Tectonique synsedimentaire d'age cretace superieur en Tunisie nord orientale; blocs bascules et reorganisation des aires de subsidence

2000 ◽  
Vol 171 (4) ◽  
pp. 431-440 ◽  
Author(s):  
Lahcen Boutib ◽  
Fetheddine Melki ◽  
Fouad Zargouni
Keyword(s):  
Structural Analysis ◽  
Upper Cretaceous ◽  
Tectonic Activity ◽  
Normal Faults ◽  
Half Graben ◽  
Combined Movements ◽  
Basin Floor ◽  
Tunisian Atlas ◽  
Facies Variation ◽  
Regional Tectonics

Abstract Structural analysis of late Cretaceous sequences from the northeastern Tunisian Atlas, led to conclude on an active basin floor instability. Regional tectonics resulted in tilted blocks with a subsidence reorganization, since the Campanian time. These structural movements are controlled both by N140 and N100-120 trending faults. The Turonian-Coniacian and Santonian sequences display lateral thickness and facies variation, due to tectonic activity at that time. During Campanian-Maastrichtian, a reorganization of the main subsidence areas occurred, the early Senonian basins, have been sealed and closed and new half graben basins developed on area which constituted previously palaeohigh structures. These syndepositional deformations are characterized by frequent slumps, synsedimentary tilting materials, sealed normal faults and progressive low angle unconformities. These tilted blocks combined to a subsidence axis migration were induced by a NE-SW trending extensional regime. This extension which affects the Tunisian margin during the Upper Cretaceous, is related to the Tethyan and Mesogean rifting phase which resulted from the combined movements of the African and European plates.

scholarly journals High resolution stratigraphy of initial stages of rifting, Sergipe-Alagoas Basin, Brazil

2017 ◽  
Vol 47 (4) ◽  
pp. 657-671 ◽  
Author(s):  
Carrel Kifumbi ◽  
Claiton Marlon dos Santos Scherer ◽  
Fábio Herbert Jones ◽  
Juliano Kuchle
Keyword(s):  
Radical Change ◽  
High Rate ◽  
Tectonic Activity ◽  
Accommodation Space ◽  
Facies Associations ◽  
Half Graben ◽  
Lateral Connection ◽  
Depositional Units ◽  
Two Parameters ◽  
Channel Deposits

ABSTRACT: The present work aims to characterize the Neo-Jurassic to Neocomian succession of the Sergipe-Alagoas Basin, located in northeast region of Brazil, in order to discover the influence of tectonics on sedimentation in detailed scale and thus separating this sedimentary succession in tectono-stratigraphic units. Fieldwork observations and stratigraphic sections analysis allowed subdividing this rift succession into three depositional units that indicate different paleogeographic contexts. Unit I, equivalent to the top of Serraria Formation, is characterized by braided fluvial channel deposits, with paleocurrent direction to SE; unit II, corresponding to the base of Feliz Deserto Formation, is composed of anastomosed fluvial channel and floodplain facies associations; and unit III, equivalent to the major part of Feliz Deserto Formation, is characterized by delta deposits with polymodal paleocurrent pattern. The changes of depositional system, as well as paleocurrent direction, suggest that the previously described units were deposited in different evolutionary stages of rifting. Units I and II represent the record of a wide and shallow basin associated with the first stage of rifting. Unit I is characterized by incipient extensional stress generating a wide synclinal depression, associated to the low rate of accommodation and low tectonic activity. These two parameters progressively increase in unit II. The paleocurrent direction of unit I indicates that the depocenter of this wide basin was located at SE of the studied area. No conclusion could be done on paleocurrent from unit II because of the low amount of measurements. Unit III suggests a second stage marked by a deeper basin context, with a high rate of accommodation space associated with the lateral connection of faults and individualization of the half-graben. The scattering in the paleocurrent direction in this unit indicates sedimentary influx coming from several sectors of the half-graben. The boundary between these two stages is marked by a flooding surface that indicates an extremely fast transition and suggests a radical change in geometric characteristics of the basin due to the increase of tectonic activity.

scholarly journals A pilot seismo-stratigraphic study on the West Greenland continental shelf

1989 ◽  
Vol 142 ◽  
pp. 1-16
Author(s):  
J.A Chalmers
Keyword(s):  
Petroleum Industry ◽  
Source Rocks ◽  
Tectonic Activity ◽  
The West ◽  
West Greenland ◽  
Main Site ◽  
Half Graben ◽  
Greenland Basin ◽  
Seismic Sections ◽  
Structural Closure

Seismo-stratigraphic interpretation of seismic sections dating from the mid-1970s has disclosed the existence of four megasequences of sediments, the oldest of which has not previously been reported from West Greenland. The basins containing these sediments developed as a series of coalescing half graben, in which the main site of tectonic activity changed with time. A structural closure of sufficient size to contain interesting quantities of hydrocarbons, given suitable source rocks, reservoir and seal, is identified. The study has shown that the evaluation of the West Greenland Basin during the 1970s was inadequate, and that abandonment of exploration by the petroleum industry may have been premature.

scholarly journals Recent active faults in Belgian Ardenne revealed in Rochefort Karstic network (Namur Province, Belgium)

2001 ◽  
Vol 80 (3-4) ◽  
pp. 297-304 ◽  
Author(s):  
S. Vandycke ◽  
Y. Quinif
Keyword(s):  
Stress Field ◽  
Active Faults ◽  
Ground Surface ◽  
Local Stress ◽  
Tectonic Activity ◽  
Normal Faults ◽  
Regional Stress ◽  
Bedding Planes ◽  
Local Modification ◽  
A Minor

AbstractThis paper presents observations of recent faulting activity in the karstic network of the Rochefort Cave (Namur Province, Belgium, Europe). The principal recent tectonic features are bedding planes reactivated as normal faults, neo-formatted normal faults in calcite flowstone, fresh scaling, extensional features, fallen blocks and displacement of karstic tube. The seismo-tectonic aspect is expanded by the presence of fallen blocks where normally the cavity must be very stable and in equilibrium. Three main N 070° fault planes and a minor one affect, at a decimetre scale, the karst features and morphology. The faults are still active because recent fresh scaling and fallen blocks are observable. The breaking of Holocene soda straw stalactites and displacements of artificial features observed since the beginning of the tourist activity, in the last century, also suggest very recent reactivation of these faults. This recent faulting can be correlated to present-day tectonic activity, already evidenced by earthquakes in the neighbouring area. Therefore, karstic caves are favourable sites for the observation and the quantification of recent tectonic activity because they constitute a 3-D framework, protected from erosion. Fault planes with this recent faulting present slickensides. Thus a quantitative analysis in term of stress inversion, with the help of striated faults, has permitted to reconstruct the stress tensor responsible for the brittle deformation. The principal NW-SE extension (σ3 horizontal) is nearly perpendicular to that of the present regional stress as illustrated by the analysis of the last strong regional earthquake (Roermond, The Netherlands) in 1992. During the Meso-Cenozoic, the main stress tectonics recorded in this part of the European platform is similar to the present one with a NE-SW direction of extension.The discrepancy between the regional stress field and the local stress in the Rochefort cave can be the result of the inversion of the σ2 and σ3 axes of the stress ellipsoid due to its symmetry or of a local modification at the ground surface of the crustal stress field as it has been already observed in active zones.

The Eastern Romanche ridge-transform intersection (Equatorial Atlantic): slow spreading under extreme low mantle temperatures. Preliminary results of the SMARTIES cruise.

2020 ◽  
Author(s):  
Marcia Maia ◽  
Daniele Brunelli ◽  
Keyword(s):  
Thick Layer ◽  
Tectonic Activity ◽  
Normal Faults ◽  
Transform Fault ◽  
Equatorial Atlantic ◽  
Ridge Axis ◽  
Nodal Basin ◽  
Spreading Axis ◽  
Geophysical Surveys ◽  
Damaged Zone

<p>A strong edge effect is predicted at the intersections between long-offset transforms and mid ocean ridge segments. The Equatorial Atlantic hosts several megatransforms, where the connections of potentially low mantle temperatures due to the large lithospheric age contrast with melt production are poorly understood. The SMARTIES cruise focused on the Romanche transform that offsets the Mid Atlantic Ridge (MAR) laterally by 900 km with an age offset of 55 Ma. The eastern Ridge-Transform Intersection (RTI) markedly shows the effects of the lateral cooling of the ridge segment. To better understand the thermal regime at these complex domains, we acquired surface geophysical data and bathymetry of the area, and geological observations and sampling during 25 HOV Nautile dives. The integrated study of rock characteristics and of geophysical surveys allows tackling the connections between magmatism and tectonics. A network of 19 OBS was also deployed to study the seismic activity during the cruise in collaboration with the ILAB project.</p><p>There is a striking change in deformation patterns along the ridge axis moving away from the transform southwards. The bathymetry is extremely complex, with several structural directions, partly resulting from transtension. A low melt supply is focused at the ridge axis resulting in a long oblique axial domain, that forms a relay zone between the roughly north-south ridge axis in the south and the area close to the transform fault, while the transform fault domain is highly complex. Trends oblique to both the main spreading axis direction and the transform fault direction are widespread. A clear Principal Transform Displacement Zone (PTDZ) can be followed as a long, near continuous alignment, on the seafloor of the wide Romanche valley. However, the valley morphology suggests a migration of the PTDZ and intense deformation within the transform domain. The RTI is complex and the position of the spreading axis clearly evolved with time, through at least two and possibly three eastward ridge jumps.</p><p>Six Nautile dives explored the northern wall of the Romanche, the damaged zone of the transform fault, and the exceptionally deep nodal basin. The north wall exposes a very thick basalt unit covered with a thick layer of sediments. Eight dives explored the southern flank of the Romanche identifying fragments of old Oceanic Core Complexes (OCCs) formed by highly deformed peridotites, and a large OCC located at the RTI that exposes mylonitized peridotites and is dissected by several normal faults. The magmatic zones of the axial domain (nine dives) are formed by volcanic ridges affected by important tectonic activity. The dives show pillow and tube volcanic flows with intersecting faults. An oblique elongated faulted and sedimented ridge (2 dives) parallel to the oblique relay zone was shown to be of peridotitic nature Recent faults have been observed, as well as traces of high-T hydrothermal activity consistent with black-smoker type venting, recently overprinted by low temperature diffuse venting related to active faulting.</p>

scholarly journals FEATURES OF TECTONIC DEVELOPMENT OF STRUCTURES IN THE MIDDLE OB BY CORRELATION OF THICKNESS ANALYSIS

2018 ◽  
pp. 77-83
Author(s):  
F. Z. Khafizov
Keyword(s):  
Correlation Analysis ◽  
Middle Jurassic ◽  
Large Scale ◽  
Upper Cretaceous ◽  
Tectonic Activity ◽  
Active Tectonic ◽  
History Of ◽  
Tectonic Development

The article is devoted to the main patterns of tectonic development in the Middle Ob for the period from the tops of the middle Jurassic to the Eocene. It is shown that during this period of time in the tectonic development of the territory there were periods of quiet sedimentation and very active tectonic activity. In the history of the tectonic development of the Middle Ob four major stages are distinguished: two is quiet (the Jurassic and the Upper Cretaceous) and two are very active with large-scale multidirectional movements that led to a significant increase in the amplitudes of the structures (from the Cretaceous to the roof of the Cenomanian century).The article describes the methodology of the correlation analysis used in the study of the history of tectonic development in the territory.

scholarly journals Slip tendency analysis of major faults in Germany

2021 ◽  
Vol 1 ◽  
pp. 77-78
Author(s):  
Luisa Röckel ◽  
Steffen Ahlers ◽  
Sophia Morawietz ◽  
Birgit Müller ◽  
Karsten Reiter ◽  
...  
Keyword(s):  
Stress Field ◽  
Stress Tensor ◽  
Anthropogenic Activities ◽  
Friction Angle ◽  
Tectonic Activity ◽  
Normal Faults ◽  
Nuclear Waste Repository ◽  
Fault Surface ◽  
Slip Tendency ◽  
Tendency Analysis

Abstract. Natural seismicity and tectonic activity are important processes for the site-selection and for the long-term safety assessment of a nuclear waste repository, as they can influence the integrity of underground structures significantly. Therefore, it is crucial to gain insight into the reactivation potential of faults. The two key factors that control the reactivation potential are (a) the geometry and properties of the fault such as strike direction and friction angle, and (b) the orientations and magnitudes of the recent stress field and future changes to it due to exogenous processes such as glacial loading as well as anthropogenic activities in the subsurface. One measure of the reactivation potential of faults is the ratio of resolved shear stress to normal stresses at the fault surface, which is called slip tendency. However, the available information on fault properties and the stress field in Germany is sparse. Geomechanical numerical modelling can provide a prediction of the required 3D stress tensor in places without stress data. Here, we present slip tendency calculations on major faults based on a 3D geomechanical numerical model of Germany and adjacent regions of the SpannEnD project (Ahlers et al., 2021). Criteria for the selection of faults relevant to the scope of the SpannEnD project were identified and 55 faults within the model area were selected. For the selected faults, simplified geometries were created. For a subset of the selected faults, vertical profiles and seismic sections could be used to generate semi-realistic 3D fault geometries. Slip tendency calculations using the stress tensor from the SpannEnD model were performed for both 3D fault sets. The slip tendencies were calculated without factoring in pore pressure and cohesion, and were normalized to a coefficient of friction of 0.6. The resulting values range mainly between 0 and 1, with 6 % of values larger than 0.4. In general, the observed slip tendency is slightly higher for faults striking in the NW and NNE directions than for faults of other strikes. Normal faults show higher slip tendencies than reverse and strike slip faults for the majority of faults. Seismic events are generally in good agreement with the regions of elevated slip tendencies; however, not all seismicity can be explained through the slip tendency analysis.

scholarly journals DEFORMATION HISTORY AND CORRELATION OF PAIKON AND TZENA TERRANES (AXIOS ZONE, CENTRAL MACEDONIA, GREECE)

2017 ◽  
Vol 50 (1) ◽  
pp. 34 ◽  
Author(s):  
E. Katrivanos ◽  
A. Kilias ◽  
D. Mountrakis
Keyword(s):  
Upper Cretaceous ◽  
Crustal Thickening ◽  
Normal Faults ◽  
Polyphase Deformation ◽  
Basement Rocks ◽  
Deformation Phase ◽  
Basin Formation ◽  
Tectonic Window ◽  
Crustal Exhumation ◽  
Terrane Accretion

Paikon and Tzena terranes are situated in the centre part of Axios zone, between Almopia and Paionia ophiolitic belts. Tectonostratigraphic data reveal that both have been affected by the same polyphase deformation and metamorphism, as well that they have the same lithostratigraphic column. The first deformation phase took place during the Middle to Late Jurassic and is associated with ophiolite obduction, nappe- stacking, terrane accretion and crustal thickening (D1). Metamorphism does not exceed greenschist facies (M1). Relict HP-LT metamorphic assemblages predating M1 metamorphism are possibly developed during subduction processes and overloading of the obducted ophiolites on the continental margin, characterized the initial stages of deformation. Compressional tectonics and intense thrusting with the same kinematics continued in Lower Cretaceous time, affected all pre-Upper Cretaceous units and the obducted ophiolites (D2). This phase is associated with low-greenschist metamorphism (M2). The first main extensional event occurs in the Late Cretaceous, related to basin formation and sedimentation (D3). During Paleocene to Eocene, D4 intense imbrication of all tectonic units towards mainly SW takes place again. Nappes collapse and finally crustal exhumation taken place during Oligocene to Miocene, associated with low - angle normal faults, with a main top to the SW sense of movement (D5). In Miocene to recent times, high - angle normal and strike-slip faults are formed in an extensional to transtensional strain regime (D6), associated with Neogene to Quaternary basin formation and terrane dispersion. The basement rocks of both terranes are of Pelagonian origin, exhumed as a multiple tectonic window.

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