Multichannel Seismic Profiles Research Articles

Submarine landslides along the Siberian termination of the Lomonosov Ridge, Arctic Ocean

Acoustic and detailed swath bathymetry data revealed a systematic picture of submarine landslides on the Siberian part of Lomonosov Ridge. Whereas numerous studies on mass movement exist along the margin of the Arctic Ocean less is known from central Arctic. A regional survey comprising swath bathymetry, sediment echo sounder and multichannel seismic profiling was performed on the southeastern Lomonosov Ridge. The data provide constraints on the present-day morphology of the Siberian part of Lomonosov Ridge, between 81°–84°N and 140°–146°E. We mapped twelve crescent-shaped escarpments located on both flanks on the crest of Lomonosov Ridge. The escarpments are 2.1 to 10.2 km wide, 1.7 to 8.2 km long and 125 to 851 m high from which 58 to 207 m are occupied by crescent-shaped headscarps. Subbottom data show chaotic reflections within most of the escarpment areas. The unit is overlain by ~110–340 m of semi-coherent parallel reflections. At its bottom the chaotic reflections are limited by a partly eroded high-amplitude reflection sequence that is inclined with <1° basinwards. We find the escarpments to be remnants of submarine landslide events that mobilized 0.09 to 7.58 km3 of sediments between mid Pliocene and mid Miocene. The relatively small amounts of mobilized sediments seem to be typical for the Lomonosov Ridge. The epoch corresponds to the ongoing subsidence of the Lomonosov Ridge below sea level. During that time deposition and the load of sediments changed. We suggest that changes in sediment type preconditioned, and co-occurring earthquakes finally triggered the submarine landslides.

Morphostructural Setting and Tectonic Evolution of the Central Part of the Sicilian Channel (Central Mediterranean)

Abstract The Plio-Quaternary tectonic evolution of the central sector of the Sicilian Channel and the resulting morphostructural setting have been analyzed using a large geophysical dataset consisting of multichannel seismic profiles, which some of them never published, and available bathymetric data. This area hosts two regional-scale tectonic domains that registered the complex pattern of deformation occurred since the Early Pliocene: (1) the Sicilian Channel Rift Zone (SCRZ), which can be divided into a western sector formed by the Pantelleria graben (PG) and in a eastern one represented by the Linosa and Malta grabens (LG and MG) and (2) the Capo Granitola-Sciacca Fault Zone (CGSFZ), a NNE-oriented lithospheric transfer zone that crosses the Sicilian Channel from the Sicily coast to the Linosa Island, of which only its northern part has been studied to date. Data interpretation has allowed achieving the following outcomes: (i) the presence of an alternation of basins and structural highs forming a NNE-oriented separation belt between the western and eastern sectors of the SCRZ, and interpreted as the shallow expression of the southern part of the CGSFZ; (ii) a NE-oriented tectonic lineament separating the MG in a northern and southern part, and interpreted as the southern prosecution of the Scicli-Ragusa Fault System; (iii) the presence of syn-rift deposits in the Plio-Quaternary fill of the grabens, suggesting that the opening of the grabens of the SCRZ was coeval, and started since Early Pliocene in the framework of a NW-oriented right-lateral transtensional mega-shear zone; (iv) continental rifting ended around the Early Calabrian, during which extensional tectonics dominated along the separation belt; (v) the CGSFZ conditioned the SCRZ configuration at a regional scale, leading to the development of the PG in the western sector and of the LG and MG in the eastern one; and (vi) after the Early Calabrian, the PG and the southern MG followed a different tectonic evolution with respect to the LG and northern MG. The syn-rift deposits of the PG and southern MG were sealed by an undeformed post-rift succession, while the LG and the northern MG suffered a basin inversion that ended around the Latest Calabrian time. During this stage, the separation belt was affected by a transpressional tectonics. At present, the grabens of the Sicilian Channel seem to be tectonically inactive, while the CGSFZ represents an active tectonic domain.

Seismic stratigraphy of the Klints Bank east of Gotland (Baltic Sea): a giant drumlin sealing thermogenic hydrocarbons

This work analyses six high-resolution multi-channel seismic profiles across the Klints Bank east of Gotland. The Klints Bank consists of a drop-shaped increase of the Quaternary thickness and is oriented in an approximately north-southern direction with a length of over 50 km, a width of about 15 km and a maximum thickness of 150 m. The glacial origin of the Klints Bank can be verified with the dataset presented in this study. We classify the feature as a (giant) drumlin due to its steep up-ice and tapered down-ice face in combination with an orientation parallel to the ice-flow direction of the Weichselian glaciation. The seismic image of the internal structure of the Quaternary unit shows no uniform stratification or deformation patterns; instead, local sub-parallel reflection patterns interlayered with transparent units are observed. The averaged seismic velocity of this unit is about 2000 m/s, which is interpreted as an autochthonous deposition of glaciogenic sediments. Signs of overprinting are interpreted based on the geometry of the flanks of the structure, which appear mostly in the form of collapse structures and lifted blocks due to compressional thrust faulting. Phase-reversed events within and beneath the Quaternary are perceived as strong evidence of fluid (hydrocarbon) presence within the Klints Bank. Organically enriched Palaeozoic shales in south-easterly direction of the Klints Bank presumably give the origin of these thermogenic hydrocarbons.

Types, characteristics, distribution, and genesis of pockmarks in the South China Sea: insights from high-resolution multibeam bathymetric and multichannel seismic data

ABSTRACT Ubiquitous pockmarks in continental margins are important to understand the tectonic and sedimentary history and flow activity of their host margins. The study of an extensive field of pockmarks in the South China Sea (SCS) is important both scientifically and economically, for the exploration of oil, gas, and gas hydrate resources and the prevention and control of marine geological disasters. We report our new findings on the characteristics, distribution, and genesis of pockmarks in the SCS based on interpretation of high-resolution multibeam bathymetric data and multichannel seismic profiles collected in the past decade. Three pockmark fields (total area 572,824 km2), are recognized in the northern, western, and southern continental margins of the SCS. The pockmarks are highly variable in shape: circular, elliptical, crescent-shaped, elongated or forming a chain in plan view and U-, V- or W-shaped in cross-section. Pockmarks are normally 10–200 m in diameter, with maximum diameters/axial lengths of 7.3 km for circular, 5.5 km for elliptical, 8.6 km for crescent-shaped, 9.5 km for elongated, and 30 km for chain-type pockmarks. Pockmarks are normally less than 35 m deep, with a maximum depth of 341 m at the southwestern SCS margin. These pockmarks might have originated from methane seepages or from pore fluids from deeper sources, which migrated vertically along gas chimneys, mud diapirs, mud volcanoes, faults or buried channels. In addition to possible structural controls, the pockmark morphologies are affected by bottom currents.

Unveiling Powell Basin’s Tectonic Domains and Understanding Its Abnormal Magnetic Anomaly Signature. Is Heat the Key?

Rifting of continental lithosphere leading to oceanic basins is a complex process conditioned by different factors such as the rheology and thermal structure of the underlying lithosphere, as well as underlying asthenospheric dynamics. All these processes, which finally lead to oceanic domains, can better be recognized in small oceanic basins. Powell Basin is a small oceanic basin bounded to the north by the South Scotia Ridge, to the east by the South Orkney Microcontinent, and to the west by the Antarctic Peninsula. It was formed between the Oligocene and Miocene, however, its age is not well defined, among other reasons due to the small amplitude of its spreading magnetic anomalies. This basin is an ideal framework to analyze the different rifting and spreading phases, which leads from continental crust to the formation of an oceanic domain through different extensional regimes. To identify the different boundaries during the formation of Powell Basin from the beginning of the rifting until the end of the spreading, we use different data sources: magnetic, gravity, multichannel seismic profiles and bathymetry data. We use seismic and bathymetry data to estimate the Total Tectonic Subsidence (TTS). TTS has proven to be useful to delineate the different tectonic regimes present from early rifting to the formation of oceanic seafloor. This result together with magnetic data has been used to delimit the oceanic domain and compare with previous authors’ proposals. This method could be applied in any other basin or margin to help delimiting its boundaries. Finally, we analyze the role that an asthenospheric branch intruding from the Scotia Sea played in the evolution of the magnetic anomaly signature on an oceanic basin.

NUMERICAL MODELLING OF THE AUSTRALIA – ANTARCTICA CONJUGATE MARGINS USING THE GALO SYSTEM: PART 2. THERMAL AND MATURATION HISTORY OF THE MAWSON SEA BASIN, EAST ANTARCTICA

The thermal evolution of the Mawson Sea Basin, offshore East Antarctic, was modelled using the GALO basin modelling programme. As there exist no deep temperature or vitrinite reflectance data for the Mawson Sea Basin, the simulation was based on a limited nonthermal database. This includes the present‐day sedimentary section along a multichannel seismic profile which crosses the western part of the Mawson Sea along with geophysical assessments of the depth of the Moho. An analysis of the variations in tectonic subsidence was used to estimate the duration and magnitude of thermal activation or stretching of the lithosphere. This analysis suggested that a proportion of the lithospheric stretching took place before the start of synrift sediment deposition at about 160 Ma (Late Jurassic). This pre‐sedimentation lithospheric stretching has been ignored in previous studies, resulting in significant underestimation of the total stretching which has occurred. The analysis also suggests that the thermal maturity of Lower Jurassic potential source rocks along the profile may reach and even exceed the onset of the oil generation window, whereas source rocks in less deeply buried parts of the profile are less mature. In general, the results of the modelling indicate that the Mawson Sea Basin is a promising area for future oil and gas exploration.

Seismic evidence for the crustal deformation and kinematic evolution of the Nansha Block, South China Sea

To understand the crustal deformation of the Nansha Block (NB), this study presents an interpretation of a recently acquired multichannel seismic profile that traverses the Southwest Subbasin (SWSB), the NB, and the Nansha Trough (NT). A total of six Cenozoic unconformities and three stratigraphic sequences are identified. On the basis of tectonic, structural and stratigraphic features, the NB is divided from northwest to southeast into two structural domains, namely, the Hyper-stretched and Forebulge Domains. Based on the interpretation of the seismic profile, the fault-derived and whole crustal extension factors (βf and βc, respectively) for the NB are calculated. The calculation results show that βc is greater than βf in a limited space of appr. 200 km, where the crust underwent depth-dependent extension. We suggest that the crustal extensional pattern of the NB may be a combination of distal limited depth-dependent extension and proximal uniform extension. The interpretation of the unconformities is also used to calculated the fault-derived crustal extension at various stages. The two main extension stages, the syn-rift and syn-drift, account for appr. 70% and 25% of the total extension, respectively. A comparison with the seismic profiles of the eastern NB shows that the crustal extension along the continental margin of the NB is heterogeneous, with more significant crustal deformation on the west side of the NB. The heterogeneity of the crustal extension along the depth and margin may be related to the thermal condition and rheological structure of the crust or lithosphere.

Statistical analysis of the structural trends in the Galician Margin and their relationship with the Cenozoic evolution of the northwestern sector of the Iberian Margin

Statistical methods of crust surface analysis based on Digital Terrain Models (DTM) and applied to structural elements have become a useful tool in tectonic studies. This paper presents a DTM morphostructural analysis of the Galicia Margin and the Iberian and Biscay abyssal plains, which has identified about 5,800 lineaments. The highest number of lineaments are located in the Charcot and Coruña Highs, in the western sector of the Galicia Bank, in the marginal platforms zone and in the Galicia northern margin. The lineaments analysis shows that they have two dominant directions, E-W and NE-SW. In addition, two other relative maxima of NW-SE and N-S directions have been determined. The cumulative total length of the identified lineaments exceeds 45,000 km. The statistical parameters have a length mode of around 5,000 m, a length average of about 7,800 m and a log-normal distribution of the length frequency. The orientations determined from the analysis of the lineaments are a reflection of the crustal scale fault systems established from gravimetric and magnetic anomalies and multi-channel seismic profiles. These faults developed in the Galicia Margin during the Variscan and Alpine orogenies and were reactivated under the recent stress field.

Evidence for a Prolonged Continental Breakup Resulting From Slow Extension Rates at the Eastern North American Volcanic Rifted Margin

AbstractWhen continental rifting is accompanied by localized magmatism under extensional stress, the breakup duration can be short and the continent/ocean transition sharp, as mantle melts are thought to be efficient at heating and weakening the lithosphere. This mode of rifting has been invoked for the Eastern North American Margin (ENAM) based on the existing geophysical data. Here, we present results from multichannel seismic profiles from the ENAM Community Seismic Experiment offshore North Carolina, U.S. Our survey area encompasses both the East Coast Magnetic Anomaly (ECMA) and the Blake Spur Magnetic Anomaly (BSMA), which lies ~200‐km farther seaward. Our prestack depth‐migrated seismic images reveal major changes in the structure of the igneous crust across the BSMA. Between the ECMA and BSMA, we image a proto‐oceanic domain of rough, faulted, and thin igneous crust. The roughness of this oceanic crust is similar to modern ultraslow spreading environments which involve the continued presence of a pre‐existing lithospheric lid. Seaward of the BSMA the basement is smooth, and the crust is relatively thick, which is typical for Jurassic oceanic crust. Across the BSMA, we image a step up in basement and crustal root, which we interpret to represent complete lithospheric breakup and a transition to steady‐state seafloor spreading in agreement with coincident refraction results. Our results would also indicate low extension rates in the final stages of rifting that may have influenced the thermal structure of the lithosphere and could explain the delay for continental breakup. All of these observations show that although continental rifting between eastern North America and northwest Africa was assisted by magmatic activity, it did not lead to rapid localization of extensional strain as previously thought.

The Lithospheric Structure of the Gibraltar Arc System From Wide‐Angle Seismic Data

AbstractIn continental settings, seismic failure is generally restricted to crustal depth. Crustal structure is therefore an important proxy to evaluate seismic hazard of continental fault systems. Here we present a seismic velocity model across the Gibraltar Arc System, from the Eurasian Betics Range (South Iberian margin), across offshore East Alboran and Pytheas (African margin) basins, and ending onshore in North Morocco. Our results reveal the nature and configuration of the crust supporting the coexistence of three different crustal domains: the continental crust of the Betics, the continental crust of the Pytheas Basin (south Alboran Basin) and onshore Morocco, and a distinct domain formed of magmatic arc crust under the East Alboran Basin. The magmatic arc under the East Alboran Basin is characterized by a velocity structure containing a relatively high‐velocity lower crust (~7 km/s) bounded at the top and base by reflections. The lateral extension of this crust is mapped integrating a second perpendicular wide‐angle seismic profile along the Eastern Alboran basin, together with basement samples, multibeam bathymetry, and a grid of deep‐penetrating multichannel seismic profiles. The transition between crustal domains is currently unrelated to extensional and magmatic processes that formed the basin. The abrupt transition zones between the different crustal domains support that they are bounded by crustal‐scale active fault systems that reactivate inherited structures. Seismicity in the area is constrained to upper‐middle crust depths, and most earthquakes nucleate outside of the magmatic arc domain.

Possible fluid discharge associated with faults observed by a high-resolution dense-2D\xa0seismic reflection survey in Uchiura Bay off Numazu, Japan

Although fluid behavior along faults has often been associated with earthquakes and hydrocarbon accumulation, few observations of active, ongoing fluid discharge along the faults exist. We conducted a dense-2D multi-channel seismic (MCS) reflection survey in Uchiura Bay off Numazu, Japan, in 2018 to obtain a high-resolution image of active faults. As a result, active faults cutting the seafloor and possibly active faults cutting reflections immediately below the seafloor have been clearly imaged on MCS profiles. The spatial variation in their displacement on the seafloor has also been quantified. The seafloor displacement of the most obvious active fault, Fault A, changes by more than 2 m within a short horizontal distance of 50 m. On one of the MCS profiles, an enigmatic wavefield (EWF) is observed within the water column above the seafloor near the faults. From careful observations of the raw field data and shot records, the EWF shows three patterns that suggest fluid flow. Based on a velocity analysis of the seawater, the velocity of the EWF zone was somewhat higher than that of its surroundings. Because the seawater velocity is a function of temperature and salinity at the same depth, the effect of temperature is generally greater than that of salinity, so that the higher velocity would suggest a higher temperature. If temperature of the fluid flow is higher than that of its surroundings, the fluid would rise with its buoyancy and spread out along the sea surface. This scenario could well explain the three EWF patterns. From the appearance and non-appearance of the most obvious EWF on adjacent seismic lines, some fluid discharge might have been occurring intermittently from the seafloor near the faults in Uchiura Bay.

Potential mass movements on the Palinuro volcanic chain (southern Tyrrhenian Sea, Italy) and consequent tsunami generation

The Palinuro volcanic chain (PVC) is located about 80 km offshore the Campania region (Italy) in the southern sector of the Tyrrhenian Sea. The chain consists of 15 volcanic edifices aligned in an E-W direction with two distinct major seamounts (Palinuro and Glabro). They cover a 90 km long and 20 km wide area, with a present-day volume of 2700 km3. Palinuro volcanism emplaced between 0.8 and 0.3 Ma, although shallow seismicity and hydrothermalism indicate an ongoing volcanic activity. A geomorphological analysis of the volcanic chain and data from a multichannel seismic profile reveal large volumes of buried chaotic material suggesting gravity mass sliding from the volcano flanks and slide scars. A stability analysis of the Palinuro flanks has been carried out to determine the sectors potentially prone to sliding in case of shallow volcanic earthquakes. Landslides are simulated by adopting a scenario-based approach. Tsunamis induced by these mass movements and their propagation across the Tyrrhenian Sea are modeled. Results suggest that shallow earthquakes (M ~4.6–4.8) are able to destabilize the flanks of the volcanic chain generating slope failures. Sliding volumes in the order of 1.5 km3 and 2.4 km3 may induce waves as high as 1.5 and 6 m, respectively, along the peri-Tyrrhenian coast. Our results underline the need for further investigations on the stability of the submarine volcanoes of the Tyrrhenian basin. These volcanoes are still poorly known although their instability could trigger large tsunamis along the southern Italy coastal sectors. Our recommendation is that multiparamertic monitoring networks on PVC and periodic oceanic cruises should be put into action, and further that a systematic evaluation of the tsunami hazard related to possible sliding phenomena on the flanks of the Tyrrhenian seamounts should be performed.

Active Extension in a Foreland Trapped Between Two Contractional Chains: The South Apulia Fault System (SAFS)

AbstractThe response of continental forelands to subduction and collision is a widely investigated topic in geodynamics. The deformation occurring within a foreland shared by two opposite‐verging chains, however, is uncommon and poorly understood. The Apulia Swell in the southern end of the Adria microplate (Africa‐Europe plate boundary, central Mediterranean Sea) represents one of these cases, as it is the common foreland of the SW verging Albanides‐Hellenides and the NE verging Southern Apennines merging into the SSE verging Calabrian Arc. We investigated the internal deformation of the Apulia Swell using multiscale geophysical data: multichannel seismic profiles recording up to 12‐s two‐way time (TWT) for a consistent image of the upper crust; high‐resolution multichannel seismic profiles, high‐resolution multibeam bathymetry, and CHIRP profiles acquired by R/V OGS Explora to constrain the Quaternary geological record. The results of our analyses characterize the geometry of the South Apulia Fault System (SAFS), a 100‐km‐long and 12‐km‐wide structure attesting an extensional (and possibly transtensional) response of the foreland to the two contractional fronts. The SAFS consists of two NW‐SE right‐stepping master faults and several secondary structures. The SAFS activity spans from the Early Pleistocene through the Holocene, as testified by the bathymetric and high‐resolution seismic data, with long‐term slip rates in the range of 0.2–0.4 mm/yr. Considering the position within an area with few or none other active faults in the surroundings, the dimension, and the activity rates, the SAFS can be a candidate causative fault of the 20 February 1743, M 6.7, earthquake.

The influence of Totten Glacier on the Late Cenozoic sedimentary record

AbstractAnalysis of multichannel seismic profiles collected on the continental rise off the Sabrina Coast, East Antarctica, has allowed the determination of the acoustic features that are indicative of major evolution steps of the East Antarctic Ice Sheet (EAIS) and highlights the role of meltwater that originated from Totten Glacier in shaping the margin architecture. The arrival of marine-terminating glaciers into the coastal region was recorded by an enhanced sediment input on the continental rise and the nucleation of channel-levees. Downslope sedimentary processes were dominant throughout the Late Cenozoic, testifying to the progressive growth of a highly dynamic, temperate ice sheet on the continent. The last evolutionary step marks the transition to when a full polar glacial regime occurred. The development of a prograding wedge with steeply dipping foresets on the continental shelf and slope exemplifies sedimentation at this time. Other sub-sea-floor observations indicate that downslope fluxes, triggered by glacial meltwater, were still able to deeply erode and deliver sediments to the rise area. This study's findings have led to the identification of expanded and well-preserved sedimentary successions, which we suggest should be considered as priority targets for future International Ocean Discovery Program deep drilling due to the sensitivity of the ice sheet in this area.

High-fold enhancement of a seismic image and detection of the low-frequency shadow below the bottom-simulating reflector

Gas hydrates are a potential energy source. Seismic methods have been extensively applied to detecting gas hydrates based on the interpretation of bottom-simulating reflectors (BSRs), for which the seismic response is characterized by many features such as a strong reflection and low-frequency shadow (LFS). Moreover, the frequency content depends of the offset, with the BSR response having a lower dominant frequency at large offsets. In this work, we intend to enhance the low amplitude of the BSR and to observe the LFS phenomena at the southern Hikurangi margin of New Zealand. To improve the resolution of the seismic image, we processed a multichannel seismic profile acquired over a distance of 125 km. The standard processing sequence for seismic reflection data has been performed with an emphasis on using high fold. The results reveal that the BSR is characterized by strong reflections and high amplitude owing to the seismic data being stacked at higher fold. In addition, a continuation of the BSR event was obtained. Moreover, the use of a higher fold allowed us to determine an LFS below the BSR event, which indicates the presence of gas. The findings support other evidence obtained through contemporary studies on identifying gas hydrates using seismic methods.

Onshore–offshore correlations of Cretaceous fluvial-deltaic sequences, southern Baltimore Canyon trough

We evaluate Cretaceous depositional sequences on approximately 4400 km (∼2700 mi) of newly released multichannel seismic profiles and five wells on the continental shelf in the southern Baltimore Canyon trough and tie the data to three wells drilled onshore in the Maryland coastal plain. Seismic geometries coupled with facies and biostratigraphy from the wells are used to delineate mid-Cretaceous (Aptian–Turonian) depositional sequences and paleogeography. Beneath these sequences, 400–1000 m (1300–3300 ft) of Lower Cretaceous sedimentary rocks underlie the modern shelf. They thicken along strike to the southwest, implying a southern sediment source. Aptian to Cenomanian sediments were deposited in shelf to nearshore settings. A landward movement of the depocenter and a shift toward facies indicative of deeper paleodepths marks a 107-yr mid-Cretaceous transgression, within which we identify five sequences. A composite maximum flooding surface (MFS) within the uppermost of these retrogradational units is associated with the Cenomanian–Turonian boundary and ocean anoxic event 2. Shingled, lower Turonian seismic reflections prograde across the outer shelf, downlapping onto the composite MFS, and are truncated by a mid-Turonian sequence boundary. The Upper Cretaceous section thickens seaward and along strike to the northeast, implying a northern source and little Late Cretaceous accommodation beneath the modern shelf. Mid-Cretaceous strata offshore Maryland are likely sand-prone, considering their proximity to the correlative fluvial facies of the onshore Potomac Group. These potential reservoir sands are capped by regional confining units generated by 107-yr global mean sea-level flooding events and are excellent targets for supercritical carbon storage.

Along-strike segmentation in the northern Caribbean plate boundary zone (Hispaniola sector): Tectonic implications

The North American (NOAM) plate converges with the Caribbean (CARIB) plate at a rate of 20.0 ± 0.4 mm/yr. towards 254 ± 1°. Plate convergence is highly oblique (20–10°), resulting in a complex crustal boundary with along-strike segmentation, strain partitioning and microplate tectonics. We study the oblique convergence of the NOAM and CARIB plates between southeastern Cuba to northern Puerto Rico using new swath multibeam bathymetry data and 2D multi-channel seismic profiles. The combined interpretation of marine geophysical data with the seismicity and geodetic data from public databases allow us to perform a regional scale analysis of the shallower structure, the seismotectonics and the slab geometry along the plate boundary. Due to differential rollback between the NOAM oceanic crust north of Puerto Rico and the relative thicker Bahamas Carbonate Province crust north of Hispaniola a slab tear is created at 68.5°W. The northern margin of Puerto Rico records the oblique high-dip subduction and rollback of the NOAM plate below the island arc. Those processes have resulted in a forearc transpressive tectonics (without strain partitioning), controlled by the Septentrional-Oriente Fault Zone (SOFZ) and the Bunce Fault Zone (BFZ). Meanwhile, in the northern margin of Hispaniola, the collision of the Bahamas Carbonate Province results in high plate coupling with strain partitioning: SOFZ and Northern Hispaniola Deformed Belt (NHDB). In the northern Haitian margin, compression is still relevant since seismicity is mostly associated with the deformation front, whereas strike slip earthquakes are hardly anecdotal. Although in Hispaniola intermediate-depth seismicity should disappear, diffuse intermediate-depth hypocenter remains evidencing the presence of remnant NOAM subducted slab below central and western Hispaniola. Results of this study improve our understanding of the active tectonics in the NE Caribbean that it is the base for future assessment studies on seismic and tsunamigenic hazard.

Northward subglacial drainage during the Mackinaw Interstade in the Cayuga basin, central New York, USA

The history of deglaciation in the Finger Lakes region since the Valley Heads readvance is questioned by recent research in the Cayuga basin, which concludes that, instead of forming a series of proglacial lakes, drainage during the Mackinaw Interstade was into the Laurentide ice sheet. First suspected in the Dryden–Virgil Valley where there is an absence of a lake outlet or surficial lacustrine deposits, this conclusion was explicitly revealed in the Sixmile–Willseyville trough where ice margin channels funneled water into the ice front. Further support was found in the Cayuga Inlet Valley, where a kettle kame terrane sloped northward into the ice front. Northward drainage was preceded by southerly drainage, with reversal occurring about 16.3 kyr ago. Multi-channel seismic profiles at the south end of Lake Cayuga reveal a south-sourced subaqueous sedimentary fan at the base of the lacustrine sequence. This fan is correlated with a coarse and heterogeneous clastic sequence penetrated in water wells in the City of Ithaca and requires northward drainage into a subglacial lake, which precludes the existence of proglacial lakes Ithaca, Newberry, and Hall. The proposed subglacial flow path is through the Cayuga trough, exiting the ice front eastward in the Mohawk Valley. Subglacial drainage from the Cayuga trough probably was part of a regional subglacial drainage system during the Mackinaw Interstade. Studies north of Lake Ontario have led to the proposal of a subglacial lake in the Ontario basin at that time, which likely also drained into the Mohawk Valley.

Recent inversion of the Tyrrhenian Basin

Abstract The Tyrrhenian Basin is a region created by Neogene extensional tectonics related to slab rollback of the east-southeast–migrating Apennine subduction system, commonly believed to be actively underthrusting the Calabrian arc. A compilation of &amp;gt;12,000 km of multichannel seismic profiles, much of them recently collected or reprocessed, provided closer scrutiny and the mapping of previously undetected large compressive structures along the Tyrrhenian margin. This new finding suggests that Tyrrhenian Basin extension recently ceased. The ongoing compressional reorganization of the basin indicates a change of the regional stress field in the area, confirming that slab rollback is no longer a driving mechanism for regional kinematics, now dominated by the Africa-Eurasia lithospheric collision

Neogene subsidence pattern in the multi-episodic extension systems: Insights from backstripping modelling of the Okinawa Trough

Abstract Extensional systems of back-arc basins have been widely recognized and studied in SE Asia, however the interactions between extensional tectonics and spatial-temporal distributions of tectonic subsidence in an active back-arc basin are poorly known. Using a backstripping technique, we analysed 33 multichannel seismic profiles to calculate the Neogene tectonic subsidence across the entire Okinawa Trough (OT) for the first time. Reconstruction of the tectonic subsidence shows that the OT can be roughly divided into four subsidence stages with variable rate. By comparing the temporal-spatial distribution of the intensive subsidence area, we confirmed that rifting events first occurred in the northern segment (NOT) and middle segment (MOT) from the Miocene to Late Pliocene, and then propagated to the southern segment (SOT) after the Late Pliocene. The factors controlling the rapid tectonic subsidence over the entire OT can be classified into two categories: 1) NE-to NNE-trending normal faulting, related to extension of the OT, and NW- to NWW-trending strike-slip faulting; i.e., the Tokara Fault and the Miyako Fault, related to subduction of the Philippine Sea Plate under the Eurasian Plate; 2) The anomalous rapid subsidence occurred in the southernmost part of the SOT is likely related to the subducted Gagua Ridge which caused magma intrusion resulting from partial melting. We suggest that magmatic bodies produced by partial melting of subducted materials intruded into the crust and created a dense lithosphere, causing this rapid tectonic subsidence.