Clay Facies Research Articles

The Cretaceous of the Spanish Central System: a review of the lithostratigraphy, palaeontology and sequence stratigraphy, including new educational perspectives

The Southern part of the Spanish Central System is formed by both terrigenous and carbonate Cretaceous rocks that have been affected by intense dolomitization. They are part of the sediments deposited on the western margin of the Iberian Basin during the Cenomanian–Maastrichtian, the depositional architecture of which has been reconstructed through a detailed sequence stratigraphical study and analysis of its fossil record. It is formed by three large transgressive–regressive cycles in which the carbonate platform moves towards the West, while the terrigenous facies of its base decreases and the overlying clay facies, with gypsum, increases. The integration of sedimentological and palaeontological data and the identification of a set of parasequences has allowed the differentiation of 13 depositional sequences. This research has been essential to carry out modern geological mapping and provide society with a model that improves the economic geology and geotechnical exploration of these areas. Furthermore, this scientific progress has also impacted on the interest of society towards the geosciences and, especially, palaeontology. This has widened the scope for new research fields related to scientific outreach for the community and learning opportunities at different educational levels.

Retention of 226Ra in the sandy Opalinus Clay facies from the Mont Terri rock laboratory, Switzerland

The safety assessment of deep geological disposal of nuclear waste requires a sound understanding of radionuclide retention in the repository host rocks. Here, we investigate the retention behaviour of the safety relevant radionuclide 226Ra in the heterogeneous sandy facies of the Opalinus Clay (OPA-SF) at the Mont Terri underground rock laboratory. Various rock samples were selected from a drill core (BAD-1) located in the lower sandy facies, which were representative for its textural and mineralogical heterogeneity. The samples were carefully characterized with respect to mineralogy and chemistry using X-Ray diffraction and electron microscopy. The amounts of quartz, carbonates and clay minerals in the samples ranged between 58 wt.% – 65 wt.%, 13 wt.% – 35 wt.% and 5 wt.% – 25 wt.%, respectively, underpinning the mineralogical heterogeneity. Rare (Ba,Sr)-sulphate precipitates were identified in the clay matrix by electron microscopy. The uptake behaviour of Ra was evaluated using batch sorption experiments. Corresponding to the mineralogical variability of the rock samples, the measured distribution ratios Rd for the 226Ra retention varied between 20 L kg−1 and 260 L kg−1 after 120 days. The experimental results and thermodynamic modelling approaches suggest that various processes contribute to the uptake of 226Ra on different time scales: fast cation exchange and surface complexation reactions by clay minerals and the (slower) formation of solid solutions during recrystallisation of (Ba,Sr)-sulphates as well as retention by carbonate minerals; the latter mechanism still requiring further investigation.

Литолого-фациальная модель бакинских отложений Астраханского Прикаспия

The influence of fluctuations in the Caspian Sea level on the lithological and facies characteristics of sedimentary deposits is analyzed. Special attention is paid to the study of periodic changes in the water level in the Caspian Sea during the Absheron and Baku time in order to determine the effect of fluctuations on sedimentation processes. The Turanian regression was considered, and its differentiation with the Absheron and Baku transgressions was carried out. The study included the study of climatic conditions of past eras and their impact on the diversity of flora and fauna, which, in turn, had an impact on sedimentation processes in various periods of the Baku stage. Geological and statistical methods were used to determine the characteristics of reservoirs in sediments, as well as to study their distribution over the territory. A lithological and facies model has been constructed that reflects two cycles of regression and transgression characteristic of the deposits of the Baku time, which made it possible to describe the distribution of sandy and clay facies in various sections of the section and interpret a map of sandiness to identify buried river valleys. It is concluded that two lithofacies bundles reflecting the transgressive-regressive cycle of the Great Caspian Sea were identified in Baku time. Hypotheses have been formed according to which the reservoirs were formed in the final stage of the Turkic regression and were later covered with sediments of the Baku transgression. It has been established that these reservoirs play a significant role for gas accumulations and are distributed almost throughout the territory of the Astrakhan Caspian Sea. The identification of areas with a high reservoir content may be important for future exploration in this region.

The late Pleistocene - Holocene sedimentary evolution in the Ba Lat River mouth area of the Red River Delta

The Ba Lat estuary is part of the downstream stretch of the Red River Delta, the second-largest Delta in Vietnam and the 12th largest in the world. This study analyses GAT borehole sediments in the Ba Lat estuary area to assess environmental changes during the Late Pleistocene - Holocene period. This entailed detailed analyses of 70 m-deep borehole data from the Ba Lat estuary area, including structural analysis of 70 m-deep sediment core samples, 230 samples of grain size, 49 samples of Foraminifera, five samples of petrographic thin slices, and four samples of radiocarbon dating.
 The data reveal nine sedimentary facies, including river channel sand facies, floodplain clayey silt facies, tidal flat sandy-silty facies, bay clayey silt facies, pro-delta clayey silt facies, delta front sandy-silty clay facies, mouth bar sand facies, tidal flat sandy - silty clay facies, and delta plain silty clay facies. The combined nine sedimentary facies formed sequentially in time, representing the evolution of the sedimentary environment from the Late Pleistocene to the Holocene and the evolutionary process from the continental to the estuarine and Delta environment.
 The results also enable the geographic identification and delineation of the incised valley in the Red River Delta during the Late Pleistocene to Holocene period. The sedimentation rate in the incised valley varies from period to period. In the sedimentation phase of the incised valley, the average accretion rate reached 11.64 mm/year. In contrast, during the open sea regime (shallow sea near the coast), the accretion rate was observed to be very low, with a rate of 1.27 mm/year and the period of delta formation had the highest accretion rate, reaching 13.41 mm/year.

Changes in aquifer properties along a seasonal river channel of the Niger Basin: Identifying groundwater recharge pathways in a dryland environment

In drylands of tropical Africa, groundwater plays a fundamental role in alleviating food insecurity and adapting to the effects of climate change. Substantial uncertainty persists in the renewability of groundwater resources in drylands and recharge pathways through the surface geology. Here we characterize the architecture and hydrogeological properties of alluvium and underlying sandstone and crystalline basement rocks along the ephemeral River Goulbi de Maradi in the Iullemmeden Basin of Niger using Magnetic Resonance Soundings (MRS), Time-Domain Electromagnetic (TDEM) soundings, and borehole lithological data. Considerable variations in lithological facies and hydrophysical properties are found along a series of 5 transects perpendicular to the seasonal/ephemeral river channel and adjacent plateaux of the Continental Hamadien (CH) sandstone. The CH aquifer comprises a pebbly sand facies upstream and sandstone clay facies downstream with Farak-type sandstones located at the base of the two facies. Consistent with these variations in facies, the geophysical parameters decrease from 19%, 390 ms, and 800 Ω m upstream to 3%, 160 ms, and 10 Ω m downstream, respectively for effective porosity, relaxation time, and resistivity. The transmissivity and specific yield estimated from the decline of MRS longitudinally also vary from upstream to downstream. The combined use of surface geophysics constrained by lithological borehole logs provides vital insight into groundwater replenishment in this dryland environment.

Late Quaternary evolution of lower reaches of the Volga River (Raygorod section) based on luminescence dating

The normally-closed Caspian Sea is known for large changes in relative sea-level (of ∼170 m) during the late Quaternary. These transgressive/regressive events influenced the topography, sedimentation and ecosystems of a large area, of up to 1 million km 2 . The Volga River has played an important role in the water balance of the Caspian Quaternary basins but our understanding of the temporal evolution is poorly constrained. Recent studies on the evolution of the Lower Volga have focused mainly on the subaerial sequence of loess-palaeosol series corresponding to a long-duration Caspian low stand (the so-called “Atelian regression” from ∼90 to ∼25 ka). In this study we address, for the first time, the temporal evolution of the Volga River during the late Quaternary, as recorded in the many layers of alluvial sands at the Raygorod reference section. This 50 m high outcrop contains a complicated sequence of different types of interlayered alluvium (channel and floodplain facies), a loess-palaeosol sequence with a weakly developed palaeosol, and marine sediments of the Khvalynian transgression (Chocolate Clay facies). The new chronology, based on 35 samples, is derived using optically stimulated luminescence (OSL) analysis of sand-sized quartz, with support from post-infra-red infra-red stimulated luminescence (post-IR IRSL) from K-rich feldspar grains to date the older parts of the section. The new ages identify five stages of the topography development in the northern parts of the Lower Volga: (1) an MIS 5a flood-plain in deltaic/estuary environments (>90 ka) during a high-stand of the Caspian Sea (Hyrcanian transgression); (2) a transition from deltaic/estuary conditions to a river valley with normal alluvial sedimentation and sporadic stabilization reflected in palaeosol development (80–70 ka); (3) a palaeo-Volga channel migration at elevations of 4–8 m msl during 69–62 ka, evidence of a brief increase in Caspian Sea-level and blocking of the Volga flow; (4) a subaerial stage with high-speed accumulation of loess during MIS 4 to MIS 2, containing one weakly developed palaeosol (MIS 3c) and pedocomplex of three combined palaeosols of the beginning of MIS2 (30–24 ka); (5) a rapid Khvalynian transgression, starting at the Raygorod location at ∼18.3 ka, with relatively weak marine erosion of the top 40–60 cm of loess cover, presumably because of the rapid migration of the coastline in the flat Northern Caspian Lowland.

Speed of propagation of a longitudinal refracted seismic wave in the river valley Lena Tuymaade

The values of the velocities of longitudinal refracted waves obtained in 1979–1999 are generalized. by the method of refracted waves during the work of the Yakut trust of engineering and construction surveys in the built-up area of the valley of the river. Lena Tuymaada. A normal probabilistic law for the spatial distribution of velocity values in all lithotypes of Quaternary deposits has been established. In the permafrost zone of the Central Yakut Plain in the Tuymaade valley, the general law of the growth of velocities with depth depending on the growth of volumetric weight has been confirmed. Local variations in the spatial variability of the speed of the refracted wave are due to the combined effect of the main ground-frost factors: salinity, ice content and porosity. The most variable was the speed of the refracted wave in clay facies — loams and sandy loams of lacustrine-marsh deposits. The average velocity with an equal volumetric weight of sedimentary rocks is practically the same in the Tuymaade valley and in the permafrost zone of South Yakutia. Such a regional petrophysical feature creates favorable engineering and geocryological conditions for the application of the refracted wave method in the permafrost zone, both in Central and South Yakutia, to solve one of the important basic engineering geological problems. Namely, determining the depth of occurrence of semi-rocky and rocky bedrocks of sedimentary genesis in the bases of the foundations of engineering structures. The analysis of theoretical variograms of refracted wave velocities showed that the reliability of probabilistic-statistical solutions in recognizing the boundary between the frozen strata of Quaternary deposits and bedrock in the Tuymaade valley is very high and amounts to 99.5 %. With a maximum but small error of 15.5 %, the boundary between the seasonally thawed cultural layer and loamy-sandy lacustrine-marsh deposits is recognized.

Impact of the heterogeneity of the sandy Opalinus clay facies at the Mont Terri underground research laboratory on radionuclide migration

Abstract. The assessment of the safety of a deep geological repository (DGR) for high-level radioactive wastes over assessment time scales of up to 1 million years requires an in-depth understanding of the multi-scale coupled processes that affect the repository system evolution over time, to reduce uncertainties and conservatism in safety analyses. This is in particular required with respect to the challenges of a comparative assessment of different repository concepts in different host rocks within the process of a site selection for a DGR for heat-generating radioactive wastes in Germany. The collaborative project “Integrity of nuclear waste repository systems – Cross-scale system understanding and analysis (iCross)” conducted jointly by five research centres of the Helmholtz Association and co-funded by the Initiative and Networking Fund of the Helmholtz Association and the Federal Ministry of Education and Research (BMBF) has been initiated with the overall objective to improve the understanding of coupled thermal-hydraulic-mechanical-chemical-(micro)biological (THMCB) processes and to develop simulation tools that enable a holistic close to reality description of the long-term evolution of the repository system. Geological formations, such as those foreseen as potential host rocks for DGRs, and their surroundings are heterogeneous on various length scales ranging from nanometers to kilometers. Therefore, the aim of this work in the context of iCross is to evaluate the effects of mineralogical, geochemical and microstructural heterogeneities of repository host rocks on radionuclide transport in the repository far field, using the sandy facies of the Opalinus clay (SF-OPA) from the Mont Terri underground research laboratory (St. Ursanne, Switzerland) as an example. Here, we address in particular the migration behaviour of Ra-226 as an important radionuclide to be considered in safety cases for deep geological disposal of spent nuclear fuel. To assess the impact of the heterogeneities in SF-OPA on radionuclide transport, a complementary approach combining microstructural characterisation methods, experimental techniques for the determination of transport parameters of the rock matrix and the mobility of Ra-226 with innovative developments in reactive transport modelling on the pore and continuum scales was pursued. One of the results was that although the limited clay content in SF-OPA decreases the total amount of Ra bound to the illite phase, the solid solutions of sulphate and carbonate compensate for this and provide a major fixation mechanism.

Characteristics of polymetallic enrichment on oceanic red bed in Matano Formation, Baturubei, Central Sulawesi, Indonesia

The Matano Formation on Sulawesi Island has Cretaceous oceanic red bed (CORB) facies, but there is no further research on the geochemical characteristics of the sedimentary rocks. This study aims to classify the CORB of the Matano Formation and reveal the polymetallic element enrichment in CORB by using the X-ray fluorescence (XRF) analysis method. Matano Formation in the research area consists of two different facies: radiolarites facies and red clay facies. Radiolarites facies grouped as Si-ORB, dominated by siliceous pelagic bioclastic and deposited under oxic environment. The red clay facies grouped as Al-ORB, the components dominated by hemipelagic material with a small amount of silica shelled pelagically and deposited under reduction environment. Red clay facies have higher enrichment elements Mn, V, Ni, Zn and La than radiolarites facies. Oceanic red bed facies of Matano Formation deposited in basin plain environment below carbonate compensation depth in a passive margin tectonic setting.

Acheulian artefacts and tephra from Upland Western Maharashtra (Deccan Volcanic Province), Peninsular India

Abstract The two Early Acheulian sites of Bori and Morgaon in the Deccan Volcanic Province in Upland Maharashtra, India bear some association with an acidic tephra deposit in a fluvial context. Acheulian artefacts in association with tephra were first reported in India from the Bori site and numerous efforts to date this tephra have since been undertaken. These efforts employed various dating methods and produced a total of 10 absolute dates ranging from the Early Pleistocene with a maximum age of 1.4 Ma to the Late Pleistocene with a minimum age of 23.4 ± 2.4 ka. However, field observations and a typo-technological analysis strongly suggests that these Early Acheulian artefacts occur in a semi-primary context, and thus contest the Late Pleistocene age of the tephra and redeposition of the artefacts as argued by some scholars. At Morgaon, the Acheulian artefacts have been recovered from basal fluvial sediments that contain clasts of laterite. These sediments are capped by two low-energy clay facies that are separated by high-energy gravel lenses. The tephra at Morgaon has been reported from the upper clay facies and has produced absolute dates ranging from the Matuyama period (>0.78 Ma) to the Late Pleistocene (41 ka). After more than two decades of investigation at these sites, the number of absolute dates procured through methods such as electron spin resonance (ESR), 39 Ar– 40 Ar, U–Th and palaeomagnetism, although encouraging, are inconclusive. This paper is therefore an attempt to gauge the nature of the palaeolandscapes that most probably existed during the Early Quaternary. This will be achieved by studying local geomorphological variability between the two sites, along with a preliminary analysis of lithic morphology.

Characteristics of late Miocene Lithofacies - Paleogeography in the Southeast Region of Hanoi Depression

The characteristics of late Miocene lithofacies in the southeast region of Hanoi depression have been revealed on the basis of sedimentary evolution in relation to sea level change and tectonic movement. During late Miocene, global sea level change has created one depositional sequence and three sedimentary systems tract. The lowstand systems tract (LST) is characterized by 5 rhythms of alluvial lithofacies. These rhythms are represented by rough, humoc seismic wave fields. This environment is not favorable condition for coal formation. The transgressive systems tract (TST) is characterized by 6 transitional lithofacies rhythms. Each lithofacies rhythm consists of 4 facies: the tidal flats sand facies of the bay, the mud facies of the river mouth lagoon, the coastal marshy mud facies creating coal and the bay greenish-gray clay facies. The pacing process involves changes in the local sea level caused by tectonic lift. Each tectonic subsidence phase takes place at a very slow velocity, so it is compensated for fine-grained sediment creating marshy mud facies to develop mangroves on a large scale. It is a prerequisite to create thick coal seams distributed near the end of each rhythm. A part of highstand systems tract (HST) are eroded due to the improved folding process, creating an angular unconformity boundary with Pliocene-Quaternary sediments. However, after reconstracting of deformated section, it was clear that this systems tract had only one rhythm including 2 facies: prodelta mud facies and alluvial fan sandstone facies.
 Keywords: Lithofacies-paleogeography, sedimentary systems tract, sedimentary rhythm

Фаціальні особливості палеоцен-еоценових відкладів передових скиб Скибової зони Українських Карпат

There three main types of facies of Paleocene-Eocene complexes: sandy, siltstone and argillite distinguished within the study area by the nature of the distribution of the strata of the forming components were highlighted. Тhey accumulated avalanche at the foot of the continental slope and formed various facial parts of the foehn (Upper, Middle and Lower foehn). In the upper part of the Foehn was accumulated coarse-grained sediments (clusters of deep boulders and other psephyto-psammitic material containing edaphogenic rocks). Under the action of geostrophic and bottom currents, silt streams of pelitic and psammitic material moved in the direction to the south and south-east of the Carpathian sedimentation basin, forming sandy-clay and clay facies (Middle and Lower foehn). During the turbidite movement of a large amount of sediment from the first (shelf) to the second (foot of the continental slope) level of avalanche sedimentation, sorting and distribution of sediments on the continental slope took place. Based on the analysis of the material composition of Paleocene-Eocene sediments of the study area by such criteria as the size of the fragment, sedimentary textures and the ratio of different rocks, 7 facies were identified, which were deposited as gravitational flows down on the continental slope. Reconstructions of Paleocene-Eocene age flysch deposits showed that terrigene material in the studied sedimentation basin came from two sources – one of which was northwest of the study area and was characterized by a predominance of coarse-grained sandy sediments, while the source wear, which was in the central part of the studied basin was characterized by a predominance of clay silt and fine-grained psammitic material. This nature of the distribution of terrigenous material had a decisive influence on the further formation of Paleocene end Eocene sedimentary strata in the process of sedimentogenesis and post-sedimentary transformations of sediments, and on the formation of reservoir rocks and rocks with potential reservoir properties for hydrocarbon exploration. It has been established that the composition of the Psamitolites of the flysch formation of the Paleocene and Eocene ages of the Carpathians was formed on the passive continental margin or in the inland and boundary seas, and their genesis mostly corresponds only to the platform source of material wear.

Late Pleistocene-Holocene sedimentary evolution in the coastal zone of the Red River Delta

The Red River Delta is considered one of the largest megadelta systems in Asia. The formation of this delta has been controlled by the continent-ocean interaction and sea-level fluctuation during the Cenozoic. In this study, we present a new sequence stratigraphic framework of the Red River Delta based on borehole lithofacies analysis and high resolution seismic data. The Late Pleistocene–Holocene sediments in the coastal zone of the Red River Delta were subdivided into three systems tracts: (1) the lowstand systems tract (LST) is characterized by a Late Pleistocene alluvial silty sand facies complex (arLSTQ13b); (2) the transgressive systems tract (TST) is illustrated by the coastal marsh facies complex and the lagoonal greenish-gray clay facies of Early-Middle Holocene (amt, mtTSTQ21−2); and (3) the highstand systems tract (HST) is composed of the Middle-Late Holocene deltaic clayish silt facies complex (amhHSTQ22−3). The boundaries between these three systems tracts are not isochronous, namely: (1) The LST-HST boundary has been associated with the Würm 2 Glaciation, which occurred at ~40-18 Ka.; (2) The TST-LST boundary is identified by a transgressive erosion surface, whose age ranges from ~12-5 Ka.; and (3) the HST-TST boundary is an unconformity between the submarine deltaic facies complex and the Middle Holocene marine flooding plain.

Lithofacies and Environmental Analysis of Reservoir Sandstones in the “ABOM” Oilfield of Eastern Niger Delta, Nigeria

Facies of part of the Coastal swamp depobelt was analyzed using well log. Electrofacies was defined based on well log signatures. The defined facies were inter-related to define a facies association. The facies association were related to deltaic depositional cycles. 10 of such facies association or deltaic cycles were seen in the interval studied. The facies association or deltaic cycles have a different composition of facies related to the level of preservation of the components of the association. The component of the facies association seen include marine clay facies, lower shoreface facies, upper shoreface facies, prograding mouth bar facies and fluvial facies. The marine clay facies underlie each facies association and the channel / prograding mouth bar cap the association where it is preserved. The lower shoreface facies, upper shorefacies, prograding mouth bar and fluvial facies form the Reservoir sandstones. The identified facies association was seen to be repeated in the interval studied though with different composition. This reflects different deltaic depositional cycles with different component of facies due to the prevailing depositional processes occurring at the period of deposition and those affecting the deposit of the cycles after deposition. The arrangements of the different components of the facies within the facies association will help in the prediction of reservoir sand bodies in any deltaic depositional cycle.

Late Pleistocene - Holocene Sedimentary Evolution of Nam Bo Plain and Correlation from the Ca Mau Peninsula to the Mekong River Delta in Midle-Late Holocene

Located in southern Vietnam, the Southern plain is one of the largest in Asia. Within the coastal area, this study has indicated that there are two plains forming by different hydrodynamic mechanisms: the river dominated Mekong Delta plain and the tidal dominated plain of the Ca Mau peninsula. Studying lithofacies based on: (i) sedimentary parameters indicating environment of 29 boreholes in tidal flat and coastal plains, hundreds of surveyed surface sediment stations; (ii) stratigraphy seismic characteristics of the 21 seismic sections; and (iii) absolute age data, evolutionary history of late Pleistocene - Holocene sediments in the Southern plain and the relationship between the Mekong Delta and the tidal plain of the Ca Mau peninsula in the middle Holocene - late be clarified. Both plains are characterized by 3 lithofacies complexes corresponding to 3 phases of sea-level change: (i) lowstand alluvial facies complex (arLST Q13b); (ii) coastal facies complex (amtTST Q21-2) and shallow marine-lagoon greenish-gray clay facies (mtTST Q21-2); (iii) the phase of the middle-late Holocene (Q22-3 HST) has a differentiation between the two plains. The Me Kong delta is characterized by three deltaic facies complexes: (1) the late middle-late Holocene buried submarine deltaic facies complex (amh1Q22-3); (2) late Holocene deltaic plain facies complex (amh2Q23) and modern submarine deltaic facies complex (amh3Q23). The tidal plain of Ca Mau peninsula is characterized by a complex of sandy bars, tidal plains and tidal channels. In the regressive process, four periods of relative sea-level stopped, creating three ancient shoreline (5ka BP, 2.5ka BP; and 1 ka BP). The delta plain is marked by deltaic lobes turning to the southeast sea, while the Ca Mau plain characterized by the sand bars that tend to change direction from the east (2.5 ka BP) to the southeast (0.5ka BP and 0.2ka BP).
 

Ramp reef depositional facies model for the Mid-Pliocene Golden Gates Reef Member of the Tamiami Formation, South Florida

The depositional setting for northern most Atlantic coral reef development during the Mid-Pliocene Warm Period is a gentle sloping mixed carbonate–siliciclastic ramp. Five core transects document the distribution of the reef complex in an area approximately 65 by 12 km, and nine repetitive depositional facies are identified. Paleoecological and sedimentological evidence documents facies development along a water depth–energy gradient. The mid-Pliocene Tamiami Formation is characterized by coral boundstone developed over level skeletal rudstone depositional units dominated by mollusks. Hyotissa haitensis (Sowerby), one of the last Gryphaeid oysters, is the dominant fossil found in the most continuous skeletal facies and overlies deeper water green clay facies, the only facies with pelagic foraminifera. Ground penetrating radar documents reef depositional topography, onlapping stratigraphy and two episodes of reef growth. Two cycles of deposition are recognized, separated by subaerial exposure. The coral boundstone and the skeletal rudstone exhibit both high primary and secondary porosity and overlie the impermeable clay facies. The upper surface of the coral boundstone lies at ~ 4 m in elevation whereas contemporaneous estuarine deposits are found to the north at elevations of 20–25 m. High porosity bank reef complexes along a shallow dipping ramp provide an alternative to the standard model of reef and porosity development along the outer shelf margin. Understanding the differences in associated facies between these two depositional environments permits better interpretation of observed heterogeneities in subsurface geobodies associated with inner shelf and platform settings.

Holocene sedimentary facies in coastal plain of the Song Ma Delta, Thanh Hoa Province

The Ma river delta located in the North Central of VietNam is the third largest ones in Vietnam following the Mekong Delta and the Red River Delta. However, there are not many researches on sedimentary. This study aims to determine the Characteristics of the Holocene sedimentary facies in coastal plain of the Song Ma Delta based on observation of sedimentary structure and analysis of grain size, diatom, flora, pollen and 14C dating collected for the drill core (LKTH2 borehole) from the coastal plain of the Song Ma river delta. Research results identify 08 facies consisting 02 facies of transgression period and 06 facies of regression period. During transgression period, 02 facies of tidal flat clayish silt and bay silty clay facies were formed. Of which, tidal flat clayish silt face was formed in 7,883 ± 43 14C yr BP. After the maximum flooding of the sea, the delta was initiated and 06 facies were formed during the regression period i.e. prodelta silty clay, delta front clayish silt, tidal flat sandy - silty clay, sand ridge, lagoonal sandy silty clay, and flood plain silty clay facies. The tidal flat sandy - silty clay facies occurred in 6.951± 38 14Cyr BP caused by sea level fall and the coastline was identified around the LKTH2 bore hole at that time. Integration of sedimentary facies of the sand ridge and lagoonal sandy silty clay facies shows that the Song Ma Delta was dominated by wave process during its evolution.

Sedimentological and paleoenvironmental analysis of chott Baghdad deposit (Northern Algerien Sahara)

The study area is located in Chott Baghdad (northern the Hedjira village) from the Wilaya of Ouargla, in the northeastern Algerian Sahara. The succession shows at the bottom an alternating of gypsiferous clay-sandstone layers, demonstrating some hydrodynamic sedimentary structures such across stratifications, escape structures, and continental trace fossils. The clay facies contains, some lacustrine microfossils specially foraminifera and ostracods. The uppermost of the succession is characterized by the presence of surrounded pebbles embedded in clay-sandstone matrix, overlain by gypseous-carbonate crust, showing on the top surface mud cracks.The granulometry and morphoscopy analysis evidence round-matt to lustrous blunt of quartz grain. Those data together with the fauna content and sedimentary structures indicate that the paleoenvironment should correspond to fluvio-lacustrine, under wind and torrential phases, linked to temporary climate change.

Quaternary Depositional Environments in the Vrgoračko Polje/Lake (SE Croatia)

The Vrgoracko polje is a karst field with a surface area of 37 km2 and an altitude of between 20 and 28 m above sea level, situated at the southern edge of the Dalmatian Zagora. During the Quaternary the polje was flooded for variable periods of time and a lacustrine environment was established. A multidisciplinary study of drill-cores, outcrops and geoelectric measurements recognised five main sedimentary facies: laminated sediment, redeposited sediment, coarse grained carbonate debris, littoral clay and lacustrine chalk. Based on the facies analysis, depositional environments developed during the Holocene include aquatic lacustrine littoral and deeper-water environments. The terrestrial environment is represented by a desiccated lake phase. The littoral clay facies (filling depressions and caverns in the karst relief) is laterally equivalent to the deep-water laminated facies (varves?). A stratigraphic break between littoral claya nd lacustrine chalk could be time-equivalent to disturbed laminated sediments deposited in deeper-water and to local intercalations of coarse-grained carbonate debris in shallow-water facies sediments. These features could have been the result of a neotectonic event (earthquake), which triggered debris flows of colluvial material from slopes around the lake, and this could also have changed the hydrological regime of the Vrgoracko polje and affected subsequent depositional facies. According to 14C dating, deposition of the lacustrine chalk started at the beginning of the Mid-Holocene Warm Period (7686±36 aBP) with a sedimentation rate of approximately 0.51 mm a-1 during the Middle, and 0.58 mm a-1 during the Late Holocene to today. Calculated carbonate production was estimated at 1050 gm-2 a-1. A temporary phase of subaerial exposure of the lake is indicated by desiccation cracks and two bioturbated palaeosol horizons. The described depositional environments and sediment facies found in the Vrgoracko polje could be considered to represent a typical Quaternary lacustrine sedimentation pattern for other Dinaric karst poljes.

Mineralogical and morphological characterization of Older Cambay Shale from North Cambay Basin, India: Implication for shale oil/gas development

Abstract Effective development of shale oil/gas reservoirs depends on the success of hydraulic fracturing. Mineralogy and morphology play a very important role in establishing brittleness and therefore controlling its hydraulic fracturing characteristics. In this paper, mineralogical and morphological characteristics of the Older Cambay Shale and the top Olpad Formation from the northern Cambay Basin, India have been characterized using well logs, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray spectroscopy (EDS or EDX) and atomic force microscopy (AFM) with the objective of identifying the fracturing potential of the units. Presence of mixed argillaceous mudstone, silica-rich argillaceous mudstone to argillaceous siliceous mudstone in the studied shale samples shows that the area under investigation is compositionally similar to the high clay facies of Marcellus and Barnett shale systems having low fracability. The studied formation is rich in kaolinite and chlorite, which aggregately contribute half of mineral composition ranging from 43 to 56%. Quartz, feldspar and mica combined to add approximately 30–43%, while siderite and magnesite varied between 8 and 12%. The interpreted results of mineralogical brittleness are supported by log based geomechanical properties. FESEM images at micro to nanoscale confirm the presence of various minerals with distinct crystal structure, along with inter-and-intra particle pores in the matrix. AFM scan at the nano scale shows mesopores ranging from 12 to 19 nm, with an average pore diameter of 17.57 nm and areal coverage of 10.9%. The log derived mechanical properties correlate with the mineralogy-based brittleness index (BI) of the studied shales indicating that the formations lie in the low to medium range of fracability. High clay content and low to moderate BI are likely to complicate the fracturing process of the potential resource rich area. Outcome of the present investigation demonstrates the limited shale oil/gas potential in the study area; however an extensive exploration program may unlock some sweet spots in the basin with distinctly different characteristics.