Shallow Processes Research Articles

Bedding and bedding surfaces in carbonate and mixed carbonate-siliciclastic successions Part 2: processes, identification and implications of diagenetic bedding

Bedding and bedding surfaces in carbonate and mixed siliciclastic-carbonate successions can be diagenetic, not depositional in origin and require interrogation to determine their true origins. This study reviews the different models and implications associated with diagenetic bedding and diagenetic bedding surfaces in such successions. Weathering, especially where strong lithological and mechanical differences occur, can make distinguishing primary and diagenetic bedding more difficult, and criteria are reviewed. Early, shallow diagenetic processes linked to mineral instability of aragonite, mediated by biochemical processes, are capable of producing bedding and bedding surfaces. Zones of early cementation within sediments can produce discrete beds and surfaces exemplified in the formation of limestone-marl alternations (LMAs). Variations in the degree of early cementation (stratified cementation in sense of Bathurst, 1987) in shallow buried argillaceous carbonate sediments, affected by later compaction can produce layering with beds showing little compaction separated by highly compacted, argillaceous fissile interbeds which develop bedding surfaces within those fissile units (“couplets” of Bathurst, 1987). Where such diagenetic limestone beds form intrastratally, as in LMAs, they do not obey the Principle of Superposition, and by virtue of never having been deposited laterally adjacent to their associated deposits, do not comply with Walther's Law of Facies. Bedding surfaces associated with LMAs only become true surfaces when exhumed to produce some types of firmgrounds and hardgrounds.

Building the Albanides by Deep Underplating

AbstractSubduction orogens grow by accretion of slices of continental lithosphere scraped off the downgoing slab. Although seismological and geophysical data now illuminate the deep structure of these orogens, understanding deep crustal underplating dynamics remains challenging. This study focuses on the Albanides, a subduction orogen in the central‐eastern Mediterranean, formed by the accretion of continental material during the eastward subduction of Adria beneath Eurasia. The thickening at depth of the crustal edifice occurred along with the development of a shallow fold‐and‐thrust belt. This process involved the deposition of progressively younger syn‐orogenic deposits as deformation migrated SW‐ward from the Cretaceous to the Miocene. To explore the relationship between deep‐seated structures and surface deformation, we investigate the recent crustal thickening of the Albanides using low‐temperature thermochronology and 3D thermokinematic modeling of a seismically constrained crustal section. Our data reveal a pulse of exhumation during the latest Miocene‐Pliocene, amounting to approximately 3–4 km, which we propose has been driven by a deep‐seated thrust system imaged by receiver function images. These inferences have significant implications for understanding the interactions between deep and shallow crustal processes and their role in shaping the Albanides. Furthermore, they provide insights into the timing and kinematics of subduction‐related orogenic processes and, potentially, on the separation of the Adria plate from Africa.

Fabrication of low‐loss symmetrical rib waveguides based on x‐cut lithium niobate on insulator for integrated quantum photonics

AbstractLithium niobate on insulator (LNOI) is a promising material platform for applications in integrated quantum photonics. A low optical loss is crucial for preserving fragile quantum states. Therefore, in this study, we have fabricated LNOI rib waveguides with a low optical propagation loss of 0.16 dB/cm by optimizing the etching conditions for various parameters. The symmetry and smoothness of the waveguides on ‐cut LNOI are improved by employing a shallow etching process. The proposed method is expected to facilitate the development of on‐chip quantum photonic devices based on LNOI.

Branched Conduit Structure Beneath the Active Craters of Sakurajima Volcano Inferred From Muography

AbstractObserving in‐conduit physical mechanism underlying the switching of eruptive activity between the craters of multi‐vent volcanoes could contribute to hazard assessment at these complex volcanic edifices. We performed monitoring of mass density changes beneath two active craters of Sakurajima volcano in Kyushu, Japan between September 2018 and July 2023 with cosmic‐ray muography. From December 2022, the mass density decreased beneath Minamidake crater and increased beneath Showa crater in accordance with a switch of eruptive activity from Minamidake crater to Showa crater. Plug formation and convective magma degassing processes have been observed with muography in accordance with the deformation of the surface of volcanic edifice measured by Interferometric Synthetic Aperture Radar. We found a moderate inverse correlation with a Pearson’s coefficient of −0.52 between the mass densities observed beneath the two active craters throughout the entire period. The inverse correlation of mass densities indicates a magmatic gas flux dynamics which characterizes a branched conduit structure. Muography thus reveals the shallow magmatic processes during switching of eruptive activity between the craters of multi‐vent volcanoes and allows to infer to the conduit structure.

Diagenesis and reservoir quality evolution of estuarine sandstones: Insights from the Cenomanian-Turonian Yolde Formation, northern Benue Trough, NE Nigeria

Estuarine sandstones often exhibit complex diagenetic pathways due to the interaction of fluvial and shallow marine processes, resulting in significant reservoir heterogeneities. The Yolde Formation is an important petroleum reservoir in the Northern Benue Trough, NE Nigeria. However, diagenetic and reservoir quality evolution of the formation are still poorly understood. This study utilizes thin-section petrography, XRD, SEM, and fluid inclusion microthermometry to analyse the composition, diagenesis, and reservoir quality of the sandstones. Results show that the sandstones are mainly arkose and subarkose in composition; they are generally well-sorted and vary in grain size from very fine-to coarse-grained. Three diagenetic stages are identified: early, middle, and late. The early stage includes feldspar dissolution, formation of kaolinite, development of clay coating, and mechanical compaction. The middle stage comprises the formation of authigenic chlorite and Fe-oxide cements. The late-stage diagenesis involves illitization of kaolinite, formation of dickite, albitization of K-feldspar, and precipitation of quartz overgrowths. The diagenetic evolution of the sandstones was strongly controlled by their compositional makeup. The feldspathic nature of the sandstones resulted in the formation of kaolinite, illite, and quartz overgrowths, through feldspar dissolution and silica supply. The inner and middle estuarine facies have inhibited the development of quartz overgrowths due to well-developed clay coatings, whereas the outer estuarine facies were well-cemented by quartz overgrowths due to lack of clay coatings. Illitic clay coatings were found to be effective in preventing quartz cementation. Fluid inclusion analysis reveals that the formation temperatures of the quartz overgrowths range from 98 °C to 135.5 °C, corresponding to burial depths ranging between 2.3 and 3.5 km. These findings would provide useful insights that would reduce the risks of exploration of the sandstones and also supplies potential input data for forward diagenetic modelling of their subsurface equivalents in similar depositional settings elsewhere.

The role of plume-lithosphere interaction in Hawaii-Emperor chain formation

Paleolatitudes of volcanic rocks reveal that prominent changes in volcanic trend of the Hawaii-Emperor hotspot chain represent meridional migration of the magma source. However, models assuming latitudinal plume migration fail to explain the observed age distribution, rock composition, and erratic paleolatitude changes of the oldest Emperor seamounts. Here we use data-assimilation models to better reproduce the Hawaii-Emperor hotspot track by systematically considering plate reconstruction, plume-lithosphere interaction, and simplified melt generation and migration. Our results show that plate drag and plume-ridge interaction are both important in explaining the observed seamount ages. These shallow dynamic processes could account for 50% of the observed paleolatitude’s secular reduction and erratic variations over time, where the necessary southward migration of the Hawaiian plume root is significantly less than previously thought. We conclude that plume-lithosphere interaction represents a common mechanism in affecting hotspot track, and has important implications in understanding mantle dynamics and plate reference frames.

Berthierine/Chamosite ooids and associated phases in Devonian deposits of the Parnaíba Basin, Brazil: Genesis and diagenetic evolution

The Parnaíba Basin Devonian deposits comprise ironstones and organic-rich sediments deposited in an epeiric sea margin under greenhouse conditions, enhanced weathering, reduction of oceanic circulation, and black shale deposition. This study aims to contribute to the understanding of the interrelation between depositional and shallow diagenetic processes of the Devonian units of the Parnaíba Basin, specifically regarding the genesis of iron minerals that constitute the ooidal ironstones of the Itaim and Pimenteiras formations. These units comprise bioturbated heterolites, ooidal ironstones, intraclastic conglomerates, and shales, deposited in a deltaic to neritic, storm-dominated platform. This research investigates drill cores from two wells in the southern part of the Parnaiba Basin, focusing on depositional and diagenetic processes. The proposed model suggests deposition of sediments originally rich in organic matter, under low siliciclastic input, and initially anoxic, transgressive conditions. Under these conditions, ferroan precursor clays were deposited, alternating with periods of reworking by storm currents, generating concentric ooids of berthierine. Bioturbation processes resulted in the concentration of previously formed berthierine ooids during intervals of low sedimentation rates. Eodiagenetic microcrystalline siderite formed along the redox boundary between oxic/bioturbated and anoxic zones. Chamosite formed by partial transformation of berthierine, upon incipient mesodiagenetic evolution of the ooidal ironstones. This study contributes to the understanding of depositional and diagenetic conditions in the Devonian section of the Parnaíba Basin, and of similar deposits, offering insights into the formation and development of berthierine ooids under the influence of sea level fluctuations, oxic/anoxic conditions, sedimentation rate, and bioturbation in sedimentary environments, providing key insights into the paleoenvironmental conditions along the northern Gondwana margin during this period.

Surface matches prevail over distant analogs during retrieval.

Laboratory studies using a reception paradigm have found that memory items sharing similar entities and relations with a working memory cue (surface matches) are easier to retrieve than items sharing only a system of abstract relations (structural matches). However, the naturalistic approach has contended that the observed supremacy of superficial similarity could have originated in a shallow processing of somewhat inconsequential stories, as well as in the inadvertent inclusion of structural similarity during the construction of surface matches. We addressed the question of which kind of similarity dominates retrieval through a hybrid paradigm that combines the ecological validity of the naturalistic production paradigm with the experimental control of the reception paradigm. In Experiment 1 we presented participants with a target story that maintained either superficial or structural similarities with two popular movies that had received a careful processing prior to the experimental session. Experiment 2 replicated the same procedure with highly viralized public events. In line with traditional laboratory results, surface matches were significantly better retrieved than structural matches, confirming the supremacy of superficial similarities during retrieval.

Semantic-to-autobiographical memory priming: the role of stimulus processing.

It is now well established that semantic processing can cause the activation of memories in the autobiographical memory system. Studies have shown that semantic processing of words, sounds, objects, or pictures primes autobiographical memories on voluntary and involuntary autobiographical memory tasks (the Crovitz cue-word task and the vigilance task). Known as semantic-to-autobiographical memory priming, our goal in the current study was to demonstrate that this form of priming occurs under different forms of processing (i.e., shallow versus deep), and that some forms of processing (e.g., visual mental imagery) may enhance priming in this domain. In Experiment 1, equivalent semantic-to-autobiographical priming was obtained on the vigilance task following shallow (e-counting) and deep (meaning judgements) word processing. In Experiment 2, word meaning judgements were compared to visual imagery of word meanings, and visual imagery led to more semantic-to-autobiographical priming on the vigilance task than meaning judgements. The results of these experiments support the idea that semantic-to-autobiographical priming occurs under a wide range of processing conditions, supporting a ubiquity claim, with some conditions producing more priming than others, and they further support the idea that this form of may play an important role in the production of involuntary memories in everyday life.

Formation and hydrothermal alteration of a volcanic center: Melt pooling and mass transfers at Langseth Ridge (Gakkel Ridge, Arctic Ocean)

Volcanic centers are characteristic features of ultraslow-spreading mid-ocean ridges, the least-explored parts of the global ridge system. Volcanic centers can provide insights into deep magmatic and metamorphic processes at these ridges. Here, we present data from the largest volcanic center on the Gakkel Ridge, the Langseth Ridge, situated at 60–62°E. Langseth is ∼10 km wide, consisting of three peaks that rise to 585 m water depth, some 3–4 km above the surrounding seafloor. It strikes perpendicular to Gakkel's spreading direction and can be traced for ∼40 km, which translates to an age of ∼8 Myr. Seafloor imaging revealed abundant (pillow) basalt but also fissures and geologic faults across the Langseth Ridge. Basaltic rocks were sampled at all summits and diabase at the slope of the northern summit that dips into the rift valley.Our samples are of normal to depleted mid-ocean ridge basalt composition and exhibit a wide range of major and trace element contents, due to magmatic processes, accumulation of macrocrysts, and hydrothermal alteration. Radiogenic isotope ratios, most notably 143Nd/144Nd and 208Pb/206Pb, trend from typical rift valley compositions to isotopically enriched values with increasing distance to the rift valley. This trend may imply melt pooling from different sources, potentially representing a shift from shallow melting beneath the rift valley to deeper melting of enriched sources and higher degrees of melting underneath Langseth. Mineral compositions and plagioclase sieve textures imply prolonged storage of magma at depth prior to eruption. Hydrothermal alteration occurred over a range of conditions. Basalt from the summits is weakly altered at temperatures ≪100 °C, which likely occurred in situ at the summit sites. Diabase samples experienced chloritization and albitization and display epidote and quartz veins, which formed at >300 °C. These assemblages and temperatures are typical for lower crustal levels and imply uplift of the samples of >1 km. Diabase samples from the Afanasenkov Seamount, another volcanic center on the Gakkel Ridge that we investigated for comparison, were altered under comparable conditions.Our findings suggest a combined volcanic–tectonic origin of the studied volcanic centers, potentially implying that such complexes may generally form due to the interplay of magmatism and tectonics. Researching volcanic centers has the potential to further our understanding of both deep and shallow crustal processes at ultraslow-spreading ridges, providing further insights into the role of these centers as linkages between lithosphere and hydrosphere and the (deep) biosphere they sustain.

Effect of levels-of-processing on rates of forgetting.

The levels-of-processing (LOP) framework, proposing that deep processing yields superior retention, has provided an important paradigm for memory research and a practical means of improving learning. However, the available levels-of-processing literature focuses on immediate memory performance. It is assumed within the LOP framework that deep processing will lead to slower forgetting than will shallow processing. However, it is unclear whether, or how, the initial level of processing affects the forgetting slopes over longer retention intervals. The present three experiments were designed to explore whether items encoded at qualitatively different LOP are forgotten at different rates. In the first two experiments, depth of processing was manipulated within-participants at encoding under deep and shallow conditions (semantic vs. rhyme judgement in Experiment 1; semantic vs. consonant-vowel pattern decision in Experiment 2). Recognition accuracy (d prime) was measured between-participants immediately after learning and at 30-min, 2-h, and 24-h delays. The third experiment employed a between-participants design, contrasting the rates of forgetting following semantic and phonological (rhyme) processing at immediate, 30-min, 2-h, and 6-h delays. Results from the three experiments consistently demonstrated a large effect size of levels of processing on immediate performance and a medium-to-large level effect size on delayed recognition, but crucially no LOP × delay group interaction. Analysis of the retention curves revealed no significant differences between the slopes of forgetting for deep and shallow processing. These results suggest that the rates of forgetting are independent of the qualitatively distinct encoding operations manipulated by levels of processing.

The smell of paper or the shine of a screen? Students’ reading comprehension, text processing, and attitudes when reading on paper and screen

With the increasing prevalence of digital devices such as smartphones, tablets and e-readers, more and more reading is happening in digital formats – also in classrooms across the world. The present study focuses on lower secondary school students and their reading comprehension and attitudes toward reading on paper and screens. The study uses an innovative methodological approach were eye-tracking technology is used to observe ten carefully sampled eight grade students with different reading levels. The students read a selection of texts and answered questions from the Norwegian national reading assessment on comparable versions on paper and on screen. By analyzing eye movement data (reading transitions), including more than 25000 fixations, in combination with text reading comprehension outcomes, students' cued retrospective reporting from reading, and interview data we have obtained detailed and comprehensive data on students' reading comprehension, reading behavior, and reading experiences across different media. A key result is that reading on screen leads to more shallow processing and can hinder reading comprehension. Importantly, our results from the students' cued retrospective reporting of their eye tracking, showed that they were unaware of their reading behavior and didn't reflect much on reading in different media. These findings have implications for the increasing shift to digital learning environments in the educational context. It is important to recognize the difference between reading processes, and policymakers and practitioners cannot assume that these processes are the same across individuals and different delivery modes.

Phylogeography of mammals in Southeast Alaska and implications for management of the Tongass National Forest

AbstractInsular evolution on archipelagos generates a significant proportion of global biodiversity, yet islands are among the ecosystems most sensitive to accelerating anthropogenic disturbance, introductions of non‐native species, and emerging pathogens, among other conservation challenges. The Alexander and Haida Gwaii archipelagos along North America's North Pacific Coast support a disproportionate number of endemic taxa compared to other high‐latitude terrestrial ecosystems. In this region, endemics in Canada are explicitly protected, but in the United States, endemics have been operationally ignored. We reviewed regional research on terrestrial mammals and endemics from 2000–2022 to guide wildlife management. Elevated regional endemism is due to a combination of deep and shallow temporal processes (i.e., long‐term refugial isolation vs. recent colonization). With adequate sampling, genomic analyses are well‐suited to identifying nuanced patterns of divergence and endemism, thereby facilitating a deeper understanding of regional diversity. We identified 18 mammalian endemics in Southeast Alaska, USA, at varying taxonomic scales, but research effort has significant taxonomic biases and sampling infrastructure remains inadequate. Of the 66 terrestrial and aquatic mammal species in Southeast Alaska, only 55% are represented by ≥10 archived samples over the last 2 decades. Across taxa, major spatial and temporal sampling gaps limit interpretations of wildlife responses to changing environmental conditions. The Tongass National Forest is spread across an island archipelago, and climate change is projected to have disproportionate impacts on island endemics worldwide. In this case, the United States Forest Service is not closely monitoring endemic taxa, as was required by the Tongass Land Management Plan in 1997. Our review underscores a need for increased consideration of how endemism can be incorporated into land and wildlife management across the Alexander Archipelago. Moving forward, we encourage state and federal agencies, Indigenous communities, and international collaborators to continue to partner with natural history biorepositories to ensure strategic wildlife sampling infrastructure is built and made accessible to the broader scientific community as part of the land management process.

Investigation of the Extent of Hydrothermal Activities of the Sikidang Crater, Dieng Volcanic Complex (Central Java), Using Geomagnetic Method

Abstract The Sikidang Crater (± 2000 m asl) is one of the active craters in the Dieng Volcanic Complex (DVC). It is situated on the southeastern flank of Mt. Pangonan. The crater is significant for development of both tourism and energy sectors in Dieng. Thermal manifestations inside the crater which consist of boiling mud pools and pots, hot springs, fumaroles, gas vents, steaming and altered ground make the place a popular tourist attraction. They also serve as windows to the shallow subsurface processes and help better understand the dynamics of the Dieng geothermal system. However, the land use of the crater and its vicinity disregards the fact that the actual extent of the hydrothermal activity of the crater has not been figured out, and that the foci of the thermal fluid discharges in the crater often shift. Some agriculture plots, housing areas, as well as tourism and geothermal infrastructures are located within or near the morphological boundary of the crater. The inherent hydrothermal hazard of the crater therefore, must be well mitigated to minimize the negative impacts to the people, as well as their assets. Our research aims to delineate the lateral and vertical extent of the hydrothermal activity of the crater by geomagnetic method. Geomagnetic anomaly in geothermal field occurs due to the difference in the intensity of hydrothermal alteration of the rocks. The equipment used was a pair of Proton Precision Magnetometers GEOTRON G5. Our result shows that low geomagnetic anomaly (-2200 to -400 nT) correlated with demagnetized, hydrothermally altered andesitic rocks covers an area of ≥ 1.15 km2, i.e., more than seven times larger than the area outlined by morphological boundary of the crater. The anomalous zone extends N/NE - S/SW from beyond the areas of inter-volcanic plain between Pangonan and Igir Binem in the north, to the areas beyond Sikunang and Kendil cones in the south. Below the Sikidang mud pool the demagnetized rock mass reaches a maximum thickness of 2000 m. The supporting data, i.e., the fluctuations of the gas discharge, and the seismicity of the DVC indicate that the recent dynamics of the Sikidang Crater is mostly controlled by the internal processes within the crater.

Interaction between shallow and deep structures: Forward-modeling kinematics sequence of a fold-and-thrust belt with double detachment

It is crucial to determine the sequence of deformation and the interaction between shallow and deep structures within the multiple detachment systems to comprehend geological processes fully in fold-and-thrust belts (FTBs). Here, we implement forward modeling to investigate the geometric, kinematic, and syntectonic sedimentary characteristics of shallow and deep structural interactions. We design four combinative patterns of geometric structures, three kinematic sequence scenarios, and two settings with different ratios of the sedimentation rate to the uplift rate to examine the influence of such settings on growth strata geometry. The most effective results of 24 groups of shallow and deep structural interactions were obtained for various combinations of fault-bend fold, detachment fold, and tectonic wedge. This study provides a sequential kinematic image of FTBs, illustrating the interaction of two sets of detachments and demonstrating how different styles of pre- and growth strata can be utilized to identify shallow and deep structure deformation processes. The geometry of pre- and growth strata observed in the models is similar to that observed in natural structures. These forward models facilitate a better understanding of the complex geometry and kinematics of the interaction between shallow and deep fault-related folds.

Linguistic inputs must be syntactically parsable to fully engage the language network.

Human language comprehension is remarkably robust to ill-formed inputs (e.g., word transpositions). This robustness has led some to argue that syntactic parsing is largely an illusion, and that incremental comprehension is more heuristic, shallow, and semantics-based than is often assumed. However, the available data are also consistent with the possibility that humans always perform rule-like symbolic parsing and simply deploy error correction mechanisms to reconstruct ill-formed inputs when needed. We put these hypotheses to a new stringent test by examining brain responses to a) stimuli that should pose a challenge for syntactic reconstruction but allow for complex meanings to be built within local contexts through associative/shallow processing (sentences presented in a backward word order), and b) grammatically well-formed but semantically implausible sentences that should impede semantics-based heuristic processing. Using a novel behavioral syntactic reconstruction paradigm, we demonstrate that backward-presented sentences indeed impede the recovery of grammatical structure during incremental comprehension. Critically, these backward-presented stimuli elicit a relatively low response in the language areas, as measured with fMRI. In contrast, semantically implausible but grammatically well-formed sentences elicit a response in the language areas similar in magnitude to naturalistic (plausible) sentences. In other words, the ability to build syntactic structures during incremental language processing is both necessary and sufficient to fully engage the language network. Taken together, these results provide strongest to date support for a generalized reliance of human language comprehension on syntactic parsing.

Determining mid-ocean ridge geography from upper mantle temperature

In this study, we examine the influence of the mantle and large-scale tectonics on the global mid-ocean ridge (MOR) system. Using solely seismically-inferred upper mantle temperatures below the melting zone (260-600 km) and an interpretable machine learning model (Random Forest and Principal Component Analysis), we can predict a priori the location (ocean basin and ridge system) of global MOR with up to 90% accuracy. Two features provide > 50% of the discriminative power: the temperature difference between the mid-layer (340-500 km) and other depths, and the depth-averaged temperature of the upper mantle. We suggest long-term (100s Myr) tectonic and large-scale convective processes primarily driven by deep subduction left ample, distinct but hidden fingerprints in the mantle that allow us to separate regions at ∼1000 km scale. Our result implies that the large-scale geophysical and geochemical differences observed along the MOR system are reflective, not primarily of shallow processes associated with melting, but of the integrated long-term tectonic, subduction, and convective flow history that determines the present-day upper mantle temperature structure.

Geohazard features of the Central-Southern Tyrrhenian seamounts

ABSTRACT The Magic project (MArine Geohazard along Italian Coasts), a large coordinated initiative that involved the whole marine geological research community in Italy in 2007–2013, produced a series of maps of the Geohazard features of the Central-Southern Tyrrhenian Seamounts. The features derive from multibeam surveys and therefore mainly rely on the morphological expression of seafloor and shallow sub-surface processes and events. Potential geohazards related to eruption and flank instability of the volcanic seamounts of the Tyrrhenian Sea are discussed and compared.

Diagenetic history and porosity evolution of the Middle Permian clastic-carbonate mixed system, Indus Basin, Pakistan: Implications for reservoir development

This study deals with unraveling the diagenesis-induced porosity evolution in a mixed clastic-carbonate sequence of the Middle Permian Indus Basin, Pakistan. Multiple data sets including outcrop, petrography, cathodoluminescence, scanning electron microscopy (SEM), mineralogy, and geochemical isotopic compositions were integrated to establish a link between porosity evolution and diagenesis. The spatial thickness and facies variations of the strata at outcrop scale are inherently controlled by the underlying bathymetry of the basin with deepening westward trend. The low values of δ18O of the target strata, relative to average values of the Permian carbonate, hints to diagenetic alteration in the strata. The data sets used in this study reveal modification of the strata in four environments, that is, i) early marine diagenesis indicated by micritization, pervasive dolomitization and isopachous fibrous cements, followed by ii) meteoric dissolution, and iii) shallow burial diagenetic processes including the precipitation of blocky cement, compaction of skeletal and non-skeletal allochems, and stylolites, and iv) a deep burial environment, characterized by pressure solution, and micro-fractures. The clastic intervals host subangular to subrounded quartz grains, floating textures, and almost complete absence of deleterious clay minerals, consequently resulting in the preservation of primary porosity. The primary porosity of carbonate intervals is preserved in the form of intercrystalline and intracrystalline porosity. The secondary porosity evolved through various diagenetic phases in the form of fractures and dissolution. The diagenetic solution mediated by organic matter in carbonates may have experienced both bacterial decomposition and thermochemical sulfate reduction, precipitating sulfides within the pores. The plug porosity/permeability analyses generally suggest high porosity in the siliciclastic unit, and carbonates with wackestone fabric while lower values were observed for the inner shelf pure carbonate facies. However, both intervals show very low permeability values probably due to isolated moldic pores and intense micritization. Therefore, clastic intervals may provide an opportunity to serve as a moderate reservoir; however, the carbonate intervals possess very low permeability values and could generally be considered as low-moderate reservoir potential.

The spatial distribution and evolution of volcanic vents in monogenetic fields in active extensional tectonic setting: Examples from the northern Main Ethiopian Rift (Ethiopia)

Monogenetic volcanic fields are present in different geo-tectonic settings (subduction, divergence and intraplate settings) consisting of tens to hundreds of volcanic constructs (cones, maars, fissures, small shields) that are the physical expression of distributed volcanism.Notably, the spatial distribution of the volcanic constructs in volcanic fields often shows a spatial clustering that is thought to be linked to shallow (i.e., crustal strain, structural inheritance) and deep processes (i.e., magma input, composition and rheology). Noteworthy, the spatial distribution of vents (cones, maars, fissures, small shields) is the final frame of the history of the volcanic field and does not provide information about its time-evolution.Consequently, when a vent spatial clustering is assessed for a particular volcanic field two questions remain unanswered: i) have the vents always been clustered during the life of the volcanic field? ii) If not, when did the clustering of vents begin? To answer these questions, the spatial distributions of vents along with their morphologic classification have been applied to volcanic fields located in an active tectonic and volcanic area. The northern Main Ethiopian Rift, being its geo-tectonic setting and its geologic evolution well known, is the locale where the time evolution of vent spatial clustering can be investigated. Spatial distribution and morphometric analysis of vents have been applied to three well known monogenetic volcanic fields (Debre Zeyt, Wonji and Kone) in the northern Main Ethiopian Rift. Vent clustering initiated when about 60% of the vents formed within each of the above mentioned fields. The Kone volcanic field show vent clustering since the beginning suggesting that, within a specific tectonic setting, vent clustering is favoured by crustal strain partitioning and associated volcanic activity.