Early Neogene Radiolarian faunal turnover in the northern Indian Ocean: Evidence from Andaman-Nicobar     

V. Sharma  Jahanbakhsh Daneshian  L. Bhagyapati Devi 《Journal of the Geological Society of India》2011,78(2):157-166

Two intervals of faunal turnover are revealed by the study of radiolarians from the Early to Middle Miocene sequence of Andaman-Nicobar belonging to Stichocorys wolffii-Calocycletta costata-Dorcadospyris alata zones. These faunal changes are reflected in the values of species diversity, change in abundance of taxa, origination and extinction events and change in radiolarian assemblages. One such faunal change is identified in the latest Early Miocene. The time of this faunal change is marked by the extinction of species like Carpocanopsis cingulata and appearance of Calocycletta costata, Giraffospyris toxaria, Acrocubus octopylus and Liriospyris parkerae, an increasing trend in percentage of cold water species and a decreasing trend in species diversity upwards. The interval coincides with the time of initiation of cooling of sea surface water. Another, and the most prominent faunal turnover of radiolarians is recognized in the Middle Miocene Dorcadospyris alata Zone at about 14.8–12.7 Ma and is characterized by almost complete disappearance of an earlier dominant assemblage and an increase in abundance of an assemblage that was practically absent in the older sequence. The time of this turnover can be correlated with the time of Middle Miocene cooling identified in the examined sequence.  相似文献   

Molluscan assemblage from the marine Palaeocene sequence in southwestern Kachchh,Gujarat     

R. P. Kachhara  K. Bigyapati Devi  R. L. Jodhawat 《Journal of the Geological Society of India》2011,78(1):81-91

Presence of oldest marine Tertiary rocks in Kachchh for a long time has remained debatable and controversial. To resolve the issue in better way authors have worked out a section along tributary of Kakdi Nadi about 0.5 km west of village Nareda in southwestern Kachchh and collected molluscan fauna. Systematic study of these fauna reveals presence of 15 taxa of which 12 are of bivalves and 3 of gastropods. This molluscan assemblage leads to the presence of marine Palaeocene sequence around Nareda. Recorded assemblage hitherto not known earlier from Kachchh.  相似文献   

Effect of Co‐culture and Nutrients Supplementation on Bioremediation of Crude Petroleum Sludge     

Mamilla Prathima Devi  Motakatla Venkateswar Reddy  Asha Juwarkar  Ponnapalli Nageswara Sarma  Srinivasula Reddy Venkata Mohan 《洁净——土壤、空气、水》2011,39(10):900-907

Ex‐situ bioremediation of real‐field crude petroleum sludge was evaluated to elucidate the role of co‐culture (bioaugmentation) and external nutrients supplementation (biostimulation) under anaerobic microenvironment. Maximum removal of total petroleum hydrocarbons (TPH) was observed by integrating biostimulation with bioaugmentation (R5, 44.01%) followed by bioaugmentation alone (R4, 34.47%), co‐substrate supplemented operations [R6, 23.36%; R3, 16.5%; R2, 9.88%] and control (R1, 4.36%). Aromatics fraction showed higher degradation in all the conditions studied. Fate of six selected polycyclic aromatic hydrocarbons (PAHs) was evaluated during bioremediation. Among these, four ring PAHs compounds showed good degradation by integration of biostimulation with bioaugmentation (R5) while bioaugmentation alone (R4) documented good degradation of three ring PAHs. Lower ring PAHs compounds showed good degradation with the application of biostimulation (R6). Fluorescent in situ hybridization (FISH) detected the presence of known PAHs degrading microorganisms viz., Bacillus, Pseudomonas, Acido bacteria, Sulphur reducing bacteria Firmicutes, etc. Application of biostimulation and bioaugmentation strategies alone or in combinations documented noticeable influence on the degradation of petroleum sludge.  相似文献   

Neotectonic study along mountain front of northeast Himalaya,Arunachal Pradesh,India     

R. K. Mrinalinee Devi  S. S. Bhakuni  P. K. Bora 《Environmental Earth Sciences》2011,63(4):751-762

To study neotectonics, the structural and morphotectonic aspects are studied along a part of mountain front region of Northeast Himalaya, Arunachal Pradesh, India. Unpaired river terraces are recognized near north of transverse Burai River exit, which is cut by an oblique fault. Across this fault, fluvial terraces are located at heights of 22.7 and 3 m, respectively, on the left and right banks. A water gap is formed along the river channel where the uplifted Middle Siwalik sandstone beds dipping 43° towards ENE direction, thrust over the Quaternary deposit consisting of boulders, cobbles, pebbles and sandy matrix. This river channel incised the bedrock across the intraformational Ramghat Thrust along which the rocks of the Middle Siwalik Formation thrust over the Upper Siwalik Formation. Recent reactivated fault activity is suggested north of the Himalayan Frontal Thrust that forms the youngest deforming front of the Himalaya. The uplifting along the stream channel is noticed extended for a distance of ~130 m and as a result the alluvial river channel became a bedrock river. The relative displacement of rocks is variable along the length of strike–slip faults developed later within the Ramghat Thrust zone. Longitudinal and Channel gradient profiles of Burai River exhibit knick points and increase in river gradient along the tapering ends of the profiles. The study suggests active out-of-sequence neotectonically active thrusting along the mountain front. Neotectonics combined with climatic factor during the Holocene times presents a virgin landscape environment for studying tectonic geomorphology.  相似文献   

Petrological and geochemical study of serpentinised peridotites from the southern part of Manipur Ophiolitic Complex, Northeast India     

N. Ibotombi Singh  L. Debala Devi  Th. Yaiphalembi Chanu 《Journal of the Geological Society of India》2013,82(2):121-132

The southern Manipur Ophiolitic Complex in the Indo-Myanmar Orogenic Belt, Northeast India comprises a set of serpentinised peridotites, pelagic sediments, podiform chromitites with minor mafic and felsic intrusives. Peridotites in the study area suffered various degrees of serpentinisation and also have been highly deformed and metamorphosed. Striations and slickenside surfaces are common features seen in these rocks indicating the effect of faulting or shearing due to tectonic movement. On the basis of mineralogy and modal composition these peridotites have been identified as serpentinised harzburgite, lherzolite, serpentinite with minor wehrlite. The serpentine minerals are mainly lizardite and chrysotile with sub-ordinate antigorite, whereas, pyroxenes are enstatite and diopside. The primary composition of Cr-spinels in these serpentinised peridotites are characterized by low SiO₂ (<0.11 wt.%), Fe₂O₃ (0.02 to 2.32 wt.%), TiO₂ (<0.15 wt.%), Cr# (0.13 to 0.23) and high Al# (0.74 to 0.86), Mg# (0.68 to 0.73). Olivine is relatively uniform in composition, ranges from Fo_89.64 to Fo_90.1. The mineralogical compositions and primary Cr-spinel chemistry of these peridotites are similar to Abyssal peridotites that formed in a mid-ocean ridge setting after low degree of partial melting. Thus, it supports that the mantle peridotites of the Manipur Ophiolitic Complex initially formed in a spreading regime.  相似文献   

Lower Oligocene bivalves of Ramanian Stage from Kachchh, Gujarat, India     

R P Kachhara  R L Jodhawat  K Bigyapati Devi 《Journal of Earth System Science》2012,121(2):405-438

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Geochemistry of mid-ocean ridge mafic intrusives from the Manipur Ophiolitic Complex,Indo-Myanmar Orogenic Belt,NE India     

A. Krishnakanta Singh  N. Ibotombi Singh  L. Debala Devi  R. K. Bikramaditya Singh 《Journal of the Geological Society of India》2012,80(2):231-240

Mafic intrusives emplaced within the mélange zone of the Manipur Ophiolitic Complex are subalkalinetholeiitic affinity with Fe-enrichment. Based on the field occurrences, textures-mineralogy and whole-rock compositions, these mafic intrusives can be identified as type-I (gabbro intrusives) and type-II (basalt-dolerite dykes). The type-I resembling enriched-type mid-ocean ridge basalt (E-MORB) shows moderate LREE enrichment (La_N/Sm_N = 2.5–2.6), slightly enriched MORB normalized HFSE patterns possibly represent melts derived from enriched MORB sub-oceanic mantle sources by small degree of partial melting. The other type-II has normal-type mid-ocean ridge basalt (N-MORB) geochemical features, as it exhibits nearly flat to depleted LREE (La_N/Sm_N = 1.0–0.6), flat MORB normalized HFSE patterns with slight LREE/HREE depletion (Ce_N/Yb_N = 1.37–0.46). It might have been derived from depleted MORB type sub-oceanic mantle source. The MORB signature displayed by these mafic intrusives indicates that they are dismembered fragments of oceanic crust generated at mid-ocean spreading ridge system and support the hypothesis that the Manipur ophiolites was initially formed in the divergent plate margin.  相似文献   

Spatial and time variations in critical frequencies of the ionospheric <Emphasis Type="Italic">F</Emphasis> region above the zone of equatorial earthquake preparation     

A. Kh. Depueva  A. V. Mikhailov  M. Devi  A. K. Barbara 《Geomagnetism and Aeronomy》2007,47(1):129-133

Spatial and time variations in the critical frequencies foF2 before the strong earthquake of August 15, 1963, with the magnitude M = 7.75 are analyzed. The epicenter of the earthquake was located in the vicinity of the magnetic equator in the American longitudinal sector. The data of the topside ionosonde on board Alouette-1 and of the series of ground-based ionosondes has been used for this purpose. The ground-based ionosondes made it possible to detect an insignificant anomalous decrease in foF2 within the zone of earthquake preparation a few days prior to the earthquake. This result confirms the conclusion drawn earlier on the basis of the satellite data. The modification of the ionosphere at the F-region level is more evident in the satellite than in the ground-based data. It is also noted that the character of the time variations in foF2 a day before the earthquake is similar to the so called “quiet time” Q-disturbances in the ionosphere, when the electron concentration at the F region maximum differs from the median values by more than 20% under undisturbed geophysical conditions.  相似文献   

A new class of bulk viscous cosmological models in a scale covariant theory of gravitation     

N. Ibotombi Singh  S. Surendra Singh  S. Romaleima Devi 《Astrophysics and Space Science》2010,326(2):293-297

Field equations of cosmological models with bulk viscosity are constructed in the scale covariant theory of gravitation. A new class of solutions for the model is found by applying a variable deceleration parameter. Some physical implications of these solutions are briefly discussed.  相似文献   

Particle creation with time dependent gravitational and cosmological constants     

N. Ibotombi Singh  Y. Bembem Devi  S. Surendra Singh 《Astrophysics and Space Science》2013,345(1):213-216

The effect of particle creation on the evolution of FRW cosmological model has been studied. The universe has been considered as an open thermodynamic system when particle creation leads to supplementary negative creation pressure in addition to the thermodynamic pressure. Dynamical behaviors of the cosmological solutions have been studied.  相似文献