Krishna Godavari Research Articles

Multidisciplinary investigations exploring indicators of gas hydrate occurrence in the Krishna–Godavari Basin offshore, east coast of India

We report some main results of multidisciplinary investigations carried out within the framework of the Indian National Gas Hydrate Program in 2002–2003 in the Krishna–Godavari Basin offshore sector, east coast of India, to explore indicators of likely gas hydrate occurrence suggested by preliminary multi-channel seismic reflection data and estimates of gas hydrate stability zone thickness. Swath bathymetry data reveal new evidence of three distinct geomorphic units representing (1) a delta front incised by several narrow valleys and mass flows, (2) a deep fan in the east and (3) a WNW–ESE-trending sedimentary ridge in the south. Deep-tow digital side-scan sonar, multi-frequency chirp sonar, and sub-bottom profiler records indicate several surface and subsurface gas-escape features with a highly resolved stratification within the upper 50 m sedimentary strata. Multi-channel seismic reflection data show the presence of bottom simulating reflections of continuous to discrete character. Textural analyses of 76 gravity cores indicate that the sediments are mostly silty clay. Geochemical analyses reveal decreasing downcore pore water sulphate (SO4 2−) concentrations (28.7 to <4 mM), increasing downcore methane (CH4) concentrations (0–20 nM) and relatively high total organic carbon contents (1–2.5%), and microbial analyses a high abundance of microbes in top core sediments and a low abundance of sulphate-reducing bacteria in bottom core sediments. Methane-derived authigenic carbonates were identified in some cores. Combined with evidence of gas-escape features in association with bottom simulating reflections, the findings strongly suggest that the physicochemical conditions prevailing in the study area are highly conducive to methane generation and gas hydrate occurrence. Deep drilling from aboard the JOIDES Resolution during 2006 has indeed confirmed the presence of gas hydrate in the Krishna–Godavari Basin offshore.

Effect of normal faulting on in-situ stress: A case study from Mandapeta Field, Krishna-Godavari basin, India

The horizontal compressive stress orientations for Mandapeta field in Krishna-Godavari (K-G) basin had been calculated from borehole breakout data using four-arm dipmeter caliper logs. The minimum horizontal stress magnitude for Mandapeta field was calculated from pore pressure data using poroelastic equation. Three-dimensional (3-D) stress modeling using finite element analyses has been carried out for layered sediments and faulted layered sediments in the Mandapeta sub-basin. The length and width of the models are chosen as 5 km and 2 km respectively. Vertical depths of models are considered for sediments at depth 2 km to 5 km. This paper presents a numerical study of stress distributions (contours and trajectories) around fault models of layered geometries, submitted to overburden and unequal horizontal compressive loads. Reorientation and magnitude variation of in-situ stresses near faults and stress discontinuities across faults are observed. Changes in the stress patterns are observed at the interfaces between sediments due to faulting and sediment-basement layers due to contrast in elastic constants. Remarkable stress gradients are observed between the sediment and basement. Magnitudes of normal component of stress decrease near the faulting whereas shear stress magnitudes increase at the faulting site. There is increase of horizontal principal stresses in the downthrown faulted layers. The maximum horizontal principal stress rotates about 90° just adjacent to the fault. Fluid flow at depth of oil reservoir could be indirectly influenced by the stress contours and by geometries of the stress trajectories. Fluid migration in low permeability reservoir may occur in response to mean stress gradients induced by the tectonic loading. The areas of high mean stress gradient are located at the interface between sediment and basement whereas the areas of low mean stress gradient is exactly coinciding with the areas of upper sediments.

Main Deccan volcanism phase ends near the K–T boundary: Evidence from the Krishna–Godavari Basin, SE India

Recent studies indicate that the bulk (80%) of the Deccan trap eruptions occurred over less than 0.8 m.y. in magnetic polarity C29r spanning the Cretaceous–Tertiary (K–T) boundary. Determining where within this major eruptive phase the K–T mass extinction occurred has remained problematic. For this reason, models estimating the biotic and environmental consequences have generally underestimated the rate and quantity of Deccan gas emissions by orders of magnitude leading to conclusions that volcanism could not have been one of the major causes for the K–T mass extinction. In this study we report that the most massive Deccan trap eruption occurred near the K–T mass extinction. These results are based on sedimentologic, microfacies and biostratigraphic data of 4–9 m thick intertrappean sediments in four quarry outcrops in the Rajahmundry area of the Krishna–Godavari Basin of southeastern India. In this area two Deccan basalt flows, known as the Rajahmundry traps, mark the longest lava flows extending 1500 km across the Indian continent and into the Bay of Bengal. The sediments directly overlying the lower Rajahmundry trap contain early Danian planktic foraminiferal assemblages of zone P1a, which mark the evolution in the aftermath of the K–T mass extinction. The upper Rajahmundry trap was deposited in magnetic polarity C29n, preceding full biotic recovery. These results suggest that volcanism may have played critical roles in both the K–T mass extinction and the delayed biotic recovery.

40K– 40Ar dating of the Main Deccan large igneous province: Further evidence of KTB age and short duration

Most mass extinctions coincide in time with outpourings of continental flood basalts (CFB). Some 20 years ago, it was shown [Courtillot, V., Besse, J., Vandamme, D., Montigny, R., Jaeger, J.-J., Cappetta, H., 1986. Deccan flood basalts at the Cretaceous/Tertiary boundary? Earth Planet. Sci. Lett. 80, 361–374; Courtillot, V., Feraud, G., Maluski, H., Vandamme, D., Moreau, M.G., Besse, J., 1988. Deccan flood basalts and the Cretaceous/Tertiary boundary. Nature 333, 843–846; Duncan, R.A., Pyle, D.G., 1988. Rapid eruption of the Deccan flood basalts at the Cretaceous/Tertiary boundary. Nature 333 841–843] that the age of the Deccan traps was close to the Cretaceous–Tertiary (KT) boundary and its duration under 1 Myr. We have undertaken a new geochronological study, using the (unconventional) 40K– 40Ar Cassignol–Gillot technique which is particularly well suited to the potassium-poor Deccan lavas. The mean of 4 determinations from the topmost (Ambenali and Mahabaleshwar) Formations is 64.5 ± 0.6 Ma. They straddle the C29r/C29n reversal boundary for which they provide a new constraint. The mean age of 3 determinations from the oldest (Jawhar) Formation is 64.8 ± 0.6 Ma. The difference in age between top and bottom of a 3500 m composite section, probably comprising 80% of the total Deccan volume, is statistically insignificant, with the overall mean age being 64.7 ± 0.6 Ma ( N = 7). Our results are consistent with the most recent 40Ar/ 39Ar determinations [Knight, K.B., Renne, P.R., Halkett, A., White, N., 2003. 40Ar/ 39Ar dating of the Rajahmundry Traps, eastern India and their relationship to the Deccan traps. Earth Planet. Sci. Lett. 208, 85–99; Knight, K.B., Renne, P.R., Baker, J., Waight, T., White, N., 2005. Reply to ‘40Ar/39Ar dating of the Rajahmundry Traps, Eastern India and their relationship to the Deccan Traps: Discussion’ by A.K. Baksi. Earth Planet. Sci. Lett. 239, 374–382], confirming that there should be no systematic difference between the two methods when they are used in an optimal way. An earlier, smaller but significant, pulse of volcanism between 68 and 67 Ma, extending over at least 500 km in latitude in the northern part of the Deccan CFB has also been identified. After 2 to 3 Ma of quiescence, the second, major phase of volcanism occurred near 65 Ma, expanding over most of the area covered by the first pulse and another 500 km to the South, consistent with drift of India by 300 to 450 km at ∼ 150 mm/yr during the quiescence period. New paleontological data from the remote Rajahmundry section [Keller, G., Adatte, T., Gardin, S., Bartolini, A., Bajpai, S., Humler, E., in prep. The Cretaceous–Tertiary boundary in Deccan Traps of the Krishna–Godavari Basin of southeastern India. EPSL to be submitted] suggest that this second pulse can itself be divided into two major pulses, one starting in C29r and ending at the KT boundary, the second starting in the upper part of C29r and ending within C29n.

Impact of phase variations on quantitative AVO analysis: An example from Krishna Godavari Basin, India

Krishna Godavari Basin on the east coast of India is one of the country's most promising petroliferous basins, with commercial accumulations of hydrocarbons on land and offshore (Figure 1). Estimated resources in the basin are around 2000 million tons of oil or oil-equivalent gas. The reservoirs are in sediments of all ages, Permian to Pliocene.

Structure of Charnockitic basement in a part of the Krishna-Godavari basin, Andhra Pradesh

A regional magnetic survey was carried out over an area of 8000 km2 in Godavari districts of Andhra Pradesh, India, which is covered by the rocks of Eastern Ghat Mobile Belt (EGMB)viz., the Khondalitic series and Charnockites in the northern half and Permian to Mesozoic and Cenozoic sediments in the southern half, and forms a part of the Krishna-Godavari (K-G) basin. The survey brought out a strong NE-SW trending anomaly in the area covered by the rocks of Eastern Ghat Mobile Belt (EGMB), and a mild ENE-WSW trending anomaly in the area covered by the sediments of the Krishna-Godavari (K-G) basin. The NE-SW trending anomaly in the northern half could be attributed to the exposed/near surface Charnockite basement that has come closer to the surface as a result of Eastern Ghat Mobile Belt (EGMB) tectonics. Explanation of the mild ENE-WSW trending anomaly over the sediments of the Krishna-Godavari (K-G) basin required a faulted magnetic basement at depth downthrown towards the south. It is therefore concluded that the Charnockitic basement together with the Khondalite group of rocks which are folded and faulted during the different phases of tectonics of Eastern Ghat Mobile Belt (EGMB) extend into the Krishna-Godavari (K-G) basin and further, were involved in faulting during the phases of formation and sedimentation in the Krishna-Godavari (K-G) basin.

Basin architecture and petroleum system of Krishna Godavari Basin, east coast of India

Krishna Godavari Basin is a peri-cratonic passive margin basin on the east coast of India (Figure 1). The onland part consists of 28 000 km2 and is mostly alluvium covered. Krishna and Godavari are the two major river systems which drain the area and discharge in the Bay of Bengal. The offshore basinal area covers 24 000 km2 to the isobath of 200 m. However, the basin extends into deeper water and covers a much larger area. The basin's characteristic feature is its en-echelon horst and graben system which is filled with a thick pile of sediments of Permian-to-Recent age and emerging as one of India's most promising petroliferous areas. Commercial accumulation of hydrocarbons occurs in sediments from the Permian to as young as the Pliocene.

Miocene deep water agglutinated foraminifera from offshore Krishna-Godavari Basin, India

Research Article| January 01, 2004 Miocene deep water agglutinated foraminifera from offshore Krishna-Godavari Basin, India Abiraman Govindan Abiraman Govindan Asian Biostratigraphic Services, H-53, Central Avenue, Chennai - 600 080, India, email: govindan@md2.vsnl.net.in Search for other works by this author on: GSW Google Scholar Micropaleontology (2004) 50 (3): 213–252. https://doi.org/10.2113/50.3.213 Article history received: 15 Sep 2003 accepted: 14 Oct 2004 first online: 06 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Abiraman Govindan; Miocene deep water agglutinated foraminifera from offshore Krishna-Godavari Basin, India. Micropaleontology 2004;; 50 (3): 213–252. doi: https://doi.org/10.2113/50.3.213 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyMicropaleontology Search Advanced Search Abstract The Krishna Godavari Basin is located in the East Coast Indian Peninsula containing 5 to 7 km of Cretaceous through Cenozoic terrigenous clastic sediments. The Miocene-Pliocene section in the offshore is known as the Ravva Formation, a major argillaceous facies with sandstone beds from which oil and gas are being produced. In this sequence, some cutting samples studied from four offshore wells were found to be rich in agglutinated benthic foraminifera, while planktic foraminifera were absent at these levels. These samples were studied in much detail for agglutinated foraminifera. A total of fifty-nine agglutinated foraminiferal species belonging to thirty-five genera have been identified. Two new species, Alveolophragmium indicum Govindan n. sp and Liebusella krishna Govindan n. sp., are described. All these species are reported for the first time from this region. The agglutinated benthic foraminiferal taxa bear close resemblance to those of Miocene agglutinated foraminifera assemblages reported from South Trinidad, the Falcon Basin of Venezuela, and offshore West Africa. The present report of alveolar genera, Alveovalvulina, Alveovalvulinella and Guppyella, and compressed, inner partitioned alveolar genera Pavonitina and Spiropsammia, together with other genera having complex reticulate inner structure as Cyclammina, Reticulophragmium and Alveolophragmium in this region are of great importance for the evaluation of biostratigraphy, paleoecology, paleobiogeography and burial history. Paleoecological analysis reveals three agglutinated foraminiferal biofacies/groupings, which characterize beyond outer shelf through bathyal slope (500 to 1500m) depth regimes in an oxygen minimum deep water setting for the deposition of these turbidite/debris flow sediments.A major marine transgression at the close of the Oligocene probably caused a moderately rich, more uniform distribution of deep water agglutinated species over this deep basin. Additional observations on the agglutinated benthic assemblage such as deformation of the tests, coloration of the tests and stratigraphic markers are also dealt with briefly. You do not currently have access to this article.

57Fe Mössbauer spectroscopic study of organic-rich sediments (source rocks) from test wells CTP-1 and MDP-1 located in Eastern Krishna–Godavari basin, India

A large number of sub-surface sedimentary samples using Mössbauer spectroscopy were obtained from various depths of wells CTP-1 and MDP-1 drilled in Eastern Krishna–Godavari basin (KG basin) of India. Results indicate that iron is distributed in pyrite, siderite and in clay minerals, apart from these minerals an anomalously large presence of sulfate minerals was also found. Their presence indicates oxidizing conditions in sediments. Significance of presence of minerals, which show oxidizing conditions in context of source rock characterization, is discussed.

Miocene deep water agglutinated foraminifera from offshore Krishna-Godavari Basin, India

Abstract The Krishna Godavari Basin is located in the East Coast Indian Peninsula containing 5 to 7 km of Cretaceous through Cenozoic terrigenous clastic sediments. The Miocene-Pliocene section in the offshore is known as the Ravva Formation, a major argillaceous facies with sandstone beds from which oil and gas are being produced. In this sequence, some cutting samples studied from four offshore wells were found to be rich in agglutinated benthic foraminifera, while planktic foraminifera were absent at these levels. These samples were studied in much detail for agglutinated foraminifera. A total of fifty-nine agglutinated foraminiferal species belonging to thirty-five genera have been identified. Two new species, Alveolophragmium indicum Govindan n. sp and Liebusella krishna Govindan n. sp., are described. All these species are reported for the first time from this region. The agglutinated benthic foraminiferal taxa bear close resemblance to those of Miocene agglutinated foraminifera assemblages reported...

Regional tectonic framework of the Pranhita–Godavari basin, India

The Pranhita-Godavari Gondwana rift (PGR) has a co-genetic relationship with Permo-Triassic reactivation of the Narmada–Son Geofracture (NSG). The Satpura Gondwana basin represents the terminal depocentre against the NSG, which restricted the northwestward propagation of the PGR. The NE–SW tensional stress responsible for the NW–SE trending PGR could not propagate beyond the ramp formed by uplift along the NSG and transformed kinetically into an ENE directed horizontal shear along the NSG, inducing large scale strike–slip movements. The latter dynamics were responsible for ENE extension of the Satpura rift as a pull-apart basin. The PGR extends up to the present east coast of India, where it is apparently terminated by the NE–SW trending Bapatla ridge along the Eastern Ghat Rift (EGR). The subsurface data, however, shows that the PGR extends across the Bapatla ridge and continues beneath the Cretaceous–Tertiary sediments of the Krishna–Godavari basin (KG) in the EGR. Thus, the Permo-Triassic PGR appears to have continued in the Indo-Antarctic plate before the Cretaceous break up. The EGR, during break up of the continents, cuts across the PGR and the KG basin was superimposed on it. The PGR site is located on a paleo-suture between the Dharwar and Bastar proto-cratons. The master faults developed bordering the rift, and the intra-rift higher order faults followed the pre-existing fabric. The transverse transfer zones manifested as basement ridges, divide the rift into segments of tectono-sedimentary domains. The major domains are the Chintalapudi, Godavari, and Chandrapur sub-basins, each of which subsided differentially. The central Godavari sub-basin subsided most and shows maximum structural complexity and sediment accommodation. The rifting started with initial half-graben faulting along the northeastern master fault and expanded by successive half graben faulting. This gave rise to intra-basinal horsts and grabens, which exercised control on the syn-rift sedimentation. The southeastern boundary fault developed as a strike–slip fault in response to plate rotation and the rift expansion was constrained by it.The basin fill sediments were deposited during two rifting events—Early Permian to (?) Early Jurassic Lower Gondwana rifting, and Early Cretaceous Upper Gondwana rifting. The Lower Gondwana sedimentation started with a pre-rift crustal sagging over the rift site and was filled by glaciogenic Talchir sediments. This was followed by syn-rift-fluvial sedimentation in repeating cycles during the early to late rift stages. Early Cretaceous Chikiala and Gangapur sediments were deposited during the Upper Gondwana rifting. The fluvial cycles were tectonically controlled during each rift stage. The absence of igneous intrusions indicates that the PGR is a passive rift in contrast to the rifts developed in the NSG zone.

Evolution in Basin Fill Style During the Mesozoic Gondwana Continental Break-up in the Godavari Triple Junction, SE India

Consistent changes are observed in the Mesozoic sedimentary lithofacies and palaeocurrents during the transition from the continental Gondwana (NW-SE trending Chintalpudi Graben - CG) to the coastal Gondwana (NE-SW trending Krishna Godavari Coastal Basin - KGCB) in the Godavari Triple Junction (GTJ). The Mesozoic continental Gondwana sediments include the Kamthi (early Triassic), Kota (Jurassic) and Gangapur (early Cretaceous) Formations. Coastal Gondwana succession comprising the Raghavapuram (early Cretaceous) and the Tirupati (Middle to late Cretaceous) Formations transversely superimpose the continental Gondwana. The Continental Gondwana is mainly cross-stratified sandstone and fossiliferous ( Glossopteris and Ptilophyllum flora) clay assemblage of alluvial environment. Palaeocurrent is towards NW in the Kamthi Formation, WNW in the Kota Formation and centripetal in the Gangapur Formation. The Raghavapuram Formation (KGCB) comprises of grey/carbonaceous clay-sandstone association of SE flowing delta plain distributories with inter-distributory swamps and fossiliferous white clay (a mix of Ptilophyllum flora and invertebrate fauna) of prodelta / shallow marine environment. The succeeding sandstone- conglomerate facies of the Tirupati Formation (Middle to late Cretaceous) with SE palaeocurrent indicates delta progradation whereas the infratrappean clay-limestone beds (mainly invertebrate fauna of Maastrichtian age) point to delta abandonment, prior to the K/T boundary volcanism. Tectono-sedimentary model presented in this communication incorporates that the change from the continental Gondwana to coastal Gondwana had occurred in four stages. During stage-I (late Carboniferous to early Jurassic) the sediments were deposited by a north-westerly flowing alluvial system whose distal source was located in southeast beyond the east coast of India. Stage -II (Middle to late Jurassic) is marked by westerly shift in palaeocurrents attributed to an obstruction caused by an upliftment of the Mailaram high parallel to the NE-SW Eastern Ghat trend. Stage-III (early Cretaceous) is heralded by the onset of deltaic sedimentation in SE due to separation of landmass that supplied detritus to the CG until the end of the Jurassic. During stage-IV, the delta progradation is accentuated by the basement uplift (Eastern Ghat Mobile Belt). It is suggested that the change over from continental Gondwana to coastal Gondwana had occurred over a time span of about 70 my between late Jurassic to Cretaceous and controlled by phase-wise upliftment of the basement as a corollary to the Gondwana continental break-up.

Gravity anomalies, sediment loading and lithospheric flexure associated with the Krishna–Godavari basin, eastern continental margin of India

Gravity anomalies constrained by seismic data have been used to examine the long-term mechanical properties of the lithosphere beneath the Krishna–Godavari basin, a deltaic sedimentary basin on the eastern continental margin of India. The gravity effect of the rift crust, sedimentary loading and erosional unloading have been computed and the sum effect of these, when compared with the observed gravity anomalies, gives a best fitting Te of 30 km at the margin. The results suggest that the lithosphere, which was weak during the early rifting-stage, has gained strength during sedimentation. The onshore dipping doublet gravity anomaly at the margin reflects a weak rifted continental lithosphere abutting a strong oceanic lithosphere. Comparison with the results of similar investigations for the Bengal basin in the north and Cauvery basin in the south suggests increasing strength for the lithosphere from north to south.

Teleseismic delay-time tomography of the upper mantle beneath southeastern India: imprint of Indo-Antarctica rifting

A 3-D P-velocity map of the crust and upper mantle beneath the southeastern part of India has been reconstructed through the inversion of teleseismic traveltimes. Salient geological features in the study region include the Archean Dharwar Craton and Eastern Ghat metamorphic belt (EGMB), and the Proterozoic Cuddapah and Godavari basins. The Krishna—Godavari basin, on the eastern coastal margin, evolved in response to the Indo—Antarctica breakup. A 24-station temporary network provided 1161 traveltimes, which were used to model 3-D P-velocity variation. The velocity model accounts of 80 per cent of the observed data variance. The velocity picture to a depth of 120 km shows two patterns: a high velocity beneath the interior domain (Dharwar craton and Cuddapah basin), and a lower velocity beneath the eastern margin region (EGMB and coastal basin). Across the array velocity variations of 7–10 per cent in the crust (0–40 km) and 3–5 per cent in the uppermost mantle (40–120 km) are observed. At deeper levels (120–210 km) the upper-mantle velocity differences are insignificant among different geological units. The presence of such a low velocity along the eastern margin suggests significantly thin lithosphere (<100 km) beneath it compared to a thick lithosphere (>200 km) beneath the eastern Dharwar craton. Such lithospheric thinning could be a consequence of Indo—Antarctica break-up.

Marine magnetic anomalies as a link between the granulite belts of east coast of India and Enderby Land of Antarctica : Murthy K.S.R., Rao M.M.M., Venkateswarlu K., Subrahmanyam A.S., Lakshminarayana S. & Rao T.C.S., Journal — Geological Society of India, 1997, 49/2 (153–158)

Magnetic data of the eastern continental margin of India (ECMI) helped in demarcating the offshore extension of the granulite belts of east coast of India and their possible link to those of the East Antarctica. Short wavelength and high amplitude negative magnetic anomalies (200 to 1600 nT) are observed over the northern part of ECMI between Kakinada and Chilka lake and also off Madras shelf, the coastal regions of which are associated with granulite facies rocks . This part of the shelf is associated with structural lineaments with predominant NE-SW trends . In contrast, the offshore basins off Cauvery, Krishna - Godavari (K-G) and Mahanadi rivers are associated with subdued positive anomalies (less than 200 nT) indicating subsidence off these basins by heavy load of Phanerozoic/younger shelf sediments. Structural lineaments with NW-SE or W-E trends delineated over these basins are related to the offshore extension of these rift related Gondwana grabens. Similarity in the trends of the magnetic anomalies and the granulite facies on the east coast of India and their correlation with the granulite belt of Enderby Land of Antarctica supports the view that the entire region comprised of a single and stable block of granulite rocks prior to the fragmentation of the Gondwanaland. The study also suggests probable continuation of Mahanadi and Godavari grabens into East Antarctica.