Syn-Collision Folding and Multi-Layers Detachment in the Molassic Basin, Northeastern Tunisia

Abstract Tunisia had been the place of various tectonic episodes which have drawn the actual structural map of the country. The Neogene period was the most active period in which the collision contributed to the mountain ranges formation such as the Atlassic chain. The contrast of mechanical behavior between the different sedimentary units of the cover and the substratum is a determining factor that has controlled the deformation style of many folding structures. Detachment folding has been studied on the basis of field and seismic data examples from the Northeastern Tunisia. We discuss different aspects of detachment to constrain the chronology of structural events and understand the cover‒substratum relationship during the major folding phases. In the present paper, we found that the deformation style admitted previously do not reflect adequately the tectonic structure of Kechabta Neogene basin (North of Tunisia). The cover-substratum relationship study at this area revealed two major shortening phases; the first had been happened during the Upper Tortonian and the second in the Lower Quaternary. The resulting folding style is characterized by disharmonic and multi-layers detachment phenomena produced by incompetent evaporitic sequences. The two described folding phases are superimposed and testify at a large scale the continental collision which controls the North African margin during the Late Miocene to the Quaternary.

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The Roman and Byzantine Defences of Lepcis Magna

Papers of the British School at Rome ◽

10.1017/s0068246200006425 ◽

1953 ◽

Vol 21 ◽

pp. 42-73 ◽

Cited By ~ 7

Author(s):

R. G. Goodchild ◽

J. B. Ward Perkins

Keyword(s):

Large Scale ◽

North African ◽

The North ◽

Ground Survey ◽

Ancient City ◽

Preliminary Study ◽

Epigraphic Evidence ◽

The City

During the North African campaigns of 1941–3 numerous air-photographs of the Tripolitanian coast were taken by the R.A.F. for operational purposes, and the site of Lepcis Magna was included in the area covered. Examination of these photographs (pl. XV) showed many suggestive features relating to the defences of the ancient city, and a preliminary ground survey was later (1947–50) undertaken to establish, with a minimum of excavation, the course of the successive wall-circuits.The results of this investigation are described below, and are discussed in relation to the historical and epigraphic evidence. It is not claimed that these results are exhaustive, or that they will not need modification in the light of future discoveries. Since, however, there is little likelihood of any early resumption of large-scale excavations at Lepcis, this preliminary study may help to illustrate the growth and subsequent decline of the city that came to be the most important centre between Carthage and Alexandria.

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Regional to Global Evolution of Impacts of Parameterized Mountain-Wave Drag in the Lower Stratosphere

Journal of Climate ◽

10.1175/jcli-d-19-0076.1 ◽

2020 ◽

Vol 33 (8) ◽

pp. 3093-3106 ◽

Cited By ~ 1

Author(s):

Christopher G. Kruse

Keyword(s):

General Circulation ◽

Large Scale ◽

Climate Model ◽

Wave Drag ◽

Mountain Wave ◽

Global Features ◽

Mountain Ranges ◽

The North ◽

Global Evolution ◽

And Diffusion

AbstractMountain ranges are regional features on Earth, as are the regions of mountain-wave drag (MWD) exerted by dissipating atmospheric gravity waves generated by flow over them. However, these regional drags have significant global- or zonal-mean impacts on Earth’s atmospheric general circulation (e.g., slowing of the polar night jet). The objective of this work is to understand the regional to global evolution of these impacts. The approach is to track the evolution of MWD-generated potential vorticity (PV) over the winter using the Whole Atmosphere Community Climate Model (WACCM). Within an ensemble of winter-long runs with and without MWD, lower-stratospheric PV is generated over mountains and advected downstream, generating large-scale PV banners. These PV banners are diffused but survive this diffusion and are reinforced over downstream mountain ranges, accumulating into zonal-mean or global features within WACCM. A simple 2D model representing sources, advection, and diffusion of “passive PV” recreates the salient features in the WACCM results, suggesting the winter-long evolution of MWD-generated PV can be crudely understood in terms of horizontal advection and diffusion within a global vortex. In the Northern Hemisphere, cyclonic, equatorward PV banners accumulate zonally into a single zonally symmetric positive PV anomaly. The anticyclonic, poleward PV banners also accumulate into a zonally symmetric feature, but then diffuse over the North Pole into a negative PV polar cap. In the Southern Hemisphere, the same processes are at work, though the different geographic configuration of mountain ranges leads to different patterns of impacts.

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The pulsating nature of large-scale Saharan dust transport as a result of interplays between mid-latitude Rossby waves and the North African Dipole Intensity

Atmospheric Environment ◽

10.1016/j.atmosenv.2017.08.059 ◽

2017 ◽

Vol 167 ◽

pp. 586-602 ◽

Cited By ~ 21

Author(s):

E. Cuevas ◽

A.J. Gómez-Peláez ◽

S. Rodríguez ◽

E. Terradellas ◽

S. Basart ◽

...

Keyword(s):

Large Scale ◽

Rossby Waves ◽

Saharan Dust ◽

North African ◽

Dust Transport ◽

The North

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Systematics of north African Agama (Reptilia: Agamidae): a new species from the central Saharan mountains

Zootaxa ◽

10.11646/zootaxa.3098.1.3 ◽

2011 ◽

Vol 3098 (1) ◽

pp. 26 ◽

Cited By ~ 5

Author(s):

PHILIPPE GENIEZ ◽

JOSÉ M. PADIAL ◽

PIERRE-ANDRÉ CROCHET

Keyword(s):

New Species ◽

Phylogenetic Analyses ◽

Taxonomic Status ◽

Species Group ◽

Gene Fragment ◽

North African ◽

Mountain Ranges ◽

The North ◽

Lineage Divergence ◽

Species Taxonomy

We studied the taxonomic status of the north African Agama species A. impalearis, A. castroviejoi, and A. boueti. The study of recently collected specimens and museum material, as well as phylogenetic analyses of a short 16S ribosomal RNA gene fragment, revealed the presence of an undescribed species in Adrar des Ifoghas (Mali), Aïr Mountains (Niger), Ahaggar Mountains (Algeria) and Tassili n’Ajjer (Algeria, Lybia), previously mistaken either as A. impalearis or A. agama. The new species, Agama tassiliensis n. sp., clearly belongs to the impalearis – boueti – spinosa species group but differs from these species, among other characters, by its red, reddish-orange or orange vertebral stripe in males, long and angular head, long limbs and toes (with 4 th toe usually slightly longer than 3 rd toe), long but low nuchal crest made of 10 to 15 spines (rarely 8–9 spines) and large number of supralabials (10–16, usually around 12). Interspecific uncorrected p- distances based on the 16S rDNA gene fragment are high, ranging from 3.9% between A. boueti and A. impalearis to 7.9% between A. spinosa and A. impalearis. The new species is sympatric with A. boueti at least in the Aïr Mountains and exhibits average mtDNA divergences of 6.2%, 7.4%, and 7.6% with A. spinosa, A. impalearis, and A. boueti, respectively. Agama boueti is paraphyletic relative to A. castroviejoi in the mtDNA tree, and mtDNA genetic divergences between populations of both species are lower than 1.0%, suggesting that A. castroviejoi is better treated as a junior synonym of A. boueti pending more detailed analyses. Scattered mountain ranges in the Sahara seem to have promoted lineage divergence and ultimately speciation in this group. Further work should be done to study species taxonomy and evolution in those areas.

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Cylindroiulus mitta n.sp., a new Tunisian millipede (Diplopoda, Julida: Julidae) and notes on the Cylindroiulus distinctus group

Zootaxa ◽

10.11646/zootaxa.1768.1.4 ◽

2008 ◽

Vol 1768 (1) ◽

pp. 61 ◽

Cited By ~ 1

Author(s):

NESRINE AKKARI ◽

HENRIK ENGHOFF

Keyword(s):

North African ◽

The North ◽

Group Members ◽

Northeastern Tunisia

Cylindroiulus mitta n.sp. is described from Cap Bon, northeastern Tunisia, and its assignment to the North African C. distinctus group is discussed. Descriptions of the female vulvae of other group members are presented, as well as illustrations of gonopods and vulvae of further Cylindroiulus species from Tunisia.

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Rift evolution and structural style in the Orphan Basin: results from regional structural restorations and crustal area balancing

10.5194/egusphere-egu21-6527 ◽

2021 ◽

Author(s):

Adam J. Cawood ◽

David A. Ferrill ◽

Alan P. Morris ◽

David Norris ◽

David McCallum ◽

...

Keyword(s):

Cross Sections ◽

Seismic Data ◽

Large Scale ◽

Structural Evolution ◽

Strike Slip ◽

Detachment Faults ◽

The North ◽

Structural Style ◽

Complex Structural ◽

Structural Configurations

The Orphan Basin on the eastern edge of the Newfoundland continental margin formed as a Mesozoic rift basin prior to continental breakup associated with the opening of the North Atlantic. Few exploration wells exist in the basin, and until recently regional interpretations have been based on sparse seismic data coverage - because of this the structural evolution of the Orphan Basin has historically not been well understood. Key uncertainties include the timing and amount of rift-related extension, dominant extension directions, and the structural styles that accommodated progressive rift development in the basin. &#160;&#160;&#160;&#160;Interpretation of newly acquired modern broadband seismic data and structural restoration of three regional, WNW-ESE oriented cross-sections across the Orphan Basin and Flemish Cap provide new insights into rift evolution and structural style in the area. Our results show that major extension in the basin occurred between 167 Ma and 135 Ma, with most extension occurring prior to 151 Ma. We show that extension after 135 Ma largely occurred east of Flemish Cap due to a shift in the locus of rifting from the Orphan Basin to east of Flemish Cap. We find no evidence for discrete rifting events in the Orphan Basin, as has been suggested by other authors.&#160; Kinematic restoration and associated heave measurements for the Orphan Basin show that extension was both widespread and relatively evenly distributed across the basin from Middle-Late Jurassic to Early Cretaceous.We provide evidence for more widespread deposition of Jurassic strata throughout the Orphan Basin than previously interpreted, and show that Jurassic deposition was controlled by the occurrence and displacement of crustal-scale extensional detachment faults. &#160;Structure in the three regional cross sections is dominated by large-scale, shallowly dipping extensional detachment faults. These faults mainly dip to the northwest and control the geometry and position of extensional basins &#8211; grabens and half-grabens &#8211; which occur at a range of scales. Stacked detachment surfaces, hyperextension, and attenuation of the crust are observed in central and eastern parts of the Orphan Basin. Zones of extreme crustal attenuation (to ca. 3.7 km) are interpreted to be coincident with large-displacement (up to 60 km) low-angle detachments. Results from crustal area balancing suggest that up to 41% of extension is not recognized through structural seismic interpretation, which we attribute to subseismic-scale ductile and brittle deformation, and uncertainties in the identification of detachment surfaces or complex structural configurations (e.g., overprinting of early extensional deformation).Rifting style in the central, northern, and eastern parts of the Orphan Basin is dominated by low-angle detachment faulting with maximum extension perpendicular to the incipient rift axis. In contrast, structural geometries in the southwestern part of the basin are suggestive of transtensional deformation, and interplay of normal and strike-slip faulting.&#160; Results from map-based interpretation show that strike-slip faults within this transtensional zone are associated with displacement transfer between half-grabens of opposing polarity, rather than regional strike-slip displacement.&#160; These structures are interpreted as contemporaneous and kinematically linked to displacement along low-angle detachment surfaces elsewhere, and are not attributed to distinct episodes of oblique extension.&#160; &#160;&#160;&#160;&#160;&#160;

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Archaeoseismological study of the Cherichira aqueduct bridge, Kairouan, Tunisia

Mediterranean Geoscience Reviews ◽

10.1007/s42990-021-00062-9 ◽

2021 ◽

Author(s):

Klaus-G. Hinzen ◽

Mustapha Meghraoui ◽

Nejib Bahrouni ◽

Yassine Houla ◽

Sharon K. Reamer

Keyword(s):

Plate Boundary ◽

Flash Floods ◽

Archaeological Sites ◽

North African ◽

Earthquake Scenarios ◽

Mountain Ranges ◽

The North ◽

The Status ◽

The City ◽

Aqueduct Bridge

AbstractIn the past, several destructive earthquakes have occurred in the North African Atlas Mountain ranges located along the Africa–Eurasia plate boundary. Although the region is rich with impressive archaeological sites, including those in modern Tunisia, few comprehensive archaeoseismological studies have been conducted. Historic sources account at least three damaging earthquakes in the Kairouan area in central Tunisia between AD 859 and 1041. Little is known about which faults triggered these earthquakes or the size of these events. The water supply of the city of Kairouan depended on a 32-km-long aqueduct with a large bridge (now partially collapsed) at the confluence of the de Mouta and Cherichira rivers. The original bridge of Roman construction was retrofitted twice during the Aghlabid period (AD 800–903) and probably in AD 995 during the Fatimid period. The ruined section of the bridge shows damage which might be related to the AD 859 earthquake shaking. Here, we present a detailed study of the history, the status and the damage of the Cherichira aqueduct bridge using previous historic accounts and written works, a 3D laser scan model, local geological and seismological characteristics, and include results of radiocarbon dating and a timeline of events. In addition to earthquake ground motions, we consider severe flash floods on the bridge as a potential cause of the damage. We estimate the severity of such flash floods and develop a model with 18 earthquake scenarios on local reverse and strike-slip faults with magnitudes between MW 6.1 and 7.2. While a few damage patterns might be indicative of flooding, most damage can be attributed to earthquakes. It is highly probable that the earthquake in AD 859 caused enough damage to the Aghlabid bridge to render it dysfunctional; however, to resolve the question of whether another earthquake in AD 911 or 1041 caused the complete destruction of the previously retrofitted aqueduct by the Fatimids requires dating of additional sections of the bridge.

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Modulation of Saharan dust export by the North African dipole

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-7471-2015 ◽

2015 ◽

Vol 15 (13) ◽

pp. 7471-7486 ◽

Cited By ~ 64

Author(s):

S. Rodríguez ◽

E. Cuevas ◽

J. M. Prospero ◽

A. Alastuey ◽

X. Querol ◽

...

Keyword(s):

Interannual Variability ◽

North Africa ◽

North Atlantic ◽

Large Scale ◽

Saharan Dust ◽

North African ◽

The North ◽

The North Atlantic ◽

The Tropics

Abstract. We have studied the relationship between the long-term interannual variability in large-scale meteorology in western North Africa – the largest and most active dust source worldwide – and Saharan dust export in summer, when enhanced dust mobilization in the hyper-arid Sahara results in maximum dust impacts throughout the North Atlantic. We address this issue by analyzing 28 years (1987–2014) of summer averaged dust concentrations at the high-altitude Izaña observatory (~ 2400 m a.s.l.) on Tenerife, and satellite and meteorological reanalysis data. The summer meteorological scenario in North Africa (aloft 850 hPa) is characterized by a high over the the subtropical Sahara and a low over the tropics linked to the monsoon. We measured the variability of this high–low dipole-like pattern in terms of the North African dipole intensity (NAFDI): the difference of geopotential height anomalies averaged over the subtropics (30–32° N, Morocco) and the tropics (10–13° N, Bamako region) close to the Atlantic coast (at 5–8° W). We focused on the 700 hPa standard level due to dust export off the coast of North Africa tending to occur between 1 and 5 km a.s.l. Variability in the NAFDI is associated with displacements of the North African anticyclone over the Sahara and this has implications for wind and dust export. The correlations we found between the 1987–2014 summer mean of NAFDI with dust at Izaña, satellite dust observations and meteorological re-analysis data indicate that increases in the NAFDI (i) result in higher wind speeds at the north of the Inter-Tropical Convergence Zone that are associated with enhanced dust export over the subtropical North Atlantic, (ii) influence the long-term variability of the size distribution of exported dust particles (increasing the load of coarse dust) and (iii) are associated with enhanced rains in the tropical and northern shifts of the tropical rain band that may affect the southern Sahel. Interannual variability in NAFDI is also connected to spatial distribution of dust over the North Atlantic; high NAFDI summers are associated with major dust export (linked to winds) in the subtropics and minor dust loads in the tropics (linked to higher rainfall), and vice versa. The evolution of the summer NAFDI values since 1950 to the present day shows connections to climatic variability (through the Sahelian drought, ENSO (El Niño–Southern Oscillation) and winds) that have implications for dust export paths. Efforts to anticipate how dust export may evolve in future decades will require a better understanding of how the large-scale meteorological systems represented by the NAFD will evolve.

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