Tidal Flat Environments Research Articles

The Three Forks playa lake depositional model: Implications for characterization and development of an unconventional carbonate play

The Upper Devonian Three Forks Formation of the Williston Basin is an important reservoir interval in the Bakken petroleum system, with estimates suggesting greater than 3.7 billion bbl of recoverable oil. Detailed stratigraphic analyses are sparse, but current studies propose shallow marine, tidal flat, or coastal sabkha environments for its deposition. Based on stratigraphic, sedimentological, and petrographic analyses of 28 cores, we infer that the Three Forks Formation was deposited in a continental setting with little to no marine influence. The setting was subaerial to subaqueous environments comparable to those found in playa lake systems or continental sabkhas. Late Devonian paleography and tectonics provided the isolation and slow subsidence of the Williston Basin that led to the accumulation of the Three Forks Formation in a hot and arid climate. Occasional floods were responsible for the deposition of the terrigenous sediments, debrite-like deposits, reworking, bedforms, scouring, and erosional surfaces. Flood waters collected in ephemeral lakes and ponds evaporated, resulting in the deposition of subaqueous dolomite, anhydrite, and even halite. The ponds and lakes progressively evaporated and contracted until they eventually dried out. The drying is characterized by dewatering structures, subaerially exposed and transported sediments with ripples, scour surfaces, evaporite cemented surfaces, evaporite removal breccias, halite pseudomorphs, and a variety of cracks. Vertical successions record an upward trend of increasing proportions of subaqueous facies, indicating a transition from arid to relatively less arid climatic conditions during Three Forks deposition. This depositional system resulted in the accumulation of a complex mosaic of lithologies composed of different proportions and textures of silt-sized detrital dolomite and quartz, clay, and evaporites in patchy to bull’s-eye configurations. This depositional model provides a coherent understanding of the existing depositional lithofacies and their petrophysical and geomechanical properties and provides the background for the prediction of their lateral distribution from wire-line logs.

Stratigraphical and Sedimentological Review of the Merawu Formation, Serayu Basin, Central Jawa, Indonesia

DOI: 10.17014/ijog.5.2.117-128Merawu Formation is widely distributed in the Serayu Basin, Central Jawa, Indonesia. The formation is dominated by fine-grained clastic sediments comprising interbedded mudstone, siltstone, and sandstone. In the field, these outcrops are well exposed and well bedded. Stratigraphically, the Merawu Formation is underlain by the Paleocene Worawari Formation and overlain by the Late Miocene Penyatan Formation. Contacts between the Merawu Formation and the Worawari Formation are always found as fault types. Twelve sections have been done during the field work. Two members were identified within the Merawu Formation (Sandstone and Mudstone Members) in the field, where they interfinger each other. Previously, researchers interpreted the Merawu Formation as a turbidite sequence of deep marine deposits and depicted Early - Middle Miocene in age. However, the interpretation from the present research shows that the Merawu Formation was deposited on a tidal flat environment and has Early Miocene - Pliocene age, based on foraminifers found in some sections.

Magnetic characteristics of sediments from a radial sand ridge field in the South Yellow Sea, eastern China, and environmental implications during the mid- to late-Holocene

Proxy records from radial sand ridge fields are essential for understanding sedimentary environmental changes forced by climate-driven coast and sea level variations that affect large river inlets. We conducted a systematic environmental magnetic study on sediments from a radial sand ridge field in the South Yellow Sea, eastern China. From 41.6 to 0 m, the sediments of core YZ07 derive from river mouth, littoral and modern tidal flat environments. Magnetic measurements indicate that magnetite and hematite dominate the studied magnetic mineral assemblages. Magnetic mineral contents are highest in the river mouth environment and lowest in the modern tidal flat environment. The magnetic minerals in the core YZ07 sediments can be attributed primarily to detrital inputs rather than biogenic sources. The highest χ and SIRM values and lowest χARM/SIRM and χARM/χ values reflect relatively warm and humid climate conditions respectively during the period ∼7000 to 2900 a B.P. (41.6–24.73 m). Compared with the period ∼7000 to 2900 a B.P. (41.6–24.73 m), the period between ∼2900 and 870 a B.P. (24.73–5.14 m) is characterized by lower χ, χARM and SIRM values and higher χARM/SIRM and χARM/χ values, which indicate cool and dry climatic conditions. Our results reconfirm known regional climatic events that demonstrate Holocene climatic instability. Gradual decreases in χ and SIRM and increases in χARM/SIRM, χARM/χ and χfd characterize the sediments after 870 a B.P. (5.14–0 m). As indicated in previous studies, these changes were influenced by diversion of the Yellow River. Additionally, spectral analysis of the χ and χARM/SIRM records reveals rapid climatic fluctuations on millennial and centennial scales that coincide with those recorded in marine sedimentary records from adjacent regional seas. These results are important for investigations into the interactions between regional systems and global change in monsoonal climatic regions, thus providing an example of the evolution of a large scale geomorphic feature resulting from river-sea interaction.

「가고 싶은 섬」의 갯벌과 토양환경 특성 (Ⅱ) - 손죽도, 장도, 생일도, 기점․소악도를 중심으로 -

「가고 싶은 섬」의 갯벌과 토양환경 특성 (Ⅱ) - 손죽도, 장도, 생일도, 기점․소악도를 중심으로 -

Paleogeography and shale development characteristics of the Late Permian Longtan Formation in southeastern Sichuan Basin, China

Abstract The Late Permian Longtan Formation is extensively developed within the southeastern Sichuan basin which lies on the western margin of the Yangtze Plate in southwestern China. The stratigraphy and sequence boundaries of the Longtan Formation were interpreted from a combined study of field data, well log data and various data analysis in order to determine the extent and thickness of shale sequences. This interpretation defined the broad sequence stratigraphic framework and separated the Longtan Formation into three 3rd-order sequences. In addition, the formation was divided into five sedimentary facies using sedimentary, paleontological, geophysical and other data. The facies identified were fluvial, low energy shore, tidal flat, melanged accumulated shelf and platform basin. Three paleogeographic maps were created based on the 3rd-order sequences: SQ1, SQ2 and SQ3. The study shows that SQ1- SQ3 sedimentary environment of the study area, which extends from the southwest to northeast, was developed followed by fluvial, shore, tide, shallow water melanged accumulation shelf, deep water melanged accumulation shelf and platform basin. The mud shale rock types of the Longtan Formation that were identified are carbonaceous mud shale, silty mudstone and lime mudstone. According to the divided standard of mud shale effective thickness, there are three mud shale assemblages present in the sequences SQ1, SQ2, SQ3, namely, mud shale with sandstone, mud shale with limestone, and mud shale. SQ1 has the thickest mud shale identified on well logs. Mud shale with sandstone was well developed in the southwest of the study area and was interpreted to have been deposited in a shore or tidal flat sedimentary environment. This rock assemblage has a large effective thickness and extensive lateral distribution. In contrast, the assemblage of mud shale with limestone was mainly developed in the northeast of the study area and was interpreted to have formed in a melanged accumulation shelf sedimentary environment. The effective thickness of the mud shale with limestone is small and the distribution is limited. There is developed mud shale in above two type's sedimentary environment, but the distribution is also limited. The Longtan Formation's mud shale reached stage B diagenesis and is principally composed of quartz and clay minerals. The average quartz content is 43.40% and the average clay mineral content, which is mainly composed of illite, mixed illite/smectite, chlorite and kaolinite, is 39.58%. The sedimentary environment has controlled the distribution of minerals within the sequences. The clay mineral content gradually decreases as the sedimentary environment changes from shore-tidal flat in the southwest to deep water melanged accumulation shelf in the northeast. Therefore this comprehensive analysis shows that the southwest of the study area is the key area for shale gas exploration in the Longtan Formation.

The sedimentary evolution of Yangtze River delta since MIS3: A new chronology evidence revealed by OSL dating

Abstract The Yangtze River delta, one of the largest tide-dominated deltas in the world, is a valuable archive for studying the land-sea interaction. Previous investigations have mainly focused on the Holocene Yangtze River delta initiation and the coastal dynamics in response to sea level changes based on analysis of the stratigraphic and sedimentologic evidences. However, the detailed depositional history of the Yangtze River delta prior to Holocene is still poorly understood owing to a deficiency of accurate absolute chronologies. In this study, a 60-m-long core (EGQD14) was drilled in the front edge of modern Yangtze River deltaic plain. The sedimentary features were analyzed based on the data of sediment particle size composition, colors, textures and intra-structure description; a total of 20 sediment samples were collected from this core for optically stimulated luminescence (OSL) dating. The single aliquot regenerative dose (SAR) protocol was applied to fine (4–11 μm in diameter) and coarse (63–100 μm or 100–200 μm) grained quartz extracts to determine their equivalent dose (De). The bleaching levels of different grain-sized fractions were investigated. We found that 63–100 μm grains and fine grains are generally well-bleached, and are appropriate for establishing the chronology of the studying core. However, ages of 100–200 μm grains appear to be problematic as potential feldspar contamination, revealed by remarkable infrared (IR) depletion ratios as low as to 0.3. Thus, ages derived only from 4–11 μm and 63–100 μm fractions were used for the reconstruction of chronological framework. The sedimentary history of the Yangtze River delta since the Marine Isotope Stage 3 (MIS3) was inferred by combination of a 50-ka spanning stratigraphic sequence of the EGQD14 core with previously investigated sedimentary stratigraphy in the study area. This study provided a new chronological evidence of the Yangtze River delta sedimentary evolution over the last ∼50 ka, which generally underwent the terrestrial fluvial, floodplain, tidal flat, estuary-neritic, deltaic and modern Yangtze River delta plain sedimentary environments.

Isotopic evidence for oxygenated Mesoarchaean shallow oceans

Mass-independent fractionation of sulfur isotopes (MIF-S) in Archaean sediments results from photochemical processing of atmospheric sulfur species in an oxygen-depleted atmosphere. Geological preservation of MIF-S provides evidence for microbial sulfate reduction (MSR) in low-sulfate Paleoarchaean (3.8–3.2 billion years ago (Ga)) and Neoarchaean (2.8–2.5 Ga) oceans, but the significance of MSR in Mesoarchaean (3.2–2.8 Ga) oceans is less clear. Here we present multiple sulfur and iron isotope data of early diagenetic pyrites from 2.97-Gyr-old stromatolitic dolomites deposited in a tidal flat environment of the Nsuze Group, Pongola Supergroup, South Africa. We identified consistently negative Δ33S values in pyrite, which indicates photochemical reactions under anoxic atmospheric conditions, but large mass-dependent sulfur isotope fractionations of ~30‰ in δ34S, identifying active MSR. Negative pyrite δ56Fe values (−1.31 to −0.88‰) record Fe oxidation in oxygen-bearing shallow oceans coupled with biogenic Fe reduction during diagenesis, consistent with the onset of local Fe cycling in oxygen oases ~3.0 Ga. We therefore suggest the presence of oxygenated near-shore shallow-marine environments with ≥5 μM sulfate at this time, in spite of the clear presence of an overall reduced Mesoarchaean atmosphere.

Facies characteristics and depositional environments of the middle Eocene (Lutetian) Harudi Formation, Kachchh, Western India

The 8.5 m thick, 1.4 km long and 0.35 km wide, ESE–WNW oriented cliff section (N 23°31′32″ E 68°41′00″) exposed across Harudi–Baranda road is extensively studied for its facies characteristics and based on that depositional environments of the middle Eocene (Lutetian) Harudi Formation are deciphered in the present study. Two cycles of grey mudstone alongwith nodular limestone–coquina limestone-gypsiferous mudstone facies in the lower part of the succession suggest sedimentation in coastal quiet-water lagoonal to tidal flat environments, while glauconitic shale, bioclastic packstone and gypsiferous foraminiferal packstone facies in the upper part suggest sedimentation on middle- to inner-shelf and tidal flat depositional environments. In all, three shallowing upward cycles have been identified in the studied outcrops and based on that lagoonal-middle shelf-inner shelf-tidal flat depositional environments are suggested for the middle Eocene Harudi Formation.

潮汐環境の堆積物 : 日本の干潟の理解に向けて( 干潟の自然,その過去と現在)

潮汐環境の堆積物 : 日本の干潟の理解に向けて( 干潟の自然,その過去と現在)

Reservoir quality along a homoclinal carbonate ramp deposit: The Permian Upper Dalan Formation, South Pars Field, Persian Gulf Basin

Permo-Triassic carbonate successions host some of the largest oil and gas reserves in the Arabian Plate, including the world's largest gas reservoirs of the Upper Dalan and the Kangan formations in the South Pars Gas Field, Persian Gulf Basin. Both formations are stratigraphically equivalent to the Upper Khuff Formation which has been long recognized as a major oil and gas reservoir in the Arabian Peninsula. The Permian Upper Dalan Formation is composed mainly of mixed carbonate-evaporite sequences that formed on a laterally continuous homoclinal carbonate ramp with significant variations in reservoir heterogeneity and quality. They can be grouped in 18 microfacies. High reservoir qualities are found within high-energy shoal environments with a tendency of the best reservoir quality to occur towards the basin in a mid-ramp setting. In contrast, low-energy tidal flat environments exhibit the poorest reservoir quality. Reservoir quality from lagoonal environments is diverse. Diagenesis has significantly affected reservoir properties by both enhancing and destroying original porosity and permeability. Bivariate plots of porosity and permeability values, combined with thin section petrography indicate that pore-filling “pervasive” and poikilotopic anhydrite cements had the greatest negative impact on the reservoir quality whereas dolomitization and dissolution of grains and cements played the most positive role. Two third-order sequence stratigraphic cycles link lithologies and depositional environments to sea-level fluctuations. HSTs are associated with better reservoir characteristics than TSTs.

Provenance and depositional variability of the Thin Mud Facies in the lower Ganges-Brahmaputra delta, West Bengal Sundarbans, India

The Sundarbans is one of the largest coastal wetland sites in the world and covers an area of approximately one million hectares of the western delta of the Ganges and Brahmaputra (G-B) rivers (located across Bangladesh and India). Since the late Holocene, the western delta has not been directly fluvially sourced, due to the Ganges shift to the east (present-day Bangladesh). The depositional facies (Thin Mud Facies) of the late-Holocene abandoned western region (The Sundarbans) is derived from dominant estuary-tidal dynamics, however the provenance of the associated TMF sedimentation in this far western zone (Indian Sundarbans per se) is as yet equivocal. In this study, sediment cores from the Indian Sundarbans (Saptamukhi-Thakuran estuary) were closely examined for grain-size distributions (GSDs), mineralogy through X-ray diffraction (XRD), and geochemistry with X-ray fluorescence (XRF). The TMF in the West Bengal Sundarbans has been determined to show intensively weathered, terrestrial sediment, derived principally from the Ganges Alluvial Plain (GAP). There is a predominance of quartz, mica and clay minerals, with quartz interpreted as a product of low-relief tropical weathering sourced via the G-B Rivers draining the Himalayas. Lithofacies interpreted through GSD analysis of the TMF is indicative of a muddy tidal flat environment with aggradation and a general fining-up trend between the adjacent estuaries. The sediment provenance indicates a continuing G-B sediment source, which moves westward along the Bay of Bengal, from the active delta front and is then reworked over the far-western abandoned delta by tidal–estuarine forcing.

Sedimentary and evolutionary characteristics of Sinian in the Tarim Basin

Analysis of Sinian outcrops in the peripheral regions of the Tarim Basin, drilling and seismic data within the Tarim Basin, and combined with previous studies, distribution of Sinian strata, tectonic setting, sedimentary system and lithofacies palaeogeography were well discussed. Results showed that three sedimentary systems were developed in the Sinian System of the Tarim Basin, i.e. the clastic sedimentary system, the clastic-carbonate mixed sedimentary system, and the carbonate sedimentary system, vertical sedimentary characteristics evolved from the clastic sedimentary system to the carbonate sedimentary system. These three sedimentary systems were corresponded to three transgression-regression cycles in the Sinian. The marine transgression during the initial period of the Early Sinian (ZSQI) resulted in development of the clastic sedimentary system in the lower part of the Lower Sinian; the transgression during the late period of the Early Sinian (ZSQII) led to formation of the clastic-carbonate mixed sedimentary system in the upper part of the Lower Sinian; the transgression during the initial period of the Late Sinian (ZSQIII) resulted in development of carbonate sedimentary system in the Upper Sinian. Three regressions resulted in formation of three unconformities, which were on the middle part of the Lower Sinian, the top of the Lower Sinian and the top of the Upper Sinian respectively. Due to breakup of Rodinia supercontinent in the Neoproterozoic, the Tarim Basin was in the continental rifting evolutionary process. In the Sinian, the basin experienced evolutionary processes of intra-cratonic depression and passive continental margin, thus characteristic of the lithofacies palaeogeography was characterized by uplifts in the south and depressions in the north. In the Early Sinian, the Tarim Basin developed the Bachu-Tazhong-Tadongnan uplift and the Tabei residual ancient land, and the shore-shelf sedimentary environment in the north as well as the shore-shelf-bathyal sedimentary environment in the southwest. In the Late Sinian, the Tabei residual ancient land disappeared; the basin developed the tidal flat sedimentary environment in the north and the neritic sedimentary environment of the passive continental margin in the southwest.

On the application of contemporary bulk sediment organic carbon isotope and geochemical datasets for Holocene sea-level reconstruction in NW Europe

Bulk organic stable carbon isotope (δ13C) and element geochemistry (total organic carbon (TOC) and organic carbon to total nitrogen (C/N)) analysis is a developing technique in Holocene relative sea-level (RSL) research. The uptake of this technique in Northern Europe is limited compared to North America, where the common existence of coastal marshes with isotopically distinctive C3 and C4 vegetation associated with well-defined inundation tolerance permits the reconstruction of RSL in the sediment record. In Northern Europe, the reduced range in δ13C values between organic matter sources in C3 estuaries can make the identification of elevation-dependent environments in the Holocene sediment record challenging and this is compounded by the potential for post-depositional alteration in bulk δ13C values. The use of contemporary regional δ13C, C/N and TOC datasets representing the range of physiographic conditions commonly encountered in coastal wetland sediment sequences opens up the potential of using absolute values of sediment geochemistry to infer depositional environments and associated reference water levels. In this paper, the application of contemporary bulk organic δ13C, C/N and TOC to reconstruct Holocene RSL is further explored. An extended contemporary regional geochemical dataset of published δ13C, C/N and TOC observations (n=142) from tidal-dominated C3 wetland deposits (representing tidal flat, saltmarsh, reedswamp and fen carr environments) in temperate NW Europe is compiled, and procedures implemented to correct for the 13C Suess effect on contemporary δ13C are detailed. Partitioning around medoids analysis identifies two distinctive geochemical groups in the NW European dataset, with tidal flat/saltmarsh and reedswamp/fen carr environments exhibiting characteristically different sediment δ13C, C/N and TOC values. A logistic regression model is developed from the NW European dataset in order to objectively identify in the sediment record geochemical groups and, more importantly, group transitions, thus allowing the altitude of reference water levels to be determined. The application of this method in RSL research is demonstrated using the Holocene sediments of the Mersey Estuary (UK), in which δ13C, C/N and TOC variability is typical of that encountered in Holocene sediments from C3 coastal wetlands in NW Europe. Group membership was predicted with high probability in the depositional contexts studied and the accuracy of group prediction is verified by microfossil evidence. The method presented facilitates the application of δ13C, C/N and TOC analysis in RSL reconstruction studies in C3 vegetated wetlands throughout temperate NW Europe.

Digitized Outcrop Geomodeling of Ramp Shoals and its Reservoirs: as an Example of Lower Triassic Feixianguan Formation of Eastern Sichuan Basin

AbstractNumerous hydrocarbon accumulations are found in ramp crest shoals worldwide and therefore this depositional setting has a high potential of being the hydrocarbon reservoir. In this paper, we combined digital outcrop geology and traditional geological mapping to build an outcrop‐based geocellular model of the ramp‐crest shoal complex of the Lower Triassic Feixianguan Formation in the Eastern Sichuan Basin. The outcrop model serves as an analogue for the subsurface reservoir of the Feixianguan Formation and illustrates the complexity of the lithofacies types, stratigraphic architecture, and reservoir heterogeneities at a scale below conventional subsurface data resolution. The studied ramp‐crest shoal complex consists of thirteen types of lithofacies that can be grouped into three facies‐groups corresponding to subtidal intraclastic shoal, sub‐ to inter‐tidal oolitic shoal, and tidal flat depositional environments respectively. The stratigraphic architecture of the shoal complex shows mostly a strong progradation of the high energy facies associated with an overall decrease of accommodation space associated with relative sea level still stand. Two reservoir facies associations have been recognized. The first one consists of supratidal dolomudstone and upper intertidal partially dolomitized oolitic packstone with anhydrite or nodules. These facies were deposited above the high energy oolitic grainstones and occurs as thin‐bedded and laterally continuous layers, characterized by high porosity and low permeability. The second reservoir facies association is composed of intertidal crystalline dolomite and subtidal intraclastic bindstone that occurs stratigraphically below the oolitic grainstones. These deposits consist of massive laterally discontinuously beds, and are characterized by high porosity and high permeability. Both types of reservoir facies tend to be stacked vertically and migrated laterally with the progradation of the shoal complex. The construction of the outcrop‐based 3D geological model provide a description and quantification of the facies distribution within a robust stratigraphic framework and the style and amount of reservoir heterogeneities associated with a ramp‐crest shoal complex reservoir such as the one found in Lower Triassic Feixianguan Formation and Cambrian Longwangmiao Formation in Sichuan Basin or other ramp‐crest reservoir worldwide.

Middle Ordovician acritarchs and problematic organic-walled microfossils from the Saq-Hanadir transitional beds in the QSIM-801 well, Saudi Arabia

Core samples from the QSIM-801 water well, drilled in central Saudi Arabia, cover a 93-foot interval spanning the transition between the Sajir Member of the Saq Formation, that consists mainly of sandstones of tidal sand flat environments, and the Hanadir Member of the Qasim Formation, characterized by argillaceous graptolitic mudstones, corresponding to a tidal delta front. The samples contain abundant, exceptionally well-preserved and diverse palynomorphs, which include cryptospores, acritarchs and chitinozoans, other problematic organic-walled microfossils as well as other organic particles such as cuticle-like fragments. The studied interval is biostratigraphically well constrained by the presence of chitinozoans of the formosa and pissotensis Zones of late-early to late Darriwilian age (Middle Ordovician) in the uppermost Saq Formation and Hanadir Member. The biostratigraphic age of the Sajir Member considered to span the Dapingian–Darriwilian boundary, is re-discussed based on the results herein. The uppermost part of the Sajir Member yielded the ichnofossil, Phycodes fusiforme. Acritarch assemblages from the Sajir Member of the Saq Formation are poorly diversified and dominated by sphaeromorphs. More diverse assemblages of acritarchs, associated with enigmatic forms, occur in the Hanadir Member of the Qasim Formation. The contact between the two formations and the transition between the palynomorph assemblages are sharp, suggesting a stratigraphic hiatus. A quantitative analysis allows us to discuss the paleoenvironmental changes and possibly climatic changes associated with an hypothesis of ice house conditions during this period. Among the diagnostic acritarch taxa observed are Frankea breviuscula, F. longiuscula, Baltisphaeridium ternatum, Dasydorus cirritus, Dicrodiacrodium ancoriforme, Poikilofusa ciliaris, Pterospermopsis colbathii and Uncinisphaera fusticula. These are associated with other typical forms known to range across the Lower–Middle Ordovician boundary, such as Aremoricanium rigaudae, Aureotesta clathrata, Barakella fortunata, B. rara, Baltisphaeridium klabavense, Glaucotesta latiramosa and Striatotheca spp. Galeate and peteinoid acritarchs are also well represented, as well as tiny forms of ultraplanctonic size. Three new species of acritarchs are proposed: Frankea longiuscula var. darriwilense var. nov, Micrhystridium regulum sp. nov, and Tyrannus proteus sp. nov. Repeated occurrences throughout the section of cryptospores, problematic microfossils such as organic filaments, cuticle-like tissues, striated and pigmented leiospheres frequently in clusters, are interpreted to reflect recurrent terrestrial and freshwater inputs in the depositional environment. Single-specimen, high-resolution analyses using Confocal Laser Scanning Microscopy on the enigmatic form Tyrannus proteus sp. nov. show fluorescence emission spectra and microstructural properties significantly different from those of typical marine acritarchs from the same levels.

Depositional facies model and reservoir characterization of USANI field 1, Niger delta basin, Nigeria

The 3-D depositional environment was built using seismic data. The depositional facies was used to locate channels with highly theif zones and distribution of various sedimentary facies. The integration core data and the gamma ray log trend from the wells within the studied interval with right boxcar/right bow-shape indicate muddy tidal flat to mixed tidal flat environments. The bell–shaped from the well logs with the core data indicate delta front with mouth bar, the blocky box- car trend from the well logs with the core data indicate tidal point bar with tidal channel fill. The integration of seismic to well log tie display a good tie in the wells across the field. The attribute map from velocity analysis revealed the presence of hydrocarbons in the identified sands (A, B, C, D1, D2, D4, D5). The major faults F1, F2, F3 and F4 with good sealing capacity are responsible for hydrocarbon accumulation in the field. Detailed petro physical analysis of well log data showed that the studied interval are characterized by sand-shale inter-beds. Eight reservoirs were mapped at depth intervals of 2886m to 3533m with their thicknesses ranging from 12m to 407m. Also the Analysis of the petrophysical results showed that porosity of the reservoirs range from 14% to 28 %; permeability range from 245.70 md to 454.7md; water saturation values from 21.65% to 54.50% and hydrocarbon saturation values from 45.50% to 78.50 %. The by-passed hydrocarbons were identified and estimated in low resistivity pay sands D1, D2 at depth of 2884m – 2940m, sand D5 at depth of 3114m – 3126m respectively. The model serve as a basis for establishing facies model in the field.

Post-glacial sequence and sedimentation in the western Bohai Sea, China, and its linkage to global sea-level changes

Post-glacial sedimentary sequences provide a unique window for observing depositional and environmental responses to rapid changes in global climate and sea level. Here, we integrate seismic records and the lithological variations of sediment cores from western Bohai Bay, China, in order to reveal the history of sedimentation and its linkages to global sea-level changes since marine isotope stage 2 (MIS 2). The post-glacial succession consists of six seismic units (SU1–SU6, in descending order) which are bounded by six key reflection surfaces (T0, R1, R2, R3, T1 and T2), respectively corresponding to six depositional units (DU1–DU6) identified in sediment cores. Together they comprise the latest sequence of infilling of western Bohai Bay, where SU6 is associated with the Lowstand Systems Tract (LST), SU5 is associated with the Transgressive Systems Tract (TST), and the last four units of SU4–SU1 comprise the complex Highstand Systems Tract (HST). During the interval of the MIS 2 (22–11.6kyrBP) sea level lowstand, the LST was formed in a long-term environment of sub-aerial exposure or fluvial floodplain. The TST is composed of transgressive deposits formed during the interval of global sea-level rise, and is characterized by a retrogradational feature, from a swamp to a tidal flat environment, and then to an estuarine subtidal environment. A series of sedimentary facies transitions represent abrupt sea-level rises in the early Holocene, which may correspond to the events MWP-1C, “8.2-ka event” and MWP-2. Erosional trenches were well developed within SU5 in the central-eastern region, and were probably part of a transgressive waterway system rooted from Bohai Strait. They demonstrate that Bohai Bay experienced strong tidal erosion in the early Holocene, as a result of its morphology which consisted of a long narrow embayment. The complex HST was initially formed at ca. 7calkyrBP when sea-level essentially stabilized in a highstand, and developed rapidly after ca. 6calkyrBP when the Yellow River supplied large amounts of sediment to the western or southwestern margin of Bohai Bay. Its complex internal structure is related to the configuration of three flooding surfaces caused by changes in sediment supply, and which in historical times separated four stages of river discharge, mainly from the Yellow River. During ca. 7.0–3.4calkyrBP, the Yellow River at one time emptied into the southwestern margin of Bohai Bay, forcing its subaqueous delta to extend over the southern area of western Bohai Bay, while open shelf sedimentation in the central and northern area of Bohai Bay consisted of the accumulation of a shelly layer subject to intensive storm-reworking. During ca. 3.4–1calkyrBP, the Yellow River once discharged into the central and northern parts of western Bohai Bay, forming two detached subaqueous deltas. During ca. 1–0.8calkyrBP, the Yellow River discharged into the central region, stacking a subaqueous delta confined by the two older underlying subaqueous deltas. During the last ~800years, the discharge of the Yellow River out of Bohai Bay has dominated coastal marine sedimentation which has a complex provenance.

Marinobacter salinus sp. nov., a moderately halophilic bacterium isolated from a tidal flat environment.

Two Gram-stain-negative, aerobic, motile, halophilic, rod-shaped bacteria, designated Hb8T and Hb20, were isolated from a tidal flat environment located on the South-West Korean peninsula. The isolates grew at 10-37 °C, at pH 5.0-9.0 and in NaCl concentrations of 0.5-15 % (w/v; optimum, 3.0-6.0 %). Sequence analysis of the 16S rRNA indicated that the isolates belong to the genus Marinobacter and are most closely related to Marinobacter sediminumR65T (98.3 %), followed by Marinobacter lipolyticus SM19T, Marinobacter salsuginis SD-14BT and Marinobacter similis A3d10T. The overall 16S rRNA gene sequence similarity with these species was 97.9 %, but Hb8T and Hb20 showed 100 % sequence similarity with each other. DNA-DNA relatedness values of H8T and Hb20 suggested that these isolates represent a single species, while DNA-DNA relatedness values of the two novel isolates with M. sediminum DSM 27079T and M. similis DSM 15400T were only 21.3 and 22.9 %, respectively. The major fatty acids present in strain Hb8T were identified as C16 : 0, C16 : 1ω9c, C18 : 1ω9c, C18 : 0 3-OH and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c). Ubiquinone-9 was the main respiratory quinone in both the novel strains. The polar lipids found to be present included diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, four unidentified phospholipids and five unidentified lipids. The genomic DNA G+C content of Hb8T and Hb20 was 54.5 mol%. Polyphasic analysis indicated that the two isolates are representatives of a novel species of the genus Marinobacte, for which the name Marinobacter salinus sp. nov. is proposed. The type strain is Hb8T (=KCTC 52255T=JCM 31416T).

Sedimentary Conditions of Evaporites in the Late Jurassic Xiali Formation, Qiangtang Basin: Evidence from Geochemistry Records

The Qiangtang Basin (QB), located in the central Tibetan Plateau, is a Jurassic marine basin and one of the most important prospective salt resource belts in China. In recent decades, many outcrops of gypsiferous bed have been found in the Jurassic marine strata in the basin. Salt springs with abnormally high sodium (Na+) contents had been identified in the Late Jurassic Xiali Formation (Fm.) in the basin in the last years. However, to date, no potash or halite deposits have been identified in the QB. Gypsum outcrops and salt springs are very important signs in the investigation of halite and potash deposits. Therefore, the Xiali Fm. is a potentially valuable layer to evaluate for the possible presence of halite and potash deposits in the basin. However, few studies have explored the formation conditions of evaporites in the unit. Here, we present detailed geochemical records from the Yanshiping section related to the study of the formation conditions of evaporites in the Xiali Fm. of the QB. Climate proxies based on the obviously increased anion concentrations of SO42- and Cl- and the significant correlation coefficients of Ca2+-SO42- (R = 0.985) and Na+-Cl- (R = 0.8974) reveal that the upper member of the Xiali Fm. (the upper Xiali Fm.) formed under an arid climate and evolved into the sulfate phase or early chloride phase. Provenance proxies based on the obviously increased K+ and Na+ ion concentrations and the significant correlation coefficient of Na+-Cl- (R = 0.8974) suggest that the upper Xiali Fm. featured optimal provenance conditions for the possible formation of halite deposits. The regression and the semi-closed tidal flat environment in the upper Xiali Fm. were favorable for the formation of potash and halite deposits. The low Mg2+ /Ca2+ values (mean value = 1.82) and significant Na+-Cl- correlation coefficient (R = 0.8974) also suggest that the upper Xiali Fm. is the layer most likely to contain potential halite deposits. In addition, the macroscopic correlations of tectonism, provenance, paleoclimate, saliferous strata and sedimentary environment between the QB and the adjoining Amu Darya Basin in Central Asia reveal that the two basins shared similar geologic settings that were favorable for the formation of evaporites during the Late Jurassic. Therefore, the upper Xiali Fm. is a valuable layer to explore for halite deposit and may be potentially valuable in the future exploration for potash deposits in the QB.

Facies Analysis and Depositional Environment of Upper Permian Rocks in Darin Section, East-Central Iran

Deposits of Permian rocks in Kalmard Block are recognized with Khan Group, showing various characteristics in different outcrops. This group is made up of three informal formations, namely Chili, Sartakht and Hermez. Upper Permian deposits (Hermez Formation) are composed chiefly of lateritic and carbonate rocks. This formation is composed of 65.5 m lateritic soils, lateritic sandstone, limestone, dolomite and dolomitic limestone in the Darin section. This formation unconformably overlies middle Permian siliciclastic and evaporite deposits (Sartakht Formation), where as it is depicted underlying an erosional unconformity above lateritic deposits of lower Triassic (Sorkh Shale Formation). According to lithologic and microscopic investigations, the deposits of Hermez Formation can be divided into 1 siliciclastic petrofacies and 14 carbonate microfacies. Field observations, along with microscopic examinations, have resulted in identifying tidal flat, lagoon, shoal and open marine environments in the rocks of the studied formation. Vertical changes of microfacies and depth variation curve point to the high thickness of the microfacies of lagoon, tidal flat and shoal environments and low thickness of open marine microfacies. Hermez Formation rocks in Darin section are deposited in a low-angle homoclinal ramp, mostly in the inner ramp, located in the southern Paleo-Tethys Ocean.