scholarly journals Diverse floodplain deposits of reworked loess in a monsoon climate (Hanzhong Basin, central China)

2021 ◽  
pp. 1-17
Author(s):  
Jef Vandenberghe ◽  
Xun Yang ◽  
Xianyan Wang ◽  
Shejiang Wang ◽  
Huayu Lu
Keyword(s):  
Soil Formation ◽  
High Energy ◽  
Central China ◽  
Energy Conditions ◽  
Middle Pleistocene ◽  
Sedimentary Sequences ◽  
Varied Intensity ◽  
Floodplain Deposits ◽  
Flooding Events ◽  
Floodplain Sediments

Abstract This paper describes an assemblage of diverse floodplain facies of reworked loess (facies b, c) in a Middle Pleistocene monsoonal setting of the Hanzhong Basin, central China. The vertical and lateral sedimentary sequences show changing energy conditions. Apart from the highest energy in the channel facies (facies a), a relatively high energy floodplain environment (facies b) prevailed in waterlogged conditions, with small, laterally migrating (sub)channels. Facies b generally interfingers with aggrading horizontal sheets of overbank deposits in alluvial pools and swamps in a floodplain with much lower energy (facies c), in which phases of stability (soil formation) occasionally interrupted overbank deposition. Reworked loess forms the main part of the floodplain deposits. The paleosols are considered to have been formed under low hydrodynamic conditions in an interglacial environment. These interglacial conditions follow the commonly assumed glacial conditions of channel facies a. The sedimentary successions in the floodplain show a recurrent composition and cyclicity between wet and dry floodplain sedimentation terminated by stability with soil formation. The cyclic rhythm of stacked high- and low-energy floodplain sediments is attributed to varied intensity of different hydrodynamic flooding events that may have been due to changing monsoonal rainfall or simple intrinsic fluvial behavior.

scholarly journals Changes in Paleovegetation and Paleoclimate in China Since the Late Middle Pleistocene: A Case Study of the Dajiuhu Basin

2021 ◽  
Vol 13 (9) ◽  
pp. 4848
Author(s):  
Liwei Wu ◽  
Xinling Li ◽  
Qinghai Xu ◽  
Manyue Li ◽  
Qiufeng Zheng ◽  
...  
Keyword(s):  
Grain Size ◽  
Asian Monsoon ◽  
East Asian Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Central China ◽  
Middle Pleistocene ◽  
Pollen Record ◽  
The Difference ◽  
Late Middle Pleistocene

The East Asian monsoon system is an important part of global atmospheric circulation; however, records of the East Asian monsoon from different regions exhibit different evolutionary rhythms. Here, we show a high-resolution record of grain size and pollen data from a lacustrine sediment core of Dajiuhu Lake in Shennongjia, Hubei Province, China, in order to reconstruct the paleovegetation and paleoeclimate evolution of the Dajiuhu Basin since the late Middle Pleistocene (~237.9 ka to the present). The results show that grain size and pollen record of the core DJH-2 are consistent with the δ18O record of stalagmites from Sanbao Cave in the same area, which is closely related to the changes of insolation at the precessional (~20-kyr) scale in the Northern Hemisphere. This is different from the records of the Asian summer monsoon recorded in the Loess Plateau of North China, which exhibited dominant 100-kyr change cyclicities. We suggest that the difference between paleoclimatic records from North and South China is closely related to the east–west-oriented mountain ranges of the Qinling Mountains in central China that blocked weakened East Asia summer monsoons across the mountains during glacial periods.

scholarly journals Involvement of Progranulin in Hypothalamic Glucose Sensing and Feeding Regulation

Endocrinology ◽  
2011 ◽  
Vol 152 (12) ◽  
pp. 4672-4682 ◽  
Author(s):  
Hyun-Kyong Kim ◽  
Mi-Seon Shin ◽  
Byung-Soo Youn ◽  
Churl Namkoong ◽  
So Young Gil ◽  
...  
Keyword(s):  
Neuropeptide Y ◽  
Energy Condition ◽  
Physiological Role ◽  
High Energy ◽  
Glucose Sensing ◽  
Energy Conditions ◽  
Related Peptide ◽  
Feeding Regulation ◽  
Nocturnal Feeding ◽  
Hypothalamic Regulation

Progranulin (PGRN) is a secreted glycoprotein with multiple biological functions, including modulation of wound healing and inflammation. Hypothalamic PGRN has been implicated in the development of sexual dimorphism. In the present study, a potential role for PGRN in the hypothalamic regulation of appetite and body weight was investigated. In adult rodents, PGRN was highly expressed in periventricular tanycytes and in hypothalamic neurons, which are known to contain glucose-sensing machinery. Hypothalamic PGRN expression levels were decreased under low-energy conditions (starvation and 2-deoxy-D-glucose administration) but increased under high-energy condition (postprandially). Intracerebrovetricular administration of PGRN significantly suppressed nocturnal feeding as well as hyperphagia induced by 2-deoxyglucose, neuropeptide Y, and Agouti-related peptide. Moreover, the inhibition of hypothalamic PGRN expression or action increased food intake and promoted weight gain, suggesting that endogenous PGRN functions as an appetite suppressor in the hypothalamus. Investigation of the mechanism of action revealed that PGRN diminished orexigenic neuropeptide Y and Agouti-related peptide production but stimulated anorexigenic proopiomelanocortin production, at least in part through the regulation of hypothalamic AMP-activated protein kinase. Notably, PGRN was also expressed in hypothalamic microglia. In diet-induced obese mice, microglial PGRN expression was increased, and the anorectic response to PGRN was blunted. These findings highlight a physiological role for PGRN in hypothalamic glucose-sensing and appetite regulation. Alterations in hypothalamic PGRN production or action may be linked to appetite dysregulation in obesity.

scholarly journals A Review of the Morphology, Physical Processes and Deposits of Modern Straits

2021 ◽  
pp. SP523-2021-76
Author(s):  
Robert W. Dalrymple
Keyword(s):  
High Energy ◽  
Energy Conditions ◽  
Physical Processes ◽  
Content Type ◽  
Fluvial Deposits ◽  
Sediment Waves ◽  
Contourite Drifts ◽  
Supplementary Material ◽  
Maximum Flooding Surface ◽  
Oceanic Currents

AbstractThis study reviews the morphology, hydrodynamics and sedimentology of 33 modern straits, including examples from diverse tectonic and climatic settings. Strait morphology ranges from short, simple straits to long, tortuous passages many 100s of kilometers long; depths range from 10 m to >1 km. The morphological building block of strait sedimentation is a constriction flanked by open basins; a single strait can contain one or several of these. Currents accelerate through the constrictions and decelerate in the basins, leading to a spatial alternation of high- and low-energy conditions. Currents in a strait can be classified as either ‘persistent’ (oceanic currents or density-driven circulation) or ‘intermittent’ (tidally or meteorologically generated currents). Constrictions tend to be bedload partings, with the development of transport paths that diverge outward. Deposition occurs where the flow decelerates, generating paired subaqueous ‘constriction-related deltas’ that can be of unequal size. Cross-bedding predominates in high-energy settings; muddy sediment waves and contourite drifts are present in some straits. In shallow straits that were exposed during the sea-level lowstand, strait deposits typically occur near or at the maximum flooding surface, and can overlie estuarine and fluvial deposits. The most energetic deposits need not occur at the time of maximum inundation.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5746061

scholarly journals The correlative behavior of sandbars and shoreline along Sulina – Sf. Gheorghe beaches (Danube Delta Coast)

2016 ◽  
Vol 18 (1) ◽  
pp. 19-31
Author(s):  
Florin TĂTUI
Keyword(s):  
High Energy ◽  
Sandy Beaches ◽  
Energy Conditions ◽  
Danube Delta ◽  
Dune System ◽  
Migration Rates ◽  
System Protection ◽  
Main Driver ◽  
Southern Central

Longshore sandbars along wave-dominated sandy beaches are important for beach-dune system protection during storms. Our analysis is based on 6 years of seasonal and annual bathymetric surveys along 16 km of erosive, stable and accumulative low-lying non-tidal beaches northward of Sf. Gheorghe arm mouth (Danube Delta – Romanian Black Sea coast). Our results show significant correlations established between longshore sandbar crest positions and morphology with more intense coupling between the inner and outer sandbar sub-systems during high-energy conditions and more frequent along the northern erosive sector in comparison with the southern/central accumulative/stable ones. There is a good connection between the long-term shoreline mobility and sandbars offshore migration rates along different sectors of the study area, with faster sandbars movement and shorter cycle return periods along the northern erosive sector in comparison with the central (stable) and southern (accretionary) sectors. The longshore variations of the nearshore slope are the main driver of the relationship between long-term sandbars dynamics and shoreline variability along the study site.

The onset of the early Toarcian flooding of the Pliensbachian carbonate platform of Central Tunisia (North-South Axis) as inferred from trace fossils and geochemistry

2021 ◽  
pp. SP514-2021-10
Author(s):  
Matías Reolid ◽  
Mohamed Soussi ◽  
Jesús Reolid ◽  
Wolfgang Ruebsam ◽  
Ilef Belhaj Taher ◽  
...  
Keyword(s):  
Carbonate Platform ◽  
High Energy ◽  
Trace Fossils ◽  
Energy Conditions ◽  
Local Conditions ◽  
Content Type ◽  
The North ◽  
Sea Bottom ◽  
Supplementary Material ◽  
South Axis

AbstractThe flooding of the Lower Jurassic shelf in the North Gondwana Palaeomargin during the early Toarcian occurred on a fragmented and irregular topography affected by differential subsidence—due to the activity of listric faults along the North-South Axis of Tunisia—that favoured lateral changes in facies and thickness at a kilometric scale. The onset of Toarcian sedimentation (Polymorphum ammonite Zone, NJT5c nannofossil Subzone) in two adjacent sections was characterised by the deposition of limestones under high-energy conditions. The Châabet El Attaris section was located in a depressed sub-basin, and recorded restricted environmental conditions owing to water stagnation and an oxygen-depleted sea-bottom. Therefore, dark mudstones developed, with increased TOC contents and enhanced accumulation of redox-sensitive elements. The sedimentation of limestones bearing gutter cast structures is related to gravity flows probably linked to storm activities. These processes favoured the remobilization of sediments at the sea floor, as well as oxygen input to bottom waters, as shown by the record of trace fossils including Zoophycos, Ophiomorpha, and secondarily, Chondrites and Diplocraterion. The thinly interbedded dark mudstones are locally rich in thin-shelled bivalves that re-colonised the sea bottom after the sedimentation of these high-energy deposits, and subsequently underwent mass mortality related to the return of oxygen-depleted conditions. The Kef El Hassine section is located in the upper part of a tilted, less subsident block, as indicated by its reduced thickness compared with the Châabet El Attaris section; the absence of dark mudstones implies oxic conditions. The Polymorphum Zone consists of limestones showing evidence of sedimentation under high-energy conditions, along with hardgrounds. The occurrence of Zoophycos (deep-tiers) in the upper part of some limestone beds of the Polymorphum Zone is linked to minor erosive processes. The top of the high-energy sequence—below the deposits of a marly interval corresponding to the Levisoni Zone—is interpreted as a hardground given the high content of belemnites and Arenicolites, some of them boring on the eroded Zoophycos and Thalassinoides. This study shows that the sedimentary expression of the Jenkyns Event is not uniform across Tunisia, supporting the importance of local conditions in determining the development of anoxic conditions.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5510162

scholarly journals CROSSING THE PHANTOM DIVIDE WITH k-ESSENCE IN BRANEWORLDS

2010 ◽  
Vol 25 (29) ◽  
pp. 2469-2481 ◽  
Author(s):  
LUIS P. CHIMENTO ◽  
MÓNICA FORTE ◽  
MARTÍN G. RICHARTE
Keyword(s):  
Equation Of State ◽  
High Energy ◽  
Chaplygin Gas ◽  
Energy Conditions ◽  
De Sitter ◽  
Effective Equation ◽  
Phantom Divide ◽  
Energy Regime ◽  
High Energy Regime ◽  
Stable Stage

We study a flat three-brane in the presence of a linear k field with nonzero cosmological constant Λ4. In this model the crossing of the phantom divide (PD) occurs when the k-essence energy density becomes negative. We show that in the high energy regime the effective equation of state has a resemblance of a modified Chaplygin gas while in the low energy regime it becomes linear. We find a scale factor that begins from a singularity and evolves to a de Sitter stable stage while other solutions have a super-accelerated regime and end with a big rip. We use the energy conditions to show when the effective equation of state of the brane-universe crosses the PD.

Observations of the Particle Size Distribution and Concentration in a Coastal System using an In Situ Laser Analyzer

2002 ◽  
Vol 36 (1) ◽  
pp. 59-69 ◽  
Author(s):  
Teresa Serra ◽  
Xavier Casamitjana ◽  
Jordi Colomer ◽  
Timothy C. Granata
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Water Column ◽  
Size Distribution ◽  
Posidonia Oceanica ◽  
High Energy ◽  
Suspended Particles ◽  
Energy Conditions ◽  
Coastal System

An in situ laser particle size analyzer (LISST-100, Sequoia Scientific, Inc.) has been used to study the particle size distribution and concentration of biological and non biological particles in the water column of a Mediterranean coastal system. Two field campaigns have been carried out during low and high energy conditions of the flow, caused by the passage of a storm front. For the low energy period, the water column remained stratified, whereas for the high energetic period the water column was warmer and well mixed. The first study dealt with the distribution of particles near the bottom of the coastal area. Here, two regions were taken into account. The first region was a sea-grass meadow of Posidonia oceanica and the second region was a barren sand area. The second study dealt with the determination of the vertical distribution of suspended particles in the whole water column of the system. The results showed a decrease in the vertical concentration of suspended particles in the water column with the passage of the storm front, which was associated with advection of warm water mass rather than by vertical mixing. In contrast, vertical resuspension determined the fate of suspended particles at the bottom of the water column and an increase of their concentration was found.

scholarly journals Linking evolutionary mode to palaeoclimate change reveals rapid radiations of staphylinoid beetles in low-energy conditions

2019 ◽  
Vol 66 (4) ◽  
pp. 435-444 ◽  
Author(s):  
Liang Lü ◽  
Chen-Yang Cai ◽  
Xi Zhang ◽  
Alfred F Newton ◽  
Margaret K Thayer ◽  
...  
Keyword(s):  
Body Size ◽  
Rapid Evolution ◽  
High Energy ◽  
Low Energy ◽  
Diversification Rate ◽  
Energy Conditions ◽  
Climate Factors ◽  
Direct Outcome ◽  
Rapid Radiations ◽  
Evolutionary Mode

Abstract Staphylinoidea (Insecta: Coleoptera) is one of the most species-rich groups in animals, but its huge diversity can hardly be explained by the popular hypothesis (co-radiation with angiosperms) that applies to phytophagous beetles. We estimated the evolutionary mode of staphylinoid beetles and investigated the relationship between the evolutionary mode and palaeoclimate change, and thus the factors underlying the current biodiversity pattern of staphylinoid beetles. Our results demonstrate that staphylinoid beetles originated at around the Triassic–Jurassic bound and the current higher level clades underwent rapid evolution (indicated by increased diversification rate and decreased body size disparity) in the Jurassic and in the Cenozoic, both with low-energy climate, and they evolved much slower during the Cretaceous with high-energy climate. Climate factors, especially low O2 and high CO2, promoted the diversification rate and among-clade body size disparification in the Jurassic. In the Cenozoic, however, climate factors had negative associations with diversification rate but little with body size disparification. Our present study does not support the explosion of staphylinoid beetles as a direct outcome of the Cretaceous Terrestrial Revolution (KTR). We suppose that occupying and diversifying in refuge niches associated with litter may elucidate rapid radiations of staphylinoid beetles in low-energy conditions.

scholarly journals Paleoecology of Cyclocrinites darwini (Miller) - a cyclocrinitid alga from the Cincinnatian series (Upper Ordovician)

1992 ◽  
Vol 6 ◽  
pp. 177-177
Author(s):  
Peter B. Lask
Keyword(s):  
Structural Similarity ◽  
High Energy ◽  
Energy Conditions ◽  
Upper Ordovician ◽  
Third Order ◽  
Coral Rubble ◽  
Lake Formation ◽  
Lateral Branches ◽  
Key Largo ◽  
Cincinnatian Series

Cyclocrinitids are considered to be calcareous green algae closely related to, or members of, the dasycladacean algae. Cyclocrinitids are characterized by a globular thallus 1-5 cm in diameter consisting of whorls of calcified meromes borne from a tubular or spherical central axis. The species Cyclocrinites darwini is distinguished from other cyclocrinitids by the presence of lateral branches arranged in a stellate pattern at the distal end of each merome.C. darwini is restricted to strata of the Cincinnatian Series. Specimens are commonly found in shale-filled channels cutting through nodular, irregularly-bedded limestones within the Mt. Auburn Formation and the lower Sunset Member of the Arnheim Formation. Numerous specimens are also known from the Bellevue Member of the Grant Lake Formation at Maysville, Kentucky. Each of these units has been interpreted to be the top of separate shoaling-upward, third-order cycles. These facies are abundantly fossiliferous, often consisting of broken, abraded, and reworked material.The modern dasyclad Neomeris is cited for its structural similarity to the cyclocrinitids and ecological parallels have been postulated as well. Neomeris and a similar dasyclad Batophora, thrive while attached to pieces of coral rubble at depths of less than 3 m in the high-energy conditions associated with a reef crest environment at Key Largo, Florida.It is likely that C. darwini lived under similar conditions, attached to rubble in shoaling areas. Preservation only occurred in instances when thalli were broken off from their holdfasts and swept into ripple troughs or downslope channels cutting across the shoals. It has been suggested that the presence of cyclocrinitids is indicative of relatively quiet environments below wave base. For Cyclocrinites darwini, the opposite would appear to be the case.

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