Plio-Quaternary Deformation Research Articles

Late Quaternary deformation in the western extension of the North Anatolian Fault (North Evia, Greece): Insights from very high-resolution seismic data (WATER surveys)

Since the Pliocene, rift basins have developed in the North Evia region at the south-western extension of the North Anatolian Fault. North Evia, therefore, is a key area for investigating Plio-Quaternary deformation within the diffuse Anatolian-Aegean–Eurasian plate boundary. In this study, we present a detailed map of offshore faults in the North Evia region based on three seismic reflection surveys: an airgun (2004) and two very high-resolution Sparker (2017 and 2021) single-channel surveys. Careful and systematic interpretation of these datasets revealed i) the identification of a new basin (Skiathos Basin) located at the western extension of the North Anatolian Fault and ii) two main fault sets striking oblique to the active N–S-directed extension. The seismicity analysis of the study area reveals pure strike-slip displacements along faults previously identified as normal. The NW–SE-striking faults bordering the North Evia Gulf rift are characterised by left-lateral displacements, and the NE–SW faults present dextral focal mechanisms, following the kinematic character of the North Anatolian Fault. We show that dextral strike-slip deformation recently occurred (in the late Quaternary) in the south-western extension of the North Anatolian Fault, suggesting the significant role of this fault system in the complex structural development of the North Evia region.

Geodynamics of the South Balkan and Northern Aegean Regions Driven by the Westward Escape of Anatolia

The Plio-Quaternary deformation pattern of the northern Aegean and south Balkan regions is interpreted as an effect of the interaction between the Anatolian-Aegean-Pelagonian system (Tethyan belt), undergoing westward extrusion and strong deformation, and the surrounding plates (Nubia, Europe and Adriatic). Since the middle-late Miocene, the collision of the Tethyan belt with the continental Adriatic domain has caused strong E-W shortening in the outer Hellenides and Albanides, also involving the southward extrusion of the Peloponnesus wedge, at the expense of the Ionian oceanic domain. The roughly E-W extension recognized in the western South Balkan zones (Macedonia and eastern Albania) is related to the divergence between the Pelagonian belt (Albanides and Hellenides) and the Rhodope-Moesia domain. Stressed by the westward displacement of the central Anatolian plateau and by the southward bowing of the Cycladic Arc, the northern Aegean zone has contemporaneously undergone E-W compression and N-S extension, which has generated a series of dextral shear faults, delimiting a number of slats. The westward displacement and deformation of such slats can explain the morphological features of the northern Aegean zone. During this phase, the push of the central Anatolian plateau also caused the separation of the Rhodope massif from the Moesian European domain, with the consequent formation of the upper Thrace basin. This hypothesis can explain the Plio-Quaternary compressional deformations recognized in a sector of the North Anatolian fault system, the Ganos-Gelibolu zone. The proposed geodynamic/tectonic interpretation may help to explain some features of the time-space distribution of major earthquakes in the study area.

Active fault segmentation in Northern Tunisia

Active shortening structures in Northern Tunisia have developed by tectonic inversion since the Pliocene, after Late Miocene extensional collapse of the whole region. Restored Plio-Quaternary deformation observed on reflection seismic lines indicates deformation rates around 0.6–0.8 mm/yr in the studied segments and larger amounts of shortening to the West of Northern Tunisia (16%) than to the East (7%), which suggests tectonic inversion started earlier to the West and later propagated eastwards, reaching Northeastern Tunisia in the Late Pliocene. This shortening is registered on striated pebbles in Quaternary alluvial terraces and fault-slip data giving two populations of strain ellipsoids with N–S and WNW-ESE maximum shortening. Morphometric analysis in combination with field fault segmentation mapping show that topographic uplift and drainage rejuvenation occurs in relation to 20–30 km long ENE-WSW reverse fault segments and related antiforms that are offset and linked by E-W to WNW-ESE dextral and NE-SW-oriented sinistral faults. The largest fully linked fault system is the Alia-Thibar fault. This 130 km long fault zone shows an helicoidal geometry with five different fault segments, including reverse, dextral, sinistral and oblique faults. Due to the young age of tectonic inversion, after late Miocene extensional collapse of the region, the present relief of Northern Tunisia is characteristic of a young thrust and fold belt, with dominating axial valleys along synforms and an incipient transverse drainage development propagating from West to East.

Analysis of the recent Plio-Quaternary deformation and the correlation with the focal mechanisms of the significant earthquakes in the Bokoya, Ras Tarf (Eastern Rif)

Relative movements of microplates developed between the African and Eurasian plate characterize the continuity of the tectonic movements in Westerner of the Mediterranean Sea. The convergence movements between these plates, at the origin of the current structuring in oriental Rif. The recent tectonics in the south ripple of Alboran Sea, translated by an important seismic activity, In the North of Morocco, exactly in the Al Hoceima region, considered as zone of plates border with important seismicity. The structural analysis made in this paper and the interpretation of focals mechanisms earthquakes characteristics in the Al Hoceima region, has allows to deduct the main directions of faults, which we compared with the results of the satellite images. This study we has provides to demonstrate the directions of faults which are able to generate earthquakes in the future. The direction NE-SW represents the overall faults dominant in oriental Rif, this major direction coincides with the breaks of surface. A reduced number of faults shows a generall direction NNE-SSO to N-S through the Quaternary formations in the NO of Al Hoceima city, the direction NO does not show a good correlation with the directions of surface rupture, as well as with the deducted directions from focals mechanisms. This study drives us to propose that faults of direction NNE-SSO to NE-SO, represent the major directions of the faults in the Al Hoceima region, which represents the main cause of the seismic activity in the region.

Analysis of the recent Plio-Quaternary deformation and the correlation with the focal mechanisms of the significant earthquakes in the Bokoya, Ras Tarf (Eastern Rif)

Analysis of the recent Plio-Quaternary deformation and the correlation with the focal mechanisms of the significant earthquakes in the Bokoya, Ras Tarf (Eastern Rif)

Contrasting terrace systems of the lower Moulouya river as indicator of crustal deformation in NE Morocco

The Moulouya river has the largest catchment in Morocco and drains an area characterized by active crustal deformation during the Late Cenozoic due to the N–S convergence between the African and Eurasian plates. As yet, its Pleistocene terrace sequence remains poorly documented. Our study focuses on the lowermost reach of the river in north-eastern Morocco, which drains the Zebra-Triffa sedimentary basin directly upstream of the estuary. New field observations, measurements and sedimentological data reveal contrasting fluvial environments on each side of a newly identified, W–E striking thrust zone disrupting the sedimentary basin. On the one hand, long-lasting fluvial aggradation, materialized by 37 m-thick stacked terraces, has occurred in the footwall of the thrust. On the other hand, the hanging wall is characterized by a well-preserved terrace staircase, with three Pleistocene terrace levels. Whilst the identification of this thrust zone question some previous interpretations about the local (hydro-)geology, it is consistent with the statement that most of the Plio-Quaternary deformation in the eastern Rif mountains has concentrated in this region of Morocco. Our new data and interpretations also agree with morphometric indicators showing that the whole Moulouya catchment is at desequilibrium state (i.e. several knickzones in its longitudinal profile), showing several knickzones in its longitudinal profile, is at disequilibrium state. We also suggest that the knickzone in the Beni Snassen gorge, located directly upstream of the Zebra-Triffa sedimentary basin, could (partly) result from a transient fluvial reaction to Late Cenozoic thrusting activity and correlated uplift in the hanging wall.

Strength of the Iberian intraplate lithosphere: Cenozoic deformations and seismicity

Previous studies about the strength of the lithosphere in the center of Iberia fail to resolve the depth of earthquakes because of the rheological uncertainties. Therefore, new contributions are considered (the crustal structure from a density model) and several parameters (tectonic regime, mantle rheology, strain rate) are checked in this paper to properly examine the role of lithospheric strength in the intraplate seismicity and the Cenozoic evolution. The strength distribution with depth, the integrated strength, the effective elastic thickness and the seismogenic thickness have been calculated by a finite element modelling of the lithosphere across the Central System mountain range and the bordering Duero and Madrid sedimentary basins. Only a dry mantle under strike-slip/extension and a strain rate of 10-15 s-1, or under extension and 10-16 s-1, causes a strong lithosphere. The integrated strength and the elastic thickness are lower in the mountain chain than in the basins. This heterogeneity has been maintained since the Cenozoic and determine the mountain uplift and the biharmonic folding of the Iberian lithosphere during the Alpine deformations. The seismogenic thickness bounds the seismic activity in the upper–middle crust, and the decreasing crustal strength from the Duero Basin towards the Madrid Basin is related to a parallel increase in Plio–Quaternary deformations and seismicity. However, elasto–plastic modelling shows that current African–Eurasian convergence is resolved elastically or ductilely, which accounts for the low seismicity recorded in this region.

Deciphering neotectonics from river profile analysis in the karst Jura Mountains (northern Alpine foreland)

The study of the neotectonic activity in the Jura Mountains (northwestern most belt of the European Alps) represents a challenge in the application of quantitative geomorphology to extract landscape metrics and discuss potential coupling between tectonic, climatic and lithospheric mechanisms during the evolution of this mountain belt. The Jura Mountains are characterized by a karst calcareous bedrock, slightly affected by Quaternary glaciations, and by moderated uplift rates (<1 mm/year). In this study, we performed river profile analyses to decipher comparable geomorphological signals along tectonic structures within the entire Jura arc. Our results suggest higher tectonic activity in the High Range of the belt (internal part) than in the External Range, which is discussed in terms of deformation mechanisms. Integration of our results with previous geomorphological, neotectonic and geodetic studies from the literature leads us to propose new potential lithospheric and tectonic mechanism(s) driving the Plio-Quaternary deformation of the Jura Mountains. Our study finally reveals a regional-scale correlation between neotectonic deformations recorded by the Jura drainage network and the predicted isostatic rebound in response to Alpine Quaternary erosion. However, the correlation between our geomorphic signals and compressive structures suggests that the Jura Mountains could be still in horizontal shortening in both the High Range and the External Range.

Plio-Quaternary extensional tectonics of the Central Anatolian Plateau: a case study from the Tuz Gölü Basin, Turkey

The Tuz Gölü Basin is the largest sedimentary depression located at the center of the Central Anatolian Plateau, an extensive, low-relief region with elevations of ca. 1 km located between the Pontide and Tauride mountains. Presently, the basin morphology and sedimentation processes are mainly controlled by the extensional Tuz Gölü Fault Zone in the east and the transtensional İnönü-Eskişehir Fault System in the west. The purpose of this study is to contribute to the understanding of the Plio-Quaternary deformation history and to refine the timing of the latest extensional phase of the Tuz Gölü Basin. Field observations, kinematic analyses, interpretations of seismic reflection lines, and ^{40}Ar/^{39}Ar dating of a key ignimbrite layer suggest that a regional phase of NNW-SSE to NE-SW contraction ended by 6.81 ± 0.24 Ma and was followed by N-S to NE-SW extension during the Pliocene-Quaternary periods. Based on sedimentological and chronostratigraphic markers, the average vertical displacement rates over the past 5 or 3 Ma with respect to the central part of Tuz Gölü Lake are 0.03 to 0.05 mm/year for the fault system at the western flank of the basin and 0.08 to 0.13 mm/year at the eastern flank. Paleo-shorelines of the Tuz Gölü Lake, vestiges of higher lake levels related to Quaternary climate change, are important strain markers and were formed during Last Glacial Maximum conditions as indicated by a radiocarbon age of 21.8 ± 0.4 ka BP obtained from a stromatolitic crust. Geomorphic observations and deformed lacustrine shorelines suggest that the main strand of the Tuz Gölü Fault Zone straddling the foothills of the Şereflikoçhisar–Aksaray range has not been active during the Holocene. Instead, deformation appears to have migrated towards the interior of the basin along an offshore fault that runs immediately west of Şereflikoçhisar Peninsula. This basinward migration of deformation is probably associated with various processes acting at the lithospheric scale, such as plateau uplift and/or microplate extrusion.

Nubia-Eurasia kinematics: an alternative interpretation from Mediterranean and North Atlantic evidence

It is argued that the Plio-Quaternary deformation pattern in the Mediterranean region is compatible with a SSWNNE convergence between Africa (Nubia) and Eurasia and that the significant difference between this kinematics and the one provided by global models (SSE-NNW convergence e.g., the NUVEL-1) may be due to the fact that those models interpret North Atlantic data by adopting an oversimplified two-plate configuration, which cannot account for the occurrence of significant seismotectonic activity inside the presumed Nubia and Eurasia blocks. It is shown that the adoption of a new plate configuration involving the Iberia and Morocco microplates, strongly suggested by geological and seismotectonic evidence, makes it possible to identify a kinematic model compatible within errors with the constraints recognized in the Mediterranean region and with the NUVEL-1 North Atlantic data set. Some considerations are made about why the present-day Nubia-Eurasia kinematic models inferred from geodetic observations are significantly different from long-term models, such as model NUVEL- 1 and the one proposed in this work.

Plio-Quaternary tectonic evolution of the Northern Apennines thrust fronts(Bologna-Ferrara section, Italy): seismotectonic implications

The outermost, NE-verging fronts of the Northern Apennines (Italy) are overlain by a thick syntectonic sedimentary wedge filling up the basin beneath the Po Plain. Due to fast sedimentation rates and comparatively low tectonic rates, the fronts are generally buried. Evidence for their activity includes scattered historical and instrumental earthquakes and drainage anomalies controlled by growing buried anticlines. The largest earthquakes, up to M w 5.8, are associated with active compression, with a GPS-documented shortening rate <1 mm/a. We used geological, structural and morphotectonic data to draw a N-S-striking section between Bologna and Ferrara, aimed at analyzing whether and how the deformation is partitioned among the frontal thrusts of the Northern Apennines and identifying the potential sources of damaging earthquakes. We pointed out active anticlines based on the correspondence among drainage anomalies, historical seismicity and buried ramps. We also analyzed the evolution of the Plio-Quaternary deformation by modeling in a sandbox the geometry, kinematics and growth patterns of the thrust fronts. Our results (i) confirm that some of the main Quaternary thrusts are still active and (ii) highlight the partitioning of deformation in the overlap zones. We note that the extent and location of some of the active thrusts are compatible with the location and size of the main historical earthquakes and discuss the hypothesis that they may correspond to their causative seismogenic faults.

Current deformation of the Digne Nappe (southwestern Alps) from a comparison between triangulation and GPS data

The negligible present‐day convergence between northern Italy and stable Europe as shown by continuous GPS measurements and the low level of Alpine seismicity both indicate that present‐day deformation in the western Alps is very moderate. Nevertheless, from historical seismicity records, the Moyenne Durance Fault can be identified as an active structure, and a brief neotectonic and geomorphological analysis indicates that Plio–Quaternary deformation occurred in the northern Valensole Basin and in the Digne Nappe. A comparison is made between 1949 and 1952 triangulation data and 1997 GPS data to estimate the current deformation in the Digne Nappe and around the Moyenne Durance Fault in the southwestern Alps. The deformation is represented by the maximum angular shear rates needed to make the characterization of the deformation independent of the rigid rotation and scale effects that are introduced in the velocity field when using triangulation data. Errors on maximum angular shear rates are simulated using a Monte Carlo analysis of the errors of the triangulation data. The main results are: (1) the existence of moderate deformation in the inner part of the Digne Nappe; (2) deformation of the northern Valensole Basin; (3) significant deformation in the southern part of the Moyenne Durance Fault; and (4) a lack of measurable deformation in the southern Valensole Basin–Provencale range area and south of the Lure Mountain.

Role of kinematically induced horizontal forces in Mediterranean tectonics: insights from numerical modeling

Finite element modeling of the central–eastern Mediterranean region has been carried out to show that the recent/present deformation pattern of this zone, inferred from neotectonic observations and seismic strain rates, may be satisfactorily reproduced as effect of the relative motion of Africa and eastern Anatolia with respect to Eurasia. Numerical modeling involved 2D elastic elements in a plane-stress approximation. The model is constituted by a mosaic of poorly deformable blocks separated by much more deformable decoupling zones, representing consuming boundaries, extensional zones and transcurrent discontinuities, whose location and geometry have been deduced by neotectonic, morphological and seismological information. The calculated displacement field obtained with the modeling parametrization which allows to match the observed strain regimes is compatible with geodetic observations in the study area, but for the Hellenic Arc, where geodetic velocities are higher than those predicted by modeling. This discrepancy could be considerably reduced by adopting a higher deformability of the model in the Hellenic trench, but this condition would contrast with the Plio-Quaternary deformation pattern of the southern Aegean zone, which suggest a considerable slowdown of western Crete since the late Pliocene. Furthermore, geodetic velocities are considerably higher than the motion rates derived by moment tensor analysis in the Hellenic trench and in the internal Aegean area and cannot easily account for the low Quaternary deformation observed in the southern Aegean zone. The above discrepancy could be due to a difference between the “instantaneous” kinematic behavior of the Aegean zone, indicated by geodetic measurements, and the average behavior over longer time intervals, inferred from geological and seismological strain indicators.

Andean reactivation of the Cretaceous Salta rift, northwestern Argentina

Throughout the Andes, foreland geometries are correlated with the orientation of the subducting Nazca Plate: fold-and-thrust belts with steep subduction and basement uplifts with flat. The geometries observed in the southern Cordillera Oriental and northern Sierras Pampeanas do not fit this pattern. Instead, inversion of the Cretaceous Salta Rift Basin and mechanical differences between rift and non-rift domains are proposed as the primary controls on both the timing of late Tertiary uplift and deformation, and foreland geometries. The influence of the rift basin is documented through field observations of structures and lithologies, kinematic analysis of minor fault data, and published data on local stratigraphy. The southern Cordillera Oriental developed within the southwestern subbasin of the Salta rift and is a basement-involved fold-and-thrust belt. The Sierras Pampeanas developed to the south of the rift and are basement uplifts. Dominant structures in both regions are N/S-trending reverse or thrust faults. They are cut by oblique strike-slip faults. Older deformation is Mio-Pliocene in age and is characterized by thrust kinematics with E-W to NW-SE shortening. Younger deformation is Plio-Quaternary in age and is characterized by strike-slip kinematics with NE-SW shortening, except along the boundary between the Cordillera Oriental and the Sierras Pampeanas where thrust kinematics with N-S shortening prevail. The similar kinematics but different geometries in the two provinces during Mio-Pliocene deformation and the anomalous thrust kinematics observed during Plio-Quaternary deformation suggest that the Salt rift is the main control on structural geometries. A rift inversion model is developed and applied to the southern Cordillera Oriental.

Ionian sea (Western Greece): Its structural outline deduced from drilling and geophysical data

This paper outlines the preliminary structural results obtained by the compilation of geological, drilling and geophysical data in western Greece. Most external geotectonic zones of the Hellenides are included in the geological setting of the marine and insular domain of western Greece: Ionian, pre-Apulian and Apulian zones. The Gavrovo and Pindus zones make a restricted contribution to the marine geological framework (continental shelf of southwest Peloponesus). Besides the geographical setting of the geotectonic units, their general tectonic characteristics allow the following remarks to be made: The main tectonic events younger than Eocene are well-marked in both Ionian and pre-Apulian zones. The detrital sequence shows a fast pinch-out towards the Apulian platform where the Plio-Quaternary clastic layers overlap what are probably late Mesozoïc or early Tertiary limestones. Taking into consideration general tectonic features, we can distinguish a northern area and a southern one, separated by a fault trending 30°N, located on the western margin of Kephallinia, Lefkas Islands: 1. (a) in the northern area we observe a strong tangential tectonism decreasing towards the Apulian platform with transitional characteristics on the pre-Apulian zone (Paxos) where asymmetrical folding occurs; 2. (b) in the southern area (from Lefkas-Kephallinia islands to the S.W. Cape of Peloponesus) the tangential tectomism is well-masked by strong vertical faulting attributed to young Plio-Quaternary deformations. The fast subsidence induces huge diapiric structures in the Ionian zone (salt walls originating from Triassic layers intersect a thick Pleistocene sequence).

Comparison between deformation deduced from the analysis of recent faults and from focal mechanisms of earthquakes (An example: The Paphos region, Cyprus)

The authors have made a comparative study of surface deformations deduced from the analysis of recent faults, and deformation in depth deduced from, focal mechanisms associated with shallow earthquakes. The initial results obtained in the Paphos region of Cyprus are presented. Study of striations on centi- to decametric-scale fracture surfaces which affect Plio-Quaternary beaches in the Paphos region has enabled the authors to determine statistically the position of the principal axes of Plio-Quaternary deformation: lengthening X (strike N32°, dip 12°NE), shortening Z (N297°, 23°NW) and intermediate Y (N138°, 65°SE). On the 10th of September 1953 a superficial earthquake (depth 6 km) of 6.5 magnitude occurred near Paphos (location 34.9°N, 32.2°E) whose focal mechanism has been studied. Fault-plane solutions were obtained using 36 data points relating to the initial movements of the P-waves measured by longand short-period seismographs. Unfortunately the distribution of data with respect to the focus is such that it does not permit a single, but rather three possible solutions. Two of these are compatible with the model of deformation deduced from surface study. While the most probable solution favours a normal fault (solution no. 3), the system of deep strike-slip faults (solution no. 2) is equally compatible with the existence of predominantly normal surface faults. The preliminary results constitute part of a more regional study of the eastern Mediterranean. The authors consider it fundamental to establish this type of correlation when studying neotectonics.

Correlation chronologique des phenomenes geodynamiques dans les Alpes, l'Apennin et l'Atlas nord-africain

Abstract A new concept of the evolution of the entire Alpine system is presented, based on a comparative study of chronodiagrams for the ranges bordering the Mediterranean both in Europe and Africa. The relation of post-paroxysmal (Miocene) nappes and Plio-Quaternary deformation to the main orogeny, the mechanism of the Mediterranean tectorogen, and some seeming anomalies are explained. A selected bibliography is appended.