Sandeep Singh - Academia.edu (original) (raw)

Papers by Sandeep Singh

Research paper thumbnail of Timing, quantification and tectonic modelling of Pliocene–Quaternary movements in the NW Himalaya: evidence from fission track dating

Earth and Planetary Science Letters, 2000

Variable exhumation rates, deduced from the Pliocene^Quaternary FT zircon^apatite ages from the H... more Variable exhumation rates, deduced from the Pliocene^Quaternary FT zircon^apatite ages from the Himalayan Metamorphic Belt (HMB) of the NW Himalaya along the Sutlej Valley in Himachal Pradesh, have been modelled in the tectonic framework of fast exhumed Lesser Himalayan windows, which caused lateral extensional sliding of the metamorphic nappe cover along the well-known Main Central Thrust (MCT) and differential movements along thrust zones as well. In the northern belt of the Higher Himalayan Crystallines (HHC), two distinct clusters of the FT apatite ages have been deciphered: apatite ages having a weighted mean of 4.9 þ 0.2 Ma (1 c) in basal parts on the hanging wall of the MCT, and 1.49 þ 0.07 Ma (1 c) in the hanging wall of a newly, recognized NE, dipping Chaura thrust further north. Fast exhumation of the Chaura thrust hanging wall has been inferred at a rate of 4.82 þ 0.55 mm/yr from the zircon^apatite cogenetic pairs during 1.54 Ma and 0.97 Ma, and 2.01 þ 0.35 mm/yr since 1.49 Ma. In comparison, its foot wall has been exhumed at a much slower rate of 0.61 þ 0.10 mm/yr since 4.9 Ma. The overlying Vaikrita Thrust zone rocks reveal an exhumation rate of 1.98 þ 0.34 mm/yr from 2.70 þ 0.40 Ma to 1.31 þ 0.22 Ma and 2.29 þ 0.66 mm/ yr since 1.31 þ 0.22 Ma. Using these data, a vertical displacement of ca. 2.08 þ 0.68 km has been calculated along the Chaura thrust between 4.9 and 1.50 Ma on an average rate of 0.6 mm/yr. It is of the order of 1.18 km from 2.70 Ma to 1.54 Ma along the Vaikrita Thrust, and 0.78 mm/yr from 1.31 Ma to 0.97 Ma, and has behaved as an extensional normal fault during these periods. Tectonic modelling of the exhumation rates in the NW Himalaya reveals fastest uplifting Himalayan domes and windows like the Nanga Parbat in Pakistan, Suru and Chisoti domes in Zanskar and Kishwar^Kulu^Rampur Window axis in SE Kashmir and Himachal Pradesh during Pliocene^Quaternary. These windows appear to have caused lateral extensional sliding of the Himalayan metamorphic nappes in the lower parts. The middle parts of the HHC belt have witnessed both overthrusting and extensional faulting due to complex and variable exhumation patterns within the hanging and foot walls of the MCT and Vaikrita Thrust along the Sutlej Valley, thus causing movement of upthrust crustal wedge between the extensional ones. Thus, FT zircon^apatite ages provide evidence for the presence of a number of crustal wedges having distinct tectonothermal history within the HHC. ß

Research paper thumbnail of The onset of India–Asia continental collision: Early, steep subduction required by the timing of UHP metamorphism in the western Himalaya

Earth and Planetary Science Letters, 2005

Ultrahigh-pressure (UHP) rocks in the NW Himalaya are some of the youngest on Earth, and allow te... more Ultrahigh-pressure (UHP) rocks in the NW Himalaya are some of the youngest on Earth, and allow testing of critical questions of UHP formation and exhumation and the timing of the India-Asia collision. Initial collision of India with Asia is widely cited as being at 55 F 1 Ma based on a paleomagnetically determined slowdown of India's plate velocity, and as being at ca. 51 Ma based on the termination of marine carbonate deposition. Even relatively small changes in this collision age force large changes in tectonic reconstructions because of the rapid India-Asia convergence rate of 134 mm/a at the time of collision. New U-Pb SHRIMP dating of zircon shows that Indian rocks of the Tso Morari Complex reached UHP depths at 53.3 F 0.7 Ma. Given the high rate of Indian subduction, this dating implies that Indian continental crust arrived at the Asian trench no later than 57 F 1 Ma, providing a metamorphic age for comparison with previous paleomagnetic and stratigraphic estimates. India's collision with Asia may be compared to modern processes in the Timor region in which initiation of collision precedes both the slowing of the convergence rate and the termination of marine carbonate deposition. The Indian UHP rocks must have traveled rapidly along a short, hence steep, path into the mantle. Early continental subduction was at a steep angle, probably vertical, comparable to modern continental subduction in the Hindu Kush, despite evidence for modern-day low-angle subduction of India beneath Tibet. Oceanic slab break-off likely coincided with exhumation of UHP terranes in the western Himalaya and led to the initiation of low-angle subduction and leucogranite generation. D

Research paper thumbnail of The effect of organic and inorganic fertilizers on soil physical condition and the productivity of a rice–lentil cropping sequence in India

Journal of Agricultural Science, 2003

A field experiment was conducted for two years at Bangalore, to study the influence of organic (v... more A field experiment was conducted for two years at Bangalore, to study the influence of organic (vermicompost) and inorganic fertilizers (NPK) on growth, yield and nutrient uptake of patchouli (Pogostemon cablin) in a semi-arid tropical climate. The results revealed that application of vermicompost (5 t ha -1 ) + 50% NPK (100 : 25 : 25 kg ha -1 ) produced significantly higher herbage and oil yield (13.98 t ha -1 and 83.4 kg ha -1 ), respectively, which was on par with recommended dose of NPK (200 : 50 : 50 kg ha -1 ). Application of vermicompost (5 t ha -1 ) + 50% NPK (100 : 25 : 25 kg ha -1 ) increased the nitrogen, phosphorus and potassium uptake, respectively, which was at par with recommended dose of NPK (200 : 50 : 50 kg ha -1 ). Oil content was not influenced by organic and inorganic fertilizers.

Research paper thumbnail of Effect of water stress at different stages of grain development on the characteristics of starch and protein of different wheat varieties

Food Chemistry, 2008

The effect of water stress (WS) at 8 and 15 days post anthesis (DPA) on the characteristics of st... more The effect of water stress (WS) at 8 and 15 days post anthesis (DPA) on the characteristics of starch and protein separated from C-306, HD-2329, PBW-175, PBW-343 and NI-5439 wheat varieties was studied. WS-induced changes in A-, B-and C-type granules distribution were variety-and stage-dependent. A-type granules increased in response to WS at both stages in all varieties, the extent of increase being greater at 15 DPA. The proportion of B-type granules decreased in all the varieties, except C-306, in response to WS at 15 DPA. C-type granules also decreased in response to 15 DPA in all varieties, except HD-2329. The starch from wheat exposed to WS at 15 DPA showed lower amylose content, lipids content and pasting temperature, and higher peak viscosity, final viscosity and setback. DSC analysis of starches showed two endotherms (associated with the melting of crystallites and amylose-lipid [AML] complexes) during heating, and an exotherm (associated with reforming of AML) during cooling. Transition temperatures (T o , T p and T c ) of AML dissociation and association were lower for starch from wheat exposed to WS, the effect being more at 15 DPA. The changes in pasting and thermal properties of starch caused by WS were observed to be related to lipids, amylose content and distribution of granules. The effect of WS on accumulation of different dimethyl formamide-soluble and insoluble proteins was significant and variety dependent.

Research paper thumbnail of Timing, quantification and tectonic modelling of Pliocene–Quaternary movements in the NW Himalaya: evidence from fission track dating

Earth and Planetary Science Letters, 2000

Variable exhumation rates, deduced from the Pliocene^Quaternary FT zircon^apatite ages from the H... more Variable exhumation rates, deduced from the Pliocene^Quaternary FT zircon^apatite ages from the Himalayan Metamorphic Belt (HMB) of the NW Himalaya along the Sutlej Valley in Himachal Pradesh, have been modelled in the tectonic framework of fast exhumed Lesser Himalayan windows, which caused lateral extensional sliding of the metamorphic nappe cover along the well-known Main Central Thrust (MCT) and differential movements along thrust zones as well. In the northern belt of the Higher Himalayan Crystallines (HHC), two distinct clusters of the FT apatite ages have been deciphered: apatite ages having a weighted mean of 4.9 þ 0.2 Ma (1 c) in basal parts on the hanging wall of the MCT, and 1.49 þ 0.07 Ma (1 c) in the hanging wall of a newly, recognized NE, dipping Chaura thrust further north. Fast exhumation of the Chaura thrust hanging wall has been inferred at a rate of 4.82 þ 0.55 mm/yr from the zircon^apatite cogenetic pairs during 1.54 Ma and 0.97 Ma, and 2.01 þ 0.35 mm/yr since 1.49 Ma. In comparison, its foot wall has been exhumed at a much slower rate of 0.61 þ 0.10 mm/yr since 4.9 Ma. The overlying Vaikrita Thrust zone rocks reveal an exhumation rate of 1.98 þ 0.34 mm/yr from 2.70 þ 0.40 Ma to 1.31 þ 0.22 Ma and 2.29 þ 0.66 mm/ yr since 1.31 þ 0.22 Ma. Using these data, a vertical displacement of ca. 2.08 þ 0.68 km has been calculated along the Chaura thrust between 4.9 and 1.50 Ma on an average rate of 0.6 mm/yr. It is of the order of 1.18 km from 2.70 Ma to 1.54 Ma along the Vaikrita Thrust, and 0.78 mm/yr from 1.31 Ma to 0.97 Ma, and has behaved as an extensional normal fault during these periods. Tectonic modelling of the exhumation rates in the NW Himalaya reveals fastest uplifting Himalayan domes and windows like the Nanga Parbat in Pakistan, Suru and Chisoti domes in Zanskar and Kishwar^Kulu^Rampur Window axis in SE Kashmir and Himachal Pradesh during Pliocene^Quaternary. These windows appear to have caused lateral extensional sliding of the Himalayan metamorphic nappes in the lower parts. The middle parts of the HHC belt have witnessed both overthrusting and extensional faulting due to complex and variable exhumation patterns within the hanging and foot walls of the MCT and Vaikrita Thrust along the Sutlej Valley, thus causing movement of upthrust crustal wedge between the extensional ones. Thus, FT zircon^apatite ages provide evidence for the presence of a number of crustal wedges having distinct tectonothermal history within the HHC. ß

Research paper thumbnail of The onset of India–Asia continental collision: Early, steep subduction required by the timing of UHP metamorphism in the western Himalaya

Earth and Planetary Science Letters, 2005

Ultrahigh-pressure (UHP) rocks in the NW Himalaya are some of the youngest on Earth, and allow te... more Ultrahigh-pressure (UHP) rocks in the NW Himalaya are some of the youngest on Earth, and allow testing of critical questions of UHP formation and exhumation and the timing of the India-Asia collision. Initial collision of India with Asia is widely cited as being at 55 F 1 Ma based on a paleomagnetically determined slowdown of India's plate velocity, and as being at ca. 51 Ma based on the termination of marine carbonate deposition. Even relatively small changes in this collision age force large changes in tectonic reconstructions because of the rapid India-Asia convergence rate of 134 mm/a at the time of collision. New U-Pb SHRIMP dating of zircon shows that Indian rocks of the Tso Morari Complex reached UHP depths at 53.3 F 0.7 Ma. Given the high rate of Indian subduction, this dating implies that Indian continental crust arrived at the Asian trench no later than 57 F 1 Ma, providing a metamorphic age for comparison with previous paleomagnetic and stratigraphic estimates. India's collision with Asia may be compared to modern processes in the Timor region in which initiation of collision precedes both the slowing of the convergence rate and the termination of marine carbonate deposition. The Indian UHP rocks must have traveled rapidly along a short, hence steep, path into the mantle. Early continental subduction was at a steep angle, probably vertical, comparable to modern continental subduction in the Hindu Kush, despite evidence for modern-day low-angle subduction of India beneath Tibet. Oceanic slab break-off likely coincided with exhumation of UHP terranes in the western Himalaya and led to the initiation of low-angle subduction and leucogranite generation. D

Research paper thumbnail of The effect of organic and inorganic fertilizers on soil physical condition and the productivity of a rice–lentil cropping sequence in India

Journal of Agricultural Science, 2003

A field experiment was conducted for two years at Bangalore, to study the influence of organic (v... more A field experiment was conducted for two years at Bangalore, to study the influence of organic (vermicompost) and inorganic fertilizers (NPK) on growth, yield and nutrient uptake of patchouli (Pogostemon cablin) in a semi-arid tropical climate. The results revealed that application of vermicompost (5 t ha -1 ) + 50% NPK (100 : 25 : 25 kg ha -1 ) produced significantly higher herbage and oil yield (13.98 t ha -1 and 83.4 kg ha -1 ), respectively, which was on par with recommended dose of NPK (200 : 50 : 50 kg ha -1 ). Application of vermicompost (5 t ha -1 ) + 50% NPK (100 : 25 : 25 kg ha -1 ) increased the nitrogen, phosphorus and potassium uptake, respectively, which was at par with recommended dose of NPK (200 : 50 : 50 kg ha -1 ). Oil content was not influenced by organic and inorganic fertilizers.

Research paper thumbnail of Effect of water stress at different stages of grain development on the characteristics of starch and protein of different wheat varieties

Food Chemistry, 2008

The effect of water stress (WS) at 8 and 15 days post anthesis (DPA) on the characteristics of st... more The effect of water stress (WS) at 8 and 15 days post anthesis (DPA) on the characteristics of starch and protein separated from C-306, HD-2329, PBW-175, PBW-343 and NI-5439 wheat varieties was studied. WS-induced changes in A-, B-and C-type granules distribution were variety-and stage-dependent. A-type granules increased in response to WS at both stages in all varieties, the extent of increase being greater at 15 DPA. The proportion of B-type granules decreased in all the varieties, except C-306, in response to WS at 15 DPA. C-type granules also decreased in response to 15 DPA in all varieties, except HD-2329. The starch from wheat exposed to WS at 15 DPA showed lower amylose content, lipids content and pasting temperature, and higher peak viscosity, final viscosity and setback. DSC analysis of starches showed two endotherms (associated with the melting of crystallites and amylose-lipid [AML] complexes) during heating, and an exotherm (associated with reforming of AML) during cooling. Transition temperatures (T o , T p and T c ) of AML dissociation and association were lower for starch from wheat exposed to WS, the effect being more at 15 DPA. The changes in pasting and thermal properties of starch caused by WS were observed to be related to lipids, amylose content and distribution of granules. The effect of WS on accumulation of different dimethyl formamide-soluble and insoluble proteins was significant and variety dependent.