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Segmentation and increasing activity in the Neogene-Quaternary Teruel Basin rift (Spain) revealed by morphotectonic approach
Abstract
The NNW-SSE trending Teruel Basin rift is the largest Late Miocene-Quaternary extensional intracontinental structure located within the central-eastern Iberian Chain (Spain). The structural and morphotectonic study carried out in the central-northern part of this half graben basin (north of Teruel city) has allowed us to analyse rift segmentation, deformation partitioning and rift evolution. Results are based on vertical displacement calculations (fault throw and bending) of the main border and intrabasin fault zones. We use two geomorfological-stratigraphical markers, the Intramiocene Erosion Surface (IES; 11.2 Ma) and the Fundamental Erosion Surface (FES; 3.5 Ma). While the first marker reveals rift initiation under an E-W extension, the late marker records vertical displacements associated to a second, Late Pliocene–Quaternary rifting stage characterized by a nearly multidirectional extension regime with prevailing ENE-WSW trending ó3. Despite the along-axis rift segmentation into three structural domains (northern, central and southern) and the distribution of deformation among border and intrabasin faults in the central and southern domains, a consistent average slip rate (post-IES) of 0.09 mm/a has been calculated on distinct transects across the basin, suggesting a homogeneous crustal-scale extension process in the region. The results also reveal that slip rates during the Late Pliocene-Quaternary (0.12–0.16 mm/a) are higher than the Late Miocene-Early Pliocene (0.05–0.07 mm/a). Slip rate increase is caused by (i) a westward propagation of deformation from the Valencia Through, and (ii) a change in the regional stress field, both enhanced by crustal doming affecting central-eastern Iberia, as well as progressive fault linkage. Throw vs. distance graphs suggest that the main faults are in a transient stage towards coalescence, less advanced within the southern domain. Regional Late Pliocene-Quaternary uplift, concomitant with increasing slip rates in the Teruel Basin rift, has caused the basin to rise, so that synrift sedimentation only took place in rapidly subsiding residual basins until the region became exorheic and the basin was incised by the present-day fluvial network.
... A number of recent fault segments have been identified and mapped at the relay zone separating the Concud and Sierra Palomera faults, on the basis of one or more of the following criteria: (i) they cut and offset one of the Pliocene planation surfaces that extend through the region (Fundamental Erosion Surface; sublevels FES2 and FES3), dated between 3.8 and 3.5 Ma (Simón-Porcar et al., 2019;Ezquerro et al., 2020); (ii) they produce abrupt and straight map contacts between Quaternary and pre-Quaternary materials, which have been inspected through image analysis and field survey; (iii) they have associated morphological scarps. ...
... Epicentral symbols are colour coded with depth, and sized according to their magnitude. The active faults mapped are those included in the QAFI database (García-Mayordomo et al., 2012), together with others described in detail in more recent publications (Simón et al., 2016Ezquerro et al., 2020;Peiro et al., 2022) and those newly mapped in the present work. (b) Synthetic projection of all hypocentres onto a vertical E-W plane. ...
... In any case, individual seisms can not be associated with the faults mapped. Concerning their depth distribution, it should be highlighted that the hypocentres are quite uniformly distributed between 0 and 14 km, which is consistent with the thickness of the brittle crust above the regional detachment level of the main fault systems (11-17 km, according to Roca andGuimerà, 1992, andEzquerro et al., 2020). For a better, 3D visualization of the spatial distribution of hypocentres, a html file is available as Supplementary Material (SM-2). ...
... The transition zone is structurally complex due to the connection with the Jiloca Basin and the existence of an ensemble of diversely oriented faults: Concud, Tortajada, Teruel, Los Mansuetos and Valdecebro faults. In the northern sector, the basin structure is controlled by faults and fault zones in its eastern margin (Moissenet, 1983;Simón et al., 2012;Ezquerro, 2017;Ezquerro et al., 2019Ezquerro et al., , 2020Liesa et al., 2019), with N-S (El Pobo Fault Zone and Cabigordo fault) and NE-SW (Peralejos and Tortajada faults) directions. In the hanging-wall block, Neogene rocks are tilted towards the eastern, active margin, forming a gentle but widely recognizable rollover monocline. ...
... The sedimentary fill almost hold the geometry and structure of the basin, hampering the entire definition of the stratigraphic architecture of the northern sector of the Teruel Basin by several factors: i) the halfgraben synclinal geometry of the basin Ezquerro et al., 2020), which determines that the sedimentary succession was mainly exposed in the central areas but only partially at the basin margins (remaining the oldest materials in subsurface positions); ii) the weak Quaternary incision of the Alfambra River, running longitudinally through the basin, and of the small ravines sourced from the basin boundaries (Sánchez-Fabre, 1989), which prevents the lower succession to crop out in the central parts of the basin; iii) the very scarce subsurface information, limited to a few shallow wells made for hydrogeological purposes. Seismic profiles are not available, and a complete characterization of the geometric arrangement and stratigraphic architecture of the syn-rift sedimentary sequence is not possible. ...
... The Neogene sedimentary fill can be divided into six genetic units (TN1 to TN6) that comprise 10 megasequences (M1 to M10). The oddnumbered, coarsening-upwards sequences correspond to alluvial progradations, and the even-numbered, fining-upwards ones to retrogradations (Ezquerro, 2017;Ezquerro et al., 2020). Boundaries between these megasequences correspond to stratigraphical trend variations, based on grain-size and facies association changes, from alluvial retrogradation to progradation and vice versa, and related lacustrine expansions and retractions. ...
The northern sector of the Teruel Basin (Spain) houses a dense and continuous record of late Neogene mammal fossil sites, as well as numerous biostratigraphic and magnetostratigraphic information making it a reference basin to define and refine the European mammal biostratigraphy from the Vallesian to the Villafranchian. The Neogene mammal chronology is in ongoing revision, and distinct correlations between basins and Europe provinces have been proposed based on their relative ages. New calibration methods based on numerical modelling have allowed the absolute ages of the paleontological sites to be refined. Nevertheless, some discrepancies arise, evidencing that anchoring between absolute ages and mammal fossil record would benefit from a stronger stratigraphical framework. This work provides such a robust 3D stratigraphic framework of the whole basin that, together with magnetostratigraphy, allows establishing an accurate chronostratigraphic model and hence a precise chronology of sedimentary units and mammal sites. The absolute age of MN zones, or mammal stages, in the Teruel Basin has been revised on the basis of a detailed and confident stratigraphic correlation, and updated to the most recent Geomagnetic Polarity Time Scale. In particular, new accurate ages have been proposed for the boundaries MN 9/10 to MN 16/17 from data exclusively located in the Teruel Basin, with a precision generally of 0.1–0.2 Ma.
... The transition zone is structurally complex due to the connection with the Jiloca Basin and the existence of an ensemble of diversely oriented faults: Concud, Tortajada, Teruel, Los Mansuetos and Valdecebro faults. In the northern sector, the basin structure is controlled by faults and fault zones in its eastern margin (Moissenet, 1983;Simón et al., 2012;Ezquerro, 2017;Ezquerro et al., 2019Ezquerro et al., , 2020Liesa et al., 2019), with N-S (El Pobo Fault Zone and Cabigordo fault) and NE-SW (Peralejos and Tortajada faults) directions. In the hanging-wall block, Neogene rocks are tilted towards the eastern, active margin, forming a gentle but widely recognizable rollover monocline. ...
... The sedimentary fill almost hold the geometry and structure of the basin, hampering the entire definition of the stratigraphic architecture of the northern sector of the Teruel Basin by several factors: i) the halfgraben synclinal geometry of the basin Ezquerro et al., 2020), which determines that the sedimentary succession was mainly exposed in the central areas but only partially at the basin margins (remaining the oldest materials in subsurface positions); ii) the weak Quaternary incision of the Alfambra River, running longitudinally through the basin, and of the small ravines sourced from the basin boundaries (Sánchez-Fabre, 1989), which prevents the lower succession to crop out in the central parts of the basin; iii) the very scarce subsurface information, limited to a few shallow wells made for hydrogeological purposes. Seismic profiles are not available, and a complete characterization of the geometric arrangement and stratigraphic architecture of the syn-rift sedimentary sequence is not possible. ...
... The Neogene sedimentary fill can be divided into six genetic units (TN1 to TN6) that comprise 10 megasequences (M1 to M10). The oddnumbered, coarsening-upwards sequences correspond to alluvial progradations, and the even-numbered, fining-upwards ones to retrogradations (Ezquerro, 2017;Ezquerro et al., 2020). Boundaries between these megasequences correspond to stratigraphical trend variations, based on grain-size and facies association changes, from alluvial retrogradation to progradation and vice versa, and related lacustrine expansions and retractions. ...
Paleoclimate reconstructions are mostly based on continuous oceanic records, but continental records, controlled by global and regional conditions, are paramount in identifying long- and short-term climatic variability between regions and investigating forcing mechanisms. Here we present a high-resolution lacustrine log from a western Mediterranean intramountain basin; it is based on calcite oxygen isotope composition (δ¹⁸Oc) and records detailed paleoclimatic information from the Late Miocene to the Early Pleistocene (9.8–1.8 Ma). Evidence is found for orbital forcing in the regional paleoclimate, with minimum and maximum eccentricity related to drier and wetter conditions respectively. Superimposed onto this variability, the long-term trend reflects the influence of global paleogeographic and climate change. Variations inferred in precipitation-evaporation (P–E) are related to SST in the North Atlantic, which evidences a connection between marine dynamics and continental climate in areas far from the coast in southwestern Europe and a relation between dry periods and high SST inland. It is proposed that the regional climate was impacted by the effect of the closure of the Central Atlantic Seaway and changes in the Atlantic Meridional Overturning Circulation (AMOC). Warmer/drier conditions were related to a more permanent, stable, high-pressure centre over the mid-Atlantic in a situation of strengthened AMOC, which would have blocked westerly winds, increasing aridity in southwestern Europe. The inferred warm/dry connection differs from other western Mediterranean records, supporting previous interpretations of a regional climate gradient in western Europe. As occurs at present, isolation from the influence of the humidity of the Mediterranean Sea during warm periods as a result of' to the local orography could well have been the cause of regional differences.
... The Calamocha and Concud faults, which bound the northern and southern sectors of the Jiloca basin (Fig. 1c), offset early Pliocene lacustrine deposits of the Calatayud and Teruel basins, respectively. This allows calculating their total throws at about 210 m for the Calamocha fault (Martín-Bello et al., 2014), and 260 m for the Concud fault (Ezquerro et al., 2020). On the contrary, no recent stratigraphic marker is available for the Sierra Palomera fault. ...
... Extensional deformation propagated onshore towards the central part of the Iberian Chain (Álvaro et al., 1979;Vegas et al., 1979) in two stages, inducing both reactivation of the main inherited Mesozoic faults and formation of new normal faults, and generating a number of diversely oriented intracontinental grabens and half-grabens (Simón, 1982(Simón, , 1989Gutiérrez et al., 2008Gutiérrez et al., , 2012Ezquerro, 2017;Liesa et al., 2019). During the first stage (Late Miocene to Early Pliocene in age), the 90-km-long, NNE-SSW to N-S trending Teruel half-graben basin developed, filled with terrestrial sediments up to 500 m thick (Simón, 1982(Simón, , 1983Moissenet, 1983;Anadón and Moissenet, 1996;Ezquerro, 2017;Ezquerro et al., 2019Ezquerro et al., , 2020. The second extensional stage that started by the mid-Pliocene has produced a more widespread deformation in the central Iberian Chain. ...
... Geometric construction of normal fault profiles of the Teruel halfgraben system allows locating the sole detachment at a depth of 14-17 km b.s.l., and estimating an average E-W stretching factor β = 1.1 since its onset (11.2 Ma ago) (Ezquerro et al., 2020). Major faults accumulated slip of a few hundred metres to ca. 1 km (computing both fault throw s.s. and associated bending). ...
The NNW-SSE trending Sierra Palomera fault is characterized as an active, nearly pure extensional fault with mean transport direction towards N230°E, consistent with the ENE-WSW extension trajectories of the recent to present-day regional stress field. Its macrostructure is described from surface geology and magnetometric and electromagnetic surveys, which have allowed identifying two subsidiary, nearly parallel normal faults (antithetic and synthetic, respectively). The structural contour map of an extensive planation surface, dated to 3.8 Ma, provides a maximum fault throw s.s. of 330 m for the main fault (480 m including bending), and a net slip rate of 0.09 mm/a (0.13 mm/a including bending). Trench study focussed on the subsidiary antithetic fault shows evidence of its activity during Middle-Late Pleistocene times, offsetting ca. 2.5 m the slope of a well-preserved alluvial fan. Detailed analysis and retrodeformation of the antithetic fault and other minor ruptures in the trench has allowed defining seven deformation events. The lack of a consistent age model for the involved sedimentary sequence makes them almost meaningless in terms of paleoseismic history. However, geometry and sequential development of meso-scale faults (intermediate between seismic-scale and analogue models) allows unravelling the extensional deformation history within the hanging-wall block of the Sierra Palomera fault. Progressive rupture patterns reveal shifting from dominantly synthetic to dominantly antithetic faulting, suggesting both kinematical control linked to rollover growth, and dynamical control by the regional stress field.
... Some landforms, either planar (planation surfaces) or linear (shorelines, river terraces) can be used as direct markers of deformation. Their geometrical reconstruction, on maps or profiles, allows the quantification of fault displacement or overall relief uplift, while their dating permits the calculation of deformation rates (Bonow et al. 2006;Wagner et al. 2011;Ezquerro et al. 2020). In other cases, the tectonic signature on the landscape is subtler, and only qualitative diagnosis of recent tectonic movements can be achieved; drainage anomalies mostly fall within this category of evidence (Leeder & Jackson, 1993;Jackson et al. 1996;Goldsworthy & Jackson, 2000). ...
... These faults are modest in size, with lengths ranging from 5 to 19 km, maximum net displacements of 180-620 m and slip rates of 0.05-0.16 mm a -1 for the last 3.8 Ma (Rubio & Simón, 2007;Lafuente et al. 2014;Simón et al. 2017Ezquerro et al. 2020). Since late Miocene -Quaternary times, a tendency for the progressive concentration of crustal deformation on a smaller number of faults has been inferred, while those that remain active increase their slip rate Ezquerro et al. 2020). ...
... mm a -1 for the last 3.8 Ma (Rubio & Simón, 2007;Lafuente et al. 2014;Simón et al. 2017Ezquerro et al. 2020). Since late Miocene -Quaternary times, a tendency for the progressive concentration of crustal deformation on a smaller number of faults has been inferred, while those that remain active increase their slip rate Ezquerro et al. 2020). ...
The NNW–SSE-trending extensional Río Grío–Pancrudo Fault Zone is a large-scale structure that obliquely cuts the Neogene NW–SE Calatayud Basin. Its negative inversion during the Neogene–Quaternary extension gave rise to structural and geomorphological rearrangement of the basin margin. Geological mapping has allowed two right-relayed fault segments to be distinguished, whose recent extensional activity has been mainly characterized using a deformed planation surface (Fundamental Erosion Surface (FES) 3; 3.5 Ma) as a geomorphic marker. Normal slip along the Río Grío–Lanzuela Fault Segment has induced hanging-wall tilting, subsequent drainage reversal at the Güeimil valley after the Pliocene–Pleistocene transition, as well as morphological scarps and surficial ruptures in Pleistocene materials. In this sector, an offset of FES3 indicates a total throw of c. 240 m, resulting in a slip rate of 0.07 mm a –1 , while retrodeformation of hanging-wall tilting affecting a younger piedmont surface allows the calculation of a minimum throw in the range of 140–220 m after the Pliocene–Pleistocene transition, with a minimum slip rate of 0.07–0.11 mm a –1 . For the late Pleistocene period, vertical displacement of c. 20 m of a sedimentary level dated to 66.6 ± 6.5 ka yields a slip rate approaching 0.30–0.36 mm a –1 . At the Cucalón–Pancrudo Fault Segment, the offset of FES3 allows the calculation of a maximum vertical slip of 300 m for the last 3.5 Ma, and hence a net slip rate close to 0.09 mm a –1 . Totalling c. 88 km in length, the Río Grío–Pancrudo Fault Zone could be the largest recent macrostructure in the Iberian Chain, probably active, with the corresponding undeniable seismogenic potential.
... However, the accommodation rate varied between 102 and 184m/Myr for different parasequences, and between 67 and 245m/Myr for elementary sequences. These values are typical of rift systems (Casas et al., 2024;Ezquerro et al., 2020;Friedmann and Burbank, 1995;Leeder, 1991). ...
The lacustrine El Castellar Formation in the Castillo de Aliaga section (Early Cretaceous Galve sub-basin, eastern Spain) features two carbonate successions of marl and limestone, separated by a mudstone and marl interval. Sequence analysis revealed small-scale (44 elementary sequences), medium-scale (ten complete and two incomplete parasequences), and large-scale (three sets of parasequences, one incomplete), high-frequency lacustrine sequences, with an average thickness of 2.9, 12.4 and 54m, respectively. These sequences start with a sudden facies change (deepening) and exhibit a shallowing-upward trend with features of subaerial exposure
(bioturbation, oxidation, or brecciation) at the top, indicating phases of climate-modulated lake expansion and retraction. The temporal framework of the lacustrine sequences is further characterized by the correlation of these sequences with sedimentary-cycle periodicities of 3.3, 13.2 and 57.3m, attributed, respectively, to the long precession cycle (22.4kyr) and the short (95kyr) and long (405kyr) eccentricity cycles of the Earth’s orbit. The hierarchical stacking of sequences aligns with orbitally driven cyclicity, with thickness variations interpreted as tectonic subsidence effects (accommodation) resulting from normal fault slip in a rift system. The three sets of parasequences (SPS-1 to SPS-3) align with stages of lake system evolution. SPS-1 represents deposition in a low-energy shallow carbonate lake. SPS-2 indicates a significant lake expansion and deepening, linked with clastic input and a mixed lake system, and correlates with a major increase in accommodation, over ~200kyr, involving fault-induced local tilting. SPS-3 represents deposition in a high-energy carbonate lake. The parasequences identified show variations in cyclic thickness tied to a >700kyr tectonic cycle. The elementary sequences, mainly corresponding to marl-limestone bundles, exhibit thickness changes probably due to shorter-term tectonic pulses.
Accelerated tectonic activity resulted in increased accommodation in shorter (40-50kyr) periods, followed by
longer (>100kyr) periods of progressive deceleration.
... In geological terms, this region is located in the Aragonese Branch of the Betic System [33,34]. The Teruel Basin is the largest Neogene extensional macrostructure within the central-eastern Iberian Chain (NE of Iberian Plate) [35]. The limonitic facies in which the raw material was obtained is made up of clays without exceptional structures, in which there are small sandy layers at the top and high carbonate concentration at the bottom with small subangular quartz grains, traces of K-feldspar, fragments of limestone rocks, fragments of quartzite, silex grains and iron oxides [36]. ...
... Many models of rift segmentation have focused on segmentation into grabens and/or half grabens like those observed along the Malawi Rift, Malawi; Gulf of Suez, Egypt; and Teruel Rift, Spain (cf. Ebinger et al., 1987;Khalil and McClay, 2001;Hammond et al., 2013;Laó-Dávila et al., 2015;Ezquerro et al., 2020). To address rift segmentation and fault interactions more completely at segment boundaries, we focused here on the interactions between strike-slip faults that separate rift segments and normal faults of the same dip polarity that transfer slip onto the strike-slip faults. ...
The interactions among dip-slip and strike-slip faults are critical features in rift segmentation, including strain and slip transfer between faults of different rift segments. Here, we focused on the influence of factors such as fault and fracture geometries, kinematics, and local stress fields on the interaction and linkage of synchronous strike-slip and normal faults. Well-exposed faults along the tectonically active boundary between the central and northern Basin and Range provided for both reliable geometric data and consideration of rift segment development. We documented relative ages and distributions of Quaternary deposits, scarps, and geometries of three ~20–65-km-long Quaternary faults: the N-striking, normal Coyote Spring fault; the ENE-striking, left-lateral Kane Springs Wash fault; and the N-striking, normal Wildcat Wash fault.
The normal faults bend to accommodate slip-type differences across linkage zones, with the strike-slip fault and local processes influencing interactions. Influenced by the local stress field of the Kane Springs Wash fault, the Coyote Spring fault bends SE as it approaches and links to the Kane Springs Wash fault. Influenced by the off-fault or process-zone fractures of the Kane Springs Wash fault, the Wildcat Wash fault bends NE and links with the Kane Springs Wash fault. The Kane Springs Wash fault continues beyond the normal fault terminations, suggesting slip transfer between them via the Kane Springs Wash fault. These relations and the ages of offset units suggest that activity on the faults was approximately synchronous despite slip-type differences. Consequently, in slip transfer, the local strike-slip stress environment and off-fault fractures influenced the geometry of the normal fault terminations; the strike-slip fault formed a boundary to dip-slip fault propagation; and this boundary facilitated kinematic and geodetic segmentation, forming a Basin and Range rift segment boundary.
... The age of the top of the Tortajada Formation is poorly constrained but appears to project at least into Zone Ib-N13b (above sites Masada del Valle 7 and Regajo 5; van Dam et al., 2001), for which a maximum age of 6.56 Ma was inferred (Table 1). From the viewpoint of general basin formation, however, there are no major indications for a major tectonic pulse in the Teruel Basin around this time, with Zone Ib-N12a positioned in the middle of a major tectonic unit (TN3, Ezquerro et al., 2020) and relief rejuvenation and alluvial fan development occurring ~1 Myr later (TN3-4 transition). In a broader context, however, the ~7.6-6.8Ma ...
... The new magnetostratigraphic and cyclostratigraphic results for the late Tortonian and early Messinian that will be presented in this work are based on sections in the Teruel and Jumilla-La Celia Basins (Figs. 1-3). The Teruel Basin is a half-graben situated within the Iberian Chain and contains a fairly complete succession of Late Miocene and Pliocene continental sediments (Anadón et al., 1990;Alonso-Zarza and Calvo, 2000;Ezquerro et al., 2020). The basin is well-known for its rich mammal record (van de Weerd, 1976;Adrover, 1986;Mein et al., 1990;Alcalá, 1994;van Dam et al., 2001;Alcalá et al., 2018). ...
... They are associated with Mesozoic and Neogene-Quaternary normal faults (e.g. Casas-Sainz & Gil-Imaz, 1998;Cortés et al., 1999;Ezquerro et al., 2020;Rodríguez-López et al., 2007) as well as linked to Cenozoic high-angle reverse faults and thrusts (Casas et al., 2000;Simón & Liesa, 2011). Around the Miravete and Cañada Vellida anticlines, there are numerous drag folds associated with faults, favoured by the proximity of the incompetent Keuper facies. ...
Many works in the last decades underline the role of evaporites, not just as a conditioning factor but as the engine for subsidence and eventually basin inversion. The western Mediterranean alpine ranges are being investigated in this regard because of the presence of discontinuous units of Permian to Triassic evaporites, deposited in the western Tethys basins. This work presents a thorough analysis of two particular structures (Cañada Vellida and Miravete anticlines) in the intraplate Maestrazgo basin (eastern Iberian Chain, Spain) in which evidence to support their reinterpretation as salt‐driven structures has been recently reported. Our analysis includes (i) a comprehensive stratigraphic and structural study of the folds along their entire trace, (ii) the compilation of thickness and distribution of evaporite–bearing and supraevaporite units, paying special attention to changes in thickness of units in relation to anticlines, and (iii) the study of fault patterns, sometimes in relation to the mechanical stratigraphy. All three aspects are also documented and discussed on a regional scale. The new data and interpretations reported here reinforce the extensional origin of the Late Jurassic–Early Cretaceous basins, and the role of regional extensional tectonics as the responsible for the development of first‐order syn‐sedimentary normal fault zones driving the formation and evolution of sub‐basins. These basins were subsequently inverted and deformed, including the formation of complex, box‐geometry anticlines that, in their turn, controlled deposition in Cenozoic basins. The review of the arguments that support the alternative of salt tectonics for the origin of such anticlines has allowed us to delve into the sedimentary and tectonic evolution of the inverted extensional basins, and to propose a specific model for the development of these faulted anticlines. The role of salt levels and other interlayered detachments in the structuring of sedimentary basins and their inversion is also pondered. The observations in the eastern Iberian Chain reported here have implications to assess ongoing reinterpretations in terms of salt tectonics in other alpine basins and ranges of the western Mediterranean.
The genus Palaeoglandina Wenz, 1914 (Gastropoda: Stylommatophora: Spiraxidae) is a common member of land snail communities in the European Cenozoic. It has been reported from numerous stratigraphic horizons in the Iberian Peninsula ranging from the Middle Eocene (Lutetian) to the Early Pleistocene (Calabrian). Investigating Late Miocene to Early Pliocene communities in the Teruel Basin in eastern Spain, we found that previous species records proved to be misidentifications of a yet undescribed species. Based on a thorough review of contemporaneous European species of the genus we introduce a new species, Palaeoglandina turolensis n. sp. It is characterized by a large oval to fusiform, comparatively stout shell with moderately convex whorls, short spire and large last whorl, large, pyriform aperture, and a characteristic protoconch ornamentation, consisting of a deep spiral groove flanked by thick, short, prosocyrt riblets. We applied geometric morphometric analyses to assess the species’ morphological variability. Our results indicate differences in the species’ morphospace occupation through time, which we interpret as a morphological shift from the Late Miocene to the Early Pliocene, from broad, short-spired shells to slender, long-spired shells.
The Iberian System in NE Spain is characterized by a distinctive graben/basin system (Calatayud, Jiloca, Alfambra/Teruel), among others, which has received much attention and discussion in earlier and very recent geological literature. A completely different approach to the formation of this graben/basin system is provided by the impact crater chain of the Rubielos de la Cérida impact basin as part of the important Middle Tertiary Azuara impact event, which has been published for about 20 years. Although the Rubielos de la Cérida impact basin is characterized by all the geological, mineralogical and petrographical impact findings recognized in international impact research, it has completely been hushed up in the Spanish geological literature to this day. The article presented here uses the example of the Jiloca graben to show the absolute incompatibility of the previous geological concepts with the impact structures that can be observed in the Jiloca graben without much effort. Digital terrain modeling and aerial photography together with structural and stratigraphic alien geology define a new lateral Singra-Jiloca complex impact structure with central uplift and an inner ring, which is positioned exactly in the middle of the Jiloca graben. Unusual topographic structures at the rim and in the area of the inner ring are interpreted as strike-slip transpression and transtension. Geological literature that still sticks to the old ideas and develops new models and concepts for the graben/basin structures, but ignores the huge meteorite impact and does not even enter into a discussion, must at best cause incomprehension.
Abstract The northern part of the eastern margin of the extensional Neogene Teruel Basin (central-eastern Spain) consists of a non-linear, zigzag fault zone made of alternating ca. 2 km long, NNW-SSE trending segments and shorter NNE-SSW ones. Good outcrop conditions made possible a comprehensive integrated stratigraphic and structural study, especially focused on coarse clastic sediments deposited along the basin margin. Well-exposed stratal relationships with boundary faults, allowed the analysis of tectonic influence on sedimentation. Synsedimentary deformation includes growth faulting, rollover anticlines, and monoclines and associated onlap stratal terminations, angular unconformities, and other complex growth strata geometries. One of them is the onlap-over-rollover bed arrangement described here for the first time, which reveals the competition between tectonic subsidence and sedimentary supply. Both, the structural inheritance (dense Mesozoic fracture grid) and the dominant, nearly ‘multidirectional’ (σ1 vertical, σ2 ≈ σ3), Pliocene extensional regime with σ3 close to E-W, are considered to have controlled the margin structure and evolution. Tectono-stratigraphic evolution includes: (i) reactivation of inherited NNW-SSE faults and development of W-SW-directed small alluvial fans (SAF) while NNE-SSW segments acted as gentle relay ramp zones; (ii) progressive activation of NNE-SSW faults and development of NW-directed very small alluvial fans (VSAF); during stages i and ii sediments were trapped close to the margin, avoiding widespread progradation; (iii) linking of NNW-SSE and NNE-SSW structural segments, overall basin sinking and widespread alluvial progradation; (iv) fault activity attenuation and alluvial retrogradation. The particular structure and kinematic evolution of this margin controlled alluvial system patterns. Size of alluvial fans, directly set up at the border faults, was conditioned by the narrowness of the margin, small catchment areas, and proximity between faults, which prevented the development of large alluvial fans. The size of the relay zones, only a few hundred meters wide, acted in the same way, avoiding them to act as large sediment transfer areas and large alluvial fans to be established. These features make the Teruel Basin margin different to widely described extensional margins models.
The area of Alfambra (NE Spain) is very representative of the relief evolution of the Eastern Iberian ranges. The geomorphological cartography (Main Map) includes the northern sector of the Alfambra-Teruel Neogene depression and its mountainous surroundings. The cartographic process started by using aerial photographs (1:30000 scale) and fieldwork. The structural reliefs, erosion surfaces, karst landforms, Quaternary pediments and terraces, and fluvial network are represented over a lithological background. The main cartography is complemented with two maps of lithological and geomorphological units. The obtained information enabled the main geological and geomorphological stages of the regional relief to be established.
The NW-SE to NNW-SSE striking Concud Fault and the N-S striking Teruel Fault are extensional structures showing a right relay arrangement. The hectometre-scale offset produced by both structures in the Neogene materials of the Teruel basin is transferred to each other by means of a relay ramp dipping towards NNW. In this study we present new information on recent (Late Pleistocene) brittle deformation structures, some of them located within the relay zone and others aligned with the northwards prolongation of the Teruel Fault. The observed faults and fractures are mostly parallel to the major faults (NNW-SSE), while signs of transverse structures (pointing to hard linkage) are negligible. The Concud and Teruel faults are independent structures from the geometrical and kinematical point of view, but we interpret that there is a mechanical interaction between them, a previous stage to linkage by hypothetical future northwards propagation
of the Teruel fault.
Movements of tectonic plates often induce oblique deformation at divergent plate boundaries. This is in striking contrast with traditional conceptual models of rifting and rifted margin formation, which often assume 2-D deformation where the rift velocity is oriented perpendicular to the plate boundary. Here we quantify the validity of this assumption by analysing the kinematics of major continent-scale rift systems in a global plate tectonic reconstruction from the onset of Pangea breakup until the present day. We evaluate rift obliquity by joint examination of relative extension velocity and local rift trend using the script-based plate reconstruction software pyGPlates. Our results show that the global mean rift obliquity since 230 Ma amounts to 34∘ with a standard deviation of 24∘, using the convention that the angle of obliquity is spanned by extension direction and rift trend normal. We find that more than ∼70 % of all rift segments exceeded an obliquity of 20∘ demonstrating that oblique rifting should be considered the rule, not the exception. In many cases, rift obliquity and extension velocity increase during rift evolution (e.g. Australia-Antarctica, Gulf of California, South Atlantic, India-Antarctica), which suggests an underlying geodynamic correlation via obliquity-dependent rift strength. Oblique rifting produces 3-D stress and strain fields that cannot be accounted for in simplified 2-D plane strain analysis. We therefore highlight the importance of 3-D approaches in modelling, surveying, and interpretation of most rift segments on Earth where oblique rifting is the dominant mode of deformation.
This chapter introduces the geodynamic processes that influence tectonic rift evolution and rifted margin architecture. Continental rifts result from geodynamic processes that continuously shape the surface of our planet. With a strong focus on numerical modeling, the chapter summarizes classical and recent insights on rift evolution with differentiation between 2D and 3D concepts and models. Hazards related to earthquakes and volcanic eruptions in active rift zones are discussed along with submarine slope failures and landslide-generated tsunamis on rifted margins. Rifts and rifted margins worldwide show a large structural variety as a result of the interaction of rock rheology, tectonics, magmatism, deformation rates, inherited lithospheric architecture, basement grain, obliquity, climate, and sediment supply. In reality, continental rifting involves several important factors that generate along-strike variability: inherited structures, segmentation, plume-lithosphere interaction, and oblique extension. All of these processes have the potential to overprint 2D properties of the rift system.
We analyze a set of 76 mapped surface ruptures for relationships between geometrical discontinuities in fault traces and earthquake rupture extent. The combined set includes 46 strike-slip, 16 normal, and 14 reverse mechanism events. The survey shows ∼90% of ruptures have at least one end at a mappable discontinuity, either a fault end or a step of 1 km or greater. Dip-slip ruptures cross larger steps than strike-slip earthquakes, with maxima of ∼12 versus ∼5 km, respectively. Large steps inside strike-slip ruptures are rare; only 8% (5 of 62) are ≥4 km. A geometric probability distribution model of steps as “challenges” to rupture propagation predicts that steps of 1 km or greater will be effective in stopping rupture about 46% of the time. The rate is similar for dip-slip earthquakes, but, within this set, steps are relatively more effective in stopping reverse ruptures and less effective in stopping normal ruptures. By comparing steps at rupture terminations to the set of steps broken in rupture, we can estimate the importance of step size for stopping rupture. We define the passing ratio for a given step size as the fraction of steps broken divided by the corresponding fraction that stop rupture. A linear model for steps from 1 to 6 km in strike-slip ruptures leads to the passing ratio 1:89–0:31× step width. Steps of ∼3 km are equally likely to be broken or to terminate rupture, and steps ≥6 km should almost always stop rupture. A similar comparison suggests that extensional steps are somewhat more effective than compressional steps in stopping ruptures. We also compiled the incidence of gaps of 1 km and longer in surface ruptures. Gaps occur in ∼43% of ruptures and occur more frequently in dip-slip than strike-slip ruptures.
The rift basins of Thailand exhibit remarkable diversity of fault displacement patterns, fault length–displacement characteristics and mapped fault patterns during late rift, and post-rift, stages. These patterns reflect influences by: (1) zones of strength anisotropy in the pre-rift basement; (2) syn-rift fault patterns on post-rift faults; (3) spatial stress deflection, commonly related to irregularities in major fault profiles, and the basement–sediment interface; (4) temporal stress rotation, usually related to changes in the regional plate setting; and (5) varying strength properties (strain hardening or softening) of fault zones during their life. These influences created strongly segmented boundary faults, and long, low-displacement post-rift fault trends. The former are commonly strongly over-displaced, while the latter can be strongly under-displaced with respect to their length compared with typical length:displacement distributions. Seismic interpretation of multi-rift fault patterns requires 3D data to identify the complexities, otherwise the linkage pattern between deeper and shallower faults, and the changing fault strike-directions with depth, may be incorrectly mapped. Incorrect identification of fault patterns as breached relay structures may also arise. Oblique extension, the influence of pre-existing trends and stress rotation in multi-phase rifts provides a more comprehensive explanation for the observed features than the strike-slip interpretation of previous studies.
A new trench excavated at the southern sector of the Concud Fault provided evidence of three palaeoseismic events dated to ca. 21, 18 and 13–3 ka BP, respectively. The two youngest ones had not been detected in previous studies. The results extend the total recorded palaeoseismic succession for the fault: eleven events since ca. 74 ka BP to the present day, with an average recurrence period between 7.1 ± 3.5 and 8.0 ± 3.3 ka; total net accumulated slip of about 20.5 m, with average coseismic slip of 1.9 m. The displacement pattern shows alternating periods of fast slip (up to 0.53 mm/a) and slow slip (0.13 mm/a), resulting in average slip rate of 0.29 mm/a. Using this palaeoseismic information, as well as the potential magnitude previously attributed to the characteristic earthquake at the Concud Fault (M ≈ 6.5–6.6), a simple probabilistic seismic hazard analysis has been performed. The estimated probability of occurrence of the characteristic earthquake within the next 500-year period ranges from 2.3 to 26.1 %, according to distinct hypotheses on the elapsed time derived from the uncertainty about the age of the youngest event.
Flat high-elevation surfaces in the Pyrenees are defined by thick weathered horizons that were developed from granitic lithology. We analysed such horizons in detail within two areas: the Bordères-Louron granite and the Aston massif. They are characterized by a lower fissured zone overlain by unconsolidated saprolite. Mapping these horizons allows a 3D reconstruction of the ancient paleosurface with an elevation uncertainty of 50 m. We discuss the age of weathering by means of stratigraphy and low-temperature thermochronology. The surfaces are clearly postorogenic, postdating Eocene-Oligocene denudation. Their incision and the fact they are stepped suggest (1) an increase of the local relief and (2) recent normal faulting.
In this paper, we review the current geophysical knowledge of the Valencia Trough Basin, and the surrounding areas. For this purpose, we summarize the most significant regional geophysical datasets acquired since the seventies to investigate the trough (seismic, gravity, geoid and heat flow data). We then focus on the discussion regarding the geometry and physical properties of the present day crustal and lithospheric structure derived from seismic images, as well as combined potential field modelling and their relationships with the Alpine geodynamic evolution of the Valencia Trough. Finally, we discuss the differences in the results regarding the geometry of the lithosphere-asthenosphere boundary obtained by different modelling approaches and the features that, in our view, require further investigation to unravel the true nature of the Valencia Trough, including what could have caused the differences between the crustal structure observed in the SW region compared to the NE region, the asymmetric style of thinning across the trough; the origin of the changes in the lower crustal reflectivity across the basin; the fabric of the uppermost mantle, characterized by anomalously low P-wave velocities; and the physical properties of the lithosphere mantle (density, Pwaves velocity, thermal conductivity, temperature distribution, mineralogical composition, etc.). © 2015, Instituto Geologico y Minero de Espana. All rights reserved.
The Iberian Chain (central-eastern Spain) is characterized by a dome-shaped topography with poorly incised and relatively flat landscape in its interior at an elevation of ~1300 m. A recent regional tectonic event started during or after the Late Pliocene induced deep valley incision on the flanks of the Iberian Chain. The rate and timing of this deformation, as well as the magnitude of the uplift-induced erosion processes, still lack a quantitative validation. We used 3D (SIGNUM) and 1-D (river profile) numerical models to investigate the landscape evolution of the Iberian Chain from the Late Pliocene to the present and to study the response of topography and rivers to tectonically induced base level lowering. Our model results are supported by geological, geomorphological and geochronological data. The results of the SIGNUM experiments show that the Iberian Chain topography has experienced regional uplift beginning ca. 3 Ma with rates between 0.25–0.55 mm y-1. In response to uplift, rivers have incised at an average long-term incision rate of about 0.22 mm y-1 and have progressively captured drainage area from the chain interior. To further validate the landscape evolution model results, we use a 1-D river incision model to explore the incision history of several rivers draining the Iberian Chain. The results of these river profile models constrain the range of values of bedrock erodibility from 5.8×10-5 to 5.0×10-4 m0.4 y-1 and predict long-term incision rates similar to those from the SIGNUM experiments.
Among the conspicuous extensional structures that accommodate the onshore deformation of the Valencia Trough at the central-eastern Iberian Chain, a number of large faults show evidence of activity during Pleistocene times. At the eastern boundary of the Jiloca graben, the Concud fault has moved since mid Pliocene times at an average rate of 0.07-0.08 mm/y, while rates from 0.08 to 0.33 mm/y have been calculated using distinct stratigraphic markers of Middle to Late Pleistocene age. A total of nine paleoseisms associated to this fault have been identified between 74.5 and 15 ka BP, with interseismic periods ranging from 4 to 11 ka, estimated coseismic displacements from 0.6 to 2.7 m, and potential magnitudes close to 6.8. The other master faults of the Jiloca graben (Calamocha and Sierra Palomera faults) have also evidence of Pliocene to Late Pleistocene displacement, with average slip rates of 0.06 and 0.11-0.15 mm/y, respectively. At the eastern boundary of the Teruel graben, the Sierra del Pobo fault has been active since Late Miocene times, at slip rates of 0.06-0.11 mm/y. Quaternary activity its better constrained for the Teruel fault, which offsets two fluvial terraces, with an estimated slip rate of 0.12 mm/y since 76 ka BP. A widespread, NNE-SSW trending fault system extends over the easternmost Iberian Chain (Maestrat sector), with abundant proofs of activity during Early to Middle Pleistocene s.l. times. Nevertheless, such proofs are mainly geomorphologic, while dated stratigraphic markers allowing precise assessment of slip rates are absent.
The results of geomorphic analysis of the Concud fault-generated mountain front (central Iberian Chain, Spain) are introduced into classifications of fault activity proposed by previous authors, and compared with slip rates calculated from geologic markers. The Concud fault is an extensional structure active since the mid Pliocene times. It gives rise to a 60 to 120 m high mountain front, where footwall rocks belonging to the Triassic and Jurassic (north-western sector) and Miocene (south-eastern sector) crop out. Conspicuous triangular facets are preserved on Jurassic rocks of the central sector, while short, generally non-incised alluvial fans make the piedmont. The value of the Mountain-front sinuosity index is Smf = 1.24 for the whole mountain front (1.17 and 1.32, respectively, for both segments showing distinct footwall lithology), as obtained by the most conservative procedure. Average valley floor width/height ratios calculated for seventeen gullies crossing the fault are Vf = 0.30 (250 m upstream from the fault trace) and Vf = 0.22 (500 m upstream). These geomorphic indices, together with qualitative features of the escarpment and piedmont landscape, indicate moderate to rapid fault activity. The range of slip rates estimated from such morphotectonic classification (0.03 to 0.5 mm/y) encloses the range calculated from offset Late Pliocene and Pleistocene stratigraphic markers (0.07 to 0.33 mm/y). Nevertheless, the highest potential slip rate (0.5 mm/y) clearly represents an overestimate: the mountain front could give the impression of an anomalously high level of activity owing to episodic rejuvenation caused by base level drop.
Uplift or reduced subsidence prior to continental breakup is a key component of the rift-drift transition. This uplift causes lateral variations in the lithospheric potential energy, which can increase intraplate deviatoric tension, thereby facilitating continental rupture. There is a growing body of evidence that pre-breakup uplift is a global phenomenon characteristic of magmatic and magma-poor rifted margins. Evidence is provided by the subaerial extrusion of lava interpreted from drill logs, stratigraphic records, the presence of breakup unconformities, and the spatial extent of uplift associated with Afar (the Ethiopian-Somali plateau), which may be at the stage of rupture. Previously discussed mechanisms contributing to this uplift include phase transitions, dynamic uplift from mantle plumes, and magmatic underplated bodies. We show in this study that dynamic uplift resulting from passive upwelling asthenosphere below the rift is limited (similar to 200 m). Isostatic arguments suggest that removal of mantle lithosphere is a necessary and effective mechanism for uplift coincident with rupture. The combination of mantle phase transitions and a very thin mantle lid produces an excess potential energy state (as evidenced by a positive geoid anomaly) and leads to tensional forces favorable for rupture. These results underpin our proposed model for continental breakup where removal of mantle lithosphere by either detachment or formation of gravitational instabilities is a characteristic process. Observations of depth-dependent thinning and geochemical data support this model.
[1] We study the upper mantle P wave velocity structure below the Euro-Mediterranean area, down to 1000 km depth, by seismic travel time tomography. We invert summary residuals constructed with both regional and teleseismic first arrival data reported by the International Seismological Centre (ISC) (1964–1995), introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure. Our high-resolution model PM0.5 is parameterized with three-dimensional (3-D) linear splines on a grid of nodes with 0.5° spacing in both horizontal directions and 50 km vertical spacing. We obtain about 26% root-mean-square (RMS) reduction of residuals by inversion in addition to roughly 31% reduction after summary rays formation and selection. Sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales. The distribution of large-scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions. The mantle dynamics of western central Europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone. Contrarily, in the eastern Mediterranean, fast velocity material sinks into the lower mantle, suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity. On a smaller scale, the existence of tears in the subducted slab (lithospheric detachment) all along both margins of the Adriatic plate, as proposed by some authors, is not supported by our tomographic images.
From scaled models, seismic profiles and theoretical considerations, we analyse two mechanisms of block deformation which are associated with two models of normal faults (detachment-rooted-fault and dominoes). According to these deformation mechanisms, we investigate graphical methods which best explain the trajectories of all the points of the block surface. This approach allowed us to define measurement extension methods and fault profile determination methods. These methods depend on the fault models. The scaled models indicate that the block undergoes internal deformation during fault movement. We propose two graphical methods to compute the extension and normal faults profiles. -from Authors
The stratigraphy of many nonmarine rift basins records a common sedimentological history consisting of a relatively abrupt increase of water depth followed by a slower shoaling upward trend. We explore in this paper the origin of these sequences through a three-dimensional physical model that incorporates the affects of fault growth, flexure, erosion, sedimentation, and isostasy. Fault growth is assumed to occur in a self-similar manner and is treated as dislocations inducing flexure in a thin elastic plate. Topography generated by faulting and flexure is allowed to undergo diffusion to simulate erosive and sedimentary processes. Isostatic response to the redistribution of mass results in additional flexure of the thin plate. The model is tested using two models of fault growth, and we compare the numerical results with the stratigraphy observed in nonmarine rifts. Basins generated using a constant-lengthening-rate mode of fault growth fail to reproduce the stratigraphy of continental rift basins. We find that the commonly observed stratigraphic succession of lacustrine to fluvial conditions requires the displacement rate of the bounding fault to decrease with time, consistent with opening at a relatively constant areal extension rate.
We study the contribution of mantle flow to surface deformation within the Mediterranean Basin. Flow is modeled numerically based on lateral changes in mantle temperature estimated from tomography models. We find that modeling results are significantly affected by the properties of the selected tomography models. Shear-velocity models based on surface-wave observations achieve the highest resolution of upper-mantle structure, and, as a result, are most successful in predicting microplate motion and dynamic topography.
The region studied is located in the Iberian small-plate, between the Pyrenees and the Betic chain, south of the Ebro basin. The aim of this paper is to de scribe its Alpine compressive structures and to discuss its dynamics and evolution.
This region has a stockwerk structure with a lower level made up by the Hercynian base ment and the Permian and the lower Triassic rocks
and an upper level comprising the Jurassic, Cretaceous and Tertiary cover. Both levels are separated by a décollement within middle and upper Triassic beds; the décollement is, in fact, the sole thrust of the co ver at the roof of the basement.
The basement structure is determined by convergent wrench-faults (sinistral NE-SW faults in the Catalan coastal range and dextral NW-SE
faults in the Iberian range) and by E-W north-verging thrusts (Sierra de la Damanda). Cover structures are parallel to basement structures; there are imbricate-fan thrusts and folds striking NW-SE, NE-SW, E-W and N-S; there are also NE-SW sinistral and NW-SE dextral strike-slip fauIts. The sense of displacement of the cover is centrifuge, towards the Ebro basin in the north and towards the Tajo-La Mancha basin in the south. The amount of shortening in the basement and in the cover must be the same, because, in the central zone of the lberian range, the cover is not affected by extensive structures synchronous to compression. Both mapping relations between structures of different directions and relations of Tertiary deposits with the se structures, allow us to deduce a synchronism between structures of the different directions. Compressive deformation took place during Paleogene and lower Miocene.
From the kinematics and the synchronism of the different structures, a N-S direction of shortening is deduced in this region during Alpine
compression.
Small-scale modeling was performed to examine the effects of the superposition of two successive extensional phases from orthogonal to oblique (type 1) and from oblique to orthogonal (type 2). In both the type 1 and type 2 models, faults produced during the first stage strongly control fault development during the second stage. In type 1 models, the oblique faults developed during the second oblique phase are confined within a first-phase graben, whereas in type 2 models the oblique faults, produced during the first phase, continue to develop during orthogonal extension and connect with each other to give sigmoidal fault blocks. Type 1 models are compared with the structural setting of the Ethiopian Rift; the evolution of the rift is related to a recent extensional event, whose principal direction of stretching trends at around 50° to preexisting major normal faults. Type 1 laboratory models are fairly comparable to the northern sector of the Ethiopian Rift, referred to here as MER. They account for both the development of the en echelon oblique faults of the Wonji Fault Belt and the sinistral shear gradient running parallel to the eastern border of the MER, which formed during an oblique rifting extension. The statistical analysis of the whole Ethiopian Rift fault pattern by reference to the experimental data allows the determination of a N100°-N110° mean direction of stretching.
We present quantitative modeling results of the dynamic interplay of passive extension and active convective thinning of the mantle lithosphere beneath intracontinental rift zones investigating the relative importance of thermal buoyancy forces associated with asthenospheric doming and far-field intraplate stresses on the style of rifting. To this aim we employ a twodimensional numerical code based on a finite element method formulation for nonlinear temperature dependent viscoelastoplastic rheology. Brittle behavior is modeled using Mohr-Coulomb plasticity. The models support a scenario in which passive stretching leads to an unstable lithospheric configuration. Thermal buoyancy related to this asthenospheric doming subsequently drives active upwelling in a lithosphere scale convection cell. In the late synrift to early postrift the lithospheric horizontal stresses caused by the active asthenospheric upwelling may start to compete with the far-field intraplate stresses. At this stage the domal forces may dominate and even drive the system causing a change from passive to active rifting mode. If this transition occurs, the model predicts (1) drastic increase of subcrustal thinning beneath the rift zone, (2) lower crustal flow towards the rift flanks, (3) middle crustal flow towards the rift center, (4) the coeval occurrence of tensional stresses within and compressive stresses around the upwelling region, and (5) possible surface uplift. Late postrift thermal cooling removes the thermal buoyancy forces. At this stage the far-field forces dominate the stress state again and the lithosphere becomes more sensitive to small changes in the intraplate stresses. The model results may explain several key observations that are characteristic of a large number of intracontinental rift basins. These features include differential thinning of extending lithosphere, the discrepancy between fault-related extension and crustal thinning, late (end of synrift to early postrift) mantle related volcanism, surface domal uplift succeeding rifting, and rift flanks uplift associated with extension of a weak lithosphere.
A new type of fault relay zone in extensional contexts, dominated by distributed along-strike or longitudinal fractures, is defined. It contrasts with the classical models reported in the literature, in which transverse connecting faults controlled by the own relay kinematics prevail. The new model is based on structural features of the Teruel graben system, as well as on analogue modelling. Relay zones between the NW-SE to NNW-SSE striking faults that delimit the eastern boundary of the Jiloca Graben (Calamocha, Sierra Palomera and Concud
faults), together with the Teruel Fault, have been studied. All of these relay faults show recent (Neogene-Quaternary) ruptures at different scales, mostly parallel to the macrostructural trend and to the maximum horizontal stress (SHmax) trajectories (i.e., orthogonal to the ENE-WSW regional extension direction that characterises
the nearly biaxial or radial stress regime active during Upper Pliocene-Quaternary times). Transverse ruptures are almost absent, with the exception of the northern relay zone (Calamocha-Sierra Palomera), where an incipient NE-SW striking connecting fault does exist. Analogue models have been run under a biaxial extension regime similar to the regional one. They allowed analysing the main factors controlling fracture propagation, depending on the ratio of extension velocities and the orientation of the master faults relative to extension directions. Laboratory fracture patterns, as in the natural studied examples, are mostly controlled by the inherited anisotropies and, in a greater extent, by the imposed extension trajectories, which results in a clear prevalence of longitudinal fractures. Such external controls, usually disregarded in numerical and analogue modelling, tend to induce fault coalescence through along-strike (parallel or at very-low-angle) propagation resulting in a final braided fault pattern.
The E–W trending, nearly pure extensional Valdecebro fault zone is a transverse structure at the central sector of the N–S Teruel graben. It was activated by the Late Ruscinian (Early Pliocene, ca. 3.7 Ma), giving rise to structural rearrangement of the graben margin. Until the Late Pleistocene, it has accommodated a net slip ca. 205 m, with slip rate of 0.055 mm/a. Paleoseismicity has been analysed in a 29-m-long, 5-m-deep trench excavated through a fault branch that offsets a Pleistocene pediment surface. The paleoseismic succession includes a minimum of 6–7 events occurred since ca. 142 ka BP, although a model with 12 events could be more realistic. The following paleoseismic parameters have been inferred, assuming a minimum of 6 and a maximum of 12 events: average coseismic slip = 58–117 cm; recurrence period = 8.4–28.4 ka; potential moment magnitude Mw = 5.8–5.9. The recorded displacement since ca. 142 ka BP totalizes 7.0 m, with slip rate of 0.05–0.07 mm/a. Slip on the transverse Valdecebro fault zone has critically contributed to bulk deformation under a prevailing ‘multidirectional’ extensional regime. Drainage patterns have been rearranged, recurrently switching between westward and southward directions as a consequence of diverse slip episodes at the Valdecebro fault zone (E–W) and the neighbouring La Hita (N–S) and Concud (NW–SE) faults. The ultimate westward drainage of the Valdecebro depression incised and dismantled a southward-sloping Pleistocene pediment sourced at the Valdecebro mountain front, representing a capture by the Alfambra river occurred between 124 and 22 ka BP.
The Teruel Basin is a NNE-SSW trending intracontinental extensional basin located in central-eastern Iberia. It is asymmetrically bounded to the east by a major fault zone, but intrabasinal faults with diverse orientation (NNE-SSW to NE-SW, E-W, or NW-SE) also appear. Offsets of the successive sedimentary units and of two planation surfaces reveal that tectonic activity initiated at the border faults, while intrabasinal ones mainly developed in a later stage. Fractures on a map scale show a prevailing N-S strike in Neogene synrift rocks, while a dense network made of four main fracture sets (NE-SW, E-W to ESE-WNW, N-S and NNW-SSE), likely inherited from Mesozoic rifting stages, is observed in pre-rift units. The results of palaeostress analyses indicate an overall predominance of σ3 directions around E-W, although two stress episodes have been distinguished during the Late Miocene-Pleistocene: (i) triaxial extension with σ3 E-W; (ii) almost ‘radial’ extension (σ1 vertical, σ2 ≈ σ3) with a somehow prevailing σ3 ENE-WSW. A scenario in which the evolving extensional stress field was able to gradually activate major basement structures with different orientation, inherited from previous tectonic events, is proposed as responsible for the evolution and overall pattern of both the eastern active margin and central parts of the central-northern sector of the Teruel Basin.
The relationship of independence, interaction or linkage between two neighbouring intraplate active extensional faults, the Teruel and Concud faults, are investigated from structural and paleoseismological data, and the results are discussed to improve seismic hazard assessment for the region. This paper provides the structural and paleoseismological characterization of the almost unknown Teruel Fault from detailed mapping and trench analysis, and discusses its kinematic and dynamic relationships with the Concud Fault. Four individual events occurred between 76.0 ka and 9.2 ka BP have been recorded at two branches of the Teruel Fault. Unfortunately, these only represent a small fraction of its overall activity during such time lapse, and their time constraints do not allow correlating them with those at the Concud Fault. The Teruel and Concud faults are independent structures from the geometric and kinematic point of view, as evinced by their distinct (i) transport directions (N275°E and N220°E, respectively), and (ii) average coseismic displacements (0.5 m and 1.9 m, respectively). These displacements are consistent with their respective lengths (9.0 km and 14.2 km) and significantly smaller than those expected for a hypothetically joint Concud-Teruel, 23 km-long fault. However, their displacement gradients close to the relay zone indicate that both faults undergo dynamic interaction, thus suggesting a transient stage from independence to linkage. We hypothesize that slip on both structures occurred, at the scale of the seismic cycle, in a broadly alternating manner, which induced strain partitioning between them and allowed accommodating bulk biaxial extension in the region. Such deformation pattern would have increased the earthquake frequency with respect to the scenario of a hypothetically linked Concud-Teruel Fault, but diminished the potential seismic magnitude.
The most evident expression of the tectonic processes that have shaped Earth is the topography of its surface. From global divisions between continents and oceans to regional divisions between mountains and plains to subtle offsets in landscape that reflect fault motion, topographic data are rich in geological information. Maps created from digital topographic data can be manipulated to maximize the geologic information inherent in such data. -from Authors
The formation and evolution of basins in the China continent are closely related to the collages of many blocks and orogenic belts. Based on a large amount of the geological, geophysical, petroleum exploration data and a large number of published research results, the basement constitutions and evolutions of tectonic–sedimentary of sedimentary basins, the main border fault belts and the orogenesis of their peripheries of the basins are analyzed. Especially, the main typical basins in the eight divisions in the continent of China are analyzed in detail, including the Tarim, Ordos, Sichuan, Songliao, Bohai Bay, Junggar, Qiadam and Qiangtang basins. The main five stages of superimposed evolutions processes of basins revealed, which accompanied with the tectonic processes of the Paleo–Asian Ocean, Tethyan and Western Pacific domains. They contained the formations of main Cratons (1850–800 Ma), developments of marine basins (800–386 Ma), developments of Marine–continental transition basins and super mantle plumes (386–252 Ma), amalgamation of China Continent and developments of continental basins (252–205 Ma) and development of the foreland basins in the western and extensional faulted basin in the eastern of China (205–0 Ma). Therefore, large scale marine sedimentary basins existed in the relatively stable continental blocks of the Proterozoic, developed during the Neoproterozoic to Paleozoic, with the property of the intracontinental cratons and peripheral foreland basins, the multistage superimposing and late reformations of basins. The continental basins developed on the weak or preexisting divisional basements, or the remnant and reformed marine basins in the Meso–Cenozoic, are mainly the continental margins, back–arc basins, retroarc foreland basins, intracontinental rifts and pull–apart basins. The styles and intensity deformation containing the faults, folds and the structural architecture of regional unconformities of the basins, responded to the openings, subductions, closures of oceans, the continent–continent collisions and reactivation of orogenies near the basins in different periods. The evolutions of the Tianshan–Mongol–Hinggan, Kunlun–Qilian–Qinling–Dabie–Sulu, Jiangshao–Shiwandashan, Helanshan–Longmengshan, Taihang–Wuling orogenic belts, the Tibet Plateau and the Altun and Tan–Lu Fault belts have importantly influenced on the tectonic–sedimentary developments, mineralization and hydrocarbon reservoir conditions of their adjacent basins in different times. The evolutions of basins also rely on the deep structures of lithosphère and the rheological properties of the mantle. The mosaic and mirroring geological structures of the deep lithosphère reflect the pre–existed divisions and hot mantle upwelling, constrain to the origins and transforms dynamics of the basins. The leading edges of the basin tectonic dynamics will focus on the basin and mountain coupling, reconstruction of the paleotectonic–paleogeography, establishing relationship between the structural deformations of shallow surface to the deep lithosphère or asthenosphere, as well as the restoring proto–basin and depicting residual basin of the Paleozoic basin, the effects of multiple stages of volcanism and paleo–earthquake events in China.
We study the upper mantle P wave velocity structure below the Euro-Mediterranean area, down to 1000 km depth, by seismic travel time tomography. We invert summary residuals constructed with both regional and teleseismic first arrival data reported by the International Seismological Centre (ISC) (1964-1995), introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure. Our high-resolution model PM0.5 is parameterized with three-dimensional (3-D) linear splines on a grid of nodes with 0.5° spacing in both horizontal directions and 50 km vertical spacing. We obtain about 26% root-mean-square (RMS) reduction of residuals by inversion in addition to roughly 31% reduction after summary rays formation and selection. Sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales. The distribution of large-scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions. The mantle dynamics of western central Europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone. Contrarily, in the eastern Mediterranean, fast velocity material sinks into the lower mantle, suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity. On a smaller scale, the existence of tears in the subducted slab (lithospheric detachment) all along both margins of the Adriatic plate, as proposed by some authors, is not supported by our tomographic images.
Traces of many normal faults form an array of closely spaced
overstepping segments. In three dimensions, fault segments may either be
unconnected or link vertically or laterally into a single continuous
fault surface. The slip distribution along segmented faults is complex
and asymmetric, and the point of maximum slip generally is not located
at the center of a segment. In relay zones between segments, slip
gradients may be gentler or steeper, depending on the spatial fault
arrangement. Branch points are characterized by steep slip gradients.
One explanation for these observations is mechanical interaction between
neighboring faults which occurs through local perturbation of the stress
field. Three-dimensional (3-D) boundary element models show that the
degree of fault interaction and hence the degree of asymmetry in the
slip distribution increases with increasing fault overlap and downdip
fault height and with decreasing fault spacing and Poisson's ratio.
Interaction is strongest for faults with uniform shear strength and
decreases if there exists a zone of greater shear strength near the tip
line. This analysis provides a mechanical rationale for more frequent
occurrence of overlapping segments relative to underlapping segments and
for the limited range of the ratio between segment overlap and spacing
along natural faults. Echelon segment configurations promote
interaction, maximize the capacity to accommodate slip, and do not
necessarily require a strike-slip movement component. Model
idealizations of some outcropping fault arrays and of branching/merging
faults capture a wide variety of common field observations. Consistent,
mechanically based 3-D normal fault models can be obtained by combining
different types of field data such as fault slip-to-length ratios,
location of maximum slip, segment overlap-to-spacing ratios, and
footwall uplift/hanging wall subsidence. By capitalizing on these data
one can understand the mechanics of faulting, constrain the boundary
conditions that govern the formation and growth of faults, and provide a
rationale for interpreting normal faults in seismic surveys.
The Jiloca basin is a large intramontane, NNWEarly Pliocene age. The geometry of these units is partially controlled by NWQuaternary infill have been interpreted from the geology of the basin margins, borehole data and hydrogeological criteria. The northern and southern sectors of the Jiloca depression are bounded by faults showing measurable hectometric-scale throws (Calamocha and Concud faults). Moreover, in the central sector, the [similar] 350Quaternary extensional evolution of eastern Spain. In contrast, they are hardly compatible with genetic models based on erosional deepening, either topographic lowering by numerous nested Tertiary erosion pediplains, or sub-alluvial Pliocene–Quaternary karstic corrosion.
In tectonically active areas, the landscape response to tectonic forcing is described and possibly quantified by regional topographic and hydrographic features as well as by spatial variation in rates of surface processes. We investigated the recent landscape evolution of the Iberian Chain (NE Spain), an intraplate thrust-belt formed in Cenozoic times and characterized by a dome-shaped topography. In its central sector the landscape is dominated by low relief surfaces, Late Neogene (?) in age, presently standing at an average altitude of 1300 m. A recent regional uplift controlled the organization of the present fluvial network and dissection of the landscape. In this framework we investigated the geomorphic responses to tectonic forcing by the calculation of morphometric parameters, focusing on topography (map of local relief, swath profiles) and hydrography (basin hypsometric curve and integral, basin asymmetry factor, river longitudinal profiles and relative indices), and using SRTM DEM. The results of morphometric analysis have been coupled with radiometric uranium-series dating of calcareous tufas lying on fluvial strath terraces. The obtained ages allow the estimation of incision rate along the High Tajo and Martín rivers. Our results indicate that uplift and rock-type erodibility are the main factors influencing landscape evolution of the study area. The incision rates are very similar throughout the central sector of the range, indicating that, despite subtle local variation, the rivers are responding to a main tectonic input: the regional uplift. In conclusion, the Iberian Chain landscape is in a transient state in response to a recent dome-like uplift. Indeed, the fluvial processes that weakly incised this landscape at a rate of ~ 0.6 mm/yr are approaching a radial pattern. On the basis of geological and geomorphic constraints, we hypothesize that the uplift started around or after 3 Ma.
Recent research on faults -- particularly normal faults -- has established that (1) cumulative displacement is highest near the fault center and decreases toward the tips and (2) faults lengthen as cumulative displacement increases. Sedimentary basins (half graben) are a fundamental manifestation of displacement on large normal fault systems, and thus are expected to be deepest near their centers and to grow in depth, width, and length through time. Basin growth models predict that progressively younger synextensional strata will onlap basement rocks, especially if sedimentation keeps pace with increasing basin capacity. The models also predict a transition from initial basin-wide fluvial sedimentation to lacustrine sedimentation if sedimentation cannot keep pace with increasing basin capacity. (Basalt flows may complicate this scenario if they dam the outlet of the basin.) The fault and basin growth models described above provide a useful framework for interpreting the stratigraphic record of extensional basins and extracting their tectonic development, as the authors demonstrate with examples from the Mesozoic rifts of eastern North America and the northern Basin and Range.
Normal faults in Cretaceous carbonates in the Balcones fault system provide important analogs for fault zone architecture and deformation in carbonate reservoirs worldwide. Mechanical layering is a fundamental control on carbonate fault zones. Relatively planar faults with low-displacement gradients develop in massive, strong, clay-poor limestones and dolomites. In less competent clay-rich strata, shale beds impede fault propagation, resulting in fault-related folding, and locally steep bedding dips. Faults in clay-poor massive limestones and dolomites tend to be steep (70° or more), whereas weaker, clay-rich limestones develop faults with shallower dips (60° or less). Fault zone rocks show evidence of cataclasis, cementation, deformation of cement by mechanical twinning and pressure solution, and multiple generations of cement with differing degrees of deformation, indicating contemporaneous cementation and fault slip. In stratigraphic sequences consisting of both competent and incompetent strata, the ratio of incompetent to competent strata by thickness is a useful guide for inferring the relative rates of fault displacement and propagation. Low displacement-to-propagation ratios associated with competent strata generate low-displacement gradients, inhibiting fault-related folding. Conversely, high displacement-to-propagation ratios associated with incompetent strata promote high-displacement gradients and fault-related folding. Copyright © 2008. The American Association of Petroleum Geologists. All rights reserved.
The spatial distribution and temporal evolution of depositional systems in active-fault bounded basins are considered to be significantly influenced by tectonics. A four-fold division relating to rift initiation, rift climax, immediate post-rift and late post-rift stages of basin evolution is proposed to characterize most basin infill stratigraphies. The three-dimensional linked depositional systems (systems tracts) associated with each of these stages will vary according to a number of factors. However, a dominant tectonic signature can still be isolated if analysis is undertaken in an appropriate fashion. The general suitability of the application of this new method of describing rift basin stratigraphies in terminal half-graben type basins is demonstrated using case studies and published examples. -from Author
The Ridge basin contains as much as 14 km of Mio-Pliocene marine and nonmarine sedimentary fill. Pliocene to Holocene deformation, uplift, and dissection of this basin provide an opportunity to study stratal geometry and sedimentary facies in what is commonly cited as a classic "strike-slip' basin. Newly acquired seismic data from the northern Ridge basin provide new evidence for the subsurface basin geometry. These data lead us to conclude that the principal northern strand of the San Gabriel fault is a listric, east-southeast-dipping, oblique-slip fault rather than a subvertical, strike-slip fault. The geometry and displacement history of the San Gabriel fault controlled sediment accommodation and resultant stratal geometries with the basin. -from Authors
Field observations of two overlapping normal faults and associated deformation document features common to many normal-fault relay zones: a topographic ramp between the fault segments, tapering slip on the faults as they enter the overlap zone, and associated fracturing, especially at the top of the ramp. These observations motivate numerical modeling of the development of a relay zone. A three-dimensional boundary element method numerical model, using simple fault-plane geometries, material properties, and boundary conditions, reproduces the principal characteristics of the observed fault scarps. The model, with overlapping, semicircular fault segments under orthogonal extension, produces a region of high Coulomb shear stress in the relay zone that would favor fault linkage at the center to upper relay ramp. If the fault height is increased, the magnitude of the stresses in the relay zone increases, but the position of the anticipated linkage does not change. The amount of fault overlap changes the magnitude of the Coulomb stress in the relay zone: the greatest potential for fault linkage occurs with the closest underlapping fault tips. Ultimately, the mechanical interaction between segments of a developing normal-fault system promote the development of connected, zigzagging fault scarps.