Arc-parallel shears in collisional orogens: Global review and paleostress analyses from the NW Lesser Himalayan Sequence (Garhwal region, Uttarakhand, India)

Interest in hydrocarbon exploration from the the Lesser Himalayan Sequence (LHS) has recently been revived amongst petroleum geoscientists. Understanding the paleostress regime and the deformation processes are the two important steps to understand the structural geology of any (petroliferous) terrane. Arc-parallel shear is an integral deformation process in orogeny. The scale of the consequent deformation features can range from micro-mm up to regional scale. Unlike orogen-perpendicular shear, different driving forces can produce orogen-parallel shears. We review these mechanisms/theories from several orogens including the Himalaya and compile 44 locations worldwide with reported orogen-parallel shear. Due to continuous crustal shortening by the India-Eurasia collision, the squeezed rock mass at the plate interface has produced the Himalayan Mountain chain. In addition, the rock mass also escapes laterally along the orogenic trend. Tectonic stress-field governs this mass flow. Field study and microstructural analysis in the northwest LHS (India) reveals orogen-parallel brittle and ductile shear movement. Y- and P- brittle shear planes, and the S- and C- ductile shear planes reveal the following shears documented on the ~ NW-SE trending natural rock selections: (i) top-to-NW up, (ii) top-to-SE up, (iii) top-to-NW down, and (iv) top-to-SE down. Our paleostress analysis indicates top-to-SE down and top-to-NW down shears occurred due to stretching along ~ 131°-311° (Dext), whereas top-to-SE up and top-to-NW up shear fabric originated due to shortening along ~133.5°-313.5° (Dcompr). Previous authors considered that the orogen-parallel extension generated ~ 15-5 Ma due to vertical thinning of the Himalaya. The NE-trending Delhi-Haridwar Ridge below the LHS plausibly acted as a barrier to the flowing mass and piled up the rock mass in the form of NW-SE/orogen-parallel compression. The NW-SE compression can be correlated with the D3 of Hintersberger et al. (2011) during ~ 4-7 Ma.

Therapeutic and Pharmaceutical Potential of Cinnamon

Cinnamon has been used as a spice, condiment, and aromatic plant since centuries ago. Cinnamon is a small evergreen tree belonging to the genus Cinnamomum in the family Lauraceae. There are more than 250 species of cinnamon worldwide. In India, Cinnamomum verum and Cinnamomum cassia are the most common species grown in the Himalaya region. They have been used as folk medicine for the treatment of nausea, flatulent dyspepsia, coughs, diarrhea, malaria, gastric disorder, and to alleviate pain and inflammation in rheumatic arthritis. Therapeutic properties of cinnamon are due to the presence of bioactive constituents such as p-coumaric, cinnamaldehyde, cinnamic acid, and eugenol. Cinnamaldehyde and eugenol are the major active constituents responsible for its characteristic flavor, aroma, and therapeutic properties. Pharmacological studies found that it could be a promising candidate with potential for designing new drugs. This review is aimed to summarize the ethanomedicinal importance, phytochemistry, and wide spectrum of pharmacological and therapeutic applications of cinnamon.

Anthropogenic Climate Change Drives the Melting of Glaciers in the Himalaya

The Himalayan glaciers supply water to a large population in south Asia for various uses and ecosystem services. Therefore, regional monitoring of glacier melting and identifying the drivers thereof is important to understand and predict the future trends of cryospheric melting. Using multi-date satellite images from 2000-2020, we investigated the shrinkage, snout retreat, thickness changes, mass loss and velocity changes of 77 glaciers in the Drass basin, western Himalaya, India. The overall glacier cover has shrunk by 5.31±0.33 km2 during the period. Snout retreat varied between 30-430 m (mean 155±9.58 m). Debris-cover showed a significant influence on the glacier melting with the clean glaciers showing a higher loss of ~5% compared to the debris-covered glaciers (~2%). The glaciers on an average have shown thickness change and mass loss of -1.27±0.37 and -1.08±0.31 m w.e.a-1 respectively. Average glacier velocity has reduced from 21.35±3.3 m a-1 in 2000 to 16.68±1.9 m a-1 by 2020 due to the continuous melting and the consequent mass loss of the glaciers. Concentration of the greenhouse gases (GHGs), black carbon and other pollutants from vehicular traffic plying in the vicinity of the glaciers has significantly increased during the observation period. Increasing temperatures, result of the significant increase of the GHGs and pollutants in the atmosphere, drive the glacier melting in the study area. If the situation continues in the future, the glaciers may disappear altogether in the Himalaya leading to significant impact on the regional water supplies, hydrological processes, ecosystem services and transboundary sharing of waters.

Not so ancient: Misclassification of alpine plants biases the dating of the evolution of alpine biota in the Himalaya-Tibet Orogen

Ding et al. (Science 2020) proposed that the extant lineages of the alpine flora of the Tibet Himalaya Hengduan region emerged by the early Oligocene. We argue that these results are based on misclassifying high montane taxa as alpine and that their data support alpine habitats only at about 7.5 mio years before present.

Accelerated mass loss of Himalayan glaciers since the Little Ice Age

Himalayan glaciers are undergoing rapid mass loss but rates of contemporary change lack long-term (centennial-scale) context. Here, we reconstruct the extent and surfaces of 14,798 Himalayan glaciers during the Little Ice Age (LIA), 400 to 700 years ago. We show that they have lost at least 40 % of their LIA area and between 390 and 586 km3 of ice; 0.92 to 1.38 mm Sea Level Equivalent. The long-term rate of ice mass loss since the LIA has been between − 0.011 and − 0.020 m w.e./year, which is an order of magnitude lower than contemporary rates reported in the literature. Rates of mass loss depend on monsoon influence and orographic effects, with the fastest losses measured in East Nepal and in Bhutan north of the main divide. Locally, rates of loss were enhanced with the presence of surface debris cover (by 2 times vs clean-ice) and/or a proglacial lake (by 2.5 times vs land-terminating). The ten-fold acceleration in ice loss we have observed across the Himalaya far exceeds any centennial-scale rates of change that have been recorded elsewhere in the world.

Exploring the potential of machine learning for simulations of urban ozone variability

Machine learning (ML) has emerged as a powerful technique in the Earth system science, nevertheless, its potential to model complex atmospheric chemistry remains largely unexplored. Here, we applied ML to simulate the variability in urban ozone (O3) over Doon valley of the Himalaya. The ML model, trained with past variations in O3 and meteorological conditions, successfully reproduced the independent O3 data (r2 ~ 0.7). Model performance is found to be similar when the variation in major precursors (CO and NOx) were included in the model, instead of the meteorology. Further the inclusion of both precursors and meteorology improved the performance significantly (r2 = 0.86) and the model could also capture the outliers, which are crucial for air quality assessments. We suggest that in absence of high-resolution measurements, ML modeling has profound implications for unraveling the feedback between pollution and meteorology in the fragile Himalayan ecosystem.