Pliocene Quaternary Research Articles

Spatial variation of biologically available strontium isotopes (87Sr/86Sr) in an archipelagic setting: a case study from the Caribbean

This paper presents the results of strontium (Sr) isotope analysis of modern and archaeological animal remains and modern plant samples from the Caribbean region. The goal is to assess if patterns of human mobility can be determined from the archaeological record in an archipelagic setting. The range of variability and spatial distribution of biologically available strontium isotope signatures is reported and data evaluated to determine if sufficient heterogeneity exists to permit the identification of mobility despite the presence of potentially large contributions of marine strontium in island and coastal ecosystems. The (is)landscape is divided into several sub-regions based on the age and lithology of underlying geology and the variability of 87Sr/86Sr ratios is reported as; mean 87Sr/86Sr ± 2 standard deviations, number of samples: 1) Volcanic and Intrusive rocks (0.7077 ± 0.0019; n = 162); 2) Cretaceous–Miocene Limestone (0.7085 ± 0.0009; n = 50); 3) Pliocene–Quaternary Limestone (0.7091 ± 0.0004; n = 54); 4) Sedimentary Deposits (0.7094 ± 0.0015; n = 16); 5) Metamorphic Deposits (0.7104 ± 0.0014; n = 6). There are substantial differences between expected 87Sr/86Sr values based on associated geology and measured 87Sr/86Sr in flora and fauna samples. These differences emphasize the importance of focusing on bioavailable strontium, as opposed to geological proxies, for estimations of Sr isotope ranges, especially in archipelagic environments. While some overlap exists between the 87Sr/86Sr ranges of certain sub-regions, other sub-regions possessed limited variation and could be distinguished based on strontium isotope data. This spatial patterning of biologically available strontium indicates that strontium isotope analyses can be successfully applied to the archaeological study of human mobility within the Caribbean region.

The River Orontes in Syria and Turkey: Downstream variation of fluvial archives in different crustal blocks

The geomorphology and Quaternary history of the River Orontes in western Syria and south-central Turkey have been studied using a combination of methods: field survey, differential GPS, satellite imagery, analysis of sediments to determine provenance, flow direction and fluvial environment, incorporation of evidence from fossils for both palaeoenvironments and biostratigraphy, uranium-series dating of calcrete cement, reconciliation of Palaeolithic archaeological contents, and uplift modelling based on terrace height distribution. The results underline the contrasting nature of different reaches of the Orontes, in part reflecting different crustal blocks, with different histories of landscape evolution. Upstream from Homs the Orontes has a system of calcreted terraces that form a staircase extending to ~200m above the river. New U-series dating provides an age constraint within the lower part of the sequence that suggests underestimation of terrace ages in previous reviews. This upper valley is separated from another terraced reach, in the Middle Orontes, by a gorge cut through the Late Miocene–Early Pliocene Homs Basalt. The Middle Orontes terraces have long been recognized as a source of mammalian fossils and Palaeolithic artefacts, particularly from Latamneh, near the downstream end of the reach. This terraced section of the valley ends at a fault scarp, marking the edge of the subsiding Ghab Basin (a segment of the Dead Sea Fault Zone), which has been filled to a depth of ~1km by dominantly lacustrine sediments of Pliocene–Quaternary age. Review of the fauna from Latamneh suggests that its age is 1.2–0.9Ma, significantly older than previously supposed, and commensurate with less uplift in this reach than both the Upper and Lower Orontes. Two localities near the downstream end of the Ghab have provided molluscan and ostracod assemblages that record somewhat saline environments, perhaps caused by desiccation within the former lacustrine basin, although they include fluvial elements. The Ghab is separated from another subsiding and formerly lacustrine depocentre, the Amik Basin of Hatay Province, Turkey, by a second gorge, implicit of uplift, this time cut through Palaeogene limestone. The NE–SW oriented lowermost reach of the Orontes is again terraced, with a third and most dramatic gorge through the northern edge of the Ziyaret Dağı mountains, which are known to have experienced rapid uplift, probably again enhanced by movement on an active fault. Indeed, a conclusion of the research, in which these various reaches are compared, is that the crust in the Hatay region is significantly more dynamic than that further upstream, where uplift has been less rapid and less continuous.

Geomorphic evidence of active tectonics in the Sierra Alhamilla (eastern Betics, SE Spain)

Active tectonic deformation influencing the streams and hillslopes of the Sierra Alhamilla ridge (anticlinorium) in southeast Spain is related to the dextral-reverse Polopos Fault Zone to the north and east of the ridge and to normal faulting in the southern side of the ridge. A fault segmentation and fluvial terrace mapping is presented in this paper. The following geomorphic indices were calculated in the area: the mountain-front sinuosity, valley floor width-to-height ratio, drainage basin asymmetry factor, basin hypsometric curve and integral, longitudinal river profile and stream-length gradient index normalized by the graded river gradient (SLk index). The SLk map shows two sets of high anomalies: a) an E–W-striking anomaly, due to the dextral-reverse Polopos Fault Zone located in the northern limb of the anticlinorium; b) a group of NNW–SSE-striking anomalies, associated with Pliocene–Quaternary NW–SE- to NNW–SSE-striking high-angle normal faults that cut the southern limb. Late Pleistocene–Holocene activity occurred along the North Alhamilla Reverse Fault and the dextral transpressive South Gafarillos Fault, two segments in the Polopos Fault Zone. The former fault produces rejuvenation of the streams at the base of the northern slope. In this area, mountain-front sinuosity and valley floor width-to-height ratio suggest Quaternary uplift rates between 0.05 and 0.5mky−1. Holocene to present-day activity of the South Gafarillos Fault is demonstrated by faulted late Pleistocene terraces and Holocene colluvial deposits and suggested by deflected streams that have complex or convex hypsometric curves. Pliocene–Quaternary high-angle normal faults control the relief in the southern limb and the western end of the Sierra Alhamilla. These faults produce low mountain-front sinuosity and valley floor width-to-height ratio indices typical of uplift rates quite higher than field-based rates from some other studies.

Late Quaternary geology of the Tunka rift basin (Lake Baikal region), Russia

The objective of this research is to obtain a better understanding of the evolution of the Tunka rift basin, part of the Baikal rift zone, and how it relates to the overall geologic history of the region, particular for the Quaternary period. The tectonically active Baikal rift zone began forming over 50million years ago and continues today. In the Tunka basin, during the Oligocene and Middle Pliocene, relatively weak tectonic disturbances took place and thick accumulations of organic-rich sands, silts, and clays were deposited in lacustrine–marshy subtropical environments. Tectonism increased between the Miocene and Pliocene and thick units of coarse alluvium and floodplain sediments were deposited. During the Late Pliocene–Quaternary, tectonism formed basins that are now filled with a variety of coarse clastic materials. Early and Middle Pleistocene sediments are poorly exposed, covered by widespread Late Pleistocene deposits. Three Late Pleistocene sedimentary facies dominate: boulder–pebble gravels (proluvial, glacial fluvial, and alluvial sediments), alluvial sand, and loess-like sediments with associated slope deposits altered by post-depositional wind erosion. The relationship between these complexes, including radiocarbon and other chronological data and fauna and flora remains, indicates that they began forming c. 70000yr ago. Paleosols, glacial deposits and cryogenic material indicate that at times the climate was cool or cold. During the early Late Pleistocene renewed tectonism took place causing increased deposition of coarse sediments. The middle Late Pleistocene deposits consist mostly of sandy, floodplain alluvium. By the end of the Late Pleistocene–Holocene, alluviation was reduced and replaced by a high degree of erosion and aeolian deposition.

Mesozoic and Cenozoic evolution of salt structures within the Polish basin: An overview

Abstract The Permian–Cretaceous Polish Basin belonged to the system of epicontinental depositional basins of Western and central Europe and was filled with several kilometres of siliciclastics, carbonates, and also thick Zechstein (approximately Upper Permian) evaporites. Its axial part (the so-called Mid-Polish Trough) characterized by the thickest Permo-Mesozoic sedimentary cover, developed above the Teisseyre–Tornquist Zone, lithospheric-scale boundary separating the East European Craton and the Palaeozoic Platform. The Polish Basin was inverted in Late Cretaceous–Paleocene times. A synthesis of studies based on seismic reflection data allowed some general rules regarding salt tectonics of the Polish Basin to be formulated. Two general classes of structures genetically related to the presence of the Zechstein evaporites have been described: peripheral structures located within NE and SW flanks of the Polish Basin, outside its axial part and structures located within its axial part. The first class of structures includes grabens bounded by listric faults detached above salt or salt pillows that developed where Zechstein evaporites were of relatively smaller thickness and where sub-Zechstein fault tectonics played a relatively smaller role. The second class of structures includes more mature salt structures such as salt pillows and salt diapirs and is related to the more axial part of the basin, characterized by relatively thicker Zechstein evaporites and by more intense basement tectonics. First salt movements (salt pillowing) took place in the Early Triassic that in certain cases was followed by the Late Triassic salt diapirism and extrusion. In Jurassic–Early Cretaceous times, no significant growth of salt structures took place. Most of the salt diapirs have been finally shaped by the Late Cretaceous inversion tectonics. Some salt diapirs also underwent Cenozoic reactivation, associated with localized Oligocene or Miocene subsidence that in some cases was followed by younger (Pliocene–Quaternary) inversion and uplift.

Pliocene and Quaternary depositional model of the Algarve margin contourite drifts (Gulf of Cadiz, SW Iberia): Seismic architecture, tectonic control and paleoceanographic insights

The contourite drifts off southwest Iberia that formed as a result of the interaction of the Mediterranean Outflow Water (MOW) with the continental middle slope were studied in the Algarve margin using multichannel reflection seismic lines, oil-wells, piston cores, and a bathymetric compilation of four datasets. The seismostratigraphic interpretation of a dense array of oil industry seismic and stratigraphic correlation allowed the identification of five seismic units of Early Pliocene through Holocene in the Faro and Albufeira drifts and four correlative seismic units in the Lagos and Sagres drifts and three in the Portimão drift. A three-phased evolutionary model for the contourite formation is proposed. Firstly, a precursory phase of Pliocene age made up of sheeted drifts represents an initial phase of deposition under bottom-current activity that is correlated with the first stages of an enhanced MOW at about 3.5Ma. Secondly, the building up phase of Early Pleistocene age is related to a strengthening of the MOW close to the onset of the Northern Hemisphere glaciations at about 2.6Ma during which were deposited low-mounded drifts. Thirdly, the growing phase from Middle-Pleistocene through Holocene suggests the presence of a stronger MOW since the beginning of the Middle-Pleistocene Transition at about 1.3–1.0Ma, accounting for the deposition of mounded drifts and formation of the Álvares Cabral moat. Seismostratigraphic interpretation and isochron maps allowed for the establishment of the main oceanographic, climatic, morphologic and tectonic factors that controlled the drifts deposition: i) the Pliocene and Quaternary MOW circulation forced by climate changes; ii) the sea bottom topography inherited from the Late Miocene, mainly shaped by the Portimão, Lagos and Bartolomeu Dias canyons system; iii) the interaction between along-slope and down-slope processes since the Pliocene; and iv) Pliocene–Quaternary fault-activity and diapirism.

Late Cenozoic tectonics of the Red River Fault Zone, Vietnam, in the light of geomorphic studies

The main episode of Pliocene–Quaternary tectonic activity in the Red River Fault Zone in Vietnam was related to dextral strike-slip motions while uplift of the SW and NE sides of the fault zone was limited. In the Vietnamese segment of this zone, traces of pre-Pliocene mature relief were preserved to a much smaller extent compared to those in Yunnan Province, China. The main factors controlling headward erosion of tributary streams were lithologic contrasts within the solid bedrock. Tectonic-geomorphic studies indicate that the amount of Quaternary dextral offset of the Red River Fault Zone in Vietnam, calculated from offset and deflection of tributary valleys of the Red River, ranges between some 400m and 5.3km, averaging 1.1–2km. The corresponding rates of slip are 0.43–1.1mm/yr for individual displaced segments and 5.5–7.8mm/yr for the inferred cumulative displacement. Fluvial terraces in the medial segment were mainly shaped in the Late Pleistocene and Holocene, except the highest one (40–50m) which was probably formed in Mid-Pleistocene time. Taking into account the amount of dextral displacement of terrace steps and related alluvial fans, the most realistic estimation of Mid-Pleistocene through Holocene slip rate is 0.9–3.9mm/yr. The axis of maximum horizontal compression associated with dextral slip of the fault zone was aligned NNW–SSE to N–S, and the fault motion in the Quaternary resulted mainly from aseismic creep.

Neotectonic evolution of the northern Laborec drainage basin (northeastern part of Slovakia)

This study investigates the influence of neotectonic activity on river and basin patterns in a mountainous area located in the northeastern part of the Carpathian Belt (the Laborecká vrchovina and Bukovské vrchy Mts. in eastern Slovakia). This area evolved within the accretionary wedge of the Carpathians during the Neogene, and it was alsowas affected by Middle to Late Miocene thrusting of the External Carpathians. Morphometric analysis, longitudinal and transverse river valley profiles, analysis of basin and valley symmetries, and investigation of alluvial terraces were carried out on the northern Laborec River and its tributaries. This was done to detect a possible relationship between their river courses and any ongoing neotectonic activity, which is otherwise difficult to detect by methods of structural geology because of the poorly exposed area. The general topography of the basin is characterized by a stepwise inclination to the SW as a result of differential uplift and subsidence. The reorganization of the river network in the Laborec drainage basin was influenced by tectonic activity along the NE–SW up to N–S fault structures during the neotectonic phase (Pliocene–Quaternary). The movement along these fault structures is predominantly normal to transtensive. The obtained data assumes that the region is under approximately NE–SW oriented S H compression and NW–SE trending S h tension. The Laborec drainage basin is characterized by a very high degree of asymmetry that sharply increases from the upper to the lower courses of the river. The right-bank tributaries of the Laborec River are < 12 km in length; however, the left-bank tributaries such as Vydraňka, Ol'šava, Výrava, Udava, and Cirocha Streams are up to 50 km long with a high potential of headward erosion and capturing. The valley asymmetry is also very variable in the upper and lower portions of the basin. Based on these presented results, the ancient river thalweg was located along the axis of the Hostovice–Habura depression, and it was captured by the Ol'šava, Výrava, and Udava Streams. The asymmetric pattern of the drainage basin is the result of active tectonics, the continual subsidence of the Transcarpathian Basin, and by the uplift of the Laborecká vrchovina and Bukovské vrchy Mts. These events caused rejuvenation of the headward erosion of streams in the southern part. Favorable lithology was also essential in the process of river capture.

Uzon volcano caldera (Kamchatka): A unique natural laboratory of the present-day naphthide genesis

Oil shows from the thermal springs of the Uzon volcano caldera have been studied by gas chromatography–mass spectrometry methods. Based on the composition and distribution of biomarker molecules, their genetic identity with the organic matter of Pliocene–Quaternary deposits has been established. It has been shown that the Uzon caldera is a unique natural laboratory of the present-day oil formation from the organic matter of Pliocene–Quaternary sediments. It has been stated that attempts to consider the compounds forming these oil shows as a product of hydrothermal abiogenic synthesis are absolutely unfounded.

Quantitative morphotectonics of the Pliocene to Quaternary Auletta basin, southern Italy

The geomorphological evolution of the Pliocene–Quaternary Auletta basin, a wide fault-bounded depression of the southern Apennines axial zone, Italy, was reconstructed using both DEM-based morphometric analysis and classical morphotectonic investigations. Morphotectonic analyses have been integrated with geological, structural and paleomagnetic data in order to reconstruct the Quaternary evolution of the area. The Auletta basin coincides with the lower valley of the Tanagro River and is filled by Pliocene to Pleistocene marine and continental sediments. The strike of the basin is N120–130°, according to the main fault systems of the area. Long-term landscape evolution results from interaction and feedback of geomorphic stages with the morphogenesis of erosional land surfaces alternating with tectonic pulses in which also block-tectonic rotation occurred. The ages of the morphological de-activation of such terraced surfaces have been roughly defined on the grounds of their morpho-stratigraphic relationships with Pliocene and Quaternary deposits, and better constrained by radiometric dating. Tectonic tilting has been established from morphological relationships between rotated blocks related to the activity of the Alburni fault line and the several generations of erosional and depositional land surfaces. The stratigraphic, structural, paleomagnetic and geomorphological data presented here suggest that the studied basin appears to have a more complex tectonic evolution than an extensional graben. Transtensional tectonics along NW–SE striking, listric faults of the Alburni margin system created the depression since Pliocene times, whereas extensional tectonics plays a key role in the middle to late Pleistocene morphotectonic evolution of the basin. This work demonstrates the usefulness of an integrated analysis in order to extract information on tectonic activity and landscape evolution in the Auletta basin, as an example for other study areas.

A new perspective on evolution of the Baikal Rift

A new model is suggested for the history of the Baikal Rift, in deviation from the classic two-stage evolution scenario, based on a synthesis of the available data from the Baikal Basin and revised correlation between tectonic–lithological–stratigraphic complexes (TLSC) in sedimentary sections around Lake Baikal and seismic stratigraphic sequences (SSS) in the lake sediments. Unlike the previous models, the revised model places the onset of rifting during Late Cretaceous and comprises three major stages which are subdivided into several substages. The stages and the substages are separated by events of tectonic activity and stress reversal when additional compression produced folds and shear structures. The events that mark the stage boundaries show up as gaps, unconformities, and deformation features in the deposition patterns. The earliest Late Cretaceous–Oligocene stage began long before the India–Eurasia collision in a setting of diffuse extension that acted over a large territory of Asia. The NW–SE far-field pure extension produced an NE-striking half-graben oriented along an old zone of weakness at the edge of the Siberian craton. That was already the onset of rift evolution recorded in weathered lacustrine deposits on the Baikal shore and in a wedge-shaped acoustically transparent seismic unit in the lake sediments. The second stage spanning Late Oligocene–Early Pliocene time began with a stress change when the effect from the Eocene India–Eurasia collision had reached the region and became a major control of its geodynamics. The EW and NE transpression and shear from the collisional front transformed the Late Cretaceous half-graben into a U-shaped one which accumulated a deformed layered sequence of sediments. Rifting at the latest stage was driven by extension from a local source associated with hot mantle material rising to the base of the rifted crust. The asthenospheric upwarp first induced the growth of the Baikal dome and the related change from finer to coarser molasse deposition. With time, the upwarp became a more powerful stress source than the collision, and the stress vector returned to the previous NW–SE extension that changed the rift geometry back to a half-graben. The layered Late Pliocene–Quaternary subaerial tectonic–lithological–stratigraphic and the Quaternary submarine seismic stratigraphic units filling the latest half-graben remained almost undeformed. The rifting mechanisms were thus passive during two earlier stages and active during the third stage. The three-stage model of the rift history does not rule out the previous division into two major stages but rather extends its limits back into time as far as the Maastrichtian. Our model is consistent with geological, stratigraphic, structural, and geophysical data and provides further insights into the understanding of rifting in the Baikal region in particular and continental rifting in general.

Geophysical evidence for cyclic sediment deposition on the southern slope of Qiongdongnan Basin, South China Sea

Gravity flow deposits form a significant component of the stratigraphic record in ancient and modern deep-water basins worldwide. Analyses of high-resolution 3D seismic reflection data in a predominantly slope setting, the southern slope of Qiongdongnan Basin, South China Sea, reveal the extensive presence of gravity flow depositional elements in the Late Pliocene−Quaternary strata. Three key elements were observed: (1) mass transport deposits (MTDs) including slumps and debris flows, (2) turbidity current deposits including distributary channel complexes, leveed channel complexes and avulsion channel complexes, and (3) deep-water drapes (highstand condensed sections). Each depositional element displays a unique seismic expression and internal structures in seismic profiles and attribute maps. Based on seismic characteristics, the studied succession is subdivided into six units in which three depositional cycles are identified. Each cycle exhibits MTDs (slump or debris) at the base, overlain by turbidities or a deep-water drape. The genesis of these cycles is mainly controlled by frequent sea-level fluctuations and high sedimentation rates in the Late Pliocene–Quaternary. Moreover, tectonics, differential subsidence, and paleo-seafloor morphology may have also contributed to their formation processes. The present study is aimed to a better understanding of deep-water depositional systems, and to a successful hydrocarbon exploration and engineering-risk assessment.

Stratigraphic, structural and geochemical features of the NE–SW trending Neogene volcano-sedimentary basins in western Anatolia: Implications for associations of supra-detachment and transtensional strike-slip basin formation in extensional tectonic setting

Western Anatolia has been the focus of many geological studies of the classical extensional tectonics in the region. The NE–SW-trending Neogene volcano-sedimentary basins that characterize western Anatolia, are mainly located on the northern part of the Menderes Massif – a progressively exhumed mid-crustal metamorphic unit that has undergone Neogene extensional tectonics in the area. The NE–SW-trending basins are the Bigadiç, Gördes, Demirci, Selendi, Emet, Güre and Uşak basins. Although many studies have been carried out in these basins, the stratigraphic and tectonic evolution of the NE–SW-trending volcano-sedimentary basins remains controversial, and hence different evolutionary models have been proposed by various authors. Recent studies concluded that there was a close relation in both space and time between the basin formation and the progressive exhumation of the Menderes Massif. In this study, we present new stratigraphic, geochemical and tectonic observations from the Gördes, Demirci and Emet basins, and couple them with data from the other NE–SW-trending basins to produce a tectono-stratigraphic evolutionary model for the area. Gördes basin was opened by strike- to oblique-slip movements on the basin-bounding faults as a result of dextral transtension, such that the transtensional Gördes basin formed where extension is oblique to the margin that bounded the basin. The Demirci, Selendi, Emet, and Güre basins, have similar stratigraphic and tectonic features, and began to develop as supra-detachment extensional basins on an early Miocene corrugated detachment fault (the Simav detachment fault, SDF). In these basins, deposition of a middle Miocene volcano-sedimentary succession was controlled by NE–SW-trending strike- to oblique-slip faults, which developed as accommodation faults in the hanging-wall of a second detachment fault located further south (the Gediz detachment fault, GDF). These data suggest that the Menderes Massif was exhumed through basin formation in the upper plate that arose from successive detachment faulting, accommodated by kinematically-linked dextral strike- to oblique-slip motion to the west. Strike-slip faulting is linked to a previously described crustal-scale zone of weakness on which the Gördes basin was formed (the İzmir–Balıkesir transfer zone). The NE–SW-trending basins were also deformed by NE–SW-trending dextral and NW–SE-trending sinistral strike-slip faulting (under pure shear) during the late Miocene, and by E–W-trending dip-slip normal faulting in the Pliocene–Quaternary. The data indicate that the region has been extended in a ∼N–S-direction since at least the early Miocene, and that this extension occurred episodically in several phases.

Small-scale mantle heterogeneity on the source of the Gran Canaria (Canary Islands) Pliocene–Quaternary magmas

New chemical and Sr–Nd–Pb isotopic data of the Plio-Quaternary mafic lavas of Gran Canaria are used to investigate their mantle source composition. The most prominent aspects of the new dataset are the slight isotopic differences between the Plio-Quaternary (Post-Roque Nublo Group) and the older Pliocene (Roque Nublo Group) mafic parental magmas, which reflect small-scale mantle heterogeneities. Melting of two mantle materials, one isotopically more depleted and similar to the Depleted Mantle (DM) and the other with more radiogenic Pb-isotope ratios comparable to a mantle with high U/Pb ratio (HIMU), accounts for the isotopic and trace element composition of the Pliocene–Quaternary magmas of Gran Canaria. Geochemical variations show that the Pliocene–Quaternary mantle source is compositionally and lithologically heterogeneous and supports the presence of a silica-deficient pyroxenite mantle component. The contribution of the pyroxenite component in the generation of the Roque Nublo and Post-Roque Nublo magmas is estimated to be in the range from 50 to 70%. Trace element ratios support mixing between the two mantle components (pyroxenite veins in a peridotite matrix) which obscure the original chemical and isotopic composition of these two end-members.

Tectonic significance of changes in post-subduction Pliocene–Quaternary magmatism in the south east part of the Carpathian–Pannonian Region

The south-eastern part of the Carpathian–Pannonian region records the cessation of convergence between the European platform/Moesia and the Tisza–Dacia microplate. Plio-Quaternary magmatic activity in this area, in close proximity to the ‘Vrancea zone’, shows a shift from normal calc-alkaline to much more diverse compositions (adakite-like calc-alkaline, K-alkalic, mafic Na-alkalic and ultrapotassic), suggesting a significant change in geodynamic processes at approximately 3 Ma. We review the tectonic setting, timing, petrology and geochemistry of the post-collisional volcanism to constrain the role of orogenic building processes such as subduction or collision on melt production and migration. The calc-alkaline volcanism (5.3–3.9 Ma) marks the end of normal subduction-related magmatism along the post-collisional Călimani–Gurghiu–Harghita volcanic chain in front of the European convergent plate margin. At ca. 3 Ma in South Harghita magma compositions changed to adakite-like calc-alkaline and continued until recent times (< 0.03 Ma) interrupted at 1.6–1.2 Ma by generation of Na and K-alkalic magmas, signifying changes in the source and melting mechanism. We attribute the changes in magma composition in front of the Moesian platform to two main geodynamic events: (1) slab-pull and steepening with opening of a tear window (adakite-like calc-alkaline magmas) and (2) renewed contraction associated with deep mantle processes such as slab steepening during post-collisional times (Na and K-alkalic magmas). Contemporaneous post-collisional volcanism at the eastern edge of the Pannonian Basin at 2.6–1.3 Ma was dominated by Na-alkalic and ultrapotassic magmas, suggesting a close relationship with thermal asthenospheric doming and strain partitioning related to the Adriatic indentation. Similar timing, magma chamber processes and volume for K-alkalic (shoshonitic) magmas in the South Apuseni Mountains (1.6 Ma) and South Harghita area at a distance of ca. 200 km imply a regional connection with the inversion tectonics.

Mechanics of basin inversion: Finite element modelling of the Pannonian Basin System

This finite element modelling study addresses the contraction of rheologically layered and laterally heterogeneous lithosphere representative for the Pannonian Basin and its surroundings. The time interval and strain rate adopted in the experiments reflect the Pliocene–Quaternary inversion of the basin. Several sets of fully coupled elastoviscoplastic thermo-mechanical, plane strain 2D models explore the evolution of buckling, and stress/strain changes across the lithosphere. The viscous rheology of the asthenosphere allows for a detailed simulation of isostatic rebound during deformation. The numerical models predict the successive development of surface undulations, caused by crustal and/or lithosphere folding, at three different characteristic wavelengths. Among these, the longest wavelength folds occur systematically at the rim of the basin as marginal bulges, while the short wavelength folds overprint the earlier folds and are observed at a later stage during compression. The thermo-mechanical evolution of the lithosphere in response to progressive horizontal contraction is described in terms of a characteristic delay of the changes in the stress regime and a reduction of elastic strain in the strong crustal layers. The models predict a change in stress state along the flanks of the basin, caused by the development of weak basin lithosphere in their vicinity. Comparing the modelling results with tectonic features of the Pannonian Basin has resulted in the identification of three different stages in the Pliocene–Quaternary basin inversion of the Pannonian–Carpathian system.

Neogene–Quaternary tectonic evolution of the Leeward Antilles islands (Aruba, Bonaire, Curaçao) from fault kinematic analysis

Aruba, Bonaire, and Curaçao are islands aligned along the crest of a 200-km-long segment of the east–west-trending Leeward Antilles ridge within the broad Caribbean–South America plate boundary zone presently characterized by east–west, right-lateral strike-slip motion. The crust of the Leeward Antilles ridge represents the western segment of the Cretaceous–early Cenozoic Great Arc of the Caribbean, which obliquely collided, with the continental margin of northern South America in early Cenozoic time. Following the collision, the ridge was affected by folding and was segmented by oblique, northwest-striking normal faults that have produced steep-sided, northwest-trending, elongate islands and narrow shelves separated by deepwater, sediment-filled and fault-controlled basins. In this paper, we present the first fault slip observations on the Neogene carbonate rocks that cover large areas of all three islands. Our main objective is to quantify the timing and nature of Neogene to Quaternary phases of faulting and folding that have affected the structure and topography of this area including offshore sedimentary basins that are being explored for their petroleum potential. These data constrain three fault phases that have affected Aruba, Bonaire, and Curaçao and likely the adjacent offshore areas: 1) NW–SE-directed late Paleogene compression; 2) middle Miocene syndepositional NNW–SSE to NNE–SSW extension that produced deep rift basins transverse to the east–west-trending Leeward Antilles ridge; and 3) Pliocene–Quaternary NNE-trending compression that produced NW–SE-trending anticlines present on Aruba, Curaçao and Bonaire islands. Our new observations – that include detailed relationships between striated fault planes, paleostress tensors, and bedding planes – show that prominent bedding dips of Neogene limestone on Aruba, Bonaire and Curaçao were produced by regional tectonic shortening across the entire Leeward Antilles ridge rather than by localized, syndepositional effects as proposed by previous workers. We interpret Pliocene–Quaternary NNE-directed shortening effects on the Leeward Antilles ridge as the result of northeastward extrusion or “tectonic escape” of continental areas of western Venezuela combined with southeastward shallow subduction of the Caribbean plate beneath the ridge.

An overview of the Late Cretaceous–Eocene positive inversions and Oligo-Miocene subsidence events in the foreland of the Tunisian Atlas: Structural style and implications for the tectonic agenda of the Maghrebian Atlas system

Structural interpretation of surface and subsurface data in the Eastern foreland basins of Tunisia, allows us to recognize positive inversion structures, i.e. related to compressional events, expressed and recorded in the Paleogene sedimentary pile of the Atlas domain. These episodes are followed by a period of relative tectonic quiescence during Oligocene–Early Miocene with development of extensional structures with slightly tilted panels, grabens and locally the development of listric normal faults branched at depth on “décollement” levels. Comparison of the seismic interpretations and field data collected along the South Atlas Front as well as in the Atlas belt, allows us to propose a tectonic scenario at the scale of Eastern Tunisia Atlas. In particular, we emphasise the role of the so-called “Atlas event” (Middle–Late Eocene), which was initially defined in Algeria but poorly outlined in Tunisia. We will show that the tectonic agenda defined in Eastern Tunisia is consistent with the one proposed elsewhere in the Maghreb allowing us to propose a unified view of the geodynamic evolution of the whole Atlas system during this period. The negative inversion recorded during Oligocene–Early Miocene along with the occurrence of synsedimentary normal faults are related to an increase of the subsidence rate in the frame of continuous shortening coeval to basin formation in the front of the Atlas. The whole Oligo-Miocene evolution results from two different mechanisms: flexuration in the front of the Atlas and the onset of the extension of the Pantelleria–Linosa–Malta rift system of central Mediterranean, which attained a climax stage later during Pliocene–Quaternary.

Ancestral Murray River on the Lacepede Shelf, southern Australia: Late Quaternary migrations of a major river outlet and strandline development

The Murray River drains the 1.06 × 106 km2 Murray–Darling Basin and discharges into the sea at the Murray mouth in southeast South Australia. The outlet faces the 180 km-wide Lacepede Shelf and forms part of a wave-dominated beach barrier/lagoon complex, the largest of its type on the Australian coast. Global glacial cycles during the Pleistocene produced lowered sea-levels and exposure of much of the Lacepede Shelf, with the paleoshoreline advancing out to the present edge of the continental shelf during glacial maxima. Mapping and sediment sampling of the Lacepede Shelf in 2006 and 2007 allowed the ancient course of the Murray River on the shelf to be traced and studied for the first time, revealing a 200 km-long system of ancient infilled channels and lagoons. The main system of anastomosing Pleistocene channels begins southeast of the present Murray mouth, off Lakes Alexandrina and Albert, runs southward initially but then veers west-southwest across the central Lacepede Shelf before heading southwest directly south of central Kangaroo Island, and splaying into the head of Sprigg Canyon at the shelf edge. The Last Glacial Maximum channel starts near the current Murray mouth and forms part of this channel system. An earlier channel system ran a more direct, shorter 150 km south-southwest path from off Lakes Alexandrina and Albert to the shelf edge. The Lacepede Shelf is founded on a platform of gently folded, shallow-marine Miocene carbonates. The top of the platform is a prominent regional flat-lying erosional unconformity with local karstic relief in the order of 10 m. Unconsolidated sediment cover (?Pliocene–Quaternary) is mostly relatively thin or absent. However, a depocentre (Lacepede Basin), commonly 6–10 m thick, underlies the central Lacepede Shelf and that part of the shelf directly south of Lakes Alexandrina and Albert. This basin comprises estuarine, lagoonal/lacustrine and fluvial facies of the paleo Murray River, including channel-fill and point-bar deposits. Sediment drifts and residual paleo dunefields are common components of the young sediments on the shelf. A Holocene yellow/red fine quartz sand less than a metre thick, likely to have formed from reworked Last Glacial Maximum eolian sheets/dunes as well as lagoonal/lacustrine sediments, is the predominant sediment type at the surface of the central and northern Lacepede Basin. Paleochannels or paleovalleys of the Murray River incised into the Miocene carbonate platform are typically 10–20 m deep, 450–1000 m wide and contain up to 25 m of sedimentary fill and cover.

The evolution of the Uralian orogen

Abstract The Uralian orogen is located along the western flank of a huge (&gt;4000 km long) intracontinental Uralo-Mongolian mobile belt. The orogen developed mainly between the Late Devonian and the Late Permian, with a brief resumption of orogenic activity in the Lower Jurassic and Pliocene–Quaternary time. Although its evolution is commonly related to the Variscides of Western Europe, its very distinctive features argue against a simple geodynamic connection. To a first order, the evolution of Uralian orogen shows similarities with the ‘Wilson cycle’, beginning with epi-continental rifting (Late Cambrian–Lower Ordovician) followed by passive margin (since Middle Ordovician) development, onset of subduction and arc-related magmatism (Late Ordovician) followed by arc–continent collision (Late Devonian in the south and Early Carboniferous in the north) and continent–continent collision (beginning in the mid-Carboniferous). In detail, however, the Uralides preserve a number of rare features. Oceanic (Ordovician to Lower Devonian) and island–arc (Ordovician to Lower Carboniferous) complexes are particularly well preserved as is the foreland belt in the Southern Urals, which exhibits very limited shortening of deformed Mesoproterozoic to Permian sediments. Geophysical studies indicate the presence of ‘cold’, isostatically equilibrated root. Other characteristic features include a Silurian platinum-rich belt of subduction-related layered plutons, a simultaneous development of orogenic and rift-related magmatism, a succession of collisions that are both diachronous and oblique, and a single dominant stage of transpressive deformation after the Early Carboniferous. The end result is a pronounced bi-vergent structure. The Uralides are also characterized by Meso-Cenozoic post-orogenic stage and plume-related tectonics in Ordovician, Devonian and especially Triassic time. The evolution of the Uralides is consistent with the development and destruction of a Palaeouralian ocean to form part of a giant Uralo-Mongolian orogen, which involved an interaction of cratonic Baltica and Siberia with a young and rheologically weak Kazakhstanian continent. The Uralides are characterized by protracted and recurrent orogenesis, interrupted in the Triassic by tectonothermal activity associated with the Uralo-Siberian superplume.