Search

Grain-size analysis of the sediments in borehole M0079A, located in the Corinth Rift, was used to explore hydrodynamic conditions and provenance in the Late Pleistocene Corinth Rift. Grain-size populations that were sensitive to the sedimentary environments were characterized by frequency distribution, particle size–standard deviation and probability cumulative curves. Our results indicate the grain-size population component in the range 0.15–0.25 µm may be used as a sensitive proxy for hyperpycnal flows, which have commonly been triggered by river floods from the southern margin of the rift since c. 0.593–0.613 Ma. The high-density plumes derived from the longer rivers of the southern rift that were prevalent before c. 0.593–0.613 Ma. When sediment is supplied as hemipelagic deposition, the proportion of the total grain-size population that is in the 0.3–0.5 µm range becomes an index for suspension fall-out deposits. The core shows coarser sediments during the marine periods, and this may be linked to the current circulation related to the Ishtmia Strait opening. The study thus illustrates how the establishment of interbasinal straits can influence the details of sedimentary hydrodynamics in the deep-water axis of an adjacent depocentre.

The morphology of coastal sequences provides fundamental observations to unravel past sea level (SL) variations. For that purpose, converting morphometric observations into a SL datum requires understanding their morphogenesis. The long-lasting sequence of coral reef terraces (CRTs) at Cape Laundi (Sumba Island, Indonesia) could serve as a benchmark. Yet, it epitomizes a pitfall that challenges the ultimate goal: the overall chronology of its development remains poorly constrained. The polycyclic nature of the terraces, involving marine erosion and reoccupation of old coral colonies by more recent ones hinders any clear assignment of Marine Isotope Stages (MIS) to specific terraces, in particular the reference datum corresponding to the last Interglacial maximum (i.e., MIS 5e). Thus, to overcome these obstacles, we numerically model the genesis of the sequence, testing a range of eustatic SL reconstructions and uplift rates, as well as exploring the parameter space to address reef growth, erosion, and sedimentation. A total of 625 model runs allowed us to improve the morpho-chronological constraints of the coastal sequence and, more particularly, to explain the morphogenesis of the several CRTs associated with MIS 5e. Our results suggest that the lowermost main terrace was first constructed during the marine transgression of MIS 5e and was later reshaped during the marine regression of MIS 5e, as well as during the MIS 5c and MIS 5a highstands. Finally, we discuss the general morphology of the sequence and the implications it may have on SL reconstructions. At Cape Laundi, as elsewhere, we emphasize the necessity to address the development of CRT sequences with a dynamic approach, i.e., considering that a CRT is a landform built continuously throughout the history of SL oscillations, and not simply during a singular SL maximum.

Coastal boulders or mega-clasts, named huracanolitos in Cuba, are found along many rocky shores. They result from storms/hurricanes or tsunamis, but despite being potentially important indicators for hazard assessment, their mode of emplacement is typically unknown. We studied a coastal boulder that is probably the largest one ever described on Cuba Island. Located on a low-lying coral reef terrace on the SE Cuban shore, the reefal limestone boulder is emplaced seaward of the ruins of the Bucanero resort. The latter was built in 1989, suffered from Hurricanes Ivan (2004) and Dennis (2005), and, in October 2012, was totally destroyed by Hurricane Sandy. Despite these extreme climatic events, satellite images obtained since 1962 show no movement of the block. In order to analyse the boulder and its morphological context, we have analysed its position, shape and its morphological environment. To determine its volume, we developed a low-cost, open-source Structure from Motion photogrammetry (SfM) procedure using a simple 3D spherical target (diameter 30 ± 0.2 x 10-3 m). Using various hydrodynamic equations, we calculated the breaking wave height and associated energy responsible for the dislocation of the coral reef terrace and transport of the boulder. To determine the exposure time of the block on the terrace, we performed 36Cl analysis and U/Th dating on post-depositional secondary calcite. From these data, the climatic or tsunamigenic (by earthquake or gravity event) origin is discussed. Notably, mapping and dating of a neighboring coastal landslide were made in order to correlate or not its effect on the setting up of the boulder.Keywords: coastal boulder; extreme-wave deposit; tsunami; hurricane; Cuba

Coral reefs and mangroves are important yet vulnerable coastal ecosystems, especially given strong anthropogenic pressure such as the projected 21st century sea-level rise. Despite the symbiotic relationship of reefs and mangroves within the context of sea-level changes, few studies provided a synchronous assessment of both systems, especially on timescales beyond a few decades. We focus on the response of coral reefs and mangroves in Belitung Island (Indonesia), where previous studies have already provided initial constraints on Holocene relative sea-level history. Along 3 different coastal transects within a distance of ~40 km, we surveyed and sampled 8 sedimentary cores of 1-3 m length, containing coral fragments, mangrove mud/sands and other types of coastal sediment. The three cross-sections evidence a surprisingly variable responses to the same sea-level history: 1) at Sidjuk, a mid-Holocene (~6 ka) coral reef within a former embayment was slowly filled up with sediments providing the substrate for estuarine mangrove development, 2) at Batu Itam, ~500 m of open coast mangroves prograded on top of a mid-Holocene reef, currently occupying around one third of the area within the intertidal zone and 3) at Mendanau, ~ 1 km of open coast mangroves prograded directly on top of basement rocks, with fossil corals seemingly sparse and isolated compared to the other sites. These results demonstrate how reef and mangrove response to sea-level changes may be extremely local in nature, and directly dictated by physical parameters such as sedimentation, wave erosion and reef construction rates. The spatial heterogeneity on the scale of a few 10s of kilometers emphasizes the need for tailored solutions with regards to future sea-level rise.

The fossil record of Quaternary reef systems, as expressed in uplifted regions by sequences of stacked terraces, has been extensively used to either understand their morphodynamics, or to unravel sea level variations. Yet, because these two aspects are intimately linked, Quaternary reef analysis is often underdetermined because the analysis often focuses on single sequences, along one-dimensional profiles. Here, we take advantage of the lateral variations of coral reef sequences by documenting the morphological variations of the reef sequence on Sumba Island. Near Tambolaka, Northwest Sumba, we analyzed a reef transect, topography, and associated sedimentological record to obtain a precise coral reef stratigraphy and geomorphic patterns that can be compared to the well documented eastern counterpart. In Tambolaka, the reef sequence displays four lower layers of bedded chalky limestone units with a weakly cemented sandy matrix, which we attribute to the Middle Miocene to Pliocene Wakabukak formation based on calcareous nannofossils and planktonic foraminifers. The uppermost layer is a calcretized reefal limestone unit with a well-lithified sandy matrix, which we attribute to the Plio-Pleistocene reef sequence of the Kalianga formation. Seven marine terraces imprint the regional morphology, four of which we correlate with MIS 5e, MIS 7e, MIS 9e, MIS 11c terraces of Cape Laundi, Northeast Sumba. When scrutinized at the light of numerical models of reef development, these results indicate that the morphodynamics of reefal sequences is strongly impacted by the tectonic evolution, even at local scales. The geodynamic context sets both the extrinsic -morphology of the basement, hydrodynamics- conditions of reef development, but also the intrinsic properties - reef growth rate in particular. While the morphodynamic evolution of the sequence is at first order representative of the interplay between uplift rates and sea level oscillations, the detailed assemblage of the reef units drastically varies along the coastline.

Several crustal and lithospheric mechanisms lead to deformation and vertical motion of the upper plate during subduction, but their relative contribution is often enigmatic. Multiple areas of the Hellenic Forearc have been uplifting since Plio-Quaternary times, yet spatiotemporal characteristics and sources of this uplift are poorly resolved. The remarkable geology and geomorphology of Kythira Island, in the southwestern Hellenic forearc, allow for a detailed tectonic reconstruction since the Late Miocene. We present a morphotectonic map of the island, together with new biostratigraphic dating and detailed analyses of active fault strikes and marine terraces. We find that the Tortonian-Pliocene stratigraphy in Kythira records ~100 m of subsidence, and a wide coastal rasa marks the ~2.8-2.4 Ma maximum transgression. Subsequent marine regression of ~300-400 m and minor E-W tilt are recorded in ~12 marine terrace levels for which we estimate uplift rates of ~0.2-0.4 mm/yr. Guided by simple landscape evolution models, we interpret the coastal morphology as the result of initial stability or of slow, gradual sea-level drop since ~2.8-2.4 Ma, followed by faster uplift since ~1.5-0.7 Ma. Our findings on- and offshore suggest that E-W extension is the dominant mode of regional active upper crustal deformation, and N-S normal faults accommodate most, if not all of the uplift on Kythira. We interpret the initiation of E-W extension as the result of a change in plate boundary conditions, in response to either propagation of the North Anatolian Fault, incipient collision with the African plate, mantle dynamics or a combination thereof.

International audience; The Java Back-arc Thrust scars the entire back-arc area of Java Island, but the faults' nature, timing, and activity remain partly elusive. Characterizing the structure and activity of the seismogenic Java Back-arc Thrust (historical earthquakes up to 7 Mw) is a cornerstone to evaluate associated geohazards. We focus on the western part of Java Back-arc Thrust that reaches the megalopolis of Jakarta. We combine morphotectonic data, seismic reflection, electric resistivity profiles, kinematic, structural field measurements, paleoseismological trenching, and sediment dating (optically stimulated luminescence and 14C). Our results suggest that the interplay between the faults, volcanoes, and sedimentary basin modulates the propagation of the fault system across and along-strike. The West Java Back-arc Thrust has been active from Pliocene to Recent, but with a laterally variable tempo and tectonic regime. While tectonic activity was sustained for longer times in the eastern part, the West Java Back-arc Thrust broke through the Jakarta Basin in the west, possibly only since the Late Pleistocene, and partitions into a network of immature transpressive structures. We conclude that the West Java Back-arc Thrust has a high seismic hazard that requires a careful risk evaluation along its trace, as it threatens the numerous infrastructures of the densely populated West Java.

Quantifying paleo sea-level changes is an important challenge given its intricate relation with paleo-climate, -ice-sheets and geodynamics, but pre-Holocene uncertainties currently span several tens of meters. The world’s coastlines provide an enormous geomorphologic dataset, and recent modelling studies have showed their potential in constraining paleo sea-level through forward landscape evolution modeling. We take a next step, by applying a Bayesian approach to invert the geometry of marine terrace sequences to paleo sea-level. Using a Markov chain Monte Carlo sampling method, we test our model on synthetic profiles and two observed marine terrace sequences. The synthetic profiles – with known input parameters – show that there are optimal values for uplift rate, erosion rate, initial slope and wave base depth to obtain a well-constrained inversion. Both the inversion of synthetic profiles and a terrace profile from Santa Cruz (Ca, US) show how sea-level peaks are easier to constrain than sea-level troughs, but that also solutions for peaks tend to be non-unique. Synthetic profiles and profiles from the Corinth Rift (Greece) both show how inverting multiple profiles from a sequence can lead to a narrower range of possible paleo sea-level, especially for sea-level troughs. This last result emphasizes the potential of inverting coastal morphology: joint inversion of globally distributed marine terrace profiles may eventually reveal not only local relative sea-level histories, but catalyse a better understanding of both global paleo sea-level and glacio-isostatic adjustments.

(IF 3.62; Q1); International audience; The emerged sequences of coral reef and marine terraces of the Cuban Archipelago have been recognized since the end of the 19th century but with noticeable exceptions, their bio-constructions and/or deposits are not dated. The northern Caribbean islands and associated archipelagos are located in a left-lateral strike-slip tectonic setting, at the boundary between the North America and Caribbean plates. Cuba is the only landmass located on the American Plate directly adjacent to this transform fault zone. Quantifying upper Pleistocene coastal uplift is thus key to elucidate the recent vertical deformation of the Caribbean geodynamic puzzle with regards to the active tectonic segmentation of this area. We compiled bibliographic data and present new measurements concerning the Cuban sequences of coral reef and marine terraces; maximum elevations, minimum number of successive strandlines and elevation of the lowermost terrace. The Cuban Archipelago exhibits five main uplifting coastal stretches separated by subsiding areas, with at least 23 emerged staircase sequences of coastal terraces. At four sites, the lowest coral reef terrace has been previously correlated to the Last Interglacial Maximum (MIS 5e, 122 ± 6 ka). At nine sites, we extended the morpho-stratigraphy to derive Upper Pleistocene apparent and eustasy-corrected uplift rates. Alongshore Cuba, MIS 5e coastal terraces and associated shoreline angles occur at elevations ranging from 7 m to 40 m, yielding eustasy-corrected uplift rates ranging from 0.06 ± 0.01 mm.yr−1 (NW Cuba) to 0.33 ± 0.01 mm.yr−1 (SE Cuba). More than 400 km northward of the transform fault, eustasy-corrected uplift rates (0.13 mm.yr−1) suggest that the whole Cuban Archipelago is affected by the North America/Caribbean plate motion, with a partitioned compressive component resulting in block tectonics with tilting controlled by regional faults.

(IF 4.45: Q1); International audience; The emerged coral reef terrace sequence at Cape Laundi, on the north coast of Sumba Island (Indonesia), with at least 18 successive strandlines, remains poorly dated in spite of numerous previous data. The age discrepancies within these coral reef terraces (CRTs) were previously explained by their polycyclic nature, triggered by marine erosion and reoccupation of old coral colonies by new ones. This study aims at highlighting these processes, as well as the continental denudation that participates in the partial stripping of the thin superficial coral reef layer overlying the pre-existing surface, exhuming older coral colonies. For this purpose, we use a combined analysis of 36Cl cosmogenic concentrations, new 230Th/U ages, and previous dating in order to quantify denudation rates affecting the sequence and to highlight the role of marine erosion in reworking the lowest CRT surface. Our results demonstrate that 1) the lowermost CRT is composite, i.e., formed by different reefal limestone units constructed and eroded during successive highstands of the last interglacial, 2) following the last deglaciation, this CRT has been subjected again to coastal erosion and reoccupation during the Mid Holocene highstand, 3) its distal edge is affected by the current marine erosion and shows denudation rates higher by one to two orders of magnitude (from 279 ± 0.4 to 581 ± 0.4 mm ka−1) than the continental denudation values of higher CRTs (14.7 ± 8.3 mm ka−1 on average), 4) at the scale of a single CRT surface, variations in continental denudation rates are caused by epikarstification roughness, and 5) the distal edges have the highest continental denudation rate due to diffusion and regressive erosion produced by the runoff occurring along the steep downward cliff.

At the far end of the Tethyan realm, the Indo-Australian plate subducts in the Java and Banda trenches. Across the trench, a checkerboard-like distribution of continental and oceanic units sets the geodynamic stage since the Australian continent docked into the subduction zone a few Myr ago: to the East, the Australian continent now subducts and collides with the mostly oceanic Wallacea while to the West, the Indian oceanic plate subducts underneath continental Sundaland. We hypothesize that this fast and transient geodynamic regime explains many observations that characterize the region over the last few Myr: slab rollback and formation of the Banda arc, subsidence of the Weber superdeep seafloor to more than 7000 m, back-arc thrusting in Flores, dynamic subsidence in Sundaland and Sahul, and controversial slab tearing underneath Timor. We set out to model subduction dynamics accounting for the complex assemblage of plates in a real-Earth perspective, using the fast thermo-mechanical code LaMEM that allows dealing with complex setups. Our results predict the winding of the subduction zone around Papua, ultimately retreating into the Banda embayment, thereby causing the extreme dynamic subsidence of the Banda seafloor. Geometrical consistency imposes coeval slab tearing underneath Timor while the slab rolls back. The formation of the Flores backthrust quickly follows Australian collision with Wallacea and propagates westward in continental Sundaland. Shortening rates quickly drop tenfold while entering Sundaland, in Java, in agreement with kinematic and structural observations. In the geologically near future, the back-arc thrust is predicted to reverse the subduction polarity, Wallacea being on the brink to subduct southward underneath Australia. Last, transient mantle flow expectedly causes dynamic subsidence in Sahul and Sundaland, thereby profoundly remodeling the physiography of the entire region.

The Baribis-Kendeng Fault System crosscuts the northern part of Java Island (Indonesia). It seems that the fault systems is the continuation westward from the active Flores thrust in the northern offshore of the Lesser Sunda Islands. While the Flores thrust in the east is well documented as an active fault in the back-arc platform (e.g., source of the 2018 Lombok 6.9 Mw earthquake), the nature, timing, and activity of the Baribis-Kendeng Fault Systems, particularly the Baribis Fault Zone (BFZ) in the westernmost part of the system remain elusive. Yet, understanding the geological risk associated with the BFZ is crucial, as it crosscuts densely-populated regions, possibly up to 30 million inhabitants in the megalopolis of Jakarta. Previous studies mostly identified the BFZ by first-order morphotectonic observations, as well as large-scale geodetic and seismotectonic investigations, and assigned historical earthquakes (estimated up to 8.5 Mw in 1780) in northern Java to the BFZ. Ground-truthing the structure and activity of the BFZ from geological arguments is a cornerstone to evaluate associated geohazards.We first focus on the Cikamurang Ridge, nearly at the eastern part of the BFZ, where uplifted Pliocene-Recent sediment sequences outcrop. Morphotectonic data include an 8-m resolution digital elevation model that we used to map fault lineaments and calculate the channel steepness index of the rivers crossing the mapped fault segments. Field data, including paleoseismological trenching at the central part of Cikamurang Ridge and sediment dating (OSL and radiocarbon) provide temporal constraints on the BFZ activity. Subsurface geophysical data include seismic reflection and resistivity imaging provide better image of the fault geometry in the sub-surface.Our results suggest that the BFZ has been active in the Cikamurang Ridge during the late-Pleistocene to Holocene times, with deformed sediment sequences dated between 55 and 7 ka. Eastward, the BFZ crosses the Cisanggarung River where the fault deformed ~13-ka old sediments. Westward of the Cikamurang Ridge, both fault lineament interpretation and channel steepness index indicates that the fault continues from Subang regency to Jatiluhur and reaches the area between Jakarta and Bogor. Even though in the area between Jakarta and Bogor the surficial trace of the BFZ is not as clear as the Cikamurang and Subang, the seismic reflection data reveal the blind fault propagation fold. We conclude that the BFZ has a high seismic hazard that requires a careful risk evaluation along its trace, as it threats the numerous infrastructures of the extremely densely-populated West Java. Comparing to the Flores back-arc thrust, the existence of the BFZ indicate the whole island of Java affected with the back-arc compressive regime as well as the existence of the Kendeng Fault Zone, in the easternmost of the Baribis-Kendeng Fault Systems.

Quaternary sea-level curves provide crucial insights to constrain tectonic and climatic processes, but require calibration with geological constraints that are particularly scarce for cold periods prior to the last glacial-interglacial cycle. To derive such constraints, we re-visit the Huon Peninsula in Papua New Guinea, which is a classic coral reef terrace (CRT) site that was used for the earliest relative sea-level (RSL) curves. We use digital surface models calculated from 0.5m Pleiades satellite imagery to improve RSL constraints, and unlike previous studies, we find that large-scale tilting of the terrace sequence is generally N-directed. This implies that RSL estimates are several meters higher than previously thought for most highstands over the past ~125 ka. We use the large-scale geometry of the terrace sequence to estimate sea-level highstands up to ~400 ka, and our results suggest that global mean sea-level curves derived from oxygen isotopes consistently underestimate sea-level during the relatively cold Marine Isotope Stages 3, 5a, 5c, 6, 9a and 11a, up to ~10-20 m. We use coral reef models to show that our age interpretation is consistent with the overall terrace sequence morphology, and fits between models and topography improve when adjusting sea-level highstands according to our findings.

Coral reef terraces (CRT) are amongst the most important indicators of Quaternary sea level fluctuations, and are therefore relevant to a wide spectrum of climatic and tectonic studies. The Huon Peninsula in Papua New Guinea accomodates one of the first CRT sequences to be mapped, measured and dated in detail through pioneering studies several decades ago. Those studies were limited by the available techniques to assess the large scale terrace sequence morphology, and thus to constrain spatiotemporal uplift rate variations that are key to determine past relative sea-level (RSL). We re-visit the Huon CRTs with the aim of refining tectonic uplift rates and RSL, using digital surface models calculated from 0.5m Pleiades satellite imagery. This allows us to constrain variations in CRT elevation, and assess tectonic deformation wavelengths in detail. We then use a numerical code for coral reef modeling to reconstruct the sequence morphology and constrain the possible range of RSL over the past few glacial-interglacial cycles. We find that large-scale tilting of the terrace sequence is generally N- instead of NW-directed, which is more compatible with the regional tectonic setting. It also implies changes of several meters for RSL highstand estimates compared to previous studies. We compare our results to other terrace sequences, and discuss the potential of combining high-resolution topography with landscape evolution modeling to constrain RSL.

(IF 4.64 [2018]; Q1); International audience; Sequences of uplifted marine terraces are widespread and reflect the interaction between climatic and tectonic processes at multiple scales, yet their analysis is typically biased by the chosen sea-level (SL) curve. Here we explore the influence of Quaternary SL curves on the geometry of marine terrace sequences using landscape evolution models (LEMs). First, we modeled the young, rapidly uplifting sequence at Xylokastro (Corinth Rift

Young rifts are shaped by combined tectonic and surface processes and climate, yet few records exist to evaluate the interplay of these processes over an extended period of early rift-basin development. Here, we present the longest and highest resolution record of sediment flux and paleoenvironmental changes when a young rift connects to the global oceans. New results from International Ocean Discovery Program (IODP) Expedition 381 in the Corinth Rift show 10s–100s of kyr cyclic variations in basin paleoenvironment as eustatic sea level fluctuated with respect to sills bounding this semi-isolated basin, and reveal substantial corresponding changes in the volume and character of sediment delivered into the rift. During interglacials, when the basin was marine, sedimentation rates were lower (excepting the Holocene), and bioturbation and organic carbon concentration higher. During glacials, the basin was isolated from the ocean, and sedimentation rates were higher (~2–7 times those in interglacials). We infer that reduced vegetation cover during glacials drove higher sediment flux from the rift flanks. These orbital-timescale changes in rate and type of basin infill will likely influence early rift sedimentary and faulting processes, potentially including syn-rift stratigraphy, sediment burial rates, and organic carbon flux and preservation on deep continental margins worldwide. 19 April 2019 A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

International audience; Understanding early rifting of continental lithosphere requires accurate descriptions of up-bended rift margins and footwalls that ought to correlate in space and time with the elastic flexural uplift that produces them. Here we characterize the geometry of elastic flexural uplift by continental rifting at its spatiotemporal scale in nature (tens of kilometers; 10 4-10 6 years) using geomorphic evidence along the uplifting margin of the Corinth Rift, Greece. Our geomorphic analyses of space-borne topography novelly outline the coherent elastic flexure of continental lithosphere along and across the rift margin and throughout faulting (~10 6 years), as defined by the distribution of footwall uplift south of the active bounding fault. Topography and river drainages outline an elastic flexure signal that increases exponentially toward the bounding fault across the footwall for >50 km and changes in amplitude along the footwall following a parabola that decays from the rift center and has a >60-km wavelength that correlates with rift length. This continental lithosphere up-bend correlates with the scale of the rift, and appears maximum in the center of the rift, where drainage reversal of large catchments suggests rapid slip rates at the bounding fault. This is consistent with the growth of a new, rift-scale, high-angle normal fault. The coherency of elastic flexure in space and time implies highly localized strain in the rift-bounding fault and suggests that the fault transects continental lithosphere with long-term strength. The unparalleled record of flexural uplift and highly localized strain in the landscape of Corinth suggest these processes are intrinsic to early continental rifting elsewhere.

This review shows how collective analysis of morphotectonic elements on uplifting rift margins can constrain the mechanical behaviour of continents during early rifting. This is shown for the modern Corinth Rift, one of the fastest-extending and most seismically active continental regions worldwide. We reconstruct the growth of the normal fault system that accommodates most of the rift strain and the uplift of the rift margin it bounds, from onset to present and at rift scale. Our approach allows first-order inferences on the mechanics and evolution of the rift, and can be used in other areas of early continental rifting. We review and re-assess known geologic evidence in the Corinth Rift, and compile morphotectonic elements into a new map. We analyse the rift topo-bathymetry, and the footwall relief, river catchments and tectonic knickpoints in its uplifting margin. We also review studies that constrain the growth of normal faults using morphotectonic elements in their footwall, and propose a novel theoretical framework to reconstruct fault time-evolution during early rifting. We couple known and new data to derive fault displacement profiles in time, and use the theoretical framework to infer the history of growth and linkage of rift border faults, in turn constraining rift growth mechanics and evolution. Our rift-scale morphotectonic investigation shows that the current rift-bounding faults are kinematically coherent at depth and constitute a fault >80 km in length. This composite master fault grew along-strike from the rift centre, linking and integrating individual fault segments that developed co-linearly at earlier times. The observed fault elastic flexure, footwall relief wavelength and high uplift and slip rates throughout the rift margin suggest the border fault is steep and highly localized in strain, and transects the entire seismogenic layer growing in a long-term strong elastic lithosphere. Integration of previous and our new findings suggest the Corinth Rift evolved in two distinct extensional phases. These extensional phases are delimited by the fast, overwriting growth of the new rift-forming fault, that switched rift mechanics in a ~300 kyr timespan, and controls rift evolution thereafter. The new rift-forming fault enlarges the modern rift as an asymmetric half-graben, along and across strike, superimposed onto the preceding ~4 My distributed extension.

The primary objective of International Ocean Discovery Program Expedition 381 was to retrieve a record of early continental rifting and basin evolution from the Corinth rift, central Greece. Continental rifting is fundamental for the formation of ocean basins, and active rift zones are dynamic regions of high geohazard potential. However, the detailed spatial and temporal evolution of a complete rift system needed to understand rift development from the fault to plate scale is poorly resolved. In the active Corinth rift, deformation rates are high, the recent synrift succession is preserved and complete offshore, earlier rift phases are preserved onshore, and a dense seismic database provides high-resolution imaging of the fault network and of seismic stratigraphy around the basin. As the basin has subsided, its depositional environment has been affected by fluctuating global sea level and its absolute position relative to sea level, and the basin sediments record this changing environment through time. In Corinth, we can therefore achieve an unprecedented precision of timing and spatial complexity of rift-fault system development, rift-controlled drainage system evolution, and basin fill in the first few million years of rift history. The following are the expedition themes: High-resolution fault slip and rift evolution history, Surface processes in active rifts, High-resolution late Quaternary Eastern Mediterranean paleoclimate and paleoenvironment of a developing rift basin, and Geohazard assessment in an active rift. These objectives were and will be accomplished as a result of successful drilling, coring, and logging at three sites in the Gulf of Corinth, which collectively yielded 1645 m of recovered core over a 1905 m cored interval. Cores recovered at these sites together provide (1) a longer rift history (Sites M0078 and M0080), (2) a high-resolution record of the most recent phase of rifting (Site M0079), and (3) the spatial variation of rift evolution (comparison of sites in the central and eastern rift). The sediments contain a rich and complex record of changing sedimentation, sediment and pore water geochemistry, and environmental conditions from micropaleontological assemblages. The preliminary chronology developed by shipboard analyses will be refined and improved during postexpedition research, providing a high-resolution chronostratigraphy down to the orbital timescale for a range of tectonic, sedimentological, and paleoenvironmental studies. This chronology will provide absolute timing of key rift events, rates of fault movement, rift extension and subsidence, and the spatial variations of these parameters. The core data will also allow us to investigate the relative roles of and feedbacks between tectonics, climate, and eustasy in sediment flux and basin evolution. Finally, the Corinth rift boreholes will provide the first long Quaternary record of Mediterranean-type climate in the region. The potential range of scientific applications for this unique data set is very large, encompassing tectonics, sedimentary processes, paleoenvironment, paleoclimate, paleoecology, geochemistry, and geohazards.

© 2019, The Author(s). This Article contains errors in Reference 40 which is incorrectly given as: Palyvos, N., Pantosti, D. & Zabci, C. Paleoseismological evidence of recent earthquakes on the 1967 Mudurnu Valley earthquake segment of the North Anatolian fault. Bull. Seis. Soc. Am. 97, 1646–1661 (2007).