The Times Atlas and actual Greenland ice loss

In September 2011 two Greenland stories hit the press, by far the bigger of which was the widespread misreporting (and consequent backlash) that Greenland had apparently lost 15 per cent of its ice cover since 1999. The public are used to an annual press bombardment of record temperatures, ever increasing melt and ice retreat in polar regions but a 15 per cent loss in 12 years does seem fanciful.     

The Soil Geochemical Atlas of Portugal: Overview and applications

The continental area of Portugal is now entirely covered by a soil geochemical survey (1 site/135 km²), taking as the sampling media topsoils (upper mineral horizons, A) and organic horizons (humus, O). Standard methods for sampling, sample preparation and analysis were used in order to achieve high quality and consistent data. Each sample was analyzed for 32 chemical elements, pH, electrical conductivity and organic matter content.The main purpose of the survey was to obtain baseline levels for various chemical elements. The compilation of all data (nearly 45,000 individual data) in an organised way, led to the production of the first Soil Geochemical Atlas of Portugal. In this Atlas it is possible to find for each chemical element a set of information statistics (basic statistical parameters, boxplots, cumulative frequency curves, etc.), maps of spatial distribution, among other information of geochemical and environmental interest. This paper gives an overview of the Soil Atlas and examples of application. The data were used to calculate reference values for 9 elements of environmental importance and to obtain empirical formulae allowing the estimation of elements in the coarse fraction of soils (< 2.00 mm) from known concentration in a finer fraction (< 0.18 mm).     

Plate tectonics and intracratonic mountain ranges in Morocco - The mesozoic-cenozoic development of the Central High Atlas and the Middle Atlas

Plate tectonic processes in the Atlantic and western Tethyan realm directed the post-Variscan sedimentary and structural evolution of the High Atlas and Middle Atlas intracontinental mountain ranges of Morocco. Plate movements caused a reactivation of an inherited pan-African or Hercynian fault pattern by the variation of stress regimes through time. This resulted in strike-slip as well as vertical tectonics. During times of relative tectonic quiescence eustatic sea-level changes governed the sedimentary development. The most important, often interacting, global tectonic determinants are: taphrogenesis of the NW-African continental margin lasting until the Early Cretaceous (Triassic rifting and subsequent mid-Atlantic spreading), strike-slip-faulting at the Newfoundland-Gibraltar fault zone (Liassic — earliest Eocene), and continental convergence between Europe (Iberia) and Africa which started in the Late Cretaceous and reached its acme in the Neogene. In the realm of the Central High Atlas and the Middle Atlas the interaction of these processes triggered continental rifting (Triassic) and subsequent marine flooding of the intergrown riftgrabens prograding from the Tethys realm (Early Jurassic — earliest Middle Jurassic). After its abortion, the former Atlas rift was filled up with marine sediments (Bajocian — Bathonian), followed by continental redbeds and final uplift (late Mid Jurassic — late Early Cretaceous). Eustatic sea-level changes mostly governed the sedimentary evolution from Aptian to latest Mid Eocene. After a first weak uplift of the central High Atlas during the Senonian major uplift of the intracontinental chains commenced at the Mid/ Late Eocene transition. Diastrophism of the Atlas ranges during the Miocene and Pliocene coincided with the main orogenic movements of the Betico-Rifean arc.

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Zusammenfassung Die post-variskische sedimentäre und strukturelle Entwicklung der intrakontinentalen Gebirgsketten des Hohen und des Mittleren Atlas wurde durch plattentektonische Prozesse im atlantischen und westmediterranen Raum gesteuert, die auf ein ererbtes panafrikanisches bzw. variskisches Störungsmuster einwirkten. Zu Zeiten relativer tektonischer Ruhe bestimmten eustatische Meeresspiegelschwankungen die sedimentäre Entwicklung. Die von horizontaler und vertikaler Bruchtektonik beherrschte Atlas-Tektonik wurde durch in der Zeit wechselnde Streßfelder bestimmt. Wichtigste großtektonische, oft zusammenwirkende Steuerungsfaktoren waren: die bis in die Unterkreide wirkende Taphrogenese im Bereich des NW-afrikanischen Kontinentalrandes (triadisches Rifting und anschließendes Spreading im Atlantik), Transform-Bewegungen an der Neufundland-Gibraltar-Störungszone zwischen Lias und ältestem Eozän sowie die Konvergenz zwischen Europa (Iberia) und Afrika, welche nach ihrem Beginn in der späten Kreide ihren Höhepunkt im Neogen erreichte. Das Zusammenspiel dieser Faktoren bewirkte im zentralen Hohen Atlas und im Mittleren Atlas die Entstehung kontinentaler Riftgräben während der Trias, die von der Tethys ausgehende Flutung der zusammengewachsenen Riftgräben im Lias und untersten Dogger (Sinemurium — Aalenium) sowie die zuerst marine (Bajocium — Bathonium), dann kontinentale Füllung und Heraushebung der stillgelegten Riftzone zwischen spätem Mitteljura und später Unterkreide. Zwischen Apt und Ende des Mitteleozän kontrollierten vor allem eustatische Meeresspiegelschwankungen die sedimentäre Entwicklung. Nach ersten Hebungen im zentralen Hohen Atlas während des Senon begann die eigentliche Heraushebung der intrakontinentalen Ketten an der Wende Mittel-/Obereozän. Die mio-/pliozäne Hauptphase der Atlas-Tektogenese war zeitgleich mit der Orogenese im Betico-Rif-Bogen.

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Résumé L'évolution sédimentaire et structurale postvarisque des chaînes intracontinentales du Haut et du Moyen Atlas a été régie par les processus de la tectonique des plaques qui se déroulaient dans l'Atlantique et dans la Méditerrannée occidentale. Ces mouvements de plaques ont réactivé un ensemble de failles héritées des phases pan-africaine et hercynienne, en y produisant des déplacements verticaux et horizontaux en réponse aux fluctuations temporelles des champs de contraintes. Au cours des périodes de calme tectonique relatif, les changements eustatiques du niveau de la mer ont déterminé le régime de la sédimentation. Les facteurs de la tectonique les plus importants, à action d'ailleurs souvent combinée, ont été: la traphrogenèse, active jusqu'au Crétacé inférieur, de la marge nord-ouest du continent africain (rifting triasique et ouverture subséquente de l'Atlantique), les mouvements de décrochement le long de la zone transformante de Terre Neuve-Gibraltar depuis le Lias jusqu'au début de l'Eocène, ainis que la convergence entre l'Europe (Ibérie) et l'Afrique qui débuta au Crétacé supérieur pour culminer au Néogène. Dans le Haut Atlas central et dans le Moyen Atlas, le jeu combiné de ces facteurs a provoqué la formation de grabens continentaux (Trias) puis leur envahissement par la mer à partir de la Téthys (Lias-Dogger inférieur). Après la fin de son activité, le rift atlasique a été comblé par des sédiments, d'abord marins (Bajocien-Bathonien), puis continentaux jusqu'au soulèvement final (fin du Jurassique moyen — fin du Crétacé inférieur). De l'Aptien à la fin de l'Eocène moyen, l'évolution sédimentaire a été régie par les changements eustatiques du niveau de la mer. Après un premier soulèvement modéré du Haut Atlas central au cours du Sénonien, le soulèvement majeur des chaînes intracontinentales débuta à la limite Eocène moyen-Eocène supérieur. Le diastrophisme de l'Atlas au cours du Mio-Pliocène a coïncidé avec les mouvements orogéniques de l'arc bético-rifain.

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Mineral Atlas of the World

In 1997 the mineral resources of Europe and neighbouring countries were presented as a printed map and a book of exhaustive information and references. This was the first published map inventory of mineral deposits from all parts of the formerly politically divided Europe (East and West), measured and evaluated according to identical geological and mining standards.     

The fifth edition of the Atlas of Finland —thematic and methodological guidelines

Finland has a most extraordinary experience in the field of thematic and expecially atlas cartography. The traditions of national atlases go almost 100 years back through five extensive editions (1899, 1910, 1920, 1960 and the fifth 1977–1991). Thematically these atlases have acted as thruthful mirrors of the rather dramatic changes Finland has lived through both from the point of environment (including political boundaries), economy, settlement and cultural features. Methodologically the series of Finnish atlases show many interesting aspects of development, in many respects important new approaches have been introduced and also the fifth edition has in international reviews been described as “innovative”. Finally one can stress the purposeful geographical emphasis in the content of these atlases; they are no mechanistic interpretations of e.g. statistical data. The presently-day work in the field of national atlases faces many new demands. Automation has enhanced the cartographic processing of data, there is a much extended information base concerning all the aspects of the modern societies which must be taken into account and there is also a number of new outlets for the ready product (printed and numerical). The greater scope and diversity must not, however, restrict the scientific unbiased editorial work of analyzing and synthetizing the data for cartographic expression; a clearcut geographical philosophy must be the guideline. In the future the thematic and atlas cartography must also be dealt increasingly in problem-oriented and international frames.     

Inverted intracontinental basin and vertical tectonics: The Saharan Atlas in Tunisia

The present-day architecture of the Saharan Atlas in Tunisia can be defined by two principal models: (1) The first model emphasizes a general SW–NE geological structure in the North forming successive and parallel bands (the Tellian zone, the diapir zone) and the central Atlas, which are cut by the southern Atlas ranges located within a NW–SE corridor. These zones are bordered to the East by the “North–South Axis”. (2) The second model defines the Tunisian Atlas in terms of an E–W strike-slip corridor, which initially controls the sedimentary facies distribution during the Meso-Cenozoïc, and which then generates elongate en echelon folds in the sedimentary cover by dextral shearing.In this study, we aim to show that the Saharan Atlas in Tunisia appears today as a triangular megablock, that we call the Tunisian Block (TB), bounded by three structural trends (N–S, SW–NE and NW–SE) belonging to the African strike-slip fault network: (1) The eastern boundary appears as a complex faulted and folded corridor limiting the folded zone of the central Atlas in the West and the depressed zone of the Sahel in the East: it corresponds to the “North–South Axis” as defined classically in the literature. (2) The southern boundary also corresponds to a faulted belt (Gafsa–Negrine-Tozeur corridor), which cuts off the continuation of the North–South axis southward into the Gabès region; it corresponds to the Southern Saharan Atlas, delimited by the Gafsa fault in the North and the Negrine-Tozeur fault in the South. (3) The northern boundary, trending SW–NE, appears rather in the form of a reverse tectonic bundle, facing SE or S (oblique convergence), whose major feature corresponds to the El Alia-Téboursouk fault. This northern boundary cuts across and delimits the N–S corridor towards the North, in such a way that its extension is limited at both extremities. Finally, the inner part of the TB actually corresponds to a mosaic of second-order blocks, each of which contains an arrangement of widely spaced SW–NE trending anticlines forming the main relief separated by vast plains very often occupied by sebkhas. The paleogeographic and structural evolution of this region during the Mesozoic and Palaeogene shows that the TB, along with its limits as defined here, developed an increasingly distinct identity at a very early stage, being characterized by an extensive and/or transtensive tectonic regime. Finally, the Tunisian Atlas Chain defines a triangular domain that owes its origin and particular character precisely because of the paleogeographic and structural history of this paleoblock. The boundaries of this paleoblock remain mobile, thus tectonically controlling the geometry and morphology of a typical intracontinental basin. The extension directions and the frequent changes of stress regime (or rotations) are related to the existence of two active basins: the strike-slip margin of the western branch of Tethys and the Mesogea oceanic basin, with tectonic activity becoming alternately dominant in one or other of the basins at different times. In this context, the Tunisian basin is characterized by rhythmic sedimentation, composed of a succession of filling sequences linked to the continuing tectonic instability of the sedimentary floor associated with two major crises: one at the end of the Aptian and the other at the end of the Ypresian. The vertical movements related to the extension and/or transtension of the blocks is accentuated by Triassic salt tectonics, giving rise to linear (salt axes) or point (salt domes) structures that lead to the formation of shoal zones during development of the basin, thus enhancing the vertical tectonics. The diapirism developed slowly and gradually from late Triassic through to Langhian times, leading to numerous sedimentary wedges on the flanks of the structures. The uprise of the diapirs exhibits three pauses corresponding to the end-Aptian, end-Ypresian and pre-Burdigalian. The vertical tectonics is characterized by abundant drape folds giving rise to an extensional fault-related folding and strike-slip/dip-slip faults creating frequent unconformities that are nevertheless always localized.Finally, the folded chain results from the structural inversion of this paleoblock from Tortonian times onward. We can only account for the various folds-axis directions in the context of an intracontinental chain where the pre-existing major vertical faults are able to develop on the surface as draped-folds in a transpressive regime by the local reorientation of stresses in crustal-scale faults. In detail, the structures produced by this vertical tectonic activity, which are profoundly controlled by inheritance, display a highly original style at very shallow levels in the crust.     

Geochemical Atlas of Finland: preliminary aspects

During 1984 and 1985, the Geological Survey of Finland carried out regional geochemical mapping of till, at a scale of 1:2,000,000, as part of a programme to produce data for the first Geochemical Atlas of Finland. The Atlas is designed to give comprehensive background information on the distribution of elements in rocks, soils, and the surficial environment.     

Faulting history at the eastern termination of the High Atlas Fault (Western High Atlas,Morocco)

At its eastern termination, the High Atlas Fault in the Western High Atlas in Morocco, consists of a splay of three faults. In the interjacent fault blocks, Neo- and Paleoproterozoic basement, forming the northernmost extremity of the NW-African Craton, is cropping out. The Precambrian basement witnesses a long history of brittle deformation starting at the end of the Pan-African Orogeny. A subsequent episode of normal faulting can be related to the development of a Hercynian basin along the northern passive margin of the cratonic promontory. With regard to the main tectonic activity in the Western High Atlas, basically two models exist: one emphasising block tectonics reflecting Mesozoic rifting followed by Alpine uplift and inversion, the other emphasising Late Paleozoic dextral wrench tectonics. The analysis of the fault activity along the splay faults reveals a predominantly Alpine history, consisting of the Triassic development of the Atlas Rift along the axial zone of the orogen, followed by uplift and inversion. The Late Jurassic to Cenozoic fault activity took place in a sinistral transpressive regime and was partitioned over the three splay faults. Dextral strike-slip fault activity could not be demonstrated in the fault blocks nor along the splay faults. Therefore the faults were probably not involved in Late Paleozoic dextral wrench tectonics.     

Major fracture zones of Morocco: The South Atlas and the Transalboran fault systems

Within the fracturai pattern of Morocco, 35–45° and 70–90° directions are predominant. Most of the faults originated already during the Upper Palaeozoic and were repeatedly reactivated, later on. Two of the large fracture systems are considered here.The South Atlas fault system (SAF) is composed of different faults with directions varying between 45–90°. They were not functionally connected to the southern hinge of the High Atlas until its Miocene uplift. Today, it seems to be inactive on the whole. Both the tectonic data and the facies distribution of Mesozoic strata contradict clearly the interpretation that the SAF is a huge wrench-fault or even the Mesozoic plate margin of Africa. The SW striking Transalboran fault system (TAF) is still active. It crosses Morocco from Melilla to Agadir, showing again singular faults which are unified to extended lineaments only in a few areas. The intervals between the faults are bridged by linear arrangements of earthquake hypocenters. Sinistral massflow within the deeper parts of the lithosphere seems to be compensated at the surface by movements along pre-existing faults. For the Moroccan segment of the TAF, a sinsitral displacement is testified at least since the Oligocene, while the northeastern segments from the Rif to Spain did not even originate until the Pliocene. This would mean that sinistral shear was transmitted from Africa into the accreted Alboran and Iberia blocks after the Miocene collision.

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Zusammenfassung Unter den großen Störungen Marokkos dominieren die Richtungen 35–45° und 70–90°. Sie wurden zumeist im Jungpaläozoikum angelegt und später wiederholt reaktiviert. Zwei der großen Bruchsysteme wurden näher untersucht:Die Südatlas-Störungszone (SAF) besteht aus unzusammenhängenden Brüchen unterschiedlichen Alters, deren Streichrichtung von 45–90° variiert. Diese wurden erst bei der miozänen Heraushebung des Hohen Atlas zu dessen südlichem Scharnier umfunktioniert. Heute sind nur wenige Störungen des Systems aktiv. Diese Befunde und ebenso die stratigraphisch-fazielle Entwicklung im Mesozoikum Marokkos verbieten, die SAF als bedeutende Lateralverschiebungszone oder gar als nördliche Plattengrenze Afrikas zu interpretieren.Das noch heute aktive, SW-streichende Transalboran-Störungssystem (TAF) setzt sich durch Marokko von Melilla bis Agadir fort. Es besteht an der Oberfläche ebenfals aus singulären Brüchen, die sich nur bereichsweise zu längeren Linien zusammenschließen. Zwischen den Störungen vermitteln linear angeordnete Herde rezenter Erdbeben: Sinistraler Massentransport an einer Tiefenstörung wird an der Oberfläche durch Teilbewegungen an präexistenten Störungen kompensiert. Während in Marokko südlich des Rifs sinistraler Versatz mindestens seit dem Oligozän nachgewiesen ist, entstand die TAF vom Rif bis nach Spanien erst im Pliozän. Die sinistrale Scherung tritt also erst nach der miozänen Kollision von Afrika aus auf die nunmehr akkretierten Mikroplatten- Alboran-Block und Iberia - über.

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Résumé Les grandes fractures du Maroc présentent les deux directions prédominantes de 35°-40° et 70°–90°. La plupart de ces fractures datent du Paléozoïque supérieur et ont été réactivées plusieurs fois au Mésozoïque et au Cénozoïque. Deux de ces grands systèmes de fractures sont considérés ici.L'accident sud-atlasien (SAF) est composé de fractures indépendantes d'âges divers dont la direction varie entre 45° et 90°. Ces fractures ne se sont connectées à la charnière du Haut Atlas qu'après le soulèvement miocène de celui-ci. Aujourd'hui, quelques failles seulement sont encore actives. Ces observations, ainsi que la distribution des faciès du Mésozoïque au Maroc sont en contradiction avec le modèle qui voit dans le SAF une grande zone de décrochement ou même la marge nord de la plaque africaine.L'accident transalboran (TAF), encore actif aujourd'hui, traverse le Maroc en direction sudouest de Mélilla à Agadir. Il est composé de failles discontinues, connectées entre elles seulement à quelques endroits. Les intervalles qui séparent ces failles sont jalonnés par des alignements rectilignes d'hypocentres de séismes récents. L'ensemble correspond à un décrochement sénestre profond compensé en surface par des mouvements le long de failles préexistantes. Ce décrochement sénestre, dans le segment du TAF situé au sud du Rif, s'est manifesté au moins depuis l'Oligocène, tandis que la partie qui s'étend du Rif à l'Espagne méridionale n'a été active qu'à partir du Pliocène. Ceci signifie que ce cisaillement sénestre ne s'est transmis de l'Afrique vers l'Europe qu'après l'accrétion, au Miocène, de la microplaque Alboran et du bloc ibérique.

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Zur Strukturgeschichte des Hohen Atlas in Marokko

Zusammenfassung Der Hohe Atlas (Marokko) entwickelte sich aus einer schmalen, kompliziert gebauten, intrakratonischen Riftstruktur, die sich teils an prÄexistenten Bruchsystemen orientierte, teils aber auch unabhÄngig davon verlief. Das Innere dieses Rifts war in rhombenförmige Schollen gegliedert, die unterschiedliche Kippbewegungen zu verschiedenen Zeiten ausführten. Eine Geosynklinale lie\ sich für dieses Gebirge nicht nachweisen. Das Riftstadium dauerte von der Trias bis in die mittlere Kreide (Turon incl.).Von der Oberkreide ab bildete sich durch Inversion, besonders im JungtertiÄr, das heutige Hochgebirge heraus. Dieser Proze\ wurde von der Einsenkung subsequenter Randsenken begleitet. Als Bewegungsbahnen dienten die Randbrüche des ehemaligen Rifts und die Schollengrenzen in seinem Inneren.Atlas und Atlantik waren im Initialstadium Teile des gro\en Bruchsystems, an dem PangÄa in postvariscischer Zeit aufbrach. SpÄter entwickelten sich beide Strukturen in antagonistischer Weise: das atlantische Rift wurde zum Atlantischen Ozean, das Atlas-Rift zum Atlas-Hochgebirge.

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The High Atlas of Morocco orginated from a narrow, complicated, intracratonic graben or rift structure. Pre-existing faults and fracture zones may have influenced its direction only in places. The interior of this rift consisted of a rhomboidal fault block pattern, the individual block of which carried out different tilting movements at separate times. The rift was active from the Triassic till to the Mid-Cretaceous (Turonian). A trough of geosynclinal type cannot be proved in the initial stage of this mountain belt.The formation of the modern High Atlas mountains was caused by structural inversion processes. In the western High Atlas they began in post-Turonian time in the Late Cretaceous. This process was accompanied by the downwarping of subsequent marginal troughs along the northern and southern flanks of the rising mountain chain. The normal faults of the earlier rift-system became thrust faults during the inversion process.During the initial stage the Atlas-Rift and the Atlantic furrow were part of the global fracture zone, along which Pangea began to break up in post-Variscan time. Lateron both rift-systems developed in an antagonistic way: From the Atlantic furrow the Atlantic Ocean originated whereas the Atlas-Rift converted to the High Atlas mountain chain.

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Résumé Le Haut Atlas marocain s'est développé à partir d'une structure de rift étroite et complexe qui se trouvait dans une position intracratonique ou íntracontinentale. Cette structure était en partie orientée suivant des systèmes de fractures préexistantes, mais aussi en partie d'une manière indépendante. L'intérieur de ce rift était subdivisé en blocs rhombiques, ce qui a permis des basculements distincts à différents moments. Cette phase de rift dura du Trias au Crétacé supérieur (y compris le Turonien), et ce, sans qu'on puisse y reconnaÎtre l'intervention d'un géosynclinal.La chaÎne actuelle, avec son haut relief, a été formée par un processus d'inversion structurale, dès le Crétacé supérieur et surtout au Tertiaire supérieur. Ce processus s'est accompagné de l'enfoncement de bassins marginaux subséquents le long des flancs nord et sud du Haut Atlas. Ces mouvements se firent suivant les failles marginales de l'ancien rift ainsi que suivant les fractures internes entre blocs.Le Haut Atlas et l'Atlantique faisaient partie, au début, du grand système de fractures qui, à l'époque post-hercyienne, a disloqué la Pangée. Plus tard les deux structures apparentées se sont développées d'une faÇon antagoniste: le rift atlantique se transforma en Océan atlantique, tandis que le rift de l'Atlas était converti en Haut Atlas.

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The Plio-Pleistocene evolution of the Southern Middle Atlas Fault Zone (SMAFZ) front of Morocco

The South Middle Atlas front constitutes a northeast-trending shear zone, located north of the Neogene Missour basin and east of the Taza Guercif basin. This paper analyses the Southern Middle Atlas Fault Zone (SMAFZ) deformation since the Pliocene. The set of structures observed suggests that reverse and thrust faulting along the central part of the SMAFZ are combined with left-lateral slip along N–S striking faults of its south-western termination and right-lateral faulting along E–NE striking faults of the east–northeast termination. Thrusts and oblique thrust-related anticlines of the two lateral ramps partly accommodate north-west directed motion of the African plate. The Thrusts probably resulted from rejuvenation of Jurassic normal faults; they were active during the Upper Miocene–Pliocene and the Pleistocene. The geometries of positive inversion structures and buttressing effects are clearly dependent on the geometry and sedimentology of the original basin-controlling fault system and on the presence of a décollement level. Field mapping is integrated with Landsat imagery and a digital elevation model to investigate the morphotectonic evolution of the south-eastern range front of the Middle Atlas. Geomorphological features provide significant information on the processes that govern lateral propagation of active anticlines. Both suggest that the deformation front may have been active since Pliocene.     

The evolution of pre-existing structures during the tectonic inversion process of the Atlas chain of Tunisia

Previous studies on the plate movement between Africa and Eurasia have pointed out the evidence of successive phases of transtension and transpression. The transtensional regime was active between Jurassic and Cretaceous times. It led to extensional structures which were reactivated during the Cenozoic transpressional regime as consequence of the Africa–Europe convergence. In this paper, we used satellite images and field observations from Central Tunisia to demonstrate the role of the previous extension tectonics in the structural evolution of the Atlassic chain for the tectonic inversion process. In the study area, the geometry of structures and fault kinematics is used to document transition from transtension to transpression. The tectono-sedimentary record reflects the mechanical influence of reactivation of previous tectonics in the structural evolution of the study area and points out the significant role of the tectonic inheritance in the development of the Atlassic chain of Tunisia.