a thick single-pulse magma intruded the Triassic red beds. Along a NE-SW section, the sill is truncated by faults along the southern border of the basin, near the mapped lava flows of the Tapirapuã Formation. This suggests that the magma propagated from the northeast to the southwest along the sedimentary strata and fed the Tapirapuã volcanism. This example highlights a single-pulse sill feeding lava flows of the Central Atlantic Magmatic Province (CAMP).

The Devonian clastic wedge and underlying strata of southwestern Canadian Arctic Archipelago: stratigraphic revisions

The Devonian clastic wedge (DCW) and underlying carbonate platforms and basinal mudrocks of the study area are re-examined using legacy seismic data and X-ray fluorescence surveys of borehole chip samples. The Ordovician–Devonian basinal succession of Melville Island is consolidated under the name Ibbett Bay Group within the Northwest Territories, whereas equivalent strata in Nunavut are grouped into the Cape Phillips Formation. The Kitson Formation black shale is correlative with the upper Ibbett Bay Group. Six horizons with high TOC and high gamma response are traced in the Ordovician–Devonian, with the fourth (4a) approximating the Silurian/Devonian boundary; the upper two (4b, 5) are Emsian and Eifelian. In the direction of progradation, the base of Kitson Formation rises stratigraphically from gamma horizon 4a to 5. The upper Kitson represents basinal toes of westward prograding DCW clinoforms. The Blackley and Cape de Bray formations of Embry and Klovan (Embry, A.F., and Klovan, J.E. 1976. The middle-upper devonian clastic wedge of the franklinian geosyncline. Bulletin of Canadian Petroleum Geology, 24: 485–639. https://pubs.geoscienceworld.org/cspg/bcpg/article/24/4/485/57135) are not traceable enough to warrant their formation rank. We revert to the original usage of Tozer and Thorsteinsson (Tozer, E.T., and Thorsteinsson, R. 1964. Western Queen Elizabeth Islands, Arctic Archipelago. Geological Survey of Canada, Memoir 332: 242 p. doi:10.4095/100556) where these units are members within the Weatherall Formation. The distinctive seismic character of the Cape de Bray in western and central Melville Island warrants its recognition as a formal member; elsewhere, it is informal as it cannot be consistently traced. The Blackey is treated as a formal member in an outcrop area of ∼2000 km 2 where it was defined; it is not recognized in the subsurface. Onset of the DCW is tentatively linked to flexural subsidence and crustal thickening caused by the Romanzof Orogeny in the hinterland.

Linking northeastern North Pacific oxygen changes to upstream surface outcrop variations

Abstract. Understanding the response of the ocean to global warming, including the renewal of ocean waters from the surface (ventilation), is important for future climate predictions. Oxygen distributions in the ocean thermocline have proven an effective way to infer changes in ventilation because physical processes (ventilation and circulation) that supply oxygen are thought to be primarily responsible for changes in interior oxygen concentrations. Here, the focus is on the North Pacific thermocline, where some of the world's oceans' largest oxygen variations have been observed. These variations, described as bi-decadal cycles on top of a small declining trend, are strongest on subsurface isopycnals that outcrop into the mixed layer of the northwestern North Pacific in late winter. In this study, surface density time series are reconstructed in this area using observational data only and focusing on the time period from 1982, the first full year of the satellite sea surface temperature record, to 2020. It is found that changes in the annual maximum outcrop area of the densest isopycnals outcropping in the northwestern North Pacific are correlated with interannual oxygen variability observed at Ocean Station P (OSP) downstream at about a 10-year lag. The hypothesis is that ocean ventilation and uptake of oxygen is greatly reduced when the outcrop areas are small and that this signal travels within the North Pacific Current to OSP, with 10 years being at the higher end of transit times reported in other studies. It is also found that sea surface salinity (SSS) dominates over sea surface temperature (SST) in driving interannual fluctuations in annual maximum surface density in the northwestern North Pacific, highlighting the role that salinity may play in altering ocean ventilation. In contrast, SSS and SST contribute about equally to the long-term declining surface density trends that are superimposed on the interannual cycles.

North Atlantic Response to Observed North Atlantic Oscillation Surface Heat Flux in Three Climate Models

Abstract We investigate how the ocean responds to 10-yr persistent surface heat flux forcing over the subpolar North Atlantic (SPNA) associated with the observed winter NAO in three CMIP6-class coupled models. The experiments reveal a broadly consistent ocean response to the imposed NAO forcing. Positive NAO forcing produces anomalously dense water masses in the SPNA, increasing the southward lower (denser) limb of the Atlantic meridional overturning circulation (AMOC) in density coordinates. The southward propagation of the anomalous dense water generates a zonal pressure gradient overlying the models’ North Atlantic Current that enhances the upper (lighter) limb of the density-space AMOC, increasing the heat and salt transport into the SPNA. However, the amplitude of the thermohaline process response differs substantially between the models. Intriguingly, the anomalous dense-water formation is not primarily driven directly by the imposed flux anomalies, but rather dominated by changes in isopycnal outcropping area and associated changes in surface water mass transformation (WMT) due to the background surface heat fluxes. The forcing initially alters the outcropping area in dense-water formation regions, but WMT due to the background surface heat fluxes through anomalous outcropping area decisively controls the total dense-water formation response and can explain the intermodel amplitude difference. Our study suggests that coupled models can simulate consistent mechanisms and spatial patterns of decadal SPNA variability when forced with the same anomalous buoyancy fluxes, but the amplitude of the response depends on the background states of the models.

Depositional Model of Early-Middle Turonian Deep Water Gulneri Formation, in Selected Outcrop and Subsurface Sections in Northern Iraq

The Gulneri Formation (Early-Middle Turonian) Deep-water depositional model was constructed using detailed microfacies analysis from the northern Iraqi wells of Kirkuk (K-116) and Bai Hassan (BH-81) as well as the Dokan outcropped area. In the outcropped section, the formation consists of 2 m of thin friable marly limestone with high organic matter and thin-bedded black shale in addition to boulder and gravel-like limestone masses in the lower part. In the K-116 and BH-81 wells, the formation is 4.3 m and 9 m thick, respectively. It is composed mainly of black bituminous, pyritic calcareous shale, and shaley limestone with scattered glauconites. Petrographic studies of seventeen thin sections of the Gulneri rocks reveal that the pelagic/deep marine faunas are the dominant skeletal grain in the micritic groundmass. Three main microfacies were recognized in the studied rocks of the Gulneri Formation, namely lime mudstone, lime wackestone, and lime packstone. However, the latter is absent in the Dokan section. According to their environmental interpretation, these microfacies were grouped into two facies associations (basinal deep water and deep shelf). Based on the results of petrographic and microfacies analyses, it is concluded that the Gulneri Formation was deposited in a basinal deep marine environment with quiet and reducing conditions in the Dokan section and a basinal deep marine environment in the K-116 and BH-81 wells which changed at intervals to a shallower deep shelf setting toward the upper part with semi reducing conditions. The euxinic deep basin that formed at the beginning of the Kurdistan foreland basin's formation was quite anoxic and deeper from the northeast to the relatively shallower basin with semi-reduced conditions towards the southwest. This is how the depositional model of the Gulneri Formation in northern Iraq changed.

Stratigraphic and cartographic review in the western part of Bauru Basin – Brazil - (Upper Cretaceous): implications for the depositional model

ABSTRACT Bauru Basin (Upper Cretaceous) spans 190,000 km² in western segment, Mato Grosso do Sul and Goiás states, Brazil. The Supersequence is a predominantly sandy siliciclastic unit. In Mato Grosso do Sul state a substantial portion of the sedimentary supersequence was considered indivisible. This research, based on regional field surveys, presents updates to the geological map, depositional model, and lithostratigraphic chart of the western Bauru Basin. In Mato Grosso do Sul, the Rio Paraná Formation was identified, directly overlaying the Serra Geral Group in the south/southwest, and the Botucatu Formation on north/central region. The Santo Anastácio Formation outcrop area was found to be smaller than previously mapped, showing lateral contacts with the Rio Paraná and Vale do Rio do Peixe formations. The Vale do Rio do Peixe Formation, conversely, now exhibits a larger mapped area. Additionally, the Marília Formation were discovered in São Gabriel do Oeste-MS, previously marked as detrital-lateritic cover.

A study on the classification of geological background source cadmium migration phases in Zhejiang Province, China

The release of cadmium during the natural weathering process of cadmium-containing strata is a significant source of cadmium pollution in both water and soil. The Hetang formations, wildly located in Jiangxi Province Zhejiang Province and Anhui Province in China, is a typical example of a cadmium-rich black shale stratum and is one of the primary sources of soil cadmium contamination. The bottom coal seam of this formation has been found to contain high levels of cadmium, with concentrations up to 11.26 mg/kg. As a result of water flow eroding the riverbed, parent rocks containing cadmium undergo continuous weathering, releasing cadmium elements. This process contributes to cadmium pollution in downstream soil, originating from the geological background. By utilizing techniques such as FE-SEM, EDS, and optical microscopy, this study investigates the distribution of iron in rock fragments with varying degrees of weathering in the riverbed. The research aims to examine the influence of iron distribution on the migration of cadmium originating from geological background sources. Based on the co-occurrence and co-migration characteristics of iron and cadmium in the study area, this research aims to reveal the migration features of geological background source cadmium by exploring the distribution patterns of iron sediment within rock fragments. By comparing sediment samples from both upstream and downstream river channels, we were able to identify three distinct stages that indicate the presence of cadmium originating from geological sources under weathering conditions: the unweathered stage; the intra-detritus migration stage, and the completely weathered stage; intra-detritus migration stage; and completely weathered stage. Furthermore, after leaving the Hetang formations shale outcrop area, there was a sharp decrease in content for Hetang formations detritus. At this point geological background source cadmium had largely escaped from constraints imposed by rock microstructure and had come into full contact with water. The findings from this research deepen our understanding regarding migration patterns for geological background source cadmium. They also reveal formation processes for geological background source cadmium pollution and provide a theoretical basis for identification and treatment for geological background source cadmium pollution.

Structural control of the deposition and subsequent deformation of the Killary Habour-Joyce Country Silurian succession

Abstract: The Killary Harbour–Joyce Country succession of Silurian rocks forms the remnant of one of three successor basins that developed after the Grampian Orogeny and which are preserved in western Ireland. Its outcrop everywhere obscures the contact between the Dalradian rocks of Connemara and the Ordovician rocks of the South Mayo Trough. The outcrop is bisected by the prominent north-west trending Maam Valley Fault Zone that is shown to have a component of synsedimentary movement down-throwing to the southwest. The original basin margins lay well outside the current outcrop area. North-south shortening and inversion of the basin was accomplished by reactivation and inversion of earlier fault structures and was exclusively in the brittle zone. Folding of the Silurian rocks with weak to moderate cleavage and deformation of the basement rocks of Connemara was accomplished by largely vertical movements along numerous strike parallel and oblique fractures. Break-back inversion structures were developed along the southern margin of the South Mayo Trough, which include thrusting associated with footwall shortcut faults and clockwise rotation. Although the timing of deformation overlaps that of diorite sill emplacement, it remains poorly constrained in absolute terms.

The Mousty Formation (Brabant Massif, Belgium): state of the art

The Mousty Formation has unique and particularly interesting lithological, mineralogical, sedimentological, metamorphic and tectonic characteristics which have been the subject of much research in connection with the new geological map of Wallonia, but also within the framework of a large amount of academic research, sometimes unpublished. An effort to synthesise and upgrade it in an updated framework seemed necessary. After a history of its definition, mapping and outcrop areas, the following topics are successively addressed in detail and illustrated with diagrams and photos: its lithostratigraphy with the probable discovery of its base near the Court-St-Etienne anticline, its well-constrained biostratigraphy and chronostratigraphy, a new estimate of its minimum thickness, its sedimentology—a subject little addressed until now—, and the resulting depositional sedimentary environment. Its geochemistry, never addressed, is comparable to black shale international standards, except for abnormally high manganese and very low calcium contents; high radon levels in buildings are related to the black slate presence in outcrops. Its mineralogy is rich in manganese-bearing metamorphic minerals, its metamorphism in which we go beyond the strict framework of the formation to deal with the entire southern outcropping rim of the Brabant Massif. Finally, the relationship between the Mousty Formation and the tectonic is discussed, with additional field data, in the context of the innovative and unifying concept of a low-angle extensional detachment called the Asquempont Detachment System. All these observations, some old and some very recent, discussed in the updated framework of the geology of the Caledonian basement of Brabant and in the global stratigraphy and palaeogeography of the lower Palaeozoic, allow us to renew in depth the vision we had of the Mousty Formation and of its place in the Brabant Massif.

Сосновые (Pinus sylvestris) леса и редколесья Северо-Западного Приладожья

Сосновые (Pinus sylvestris) леса и редколесья Северо-Западного Приладожья

Structural Control of the Deposition and Subsequent Deformation of the Killary Habour-Joyce Country Silurian Succession

The Killary Harbour–Joyce Country succession of Silurian rocks forms the remnant of one of three successor basins that developed after the Grampian Orogeny and which are preserved in western Ireland. Its outcrop everywhere obscures the contact between the Dalradian rocks of Connemara and the Ordovician rocks of the South Mayo Trough. The outcrop is bisected by the prominent north-west trending Maam Valley Fault Zone that is shown to have a component of synsedimentary movement down-throwing to the southwest. The original basin margins lay well outside the current outcrop area. North-south shortening and inversion of the basin was accomplished by reactivation and inversion of earlier fault structures and was exclusively in the brittle zone. Folding of the Silurian rocks with weak to moderate cleavage and deformation of the basement rocks of Connemara was accomplished by largely vertical movements along numerous strike parallel and oblique fractures. Break-back inversion structures were developed along the southern margin of the South Mayo Trough, which include thrusting associated with footwall shortcut faults and clockwise rotation. Although the timing of deformation overlaps that of diorite sill emplacement, it remains poorly constrained in absolute terms.

Diagenetic history of calcite fractures in Vaca Muerta shales (Argentina) inferred from paired Δ47 and fluid inclusion geothermometry

Many low-permeability, hydrocarbon-bearing rocks are productive for petroleum because natural fractures enhance hydrocarbon delivery to wellbores. Exploration and development decisions often must be made in the face of uncertainty about the presence and properties of natural fractures at scales of beds, field and plays, and how they contribute to production. Fractures patterns in subsurface rocks are challenging to predict or characterize owing to the difficulty in obtaining representative samples of fractures and the sparse set of tools for reconstructing how and when fractures grow during sedimentary basin evolution. In this study, we investigate bed-parallel fracture diagenesis in the Vaca Muerta shales (Argentina) based on a set of calcite vein collected from core across a thermal maturity sequence that ranges from the oil to dry gas window. We characterize these samples using secondary ions mass spectrometry (SIMS) measurements of stable isotope ratios, carbonate clumped isotope geothermometry and fluid inclusion analysis. These measurements precisely reconstruct the evolution of fluid geochemistry, temperature and pore fluid pressure during fracture opening. Here we show that within each studied site, all bedding parallel fibrous veins calcite formed at similar ranges of temperature. The fracture mineralization temperature increases substantially at the basin scale, from 90 °C to 120 °C, correlated with host-rock thermal maturity. We compare our constraints on carbonate and fluid temperature with apatite fission track thermal models and find that most of the fractures of the Vaca Muerta shales have formed in a relatively early stage of subsidence of the basin (c.a. 90 to 70 Ma). These ages estimations are consistent with recently published U–Pb ages on calcite veins from the outcropping area (117–61 Ma). The presence of petroleum inclusions (oil, condensate, and gas) in most of the vein's calcite fibers from cores also provides clear evidence that fracture formation was contemporaneous or posterior with petroleum generation, constraining the timing of catagenesis in the Vaca Muerta. Reconstructed paleo pressures conditions of veins formation from fluid inclusion analysis highlight significant fluid overpressure in the shale interval, which likely contributed to fracture initiation and growth. Preserved apparent Δ47 temperatures in fibrous veins carbonates mineralization evolves gradually from 130 °C to 175 °C with increasing host rock thermal maturity. These clumped-isotope-based temperatures are systematically higher than trapping temperatures of associated fluid inclusions; one interpretation of this observation is that carbonate clumped isotope compositions re-equilibrated to near maximum burial conditions by solid-state isotopic re-ordering, yielding a record of the maximum burial temperature the shale unit experienced. The combination of paleothermometry techniques used in this study illustrates the importance of simultaneously exploring several independent geothermometers, particularly the informative combination of fluid inclusion and clumped isotope constraints, which provides a means of understanding the complex diagenesis of old sedimentary rocks that have experienced burial temperatures in the oil and gas thermal windows.

Evaluation of Mangroves Effectiveness in Strengthening Coastal Bund Using Geophysical Method (Non-Destructive Testing) at Tanjong Laboh, Batu Pahat, Johor

In recent years, mangrove forests have rapidly become an endangered ecosystem in the world. On the coastal shorelines, the saltwater intrusion (SI) phenomenon is a main concern that can affect the quality of water. The saltwater intrusion might occur due to sea level rise, and extreme natural disasters along with changes in mangrove ecosystem distribution. The purpose of this research is to evaluate the effectiveness of mangroves for strengthening coastal bunds in Tanjong Laboh, Batu Pahat, Johor. By using the non-destructive geophysical method, the presence of saltwater intrusion and subsurface profile of the survey line in the coastal area with and without mangroves was determined. The coastal bund conditions with and without mangroves were also compared in order to evaluate how the mangrove forest acts as coastal protection. The result shows that the resistivity values of 0.1 to 1.0 ohm are more dominant in the mangrove bund area than in the engineered coastal bund and rock outcrop areas. The saltwater intrusion integrity map was produced from the 2D subsurface image profiles for both survey lines. The comparison of the coastal bund conditions for two different scenarios, which with and without mangroves, has shown that the coastal bund without the mangroves experienced cracking and erosion compared to the coastal bund with the presence of mangroves. This indicates the importance of mangroves in protecting the coastal regions.

Using machine learning to predict selenium and cadmium contents in rice grains from black shale-distributed farmland area

Cadmium (Cd) and selenium (Se) are widely enriched in soil at black shale outcropping areas, with Cd levels exceeding the standard (2.0 mg/kg in 5.5 < pH ≤ 6.5) commonly. The prevention of Cd hazards and the safe development of Se-rich land resources are key issues that need to be urgently addressed. To ensure safe utilization of Se-rich land in the CdSe coexisting areas, 158 rice samples, their corresponding rhizosphere soils, and 8069 topsoil samples were collected and tested in the paddy fields of Ankang City, Shaanxi Province, where black shales are widely exposed. The results showed that 43 % of the topsoil samples were Se-rich soil (Se > 0.4 mg/kg) wherein 79 % and 3 % of Cd concentrations exceeded the screening value and control value, respectively, according to the GB15618-2018 standard. Meanwhile, 63 % of the rice samples were Se rich (Se > 0.04 mg/kg) and the Cd content exceeded the prescribed limit (0.2 mg/kg) in Se-rich rice by 26 %. There was no significant positive correlation between the Se and Cd contents in the rice grains and the Se and Cd contents in the corresponding rhizosphere soil. The factors influencing Se and Cd uptake in rice were SiO2, CaO, P, S, pH, and TFe2O3. Accordingly, an artificial neural network (ANN) and multiple linear regression model (MLR) were used to predict Cd and Se bioaccumulation in rice grains. The stability and accuracy of the ANN model were better than those of the MLR model. Based on survey data and the prediction results of the ANN model, a safe planting zoning of Se-rich rice was proposed, which provided a reference for the scientific planning of land resources.