Papers by Mohammad Ismaiel
Logging data are measurements of physical properties of the formation surrounding a borehole, acq... more Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.
Proceedings of the International Ocean Discovery Program, 2019
Proceedings of the International Ocean Discovery Program, 2019
This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) lic... more This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Contents 1 Operations 5 Lithostratigraphy 16 Structural geology 20 Micropaleontology 25 Geochemistry 30 Physical properties 37 Paleomagnetism 41 Downhole measurements 45 Core-log-seismic integration 51 References Operations During International Ocean Discovery Program (IODP) Expedition 381, cores were recovered from one hole at Site M0080 (Figures F1, F2). Drilling and coring in Hole M0080A was completed to 534.1 meters below seafloor (mbsf) in 13 days, achieving an average core recovery of 84% (see Table T1 for details). The Fugro Corer in both push and percussive modes was used to collect the upper 141 m of sediment. The Fugro Extended Marine Core Barrel (FXMCB) was used to complete the lower 393 m of the borehole. Wireline logging operations were then conducted over 2 days.
Proceedings of the International Ocean Discovery Program, 2019
This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) lic... more This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Contents 1 Operations 7 Lithostratigraphy 15 Structural geology 18 Micropaleontology 25 Geochemistry 30 Physical properties 38 Paleomagnetism 44 Core-log-seismic integration 47 References
Proceedings of the International Ocean Discovery Program, 2019
This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) lic... more This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Contents 1 Operations 5 Lithostratigraphy 14 Structural geology 16 Micropaleontology 22 Geochemistry 27 Physical properties 34 Paleomagnetism 38 Downhole measurements 42 Core-log-seismic integration 45 References Operations During International Ocean Discovery Program (IODP) Expedition 381, cores were recovered from one hole at Site M0079 (Figures F1, F2). In total, 18 days were spent on station, with an average core recovery of 86.65% for the site (Table T1). Drilling and coring in Hole M0079A was completed to 704.9 meters below seafloor (mbsf) using two tools in 14 days. The Fugro Corer in push mode collected the upper 67 m of sediment, and the Fugro Corer in percussive mode collected the next 81 m. The Fugro Extended Marine Core Barrel (FXMCB) was then used to complete the lowermost 556 m of the borehole.
Social Science Research Network, 2023
A voyage from Chennai across the Bay of Bengal takes one eventually to the Andaman Islands. But i... more A voyage from Chennai across the Bay of Bengal takes one eventually to the Andaman Islands. But it was a different situation in the geologic past during the Late Cretaceous (80–68 m.y. BP). There was a chain of islands somewhere midway which currently lies as the buried 85E Ridge beneath enormously thick sediments discharged by the Ganges and Brahmaputra river systems. The 85E Ridge, located in the Bay of Bengal extends from the Mahanadi Basin in north Bay of Bengal to the Afanasy Nikitin seamounts in equatorial Indian Ocean for a distance of about 2500 km (Figure 1). This is an enigmatic geological feature as it possesses inexplicable gravity and magnetic signatures. The ridge structure in the Bay of Bengal is associated with prominent negative freeair gravity anomaly, despite its excess mass and alternative streaks of unevenly distributed positive and negative magnetic anomalies. Therefore, the 85E
Journal of Asian Earth Sciences, 2018
The ocean floor in the Bay of Bengal has evolved after the breakup of India from Antarctica since... more The ocean floor in the Bay of Bengal has evolved after the breakup of India from Antarctica since the Early Cretaceous. Recent geophysical investigations including updated satellite derived gravity map postulated two phases for the tectonic evolution of the Bay of Bengal, the first phase of spreading occurred in the NW-SE direction forming its Western Basin, while the second phase occurred in the N-S direction resulting in its Eastern Basin. Lack of magnetic data along the spreading direction in the Western Basin prompted us to acquire new magnetic data along four tracks (totaling ∼3000 km) to validate the previously identified magnetic anomaly picks. Comparison of the synthetic seafloor spreading model with the observed magnetic anomalies confirmed the presence of Mesozoic anomalies M12n to M0 in the Western Basin. Further, the model suggests that this spreading between India and Antarctica took place with half-spreading rates of 2.7-4.5 cm/yr. The trend of the fracture zones in the Western Basin with respect to that of the Southeastern Continental Margin of India (SCMI) suggests that SCMI is an oblique transform margin with 37°obliquity. Further, the SCMI consists of two oblique transform segments separated by a small rift segment. The strike-slip motion along the SCMI is bounded by the rift segments of the Northeastern Continental Margin of India and the southern margin of Sri Lanka. The margin configuration and fracture zones inferred in its conjugate Western Enderby Basin, East Antarctica helped in inferring three spreading corridors off the SCMI in the Western Basin of the Bay of Bengal. Detailed grid reconstruction models traced the oblique strike-slip motion off the SCMI since M12n time. The strike-slip motion along the short northern transform segment ended by M11n time. The longer transform segment, found east of Sri Lanka lost its obliquity and became a pure oceanic transform fault by M0 time. The eastward propagation of the Africa-Antarctica spreading center initiated the anticlockwise separation of Sri Lanka from India by M12n time. Seafloor spreading south of Sri Lanka due to the India-Antarctica spreading episode and the simultaneously occurring strike-slip motion east of Sri Lanka restricted this separation resulting in a failed rift. Thus Sri Lanka with strike-slip motion to its east, failed rift towards west, continental extension to its north and rifting to its south behaved as a short lived microplate during the Early Cretaceous period and remained attached to India thereafter.
Journal of Geophysical Research: Solid Earth, 2019
We evaluate the environmental magnetic, geochemical, and sedimentological records from three sedi... more We evaluate the environmental magnetic, geochemical, and sedimentological records from three sediment cores from potential methane-hydrate bearing sites to unravel linkages between sedimentation, shale tectonics, magnetite enrichment, diagenesis, and gas hydrate formation in the Krishna-Godavari basin. Based on downcore rock magnetic variations, four sedimentary magnetic property zones (I-IV) are demarcated. A uniform band of enhanced magnetic susceptibility (zone III) appears to reflect a period of high-sedimentation events in the Krishna-Godavari basin. Highly pressurized sedimentary strata developed as a result of increased sedimentation that triggered the development of a fault system that provided conduits for upward methane migration to enter the gas hydrate stability zone, leading to the formation of gas hydrate deposits that potentially seal the fault system. Magnetic susceptibility fluctuations and the presence of iron sulfides in a magnetically enhanced zone suggest that fault system growth facilitated episodic methane venting from deeper sources that led to multiple methane seepage events. Pyrite formation along sediment fractures resulted in diagenetic depletion of magnetic signals and potentially indicates paleo sulfate-methane transition zone positions. We demonstrate that a close correlation between magnetic susceptibility and chromium reducible sulfur concentration can be used as a proxy to constrain paleomethane seepage events. Our findings suggest that the interplay between higher sedimentation events and shale tectonism facilitated fluid/gas migration and trapping and the development of the gas hydrate system in the Krishna-Godavari basin. The proposed magnetic mineralogical approach has wider scope to constrain the understanding of gas hydrate systems in marine sediments.
Journal of the Geological Society, 2019
The thick sedimentary cover (≤18 km) along the Eastern Continental Margin of India (ECMI) and ove... more The thick sedimentary cover (≤18 km) along the Eastern Continental Margin of India (ECMI) and over the Bay of Bengal has hindered understanding of the mechanisms of rifting that operated on the eastern Indian and Bangladesh margins. Analysis of multichannel seismic reflection data, together with 3D gravity inversion and 2D gravity forward modelling, illuminates basement configuration, crustal thickness and Moho topography, thereby revealing the modes of rift evolution and the location of the continent–ocean boundary (COB) along these margins. The basement, particularly in the shelf and slope regions of eastern peninsular India, is traversed by nearly coast-perpendicular graben, and their seaward continuity is delineated up to 125 km from the coastline. Three different types of continental margin are present along the ECMI: (1) sheared rift on the southern segment of the ECMI, up to 14° N latitude (offshore the Southern Granulite Terrain); (2) hyper-extended rift in the central segment between 14° N and 17° N (offshore the Dharwar Craton); and (3) hypo-extended rift on the northern segment between 17° N and 20° N (offshore the Eastern Ghats Mobile Belt). The graben terminations, crustal thickness and Moho topography of both the ECMI and offshore Bengal Basin clearly suggest that the COB runs nearly parallel to the coastline of peninsular India, but takes an orthogonal turn offshore in the Bengal Basin and connects the palaeo-continental shelf and the Rajmahal–Sylhet Line onshore in the Bengal Basin. Crustal thickness (8–10 km) and depth to the Moho discontinuity (≤28 km) beneath the Bangladesh margin are unusual because the crustal thickness increased through interaction of the Kerguelen plume with the existing oceanic lithosphere. The Moho deepened largely due to the load of the Bengal Fan sediments. The absence of rifted crustal blocks on the Bangladesh margin and the continuity of the COB into the onshore Bengal Basin together imply that the present Bangladesh region was under marine conditions at least until the beginning of Bengal Fan sedimentation (i.e. no less than 23 Ma).
Marine and Petroleum Geology, 2016
Marine and Petroleum Geology, 2017
Key Points: 1. High-quality seismic data image the internal structure of the 85°E Ridge 2. Volcan... more Key Points: 1. High-quality seismic data image the internal structure of the 85°E Ridge 2. Volcanic conduit and series of lava deltas identified within the 85°E Ridge reveal nature of the ridge 3. Tectonic model proposed for the emplacement of the 85°E Ridge and its growth through time
Journal of Geophysical Research: Solid Earth, 2016
KEY POINTS 1. Identification of marine magnetic anomalies M12n to M0 in the Western Basin of the ... more KEY POINTS 1. Identification of marine magnetic anomalies M12n to M0 in the Western Basin of the Bay of Bengal conjugate to the Western Enderby Basin, off East Antarctica. 2. Establishment of boundary between continental and oceanic crust in Bangladesh along line joining the Rajmahal and Sylhet traps (R-S line). 3. Ridge jumpby~118Ma from the Western Enderby Basin to the R-S line with a likely change in spreading direction for the Indian plate. 4. The 85°E Ridge was initially evolved as a fracture zone, and subsequently associated with volcanism. 5. The oceanic crust of the Western Basin of the Bay of Bengal is older than the crust of the Eastern Basin and Bangladesh.
Current Science, 2016
The sediment succession in the Bay of Bengal (BoB) records the signatures corresponding to India-... more The sediment succession in the Bay of Bengal (BoB) records the signatures corresponding to India-Asia collision, regional climate change, and erosional processes of both the Himalayan orogen and Indian subcontinent. The Bengal Fan-the world's largest submarine fan-has long been studied to understand the link between the Himalayan tectonics and Asian monsoon. But, lack of detailed information on corresponding signals hampered the understanding of related processes of tectonics, climate and erosion. The present study of long-streamer seismic reflection profile data and information from deep drill well logs in the western BoB has revealed two different phases of sediment deposition. In the first phase, until Oligocene-Miocene (~23 Ma), Indian peninsular rivers discharged sediments to the BoB which accumulated at a rate ~20 m/m.y. with an aberration of two fairly enhanced sediment pulses during the periods from 65 to 54 Ma and 34 to 23 Ma. In the second phase, since 23 Ma, the Ganges and Brahmaputra rivers added huge volumes of sediments to the bay at variable rates ranging from 40 to >1000 m/m.y. A distinct increase in sediment discharge (~140 m/m.y.) during the Oligocene-Miocene (~23 Ma) together with the development of regional onlap unconformity and the start of turbidity system provide an important age marker corresponding to rapid exhumation of the Himalaya, which intensified the erosional process and commencement of Bengal Fan sedimentation. Further rise in the rate of sedimentation during the period 6.8-0.8 Ma is coincident with the change in monsoon intensity, but surprisingly not in agreement with the decrease in sediment rate reported at ODP Leg 116 sites in the distal Bengal Fan. Here we provide wellconstrained ages for the commencement and growth of the Bengal Fan, which can serve as benchmark information for understanding the interaction between the Himalayan exhumation and Asian climate.
Logging data are measurements of physical properties of the formation surrounding a borehole, acq... more Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.
Scientific Reports
Young rifts are shaped by combined tectonic and surface processes and climate, yet few records ex... more Young rifts are shaped by combined tectonic and surface processes and climate, yet few records exist to evaluate the interplay of these processes over an extended period of early rift-basin development. Here, we present the longest and highest resolution record of sediment flux and paleoenvironmental changes when a young rift connects to the global oceans. New results from International ocean Discovery Program (IODP) Expedition 381 in the Corinth Rift show 10s-100s of kyr cyclic variations in basin paleoenvironment as eustatic sea level fluctuated with respect to sills bounding this semiisolated basin, and reveal substantial corresponding changes in the volume and character of sediment delivered into the rift. During interglacials, when the basin was marine, sedimentation rates were lower
The ocean floor in the Bay of Bengal has evolved after the breakup of India from Antarctica since... more The ocean floor in the Bay of Bengal has evolved after the breakup of India from Antarctica since the Early Cretaceous. Recent geophysical investigations including updated satellite derived gravity map postulated two phases for the tectonic evolution of the Bay of Bengal, the first phase of spreading occurred in the NW-SE direction forming its Western Basin, while the second phase occurred in the N-S direction resulting in its Eastern Basin.
A voyage from Chennai across the Bay of Bengal takes one eventually to the Andaman Islands. But i... more A voyage from Chennai across the Bay of Bengal takes one eventually to the Andaman Islands. But it was a different situation in the geologic past during the Late Cretaceous (80–68 m.y. BP). There was a chain of islands somewhere midwy which currently lies as the buried 85E Ridge beneath enormously thick sediments discharged by the Ganges and Brahmaputra river systems.
The 85 E Ridge, located in the Bay of Bengal of the northeastern Indian Ocean is an enigmatic geo... more The 85 E Ridge, located in the Bay of Bengal of the northeastern Indian Ocean is an enigmatic geological feature as it possesses unusual geophysical signatures. The ridge's internal structure and mode of eruptions are unknown due to lack of deep seismic reflection and borehole data control. Here, we analyze 10 km of long-streamer seismic reflection data to unravel the ridge's internal structure, and thereby to enhance the understanding of how the ridge was originated and grew over a geologic time. Seismic facies analysis reveals the ridge structure consisting of volcanic vent and several stratigraphic units including packs of prograding clinoforms. The clinoform sequences are interpreted as volcanic successions, and led to the formation of lava-delta fronts. Interpreted features of lava-fed deltas and intervening erosional surfaces, and mass flows along ridge flanks suggest that the 85 E Ridge is a volcanic construct, and was built by both subaqueous and multiphase submarine volcanism during the Late Cretaceous (approximately from 85 to 80 Ma). At later time, from Oligocene-Miocene (~23 Ma) onwards the ridge was buried under the thick sediments of the Bengal Fan system.
We are able to decipher the tectonic evolution of the Bay of Bengal, a puzzle which has not been ... more We are able to decipher the tectonic evolution of the Bay of Bengal, a puzzle which has not been satisfactorily solved in the past, and we are also able to shed new light on origin of the buried 85°E Ridge. We do so by incorporating a number of disparate items into a unified solution. These items are the marine magnetic anomalies in the Western Basin of the Bay of Bengal, the Rajmahal and Sylhet traps, and Deep Seismic Sounding lines in India, a prominent magnetic anomaly doublet and seismic Seaward Dipping Reflectors in Bangladesh, and a new precise gravity map of the Bay of Bengal. We identify seafloor-spreading magnetic anomalies ranging in age from 132 Ma (M12n) to 120 Ma (M0) in the Western Basin. These anomalies are " one sided " ; the conjugate anomalies lie in the Western Enderby Basin, off East Antarctica. The direction of spreading was approximately NW-SE, and the half-spreading rates varied from 2.5 to 4.0 cm/yr. With the arrival of the Kerguelen plume around M0 time, seafloor spreading was reorganized and a new spreading axis opened at or close to the line joining the Rajmahal and Sylhet traps. The prominent magnetic anomaly doublet connecting the Rajmahal and Sylhet traps indicates that these traps are not individual eruptions at about 118 Ma, but rather, together, define the new line of opening. Spreading started at this line, and subsequently, India changed direction from west to north. The new oceanic crust, thus generated, underlies Bangladesh and the Eastern Basin of the Bay of Bengal and is younger than 118 Ma. The western boundary of the new ocean floor is a transform fault, which was generated by the spreading axis jump. This transform fault appears as the 85°E Ridge, and further north, on land, as a negative free-air gravity anomaly strip. A unique feature of the northern boundary of the new oceanic crust is that due to the later deposition of enormous sediments derived from the Himalayan orogeny, it lies onshore Bangladesh, in contrast to most continent-ocean boundaries in the world, which lie offshore.
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Papers by Mohammad Ismaiel