Sedimentology

A steep-margined carbonate platform is developed in the Carboniferous synorogenic foreland basin of northern Spain. Dips of 60–90° produced during Late Carboniferous thrusting enable cross-sections of a 4-km-wide portion of the marginal area of this platform (Las Llacerias outcrop) to be studied in aerial photographs at a seismic scale. Three stratal domains are observed: (1) a horizontal-bedded platform; (2) a clinoformal-bedded margin with a relief of up to 500 m; and (3) a low-angle toe-of-slope, where slope beds interfinger with basin sediments. The slope shows well-bedded sigmoidal clinoforms with depositional dips ranging from 15° to 32°. Based on lithology and stratal patterns, four facies groups have been recognized: (1) a flat-topped platform, in which thick algal boundstone, skeletal packstone–grainstone and peloidal micrite wackestone with a poorly rhythmic character prevail; (2) the platform margin and upper slope, characterized by microbial boundstone spanning a bathymetric range of ≈150 m measured from the break of slope; (3) a slope, predominantly composed of margin-derived rudstones and breccias; and (4) a toe-of-slope to basin zone, where a cyclic alternation of spiculitic siltstones, packstone to grainstone calciturbidites and rudstone/breccia is visible. Five successive stages of platform development are deduced: (1) Bashkirian: flooding of the pre-existing Serpukhovian platform giving rise to the nucleation of a low-angle ramp to the south-east of the study area with microbial mud-mound accumulations, and breccias and calciturbidites on the margins; (2) Early Moscovian: an influx of siliciclastic sediment buried part of the platform and reduced the area of carbonate sedimentation; (3) Moscovian: aggradation and progradation of the carbonate system produced an extensive steep-margined and flat-topped shallow-water platform (shelf system); (4) Latest Moscovian–earliest Kasimovian: drowning of the platform; and (5) Kasimovian: covering of the platform by marly calcareous ramp sediments.

This study focusses on aspects related to carbonate build-ups in an upper Paleozoic succession in the south central Norwegian Barents Sea. Seismic and well data are used to map and characterize the protozoan and heterozoan carbonate build-ups in order to assess the factors that control their distribution within the Gipsdalen- and Bjarmeland Groups. The main objectives are (1) to describe, compare, and contrast geomorphological characteristics of the carbonate succession on the Bjarmeland and Finnmark Platforms, (2) to determine the controlling factors on the distribution of the carbonate build-up development, and lastly (3) examine the impact of evaporites on the distribution and development of the carbonate build-ups.

The upper section of the Gipsdalen Group consists of protozoan carbonates and evaporites with occasional carbonate build-ups that were deposited in an arid-warm marine environment in a global icehouse period. The Bjarmeland Group consists of heterozoan carbonates with build-ups deposited in post-glacial environment. Previous studies have suggested that faults play a role in the distribution of carbonate build-ups in the Norwegian Barents Sea.

The two areas on the Finnmark Platform (north and south) have been used in order to compare against two areas on Bjarmeland Platform (east and west). The carbonate build-up sequence observed on the eastern Bjarmeland Platform is comparable with the build-up sequence on the northern Finnmark Platform. The two areas share similarities as both are located on footwall uplifts. The geomorphology of these carbonate units are characterized as large build-up complexes. In contrast, the geomorphology of the western Bjarmeland Platform and the southern Finnmark Platform differs significantly. These units consist of polygonal build-up morphologies of reticulated arrangement with cellular structures of various scales; this depositional pattern is similar in architecture to modern patch and pinnacle reef systems observed in Holocene carbonate systems (e.g. Abrolhos Islands in Western Australia). The similarities defining these elements are that carbonate build-ups stack vertically above the layered evaporite sequence of the Gipsdalen Group. The layered evaporite sequences are observed on both platforms where salt pillows are a main characteristic. The carbonate build-ups deposit vertically above thin units of evaporites, opposed to laterally absent where the salt pillows are present, suggesting that salt has been displaced by the weight of the growing build-up. The result supports antecedent topography as a dominant component affecting the carbonate build-up succession in the eastern Bjarmeland Platform and the northern Finnmark Platform. Furthermore, the build-up development in the two areas on western Bjarmeland Platform, and southern Finnmark Platform, has been controlled by physical conditions influenced by a combination of biotic self-organization, fossil reef growth and karst-induced structures caused by dissolution of the underlying carbonate strata. The current geomorphology of the carbonate build-up succession has been enhanced due to remobilization of the mobile evaporite unit as a result of differential loading by the carbonate build-ups.

The Bingham model has been suggested for the rheological behaviour of debris flow. Velocity plotted against yield strength uniquely defines turbulent and laminar flow in published experimental data on flow of Bingham materials. These regimes are not defined by a unique value of ...

The geometry and sedimentology of 49 talus slope deposits have been analysed in the French Alps to show the effects of snow avalanche activity on their characteristics. Twenty slopes are heavily avalanche-modified, 15 are snow-avalanche boulder tongues and 14 are rockfall-talus slopes. Slope angle, slope segmentation, longitudinal and sorting indices provide criteria to differentiate these deposits. Although the transition from rockfall-to avalanche-dominated slopes is gradational, a Atransitional talusB is identified with distinctive characteristics. q

To understand the sedimentary processes in a lake environment, it is essential to investigate the morphological, sedimentalogical and limnological features of the basin. The present study was developed at Violão Lake, Serra Sul de Carajás. The methodological approach comprises the collection of bathymetric and sedimentary data, and shallow seismic profiles. Lake Violão has a NE-SW elongated guitar-shaped form and ~0.3 km2 of surface area, with a perimeter of ~2.7 km. The lake presents washing basin morphology and it is marked by a steep margin carved in duricrust outcrops, while the bottom is flat and constituted mainly by muddy sediments. The water column is stratified only during the dry season and it is mixed in the rainy season. Three seismic stratigraphic successions were identified in the lake resting on prominent basal reflector (bedrock), which reaches a maximum depth of ~15 m. Small lobate masses are deposited in the bottom of the lake from underflows, while the central par...

Low-frequency components of seismic data tend to characterize thicker litho-stratigraphic units, while high-frequency components tend to characterize thinner isochronous-stratigraphic units. Thus, frequency dependent interpretation can help to achieve fine sedimentary sequence analysis. However, in current seismic sedimentology method, a certain frequency profile generated by frequency filtering, loses some stratum reflection information, which is out of the limited frequency band. To achieve real frequency dependent stratum reflection profiles with whole stratum information, a time-varying sparse-spiking deconvolution based method is proposed in this paper. A synthetic example and a real delta progradation example show the accuracy and effectiveness of proposed method.

Bara Formation (Middle Paleocene) at Ranikot area is investigated for the purpose to interpret its environments of deposition, grain texture and textural maturity. Out of sieving data statistical parameters are calculated which are used to determine textural maturity and are plotted on interpretation diagrams. With multiple approaches such as the study of grains texture, plotting the statistical data on the diagrams of Passega (1964) and Stewart (1958) and by evaluating the textural maturity, it is interpreted that the Bara Formation sediments at Ranikot area were deposited under fluviatile/continental environments. The sandstone of Bara Formation at Ranikot has been classified as sub-mature and sub-mature to mature sandstones, respectively. Keywords: Sieving, Statistical parameters, Textural maturity, Interpretation diagrams, Depositional Environment

The laser diffraction (LD) is one of the most widely applied grain size measurement methods. The main advantages of LD are: (1) relatively short time of single measurement, (2) low cost of analysis, (3) simplicity of sample preparation, (4) great amount of acquired numerical data. One of the less frequently obtained parameters, often provided only by application of dedicated external hardware, is so-called “elongation parameter”, “grain shape factor” or “grain shape parameter”.
Due to the inability of direct export of numerical grain shape data from the Malvern Hydro Sight camera, authors proposed own method of digitalization and recalculation
of grain shape graphs produced by the Malvern software.
Acquired sedimentological and geochemical data were analysed using statistical methods, such as correlation/regression analysis and principal components analysis (PCA).
Proposed method of data extraction and analysis of grain shape parameters may be especially useful tool during investigation of Quaternary sediments and reconstruction of environmental changes.

The Mesoproterozoic Kaimur Group belonging to upper part of Vindhyan Supergroup, conformably overlies the carbonate sequence of Semri Group (Lower Vindhyan) in the Son Valley, central India. The Upper Kaimur Group consists of Dhandraul sandstone, Scarp sandstone and Bijaigarh shale. The detrital contents of the Dhandraul and Scarp sandstones are mainly composed of several varieties of quartz followed by feldspar, rock fragments, micas and heavy minerals. Fluid inclusion studies are carried out on the detrital and recrystallized quartz grains of the Dhandraul and Scarp sandstone to know about the fluid phases already present in the source rock and / or introduced in the recrystallisation process. Fluid micro-thermometry reveals the presence of two types of fluids: (i) bi-phase low saline aqueous inclusions, (ii) bi-phase high saline aqueous inclusion. These fluids were trapped during the development of grain and recrystallization processes. The salinity of these inclusions in the quartz grain is in the range of 5.7 to 13.4% suggests that initially there was good proportion of marine water during the initiation of sedimentation.

Low-temperature synthesis experiments on ferric oxide–water systems have resulted in disparate oxygen isotope fractionation–temperature (α-T) curves. In this study, recent ferric oxides, mostly goethites of Holocene age, were collected and analyzed from a variety of modern soil, stream, and marine environments, where formation temperature and the oxygen isotopic composition (δ18O) of the water from which ferric oxides precipitated can be independently measured or estimated. This allows comparison of experimental α-T relationships with data from natural systems.

Selective dissolution methods were refined for the pretreatment of fine-grained minerals in order to obtain reliable δ18O values for pure and crystalline ferric oxides. The difference (Δδ18O) between the δ18O value of goethite and that of local mean meteoric water ranges from −1.5 to +6.3‰ for soil goethites from New Jersey, Indiana, Michigan, Iowa, South Dakota, and Taiwan. We argue that these variations are largely the result of differences between the δ18O of formation water and that of local mean meteoric water, induced probably by 18O-enrichment of soil waters by evaporation or other processes in soil horizons where ferric oxides are forming. A marine goethite sample from Scotland and a subaqueous bog iron sample from New Jersey, which can not be biased by evaporative processes, provide crucial natural evidence that the difference in δ18O between goethite and formation water is ∼−1.5‰ at ∼10°C. This result is consistent with our prior laboratory synthesis results (Bao and Koch, 1999), but in conflict with other experimental calibrations. Given the highly variable δ18O value of soil or other surface water, as well as the potential of initially formed ferric oxides for reequilibration with subsurface burial fluids during maturation to crystalline phases, an understanding of formational and diagenetic conditions is absolutely essential when attempting to use the oxygen isotope composition of ferric oxides as a paleoclimatic proxy.

The succession of Early Jurassic formations was studied in terms of reservoir characters in two wells: Atrush-1 and Shaikhan-1B from the Atrush and Shaikhan oilfields, respectively, in the Duhok Governorate, Iraqi Kurdistan Region. The well Log data from these wells were used to achieve the objectives of the research. Well log data are commonly used to study petrophysical properties of the reservoir rocks. This task is accomplished through running Interactive Petrophysics software (IP). Log interpretation was supportive for: (1) Prediction of lithological characters and (2) calculation of shale volume, total porosity, effective porosity, secondary porosity, water saturation, water bulk volume, residual hydrocarbon, and movable hydrocarbon of each formation in the studied wells.

2017, Baralis A., Lungu V., Dupont P., Bastide M., Bony G., Caraire G., Comfort A., Delfieu R., Guy M., Jubeau T., Kaniewski D., Lebouteiller P., Marinova-Wolff E., BMontagne-Perruchon B., Morhange C., Musat-Streinu A., Popova T., Petrescu M., Rossignol I., Slavova I., Streinu M., Sternberg M., L’établissement d’Acic-Suat (commune de Baia, département de Tulcéa). Méthodologie d’une enquête pluri-disciplinaire, Pontica, 50, pp. 455-488.

In certain cases, the rivers draining mountain ranges create unusually large fan-shaped bodies of sediment that are referred to as fluvial megafans. We combine information from satellite imagery, monthly discharge and precipitation records, digital elevation models, and other sources to show that the formation of fluvial megafans requires particular climatic conditions. Specifically, modern fluvial megafans in actively aggrading basins are produced by rivers that undergo moderate to extreme seasonal fluctuations in discharge that result from highly seasonal precipitation patterns. The global distribution of modern megafans is primarily restricted to 15–35 latitude in the Northern and Southern Hemispheres , corresponding to climatic belts that fringe the tropical climatic zone. No relationship exists between megafan occurrence and drainage-basin relief or area. The tendency of rivers with large fluctuations in discharge to construct megafans is related to the instability of channels subject to such conditions. Because of the correlation between seasonal precipitation and megafan occurrence, the recognition of fluvial megafan deposits in ancient stratigraphic successions may provide critical information for paleoclimate reconstructions.

Human intervention in the hydrologic basin of the Colorado River has eliminated water discharge and sediment supply to the river's mouth and its delta. After ∼95 years of applying strong flow control policies, the previous sedimentary budget in the delta has changed, the delta now being entirely exposed to the hydrodynamic forces in its basin. In order to assess the anthropogenic impact of water diversion on deltaic sedimentary processes and short-term delta geomorphic evolution, textural and mineralogical analyses were performed on 68 sediment samples collected from the river, estuary, beach, continental shelf, delta plain and desert. The results show a consistent NE to SW textural gradient on the shallow-marine platform adjacent to the Colorado River delta (an area known as the Upper Gulf of California), and a net cross-basinal sediment transport occurring in the same direction. Two opposing littoral transport components exist along the Sonoran and Baja Californian coasts: (1) net sediment transport from SE to NW along the Sonoran coast delivers sediments from the ocean into the estuarine basin through the Sonora channel of the deltaic system of the Colorado River; and (2) sediment transport from N to S along the Baja Californian coast removes sediments from the estuarine basin of the Colorado River into the Northern Gulf of California (NGC). The residual sediment transport pattern observed suggests a counterclockwise path of exchange of materials between the estuarine basin of the Colorado River and the NGC. Multivariate cluster and factor analyses of the heavy-mineral data reveal the existence of a sedimentary system dominated by two end-members, representing two heavy-mineral sedimentary provinces: (1) the Sonora province is characterized by a heavy-mineral suite of garnet and zircon (G–Z), whose sediment supply originates from the sandy sediments of the Sonora Mesa deposits and Sonora's Gran Desierto; and (2) the Baja California province is characterized by a hornblende–epidote–pyroxene (H–E–P) suite, whose sediments originate from the earlier supply of the Colorado River. Since the Colorado River is no longer supplying sediments from its drainage basin, the H–E–P-rich sediments now actively dispersed in the system have mainly originated through intense reworking of the delta. Moreover, G–Z-rich sediments are starting to invade areas previously dominated by H–E–P sediments. On the basis of the prevailing hydraulic regime, textural and mineralogical characteristics of the sediments, and hydrographic and bathymetric information from the region, a hypothetical sediment dynamics model for the delta region is proposed, in which the tidally influenced, wave-dominated, sediment-reworked, slightly eroding Sonoran coast changes into a tide-dominated, depositional, very slowly prograding Baja Californian coast. This study shows that human intervention of the hydrologic basin of the Colorado River is not only responsible for inducing drastic hydrologic changes in its estuary (i.e., from brackish to hypersaline), but also for inducing drastic changes in the hydrographic circulation of the receiving basin (i.e., from long-basinal to cross-basinal). These changes are ultimately responsible for the relocation of massive volumes of the delta's sediment inventory, and for the serious ecological impact of habitat loss of indigenous species, such as the now endangered Totoaba (Totoaba macdonaldi) and Vaquita (Phocoena sinus).

ABSTRACT Particles projecting from the bed of an alluvial channel distort the fluid stream to produce a distinctive pressure field. This has considerable significance for both the entrapment and entrainment of other particles and is a primary cause of the widespread occurrence of pebble clusters and boulder shadows. Lift and drag forces are determined on clustered hemispherical particles of varying size. In the wake of an obstructing particle both forces are shown to vary directly with particle separation in a linear fashion. On the stoss side of the cluster, drag is uniform regardless of the separation of the component particles, but lift is shown to increase when particle separation is small, so affecting stability. This mutual interference of neighbouring clustered bed particles is a vital consideration of incipient motion and is shown by field evidence to cause a wide range in transport stage for particles of similar size and shape. On average, 46% of clustered particles are entrained by flood flow compared to 87% of particles in open plane-beds. The influence of clusters is a major determinant of sedimentary sorting.

This Article is about the Unconventional reservoirs; what are they, what are the differences between them and the normal Conventional reservoirs and what made us in need for studying and exploring these reservoirs even if they are very hard to produce and need much money and sacrifices. 
It also describes a geological, petrophysical, geochemical and geomechanical study of shale gas/oil characteristics that without it we can’t have a successful exploration and our target is to reach the sweet spots which are defined as the most prospective volumes of the shale play, they are primarily targeted to achieve early economic production. From all these studies we can conclude the methodology of exploration, as well as having a general view about the techniques used for investigation of the shale gas/oil, and also discussing the worldwide production and in Egypt.

One of the most continuous and best studied continental stratigraphic sections spanning the Paleocene-Eocene boundary is preserved on Polecat Bench in the northern Bighorn Basin. The mammalian biostratigraphy of Polecat Bench sediments has been well documented, and includes a major reorganization of faunas at or near the P-E boundary. To complement the existing biostratigraphy, we measured the isotopic composition of paleosol carbonate nodules at soil-by-soil temporal resolution through the P-E boundary interval. These measurements provide a detailed record of the abrupt, transient, carbon isotope excursion that affected atmospheric and oceanic carbon reservoirs at ca. 55 million years before present [Ma]. Tests of soil thickness and diagenesis indicate that trends in the record are primary, and reflect syndepositional changes in the delta (super 13) C value of atmospheric CO (sub 2) . The carbon isotope record suggests that the delta (super 13) C value of atmospheric CO (sub 2) dropped by ca. 8 per mil during this interval, and then rebounded. The pattern of change is very similar to that of an independent high-resolution record of Bains et al. (submitted). Changes in the delta (super 18) O of paleosol carbonates are consistent with a significant increase in local mean annual temperature during the P-E boundary event. Comparison of biotic and isotopic stratigraphies on Polecat Bench shows that faunal changes at the P-E boundary lag behind major events in the carbon and oxygen isotope records by about 10 thousand years [k.y.].

In this study, we report for the first time, concentrations of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in sediments from a South African environment, particularly for the
largest  catchment  areas  of  the  Western  Cape,  South  Africa,  an  area  associated  with  the  largest agricultural  sector  with  some  of  the  produce  and  end-products  intended  for  the  international  markets.
Sample  preparation  and  analysis  were  based  on  the  ISO  25101:  2009(E)  method,  using  solid  phase extraction  (SPE)  followed  by  liquid  chromatography  combined  with  electrospray  tandem  mass
spectrometry  (LC-MS/MS).  Sediment  grain  size  analysis,  core  water  characteristics  and  percent  total organic carbon were also quantified. From the results, PFOS and PFOA were observed in all the river
sediment samples and were found in concentrations up to 19 ng/g and 187 ng/g for Salt River, 121 ng/g and 772 ng/g for Diep River, and 75 ng/g and 193 ng/g  for Eerste River,  for both PFOS and PFOA,
respectively. Some of these concentrations are higher than those previously reported in similar studies in various  countries;  this  suggests  there  is  cause  for  concern.  Although  sediment  has  a  poor  sorption capacity  for  both  PFOS  and  PFOA  in  comparison  with  plants,  the  prevalence  of  PFOS  and  PFOA  in sediment samples from rivers from which irrigation water is sourced for agricultural purposes, indicates a risk of agricultural produce contamination.