Binita Phartiyal

Evidence of enhanced winter precipitation and the prevalence of a cool and dry climate during the mid to late Holocene in mainland Gujarat, India

The Kothiyakhad sedimentary sequence of Mahi estuary in mainland Gujarat, India, contains valuable information on late- to mid-Holocene climatic conditions as inferred by phytolith, palynofacies, magnetic susceptibility and clay mineralogical studies. Three distinct climatic regimes, ie, Phase I, II and III, were established. Phase I (3660—~3400 yr BP) shows a gradual weakening of SW monsoonal activity, though overlapped by enhanced western disturbances which led to the development of cool climatic conditions. The coupled effect of SW monsoon and enhanced winter precipitation produced improved hydrological conditions, which supported the agrarian society of the Indus Valley civilization until the beginning of Phase II (~3400—~3000 yr BP). During Phase II the SW monsoon was in a state of severe recession, leading to severe drought-like conditions, other than for a brief but intensely warm and humid pulse recorded at ~3320 yr BP, associated with SW monsoonal activity. In Phase III (~3000—2850 yr BP), SW precipitation fluctuated greatly with a considerable increase in warm summer conditions, similar to present-day conditions. The weak SW monsoonal activity ~3500 yr BP also coincided with a global cool and arid phase and this probably explains the timing as well as the cause of why the population of the Indus civilization migrated to more humid areas to sustain their livelihoods.

Impact of neotectonics on drainage network evolution reconstructed from morphometric indices: case study from NW Indian Himalaya

Summary. The Spiti river basin in North West Indian Himalaya (31–33° E; 77–79° S), is tectonically unstable, exhibits a complex topography, landscape relief and varied Quaternary sedimentation. The major geomorphic landforms viz., alluvial terraces, strath terraces, alluvial fans, debris cone, fluvio-lacustrine deposits, scree and talus cone are present throughout the valley. An attempt has been made by using the geomorphometry approach to access the area in terms of its neotectonic instability, as this basin feeds the river Sutlej. We tried to see the Spiti and the Parachu basin of draining into Sutlej valley, which have been in news several times in the last decade causing floods downstream, due to the outburst of glacial lakes and the formation of temporary lakes during the sliding events, even by the slight disturbance in the monsoon pattern and tectonic activity. Thus the landforms were mapped and assessed in the valley to elucidate spatio-temporal scale dependencies of surface processes active in this region. The Spiti river (constituting of Spiti and Parachu basins) was examined using geomorphic field methods (Spiti basin) and OSL dating. The Quaternary saw ubiquitous mass movements and catastrophic landslides which transported material from steep slopes to valley bottoms and were responsible for the formation of lakes (preserved as thick sequences of fine sediment), while the outburst floods redistributed sediment downvalley affecting life and property downstream. The morphometric approach such as Basin Asymmetry (AF), Topographic Symmetric Factor (T), Stream length Gradient Index (GI) Hydauralic Sinuosity Index (HSI), Topographic sinuosity Index (TSI) and Standard Sinuosity Index (SSI) have helped in understanding tectonic and climatic perturbation. Our observations point towards a tectonically active region with enormous piles of loose, unconsolidated sediment cover which could be disastrous during the slight shift of the climatic and tectonic forces operating in this area.

Trans- and Tethyan Himalayan Rivers: In Reference to Ladakh and Lahaul-Spiti, NW Himalaya

The Himalayan system is a complex and young fold mountain chain, rightly known as the water tower of Asia. Trans-Himalaya and the Tethyan Himalaya consist of a mountainous region about 1,000 km long and 225 km wide in the center, narrowing to ~32 km width at the eastern and western ends toward the northwestern side of the Himalayan chain in the Indian territory. The rivers of the Trans- and Tethyan Himalayan terrains follow the fault lines (Indus Suture Zone, Karakorum Fault, Spiti fault) and have a tectonic/structural control. These rivers as of today are unpolluted and still away from the anthropogenic and economic impact. They have enough potential which has not been utilized properly perhaps because of its strategic location. Vast exposures of the Quaternary sediments (lacustrine and fluvial) along the Indus (Ladakh, J&K) and Spiti rivers (Lahaul-Spiti, HP) are helpful in generating data on landscape evolution, paleoclimate, tectonics, and earth surface processes.

Late Quaternary Palaeoclimate and Contemporary Moisture Source to Extreme NW India: A Review on Present Understanding and Future Perspectives

The trans-Himalayan region of NW India along with western part of Tibet, Karakoram,and Hindukush range is hosting thousands of glaciers ensuring perennial freshwater supply to the Indian subcontinent and supporting a large fraction of the global population. The peculiar physiography not only limits the entry of water enriched Indian Summer Monsoon winds to this region but also give passage to dry winds of barren desert of Taklamakan, the Aksai Chin,and western Tibet, making it a cold desert. The Quaternary glacial and interglacial phases govern the present geomorphological setup of the region, wherein the glacial process designed the basic framework, which subsequently modified by the fluvial-lacustrine-aeolian processes.Over the years, our understanding in drawing climatic inferences from the sedimentary archives has improved significantly. However, the discrepancy in chronological results among and within different dating techniques is posing a serious challenge. Since the region is experiencing cold desertic climate and being in the rain shadow zone of the Indian Summer Monsoon (ISM), earlier studies show that the major source of moisture received by the Mediterranean Sea.However, the recent isotopic study of the Indus river water along with other major tributaries and minor streams, it is concluded that ISM source is equally important supplier of the moisture in the Ladakh region of NW India.