Basal Sand Research Articles

An integrated dynamic modeling workflow for acid gas and CO2 geologic storage screening in saline aquifers with faults: A case study in Western Canada

This study investigates the feasibility of storing the acid gas produced from the oil and gas facilities in Southern Saskatchewan into the Basal Sand aquifer using a coupled wellbore-aquifer-compositional reservoir model. The simulations investigate the pressure change around the fault in proximity of the primary storage location incorporating the influence of reservoir permeability, fault transmissibility, and wellbore configuration, on the factors critical to safe and efficient storage, such as plume migration, pressure changes, and CO2 storage capacity. A compositional fluid model created using an equation of state was integrated into the reservoir model. Simultaneous incorporation of fault transmissibility, phase solubility, water salinity, temporal in-situ hysteresis and structural trapping, and in-situ compositional tracking of individual gas components is considered as the main novelty of this work. The main challenge of the study was the lack of available data to characterize the aquifer. To this end, a comprehensive workflow of reservoir studies and modeling was applied to reduce the uncertainties and evaluate the site selection. The Basal sand scoping models reveal that the aquifer is expected to handle the required disposal volume given its extent. The injected acid gas plume migrates laterally and preferentially towards the northwest, away from the fault, owing to the aquifer's geological structure. CO2 remains entirely in the supercritical state, offering storage advantages due to its lower volume. The reservoir permeability significantly impacts the pressure patterns with lower permeability formations triggering higher wellhead injection pressures. Substantial pressure increases around the sealing fault can be observed. Pressure changes of 110 kPa (16 psi) to over 400 kPa (58 psi) were observed at the fault segment after 20 years of continuous gas injection for the expected range of reservoir properties. Mitigation strategies to minimize the increase in fault pressure entail relocating the injection site away from the fault or utilizing a horizontal well trajectory and using an observation well near the fault for monitoring any pressure buildup and slippage.

Palynological, tephra, and 14C records from southern Kaitoke, Great Barrier (Aotea) Island, New Zealand, since c. 30,000 cal. yr BP

ABSTRACT Here we present results of the last remaining three, unreported pollen and stratigraphic profiles from our previous investigations on Great Barrier Island from southern Kaitoke. The 14C and pollen data extend the island’s previous maximum pollen-vegetation date from c. 7000 cal. yr BP to close to the end of MIS 3 c. 30,000 cal. yr BP. The oldest 14C date (34,380-28,190 cal. yr BP) and the presence of secondary deposition fragments of Rotoehu Tephra in the basal brown sands and nearby dune deposits implies their formation between c. 30,000 and 45,000 yr BP. The basal sand deposits and palynology in Profile 1 indicate that the site was close to sea-level at the time. Subsequently, the sediments reflect the Last Glacial Coldest Period, characterised by increased Fuscospora pollen. Following the relative stability of the mid-Holocene high sea-level stand, alternations between drier and wetter (freshwater) conditions, with depositional hiatuses, are congruent with evidence for erratic sea-level falls causing blockage of coastal drainage and rear-dune flooding since c. 2,700 cal. yr BP; layers of preserved wood and in-situ stumps overlying firmer palaeosols were followed by fresh-water peats at two of the sites reported here and other, previously reported sites. Polynesian settlement and forest clearance occurs around the time of the 1314 ± 12 AD Kaharoa Tephra, consistent with the project’s previous reports, and with the timing from elsewhere in New Zealand.

Earthquake-induced soft-sediment deformation in the Pleistocene succession, Noarlunga Embayment, South Australia

ABSTRACT A suite of soft-sediment deformation structures occurs within the basal sands and gravels in the non-marine Pleistocene succession in the Noarlunga Embayment of the Cenozoic St Vincent Basin south of Adelaide, South Australia, the significance of which has hitherto gone unrecognised. The inclusion of large, isolated blocks of well-bedded sands randomly encased within fluidised, structureless clayey sands indicates that the soft-sediment deformation was intense, occurring soon after deposition by liquefaction of a still saturated sediment. Seismic activity has been, and continues to be, a regular occurrence along the adjacent Adelaide fold belt. The intensity of the deformation is comparable to the thixotropic response to earthquake activity observed during the Christchurch (New Zealand) earthquakes of 2010 and 2011, the earthquakes and aftershocks near Quorn, South Australia, in January 1887, in the southeast of South Australia in May 1899, and west of Adelaide in April 1954. This, however, is the first record of an interpreted seismite in the St Vincent Basin, although its full extent is yet to be mapped.

Sedimentary evidence of the Late Holocene tsunami in the Shetland Islands (UK) at Loch Flugarth, northern Mainland

Tsunami deposits around the North Sea basin are needed to assess the long‐term hazard of tsunamis. Here, we present sedimentary evidence of the youngest tsunami on the Shetland Islands from Loch Flugarth, a coastal lake on northern Mainland. Three gravity cores show organic‐rich background sedimentation with many sub‐centimetre‐scale sand layers, reflecting recurring storm overwash and a sediment source limited to the active beach and uppermost subtidal zone. A basal 13‐cm‐thick sand layer, dated to 426–787 cal. a CE based on 14C, 137Cs and Bayesian age–depth modelling, was found in all cores. High‐resolution grain‐size analysis identified four normally graded or massive sublayers with inversely graded traction carpets at the base of two sublayers. A thin organic‐rich ‘mud’ drape and a ‘mud’ cap cover the two uppermost sublayers, which also contain small rip‐up clasts. Grain‐size distributions show a difference between the basal sand layer and the coarser and better sorted storm layers above. Multivariate statistical analysis of X‐ray fluorescence core scanning data also distinguishes both sand units: Zr, Fe and Ti dominate the thick basal sand, while the thin storm layers are high in K and Si. Enriched Zr and Ti in the basal sand layer, in combination with increased magnetic susceptibility, may be related to higher heavy mineral content reflecting an additional marine sediment source below the storm‐wave base that is activated by a tsunami. Based on reinterpretation of chronological data from two different published sites and the chronostratigraphy of the present study, the tsunami seems to date to c. 1400 cal. a BP. Although the source of the tsunami remains unclear, the lack of evidence for this event outside of the Shetland Islands suggests that it had a local source and was smaller than the older Storegga tsunami (8.15 cal. ka BP), which affected most of the North Sea basin.

LOW RESISTIVITY PAY DEVELOPMENT: CASE STUDY OF TALANGAKAR FORMATION ASRI BASIN, OFFSHORE SOUTHEAST SUMATRA, INDONESIA

Southeast Sumatra is a prolific oil and gas block located offshore in the Java Sea, 90 km north of Jakarta Bay. This area covers two major basins, namely Sunda Basin and Asri Basin. The initial development of the area focused on faulted and high closures and high-resistivity reservoirs. Further analysis shows that there are special low-resistivity reservoirs in Widuri Area, especially in the Aryani field. This paper will discuss the low resistivity pay zone reservoirs and fluid containment of the intervals. The paper will also include further assesment this undeveloped interval to increase oil production, considering the upside potential of the reservoirs using current geological, geophysical, and reservoir engineering approaches. Additionally, it will describe the operational challenges faced during the production period. The low-resistivity pay zone, a hydrocarbon-bearing reservoir in the Aryani field of the Widuri area, was identified using gas readings in the daily drilling reports, complemented with mud logging data. The Basal Sand interval, which drapes above the basement, was the site of the first producing well of Basal Sand, Aryani AC-X, preceded by a hydraulic fracturing job. Lambda-mu-rho inversion was implemented to delineate this reservoir. To recognize the potency in those wells, data reconfirmation was conducted between the elan summary, sidewall core, and cutting data. Aryani AC-X has successfully drained oil using a submersible pump, with an initial production of 408 bopd and cumulative production of 240 MBO.

Structural Styles and their Suitability for Hydrocarbon in Eastern Sindh Monocline, Lower Indus Basin, Pakistan

The present study is aimed to recognize the structural styles of hydrocarbon exploration and petrophysical properties of the LGF. The 2-D seismic and well log data set is composed of three seismic lines and well log data of Chak 66–1. Five horizons have been marked with the help of well to seismic tie namely tops of Ranikot, Parh, upper Goru, lower Goru, basal and top massive sands, and out of which basal and massive sands are the objective focus of the present study. Based on seismic data, the study area is characterized by normal faults showing NW–SE dipping trend. Horst and graben structural features are prominent on the seismic lines, which indicated the extensional tectonic regime. Time–depth contour maps and 3D surfaces of objective horizons depict their actual spatial distribution in this area. Wireline logging analysis revealed the physical properties of both basal and massive grains of sand, as 17% effective porosity, 25% average volume of shale (Vsh), 40% water and 60% hydrocarbon saturations for basal sands, Whereas, 16% effective porosity, 35% Vsh, 30% water and 70% hydrocarbon saturations are interpreted for massive sands. Cross–plots of Nphi–Dt and Dt–Rhob also identified that both areas of sand are clean, gas–saturated and have the potential to produce hydrocarbons.

Delineating the fluvial sedimentary reservoirs of Cretaceous sedimentation using seismic attributes and seismic‐petrophysical simulations, Southwest Pakistan

Channels filled with coarse‐grained sands are one of the hot issues in stratigraphic explorations. However, the sub‐surface uncertainty restricts the prediction of porous channel sandstones using the conventional seismic attributes, which is a concern for the demarcation of stratigraphic plays. The amplitude‐based frequency attributes and seismic‐petrophysical simulation tools were applied to characterize the fluvial channel system from the Indus Basin, Pakistan. The conventional amplitude of the Basal Sand Formation shows limited imaging ability to detect the dimensions of channel‐levee and point bars. The continuous wavelet transforms (CWT) tool distinguishes the whole channel‐levee reservoir system at tuning frequencies of 21, 25, 29, and 34 Hz. The amplitudes extracted along the pseudo‐porosity wells depict the low‐density and low‐velocity profiles within the gas‐bearing zones. The zone between 20% and 30% porosity displays low‐density and low‐velocity compartments within the point bars. Hence, it implicates the zone of deposition for hydrocarbon‐bearing fluvial facies. Based on the porosity constraint, the gas‐bearing fluvial reservoirs have high (>25%) porosity, which implicates the development of aggradational parasequences. The oil‐dominated sandstone facies experience relatively low‐porosity of <12% and negligibly high density and high velocity, which implicates the development of transgressive parasequences. The reservoir system shows an eastward shale‐out zone, where the high‐density and high‐velocity shales mask the channel‐levee systems. Consequently, these stratigraphic configurations are developing into a cost‐effective stratigraphic trap, and hence, this exploration scheme serves as an analogue for global fluvial depositional systems.

Formation Evaluation of Lower Goru Sands of Khipro Block, Lower Indus Basin, Pakistan

Formation evaluation is widely used in exploration and production in order to minimize the risk, uncertainty, and understanding of the detailed characteristics of potential reservoir rocks. This study is aimed to evaluate the Petrophysical characteristics of upper and lower basal sands of the Cretaceous lower Goru Formation in Niamat-01 and Siraj-01 wells and to focus on hydrocarbon exploration potential. These wells have been drilled in the Khipro block, lower Indus basin, which is the least explored for the reservoir quality evaluation. Present study characterized the lower Goru sands of the Khipro block. It is interpreted that the thickness of upper and lower Basal sands are 13m and 10m, respectively in Naimat Basal 01, whereas 9m and 17m, respectively, are reported in SirajSouth-01. The average effective porosity is 11% in upper Basal sands while 26% is interpreted for lower Basal sand in Naimat Basal-01. An average porosity of 11% is found for upper Basal sands in Siraj South-01 and 11% for lower Basal sand. Water saturation (Sw) calculated for upper and lower Basal sands are 22% and 19%, respectively. The hydrocarbon saturation (Sh) of 78% is interpreted for upper Basal sands and 81% hydrocarbon saturation reported for lower Basal sands in Naimat basal-01. However, 36% and 45% Sw have been recognized for upper and lower Basal sands, respectively. Whereas hydrocarbon saturations of 64% and 55% are reported for the upper and lower basal sands, respectively, in SirajSouth-01. Crossover effects in front of targeted formations confirmed the presence of hydrocarbons in the zone of interest. Lower sands of the lower Goru Formation in the Khipro block are favorable for hydrocarbon production and have potential for future hydrocarbon exploration activities.

Study of the local raw materials for usingin the production of the foam concrete materials

The article discusses the importance of affordable, high-quality, easily accessible thermal insulation materials for the construction industry, based on the new technologies. It is believed that clay and silicon rocks, which are found in all regions of the Republic of Kazakhstan, can be used as the raw materials for a modified composition, and create favorable conditions for the development of the construction industry. The raw material for the research has been the sand of the “Belaya Gorka” depositof the West Kazakhstan region. The chemical composition of the raw material has been studied by the physicochemical methods of XRD and SEM. The X-ray phase analysis of the foam concrete without impurities consists of the following phases: tricalcium silicate (alite - C3S) - d/n = 1.5; 2.50; 2.67; 2.83 Å; slaked lime (Ca (OH) 2) - d/n = 1.91; 2.62; 4.90,9; Clinker content (%): C3S - 40-68, - d/n = 1.83; 2.40; 2.80; 3.07 Å. According to the mechanism of the foam concrete sintering, in the solution, quartz forms H3SiO4- and H2ЅiO42- ions, the interaction of which with the Ca2 + ions leads to the formation of calcium hydrolyzate, rich in lime on the surface of quartz. As a result, the crystals of successive calcium hydrosilicates are formed in the crystallization medium, and their volume increases. The formation of the CSH (I) phase is influenced by the formation of calcium oxide and the fine grinding of the sand. The formation of the C3S (III) phase of the binder mainly determines its strength. According to the results of the laboratory studies, it has been experimentally proven that the heat-insulating materials with pores of various sizes are formed on the basis of sand.

Structural Styles and their Suitability for Hydrocarbon in Eastern Sindh Monocline, Lower Indus Basin, Pakistan

The present study is aimed to recognize the structural styles of hydrocarbon exploration and petrophysical properties of the LGF. The 2-D seismic and well log data set is composed of three seismic lines and well log data of Chak 66–1. Five horizons have been marked with the help of well to seismic tie namely tops of Ranikot, Parh, upper Goru, lower Goru, basal and top massive sands, and out of which basal and massive sands are the objective focus of the present study. Based on seismic data, the study area is characterized by normal faults showing NW–SE dipping trend. Horst and graben structural features are prominent on the seismic lines, which indicated the extensional tectonic regime. Time–depth contour maps and 3D surfaces of objective horizons depict their actual spatial distribution in this area. Wireline logging analysis revealed the physical properties of both basal and massive grains of sand, as 17% effective porosity, 25% average volume of shale (Vsh), 40% water and 60% hydrocarbon saturations for basal sands, Whereas, 16% effective porosity, 35% Vsh, 30% water and 70% hydrocarbon saturations are interpreted for massive sands. Cross–plots of Nphi–Dt and Dt–Rhob also identified that both areas of sand are clean, gas–saturated and have the potential to produce hydrocarbons.

Sole marks reveal deep-marine depositional process and environment: Implications for flow transformation and hybrid-event-bed models

ABSTRACTDeposits of sediment gravity flows in the Aberystwyth Grits Group (Silurian, west Wales, United Kingdom) display evidence that sole marks are suitable for reconstructing depositional processes and environments in deep-marine sedimentary successions. Based on drone imagery, 3D laser scanning, high-resolution sedimentary logging, and detailed descriptions of sole marks, an outcrop 1600 m long between the villages of Aberarth and Llannon was subdivided into seven lithological units, representing: a) mudstone-poor, coarse-grained and thick-bedded submarine channel fills, dominated by the deposits of erosive high-density turbidity currents with flute marks; b) mudstone-rich levee deposits with thin-bedded, fine-grained sandstones formed by low-density turbidity currents that scoured the bed to form flute marks; c) channel–lobe transition-zone deposits, dominated by thick beds, formed by weakly erosive, coarse-grained hybrid events, with pronounced mudstone-rich or sandstone-dominated debritic divisions and groove marks below basal turbiditic divisions, and with subordinate amounts of turbidites and debris-flow deposits; d) tabular, medium- to thick-bedded turbiditic sandstones with flute marks and mixed sandstone–mudstone hybrid event beds mainly with groove marks, interpreted as submarine lobe-axis (or off-axis) deposits; and e) tabular, thin- to medium-bedded, fine-grained, mainly turbiditic sandstones mostly with flute marks, formed in a lobe-fringe environment. Both lobe environments also comprised turbidites with low-amplitude bed waves and large ripples, which are interpreted to represent transient-turbulent flows. The strong relationship between flute marks and turbidites agrees with earlier predictions that turbulent shear flows are essential for the formation of flute marks. Moreover, the observation as part of this study that debris-flow deposits are exclusively associated with groove marks signifies that clay-charged, laminar flows are carriers for tools that are in continuous contact with the bed. A new process model for hybrid event beds, informed by the dominance of tool marks, in particular grooves, below the basal sand division (H1 division of Haughton et al. 2009) and by the rapid change from turbidites in the channel to hybrid event beds in the channel–lobe transition zone, is proposed. This model incorporates profound erosion of clay in the channel by the head of a high-density turbidity current and subsequent transformation of the head into a debris flow following rapid lateral flow expansion at the mouth of the channel. This debris flow forms the groove marks below the H1 division in hybrid event beds. A temporal increase in cohesivity in the body of the hybrid event is used to explain the generation of the H1, H2, and H3 divisions (sensuHaughton et al. 2009) on top of the groove surfaces, involving a combination of longitudinal segregation of bedload and vertical segregation of suspension load. This study thus demonstrates that sole marks can be an integral part of sedimentological studies at different scales, well beyond their traditional use as indicators of paleoflow direction or orientation.

Effect of reservoir heterogeneities on elastic and seismic properties of Lower Cretaceous Sand Intervals, Lower Indus Basin of Pakistan

The use of rock physics modeling and petrophysical analysis has become an integral part of quantitative seismic interpretation. In the present study, the above-mentioned techniques are applied to the reservoir interval of Basal Sand of Cretaceous age widely distributed in the Lower Indus Basin of Pakistan. The data used for this purpose consists of complete suits of wireline logs from four well A, B, C and D. The primary goal of this work is to understand the trends of seismic parameters such as P-wave velocity (VP), S-wave velocity (VS), bulk modulus, bulk density as a function of fluid saturation and porosity in this sand interval. Petrophysical analysis based on well logs is used to obtain petrophysical properties such as porosity, the volume of shale, fluid saturation, P-wave velocity (VP), S-wave velocity (VS) and density at reservoir conditions. The results show that seismic parameters are very sensitive to fluid saturation, fluid types and rock-forming sediments. Reservoir porosity and fluid saturation control the elastic response of Basal Sand due to which seismic velocities decrease with an increase in porosity and fluid saturation.

Architecture, sedimentary facies and chronology of a composite island: A model from the Upper Paraná River, Brazil

Composite islands that originate from central bars are one of the most frequent types of islands in the Paraná River and in many large rivers in the world. The aim of this study is to highlight island-forming processes and the evolution of an island on a large anabranching tropical river over a period of 101–104 yr. Mutum Island in the Upper Paraná River, Brazil (mean discharge = 9000 m3 s−1), was chosen because of its large size (>15 km in length) and by the formative processes that have been active over the last 8 ka. Our analysis used a 60-yr series of satellite images and aerial photos, and 16 absolute dates (14C and OSL) from 11 vibro-cores and outcrops. Mutum Island was formed by the stabilization, vertical aggradation, and vegetal development of a central bar. Island expansion occurred through the addition of lateral and frontal bars. Island deposits exhibit three main lithosomes: coarse to fine basal sand deposits more than 3 m below the island surface related to channel processes; middle sandy mud layers 2–4 m thick formed by annexation processes; and upper massive mud formed by flood flow deceleration over the island. The age of deposits decreased from the center (8200 BP) to the banks (present day) of the island. The predominantly lateral expansion of island deposits resulted in a different depositional architecture to that described for other anabranching rivers. This study demonstrates that the formation and evolution of Mutum Island has been relatively stable since the beginning of the Holocene. The model presented for the Mutum Island represents a useful contribution on the understanding of large anabranching river systems.

Understanding Wetlands Stratigraphy: Geophysics and Soil Parameters for Investigating Ancient Basin Development at Lake Duvensee

We present a case study of a bog showing how an integrated approach of multi-method geophysical sounding and local soil sampling can be used to identify, differentiate, and map organic sediments. Our study is based on ground-penetrating radar (GPR), electrical resistivity tomography (ERT) and shear-wave seismic (SH seismic) profiling applied to sediments of the former Lake Duvensee (northern Germany), nowadays a bog. This is a well-known locality for remains from the Mesolithic hunter-gatherers’ occupation that has been attracting archaeological and geoarchaeological research for100 years. The bog is embedded in low conductive glacial sand and is characterized by layers of different gyttja sediments (detritus and calcareous). The present study was conducted in order to identify the bog morphology and the thickness of the peat body and lake sediments, in order to understand the basin evolution. To validate the geophysical results, derived from surface measurements, drilling, soil analyses as well as borehole guided wave analysis of electromagnetic waves and Direct-Push (DP-EC) have been carried out and used for comparison. It turned out that each method can distinguish between sediments that differ in grain size, particularly between peat, lake sediments (gyttjas and mud) and basal glacial sand deposits. GPR is even able to separate between strongly and weakly decomposed peat layers, which is also clear considering resistivity variations in the ERT computation. From the association between geophysical properties and sediment analysis (e.g., water content and organic matter) different gyttjas were distinguished (coarse and fine) and seismic velocity was correlated to bulk density. Moreover, GPR and SH-wave seismics present different resolutions, confirming that the latter allows measurements, which are more focused on determining the extension of basal sand deposits, the depth of which is difficult to reach with GPR. Representative values of electrical resistivity, dielectric permittivity, and shear wave velocity have been determined for each sediment type and are therefore available to complete the investigation of wetland environments. Fine grained lake sediments were difficult to differentiate by the applied methods. This could be a result of high ionic concentration within the permanent groundwater body, partly masking the sediment properties.

Carbonate laminae recorded in a siliciclastic tidal flat colonized by microbial mats

Microbial mats in siliciclastic coastal environments are considered as non-lithifying systems that lack the potential for calcification. This work documents precipitation and preservation of well-defined, laterally continuous carbonate laminae in low-relief microbial mats from a siliciclastic supratidal flat in northern Patagonia (Paso Seco, Argentina). Petrographic, epifluorescence, and SEM-EDS studies of surficial and buried microbial mats show that they are composed of repeated sediment sequences comprised of four different types of laminae, which are, from base to top: (A) a sand and silt lamina, (B) a lamina largely composed of organic matter displaying moulds of subvertical cyanobacteria filaments, (C) a lamina composed of dense micritic carbonate, which is cut by moulds of vertical cyanobacteria filaments, and (D) a lamina composed of organic matter containing abundant horizontal cyanobacteria filaments. The formation of each different lamina is strongly controlled by the environmental conditions, characterized by episodic seawater flooding, followed by several days to weeks in which water remains covering the sediment and gradually evaporates producing a salinity increase and the precipitation of calcite, gypsum and halite. Thus, the basal sand and silt lamina forms as the result of the transport of siliciclastic grains and particles during seawater flooding. The overlying lamina B, composed of organic matter with moulds of subvertical cyanobacteria filaments, is formed when calm water conditions are recovered and organic material is produced by photosynthetic microbial activity. The following lamina C, composed of dense micritic carbonate, precipitates when the salinity of stagnant water reaches CaCO3 supersaturation. Finally, the uppermost lamina D, composed of organic matter with horizontal cyanobacteria filaments, is developed while the sediment surface is drying and gypsum and halite precipitate, although these minerals are not preserved in the sediment because they dissolve during subsequent inundations. All these observations show that well-developed, laterally-continuous carbonate laminae may be formed and preserved in a siliciclastic tidal environment if biotic and abiotic sedimentary processes closely interact to create the required conditions. The studied microbial mats increase sediment impermeability, which favours water retention in the flat and, thus, subsequent evaporation of the retained seawater. Moreover, microbial cells and EPS (extracellular polymeric substance) suspended in seawater might act as nuclei for CaCO3 precipitation, which will later settle down on the microbial mat. In addition, EPS of the microbial mats may also serve as nucleus for in situ carbonate precipitation.

STRUCTURES BIOGENIQUES ET PHYSIQUES DANS LES SABLES DE PAVIGLIANA REGGIO CALABRIA (ITALIE)

The most representative biogenic sedimentar y structures in the basal sand of the Plio— Pleistocene sequence belonging to the Pavigliana (Reggio Calabria) tectono sedimentary unit, have been analyzed. The bioturbation structures are attributed to domichnia / fodinichnia of decapod crustaceans; the bioerosion structures are mostly represented by domichnia of numerous boring organisms. The entire assemblage forms an high diversity ichnocoenosis indicative of the infralittoral zone. The lithologic features, the body fossils, and the trace fossils allow to recognize a succession of paleocommunities likely related to changes in edaphic factors. The enigmatic invaginated structures found in the upper part of the examined beds, can be possibly interpreted as thixotropic figures indicating palaeoseismicity

Reconstructing the palaeoenvironment at the early Mesolithic site of Lake Duvensee: Ground-penetrating radar and geoarchaeology for 3D facies mapping

We investigate the landscape development of the early Mesolithic hunter-gatherer sites of Duvensee (10000–6500 cal. BCE). Based on ground-penetrating radar (GPR) and geoarchaeological drillings, we present for the first time a three-dimensional (3D) reconstruction of the palaeoenvironment of 63 ha covering subarea of the former lake during the Mesolithic. The archaeological aims were (1) to detect the location of former islands possibly hosting hunter-gatherer settlements and (2) to reconstruct the ancient landscape development for understanding prehistoric land use. The research in Duvensee lasts almost 100 years, providing vivid illustrations of early Mesolithic life. Clusters of Mesolithic camps have been found located on small sand hills that formed islands in the prehistoric lake. For this environment, we present depth maps of the three most important sedimentary facies interfaces of the ancient Lake Duvensee. Interface1 represents the transition between coarse organic sediments (peat and coarse detritus gyttja) and fine-grained organic sediments (fine detritus gyttja, calcareous gyttja), Interface2 represents the transition to the underlying clayish-loamy sediments, and Interface3 marks the top of the basal sand deposits at the lake bottom. From Interface3, we identified the location and extent of five former islands with Mesolithic camps. Stratigraphic information from the corings enabled us to create a 3D model of the spatio-temporal development of the Duvensee bog. The locations of the islands and their estimated dive-up times agree with the spatio-temporal pattern of the previous archaeological finds. The model shows where hunter-gatherers could settle and move from one island to another following the shorelines of the overgrowing lake. The 3D stratigraphic model provides growth and shrinking rates of the island and lake areas in the Mesolithic, and volumes of organic and non-organic deposited lake sediments. Besides, it provides a basis for a sustainable groundwater management needed for heritage preservation.

HUBUNGAN KANDUNGAN NITRAT TERHADAP PERTUMBUHAN LAMUN (Enhalus acoroides) DI PESISIR PANTAI NEGERI SULI KECAMATAN SALAHUTU KABUPATEN MALUKU TENGAH

Background: Seagrass (Enhalus acoroides) is a type of seagrass that has the largest size, leaf strands can reach sizes> 1m. This type grows in shallow waters to a depth of 4 meters, on the basis of sand, mud sand or mud. The purpose of this study was to determine the relationship of nitrate content to the growth of seagrass (Enhalus acoroides) on the coast of Suli Village Salahutu District, Central Maluku Regency.
 Method: The type of research used in this study was descriptive to determine the relationship of nitrate content to growth of seagrass Enhalus acoroides on the coast of Suli State Salahutu District, Central Maluku Regency. The study was conducted on February 1-15, 2018.
 Results: This study showed that each transect had different growths of seagrass length, namely on transect 1, seagrass growth, reaching an average of 1.05, transect 2 averaging 1.01, while on transect 3 seagrass growth reached 1 average. , 35. Transect 3 has a greater growth rate than transect 1 and transect 2 while transect 2 has a lower growth rate than transect 1 and transect 3, while the results of the measurement of the average nitrate level on all transects are the same namely at transect 1 of 0.020 mg / l, transect 2 is 0.010 mg / l and transect 3 is 0.210 mg / l.
 Conclusion: Oligtrofic waters have nitrate levels between 0-5 mg / l, mesotrophic waters have nitrate levels between 1-5 mg / l, and eutrophic waters have nitrate levels ranging from 5-50 mg / l.

Porosity and carbon dioxide storage capacity of the Maryville–Basal sands section (middle Cambrian), Southern Appalachian Basin, Kentucky

The middle Cambrian Maryville–Basal sands in the interval of 4600–4720 ft (1402.1–1438.7 m) in the Kentucky Geological Survey 1 Hanson Aggregates well (i.e., muddy sandstones separated by sandy mudstones) were evaluated to determine effective porosity (φe), clay volume (Vc), and supercritical CO2 storage capacity. Average porosity and permeability measured in core plugs were 8.71% porosity and 2.17 md permeability in the Maryville sand and 10.61% porosity and 15.79 md permeability in the Basal sand. The φe and Vc were calculated from the density log using a multiple-matrix shaly sand model to identify four formation lithologies: muddy sandstone, sandy mudstone, dolomitic mudstone, and dolomitic claystone. Average φe and Vc calculated in the Maryville sand were 8.9% and 35.3%, respectively, and an average of 8.7% and 41.2% in the Basal sand, respectively. Calculated φe exhibits a good match with porosity measured in core plugs. Prior to step-rate testing, static reservoir pressure was 2020 psi (13.9 MPa), representing a 0.435 psi/ft (9.8 kPa/m) hydrostatic gradient, which is consistent with other underpressured reservoirs in Kentucky. The interval fractured at 2698 psi (18.0 MPa), yielding a fracture gradient of 0.581 psi/ft (12.7 kPa/m). Pressure falloff analysis suggests a dual-porosity/dual-permeability reservoir consistent with core data. Estimated 50th percentile supercritical CO2 storage volume supercritical CO2 storage volume, using 7% porosity cutoff for determining net reservoir volume, is 0.538 tons/ac (1.33 t/ha). Thin reservoir sands, low porosity and permeability, and low fracture gradient, however, preclude the Maryville–Basal sands as large-volume deep-saline CO2 storage reservoirs in this area.

Application of the pore water stable isotope method and hydrogeological approaches to characterise a wetland system

Abstract. Three naturally intact wetland systems (swamps) were characterised based on sediment cores, analysis of surface water, swamp groundwater, regional groundwater and pore water stable isotopes. These swamps are classified as temperate highland peat swamps on sandstone (THPSS) and in Australia they are listed as threatened endangered ecological communities under state and federal legislation. This study applies the stable isotope direct vapour equilibration method in a wetland, aiming at quantification of the contributions of evaporation, rainfall and groundwater to swamp water balance. This technique potentially enables understanding of the depth of evaporative losses and the relative importance of groundwater flow within the swamp environment without the need for intrusive piezometer installation at multiple locations and depths. Additional advantages of the stable isotope direct vapour equilibration technique include detailed spatial and vertical depth profiles of δ18O and δ2H, with good accuracy comparable to other physical and chemical extraction methods. Depletion of δ18O and δ2H in pore water with increasing depth (to around 40–60 cm depth) was observed in two swamps but remained uniform with depth in the third swamp. Within the upper surficial zone, the measurements respond to seasonal trends and are subject to evaporation in the capillary zone. Below this depth the pore water δ18O and δ2H signature approaches that of regional groundwater, indicating lateral groundwater contribution. Significant differences were found in stable pore water isotope samples collected after the dry weather period compared to wet periods where recharge of depleted rainfall (with low δ18O and δ2H values) was apparent. The organic-rich soil in the upper 40 to 60 cm retains significant saturation following precipitation events and maintains moisture necessary for ecosystem functioning. An important finding for wetland and ecosystem response to changing swamp groundwater conditions (and potential ground movement) is that basal sands are observed to underlay these swamps, allowing relatively rapid drainage at the base of the swamp and lateral groundwater contribution. Based on the novel stable isotope direct vapour equilibration analysis of swamp sediment, our study identified the following important processes: rapid infiltration of rainfall to the water table with longer retention of moisture in the upper 40–60 cm and lateral groundwater flow contribution at the base. This study also found that evaporation estimated using the stable isotope direct vapour equilibration method is more realistic compared to reference evapotranspiration (ET). Importantly, if swamp discharge data were available in combination with pore water isotope profiles, an appropriate transpiration rate could be determined for these swamps. Based on the results, the groundwater contribution to the swamp is a significant and perhaps dominant component of the water balance. Our methods could complement other monitoring studies and numerical water balance models to improve prediction of the hydrological response of the swamp to changes in water conditions due to natural or anthropogenic influences.