Abstract: In this paper,we test the role of vertical axis rotations during transpressional mountain building. To this end, we carried out a palaeomagnetic study in the NE Gobi Altai of southern Mongolia, sampling widely exposed lower Cretaceous lavas allowing comparison of rotation histories of the Ih Bogd, Baga Bogd and Artz Bogd restraining bends at the eastern termination of the Bogd strike-slip zone. We provide new 40Ar/39Ar ages to show that the stratigraphy of mafic lavas and fluvio-lacustrine sediments on the southern flanks of Mt Ih Bogd and Mt Baga Bogd have ages between �125 and �122 Ma, and a mafic sill that intrudes the sequence has an age of 118.2 ± 0.8 Ma. The lavas are older than previously dated lavas south of Artz Bogd, with ages of 119�115 Ma. Palaeomagnetic results from the 119�115 Ma lavas south of Artz Bogd show a significant steeper inclination than both results from 125 to 122 Ma lavas of Baga Bogd and Ih Bogd, as well as from newly sampled and previously published younger lavas and necks of the 107�92 Ma Tsost Magmatic Field and Shovon and Khurmen Uul basalts. We explain this result by insufficient averaging of secular variation and small errors induced by overcorrection of bedding tilt. We show that individual lavas in the SE Artz Bogd locality represent individual spot readings of the Earth�s magnetic field and integrate all results obtained from lower Cretaceous lavas in the Gobi Altai. We present a pole, or rather, an apparent polar wander path without significant plate motion from the reference positions of Eurasia, from �125 to 95 Ma, with n = 126, λ = 80.8�, � = 158.4�, κ = 25.3, A95 = 2.5, palaeolatitude = 48.2 with a scatter Sλ = 16.7 (Sl = 15.3, Su = 17.8) and a regionally consistent direction for the Gobi Altai of D/I = 11.1�/65.9�, D/I = 3.8�/1.9�. This is one of the best-determined palaeopoles/APWP�s for Asia. Formation of the Ih Bogd, Baga Bogd and Artz Bogd restraining bends was thus not associated with vertical axis rotations larger than our error margin of �10�. From this we conclude that the Bogd strike-slip zone is a weak fault zone, in which shear is localized.

Abstract: It is now widely thought that geomagnetic polarity reversals occur spontaneously as a result of normal dynamo action rather than being externally triggered. If this is the case, then it may well be that periods of time in which the geomagnetic reversal frequency was dramatically different were characterised by different styles of secular variation. Two such periods were the Cretaceous Normal Superchron (CNS: 84�125 Ma) when the field was dominantly of a single polarity for 40 Myr and the Jurassic period (145�200 Ma) when reversals occurred at an average rate of as much as 4.6 Myr�1. Here, we analyse a database of new and published palaeomagnetic directions from lavas emplaced during these periods in order to obtain first-order descriptions of the palaeosecular variation (PSV) during these times. We then compare these records with one another and with that produced for the period 0�5Ma (with average reversal frequency of 4.0 Myr�1). Our results are more equivocal than those obtained in a previous similar study [McFadden, P.L., Merrill, R.T., McElhinny, M.W., Lee, S.H., 1991. Reversals of the Earths magnetic-field and temporal variations of the dynamo families. Journal of Geophysical Research-Solid Earth and Planets 96, 3923�3933].We demonstrate that this is probably a result of the previous study being affected by an artefact of their correction for within-site scatter. The usefulness of our Jurassic record is severely limited by the restricted palaeolatitudinal span of the available data. However, our record for the CNS is sufficient to allow us to conclude that it was likely that secular variation then was different from that in the 0�5Ma period. This supports the hypothesis of a link between PSV and reversal frequency and therefore endorses PSV analysis as a first-order tool for determining geomagnetic stability in the past.

Abstract: Reconstruction of the vertical motion history of Crete and Karpathos (southeastern Aegean region, Greece) from the Messinian to Recent revealed a previously poorly documented late Messinian phase of strong subsidence with rates of 50�100 cm/k.y. followed by stasis during the fi rst 250 k.y. of the Pliocene and then by uplift of 500�700 m during the late early to early middle Pliocene. Uplift continued up to Recent albeit at a slower pace and at different rates in different areas. The lower Pliocene in Crete and Karpathos is characterized by widespread occurrences of mass-wasting deposits, which were emplaced over a period of time spanning the fi rst 1.35 m.y. of the Pliocene. The origin of these masswasting deposits has long been enigmatic but is here related to uplift which started in Crete as early as ca 5 Ma. It is suggested that the beginning uplift following strong subsidence of various fault blocks until late in the Messinian is related to the onset of south Aegean strike-slip faulting. We postulate that small-scale tilting of fault blocks by transtensional strike-slip faulting and increased seismic activity generated slope failures and subsequent sliding of poorly cemented lower Pliocene and uppermost Messinian Lago Mare sediments overlying the terminal Miocene erosional unconformity. The absence of mass-wasting deposits after 3.98 Ma, while uplift continued, is most likely the result of progressive compaction and cementation of the increasingly deeper buried Lago Mare and lower Pliocene sediments, thereby preventing slope failure to a depth of the terminal Miocene unconformity. Hiatuses in some places in Crete and on Karpathos, however, indicate that slope failures continued to occur although on a smaller scale and less frequent than before. Connecting the change from subsidence to uplift in the earliest Pliocene with the onset of left-lateral, strike-slip tectonics in the southeastern Aegean arc would make this major strike-slip system much older (by ~2 m.y.) than the generally accepted age of middle to late Pliocene. A recently postulated scenario of �Subduction Transform Edge Propagator� (STEP) faulting to explain the south Aegean strike-slip system predicts rates, distribution, and amount of uplift as rebound to southwestward retreat of the subducted slab along a transform fault zone that is in line with our fi ndings on Crete and Karpathos and explains the absence of compressional structures associated with the uplift, as well as the ongoing southwestward motion of Crete.

Abstract: The region located between the Carpathian�Balkan and Aegean arcs, the Moesian Platform and Bulgarian Rhodope, is generally assumed to have been stably attached to the East European craton during the Cenozoic evolution of these arcs. The kinematic evolution of this region is, however, poorly constrained by paleomagnetic analysis. In this paper we provide new paleomagnetic data (800 volcanic and sedimentary samples from 12 localities) showing no significant post-Eocene rotation of the Moesian platform and Rhodope with respect to Eurasia, therefore confirming the stability of this region. We compare this result to a provided review of paleomagnetic data fromthe South Carpathians (Tisza block) and the Aegean region. The Tisza block underwent 68.4±16.7° ofmiddleMiocene (�15�10 Ma) clockwise rotationwith respect to the Moesian Platform, in line with previous rotation estimates based on structural geology. The stability of the Moesian platform during middle Miocene eastward emplacement of the Tisza block into the Carpathian back-arc supports dextral shear along the Southern Carpathians recorded by 13�6 Ma clockwise strike-slip related rotations in foreland deposits. The new reference direction for the Moesian platform and Rhodope allows accurate quantification of the rotation difference with the west Aegean domain at 38.0±7.2° occurring between 15 and 8 Ma. To accommodate this rotation,we propose that the pivot point of thewest-Aegean rotationwas located approximately in themiddle of the rotating domain rather than at the northern tip as previously proposed. This new scenario predicts less extension southeast of the pivot point, in good agreement with estimates from Aegean structural geology. Northwest of the pivot point, the model requires contraction or extrusion that can be accommodated by the coeval motion of the Tisza Block around the northwestern edge of the Moesian platform.

Abstract:

Abstract: Paleogene deposits of north-central Cuba have been identified as a deformed foredeep basin, whose stratigraphy recorded very well the collision of the Bahamas�Proto-Caribbean realm (North American plate) with the Caribbean plate, a process that occurred since latest Cretaceous to early Late Eocene time. The debris incorporated in the foredeep basin has two provenance regions and four tectonostratigraphic sources, including: (1) the Caribbean Plate (1a = allochthonous Cretaceous arcs, 1b = serpentinite mélanges and ophiolites); (2) the North American plate (2a = Pre-Paleogene sedimentary rocks derived from the substrate of the foredeep basin, 2b = Cretaceous Bahamian carbonate platform rocks). Evaluation of the age, size, and volume of the debris demonstrate the formation of a forebulge within the Bahamas platform in response to the collision between the Caribbean and North American plates, and the northeastward migration of the axis of maximum subsidence of the foredeep basin since the Paleocene. By the early Late Eocene, structural NE-SW shortening ended in central Cuba, with uplift and deep erosion, followed by a quick transgression before the end of the Eocene. The resulting Upper Eocene sediments unconformably cover the deformed foredeep deposits and underlying rocks, finishing the formation of the North Cuba� Bahamas fold-and-thrust belt. Palinspastic reconstructions suggest that this belt accommodated nearly 1000 kilometers of shortening, during underthrusting of the Proto-Caribbean crust below the Caribbean Plate.

Abstract: The island of Rhodos represents an uplifted block in the largely submerged southeastern Aegean forearc. It has a complex history of subsidence, uplift and counterclockwise rotation during the Plio- Pleistocene, in response to the interplay between large-scale geodynamic processes. In this paper, we present a new chronostratigraphic framework for the continental Pliocene Apolakkia basin of southwestern Rhodos. We combine these time constraints with recently published chronostratigraphic data from the marine Plio- Pleistocene basins of northeastern Rhodos to reconstruct rotational and vertical motions. Our palaeomagnetic results identify two rotation phases for Rhodos: c. 108 (9 68) counterclockwise (ccw) rotation between 3.8 and 3.6 Ma, and c. 17 68 ccw rotation since 0.8 Ma. Between these phases, Rhodos tilted to the SE, drowning the southeastern coast to a depth of 500�600 m between 2.5 and 1.8 Ma, then to the NW, which resulted in the re-emergence of the drowned relief between 1.5 and 1.1 Ma. We relate the rotations of Rhodos to incipient formation of the south Aegean sinistral strike-slip system and the foundering of the Rhodos basin. The previously shown absence of Messinian evaporites in the deep-marine Rhodos basin in combination with the 3.8 Ma onset of ccw rotation of Rhodos constrains the onset of the formation of the south Aegean strikeslip system between 5.3 and 3.8 Ma. The formation of this strike-slip system is probably related to the interplay of oblique collision between the southeastern Aegean region and the northward moving African plate, the westward motion of Anatolia, gravitational spreading of the overthickened Aegean lithosphere and the recently postulated southwestward retreat of the African subducted slab along a subduction-transform edge-propagator fault

Abstract: Tertiary extension in the Aegean region has led to extensional detachment faulting, along which metamorphic core complexes were exhumed, among which is the Early toMiddleMiocene South Aegean core complex.This paper focuses on the supradetachment basin developed during the ¢nal stages of exhumation of the South Aegean core complex along the Cretan detachment, plus the Late Miocene to Pliocene basin development and palaeogeography associatedwith the southward motion of Crete during the opening of the Aegean arc. For the latter purpose, the sedimentary and palaeobathymetric evolutions of a large number ofMiddleMiocene to Late Pliocene sequences exposed on Crete,Gavdos and Koufonisi were studied.The supradetachment basin development of Crete is characterised by a break-up of the hanging wall of the Cretan detachment into extensional klippen and subsequent migration of laterally coexisting sedimentary systems, and ¢nally the deformation of the exhumed core complex by processes related to the opening of the Aegean arc. Hence, three main tectonic phases are recognised: (1) Early toMiddleMioceneN^S extension formed during the Cretan detachment, exhumed in the South Aegean core complex.The Cretan detachment remained active until 11^10Ma, based on the oldest sediments that unconformably overlie the metamorphic rocks. Successions older than11^10Ma unconformably overlie only the hanging wall of the Cretan detachment, and do not contain fragments of the footwall rocks; they therefore predate the oldest exposure of the metamorphic rocks of the footwall.The hanging wall rocks andMiddleMiocene sediments form isolated blocks on top of the exhumed metamorphic rocks, which are interpreted as extensional klippen. (2) Fromapproximately10Ma onward, southward migration of the area that presently coversCretewas accompanied byE^Wextension, and the opening of the Sea of Crete to the north. Contemporaneously, large folds withWNW^ESE striking,NNE dipping axial planes developed, possibly in response to sinistral transpression. (3) During the Pliocene,Crete emerged and tilted to theNNW, probably as a result of left-lateral transpression in the Hellenic fore-arc, induced by the collision with the African promontory.

Abstract: Following an Early Miocene phase of N�S extension affecting the entire Hellenides, 50 clockwise rotation affected western Greece. Modern GPS analyses show rapid southwestward motion in southwestern Greece over subducting oceanic lithosphere and no motion in the northwest, where Greece collided with Apulia. We aim to identify the deformation history of western Greece associated with the rotation and the collision with Apulia. The timing of the various phases of deformation is constrained via detailed analysis of vertical motions based on paleobathymetry evolution of sedimentary sequences overlying the evolving structures. The results show that accompanying the onset of rotation, compression was re-established in western Greece in the early Langhian, around 15 Ma. Subsequently, western Greece collided with the Apulian platform, leading in the Late Miocene to a right-lateral strike-slip system running from the Aliakmon Fault Zone in northern Greece via the Kastaniotikos Fault and the Thesprotiko Shear Zone to the Kefallonia Fault Zone, offshore western Greece. NE�SW compression and uplift of the Ionian Islands was accompanied by NE�SW extension in southwestern Greece, associated with faster southwestward motion in the south than in the north. This led in the middle Pliocene (around 3.5 Ma) to collision without further shortening in northwestern Greece. From then onward, NW�SE to N�S extension east of Apulia, and gradually increasing influence of E�W extension in the south accommodated motion of the Hellenides around the Apulian platform. As a result, curved extensional basin systems evolved, including the Gulf of Amvrakikos-Sperchios Basin�Gulf of Evia system and the Gulf of Corinth�Saronic Gulf system.

Abstract: To evaluate the dimension and the timing of the clockwise rotating domain and the nature of the structures that accommodate the rotating domain in the western Aegean region, paleomagnetic analyses were carried out in northern, western and southwestern Greece. The results show that the rotating domain covers an area including the external Albanides, western mainland Greece including Evia and probably at least partly the Peloponnesos. Smaller clockwise rotations on the order of 30� 408 were reported previously from the Chalkidiki peninsula and the islands of Skyros and Limnos. Previously, two phases of approximately 258 of rotation were suggested, the last one during the Plio-Pleistocene. Our analysis shows that the western Aegean domain rotated approximately 408 clockwise between 15�13 and 8 Ma, followed by an additional 108 after 4 Ma. The rotating domain is accommodated in the north by deformation associated with the Scutari�Pec fault zone and in the west by the Ionian thrust and the Hellenic subduction zone. To the south, no rocks older than ~10 Ma are available so no conclusive data are obtained. To the east of the rotating domain, extensional detachment systems of the Cyclades and Rhodope areas were active during the rotation phase and may explain at least part of the differences in finite amounts of rotation between nonrotation or counterclockwise rotations observed in northern and eastern Greece and the large clockwise rotations in western Greece.

Abstract: We quantitatively investigate the relation between nappe stacking and subduction in the Aegean region. If nappe stacking is the result of the decoupling of upper-crustal parts (5�10 km thick) from subducting lithosphere, then the amount of convergence estimated from balancing the nappe stack provides a lower limit to the amount of convergence accommodated by subduction. The balanced nappe stack combined with the estimated amount of completely subducted lithosphere indicates 700 km of Jurassic and 2400 km of post-Jurassic convergence. From seismic tomographic images of the underlying mantle, we estimate 2100�2500 km of post-Jurassic convergence. We conclude that (1) the imaged slab represents the subducted lithosphere that originally underlay the nappes, (2) since the Early Cretaceous, subduction in the Aegean has occurred in one single subduction zone, and (3) the composition of the original basement of the nappes indicates that at least 900 km of sub-upper-crust continental lithosphere subducted in the Aegean.

Abstract: After their emplacement in the course of the late Mesozoic and the Cenozoic, the Hellenic nappes became fragmented during late orogenic extension since the late Eocene. Here we focus on the transition of underthrusting during nappe emplacement to exhumation during late orogenic extension. To this end, we compared previously published data on the structural geological and metamorphic history of the underthrusted parts of the Tripolitza and Ionian nappes, which were exhumed in the Cycladic and South Aegean windows, with newly obtained data on the sedimentary, stratigraphic, and structural development of the part of these nappes in the foreland, in front of the subduction thrust. The results allow the identification of two major events: Event 1 took place around the Eocene-Oligocene transition and marks the onset of underthrusting of the Tripolitza nappe below the Pindos nappe and the Ionian nappe below the Tripolitza nappe, respectively. This led to the uplift and erosion of the Pindos unit and the onset of deposition of the Tripolitza and Ionian flysch in front of the Pindos thrust, together with the formation of mylonites at the base of the metamorphosed portions of the Pindos unit related to the underthrusting of the Tripolitza unit. Event 2 occurred in the latest Oligocene to earliest Miocene and marks the decoupling of the Ionian unit from the underthrusting plate, the accretion of the Tripolitza and Ionian units to the overriding plate, and the onset of late orogenic extension and exhumation in the overriding plate. This led to the formation of the South Aegean and Cycladic core complexes and the subsidence of the Klematia-Paramythia half-graben throughout the early Miocene.

Abstract: A procedure for the consistent application of digital terrain analysis methods to identify tectonic phenomena from geomorphology is developed and presented through two case studies. Based on the study of landforms related to faults, geomorphological characteristics are translated into mathematical and numerical algorithms. Topographic features represented by digital elevation models of the test areas were extracted, described and interpreted in terms of structural geology and geomorphology. Digital terrain modelling was carried out by means of the combined use of: (1) numerical differential geometry methods, (2) digital drainage network analysis, (3) digital geomorphometry, (4) digital image processing, (5) lineament extraction and analysis, (6) spatial and statistical analysis and (7) digital elevation model-specific digital methods, such as shaded relief models, digital cross-sections and 3D surface modelling. A sequential modelling scheme was developed and implemented to analyse two selected study sites, in Hungary andNWGreece on local and regional scales. Structural information from other sources, such as geological and geophysical maps, remotely sensed images and field observations were analysed with geographic information system techniques. Digital terrain analysis methods applied in the proposed way in this study could extract morphotectonic features from DEMs along known faults and they contributed to the tectonic interpretation of the study areas.

Abstract: This paper aims to provide a straightforward and easily applicable method for estimating the depositional depth evolution of marine basins. Vertical movements of the basin floor can be reconstructed from the sedimentary record, and more accurately constrained when information from the sedimentary history is combined with palaeodepth estimates derived from fauna. To this end we propose to extend an existing method based on the percentage of planktonic foraminifera with respect to the total (planktonic and benthic) foraminiferal association, which is expressed as the percentage planktonics (%P). The ratio between planktonic and benthic foraminifera is related to water depth, and the %P generally increases with increasing distance to shore. However, next to water depth the oxygen level of bottom waters has a profound effect on the abundance of benthic foraminifera, and as such influences the %P. Depending on basin configuration, the oxygen level at the sea floor can vary on Milankovitch time scales and is reflected by the fraction of benthic foraminiferal species that indicate an effect of oxygen stress on the biotic system. These species can be used as stress-markers and their percentage with respect to the total benthic population is here expressed as %S. To assess whether the effect of sea-floor oxygenation impairs depth reconstructions, we studied the percentage of planktonic foraminifera (%P) in five well-dated sedimentary successions from the Lower Pliocene of Crete, Corfu and Milos in Greece. Additionally, we assessed whether different foraminiferal size fractions and counting methods affect the determination of the percentage of planktonic foraminifera. The palaeobathymetric evolution calculated for each basin was confirmed for all successions by an independent check on depth-related occurrences of benthic foraminifera. After correction for bathymetry changes of the basin due to sedimentation, compaction and eustatic sea level variations, the vertical movement history of the basin floor was inferred. We propose a standard methodology for reconstructions of palaeobathymetry of marine sedimentary successions from foraminiferal associations.

Abstract: Late-orogenic extension in the Aegean region has been ongoing since the late Eocene or early Oligocene. Contemporaneously, numerous volcanic centres developed. In the south-central Aegean region, Plio-Pleistocene volcanism formed a number of islands. On two of these�Milos and Aegina�a sequence of late Miocene and Pliocene marine sediments underlie the oldest volcaniclastics. To determine whether extension of the Aegean lithosphere played a role in the formation and location of the early Pliocene volcanoes of the Aegean, we aimed to reconstruct the vertical motion history as it occurred prior to the onset of volcanism. To this end we reconstructed the paleobathymetry evolution using foraminifera recovered from sedimentary sections in the lower Pliocene of Milos and Aegina. Age dating on the Milos sections was based on bio-magnetoand cyclostratigraphy; from Aegina only bio- and magnetostratigraphy were available. The results show that prior to the onset of volcanism on both islands, many hundreds of metres of early Pliocene subsidence occurred�on Milos even 900 m between 5.0 and 4.4 Ma. It is unlikely that extension of the Aegean lithosphere led to melting of the underlying mantle. However, the extension probably did play a significant role in the timing of the onset of Pliocene volcanic activity in the Aegean. The position of the volcanic centres is probably the result of the depth of the subducted slab below the Aegean and the formation of a network of extensional faults in the overriding Aegean lithosphere.