Stratigraphic Data Research Articles

The Hondelange Formation and the sequence stratigraphic model of Belgian Lorraine

1. Introduction This work follows up former papers dedicated to major boreholes in Belgian Lorraine and Grand Duchy of Luxembourg: the Latour borehole (Boulvain & Monteyne, 1993, revised by Boulvain et al., 1995), the Neulimont, Aubange, Saint-Mard and Toernich boreholes (Boulvain et al., 1995), the Villers-devant-Orval borehole (Boulvain et al., 1996) and more recently, the Bonnert, Haebicht, Grouft, Grund, and Consdorf boreholes (Boulvain et al., 2017). These studies, together with data resulting from the geological mapping project for Wallonia (Belanger et al., 2002; Ghysel et al., 2002; Belanger, 2006 a, b; Ghysel & Belanger, 2006) led to a synthesis formalized by a new lithostratigraphical scheme for Belgian Lorraine (Boulvain et al., 2001 a, b). Besides stratigraphical data, the boreholes survey provided results for petrography, clay mineralogy, palynology and paleontology (Boulvain et al., 2001a; Boulvain et al., 2017). The purpose of the current work is (1) to suggest a new status for the Hondelange Formation, formerly considered as a member of the Arlon Formation (Boulvain et al., 2001b) and (2) by synthetizing all the information acquired from the boreholes and outcrops, to propose a sequence stratigraphic interpretation for the Triassic and Jurassic of Belgian Lorraine and border areas. 2. Geological setting The studied Triassic to Jurassic successions are confined to the south eastern part of Belgium, i.e. the Belgian Lorraine and to the Guttland region of G.-D. o

An Application of Gravity Method to Estimate a Storage Capacity of Ngrayong Formation for Carbon Capture and Storage (CCS) Pilot Project of Gundih Field, East Java, Indonesia

Indonesia has committed in Global Initiative as non-Annex I country to reduce 26% of GHG emission reduction further up to 41% reduction with incoming international support. Initiated by the scheme of SATREPS (Science and Technology Research Partnership for Sustainable Development) program co-funded by Japan International Agency, Indonesia works on the pilot project implementation of Carbon Capture and Storage (CCS). CCS is one of technology to be used to reduced CO2 gas emission in the atmosphere. The CO2 is captured from the source or atmosphere, then purified and liquefied. The liquefied CO2 then injected into underground reservoir. The underground reservoir could be a porous geologic formation such as an old hydrocarbon reservoir. At present, as guiding by regional and geoscience characterization at the further stage called as engineering characterization well integrity as an early stage of injection phase is done. Based on the evaluation of Regional Characterization study for CCS Pilot Project in Indonesia, Gundih Field was selected as the most suitable target. Gundih Field is a gas field located in the Northeast Java Basin, East Java, Indonesia. Accordingly, Geoscience Characterization has been done including structural and stratigraphic model of the region. Stratigraphically, the oldest formation at Gundih Field area consist of Basement, underlie uncomfortably by Tawun Formation, Ngrayong Formation, Wonocolo Formation, Ledok Formation, Mundu Formation and Lidah Formation. The Ngrayong Formation was decided as a targeted bed to be injected by CO2 liquid. Therefore, the study consists of injectivity, containment and capacity of the Ngrayong Formation reservoir. This formation mainly contains of sandstone intercalated by limestone beds. The age of this formation is Middle Miocene. There is one abandoned well available in the field namely Japon-1 well. The JPN-1 well will be utilized as an injected well. As the pilot project, the total CO2 planed will be stored in the formation around 20.000 tons within 2 years. Therefore, it could be calculated that approximately 52.300 m3 pore space is needed in the reservoir formation. Some studies related in to Geoscience Characterization for CCS implementation has been done, included geological and geophysical studies to evaluate the capacity of Ngrayong reservoir. In order to estimate the storage capacity of Ngrayong Formation, the gravity method was applied. The gravity acquisition was done in September 2014 using gravimeter Scintrex CG-5. The measurement was done in the surrounding of Japon-1 well for about 25 km2 area. In order to get better accuracy, the point of measurement was done with the interval of 250 m. Based on the measurement data the Complete Bouguer Anomaly Map was constructed on the assumption that the rocks had an average Bouguer density of 2.5 gr/cc. The result of Complete Bouguer Anomaly Map contain noise, then moving average filtering method based on spectral analysis calculation was applied. This Complete Bouguer Anomaly Map was used to make an interpretation of subsurface condition of Ngrayong Formation. By using this map, further process was done as separation between regional and residual anomalies. The separation anomalies were done as similar previous method using moving average filtering method based on spectral analysis. Using residual anomaly map, the 2.5D density model was calculated using forward modelling method. Some supporting data was used such as data of JPN-1 Well which the depth of Ngrayong Formation is 816 m, seismic data as the time structure map of nearly top of Ngrayong Formation and seismic section across the region, geology and stratigraphy of Rembang Zone. In order to get approximate volume of the formation, then the “pseudo-3D” model was developed. Based on this model the estimated capacity of the porous space of the reservoir could be calculated. According to well data of Japon-1, the porosity of Ngrayong Formation was 28%. Based on well stratigraphic data, the volume of sandstone in this formation is calculated 5%. By assumption that only 50% could be injected by CO2 fluid, the injection capacity of Ngrayong Formation using Japon-1 well could be calculated. The result of calculation, the porous space volume of Ngrayong Formation is approximately 17.168 x 10 m3 and pore space volume 30,044 x 106 m3. The result calculation of pore space volume of Ngrayong Formation is more than enough to accommodate injected CO2.

Parachoerus carlesi (Mammalia, Tayassuidae) in the Late Pleistocene (northern Argentina, South America): paleoecological and palaeobiogeographic considerations

The Tayassuidae is one of the first families of North American immigrant mammals that arrived into South America during the ‘Great American Biotic Interchange’. They have been found associated with Late Cenozoic deposits mainly in Argentina and Brazil, but also in Uruguay, Bolivia, Colombia, Peru and Venezuela. Theirs records within Argentina come from the Pampean Region, Mesopotamia and north-central region. Here, we report the first record of P. carlesi with precise stratigraphic (26.630 ± 370 14C years BP, Late Pleistocene) data in Argentina, precisely from the Chacoan region. This specimen represents the most complete fossil material of this extinct species, increasing its morphological and morphometrical knowledge, and it provides relevant ecological and climatic information. From a palaeoenvironmental point of view, the fauna registered in this paleontological site, includes taxa mainly adapted to open or semi-open and arid or semi-arid environments. The bearing sediments and the peculiarities of the faunal assemblages, as well as the chronological data, allow confirming that arid and semiarid conditions, with scarce or absent vegetation cover were developed in this area of Argentina during the last part of MIS 3 and beginning of MIS 2. These environmental conditions favored the settlement of megamammals adapted to open environments.

Coupled Re-Os and U-Pb geochronology of the Tonian Chuar Group, Grand Canyon

Well-preserved strata of the late Tonian Chuar Group exposed in the Grand Canyon host fossil evidence for the development of eukaryotic predation, the presence of unique biomarkers, and large changes in C, S, and Mo isotope chemostratigraphy. Despite the importance of this critical succession, few radioisotopic age constraints are available to place these records into a global context. Here, we couple high-precision U-Pb chemical abrasion−isotope dilution−thermal ionization mass spectrometry (CA-ID-TIMS) on zircon crystals with the rhenium-osmium (Re-Os) sedimentary and sulfide geochronometer to refine the temporal framework of this pivotal interval of Earth history. Zircons recovered from a tuff within the uppermost Walcott Member of the Kwagunt Formation yield a weighted mean 206Pb-238U age of 729.0 ± 0.9 Ma (mean square of weighted deviates [MSWD] = 0.86), differing significantly from the previous air-abrasion upper-intercept age of 742 ± 6 Ma on zircons from this same horizon. Organic-rich carbonates from the Carbon Canyon Member of the Galeros Formation yield a model 1 Re-Os age of 757.0 ± 6.8 Ma (MSWD = 0.47, n = 8), and an initial Os isotope (187Os/188Os [Osi]) composition of 1.13 ± 0.02. The radiogenic Osi value from this horizon suggests that the basin was restricted from the open ocean during deposition of the Carbon Canyon Member, in agreement with sedimentological and stratigraphic data. The Re-Os geochronology of marcasite (FeS2) nodules from the Awatubi Member of the Kwagunt Formation yield a model 1 age of 751.0 ± 7.6 Ma (MSWD = 0.37, n = 5), with an Osi of 0.44 ± 0.01. This Re-Os date is interpreted to constrain the growth of the marcasite nodules in the Awatubi Member during deposition. The formation of sulfides and the less radiogenic Osi value are consistent with an influx of sulfate-laden seawater to the basin during deposition of the Kwagunt Formation. Attempts to apply the Re-Os geochronometer to the Walcott and Tanner Members of the Chuar Group failed to yield meaningful ages, despite elevated Re enrichments (>20 ng/g). The Re-Os data from these units yielded negative Osi values, which suggest disturbance to the Re-Os system. The low Os abundances (typically <100 pg/g) relative to the amount expected based on the elevated Re abundances suggest leaching of Os due to oxidative weathering on geologically recent time scales. Finally, the Carbon Canyon Member provides a useful case study for quantifying how input uncertainties in the Re-Os geochronometer propagate into the resulting age uncertainty, and we discuss the protocols that will yield the best improvement in age precision for future studies. The U-Pb and Re-Os geochronology presented here illustrates the power of coupling these systems and the importance of recent improvements in both methods. Our analysis suggests that for our data, the most efficient way of reducing uncertainties in the presented Re-Os dates is through improved precision of measured Os values.

Migration of chlorinated hydrocarbons in multilayer unconsolidated porous media: a case study from the Po Plain, Italy

Chlorinated solvents are the most ubiquitous organic contaminants found in groundwater since the last six decades. Due to their high degree of carcinogenicity/toxicity and the relatively high mobility and persistence, they represent a serious threat against the human health and the environment. These contaminants generally reach groundwater as Dense Non-Aqueous Phase Liquid (DNAPL) that can migrate through aquifers easier than aqueous contaminants. The complex phase partitioning to which chlorinated solvent DNAPLs can undergo (i.e. to the dissolved, vapor or sorbed phase), as well as their transformations (e.g. degradation), depend on the physico-chemical properties of the contaminants and on the features of the hydrogeological system in which they migrate. The hydrogeologic setting below the city of Ferrara (Po plain, northern Italy), which is affected by scattered contamination by chlorinated solvents, has been investigated. In particular, a limited-inspace high-resolution investigation was performed in one selected contaminated test-site, known as “Caretti site”. Here, high-resolution vertical profiling of different kind of data (i.e. stratigraphic data, hydraulic heads, hydrochemical composition of water, stable isotopes of water and contaminants) were collected by means of multilevel monitoring systems and other innovative sampling and analytical techniques. The main goals of the research were to assess the intrinsic vulnerability of the aquifers and to identify the dynamics of migration and transformation of the chloroethene contaminants in relationship to the features of the hosting porous medium. The confined aquifers turned out to be more vulnerable to DNAPLs than aqueous contaminants due to the occurrence of microfractures in the overlying clayey aquitards. The presence of organic-rich deposits in the local stratigraphy enhanced the biodegradation of chloroethenes causing accumulation of Vinyl Chloride. The results are useful at the local scale, e.g. to interpret the origin of contamination in other sites of the Ferrara area, and also at the global scale, to better address future remediation and protection actions in similar settings.

Deformation patterns in the southwestern part of the Mediterranean Ridge (South Matapan Trench, Western Greece)

Seismic reflection data and bathymetry analyses, together with geological information, are combined in the present work to identify seabed structural deformation and crustal structure in the Western Mediterranean Ridge (the backstop and the South Matapan Trench). As a first step, we apply bathymetric data and state of art methods of pattern recognition to automatically detect seabed lineaments, which are possibly related to the presence of tectonic structures (faults). The resulting pattern is tied to seismic reflection data, further assisting in the construction of a stratigraphic and structural model for this part of the Mediterranean Ridge. Structural elements and stratigraphic units in the final model are estimated based on: (a) the detected lineaments on the seabed, (b) the distribution of the interval velocities and the presence of velocity inversions, (c) the continuity and the amplitudes of the seismic reflections, the seismic structure of the units and (d) well and stratigraphic data as well as the main tectonic structures from the nearest onshore areas. Seabed morphology in the study area is probably related with the past and recent tectonics movements that result from African and European plates’ convergence. Backthrusts and reverse faults, flower structures and deep normal faults are among the most important extensional/compressional structures interpreted in the study area.

A HARD TIME TO DATE: THE SCOTT COUNTY PUEBLO (14SC1) AND PUEBLOAN RESIDENTS OF THE HIGH PLAINS

During the seventeenth and eighteenth centuries, Puebloan women (if not entire families) were incorporated into Apache Dismal River communities in western Kansas. In at least one site (14SC1), Puebloan people lived in a small masonry pueblo. We evaluate the timing and nature of the Puebloan occupation at 14SC1 and its relationship to the Dismal River population at the site. We use a Bayesian analytical framework to evaluate different models of the pueblo's use history, constraining 12 radiocarbon dates by their stratigraphic data and then comparing this framework with different temporal models based on the historical record. We conclude that Dismal River people lived at 14SC1 prior to the appearance of Pueblo migrants, sometime between cal AD 1490 and 1650. Construction and early use of the pueblo by migrants from the Rio Grande valley occurred between cal AD 1630 and 1660, and the pueblo was closed by burning sometime between cal AD 1640 and 1690. Site 14SC1 lacks Rio Grande Glaze Ware, and its residents seem rarely to have engaged with the groups in the Southern Plains Macroeconomy. Our results contribute to studies of indigenous community formation and Puebloan residential mobility during the Spanish colonial period.

Re-evaluation of the Haarlem Archaeopteryx and the radiation of maniraptoran theropod dinosaurs

BackgroundArchaeopteryx is an iconic fossil that has long been pivotal for our understanding of the origin of birds. Remains of this important taxon have only been found in the Late Jurassic lithographic limestones of Bavaria, Germany. Twelve skeletal specimens are reported so far. Archaeopteryx was long the only pre-Cretaceous paravian theropod known, but recent discoveries from the Tiaojishan Formation, China, yielded a remarkable diversity of this clade, including the possibly oldest and most basal known clade of avialan, here named Anchiornithidae. However, Archaeopteryx remains the only Jurassic paravian theropod based on diagnostic material reported outside China.ResultsRe-examination of the incomplete Haarlem Archaeopteryx specimen did not find any diagnostic features of this genus. In contrast, the specimen markedly differs in proportions from other Archaeopteryx specimens and shares two distinct characters with anchiornithids. Phylogenetic analysis confirms it as the first anchiornithid recorded outside the Tiaojushan Formation of China, for which the new generic name Ostromia is proposed here.ConclusionsIn combination with a biogeographic analysis of coelurosaurian theropods and palaeogeographic and stratigraphic data, our results indicate an explosive radiation of maniraptoran coelurosaurs probably in isolation in eastern Asia in the late Middle Jurassic and a rapid, at least Laurasian dispersal of the different subclades in the Late Jurassic. Small body size and, possibly, a multiple origin of flight capabilities enhanced dispersal capabilities of paravian theropods and might thus have been crucial for their evolutionary success.

Refined δ13С trend of the Dal’nyaya Taiga series of the Ura uplift (Vendian, southern part of Middle Siberia)

New data were obtained on δ13Сcarb and δ18O variations in the sequence of deposits of the Dal’nyaya Taiga series at the western and eastern flanks of the Ura anticline. The summary δ13С curve was plotted in view of the correlation of sequence–stratigraphic data of the basin analysis. A series of positive anomalies was found within the succession. Alternatives for global chemostratigraphic correlation of the Dal’nyaya Taiga series of the Ura uplift were considered.

Magnetic stratigraphic dating of marine hydrogenetic ferromanganese crusts

Deep-sea hydrogenetic ferromanganese crusts are both potential polymetallic resources and records of long-term environmental changes. For palaeoceanographic studies, it is important to construct a detailed and reliable chronological framework. Here, we report the results of a detailed magnetostratigraphic and rock magnetic study of four hydrogenetic Fe-Mn crusts from the Pacific Ocean (PO-01), South China Sea (SCS-01, SCS-02) and Indian Ocean (IO-01). Two groups of characteristic remanent magnetization directions were defined with nearly antipodal normal and reversed polarities for samples PO-01, SCS-01 and SCS-02, indicating a primary record of the Earth’s magnetic field. The magnetostratigraphic framework, established via correlation with the Geomagnetic Polarity Time Scale 2012, implies growth rates of 4.82 mm/Ma, 4.95 mm/Ma, 4.48 mm/Ma and 11.28 mm/Ma for samples PO-01, SCS-01, SCS-02 and IO-01, respectively. Rock magnetic measurements revealed that the Fe-Mn crust samples from the Pacific Ocean and Indian Ocean were dominated by low coercivity, non-interacting, single-domain (SD) magnetite particles, whereas the South China Sea samples were dominated by SD/pseudo-single-domain (PSD) particles. Multidomain (MD) magnetite may also be present in all samples.

Neogene-Quaternary seismic stratigraphy of the Llancanelo Lake Basin, Mendoza, Argentina

A new shallow multichannel seismic survey was carried out in the Llancanelo Lake region (Southern Mendoza Province, Argentina), in order to complete and extend previously surveyed seismic sections. The new seismic data allowed to double the already existing data. The obtained information was correlated with seismic and stratigraphic data from the industry. In this way it was possible to depict the major Neogene-Quaternary sedimentary-volcanic sequences and the regional evolution of a tectonic-volcanic basin located in a key region at the eastern foot of the Andes cordillera. This research is settled on early studies that comprised seismic works reaching depths of 600-700 m as well as geoelectric and electromagnetic surveys reaching the uppermost 80-100 m of the sequences. The obtained results indicate the presence of three major sedimentary units separated by conspicuous seismic horizons SR1, SR2 and SR3, respectively considered as representing the late Mesozoic transition from marine to continental deposition, the beginning of the Cenozoic basaltic volcanism, and the change from dominantly sedimentary to dominantly volcanic processes at the base of the Quaternary. The resulting stratigraphic scheme reveals increasing volcanic (basaltic layers) intercalations with depth that accommodate to the geometry of the depocenter.

Was the Mw 7.5 1952 Kern County, California, earthquake induced (or triggered)?

Several recent studies have presented evidence that significant induced earthquakes occurred in a number of oil-producing regions during the early and mid-twentieth century related to either production or wastewater injection. We consider whether the 21 July 1952 Mw 7.5 Kern County earthquake might have been induced by production in the Wheeler Ridge oil field. The mainshock, which was not preceded by any significant foreshocks, occurred 98 days after the initial production of oil in Eocene strata at depths reaching 3 km, within ~1 km of the White Wolf fault (WWF). Based on this spatial and temporal proximity, we explore a potential causal relationship between the earthquake and oil production. While production would have normally be expected to have reduced pore pressure, inhibiting failure on the WWF, we present an analytical model based on industry stratigraphic data and best estimates of parameters whereby an impermeable splay fault adjacent to the main WWF could plausibly have blocked direct pore pressure effects, allowing the poroelastic stress change associated with production to destabilize the WWF, promoting initial failure. This proof-of-concept model can also account for the 98-day delay between the onset of production and the earthquake. While the earthquake clearly released stored tectonic stress, any initial perturbation on or near a major fault system can trigger a larger rupture. Our proposed mechanism provides an explanation for why significant earthquakes are not commonly induced by production in proximity to major faults.

Taxonomy, Stratigraphy and Phylogeny of the Middle Miocene Fohsella Lineage: Geometric Morphometric Evidence

Abstract The taxonomy and phylogeny of the planktonic foraminifera Fohsella lineage has been controversial for nearly 50 years, despite its widespread application in Middle Miocene stratigraphy. We have re-examined type specimens of this lineage together with specimens from a continuous deep-sea record (Ocean Drilling Program Site 806, Ontong Java Plateau, western equatorial Pacific Ocean) with an astronomic chronology. Landmark-based geometric morphometry is employed to visualize and quantify morphologic variation within this lineage. Combined morphologic and stratigraphic data help clarify the evolutionary occurrence of diagnostic traits that characterize two problematic taxa, F. praefohsi and F. “praefohsi”, resulting in a revised taxonomy and phylogeny of the lineage. We emphasize the importance of biometric studies of populations from continuous geologic records in establishing taxonomy and phylogeny of planktonic foraminifera. In the past, over-emphasis on the importance of type specimens as reference points in delineating various evolutionary stages of the Fohsella lineage has resulted in inaccurate phylogenetic reconstructions.

Tracking sand‐fairways through a deformed turbidite system: the Numidian (Miocene) of Central Sicily, Italy

AbstractUnderstanding ancient deep‐water sedimentary systems that accumulated at complex plate boundaries requires confronting the stratigraphic record of deformed sedimentary successions by tracking sand‐fairways and identifying original relationships in later deformed sequences. Here, we investigate the Numidian turbidite system (early to mid‐Miocene) of Central‐East Sicily to explore a deep‐water sedimentary system deposited at an active thrust belt on the Central Mediterranean. Turbidites include multi‐metre thick‐bedded, ultra‐mature quartz sandstones that were sourced from North Africa and are now deformed and dismembered within the Apennine‐Maghrebian orogen. To date, much research has focused on the little‐deformed sections that sample discrete parts of the original turbidite pathways. Yet the bulk of these systems are represented by deformed successions and these have attracted little modern sedimentological and stratigraphic investigation. We present new data based on field mapping, sedimentological/structural fieldwork, and biostratigraphy (planktonic foraminifera and nannofossils) that focus on the Numidian turbidites of Central‐East Sicily. Thickness and facies variations, together with evidence of large‐scale sediment bypass and local substrate reworking, characterize the Numidian turbidites of the study area, consistent with a partially confined turbidite system. Our work demonstrates that the Numidian turbidite system accumulated across active structures and these provided tortuous, evolving corridors through which turbidity currents were routed, transporting coarse sand over many hundreds of km. These results provide insight on structurally confined turbidites in analogous tectonic settings and demonstrate the need to seek sedimentological and stratigraphic data from deformed and dismembered parts of deep‐water systems.

Late Holocene Records of Changing Moisture Regime from Wetlands in Southwestern Nova Scotia, Canada: Implications for Wetland Conservation and Restoration

An understanding of the morphological stability and succession of open water and wetland ecosystems in Nova Scotia is a priority for informing the conservation management of critical habitats for a complex of nationally listed, rare, disjunct wetland species. Baltzer Bog and Big Meadow Bog in southwestern Nova Scotia contain stratigraphic records of late Holocene moisture variability. Baltzer Bog is a shrub bog that formed in an elevated, enclosed kettle basin. Excavated sections exposed by peat mining revealed 2 distinct wood-rich horizons that are located above a well-developed soil and wood horizon that yielded a radiocarbon-dated age of 3260 cal. BP from an upright stump. The overlying wood-rich horizons were dated at 1640 and 1045 cal. BP and were overlain by Sphagnum species transitions indicative of increasing wetness. At Big Meadow Bog, a thin wood mat in Sphagnum at 90 cm depth was dated at 1760 cal. BP. These records are broadly correlative with pollen and stratigraphic data from Pleasant River Fen in central Nova Scotia that indicate periods of high and low productivity and a fluctuating water table from 1950 cal. BP until present. Though other high-resolution paleoclimate records from the region indicate that the late Holocene was a time of increasing precipitation and cooler air temperatures, these wetland records demonstrate that in Nova Scotia this time period was characterized by rapid variations in effective moisture and that significant and sustained dry periods likely occurred. This record of late Holocene moisture variability and its influence on habitat structure serves to better establish the potential for long-term residency of threatened and endangered species at wetland sites.

Numerical Simulation and Application of Mine TEM Detection in a Hidden Water-bearing Coal Mine Collapse Column

ABSTRACT A hidden water-bearing collapse column (WBCC), directly exposed during coal mining, is a potential source of serious mine flooding. Presently, the transient electromagnetic method (TEM) is widely used, which shows good performance in detecting WBCCs in coal mines. However, traditional numerical simulation approaches have failed to be adapted to complicated underground environments affected by roadways, and the application of boundary conditions require a large grid. Considering this, the authors chose the convolutional perfectly matched layer (CPML) as a boundary condition, whose effects were found to be superior to the traditional Dirichlet boundary condition. Then, based on stratigraphic data related to coal measures located in North and Mid-eastern China, the whole-space geoelectric model was established. The whole-space TEM response of the WBCC at different depths of the stope face floor and ahead of the driving face were also simulated by the finite-difference time-domain method. The numeric...

Classifying zones of suitability for manual drilling using textural and hydraulic parameters of shallow aquifers: a case study in northwestern Senegal

A method is proposed that uses analysis of borehole stratigraphic logs for the characterization of shallow aquifers and for the assessment of areas suitable for manual drilling. The model is based on available borehole-log parameters: depth to hard rock, depth to water, thickness of laterite and hydraulic transmissivity of the shallow aquifer. The model is applied to a study area in northwestern Senegal. A dataset of boreholes logs has been processed using a software package (TANGAFRIC) developed during the research. After a manual procedure to assign a standard category describing the lithological characteristics, the next step is the automated extraction of different textural parameters and the estimation of hydraulic conductivity using reference values available in the literature. The hydraulic conductivity values estimated from stratigraphic data have been partially validated, by comparing them with measured values from a series of pumping tests carried out in large-diameter wells. The results show that this method is able to produce a reliable interpretation of the shallow hydrogeological context using information generally available in the region. The research contributes to improving the identification of areas where conditions are suitable for manual drilling. This is achieved by applying the described method, based on a structured and semi-quantitative approach, to classify the zones of suitability for given manual drilling techniques using data available in most African countries. Ultimately, this work will support proposed international programs aimed at promoting low-cost water supply in Africa and enhancing access to safe drinking water for the population.

The church of Santa Comba de Bande and early medieval Iberian architecture: new chronological results

Abstract

APPLICATION OF OSL METHOD IN DATING PAST EARTHQUAKES

The aim of this study was to establish a chronological frame of paleoseismic events of Gyrtoni Fault, (Thessaly, Central Greece), with the use of OSL dating method. The Gyrtoni Fault, defines the north-eastern boundary of the Middle-Late Quaternary Tyrnavos Basin, and was previously investigated with geological methods. Twenty five fluvial-colluvial sediment and pottery samples were collected from two paleoseismological trenches, excavated along the Gyrtoni Fault, from both the upthrown and the downthrown fault blocks. Optically Stimulated Luminescence (OSL) dating was applied to coarse grain quartz using the single-aliquot regenerative-dose (SAR) protocol. Investigations of luminescence characteristics using various tests confirmed the suitability of the material for OSL dating using the SAR protocol. Radioactivity measurements were performed in order to estimate the annual dose rateof the surrounding soils to which the quartz grains were submitted during the burial period of the collected samples. The estimated OSL ages agreed well with the available stratigraphical data, and archaeological evidence. The occurrence of three surface faulting events in a time span between 1.42 ± 0.06 ka and 5.59 ± 0.13 ka was revealed while an earlier faulting event (fourth) was also recognized to be older than 5.59 ± 0.13 ka.

Explaining gregarious behaviour in Banffia constricta from the Middle Cambrian Burgess Shale, British Columbia

Banffia constricta is an enigmatic Burgess Shale animal originally described by Charles Walcott in 1911 as an annelid, and more recently as a stem-group deuterostome. Interpreted, on the basis of anatomy, to have been bottom-feeders, there are few other data from which to draw interpretations of Banffia's life habit. A slab of Burgess Shale with a dense aggregation of B. constricta may indicate a gregarious habit for the animal, as taphonomic and stratigraphical data indicate an in situ origin for the assemblage. Clustering of individuals, high density of the individuals and non-random within-cluster orientation support the hypothesis that detritus-feeding B. constricta congregated to feed on a local, rich food source. Presumed opportunistic feeding aggregations have been documented in at least one other Burgess Shale taxon and have been described for other fossil benthic marine invertebrates. Extant benthic marine invertebrates such as holothurians and echinoids exhibit mass feeding behaviour and may serve as modern analogs for the behaviour represented by the B. constricta assemblage.