Search

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

Abstract: Detailed analysis of the stratigraphic architecture and deformation of lower trench-slope sedimentary basins permits the tectonic evolution of subduction margins to be constrained. This study utilises offshore seismic reflection profiles and onshore outcrop data to examine the entire lower trench-slope of the Hikurangi subduction margin in the eastern North Island, New Zealand. Our results constrain the main spatial and temporal changes of facies and sedimentary units since about 25Ma. We demonstrate that the geometries and locations of Miocene to Quaternary sedimentary basins are controlled by tectonic activity and reflect stages of subduction wedge development. Four types of sedimentary basins have been recognized: 1) flysch basins with local olistostromes at the front of seaward propagating thrust sheets; 2) 5–10km wide turbidite-rich trench-slope basins between uplifting structural ridges (i.e. anticlines) associated with shortening within 100km of the subduction front at the seafloor; 3) 30–40km wide trench-slope basins associated with an upslope increase in thrust and ridge spacing; and 4) mixed siliciclastic-carbonate shelves formed in association with margin uplift after filling of the wider (30–40km) trench-slope basins. The lateral and vertical successions of basin geometries and sedimentary infill are consistent with the overall progressive uplift of the subduction wedge. Formation of some of the wide trench-slope basins may be accompanied by significant local subsidence and normal faulting synchronous with active shortening at the subduction front. Margin-wide normal faulting during the Middle–Late Miocene may have formed due to upslope collapse related to tectonic erosion. All of the basins studied contain major unconformities at their base and top, with basin strata deposited over about 2–8Myr. The short life span of these lower trench-slope sedimentary basins is consistent with a succession of short paroxysmal tectonic episodes rather than continuous deformation for the duration of subduction. Stratigraphic discontinuities within basins (e.g., facies changes and reversal of paleo-currents) also record short-term tectonic events (c. 1–2Myr) on the basin-bounding structures and attest to the episodic nature of upper-plate deformation in response to continuous subduction beneath the active margin. [Copyright &y& Elsevier]

The Balearic Promontory (Spain) is of key importance to understand the tectonic kinematics of the westernmost Mediterranean, because its continued marine sedimentation has recorded the contrasting effects expected from competing geodynamic models proposed for the region. Near the center of this promontory, between the islands of Mallorca and Ibiza, the Miocene to Pleistocene stratigraphy of the Central Mallorca Depression presents an ideal record of the tectonic deformation that has received only limited attention. We use a widespread dataset of 2D seismic reflection profiles to identify, interpret and map the main prominent reflectors and extrapolate the thickness of the pre-Messinian and Pliocene-Quaternary sedimentary units. We then quantify the timing and style of deformation related to the various fault systems. Our results reveal for the first time a series of aligned small depressions bounded by extensional and strike-slip faults and filled with Plio-Quaternary sediment, perfectly aligned with the sub-basins of the onshore Mallorca Graben. A subsidence analysis confirms this correlation. We identify non-cylindrical deformation within the Plio-Quaternary unit that is remarkably similar to that observed onshore, suggesting continuous fault zones from the Central Mallorca Depression to Mallorca Island. We interpret an intra-PQ unconformity as the marker of a transition from extensional to strike-slip tectonic regime. The strike-slip stage is represented by both transpressional and transtensional structures, interpreted as restraining/releasing bends respectively and step overs along the faults. We show that these offshore faults in the Central Mallorca Depression overlap well with seismic epicenters and suggest major active strike-slip corridors that have an onshore continuity both until eastern Mallorca and in the southwestern Ibiza margin. The role of previous tectonic inherited structures (rifting, Betic thrusts, post-orogenic collapse) on the deformation reported here is discussed and we propose a tentative sketch that integrates our results in a Miocene to Present-day evolution at regional scale. • Post-Messinian deformation affects the Central Mallorca Depression. • Strike-slip fault systems correlate onland-offshore Mallorca and Ibiza Islands. • The systems localize extensional / compressional structures into long corridors. • Small depocenters of PQ units align onland-offshore. • Recent tectonics and important structural inheritance control local subsidence. [ABSTRACT FROM AUTHOR]

The forearc of the North-Central Peruvian Andes (FNCPA, 6–10°S) provides an exceptional opportunity to study the long-term processes that affect a convergent plate boundary. First, it shows long-term subsidence, depocenter superimposition and individualization. Second, although being mostly extensional and characterized as a typical erosive margin, the FNCPA shows complex uplifted regions. Older deformation is expressed by basement horst and grabens disposed in a complex geometry which onset may have resulted from strike-slip tectonics. A long-lived episode of regional subsidence affected the forearc and led to the relatively thick and regional deposition of the lower Miocene series coeval with a significant increase of the convergence velocity. This period was followed by an episodic uplift of trench-parallel corridors along the so-called Main Deformation Zone. Uplift ceased through the late Miocene and restarted during Pliocene and Quaternary, generating accommodation space by basin flank uplift for a forearc depocenter characterized by landward tilted strata. Significant along-strike differences in the degree of uplift resulted in either uplifting series producing sharp seaward dipping erosional surfaces or less uplifted areas covered by seawards prograding clinoforms. As a consequence of the shallow-water marine setting, the seismic strata geometry, lateral extent and thickness of the deposits for the Neogene successions in the FNCPA have been also tightly controlled by accommodation changes. Uplift is uneven along-strike independently of fault direction and closely followed the increase of the subsidence of the continental slope produced by subduction-erosion. Therefore, sediment underplating seems the most appropriate mechanism at the origin of uplift; as observed in other parts of the Peruvian and Chilean margins. Although the erosive character of the margin, the effects on basin geometry of the raised zone resemble that of typical outer forearc highs in accretionary margins such as in the Kumano basin in Japan. • Transtensional depocenters resulted from high obliquity convergence during the Paleogene. • A trench-parallel uplift affected unevenly and episodically the transtensional depocenters since middle Miocene. • Formation of an outer forearc high, similar to those of accretionary settings, individualized a depocenter during Neogene. • Formation of the outer forearc high may have been induced by sediment underplating. [ABSTRACT FROM AUTHOR]