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Geosphere ◽  
2022 ◽  
Author(s):  
Charles C. Trexler ◽  
Eric Cowgill ◽  
Nathan A. Niemi ◽  
Dylan A. Vasey ◽  
Tea Godoladze

Although the Greater Caucasus Mountains have played a central role in absorbing late Cenozoic convergence between the Arabian and Eurasian plates, the orogenic architecture and the ways in which it accommodates modern shortening remain debated. Here, we addressed this problem using geologic mapping along two transects across the southern half of the western Greater Caucasus to reveal a suite of regionally coherent stratigraphic packages that are juxtaposed across a series of thrust faults, which we call the North Georgia fault system. From south to north within this system, stratigraphically repeated ~5–10-km-thick thrust sheets show systematically increasing bedding dip angles (<30° in the south to subvertical in the core of the range). Likewise, exhumation depth increases toward the core of the range, based on low-temperature thermochronologic data and metamorphic grade of exposed rocks. In contrast, active shortening in the modern system is accommodated, at least in part, by thrust faults along the southern margin of the orogen. Facilitated by the North Georgia fault system, the western Greater Caucasus Mountains broadly behave as an in-sequence, southward-propagating imbricate thrust fan, with older faults within the range progressively abandoned and new structures forming to accommodate shortening as the thrust propagates southward. We suggest that the single-fault-centric “Main Caucasus thrust” paradigm is no longer appropriate, as it is a system of faults, the North Georgia fault system, that dominates the architecture of the western Greater Caucasus Mountains.


2021 ◽  
Vol 126 (4) ◽  
pp. 513-519
Author(s):  
Jean-Pierre Vacher ◽  
Roberto D'Agostino ◽  
Sylvain Ursenbacher

Sphingonotus is a genus of grasshoppers that contains species groups with several closely related species, among which Sphingonotus caerulans and an unnamed Sphingonotus that are found in continental France. The exact distribution of both species is still under investigation, but it is believed that S. caerulans might be restricted to the northern part of the country, and that Sphingonotus sp. occurs in the southern half and might reach the north east. We explored the genetic identity of Sphingonotus grasshoppers in the upper Rhine Valley of Alsace (northeastern France) using combined fragments of mtDNA ND5 and cytb genes included with other available samples in ML and Bayesian phylogenetic analyses. The results indicate that the five specimens sampled within this region belong to S. caerulans. The actual distribution of Sphingonotus sp. in France remains to be investigated with wider sampling, especially to get a better knowledge on its northern limit.


Author(s):  
P. Clariana ◽  
R. Soto ◽  
C. Ayala ◽  
A. M. Casas-Sainz ◽  
T. Román-Berdiel ◽  
...  

AbstractA new gravity survey (1164 gravity stations and 180 samples for density analysis) combined with two new geological cross sections has been carried out in a sector of the Central Pyrenees in order to improve the characterization of basement and cover architecture. From North to South, the study area comprises the southern half of the Axial Zone and the northernmost part of the South-Pyrenean Zone. New gravity data were combined with previous existing databases to obtain the Bouguer and residual anomaly maps of the study area. The two cross sections, oriented NNE–SSW, were built from field data and previous surficial and subsurface data and cross the La Maladeta plutonic complex. The residual anomaly map shows values ranging from −18 to 16 mGal and anomalies mainly oriented N120E. The two 2.5D modelled cross sections show similar observed gravity curves coinciding with similar interpreted structural architecture. Data show a gravity high oriented N120E coinciding with the Orri basement thrust sheet and an important gravity depression, with the same orientation, coinciding with the leading edge at depth of the Rialp basement thrust sheet and interpreted as linked to a large subsurface accumulation of Triassic evaporites. The volume at depth of the La Maladeta and Arties granites has been constrained through gravity modelling. This work highlights that the combination of structural geology and gravity modelling can help to determine the structural architecture of an orogen and localize accumulations of evaporites at depth.


2021 ◽  
Vol 958 (1) ◽  
pp. 012023
Author(s):  
K Al-Salem ◽  
A Al-Rashed

Abstract Failaka Island is the second-largest and one of the most important islands of Kuwait from the point of view of tourism located in the north Arabian Gulf. It has a marina constructed in 1979 and managed by the Ministry of Communication (MOC) and a tourism enterprise, and is widely used for its ferry landing facility. The coastal waters around Failaka are turbid and current velocities tend to be as high as ~0.5 m/s during spring tide. The marina basin, with axial plan view dimensions of about 285 m by 260 m experiences shoaling of naturally flocculated fine (cohesive) sediment and coarse sand in the entrance channel and more generally in the southern half of the basin. A particularly noteworthy zone of heavy and visible shoaling is along the inner side of the south breakwater close to the entrance. The marina at Failaka Island is suffering from siltation and sediment deposing issues. This study was carried out numerically to assess the annual sedimentation, sediment direction, and longshore current from locations around the existing marina to help in a suggestion of the solutions to reduce the siltation and sediment deposing based on sediments transport direction on marina entrance. A newly developed numerical solution for annual longshore sediments transport was used to estimate the total sediment transport and its direction. The study shows that the annual sediment transport directions which affect the Fialaka marina entrance are coming from the south to north due to wave action.


Author(s):  
А. В. Михайлов ◽  
М. И. Кулакова

В 2018 г. были продолжены археологические исследования поселения X-XI вв. у д. Горожане (Новосокольнический район Псковской области). Была доисследована южная половина раскопа 1 (24 кв. м). Раскоп 2 (площадь 16 кв. м) был заложен в южной части поселения у западного края площадки. Общая площадь исследований составила 40 кв. м. Под слоем распашки в раскопе 1 сохранился непотревоженный культурный слой мощностью до 0,2 м, который содержит следы крупного пожара. Предварительная датировка пожара - середина - вторая половина X в. В раскопе 2 слой перепахан до самого материка - борозды тракторной распашки прослежены на всей площади раскопа. Керамический комплекс более чем на 90% состоит из лепной керамики. Находки гончарной керамики немногочисленны. Впервые на памятнике встречены фрагменты западнославянской («балтийской») керамики. Коллекция индивидуальных находок представлена 327 предметами. Значительную часть коллекции составляют стеклянные и каменные бусы. Кроме того, среди находок представлены предметы вооружения, украшения, торговый инвентарь, бытовые предметы, несколько дирхемов. In 2018, archaeological excavations of the 10-11 centuries settlement near Gorozhane (Novosokolnichesky district, Pskov Region) were continued. The excavations of the southern half of the site 1 (24 sq. m.) was completed. In the southern part of the settlement at the western edge of the site, excavation 2 (16 sq. m.) was started. The total area of the research was 40 sq. m. Under the plowed layer in excavation 1, there has been preserved an undisturbed cultural layer thick to 0.2 m, which contains traces of a large fire. The fire is preliminary dated by the middle of the second half of the 10 century. In excavation 2, the layer was plowed to the very mainland - the furrows of tractor plowing were traced throughout the entire area of the excavation. The 90 % of the ceramic complex is stucco ceramics. Pottery items are few. For the first time, fragments of West Slavic (“Baltic”) ceramics were found on the site. The collection of individual finds is represented by 327 items. A significant part of the collection consists of glass and stone beads. Besides, the finds are represented by weapons, jewelry, trade equipment, household items, several dirhams.


2021 ◽  
Author(s):  
◽  
Rollo D Arnold

<p>In undertaking this study I had the two-fold object of investigating an area of our history which appears to me to have been too long neglected, and, in presenting my results, of grappling with the problems of writing colonial social history. So far we have only had limited studies of selected aspects of the bush settlement era of North Island history. I believe we cannot properly understand this great colonising effort unless we endeavour both to view it whole and to place it in the larger context of colonial history. I have therefore taken the whole southern half of the North Island as my area of study, and have endeavoured to show how the assault on the Great Bush relates to the aftermath of the Maori Wars, the larger social history of the colony as a whole, and the agrarian history of the Old World from which so many of the bush settlers came. I had hoped originally to carry the story through at least three decades, but it became apparent that my broad canvas required some kind of narrowing, and I reluctantly decided to limit myself to the period 1869-1881, which seemed to have a sufficient political and economic unity to stand on its own. I have, however, done a good deal of research on through the 1880s and 1890s, and this, I trust, has enabled me to see the significance of the 1870s with a sense of perspective.</p>


2021 ◽  
Author(s):  
◽  
Rollo D Arnold

<p>In undertaking this study I had the two-fold object of investigating an area of our history which appears to me to have been too long neglected, and, in presenting my results, of grappling with the problems of writing colonial social history. So far we have only had limited studies of selected aspects of the bush settlement era of North Island history. I believe we cannot properly understand this great colonising effort unless we endeavour both to view it whole and to place it in the larger context of colonial history. I have therefore taken the whole southern half of the North Island as my area of study, and have endeavoured to show how the assault on the Great Bush relates to the aftermath of the Maori Wars, the larger social history of the colony as a whole, and the agrarian history of the Old World from which so many of the bush settlers came. I had hoped originally to carry the story through at least three decades, but it became apparent that my broad canvas required some kind of narrowing, and I reluctantly decided to limit myself to the period 1869-1881, which seemed to have a sufficient political and economic unity to stand on its own. I have, however, done a good deal of research on through the 1880s and 1890s, and this, I trust, has enabled me to see the significance of the 1870s with a sense of perspective.</p>


Geosciences ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 358
Author(s):  
Emma Wilson Kelly ◽  
Felix Jose

Hurricane Charley made landfall on the Gulf Coast of Florida on 13 August 2004 as a category 4 hurricane, devastating North Captiva Island. The hurricane caused a breach to occur to the southern end of the island, which naturally healed itself over the course of three years. By 2008, the cut was completely repaired geomorphologically. LiDAR data analysis shows the northern half of the island has been subjected to persistent erosion from 1998–2018, while the southern half experienced accretion since 2004, including the complete closure of the “Charley cut”. The maximum volume of sediment erosion in the northern sector of the island (R71–R73) from 2004–2018 was −85,710.1 m3, which was the source of southern accretion. The breached area of the island (R78b–R79a) obtained 500,163.9 m3 of sediments from 2004–2018 to heal the cut made by Hurricane Charley. Along with LiDAR data analysis, Google Earth Pro historical imageries and SANDS volumetric analysis confirmed the longshore transport of sediments from the northern to the southern end of the island. Winter storms are mainly responsible for this southerly longshore transport and are hypothesized to be the main factor driving the coastal dynamics that restored the breach and helps in widening the southern end of North Captiva Island.


2021 ◽  
Vol 288 (1957) ◽  
pp. 20211195
Author(s):  
S. L. Hamilton ◽  
V. R. Saccomanno ◽  
W. N. Heady ◽  
A. L. Gehman ◽  
S. I. Lonhart ◽  
...  

The prevalence of disease-driven mass mortality events is increasing, but our understanding of spatial variation in their magnitude, timing and triggers are often poorly resolved. Here, we use a novel range-wide dataset comprised 48 810 surveys to quantify how sea star wasting disease affected Pycnopodia helianthoides , the sunflower sea star, across its range from Baja California, Mexico to the Aleutian Islands, USA. We found that the outbreak occurred more rapidly, killed a greater percentage of the population and left fewer survivors in the southern half of the species's range. Pycnopodia now appears to be functionally extinct (greater than 99.2% declines) from Baja California, Mexico to Cape Flattery, Washington, USA and exhibited severe declines (greater than 87.8%) from the Salish Sea to the Gulf of Alaska. The importance of temperature in predicting Pycnopodia distribution rose more than fourfold after the outbreak, suggesting latitudinal variation in outbreak severity may stem from an interaction between disease severity and warmer waters. We found no evidence of population recovery in the years since the outbreak. Natural recovery in the southern half of the range is unlikely over the short term. Thus, assisted recovery will probably be required to restore the functional role of this predator on ecologically relevant time scales.


MAUSAM ◽  
2021 ◽  
Vol 71 (1) ◽  
pp. 79-94
Author(s):  
MAHMOUDI PEYMAN ◽  
JAHANSHAHI SEYED MAHDI AMIR ◽  
MORADI ZOHREH

The current study aims to model the behaviour of wet and dry days in Iran using Markov Chain Models. To this end, data related to daily precipitation of 44 synoptic stations for a 25-years interval (1991-2015) was obtained from Iran Meteorological Organization. Then, the Markov features of dry and wet days of Iran including stationary probabilities of dry and wet days occurrence, the expected length of dry periods, the expected length of wet periods, dry-wet spells cycle, return periods for dry or wet episodes and finally, the possibility of occurrence of the continuity of dry days for 5, 10, 15, 20, 25 and 30 days were calculated for all the synoptic stations in a seasonal scale. The results showed that there is the occurrence of dry short continuities (5 and 10 days) in three seasons of autumn, winter and spring with different possibilities all over Iran. However, the possibility of occurrence of long-term dry continuities (more than 20 days) is variable in terms of season and place so that in winter, no possibility of occurrence of this type of continuities is obvious in the northern half of Iran. As in autumn and spring those are the end and beginning of long-term stability conditions of the atmosphere in the upper atmosphere levels of Iran, the possibility of periodical occurrence of 30-days dry days, particularly in the southern half of Iran increases. In addition, the expected return periods for dry days is almost steady for every part of Iran and is in the range between 1 and 2 days. However, the number of return days to a precipitation period does not follow this rule and varies for every part of Iran so that from 2.15 days in autumn to 79 days in spring is variable, pointing to the climate diversity of Iran.


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