Clay minerals in the sediments around the Andaman Islands

Clay minerals in the eastern side of Andaman Islands consist of montmorillonite, kaolinite, illite and Fe-rich chlorites while on western side they consist of illite and Fe-poor chlorite with minor kaolinite and montmorillonite. These assemblages have different provenances. The Andaman sea clays are derived largely from the sediments transported by the Irrawady river, while the western side shelf sediments(on the Bay of Bengal side) are derived from the weathering products of the rocks on the Island proper and the slope samples show contribution from the Ganges. Distribution of detrital minerals such as quartz and feldspar support the above conclusions. The 2 distinct clay mineral provenances result because the Andaman Islands appear to be a barrier to the mixing of the 2 clay mineral suites

ENHANCED SLAP ALGORITHM TO FIND TOP FREQUENT ITEMSETS IN THE ONLINE RETAIL STORE

Online shopping plays an important role from the past few decades. E-commerce websites to increase their profits by performing business analytics on the top utility items. Existing transactional databases implemented sequential patterns to find top utilities. More number of resources and computations are required to access these databases. In the proposed research, the model recognizes the frequent patterns by extending the Genetic Approach known as “Slap”, a swarm optimization which finds the best solution for the frequent activities. Optimization technique in this research is associated with finding the top-k utilities with maximum accuracy. The major advantage of this approach lies in its colony formation in perfect shape by communicating with neighbours.  The elements in the local search space continuously communicate with their agents and update their positions in global space. The implementation of genetic approaches with multi objective function helps the model to reduce the features and improve the accuracy. The proposed approach has obtained 97.1% accuracy

Phosphorite occurrence off Chennai

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Organic carbon in sediments of the Southwestern margin of India: influence of productivity and monsoon variability during the late Quaternary

The texture, organic carbon (OC), CaC03 and Rock-Eval parameters of the sediments from two gravity cores collected at depths below the oxygen minimum zone (OMZ) of the southwestern margin of India are presented and compared the results with those within the OMZ. Clayey silt/ silty clays are the characteristic sediments. The OC in the core top sediments between Cape Comorin and Mangalore is higher below the OMZ than those from the OMZ. However, it is higher within the OMZ than those below the OMZ in the sediments between Mangalore and Goa. The down-core variations of OC are identical in these cores. In both the cores, relatively high OC content and low sedimentation rates correspond to the intervals of late Holocene and Last Glacial Maximum (LGM) and, low OC and high sedimentation rates to the early Holocene sediments. The CaC03 follows sand content in a core off Cape Comorin, with low values at the core top, increase marginally in the early Holocene and LGM and then decrease in the late Pleistocene sediments. The CaC03 values in a core off Mangalore are higher in the intervals of the late Holocene and early deglaciation than m early Holocene and LGM intervals. Rock-Eval parameters distinguish the sources of organic matter only at high OC concentrations. The high OC during the LGM may be related to the productivity, associated with convective mixing occurring during the NE monsoon. The low OC/CaC03 and high clay content during the early Holocene may be the consequences of the intensified SW monsoon that results in stronger near-surface stratification leading to low productivity High OC and low CaC03 during the late Holocene suggest increased productivity and early diagenesis in the near surface sediments. We suggest that the variations in productivity and downslope transport of sediment controlled the OC enrichment

Clay mineral distribution in the continental shelf and slope off Saurashtra, West coast of India

Clay mineral distribution in the sediments of the west coast of India indicates that the illite and chlorite-rich sediments, derived from the Indus, occupy the continental shelf of the northern part of the Gulf of Kutch. Montmorillonite derived from the Deccan trap coastal province is the predominant clay mineral in the sediments of the continental shelf south of the Gulf of Kutch. Lateral variations reveal that the montmorillonite contents are high in the innershelf and on the continental slope with relatively low values on the outer shelf. Illite and chlorite contents are high on the outer shelf. These variations are attributed to the influence of depositional environment and individual property of the clay minerals. Distinct differences in the nature of montmorillonite derived from basic and gneissic rocks are identified. Review of the clay mineralogy suggests that their distribution is related to the provenance, and the latitudinal zonation of clay minerals may not be valid in this part of the Arabian Sea

Dune associated calcretes, rhizoliths and paleosols from the Western continental shelf of India

The calcareous deposits on the western continental shelf of India, off Bhatkal (water depths 50 to 58 m) occur as crusts, sheets, cylinders and reddish brown mudstones. The outer layers of the crusts are micrite-dominated and beneath this layer detrital/carbonate sands with thin heavy mineral laminations are found. Textural studies indicate that the detrital sands are derived from dunes. Drusy calcite and neomorphic calcite cements are associated with the sands. Sheet deposits contain coarse calcareous component-dominated layer within micrite layers and abundant micrite cements. These are similar to dune associated calcretes. Cylinders are rhizoliths and show different stages of root calcification. Circular bodies, about 0.15 mm to 0.70 mm diameter, interpreted as vascular cylinders of the root tissues are typical. Radial fibrous calcite and spar calcite with inclusions indicate neomorphic cements. Reddish brown mudstones contain calcified root-hair sheaths, micrite glaebules and reworked pollen suggesting that these are indurated soils. X-ray diffraction studies indicate the presence of ferroan calcite, quartz, pyriie and dolomite in rhizoliths and ferroan calcite, goethite and quartz in mudstones. Mudstones and some rhizoliths are Fe-rich and some other rhizoliths are Fe-poor but enriched with Mg and Mn. The particulate matter in the calcareous deposits were initially at the proximity of the coast and cemented by metastable calcites during the ultimate Pleistocene intcrglacial sea-level stands on the shelf. Pedogenic cementation processes overprinted and developed them into eolianites and paleosols during the subsequent Late Pleistocene sea-level regression. The compositional differences of these deposits were apparently controlled by type of sediments and associated sedimentary environments

Geomorphology and surficial geology of the Western continental shelf and upper slope of India: a review

The geomorphology and geology of the western con­tinental margin of India have become better known only after the International Indian Ocean Expedition (1962-1965). The continental shelf of western India is wide off the river mouths, becoming narrower south-eastwards and narrowest on the SW margin. Shelf break occurs at depths between 60 and 150 m. The Fifty Fathom Flat is a prominent feature on the outer shelf. Submarine terraces at depths between 35 and 170 m and shelf edge reefs are also present along the margin. Coastal geology and geomorphology of the area and nearshore currents played a significant role in the distribution of placer minerals off Kerala and Maharashtra. Transport and sedimentation of fine­ grained materials at places on the shelf are influ­enced by high-energy conditions. Clay minerals de­ rived from the Indus, Deccan Trap basalt and Gneissic provinces are distinct along the inner shelf, but bypassed the outer shelf and got deposited on the continental slope. Relict biogenic carbonates com­ prising Halimeda litho-facies, rhodalgal-coral facies and molechfer facies, occur in the northern, central and southwestern shelf, respectively. Terrestrial limestones described as palaeo-shoreline indicators occur at mid-shelf. Several evidences exist in favour of Late Quaternary neotectonic activity and subsidence. Phosphorites and phosphatized limestones occur on the shelf and slope and phosphatization seems to be a short event in the Early Holocene. Verdine and Glau­cony facies occur on the shelf and slope of the central and southwestern margin of India. Systematic sampling/radiocarbon dating is lacking on many geomorphic features. Some coastal bays in Maharashtra are least explored for heavy minerals. Phosphorites at places could prove economic, if de­tailed exploration is done. Several gaps exist in the data on sea level changes during the Late Quater­nary. Shelf edge exchange processes are to be studied in understanding the organic carbon distribution. Attention should be directed in solving the problems highlighted

Late Quaternary sea level and environmental changes from relic carbonate deposits of the Western margin of India

Relic carbonate deposits along the western margin of India occur as dolomite crusts, aragonite sands (pelletal/oolitic) and aragonite-cemented limestones, oyster shells, corals, encrusted coralline algal and foraminiferal-dominated nodules. The petrology and mineralogy of the deposits indicate that except for aragonite sands and foraminiferal nodules, the others were formed in shallow marine conditions and serve as sea level indicators. Radiocarbon dates were measured for 62 relic deposits covering the entire margin. The age of these deposits on the continental shelf off Cape Comorin and Mangalore, between 110 and 18 m depth, ranges between 12, 610 14C yr BP and 6,390 14C yr BP. On the northwestern margin of India, especially on the carbonate platform (between 64 and 100 m), the age ranges from 17,250 to 6,73014C yr BP. The relic deposits of the Gulf of Kachchh at depths between 35 and 25 m are dated at 12,550-9,63014C yr BP. The age vs. depth plot of the relic deposits further indicates that the Gulf of Kachchh was inundated much early, atleast by 15 ka, after the Last Glacial Maximum, and was subjected to uplift and subsidence during the Holocene. The carbonate platform subsided during the early Holocene. Some of the relic deposits between Cape Comorin and Mangalore plot on or, closely follow the glacio-eustatic sea level curve. Despite abundant siliciclastic flux discharged by the Narmada and Tapti during the early Holocene, the platform off these rivers is largely devoid of this flux and carbonate sedimentation continued until 6,700 14C yr BP. We suggest that the river-derived sediment flux diverted southwards under the influence of the SW monsoon current and, thereby, increased the turbidity on the shelf and slope southeast of the carbonate platform and facilitated the formation of deeper water foraminiferal nodules off Vengurla-Goa

Quartz and feldspar distribution in continental shelf sediments of East coast of India

Coarse fractions of 57 sediment samples from the eastern continental shelf of India between the Hoogly mouth and Krishna mouth have been analysed for quartz and feldspar distribution. Highest concentrations (80-90%) of quartz are in the sediments between Kalingapatnam and Chilka lake and in the area north of the Mahanadi. It is lowest (50-60%) in the sediments off the Krishna and Godavari and in the outer continental shelf off Visakhapatnam. Plagioclase feldspar concentrations are high (20-40%) in the clayey silt sediments off the Krishna and Godavari and low (< 10%) in the sandy sediments which occur in the northern part. Alkali feldspar to quartz ratios range from 0.05 to 0.27 in the inner shelf and 0.4 to 0.9 in the outer shelf sediments off Visakhapatnam. Variations in the distribution of quartz and feldspar have been attributed to coastal geology and rock formations in the drainage basins of the rivers. It is further suggested that the feldspar quantity cannot be regarded as a climatic indicator in all the regions

Wind-driven estuarine turbidity maxima in Mandovi Estuary, central West coast of India

Systematic studies on the suspended particulate matter (SPM) measured on a seasonal cycle in the Mandovi Estuary, Goa indicate that the average concentrations of SPM at the regular station are ~20mg/l, 5mg/l, 19mg/l and 5mg/l for June–September, October–January, February–April and May, respectively. SPM exhibits low-to-moderate correlation with rainfall indicating that SPM is also influenced by other processes. Transect stations reveal that the SPM at sea-end stations of the estuary are at least two orders of magnitude greater than those at the river-end during the monsoon. Estuarine turbidity maximum (ETM) of nearly similar magnitude occurs at the same location in two periods, interrupted by a period with very low SPM concentrations. The ETM occurring in June–September is associated with low salinities; its formation is attributed to the interactions between strong southwesterly winds (5.1–5.6ms-1) and wind-induced waves and tidal currents and, dominant easterly river flow at the mouth of the estuary. The ETM occurring in February–April is associated with high salinity and is conspicuous. The strong NW and SW winds (3.2–3.7ms-1) and wind-driven waves and currents seem to have acted effectively at the mouth of the estuary in developing turbidity maximum. The impact of sea breeze appears nearly same as that of trade winds and cannot be underestimated in sediment resuspension and deposition