Thrust Belt System Research Articles

Seismo-stratigraphic and morpho-bathymetric analysis revealing recent fluid-rising phenomena on the Adventure Plateau (northwestern Sicily Channel)

The northwestern region of the Sicily Channel hosts a great number of morphological highs, the widest of which is the Adventure Plateau that is part of the Sicilian Maghrebian Fold and Thrust Belt system, formed since the Neogene. The Adventure Plateau was shaped in the Early Pliocene by an extensional phase that produced high-angle normal faults mostly WNW-ESE to N-S oriented. Through these faults, magmatic fluids ascended and produced widespread volcanic manifestations often associated to fluid flow processes. The interpretation of multibeam echosounder, seismic reflection (sparker, airgun) and well-log data allow us to identify several features related to the presence of fluids in the study area. The morpho-structural analysis showed a NW–SE oriented fault system and a string of pockmarks that follow the same trend. A detailed well-log analysis confirmed the presence of oil traces, at a depth of ~ 250 m, and gas (i.e., CO2) at a depth of ~ 450 m. The seismo-stratigraphic analysis highlighted seismic signals located below the pockmarks, (e.g. seismic chimneys, bright spots) which suggest the presence of fluids that would rise to a few meters’ depth. Based on the observations, two sources and two corresponding rising mechanisms have been identified. Morphometric analysis of pockmarks has been performed to delineate their possible interaction with the bottom currents. A fluids pathway model has been reconstructed, revealing the source of fluids emissions at depth in the Adventure Plateau, and providing new insights into the identification of fluid leakage pathways.

Radial and azimuthal seismic anisotropy in NW South America: Insights into crustal deformation and mantle flow using ambient noise and surface wave tomography

We illuminate the crustal and upper mantle structure of the northwestern corner of South America by mapping radial and azimuthal seismic anisotropy. Radial anisotropy is inferred from the discrepancy between VSV and VSH polarized S-velocities in horizontally propagating Rayleigh and Love waves, respectively. First, short-period (7–35 s) phase and group velocities are estimated from ambient noise cross-correlations, and long-period (40–170 s) group velocities are determined from fundamental-mode, surface-wave trains from earthquake sources at regional and teleseismic epicentral distances. Dispersion velocities are then tomographically inverted to develop maps of group velocity variation for periods between 7 and 170 s including azimuthal velocity dependence. We observe that positive anisotropy in the upper crust is related to thick Quaternary sequences in sedimentary basins, while negative anisotropy is found beneath active volcanoes and igneous-metamorphic terrains. Negative anisotropy features observed in the lower crust beneath the Eastern Cordillera suggest the existence of sill-like intrusions that penetrate the lower crust, thus supporting underplating mechanisms. Our study reveals SW-NE oriented fast axes of azimuthal anisotropy beneath the Eastern Cordillera, which strongly suggest the presence of shear zones within the fold and thrust belt system. Notably, the fast axes align parallel to the regional faults in the area, indicating a significant role in controlling faulting processes. Finally, we observe a wide trench-parallel zone of azimuthal anisotropy beneath the Nazca Plate, the Panama Block, and the Caribbean, which we associate with subslab mantle flow.

Tectonic framework of surface and blind structures from neotectonic and geophysical (gravimetry) analyses, Central Andes of Argentina

This work describes new evidence of N–S and oblique trending surface and blind structures in the La Cantera-Gualilán tectonic depression in the Central Precordillera, San Juan Province, Argentina. Two main N–S Quaternary thrusts cross longitudinally the valley located ∼60 km west of San Juan city (30° 50′- 31° 17′ S and 68° 55′- 69° 05′ W). One of them is located in the eastern piedmont of the Sierra de La Invernada (San Juan Fault) and the other in the western piedmont of the Sierra de La Cantera (La Cantera Fault System), although the northward continuation of this structure has not yet been confirmed.Besides, a smooth water divide or “portezuelo” controlled by an oblique transpressive structure (Divisadero Coba Rubia Fault) separates two N–S elongated river basins with opposite water flow directions. One of these is the Gualilán River, which flows from south to north, and the other corresponds to the La Cantera River, running from north to south.In the present work, we describe some new natural exposures and subtle geomorphological evidence of Quaternary structures identified in the Gualilán-La Cantera tectonic depression. We also use regional and local gravity data to analyze and interpret gravity anomalies related to these surface or blind active structures. Then, based on our geologic and geophysical interpretations, we infer the presence of several, buried cross-strike structures with NW and NE trends, one of them coincident with the drainage divide between the Gualilán and La Cantera opposite river basins, possibly related to the Coba Rubia Fault. Also, we suggest the northward continuation of the La Cantera Fault System (LCFS) as a buried structure in coincidence with the Gualilán River alluvial plain. In this sense, the gravity response of the basement and these river sub-basins shows a close relationship with the surface and subsurface structures. We propose that the oblique structures could represent pre-existing crustal fabrics reactivated during the Andean orogeny, segmenting the N–S Precordillera fold and thrust belt system. Finally, according to the analyzed neotectonic and gravimetric features, we consider the La Cantera-Gualilán Valley as a potentially seismogenic source in this intraplate portion of the Andean Precordillera, crossed by several N–S and oblique surficial and buried/blind active structures. These tectonic features could play a significant role in a regional seismic hazard assessment.

Sequence Stratigraphy of Miocene Mixed Carbonate-Siliciclastic in Fold and Thrust Belt System, Banggai Basin

This study was specifically analyzed in the southern part of the Banggai Basin, precisely in the TKA Field. In the Tertiary, regional stratigraphy reveals, the Banggai Sula microplate comprises carbonate shelf and siliciclastic sequence. Several previous studies had been concluding, the tertiary limestone was deposited during the Early Eocene to Middle Miocene. Carbonate formations which has been known by Tomori and Minahaki Formation. Meanwhile, their siliciclastic dominated is Matindok Formation and Celebes Mollase. These sequences formed a distinct stratigraphic style in the geophysical well log and seismic data. Four cycles are distinguished, the lower part of Tomori Formation at the outer shelf and directly overlying by the upper part of inner shelf Tomori Formation. it was superimposed by siliciclastic sediments that have been deposited in the outer litoral during regressive phase. Whereas during rising sea level or highstand, the litoral system migrated to basinward wherein Minahaki Formation was deposited. Sequence stratigraphy provides a reliable methodology for correlate both carbonate and siliciclastic successions. It was analyzed based on 4 wells, 2D, and 3D seismic data which has been available. Sequence stratigraphy analysis using T-R sequence concept by Embry and Johanessen. Trasngressive and regressive phases were obviously determined by lithofacies, coral colony and foram that were recorded on biostratigraphic analyses. In this study, cyclic sea-level change will be recognized as system tract record of mixed carbonate-siliciclastic sequence.

Coeval Miocene development of thrust belt-backarc and forearc extension during the subduction of a continental margin (Western-Central Mediterranean Sea)

The position of the middle-upper Miocene volcanic arc, encompassing the Maghrebides, the Sardinia Channel and the Sardinia-Corsica block, implies that the Algerian and Tyrrhenian basins developed, respectively, as backarc and forearc extensional zones in the Western-Central Mediterranean. The opening of the Western-Central Mediterranean Neogene extensional basin has been commonly interpreted as a two-step process: the opening of the Provençal-Algerian basin during the early-middle Miocene, followed, in the late Miocene, by the formation of the Tyrrhenian Basin. This article is an attempt to synthesize knowledge about the hinge zone between Algerian and Tyrrhenian basins by combining the analysis of seismic reflection profiles with dredge and borehole data in order to investigate how the transition between the eastern Algerian backarc and Tyrrhenian forearc geodynamic settings took place. We identified three sectors: the western Tyrrhenian characterized by a Tortonian forearc extension; the Sardinia Channel, which preserves the architecture of the lower Miocene Maghrebian thrust belt formed during the collision between Europe and Africa plates; and the easternmost Algerian basin-Sicily Channel where a backarc–thrust belt system developed during the Tortonian stage. During the extensional events, we hypothesize the re-activation of inherited structures during Tortonian rifting, (that is a negative tectonic inversion of pre-existing Eocene and early Miocene thrust faults). The contemporaneity of two different geodynamic environments, the forearc extension in the northern area and backarc–thrust belt system in the southern area, can be directly related with a lateral variation of the lower plate paleogeography of the Africa continental margin. This evidence contributes to the understanding of how the paleogeography of the lower plate can control, to a certain extent, the tectonic evolution of the upper plate in a subduction setting.

Activity maps of multi-source mudslides from the Daunia Apennines (Apulia, southern Italy)

Multi-source mudslides are common in the Daunia Apennines, i.e., the Apulian sector of the Southern Apennines of Italy, and play an important role in the historical evolution of the landscape, with significant impact on the social and economic activities of the area. They also represent the most relevant geological hazard along the front of the Apennine Chain and expose to a considerable risk the local population and infrastructures. The outer sector of the Daunia Apennines is part of the foreland thrust belt system, made up of fissured fine-grained materials, belonging to the Daunia tectonic unit formations. Concerning landslide typology, the most frequent slope movements are represented by flows and composite mudslides, the latter typically starting as slumps evolving from flows. This paper deals with the production of landslide activity maps of three case studies of composite mudslides from the front of the Daunia Apennines. The maps were produced integrating traditional interpretation of multi-year aerial photograph coverage and field surveys with the available digital elevation models to analyze surface morphology. Each landslide activity map corresponds to multi-temporal landslide inventories compiled for the last 15–20 years. This paper outlined that in the last 20 years the front of the Daunia Apennines underwent a significant reactivation of slope failure phenomena after years of quiescence, or of limited activity. The three case studies clearly confirm that: (i) the active portions of the mudslides are located inside or near preexisting slope failures, and (ii) the spatial distribution of instability phenomena is strictly dependent upon the presence of older, larger and dormant, phenomena. Landslide activity maps are an important tool for the evaluation of landslide susceptibility and hazard in the study area, and for quantitative geomorphological analyses it aimed at understanding the long-term geomorphological evolution of this portion of the Southern Apennines. Moreover, we argue that high-quality multi-temporal inventories could have positive effects on all derivative products and analyses, including erosion studies and landscape modeling, susceptibility and hazard assessments, and risk evaluations as well.

Quaternary Seismostratigraphy and Tectonosedimentary Evolution of the North Tunisian Continental Margin

AbstractNorthern Tunisia contains the poorly defined boundary between the Nubia and Eurasian plates. Offshore north Tunisia, the continental margin is interpreted to be part of the North Africa collisional fold and thrust belt system, linking the Maghrebian and the Sicilian‐Apennine chains. The Tunisia margin deforms by a slow NW‐SE trending convergence resulting in a diffuse deformation zone with scarce and scattered seismicity, in contrast to the neighboring regions of north Algeria and north Sicily. The complex recent evolution of this region is poorly known due to the paucity of studies, particularly offshore in the north Tunisian continental margin. Here, we present the seismostratigraphic analysis of the last ~1.8 Ma tectonosedimentary evolution of this area. The seismostratigraphic analysis supports that individual Quaternary depocenters developed syntectonic to faulting and that faulting influenced sedimentation patterns. We identify an abrupt variation in the sediment accumulation rates (SARs) coeval to a change in the strata geometry of the units located near faults at 402 ± 5 ka (mid‐Middle Pleistocene), supporting a change in the rate of faulting associated to contraction tectonics. This change indicates that deformation is controlled by the NW‐SE convergence between Nubia and Eurasia, probably accelerated at the end of extension in the Tyrrhenian back‐arc. Therefore, the current driving mechanism in the Central Mediterranean is possibly lithospheric collision between Nubia and Eurasia.

Control of syntectonic erosion and sedimentation on kinematic evolution of a multidecollement fold and thrust zone: Analogue modeling of folding in the southern subandean of Bolivia

Several analogue modeling studies have been conducted during the past fifteen years with the aim to discuss the effects of sedimentation and erosion on Foreland Fold and Thrust Belt, among which a few have analyzed these processes at kilometric scale (Malavieille et al., 1993; Nalpas et al., 1999; Barrier et al., 2002; Pichot and Nalpas, 2009). The influence of syn-deformation sedimentation and erosion on the structural evolution of FFTB has been clearly demonstrated. Here, we propose to go further in this approach by the study of a more complex system with a double decollement level. The natural study case is the Bolivian sub-Andean thrust and fold belt, which present all the required criteria, such as the double decollement level. A set of analogue models performed under a CT-scan have been used to test the influence of several parameters on a fold and thrust belt system, among which: (i) the spatial variation of the sediment input, (ii) the spatial variation of the erosion rate, (iii) the relative distribution of sedimentation between foreland and hinterland. These experiments led to the following observations:1. The upper decollement level acts as a decoupling level in case of increased sedimentation rate: it results in the verticalization of the shallower part (above the upper decollement level), while the deeper parts are not impacted.2. Similarly, the increase of the erosion rate involves the uplift of the deeper part (below the upper decollement level), whereas the shallower parts are not impacted.3. A high sedimentation rate in the foreland involves a fault and fold vergence reversal, followed by a back-thrusting of the shallower part.4. A high sedimentation rate in the hinterland favours thrust development toward the foreland in the shallower parts.

Interplay of thrust, back-thrust, strike-slip and salt tectonics in a fold and thrust belt system: an example from Zakynthos Island, Greece

The southwestern flank of the Hellenic fold and thrust belt, situated along the southern edge of the Dinarides–Albanides–Hellenides continental convergent zone, was examined for reconstructing the tectonic deformation. This investigation presents an integrated study of onshore sedimentological and structural analyses, as well as offshore seismic lines, across the Pliocene–Pleistocene sedimentary succession in Zakynthos Island. Back-thrust faults, using the Triassic evaporites as decollement surface, during the Pliocene, and coeval diapiric intrusions formed three sub-basins on the hangingwall of the Kalamaki back-thrust fault. This interaction is responsible for the growth of the Skopos Mountain and the soft sediment deformation that formed synclines and slumps, respectively. Back-thrust and strike-slip faults were active during the early Pleistocene, and diapiric intrusions modified the bathymetry on the sea floor, giving rise to slumps and recumbent folds. At least five events of synsedimentary diapiric intrusions have been recognized and are marked by five slump horizons. During the Holocene, the diapiric intrusions between the Kalamaki back-thrust and the Vrachionas anticline could be either related to normal faults or gravitationally driven.

Structural context of meso-scale and cartographical duplex structure genesis in thrusting tectonics: role of tear faults. Zaghouan thrust belt. Case of Bir M'Cherga-Ain Asker area

Bir M'Cherga-Ain Asker area, situated in the hinterland of Zaghouan thrust (Tunisian dorsal), was the land example treated with metric and cartographic scale in order to identify duplex genesis criteria and to include thrusting tectonics associated with tear faults, which are in fact the directory response generating duplex structures identified in outcrop for the first time through Tunisia in this case. Given its geological location between the "dome" and the "dorsal" zone of Tunisia, this area was the most exposed to a highly paleostress history expressed by a huge fault system remobilization and reactivation through several tectonic events from NE–SW middle Cretaceous distension to a NW–SE and NNW–SSE Paleogene compression. Regarding fault planes generated analysis, they show numerous streak generation of normal, strike-slip, and reverse faults that go with geodynamic and paleostress evolution of the studied area; we note that each streak generation is perfectly matching with one of the tectonic event (mentioned before) affecting the area. In this paper, we analyze duplex structure elaboration scenarios to assess the involved kinematics and their geometrical recognition criterious. We propose to discuss the causes of duplex structures installation in a thrust belt system and the predictable geometrical styles after its installation on foreland or backland. Using the geometrical criteria acquired through this analysis, we will show that such, however, exceptionable structures exist on the land, and that they record the mechanisms of their genesis linked to the tear faults acting in this case. We describe "tear faults" as the sliding breaks which disunite two compartments during deformation, allowing them to undergo different independent deformations in their drawing and their width (for example more or less stretched folds). These types of faults differ from that of the true stick-slip faults, which slice and shift preformed structures (it's even this shift which makes it possible to highlight them); here, there are no shift but dissimilarity of the structures on both sides of the fault; therefore, deformations are the direct results of displacements; they are expressed in thrust belts by ramp folds, intense internal deformations, and even by complex duplex structures. A duplex feature that is not mainly studied is made up by tilted imbricate sedimentary sequences (or horses), separated by link thrusts and underlined respectively at their tops and bottoms by roof and floor thrusts. Imbrications cause a shortening, a thickening, or a thinning of stratigraphic columns and even its crushing and inverting. In thrust belts, duplexes are usually set up following two or even more deformational events; those structures start typically with decollement and imbricate sedimentary unit ones which are made cover by a roof thrust sometimes visible at outcrop. Through this paper, we suggest to discuss geometrical duplex criteria, and we will try a zooming through different scales, from regional to local one in order to show how the shape (expression) of the deformation differs.

Forward modeling the kinematic sequence of the central Himalayan thrust belt, western Nepal

The Himalayan thrust belt is often cited as an example of a thrust system that propagated from hinterland to foreland; however, this kinematic sequence is not well documented, and the process of formation of the thrust belt has not been well supported. This study uses forward modeling and timing data to reveal a detailed view of the evolution of the central Himalayan thrust belt from the footwall of the South Tibetan detachment system southward to the Main Frontal thrust. By using a reasonable configuration of undeformed stratigraphy, the surface deformation in western Nepal can be dynamically reproduced, confirming that the cross sections from which the undeformed sections were derived are viable and propagated from hinterland to foreland. In addition, this study yields detailed step-by-step reconstructions of three cross sections and is the first of its kind in any thrust belt system. These detailed views are useful for understanding and bracketing erosion data, the basin sediments, and geodynamic models. Modeling shortening estimates are between 495 and 733 km from the Main Frontal thrust to the South Tibetan detachment system, and are within the range predicted for shortening in western Nepal obtained from balanced cross sections (485–743 km). Thus, the Himalayan thrust belt in western Nepal is essentially a forward-propagating thrust belt from hinterland to foreland, with minor out-of-sequence (

Proveniência e idade do metamorfismo das rochas da Faixa Brasília, na Região de Tapira (SW de Minas Gerais)

The Brasilia Fold Thrust Belt at Tapira area (SW of Minas Gerais State, Brazil) has four different litho-tectonic domains imbricated by thrust faults with vergency to the Sao Francisco Craton. Sm/Nd isotopic studies were undertaken and the results show different model and metamorphic ages for the thrust sheets. Rocks from the lower thrust sheet yield a metamorphic age of 543 Ma while the upper thrust sheet has a metamorphic age of 581 Ma. The TDM model ages are similar for both thrust sheets, between 1.7 and 2.2 Ga. Because of their lithologic characteristics, the thrust sheets are interpreted as having been deposited in a distal continental platform environment, their main source being Paleoproterozoic rocks of the Sao Francisco Craton. The upper thrust sheet rocks presents a metamorphism age of 612 Ma and a bimodal distribution of TDM model ages between 1.3 and 1.9 - 2.0 Ga, respectively. The lithologic and isotopic characteristics of this thrust sheet the rocks are interpreted as a result of deposition on a continental slope or oceanic floor environment, with mixed contributions from Paleo - and Mesoproterozoic rocks of the Sao Francisco Craton. In spite of the small number of analyzed samples and the uncertainties inherent to the Sm/Nd method the metamorphisms are not considered to be synchronous in the different thrust sheets. This is to be expected in a thrust belt system, in which the more metamorphosed thrust sheets are juxtaposed to less metamorphosed ones.

Crustal section based on CROP seismic data across the North Tyrrhenian–Northern Apennines–Adriatic Sea

Using deep seismic reflection data from the Italian lithospheric exploration project CROP in the Central Mediterranean region, a 400-km-long section, composed of three different profiles crossing the Northern Tyrrhenian Sea (CROP M-12A profile), the Northern Apennines (CROP-03) and the Adriatic Sea (CROP M-16) is reconstructed and discussed. New data allow us to outline a seismically consistent tectono-stratigraphic setting for the crust and upper mantle of the Northern Apennines thrust–belt system and its Adriatic foreland. Time–space analysis of the deformation of the investigated chain and identification of existing macrostratigraphic crustal intervals and tectonic units allow a reasonably controlled interpretation of the geodynamic evolution and of the main orogenic stages. Careful seismic reprocessing and application of advanced techniques to key zones of the explored area (such as the Tuscan Archipelago) were determinants in obtaining fundamental information for understanding of the complex lithospheric structures and their evolution. Profile interpretation supports that the Northern Apennine chain is dominated by a compressive thrust system. Crustal extension, assumed by some authors as the dominating tectonic process for the whole Tuscan Apennine area, represents a subordinate geodynamic event of the last stage (Tyrrhenian). In the Early Cretaceous–Late Jurassic, the paleogeographic framework consisted of the Europe and Adria plates separated by the Alpine Tethys Ocean. During the Late Cretaceous–Early Eocene, Adria–Europe convergence (eo-Alpine stage) and subduction beneath the Adria plate closed the Alpine Tethys Sea, with the Tethyan slab being clearly seismically imaged. The first Apenninic geodynamic stage occurred in the Late Oligocene–Early Miocene with the opening of the Balearic Basin, which generated a first “lithospheric root” of the Apenninic chain in the Tuscan Archipelago area. This root is represented by Adria-verging thrust faults that progressively flatten eastward. Upper parts of the west-verging eo-Alpine thrust blocks were truncated by the east-verging thrust faults of the Balearic stage. A deeper seismic reflector, attributed to the top of the asthenosphere, forms a mantle high below the Elba Island. From the Late Miocene to Present, the Corsica basin and western hinterland area were affected by extensional tectonics related to the Tyrrhenian opening, whereas compressional tectonics continued in the eastern hinterland and mostly on the eastward migrating foreland, with development of a second “lithospheric root” constituted by high-angle thrust faults. These faults give rise to a huge basement culmination below the main Apennines watershed. Impressive E-directed gravity-sliding of sedimentary blocks over their sloping basement occur, generating the Umbria–Marche shallow seismicity. Crustal shortening of the Apennines system amounts to 170 km, 14 km of which are due to the eo-Alpine stage, 71 km to the Balearic and 85 km to the Tyrrhenian one. In the frame of Africa–Europe convergence, the Tyrrhenian–Apennines tectonodynamics were mainly conditioned by the Mesozoic paleogeography.

Pleistocene strike‐slip tectonics in the Lucanian Apennine (southern Italy)

Structural studies carried out in the Lucanian Apennines (Southern Italy) show that strike‐slip faulting was the principal mode of deformation of this area during middle‐upper Pleistocene time. W‐NW to E‐SE trending left strike‐slip fault systems dissect the entire Apennine mountain belt and affect the preexisting thrust geometry. Strike‐slip faults, activated by a roughly E‐W shortening, are characterized by different geometries representing the surface response to lateral motion occurring along deep‐seated structures. The occurrence of different structural patterns which characterize different segments of strike‐slip system is related to (1) the depth of a major decoupling surface which separates the upper tectonic multilayered horizon (Apennines thrust belt system) from the lower rigid horizon (Apulian belt) in which strike‐slip structures have originated and (2) the geometric relationships between the strike‐slip faults and the thrust belt pattern which characterize the upper horizon. The different segments of the strike‐slip system are interpreted as internal deformation developed within a crustal shear zone. This zone, which corresponds to the boundary between the Apulian block and the Apennine chain, is characterized by sinistral movement as a response to the northwesterly convergent motion of the African plate with respect to Europe.