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Palaeogeography and evolution of the Godavari delta, east coast of India during the Holocene: An example of wave-dominated and fan-delta settings
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Data
September 2015
... Although millennial-scale variations in coastline migration and accumulated sediment volume have been reported for several deltas (Nageswara Rao et al., 2015;Tamura et al., 2009;, centennial scale delta evolution over the last 2000 years, a period of marked climate changes as well as increasing human activity, remains poorly studied (Maselli & Trincardi, 2013), especially for large river deltas in Asia. This paucity partly reflects the poor chronological constraint on deltaic deposits using 14 C as a dating technique. ...
... Globally, accelerated delta growth in the last 500 years has been found in deltas in the Mediterranean Sea (Maselli & Trincardi, 2013), the Godavari delta (Nageswara Rao et al., 2015) in the Indian Ocean, and the Mekong delta (Tamura et al., 2020) in the South China Sea. Investigation of the largest southern European deltas showed that delta outbuilding peaked during the LIA in addition to growth during the mild climatic conditions of the Roman Empire (350 BCE-250 CE) (Maselli & Trincardi, 2013). ...
... Investigation of the largest southern European deltas showed that delta outbuilding peaked during the LIA in addition to growth during the mild climatic conditions of the Roman Empire (350 BCE-250 CE) (Maselli & Trincardi, 2013). The land area of the Godavari delta in India has averaged 225-301 km 2 during the last 2000-500 years, but increased by 2-3 times (∼632 km 2 ) over the last 500 years (Nageswara Rao et al., 2015). The muddy deltaic protrusion at Camau within the Mekong delta had an accumulation rate of less than 1 km 2 /a before 600 CE, but increased significantly to 4 km 2 /a during the last 600 years (Tamura et al., 2020). ...
Reconstruction of sediment accumulation in river deltas over the Holocene provides a basis for understanding the relationship between climate change, human activities and delta growth. However, variations in deposition rates on a centennial‐scale over the last 2000 years remain poorly studied for mega‐deltas. Based on optically stimulated luminescence and AMS ¹⁴C ages, we calculated deposited sediment volumes in the Yangtze River Delta (YRD) for 500‐year intervals over the last two millennia for the first time. Our results reveal that the 2.0–1.5 and 0.5–0 ka periods had higher sediment deposition rates than in 1.5–1.0 and 1.0–0.5 ka, with maximum value about two times that of the minimum. A comparison with historical records of flooding and drought events indicates that a wetter climate led to a higher sediment deposition, reflecting the role of fluvial discharge in delta growth. However, the highest sediment deposition (205 ± 29 × 10⁶ m³/a) over the last 500 years is not only related to the wetter conditions of the Little Ice Age, but also linked to dramatic regional population growth. We suggest that human activities have predominated over natural forcing in determining the deltaic growth over the last five centuries. Taking the Medieval Climate Anomaly with the lowest deposition volume as an analog of current climate warming, and considering the decline in sediment loads due to recent damming and soil conservation, the YRD is likely to face an even more severe deficit in sediment supply and higher risk of delta destruction in the coming centuries.
... Chronologies of linear and predominantly sandy wave-and winddeposited relict beach ridges along the prograding coasts (Otvos, 2000;Tamura, 2012) help constraining the ages of former shorelines of coastal and delta plains (Giosan et al., 2017;Stattegger et al., 2013;Tamura et al., 2012aTamura et al., , 2012b. Several studies inferred the ages of beach ridges using radiocarbon dating of fossil shells and plant material in sands associated with the marine muds beneath the ridges (Nageswara Rao et al., 2015Rao et al., , 2020. Limitations of radiocarbon dating of coastal sediments are, 1) the uncertainty in the amount of reservoir effect of the marine deposits, 2) reworking of sediments and 3) applicability to organic matter, whose formation may or may not be syn-sedimentary (Nageswara Rao et al., 2015;Nian et al., 2018). ...
... Several studies inferred the ages of beach ridges using radiocarbon dating of fossil shells and plant material in sands associated with the marine muds beneath the ridges (Nageswara Rao et al., 2015Rao et al., , 2020. Limitations of radiocarbon dating of coastal sediments are, 1) the uncertainty in the amount of reservoir effect of the marine deposits, 2) reworking of sediments and 3) applicability to organic matter, whose formation may or may not be syn-sedimentary (Nageswara Rao et al., 2015;Nian et al., 2018). ...
... Relative orientation of beach ridges vis-à-vis the inferred abandoned distributary mouths led to the suggestion of four to five strandlines, each representing a major stage in the evolution of these deltas (Nageswara Rao and Sadakata, 1993;Nageswara Rao and Vaidyanadhan, 1978;Rengamannar and Pradhan, 1991;Sambasiva Rao and Vaidyanathan, 1979). A detailed Holocene chronology of this beach-ridge plain is available from the analyses of 12 sediment cores with 126 AMS radiocarbon dates from the Godavari Delta (Nageswara Rao et al., 2015) and 11 sediment cores with 59 AMS radiocarbon dates from the Krishna delta (Nageswara Rao et al., 2020). The thick dotted line represents the landward limit of the beach-ridge plain. ...
Luminescence ages of eight sandy beach-ridge samples from the Krishna–Godavari delta region on the east coast of India were obtained by synthesizing ages based on three luminescence signals, i.e., optically stimulated luminescence (OSL) from quartz, infrared stimulated luminescence (IRSL), and post-infrared (pIR) IRSL290°C from feldspar. Standard statistical procedures and hierarchical Bayesian modeling (ChronoModel) were used to synthesize the ages that are consistent within an uncertainty of ±10% and conforming to most of the published radiocarbon (AMS 14C) ages from this region. This approach, therefore, provides for the conjunctive use of luminescence signals of quartz and feldspar for a single and possibly more accurate age. Additionally, our study showed the potential that the reworked sediment could be identified, and pristine beach ridge sand grains could be isolated using single grain quartz luminescence measurements using appropriate statistical models. Further methodological development may improve the precision of these ages, if not the accuracy.
... Mann et al. (2019a, b) compiled available sea-level data from Southeast Asia, including the southern part of the Indian Peninsula and South Asia, and compared them with glacial isostatic adjustment numerical models. Based on an analysis of 12 undisturbed cores supported by 113 14 C dates from the Godavari Delta, on the east coast of India, Nageswara Rao et al. (2015) inferred a rapid rise of sea level, from -43 m to -7.5 m during the interval 10.9-8.2 cal ka BP, before stabilization at the present level around 5 cal ka BP, similar to the observations of Hendy et al. (2016) from analysis of a marine core collected off southern Mexico. Aside from the study of Nageswara Rao et al. (2015) from the Godavari Delta, no data are available on the Holocene sea-level history of the east coast of India. ...
... Based on an analysis of 12 undisturbed cores supported by 113 14 C dates from the Godavari Delta, on the east coast of India, Nageswara Rao et al. (2015) inferred a rapid rise of sea level, from -43 m to -7.5 m during the interval 10.9-8.2 cal ka BP, before stabilization at the present level around 5 cal ka BP, similar to the observations of Hendy et al. (2016) from analysis of a marine core collected off southern Mexico. Aside from the study of Nageswara Rao et al. (2015) from the Godavari Delta, no data are available on the Holocene sea-level history of the east coast of India. ...
... Based on the 14 C date on a marine shell from 8.0 m depth in a sediment borehole from the innermost beach ridge (KK site in Figs. 1, 2), Sadakata et al. (1998) inferred that the beach-ridge formation in the area was initiated * 6.8 cal ka BP. However, the area being a topographic depression, was flooded as a coastal embayment by a middle Holocene marine transgression, prior to the formation of the beach ridges (Nageswara Rao et al. 2015). ...
The Holocene sea-level history of the east coast of India is relatively unexplored. We analysed a 17.37-m-long sediment core from Kolleru Lake, a fresh waterbody located in a deltaic setting along the east coast of India, to reconstruct the climate, environmental, and sea-level history of the region. Sedimentary facies and pollen assemblages, with nine accelerator mass spectrometry 14C dates (two mollusk shells and seven plant samples) from the core revealed Holocene relative sea-level changes, and provide the first insights into the climate of the region from the Last Glacial Maximum (LGM) to present. A layer of anhydrous calcium sulfate at the core bottom, along with a 14C age of 18.4 cal ka BP, combined with the absence of pollen in mottled yellowish clay, indicated a desiccated lake surface, reflecting a dry LGM climate. Palynomorphs in the overlying calcareous-concretion-bearing light brown silty clay showed a change from arid terrestrial herbaceous plants to freshwater taxa, indicating a change from dry to wet climate after the LGM and before 8.0 cal ka BP. Further upward in the core, black, sticky silty clay with abundant mangrove pollen and mollusk shells, indicated a marine environment in Kolleru Lake and aggradational sediment stacking related to the middle Holocene sea-level rise from 8.0 to 4.9 cal ka BP. The uppermost sandy/silty clay, with terrestrial/aquatic pollen and a 14C age of 3.7 cal ka BP, indicated a freshwater environment during the late Holocene. Our results show that Kolleru Lake, on the east coast of India, changed from a desiccated state during the dry LGM to a brackish lagoon during the middle Holocene, and then to a freshwater lake by the late Holocene, under the influence of climate and relative sea-level changes.
... Mann et al. (2019a, b) compiled available sea-level data from Southeast Asia, including the southern part of the Indian Peninsula and South Asia, and compared them with glacial isostatic adjustment numerical models. Based on an analysis of 12 undisturbed cores supported by 113 14 C dates from the Godavari Delta, on the east coast of India, Nageswara Rao et al. (2015) inferred a rapid rise of sea level, from -43 m to -7.5 m during the interval 10.9-8.2 cal ka BP, before stabilization at the present level around 5 cal ka BP, similar to the observations of Hendy et al. (2016) from analysis of a marine core collected off southern Mexico. Aside from the study of Nageswara Rao et al. (2015) from the Godavari Delta, no data are available on the Holocene sea-level history of the east coast of India. ...
... Based on an analysis of 12 undisturbed cores supported by 113 14 C dates from the Godavari Delta, on the east coast of India, Nageswara Rao et al. (2015) inferred a rapid rise of sea level, from -43 m to -7.5 m during the interval 10.9-8.2 cal ka BP, before stabilization at the present level around 5 cal ka BP, similar to the observations of Hendy et al. (2016) from analysis of a marine core collected off southern Mexico. Aside from the study of Nageswara Rao et al. (2015) from the Godavari Delta, no data are available on the Holocene sea-level history of the east coast of India. ...
... Based on the 14 C date on a marine shell from 8.0 m depth in a sediment borehole from the innermost beach ridge (KK site in Figs. 1, 2), Sadakata et al. (1998) inferred that the beach-ridge formation in the area was initiated * 6.8 cal ka BP. However, the area being a topographic depression, was flooded as a coastal embayment by a middle Holocene marine transgression, prior to the formation of the beach ridges (Nageswara Rao et al. 2015). ...
The Holocene sea-level history of the east coast of India is relatively unexplored. We analysed a 17.37-m-long sediment core from Kolleru Lake, a fresh waterbody located in a deltaic setting along the east coast of India, to reconstruct the climate, environmental, and sea-level history of the region. Sedimentary facies and pollen assemblages, with nine accelerator mass spectrometry 14C dates (two mollusk shells and seven plant samples) from the core revealed Holocene relative sea-level changes, and provide the first insights into the climate of the region from the Last Glacial Maximum (LGM) to present. A layer of anhydrous calcium sulfate at the core bottom, along with a 14C age of 18.4 cal ka BP, combined with the absence of pollen in mottled yellowish clay, indicated a desiccated lake surface, reflecting a dry LGM climate. Palynomorphs in the overlying calcareous-concretion-bearing light brown silty clay showed a change from arid terrestrial herbaceous plants to freshwater taxa, indicating a change from dry to wet climate after the LGM and before 8.0 cal ka BP. Further upward in the core, black, sticky silty clay with abundant mangrove pollen and mollusk shells indicated a marine environment in Kolleru Lake and aggradational sediment stacking related to the middle Holocene sea-level rise from 8.0 to 4.9 cal ka BP. The uppermost sandy/silty clay, with terrestrial/aquatic pollen and a 14C age of 3.7 cal ka BP indicated a freshwater environment during the late Holocene. Our results show that Kolleru Lake, on the east coast of India, changed from a desiccated state during the dry LGM to a brackish lagoon during the middle Holocene, and then to a freshwater lake by the late Holocene, under the influence of climate and relative sea-level changes.
... In general, the geomorphic and sedimentary characteristics of the LFD are similar to those of perennial rivers with relatively large drainage basins and broad piedmont plains, such as the Godavari fan delta (Rao et al., 2015). The LFD obviously differs from typical fan-delta systems which have with steep gradients, are often gravelly and associated with cone-shaped fluvial systems. ...
... Evidence of such shifts has been documented by six delta lobes in the Godavari fan delta (Rao et al., 2015), and at least five delta lobes in the Lilas River fan delta (Karymbalis et al., 2018). According to our data, the LFD system contains at least two superlobes due to the river avulsion in the upper alluvial fan. ...
... Tectonically-controlled river avulsions have been primarily documented in rivers that flow across tectonically active regions, such as the Rhine-Meuse system (Berendsen and Stouthamer, 2000), the Tisza River (Timár et al., 2005) and the Pearl River (Yao et al., 2013). These avulsions typically imply fan-delta abandonment and the building of a new system, such as in the case of the Godavari delta (Rao et al., 2015). In addition, the tectonic activity that can also govern sedimentary processes in foreland lacustrine or marine basins (Dorsey et al., 1995;Benvenuti, 2003), may have a large impact on the distal portion of fan-deltas. ...
The Luanhe Fan-Delta (LFD) is one of the most important coastal deltas in North China. Numerous investigations on the late Quaternary evolution of this fan-delta system have been implemented during the 1980s. However, few detailed sedimentologic studies have been undertaken. Based on comprehensive analysis of sedimentary facies, grain size, microfossils, radiocarbon dates (AMS¹⁴C) and optically stimulated luminescence (OSL) ages from three ~30 m-long cores, along with recent reports from a series of cores and seismic profiles from the coastal areas, we reconstructed the detailed late Quaternary sedimentary evolution of the northern Bohai coast, which evolved from a coastal barrier-lagoon system during MIS5 to an alluvial plain, with river channels and floodplains between MIS4 and the Early Holocene. A variety of transgressive coastal depositional environments (freshwater marshes, beach ridges, sandy barriers, shallow seas) developed during the early Holocene. These environments were followed by delta progradation. The delta system then gradually turned into a coastal barrier-lagoon system under the combined impact of prevailing wave-driven currents and local subsidence. Two dramatic 90-degree diversions of the lower Luanhe River course likely influenced the sedimentary evolution of the LFD in its inner portion. The first avulsion took place in Qianxi, probably at the end of the Late Pleistocene (~15,000 cal a BP). It led to the abandonment of the Luanhe alluvial fan in the western part of the northern Bohai coastal plain (NBCP), and to the formation of a new alluvial fan in the eastern NBCP. This alluvial fan evolved into a fan-delta system (7000–3500 cal a BP) during the Holocene transgression. The second avulsion occurred at Zhuacun during the Late Holocene, probably at 3600 ± 100 cal a BP. Following this latter avulsion, the Luanhe River shifted toward the east and formed a new fan-delta system (~3700 cal a BP–present), with its apex in Luanzhou. Abrupt tectonic uplift in this highly seismic region likely controlled the two avulsions and the dramatic shift of the alluvial-fan complexes. Climate and sea-level changes may also have partly influenced the development of the LFD.
... We then presented a continuous high-resolution record of vegetation, sediment source and erosion vis-à-vis the monsoon decline and human activity for the period from 6.1 to 1.3 cal. ka BP, taking advantage of the high sedimentation rate and high sensitivity of proxies to the monsoon climate and sediment sources in sediment core CY from the Godavari Delta, India (Nageswara Rao et al., 2015). Our study will not only unravel the linkage between climate and human society but also reveal the ecosystem sensitivity in a semi-arid climate setting. ...
... (b) Distribution of the ecological communities in the Godavari drainage basin (after Zorzi et al., 2015). (c) SRTM 90 m DEM showing the Godavari delta with the six delta growth lobes outlined (after Nageswara Rao et al., 2015). The red circle indicates the location of core CY. ...
... The Godavari Delta developed during ~6 cal. ka BP through six stages (lobes 1-6; Figure 1c) of successive migration of the main depocenter (Nageswara Rao et al., 2015); the corresponding time intervals of each lobe are shown in Figure 2. The sediment accumulation rate in the delta had progressively increased from as low as ~12 Mt/yr during 6-4 cal. ka BP to ~27 Mt/yr during 4-3 cal. ...
Sediment is the most dominant reservoir of organic pollutants in the aquatic environment. Understanding carbon and nitrogen sources in sediments and factors that controls distribution enhances our understanding of biogeochemical cycles of carbon and nitrogen. Different end-members and surface sediments of rivers and sediments profiles of lakes were collected. The concentrations of TOC and TON and their δ¹³C and δ¹⁵N were studied for qualitative and quantitative analysis of natural and anthropogenic sources. The results show that TOC and TON concentrations of the sediments from rivers range from 0.63% to 10.83% and 0.06%–0.86%, respectively, indicating substantial great environmental risks in these rivers. The concentrations of TOC and TON for the four sediment profiles below the 5 cm, increase in the order of Miyun < Chuidiao < Qunming < Houhai, as influenced by their respective environment condition. Moreover, water quality was quite good and there was no risk of eutrophication in Miyun reservoir. δ¹³Corg and δ¹⁵Norg in surface sediments of the studied 18 rivers range from −27.2‰ to −24.9‰ and −2.2‰ to +10.9‰, respectively. Based on a simple δ¹³C-based end-member mixing and a C/N ratio model, organic matter in the surface sediments of these rivers were mainly derived from sewage and C3 plant. In addition, the sources of organic matter differed in each layer of the four sediment profiles. This study provides a reliable method for qualitative and quantitative identification of the source of organic matter in sediments, and offers theoretical basis for better management of rivers and lakes.
... lake built in the mid-19th century at Rajahmundry controls the flow to the tidally influenced delta. In the delta, the river splits into three branches, of which the northern (Gautami) branch carries the majority (67 %) of the discharge and sediment load via an estuary to the Bay of Bengal (Rao et al., 2015). Smaller dams that control the river flow year-round are abundant in the upper basin (Pradhan et al., 2014). ...
... The southwest monsoon, with its main moisture source in the Indian Ocean and Arabian Sea, brings 75 %-85 % of the annual rainfall to the Godavari basin in the wet season (Balakrishna and Probst, 2005;Kirkels et al., 2020b). Approximately 94 % of the annual discharge and ∼ 98 % of the sediment load is exported during the monsoon (wet) season (Rao et al., 2015). The upper Godavari subbasin lies in the rain shadow of the Western Ghats mountain range and receives limited precipitation (∼ 430 mm yr −1 ). ...
Monsoonal rivers play an important role in the land-to-sea transport of soil-derived organic carbon (OC). However, spatial and temporal variation in the concentration, composition, and fate of this OC in these rivers remains poorly understood. We investigate soil-to-sea transport of soil OC by the Godavari River in India using glycerol dialkyl glycerol tetraether (GDGT) lipids in soils, river suspended particulate matter (SPM), and riverbed sediments, as well as in a marine sediment core from the Bay of Bengal. The abundance and composition of GDGTs in SPM and sediments in the Godavari River differs between the dry and wet season. In the dry season, SPM and riverbed sediments from the whole basin contain more 6-methyl branched GDGTs (brGDGTs) than the soils. In the upper basin, where mobilisation and transport of soils is limited due to deficient rainfall and damming, contributions of 6-methyl brGDGTs in SPM and riverbed sediments are relatively high year-round, suggesting that they have an aquatic source. Aquatic brGDGT production coincides with elevated values of the isoprenoid GDGT-0 / crenarchaeol ratio in SPM and riverbed sediments from the upper basin, indicating low-oxygen conditions. In the wet season, brGDGT distributions in SPM from the lower basin closely resemble those in soils, mostly from the north and east tributaries, corresponding to precipitation patterns. The brGDGT composition in SPM and sediments from the delta suggests that soil OC is only effectively transported to the Bay of Bengal in the wet season, when the river plume extends beyond the river mouth. The sediment geochemistry indicates that also the mineral particles exported by the Godavari River primarily originate from the lower basin, similar to the brGDGTs, suggesting that they are transported together. However, river depth profiles in the downstream Godavari reveal no hydrodynamic sorting effect on brGDGTs in either season, indicating that brGDGTs are not closely associated with mineral particles. The similarity of brGDGT distributions in bulk and fine-grained sediments (≤ 63 µm) further confirms the absence of selective transport mechanisms. Nevertheless, the composition of brGDGTs in a Holocene, marine sediment core near the river mouth appears substantially different from that in the modern Godavari basin, suggesting that terrestrial-derived brGDGTs are rapidly lost upon discharge into the Bay of Bengal and/or overprinted by marine in situ production. The large change in brGDGT distributions at the river–sea transition implies that this zone is key in the transfer of soil OC, as well as that of the environmental signal carried by brGDGTs from the river basin.
... This dramatic decline in sediment load has become a serious concern to the ecosystem of the deltaic environment. Previous studies observed an intensifying erosion of the coastal land in the past several decades, mainly due to the decreasing sediment load in the Godavari (Nageshwara Rao et al., 2010Rao et al., , 2015. Although the Godavari River is internationally recognised for its high sediment load behaviour before the dam construction period (Milliman and Meade, 1983), the controlling factors of recent sediment load variation are poorly understood. ...
... The Godavari delta has experienced erosion at a progressive rate, resulting in a significant loss of land between 1965 and 2008, mainly because of sediment load decline in the delta (Nageshwara Rao et al., 2010). Coastal erosion and loss of lands in the Godavari delta may further intensify into an irreversible destruction phase as more dams are intended (Nageshwara Rao et al. 2015;Das, 2021;Das et al., 2021) under a warming and wetter climate (Mukherjee et al., 2018) with the increasing intensity of tropical cyclones (Sil et al., 2021;Singh and Roxy, 2022) and progressive sea-level rise (Kusche et al., 2016) in the near future. ...
River sediment, the most crucial component of the land-ocean interaction, is enduring substantial changes worldwide because of anthropogenic alterations and climate change. Our study assesses the interaction of sediment load variability and yield to the rainfall, land-use, and dam constructions at both spatial and temporal scales in the Godavari and its major tributaries. The most important river basin in Peninsular India, the Godavari, has witnessed a dramatic decline (p-value <0.001) in sediment load over the past five decades, with average annual rates of 2 million tons (Mt) yr-1. Sediment load in the Godavari reduced from 150 Mt between 1970-1979, to 115 Mt in 1980-1989, 98 Mt in 1990-1999, 48 Mt in 2000-2009, and 47 Mt in 2010-2019, respectively. While sediment load in the Godavari and its major tributaries is declining significantly, rainfall showed an overall insignificant increasing trend barring the Sabari sub-catchment. In Sabari, rainfall is increasing at a significant rate of 7 mm yr-1 (p-value = 0.001). Twenty-five sub-basins in the Godavari showed a large variation in sediment yield (28 to 3404 t km-2 yr-1). Our results revealed that spatial variability in sediment yield is primarily associated with both rainfall and land-use variation. The temporal variation in sediment load in the Godavari and Pranhita is associated with intensified human activities during the most recent decades, while climate is the primary controlling factor in Indravati and Sabari sub-catchments. Sediment entrapment under a high rate of siltation by reservoirs in the Godavari has sharply reduced the sediment flux to the Bay of Bengal, causing aggravated delta erosion by wave actions. The findings of this study have significant implications for understanding the complex interrelationship between the management of reservoirs, land use, sediment loads, denudation, and coastal erosion in the Godavari catchment.
... Climate of the Earth has changed throughout the geological time either in the form of drastic changes over millions of years or as minor fluctuations (Juyal et al., 2003;Jayalakshmi et al., 2004;Kumaran et al., 2005;Anderson et al., 2007;Nair et al., 2010). Due to absence of long-term direct climatic records, the paleoclimatic changes are inferred using proxy sources (Vaz and Banerjee, 1997;Roberts, 1998;Alappat et al., 2011;Jayangondaperumal et al., 2012;Srivastava and Farooqui, 2013;Tripathi et al., 2014;Limaye et al., 2014;Malik et al., 2015;Rao et al., 2015;Govil et al., 2016;Makwana et al., 2019). A cautious examination of the landform stratigraphy also yields clues to the past climate (Babu, 1975;Banerjee et al., 1993;Chauhan et al., 1993;Agnihotri et al., 2003;Banerjee, 2000;Kumaran et al., 2005;Coltorti et al., 2010;Farooqui and Naidu, 2010;Rao et al., 2012;Selvakumar et al., 2012;Singh et al., 2014;Alappat et al., 2015;Basaviah et al., 2015;Das et al., 2017;Narayana et al., 2017). ...
... From the above analysis, it is apparent that the region has gone through significant climatic changes in the past that was accompanied by sea level fluctuations owing to its proximity to the east coast of India (Banerjee, 2000;Khandelwal et al., 2008;Farooqui and Naidu, 2010;Jayagondaperumal et al., 2012;Limaye and Kumaran, 2012;Rao et al., 2015;Band et al., 2018). ...
Abstract: The subsurface sediment archives provide clues to the past climate of the Earth. To reconstruct the paleoclimate of Lower Baitarani Basin, a 1000 cm deep sediment core (JP) was collected from the flood plain located in Jhumpuri village of Jajpur, Odisha. A total number of eleven distinct layers were identified based on variations in the sediment colour and textural at varying depths. From each layer, a representative sample was collected and carried to the laboratory for further assessment. Each of these sub-samples was examined for particle size analysis, availability of total organic carbon (TOC), and elemental concentration. The physical and geochemical proxies as paleoproductivity, terrestrial flux, weathering, level of salinity, colour, and texture variations were utilised to examine the paleoclimate of the area. The colour variations of the subsurface sequences suggest that the deposition has occurred under both freshwater and stagnated/marshy conditions. The texture variations—clay, silty clay, and loamy fine sand—also indicate deviations in sediment supply and rate of sediment aggradation during climatic shift between warm-humid and cold-arid episodes.
With the help of geochemical proxies to illustrate the terrestrial flux: Fe2O3, Al2O3, TiO2, MgO, CaO, Cu, Co, Ba, and Zn; paleoproductivity: TOC,CaO/Al2O3, Zn/Al2O3,Sr/Al2O3, Cu/Al2O3, and Ba/Al2O3; weathering: Fe2O3/Al2O3, TiO2/Al2O3, and MgO/Al2O3; and the salinity index, a relatively cold-dry climate is inferred during the sedimentation of basal layers. Subsequently, a shift to the relatively warm-humid phase is suggested which again was followed by a cold-dry, and warm-humid phases. In the recent deposits, the proxies have not shown any considerable variation indicating prolongation of the existing warm-humid phase. However, some indications of a climatic shift to colder climate is also marked in the surface layer (JPL1).
Keywords: Paleoclimate; Geochemical proxies; Grain size; Sedimentation; Flood plain.
... Climate of the Earth has changed throughout the geological time either in the form of drastic changes over millions of years or as minor fluctuations (Juyal et al., 2003;Jayalakshmi et al., 2004;Kumaran et al., 2005;Anderson et al., 2007;Nair et al., 2010). Due to absence of long-term direct climatic records, the paleoclimatic changes are inferred using proxy sources (Vaz and Banerjee, 1997;Roberts, 1998;Alappat et al., 2011;Jayangondaperumal et al., 2012;Srivastava and Farooqui, 2013;Tripathi et al., 2014;Limaye et al., 2014;Malik et al., 2015;Rao et al., 2015;Govil et al., 2016;Makwana et al., 2019). A cautious examination of the landform stratigraphy also yields clues to the past climate (Babu, 1975;Banerjee et al., 1993;Chauhan et al., 1993;Agnihotri et al., 2003;Banerjee, 2000;Kumaran et al., 2005;Coltorti et al., 2010;Farooqui and Naidu, 2010;Rao et al., 2012;Selvakumar et al., 2012;Singh et al., 2014;Alappat et al., 2015;Basaviah et al., 2015;Das et al., 2017;Narayana et al., 2017). ...
... From the above analysis, it is apparent that the region has gone through significant climatic changes in the past that was accompanied by sea level fluctuations owing to its proximity to the east coast of India (Banerjee, 2000;Khandelwal et al., 2008;Farooqui and Naidu, 2010;Jayagondaperumal et al., 2012;Limaye and Kumaran, 2012;Rao et al., 2015;Band et al., 2018). ...
The distribution of redox sensitive trace elements and rare earth elements (REEs) has provided the opportunity to interpret conditions observable during the deposition time. The trace and rare earth elements are sensitive to redox changes and highly enriched in reducing sediments, potentially making them robust proxies to study paleoredox conditions. The variability and concentration of the redox sensitive metals have been widely studied as a paleo-redox proxy both in marine and fluvial environments. The present study is an attempt to analyze the paleo-redox condition in the lower reaches of the Baitarani Basin, Odisha, East Coast of India.
... The second-longest river in India (Rao et al. 2015), the Godavari River, gives rise to an extensive delta comprising an array of riverine and coastal features at its confluence with the Bay of Bengal on the eastern coast of India. The Godavari delta includes the second largest contiguous patch of riverine mangroves in India, of which 273.5 km² is protected inside Coringa Wildlife Sanctuary WLS (16°59'-16°44' N / 82°15'-82°20'E) (Ravishankar et al. 2004;Fig. ...
The Godavari delta in Andhra Pradesh supports a viable population of vulnerable fishing cats Prionailurus viverrinus in India. This threatened cat species is wetland dependent, and degradation of wetlands, including mangroves, is one of the significant threats to its long-term conservation. The occurrence of fishing cats has been found to be higher in the mangrove forests of the Godavari delta than other coastal habitats in this delta. The close association of fishing cats with the mangroves in the Godavari delta puts them at a high degree of vulnerability due to the ongoing degradation and loss of intact mangrove forests. Here, we discuss the future of the threatened fishing cats and their habitats in the Godavari delta, which is faced with a myriad of issues, including altered river discharge and reduced sediment flow due to dams, sea-level rise, coastal erosion, and cyclonic storms.
... Additionally, as the eastern margin of Indian subcontinent is tectonically stable, thus the change in its landscape and sediment delivered to the coastal basins located at this margin are the effect of long-term climatic fluctuations (Dash et al., 2020;Vaidyanadhan and Ghosh, 1993). Many multi-proxy studies have been carried out to unravel these long-term climatic fluctuations in the coastal regions of India (Farooqui and Nautiyal, 2016;Rao et al., 2015Rao et al., , 2020Shah et al., 2022;Srivastava and Farooqui, 2013). Since the Neolithic period (2300-2100 BCE), the eastern part of Odisha has given shelter to early humans (Pradhan, 2005;Tripati and Vora, 2005). ...
Understanding the impact of climate change on the vegetation cover in the past is crucial for predicting the future warming scenario and its consequences. The present study integrates biotic (palynological analysis) and abiotic proxy (sediment chemistry, clay mineral assemblages and grain size end member (EM) analysis) records in a chronologically constrained sedimentary sequence from the southeastern part of the Mahanadi River delta to reconstruct the hydroclimate since 2600 years. The Mahanadi delta sediments are primarily derived from felsic rock source possibly composed of granites or granulites. The dominance of herbaceous taxa, high aridity index and deposition of fine grain (EM1) sediment possibly suggest a relatively cold and dry climate in the study region during ~2600–2100 cal yr BP corresponding to the Iron Age Cold Period (IACP). Presence of diverse mangrove and tree taxa, deposition of coarser sediment (EM3) and relatively high abundance of secondary clay minerals possibly indicate high precipitation associated with the Roman Warm Period (RWP, ~2100–1800 cal yr BP). A decline in mangroves, dominance of herbaceous taxa and high deposition of fine grain (EM2) sediment from ~1800 to 1300 cal yr BP may indicate a relatively drier climate coinciding with the Dark Age Cold Period (DACP). High moisture index and an increased value of Rb/Sr during ~1300 cal yr BP may suggest a wet phase with the onset of the Medieval Climatic Anomaly (MCA) and later shifted to an arid climate during ~1100–800 cal yr BP. After ~800 cal yr BP, a sharp decline in all weathering indices and vegetation cover, dominance of illite indicates a relatively dry climate which could mark the Little Ice Age (LIA, ~800–300 cal yr BP). A small increase in the terrestrial flux, as well as the weathering indices after ~300 cal yr BP, may suggest the onset of recent warming.
... The eastern coast of southern India is home to one of India's biggest mangrove forests, the Godavari forest. The Godavari mangrove forest has major ecological and biological functions in its estuary locations [3]. Due to its importance as a marine ecosystem, the Godavari mangroves have been declared as a "Coringa Wildlife Sanctuary." ...
Mangrove forest is one of the productive ecosystems that provide essential habitats for various fauna as breeding and feeding drives. However, heavy metal pollution in the mangrove forest has led to severe health problems for several aquatic species. Biomonitoring of metals using a nondestructive method is an emerging technique. Scats of the fishing cat (Prionailurus viverrinus) were collected from five locations in the Godavari estuary mangrove habitats, Coringa Wildlife Sanctuary, Andhra Pradesh, India, to determine the level of various metals. An opportunistic method was applied to collect scats in the mangrove forest. Six scat samples were collected from each of the sampling sites. The following prey species, such as crabs, fishes, birds, rodents, plants, plastics, and unidentifiable prey matters, were found in the scats. Select metals, such as chromium (Cr), copper (Cu), and lead (Pb) were analyzed from the scats of the fishing cat since they intensively influence the physiology and behavior of top predators. The concentration of Cu in fishing cat scats was higher than the other two metals assessed. Metals showed statistically substantial variation across locations (p < 0.05). According to the current study, heavy metals may significantly threaten the fishing cat in the Coringa Wildlife Sanctuary. The fishing cat is a vulnerable species in accordance with the ICUN categories. Due to pollution and other human pressures, the fishing cat may soon be categorized as a threatened or endangered species; the research advises that authorities should prioritize the protection of the vulnerable species of the fishing cat from the Coringa Wildlife Sanctuary, Andhra Pradesh, India.
... Additionally, as the eastern margin of Indian subcontinent is tectonically stable, thus the change in its landscape and sediment delivered to the coastal basins located at this margin are the effect of long-term climatic fluctuations (Dash et al., 2020;Vaidyanadhan and Ghosh, 1993). Many multi-proxy studies have been carried out to unravel these long-term climatic fluctuations in the coastal regions of India (Farooqui and Nautiyal, 2016;Rao et al., 2015Rao et al., , 2020Shah et al., 2022;Srivastava and Farooqui, 2013). Since the Neolithic period (2300-2100 BCE), the eastern part of Odisha has given shelter to early humans (Pradhan, 2005;Tripati and Vora, 2005). ...
... Remote-sensing observations and geomorphological maps prepared by the Geological Survey of India provide a synoptic view of the features in the terrain ( Figure 2). Nageswara Rao 13 reported that the Godavari delta plain is divided into two typical landform assemblages: the upper fluvial plain with palaeo distributary courses and natural levees, and the lower beach-ridge plain with beach ridges, mangrove swamps and mudflats. Delta plain, coastal plain, flood plain, beach ridge, tidal flat, mud flat, natural levee, creek, channel bar and palaeochannels are observed in the study area. ...
... Where an alluvial fan combines with a coastal fringe delta, active delta lobes are controlled by the river courses on the alluvial plain. The Ganges (Wilson and Goodbred Jr., 2015), Irrawaddy (Chen et al., 2020;Giosan et al., 2018), Godavari (Nageswara Rao et al., 2015), Krishna (Nageswara Rao et al., 2020), and Nile (Stanley and Warne, 1993) deltas, and many famous deltas belong to this class of deltas where there is no deltaic marine sediment distribution in the alluvial plains. Deltaic marine sediment is located only within the coastal fringe delta. ...
Deltas are subaerial landforms that cap underlying deposits with subaqueous extensions that result from a river feeding sediment directly into a standing body of water at a rate that overwhelms any effective dispersal processes derived from the ambient basin. This definition encapsulates both the terrestrial surface expression and the geological focus on the entire sediment mass. Environmental studies also focus on the ecology of deltaic wetlands, their drowning history, and related sustainability issues including societal considerations, history, and culture. A mean 76 ± 16% drop in hydraulic energy occurs in all subaerial deltas regardless of size, given the break in gradients separating fluvial and deltaic surfaces, driving an ever-decreasing bed-material transport, shallowing of distributary channels and concomitant overbank flooding. A delta's sediment mass grows from the addition of new river loads but can also include aeolian and marine sediment derived from outside the delta domain, growth of peat and other biomass, and inputs from human action. Removal of sediment is via river plumes interacting with marine currents, wave-induced transport, sediment failures and gravity flows, high-tide inundation onto the delta plain, tidal channel widening and deepening, and human action (peat, clay, sand and gravel mining). A delta's trapping efficiency ranges from 0 for small-load rivers that discharge directly into an energetic ocean, to 80% for large deltas, and up to 100% for some semi-enclosed bayhead deltas, including fjords. The global (ensemble) subaerial delta aggradation rate is ~1.6 mm/y if 70% of the global sediment load exits the river mouth(s), a reminder of how much sediment can be expected to be delivered to the surfaces of global deltas at a time when the 2022 CE sea level rise is ~4 mm/y.
At the planetary scale, deltas are environmentally complex given Earth's range in climate, hydrodynamics, tectonic settings, relative sea-level provinces, sediment input, redistribution processes, and human actions. Under natural conditions, the subaerial portion of deltas adapt to change by advancing, retreating, switching, aggrading, and/or drowning, whereas many modern deltas are structurally constrained by societal needs. The 89 large and mud-rich coastal marine deltas (i.e. subaerial area > 1000 km²) account for 84.3% of Earth's total deltaic area that hosts >89% of all humans occupying deltas, many living within megacities. The 885 medium-size deltas (i.e. subaerial areas 10–1000 km²) account for 15.5% of the global delta area and 10.5% of humans living on deltas, with characteristics that fall between the small and large delta categories. The 1460 small and essentially sandy deltas (1–10 km²), including all fjord deltas, are impacted less from human action (with exceptions) and most are better able to withstand climate change. Recognizing the limits of big data in capturing delta complexity, field data remains a necessary gold standard for site investigators.
... Delta progradation can amount to several tens of meters per year (e.g., 50 m/yr in the Mekong delta (Zoccarato et al., 2018) and 100-150 m/yr in the Lafourche subdelta of the Mississippi river (Chamberlain et al., 2018)), with thicknesses of the Holocene deposits ranging from a few meters (e.g., in the Danube (Vespremeanu-Stroe et al., 2017) and Chao Praya deltas (Tanabe et al., 2003)) to several tens of meters (e.g., in the Godavari (Nageswara Rao et al., 2015) and Mississippi deltas (Bridgeman, 2018)). Here, we simulate the aggradation of a schematic delta lobe over a period (T) of 1,000 years with a prodelta progradation rate (v pro ) of 10 m/yr and an active sedimentation phase (ΔT) lasting 250 years. ...
Natural environments such as coastal wetlands, lowland river floodplains, and deltas are formed by sediment, transported by watercourses and the sea, and deposited over century to millennium timescales. These dynamic environments host vulnerable ecosystems with an essential role for biodiversity conservation, coastal protection and human activities. The body of these landforms consists of unconsolidated sediments with high porosity and compressibility. Consequently, they often experience significant compaction due to their own weight, that is, autocompaction, which creates an important feedback within the geomorphological evolution of the landform. However, this process is generally oversimplified in morphological simulators. We present a novel finite element (FE) simulator that quantifies the impact of natural compaction on landform evolution in a three‐dimensional setting. The model couples a groundwater flow and a compaction module that interact in a time‐evolving domain following landform aggradation. The model input consists of sedimentation varying in time, space and sediment type. A Lagrangian approach underlies the model by means of an adaptive mesh. The number of FEs gradually increases to accommodate newly deposited sediments and each FE changes its shape, that is, becomes compressed, following sediment compaction. We showcase the model capabilities by simulating three long‐term depositional processes at different spatial scales: (a) vertical growth of a tidal marsh, (b) infilling of an oxbow lake, and (c) progradation of a delta lobe. Our simulations show that compaction is the primary process governing the elevation and geomorphological evolution of these landforms. This highlights that autocompaction is an important process that determines the resilience of these low‐lying landforms to climate change.
... Surface wave energy causes sandy, bioturbated lag deposits to form during the trade wind season (March-November), and then low surface wave activity during the northwest monsoon (December-March) results in a mud drape being deposited, covering the sand deposits. Sand and mud alternations also comprise the transition zone between delta front/shoreface sand and prodelta mud in a wave-dominated Godavari Delta, India (Nageswara Rao et al. 2015). ...
This chapter focuses on major deltas built by large rivers with high sediment discharge and discusses their morphology, sedimentology, and evolution based mainly on data from recent studies. A ternary diagram originally proposed by Galloway is the best‐known system for classifying deltas. It builds on a concept by Fisher, who subdivided deltas into two major types: high‐constructive and high‐destructive deltas. Deltas develop well at river mouths during regressive phases. When considering the transfer of sediment from the land to the sea, it is important to estimate past sediment discharge quantitatively either from the rate of advance of the delta front or by calculating the total sediment volume of a delta. It is desirable to analyze both natural and anthropogenic changes in deltas from the viewpoints of geology and sedimentology in order to evaluate the current status of deltas and human activities in both deltas and drainage basins.
... The bar graphs depict the sediment loads for four medium-to-large Asian rivers: the Godavari River (India)234,235 , the Huanghe (or Yellow) River (China)80,81 , the Song Hong (or Red) River (Vietnam)236 and the Yangtze River (China)77 . Records are of unequal duration and intervals. ...
The global sediment cycle is a fundamental feature of the Earth system, balancing competing factors such as orogeny, physical–chemical erosion and human action. In this Review, values of the magnitudes of several sources and sinks within the cycle are suggested, although the record remains fragmented with uncertainties. Between 1950 and 2010, humans have transformed the mobilization, transport and sequestration of sediment, to the point where human action now dominates these fluxes at the global scale. Human activities have increased fluvial sediment delivery by 215% while simultaneously decreasing the amount of fluvial sediment that reaches the ocean by 49%, and societal consumption of sediment over the same period has increased by more than 2,500%. Global warming is also substantially affecting the global sediment cycle through temperature impacts (sediment production and transport, sea ice cover, glacial ice ablation and loss of permafrost), precipitation changes, desertification and wind intensities, forest fire extent and intensity, and acceleration of sea-level rise. With progressive improvements in global digital datasets and modelling, we should be able to obtain a comprehensive picture of the impacts of human activities and climate warming.
... Rao et al. [7] analysed the six gradual evolution in the Godavari delta with distinguished avulsions formed by the cyclic shifts of delta lobes. The lobes were analysed and the patterns of the Godavari delta were observed. ...
A river network is usually a system wherever in all the tributaries of the rivers, lakes or streams be a part of to create a basin. The basin includes of the laborious and soft rocks that square measure fashioned by the influence of weather conditions, vegetation and transport of sediments and water. The stream network model identity's the placement of water bodies, determines the causes of floods, deposit, pollution of stream bodies and preventive ways. The pre-processing of the data obtained from the GSI helps to evaluate and investigate the data more accurately and efficiently in predicting the water resources and determining the quality of the water. Some of the problems that are addressed in the proposed research study are caused by the pixel-based indexes leads to an error in the detection of water due to the other occlusions like the cloud shadows and the noise that is incorporated during the image fusion process has to be eliminated for a more enhanced quality of image. The primary aim of the proposed research model are to develop an enhanced multi-temporal pixel level image fusion with advanced image classification technique that detects the changes in the surface of water and demonstrate GIS image segmentation based on convolution wavelet neural network by adding an adaptive filter to further improve the segmentation process. The proposed model will be extended by integrating the other machine learning models to create a hybrid or both can be compared such as SVM (support vector machine), ANN (Artificial neural network) or ML (maximum likelihood) classification. Further, the model is developed by adding filters that completely eliminates the noise and that are more adaptive and robust in nature..
... The recentstudies that are based on mapping of landforms, mainly concentrate on beach ridges andpaleo-distributary courses that are present in the Godavari basin. The annual rainfall thatdelta receives is 1000-1100mm and the maximum temperature is about 45 0 C in summerand 17 0 C in winters [19,20] ...
The water bodies are observed with the help of remote sensing images, and it is of high significance as it provides the information of the water resources available and its on going transformations. Image processing of the water bodies helps to control and find the measures related to the water scarcity, pollution, and also predicts the flood occurrence. The location of water bodies are finds. It is also important for the analysis of the hydrological features and for water resource management. Over the past decade, a significant amount of research been conducted to extract the water body information from various multi-resolution satellite images. The objective of this paper is to review methodologies applied for water body extraction using satellite remote sensing. [1] Further, the sections in this proposed research development identity the water bodies to predict the location of the water resources. Index Terms-DEM, Remote Sensing, Satellite image and water body.
... This river originates near Nasik in the Western Ghats mountain range and traverses eastward for *1465 km before draining into the Bay of Bengal. Its basin receives rainfall of about 1000-1100 mm y À1 (Rao et al. 2015) with the highest (*84%) occurring during the southwest monsoon (June to September). Its annual discharge is *105 km 3 , which occurs through 25 tributaries. ...
Absorption spectra of coloured dissolved organic matter (CDOM) and their derived parameters such as, absorption coefficient and spectral slopes are useful to study the molecular weight distribution of DOM. Here CDOM absorption characteristics were assessed in two distributaries [Gautami (GGE) and Vasishta (VGE)] of the Godavari estuary to examine the differences in molecular weight characterization of CDOM and its origin with reference to the geomorphological features during post southwest monsoon (PSM), late northeast monsoon (LNM) and early southwest monsoon (ESM) seasons. In VGE, absorption coefficient (aCDOM350) exhibited significant negative correlation with total suspended matter (TSM) and salinity during PSM and LNM due to the local anthropogenic inputs. In GGE, the values of spectral slope S275–295, and S350–400 were low and high, respectively during PSM, indicating the presence of pronounced terrestrial derived organic matter. In VGE, S350–400 showed increasing and decreasing trends from upstream to downstream in surface and bottom waters respectively during LNM, indicating that organic matter originated through in-situ microbiological processes. The spectral slope ratio, SR (S275–295/S350–400) was higher in GGE during LNM (Avg ± SD = 1.19 ± 0.14) and ESM (1.47 ± 0.27), which suggests the lower molecular weight organic matter formation through microbiological and photodegradation processes. However, in VGE, the values of SR during LNM (1.04 ± 0.11) and ESM (1.08 ± 0.17) were low, which indicates higher molecular weight organic matter formation due to biological production driven by local anthropogenic inputs or aquaculture effluents. This is first of its kind on the absorption characteristics of coloured dissolved organic matter (CDOM) with reference to the different geomorphological features of Godavari estuary.Seasonal variation in the molecular weight characteristics of CDOM were studied in the Gautami and Vasishta Godavari estuaries.High molecular weight terrestrial derived organic matter was more pronounced in the river dominated Gautami Godavari estuary during post southwest monsoon season.High molecular weight in situ produced organic matter was more in the wave dominated Visishta Godavari estuary during late northeast and early southwest monsoon seasons driven by anthropogenic or aquaculture inputs. This is first of its kind on the absorption characteristics of coloured dissolved organic matter (CDOM) with reference to the different geomorphological features of Godavari estuary. Seasonal variation in the molecular weight characteristics of CDOM were studied in the Gautami and Vasishta Godavari estuaries. High molecular weight terrestrial derived organic matter was more pronounced in the river dominated Gautami Godavari estuary during post southwest monsoon season. High molecular weight in situ produced organic matter was more in the wave dominated Visishta Godavari estuary during late northeast and early southwest monsoon seasons driven by anthropogenic or aquaculture inputs.
... In wave-dominated deltas, the deltaic plain is characterized by the presence of beach ridges, which mark the successive positions of the coastline during delta construction. The geometry of these beach ridges is indicative of past patterns of sediment dispersion, and their truncations testify to past episodes of severe erosion (Vella et al., 2005;Rey et al., 2009;Kakani et al., 2015;Preoteasa et al., 2016;Vespremeanu-Stroe et al., 2017). ...
The São Francisco River is the fourth longest river in South America and one of the most regulated. Severe coastal erosion has affected the delta shoreline since 1985, leading to the complete destruction of Cabeço village between 1997 and 1999. In this study, we mapped and radiocarbon dated the beach ridge sets occurring on the delta plain and performed a detailed analysis of the delta shoreline changes since 1960. During the Holocene, the delta plain construction was punctuated and took place during episodes of higher river discharges coincident with Bond events 4, 2 and 1 and periods of higher precipitation in the river basin, as reconstructed by δ¹⁸O measurements in cave speleothems. The last major episode of delta construction apparently ended at approximately 1.0 ka cal. BP. Since that time, riverine sediment input has been just sufficient to maintain the shoreline. A comparison of historical maps and aerial photographs showed that from 1853 to 1960, the shoreline at the river mouth remained in approximately the same position. A decrease in rainfall in combination with river regulation, particularly after 1985, triggered extensive erosion at the delta shoreline. This erosion was not caused by sediment retention behind the major dams but instead resulted from changes in the backwater/drawdown effects deriving from river regulation. Shoreline erosion mostly affected the river mouth. The mobilized sediments caused progradation of the downdrift shoreline. Updrift of the river mouth, the shoreline remained stable, as it had already reached an equilibrium orientation in which the net longshore transport was zero.
... GG was surrounded by extensive mangrove swamps, which were intermixed by thin beach ridges appears to be a river dominated estuary. In contrast, Vasishta, with the closely spaced beach ridge plains seems to reflect a more wave-dominated system 5 . Because of this contrasting geomorphic features and anthropogenic activities, significant difference in biogeochemical processes may be taking place in these estuaries. ...
... The first capture of this female was on 7 May 2014. The movement of C1 was With a huge catchment area of >300,000 km 2 , the Godavari River is the second longest river in India (Rao et al. 2015). An extensive stretch of riverine mangrove forests is formed at its mouth into the Bay of Bengal in the East Coast, making them as the second largest contiguous patch of mangroves in India. ...
Most of the wild cats tend towards temporal and spatial partitioning among each other to avoid encounters or competition for resources. However, little information is available on the fine-scale spatial and temporal interactions among fishing cats Prio- nailurus viverrinus in the wild. Herewith, we describe the spatial distribution pattern of fishing cat individuals within a population in order to understand their intra-speci- fic interactions based on our 4 years of camera trap observations in mangrove forests of Godavari delta, India. Further, we used kernel density estimation method to look for temporal overlap in diurnal activity patterns of individual fishing cats which indicated a potential temporal partitioning between closely occurring male individuals.
... As North China Plain is quite flat with maximum elevation< 50 m and ground inclination between 1/2000 and 1/ 10000 (Ye, 1989), minor river shifts in the fan apex area may lead to a butterfly effect, with the shift of the deltaic complex from the Bohai Sea to the Yellow Sea, and vice versa. A similar evolution has been documented for the Godavari River Fan-delta (Rao et al., 2015), and in part, for the Nile, Rhône and Ganges-Brahmaputra deltas (Stanley and Warne, 1993a;Allison et al., 2003;Fanget et al., 2014). ...
... References for shoreline change analysis Period covered in the literature This study Adra Jabaloy- Sánchez et al. (2010) 1956-2015Amazon - - 1984-2015Arno Bini et al. (2008; Besset et al. (2017) 1938-2015- Ayeyarwady Hedley et al. (2010) 19251974-2015Brazos Morton and Pieper (1975Paine et al. (2011) 1853-20012001-2015Burdekin - - 1974-2015Ceyhan-Seyhan Besset et al. (2017) 1984-2015- Chang Jiang Chu et al. (2013; Wang et al. (2017) 1974- Chao Phraya Uehara et al. (2010) 1969-20011996-2015Colorado (Mx) - - 1989-2015Colorado (Tx) Morton and Pieper (1975Paine et al. (2011) 18562005-2015Colville - - 1985-2015Congo - - 1989-2015Cunene - - 1984-2015Danube Vespremeanu-Stroe et al. (2017; Besset et al. (2017) 1978- Dneiper - - 1984Ebro Besset et al. (2017) 1985-2015- Fly - - 1989-2015Ganges-Brahmaputra Allison (1998) 1792-19841972-2015Godavari Malini and Nageswara Rao (2004; Nageswara Rao et al. (2010); Nageswara Rao et al. (2015) 1930-2012-2015Grijalva - - 1986-2015Guadalfeo Bergillos et al. (2016- Indus - - 1979-2015Krishna Anand Rao et al. (2006) 1920-2015Limpopo - - 1979-2015Mackenzie Salomon (2005; Hese and Overduin (2014) 1950-2013- Magdalena - - 1973-2015Magra - - 1984-2015Mahanadi Murali et al. (2009) 1972-20052005-2015Mangoky - - 1973-2015Medjerda Besset et al. (2017) 1972-2015- Mekong Anthony et al. (2015) 2003-20121972-2015Mississippi Morgan and Larimore (1957 - 1984-2015Orinoco - - 1986-2015Paraiba do Sol - - 1976-2015Parana - - 1995-2015Pearl - - 1986-2015Po Besset et al. (2017) 1975-2015- Red River Dien et al. (2003; Thanh et al. (2005);Thao (2008) 1930-2015Rhône Suanez and Provansal (1996 ) 1972-20041972-2015M. Besset, et al. Earth-Science Reviews 193 (2019 ...
The inception, growth, and decline of numerous large and small river deltas on Earth have been strongly influenced by human population dynamics and interventions on catchments, notably deforestation and reforestation. Over the last half century, the effects of catchment conditions in determining fluvial sediment supply have been exacerbated or moderated by dams and reservoirs. The sediment balance of river deltas, crucial in terms of delta shoreline stability, advance or retreat, and subsidence, has, in turn, been affected by variations in fluvial sediment supply. The shoreline mobility and resulting subaerial coastal area changes of a selection of 54 of the world’s deltas was quantified over 30 years based on data culled from the literature and from satellite images. These changes were analyzed alongside fluvial sediment loads. Delta shoreline mobility to changing fluvial loads has been variable, reflecting the miscellaneous factors that influence the supply of sediment to deltas. 29 deltas are in overall erosion, 18 show shoreline advance, whereas seven do not show any significant change. The sediment loads received by 42 deltas diminished relative to values prior to 1970, by more than 50% for 28 of them. Ten deltas showed advance, some significantly, notwithstanding fluvial sediment load decreases exceeding 25%. Overall, with the exception of the Colorado (Tx) and the Indus, losses in subaerial coastal area have been rather low. It would appear that diminishing fluvial sediment supply, the driving force in deltaic equilibrium at a multi-decadal timescale, has not, thus far, had a significant negative impact on multi-decadal delta shoreline mobility. This is important in terms of gauging currently perceived delta vulnerability. Notwithstanding, a clear link exists between the mobility of delta shorelines and the reduction in fluvial sediment loads. Eroding deltas have been affected by a reduction that is twice as important as that of stable or advancing deltas since 1970. Dams currently in place will reduce, in the future, the sediment load to their deltas of 25 of the 54 rivers by more than 50% and 100% for 15 of them. It is important to envisage the supply of sediment to deltas less in terms of its direct role in generating accretion, and eventual delta shoreline advance, and more in terms of an agent of resilience. The reduction of fluvial sediment supply to deltas will negatively impact their resilience to other drivers in the future: anthropogenic, climate change, and sea-level rise. The variability of delta shoreline behavior in the face of changing fluvial sediment loads also calls for more in-depth studies of individual deltas in order to build up future management plans addressing vulnerability and loss of resilience to marine forcing, subsidence, and sea-level rise.
... References for shoreline change analysis Period covered in the literature This study Adra Jabaloy- Sánchez et al. (2010) 1956-2015Amazon - - 1984-2015Arno Bini et al. (2008; Besset et al. (2017) 1938-2015- Ayeyarwady Hedley et al. (2010) 19251974-2015Brazos Morton and Pieper (1975Paine et al. (2011) 1853-20012001-2015Burdekin - - 1974-2015Ceyhan-Seyhan Besset et al. (2017) 1984-2015- Chang Jiang Chu et al. (2013; Wang et al. (2017) 1974- Chao Phraya Uehara et al. (2010) 1969-20011996-2015Colorado (Mx) - - 1989-2015Colorado (Tx) Morton and Pieper (1975Paine et al. (2011) 18562005-2015Colville - - 1985-2015Congo - - 1989-2015Cunene - - 1984-2015Danube Vespremeanu-Stroe et al. (2017; Besset et al. (2017) 1978- Dneiper - - 1984Ebro Besset et al. (2017) 1985-2015- Fly - - 1989-2015Ganges-Brahmaputra Allison (1998) 1792-19841972-2015Godavari Malini and Nageswara Rao (2004; Nageswara Rao et al. (2010); Nageswara Rao et al. (2015) 1930-2012-2015Grijalva - - 1986-2015Guadalfeo Bergillos et al. (2016- Indus - - 1979-2015Krishna Anand Rao et al. (2006) 1920-2015Limpopo - - 1979-2015Mackenzie Salomon (2005; Hese and Overduin (2014) 1950-2013- Magdalena - - 1973-2015Magra - - 1984-2015Mahanadi Murali et al. (2009) 1972-20052005-2015Mangoky - - 1973-2015Medjerda Besset et al. (2017) 1972-2015- Mekong Anthony et al. (2015) 2003-20121972-2015Mississippi Morgan and Larimore (1957 - 1984-2015Orinoco - - 1986-2015Paraiba do Sol - - 1976-2015Parana - - 1995-2015Pearl - - 1986-2015Po Besset et al. (2017) 1975-2015- Red River Dien et al. (2003; Thanh et al. (2005);Thao (2008) 1930-2015Rhône Suanez and Provansal (1996 ) 1972-20041972-2015M. Besset, et al. Earth-Science Reviews 193 (2019 ...
The inception, growth, and decline of numerous large and small river deltas on Earth have been strongly influenced by human population dynamics and interventions on catchments, notably deforestation and reforestation. Over the last half century, the effects of catchment conditions in determining fluvial sediment supply have been exacerbated or moderated by dams and reservoirs. The sediment balance of river deltas, crucial in terms of delta shoreline stability, advance or retreat, and subsidence, has, in turn, been affected by variations in fluvial sediment supply. The shoreline mobility and resulting subaerial coastal area changes of a selection of 54 of the world’s deltas was quantified over 30 years based on data culled from the literature and from satellite images. These changes were analyzed alongside fluvial sediment loads. Delta shoreline mobility to changing fluvial loads has been variable, reflecting the miscellaneous factors that influence the supply of sediment to deltas. 29 deltas are in overall erosion, 18 show shoreline advance, whereas seven do not show any significant change. The sediment loads received by 42 deltas diminished relative to values prior to 1970, by more than 50% for 28 of them. Ten deltas showed advance, some significantly, notwithstanding fluvial sediment load decreases exceeding 25%. Overall, with the exception of the Colorado (Tx) and the Indus, losses in subaerial coastal area have been rather low. It would appear that diminishing fluvial sediment supply, the driving force in deltaic equilibrium at a multi-decadal timescale, has not, thus far, had a significant negative impact on multi-decadal delta shoreline mobility. This is important in terms of gauging currently perceived delta vulnerability. Notwithstanding, a clear link exists between the mobility of delta shorelines and the reduction in fluvial sediment loads. Eroding deltas have been affected by a reduction that is twice as important as that of stable or advancing deltas since 1970. Dams currently in place will reduce, in the future, the sediment load to their deltas of 25 of the 54 rivers by more than 50% and 100% for 15 of them. It is important to envisage the supply of sediment to deltas less in terms of its direct role in generating accretion, and eventual delta shoreline advance, and more in terms of an agent of resilience. The reduction of fluvial sediment supply to deltas will negatively impact their resilience to other drivers in the future: anthropogenic, climate change, and sea-level rise. The variability of delta shoreline behavior in the face of changing fluvial sediment loads also calls for more in-depth studies of individual deltas in order to build up future management plans addressing vulnerability and loss of resilience to marine forcing, subsidence, and sea-level rise.
... Some aspects of the modern wave-dominated Godavari delta system differ from the Pliocene system, such as the impact of human activities in the drainage basin and on the delta plain and strandline (Chandramohan et al., 2001;Rao et al., 2015). Nevertheless, many characteristics of the system remain substantially unchanged. ...
Combined seismic images and core data from shallow gas-charged, deep-water sands in the western Bay of Bengal provide a detailed record of channel formation and evolution. The KG-D6 Block, western Bay of Bengal, includes two main Pliocene deep-water channel complex sets, termed the A and B complex sets, currently under gas production by Reliance Industries. These represent sinuous channels developed at the base of the delta slope off of the Godavari River and at the head of a long continental slope into the deep Bay of Bengal. The A complex set includes two main channel complexes, the older A150 and younger A100 channel complexes. The A complex provides an excellent opportunity to explore the geometry, sedimentation, and evolution of a small submarine channel system because of shallow reservoir depth, excellent 3D seismic coverage, availability of cores, and the nearly complete system-wide gas charge of the sandstones. Relict sea-floor topography and the processes of avulsion and splay development figure importantly in the overall evolution of slope channel systems. In the KG-D6 area, a sand-rich avulsion splay derived from an older channel complex became the template upon which the A channel complex set evolved. The component A150 and A100 channel complexes developed along a single sinuous course, with the channel complexes building through coupled channel erosion and coeval levee construction. The Godavari slope channels are not confined by scalloped valley walls and did not migrate laterally during their evolution. Mass transport deposits (MTDs) occur in all parts of the channel-fill section. The A100 channel complex displays a well-developed fining-upward cycle in most sections apparently not reflecting shifts in channel position or meander cuts offs, as inferred for some other deep-water channel systems, but rather through changes in the activity within the channels and through advances and retreats of frontal splays up and down the channel system. The Godavari data demonstrate the importance of avulsion and splay development in the evolution of deep-water sedimentary deposits, even high on passive margin slopes, which has implications for understanding the evolution of sinuous submarine channels and the development and distribution of hydrocarbon reservoir compartments.
... A reduction in freshwater discharge and sedimentation at river mouths was also reported as a response to to the weakening of the mid-Holocene Asian Summer Monsoon (ASM) after~6 cal. kyr BP (Zong et al., 2006;Zhan et al., 2012;Hu et al., 2013;Nageswara Rao et al., 2015). Sedimentary hiatuses have been observed in the post-glacial stratigraphic sequence of the Yangtze coast and many of these are believed to be generated by tidal current and storm wave erosion (Li and Zhang, 1996). ...
The Yangtze (Changjiang) mega-delta, China, has a high risk of coastal erosion owing to the recent high rate of relative sea-level rise and reduced sediment supply. The study of the Holocene evolution of the delta can provide information about its response to rapid sea-level rise and changes in sediment supply caused by climate or human activity, although this has yet to be fully explored because of the lack of integrated studies using age-constrained sedimentary records. Here we document stratigraphic architecture and morphological changes over the last 11,700 years and estimate the amount of sediment trapped in the delta region on a millennial scale using a dataset of 344 sediment cores, 658 radiocarbon and 28 optically stimulated luminescence (OSL) ages (of which we obtained 64 cores, 345 radiocarbon and 28 OSL ages, and the others we sourced from the literature). Using this dataset we present the temporal and spatial morphodynamic evolution of the entire Yangtze River mouth from its early Holocene transgressive estuary to a mid- to late-Holocene regressive delta, making it possible to produce a quantitative and sequential analysis of sediment deposition. A destructive phase of the river mouth region was identified at 10 to 8 cal. kyr BP, including significant coastal erosion of tidal flats and troughs within the estuary and of tidal ridge-and-trough topography offshore; these resulted from the reshaping of the river mouth morphology caused by rapid sea-level rise at that time. As a result, the rate of sediment trapping at the river mouth declined from an average of 224 Mt yr⁻¹ at 11.7–10 cal. kyr BP to 137 Mt yr⁻¹ between 10 and 8 cal. kyr BP. Since delta initiation 8000 years ago, a retreat of the subaqueous delta occurred and the sediment trapping rate declined from 151 Mt yr⁻¹ at 8–6 cal. kyr BP to 99–113 Mt yr⁻¹ between 6 and 2 cal. kyr BP, caused by the reduction in sediment supply linked to summer monsoon weakening ~6000 years ago. In the last 2000 years the sediment trapping rate has increased to 162 Mt yr⁻¹ due to intensified human activity. The present-day level of sedimentation in delta (49 Mt yr⁻¹ in 2003–2011), after the completion of the Three Gorges Dam, is far lower than the ‘natural’ range in the Holocene. We thus infer a potential for system regime shift in terms of coastal erosion and a transition to a new equilibrium in delta morphology in the near future.
... The Godavari River (1,465 km) is the second longest river in India (Rao et al. 2015), emptying into the Bay of Bengal in Andhra Pradesh. At its confluence with the sea there is an extensive area of mangrove forest, of which 235.7 km² is protected as the Coringa Wildlife Sanctuary (Ravishankar et al. 2004). ...
... Maximal rainfall is experienced during the southwest monsoon over India (annual rainfall is 1185 mm with 84 % falling during monsoonal months, June to September; Biksham and Subramanian, 1988;Pradhan et al., 2014). Approximately 98 % of the total suspended sediment load of the Godavari River is transported during the monsoon period (Rao et al., 2015). ...
Long-chain diols (LCDs) occur widespread in marine environments
and also in lakes and rivers. Transport of LCDs from rivers may impact the
distribution of LCDs in coastal environments, however relatively little is
known about the distribution and biological sources of LCDs in river systems.
In this study, we investigated the distribution of LCDs in suspended
particulate matter (SPM) of three river systems (Godavari, Danube, and Rhine)
in relation with precipitation, temperature, and source catchments. The
dominant long-chain diol is the C32 1,15-diol followed by the
C30 1,15-diol in all studied river systems. In regions influenced
by marine waters, such as delta systems, the fractional abundance of the
C30 1,15-diol is substantially higher than in the river itself,
suggesting different LCD producers in marine and freshwater environments. A
change in the LCD distribution along the downstream transects of the rivers
studied was not observed. However, an effect of river flow is observed; i.e.,
the concentration of the C32 1,15-diol is higher in stagnant
waters such as reservoirs and during seasons with river low stands. A
seasonal change in the LCD distribution was observed in the Rhine, likely due
to a change in the producers. Eukaryotic diversity analysis by 18S rRNA gene
sequencing of SPM from the Rhine showed extremely low abundances of sequences
(i.e., < 0.32 % of total reads) related to known algal LCD
producers. Furthermore, incubation of the river water with
13C-labeled bicarbonate did not result in 13C
incorporation into LCDs. This indicates that the LCDs present are mainly of
fossil origin in the fast-flowing part of the Rhine. Overall, our results
suggest that the LCD producers in rivers predominantly reside in lakes or
side ponds that are part of the river system.
... About 5-km of sediments with several depositional sequences ranges in age from Late Carboniferous to Pleistocene (Gupta, 2006) were deposited in the offshore portion of the Godavari Basin. The Godavari Delta along the east coast of India is one of the world's largest wave-dominated deltas fringed by a ∼30 km wide beach-ridge plain (Rao et al., 2012(Rao et al., , 2015. Sediment supplied from the Krishna-Godavari Basin by the Krishna and Godavari Rivers is trapped in either the delta or transported into the deep-marine environment. ...
The Indian National Gas Hydrate Program Expedition 02 (NGHP-02) was designed to study the occurrence of gas hydrate along the passive continental margin of the Indian Peninsula in the Bay of Bengal. Twelve holes were logged and measured with logging-while-drilling (LWD) and five holes were cored in Area-B of NGHP-02. The LWD and coring results in Area-B helped to understand the geological significance of sequence stratigraphy in Krishna-Godavari Basin and identified the occurrence of gas hydrate. This study summarized the log- and litho-units in Area-B and establish three integrated units based on the core-log-seismic integration. Most of the downhole log and core inferred gas hydrate occurrences are in the Late Miocene Integrated-Unit B with several sets of reservoir sections exhibiting favorable conditions for hosting gas hydrate. The gas hydrates reservoirs associated with reflectors R1 and R2 were identified and the R1 reservoirs are characterized by fracture- and pore-filling gas hydrate, and the R2 is in sand-rich sediments with pore-filling gas hydrate at high saturations. The thickness variations associated with the R1 and R2 are possibly associated with the development anticlinal structure and are likely related to syn-sedimentary growth of the folding structures. Major gas hydrate zones exist in and around the R1 and R2 near the BSR depth, and mostly have coincident with the fractures and mass-transport deposits. The spatial distribution of gas hydrate in the R1 and R2 reservoirs is highly influenced by the anticlinal structure. This study can be considered a good case for the future gas hydrate studies and explorations in the nearby areas.
... Thirty-seven surface sediment samples (5 £ 5 cm surface, and 2 cm depth) were collected with the use of a soil knife from all the mangrove communities: (i) Matlapalem (M): Avicennia marina-Excoecaria agallocha community; (ii) Ramannapalem (R): Rhizophoraceae-Lumnitzera racemosa community; (iii) Boddu Venkatapalem (B): Aegiceras corniculatum community; (iv) Chinnavalasala (CV): Lumnitzera racemosa community; and (v) Gadimoga (G): Rhizophora-Sonneratia community (Supplementary file 1). The surface samples span not more than 10 years, with no significant change in the plant communities and mangrove zonation pattern (Satyanarayana et al. 2002) except the loss in plant diversity due to a considerable decrease in sediment discharge caused by dam construction and water diversion since the 1970s (Nageshwara Rao et al. 2015). Five transects (M 1-4 , R 1-8 , B 1-10 , CV 1-6 and G 1-9 ) covering a 500-800 m path were traced through the mangrove communities. ...
Pollen in the surface sediment collected in a transect from sea to land in the Coringa mangrove wetland was analysed to determine the spatial and quantitative composition of the pollen record for palaeoecological interpretation. Autochthonous pollen preservation of the existing mangrove species was predominant in the sediments and serves as a potential indicator of coastal wetlands. The low quantity of allochthonous and parautochthonous pollen in the sediment reflects the regional plant community. Statistical analysis of the palynological data shows a high association between pollen from Avicennia marina and Clerodendrum inerme and their vegetation. Aegiceras corniculatum, Sonneratia, Ceriops decandra, Xylocarpus mekongenesis, Cocos nucifera, Azadirachta indica, Syzygium, Chenopodiaceae, Poaceae and Cyperaceae show overrepresentation. Ordination techniques for individual species using fidelity and dispersibility indices and regression analyses suggest four different floristic groups, of (i) high dispersibility-moderate fidelity taxa; (ii) high dispersibility-low fidelity taxa; (iii) moderate dispersibility-low fidelity taxa; and (iv) low dispersibility-high fidelity taxa. Species with high fidelity and moderate-low dispersibility indices could be used to identify the vegetation types in sedimentary sequences. The presence of discriminatory taxa (Avicennia marina, Sonneratia sp.), even in small quantities, helps in accurate identification of the local vegetation. Results indicate that while mangrove pollen is transported over short distances, non-mangrove pollen and spores are transported from longer distances. Thus, the status of mangrove and non-mangrove pollen in the sediments provides a clue to the (palaeo)coastal ecology and the (palaeo)climatic conditions.
Megafans are partial cones of river sediment that reach unexpectedly large dimensions, with the largest on Earth being 700 km long. Due to recent developments in space-based observations, global mapping efforts have shown that modern megafan features cover vast landscapes on most continents. This book provides a new inventory of nearly 300 megafans across five continents. Chapters focus on regional studies of megafans from all continents barring North America and Antarctica. The major morphological attributes of megafans and multi-megafan landscapes are discussed, and the principal controls on megafan development are examined. The book also compares megafans with alluvial fans, deltas, floodplains and the recently recognised 'major avulsive fluvial system' (MAFS). The final part of the book discusses the application of megafan research to economic geology, aquifers and planetary geology including layered deposits on Mars. This is an invaluable reference for researchers in geomorphology, sedimentology and physical geography.
The avulsion frequency of coastal‐plain rivers is primarily governed by the rate at which channels become superelevated over neighboring plains, which is itself controlled by multiple factors. Notably, the importance of wave and tidal processes, the rates of relative sea‐level (RSL) change, and the bathymetry of the receiving basin are thought to affect channel morphodynamics and channel‐mouth progradation, thereby controlling streambed aggradation and influencing the avulsion frequency and drainage density of coastal plains and deltas. This work tests the significance of these downstream factors on the avulsion histories of 57 Holocene lowland river systems. A quantitative analysis is performed of relationships between variables that quantify downstream controls and estimations of avulsion frequency, based on the number of avulsion events, active or abandoned channel paths, and delta lobes; measures of spatiotemporal avulsion “density” are also derived by normalizing these metrics by the size of study areas and the number of distinct drainage systems. Relationships between avulsion‐frequency metrics and descriptors of process regime indicate that wave and tidal processes may stabilize coastal channel systems, but also that their influence may be modest. No consistent relationship is seen between avulsion‐frequency proxies and the offshore bathymetric gradient, which in the studied examples does not scale with the rate of shoreline progradation. No evident trend exists between measures of avulsion frequency and estimated rates of either eustatic or RSL fluctuations. Overall, the considered variables do not leave a clear statistical signature in Holocene avulsion histories, suggesting that upstream or intrabasinal factors may represent more important controls.
The Tone River and the Arakawa River merged in the central part of the Kanto Plain in the early Edo period (17th Century) and flowed into Tokyo Bay. The current Tone River has moved its mainstream from the Kazo Lowland to the lower Kinugawa Lowland, and the current Arakawa River flows down through the Arakawa Lowland to the Tokyo Lowland. Based on the historical and prehistoric topographical changes in the Tokyo Lowland, the author considered the pre-modern channels and ages of the Tone and Arakawa rivers, using the microtopography of the plains as clues. In the Kazo and Nakagawa Lowlands, the former Tone River channel can be traced by the development of natural levees and riverine sand dunes. It is required, however, to elucidate where the Tone merged with the Watarase River and the origin of fragmentary former river channels. A large-scale meandering channel trace can be seen from the Arakawa Lowland to the Tokyo Lowland, but there is no record of the trunk river there in the historical era. From the composition of sediments and archaeological data, this can be considered as the trunk river of the Tone River, but it is necessary to clarify the relationship between its age, the river channel transition, and volcanic activity in the basin.
Fluvial and coastal landforms are indicative of landscape river delta evolution over time and provide clues for understanding coastal adjustments to sea-level and fluvial dynamics fluctuations, tectonic displacements, and extreme waves. We have mapped the surface and sub-surface footprints of fluvial and coastal geomorphological features in the Aceh River delta, northern Sumatra, using imagery dataset, vertical facies logging and helicopter electromagnetic surveys. The result is a geomorphological map at the scale of 1:75.000 which outlines the main features of the deltaic plain, including rivers, tidal and buried channels, fluvial levees, beach ridges, swales, tidal flats and lagoons. We compare their spatial distribution to the geometry of buried sediment bodies, revealed by boreholes and resistivity maps. Buried channel belts and floodplain deposits document the former locations of the distributary channels of the Aceh River. Coastal-parallel beach ridges evidence 7–8 km of asymmetric delta progradation since the mid-Holocene sea-level high stand.
The fish diversity of different estuarine habitats of the Gowthami-Godavari River was studied from 2014 to 2017. We recorded 231 species of finfishes belonging to 27 orders, 81 families, and 167 genera. Perciformes was the most speciose order, followed by Carangiformes and Clupeiformes. Of the 231 species, one is an Endangered species (Silonia childreni), three are Vulnerable (Tenualosa toli, Cirrhinus cirrhosis, and Wallago attu), three are Near Threatened, and 11 are Data Deficient species. We also recorded five exotic species from the study area, of which Oreochromis mossambicus was the most dominant. The major threats, including potential impacts of river regulation and climate change on the estuarine habitats of Gowthami-Godavari, are also discussed.
Beach‐ridge systems are geomorphological features common in every type of coast and have been widely interpreted as geo‐archives of past sea‐level, climatic, or tectonic changes. These relict morphological elements are well‐known by their facies, architecture, stratigraphy, and evolution. However, the coastal context where beach ridges are formed has never been evaluated. Coastal beach‐ridge systems were classified into four main types corresponding to deltaic strandplains, non‐deltaic strandplains, spits, and barrier islands. Our study consisted of three scales of analysis: (1) the entire beach‐ridge system; (2) beach‐ridge sets; and (3) individual beach ridges.
Several beach‐ridge systems having formed in different types of coastal settings are compared by their present characteristics. Geomorphic data generated from processing and interpreting satellite images combined with previous studies are used to quantify multi‐scale attributes of beach‐ridge systems. These attributes include the area, length, width, number of sets, number of ridges per set, set rotation, ridge spacing, and ridge elevation. Our findings demonstrate that significant differences define beach‐ridge systems including deltaic strandplains, large non‐deltaic strandplains, small non‐deltaic strandplains, large spits (cuspate forelands), small spits (flying spits, bay‐mouth spits and tombolos) and barrier islands. A more comprehensive characterization of the factors controlling beach‐ridge variability will improve our ability to recognize the sedimentary record of ancient of these systems. The proposed basic platform can be used to isolated different beach‐ridge types and systems to facilitate future process and morphodynamic studies.
Monsoonal rivers play an important role in the land-to-sea transport of soil-derived organic carbon (OC). However, spatial and temporal variation in the concentration, composition, and fate of OC in these rivers remains poorly understood. We investigate soil-to-sea transport of OC by the Godavari River in India using branched glycerol dialkyl glycerol tetraether (brGDGT) lipids in soils, river suspended particulate matter (SPM), riverbed sediments, and in a marine sediment core from the Bay of Bengal. The abundance and composition of brGDGTs in SPM and sediments in the Godavari River differs between the dry and wet season. In the dry season, 6-methyl brGDGTs dominate SPM and riverbed sediments in the whole basin. Currently, mobilisation and transport of soils from the upper basin is limited due to deficient rainfall and damming. This promotes aquatic brGDGT production in this part of the basin, which is reflected by a high relative abundance of 6-methyl brGDGTs in both seasons. In the wet season, brGDGT distributions in SPM from the lower basin closely resemble those in soils, mostly from the North and East Tributaries, corresponding to precipitation patterns. The brGDGT composition in SPM and sediments from the delta suggests that soil OC is only effectively transported to the Bay of Bengal in the wet season, when the river plume extends beyond the river mouth. The sediment geochemistry indicates that also the mineral particles exported by the Godavari River primarily originate from the lower basin, similar to the brGDGTs. River depth profiles of brGDGTs in the downstream Godavari reveal no hydrodynamic sorting effect in either season, indicating that brGDGTs are not associated with certain minerals. The similarity of brGDGT distributions in bulk and fine-grained sediments (≤63 μm) further confirms the absence of selective transport mechanisms. Nevertheless, the composition of brGDGTs in a Holocene, marine sediment core near the river mouth appears substantially different from that in the modern Godavari basin, suggesting that terrestrial-derived brGDGTs are rapidly lost upon discharge into the Bay of Bengal and/or overprinted by marine in situ production. The change in brGDGT distributions at the river-sea transition implies that this zone is key in the effective transfer of soil OC, as well as for the interpretation of paleorecords based on brGDGTs in coastal marine sediment archives.
Quantification of the frequency with which coastal-plain rivers avulse is important for elucidating autogenic dynamics and their role as controls on landscape change and stratigraphic architectures. An outstanding question exists, however, as to whether measures of avulsion frequency are inherently affected by the spatial and temporal scales at which they are evaluated, which has implications regarding our ability to make direct comparisons between different river systems or deltas. To address this problem, a quantitative analysis of the avulsion histories of 57 coastal-plain river systems is undertaken. Nine alternative measures of avulsion frequency are extracted. These are based on numbers of (i) avulsion events, (ii) active or abandoned channel courses, and (iii) delta lobes, all considered per unit time. Additional sets of avulsion-frequency proxies are established based on normalization of these numbers relative to the size of the area being studied, and to the number of distinct river systems that drain into that area. The sensitivity of these quantities to the spatial and temporal extent of study areas and time intervals, and their relationships with quantities describing the scale of the river systems, are assessed. All avulsion-frequency estimates demonstrate apparent negative relationships with the timespan over which they are determined; this may reflect global Holocene trends, or variations in resolution with the time window. Avulsion metrics that are not normalized by the planform extent of the study area do not show proportionality with the size of the study areas themselves, nor with the scale of the river systems; correspondingly, the spatio-temporal density of avulsion events tends to be higher for smaller rivers and associated study areas. This may be due to systematic variations in data resolution, to the influence of external controls that relate to the scale of deltas, or to inherent non-stationarity in the avulsion dynamics of lowland rivers, in association with forms of self-organization that do not vary with scale. Although non-normalized avulsion-frequency estimates do not scale with measures of river-system size, they are seen to correlate with progradation rates, which are themselves scaled to sediment discharge and catchment size. Practical considerations can be drawn on how avulsion frequency may be appropriately quantified to enable meaningful comparisons of the autogenic dynamics of coastal-plain rivers.
Radiocarbon dates and luminescence ages of Holocene alluvial and flood deposits from over three dozen sites indicate that the variations in the monsoon strength have primarily dictated the fluvial activity in the Indian Peninsula. Although there are some intraregional differences and large geographical gaps with no chronological data, the available records indicate that the region-wide phase of river incision and excavation in the early Holocene was driven by stronger monsoon and higher discharges. Principal rivers show evidence of a minor, but region-wide phase of aggradation coinciding with the mid-Holocene weakening of the monsoon. These deposits occur as inset terraces. In the last 3–4 millennia, intermittent deposition, superimposed on a slow, steady incision has dominated the fluvial regimes. Paleoflood records indicate clustering of large floods during the Medieval Climate Anomaly, around the onset and end of the Little Ice Age as well as the Current Warm Period.
This paper describes the geotechnical site characterisation of a project in deep water offshore eastern India. It presents the key results and findings of a recent offshore geotechnical site investigation and subsequent comprehensive onshore laboratory testing and interpretation. The interpretation was carried out using a consistent framework leveraging site-wide data to characterise the undrained shear strength, shearing rate effect and the cyclic and seismic behaviours of the range of materials found across the site. Based on this efficient and holistic approach for characterising the strain rate, cyclic and seismic soil behaviours, a shear strength model, a rate effects model and a generalised cyclic strength degradation model and design seismic parameters were developed for the site. Some of these key results are presented and discussed along with comparisons to selected clays in the literature.
The Holocene evolution of the Krishna Delta was inferred using landform characteristics and 11 sediment cores with 59 Accelerator Mass Spectrometry ¹⁴C dates. The landform assemblages in a 5880 km² area of the Krishna Delta indicate an upper (landward) river-built fluvial plain and a lower (seaward) marine-built beach-ridge plain. Holocene sediment unconformably overlying a Pleistocene basement consists of 11 sedimentary facies, mainly shallowing-upward and deltaic succession. Sea level indicators such as the basal mangrove peat layers above the Pleistocene basement and the foreshore sediments indicate that the sea level rose from −9 m to −3 m during 8.3–6.3 cal ky BP, and stabilised at the present level around 5 cal ky BP. The 3539 km² area of the Krishna Delta beach-ridge plain developed in five major stages during the last 6 cal ky, with distinct lateral and seaward migration of delta lobes (depocentre shifts). Delta progradation accelerated in the last 500 years, forming an out-building lobate delta. However, predominant erosion along the sediment-starved coast during the past five decades, due to impoundment of riverine inputs at the burgeoning upstream dams, has pushed the Krishna Delta into a persistent destruction phase.
This work is presented as Chapter 7 in an edited book on Coastal Zone Management published by Elsevier. This chapter brought out the decadal scale changes that occurred along parts of east and west coasts of India based on an analysis of series of satellite remote sensing data. The impact of global, regional, and local scale causes and the coastal responses are discussed with case studies from different coastal sectors of India.
Recent acceleration of sand extraction for anthropic use threatens the sustainability of this major resource. However, continental erosion and river transport, which produce sand and sediment in general, lack quantification at the global scale. Here, we develop a new geodetic method to infer the sediment discharge to ocean of the world's largest rivers. It combines the spatial distribution of modern sedimentation zones with new high-resolution (~170 km) data from the Gravity Recovery and Climate Experiment (GRACE) mission launched in 2002. We obtain sediment discharges consistent with in situ measurements for the Amazon, Ganges-Brahmaputra, Changjiang, Indus, and Magdalena rivers. This new approach enables to quantitatively monitor the contemporary erosion of continental basins drained by rivers with large sediment discharges and paves the way toward a better understanding of how natural and anthropic changes influence landscape dynamics.
This paper is an attempt to understand the role of coastal topography in the impact of the tsunami. Field surveys using a palmtop computer-based mobile GIS-GPS integrated system were conducted
to map the tsunami inundation limits, zones of erosion and deposition at two selected locations namely Manginapudi in the Krishna delta and Chinamailavani Lanka in Godavari delta where
many persons were killed by the tsunami on 26 December 2004. Topographic profiles were obtained along four transects each at these two coastal sectors showing the nature of gradients, erosion and deposition limits, besides estimating the elevations of the tsunami run-up at the inundation limits. A maximum inundation distance of 830 m is associated with the minimum run-up elevation of 1.27 m above sea level, whereas the minimum inundation distance of 340 m is observed where the run-up elevation is a maximum of 2.52 m. A simple plot of inundation distances vs. the run-up elevations from both the locations showed an inverse relationship indicating the role of topography in tsunami impact. Further, based on the area and depth of erosion and thickness of deposition, it is found that the volume of sediment lost due to erosion is more than volume of sediment deposited by the tsunami indicating perhaps the return flow of the tsunami was stronger due to the steeper gradients
of the foreshore zones at these locations again highlighting the role of coastal topography in tsunami impact.
Indian Summer Monsoon (ISM) shows a weak correlation with solar variability in the 20th century. However, such climatological observations on solar activity-monsoon relationship are very short and hence uncertain. A few paleomonsoon records also exhibit prominent correspondence with solar activity during early Holocene and beyond. But despite the strong recent solar minima (e.g. Maunder, Spörer, Oort, Wolf), their correlation with monsoon precipitation is weak and inconclusive. Additionally, many of the earlier studies have been from the western Arabian Sea that provides records of the ISM wind intensity instead of the ISM precipitation. We present here mid-Holocene to recent sea surface temperature (SST) reconstructed from Mg/Ca measurements of planktic foraminifera (Globigerinoides ruber; white, sensu stricto) on a centennial-scale resolution from the southeastern Arabian. These measurements are used to correct the oxygen isotope ratios of G. ruber to reconstruct salinity related to monsoon runoff in this region more precisely than hitherto. The long-term trend indicates that the ISM precipitation has declined since the mid-Holocene similar to the solar activity. On shorter multi-centennial timescale, we show that the ISM precipitation declined concurrently with the recent periods of strong solar minima, but lagged by a couple of hundred years beyond 1300 yr BP toward the mid-Holocene - confirmed statistically using wavelet analysis. This nonstationary phase relationship between the ISM and the solar activity indicates the possible influence of the tropical coupled ocean-atmosphere phenomenon.
Sea-level rise and river engineering spell disaster, say Liviu Giosan and colleagues.
A new sea-level record derived from coastal deposits of the South Vietnam shelf covers the deglacial sea-level history between 13.0 and 9.0 ka BP. This record reveals a relatively constant rate of sea-level rise and matches well with model results based on the RSES-ANU global ice-sheet model. However, the sea-level observations reveal a significant discrepancy with model results based on the ICE-5G global ice-sheet model, which further questions the existence of Meltwater Pulse 1B The incised-valley deposits of the South Vietnam shelf also complete the deglacial coastal evolution of southern Vietnam. The regional sea-level records of the South Vietnam shelf, the Mekong Delta and the Cambodian lowlands reveal an offset of about 18m between 9.0 and 8.2 ka BP. The shoreline retreat of more than 200 km related to this offset was mainly caused by the differential hydro-isostatic adjustment between the South Vietnam shelf and the Cambodian lowlands. However, the GIAmodel results cannot fully explain this fast relative sea-level rise due to the topographic changes and, possibly, alternative melt-water sources not accounted for in the current models
Climate change has been suggested as a possible cause for the decline of urban centers of the Indus Civilization similar to 4000 yr ago, but extant paleoclimatic evidence has been derived from locations well outside the distribution of Indus settlements. Here we report an oxygen isotope record of gastropod aragonite (PO.) from Holocene sediments of paleolake Kotla Dahar (Haryana, India), which is adjacent to Indus settlements and documents Indian summer monsoon (ISM) variability for the past 6.5 k.y. A4% increase in delta O-18(a) occurred at ca. 4.1 ka marking a peak in the evaporation/precipitation ratio in the lake catchment related to weakening of the ISM. Although dating uncertainty exists in both climate and archaeological records, the drought event 4.1 ka on the northwestern Indian plains is within the radiocarbon age range for the beginning of Indus de-urbanization, suggesting that climate may have played a role in the Indus cultural transformation.
Many of the world’s largest deltas are densely populated and heavily farmed. Yet many of their inhabitants are becoming increasingly vulnerable to flooding and conversions of their land to open ocean. The vulnerability is a result of sediment compaction from the removal of oil, gas and water from the delta’s underlying sediments, the trapping of sediment in reservoirs upstream and floodplain engineering in combination with rising global sea level. Here we present an assessment of 33 deltas chosen to represent the world’s deltas. We find that in the past decade, 85% of the deltas experienced severe flooding, resulting in the temporary submergence of 260,000 km2. We conservatively estimate that the delta surface area vulnerable to flooding could increase by 50% under the current projected values for sea-level rise in the twenty-first century. This figure could increase if the capture of sediment upstream persists and continues to prevent the growth and buffering of the deltas.
We used AMS 14C dated sediments of the Holocene basal supratidal flat to upper tidal flat facies in 11 cores on the southern Yangtze delta plain to reconstruct relative sea levels of 8.5–8.0 cal ka BP. Three cores were further AMS 14C dated and used to examine the evolution of sedimentary geomorphologic environments in response to the rapid sea-level rise during the early- to mid-Holocene. Results demonstrate relative sea-level rise of around 30 mm a–1 from 8.5 to 8.3 cal ka BP and around 10 mm a–1 from 8.3 to 8.0 cal ka BP. Retrogradation from supratidal to lower tidal flat environments occurred in response to the rapid sea-level rise at 8.5–8.3 cal ka BP, and aggradation from middle to upper tidal flat occurred at 8.3–7.9 cal ka BP. Further retreat of the tidal flat at 7.9–7.2 cal ka BP implies a mean sea-level rise rate exceeding 5 mm a–1 at this time. We suggest that the rapid relative sea-level rise during 8.3–8.5 cal ka BP and subsequent slower rise caused drastic changes in the coastal zone and that these changes are key phenomena for understanding the coastal response to the future sea-level rise.
Whether eustatic sea-level rise through the Holocene has been punctuated or continuous has remained controversial for almost two decades. Resolving this debate has implications for predicting future responses of remaining ice sheets to climate change and also for understanding the drivers of human settlement and dispersal patterns through prehistory. Here we present a sea-level curve for the past 8900 yr from Singapore, a tectonically stable location remote from ice-loading effects. We also present critical and unique sedimentation rate, organic delta C-13, and foraminiferal delta C-13 proxy records of sea-level change derived from a shallow-marine sediment core from the same area over the same time interval. The sea-level curve, corroborated by the independent proxy records, suggests rapid rise at a rate of 1.8 m/100 yr until 8100 cal (calibrated) yr B.P., a near cessation in the rate of sea-level rise between 7800 and 7400 cal yr B.P., followed by a renewed rise of 4-5 m that was complete by 6500 cal yr B.P. We suggest that this period of relatively stable sea level during the early to mid-Holocene enabled modern deltas to advance, providing a highly productive environment for the establishment of coastal sedentary agriculture. Periods of rapid sea-level rise before and after may have catalyzed significant postglacial episodes of human dispersal in coastal regions.
New radiocarbon and optical dates show that the Holocene Danube delta started to build out of a Black Sea embayment ˜5200 yr ago. Delta lobe development phases differ by as much as 5 k.y. from previously proposed ages. The new chronology allows for a better understanding of the Danube delta paleogeography, including the demise of Istria, the main ancient Greek-Roman city in the region. Prior reconstructions of sea level in the Black Sea inferred fluctuations to 15 m in range; however, stratigraphy of beach ridges in the delta shows that the relative Black Sea level for the past 5 k.y. was stable in the Danube delta region within -2 m and +1.5 of the current level. Hydroisostatic effects related to a proposed catastrophic reconnection of the Black Sea to the World Ocean in the early Holocene may have been responsible for the sea level reaching the highstand earlier than estimated by models. The new sea-level data suggest that submergence at several ancient settlements around the Black Sea may be better explained by local factors such as subsidence rather than by basin-wide sea-level fluctuations.
Analysis of data from 280 rivers discharging to the ocean indicates that sediment loads/yields are a log-linear function of basin area and maximum elevation of the river basin. Other factors controlling sediment discharge (e.g., climate, runoff) appear to have secondary importance. A notable exception is the influence of human activity, climate, and geology on the rivers draining southern Asia and Oceania. Sediment fluxes from small mountainous rivers, many of which discharge directly onto active margins (e.g., western South and North America and most high-standing oceanic islands), have been greatly underestimated in previous global sediment budgets, perhaps by as much as a factor of three. In contrast, sediment fluxes to the ocean from large rivers (nearly all of which discharge onto passive margins or marginal seas) have been overestimated, as some of the sediment load is subaerially sequestered in subsiding deltas. Before the proliferation of dam construction in the latter half of this century, riv
The Mekong River Delta in southern Vietnam is a typical mixed tide-and wave-dominated delta with a wide delta plain formed during the last 6 to 8 ky. The late Pleistocene–Holocene sequence in this region since the last sea-level lowstand is composed of an incised-valley fill, comprising late Pleistocene to early Holocene fluvial to estuarine sediments, and Holocene deltaic sediments. The deltaic sediments are composed of early Holocene aggradational sediments and progradational sediments of middle to late Holocene age. The progradational delta has evolved from a tide-dominated delta to the present mixed wave-and tide-dominated delta during the last 3 ky and shows a sudden regime shift of coastal environment. The tide-dominated delta was characterized by a well-developed mangrove forest on the subaerial delta plain, cross-shore sediment dispersal, and tide-influenced sedimentary facies. The tide-and wave-dominated delta exhibits a beach-ridge system in the subaerial delta plain, longshore sediment dispersal, and a steep delta-front topography, in which the sediments of the proximal river-mouth area are coarse-grained and those more distal are fine-grained. As river-mouth coastal systems evolve from estuaries to deltas in response to sea-level changes, the formation of a tide-dominated delta marks the initiation of the highstand systems tract.
discoveries that showed that abrupt climate change is possible and for engaging his stu-dents, policy makers, and the public. Joan Kleypas, a marine ecologist and geologist at the National Atmospheric and Oceanic Administration's National Center for Atmo-spheric Research, was honored for conduct-ing seminal research on how changes in tem-perature and in sea water chemistry and acid-ity have affected coral reefs and for identify-ing ways to bolster coral reef health. Nancy Rabalais, executive director of the Louisiana Universities Marine Consortium, in Chauvin, was cited for her pioneering research of severe oxygen depletion in the Gulf of Mexico and her commitment to reducing water pol-lution through education and public policy. The awards program "recognizes individuals creating and implementing workable solu-tions to the problems the world faces through invention, research, and education while inspiring the next generation of modern thinkers," according to the foundation. Each recipient receives an unrestricted cash prize of $100,000.
Recent sediments in river deltas are subject to subsidence as revealed in number of studies from different deltas. The present study is a first-ever attempt to estimate the rates of subsidence in the Holocene sediments of the Godavari delta along the east coast of India. Two boreholes dug at Panangipalli village in the delta revealed Megalithic culture material such as potsherds including Coarse Red ware, Red-Slipped ware, Coarse Grey ware, and Black and Red ware, besides a glass bead, an otolith, and a few animal bones between 3.5m to 9.5m below the surface level indicating that the location was a human settlement of Andhra Satavahana period bracketed into 3rd century BC - 3rd century AD. The fossil shells of Anadara sp. recovered from the borehole further downward at 11.5 m below the surface are considered to represent the intertidal swampy/ lagoonal environment. The age of the shells was determined through 14C AMS as 6400 cal yr BP. The presence of intertidal swampy / lagoonal material at 11.5m depth, which is 7.5 m below the present sea level (after accounting for the surface elevation of the site at 4 m above the sea level), suggests post-depositional subsidence at an average rate of ~1.1mm/year. The occurrence of the Megalithic culture remains between 3.5 m and 9.5m below the general ground level also suggests burial of a historical human settlement by subsequent sedimentation and land subsidence in this part of the Godavari delta.
Petrographic modal analysis of the medium sand fraction (0.35 to 0.50 mm in diameter) of 274 samples principally from the shore zone of Lake Tahoe indicates that source-rock composition and mechanical-energy level at the depositional site explain approximately 46 and 32 percent of the total sample variance, respectively. A strong mechanical-energy signal may persist within a restricted grain-size interval. Q-mode factor analysis and stepwise discriminant function analysis were used to define six petrofacies, which reflect source-rock composition and relative mechanical-energy levels. Mean values for total quartz, total feldspar, and total rock fragments for petrofacies 1, 2, 3, 4, and 6 fall in the lithic arkose field of McBride (1963), whereas the mean for petrofacies 5 falls in the feldspathic litharenite field. The areal distribution of these six petrofacies may be used to identify nine shore-zone divisions, one of which is due to a major beach-nourishment project completed near Tahoe City in the early 1900s. Given the 1-km sampling interval employed, the areal positions of seven of the nine divisional boundaries showed no change from September 1978 to October 1988. This compositional stability reflects the consistency of the upland drainage systems and that of the wind-derived current systems operative in Lake Tahoe. The importance of source-rock composition, relative mechanical-energy level, and the apparent temporal consistency of the areal distribution of the shore-zone petrofacies should prove useful in constraining interpretations of older siliciclastic shoreline deposits associated with large lakes.
Interpretation of landforms through high-resolution satellite imagery, supported by accelerator mass spectrometry 14C dating of fossil shells recovered from the subsurface sediments, has indicated that the strandplain of the Godavari delta has evolved through three major stages of progradation. After the slow development of parallel to subparallel beach ridge/swale complexes during Stage I in a wave-dominated environment, a series of cuspate delta lobes with convergent beach ridges at the distributary mouths (both past and present) developed under conditions of increased fluvial energy during stages II and III. A part of sandy beach ridge complexes belonging to Stage II was formed around 2 ka. On the other hand, during Stage III, beginning around 1 ka, the strandplain experienced rapid growth of beach ridge complexes due to increase in sediment supply.
Facies reconstruction and reservoir modeling of ancient deltas entail possibilities of over-, or under-estimation of reservoir distribution and quality, since such studies are often based on drill-hole data from a few locations, which could be potentially unrepresentative of the subsurface conditions. Recent studies indicate significant asymmetries in sedimentation on both sides of the river mouths in the wave-influenced systems. The present study is an attempt to analyse the asymmetry in the depositional processes and its implications to the possible reservoir heterogeneity of the Godavari delta.
The Godavari delta on the east coast of India exhibits wave-influenced morphologies by the presence of a number of spits and barrier islands at its two active distributary lobes of the Gautami and the Vasishta. The most prominent of them is the 21-km-long Kakinada spit, which in its initial stages in the late nineteenth century had even deflected the Gautami course. As a result, the Gautami has built an extensive bayhead delta behind the spit. The 1965 satellite imagery showed several other smaller spits, especially at the southwestern side of the Gautami mouth and the northeastern side of the Vasishta, whereas barrier islands that are welded to the main coast by the backbarrier mudflats occur on the other sides of the mouths.
A comparison of a series of satellite imagery showed that the 15-km-long shoreline in the central part of the delta in between the Gautami and the Vasishta lobes retreated landward by about 500 m during the past four decades. The material eroded from this part, presumably, drifted in both the directions – northeastward toward the Gautami and southwestward toward the Vasishta. As the river effluent plumes act like groynes, the material drifted alongshore from the central part toward both the lobes is deposited at the respective updrift sides of the distributary mouths forming into spits, whereas the river-borne sediments are deposited at the downdrift sides, initially as bars that emerge as barrier islands, followed by the backbarrier-bay-filling with riverine muds. The presence of closely spaced beach ridges on the updrift side, and wide mudflats interspersed with narrow sand bodies on the downdrift side, that especially characterize the Vasishta lobe, indicate asymmetry of the sedimentation processes and facies architecture. The likely occurrence of better quality reservoir facies on the updrift side than on the downdrift side, besides the presumable shore-parallel than shore-normal prodelta clinoforms of the bayhead delta in the Kakinada Bay reflect the possible reservoir heterogeneity in the Godavari sedimentary basin, considering that similar asymmetries possibly prevailed in the geological past.
A high-resolution pollen record from 2 boreholes from the Changjiang (Yangtze River) delta shows a series of well-defined changes in vegetation and climate over the last 13, 000 yr. In latest Pleistocene to early Holocene time (12,900-10, 300 cal yr BP), pollen dominated by the xerophytic herb Artemisia and common conifers indicate coniferous forest and grasslands and a cool, dry climates, possibly represented by the Younger Dryas. From 10,300 to 9000 cal yr BP, a warm, wet climate fostered the development of mixed broadleaved evergreen-deciduous forests to grow on the grasslands and surrounding hills and uplands. From 9000 to 7600 cal yr BP, the dominance of conifers and the reduction in broadleaved evergreen trees pollen suggest cool, dry conditions. The mid-Holocene hypsithermal (7600-4800 cal yr BP) is represented by a large expansion of subtropical evergreen-deciduous broadleaved forests. Between 4800 and 1300 cal yr BP, which corresponds to a Neoglacial period elsewhere, conifers are dominant,
The Song Hong (Red River) delta, located on the western coast of the Gulf of Bac Bo (Tonkin) in the South China Sea, formed as a result of the Song Hong sediment discharge throughout the Holocene. The river's sedimentary basin upstream from the delta plain is not large. The delta plain comprises emerged tidal/mangrove flats formed during the sea-level highstand at + 2–3 m (6–4 cal. kyr BP) and a beach-ridge strandplain, with straight-to-lobate beach ridges, on the landward and seaward sides of the delta plain, respectively. The delta affords us the opportunity to examine river-mouth morphodynamics comprehensively in relation to sediment discharge and sea-level changes. In this paper, we describe the Holocene evolution of the Song Hong delta system and the river-mouth morphodynamics on the basis of seven sediment cores, each 30–70 m long, taken from the delta plain during 1999–2001 and 101 radiocarbon dates obtained from the core sediments.
The paleo-Changjiang (Yangtze) incised-valley fills, approximately 80-90 m thick, provide an opportunity to document the evolution of coastal depositional systems with large sediment supply in response to late Pleistocene-Holocene sea-level fluctuations on time scales of 10(3) to 10(4) years. The sedimentary facies of the incised-valley fills record three main depositional systems: fluvial, tide-dominated estuary, and tide-dominated delta. Radiocarbon ages for the incised-valley fills suggest that these depositional systems developed before about 11 ka, between 11 and 8 ka, and after approximately 8 ka, respectively. By applying sequence-stratigraphic concepts, the evolution of the depositional systems can be divided into three systems tracts-a lowstand systems tract (LST), a transgressive systems tract (TST), and a high-stand systems tract (HST). Sea-level changes on a 10(4)-year time scale controlled the basic architecture of the sequence of the incised-valley fill. On the other hand, sea-level chang
To clarify Holocene development of the Huanghe (Yellow River) delta and the relationship between delta progradation and chenier formation, detailed sediment analyses and high-resolution radiocarbon dating were done on borehole samples taken from two sites on the present Huanghe; H9601 (Latitude 37 degrees 40.5'N and Longitude 118 degrees 28.7'E with an altitude of + 5.5 m) and H9602 (Lat. 37 degrees 47.8'N and Long. 118 degrees 54.3'E, + 4.8 m). Downcore changes of sediment facies and accumulation rate show that delta progradation occurred at least twice during ca 2.6-1.2 C-14 yrBP and 1855-present at the two borehole sites. These phases of progradation correlate with Superlobes 6 and 7 and Superlobe 10 respectively, of ten superlobes composing the Holocene Huanghe Delta shown by C. Xue (Historical changes in the Yellow River delta, China, Marine Geology 113, 321-329, 1993). The boundary of these sediments at H9602 is sharp and erosional, and correlates with cheniers located between borehole sites on the delta plain. The diastem period between these phases of progradation almost coincides with the periods when the river mouth of the Huanghe was located in the northwestern part of the Bohai Sea during 1048-1128 AD (Superlobe 8), and the jiangsu region facing the Yellow Sea during 1128-1855 (Superlobe 9). This suggests that chenier formation and delta progradation are linked, and controlled by sediment supply and river course shifts of the lower reaches of the Huanghe. (C) 2000 Elsevier Science Ltd. All rights reserved.
This delta covers an area of 5500 km² with a maximum width of 70km and a delta front of 150km. Aerial photographs covering the entire region (scale 1:60 000) and Landsat imageries (Band 7) have been studied with to delineate any different geomorphic forms and structural features. Among the important features recognised are the ancient channels in a number of meander belts, ancient beach ridges, fractures, lineaments and morphostructures. About 4 major strandlines, each of which is considered to be represented by a set of parallel to sub-parallel ancient beach ridges, and about 14 abandoned distributary channels constitute the major landforms in the delta. -from English summary
This second edition bridges the gap between process-related out-crop studies of sedimentary rocks and the three-dimensional subsurface world of the mineral fuel geologist and hydrogeologist. It remains unique in its focus on the application of subsurface facies analysis to problems of petroleum, coal, uranium, and ground water resource discovery, delineation, and production. New chapters summarize applications of sequence stratigraphy to facies analysis and the use of detailed facies interpretation in reservoir and aquifer characterization.