69 research outputs found
Caribbean intra-plate deformation: Paleomagnetic evidence from St. 2 Barthélemy Island for post-Oligocene rotation in the Lesser Antilles forearc
As subduction zones and their related processes are often studied in 2D, or cylindrical 3D sections, the dynamic effects of trench curvature and its evolution through time remain under-explored. Whereas temporal variations in trench trend may be estimated through restoring upper plate deformation, we investigate the forearc deformation history of the strongly curved northern Lesser Antilles trench, connecting the near-orthogonal Lesser Antilles subduction zone with the Motagua-Cayman transform plate boundary. Our new paleomagnetic dataset consists of 310 cores from Eo-Oligocene magmatic rocks and limestones from St. Barthélemy Island. The limestones yielded a post-folding magnetization containing a similar magnetic direction to those stored in magmatic rocks that intrude the folded carbonates, both indicating a post-Oligocene ~15°, and perhaps up to 25° counterclockwise rotation of the island. Our results highlight that the present-day trench curvature formed progressively during the Cenozoic, allowing us to discuss different tectonic scenarios explaining NE Caribbean plate deformation, and to identify key targets for future research on tectonic architecture and the potential present-day activity of intra-plate deformation that may pose seismic hazards
Eocene intra-plate shortening responsible for the rise of a faunal pathway in the northeastern Caribbean realm
Intriguing latest Eocene land-faunal dispersals between South America and the Greater Antilles (northern Caribbean) has inspired the hypothesis of the GAARlandia (Greater Antilles Aves Ridge) land bridge. This landbridge, however, should have crossed the Caribbean oceanic plate, and the geological evolution of its rise and demise, or its geodynamic forcing, remain unknown. Here we present the results of a land-sea survey from the northeast Caribbean plate, combined with chronostratigraphic data, revealing a regional episode of mid to late Eocene, trench-normal, E-W shortening and crustal thickening by ∼25%. This shortening led to a regional late Eocene–early Oligocene hiatus in the sedimentary record revealing the location of an emerged land (the Greater Antilles-Northern Lesser Antilles, or GrANoLA, landmass), consistent with the GAARlandia hypothesis. Subsequent submergence is explained by combined trench-parallel extension and thermal relaxation following a shift of arc magmatism, expressed by a regional early Miocene transgression. We tentatively link the NE Caribbean intra-plate shortening to a well-known absolute and relative North American and Caribbean plate motion change, which may provide focus for the search of the remaining connection between ‘GrANoLA’ land and South America, through the Aves Ridge or Lesser Antilles island arc. Our study highlights the how regional geodynamic evolution may have driven paleogeographic change that is still reflected in current biology
High-K volcanism in the Afyon region, western Turkey: from Si-oversaturated to Si-undersaturated volcanism
Volcanic rocks of the Afyon province (eastern
part of western Anatolia) make up a multistage potassic and ultrapotassic alkaline series dated from 14 to 12 Ma. The early-stage Si-oversaturated volcanic rocks around the Afyon city and further southward are trachyandesitic volcanic activity (14.23 ± 0.09 Ma). Late-stage Si-undersaturated volcanism in the southernmost part of the Afyon volcanic province took place in three episodes inferred from their stratigraphic relationships and ages. Melilite–
leucitites (11.50 ± 0.03 Ma), spotted rachyandesites, tephryphonolites and lamproites (11.91 ± 0.13 Ma) formed in the first episode; trachyandesites in the second episode and finally phonotephrites, phonolite, basaltic trachyandesites and nosean-bearing trachyandesites during the last episode.
The parameter Q [normative q-(ne + lc + kls + ol)] of western Anatolia volcanism clearly decreased southward with time becoming zero in the time interval 10–15 Ma.
The magmatism experienced a sudden change in the extent of Si saturation after 14 Ma, during late-stage volcanic activity of Afyon volcanic province at around 12 Ma, though there was some coexistence of Si-oversaturated and Si-undersaturated magmas during the whole life of Afyon volcanic province
Tsunami hazards in the Catalan Coast, a low-intensity seismic activity area
The final publication is available at Springer via http://dx.doi.org/10.1007/s11069-017-2918-zThe potential impacts of tsunamis along the Catalan Coast (NW Mediterranean) are analysed using numerical modelling. The region is characterized by moderate to low seismic activity and by moderate- to low-magnitude earthquakes. However, the occurrence of historical strong earthquakes and the location of several active offshore faults in front of the coast suggest that the possibility of an earthquake-triggered tsunami is not negligible although of low probability. Up to five faults have been identified to generate tsunamis, being the highest associated possible seismic magnitudes of up to 7.6. Coastal flooding and port agitation are characterized using the Worst-case Credible Tsunami Scenario Analysis approach. The results show a multiple fault source contribution to tsunami hazard. The shelf dimensions and the existence of submerged canyons control the tsunami propagation. In wide shelves, waves travelling offshore may become trapped by refraction causing the wave energy to reach the coastline at some distance from the origin. The free surface water elevation increases at the head of the canyons due to the sharp depth gradients. The effects of potential tsunamis would be very harmful in low-lying coastal stretches, such as deltas, with a high population concentration, assets and infrastructures. The Ebro delta appears to be the most exposed coast, and about the 20% of the delta surface is prone to flooding due to its extremely low-lying nature. The activity at Barcelona port will be severely affected by inflow backflow current at the entrance of up to 2 m/s.Peer ReviewedPostprint (author's final draft
Reconciling the stratigraphy and depositional history of the Lycian orogen-top basins, SW Anatolia
Terrestrial fossil records from the SWAnatolian basins are crucial both for regional correlations and palaeoenvironmental reconstructions.
By reassessing biostratigraphic constraints and incorporating new fossil data, we calibrated and reconstructed the late Neogene
andQuaternary palaeoenvironments within a regional palaeogeographical framework. The culmination of the Taurides inSWAnatolia
was followed by a regional crustal extension from the late Tortonian onwards that created a broad array of NE-trending orogen-top
basins with synchronic associations of alluvial fan, fluvial and lacustrine deposits. The terrestrial basins are superimposed on the upper
Burdigalian marine units with a c. 7 myr of hiatus that corresponds to a shift from regional shortening to extension. The initial infill of
these basins is documented by a transition from marginal alluvial fans and axial fluvial systems into central shallow-perennial lakes
coinciding with a climatic shift from warm/humid to arid conditions. The basal alluvial fan deposits abound in fossil macro-mammals
of an early Turolian (MN11–12; late Tortonian) age. The Pliocene epoch in the region was punctuated by subhumid/humid conditions
resulting in a rise of local base levels and expansion of lakes as evidenced by marsh-swamp deposits containing diverse fossilmammal
assemblages indicating late Ruscinian (lateMN15; late Zanclean) ageWe are grateful for the support of the international
bilateral project between The Scientific and Technological Research
Council of Turkey (TUBITAK) and The Russian Scientific Foundation
(RFBR) with grant a number of 111Y192. M.C.A. is grateful to the
Turkish Academy of Sciences (TUBA) for a GEBIP (Young Scientist
Award) grant. T.K. and S.M. are grateful to the Ege University
Scientific Research Center for the TTM/002/2016 and TTM/001/2016
projects. M.C.A., H.A., S.M. and M.B. have obtained Martin and
Temmick Fellowships at Naturalis Biodiversity Center (Leiden). F.A.D.
is supported by a Mehmet Akif Ersoy University Scientific Research
Grant. T.A.N. is supported by an Alexander-von-Humboldt
Scholarship. L.H.O. received support from TUBITAK under the 2221
program for visiting scientists
The topographic evolution of the Tibetan Region as revealed by palaeontology
The Tibetan Plateau was built through a succession of Gondwanan terranes colliding with Asia during the Mesozoic. These accretions produced a complex Paleogene topography of several predominantly east–west trending mountain ranges separated by deep valleys. Despite this piecemeal assembly and resultant complex relief, Tibet has traditionally been thought of as a coherent entity rising as one unit. This has led to the widely used phrase ‘the uplift of the Tibetan Plateau’, which is a false concept borne of simplistic modelling and confounds understanding the complex interactions between topography climate and biodiversity. Here, using the rich palaeontological record of the Tibetan region, we review what is known about the past topography of the Tibetan region using a combination of quantitative isotope and fossil palaeoaltimetric proxies, and present a new synthesis of the orography of Tibet throughout the Paleogene. We show why ‘the uplift of the Tibetan Plateau’ never occurred, and quantify a new pattern of topographic and landscape evolution that contributed to the development of today’s extraordinary Asian biodiversity
Megablocks and the Stratigraphic Record of Continental Margins: How Large an Event Do They Materialise?
Three-dimensional seismic data from continental slopes commonly show submarine landslide deposits that contain large-scale megablocks, suggesting sudden catastrophic instability events. However, the true temporal and volumetric scales of such events are not well documented in the literature. This study reviews data from three independent projects to provide insights into the importance of large-scale instability events to both stratigraphy and petroleum systems. On the basis of data from the three case studies, some conclusions about the impact of these “megaslides” on petroleum systems are shown by modelling leakage tendencies across basal shear zones. Offshore of Japan, a ~65-m landslide drilled during IODP Expedition 333 shows distinct degrees of erosion at its basal shear zone, whose morphology has responded to the tectonic activity of underlying faults during the Quaternary. In Crete, medium-size blocks of a Miocene submarine landslide show that more than 100 m of continental slope strata were disrupted and moved over shaly marine mudstones of a palaeo continental slope, now fully exposed. Offshore of Brazil, ~400-m blocks were left in situ during the sudden collapse of the Espírito Santo continental slope. The data in this study show that these large-scale events can place important limitations on the correlation of seismic and stratigraphic units across sedimentary basins, as the erosional character of such events can be underestimated, thus implying that potential hiatuses and unconformities are not identified when interpreting older landslide successions. However, the erosional character of these large-scale landslides is recorded mainly in proximal areas, where the sudden release of vertical confining pressure has a significant impact on petroleum systems. In this study, results are presented from fluid-flow modelling across landslide strata in the collapse of large-scale (mega) slides
Did Adria rotate relative to Africa?
The first and foremost boundary condition for
kinematic reconstructions of the Mediterranean region is
the relative motion between Africa and Eurasia, constrained
through reconstructions of the Atlantic Ocean. The Adria
continental block is in a downgoing plate position relative
to the strongly curved central Mediterranean subductionrelated
orogens, and forms the foreland of the Apennines,
Alps, Dinarides, and Albanides–Hellenides. It is connected
to the African plate through the Ionian Basin, likely with
Lower Mesozoic oceanic lithosphere. If the relative motion
of Adria versus Africa is known, its position relative to Eurasia
can be constrained through a plate circuit, thus allowing
robust boundary conditions for the reconstruction of the complex
kinematic history of the Mediterranean region. Based on
kinematic reconstructions for the Neogene motion of Adria
versus Africa, as interpreted from the Alps and from Ionian
Basin and its surrounding areas, it has been suggested that
Adria underwent counterclockwise (ccw) vertical axis rotations
ranging from 0 to 20. Here, we provide six new paleomagnetic
poles from Adria, derived from the Lower Cretaceous
to Upper Miocene carbonatic units of the Apulian
peninsula (southern Italy). These, in combination with published
poles from the Po Plain (Italy), the Istrian peninsula
(Croatia), and the Gargano promontory (Italy), document a
post-Eocene 9.8±9.5 counterclockwise vertical axis rotation
of Adria. Our results do not show evidence of significant
Africa–Adria rotation between the Early Cretaceous
and Eocene. Models based on reconstructions of the Alps,
invoking 17 ccw rotation, and based on the Ionian Basin,
invoking 2 ccw rotation, are both permitted within the documented
rotation range, yet are mutually exclusive. This apparent
enigma could possibly be solved only if one or more
of the following conditions are satisfied: (i) Neogene shortening
in the western Alps has been significantly underestimated
(by as much as 150 km); (ii) Neogene extension in the Ionian
Basin has been significantly underestimated (by as much as
420 km); and/or (iii) a major sinistral strike-slip zone has decoupled
northern and southern Adria in Neogene time. Here
we present five alternative reconstructions of Adria at 20 Ma,
highlighting the kinematic uncertainties, and satisfying the
inferred rotation pattern from this study and/or from previously
proposed kinematic reconstructions
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