Facies analysis and sequence stratigraphy of Kometan Formation (Upper Cretaceous) in the imbricated zone,northeastern Iraq

Facies and sequence stratigraphic analysis of the Kometan Formation (Upper Cretaceous) were studied from Kometan village, Kurdistan region of northeastern Iraq. Lithologically, the formation consists of 44 m of white weathering, light grey, thin to medium-bedded highly fractured limestones with chert nodules. Petrographic study of the carbonates shows that both skeletal and non-skeletal grains were present. The skeletal grains include a variety of planktonic foraminifera (including Oligostegina), calcispheres, ostracods, pelecypods, larva ammonite, and echinoderms. Non-skeletal grains include peloids only. Three main microfacies types are distinguished in the studied formation. The results of stable carbon and oxygen isotopes of the studied carbonate samples show negative values of δ¹⁸O. These indicate that the seawater was warm with low salinity during precipitation of the carbonates in the Kometan Formation in northeastern Iraq. The positive δ¹³C values of carbonate samples, in the middle part of the formation, reflect the widespread deposition of organic-rich marine sediments during a transgression and deepening of the basin. Petrographic, facies and stable isotopic analyses revealed that the Kometan Formation was deposited in a warm, basinal, pelagic (open marine) environment with low salinity. The Kometan Formation consists of one complete third-order depositional sequence, separated by a sequence boundary (SB) of type 2. The third-order sequence is subdivided into a transgressive systems tract (TST) and highstand systems tract (HST). This reflects episodes of transgression and still stands of the relative sea level. The TSTs are topped by maximum flooding surface (MFS) characterized by deepening-/fining-upward parasequences implying a retrogradational stacking pattern. The HST is marked by shallowing-/coarsening-upward parasequences implying a progradational stacking pattern.     

Automatic identification of fake patterns caused by short-width wavelets in seismic data

Despite the popularity of using the Haar wavelet filter in many applications, it sometimes introduces fake patterns into the multi resolution analysis (MRA) of seismic data. In this work, we compared different wavelet filters to demonstrate that these patterns are fake and not part of the original waveforms and to show that they are a result of using the Haar wavelet filter as a short-width wavelet. To achieve this, many seismic waveforms from two different sources: the Egyptian National Seismic Network (ENSN) and the High Sensitivity Seismograph Network Japan (Hi-net) are used with different wavelet filters. We propose an algorithm based on an autoregressive (AR) model to detect these patterns automatically and fully.     

Using cloud water path and cloud top temperature for estimating convective and stratiform rainfall from SEVIRI daytime data

A satellite rainfall retrieval technique is proposed here. The relationships of rain rate with each of cloud water path (CWP) and cloud top temperature (CTT) are investigated. The CWP and CTT are retrieved from SEVIRI data (spinning enhanced visible and infrared imager), and corresponding rain rates are measured by weather radar. The rain rates are compared to corresponding CWP and then to corresponding CTT. The investigation demonstrates an exponential functional dependency between rain rates and CWP for low and moderate rain rates (stratiform rainfall). Conversely, the rain rates are more closely related to CTT for high rain rates (convective rainfall). Therefore, two separate relationships are established for rain rate retrievals. The results show rain rates estimated by the developed scheme are in good correlation with those observed by weather radar.     

Anomalous optical variations in the grossular garnet from the Eden Mills,Belvidere Mountain (Vermont,USA)

The optical anomalies, and surface and lamellar textures of a birefringent grossular garnet crystal from the Eden Mills, Belvidere Mountain, Vermont, USA, have been investigated by optical polarizing microscope, electron-probe micro-analyzer, back-scattered electron imaging, infrared spectroscopy, and single-crystal X-ray diffractometer from the standpoint of crystal growth. This grossular shows one-to-one correlation between natural surface features and its internal textures under crossed polarizers. Electron-probe micro-analyzer (EPMA) gave average chemical composition in (110) thin section, of bright lamella {Ca_2.97Mn_0.06}_∑3.03 [Al_1.59Fe_0.37Ti_0.01]_∑1.97(Si_3.00)_∑3.00 (Gros_79.5And_18.9Sps_1.6) and of dark host {Ca_2.99Mn _0.06}_∑3.05 [Al_1.73Fe_0.26 Ti_0.01]_∑2.00(Si_2.97OH_0.03)_∑3.00 (Gros_85.4And₁₃Sps_1.6). The correspondence of surface features and the internal textures with spiral or pyramidal growth mechanism suggest that the internal textures of the Eden Mills grossular are formed during growth process. The optical vibrational orientations and the growth steps inclination along [001] and \( \left[\overset{-}{1}10\right] \) directions predict monoclinic symmetry. With X-ray diffractometer (XRD) method, pseudocubic parameters are a = 11.839(2) Å, b = 11.855(1) Å, and c = 11.868(2) Å with interaxial angles α = 90.00(1)°, β = 89.99(1)°, and γ = 90.02(2)° that show orthorhombic symmetry of this crystal. Lamellar texture of Al³⁺-rich host with Fe³⁺-rich lamella infers cation ordering at octahedral site of the garnet structure. IR data favors the non-cubic orientation of [(OH) ₄] at tetrahedral position in this grossular structure.     

Regional debris flow susceptibility analysis based on principal component analysis and self-organizing map: a case study in Southwest China

A method was developed to analyze the susceptibilities of 541 regional basins affected by debris flows at the Wudongde Dam site in southwest China. Determining susceptibility requires information on source material quantity and occurrence frequency. However, the large number of debris flows can hinder the individual field investigation in a each small basin. Factors that may trigger debris flows can be identified using remotely sensed interpretation information. Susceptibility analysis can then be conducted based on these factors. In this study, SPOT5 satellite imagery, digital elevation models (DEM), a lithology distribution map, and rainfall monitoring data were used to identify 12 debris flow trigger factors: basin relief ratio, slope gradient in the initiation zone, drainage density, downslope curvature of the main channel, vegetation coverage, main channel aspect, topographic wetness index, Melton’s ruggedness number, lithology, annual rainfall, form factor, and cross-slope curvature of the transportation zone. Principal component analysis was used to obtain the eight principal components of these factors that contribute to susceptibility results. Then, a self-organizing map method was adopted to analyze the principal components, which resulted in a debris flow susceptibility classification. Field validation of 26 debris flow basins was used to evaluate the errors of the susceptibility classification, as well as assess the causes of such errors. The study found that principle component analysis and self-organizing map methodologies are good predictors of basin susceptibility to debris flows.     

Ground penetrating radar and 2D electric resistivity studies for tracing hydrocarbon leakage site,close to Abha City: a case study

This work presents the application of the ground-penetrating radar (GPR) method and electric resistivity tomography (ERT) technique in outlining a zone of contamination due to the light non-aqueous phase liquid (LNAPL) plume underground in the area of an impacted fuel station, close to Abha City. The GPR has been performed using SIR3000 unit with the 100 and 400 MHz antennas. The main objective of the GPR survey was to evaluate the lateral extension of contamination. The complex GPR signature of the plume was well characterized. Low reflectivity zone corresponds to hydrocarbon vapor phase in the vadose zone. Enhanced reflections are associated with free and residual products in the fractured saturated zone directly above the water table. An electric resistivity tomography (ERT) survey was performed on four profiles within the site to investigate the vertical and horizontal extent of the contamination plume and to define the bottom of the landfill. The 2D electric profiles show the presence of low-resistivity (4O to 37 Ω m) anomalies that refers to the presence of accumulated hydrocarbons. From the interpretation of the GPR and ERT profile, it was possible to locate the top and bottom of the contamination plume of the waste disposal site. The radar signal penetrated deep enough and enabled the identification of a second reflector at approximately 10-m deep, interpreted as the hard basement surface which causes the strong amplitude reflection in the GPR profile. The results of GPR and ERT showed good agreement.     

Limited differences among habitats in deep‐sea macro‐infaunal communities off New Zealand: implications for their vulnerability to anthropogenic disturbance

The spread of human activities into the deep sea may pose a high risk to benthic communities and affect ecosystem integrity. The deep sea is characterized by physical and biological heterogeneity and different habitat types are likely to differ in their vulnerability to anthropogenic impacts. However, across‐habitat comparisons are rare, and no comprehensive ecological risk assessment has yet been developed. To address this gap in our knowledge, we compared macro‐infaunal community structure in four habitats (slope, canyons, seamounts and methane seeps) at depths between 700 and 1500 m in the Hikurangi Margin and Bay of Plenty regions off New Zealand. The most striking contrast in community structure was between the two study regions, due to an order of magnitude difference in macro‐infaunal abundance that we believe was caused by differences in surface productivity and food availability at the sea bed. We found differences in structural and functional attributes of macro‐infaunal communities among some habitats in the Hikurangi Margin (slope, canyon and seep), but not in the Bay of Plenty. We posit that differences between canyon and slope communities on the Hikurangi Margin are due to enhanced food availability inside canyons compared with adjacent slope habitats. Seep communities were characterized by elevated abundance of both symbiont‐bearing and heterotrophic taxa, and were the most distinct, and variable, among the habitats that we considered on the Hikurangi Margin. Communities of seamounts were not distinct from slope or canyon communities on the Hikurangi Margin, probably reflecting similar environmental conditions in these habitats. The communities of deep‐sea canyon and seep habitats on the Hikurangi Margin were sufficiently dissimilar from each other and from slope habitats to warrant separate management consideration. By contrast, the low dissimilarity between communities of canyon and slope habitats in the Bay of Plenty suggests that habitat‐based management is not required in this region, for macro‐infauna at least. Although the two study regions share similar species pools, populations of the Hikurangi Margin region may be less vulnerable than the sparser populations of the Bay of Plenty due to the higher availability of potential colonizers and faster population growth. Thus regions, and habitats in some regions, should be subject to separate ecological risk assessment to help identify the key risks and consequences of human activities, and to inform options for reducing or mitigating impacts.     

Sequence stratigraphic analysis of Eocene Rock Strata,Offshore Indus,southwest Pakistan

In this study, seismic data from two wells (Pak G2-1 and Indus Marine-1C) and age diagnostic larger benthic foraminifera (LBF) within drill cuttings has been used for the first time to identify depositional sequences within the carbonates in the Offshore Indus Basin, Pakistan. The Offshore Indus is tectonically categorized as a passive continental margin where carbonates occur as shelf carbonates in the near offshore and on volcanic seamounts in deeper waters. Seismic data analysis has indicated the presence of minor faults and carbonate buildups above the igneous basement in the south. Patterns of the seismic reflections enabled definition of three seismic facies units identified as: Unit 1 basement, represented by chaotic, moderate amplitude reflection configuration; while parallel bedding and the drape of overlying strata is typical character of Unit 2, carbonate mound facies. The younger Miocene channels represent Unit 3. The diagnosis of Alveolina vredenburgi/cucumiformis biozone confirmed the Ilerdian (55–52 Ma) stage constituting a second order cycle of deposition for the Eocene carbonates (identified as Unit 2). The carbonate succession has been mainly attributed to an early highstand system tract (HST). The environmental conditions remained favorable leading to the development of keep-up carbonates similar to pinnacle buildups as a result of aggradation during late transgressive system tract and an early HST. The carbonate sequence in the south (Pak G2-1) is thicker and fossiliferous representing inner to middle shelf depths based on fauna compared to the Indus Marine-1C in the north, which is devoid of fossils. Three biozones (SBZ 5, SBZ 6 and SBZ 8) were identified based on the occurrence of LBF. The base of the SBZ 5 zone marks the larger foraminifera turnover and the Paleocene–Eocene (P–E) boundary. The LBF encountered in this study coincides with earlier findings for the P–E boundary. Our findings indicate that the entire Ilerdian stage ranges from 55.5 to 52 Ma that was the episode of warmer water conditions on the carbonate shelves leading to the diversification of K-strategist larger foraminifera. The larger foraminiferal assemblage encountered in this study confirms the findings. The possible indication of stratigraphic-combination traps, revealed as reflection terminations, make carbonate mounds in the south a potential exploration target.     

Heat and mass transfer effects during displacement of deepwater methane hydrate to the surface of Lake Baikal

The present paper focuses on heat and mass exchange processes in methane hydrate fragments during in situ displacement from the gas hydrate stability zone (GHSZ) to the water surface of Lake Baikal. After being extracted from the methane hydrate deposit at the lakebed, hydrate fragments were placed into a container with transparent walls and a bottom grid. There were no changes in the hydrate fragments during ascent within the GHSZ. The water temperature in the container remained the same as that of the ambient water (~3.5 °С). However, as soon as the container crossed the upper border of the GHSZ, first signs of hydrate decomposition and transformation into free methane gas were observed. The gas filled the container and displaced water from it. At 300 m depth, the upper and lower thermometers in the container simultaneously recorded noticeable decreases of temperature. The temperature in the upper part of the container decreased to –0.25 °С at about 200 m depth, after which the temperature remained constant until the water surface was reached. The temperature at the bottom of the container reached –0.25 °С at about 100 m depth, after which it did not vary during further ascent. These observed effects could be explained by the formation of a gas phase in the container and an ice layer on the hydrate surface caused by heat consumption during hydrate decomposition (self-preservation effect). However, steady-state simulations suggest that the forming ice layer is too thin to sustain the hydrate internal pressure required to protect the hydrate from decomposition. Thus, the mechanism of self-preservation remains unclear.