Ridge System Research Articles

Waterlogging and coastal salinity management through land shaping and cropping intensification in climatically vulnerable Indian Sundarbans

Sundarbans in West Bengal, India located in the eastern coast of the Bay of Bengal is one of the vulnerable zones subjected to abrupt climate change. The region receives 2.7 times surplus rainfall as compared to crop evapotranspiration during monsoon months causing widespread waterlogging of the low lying agricultural fields and impedes the productivity. The present study assessed the effects of different land shaping models namely, farm pond (FP), deep furrow and high ridge (RF) and paddy cum fish (PCF) systems for rainwater harvesting in restoring the productivity of degraded coastal soils in Sundarbans. A water balance was run to estimate the soil moisture, crop evapotranspiration, runoff and water depth in the reservoir during normal, excess and deficit rainfall years. The average annual harvested runoff was 2709, 1650 and 1169 m3 per hectare in FP, RF and PCF systems, respectively. The runoff going out of the system was 19.5, 29.1 and 27.75% of the annual rainfall in FP, RF and PCF systems, respectively, whereas in monocrop rice-fallow system it was 34.6% of the annual rainfall. We estimated all the three components of water footprints (WF) i.e., blue WF (WFblue), green WF (WFgreen) and gray WF (WFgray) as an aggregative indicator to evaluate environmental impact. The results indicated that total as well as the components of WF was higher in rice-fallow and rice-rice systems than in each of the land shaping system. Large scale adoption of different land shaping systems increased the cropping intensity and net farm income and there was reduction in salinity during summer and waterlogging during rainy season and overall improvement in soil quality. The dominant soluble salts identified in the study region were NaCl and MgSO4.

Revisiting theLepetodrilus elevatusspecies complex (Vetigastropoda: Lepetodrilidae), using samples from the Galápagos and Guaymas hydrothermal vent systems

The current distribution ranges of vent species result from the complex tectonic history of oceanic ridges. A growing number of DNA barcode studies report the presence of cryptic species across geological discontinuities that offset ridge systems and have gradually helped to draw a more precise picture of the historical migration pathways of vent fauna. We reexamined the phylogeny of species within the Lepetodrilus elevatus complex along the East Pacific Rise (EPR) ridge system in the light of new samples from the Galapagos Rift and the Guaymas Basin. Our analyses of mitochondrial cytochrome c oxidase subunit I gene sequences, coupled with morphological data, highlight the occurrence of a distinct lineage along the Galapagos Rift and offer new insight into the current distribution range of this species complex. Due to the absence of clear morphological diagnostic criteria and the potential overlap of these lineages at key locations, we recommend reassigning the taxon L. galriftensis to the subspecies level and maintaining the name L. elevatus for all clades along the EPR/Galapagos Rift system.

Upper Crustal Vp/Vs Ratios at the Endeavour Segment, Juan de Fuca Ridge, From Joint Inversion of P and S Traveltimes: Implications for Hydrothermal Circulation

AbstractThe Endeavour segment of the Juan de Fuca Ridge is one of the most active and long‐lived hydrothermal areas of the mid‐ocean ridge system. However, the permeability structure that gives rise to long‐term venting at well‐established fields, such as the High Rise, Main Endeavour, and Mothra fields, is not fully understood. Here we jointly invert Pg and Sg traveltimes from a seismic refraction experiment conducted at the Endeavour segment using P‐to‐S coupling constraints. We then calculate porosity and crack density as a function of crack aspect ratio by applying the differential effective medium theory to the seismic velocities. At 1.4‐km depth, average Vp ~5 km off axis increases by ~0.4 km/s compared to the ridge axis. The average Vp/Vs has a minimum of ~1.75 on the ridge axis and increases to a maximum of ~1.84 off axis. The inferred porosity and crack density distributions show that the proportion of thick versus thin cracks decreases from the ridge axis to the flanks, since theoretical models indicate that Vp/Vs increases going from thick to thin cracks (aspect ratio decreasing from 0.1 to 0.01). The dominant presence of thick cracks on the axis may provide long‐term conduits for upflow in high‐temperature hydrothermal circulation potentially forming the vent fields. The increased proportion of thin cracks on the flanks, coupled with the increased seismic velocity, indicates a decrease in permeability caused by progressive clogging of thick cracks due to mineral precipitation likely in the downflow zone of hydrothermal circulation.

Two Types of Plagiogranite from Mesozoic Ashin Ophiolite (Central Iran): a Mark of Tectonic Setting Change from Jurassic to Cretaceous

The Ashin ophiolite is situated in the western part of Central Iran and presents two stages of Jurassic and Cretaceous spreading. The Ashin ophiolite represents fragments of the Neo-Tethys oceanic lithosphere. Plagiogranite intrusions of this ophiolite have good exposures. Plagiogranites of Cretaceous are more fresh than the metamorphosed samples of Jurassic. The main minerals of plagiogranites from the Ashin ophiolite are plagioclase, quartz and amphibole. Plagiogranites of the Jurassic have tholeitic nature with higher amounts of amphibole, $${\text{F}}{{{\text{e}}}_{2}}{\text{O}}_{3}^{*},$$ TiO2, Co and lower values of Mg#, Th and Sr than the Cretaceous calc-alkaline plagiogranites. The chondrite-normalized REE patterns of these plagiogranites are characterized by higher values of REEs and negative Eu anomalies for the Jurassic samples and low values of REEs and positive Eu anomalies for the Cretaceous ones. Very low values of HREEs in the Cretaceous plagiogranites indicates a non-peridotitic source rock. We suggest that the Jurassic plagiogranites are formed by fractional crystallization of a low-K tholeitic magma; and the adakitic Cretaceous plagiogranites are formed by partial melting of an amphibolite in the subducting slab. Geochemical criteria of the Ashin plagiogranites indicate changing the Ashin ophiolite tectonic setting from a mid-ocean ridge system in the Jurassic to a supra-subduction zone in the Cretaceous.

NUMERICAL SIMULATIONS OF RIDGE ACCRETION AND ONSHORE MIGRATION BASED ON FIELD DATA FROM A STEEP MESO-TIDAL ENGINEERED BEACH

Previously, the accretion of a slip-faced ridge and runnel (RR) system was observed during a 3-week field experiment on a steep meso-tidal engineered beach at South Bethany Beach, Delaware. Detailed measurements of wading depth beach profiles and nearbed flow velocities were obtained in the inner surf and swash zones along with offshore wave and current records. In the beginning of this 3-week field campaign on February 13, 2014 a Nor’easter eroded significant portions of the inner beach during this 1-day long storm event. Immediately after the storm during the less energetic conditions, the rapid formation of a pronounced RR system was observed which then continuously evolved over the duration of 2-week poststorm recovery periods. In the last day of the field campaign, 85% of the sediment volume eroded during the storm was recovered in the swash zone. However, no more evolution of the RR system toward the runnel infilling or landward migration was observed.

Human settlement and Mid-Late Holocene coastal environmental change at Cape Krusenstern, Northwest Alaska

Archaeologists hypothesize that mid-late Holocene environmental variability played a role in several significant western Arctic cultural developments including population fluctuations, the evolution of Arctic maritime adaptations, and Arctic-wide migrations. Further evaluation of these hypotheses requires higher resolution archaeological and paleoecological datasets than are currently available. In response, we undertook an interdisciplinary study at Cape Krusenstern, a large coastal site complex in northwest Alaska, which was occupied over the last ca. 5000–6000 years. Our goals were to refine local cultural and paleoenvironmental chronologies and to explore the question of how local environmental change may have influenced local settlement history. The resulting revised chronology and depositional units confirm and refine prior interpretation of the local archaeological settlement history. New geomorphological data on coastal environmental change and post-depositional modification of the Cape Krusenstern beach ridge system also provide information about patterns of archaeological site preservation, indicating periods of potentially poorer site preservation around 3990 cal BP; this informs interpretation of forager settlement data. Furthermore, our findings suggest that climate-driven changes in the coastal environment at Cape Krusenstern may not be as determinative in terms of landscape evolution as previously thought. Future work should focus on further investigating the relationship between beach ridge development and regional climatic patterns on a regional scale, as this has implications for use of beach ridges as a mid-late Holocene climate proxy. Continued efforts to build paleoenvironmental reconstructions of higher temporal and spatial resolution for the region will help address remaining questions about the relationship between local coastal environmental changes and regional patterns, and the impacts of these environmental shifts on local residents.

Flipping detachments: The kinematics of ultraslow spreading ridges

Although the seafloor spreading Hess initially proposed was a virtually amagmatic process, little attention has been paid to that possibility since. We construct a kinematic framework for virtually amagmatic and magma-poor Hess-style seafloor spreading, and successfully apply it to processes operating at the Southwest Indian Ridge (SWIR). The kinematic model is based on symmetric divergence about a rift axis at depth, with a repeating cycle in which a fault propagates up from the rift axis, develops into a detachment fault accommodating the plate divergence, migrates beyond the rift axis and is abandoned when a new fault propagates up through the footwall from the rift axis. We rigorously explore the controls on the depth, dip and timing of fault initiation and abandonment and use the kinematic framework to reconstruct the evolution of smooth mantle-dominated seafloor at the SWIR through symmetric divergence about a fixed rift axis. The model predicts the development of successive detachments of flipping polarity, as observed, each rooting along a narrow and fixed rift axis at 20 km depth, the base of the seismically defined brittle lithosphere. The detachments root at 80° (consistent with constraints on seismicity-defined detachment orientation at oceanic core complexes), and exhume mantle. Based on the continuity of basement ridges, of magnetic anomalies and of the seismic activity at the base of the lithosphere, it appears that these exhumation detachments transition laterally into rafting detachments, transporting fault-bounded volcanic slices up and away from the spreading axis to form the rougher volcanic seafloor found between mantle-dominated domains. The kinematic framework shows that increased magmatic divergence requires the detachments to root at shallower depths, consistent with the seismicity-defined shallowing of the base of the brittle lithosphere moving along the ridge axis towards the volcanic centres. Only in the immediate vicinity of volcanic centres, where the seismicity dies out, may magmatism dominate. We conclude that detachment tectonics dominate the process of ultraslow seafloor spreading as well as much of slow seafloor spreading, totalling about one third of the global ridge system, and present the first 3D tectonic model for ultraslow seafloor spreading.

Delivery of deep-sourced, volatile-rich plume material to the global ridge system

The global mid-ocean ridge (MOR) system represents a major site for outgassing of volatiles from Earth's mantle. The amount of H2O released via eruption of mid-ocean ridge basalts varies along the global ridge system and greatest at sites of interaction with mantle plumes. These deep-sourced thermal anomalies affect approximately one-third of all MORs – as reflected in enrichment of incompatible trace elements, isotope signatures and elevated ridge topography (excess melting) – but the physical mechanisms involved are controversial. The “standard model” involves solid-state flow interaction, wherein an actively upwelling plume influences the divergent upwelling generated by a mid-ocean ridge so that melting occurs at higher pressures and in greater amounts than at a normal spreading ridge. This model does not explain, however, certain enigmatic features including linear volcanic ridges radiating from the active plume to the nearby MOR. Examples of these are the Wolf–Darwin lineament (Galápagos), Rodrigues Ridge (La Réunion), Discovery Ridge (Discovery), and numerous smaller ridge-like structures associated with the Azores and Easter–Salas y Gómez hot spots. An important observation from our study is that fractionation-corrected MORB with exceptionally-high H2O contents (up to 1.3 wt.%) are found in close proximity to intersections of long-lived plume-related volcanic lineaments with spreading centres.New algorithms in the rare-earth element inversion melting (INVMEL) program allow us to simulate plume–ridge interactions by mixing the compositions of volatile-bearing melts generated during both active upwelling and passively-driven corner-flow. Our findings from these empirical models suggest that at sites of plume–ridge interaction, moderately-enriched MORBs (with 0.2–0.4 wt.% H2O) result from mixing of melts formed by: (i) active upwelling of plume material to minimum depths of ∼35 km; and (ii) those generated by passive melting at shallower depths beneath the ridge. The most volatile-rich MORB (0.4–1.3 wt.% H2O) may form by the further addition of up to 25% of “deep” small-fraction plume stem melts that contain >3 wt.% H2O. We propose that these volatile-rich melts are transported directly to nearby MOR segments via pressure-induced, highly-channelised flow embedded within a broader “puddle” of mostly solid-state plume material, spreading beneath the plate as a gravity flow. This accounts for the short wavelength variability (over 10s of km) in geochemistry and bathymetry that is superimposed on the much larger (many 100s of km) “waist width” of plume-influenced ridge.Melt channels may constitute a primary delivery mechanism for volatiles from plume stems to nearby MORs and, in some instances, be expressed at the surface as volcanic lineaments and ridges. The delivery of small-fraction hydrous melts from plume stems to ridges via a two-phase (melt-matrix) regime implies that a parallel, bimodal transport system is involved at sites of plume–ridge interaction. We estimate that the rate of emplacement of deep-sourced volatile-rich melts in channels beneath the volcanic lineaments is high and involves 10s of thousands of km3/Ma. Since mantle plumes account for more than half of the melt production at MORs our findings have important implications for our understanding of deep Earth volatile cycling.

Sub-marine Continuation of Peat Deposits From a Coastal Peatland in the Southern Baltic Sea and its Holocene Development

Coastal low-lying areas along the southern Baltic Sea provide good conditions for coastal peatland formation. During the Holocene, the transgression of the Littorina Sea has caused coastal flooding, submergence and erosion of ancient coastlines and former terrestrial material. The present Heiligensee & Hutelmoor peatland (located near Rostock in Northern Germany) was found to continue more than 90 m in front of the coastline based on on- and offshore sediment cores and geo-acoustic surveys. The seaward areal extent of the peatland is estimated with 0.16-0.2km2. The offshore limit of the former peatland roughly coincides with the offshore limit of a dynamic coast-parallel longshore bar, with peat deposits eroded seawards. While additional organic-rich layers were found further offshore below a small sand ridge system, no connection to the former peatlands can be established based on 14C age and C/N ratios. The preserved submerged peat deposits with organic carbon contents of 37 % in front of the coastal peatland Heiligensee & Hutelmoor was radiocarbon-dated to 6725 +/- 87 and 7024 +/-73 cal yr BP, respectively, indicating an earlier onset of the peatland as presently published. The formation time of the peat layers gives information about the local sea level rise. The local sea level curve derived from our 14C-dated organic-rich layers is in general agreement to nearby sea level reconstructions (North Rugen and Fischland, Northern Germany), with differences explained by local isostatic movements.

Effects of different fertilizer strategies on soil water utilization and maize yield in the ridge and furrow rainfall harvesting system in semiarid regions of China

Shortages of water resources and low soil fertility are two key factors that limit crop production in semiarid areas. The ridge and furrow rainfall harvesting (RFRH) system is an effective method for enhancing the efficiency of rainfall water use and fertility. In this study, we conducted a field experiment over five years (2012–2016) to determine the effects of different fertilizer application rates on the soil water consumption properties, water use efficiency, and maize yield under RFRH. We found that the evapotranspiration (ET), maize dry matter (DM), water consumption strength (CD), and soil water use rate (SP) increased with the fertilizer application rate. Compared with the no fertilizer treatment (RCK), ET, DM, CD, and SP increased significantly by 7.2%, 38.3%, 16.4%, and 37.6% under high fertilizer (RH) treatment, respectively, by 6.7%, 35.8%, 18.0%, and 39.1% with medium fertilizer (RM) treatment, and by 5.5%, 31.1%, 16.1%, and 32.6% with low fertilizer (RL) treatment. RM achieved the highest average yield of 11.3 t ha–1 and the lowest coefficient of variation at 12.9%. The yield, DM, and water use efficiency did not differ significantly between RH and RM. Regression analysis showed that the highest yield could be obtained by applying nitrogen at 265.0 kg ha–1 combined with P2O5 at 132.5 kg ha–1. The yield and water use efficiency were significantly higher under RL compared with RH and RM in wet year. However, in both normal and drought years, the grain yield and water use efficiency was significantly higher under RM. These results indicate that the RFRH system can promote crop use of fertilizers by regulating soil moisture. The best fertilization strategy for planting maize with RFRH system was 265.0 kg ha–1 of pure nitrogen combined with 132.5 kg ha–1 of P2O5 in the semiarid area of the Loess Plateau, in China.

Sedimentary records of extreme wave events in the southwestern Caribbean

High-energy events in the Caribbean Sea include hurricanes, tropical storms, cold fronts and tsunamis. El Rosario Archipelago, located on the Colombian Caribbean shelf (SW Caribbean) consists of a set of ancient and successive coralline formations, uplifted by tectonic and diapiric activity. We undertook an integrated analysis of instrumental climate records and sediment records from a beach ridge system, a reef lagoon and a mangrove lagoon in the Archipelago, to determine whether historical extreme weather events influenced the coastal geomorphology and reef sedimentation. Statistical analysis of historical extreme winds and waves was accomplished using ERA-Interim reanalysis data. Extreme sea-level events were identified with calibrated data from the nearest tide gauge. Sediments from the reef and mangrove lagoon were dated using 210Pb and 14C. Beach ridges were dated indirectly thorough their relationship with the closure of the mangrove lagoon. The eroding capacity of the historical extreme waves (i.e. maximum grain size that could be entrained by the orbital velocity of the waves) was compared with the grain sizes present in the deposits, and foraminifera species helped to determine the provenance of those deposits. Storms typically occur during the dry season associated with cold fronts. Foraminifera and coral fragments indicated that beach ridges were supplied with sediment that eroded from ancient terraces. In the reef lagoon, a 56-cm-thick unit of coarse coral and shell debris, grading to a finer sediment, represents a major high-energy event that occurred after ca. 1655 CE. This event was also recorded by the beach ridges. The probable explanation for this high energy unit is that a strong event carried coarse sediments into the lagoon, with subsequent reworking by minor events, such as those reported in the historical record. Two tsunamis occurred in the Caribbean after 1655, but the associated waves reaching the area were not strong enough to deposit the coarser clasts of the unit. Thus, coarser material was probably delivered to the lagoon as a consequence of sudden diapiric and/or tectonic activity. Our data show that major storms and other high-wind, extreme-wave events shape the beach ridges on Rosario Island, every 70 years. The findings suggest that if global climate change increases the frequency and/or magnitude of major storms and other high-wind, extreme wave events that impact the Caribbean coast of Colombia, then El Rosario Archipelago will be susceptible to future, significant landscape transformations.

Holocene sea-level change and coastal landscape evolution in the southern Gulf of Carpentaria, Australia

A revised Holocene sea-level history for the southern Gulf of Carpentaria is presented based on new data from the South Wellesley Archipelago and age recalibration of previous research. Results confirm that rising sea levels during the most recent post-glacial marine transgression breached the Arafura Sill ca. 11,700 cal. yr BP. Sea levels continued to rise to ca. –30 m by 10,000 cal. yr BP, leading to full marine conditions. By 7700 cal. yr BP, sea-level reached present mean sea-level (PMSL) and continued to rise to an elevation of between 1.5 m and 2 m above PMSL. Sea level remained ca. + 1.5 between 7000 and 4000 cal. yr BP, followed by rapid regression to within ± 0.5 m of PMSL by ca. 3500 cal. yr BP. When placed into a wider regional context results from this study show that coastal landscape evolution in the tropical north of Australia was not only dependent on sea-level change but also show a direct correlation with Holocene climate variability. Specifically, the formation and preservation of beach-rock deposits, intertidal successions, beach and chenier ridge systems hold valuable sea-level and Holocene climate proxies that can contribute to the growing research into lower latitude Holocene sea-level and climate histories.

The evolution of Chabahar beach ridge system in SE Iran in response to Holocene relative sea level changes

The Chabahar Strandplain (CHS) stretches along the Chabahar bay at a width of more than 5 km along the northern coast of the Gulf of Oman and SE Iran; an area that has been subjected to tectonic uplift as a part of the Makran accretionary prism. The CHS comprises of beach ridges, inter-ridge swales, sand dunes, tidal channels and fluvial deposits. We present the first documentation of the spatial distribution and the internal architecture of the CHS based on topographic surveys, sediment percussive coring, trenching and ground penetrating radar (GPR) transects. Radiocarbon dating on marine shells from foreshore deposits of 8 representative beach ridges yielded ages between 4800 and 270 cal. years BP at respective distances of 4800 to 670 m from the present shoreline. We interpret the boundary between the foreshore (beach) and the foredune deposits as indicator of past sea levels by analogy to present shore processes. This boundary is readily recognizable in sediment profiles from cores and trenches as well as GPR reflectors. Based on the age model and depositional features, we estimate relative sea level fall of up to 15 m over the past 4800 years. Considering that the eustatic sea level changes for this period are negligible for the Makran coast, this relative sea level fall is related to tectonic uplift across the coastal Makran. The elevation of palaeo-shorelines with similar ages decrease from east to west of the CHS, which suggest that alongshore variations in uplift rates are likely related to different movements of coastal fault blocks.

A Visual Survey of Global Slab Geometries With ShowEarthModel and Implications for a Three‐Dimensional Subduction Paradigm

Increasing volumes of digital data, combined with advances in visualization, allow for a new three‐dimensional (3D) conceptualization of modern subduction systems. Here we present 16 visual exploration sessions with the ShowEarthModel program that interrogate modern slab morphologies on Earth. These virtual voyages through the Earth's interior provide a snapshot into the four‐dimensional evolution of plate tectonics, captured by the modern state of slab structure. Examining the modern subduction system in an interactive 3‐D framework provides an improved conceptualization of the morphology of slabs. The movies demonstrate that unlike the modern mid‐ocean ridge system, modern subduction systems are laterally discontinuous features, making lateral slab edges prevalent. The 3‐D visualizations elucidate the manner in which slabs intersect and overlap, processes that occur in at least six of the Earth's major subduction zones. The observed variability within a given subduction zone as well as the physical presence of intersecting slabs suggests that slab gaps and slab windows are common. The 3‐D rendering shows relative differences in the radius of curvature for arcuate slabs, as well as the variability in dip within a given subduction zone. Addressing the complex geometries of subducted lithosphere in this way can place constraints on outstanding questions of subduction dynamics including slab strength, mantle rheology, mantle flow circulation, and plate‐asthenosphere coupling. By conceptualizing the modern subduction system on Earth in 3‐D space, this paper contributes to the paradigm shift from a two‐dimensional (2‐D) to 3‐D framework for interpreting the subduction process.

Water Masses and Depth Structure Prokaryotic and T4-Like Viral Communities Around Hydrothermal Systems of the Nordic Seas

The oceanographic features of the Nordic Seas, situated between Iceland and Svalbard, have been extensively studied over the last decades. As well, the Nordic Seas hydrothermal systems situated on the Arctic Mid-Ocean Ridge System have received an increasing interest. However, there is very little knowledge on the microbial communities inhabiting the water column of the Nordic Seas, and nothing is known about the influence of the different water masses and hydrothermal plumes on the microbial community structures. In this study, we aimed at characterizing the impact of hydrothermal plumes on prokaryotic and T4-like viral communities around the island of Jan Mayen. To this end, we used 16S rRNA-gene and g23-gene profiling as well as flow cytometry counts to examine prokaryotic and viral communities in 27 samples obtained from different water masses in this area. While Thaumarchaeota and Marine group II Archaea dominated the waters deeper than 500 m, members of Flavobacteria generally dominated the shallower waters. Furthermore, extensive chemical and physical characteristics of all samples were obtained, including temperature measurements and concentrations of major ions and gases. The effect of these physiochemical variables on the communities was measured by using constrained and unconstrained multivariate analyzes, Mantel tests, network analyzes, phylogenetic analyzes, taxonomic analyzes and temperature-salinity (Θ-S) plots. Our results suggest that hydrothermal activity has little effect on pelagic microbial communities in hydrothermal plumes of the Nordic Seas. However, we provide evidences that observed differences in prokaryotic community structure can largely be attributed to which water mass each sample was taken from. In contrast, depth was the major factor structuring the T4-like viral communities. Our results also show that it is crucial to include water masses when studying the influence of hydrothermal plumes on microbial communities, as it could prevent to falsely associate a change in community structure with the presence of a plume.

Spatial distribution of wintertime air pollution in major cities over eastern China: Relationship with the evolution of trough, ridge and synoptic system over East Asia

Hourly air quality index (AQI) data from the Ministry of Environment Protection of China are used to investigate spatial distribution of air pollution in major cities over eastern China (ECN) in winter 2015. The wintertime averaging identifies a pollution center in east Shanxi (IV, the identifier number in Fig. 1), south Hebei (III), west Shandong (V) and Henan (VI) provinces with mean AQI > 100. Four typical types of air pollution spatial distribution are identified. The low level southerly winds are found to be associated with the occurrence of regional air pollution episodes over ECN. The spatial distribution of air pollution is mainly related to the low level meridional wind, which is determined by the specific evolution process of the trough, ridge and synoptic system. The longitudinal position, the deepening (or weakening) and the southward extension (or northward retreat) of the trough over East Asia are the crucial factors determining where the regional air pollution could occur. The influence of precipitation on air pollution is complicated; the initial stage of precipitation with limited precipitation amount promotes the secondary formation and hygroscopic growth of aerosol due to increased supply of moisture, thus favors an aggravation of air pollution; in contrast, only the persisting and intensifying of precipitation are accompanied with more effective wet scavenging and an improvement of air quality. Fireworks emission is found to exacerbate air pollution during the Spring Festival, resulting in a unique distribution of air pollution over a large area of China, suggesting that prohibiting fireworks is necessary under adverse synoptic situation.

Influence of improved agronomical practices on yield and economics of chickpea (Cicer arietinum L.)in gird zone of Madhya Pradesh on farmers field

The results of twenty replicated demonstrations on Chickpea Cultivation practices conducted under Harshi command area of district, Gwalior, Madhya Pradesh, were analysed to differences in crop grown under improved package of practice and farmers practice, which explore the potential of farmers for enhancement crop and water productivity of chickpea crop. Sowing on ridge and furrow system with recommended row spacing improved the seed yield of chickpea by 59.38% as compared to narrow sowing on flat land of farmers practices. As compared to fertilizers by farmers practices, recommended dose of fertilizer could enhance the seed yield by 36.20%. Improvement in pest management practices led to 29.41% increase over farmers practices. Similarly, use of improved seed over farm saved seed and appropriate weed management over farmers practices, enhance the yield by 25.41% and 41.25%, respectively. The improved technology gave higher net return and B:C ratio as compared to farmers practices.

Chronology and late-Holocene evolution of Caleta de los Loros, NE Patagonia, Argentina

Geomorphological and sedimentary records of Holocene coastal deposits may serve as archives for the local reconstruction of trends in coastal evolution and of the key forcing parameters controlling long-term change. We here present new observations on the sedimentology, chronology, and surface properties of a coupled beach ridge and coastal lagoon system located on the northern shore of San Matías Gulf, NE Patagonia, Argentina. The study is based on remotely sensed data, sediment cores, and a large number of samples dated using optically stimulated luminescence (OSL). The field site is located in a topographical depression within a cliffed shoreline composed of friable sand and gravel stones. The oldest preserved lagoonal deposits formed in the protected inner part of the system c. 2300 years ago. An up to 4-km-wide strandplain prograded rapidly between c. 1000 and 500 years in the more exposed western part of the system. Lagoonal deposition occurred primarily during the last 500 years. The chronology and spatial arrangement of landforms appear to result from a switch-over in sediment delivery probably caused by local implications of major shifts in climate regime. Even though we were not able to identify or benchmark the precise triggers of geomorphological change at Caleta de los Loros, our study presents an example of the potential importance of environmental changes on the rapid and non-linear development of coastal sedimentary systems.

Characterization of vent fauna at three hydrothermal vent fields on the Southwest Indian Ridge: Implications for biogeography and interannual dynamics on ultraslow-spreading ridges

The Southwest Indian Ridge (SWIR) is an important section of the global mid-ocean ridge system providing a corridor for dispersion of vent fauna between the Pacific and Atlantic Oceans. However, very few studies focusing on the biodiversity and biogeography of this region have been performed. To better understand the biological baseline and biogeography of vent fields on SWIR, we have described the faunal assemblages at three hydrothermal fields on SWIR, the biogeographical relationships among the three fields and fields on neighboring ridges as well as community dynamics at Longqi on a short time-scale (3 years). Communities at two fields, Duanqiao and Tiancheng, were reported for the first time, and the Longqi community was characterized more comprehensively. Collected specimens, videos and images were examined and taxa identification was conducted by both morphological and molecular approaches (cytochrome oxidase I (COI) or 16 S ribosomal RNA gene). In total, 39 species were recorded, 18 of which were reported from SWIR for the first time. According to the multivariate analysis of occurrence of fauna from 16 vent fields on four ridge systems, the SWIR vent sites were generally more similar to Central Indian Ridge. Within Indian Ocean, Longqi and Duanqiao formed a subcluster, which appeared to be intermediate between the Central Indian Ridge, Mid-Atlantic Ridge and East Scotia Ridge. Distinct faunal zonation was described at Tiancheng and Longqi. Comparison of vent fauna discovered in 2011 and 2014/2015 revealed an interannual constancy in faunal zonation on most vents at Longqi, except DFF1 chimney, which displayed a successional change from an early stage featuring high-temperature venting and low species diversity, to a more mature stage characterized by diffuse fluid and more colonized taxa. Thus, the present study is the first interannual variation study on the ultra-slow spreading ridges, and will expand our understanding of biodiversity and biogeography of vent fields on SWIR.

Rhythmic Patterns of Coastal Formations as Signs of Past Climate Fluctuations on Uplifting Coasts of Estonia, the Baltic Sea

ABSTRACT Tonisson, H.; Suursaar, U.; Kont, A.; Muru, M.; Rivis, R.; Rosentau, A.; Tamura, T., and Vilumaa, K., 2018. Rhythmic patterns of coastal formations as signs of past climate fluctuations on uplifting coasts of Estonia, the Baltic Sea. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 611–615. Coconut Creek (Florida), ISSN 0749-0208. On uplifting and tideless Baltic Sea Coasts in Estonia, a number of elevated mid to late Holocene beach ridge systems with rhythmic patterns are identified. Such uplifted coastal formations serve as archives of past variations in sea level and climate, as well as extreme events. Luminescence dating and interpretation of airborne LiDAR elevation data were used to identify the main formation mechanisms of such beach ridge systems. More extensive (up to 100–150 ridges) and clearer ridge patterns were found on faster emerging (up...