Marly Clay Research Articles

Integrated approach to sustainable utilization of phosphate waste rock in road embankments: Experimental insights, stability analysis, and preliminary economic evaluation

This paper highlights an issue that has not received much attention which is the use of phosphate waste rock (PWR) in road embankments. This study focuses on the valorization of marly clay and marly limestone lithologies, which are abundant but often unused or undervalued, being simply deposited around mine sites. Investigating the potential use of these materials in road embankments requires a combination of experimentation, stability analysis, and economic evaluation. The materials were collected from mining trenches in the Benguerir mine (Morocco). The samples were subjected to i) chemical and mineralogical characterization; ii) environmental characterization; and iii) geotechnical characterization. The results of the characterization show that the samples are chemically dominated by CaO (12–33 wt%), SiO2 (23–38 wt%), and MgO (7 – 9 wt%); mineralogically, the main phases are quartz, calcite, dolomite, apatite, and clay minerals. The environmental characterization classified the studied materials as non-hazardous waste. In terms of geotechnical characterization, the marly limestone and marly clay belong to the A3 and R33 categories, which means that they can be successfully used as a sustainable alternative material for the embankment. This finding supports their safe utilization. The stability analysis reveals that embankments up to 10 m in height can be constructed with marly clay without significant physical instability risks. Satisfactory safety factors (SF) were found (SF=1.97 for H=5 m and SF=1.54 for H=10 m). For marly limestone, the height limit is less than 10 m (SF=1.74 for H=5 m and SF=1.33 for H=10 m), but it can be increased to 10 m by adding a bench of rock fill with a safety factor of 1.64. Finally, an economic evaluation demonstrates that PWR can be used as embankment materials within a radius of 28 km around the mine site. It appears to be a cost-effective alternative compared to conventional materials.

Sicilian clay sediments as precursor for alkali activated materials

In this work, we focused on the possibility of using clay sediments found in Sicily as precursors to produce alkali activated materials (AAMs) with properties comparable to those of traditional materials used in construction. Two different clays were selected: Plio-Pleistocenic marly clay (PP) and Numidian Flysh clay (NU) to test the use of sediments with and without calcite. AAMs were prepared using precursors thermally treated at 700 °C and alkaline activator solutions as NaOH 4, 6 and 8 M with or without sodium silicate. All samples were cured at 85 °C for 20 h and at room temperature for 28d. Mineralogical analyses, FTIR data, SEM/EDS morphological and chemical observations showed the formation of a polycondensed gel after 20 h. AAMs obtained from calcite-rich clayey sediments (thermally treated) achieved good compressive strength after 28 days with all activators. However, AAMs based on thermally treated calcite-free clays only showed good compressive strength development only when activated with 8 M NaOH and sodium silicate.

Geological and Geomechanical Characterization of Phosphate Mine Waste Rock in View of Their Potential Civil Applications: A Case Study of the Benguerir Mine Site, Morocco

Sedimentary phosphate extraction in open-pit operations generates large volumes of waste rock (WR), which are mainly overburdens and interburdens. Traditionally, the WR is mixed and stored on the surface in waste rock piles (WRPs). This paper presents a case study of the Benguerir mine site in Morocco. It investigates the potential valorization of each WR lithology based on the geological and geomechanical properties to reduce their environmental footprint and create added value to “waste.” The WR samples (soils and rocks) were collected from drill cores and mining trenches in the Benguerir mine. The geological characterization results using petrographic descriptions indicate the presence of nine phosphate layers and, in addition to the overburdens, eight interburdens. Four types of WR are identified: carbonate, siliceous, marly clay, and phosphate. The geomechanical characterization of soil-like samples showed an average plasticity index (PI) of 50% according to the methylene blue value (MBV) of 7.1, classifying them in the A3–A4 categories as plastic and clayey marl soils. The hard rock samples have excellent mechanical properties in terms of their uniaxial compressive strength (UCS), Los Angeles abrasion value (LA), and micro-Deval value (MD). The average compressive strength is 104 MPa for the flint, 35 MPa for the phosphate flint, 32 MPa for the silexite, 26 MPa for the limestone, 11 MPa for the indurated phosphate, and 8 MPa for the marly limestone. Based on the obtained results, these WRs can be considered as an excellent alternative secondary raw material for use in civil engineering applications, ceramics, and cement industries.

Mapping of clay soils by remote sensing in the area of Mers El Kébir, Algeria

The identification of clay soils is of great importance for the construction industry. Indeed, this type of soil presents an economic interest related to the exploitation of its clayey materials. Furthermore, the assessment of the potential for differential ground movement through the dryness of the soils and their rehydration is also an important issue to identify in order to reduce the swelling-shrinking hazard. The region of Mers El Kébir located in northwest Algeria, is at risk of this phenomenon because it is known for its marly clay compositions. Mapping this type of soil using satellite imagery offers an alternative to the engineering practice of establishing soil mineralogy, based on X-ray diffraction analysis, which is expensive and time-consuming. The objective of this research is to use ASTER satellite images to map different clay minerals. This analysis is based on remote sensing of spectral signatures corresponding to illite, kaolinite, and montmorillonite.The study of satellite images of the Mers El Kébir region validates the methodology developed, which could be used to help in the development and planning of new infrastructures adapted to the different types of soil.

Influence of local mineral raw materials on the commercial success of Aveiro production of ancient ceramic sugar jars

Ceramic sugar jars played a paramount role in the sugar production cycle, being used for the maturation of the sugar. These pieces were conic having a hole at the bottom, being used specifically for the stage of the purge of the sugar cake. From the 15th until the beginning of the nineteenth centuries, the old pottery centres from Aveiro and Lisbon regions (Portugal) produced heavily these “formas de açúcar” (“sugar jars”), which were exported to sugar production areas, at places as diverse as Madeira, Canaries, Cape Verde, Cuba and Brazil. Mineralogical and chemical data obtained in samples from Aveiro point to local production, using the upper Cretaceous (Maastrichtian) marly (dolomitic) clays and clayey sands as primary raw materials. Ceramics from Barreiro (Lisbon) are generally more silicated and less carbonated, a composition close to the Tagus Cenozoic Basin clays. The higher iron content of Aveiro clays favours the glazing of ceramic paste at lower temperatures, giving better mechanical resistance, which can justify “their best quality”. This study highligths the influence of local mineral raw materials on the technological characteristics of produced sugarware and the actual reasons that allowed Aveiro sugarware production to be competitive to Lisbon (Barreiro) one.

The Behavior of a Thread-Bar Grouted Anchor in Soils from Local Strain Monitoring

International standards discourage the use of grouted anchors with a fixed length exceeding 10 m. However, grouted anchors with a fixed length between 10 and 20 m are frequently used in Italy to transfer high loads to ground with poor geotechnical properties. This paper presents the results of investigation tests on an anchor with a length of 36 m, of which 18 m is fixed, sloping 40° from the horizontal; the anchor is comprised of a reinforced thread-bar which was instrumented with strain gauges and founded in nonhomogeneous ground, a sand deposit followed by marly clay. The test aimed at investigating the progressive mobilization of the shear strength along the foundation. The results indicate a very low shear strength offered by the sand, probably disturbed by the drilling, and an unusually fast mobilization of the shear strength in the marly clay at the deep end of the anchor. The results are particularly useful to identify the reasons for the observed poor performance of the grouted anchor. In particular, the study once again made it clear how important the influence of the execution details on reaching the expected load capacity may be, and likewise the practice of investigation tests on suitably instrumented test anchors.

Marine transgression(s) to evaporite basin: The case of middle Miocene (Badenian) gypsum in the Central Paratethys, SE Poland

The middle Miocene Badenian evaporite basin of the Carpathian Foredeep Basin was a saline lake, separated by a barrier from the sea and supplied with seawater seeping through the barrier or overflowing it occasionally in the form of short-lived marine transgressions. Such transgressions could leave behind marine microfossils in marly clay intercalations. One of them (2.3 m thick) occurs in the uppermost part of the sulphate sequence, in the unit ‘o’, in the Babczyn 2 borehole section. It contains marine palynomorphs (dinoflagellate cysts) and foraminiferal assemblages indicating a marine environment. The low-diversity benthic foraminiferal assemblages are dominated by opportunistic, shallow infaunally living species, preferring muddy or clayey substrate for thriving, brackish to normal marine salinity, and inner shelf environment. Dinoflagellate cyst assemblages, although taxonomically impoverished, consist of marine species; euryhaline forms that tolerate increased salinity are missing. Relatively common microfossils found in clay intercalations within gypsum have important palaeogeographical implications: they strongly suggest that there existed an additional inflow channel supplying the Polish Carpathian Basin from the south during the evaporite deposition and afterwards.

Effect of freeze-thaw cycles on characteristics of marl soils treated by electroosmosis application

Marly clay consists of 35 to 65% calcareous materials and it has a very low load bearing capacity, particularly after experiencing the freeze-thaw cycles. Since the presence of this soil may cause erosion and the probable succeeding destruction of foundations and embankments, and occurrence of tensile cracks in roads, the treatment of marl is desirable in construction. In this study, initial tests revealed that the Unconfined Compressive Strength (UCS) of a highly calcareous marl was dramatically decreased to almost zero only after the first freeze-thaw cycle. Afterwards, the marl samples were treated by electroosmosis application in an electroosmosis cell designed for this study. The effects of various voltage gradients of 0.46, 0.92 and 1.84 V/cm and the treatment periods of 1, 3 and 7 days on characteristics of marl were investigated experimentally. After the electroosmosis treatment, undisturbed samples were taken from the zones around anode, cathode and in-between of the poles. The UCS of the samples was measured after applying up to 16 freeze-thaw cycles. The results indicated that the electroosmosis treatment increased the load bearing capacity of the marl significantly. The UCS of a sample taken from around the anode increased by 2.8 times in comparison with the untreated one. As the best case, a seven-day application of electroosmosis under the voltage gradient of 0.92 V/cm showed a UCS value of about 271 kPa even after 16 freeze-thaw cycles.

Research on Soil Resources of the NorthWest Part of the Cracau-Bistrita Depresion for Sustainable Agriculture

Cracau-Bistrita Depression it belongs to the investigated it is a unique physical geographical unit within Moldavian Subcarpatians, which occupies the center of the groove subcarpathic between Moldova and the Trotus Rivers. In geological terms we refer territory corresponds to a restricted part of the Moldavian Platform appears as an extension to the southwest of Russian platform. Geological rocks that are part of the northwest Cracau-Bistrita Depression parent materials generated relatively differentiated by features and nature that can be eluvial, colluvial and alluvial. After compiling size, they are made of clay and marly clay, sand, alluvial deposits. The main pedogenetic processes which led to differentiation and the formation horizons of soil the soil cover of the northwest Cracau-Bistrita Depression may be mentioned bioaccumulation, clay migration, argillisation, gleyzation and stagnogleyzation. Ensemble pedogenetic factors and pedogenetic processes specific area led to the formation of a coating on the ground floor consists of relatively varied protisols, cernisols, cambisols, luvisols, hidrisols and antrisols. Of these, the largest share is occupied by cernisols. Arable land suitability is limited by several factors, of which the most important are considered the soil, topography and drainage. So outstanding were six classes of land: from those with very good suitability for field crops, without restriction, to land that can be used only for forests as those from nearby watercourses due to flooding. Misuse of the land has led to extreme natural phenomena, considered risks that go to produce immense damage by reducing agricultural production. I particularly physical, chemical and complex risks. Most worthy of notice covers the main physical and chemical properties of soil and land degradation by destroying the soil. In order to eliminate the negative effects of limiting factors of agricultural production, reducing risk and thereby improving the productive potential of the northwest Cracau-Bistrita Depression were proposed a series of works agropedoameliorative such as regulation of water and embankment works, paper land on the contour and avoiding weeding plant cultivation on slopes, erosion control works and avoid prolonged grazing early spring or fall, ripping papers for land compacted or affected by excess moisture.

Influence of natural additions on the physicochemical characteristics of cemented radioactive resins

The study aims to perform the immobilization/stabilization process quality of ions exchange resins by cementation. For this purpose, three natural and local materials were tested as additions: (1) limestone, (2) marly clay and (3) marly limestone. After characterization of these additions, mainly by X-ray diffraction, the experimental study was initiated by the preparation of cemented packages according to two formulations. The first was carried out without addition and the second with addition. The second stage of the work was focused on studying the additions effects on the physicochemical properties and the mechanical behavior of the cemented resins packages. The obtained results showed that additions improve significantly the mechanical strength and the physicochemical properties of the studied packages. Local marly clay, rich in kaolinite and free silica, has made it possible, as a natural addition, to prepare the most efficient cemented resins packages.

Research on the Presence Greyic Phaeozems in Romania

Areas under greyic phaeozems of Romania corresponding geographical areas as compared lithostratigraphic are made of clay and marly clay with frequent intercalations of sands and sandstones in a thick package, belonging Sarmatian, respectively, Volhinian and Basarabian, which directly influences the characteristics of the parent material of the soil.In this way, due to differences in altitude, these soils were formed and evolved deposits vary in granulometric composition, it is represented by loess, loess-like deposit, loam and loess, marly clay.Thus, we believe that the presence greyic phaeozems of our country in eastern, the genesis and evolution of the important role they have parental materials rich in fine sand fraction (31-41%). Specific these soils is the formation of humic acids and precipitate in place, under the influence of calcium ions, contributing to the development and the individualization of the horizon Am.Fulvic acids from the breakdown of litter cvercinee does not precipitate in the upper horizon, but migrate to the base, they favoring the migration is known as the iron and aluminum hydroxides and enriching the waste in the lower part of the quartz diagnostic horizon for greyic phaeozems, and a clay horizon B argic migrated upper horizon.

Nuclear techniques applied to provenance and technological studies of Renaissance majolica roundels from Portuguese museums attributed to della Robbia Italian workshop

Artistic and historical examination of high-quality glazed terracotta sculptures displayed in various Portuguese museums point to their production in della Robbia workshop of Florence (Italy). A multitechnique analytical approach is applied for the first time to these sculptures, aiming to confirm their origin. Materials were analyzed using Instrumental Neutron Activation Analysis, Prompt Gamma Activation Analysis and X-ray Diffraction. The compositional results are similar to other della Robbia sculptures, suggesting a common origin for the raw material that was identified as carbonate rich marine origin marly clay. The applied firing temperatures was proved to be around 900 °C. The differences found within each sculpture are explained by the production technique of assembling separate parts to produce these huge sculptures, and the clay pit heterogeneity.

Effects of lime treatments on marls

Marly clay was treated with calcitic and Mg-rich lime in order to determine the influence of the clay's high carbonate content on the stabilization effectiveness. The evolution of mineralogical and physical properties over the course of the treatment were studied using XRD, TEM, SEM, elemental analysis, TG, granulometry, and nitrogen sorption and correlated with the marly clay's improved geotechnical behaviour. Only a small portion of smectites and other clay minerals dissolved upon lime treatment. Changes in clay mineralogy had, thus, only very limited influence in the improvement of the material's plasticity and swelling behaviour, which was rather modified by an increase in particle size. This increase was primarily caused by aggregation induced by calcium silicate aluminium hydrate (C-(A)-S-H) formation, whereas flocculation had an only minor effect. After the initial improvement, disaggregation of clay particles occurred which resulted in a particle size decrease, most likely, caused by carbonation of C-(A)-S-H phases. These findings question the effectiveness of lime stabilization for marl using currently applied standard treatment protocols.

Magnetic fabric of Plio-Pleistocene sediments from the Crotone fore-arc basin: Insights on the recent tectonic evolution of the Calabrian Arc (Italy)

Low-field anisotropy of magnetic susceptibility (AMS) analyses were performed on 532 samples collected in 36 (mostly lower Pliocene to lower Pleistocene) marine clay sites from the Crotone basin, a fore-arc basin located on top of the external Calabrian accretionary wedge. The Crotone basin formed since mid-late Miocene under a predominant extensional tectonic regime, but it was influenced thereafter by complex interactions with NW–SE left-lateral strike-faults bounding the basin, which also yielded post-1.2Ma ∼30° counterclockwise block rotations. The basin is filled by continental to marine sediments yielding one of the thickest and best-exposed Neogene succession available worldwide. The deep-marine facies – represented by blue-grey marly clays gave the best results, as they both preserved a clear magnetic fabric, and provided accurate chronology based on previously published magnetostratigraphy and calcareous plankton (i.e. foraminifers and nannofossils) biostratigraphy. Magnetic susceptibility range and rock magnetic analyses both indicate that AMS reflects paramagnetic clay matrix crystal arrangement. The fabric is predominantly oblate to triaxial, the anisotropy degree low (<1.06), and the magnetic foliation mostly subparallel to bedding. Magnetic lineation is defined in 30 out of 36 sites (where the e12 angle is <35°). By also considering local structural analysis data, we find that magnetic fabric was generally acquired during the first tectonic phases occurring after sediment deposition, thus validating its use as temporally dependent strain proxy. Although most of the magnetic lineations trend NW–SE and are orthogonal to normal faults (as observed elsewhere in Calabria), few NE–SW compressive lineations show that the Neogene extensional regime of the Crotone basin was punctuated by compressive episodes. Finally, compressive lineations (prolate magnetic fabric) documented along the strike-slip fault bounding the basin to the south support the significance of Pleistocene strike-slip tectonics. Thus the Crotone basin shows a markedly different tectonics with respect to other internal and western basins of Calabria, as it yields a magnetic fabric still dominated by extensional tectonics but also revealing arc-normal shortening episodes and recent strike-slip fault activity. The tectonics documented in the Crotone basin is compatible with a continuous upper crustal structural reorganization occurring during the SE-migration of the Calabria terrane above the Ionian subduction system.

Caractérisation minéralogique et géotechnique des argiles marneuses gonflantes de la région de Médéa, Algérie

This paper presents the approach followed for the geological, mineralogical, and geotechnical characterization of swelling marly clays in the Medea region. This investigation is conducted in order to estimate the swelling potential of this marly clay layer. The studied sites, located at about 80 km south of Algiers, Algeria, cover an area of approximatively 400 hectares. Five sites are considered. In the first step, the geological, tectonic, climatic, and hydrological contexts of the region are described. According to the geological map of Medea, most of the formations encountered in the area are composed of Miocene layers represented by marly clays (Fig. 2). This region is characterized by its high and low temperature in summer and winter, respectively, and variable humidity (Fig. 3). In a second step, the results of geotechnical studies, X-ray diffraction tests, chemical analyses, and scanning electron microscope (SEM) observations are presented (Figs. 3, 4, 5, 6, 7, 8, 9). The soils contain quartz (20–26 %), calcium carbonates (11–55 %), kaolinite (8–13 %), illite (6–14 %) and Montmorillonite (18–26 %). The study of their microstructure by means of SEM indicates that these soils are formed by a compact marly clay matrix that is relatively homogeneous and oriented in the dip direction of bedding. A grain size analysis shows that the clay content varies between 17 and 70 %. The water content of all samples varies between 8 and 30 %. The values of the liquidity limit (LL) and plasticity index (PI) vary between 28–76 % and 16–36 % respectively, indicating a highly plastic soil; this is also confirmed by a specific surface varying between 99 and 179 m2/g. The dry density γd varies between 15 and 19 kN/m3. The swelling potential of the marly clay samples is evaluated firstly using various indirect methods. In literature, a number of empirical classifications are proposed by different authors (BRE 1980; Chen 1988; Komornik and David 1969; Seed et al. 1962; Snethen 1984; Vijayvergiya et Ghazzaly 1973 et Williams and Donaldson 1980). The swelling potential is related to certain physical properties of soils, such as consistency limits, clay content, methylene blue value, etc. In general, these methods indicate that all the tested soils have a high swelling potential, which confirms the results of mineralogical analysis. Secondly, direct measurements of swelling parameters are performed. Swelling tests are carried out using a standard slaved one-dimensional odometer using two methods: free swell and constant volume, according to standard ASTM D 4546-90 and AFNOR (1995). The swell pressure, the swell percentage and the swell index are given in Fig. 16. It is noted that the soils develop very significant swell pressures which vary between 25 and 900 kPa. This is in agreement with the results obtained by empirical methods. This investigation clearly shows that the marly clays of the Medea region have a high swelling potential. Therefore, taking into account the phenomenon of soil swelling in structure design is essential.

Characterization, Modeling and Mapping of the landslide affecting the centre-town of Azazga (Algeria)

The morphology of the North Algerian basins characterized by precarious stability constitutes an important issue for the development and the economy of many cities in the region. The landslide affecting the city of Azazga represents one of the most active and dramatic land movements experienced by the region in recent years. The city affected by the movement is situated at about 20 Kms in the East of the Wilaya of Tizi - Ouzou (in northern Algeria); the instability is located in a slope, composed of flysch (Azazga flysch are compounds of two terms of marly clay with small sandstone beds), with an inclination of about 13 °. Several factors have acted to activate this instability. Furthermore, water factor and geological conditions of this region are the main parameters of the susceptibility of the site to landslides.The Geographic Information Systems (GIS) are an effective alternative for the analysis of large-scale instabilities (such as Azazga landslides). GIS made for the site of Azazga allowed better management and interpretation of spatial data as well as good understanding of deformation mechanisms and the extent of this landslide. Geological profile has been defined for this slope using the results of spatial data analysis. Numerical modeling of this slope was then carried out, using the finite element software PLAXIS 2D , with taking in consideration the effect of the water level. Those studies show the important influence of the position of water table on the activity of the landslide and the safety factor.

A major change in the sedimentation regime in the Crotone Basin (Southern Italy) around 3.7–3.6 Ma

The Lower Pliocene succession of the Crotone Basin (Calabrian Arc, Southern Italy) is mainly comprised of blue-grey marly clay with good magnetic properties. Here the bio-magnetostratigraphic data indicate a mean sedimentation rate of about 12–15cm/kyr. Around 3.7–3.6Ma a major change in the sedimentation regime occurred: the blue-grey hemipelagic marls grade rapidly into silty marls with a significant increase in the terrigenous fraction and with abundant siliceous remains throughout the whole interval. Magnetic properties of these sediments are very poor, but an integrated calcareous plankton biostratigraphy (foraminifera and nannofossils) infers a high average sedimentation rate (about 50–60cm/kyr). The abrupt onset of this sedimentation regime in the Crotone Basin is contemporaneous with a major unconformity already recognized in the northern sector of the basin, part of a major reorganization phase in the whole Apenninic–Maghrebid Chain known as “Globorotalia puncticulata event”. Reports of coeval siliceous sediments in other marginal basins of the Apennines (Southern Calabria, Southern and Northern Apennines) suggest that this “siliceous event” might have been regionally extensive, having important palaeoceanographical implications. We infer that the “siliceous event” is characterized by a combined tectonic- and climate-induced change in palaeoceanographic conditions. The tectonic triggering factors may have been linked to two synchronous events in the Tyrrhenian–Apennine system: 1) the shortening event also known as “G. puncticulata event”, and 2) the coeval opening of the Vavilov Basin in the Tyrrhenian Sea which yielded profound influences in terms of physiography and characteristics of the Crotone Basin. The consequent uplift of the Southern Apennines would have increased sediment supply and availability of silica, resulting in eutrophication and enhanced silica preservation. Strong winter mixing and possibly upwelling conditions could have increased primary productivity during heavy isotope stages Gi4, Gi2 and MG8, at the onset of the “siliceous event”. This important event, lasting from ca. 3.6Ma to ca. 3.2Ma, would have recorded a peculiar transitional period before further climatic deterioration and more drastic palaeoceanographic changes occurred around 3.1Ma, leading to cyclic sapropel deposition in the whole of the Mediterranean sea.

IMPROVEMENT OF EXPANSIVE SUBGRADE BY LIME ADDITION

Qena - Safaga road is considered to be one of the most important roads connecting southern Egypt governorates to the Red-Sea.The swelling action of the subgrade of this road ( between Km 18 to Km 32 ) has led to many cracklings' of the pavements, building foundations and water lines. Sediments had been observed. This action led to a heave and cracking of pavements, building foundations, water lines. This research deals with an investigation of the important properties of the road subgrade soil including plasticity, unconfined compressive strength and swelling pressure. The research also deals with the effect of hydrated lime addition and curing time on improving the important properties of such kind of subgrade, expansive marly clay. Using the optimum lime content of 6% by the same, the properties showed many satisfactory results. Plasticity and swelling pressure values decreased and unconfined compressive strength value increased. Also, the test results showed the strong effect of the curing time on enhancing this type of subgrade. Keywords: Swelling Subgrade, Expansive soil, hydrated lime, microstructural analysis, unconfined strength, California bearing ratio.

Foraminiferal record of marine transgression during deposition of the Middle Miocene Badenian evaporites in Central Paratethys (Borków section, Polish Carpathian Foredeep)

AbstractBenthic and planktonic foraminifera from a marly clay intercalation sandwiched between mid‐Badenian (Middle Miocene) gypsum deposited in an environment of an evaporitic shoal (&lt;1 m deep) at Borków (southern Poland) indicate a major marine flooding event in the previously isolated Carpathian Foredeep Basin (Central Paratethys). After this very short‐term environmental change, benthic foraminifers started to colonize a new niche which was previously defaunated, and the pattern of benthic foraminiferal colonization is similar to that related to the reflooding which terminated the Badenian evaporite deposition. The benthic foraminifer assemblages are composed of pioneer, opportunistic, r‐selected species dominated by elphidiids. The connection of the Carpathian Foredeep Basin with the marine reservoir was short‐lived. The marly clay intercalations in evaporite sequences originating in bared basins can thus register major environmental changes.

The Miocene/Pliocene boundary in the Mediterranean area: New insights from a high-resolution micropalaeontological and cyclostratigraphical study (Cava Serredi section, Central Italy)

Tuscany (Central Italy) is a key area for studying the Messinian Salinity Crisis and overlying Lower Pliocene deposits due to the high number and excellence of the outcrops. Although the Miocene/Pliocene transition is well exposed and suitable for detailed analyses, a high-resolution integrated stratigraphic study of such a crucial time span for the geological history of the Mediterranean has never been attempted. In the Fine Basin (Central Tuscany), the Cava Serredi section is one of the best exposures of the upper Messinian–Lower Pliocene transition of the Northern Apennines. The Miocene/Pliocene boundary corresponds to a surface separating thinly laminated lacustrine (“Lago-Mare”) marls from homogeneous circalittoral to upper bathyal marly clays. Detailed quantitative micropalaeontological analyses have been performed on 111 samples from the 22 m-thick Lower Pliocene succession. They resulted in the improvement of the biostratigraphic resolution of the basal Zanclean interval due to the recognition of several chronologically constrained bioevents typical of the Mediterranean region and based on benthic and planktonic foraminifera and calcareous nannofossils. Moreover, to unravel cyclical patterns of deposition, and given that the investigated succession shows no evident lithological pattern, micropalaeontological analyses have been coupled with calcium carbonate content variations. The latter revealed more-regular fluctuations, which are especially evident if the exclusive contribution of the planktonic foraminifer fraction ( PCaCO 3) is considered. Spectral analysis of the CaCO 3 curve indicates that sedimentation occurred under the control of Earth's precession. This datum is also confirmed by the cyclical patterns of Neogloboquadrina acostaensis and Sphenolithus spp. among foraminifers and nannofossils, respectively. According to the proposed cyclostratigraphic and astrochronological reconstruction, the Lower Pliocene interval of the Cava Serredi section consists of eight precession-controlled cycles ranging from the i-cycle 510 (5.33 Ma) to the i-cycle 494 (5.16 Ma). Finally, the comparison with other astronomically calibrated sections, including the Zanclean GSSP (Eraclea Minoa, Sicily), allowed us to prove the completeness of the basal Zanclean interval of the study section and to state that Pliocene re-flooding after the Messinian Salinity Crisis occurred synchronously with respect to other deeper sectors of the Mediterranean Basin.