Adjacent Horizons Research Articles

Intensification of oil production in long-term developed offshore fields


 
 
 Reasonable allocation of operational facilities in the context of multilayered reservoirs is the foundation of all scientific and practical work on the development of petroleum fields. The parameters of deposits are subject to changes over the course of development, and therefore the previously identified system of objects should be updated periodically. This is especially true for offshore multilayered fields, mining which is time-limited due to corrosion of hydraulic structures and high costs for their renewal. In this regard, the rate of using offshore deposits should be quite high not only at the initial stages, but also remain so in subsequent mining periods. Maintaining a high rate of mining is often associated with high material costs (drilling new wells to compact the well network, applying new methods of enhanced oil recovery, etc.), which is not economically viable for the fields in long-term operation. As the practice of mining multilayered fields in Azerbaijan shows, the enlargement of objects allows compacting a mining network while maintaining the total number of wells for a field. At the same time, average daily oil production rates significantly increase as a result having included capacities of contiguous objects. The research aimed at identifying similarities or differences between adjacent horizons of the section of multilayered deposits. Based on the delineated boundaries, there are possibilities of their joint operation as one object, separate or simultaneous-separate operation of wells under appropriate technical conditions. As a result of such measures, all the wells are used rationally and the development rates are increased without additional capital investment. Section of objects of the 3rd tectonic block of the Neft Daşları offshore field, confined to the Apsheron archipelago of the South Caspian Depression (SCW). The Rodionov’s method was used for a substantial and reliable identification of stratigraphic boundaries. Preliminarily, based on averaged data on 11 parameters, we calculated ꭓ2g:m critical value at 95% significance, corresponding to m=0.05, which is used to assess the state of boundaries between the horizons. Then, by implementing software, the values for the boundaries of adjacent objects were calculated, comparing which with the critical value allowed for a conclusion about possible joint or separate mining of those productive strata. As a result of the implementation of the corresponding program, the clarity of the boundaries between the objects of the 3rd tectonic block of the offshore Neft Dashlari field was determined. The need for joint exploita- tion of horizons VII and VIIa, KS1 and KS2, as well as KaS1 and KaS2 horizons has been determined, which would optimize the mining of the field and is economically feasible.
 
 

Spodosol formation on sandy ruins in a semi-arid climate in the Catimbau National Park, Northeast Brazil

The Catimbau National Park (CNP) is found in the Caatinga biome under a semi-arid climate. The soils of certain humid areas have horizons with morphology typical of Spodosols, and their occurrence in the CNP seems to be in discord with their formation model. This study aimed to investigate the genesis of Spodosols in the semi-arid climate of the CNP, testing the hypothesis that these soils are the result of local tectonic conditions associated with a past climate. As such, a sandy soils toposequence over sandstone of the Tacaratu Formation, under Caatinga vegetation and a semi-arid climate in northeast Brazil was studied. Sampling was based on the structural model of the pedological coverage, whereby physical and chemical analyses, Fourier transform infrared spectroscopy, X-ray diffraction, and soil micromorphological analysis were carried out. The results indicate that paludization of the soils occurred in two more humid phases, being compounded by the occurrence of distended faults/fractures related to the geology of the CNP. Microbiological decomposition under hydromorphic conditions led to humification of the organic constituents, which acidified the environment and increased Al solubility, forming organometallic complexes with fulvic and humic acids. The FTIR spectra and the presence of charcoal confirm the condensed aromatic nature and the abundance of carboxylic groups in the soils, these being related to the pyrolysis of biotransformed plant residues. Podzolization occurred in pulses promoted by intense rains under a dry climate and Fe-poor parent material, which favored the translocation of organometallic compounds of Al. The dense packing of fine organomineral material in the Bh horizons and the open matrix in the adjacent horizons indicate that the narrowing of the porous environment may be an important factor for the immobilization of translocated material. With the return of the current drier conditions in Brazil’s semi-arid, the podzolization process remains incipient.

Pedological Development of Soils in Eastern Agroclimatic Zone of Haryana through Field Morphology Rating System

A study was carried out to evaluate the pedological development of soils in Eastern agroclimatic zone of Haryana using field morphology rating system. For this, nine pedons were excavated to study the morphological properties in field and rating scale was used to compare adjacent horizons with each other to give a comparison of the relative distinctness of horizons or to compare horizons in the solum with the C-horizon to give a relative profile development in soils occurring in different physiographic positions i.e. Shiwalik hills, recent and old alluvial plains with different precipitations throughout the study area. Some chemical properties were also used to evaluate the pedogenic factors as a result of being affected by process and factors of soil formation due to the distinct effect of climate. The Relative Horizons Distinctness (RHD) ratings were made by a comparison of adjacent horizons. The soils of Shiwalik hills, recent and old alluvial plains have RHD ratings from 6 to 14, 3 to 11 & 3 to 12, respectively. The RPD ratings were made by a comparison of the C horizon to the horizons above it in the profile. The soils of Shiwalik hills, recent and old alluvial plains have RPD ratings from 7 to 15, 3 to 14 & 5 to 16. The RPD values of all the profiles were maximum in A horizon due to maximum pedological development influenced by weathering. So, studies of these soils indicated the pedological development in the order of Shiwalik hills > old alluvial plains > recent alluvial plains.

Effects of shear on development characteristics of organic matter pores in shale: A case study of shale in the Niutitang Formation of the well XAD1

The development characteristics of organic matter pores (OMPs) in shales is fundamental to the gas-bearing property of the shales. Detachment is one of the most common types of structural deformation in shale formations. To investigate the characteristics of OMPs in shear-deformed shale and the associated effects on the pore structure of shale gas reservoir, two sets of detachment zones and the intercalated non-detachment zone of shale formations in the Niutitang Formation of the Well XAD1 are studied. Based on scanning electron microscope observations and low-pressure gas adsorption tests, the impacts of shear on the shale pore structure are evaluated quantitively and the deformation mechanism for OMPs in shale is established.Results indicate that the dominant pore type of shale in the Niutitang Formation of the Well XAD1 is OMPs. With the mineral rheology, organic matters are enriched in the clay gouge, which are more prone to shear deformation compared with those outside the gouge. Under shear, pores developed within the organic matter experienced directional elongation and compression, decreasing the pore sizes and lowering the volumes of the corresponding pores <30 nm; and the contact surface between organic matter and minerals becomes dislocated and open, increasing the volumes of the corresponding pores >30 nm. The effect of shear on OMPs is dominated by pore reduction. The volume loss ratio of shale micropores in detachment zones is the highest which can reach over 90%. The impact of shear on pore structures of non-detachment zone cannot be neglected within the thickness range of 5–20 m from the detachment surface, and the degree of pore reduction gradually decreases as the distance from the detachment zones increases. It is indicated that the detachment and its adjacent horizons are not favorable for shale gas exploration because of the low porosity and adsorption capacity.

A new Late Devonian flora from Sonid Zuoqi, Inner Mongolia, northeastern China

AbstractThe Silurian and Devonian plant fossil record is the basis for our understanding of the early evolution of land plants, yet our appreciation of early global phytogeographic evolution has been constrained by the focus of most studies on deposits from Europe, North America, and, more recently, South China. Devonian plants have been recorded rarely from northeastern China, and among previous records, few plants have been illustrated and formally described. In this article, megafossil plants representing a Late Devonian-aged (probably Famennian) flora are described from a locality at northern Sonid Zuoqi, Inner Mongolia, NE China. The flora includes Melvillipteris sonidia new species, Archaeopteris sp., and fragments of some other plants. The new plant shows main axes and two orders of lateral branches. The first-order branches of this plant show a typical zigzag appearance and are borne in pairs on main axes. Second-order branches are straight or slightly flexed, and are borne helically or alternately on first-order branches. Sterile ultimate appendages and fertile structures of M. sonidia n. sp. are borne alternately on second-order branches. An associated palynological assemblage, as well as U-Pb ages of detrital zircon grains from adjacent horizons, are also reported, indicating a Late Devonian age in accord with the megafossil plants. The present study contributes to our appreciation of the Devonian floristic diversity of the Xing'an Block, and, through our review of the record of early vascular plants from NE China, more broadly to the understanding of the mid-latitude vegetation of the Northern Hemisphere during the Late Devonian.

INFLUENCE OF TECTONIC DISTURBANCES OF COAL LAYER ON HIS GAS DYNAMIC STATE

Problem Statement and Purpose. At one of the coal mines of the Donetsk basin, there was a sudden release of coal and gas. The peculiarity of this case is that the accident happened in the place of the alleged development of a geological disturbance, but without any visible signs of this. Inspection of the ejection site and adjacent horizons made it possible to conclude that the emergency site is located in the place of the plicative disturbance development. Thus, it is necessary to study in more detail the influence of disturbed zones hidden nature on the gas-dynamic state of the reservoir, as well as to develop and implement methods for determining such zones. Data &amp; Methods. To achieve this goal, a new method was tested, based on the property of structureless substances to form crystal-like units. This phenomenon has been studied for decades; therefore, such new formations have long been given the name quasicrystals. It was noted that the increase in the concentration of such forms is associated with the presence of geological disturbances. Consequently, the increase in quasicrystals in the rock is an indicator of its disturbance due to the influence of tectonic pressure. Thus, in order to test the technique and reveal the hidden geological disturbance of the coal seam, coal samples were taken, microstructural features were studied, and the strength of the coal seam was measured at 56 points. Result. As a result the values of the concentration of quasicrystals, data on the strength of the formation were obtained, a schematic map of the development of the disturbance in this area was built, its contours were determined, the center of the disturbed zone was identified and the role of such disturbances in the outburst hazard of the formation was substantiated. It has been established that geological disturbances, even of plicative nature, have a high degree of fracturing. Such pores and cracks in coal reduce the strength properties and are able to concentrate sufficient volumes of gas for manifestation of GDP.

Microbial community structure in hadal sediments: high similarity along trench axes and strong changes along redox gradients

Hadal trench sediments are hotspots of biogeochemical activity in the deep sea, but the biogeochemical and ecological factors that shape benthic hadal microbial communities remain unknown. Here, we sampled ten hadal sites from two trench regions with a vertical resolution of down to 1 cm. We sequenced 16S rRNA gene amplicons using universal and archaea-specific primer sets and compared the results to biogeochemical parameters. Despite bathymetric and depositional heterogeneity we found a high similarity of microbial communities within each of the two trench axes, while composition at the phylum level varied strongly with sediment depth in conjunction with the redox stratification into oxic, nitrogenous, and ferruginous zones. As a result, communities of a given sediment horizon were more similar to each other across a distance of hundreds of kilometers within each trench, than to those of adjacent horizons from the same sites separated only by centimeters. Total organic carbon content statistically only explained a small part of the variation within and between trenches, and did not explain the community differences observed between the hadal and adjacent shallower sites. Anaerobic taxa increased in abundance at the top of the ferruginous zone, seeded by organisms deposited at the sediment surface and surviving burial through the upper redox zones. While an influence of other potential factors such as geographic isolation, hydrostatic pressure, and non-steady state depositional regimes could not be discerned, redox stratification and diagenesis appear to be the main selective forces that structure community composition in hadal sediments.

Pedological Characteristics of Soils under Different Cultivation Periods in Harrad Center and Al-Kharj, Kingdom of Saudi Arabia

A detailed pedological characterization of soils earmarked as benchmark soils of Harrad Center and Al-Kharj region, Saudi Arabia, was carried out to provide data required for planning and execution of soil fertility studies and transfer of technology in the regions. The present study aims to study the effect of cultivation periods on the morphological properties of soil profiles represented by a number of farms in the Haradh center and Al-Kharj governorate. The field morphology rating scale was used to compare adjacent horizons to calculate a relative profile development in soils. Soil samples representative of the benchmark soil profiles were described and analyzed for their pedological characteristics. The results indicated that, the relative horizon distinctness (RHD) values ​​of the Haradh center profiles showed the highest values (10-17) ​​in the surface layers only, and it decreased with soil depth, except for profile No.9. The results data did not show a uniform distribution of RHD values ​​in the deeper layers. The most morphological characteristics affected by soils cultivation and contributing to the RHD values ​​are color in dry and moist state followed by decaying organic matter, and soil consistence. Other morphological characteristics have a limited contribution on RHD values, such as structure and soil mottles, with various contributions to some other morphological properties such as textures and boundaries between layers in soil profiles. The boundaries between layers show converging contribution to RHD values ​​in Harrad and Al-Kharj profiles. The data obtained through this study presents a substantial base for sound land use planning and will facilitate transfer of technology from one area to another with similar ecological conditions.

Semiautomated seismic horizon interpretation using the encoder-decoder convolutional neural network

The seismic horizon is a critical input for the structure and stratigraphy modeling of reservoirs. It is extremely hard to automatically obtain an accurate horizon interpretation for seismic data in which the lateral continuity of reflections is interrupted by faults and unconformities. The process of seismic horizon interpretation can be viewed as segmenting the seismic traces into different parts and each part is a unique object. Thus, we have considered the horizon interpretation as an object detection problem. We use the encoder-decoder convolutional neural network (CNN) to detect the “objects” contained in the seismic traces. The boundary of the objects is regarded as the horizons. The training data are the seismic traces located on a user-defined coarse grid. We give a unique training label to the time window of seismic traces bounded by two manually picked horizons. To efficiently learn the waveform pattern that is bounded by two adjacent horizons, we use variable sizes for the convolution filters, which is different than current CNN-based image segmentation methods. Two field data examples demonstrate that our method is capable of producing accurate horizons across the fault surface and near the unconformity which is beyond the current capability of horizon picking method.

Morphology and pedogenesis of placic horizons in podzolic Ultisols with high clay content in humid subtropical forests

Placic (Bsm) horizons are commonly found in different types of soils worldwide, but are very rare in Ultisols. The formation of Bsm horizon and podzolization are different processes in pedogenesis. This study collected five podzolic Ultisols containing Bsm horizons from the subalpine forests in Taiwan to illustrate the morphological characteristics and genesis of the Bsm horizons in these soils with both clay illuviation and podzolization. The distinctive Bsm horizons were 3 to 10 mm thick and had abrupt and wavy boundaries with overlying albic (E) and underlying argillic (Bt) horizons. All Bsm horizons contained over 35% of clay fraction which significantly increased from E horizon to B horizons in the pedons. The Bsm horizons showed much higher bulk density than adjacent horizons above or below them, elucidating that such iron pans were relatively impermeable to water and plant roots. The maximum contents of pedogenic Fe occurred in the Bsm horizons mainly cemented by poorly crystalline Fe oxides associated with high amounts of organic matter and epiaquic conditions. Pedogenic Al appeared to be accumulated in the Bt horizons where spodic materials were identified according to the oxalate-extractable amount of Fe and Al. The polygenetic processes of these podzolic Ultisols with Bsm horizons were proposed as three stages. Firstly, clay illuviation predominantly occurred to form Bt horizon in the interglacial periods during the mid to late Pleistocene. Then, podzolization gradually became a major process to accumulate spodic materials in the Bt horizon because of the coniferous forest formation under the cool and humid climates close to the late Pleistocene; however, water was perched at the soil surface due to poor drainage and abrupt textural change between E and Bt horizons after the Holocene. Eventually, the reduced iron from E horizon was gradually re-oxidized and precipitated on the top of Bt horizon where exhibited oxidizing condition to form Bsm horizon until today. Because of the occurrence of Bsm horizon in these Ultisols, a new subgroup Placic Epiaquults, was therefore proposed to the keys to Soil Taxonomy.

On the restoration of the level of underground water after withdrawal from the layered aquifers with overflow

The patterns of restoration of the piezometric level of groundwater in the aquifer under test in a layered aquifer system with the overflow of water from the adjacent horizon after stopping the experimental constant-rate pumping tests, have been analyzed; the physico-mathematical model of piezometric level restoration has been formed and analyzed. It has been shown that the restoration of the level is carried out in the same way as after stopping the pumping from a pressure isolated aquifer. In other words, it has been assumed that pumping with a constant flow rate continues even after it has been stopped, and at the time of self-stopping through the well from which the pumping is performed, water is pumped into the test aquifer with the same flow rate. As a result, the disturbance flow rate becomes zero, and the groundwater level in the tested horizon is restored to an unperturbed position. In addition to this, during test filtration testing of layered systems with overflow, the groundwater flow formed during the injection, directed from the tested horizon to the adjacent one, completely "locks" the groundwater flow formed during the pumping out of the adjacent horizon to the tested one. Accordingly, the processing and interpretation of the results of tracking the recovery level should be carried out in full compliance with the existing methodological recommendations.

Comprehensive Utilization of Low-Potential Geothermal Waters of Southern Russia for Heat and Water Supply and Solution of Environmental Problems

The current state of exploitation of low-potential thermal waters of the East Ciscaucasia Artesian Basin has been evaluated. Low-potential waters, which are the only source of water supply for a considerable number of consumers in the North Caucasus, are being exploited in an extremely inefficient way with at most 20% of the allocated resources being utilized to the fullest extent. Abusive exploitation of the wells resulted in the bogging of large areas around them, depletion of water resources, and deterioration of the latter as a consequence of backflow of low-quality water from adjacent horizons into those being exploited. The quality of the water has drastically deteriorated; in most wells, contaminants, such as arsenic and various organic compounds, have been detected in quantities that considerably exceed the maximum permissible concentrations set for potable water. These thermal waters are not being used for generation of heat and power since their temperature is too low for heat and hot-water supply purpose. However, the resources of low-potential waters are sufficient to solve the problems of heat and hot-water supply and to provide a considerable number of consumers in the region with potable and process water provided that these resources are exploited in a sensible way using new complex technologies. Complex engineering systems comprise a system of heat pump plants in which the low-potential heat of thermal waters is utilized and a chemical treatment plant in which the cooled water is purified from contaminants, thus raising its quality to the potable water standard. The designs and technological parameters of the chemical treatment plants differ depending on the composition and amount of contaminants. The complex systems allow utilization of the product of thermal artesian wells to the fullest possible extent and large-scale introduction of such systems will facilitate the solution of environmental and economic problems in the region and improve sanitary, hygienic, social, and living conditions of people.

Accuracy, unbiasedness, and efficiency of current account growth forecast: Evidence from a large cross section of developed and developing economies

We use a previously unexploited consensus survey data set to compare accuracy, unbiasedness and efficiency of Current Account growth forecasts between two panels of 25 developed and 18 developing countries following the methodologies in the existing literature. Forecast errors are bigger for the developing country comparing to the developed country. Developed country forecast errors are unbiased but inefficient. The developing country forecast errors are biased but relatively more efficient. In both the panels, forecast revisions are efficient for the same forecast horizons, but inefficient for the adjacent horizons. Additionally, we find less evidence of forecast smoothing compared to some earlier studies. Forecasters do improve their forecasts as the horizons become shorter although the forecasts fall short of being unbiased and efficient statistically.

Pressure field characteristics of petroliferous sags in Bohai Bay Basin: Implication for hydrocarbon enrichment

Pressure fields of different sags in a petroliferous basin were significantly different, and it was related to hydrocarbon enrichment. Based on pressure data of different sags in Bohai Bay Basin, types of pressure field and its distribution characteristics were well discussed, and relationships between overpressure and hydrocarbon generation, pressure field and hydrocarbon enrichment were also investigated. Results showed that the Paleogene pressure fields of different sags in Bohai Bay Basin could be divided into three types: normal pressure type, single overpressure type and double overpressure type. These three types of pressure fields had the zoned features in their distributions. The normal pressure fields were mostly distributed in peripheral sags of the basin, while the single overpressure fields were widespread in the basin, and the double overpressure fields were concentrated in the areas around the Bohai Sea. Hydrocarbon generation had a significant effect on overpressure formation, thus overpressure horizons generally were corresponded to major source rock horizons, and differences of filling evolution history and main hydrocarbon-generation strata of different sags might be important factors for the formation of these three types of pressure fields. Overpressure in source rock horizons was closely related to hydrocarbon enrichment. Horizontally, hydrocarbons were mainly distributed around the overpressure center, and the secondary migration distance of hydrocarbons was affected by the degree of overpressure. Vertically, hydrocarbon distribution was controlled by the type of pressure fields. Hydrocarbons in the normal pressure sags were mainly enriched in the major hydrocarbon-generation horizons and their adjacent horizons, hydrocarbons in the single overpressure sags were mainly distributed in the hydrocarbon-generation horizons and its upper and lower horizons, while in the double overpressure sags, the hydrocarbon enrichment degree in Neogene was high. Hydrocarbon enrichment in sags was controlled by the degree of overpressure in hydrocarbon-generation horizons, and these oil-rich sags had relatively large overpressure degree.

Reflection of seismic paleoevents in Mesozoic–Cenozoic terrigenous sequences of the northern Caucasus

Numerous traces of paleoseismic events (seismites) were established in Mesozoic–Cenozoic marine sedimentary sequences of the northern Caucasus. These traces are most prominent in the terrigenous Middle Miocene sandy–clayey sediments. Impact of seismic shocks upon the relatively weakly lithified sediments provoked distortion of the primary sedimentary structure, liquefaction of the sandy material, and injections of different morphologies (neptunic dikes and sills). The formation of jointing in sediments fostered their vertical permeability and promoted the migration of diagenetic solutions into the adjacent horizons, which stimulated the formation of subvertical carbonate bodies. The amount and intensity of seismic events varied at different stages of the accumulation of sequences and in different areas of the paleobasin. In the eastern sector of the northern Caucasus, seismic activity similar to the present-day general pattern was likely developed as early as the Middle Miocene: maximum activity in the Dagestan and its westward attenuation. Traces of seismic activity are also recorded in the Maikopian (Oligocene–Lower Miocene) and Lower–Middle Jurassic rocks.

Kerr Black Hole Entropy and its Quantization

By constructing the four-dimensional phase space based on the observable physical quantity of Kerr black hole and gauge transformation, the Kerr black hole entropy in the phase space was obtained. Then considering the corresponding mechanical quantities as operators and making the operators quantized, entropy spectrum of Kerr black hole was obtained. Our results show that the Kerr black hole has the entropy spectrum with equal intervals, which is in agreement with the idea of Bekenstein. In the limit of large event horizon, the area of the adjacent event horizon of the black hole have equal intervals. The results are in consistent with the results based on the loop quantum gravity theory by Dreyer et al.

Accumulation of free oxyhydroxides in termite (Macrotermes bellicosus (Smeathman)) mounds and the implications for their dynamics in an African savannah Ultisol

ABSTRACTThe present study aimed to assess the dynamics of oxyhydroxides via termite mounds in a tropical savannah of Central Nigeria, where the soils often contain oxyhydroxides as a major component of soil minerals. To this end, the quantities of oxyhydroxides stored in mounds built by Macrotermes bellicosus (Smeathman) were compared to those stored in surface (Ap1) soils, and their turnover rates were estimated. Both the mound wall and nest of M. bellicosus were enriched two- to 10-fold with acidified ammonium oxalate soluble iron (Feo) and aluminum (Alo) and dithionite-citrate-bicarbonate (DCB) soluble iron (Fed) and aluminum (Ald) relative to the adjacent surface soil horizon. These oxyhydroxide contents were positively correlated with the clay content (P < 0.05), suggesting that M. bellicosus preferentially used silicate clay-associated oxyhydroxides for mound construction. The Fed, Ald and DCB-soluble manganese (Mnd) preserved in the M. bellicosus mounds ran up to 112 ± 25.6, 5.72 ± 1.41 and 2.17 ± 0.68 kg ha−1, accounting for 1.91 ± 0.23%, 1.00 ± 0.60% and 0.35 ± 0.09% of the total amount stored in the surface soil horizon, respectively. Furthermore, the estimated turnover rates of Fed, Ald and Mnd were 6.6, 0.33 and 0.14 kg ha−1 year−1, respectively. These findings suggest that the mound-building termites significantly impacted the dynamics of free oxyhydroxides in an African savannah soil.

Pacific 187Os/188Os isotope chemistry and U–Pb geochronology: Synchroneity of global Os isotope change across OAE 2

Studies of OAE 2 sections beyond the Atlantic Ocean, Western Interior Seaway (WIS) and European pelagic shelf are limited. Here, we present initial osmium isotope stratigraphy (187Os/188Os–Osi) from two proto-Pacific sites that span the Cenomanian–Turonian boundary interval (CTBI): the Yezo Group (YG) section, Hokkaido, Japan, and the Great Valley Sequence (GVS), California, USA; to evaluate the 187Os/188Os seawater chemistry of the proto-Pacific. Additionally we combine new 206Pb/238U zircon CA-ID-TIMS geochronology from five volcanic tuff horizons of the Yezo Group section to test and facilitate inter-basinal integration with the WIS using radio-isotopically constrained age–depth models for both sections, and quantitatively constrain the absolute timing and duration of events across the CTBI.The YG shows an almost identical Osi profile to that of the WIS, and very similar to that of other sites of the proto-Atlantic and European pelagic oceans (Turgeon and Creaser, 2008; Du Vivier et al., 2014). The characteristics of the Osi profile are radiogenic and heterogeneous (∼0.55–0.85) prior to the OAE 2, and synchronous with the inferred OAE 2 onset the Osi abruptly become unradiogenic and remain relatively homogeneous (∼0.20–0.30) before showing a gradual return to more radiogenic Osi(∼0.70) throughout the middle to late OAE 2. A206Pb/238U zircon age of an interbedded tuff (HK017) in the adjacent horizon to the first unradiogenic Osi value constrains the age of the Osi inflection at 94.44±0.14 Ma. This age, including uncertainty, agrees with the interpolated age of the same point in the Osi profile (94.28±0.25 Ma) in the only other dated OAE 2 section, the WIS; indicating a coeval shift in seawater chemistry associated with volcanism at the OAE 2 onset at the levels of temporal resolution (ca. 0.1 Myr). Further, prior to the onset of OAE 2 an enhanced radiogenic inflection in the Osi profile of the YG is correlative, within uncertainty, with a similar trend in the WIS based on the U–Pb age–depth model. The interpolated ages, 94.78±0.12 Ma and 94.66±0.25 Ma for this Osi inflection in the YG and WIS, respectively, indicate that palaeocirculation was sufficient to simultaneously influence transbasinal seawater chemistry. In contrast, the pre-OAE 2 Osi profile for the GVS is disparate to that of the YG and those of the proto-Atlantic and European pelagic shelf locations. We interpret the pre OAE 2 heterogeneous Osi values (0.30–0.95) to record a palaeobasin that was regionally influenced interchangeably by both unradiogenic (hydrothermal flux) and radiogenic (continental flux) Os.We conclude that the Osi profiles from the proto-Pacific sections record both trends that are consistent globally (OAE 2 onset, syn and post OAE 2), but also show regional differences (pre OAE 2) between OAE 2 sections worldwide. As such the Osi profiles coupled with U–Pb geochronology facilitate the correlation of OAE 2 stratigraphy, and demonstrate both regional and global ocean dynamics.

Phytolith aided paleoenvironmental studies fromthe Dutch Neolithic

AbstractThere is increasing evidence for crop cultivationat sites of the Neolithic Swifterbant culture fromca. 4300 B.C. onwards. Presence of cereal fields at theSwifterbant S2, S3 and S4 sites has been corroborated frommicro morphological studies of soil samples. Swifterbantsites with evidence for cultivated plants are still scarcethough and only emerging, and have produced very lownumbers of charred cereals only. The major aim of ourwork was to elucidate the environmental background ofthe Dutch Neolithic site Swifterbant S4 based on the investigationof phytolith remains retrieved from soil samples.In addition to find evidence for crop cultivation independentlyfrom other studies. Samples were taken at1 cm intervals vertically from the soil section at the centralprofile of site S4. Additional samples were taken frompocket-like structures and adjacent horizons above andbelow. Pig coprolites yielded an astonishing phytolith assemblagewhich was compared to that of the soil samples.A pig tooth also yielded evaluable material via detailed investigationusing SEM. The evaluation of phytolith assemblagesretrieved from the soil horizons plus those endingup in the droppings of pigs feasting in the area enabledto draw a relatively reliable environmental picture of thearea. All these refer to the presence of a Neolithic horticulture(cereal cultivation) under balanced micro-climaticconditions as a result of the vicinity of the nearby floodplain.These findings corroborate those of previous soilmicro-morphological studies.

Iceberg ploughmarks illuminated by shallow gas in the central North Sea

Conventional 3D seismic data provides direct evidence for glacial influence during the early Pleistocene sedimentation in the Central North Sea. We identify iceberg ploughmarks as dim linear to curve-linear features in three early Pleistocene horizons that have high reflection amplitude compared to adjacent horizons. The anomalous horizons are interpreted to be reflections from thin sandy layers saturated with gas. The gas acts as a contrast liquid illuminating the thin sand layers. The reason for this is the difference in acoustic properties between water and gas saturated sand layers. The combination of thin bed effects and shallow gas makes the iceberg ploughmarks easily detectable as dim features in seismic reflection amplitude maps. Our interpretation is based on analysis of real seismic data, well logs and modeled seismic response. The methods we use include interpretation of horizons followed by extraction of reflection amplitudes, well log analysis, pre-stack amplitude versus offset analysis of high resolution 2D seismic data and time-lapse analysis of seismic. Seismic modeling is performed to study interactions between thin sand beds, shallow gas and iceberg ploughmarks. A new trapping mechanism for shallow gas is presented and seismic modeling of this trap strengthens our interpretation. The trap is created by iceberg ploughmarks in sandy layers that are covered by finer and less permeable sediments. For this area we find that conventional seismic interpretation is superior to the much used method of studying seismic time-slices for detection of iceberg ploughmarks, both with respect to time and detectability. This study shows that the interpreter should look for high amplitude horizons with amplitude variations laterally when trying to detect iceberg ploughmarks.