Journal articles on the topic 'Geological depositional environments'
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Friday, Uhuo, Kenneth, Okoro, Anthony U., Igwe Ezekiel O., and Ukandu James S. "ANALYSIS OF DEPOSITIONAL ENVIRONMENTS OF UK FIELD RESERVOIR SANDS IN NIGER DELTA BASIN, NIGERIA." American Journal of Applied sciences 04, no. 12 (December 30, 2022): 05–32. http://dx.doi.org/10.37547/tajas/volume04issue12-02.
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The environments of deposition play a vital role during hydrocarbon formation, migration, trapping and storage. Since the reservoir rocks are a function of their depositional environments, the successful tapping of hydrocarbon from its host rock when wells are drilled depends largely on the petrophysical characteristics of the reservoir rocks which in turn originated from and are influenced by their depositional environment. The reservoir facies in Niger Delta shows a broad range of characteristic sedimentological complexities that gave rise to subsurface geological, drilling and production problems occurring in UK Field. The problems include inaccurate determination of environments of deposition, imperfect stratigraphic correlations and reservoir top uncertainty across the UK Field which are targeted by this research in other to help resolve these challenges facing oil and gas industries in the Niger Delta basin of Nigeria. The research findings will assist in the evaluation of depositional environments and well-to-well lithologic correlation within the UK Field and Niger Delta Basin at large. It will also help to unravel major causes of reservoir top uncertainty in UK Field. Also, it will help in future planning and drilling of new wells within UK Field. The determination of the depositional environments of UK Field reservoir sands were carried out to determine the depositional environment of reservoir sand bodies based on data from seven (7) wells. The determination of depositional environments of sand facies penetrated by wells UK1, UK2, UK3, UK4, UK5, UK6 and UK8 was achieved through a side-by-side comparison of their log suites to standard log motifs. Results of facies analysis showed that the reservoir sands belong to mostly (i) fluvial channel, (ii) barrier bar, (iii) lower-middle shoreface, (iv) distributary mouth bar, (v) distributary channel, (vi) point bar and (vii) tidal channel environments that belonged to parts of a deltaic system. Lithologic correlation result reveals the existence of good correlation among all wells in UK Field due to good geological similarities except well UK8 that failed to correlate perfectly with others thereby establishing the existence of reservoir top uncertainty within UK Field. Therefore, reservoir top uncertainty within UK Field is geologically controlled.
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MacCormack, Kelsey, Emmanuelle Arnaud, and Beth L. Parker. "Using a multiple variogram approach to improve the accuracy of subsurface geological models." Canadian Journal of Earth Sciences 55, no. 7 (July 2018): 786–801. http://dx.doi.org/10.1139/cjes-2016-0112.
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Subsurface geological models are often used to visualize and analyze the nature, geometry, and variability of geologic and hydrogeologic units in the context of groundwater resource studies. The development of three-dimensional (3D) subsurface geological models covering increasingly larger model domains has steadily increased in recent years, in step with the rapid development of computing technology and software, and the increasing need to understand and manage groundwater resources at the regional scale. The models are then used by decision makers to guide activities and policies related to source water protection, well field development, and industrial or agricultural water use. It is important to ensure that the modelling techniques and procedures are able to accurately delineate and characterize the heterogeneity of the various geological environments included within the regional model domain. The purpose of this study is to examine if 3D stratigraphic models covering complex Quaternary deposits can be improved by splitting the regional model into multiple submodels based on the degree of variability observed between surrounding data points and informed by expert geological knowledge of the geological–depositional framework. This is demonstrated using subsurface data from the Paris Moraine area near Guelph in southern Ontario. The variogram models produced for each submodel region were able to better characterize the data variability, resulting in a more geologically realistic interpolation of the entire model domain as demonstrated by the comparison of the model output with preexisting maps of surficial geology and bedrock topography as well as depositional models for these complex glacial environments. Importantly, comparison between model outputs reveals significant differences in the resulting subsurface stratigraphy, complexity, and variability, which would in turn impact groundwater flow model predictions.
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Aiello, Gemma, and Mauro Caccavale. "The Depositional Environments in the Cilento Offshore (Southern Tyrrhenian Sea, Italy) Based on Marine Geological Data." Journal of Marine Science and Engineering 9, no. 10 (October 4, 2021): 1083. http://dx.doi.org/10.3390/jmse9101083.
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The depositional environments offshore of the Cilento Promontory have been reconstructed based on the geological studies performed in the frame of the marine geological mapping of the geological sheet n. 502 “Agropoli”. The littoral environment (toe-of-coastal cliff deposits and submerged beach deposits), the inner continental shelf environment (inner shelf deposits and bioclastic deposits), the outer continental shelf environment (outer shelf deposits and bioclastic deposits), the lowstand system tract and the Pleistocene relict marine units have been singled out. The littoral, inner shelf and outer shelf environments have been interpreted as the highstand system tract of the Late Quaternary depositional sequence. This sequence overlies the Cenozoic substratum (ssi unit), composed of Cenozoic siliciclastic rocks, genetically related with the Cilento Flysch. On the inner shelf four main seismo-stratigraphic units, overlying the undifferentiated acoustic basement have been recognized based on the geological interpretation of seismic profiles. On the outer shelf, palimpsest deposits of emerged to submerged beach and forming elongated dunes have been recognized on sub-bottom profiles and calibrated with gravity core data collected in previous papers. The sedimentological analysis of sea bottom samples has shown the occurrence of several grain sizes occurring in this portion of the Cilento offshore.
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Sestini, G. "Nile Delta: a review of depositional environments and geological history." Geological Society, London, Special Publications 41, no. 1 (1989): 99–127. http://dx.doi.org/10.1144/gsl.sp.1989.041.01.09.
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Cahyaningsih, Catur, Anjas Latif Ritonga, Shaury Aldila, and Zulhikmah Zulhikmah. "Lithofacies And Depositional Analysis Environment Of West Section Kolok Nan Tuo Village, Sawahlunto City, West Of Sumatera." Journal of Geoscience, Engineering, Environment, and Technology 3, no. 2 (June 1, 2018): 128. http://dx.doi.org/10.24273/jgeet.2018.3.2.340.
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Research areas were located in the west of Kolok Nan Tuo Village. Geographically this area is located at coordinates 00 ° 36'57,85 '' - 00 ° 37'56,89 '' latitude and 100 ° 42'10,08 '' 100 ° 43'47,28 " BT. The methods used in research is geological mapping. Based on the results of stratigraphic research area is divided into three units consist of: Crystalline Limestone Unit (SBGK) consisting Crystalline Limestone of and mudstone lithofacies, Conglomerate Units (SK) consists of polymic conglomerate and sandstones greywacke lithofacies while claystone Unit (SBL) lithofacies consists of claystone with sedimentary structures is flake. Result of research can interpreted Depositional environment based on type of lithofacies include of grain size, sedimentary structures and content of fossils. SBGK interpretated depositional environment is a basement of basin, SK depositional environment debris unit limestones can be seen from fragments of conglomerates that many there are crystalline limestones and mudstone that make up the alluvial fan (deposition surface) and lithologies clay from sedimentary structures where rock mudstone generally in doposition the current flow that quiet can form sedimentary structures flake and properties of claystone which carbonated an identifier depositional environments sea so can be determined that the environment in the form of neritic environment.
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Frolova, E. V. "LOWER MIOCENE RESERVOIRS STRUCTURE AND DEPOSITIONAL ENVIRONMENTS OF THE CENTRAL PART OF DRAGON OILFIELD (VIETNAM)." Oil and Gas Studies, no. 3 (June 30, 2015): 40–45. http://dx.doi.org/10.31660/0445-0108-2015-3-40-45.
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The paper presents the results of the study of the structure and depositional environments formation in the lower Miocene reservoirs in the Central area of Dragon field (Cuu Long basin, Vietnam offshore) based on litho-facial, electro-facial, seismic-facial analyses, and biostratigraphy data and the deposits thickness analysis. The geological model refining had been done through the core analysis, seismic interpretation, wireline logs integration and via defi-nition of the depositional environments. The results received permit to predict the depositional environments distribu-tion in the areas that were not identified by drilling, to make more exact the area oil reserves evaluation, to enhance the oil recovery.
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Tabuni, Yorana, Hermina Haluk, and Nur Alzair. "KARAKTERISTIK BATUGAMPING FORMASI MARUNI DAERAH WARMARE DAN SEKITARNYA KABUPATEN MANOKWARI PROVINSI PAPUA BARAT." INTAN Jurnal Penelitian Tambang 4, no. 2 (April 1, 2022): 87–92. http://dx.doi.org/10.56139/intan.v4i2.88.
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This study aims to determine the characteristics of the Maruni Formation limestones in the Warmare area and its surroundings in Manokwari Regency by using geological mapping, and petrographic and paleontological analysis. Based on physical, petrographic and paleontological characteristics, the limestone facies in the study area consist of packstone, wackestone, mudstone and crystalline. Limestone diagenetic processes that occur in the study area are cementation diagenesis and neomorphism. Limestone depositional environment consists of two depositional environments. First, the depositional environment is in a shallow ocean shelf with limited circulation (SMF10: bioclastic packstone/wackestone with worm skeletal grains and SMF18: Grainstone or packstone with abundant foraminifera or algae; FZ7-FZ8; Platform Interior – Openmarine, Restricted). After that, sea level conditions decreased, so that the depositional environment shifted towards the sea (SMF2: Micobioclastic peloidal calcisiltite and SMF3: Pelagic mudstone/wackstone – FZ3: Toe of Slope). However, in the complex classification of facies, the research area is included in the lagoon depositional environment.
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Li, Jun, Xiaoying Zhang, Bin Lu, Raheel Ahmed, and Qian Zhang. "Static Geological Modelling with Knowledge Driven Methodology." Energies 12, no. 19 (October 8, 2019): 3802. http://dx.doi.org/10.3390/en12193802.
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Geological modelling is an important topic of oil and gas exploration and production. A new knowledge driven methodology of geological modelling is proposed to address the problem of “hard data” limitation and modelling efficiency of the conventional data driven methodology. Accordingly, a new geological modelling software (DMatlas) (V1.0, Dimue, Wuhan, China) has been developed adopting a grid-free, object-based methodology. Conceptual facies models can be created for various depositional environments (such as fluvial, delta and carbonates). The models can be built largely based on geologists’ understandings with “soft data” such as outcrops analysis and geological maps from public literatures. Basic structures (fault, folds, and discrete fracture network) can be easily constructed according to their main features. In this methodology, models can be shared and re-used by other modelers or projects. Large number of model templates help to improve the modelling work efficiency. To demonstrate the tool, two case studies of geological modelling with knowledge driven methodology are introduced: (1) Suizhong 36-1 field which is a delta depositional environment in Bohai basin, China; (2) a site of the north Oman fracture system. The case studies show the efficiency and reliability within the new methodology.
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Song, Jian, Zhidong Bao, Xingmin Zhao, Yinshan Gao, Xinmin Song, Yanzhen Zhu, Jian Deng, et al. "Sedimentology and geochemistry of Middle–Upper Permian in northwestern Turpan–Hami Basin, China: Implication for depositional environments and petroleum geology." Energy Exploration & Exploitation 36, no. 4 (May 29, 2018): 910–41. http://dx.doi.org/10.1177/0144598718779100.
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Studies have found that the Permian is another important stratum for petroleum exploration except the Jurassic coal measures within Turpan–Hami Basin recently. However, the knowledge of the depositional environments and its petroleum geological significances during the Middle–Late Permian is still limited. Based on the analysis about the sedimentological features of the outcrop and the geochemical characteristics of mudstones from the Middle Permian Taerlang Formation and Upper Permian Quanzijie Formation in the Taoshuyuanzi profile, northwest Turpan–Hami Basin, this paper makes a detailed discussion on the Middle–Late Permian paleoenvironment and its petroleum geological significances. The Middle–Upper Permian delta–lacustrine depositional system was characterized by complex vertical lithofacies assemblages, which were primarily influenced by tectonism and frequent lake-level variations in this area. The Taerlang Formation showed a significant lake transgression trend, whereas the regressive trend of the Quanzijie Formation was relatively weaker. The provenance of Taerlang and Quanzijie Formations was derived from the rift shoulder (Bogda Mountain area now) to the north and might be composed of a mixture of andesite and felsic volcanic source rocks. The Lower Taerlang Formation was deposited in a relatively hot–dry climate, whereas the Upper Taerlang and Quanzijie Formations were deposited in a relatively humid climate. During the Middle–Late Permian, this area belonged to an overall semi-saline water depositional environment. The paleosalinity values showed stepwise decreases from the Lower Taerlang Formation to the Upper Quanzijie Formation, which was influenced by the changes of paleoclimate in this region. During the Middle–Late Permian, the study area was in an overall anoxic depositional environment. The paleoenvironment with humid climate, lower paleosalinity, anoxic condition, and semi-deep to deep water during the deposition of the Upper Taerlang Formation was suitable for the accumulation of mudstones with higher TOC values.
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Gutak, Jaroslav M., Dmitry A. Ruban, and Natalia N. Yashalova. "New Marine Geoheritage from the Russian Altai." Journal of Marine Science and Engineering 9, no. 1 (January 16, 2021): 92. http://dx.doi.org/10.3390/jmse9010092.
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Marine geoheritage comprises unique geological features of modern and ancient seas and oceans. The Russian Altai (southern Siberia) is a vast and geologically rich area, which was covered by a marginal sea of the Panthalassa Ocean in the Devonian. New geosites representing shallow- and deep-marine depositional environments and palaeoecosystems of submarine volcano slopes are proposed, namely, Melnichnye Sopki and Zavodskie Sopki. They are located near the town of Zmeinogorsk (Altai Region of the Russian Federation). These pieces of marine geoheritage are valuable on an international scale. Special geoconservation procedures are recommended to manage the proposed geosites efficiently. They can be included in a geopark, which is reasonable to create due to the concentration of geological and mining heritage in the study area.
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Ndukwe, O. S., G. J. Udom, and C. U. Ugwueze. "Lithofacies control on depositional environments in shallow offshore Niger Delta: implication on reservoir quality." Scientia Africana 21, no. 2 (September 8, 2022): 59–74. http://dx.doi.org/10.4314/sa.v21i2.7.
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The KEN field lies within latitude 4⁰52ꞌ44ꞌꞌ N to 4⁰53'04'' N and 6⁰22'50'' E to 6⁰22'26'' E. The geological and geophysical data sets were used to describe reservoir depositional facies and their environment of deposition. A detailed and accurate environment of sediment delineation is a solid basis to enhance characterization and providing measures for improving hydrocarbon reservoirs. This study aims to presents an effective method for accurately defining depositional environment with different data sets. The data used comprises of biostratigraphy, well logs from three wells and 3D full angle stack seismic data. The biostratigraphic data help to ascertain the age of the formation delineated to be middle Miocene to late Miocene based on the marker shale. It also helps in picking the stratigraphic surfaces. Three depositional sequences were delineated and dated with maximum flooding surfaces of 15.0, 12.6 and 11.5 Ma, respectively. Log sequence analysis reveals the internal geometry and stacking pattern of the mapped sequences. The gamma ray signature varies from serrated cylindrical, funnel to the bell-shaped log motif. The seismic stratigraphy involved facies analysis and reflection termination patterns, which aided the mapping of depositional sequence. The internal geometry is composed of Highstand, transgressive, and lowstand systems tracts. The stacking patterns vary from progradational, aggradational and retrogradational. Based on the seismic facies analysis, the integrated results show that the field of study is of pelagic and debris flow origin deposited in shallow marine settings, which also conform with the other data sets used for this study. The depositional environment of the three delineated reservoirs (Reservoir A, B and C) vary from deltaic upper to lower shoreface channels sand. Reservoir C, which is laterally continuous across the three studied wells shows that the connectivity of reservoir C is loosely amalgamated. The integrated data used for this study indicate that the environment of deposition varies from inner neritic to outer neritic environment. The results of this research are essential for reservoir quality, exploration, appraisal and development phases.
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Manche, Cameron J., and Stephen E. Kaczmarek. "A global study of dolomite stoichiometry and cation ordering through the Phanerozoic." Journal of Sedimentary Research 91, no. 5 (May 31, 2021): 520–46. http://dx.doi.org/10.2110/jsr.2020.204.
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ABSTRACT Various geochemical proxies are used to constrain the diagenetic origin and evolution of ancient dolomites. Dolomite stoichiometry (mole % MgCO3) and cation ordering, two mineralogical attributes that define dolomite, have also been shown to demonstrate utility in this regard. Observations from laboratory experiments and field studies suggest that these attributes broadly reflect the fluid chemistry and temperature of the dolomitizing environment. The degree to which these parameters reflect global conditions during dolomitization (e.g., seawater chemistry, eustasy, atmospheric pCO2) and long-term geological processes is poorly understood, however. Here, a large dataset consisting of mineralogical data from over 1,690 Phanerozoic dolomites from various geographic locations, stratigraphic ages, platform types, and depositional environments are queried to investigate the broader geological controls on dolomite stoichiometry and cation ordering in dolomites formed by early, near-surface dolomitization. A suite of statistical analyses performed on the global dataset indicate: 1) despite wide ranges at the eon, period, and epoch level, dolomite stoichiometry and cation ordering broadly increase with geologic age; 2) significant variations in dolomite stoichiometry and cation ordering throughout the Phanerozoic do not correlate with global parameters, such as seawater chemistry, eustasy, orogenic events, and ocean crust production; 3) dolomites associated with restricted depositional settings, such as restricted lagoons, and the intertidal and supratidal zones, are more stoichiometric than dolomites associated with open marine settings, such as the deep-subtidal and shallow-subtidal zones; and 4) dolomites from shallow ramps and epeiric carbonate platforms are generally more stoichiometric than dolomites from open shelves and isolated carbonate platforms. These observations permit a number of inferences to be drawn. First, the principal signal observed in the data is that local environmental conditions associated with platform type and depositional setting are the strongest control on dolomite mineralogy. The observation that more stoichiometric dolomites correlate with shallow and restricted depositional environments is consistent with laboratory experiments that show environmental factors, such as higher Mg:Ca, temperature, and salinity of the dolomitizing fluids yield more stoichiometric dolomite. Second, a weaker secondary signal is also observed such that dolomite stoichiometry and cation ordering both increase with geologic age, suggesting that progressive recrystallization driven by mineralogical stabilization during burial is also occurring. Collectively, these data suggest that spatial and temporal variations in stoichiometry and cation ordering reflect the interplay between local dolomitizing conditions near the surface and long-term mineralogical stabilization during burial.
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Raggatt, Jim, Tim Gibbons, James Stockley, and Ian Deighton. "Browse Basin sequence stratigraphic study." APPEA Journal 52, no. 2 (2012): 703. http://dx.doi.org/10.1071/aj11117.
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In addition to the large gas fields already discovered in the Browse Basin, there is considerable scope for further exploration success because this basin holds an estimated recoverable reserve of 30 tcf gas. TGS has completed the Browse Basin Sequence stratigraphic study to specifically understand the many depositional environments of this basin by a comprehensive analysis of 75 key wells all tied to extensive 2D seismic interpretation. With a standardized lithostratigraphic and chronostratigraphic interpretation, each well has a full 3rd order sequence boundary record across all logged sections, and was subsequently assigned detailed gross depositional environments (GDE). Tied to the GDE’s are specific and highly detailed facies associations, displayed in 26 facies maps, thereby building a robust multi-sequence geological model constrained by sequences. These basin-wide facies maps delineate known source, reservoir and seal and propose where—within the robust geological model—potentially similar facies have been deposited and preserved. This extended abstract is delivered by the Facies Map Browser (FMB), a unique product, containing all data and interpreted maps. The Browse Basin FMB allows users to quickly understand the basin-wide depositional history and interpreted facies. With the multi-well and multi-source background database, the FMB product has proven to shorten the exploration cycle by its sheer level of detail and wide ranging interpretation.
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Eilrich, Bernd, and Jürgen Grötsch. "The Lower Cretaceous carbonate slope-to-platform-margin succession near Khatt, United Arab Emirates: sedimentary facies and depositional geometries." GeoArabia 8, no. 2 (April 1, 2003): 275–94. http://dx.doi.org/10.2113/geoarabia0802275.
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ABSTRACT The Jurassic and Lower Cretaceous carbonate succession exposed near Khatt provides exceptional conditions for the investigation of sedimentary facies and depositional geometries in a carbonate slope-to-platform-margin setting. A coarsening-upward sequence in Lower Cretaceous limestones indicates decreasing depth of deposition and platform progradation. A pronounced shedding of sediments containing reefal fragments occurs in a slope environment with a well exposed basin-to-platform transect. The carbonate succession consists of mudstone, wackestone, grainstone, coarse rudstone with conglomerate/breccia interbeds, and framestone at the top. The depositional architecture is characterized by the abundance of massive sheet- or channel-like limestone bodies within thinly bedded and generally uniform strata. Quantitative analysis of many carbonate channel deposits and their geometries measured in outcrop led to the distinction of two major types. Type I channel deposits are thin (0.3 to 5 m) but massive, and are commonly irregularly shaped in cross-section. They are as much as 200 m wide. Type I channel deposits are characterized by a wide size range of skeletal and non-skeletal carbonate components. Type II channel deposits, by contrast, are more regularly bedded and have much larger thickness-to-width ratios, in general close to 1:10. Furthermore, they are composed of packstone to grainstone calciturbidite sediments. As with some sheet deposits, they can be correlated through most of the 5.5-km-long Khatt outcrop. Stratigraphically, however, their occurrence is very much restricted, indicating significant alternation of depositional styles as a consequence of changing carbonate platform production and changing sedimentary environments. The data presented here can serve as input for 3-D geological modeling of equivalent depositional environments in the subsurface. They can also be applied to object-based deterministic and stochastic facies modeling.
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Cosgrove, G. I. E., L. Colombera, and N. P. Mountney. "Eolian stratigraphic record of environmental change through geological time." Geology 50, no. 3 (November 22, 2021): 289–94. http://dx.doi.org/10.1130/g49474.1.
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Abstract The terrestrial sedimentary record provides a valuable archive of how ancient depositional systems responded to and recorded changes in Earth's atmosphere, biosphere, and geosphere. However, the record of these environmental changes in eolian sedimentary successions is poorly constrained and largely unquantified. Our study presents the first global-scale, quantitative investigation of the architecture of eolian systems through geological time via analysis of 55 case studies of eolian successions. Eolian deposits accumulating (1) under greenhouse conditions, (2) in the presence of vascular plants and grasses, and (3) in rapidly subsiding basins associated with the rifting of supercontinents are represented by significantly thicker eolian dune-set, sand-sheet, and interdune architectural elements. Pre-vegetation eolian systems are also associated with more frequent interactions with non-eolian environments. The interplay of these forcings has resulted in dune-set thicknesses that tend to be smallest and largest in Proterozoic and Mesozoic successions, respectively. In the Proterozoic, the absence of sediment-binding plant roots rendered eolian deposits susceptible to post-depositional wind deflation and reworking by fluvial systems, whereby highly mobile channels reworked contiguous eolian deposits. During the Mesozoic, humid greenhouse conditions (associated with relatively elevated water tables) and high rates of basin subsidence (associated with the breakup of Pangea) favored the rapid transfer of eolian sediment beneath the erosional baseline. The common presence of vegetation promoted accumulation of stabilizing eolian systems. These factors acted to limit post-depositional reworking. Eolian sedimentary deposits record a fingerprint of major environmental changes in Earth history: climate, continental configuration, tectonics, and land-plant evolution.
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KLUNK, M. A., S. DASGUPTA, M. DAS, P. R. WANDER, and A. DI CAPUA. "GEOCHEMICAL SPECIATION AND BATCH MODE SIMULATION IN THE CARBONATE DEPOSITIONAL ENVIRONMENTS." Periódico Tchê Química 16, no. 33 (March 20, 2019): 736–48. http://dx.doi.org/10.52571/ptq.v16.n33.2019.751_periodico33_pgs_736_748.pdf.
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Geochemical modeling has been frequently used to understand and interpret water-rock interactions in sedimentary basins. Thermodynamic data, kinetic parameters, numerical methods, boundary history, and boundary conditions are factors affecting any geochemical modeling system. In the present study, we have attempted to establish a geochemical speciation model by comparing the interaction of formation water and carbonate rock in the carbonate depositional settings of Cambrian successions of Bachu and Tarim area. A comparative study of geochemical speciation has been performed using four different software: PHREEQCTM, GWBTM, TOUGHREACTTM, and GEODELING. GEODELING is a geochemical code simulator that we have developed, and the details are presented further in this work. All the software has been analyzed minutely, considering the distribution, mobility, and availability of chemical species in geological environments. Very similar results in speciation are observed while working with low-temperature systems. A discrepancy can be observed in the results while working with high temperatures. However, a thorough Newton-Raphson formulation, scaling of algebraic equations and master-species switching helps to reduce the possibility of failures of the numerical method used in PHREEQCTM.
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Ineson, Jon R., and John S. Peel. "Geological and depositional setting of the Sirius Passet Lagerstätte (Early Cambrian), North Greenland." Canadian Journal of Earth Sciences 48, no. 8 (August 2011): 1259–81. http://dx.doi.org/10.1139/e11-018.
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The Early Cambrian Sirius Passet Lagerstätte of North Greenland occurs in marine mudstones (Buen Formation) deposited in a slope environment along the eroded scarp of a pre-existing carbonate platform. The shallow-water platform is represented by dolostones of the Portfjeld Formation (Neoproterozoic – earliest Cambrian), which record a belt of tide-swept subtidal ooid shoals and microbial patch reefs at the outer edge of the platform. Solution features and meteoric cements attest to exposure of the platform, accompanied by fracturing, mass wastage and erosional retreat of the escarpment producing slope talus, and extensive debris sheets and olistoliths in basinal deposits. The marine mud-dominated siliciclastics of the Buen Formation, deposited in slope and shelf environments, record the transgression and onlap of the degraded platform in the Early Cambrian. The Sirius Passet Lagerstätte has yielded an arthropod-dominated fossil assemblage of over 40 species, many showing exceptional preservation of soft tissues; the finely laminated mudstones hosting this fauna accumulated from suspension in a poorly oxygenated slope sub-environment, such as an erosional embayment or abandoned slope gully. Although taphonomic features suggest that the fauna is mainly parautochthonous, some components (e.g., sponges, worms, the halkieriids and certain sightless arthropods) may be truly autochthonous. Comparison of the Sirius Passet locality with the renowned Middle Cambrian Burgess Shale of western Canada reveals similarities in overall depositional and tectonic setting: both accumulated in deep water adjacent to the steep, eroded margins of carbonate platforms — settings that subsequently sheltered the faunas from tectonic and metamorphic obliteration.
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Yan, Zhiming, Jinlong Wang, and Xuetian Wang. "Sedimentary Environments and Coal Accumulation of the Middle Xishanyao Formation, Jurassic, in the Western Dananhu Coalfield, Turpan-Hami Basin." Geofluids 2021 (November 2, 2021): 1–10. http://dx.doi.org/10.1155/2021/6034055.
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The Dananhu coalfield, at the southern margin of Turpan-Hami Basin, Xinjiang, has good coal-forming geological conditions. Due to the low research level on the depositional environment and coal accumulation, the comprehensive coal mining is restricted. Based on drilling and sectioning outcrop data, the depositional characteristics, lithofacies, paleogeography, and coal accumulation of the coal-bearing formations in western Dananhu coalfield are analyzed. The middle member of the Xishanyao Formation is the major coal-bearing strata of the Dananhu coalfield, composed of conglomerate, sandstone, siltstone, mudstone, and combustible organic rock, which can be further subdivided into 14 lithofacies according to substance composition, sediment texture, and structure. During the early Middle Jurassic coal-accumulating period, alluvial fan, fluvial plain, fluvial delta, and shallow lacustrine deposits were developed from northeast to southwest in the western Dananhu mining area. Coal accumulation was most developed in the center regions of the study area extending from northeast to southwest, which were primarily concentrated in margin fans, floodplains, interdeltaic bays, and lakeshore environments, especially the transitional zone between the fluvial plain and the delta plain in the west of No. 1 mining area. This coal accumulation was mainly controlled by synsedimentary tectonic subsidence and clastic sediments supply or sedimentary environment, where tectonic subsidence was the primary controlling factor and the source supply was the secondary controlling factor for coal accumulation, which provided theoretical support for the coal prediction and geological exploration in western Dananhu coalfield.
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Nash, M. C., U. Troitzsch, B. N. Opdyke, J. M. Trafford, B. D. Russell, and D. I. Kline. "Biomineralization of dolomite and magnesite discovered in tropical coralline algae: a biological solution to the geological dolomite problem." Biogeosciences Discussions 8, no. 3 (June 27, 2011): 5881–906. http://dx.doi.org/10.5194/bgd-8-5881-2011.
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Abstract. Dolomite is a magnesium-rich carbonate mineral abundant in fossil carbonate reef platforms but surprisingly rare in modern sedimentary environments, a conundrum known as the ''Dolomite Problem". Marine sedimentary dolomite has been interpreted to form by an unconfirmed, post-depositional diagenetic process, despite minimal experimental success at replicating this. Here we show that dolomite, accompanied by magnesite, forms within living crustose coralline alga, Hydrolithon onkodes, a prolific global tropical reef species. Chemical micro-analysis of the coralline skeleton reveals that not only are the cell walls calcitised, but that cell spaces are typically filled with magnesite, rimmed by dolomite, or both. Mineralogy was confirmed by X-ray diffraction. Thus there are at least three mineral phases present (magnesium calcite, dolomite and magnesite) rather than one or two (magnesium calcite and brucite) as previously thought. Our results are consistent with dolomite occurrences in coralline algae rich environments in fossil reefs. Instead of a theory of post-depositional dolomitisation, we present evidence revealing biomineralization that can account for the massive formations seen in the geologic record. Additionally, our findings imply that previously unrecognized dolomite and magnesite have formed throughout the Holocene. This discovery together with the scale of coralline algae dominance in past shallow carbonate environments raises the possibility that environmental factors driving this biological dolomitisation process have influenced the global marine magnesium/calcium cycle. Perhaps, most importantly, we reveal that what has been considered a geological process can be a biological process, having many implications for both disciplines.
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Pochocka-Szwarc, Katarzyna, and Dariusz Krzyszkowski. "The Outwash Plain Of The Rospuda River Valley – A Record Of Depositional Environments." Studia Quaternaria 32, no. 2 (December 1, 2015): 63–78. http://dx.doi.org/10.1515/squa-2015-0006.
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Abstract The Rospuda subglacial channel hosts not only deep ribbon lakes and the Rospuda River itself, but also an outwash plain. The paper deals with a lithofacies analysis of deposits from exposures within the Rospuda outwash plain. With the support of geomorphological and geological analyses, it has been found that the outwash plain formed along the Rospuda subglacial channel that was being exposed from under the ice cover. The lithological record of the Rospuda outwash plain shows a distinct division into a proximal and a distal zone. The deposits under study reveal a record of a break in basial sedimentation, when ice-wedge casts developed under conditions of periglacial climate. The development of the Rospuda outwash plain is linked with the ice-marginal zone of the Pomeranian phase, similarly to the Olecko-Rajgród outwash plain that is located to the west.
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Radaszewski, Robert, and Jędrzej Wierzbicki. "On the applicability of in situ soil probings to geological analyses." Geologos 17, no. 1 (April 1, 2011): 5–16. http://dx.doi.org/10.2478/v10118-011-0001-x.
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On the applicability of in situ soil probings to geological analyses Examples of geoengineering methods (static and dynamic probings) that can be applied to analyses of geological environments are presented. The potential is shown by the results of the determination of the values of the soil-density index (ID), the soil-behaviour index (Ic), the constrained modulus (M), the overconsolidation ratio (OCR) and their vertical changes. The values obtained for ID and Ic facilitate the determination of layers with a specific character. This is demonstrated for several aeolian and glacial deposits in Poland. The application of static probings to the analyses of changes in OCR and M made it possible to identify several depositional phases and the effect of postdepositional processes. Usages of the probings can significantly contribute to the interpretation of palaeo-environments (e.g. in the context of geostatistical models), but the results obtained should be handled cautiously.
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Gaifulina, E. F., N. V. Nadeznitskaya, S. L. Belousov, Yu S. Kapustina, A. N. Fishenko, and Yu V. Miheev. "Comprehensive analysis of geological and geophysical information for the facies depositional environment prediction of Ju2 strata of Tyumen suite." Oil and Gas Studies, no. 6 (January 15, 2021): 25–39. http://dx.doi.org/10.31660/0445-0108-2020-6-25-39.
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Hydrocarbon reserves within the middle Jurassic deposits are predominantly classified as hard-to-recover. The legislation of the Russian Federation stimulates extraction of this type of reserves by providing tax incentives, which currently make field development more attractive for oil companies. A particular interest is the Ju2 deposits of Tyumen suite because they are considered as productive almost on all explored fields. However, at the moment, the majority of deposits within this formation remain undeveloped. The main reason for this is the failure in prediction of net pay (thickness) and as a consequence mistakes in geological models for drilling production wells. This article is dedicated to the problem of spatial depositional environments prediction of the Ju2 deposits of Tyumen suite. As part of the problem solving, the geological model of studied field has been improved by integrated use of geological and geophysical information on different scales involving cutting-edge technologies in seismic interpretation.
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Nainggolan, T. B., U. Nurhasanah, and I. Setiadi. "Depositional sequence interpretation using seismic and well data of offshore Central Sumatra Basin." IOP Conference Series: Earth and Environmental Science 944, no. 1 (December 1, 2021): 012002. http://dx.doi.org/10.1088/1755-1315/944/1/012002.
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Abstract Offshore Central Sumatra Basin is an integral part of Central Sumatra Basin known for producing hydrocarbon basins. The derivation of stratigraphic study of seismic and well data is intended to improve accuracy of geological interpretation. Sequence stratigraphy studies have a significant role in exploratory studies to determine which depositional sequence can be inferred as hydrocarbon reservoir and its correlation in petroleum system. This study aims to identify biogenic gas sequential interpretation using seismic and well data of offshore Central Sumatra Basin. The procedure to analyze sequence stratigraphy is to identify stratigraphy surface markers using GR log, then map these markers to the seismic section that has been tied with good data to determine the distribution of each stratigraphy sequence. This study area has five depositional sequences, which are predominantly formed in marine depositional environments. Potential source rock in this area is at DS-1 which has a lacustrine depositional environment with euxinic conditions. The euxinic shale at the upper TST-1 deposit could be a source rock with hydrocarbon migration through faults. Biogenic gas reservoir potential is in Petani Formation (DS-5). Shale in MFS-5 and HST-5 could be a hydrocarbon trap, whereas LST-5 and TST-5 sandstone deposits can be a reservoir.
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Zheng, Xue, Baruch Spiro, and Zuozhen Han. "Comparison of Geochemical and Mineralogical Characteristics of Palaeogene Oil Shales and Coals from the Huangxian Basin, Shandong Province, East China." Minerals 10, no. 6 (May 29, 2020): 496. http://dx.doi.org/10.3390/min10060496.
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Coal and oil shale are both organic matter-rich sedimentary rocks. However, their sources of organic matter and their depositional environments are different. The present study focuses on the Palaeogene Lijiaya Formation sequence in the Huangxian Basin, Shandong Province, East China, which has oil shales showing marine geochemical indicators overlain by coals indicating marine regression. We investigated the C1 coal seam and underlying OS2 oil shale layers, compared their geochemical and mineralogical characteristics, clarified the details of their constituents, in order to elucidate the features of their sources, their depositional environments, and the post depositional processes in the context of the geological evolution of the basin. The Al2O3/TiO2 (18.1–64.9) and TiO2/Zr ratios (28.2–66.5) in the C1 coals and OS2 oil shales, respectively, suggest a felsic to intermediate source, and the Mesozoic granite on the South of Huangxian Fault may be one of the provenances of these sediments. The low sulphur content (0.53–0.59%) and low Sr/Ba ratios (0.32–0.67) suggest a freshwater depositional environment for the C1 coals. In contrast, the higher total sulphur contents (0.60–1.44%), the higher Sr/Ba ratios (0.31–1.11%), and the occurrence of calcareous shells, indicate seawater intrusions during deposition of the oil shales. The V/Ni, V/(V + Ni), and V/Cr ratios of the OS2 oil shale suggest oxic to suboxic conditions with a distinct change in palaeo-redox between the lower and upper parts of OS2 seam. The high boron contents in C1 coals (average, 504 ppm) is related to the high content of analcime (with the correlation coefficient of 0.96), and the high concentration of boron was attributed to a secondary enrichment by epigenetic hydrothermal solutions. The occurrence of idiomorphic-authigenic albite in association with analcime and quartz in veins in the coals suggests that albite is a product of a reaction between analcime and silica, both of volcanic origin. The reaction takes place at about 190 °C, indicating that the area was affected by hydrothermal fluids.
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Groves, M. R., J. S. Birnie, M. P. Creighton, and D. P. Giles. "Development of the ground model in an area of significant faulting and periglacial legacy: case study from Royal Tunbridge Wells, Kent." Quarterly Journal of Engineering Geology and Hydrogeology 54, no. 2 (February 5, 2021): qjegh2020–076. http://dx.doi.org/10.1144/qjegh2020-076.
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This case study describes a proposed commercial redevelopment at Royal Tunbridge Wells, Kent. The site, located on the Tunbridge Wells Sand and Wadhurst Clay formations, has been affected by major structural faulting as well as by periglacial conditions during the Quaternary. A key aspect of the project was the development of a geological model to inform the engineering design. This study presents the ground model development process, starting with an appreciation of the macro geological setting, understanding the Quaternary landsystem, to focusing on the data from the intrusive ground investigation. The understanding of the primary sedimentary depositional system is critical to the development of a site geological conceptual model. Sediments from highly variable environments of deposition, such as were present in the Early Cretaceous, will present geotechnical and geohazard challenges to a site's development and this first-principles understanding is important in this process. The link from these fundamental geological principles to engineering design, communicated through the ground model, as demonstrated in this paper, is the requirement of the engineering geological appraisal. Locally complex geology demanded a phased site investigation approach, responding to an evolving design and to construction demands, and to meet defined programme requirements for a second-stage tender, to ultimately de-risk key areas with regard to the dynamic ground and groundwater conditions.Thematic collection: This article is part of the Ground models in engineering geology and hydrogeology collection available at: https://www.lyellcollection.org/cc/Ground-models-in-engineering-geology-and-hydrogeology
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Alberts, L. J. H., C. R. Geel, and J. J. Klasen. "Reservoir characterisation using process-response simulations: the Lower Cretaceous Rijn Field, West Netherlands Basin." Netherlands Journal of Geosciences - Geologie en Mijnbouw 82, no. 4 (December 2003): 313–24. http://dx.doi.org/10.1017/s001677460002014x.
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AbstractPetroleum geologists always need to deal with large gaps in data resolution and coverage during reservoir characterisation. Seismic data show only large geological structures, whereas small-scale structures and reservoir properties can be observed only at well locations. In the area between wells, these properties are often estimated by means of geostatistics. Numerical simulation of sedimentary processes offers an alternative method to predict these properties and can improve the understanding of the controls on reservoir heterogeneity. Although this kind of modelling is widely used on basin scale in exploration geology, its application on field scale in production geology is virtually non-existent. We have assessed whether the recent developments in numerical modelling can also aid petroleum geologists in the interpretation of the reservoir geology.Seismic data, well data and a process-response model for coastal environments were used to characterise the Lower Cretaceous oil-bearing Rijn Field. Interpretation of seismic and well data led to a definition of the structural setting and the depositional model of the Rijn Member in the area. From the sedimentological interpretation the sea-level history could be estimated, which is the one of the most important input parameters for the process-response model.Application of the process-response simulator to the Rijn Field resulted in approval of the depositional model. The output was presented in a 2-dimensional north-south profile, which corresponds very well to the well logs along this section. The results demonstrate that numerical simulations of geological processes can be very useful as a tool to explore many likely geological scenarios. While it cannot be used to supply a unique solution in many cases, it forms a helpful guide during reservoir characterisation to find an optimal scenario of the controls on deposition of the Rijn Member, which contributes to the understanding of the inter-well reservoir heterogeneity.
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Garcia, Amanda K., J. William Schopf, Shin-ichi Yokobori, Satoshi Akanuma, and Akihiko Yamagishi. "Reconstructed ancestral enzymes suggest long-term cooling of Earth’s photic zone since the Archean." Proceedings of the National Academy of Sciences 114, no. 18 (April 17, 2017): 4619–24. http://dx.doi.org/10.1073/pnas.1702729114.
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Paleotemperatures inferred from the isotopic compositions (δ18O and δ30Si) of marine cherts suggest that Earth’s oceans cooled from 70 ± 15 °C in the Archean to the present ∼15 °C. This interpretation, however, has been subject to question due to uncertainties regarding oceanic isotopic compositions, diagenetic or metamorphic resetting of the isotopic record, and depositional environments. Analyses of the thermostability of reconstructed ancestral enzymes provide an independent method by which to assess the temperature history inferred from the isotopic evidence. Although previous studies have demonstrated extreme thermostability in reconstructed archaeal and bacterial proteins compatible with a hot early Earth, taxa investigated may have inhabited local thermal environments that differed significantly from average surface conditions. We here present thermostability measurements of reconstructed ancestral enzymatically active nucleoside diphosphate kinases (NDKs) derived from light-requiring prokaryotic and eukaryotic phototrophs having widely separated fossil-based divergence ages. The ancestral environmental temperatures thereby determined for these photic-zone organisms––shown in modern taxa to correlate strongly with NDK thermostability––are inferred to reflect ancient surface-environment paleotemperatures. Our results suggest that Earth's surface temperature decreased over geological time from ∼65–80 °C in the Archean, a finding consistent both with previous isotope-based and protein reconstruction-based interpretations. Interdisciplinary studies such as those reported here integrating genomic, geologic, and paleontologic data hold promise for providing new insight into the coevolution of life and environment over Earth history.
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Wallinga, J., F. Davids, and J. W. A. Dijkmans. "Luminescence dating of Netherlands’ sediments." Netherlands Journal of Geosciences 86, no. 3 (September 2007): 179–96. http://dx.doi.org/10.1017/s0016774600077799.
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AbstractOver the last decades luminescence dating techniques have been developed that allow earth scientists to determine the time of deposition of sediments. In this contribution we review: 1) the development of the methodology; 2) tests of the reliability of luminescence dating on Netherlands’ sediments; and 3) geological applications of the method in the Netherlands. Our review shows that optically stimulated luminescence dating of quartz grains using the single aliquot regenerative dose method yields results in agreement with independent age control for deposits ranging in age from a few years up to 125 ka. Optical dating of quartz has successfully been applied to sediments from a wide range of depositional environments such as coastal dunes, cover sands, fluvial channel deposits, colluvial deposits and fimic soils. These results demonstrate that optical dating is a powerful tool to explore the natural archive of the Netherlands’ subsurface.
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Zhemchugova, Valentina A., Vadim V. Rybalchenko, and Tatiana A. Shardanova. "Sequence-stratigraphic model of the West Siberia Lower Cretaceous." Georesursy 23, no. 2 (May 25, 2021): 179–91. http://dx.doi.org/10.18599/grs.2021.2.18.
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Apparently, conceptual base of the sequence stratigraphy is one of the most acknowledged methodologies in the geological world at the present time for the sedimentary strata structure prediction. It is based on the complex analysis of the seismic, stratigraphic and sedimentary data on the depositional bodies where the structure and facies filling is regulated by the relative sea level changes. The Lower Cretaceous section of the Western Siberia in this regard is the unique object, as it is represented by the full range of the clastic depositional environments – from relatively deep-water to the continental, which are very sensitive to the conditions changes. Sequence-stratigraphic analysis results can be used to complete the pragmatic tasks in the petroleum geology as the analysis is based on the reconstruction of the sedimentogenesis processes in the past, and the understanding of that processes is the key to the generalized depositional model development. This model can be used to create the models, which can be applied to the unique local objects that occur in the Lower Cretaceous section.
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Draper, J. J., and C. J. Boreham. "GEOLOGICAL CONTROLS ON EXPLOITABLE COAL SEAM GAS DISTRIBUTION IN QUEENSLAND." APPEA Journal 46, no. 1 (2006): 343. http://dx.doi.org/10.1071/aj05019.
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Methane is present in all coals, but a number of geological factors influence the potential economic concentration of gas. The key factors are (1) depositional environment, (2) tectonic and structural setting, (3) rank and gas generation, (4) gas content, (5) permeability, and (6) hydrogeology. Commercial coal seam gas production in Queensland has been entirely from the Permian coals of the Bowen Basin, but the Jurassic coals of the Surat and Clarence-Moreton basins are poised to deliver commercial gas volumes.Depositional environments range from fluvial to delta plain to paralic and marginal marine—coals in the Bowen Basin are laterally more continuous than those in the Surat and Clarence-Moreton basins. The tectonic and structural settings are important as they control the coal characteristics both in terms of deposition and burial history. The important coal seam gas seams were deposited in a foreland setting in the Bowen Basin and an intracratonic setting in the Surat and Clarence-Moreton basins. Both of these settings resulted in widespread coal deposition. The complex burial history of the Bowen Basin has resulted in a wide range of coal ranks and properties. Rank in the Bowen Basin coal seam gas fields varies from vitrinite reflectance of 0.55% to >1.1% Rv and from Rv 0.35-0.6% in the Surat and Clarence-Moreton basins in Queensland. High vitrinite coals provide optimal gas generation and cleat formation. The commercial gas fields and the prospective ones contain coals with >60% vitrinite.Gas generation in the Queensland basins is complex with isotopic studies indicating that biogenic gas, thermogenic gas and mixed gases are present. Biogenic processes occur at depths of up to a kilometre. Gas content is important, but lower gas contents can be economic if deliverability is good. Free gas is also present. Drilling and production techniques play an important role in making lower gas content coals viable. Since the Bowen and Surat basins are in a compressive regime, permeability becomes a defining parameter. Areas where the compression is offset by tensional forces provide the best chances for commercial coal seam gas production. Tensional setting such as anticline or structural hinges are important plays. Hydrodynamics control the production rate though water quality varies between the fields.
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Amos, Kathryn, Carley Goodwin, and Angel Soria. "Incised valleys in marginal-lacustrine depositional environments: a new reservoir analogue from Lake Eyre, central Australia." APPEA Journal 52, no. 1 (2012): 513. http://dx.doi.org/10.1071/aj11040.
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Incised-valley fill deposits can form important hydrocarbon reservoirs and provide pathways for hydrocarbon migration. Incised-valleys formed in marginal-marine environments are well described, however, marginal-lacustrine incised-valleys have been the focus of extremely few investigations and are poorly understood. This paper provides a new description of incised-fluvial systems that are presently constructing terminal deposits in embayments around the shoreline of Lake Eyre, central Australia. It is anticipated that better awareness of such deposits will assist in the recognition of these depositional environments in the rock record, which should be useful for exploration purposes and for the generation of improved models for continental dryland fluvial-lacustrine reservoir deposits. A classification of all significant river mouth deposits around Lake Eyre (width >300 m; n = 104), from topographic map and satellite image data, found that 54% are incised-valleys presently accreting a terminal deposit in a shoreline embayment (playa lake estuary). The depositional elements of three incised-valley systems have been mapped using satellite imagery in a GIS platform, from which element geometries are described. Controls on incised-valley formation are investigated by comparing these observations with evidence for past lake highstands and neotectonics and observations from satellite images, geological map data, and digital elevation model data. The terminal splay deposits of rivers around Lake Eyre are well-used analogues for dryland reservoirs; however, the focus has been on deposits accreting directly onto the playa. It is likely the incised-valleys and terminal deposits in the embayments described here will be of interest to companies exploring in, and producing from, ancient drylands and other lacustrine depositional environments.
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Rahayu, Nila, Ratnayu Sitaresmi, and Moeh Ali Jambak. "Penentuan OOIP Berdasarkan Pemodelan Geologi dan Reservoir di Daerah Tanisha Cekungan Sumatra Selatan." Jurnal Offshore: Oil, Production Facilities and Renewable Energy 2, no. 2 (December 31, 2018): 14. http://dx.doi.org/10.30588/jo.v2i2.401.
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<p>Perkembangan teknologi dapat dimanfaatkan untuk mengetahui karakteristik reservoir sebelum dilakukannya kegiatan eksplorasi dan eksploitasi. Salah satunya dengan pemodelan geologi dan pemodelan reservoir untuk mendapatkan gambaran bentuk bawah permukaan, karakteristik reservoir, dan <em>OOIP</em>. Analisis data log dan interpretasi geologi dilakukan untuk mendapatkan informasi lingkungan pengendapan, marker lapisan, dan bentukan struktur reservoir yang digunakan sebagai dasar pembuatan model geologi. Analisis petrofisik akan memberikan informasi mengenai karakteristik batuan reservoir. Untuk mendapatkan model reservoir, hasil analisis petrofisik akan didistribusikan pada model geologi. Kemudian penentuan <em>OOIP</em> dapat dihitung dengan menggunakan metode volumetrik. Reservoir batupasir sudah terbukti menjadi reservoir produktif di berbagai lapangan migas, seperti reservoir batupasir pada Formasi Talang Akar di Lapangan Sungai Lilin. Terdapat enam lapisan yang menjadi obyek penelitian pada Formasi Talang Akar yaitu lapisan D1, D2, E1, E2, F, dan H yang diendapkan pada lingkungan delta plain–delta front terlihat dari pola log yang berkembang yaitu <em>funnel shape, serrated shape</em>, dan <em>bell shape</em>. Perbedaan lingkungan pengendapan akan mempengaruhi geometri dan karakteristik reservoir. Didapatkan nilai <em>cut-off</em> untuk Vcl ≤0.40, porositas ≥0.10 dan saturasi air ≤0.7. Hasil analisis petrofisika kemudian didistribusikan pada model geologi dengan metode <em>Sequential Gaussian Simulation</em> , dimana penyebaran lingkungan pengendapan menjadi arahan dasar penyebaran properti reservoir. Perhitungan <em>OOIP</em> pada enam lapisan di Formasi Talang Akar berdasarkan pemodelan reservoir sebesar 8,387 MSTB, dengan lapisan menarik terdapat pada lapisan E2 2,340 MSTB. </p><p><em>Technological developments can be utilized to determine reservoir characteristics prior to exploration and exploitation activities. One of them is by geological modeling and reservoir modeling to get a picture of subsurface shapes, reservoir characteristics, and OOIP. Log data analysis and geological interpretation were carried out to obtain information on depositional environments, layer markers, and reservoir structure formations that were used as the basis for making geological models. Petrophysical analysis will provide information about reservoir rock characteristics. To get the reservoir model, the results of the petrophysical analysis will be distributed to the geological model. Then the determination of OOIP can be calculated using the volumetric method. </em><em>Sandstone reservoirs have proven to be productive reservoirs in various oil and gas fields, such as sandstone reservoirs in the Talang Akar Formation in Sungai Lilin Field. There are six layers that are the object of research in the Talang Root Formation, namely layers D1, D2, E1, E2, F, and H which are deposited in the plain-delta front delta environment as seen from the developing log pattern, namely funnel shape, serrated shape, and bell shape. The difference in depositional environments will affect the geometry and characteristics of the reservoir. Obtained cut-off values for Vcl ≤0.40, porosity ≥0.10 and water saturation ≤0.7. The results of the petrophysical analysis are then distributed to the geological model using the Sequential Gaussian Simulation method, where the spread of the depositional environment is the basis for spreading reservoir properties. The OOIP calculation for the six layers in the Talang Akar Formation is based on reservoir modeling of 8,387 MSTB, with an interesting layer found at the E2 layer 2,340 MSTB.</em></p>
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Kuzmina, Svetlana. "Wetlands in the Pleistocene Steppe-Tundra Landscapes of Beringia, Their Insects, and the Role of Aeolian Sedimentation." Water 15, no. 3 (January 26, 2023): 494. http://dx.doi.org/10.3390/w15030494.
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Analysis of the database of Beringian subfossil insect assemblages showed a relatively low role of aquatic, riparian, and wetland species of insects with hard exoskeleton in the Pleistocene communities and an increase in their proportions and taxonomic diversity in the Holocene. Aquatic insects were represented in all types of geological deposits and in some paleosols, but their proportions varied in different depositional environments. Poor representation of aquatic insects and a lack of freshwater invertebrates in the Late Pleistocene ice-rich deposits of Beringia called Siberian Yedoma or Yukon Muck attest to the predominantly aeolian origin of this phenomenon.
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Cai, Jiang Dong, Ding Ceng Yu, Ya Dong Chen, and Qing You. "Study on Depositional Environment of Soil Based on Multi-Fractal Theory." Advanced Materials Research 255-260 (May 2011): 3530–34. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.3530.
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Fluvial action is the most universal erosion process in geological history. Rivers in the surface of the Earth had molded different kinds of geomorphic features and varied landforms; also they had great effect on the human beings. Evaluating the fluvial landforms correctly and objectively will help people to exploit the living space adequately and utilize natural environment reasonably. Moreover studying on the spatial distribution of the rivers in a local area will help people to understand the situation of the river at present and forecast the development of the river in the future. Fractal and multi- fractal theory is a new and developing subject in modern science; it is widely used in many fields of earth science. Static Cone Penetrate Test is an exploration technology which can obtain the physical indices of soil. A study had found that specific penetration resistances varied with the buried depth of the strata and the curves of test values have characteristics of fractal. In this paper, with the assistance of fractal and multi-fractal theory, we analyzed the simple dimension and multi-fractal properties of these curves. Results suggested that simple dimension as well as the multi-fractal spectrum can tell the difference between the soils deposited in distinct sedimentary environments.
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Chase, Jasmine E., Maria L. Arizaleta, and Benjamin M. Tutolo. "A Series of Data-Driven Hypotheses for Inferring Biogeochemical Conditions in Alkaline Lakes and Their Deposits Based on the Behavior of Mg and SiO2." Minerals 11, no. 2 (January 22, 2021): 106. http://dx.doi.org/10.3390/min11020106.
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Alkaline (pH > 8.5) lakes have been common features of Earth’s surface environments throughout its history and are currently among the most biologically productive environments on the planet. The chemistry of alkaline lakes favors the deposition of aluminum-poor magnesian clays (e.g., sepiolite, stevensite, and kerolite) whose chemistry and mineralogy may provide a useful record of the biogeochemistry of the lake waters from which they were precipitated. In this forward-looking review, we present six data-driven, testable hypotheses devoted to furthering our understanding of the biogeochemical conditions in paleolake waters based on the geochemical behavior of Mg and SiO2. In the development of these hypotheses, we bring together a compilation of modern lake water chemistry, recently published and new experimental data, and empirical, thermodynamic, and kinetic relationships developed from these data. We subdivide the hypotheses and supporting evidence into three categories: (1) interpreting paleolake chemistry from mineralogy; (2) interpreting the impact of diatoms on alkaline lake sedimentation; and (3) interpreting depositional mineralogy based on water chemistry. We demonstrate the need for further investigation by discussing evidence both for and against each hypothesis, which, in turn, highlights the gaps in our knowledge and the importance of furthering our understanding of the relevant geological and biological systems. The focused testing of these hypotheses against modern occurrences and the geologic record of alkaline lakes can have profound implications for the interpretation of the paleo-biogeochemistry and paleohabitability of these systems on Earth and beyond.
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Chao, Hui, Mingcai Hou, Wenjian Jiang, Haiyang Cao, Xiaolin Chang, Wen Luo, and James G. Ogg. "Paleoclimatic and Redox Condition Changes during Early-Middle Jurassic in the Yili Basin, Northwest China." Minerals 11, no. 7 (June 24, 2021): 675. http://dx.doi.org/10.3390/min11070675.
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The Jurassic was mainly a “greenhouse” period characterized by global warming and by significant peat accumulations in some continental basins. However, studies of Jurassic climate and environments have mainly focused on marine records and only a few on terrestrial sediments. Yili Basin, a mid-latitude terrestrial basin in present Northwest China, included accumulation of the important recoverable coal seams. In this study, geological data, clay mineral analysis, and palynological assemblages were employed on fine-grained samples from the Su’asugou section in southern Yili Basin. The factors (paleoclimate, depositional conditions, and paleo-vegetation) impacting peat accumulation were investigated. The results suggest that the siliciclastics may have been derived from exposed Carboniferous rocks in a continental arc environment. A warm and humid paleoclimate in the Yili basin dominated during the early-Early Jurassic deposition of the Badaowan Formation and the Middle Jurassic deposition of the Xishanyao Formation. This climate contributed to high sedimentary rates and to a high productivity of peat-forming paleo-vegetation that was preserved under dysoxic conditions. In contrast, during the late-Early Jurassic between these two formations, the Sangonghe Formation was an interval of relatively aridity that included red beds preserved under more hypoxic sedimentary conditions, and with an interruption in peat formation and preservation.
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Obi, Ifeanyichukwu S., K. Mosto Onuoha, Olusegun T. Obilaja, and C. I. Princeton Dim. "Understanding reservoir heterogeneity using variography and data analysis: an example from coastal swamp deposits, Niger Delta Basin (Nigeria)." Geologos 26, no. 3 (December 1, 2020): 207–18. http://dx.doi.org/10.2478/logos-2020-0020.
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Abstract For efficient reservoir management and long-term field development strategies, most geologists and asset managers pay special attention to reservoir chance of success. To minimise this uncertainty, a good understanding of reservoir presence and adequacy is required for better ranking of infill opportunities and optimal well placement. This can be quite challenging due to insufficient data and complexities that are typically associated with areas with compounded tectonostratigraphic framework. For the present paper, data analysis and variography were used firstly to examine possible geological factors that determine directions in which reservoirs show minimum heterogeneity for both discrete and continuous properties; secondly, to determine the maximum range and degree of variability of key reservoir petro-physical properties from the variogram, and thirdly, to highlight possible geological controls on reservoir distribution trends as well as areas with optimal reservoir quality. Discrete properties evaluated were lithology and genetic units, while continuous properties examined were porosity and net-to-gross (NtG). From the variogram analysis, the sandy lithology shows minimum heterogeneity in east-west (E–W) and north-south (N–S) directions, for Upper Shoreface Sands (USF) and Fluvial/Tidal Channel Sands (FCX/TCS), respectively. Porosity and NtG both show the least heterogeneity in the E–W axis for reservoirs belonging to both Upper Shoreface and Fluvial Channel environments with porosity showing a slightly higher range than NtG. The vertical ranges for both continuous properties did not show a clear trend. The Sequential Indicator Simulation (SIS) and Object modelling algorithm were used for modelling the discrete properties, while Sequential Gaussian Simulation (SGS) was used for modelling of the continuous properties. Results from this exercise show that depositional environment, sediment provenance, topographical slope, sub-regional structural trends, shoreline orientation and longshore currents, could have significant impacts on reservoir spatial distribution and property trends. This understanding could be applied in reservoir prediction and for generating stochastic estimates of petrophysical properties for nearby exploration assets of similar depositional environments.
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Gilstrap, William D., Jennifer L. Meanwell, Elizabeth H. Paris, Roberto López Bravo, and Peter M. Day. "Post-Depositional Alteration of Calcium Carbonate Phases in Archaeological Ceramics: Depletion and Redistribution Effects." Minerals 11, no. 7 (July 9, 2021): 749. http://dx.doi.org/10.3390/min11070749.
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The final stage in the life history of prehistoric pottery prior to archaeological recovery is usually the longest, and frequently the most dynamic. The remains of archaeological ceramics spend hundreds to thousands of years deposited within the upper layers of the earth’s crust where they encounter the same diagenetic environmental processes as the surrounding natural materials. Harsh conditions of subterranean environments induce physical stresses and chemical reactions, causing alterations of ceramic structure and composition. This is especially true of carbonate-rich ceramics, as carbonate phases are soluble when deposited within acidic environments. This paper examines common carbonate depletion and accretion effects of post-depositional environments on ancient ceramics from two rather different geological and archaeological contexts: Mesoamerica and the Mediterranean. Potters in both regions produce vessels with carbonate-rich materials—clays, calcite, limestone—that alter due to long exposure to low-pH sediments and continual water table fluctuations. Ceramic petrography is employed to identify traces of carbonate alterations within ceramic microstructure and to characterize fabrics. Elemental compositions of the same sherds are characterized through either scanning electron microscopy coupled with energy-dispersive spectrometry (SEM-EDS), inductively coupled plasma mass spectrometry and optical emission spectrometry (ICP-MS/OES) or neutron activation analysis (NAA). This method enabled comparison of the differing effects of post-depositional alteration of carbonate phases on bulk composition signatures commonly used to determine provenance.
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Harris, Brette S., Maya T. LaGrange, Sara K. Biddle, Tiffany L. Playter, Kathryn M. Fiess, and Murray K. Gingras. "Chemostratigraphy as a tool for sequence stratigraphy in the Devonian Hare Indian Formation in the Mackenzie Mountains and Central Mackenzie Valley, Northwest Territories, Canada." Canadian Journal of Earth Sciences 59, no. 1 (January 2022): 29–45. http://dx.doi.org/10.1139/cjes-2020-0198.
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The Hare Indian Formation (HIF) is a late Eifelian to Givetian organic-rich mudstone constituting the lower portion of the Horn River Group (HRG), which has been minimally scrutinized in the literature. This paper proposes depositional environments and a sequence stratigraphic framework for the HIF. Using composition data collected via energy-dispersive X-ray fluorescence, geochemical proxies inform detrital input, silica source, and paleoredox conditions. Cross-plots and chemostratigraphic profiles of detritally sourced Al, Ti, and K and redox-sensitive Mo and V inform depositional and stratigraphic constraints. Silica proportions vary, indicating that sediment was derived from detrital and biogenic sources. Al, Ti, and K distributions increase upwards, showing increased continentally sourced minerals. Redox-sensitive metals are highest in the Bluefish Member (BM), suggesting intermittent euxinia. Based on the presence of continental and pelagic sediments, the sedimentary environment is interpreted as proximal- to mid-shelf. These proxies guide systems tract interpretations. Si and redox-sensitive metal concentrations peak higher in the BM, accompanied by lowered concentrations of Al, Ti, and K, suggesting a maximum flooding surface. At the top of the Prohibition and Bell Creek members, redox-sensitive enrichments are lower with higher concentrations of Al, Ti, and K, suggesting a maximum regressive surface. Transgression occurred during the initial deposition of the BM, followed by regression for the remainder of the HIF. The sedimentology of the HIF can be difficult to decipher; the use of chemostratigraphy supports its geological history (including sedimentation trends and a local record of relative sea level) using methods that may be applied to other fine-grained successions.
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Elatrash, Ahmed M., Mohammad A. Abdelwahhab, Hamdalla A. Wanas, Samir I. El-Naggar, and Hasan M. Elshayeb. "Multi-disciplinary approach to sedimentary facies analysis of Messinian Salinity Crisis tectono-sequences (South-Mansoura Area, Nile Delta): Incised-valley fill geological model reconstruction and petroleum geology–reservoir element delineation." Journal of Petroleum Exploration and Production Technology 11, no. 4 (March 30, 2021): 1643–66. http://dx.doi.org/10.1007/s13202-021-01124-2.
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AbstractThe quality of a hydrocarbon reservoir is strongly controlled by the depositional and diagenetic facies nature of the given rock. Therefore, building a precise geological/depositional model of the reservoir rock is critical to reducing risks while exploring for petroleum. Ultimate reservoir characterization for constructing an adequate geological model is still challenging due to the in general insufficiency of data; particularly integrating them through combined approaches. In this paper, we integrated seismic geomorphology, sequence stratigraphy, and sedimentology, to efficiently characterize the Upper Miocene, incised-valley fill, Abu Madi Formation at South Mansoura Area (Onshore Nile Delta, Egypt). Abu Madi Formation, in the study area, is a SW-NE trending reservoir fairway consisting of alternative sequences of shales and channel-fill sandstones, of the Messinian age, that were built as a result of the River Nile sediment supply upon the Messinian Salinity Crisis. Hence, it comprises a range of continental to coastal depositional facies. We utilized dataset including seismic data, complete set of well logs, and core samples. We performed seismic attribute analysis, particularly spectral decomposition, over stratal slices to outline the geometry of the incised-valley fill. Moreover, well log analysis was done to distinguish different facies and lithofacies associations, and define their paleo-depositional environments; a preceding further look was given to the well log-based sequence stratigraphic setting as well. Furthermore, mineralogical composition and post-depositional diagenesis were identified performing petrographical analysis of some thin sections adopted from the core samples. A linkage between such approaches, performed in this study, and their impact on reservoir quality determination was aimed to shed light on a successful integrated reservoir characterization, capable of giving a robust insight into the depositional facies, and the associated petroleum potential. The results show that MSC Abu Madi Formation constitutes a third-order depositional sequence of fluvial to estuarine units, infilling the Eonile-canyon, with five sedimentary facies associations; overbank mud, fluvial channel complex, estuarine mud, tidal channels, and tidal bars; trending SW-NE with a Y-shape channel geometry. The fluvial facies association (zone 1 and 3) enriches coarse-grained sandstones, deposited in subaerial setting, with significantly higher reservoir quality, acting as the best reservoir facies of the area. Although the dissolution of detrital components, mainly feldspars, enhanced a secondary porosity, improving reservoir quality of MSC Abu Madi sediments, continental fluvial channel facies represent the main fluid flow conduits, where marine influence is limited.
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Irzon, Ronaldo, Kurnia Kurnia, Agus Didit Haryanto, Sigit Maryanto, and Undang Hernawan. "Distinct Depositional Environments Of Two Internal Reference Materials With Marine Sediment Matrix From Nearby Bangka Island." Bulletin of the Geological Society of Malaysia 73, no. 1 (May 23, 2022): 181–89. http://dx.doi.org/10.7186/bgsm73202215.
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Internal reference materials are generated by laboratories to overcome the high cost and limited matrix of certified reference materials (CRM). Rare earth elements (REE) are strategic metals which is used in modern technology and explored within different matrices. Rare earth elements exploration surely needs appropriate reference materials for accurate interpretation. The current study aims to explain internal standard reference materials generation of marine sediment matrices from nearby the tin Bangka Island, especially the rare earth elements character, to overcome the CRM dependency. The first sample was taken with a dredger while the second one using a suction vessel. Repeated samples measurements were done by applying inductively coupled plasma - mass spectrometry (ICP-MS) from the Center for Geological Survey Indonesia for repeatability tests. The samples were analyzed in another certified laboratory in Indonesia using the same device for reproducibility assessment. The two candidates should be deposited in different environments with different influx material due to their distinct rare earth elements characters. Most of the analytes’ contents are suitable to be set as internal reference material values according to acceptable repeatability and reproducibility evaluations. The internal reference materials are ready for studying suitable matrices in the future.
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Holland, Steven M. "The non-uniformity of fossil preservation." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1699 (July 19, 2016): 20150130. http://dx.doi.org/10.1098/rstb.2015.0130.
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The fossil record provides the primary source of data for calibrating the origin of clades. Although minimum ages of clades are given by the oldest preserved fossil, these underestimate the true age, which must be bracketed by probabilistic methods based on multiple fossil occurrences. Although most of these methods assume uniform preservation rates, this assumption is unsupported over geological timescales. On geologically long timescales (more than 10 Myr), the origin and cessation of sedimentary basins, and long-term variations in tectonic subsidence, eustatic sea level and sedimentation rate control the availability of depositional facies that preserve the environments in which species lived. The loss of doomed sediments, those with a low probability of preservation, imparts a secular trend to fossil preservation. As a result, the fossil record is spatially and temporally non-uniform. Models of fossil preservation should reflect this non-uniformity by using empirical estimates of fossil preservation that are spatially and temporally partitioned, or by using indirect proxies of fossil preservation. Geologically, realistic models of preservation will provide substantially more reliable estimates of the origination of clades. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’.
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Bonetti, Jarbas, Fabrizio Del Bianco, Leonardo Schippa, Alina Polonia, Giuseppe Stanghellini, Nicola Cenni, Stefano Draghetti, Francesco Marabini, and Luca Gasperini. "Anatomy of Anthropically Controlled Natural Lagoons through Geophysical, Geological, and Remote Sensing Observations: The Valli Di Comacchio (NE Italy) Case Study." Remote Sensing 14, no. 4 (February 17, 2022): 987. http://dx.doi.org/10.3390/rs14040987.
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Newly collected morphobathymetric and seismic reflection data from the Valli di Comacchio coastal lagoons, south of the Po River delta (Northeast Italy), combined with historical, remote sensing, and geodetic data highlight a complex geological evolution during the Holocene, strongly affected by anthropic control. All data allowed us to define the present-day depositional environment of the lagoons and reconstruct their recent (late Pleistocene/Holocene) geo-history. We focused on the effects of the anthropic impacts in modifying the pristine environments created by the Holocene transgression along the Adriatic Sea coast, at the mouth of a major river. They include land reclamation works, artificial damming, channel excavations, fluvial diversions, and a recent (last decades) increase in subsidence rate due to gas and water withdrawals. Despite the development of economic activities, which promoted occupation and exploitation of this area in the last millennia, the post-Glacial evolution of the lagoons shows the important role of inherited morphological features, such as sand ridges and barriers. This complex and relatively well-documented evolution makes the Comacchio lagoons a unique example of deep connections between natural processes and long-term human controls, offering insights into the management policies of these important and delicate environments challenged by global changes.
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Melezhik, V. A., A. B. Kuznetsov, A. F. Fallick, R. A. Smith, I. M. Gorokhov, D. Jamal, and F. Catuane. "Depositional environments and an apparent age for the Geci meta-limestones: Constraints on the geological history of northern Mozambique." Precambrian Research 148, no. 1-2 (July 20, 2006): 19–31. http://dx.doi.org/10.1016/j.precamres.2006.03.003.
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Messent, B. E. J., and C. M. Yacopetti. "THE VALUE OF INTEGRATING BOREHOLE RESISTIVITY IMAGES WITH GEOLOGICAL DATA: RELEVANCE TO HYDROCARBON EXPLORATION." APPEA Journal 37, no. 1 (1997): 301. http://dx.doi.org/10.1071/aj96019.
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This paper outlines the contribution borehole resistivity images can make in a frontier exploration program when they are integrated with all available geological data. Specific examples are given from the Duntroon Basin.Dipmeter data and borehole resistivity images can be used to validate seismic structural interpretations. An example is given to show the comparison in interpretation of the different methods.Faults are identified on the borehole images and in addition, qualitative assessment of sealing potential can be made by determining the occurrence and extent of mineralisation. In Greenly-1 the hydrocarbon shows, which are interpreted as migrated hydrocarbons, are found In close proximity to faults identified on borehole images. It is postulated that the faults acted as a conduit for the migrating hydrocarbons. However, these fault planes are now mineralised and interpreted to be sealing. This interpretation is supported by the presence of isolated, over-pressured sandstones.Resistivity images readily identify the orientation of present day horizontal stresses with its implications for fault-trap integrity. However, this is not deemed to be an issue in the Duntroon Basin as there is evidence that at least some of the faults are sealing. Borehole images can also be used to assess caprock integrity by determining the presence or absence of fractures.Within potential reservoir units, borehole resistivity images assist in the interpretation of depositional environments, reservoir geometries and post-depositional changes which affect reservoir quality.Borehole resistivity images provide qualitative interpretations of permeability. It is therefore possible to use the images in the selection of pre-test seats and sampling points in poor quality boreholes or low permeability reservoirs.
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Paudel, Mukunda Raj, and Harutaka Sakai. "Stratigraphy and depositional environment of late Pleistocene Sunakothi Formation in Kathmandu Basin, central Nepal." Journal of Nepal Geological Society 39 (September 25, 2009): 33–44. http://dx.doi.org/10.3126/jngs.v39i0.31486.
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Thick sandy sequences were recognised between the central and southern part of the basin, it was named as the Sunakothi Formation. We designate the type locality of this formation at Sunakothi, a village lying 3.0 km south of Patan. This formation is extensively distributed in the Nakhu, Kodku, and Godavari Kholas ranging in altitude from ca 1420 m in the southern margin to 1300 m in the central part. The average thickness of this formation ranges from 34 to 60 m. The sedimentary strata are gently inclined towards the north. On the basis of geological mapping this formation is located between the muddy part of the Kalimati Formation of the ancient lake and the terrace gravel deposits. It is further divided into the following four parts: (1) muddy rhythmic basal part, (2) sandy lower part, (3) muddy, sandy, and gravelly middle part, and (4) laminated silty upper part. The basal part shows a transition from the lacustrine to fluvial environment in the south and the prodeltaic environment towards the basin centre. Its lower part contains sandy fluvial to lacustrine delta front deposits whereas the middle part comprises sandy bar, muddy floodplain, and gravelly channel-fill deposits. The upper part of this formation is restricted only to the southern end of the basin and shows marginal shallow lacustrine environments. The sedimentological evidence indicates that the Palaeo-Kathmandu Lake was drained out from the south due to tectonic activities as well as late Pleistocene climatic changes.
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Kałmykow-Piwińska, Agnieszka, and Ewa Falkowska. "Morphodynamic conditions of heavy metal concentration in deposits of the Vistula River valley near Kępa Gostecka (central Poland)." Open Geosciences 12, no. 1 (October 17, 2020): 1036–51. http://dx.doi.org/10.1515/geo-2020-0058.
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AbstractThe influence of morphodynamics of individual river valley zones on the anthropogenically induced distribution of heavy metals in the Małopolska Gorge of the Vistula River near Kępa Gostecka was studied. Based on the analysis of cartographic and geological mapping data, several floodplain features were distinguished. For each feature, lithological analysis of the deposits was carried out. It comprised determination of clay content, organic matter, carbonates and iron oxides and hydroxides, as well as analysis of heavy metal concentration. The investigations show that the concentration of heavy metals in floodplain surface deposits is strictly linked with the variability of depositional environments, which reflected in the intricate feature pattern. The highest contents of heavy metals have been found in the deposits of the contemporary floodplain, stagnation zones of floodwaters, oxbow lakes buried under floodplain or organic deposits and escarpment foot back swamps, while the lowest in deposits of the Pleistocene terrace and slope wash zones. Variability of floodwater dynamics modelling the floodplain surface is associated with the specific geological setting of the Vistula River valley stretch analysed.
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Fahad Al-Ajmi, Hussain, Martin Keller, Matthias Hinderer, and Claudio Miro Filomena. "Lithofacies, depositional environments and stratigraphic architecture of the Wajid Group outcrops in southern Saudi Arabia." GeoArabia 20, no. 1 (January 1, 2015): 49–94. http://dx.doi.org/10.2113/geoarabia200149.
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ABSTRACT The Wajid Group is a Palaeozoic siliciclastic succession of southern Saudi Arabia. In the outcrop belt it is ca. 500 m thick, whereas in the subsurface, the thickness increases to more than 4,500 m. The siliciclastic sediments have great reservoir potential for hydrocarbons and for groundwater. Although they represent one of the most important aquifers of the Arabian Peninsula, neither their sedimentologic, lithostratigraphic, nor their reservoir characteristics are satisfactorily known. In this study, a detailed description of lithology and sedimentology is given and the Wajid Group sediments are interpreted in terms of depositional environment and facies architecture. Thirteen lithofacies (LF 1 to LF 13) have been recognised, most of them composed of different subfacies. These lithofacies are grouped into 9 lithofacies associations (LF-A1 through LF-A9). LF-A1 through LF-A3 and LF-A7 represent shallow-marine siliciclastic environments. The remaining lithofacies associations describe periglacial environments of the Hirnantian (Late Ordovician) and Permian Gondwana glaciations. Except for a few pro-glacial fluvial deposits, fluvial successions and aeolian sediments are absent in the outcrops of the Wajid Sandstone. Five formations are recognised in the Wajid Group: the Dibsiyah, Sanamah, Qalibah, Khusayyayn, and Juwayl formations. They are all separated by major unconformities. The Dibsiyah Formation represents a vast sand-sheet complex with core and margin facies formed under shallow-marine conditions. These marine conditions enabled an abundant fauna to proliferate and leave its traces in the form of Skolithos piperock and Cruziana sp. A late Cambrian to Early Ordovician age is inferred for these deposits from regional considerations. The Sanamah Formation records the Late Ordovician Hirnantian glaciation with coarse sandstones and conglomerates. A variety of glacier-induced sedimentary structures are present. The internal succession is composed of three major sediment packages reflecting three ice advance-retreat cycles. The latest of these cycles is overlain by a few metres of marginal-marine sediments of the Qalibah Formation. The Khusayyayn Formation was deposited probably during Early Devonian times. It also represents a sand-sheet environment characterised by the dominance of mega-scale and giant cross beds and bed sets. A marine depositional environment is assumed from scarce Skolithos sp., and because nearly all indicators of a braided river system are absent. The Juwayl Formation of Permian age was deposited at the interface of the Late Palaeozoic Gondwana ice shield with a large lake that may have covered most of southern Arabia and adjacent areas. Proglacial sandstones and conglomerates were deposited close to the glaciers, whereas fine-grained sediment with dropstones, boulder pavements and a wide spectrum of soft-sediment deformation are characteristic of the lake environment. While the two glacial successions and the Khusayyayn Formation can rather confidently be attributed to the geological time scale, either through seismic correlation or biostratigraphically, the Dibsiyah Formation has not yet been biostratigraphically well dated.
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Ferreira Júnior, Paulo Dias, and Paulo de Tarso Amorim Castro. "Geological control of Podocnemis expansa and Podocnemis unifilis nesting areas in Rio Javaés, Bananal Island, Brazil." Acta Amazonica 33, no. 3 (2003): 445–68. http://dx.doi.org/10.1590/s0044-59672003000300010.
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The distribution of the nests of Podocnemis expansa (Amazon turtle) and Podocnemis unifilis (yellow-spotted side neck turtle) along the point bars of the Javaés River in Bananal Island, demonstrates a clear preference of these chelonians for differentiated geological environments, in respect to the morphology, grain size or height of the nests in relation to the level of the river. The topographical distribution and the differences in the grain size of the sediments that compose the point bars of the river, originated from the multiple sedimentary processes, and make possible the creation and separation of different nesting environments. Each turtle species takes advantage of the place that presents physiographic characteristics appropriate to the hatching success of their eggs. The superposition of the P. expansa and P. unifilis nest placement areas is rare. The P. expansa nests are concentrated on the central portion of the beaches where successive depositional sedimentary events produced sandy banks more than 3.3 m above the river water level. The P. unifilis nests are distributed preferentially in the upstream and downstream portions along the point bars where the sandy deposits rarely surpass 1.5 m at the moment of laying. P. expansa nests located on the beaches of fine to medium sized sand hatch in a mean of 68 days, while those incubated on beaches of medium to coarse sand size take a mean of 54 days to hatch.
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Havryshkiv, Halyna, and Natalia Radkovets. "Paleocene deposits of the Ukrainian Carpathians: geological and petrographic characteristics, reservoir properties." Baltica 33, no. 2 (December 28, 2020): 109–27. http://dx.doi.org/10.5200/baltica.2020.2.1.
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The Paleocene Yamna Formation represents one of the main oil-bearing sequences in the Ukrainian part of the Carpathian petroleum province. Major oil accumulations occur in the Boryslav-Pokuttya and Skyba Units of the Ukrainian Carpathians. In the great part of the study area, the Yamna Formation is made up of thick turbiditic sandstone layers functioning as reservoir rocks for oil and gas. The reconstructions of depositional environments of the Paleocene flysch deposits performed based on well log data, lithological and petrographic investigations showed that the terrigenous material was supplied into the sedimentary basin from two sources. One of them was located in the northwest of the study area and was characterized by the predominance of coarse-grained sandy sediments. Debris coming from the source located in its central part showed the predominance of clay muds and fine-grained psammitic material. The peculiarities of the terrigenous material distribution in the Paleocene sequence allowed singling out four areas with the maximum development (> 50% of the total section) of sandstones, siltstones and mudstones. The performed petrographic investigations and the estimation of reservoir properties of the Yamna Formation rocks in these four areas allowed establishing priority directions of further exploration works for hydrocarbons in the study territory.