Sedimentology

Heavy metals are ecologically significant for their toxicity and accumulative behavior. The geoaccumulation index (I geo) in 12 stations in Indian Sundarbans estuarine region (i.e Kakdwip, Harinbari, Chemaguri, Sagar South, Lothian island, Jambu island, Frasergunge, Gosaba, Chotomollakhali, Bali island, Sajnekhali and Bagmara) was calculated in this article. The degree of sediment pollution was investigated by following the concentration of 3 heavy metals namely copper, lead and cadmium. Atomic Absorption Spectrophotometer (AAS) was used for metal analysis. According to the geoaccumulation index (I geo) the results of all the 12 stations were analyzed and discussed in detail. In one of the selected stations-Kakdwip I geo value was 3, which signifies strongly contaminated ambient sediment in this area.

The East China Sea Shelf has an unusually wide and low gradient shelf, supplied from sediment-charged rivers and large river delta systems, with bottom currents sweeping the sea floor and located in the path of strong typhoons. Sediment gravity flow deposits, including four hybrid event beds and a high density turbidite, are identified in a core from the mid-shelf of the East China Sea. The hybrid event beds typically comprise three or two internal divisions from the base to the top: (i) H1, H3 and H5; or (ii) H3 and H5. Radiocarbon ages of the hybrid event beds were in the range of 3821 to 8526 yr BP. Based on correlation with surrounding cores, the hybrid events may have happened at any time between 1930 yr BP and 3890 yr BP. The d 13 C values in hybrid event beds together with bathymetry data suggest local erosion on the shelf. The average d 13 C value for the H1 division is similar to the H3 division in the hybrid event beds, implying that the organic matter in the H1 and H3 divisions may come from the same source area. Cross-plots of upper continental crust normalized rare earth elements in the five units reveal that the sediment source of the four hybrid event beds and the tur-bidite was ultimately primarily from Korean rivers. Partial transformation from a moderate-strength debris flow with the additional role of erosional bulking can explain occurrences of hybrid event beds on the East China Sea Shelf. The data indicate that hybrid sediment gravity flow deposits were 1

We report initial results from our recent field survey documenting the inundation and resultant deposits of the 2011 Tohoku-oki tsunami from Sendai Plain, Japan. The tsunami inundated up to 4.5 km inland but the> 0.5 cm-thick sand deposit extended only 2.8 km ( ...

Hooghly estuary is a dynamic zone, where the erosion-accretion process is active because of the combined effects of the fluvio-tidal-wave activities and supported by frequent cyclones, sea-level fluctuations, sediment supplies from upland sources, and neotectonic activities. The Sagar island, the largest in the Hooghly estuary, is suffering erosion since its evolution. The present study shows that for the period 1972 and 2010, an area of 6.84 sq. km of the island has been subjected to changes. The total area has reduced during 1972-90, whereas the net area has increased during 1990-2010 indicating an oscillatory pattern of island growth (which may be controlled by the combined fluvio-tidal hydrodynamics and climate). In general the eastern portion of the island is more silty-clayey and the western portion is relatively sandy. Numerical modeling is indicative of a close match of the fluid-sediment path with the erosion-accretion pattern. In the Hooghly estuary, as the duration of flood tide is much less than the ebb tide, the fluid flow velocity is more during the flood tide. The erosion is maximum during the mid tide whereas the sediment deposition phase is maximum during the slack period. Overall, the pattern of erosion-accretion as well as the sediment transport is controlled by the time in the tidal cycle, the geometry of the river channel and the sediment discharge.

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.

Devonian reefs are widespread in the West Canada Basin in three regions: lower Givetian in the north (Elk Point subbasin), upper Givetian and middle Frasnian in the central part (framing of the Peace
River Arch), and middle Frasnian (southern end of the basin). Each stage of reef formation ended with regression, and the last reefs terminated long before the Frasnian/Famennian biotic crisis and mass extinction.
Reefs of this basin are petroliferous. Moreover, the structure of reservoirs is determined by the reef type, and the highest reservoir properties are related to bioherm varieties in reefs.
Original Russian Text © V.G. Kuznetsov, L.M. Zhuravleva, 2018, published in Litologiya i Poleznye Iskopaemye, 2018, No. 3, pp. 255–271.

The evolution of sedimentary rock formation of a highly organized level (paragenetic rock associations) is more complex than that of a poorly organized level (rocks). Subjacent rock associations are established for the entire geological evolution of the Earth: they varied in time and were obsolescent or, in contrast, nascent and momentary. A certain cyclicity of evolution is identified along with directed changes.
Original Russian Text © V.G. Kuznetsov, 2017, published in Doklady Akademii Nauk, 2017, Vol. 475, No. 1, pp. 68–71.

The recent geological, geomorphological, pedological and structural surveys performed at the San Colombano tectonic relief document a Late Quaternary tectonic activity of the structure, located at the Po Plain-Northern Apennine border in Lombardy (Italy). The new maps, corroborated with (palaeo-) geopedological analyses, allow to unravel the composite nature of the morphological and stratigraphic surfaces bounding the observed units and landforms, and to relate them to the climatic and tectonic events that interacted during the Late Quaternary at the Apennine-Po Plain border.

The Paleocene-Eocene boundary (55.8 Ma) ago involved and characterized by a relatively brief interval of extreme warming and exceptional events termed collectively the Paleocene Eocene thermal maximum (PETM). The need to provide a valued and complementary addition to all local geological studies of the upper Paleocene-lower Eocene period as well as knowing the role of warm climatic anomaly disaster on geological and environmental events were the most important research justifications. Hence, in order to identification of PETM global disaster phenomena and tracing its geological responses in detail in the Iraqi geological record, three outcropping sections are selected carefully to represent the northern of Iraq in Sinjar, Dohuk, and Shaqlawa areas included Aaliji and Kolosh Formations. The samples analyzed by adopting multidisciplinary approach manner as a recent mode in paleoclimatic recognition. PETM stratigraphical signatures represented lithologically by the fresh lithological color change to brown, yellowish brown or yellowish white colors as a distinctive field feature of PETM lithosomes. Foraminiferal, the Aaliji Formation planktonic foraminifera respond to PETM is represented by species reorganization (decline, abundance) and morphological optimal adaptation (shape, size). Kolosh Formation benthic foraminferal respond is identified by benthic foraminferal extinction event (BFEE) in Shaqlawa section, while the general decrease in generic diversity of photoautotrophic larger foraminifera was the most notable feature in Dohuk section. Magnetostratigraphically, magnetic susceptibility signals are attributed to two sources: biogenic minerals source (mainly in Aaliji Formation) and transported terrigenous materials source, the latter source refers indirectly to enhanced hydrological and weathering cycles. Thus, both sources in combination with rock magnetic identification of greigite mineral are considered as evidences to PETM environmental conditions. PETM sedimentological evidences are extrapolated through petrography, facies analysis, and clay minerals assemblages study. Several signatures are recorded by petrography such as high micritic matrix ratio in Aaliji Formation, and magnetosomes (bacterial biomineralize), appearance of green algae (Dasycladacean) in Kolosh Formation at Shaqlawa and Dohuk areas

The petrography of the detrital part of Hussainiyat Formation Jurassic (Upper Liassic) in its ideal section, at the western Desert, Iraq, was studied. The aim of this study was to infer the climatic and tectonic evidence that affected the deposition of the sandstones of this formation. It has been shown that the most abundant mineral in these sandstones was quartz. These sandstones were derived from a scarce area with relatively low relief topography with an equatorial humid environment. Most of these rocks were derived from continental regions of cratonic zones. However, some of them were derived from orogenic belt marginal to continental regions as a first cycle, them recycled into deposits within the craton. These rocks are mostly of granitic igneous origin, and to a less extent of metamorphic and redeposited sedimentary rocks derived from the Arabian shield.

Sandstones petrographical study of the upper part of the Kolosh Formation (Paleocene)at the southern limb of Bekhair anticline in Dohuk city showed clues of the effect of multivariate diagenetic processes and identified eogenesis (bioturbation, glauconite and pyrite authigenesis), mesogenesis induced by the pressure and tempreture deformation as a result of tectonic activities in the area which are amplified the pressure, tempreture conditions accompanied with relative deep burial leading to development of (compaction, cementation, replacement and recrystallization). Finally as a response to tectonic effects, the rocks were exposed and telogenesis stage begins including (dissolution, alteration and calcite, iron oxides cementation). Most of the diagenetic processes occured in meteoric and burial pheratic water diagenetic environments.At the same time, more than one diagenetic process had an effect on the rocks but in different proportions.

Petrographic description of sandstones of the Injana Formation (Upper Miocene) from several selected sections in Iraq shows similarity in mineralogical composition. This is represented by litharenite and feldspathic litharenite eroded from precursor sedimentary, metamorphic and igneous rocks and transported for short distance to be deposited within the fluvial environment. Generally, the sandstone are mineralogically immature; due to increased rates of erosion and deposition associated with dominant mechanical weathering and subdued chemical action. Presentation of petrographic results as specific relationships point to the deposition under semiarid-semihumed climatic conditions accompanied by little ineffective chemical weathering induced by high relief of source area. Likewise semiarid conditions promoted sparse plant cover, thus providing large quantities of eroded sediments.

Petrographic study of the sandstones of Injana Formation in the well (KH8/9) revealed them to consist dominantly of carbonate rock fragments with subordinate monopoly crystalline quartz, K-Na feldspars fragments, igneous-metamorphic rock fragments and mica, in addition to matrix and cement of variable composition (carbonate, iron oxide, silica and sulphates). This suits of components can be related to provenance overwhelmed by sedimentary rocks with lesser contribution of igneous and metamorphic rocks. This sandstone is mineralogically and texturally immature and of calclithite variety originated from source rock under colder conditions compared to their semi-arid environment of deposition. The tectonic setting of back-arc attributes as a consequence of plate-collision and overthrusting played a dominate role in sourcing the sediments.

Textural grain-size analysis of Injana Formation in borehole (KH8/9) indicate the dominance of sandstones and siltstones. Cumulative frequency curves imply transportation in different modes: suspension, saltation and rolling with the last of minor importance. Textural attributes of the clastics showed them to be composed of fine sand, medium sorting with very positive skewed and being leptokurtic. The data point to the deposition by weak current and rapid accumulation. Bivariant plots of statistical parameters and applying of (C-M) diagram elucidated deposition in meandering river system.