Global overturning circulation underwent significant changes in the late Miocene, driven by tecto... more Global overturning circulation underwent significant changes in the late Miocene, driven by tectonic forcing, and impacted the global climate. Prevailing hypotheses related to the late Miocene deep water circulation (DWC) changes driven by the closure of the Central American Seaways (CAS) and its widespread impact remains untested due to the paucity of suitable records away from the CAS region. Here, we test the hypothesis of the large-scale circulation changes by providing a high-resolution record of DWC since the late Miocene (11.3 to ~2 Ma) from the north-western Indian Ocean. Our investigation reveals a progressive shift from Pacific-dominated DWC before ~9.0 Ma to the onset of a modern-like DWC system in the Indian Ocean comprising of Antarctic bottom water and northern component water during the Miocene-Pliocene transition (~6 Ma) caused by progressive shoaling of the CAS and suggests its widespread impact.
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.
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.
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.
... Sagar Kanya, Sagar Purvi and Sagar Paschimi ??? the vessels of the Ministry of Earth Sciences... more ... Sagar Kanya, Sagar Purvi and Sagar Paschimi ??? the vessels of the Ministry of Earth Sciences, Government of India, and Akademik Boris Petrov, a research vessel that was hired, were deployed in search and recovery opera-tions. ...
The Larsemann Hills area in the eastern Antarctica constitutes a few of the small islands apart f... more The Larsemann Hills area in the eastern Antarctica constitutes a few of the small islands apart from the mainland. Many freshwater lakes are identified in the main land of the Larsemann Hills and in the McLeod Island. We have collected sediment samples from the exposed ...
The Arabian Sea in the northern Indian Ocean pre-serves regional sedimentary records of rifting, ... more The Arabian Sea in the northern Indian Ocean pre-serves regional sedimentary records of rifting, tectonic subsidence, and paleoceanographic history, and also provides archives of long-term erosion of the Himalaya since the start of collision between In?dia and Eurasia. Investigations reveal that drilling in this region can provide erosion records through analyses of the sediment cores, along with providing age control for the regional seismic stratigraphy. It is only by quantifying the volume of sedi?ment deposited in the fan that researchers can mass balance the volume of bedrock eroded from the mountains, constrained by thermochronology, with the volume of eroded rock deposited in the offshore and in the foreland basin.
A sediment gravity core recovered from the NorthEastern Arabian Sea was investigated for sediment... more A sediment gravity core recovered from the NorthEastern Arabian Sea was investigated for sediment grain size, total organic carbon (TOC) and selected trace metals to understand the changes in the depositional environment over time. The core exhibited three distinct zones of sediment, the lower zone I, middle zone II and upper zone III, representing the varying conditions of sediment deposition. The lower zone is dominated by the silt-sized fraction with low organic carbon that revealed a shallow depositional environment and led to oxidation of organic matter, while the low metal concentration in this zone was either due to the low intensity of monsoon or the dilution by biogenic components and aeolian sediment influx. On other hand, the middle zone represented a transition phase where metal along with clay and organic carbon concentration started increasing due to strengthening monsoon intensity. Further, the upper zone that represented the Holocene sediments pointed to the increase in concentration of metals Al, Fe, Co and Cu that indicated an increase in the intensity of the SouthWest Monsoon and led to large fluvial inputs. TOC also increased towards the surface, indicating an increase in productivity that was controlled by SouthWest Monsoon.
the Expedition 355 Scientists, Arabian Sea Monsoon. Proceedings of the International Ocean Discov... more the Expedition 355 Scientists, Arabian Sea Monsoon. Proceedings of the International Ocean Discovery Program , 355: College Station, TX (International Ocean Discovery Program).
In the Arabian Sea, South Asian monsoon (SAM)-induced high surface water productivity coupled wit... more In the Arabian Sea, South Asian monsoon (SAM)-induced high surface water productivity coupled with poor ventilation of intermediate water results in strong denitrification within the oxygen minimum zone (OMZ). Despite the significance of denitrification in the Arabian Sea, we have no long-term record of its evolution spanning the past several million years. Here, we present the first record of denitrification evolution since Late Miocene (~10.2 Ma) in the Eastern Arabian Sea, where the SAM generates moderate surface water productivity, based on the samples retrieved during the International Ocean Discovery Program (IODP) Expedition 355. We find that (i) the SAM was persistently weaker from ~10.2 to 3.1 Ma; it did not intensify at ~8 Ma in contrast to a few previous studies, (ii) on tectonic timescale, both the SAM and the East Asian Monsoon (EAM) varied synchronously, (iii) the first evidence of denitrification and productivity/SAM intensification was at ~3.2-2.8 Ma that coincided w...
Deep sea channel systems are recognized in most submarine fans worldwide as well as in the geolog... more Deep sea channel systems are recognized in most submarine fans worldwide as well as in the geological record. The Indus Fan is the second largest modern submarine fan, having a well-developed active canyon and deep sea channel system. Previous studies from the upper Indus Fan have reported several active channel systems. In the present study, deep sea channel systems were identified within the middle Indus Fan using high resolution multibeam bathymetric data. Prominent morphological features within the survey block include the Raman Seamount and Laxmi Ridge. The origin of the newly discovered channels in the middle fan has been inferred using medium resolution satellite bathymetry data. Interpretation of new data shows that the highly sinuous deep sea channel systems also extend to the east of Laxmi Ridge, as well as to the west of Laxmi Ridge, as previously reported. A decrease in sinuosity southward can be attributed to the morphological constraints imposed by the elevated features. These findings have significance in determining the pathways for active sediment transport systems, as well as their source characterization. The geometry suggests a series of punctuated avulsion events leading to the present array of disconnected channels. Such channels have affected the Laxmi Basin since the Pliocene and are responsible for reworking older fan sediments, resulting in loss of the original erosional signature supplied from the river mouth. This implies that distal fan sediments have experienced significant signal shredding and may not represent the erosion and weathering conditions within the onshore basin at the time of sedimentation.
Multibeam swath bathymetry survey was carried out in the middle Indus fan region in the eastern A... more Multibeam swath bathymetry survey was carried out in the middle Indus fan region in the eastern Arabian Sea. Using high-resolution bathymetry data, major morphological features such as the Raman seamount and the Laxmi ridge have been mapped. This study also reveals the presence of sinuous channel systems, continuing towards the distal fan. Though there are several reports on the presence of channels in different regions of the Indus fan, we report here the presence of active channels to the east of the Laxmi ridge. The total length of all channels along the channel axis is about 915 km. The individual spreads of the channels vary from 189.8 to 1980.5 m. Most of the channels are shallow with the average depth measuring about 60 m. The longest channel is about 256.3 km long, 702 m wide and about 57 m deep. The channels observed are similar to the land-based fluvial channels. The channels identified are highly sinuous in nature, their meanders and cut-off meanders are similar to the ch...
Seabed topography of the Approach Channel to the Larsemann Hills in the Prydz Bay is important to... more Seabed topography of the Approach Channel to the Larsemann Hills in the Prydz Bay is important to understand the Prydz Bay drainage basin and inter-linkage between its major topographic features. As India proposes to establish her third permanent sta-tion in Larsemann Hills, ...
A giant mass-transport complex was recently discovered in the eastern Arabian Sea, exceeding in v... more A giant mass-transport complex was recently discovered in the eastern Arabian Sea, exceeding in volume all but one other known complex on passive margins worldwide. The complex, named the Nataraja Slide, was drilled by International Ocean Discovery Program (IODP) Expedition 355 in two locations where it is ∼300 m (Site U1456) and ∼200 m thick (Site U1457). The top of this mass-transport complex is defined by the presence of both reworked microfossil assemblages and deformation structures, such as folding and faulting. The deposit consists of two main phases of mass wasting, each consisting of smaller pulses, with generally fining-upward cycles, all emplaced just prior to 10.8 Ma based on biostratigraphy. The base of the deposit at each site is composed largely of matrix-supported carbonate breccia that is interpreted as the product of debris-flows. In the first phase, these breccias alternate with well-sorted calcarenites deposited from a high-energy current, coherent limestone bloc...
Global overturning circulation underwent significant changes in the late Miocene, driven by tecto... more Global overturning circulation underwent significant changes in the late Miocene, driven by tectonic forcing, and impacted the global climate. Prevailing hypotheses related to the late Miocene deep water circulation (DWC) changes driven by the closure of the Central American Seaways (CAS) and its widespread impact remains untested due to the paucity of suitable records away from the CAS region. Here, we test the hypothesis of the large-scale circulation changes by providing a high-resolution record of DWC since the late Miocene (11.3 to ~2 Ma) from the north-western Indian Ocean. Our investigation reveals a progressive shift from Pacific-dominated DWC before ~9.0 Ma to the onset of a modern-like DWC system in the Indian Ocean comprising of Antarctic bottom water and northern component water during the Miocene-Pliocene transition (~6 Ma) caused by progressive shoaling of the CAS and suggests its widespread impact.
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.
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.
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.
... Sagar Kanya, Sagar Purvi and Sagar Paschimi ??? the vessels of the Ministry of Earth Sciences... more ... Sagar Kanya, Sagar Purvi and Sagar Paschimi ??? the vessels of the Ministry of Earth Sciences, Government of India, and Akademik Boris Petrov, a research vessel that was hired, were deployed in search and recovery opera-tions. ...
The Larsemann Hills area in the eastern Antarctica constitutes a few of the small islands apart f... more The Larsemann Hills area in the eastern Antarctica constitutes a few of the small islands apart from the mainland. Many freshwater lakes are identified in the main land of the Larsemann Hills and in the McLeod Island. We have collected sediment samples from the exposed ...
The Arabian Sea in the northern Indian Ocean pre-serves regional sedimentary records of rifting, ... more The Arabian Sea in the northern Indian Ocean pre-serves regional sedimentary records of rifting, tectonic subsidence, and paleoceanographic history, and also provides archives of long-term erosion of the Himalaya since the start of collision between In?dia and Eurasia. Investigations reveal that drilling in this region can provide erosion records through analyses of the sediment cores, along with providing age control for the regional seismic stratigraphy. It is only by quantifying the volume of sedi?ment deposited in the fan that researchers can mass balance the volume of bedrock eroded from the mountains, constrained by thermochronology, with the volume of eroded rock deposited in the offshore and in the foreland basin.
A sediment gravity core recovered from the NorthEastern Arabian Sea was investigated for sediment... more A sediment gravity core recovered from the NorthEastern Arabian Sea was investigated for sediment grain size, total organic carbon (TOC) and selected trace metals to understand the changes in the depositional environment over time. The core exhibited three distinct zones of sediment, the lower zone I, middle zone II and upper zone III, representing the varying conditions of sediment deposition. The lower zone is dominated by the silt-sized fraction with low organic carbon that revealed a shallow depositional environment and led to oxidation of organic matter, while the low metal concentration in this zone was either due to the low intensity of monsoon or the dilution by biogenic components and aeolian sediment influx. On other hand, the middle zone represented a transition phase where metal along with clay and organic carbon concentration started increasing due to strengthening monsoon intensity. Further, the upper zone that represented the Holocene sediments pointed to the increase in concentration of metals Al, Fe, Co and Cu that indicated an increase in the intensity of the SouthWest Monsoon and led to large fluvial inputs. TOC also increased towards the surface, indicating an increase in productivity that was controlled by SouthWest Monsoon.
the Expedition 355 Scientists, Arabian Sea Monsoon. Proceedings of the International Ocean Discov... more the Expedition 355 Scientists, Arabian Sea Monsoon. Proceedings of the International Ocean Discovery Program , 355: College Station, TX (International Ocean Discovery Program).
In the Arabian Sea, South Asian monsoon (SAM)-induced high surface water productivity coupled wit... more In the Arabian Sea, South Asian monsoon (SAM)-induced high surface water productivity coupled with poor ventilation of intermediate water results in strong denitrification within the oxygen minimum zone (OMZ). Despite the significance of denitrification in the Arabian Sea, we have no long-term record of its evolution spanning the past several million years. Here, we present the first record of denitrification evolution since Late Miocene (~10.2 Ma) in the Eastern Arabian Sea, where the SAM generates moderate surface water productivity, based on the samples retrieved during the International Ocean Discovery Program (IODP) Expedition 355. We find that (i) the SAM was persistently weaker from ~10.2 to 3.1 Ma; it did not intensify at ~8 Ma in contrast to a few previous studies, (ii) on tectonic timescale, both the SAM and the East Asian Monsoon (EAM) varied synchronously, (iii) the first evidence of denitrification and productivity/SAM intensification was at ~3.2-2.8 Ma that coincided w...
Deep sea channel systems are recognized in most submarine fans worldwide as well as in the geolog... more Deep sea channel systems are recognized in most submarine fans worldwide as well as in the geological record. The Indus Fan is the second largest modern submarine fan, having a well-developed active canyon and deep sea channel system. Previous studies from the upper Indus Fan have reported several active channel systems. In the present study, deep sea channel systems were identified within the middle Indus Fan using high resolution multibeam bathymetric data. Prominent morphological features within the survey block include the Raman Seamount and Laxmi Ridge. The origin of the newly discovered channels in the middle fan has been inferred using medium resolution satellite bathymetry data. Interpretation of new data shows that the highly sinuous deep sea channel systems also extend to the east of Laxmi Ridge, as well as to the west of Laxmi Ridge, as previously reported. A decrease in sinuosity southward can be attributed to the morphological constraints imposed by the elevated features. These findings have significance in determining the pathways for active sediment transport systems, as well as their source characterization. The geometry suggests a series of punctuated avulsion events leading to the present array of disconnected channels. Such channels have affected the Laxmi Basin since the Pliocene and are responsible for reworking older fan sediments, resulting in loss of the original erosional signature supplied from the river mouth. This implies that distal fan sediments have experienced significant signal shredding and may not represent the erosion and weathering conditions within the onshore basin at the time of sedimentation.
Multibeam swath bathymetry survey was carried out in the middle Indus fan region in the eastern A... more Multibeam swath bathymetry survey was carried out in the middle Indus fan region in the eastern Arabian Sea. Using high-resolution bathymetry data, major morphological features such as the Raman seamount and the Laxmi ridge have been mapped. This study also reveals the presence of sinuous channel systems, continuing towards the distal fan. Though there are several reports on the presence of channels in different regions of the Indus fan, we report here the presence of active channels to the east of the Laxmi ridge. The total length of all channels along the channel axis is about 915 km. The individual spreads of the channels vary from 189.8 to 1980.5 m. Most of the channels are shallow with the average depth measuring about 60 m. The longest channel is about 256.3 km long, 702 m wide and about 57 m deep. The channels observed are similar to the land-based fluvial channels. The channels identified are highly sinuous in nature, their meanders and cut-off meanders are similar to the ch...
Seabed topography of the Approach Channel to the Larsemann Hills in the Prydz Bay is important to... more Seabed topography of the Approach Channel to the Larsemann Hills in the Prydz Bay is important to understand the Prydz Bay drainage basin and inter-linkage between its major topographic features. As India proposes to establish her third permanent sta-tion in Larsemann Hills, ...
A giant mass-transport complex was recently discovered in the eastern Arabian Sea, exceeding in v... more A giant mass-transport complex was recently discovered in the eastern Arabian Sea, exceeding in volume all but one other known complex on passive margins worldwide. The complex, named the Nataraja Slide, was drilled by International Ocean Discovery Program (IODP) Expedition 355 in two locations where it is ∼300 m (Site U1456) and ∼200 m thick (Site U1457). The top of this mass-transport complex is defined by the presence of both reworked microfossil assemblages and deformation structures, such as folding and faulting. The deposit consists of two main phases of mass wasting, each consisting of smaller pulses, with generally fining-upward cycles, all emplaced just prior to 10.8 Ma based on biostratigraphy. The base of the deposit at each site is composed largely of matrix-supported carbonate breccia that is interpreted as the product of debris-flows. In the first phase, these breccias alternate with well-sorted calcarenites deposited from a high-energy current, coherent limestone bloc...
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