scholarly journals Application de la géophysique (méthode géoélectrique) à la reconnaissance du plateau de Meknès (Bassin de Saïss), Maroc [Application of geophysical prospecting (geoelectrical method) for the hydrogeological reconnaissance of the Meknes Plateau (Saiss basin), Morocco]

2001 ◽  
Vol 3 (1-2) ◽  
pp. 35-53
Author(s):  
Ali ESSAHLAOUI ◽  
Hassane SAHBI ◽  
Nacer EL YAMINE
Keyword(s):  
Global Structure ◽  
Mountain Range ◽  
Quantitative Interpretation ◽  
Geophysical Prospecting ◽  
The South ◽  
Borehole Data ◽  
The North ◽  
Geophysical Study ◽  
Electrical Soundings ◽  
Middle Atlas

A geophysical study by the geoelectrical method using electrical soundings, has been carried out in the south-western and southern parts of the Meknes plateau which belongs to the Saïss basin located between the Rif mountain range to the North and the Middle Atlas range to the South. Two significant aquifers are found in the Meknes Plateau: the first one is located in the shallow Plio-Quaternary formations while the second one is inside the deep carbonate beds of the Lias. The quantitative interpretation of electrical soundings from both surface and borehole data resulted in isoresistivity, isopach and longitudinal isoconductance maps that have both a quantitative and a qualitative interest for a better understanding of the global structure of the hydrogeological basin of Saiss.

scholarly journals Effect of Extreme Weather Events on the Sedimentation of the Bay of Samaná, Dominican Republic (1900–2016)

2019 ◽  
Vol 11 (3) ◽  
pp. 56 ◽  
Author(s):  
Ramón A. Delanoy ◽  
Misael Díaz-Asencio ◽  
Rafael Méndez-Tejeda
Keyword(s):  
Accumulation Rate ◽  
Marine Species ◽  
Extreme Weather ◽  
Extreme Weather Events ◽  
Rainfall Regime ◽  
Mountainous Area ◽  
Mountain Range ◽  
The South ◽  
The North ◽  
Weather Events

The Bay of Samaná, formed by tectonism and sedimentation, is delimited to the north by the peninsula of the same name, to the south by the north slope of the Eastern Mountain Range and Los Haitises National Park, to the east by the Atlantic Ocean, and to the west by the ancient Gran Estero, today the Lower Yuna. There follows a process of continuous degradation by the existing tectonic forces and the sediment contributions by the Yuna, Yabón, and La Yeguada rivers to the south as well as by the landslides of the mountainous area of the Samaná Peninsula, during periods of storms and hurricanes. The coastal area of Samaná Bay has altered by 2.17 km2 at the mouth of the Yuna River from 2003–2015. The high turbidity level has affected coral reefs and marine species.  The  mangroves  are  lost  faster  than  they  are  regenerated  by  the  coastline’s change. Variations in the elemental compositions of calcium and iron show the terrigenous influence on the dynamics of the bay during Extreme Weather Events (EWP) in the river basins that flow into it. Abrupt changes in the rainfall regime produced an equal change in the estuary sedimentation regime, according to the 210Pb. In the 2007–2016 period, a column of sediment that reached 38 cm and a 12 cm to 8.4 km column were deposited 4 km southeast of the municipality of Sánchez and east of the mouth of the Yuna River. The Sedimentary Accumulation Rate is very high, and the content of heavy metals exceeds the threshold values of Table SQuirt.

scholarly journals The Tsakonian Dialect.—I

1913 ◽  
Vol 19 ◽  
pp. 133-173 ◽  
Author(s):  
C. A. Scutt
Keyword(s):  
East Coast ◽  
Mountain Range ◽  
The South ◽  
The West ◽  
Northern Boundary ◽  
Grazing Land ◽  
Bare Rock ◽  
The North ◽  
Cultivable Land ◽  
The Village

The area over which the Tsakonian dialect is spoken lies on the east coast of the Peloponnese between the Parnon range and the sea. Its northern boundary is roughly the torrent which, rising on Parnon above Kastánitsa, flows into the sea near Ayios Andréas, its southern the torrent which, also rising on Parnon, passes through Lenídhi to the sea. A mountain range stretches along the coast from end to end of the district, reaching its highest point (1114 metres) in Mt. Sevetíla above the village of Korakovúni. Between Tyrós and Pramateftí, the seaward slopes of this range are gentle and well covered with soil. Behind these coast hills there stretches a long highland plain, known as the Palaiókhora, which, in the north, is fairly well covered with soil, but gradually rises towards the south into a region of stony grazing land, and terminates abruptly in the heights above Lenídhi. The high hill of Oríonda rises out of the Palaiókhora to the west and forms a natural centre-point of the whole district. Behind it stretching up to the bare rock of Parnon, is rough hilly country, cut here and there by ravines and offering but rare patches of cultivable land.

The Rediscovery of Sphenomorphus malayanus Doria, 1888 (Squamata: Scincidae) from the Titiwangsa Mountain Range of Peninsular Malaysia and its re-description as S. senja sp. nov.

Zootaxa ◽  
2015 ◽  
Vol 3931 (1) ◽  
pp. 63 ◽  
Author(s):  
L. LEE GRISMER ◽  
EVAN S. H. QUAH
Keyword(s):  
New Species ◽  
Type Specimen ◽  
Peninsular Malaysia ◽  
Mountain Range ◽  
The South ◽  
Additional Specimen ◽  
The North ◽  
West Sumatra ◽  
Cameron Highlands

The discovery of an additional specimen of Sphenomorphus malayanus Doria, 1888 from Gunung Brinchang, Cameron Highlands, Pahang in Peninsular Malaysia reveals that it is not conspecific with the type specimen from Gunung Singgalan, West Sumatra, 600 km to the south. The new specimen and an additional specimen previously collected from Gunung Gerah, Perak, Peninsular Malaysia, 56 km to the north, are described here as the new species S. senja sp. nov. and differ from S. malayanus by having a larger SVL (60.0–65 mm versus 53 mm); a deeply recessed as opposed to a shallow tympanum; 72 or 73 versus 76 paravertebral scales; eight or nine superciliary scales as opposed to 10; and the posteriormost superciliary scale being large as opposed to small. Cameron Highlands is unique among other upland areas in Peninsular Malaysia in that it harbors an unprecedented number of closely related ecological equivalents living in close sympatry or syntopy. 

General characteristics of active andean volcanoes and a summary of their activities during recent centuries

1963 ◽  
Vol 53 (6) ◽  
pp. 1415-1433
Author(s):  
Lorenzo Casertano
Keyword(s):  
Volcanic Activity ◽  
Central Valley ◽  
Mountain Range ◽  
Historical Account ◽  
The South ◽  
Chilean Coast ◽  
The North ◽  
The Andes ◽  
Transverse Fractures ◽  
Coastal Mountain

ABSTRACT An oceanic deep lies off the Chilean coast, bordered on the east by a coastal mountain range, a discontinuous central valley, and the high cordillera of the Andes. The Chilean volcanoes are found on lineaments that in general coincide with, or are sub parallel to, axis of the Andes. In north Chile they lie along en echelon fractures and, in some cases, along transverse fractures. In the south, the alignment of the volcanoes lies west of the axis of the Andes. Where the Central Valley is not well developed, active volcanoes are scarce. Recent lavas range from basalt in the south to rhyolite in the north. Volcanic activity appears to be decreasing. Details are given of individual volcanoes, and a list of active Andean volcanoes south of Volcan Misti is presented with a historical account of their activity.

Chronologie de l'ouverture du bassin des Ksour (Atlas Saharien, Algerie) au debut du Mesozoique

2001 ◽  
Vol 172 (3) ◽  
pp. 285-293 ◽  
Author(s):  
A. K. Yelles-Chaouche ◽  
R. Ait Ouali ◽  
R. Bracene ◽  
M. E. M. Derder ◽  
H. Djellit
Keyword(s):  
The South ◽  
Borehole Data ◽  
The West ◽  
High Atlas ◽  
High Plateau ◽  
The North ◽  
Seismic Lines

Abstract The Ksour mountains (northwest Algeria) belong to the western part of the Saharan Atlas. They are located between the High Plateau to the north, the South Atlas Front to the south and the Moroccan High Atlas to the west (fig. 1a). During the last decades, the Ksour mountains were the focus of several studies, mainly based on sedimentary analyses [Cornet, 1952; Bassoulet, 1973; Baiche, 1975; Ameur, 1978; Ait Ouali, 1991; Mekahli, 1995; Elmi et al., 1998]. These studies indicate that the Ksour mountains correspond to an old asymmetric rift, trending NE-SW, which underwent extension during the Triassic and Liassic [Ait Ouali, 1991; Frizon de Lamotte et al., 2000]. In order to precise the timing of the rifting processes we have analysed subsurface data (seismic lines and borehole data) from the Sonatrach Company.

scholarly journals VÝZNAM VALOUNOVÝCH ANALÝZ LEDOVCOVÝCH SEDIMENTŮ PRO PALEOGEOGRAFICKÉ REKONSTRUKCE PLEISTOCENNÍHO KONTINENTÁLNÍHO ZALEDNĚNÍ JESENICKA

2014 ◽  
Vol 21 (1-2) ◽  
Author(s):  
Martin Hanáček
Keyword(s):  
Ice Sheet ◽  
Middle Pleistocene ◽  
Mountain Range ◽  
The South ◽  
Glacial Sediments ◽  
The North ◽  
Depositional System ◽  
New Interpretation ◽  
Mountain Part ◽  
Continental Glaciation

Sediments of Middle Pleistocene continental glaciation at the northern foothill of Rychleby Mts. and Zlaté Hory Highland contain clasts of local to Nordic provenance. Local clasts originating from crystalline units of the above-mentioned mountains prevail. These clasts have palaeogeographical importance for a local reconstruction of ice sheet advance directions. General advance direction from NW to SE has been reconstructed basing on local clasts in earlier studies (mainly Gába 1981a, b; Gába – Pek 1999). This interpretation has been based on the fact that the shares of clasts of rocks cropping primarily in NW part of the Rychleby Mts. decrease towards the SE. New, in this contribution presented, interpretation reconstructs the ice sheet advance generally from the North to the South, with variations conditioned by local landscape. Glacial sediments have at each site in the NW–SE direction petrological composition, which corresponds to the lithology of a mountain part south of the site of concern. Gierałtow orthogneiss clasts predominate in glacial deposits of the NW part of the main ridge forefield of Rychleby Mts. The share of amphibolites rises significantly in the forefield of the central part of the Rychleby Mts. main ridge. Feldspar and muscovite quartzites dominate in the area of Sokol Ridge and Zlaté Hory Highlands. The new interpretation presumes the colluvial, alluvial and fluvial transport of the debris towards the northern and north-eastern mountain forefi eld before the ice sheet advance. Ice sheet advancing from the North eroded and transported this debris towards the South. Preglacial sediments corresponded petrologically to the mountain parts, from which they originated. Thus, glacial sediments have petrological composition, which corresponds to the lithology of those mountain parts, which lies south of the sediment occurrence. Part of the debris has been transported by Nisa Kłodzka River from the West towards the East already before the glaciation.The following pattern could be found in the petrological composition of the glacial sediments gravel fraction. Sediments with monotonous composition of local clasts contain low shares of Nordic and Poland clasts (~2–4 %). On the contrary, sediments with polymict composition of local clasts contain relatively high shares of Nordic and Poland clasts (up to 27 %). Monotonous and distant provenance poor sediments originated at places, where the source preglacial deposits must have been petrologically monotonous considering the lithology of source areas. Concurrently, morphologically conditioned preglacial accumulation of vast lithologically monotonous deposits took place at some places (proximal parts of mountain ridges and saddles foothill). Rather polymict and distant provenance clast rich sediments originated during the later phase of ice sheet decay. Debris from the whole ice sheet body, not only from the glacier base or its front, released to the depositional system at that time. Sites with these sediments are located beyond the mountain foothill, where mixing of debris originating from alluvial fans or rivers flowing form the mountain range took place. Petrologically by far more monotonous sediments have been deposited closer to the mountain foothill. Quartz clasts are mostly of local origin and have together with other clasts been part of preglacial sediments. Part of quartz clasts has been reworked from fluvial deposits of present Poland or they might originate from the Nordic areas.

scholarly journals Geometry of glaciofluvial deposits and dynamics of the Lyonnais lobe ice front during the last glacial period (France, Northern Alps)

2021 ◽  
Author(s):  
Thibault ROATTINO ◽  
Christian CROUZET ◽  
Jean-Francois BUONCRISTIANI ◽  
Hélène TISSOUX
Keyword(s):  
Western Alps ◽  
The South ◽  
Borehole Data ◽  
Maximum Extension ◽  
Last Glacial ◽  
The North ◽  
River Terraces ◽  
Glaciofluvial Deposits ◽  
Elevation Model ◽  
The Last Glacial

Previous studies in the foreland of the French Western Alps, based on the analysis of geomorphological criteria for the internal moraine complex, show several stages of retreat or stagnation of the Lyonnais ice lobe during marine isotopic stages 4 and 2. Based on the results of several dating techniques, the age of the maximum extension of the Lyon ice lobe must have occurred during MIS 4. This result is in contrast with a consensus on the maximum extension of alpine glaciers during MIS 2. During the Last Glacial Maximum, in the western part of the Lyonnais ice lobe, glaciofluvial corridors were active during flash floods with Würmian meltwater. Today, these corridors are dead valleys and display a series of terraces. In this paper, we analyse the sedimentary geometries and dynamics of three glaciofluvial corridors (Moidieu, Septeme and Heyrieux) located at the front of the internal moraine complex of the Lyonnais ice lobe. Upstream, the Moidieu corridor then splits into three branches called North Moidieu, Central Moidieu and South Moidieu. Glaciofluvial deposits in the corridors are composed of pebbles and gravels in a sandy matrix. Sedimentary structures show mass flow events and the migration of river bars in braided channels which is characteristic of proximal glaciofluvial rivers in a proglacial environment. According to a new geomorphological map built using a high-resolution digital elevation model and an isopach map of the Quaternary deposits created from a compilation of the borehole data, we suggest that these corridors correspond to ‘tunnel valleys’ built during the most extensive Riss glaciation. Then during the Würm maximum glacial extension, these ‘tunnel valleys’ show complex infilling due to various glaciofluvial events. In the three corridors, the number of river terraces can be better defined by using new geomorphological analyses. A total of five Würm terraces can be observed: two in the north and three in the south. This difference between the south and north is probably a result of climatic and tectonic forcing.

New constraints on the geometry of the Lac Bouchette gabbro – anorthosite from magnetotellurics and magnetics

1995 ◽  
Vol 32 (9) ◽  
pp. 1365-1377 ◽  
Author(s):  
R. L. Kellett
Keyword(s):  
High Frequency ◽  
Seismic Reflection ◽  
Fault Zones ◽  
The South ◽  
Grenville Province ◽  
Magnetotelluric Soundings ◽  
The North ◽  
Geophysical Study ◽  
Magnetic Modelling ◽  
Tectonic Boundaries

A cross section of the resistivity structure through the Lac Bouchette gabbro–anorthosite provides a new image of the thin-skinned geometry of an allochthonous terrane in the western Grenville Province of Canada. Two-dimensional inversion of high-frequency magnetotelluric soundings and magnetic modelling indicate that the gabbro–anorthosite is a 1.5 km thick slice bounded by conductive thrust faults. Graphite, which is present at the margins of the gabbro–anorthosite and in the metasedimentary Réservoir Cabonga terrane to the south, is the most likely source of the enhanced electrical conductivity in the fault zones. The southern margin of the gabbro–anorthosite dips at about 15° to the south beneath the Réservoir Cabonga terrane. The gabbro–anorthosite can be divided into a highly magnetic gabbroic body in the south, a less magnetic metagabbro in the north, and a thin anorthositic lense in the centre. The combination of closely spaced magnetotelluric soundings and magnetic modelling provides independent constraints for gravity and seismic reflection studies in progress. The geometry of the Lac Bouchette gabbro–anorthosite, revealed by this geophysical study, supports a hypothesis that some gabbro–anorthosites behave as competent blocks adjacent to the major tectonic boundaries of the Grenville Province.

Spatial distribution of denudation processes in Bhutan

2021 ◽  
Author(s):  
Małgorzata Mazurek ◽  
Zbigniew Zwoliński ◽  
Przemysław Niedzielski
Keyword(s):  
Water Samples ◽  
Geological Structure ◽  
Middle Part ◽  
Mountain Range ◽  
River Channels ◽  
The South ◽  
Monsoon Period ◽  
River Waters ◽  
The North ◽  
Belt System

<p>Bhutan, being a Himalayan mountain country, extends ca. 305 km from west to east and 145 km from south to north, covering an area of 47,000 km<sup>2</sup>. Bhutanese Himalaya mountains are divided into three latitudinal belts from south to north: the sub-Himalayas or Himalayan foothills (up to 1,500 m in altitude), the inner Himalayas or middle ranges with flat valleys (from 1,500 to 4,500 m), and the Great Himalayas of high mountains (about 4 500 m). The Black Mountain Range, stretching longitudinally, divides this country into the eastern and western parts. The belt system of landforms is closely related to the geological structure. In the north, metamorphic and crystalline rocks (mainly gneisses and granites) dominate, while in the south there are sedimentary rocks associated with the molasse-like sediments in the Siwalik range. The distribution of precipitation from approx. 500 mm in the north to 5000 mm in the south of the country relates to this geological and morphological belt system. The main rivers flow longitudinally and have perpendicular tributaries. The digital elevation model of Bhutan was analysed geomorphometrically and, on this basis, places with high potential mechanical denudation were identified. The most evident manifestation of this denudation are numerous landslides occurring on the valley slopes. These landslides, especially in the monsoons period, deliver enormous amounts of landslide material to the valley bottoms, and most often directly to the river channels. The landslide material in the form of fluvial material is further transported along the rivers and deposited in the foreland of the Himalayas. After the summer monsoon period, water samples were collected in selected rivers. The collected water samples were subjected to hydrochemical analyzes. The studied river waters in the middle part of the country are characterized by low mineralization. The obtained results allow for a preliminary characterization of the spatial diversification of the denudation potential of Bhutan's river waters. Referring to the physiographic division of Bhutan, it can be confirmed that the middle zones, meridional ridges and valleys of this country are characterized by low chemical denudation and high mechanical denudation, while the southern tips of the country Front Hills and Piedmont are dominated by accumulation processes due to a significant reduction in river gradient.</p>

scholarly journals 3D density modelling of Gemeric granites of the Western Carpathians

2017 ◽  
Vol 68 (3) ◽  
pp. 177-192 ◽  
Author(s):  
Ján Šefara ◽  
Miroslav Bielik ◽  
Jozef Vozár ◽  
Martin Katona ◽  
Viktória Szalaiová ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
Lower Boundary ◽  
Western Carpathians ◽  
Mountain Range ◽  
The South ◽  
Geophysical Research ◽  
The North ◽  
Basement Rocks ◽  
Tectonic Contact ◽  
Upper Boundary

Abstract The position of the Gemeric Superunit within the Western Carpathians is unique due to the occurrence of the Lower Palaeozoic basement rocks together with the autochthonous Upper Palaeozoic cover. The Gemeric granites play one of the most important roles in the framework of the tectonic evolution of this mountain range. They can be observed in several small intrusions outcropping in the western and south-eastern parts of the Gemeric Superunit. Moreover, these granites are particularly interesting in terms of their mineralogy, petrology and ages. The comprehensive geological and geophysical research of the Gemeric granites can help us to better understand structures and tectonic evolution of the Western Carpathians. Therefore, a new and original 3D density model of the Gemeric granites was created by using the interactive geophysical program IGMAS. The results show clearly that the Gemeric granites represent the most significant upper crustal anomalous low-density body in the structure of the Gemeric Superunit. Their average thickness varies in the range of 5–8 km. The upper boundary of the Gemeric granites is much more rugged in comparison with the lower boundary. There are areas, where the granite body outcrops and/or is very close to the surface and places in which its upper boundary is deeper (on average 1 km in the north and 4–5 km in the south). While the depth of the lower boundary varies from 5–7 km in the north to 9–10 km in the south. The northern boundary of the Gemeric granites along the tectonic contact with the Rakovec and Klátov Groups (North Gemeric Units) was interpreted as very steep (almost vertical). The results of the 3D modelling show that the whole structure of the Gemeric Unit, not only the Gemeric granite itself, has an Alpine north-vergent nappe structure. Also, the model suggests that the Silicicum–Turnaicum and Meliaticum nappe units have been overthrusted onto the Golčatov Group.

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