scholarly journals A Quantitative Evaluation of Hyperpycnal Flow Occurrence in a Temperate Coastal Zone: The Example of the Salerno Gulf (Southern Italy)

Geosciences ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 501
Author(s):  
Ines Alberico ◽  
Francesca Budillon
Keyword(s):  
Return Period ◽  
Sediment Concentration ◽  
Time Interval ◽  
Tyrrhenian Sea ◽  
Shallow Marine ◽  
Main River ◽  
Hyperpycnal Flows ◽  
Source To Sink ◽  
Hypsometric Integral ◽  
Hyperpycnal Flow

The inner continental shelf is regarded as a repository of hyperpycnal flow (HF) deposits the analysis of which may contribute to hydrogeological risk assessment in coastal areas. In line with the source to sink paradigm, we examined the dynamics of the coastal watersheds facing the Salerno Gulf (Southern Tyrrhenian Sea) in generating hyperpycnal flows and investigated the shallow marine sediment record to verify their possible occurrence in the recent past. Thus, the morphometric properties (hypsometric integral, hypsometric skewness, hypsometric kurtosis, density skewness and density kurtosis) of the watersheds together with the potential rivers’ discharge and sediment concentration, calculated by applying altitude- and extent -based experimental relations, allowed to detect the rivers that were prone to producing HFs. In the shallow marine environment record of the last 2 kyr, anomalous sedimentation, possibly linked to HF events, was identified by comparing the sand-mud ratio (S/M) down-core —at three sites off the main river mouths — to the expected S/M calculated by applying the relation governing the present-day distribution of sand at the seabed in the Salerno Gulf. A return period of major HF events ≤ 0.1 kyr can be inferred for rivers which fall into the category “dirty rivers”. In these cases, the watersheds have a hypsometric index ranging between 0.2 and 0.3, coastal plains not exceeding 30% of the entire catchment area and a maximum topographic height ≥1000 m. A return period of about 0.3 kyr has been inferred for the “moderately dirty rivers”. In these other cases, about 50% of the watersheds develop into a low gradient coastal plain and have a hypsometric index ranging between 0.09 and 0.2. The observations on land and offshore have been complemented to reach a more comprehensive vision of the coastal area dynamics. The method here proposed corroborates the effectiveness of the source to sink approach and is applicable to analogous sediment records in temperate continental shelves which encompass the last 3 kyr, a time interval in which the oscillations of relative sea level can be overlooked.

scholarly journals Reticulate Nummulites (N. fabianii Linage) and Age of the Pellatispira-Beds of the Drazinda Formation, Sulaiman Range, Pakistan

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Ozcan E
Keyword(s):  
Mediterranean Region ◽  
Late Eocene ◽  
Test Surface ◽  
Time Interval ◽  
Late Oligocene ◽  
Shallow Marine ◽  
Western Tethys ◽  
Two Samples ◽  
Evolutionary Scheme ◽  
Weak Surface

The Eocene shallow marine Pellatispira-beds in the upper part of the Drazinda Formation represent the latest phase of Cenozoic Tethyan marine deposition in the Sulaiman Range, West Pakistan. The unit consists of stratigraphically important taxa as Heterostegina,Silvestriella, Pellatispira, a new Baculogypsina (possibly ancestral to modern Baculogypsina) and reticulate Nummulites implying a latest middle to late Eocene (late Bartonian-Priabonian) age. A more precise age of the unit requires the biometric study of reticulate Nummulites, the evolutionary scheme of which is better known from the peri-Mediterranean region in the Tethys. This group, which was subdivided into a series of successive chrono-species based on the biometry of inner cross-diameter of proloculus and changes in the types of granulation/reticulation on the test surface in the late Eocene-late Oligocene interval, appears to have a significant biostratigraphic potential for a high-resolution biostratigraphy in the peri-Mediterranean region (Western Tethys). The reticulate Nummulites in two samples from Rakhi Nala and Zinda Pir, ZP22 and RNB10, were studied and compared with those from the peri-Mediterranean region. The isolated specimens have a weak surface granulation externally, a distinct small umbonal granule (pile) and typical reticulation. The samples ZP22 and RNB10 from Zinda Pir and and Rakhi Nala sections have an average inner cross diameter of proloculus of 152.0 and 153.0 μm respectively. The reticulate Nummulites in both samples are assigned to N. hormoensis, a chrono-species characteristic for the shallow benthic zone (SBZ 18), referable to latest Bartonian-early Priabonian time interval. Since Heterostegina in peri-Mediterranean region and in Pakistan belongs to different lineages, a correlation of N. hormoensis in the studied samples with the wellestablished evolutionary scheme of Heterostegina reticulata and H.armenica lineages from the Western Tethys was not possible.

PECULIARITIES OF THE SAND PARTICLES SUSPENDING UNDER INFLUENCE OF THE REGULAR WAVES

2018 ◽  
Author(s):  
М. Крыленко ◽  
M. Krylenko ◽  
Й. Грюне ◽  
Y. Gryune ◽  
Р. Косьян ◽  
...  
Keyword(s):  
Laboratory Experiment ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Time Interval ◽  
Regular Waves ◽  
Large Wave ◽  
Wave Channel ◽  
Sand Particles ◽  
Using Data

In the presented paper some peculiarities of suspending and distribution of sand particles under influence of the regular waves in time interval less than the wave period are discussed using data from laboratory experiment “Hannover 2008”. The experiment was carried out in the Large Wave Channel (GWK). The presented data show that fluctuations of suspended sediment concentration are very largely initiated by individual waves.

Experimental Study on Formation Cause of Sink Reach’s River Pattern of Alluvial River Flowing into the Lake

2012 ◽  
Vol 212-213 ◽  
pp. 461-465
Author(s):  
Jun Chen ◽  
Xiao Feng Zhang ◽  
Hong Chen ◽  
Cai Wen Shu
Keyword(s):  
Lake Level ◽  
Sediment Concentration ◽  
Formation Condition ◽  
Channel Evolution ◽  
Alluvial River ◽  
Factors Influencing ◽  
Main River ◽  
Experiment Method ◽  
Major Factors ◽  
River Pattern

The formation cause of sink reach’s river pattern of the alluvial river flowing into the lake was studied by the experiment method. The results showed that: the change of lake level was the important formation condition of the alluvial river’s sink reach. The sediment concentration, the riverbed gradient were the major factors influencing the river pattern’s evolution of the sink reach. When the sediment concentration of upstream river was less, the sink reach was inclined to form a straight river, and with the increase of the sediment concentration, the bifurcated river was the chief river pattern. When the sediment concentration increased to a certain value, the sink reach was inclined to form a wandering river. When the riverbed gradient was less, the sink reach was inclined to form a bifurcated river, and with the increased of the gradient, the wandering river was the main river pattern. The sediment diameter affected channel evolution, but the influence extent was less.

Sediment records of the influence of river damming on the dynamics of the Nelson and Churchill Rivers, western Hudson Bay, Canada, during the last centuries

The Holocene ◽  
2016 ◽  
Vol 27 (5) ◽  
pp. 712-725 ◽  
Author(s):  
Quentin Duboc ◽  
Guillaume St-Onge ◽  
Patrick Lajeunesse
Keyword(s):  
River Mouth ◽  
Sediment Concentration ◽  
Hudson Bay ◽  
Continuous Control ◽  
Dam Construction ◽  
Physical Chemical ◽  
Hyperpycnal Flows ◽  
Western Hudson Bay ◽  
The 1960S ◽  
The Impact

Two gravity cores (778 and 780) sampled at the Nelson River mouth and one (776) at the Churchill River mouth in western Hudson Bay, Canada, were analyzed in order to identify the impact of dam construction on hydrology and sedimentary regime of both rivers. Another core (772) was sampled offshore and used as a reference core without a direct river influence. Core chronology was established using 14C and 210Pb measurements. Cores 778 and 780 show greater variability than the others, and the physical, chemical, magnetic, and sedimentological properties measured on these cores reveal the presence of several hyperpycnites, indicating the occurrence of hyperpycnal flows associated with floods of the Nelson River. These hyperpycnal flows were probably caused by ice-jam formation, which can increase both the flow and the sediment concentration following the breaching of such natural dams. However, these hyperpycnites are only observed in the lower parts of cores 778 and 780. It was not possible to establish a precise chronology because of the remobilization of sediments by the floods. Nevertheless, some modern 14C ages suggest that this change in sedimentary regime is recent and could be concurrent with the dam construction on the Nelson River, which allows a continuous control of its flow since the 1960s. This control prevented the formation of hyperpycnal flows and the deposition of hyperpycnites. Finally, core 776 contains only one rapidly deposited layer. This lower frequency may be related to the enclosed estuary of the Churchill River, its weaker discharge, and the distance of the site from shore.

scholarly journals Infralittoral ostracoda and benthic foraminifera of the Gulf of Pozzuoli (Tyrrhenian Sea, Italy)

2021 ◽  
Author(s):  
Giuseppe Aiello ◽  
Diana Barra ◽  
Roberta Parisi ◽  
Michele Arienzo ◽  
Carlo Donadio ◽  
...  
Keyword(s):  
Industrial Pollution ◽  
Historical Data ◽  
Diversity Indices ◽  
Tyrrhenian Sea ◽  
Benthic Foraminifers ◽  
Shallow Marine ◽  
Assemblage Composition ◽  
Environmental Variations ◽  
The Relationship ◽  
High Diversity

AbstractThe shallow water benthic foraminiferal and ostracod assemblages of the Gulf of Pozzuoli, located in the central Tyrrhenian Sea, were studied to investigate the relationship between calcareous meiofaunas and contaminant concentrations in bottom sediments exposed to prolonged industrial pollution. Both benthic foraminifers and ostracods displayed high-diversity and low-dominance, unusual features in highly contaminated environments. High-diversity values were possibly linked to the oligotrophic, well-oxygenated, and CaCO3-supersaturated coastal Mediterranean waters. The comparison with historical data suggested that assemblage composition changed in the last decades, with an increase in the relative abundance of benthic foraminiferal (Quinqueloculina seminulum, Bulimina elongata) and ostracod (Xestoleberis, Loxoconcha, Semicytherura rarecostata) taxa. They probably represent organisms tolerant to the environmental variations in the last decades. The relationships between granulometry and diversity indices, high correlation values between Quinqueloculina lata and heavy metal pollution, and the preference of the ostracod genera Urocythereis and Paracytheridea for very shallow marine waters were highlighted.

scholarly journals Extreme Wind and Waves in U.S. East Coast Offshore Wind Energy Lease Areas

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1053
Author(s):  
Rebecca J. Barthelmie ◽  
Kaitlyn E. Dantuono ◽  
Emma J. Renner ◽  
Frederick L. Letson ◽  
Sara C. Pryor
Keyword(s):  
Return Period ◽  
East Coast ◽  
Offshore Wind ◽  
Time Interval ◽  
Annual Maximum ◽  
Outer Continental Shelf ◽  
Reanalysis Dataset ◽  
Maximum Wind ◽  
Wind Speeds ◽  
Extreme Wind

The Outer Continental Shelf along the U.S. east coast exhibits abundant wind resources and is now a geographic focus for offshore wind deployments. This analysis derives and presents expected extreme wind and wave conditions for the sixteen lease areas that are currently being developed. Using the homogeneous ERA5 reanalysis dataset it is shown that the fifty-year return period wind speed (U50) at 100 m a.s.l. in the lease areas ranges from 29.2 to 39.7 ms−1. After applying corrections to account for spectral smoothing and averaging period, the associated pseudo-point U50 estimates are 34 to 46 ms−1. The derived uncertainty in U50 estimates due to different distributional fitting is smaller than the uncertainty associated with under-sampling of the interannual variability in annual maximum wind speeds. It is shown that, in the northern lease areas, annual maximum wind speeds are generally associated with intense extratropical cyclones rather than cyclones of tropical origin. Extreme wave statistics are also presented and indicate that the 50-year return period maximum wave height may substantially exceed 15 m. From this analysis, there is evidence that annual maximum wind speeds and waves frequently derive from the same cyclone source and often occur within a 6 h time interval.

scholarly journals Paleotemperature record of the Middle Devonian Kačák Episode

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Thomas J. Suttner ◽  
Erika Kido ◽  
Michael M. Joachimski ◽  
Stanislava Vodrážková ◽  
Monica Pondrelli ◽  
...  
Keyword(s):  
Middle Devonian ◽  
Seawater Temperature ◽  
Sea Surface ◽  
Time Interval ◽  
Marine Biota ◽  
Carnic Alps ◽  
Climate Conditions ◽  
Shallow Marine ◽  
Low Latitudes ◽  
Mean Sea Surface

AbstractThe Middle Devonian Epoch, ~ 393–383 million years ago, is known for a peak in diversity and highest latitudinal distribution of coral and stromatoporoid reefs. About 388 million years ago, during the late Eifelian and earliest Givetian, climax conditions were interrupted by the polyphased Kačák Episode, a short-lived period of marine dys-/anoxia associated with climate warming that lasted less than 500 kyr. Reconstruction of the seawater temperature contributes to a better understanding of the climate conditions marine biota were exposed to during the event interval. To date, conodont apatite-based paleotemperatures across the Eifelian–Givetian boundary interval have been published from Belarus, France, Germany and North America (10–36° S paleolatitude). Here we provide new δ18Oapatite data from the Carnic Alps (Austria, Italy) and the Prague Synform (Czech Republic). For better approximation of the paleotemperature record across the Kačák Episode, a latitude-dependent correction for Middle Devonian seawater δ18O is applied. Because δ18Oapatite data from shallow marine sections are influenced by regional salinity variations, calculated mean sea surface temperatures (SST) are restricted to more open marine settings (22–34° S paleolatitude). Water temperatures reach ~ 34 °C in the Prague Synform and ~ 33 °C in the Carnic Alps and suggest that SSTs of the southern hemisphere low latitudes were ~ 6 °C higher than previously assumed for this time interval.

scholarly journals Floodplain sediment from a 30-year-recurrence flood in 2005 of the Ping River in northern Thailand

2007 ◽  
Vol 4 (5) ◽  
pp. 3839-3868 ◽  
Author(s):  
S. H. Wood ◽  
A. D. Ziegler
Keyword(s):  
Fine Sand ◽  
Sediment Concentration ◽  
Main Channel ◽  
River Channel ◽  
Northern Thailand ◽  
Main River ◽  
Main River Channel ◽  
Clayey Silt ◽  
Secondary Objective ◽  
Sedimentation Processes

Abstract. This paper documents the nature of flood-producing storms and floodplain deposition associated with the 28 September–2 October 2005 30-year-recurrence flood on the Ping River in northern Thailand. The primary purpose of the study is to understand the extent that deposits from summer-monsoon floods can be identified in floodplain stratigraphy A secondary objective is to document the sedimentation processes/patterns associated with a large contemporary flood event on a medium-sized Asian river. Maximum sediment depths of 15 cm were found on the river levee, within 30 m of the main channel, and at 350 m thickness was 4 cm. Sediment depth generally decreased exponentially with distance away from the main channel. The extent of sediment deposition was about 1 km from the river channel. However, 72% of the sediment was deposited within an oval-shaped area 200–400 m from the main channel and centered on a tributary stream, through which sediment-laden water entered the floodplain, in addition to overtopping the levee of the main channel. Sediment concentration during the flood was estimated at 800–1500 mg L−1; and we believe the sediment was delivered by flows of well-mixed flood water occurring over a 1–2 day period. These data suggest that flood-deposited strata related to 30-year recurrence floods is only likely to be preserved in deposits located relatively close to the main river channel where fine sand and clayey coarse silt deposits have thicknesses of at least 5–10 cm. These relatively thick deposits would survive bioturbation, whereas more distal areas with thin clayey silt deposits would not.

Gravity flows: Types, definitions, origins, identification markers, and problems

2020 ◽  
Vol 37 (2) ◽  
pp. 61-90
Author(s):  
Shanmugam G
Keyword(s):  
Debris Flow ◽  
Deep Water ◽  
Sediment Concentration ◽  
Gravity Flow ◽  
Turbidity Currents ◽  
Hyperpycnal Flows ◽  
Gravity Flows ◽  
Sediment Gravity Flow ◽  
Aeolian Dunes ◽  
C 50

Abstract This review covers 135 years of research on gravity flows since the first reporting of density plumes in the Lake Geneva, Switzerland, by Forel (1885). Six basic types of gravity flows have been identified in subaerial and suaqueous environments. They are: (1) hyperpycnal flows, (2) turbidity currents, (3) debris flows, (4) liquefied/fluidized flows, (5) grain flows, and (6) thermohaline contour currents. The first five types are flows in which the density is caused by sediment in the flow, whereas in the sixth type, the density is caused by variations in temperature and salinity. Although all six types originate initially as downslope gravity flows, only the first five types are truly downslope processes, whereas the sixth type eventually becomes an alongslope process. (1) Hyperpycnal flows are triggered by river floods in which density of incoming river water is greater than the basin water. These flows  are confined to proximity of the shoreline. They transport mud, and they do not transport sand into the deep sea. There are no sedimentological criteria yet to identify hyperpycnites in the ancient sedimentary record.  (2) A turbidity current is a sediment-gravity flow with Newtonian rheology  and turbulent state in which sediment is supported by flow turbulence and from which deposition occurs through suspension settling. Typical turbidity currents can function as truly turbulent suspensions only when their sediment concentration by volume is below 9% or C < 9%. This requirement firmly excludes the existence of 'high-density turbidity currents'. Turbidites are recognized by their distinct normal grading in deep-water deposits.  (3) A debris flow (C: 25-100%) is a sediment-gravity flow with plastic rheology and laminar state from which deposition occurs through freezing en masse. The terms debris flow and mass flow are used interchangeably. General characteristics of muddy and sandy debrites are floating clasts, planar clast fabric, inverse grading, etc.  Most sandy deep-water deposits are sandy debrites and they comprise important petroleum reservoirs worldwide. (4) A liquefied/fluidized low (>25%) is a sediment-gravity flow in which sediment is supported by upward-moving intergranular fluid. They are commonly triggered by seismicity. Water-escape structures, dish and pillar structures, and SSDS are common. (5) A grain flow (C: 50-100%) is a sediment-gravity flow in which grains are supported by dispersive pressure caused by grain collision. These flows are common on the slip face of aeolian dunes. Massive sand and inverse grading are potential identification markers.  (6) Thermohaline contour currents originate in the Antarctic region due to shelf freezing and  the related increase in the density of cold saline (i.e., thermohaline) water. Although they begin their journey as downslope gravity flows, they eventually flow alongslope as contour currents. Hybridites are deposits that result from intersection of downslope gravity flows and alongslope contour currents. Hybridites mimic the "Bouma Sequence" with traction structures (Tb and Tc). Facies models of hyperpycnites, turbidites, and contourites  are obsolete. Of the six types of density flows, hyperpycnal flows and their deposits are the least understood.

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