New Paradigms of Quaternary for global well-being and Sustainability

Mighty Himalaya

The entire Himalayan system is a complex of thrust and fold mountain chain. It comprises of the Trans-Himalaya (north of Indus Suture zone (ISZ)); the suture zone; the Tethyan Himalaya; the Higher Himalaya, the lesser Himalaya and the Siwalik ranges showing an average relief of ~6 kms. The Himalaya provides an excellent laboratory to understand: (i) thrust and fold belt tectonics; (ii) mountain-climate interactions; (iii) Glaciers and glacial landscapes; (iv) palaeoglacial deposits and karst topography; (v) river systems; (vi) glacial lakes, meadows and tropical to alpine vegetation diversity; (vii) dendro-climatology and many more. This region offers troves of valuable data on natural hazards like floods, landslides, earthquakes etc.
Vast palaeolake deposits, e.g. Lamayuru, Spituk-Gupuk (Jammu and Kashmir); Kioto, Atargu (Himachal Pradesh) and several lakes in Uttarakhand Himalaya have been used increasingly in recent years to infer past fluctuations in climate. Processes governing the origin and nature of chemical and clastic sediments within lakes provide a record of past climatic fluctuations and weathering processes in the source region and imply strongly on climate forcing factors. Further, sediments of intermontane basin of Karewa (Jammu and Kashmir) provided academic treasures of many human civilizations and habitations.

The entire region of Ladakh and Kashmir Himalaya in the rain shadow of the SW Monsoon has an arid to hyper arid climate with steppe vegetation. The region is drained by the Indus River and its tributaries having glaciers in their headwaters. The river banks are flanked by fill and bedrock terraces, large fans, sand ramps, palaeolakes sequences. There are evidences of past occurrences of extreme floods as well. The terraces, palaeolake and sand ramp sequences in the region provide clues towards landscape response to climate variability and suture zone tectonics. The periglacial regions preserve the evidences of past glacial advances in series of well dated moraines. Himalaya houses some of the world’s highest passes - Khardung La (La=mountain pass) at an altitude of 5,359 m connects the Indus river valley to the Shyok river valley. The others being Chang La, Tang La, Zozi La, Fotu La, Pensi ILa, Kumjum La, Nathu La etc., connecting different valleys in the Himalayan regions.
The Ladakh Himalaya is also known for occurrence of several brackish lakes (e.g. Pangong Tso, Tso kar, Tso Moriri) with unique brackish and fresh water ecosystem. Pangong Tso (Tso=lake), is at an altitude of 4257 m occupying a long-submerged valley of ~200 km exhibits several palaeolake strands and prograding lake delta. They appear as elongated terrace-like ridges of a few decimetres’ height, suggesting gradual shrinkage in lake level since its time of formation. It is a lake with swamp and salt deposits around, perfect breeding ground for the rare black neck crane.

The southern front of Himalaya is influenced by full spectrum of Indian summer monsoon and the rivers draining the region cut all the structural discontinuities orthogonally. These rivers originate from the active mountain belts and cross several thrust sheets characterized by different uplift rates. This leads to different shapes of river long profiles and significant spatial variability in-channel slope. These rivers receive water from different sources namely glaciers, rainfall and groundwater marked by spatio-temporal variability. Sediment supply is also quite variable and sediments are generated from different litho-tectonic units of the Himalaya. Spatio-temporal variability in erosion processes is governed by relief, lithology, rainfall gradient, landuse-landcover and glacial contributions. The region presents a multifaceted interface between the climate-thrust tectonic and landscape evolution. There are chronologically well constrained records of widespread valley aggradation and river incision that are modulated by climate change over the past 100 ka. The studies have also tested various models of neotectonic evolution of collisional mountains.
The Himalayan Rivers provide subsistence to agricultural economy of 1/5th of the global population. The occurrences of large floods, landslides and earthquakes serve severe jolt to the growth of human kind and the region provides an excellent laboratory to understand these natural disasters. Established decadal to centennial scale monsoon records from Himalaya show an abrupt negative ISM shift during the termination of Younger Dryas between ~11.7 and 11.4 ka. While, ISM was stable between ~11 and 6 ka, and declined prominently between 6 and 3 ka. The shifting drainage patterns along the Himalayan faults record the neotectonic activities.
Himalaya has provided a wealth of Dendrochronology and Dendroclimatology data. Distinct and precisely datable growth rings in many conifers and broadleaved Himalayan species allowed focusing on many dendrochronological applications in the area. The Himalayan pencil Juniper (Juniperus polycarpos) has been found to be the longest living tree in India extending >2 ka and still growing healthy. The tree ring series from semi-arid to arid regions contain strong signatures of temporal variability in precipitation.

The Indian Foreland Basin:

The frontal part of Himalayan thrust fold belt makes a flexural asymmetrical basin called as the Indus-Ganga Brahmaputra peripheral Foreland basin. This basin is bounded in the north by a rising mountain (Himalaya) and deformed foreland deposits and in south lies a subdued fore bulge. The west is bound by Delhi Aravalli Ridge and east by Rajmahal hills.
The Indian foreland basin is also one of the most densely populated landmasses characterized by diverse-human cultures having different ancestral origins. The recent archaeological researches from the region are challenging pre-existing conceptual understanding about the origin and divergence of human populations from the continent of Africa. Early Middle Palaeolithic culture in India around 385–172 ka reframes Out of Africa models. The observed human diversity on the sub-continent is attributed to amicable and adequate shelters with conducive climatic/ environmental conditions that offered life to variety of human populations from the Late Pleistocene to today’s environment.

Indus-Ganga-Saraswati basins
The Ganga is the axial river of the Indo-Gangetic basin and joined by a number of major Himalayan tributaries including the Yamuna, Ramganga, Ghaghra, Gandak, Kosi, and Tista before draining into the Bay of Bengal.
The sequence in drilled core in central Ganga plain suggests tight coupling amongst climate variability, monsoon front migration, orography of Himalaya over the past 100 ka. Whereas, the stratigraphic sections lying in the vicinity of peripheral bulge indicated a propagation of large craton derived gravelly fans towards the central part of the foreland. The fans predated the ravine formation and the arrival of the axial river Yamuna in the region between >100 ka and 35 ka BP. These sections show preservation of large vertebrate fauna including Elephas Namadicus, Equus, Bos, Sus, crocodile, turtle.

Brahmaputra Plains
The mighty Brahmaputra also meets the Ganga and forms a major deltaic depocenter in the Bengal Basin. The Brahmaputra River flows for 1,800 miles through Tibet, India, and Bangladesh. The stratigraphy of eastern part of this basin exhibits an interplay of sea level changes and sediment supply from Himalaya over the past 125 ka. The vast alluvial tract of this foreland exhibits a varied geomorphology comprising classic Megafans, incised river valleys in western & central plains and large interfluve areas. Its vertical stratigraphy archives >100 ka history of climate and foreland tectonics interplay.
The great Brahmaputra Valley, covering an area of 3000 km2 cradles one of largest braided rivers in the world. It is one of the richest biodiversity zones consisting of a unique combination of tropical evergreen, deciduous forests, mixed deciduous forest, riverine grasslands, bamboo orchards, and numerous wetland ecosystems. In this high rainfall prone area, changes in vegetational succession under climatic shifts is a subject of concern. The Majuli Island is one of the largest tropical river islands in the world and is located in Assam at an elevation ranging from 60 to 85 m above mean sea level.
The Brahmputra Basin, contains significant portions of Himalayan and Indo-Burmese biodiversity hotspots and is globally known for Mawsynram (the wettest place on Earth) and the living root bridges made by morphing aerial roots. This region of the world is considered by botanists and geographers as one of the nuclear areas of early plant domestication.

The Indian Peninsula

This triangular peninsula, surrounded by Arabian Sea on the west, Bay of Bengal on the east and Indian Ocean on the south, is the region of relative tectonic stability, riverine landscape and deposits and has provided longer records of the past.

Central Narmada Valley
The central Narmada Valley is known for rich and diverse natural resources in terms of flora and fauna. Vindhyan Supergroup sections along this Valley contain caves famous for having relics of human culture in the form of artistic expressions of Palaeolithic and later times. The Quaternary sediments here preserve a great wealth of contemporary palaeontological records particularly a diverse assemblage of mammalian fossils, archaeological archives and volcanic ash beds.
The oldest known human fossil of middle Pleistocene age recovered from Hathnora in central Narmada Valley is significant from the viewpoint of the origin of early Homo in South Asia and is ascribed to Homo erectus, archaic H. sapiens, or H. heidelbergensis by different investigators. Its maximum age is estimated to be >236 ka but not older than the early middle Pleistocene. The alluvial archives of the central Narmada Valley are also well known for their middle Palaeolithic and Acheulian tools.

Meghalayan Age Cave
The Latest Stage in Earth’s history is the Meghalayan Age. Its Global Boundary Stratotype Section and Point (GSSP) is Mawmluh cave in Meghalaya, northeast India. Mawmluh cave is one of the longest and deepest caves in India, and conditions here were suitable for preserving chemical signs of the transition in ages. The Meghalayan, the youngest stage, runs from 4.2 ka to present. The Meghalayan Age is unique among the many intervals of the geologic timescale in that its beginning coincides with a global cultural event produced by a global climatic event. The Stratotype speleothem section is housed in the Museum of BSIP, Lucknow.
Rock/Cave art and paintings, e.g. Bhimbetka (UNESCO world heritage site), Madhya Pradesh and Mirzapur, Uttar Pradesh, etc. have encouraged a number of researchers to study people–landscape interaction as depicted in its cave paintings. The records of mammalian existence, including that of man, cultural tools and paintings in caves make the rift valleys in the Son-Narmada-Tapti lineament, an ultimate arena to study human evolution in an integrated perspective with changing climate since Pleistocene time.

Lonar Crater

Earth’s only hyper-velocity impact crater on basaltic rock ringed by fascinating temples, the Lonar crater was formed fifty-two thousand years ago, by a 2 million ton meteor which impacted at an estimated speed of 90,000 km/h. It gouged a hole that was 1.8 km wide and 150 m deep. Lonar Lake has prompted scientists to attempt answers to questions like: Why is the lake alkaline and saline at the same time? Why does it support micro-organisms rarely found elsewhere on Earth? Why do compasses fail to work in certain parts of the crater? And what lurks at the bottom?

Southern highlands and lakes
The hot and wet coastal plain gradually rising in elevation to the high hills and mountain topography of the Western Ghats in Kerala receives strong south-west monsoon. There are several lakes placed in the eastern highland (Pookode and Vagamon) and in the western low land area (Vellayani). These lakes are enclosed fresh water basins with no distinct outlet. Some of these lakes like the Ashtamudi and Vembanad are affected due to the urbanization and elevation in population, practice of domestic waste disposal, industrial discharge, enormous use of agrochemicals, and enhance of antibiotics in aquaculture.

The Core Monsoon Zone
The Core Monsoon Zone of Central India is very sensitive to the variations in Indian Summer Monsoon precipitation, is the key region for the identification of weak or intense monsoon periods, referred to break and active spells, respectively. The vegetation-based palaeoclimatic studies shows the change in climate and its effect on the vegetation dynamics during the last 12.7 Ka. The Deccan produced some of the most significant dynasties in Indian History like the Cholas (3rd century BCE to 12th century CE), Chalukyas (6th to 12th centuries), Rashtrakutas (753–982), Hoysalas (10th to 14th centuries), Kakatiya (1083 to 1323 CE) and Vijayanagara Empire (1336–1646).

The Arid West

Thar Desert
The Thar Desert Sand dunes cover extensive area of the Thar Desert which lies between the Aravalli Hills in the east and the Nara River in the west. The northern limit of the Thar is along the Indo-Gangetic plains and its southern limits along the north Gujarat plains. Thar Desert is known for parabolic dunes and playas with height ranging from 2 m to 50 m or more. Low sand streaks and sandy hummocks are also numerous.
Strong aeolian activity is a characteristic of the latest 200-300 ka period and is marked by several episodes of greater aridity, strong wind regime and sand dynamism followed by periods of stability implying climate amelioration and some pedogenesis. The preceding mid and early Quaternary periods are marked by alluvio-colluvial and sheetwash aggradations with pronounced, well-evolved calcretes. For much of the Quaternary period, the Thar region had a semiarid climate and the current desertic conditions are recent.

The Great Rann of Kachchh
A unique geomorphic entity of the Indian sub-continent, the Rann is a mysterious and fascinating landscape generated during the last 10,000 years, due to an interplay of sea-level changes and tectonic uplift. This salt marsh is among the largest in the world that came to existence between past ~2000 to 500 years before present.
The present view of the Rann appears like desertic, monotonous, salt encrusted flat terrain which is almost devoid of exposures with former islands rising above it like hills. It attracts common man and geoscientists due to its unique annual inundation cycle that keeps it underwater for more than half of the year and completely dried (with salt crust on its surface) during summer months. The Rann is a natural laboratory for understanding modern biotic response to temperature, salinity, nutrient changes, etc. during its annual cycles. During winters, this area annually attracts large population of migratory birds and become one of the largest nesting sites for species like Flamingos. Similarly, low lying regions also host a few varieties of fishes which tolerate the wide scale changes that their preferred niche conditions and eventually die with hyper-saline conditions.
The Great Rann of Kachchh (GRK) hosts a significant amount of archaeological sites of Bronze age Harappan people. One of the largest archaeological town of Harappan times ‘Dholavira’ is situated on Khadir Island of the GRK Basin. GRK provided marine waterways / tradeways to Harappans for a long time. Artifacts include terracotta pottery, beads, gold and copper ornaments, seals, fish hooks, animal figurines, tools, urns, and some imported vessels that indicate trade links with lands as far away as Mesopotamia along with 10 large stone inscriptions, carved in Indus Valley script, perhaps the world’s earliest signboard.

The Indian shoreline

India flaunts a more than 7500 km long coastline fringing the peninsula. The Indian coastline falls in humid (having two monsoons), semi-arid and arid climate with rocky, muddy and sandy segments. The coastal wetlands sustain millions of people and are more vulnerable to the effects of rise in Relative Sea Level and changes in marine ecosystems. The sediment depositional environments vary from fluvial, fluvio-marine to purely marine depending upon the geomorphology and distance from the shoreline. The deltaic dynamism is largely influenced by monsoon driven active channels, tectonic nature of the basin, sea level changes, relief of the drainage basin and climate. The temporal and spatial change in these deltaic variables brings about profound alterations in the geomorphology either through erosion or accretion processes. Land subsidence in modern coastal or deltaic plains is a common and is susceptible to sea invasion. The rate of sediment deposition and texture in the coastal wetlands largely varies from time to time and depends on the direction and energy of the rivers/streams which feed them, coupled with the magnitude of wave action. 43% of 1030-km long Andhra Pradesh coastline is under very high risk if the sea level rises by 0.6 m resulting in an estimated loss of _1.2 million people residing within an elevation of 2.0 m.

The East Coast
The East Coast is characterized by gentle slope gradient of _1–2 m above mean sea level covering more than 4–6 km from the present shoreline. About 2–3 km of coastal zone is shallow, ranging from 0.4 to 1 m amsl, and is at a very high risk of inundation even if a slight rise in sea level occurs in future either because of climate or geomorphological changes.
Due to variations in ecological conditions, the magnitude of impact on mangroves varies from place to place depending upon hydrostatic changes. The apparent rise in relative sea level in several pockets along the East Coast of India is attributed to vertical displacement of the unconsolidated sediments rather than a net increase in global sea level rise. The average rate of sea level rise in India is 1.34 mm/yr. The southern part of the East Coast was severely impacted by December 2004 Tsunami due to the wide coastal plains.

Deltas are the most productive landforms along the river topography and are incredibly important to the human geography of a region being most densely populated areas in the world. In Indian subcontinent, most of the major rivers, such as Ganga and Brahmaputra, Kaveri, Krishna, Godavari and Mahanadi flow eastwards and empty into the Bay of Bengal via deltas. The Ganga-Brahmaputra Delta is the largest delta in the world. The Sunderbans, comprising of four UNESCO World Heritage Sites, covers the southernmost part of this delta.

Mangroves play an important role in understanding the extent, magnitude and duration of sea level changes either induced by climate or geomorphology of the area. Mangrove diversity is highest in the East Coast (91.6% of the total mangroves) favoured by the numerous rivers feeding the estuaries/ lagoons. Shallow protected intertidal zones of bay islands such as Lakshadweep and Andaman constitute 16% of the total mangroves.
On the basis of fossil mangrove deposits, it is seen that Holocene sea rose from below -12.8 to 1.2 m above present level between 8 to 6 ka and later between 5 to 4 ka. Records from contemporary East Coast of India show that the sea transgressed until 5-6 ka encroaching land (_15–25 km), and since then the delta prograded continuously but with intermittent short periods of rise and fall in relative sea level during late-Holocene. The amelioration of climate from strengthened to weakened monsoon has been observed in different parts of Indian peninsula and the central/western part of India since 6 ka.

Sunderbans is the largest mangrove forest in the world, covering an area about 9,600 km2 in India. This area is known to serve as a marine habitat for sea turtles, saltwater crocodiles and other reptiles. The overall subsidence of _1.3-2.2 cm/yr is observed in Sundarbans, because of which an estimated rise in relative sea level is 2.3 cm/yr versus the global estimates of subsidence rates and a rise in sea level are 3.4 mm/yr and 1.7 to 3 mm/yr, respectively.

Bhittarkanika is the second largest mangrove ecosystem of India, next to Sundarbans mangroves. It covers an area of 650 km2 and harbours one of India’s largest populations of saltwater crocodiles Crocodylus porosus. Subarnarekha mangroves, Mahanadi, Godavari and Krishna deltas, Pichavaram and Cauvery estuaries are deltaic mangrove forest situated at the mouth of major rivers carrying freshwater facing Bay of Bengal. Cochin estuary, Coondapur/Malpe area, Zuary estuary, Bombay mangrove creeks, Gulf of Kutch and Bhavnagar estuary, are coastal mangrove habitats in the intertidal zones along with mouths of minor rivers or minor estuaries and back waters facing Arabian Sea. Chilka Lagoon is the largest brackish water lagoon in Asia and stretches over an area of 1100 km. It is a paradise for birding, biodiversity hotspot and largest habitat of Irrawaddy Dolphins.

West Coast
Straight long sandy beaches of Karwar (Karnataka-Goa), rocky and sandy coasts of Maharashtra,tidal flats of the Gulf of Khambhat and Gulf of Kachchh in Gujarat along with rocky cliffs and shore platforms of Saurashtra Coast.
Coastal landscape is a net result of an equilibrium attained between a large number of interacting variables over very small (daily) to long (millennial) time periods. The present coastal system is an expression of a dynamic equilibrium established after the major sea level rise since the LGM, i.e. ~110 m rise in 10 ka.

The Islands of India

Andaman and Nicobar Islands in the Bay of Bengal in east is an island archipelago with diverse and encompass unique habitats and complex ecosystems. An area of 513.70 km2 along the West Coast of South Andaman Island is notified as a tribal reserve for the Jarawa people. To the south west of South Andaman Island is North Sentinel Island with an area of 59. 67 km2 and is inhabited by the Sentinalese people. An area of 885 km2 includes the Nicobar Biosphere Reserve and all these parks are within the tribal area. These parks are unique, very diverse and are important biodiversity hot spots, besides being the last remaining 12 pristine areas in the archipelago. Some of these national parks needs to be recognized as world Heritage sites and some should come under the Ramsar Wetlands.
The Lakshadweep Islands in the Arabian Sea in west have a vast expanse of the blue sea with precious heritage of ecology and environment. Indian coral reefs cover total area of 5,790 km2 and are mainly distributed in the Andaman & Nicobar and Lakshadweep Islands. The Andaman and Nicobar Islands have fringing reefs around many islands, and a long barrier reef about 329 km on the West Coast. Three major reef types are in India are Atoll, Fringing and Barrier. Within these habitats some of the most diverse, extensive and least disturbed reefs exist.