Crustal-scale high-displacement (>10 km) normal faults are not captured in existing tectono-sedimentary models of rift basins. We used 2D and 3D seismic reflection and well data to perform a structural and source-to-sink analysis of the southern part of the Klakk Fault Complex and the western part of the Vingleia Fault Complex, Mid-Norwegian rifted margin. The north-south trending Klakk Fault Complex has a zig-zag to sinuous plan-view geometry, forming a series of structural recesses and salients along strike. In cross-section, the fault complex has a listric to convex-up or low-angle planar geometry with displacements above 20 km. This fault complex exhumed basement highs, the Froya High and Sklinna Ridge, in its footwall and created a series of supradetachment basins, for example, the R & aring;s Basin, in its hanging wall. In contrast, the northeast-southwest trending Vingleia Fault Complex has a zig-zag geometry in plan view and planar to listric geometry in cross-section and displacement of up to 5 km. This fault has the Froya High in its footwall and the southern Halten Terrace in its hanging wall. Restoration of selected structural cross-sections shows a prominent fault-parallel ridge, up to 15 km east of the Klakk Fault Complex interpreted as a palaeodrainage divide. This divide separates steep drainages developed along the west-dipping footwall scarp to the Klakk Fault Complex, from broader, gentler east-dipping drainages up to ca. 10 km long developed on a back-tilted dip slopes along the eastern side of the Froya High and Sklinna Ridge. Progressive headward erosion of active flank catchments was enhanced around topographically elevated structural salients to the point of capturing previous dip-slope-directed drainages during the earliest Cretaceous. A network of submarine canyons develop down-dip of the drainage catchments along the Klakk Fault Complex scarp, whose geometries and length are controlled by their location with respect to the structural salients or recesses, and the presence of fault terraces. The middle Jurassic-earliest Cretaceous synrift deposits form two seismic sequences that are filled with five distinctive seismic facies that record the evolution from a linked normal fault during rift climax to a high-displacement stage. During the high displacement stage, exhumed local continental core complexes formed structural salients, separated along strike by structural recesses at the heads of supradetachment basins. Key elements of the high-displacement fault stage include (i) the development of structural salients at sites of rift climax displacement maxima, (ii) development of supradetachment basins in rift climax displacement minima and (iii) migration of major depocentres away from the centre of rift climax fault segments. We synthesise these observations into a generic tectono-sedimentary model for high-displacement faults.

Summary Continental rifting is accommodated by the development and progressive localisation of normal faults. The variability of timing and different styles of localisation within rift basins, resultant geometry and evolution of rift depocentres remains poorly understood. Using high resolution subsurface dataset, we recognize varied along strike rift physiography and two stages of structural development during the second rift phase of the SVG – western flank of the Utsira High, northern North Sea. (1) An early distributed deformation stage (Mid Bathonian – Early-Mid Callovian), characterized by the development of numerous intra-basinal faults in multiple sub-basins and a well-defined record of intra-basinal fault activity termination in the progression to 2) a later localized deformation stage (Early-Mid Callovian – Late Ryazanian), characterized by focused activity on the NE-SW-trending, east-dipping SVG bounding faults and terrace bounding faults. The complexity seen in the study area sits within a broader step in the location of the rift margin and widening of the northern North Sea rift at the northern edge of the Utsira High. The study highlights the importance of larger, regional changes in tectonic framework in controlling structural style, basin architecture, timing of depocentre development including the evolution terraces: timing and placement within a rift system.

Basement highs form one of many potential sediment source areas during the evolution of continental rifts and rifted margins and add to the topographic complexity typical of active rifts. Footwall basement highs acting as a source area to sedimentary systems in the hangingwall of major faults has been documented in many systems worldwide. However, the back-tilted footwall dip slopes of such highs have received comparatively little attention. Here we investigate a subsurface case study from the Norwegian continental shelf, where catchments and shallow marine syn-rift sedimentary systems on a dip slope are preserved due to early transgression of an intra-rift high. At the onset of Late Jurassic rifting, the Frøya High emerged as a prominent, N-S trending, 25 km wide basement high tilted towards the east in response to several kilometers of displacement along the Klakk Fault Complex, a major normal fault zone at the Frøya High’s western edge. Using well-calibrated 3D seismic reflection data, we observe a series of conspicuous Upper Jurassic wedges along the eastern edge of the Frøya High along the margin of the Froan Basin. Internally, these wedges show sigmoidal geometries marking top- and foresets of clinoform packages with a maximum thickness of ca. 200 meters with foresets between 30 – 200 m high, dipping ca. 10 degrees towards the east, south east and north east. We interpret these wedges to represent a series of eastward prograding deltas positioned along a constructional shoreline, connected to E-W trending valleys and river catchments updip. The deltas show strong progradation, interpreted to reflect the impact of continued uplift of their catchments. prior to abrupt termination of sediment supply from drainage capture by footwall scarp drainages. The presence of a connected, largely constructional shoreline has implications for Late Jurassic sediment distribution around the Frøya High, providing primary sedimentary input for longshore driven sedimentary systems in the Draugen Ridge to the north. Comparisons with other syn-rift dip slope systems highlights a broadly similar evolution but shows a distinct lack of the protracted backstepping observed in other dip slope systems. We postulate that different structural configurations of dip slope systems, being footwall uplift, or hangingwall subsidence driven, may drive the strongly progradational character of the deltaic systems on the Frøya High. The Frøya High example highlights the need to constrain primary sediment input points to aid interpretation of volumetrically significant, but short-lived and subtle depositional systems, especially within complex, tectonically active settings.

The timing and character of coarse siliciclastic sediment delivered to deep-water environments in active rift basins is governed by the complicated interactions of tectonics, climate, eustasy, hinterland geology, and shelf process regime. The stratigraphic archives of deep-water syn-rift basin-fills provide records of palaeoenvironmental changes (e.g. climate and vegetation) in onshore catchments, particularly where they are connected by narrow shelves. However, a chronostratigraphically constrained record of climatic fluctuations and process responses in the hinterland source area recorded in deep-water deposits is rare. Here, we integrate a fully cored research borehole with outcrop exposures of deep-water syn-rift stratigraphy to reconstruct palaeoenvironmental change within the stratigraphy of the West Xylokastro Fault Block in the Corinth Rift, Greece. We used palaeomagnetic and palynological analyses from borehole core samples to develop a chronostratigraphic and palaeoenvironmental model, which we compare to global records of Early-Mid Pleistocene climate and eustatic change. This framework allows establishment of a chronostratigraphic and palaeoenvironmental context to stratigraphic variability encountered in outcrop and in the borehole. Our results show that the ∼240 m thick studied succession was deposited from ∼1.1 to 0.6 Ma across the Early-to Mid-Pleistocene transition. During the Early Pleistocene, obliquity-paced climatic variability is largely coherent with vegetation changes of forest coverage within catchments on the southern margin of the Corinth Rift. Large magnitude, eccentricity-paced cyclicity dominant after the Mid-Pleistocene Transition can alter sediment supply from onshore catchments during the warming stages of severe interglacials where expansion of forest cover may trap sediment within catchments. Conglomeratic grade sediment delivery to the deep-water is enhanced during glacial periods, interpreted to reflect sparse forest cover and large winter storms, and during semi-arid, grassland-dominated interglacial highstands during severe interglacials. Base-level rise during minor interglacials is easily outpaced by high sediment supply and is seldom represented stratigraphically. The study demonstrates the value of integrated palynological and sedimentological studies, whilst applying a conservative approach to interpretation when dealing with sparse palynological records from proximal deep-water stratigraphy. The case study provides conceptual models where climatic and vegetation changes can begin to be incorporated as a key control on sediment flux from onshore drainage basins to deep-water syn-rift successions.

Deep-water syn-rift systems develop in partially- or transiently-linked depocentres to form complicated depositional architectures, which are characterised by short transport distances, coarse grain sizes and a wide range of sedimentary processes. Exhumed systems that can help to constrain the tectono-stratigraphic evolution of such systems are rare or complicated by inversion tectonics. Here, we document a mid-Pleistocene deep-water syn-rift system fed by Gilbert-type fan deltas in the hangingwall of a rift margin fault bounding the West Xylokastro Horst block, on the southern margin of the Gulf of Corinth, Greece. Structural and stratigraphic mapping combined with digital outcrop models permit observations along this syn-rift depositional system from hinterland source to deep-water sink. The West Xylokastro Fault hangingwall is filled by two distinct sediment systems; an axial system fed by coarse-grained sediment gravity flows derived from fault-tip Gilbert-type fan deltas and a lateral system dominated by mass transport deposits fed from an evolving fault-scarp apron. Abrupt changes in stratigraphic architecture across the axial system are interpreted to record changes in relative base level, sediment supply and tectonics. Locally, depositional topography and intra-basinal structures controlled sediment dispersal patterns, from bed-scale infilling of local rugose topography above mass transport complexes, to basin-scale confinement from the fault scarp apron. These acted to generate a temporally and spatially variable, heterogeneous stratigraphic architecture throughout the basin-fill. The transition of the locus of sedimentation from a rift margin to a fault terrace through the syn-sedimentary growth of a basinward fault produced regressive surfaces updip, which manifest themselves as channels in the deep-water realm and acted to prograde the system. We present a new conceptual model that recognises coeval axial and transverse systems based on the stratigraphic architecture around the West Xylokastro fault block that emphasizes the lateral and vertical heterogeneity of rift basin-fills with multiple entry points.

AbstractModels that aim to capture the interactions between sediment supply, base level and tectonism recorded in fan delta successions in rift basins have not considered the stratigraphic archive preserved in interfan areas; yet interfan stratigraphy can provide a complementary record to the fan delta axes. The exhumed Early–Middle Pleistocene Kerinitis and Selinous fan deltas, in the hangingwall of the Pyrgaki–Mamoussia (P‐M) Fault, Corinth Rift, Greece, offer an ideal laboratory for the assessment of interfan architecture. Furthermore, using the geometry of adjacent present‐day fan deltas, interfans are classified into three end‐members. The classification is based on their lateral separation, which determines the degree of interfingering of topset, foreset and bottomset deposits. Qualitative (facies, stratal geometries, nature of key surfaces) and quantitative (stratigraphic thickness, bedding dip, palaeocurrents, breakpoint trajectories) data were collected in the field and from unmanned aerial vehicle photogrammetry‐based 3D outcrop models of the exhumed fan delta successions. The ancient Kerinitis–Selinous interfan architectures record: (a) initial westward progradation of the Kerinitis fan delta into the interfan area (Phase 1), (b) subsequent progradation of the Selinous fan delta into the interfan area and asymmetric growth of both fan deltas eastward (Phase 2), (c) stratal interfingering of foresets from both systems (Phase 3), and (d) relative base‐level fall, erosion and reworking of sediments into the interfan area (Phases 4 and 5). The Kerinitis–Selinous interfan evolution is linked to initial net subsidence of the P‐M Fault (Phases 1–3) and subsequent net uplift (Phases 4 and 5) resulting from a northward shift in fault activity. The interfan area provides a more complete stratigraphic record than the proximal axial areas of the fan deltas of the early stages of basin uplift, through higher preservation potential and protracted submergence. Therefore, for the most comprehensive insight into basin evolution, interfan analysis should be undertaken in concert with analysis of the fan delta axes.

ABSTRACTThe inception and evolution of channels in deep-water systems is controlled by the axial gradient and lateral confinement experienced by their formative flows. These parameters are often shaped by the action of tectonic structures and/or the emplacement of mass-transport deposits (MTDs). The Arro turbidite system (Aínsa depocenter, Spanish Pyrenees) is an ancient example of a deep-water channelized system from a bathymetrically complex basin, deposited in an active tectonic setting. Sedimentologic fieldwork and geologic mapping of the Arro system has been undertaken to provide context for a detailed study of three of the best-exposed outcrops: Sierra de Soto Gully, Barranco de la Caxigosa, and Muro de Bellos. These locations exemplify the role of confinement in controlling the facies and architecture in the system. Sedimentologic characterization of the deposits has allowed the identification of fifteen facies and eight facies associations; these form a continuum and are non-unique to any depositional environment. However, architectural characterization allowed the grouping of facies associations into four depositional elements: i) weakly confined, increasing-to-decreasing energy deposits; ii) progradational, weakly confined to overbank deposits; iii) alternations of MTDs and turbidites; iv) channel fills. Different styles of channel architecture are observed. In Barranco de la Caxigosa, a master surface which was cut and subsequently filled hosts three channel stories with erosional bases; channelization was enhanced by quasi-instantaneous imposition of lateral confinement by the emplacement of MTDs. In Muro de Bellos, the inception of partially levee-confined channel stories was enhanced by progressive narrowing of the depositional fairway by tectonic structures, which also controlled their migration. Results of this study suggest that deep-water channelization in active tectonic settings may be enhanced or hindered due to: 1) flow interaction with MTD-margin topography or; 2) MTD-top topography; 3) differential compaction of MTDs and/or sediment being loaded into MTDs; 4) formation of megascours by erosive MTDs; 5) basin-floor topography being reset by MTDs. Therefore, the Arro system can be used as an analog for ancient subsurface or outcrop of channelized deposits in bathymetrically complex basins, or as an ancient record of deposits left by flow types observed in modern confined systems.

Quantification of allogenic controls in rift basin‐fills requires analysis of multiple depositional systems because of marked along‐strike changes in depositional architecture. Here, we compare two coeval Early‐Middle Pleistocene syn‐rift fan deltas that sit 6 km apart in the hangingwall of the Pirgaki‐Mamoussia Fault, along the southern margin of the Gulf of Corinth, Greece. The Selinous fan delta is located near the fault tip and the Kerinitis fan delta towards the fault centre. Selinous and Kerinitis have comparable overall aggradational stacking patterns. Selinous comprises 15 cyclic stratal units (ca. 25 m thick), whereas at Kerinitis 11 (ca. 60 m thick) are present. Eight facies associations are identified. Fluvial and shallow water facies dominate the major stratal units in the topset region, with shelfal fine‐grained facies constituting ca. 2 m thick intervals between major topset units and thick conglomeratic foresets building down‐dip. It is possible to quantify delta build times (Selinous: 615 kyr; Kerinitis: >450 kyr) and average subsidence and equivalent sedimentation rates (Selinous: 0.65 m/kyr; Kerinitis: >1.77 m/kyr). The presence of sequence boundaries at Selinous, but their absence at Kerinitis, enables sensitivity analysis of the most uncertain variables using a numerical model, ‘Syn‐Strat’, supported by an independent unit thickness extrapolation method. Our study has three broad outcomes: (a) the first estimate of lake level change amplitude in Lake Corinth for the Early‐Middle Pleistocene (10–15 m), which can aid regional palaeoclimate studies and inform broader climate‐system models; (b) demonstration of two complementary methods to quantify faulting and base level signals in the stratigraphic record—forward modelling with Syn‐Strat and a unit thickness extrapolation—which can be applied to other rift basin‐fills; and (c) a quantitative approach to the analysis of stacking patterns and key surfaces that could be applied to stratigraphic pinch‐out assessment and cross‐hole correlations in reservoir analysis.

Summary Deep-water syn-rift deposits are challenging to characterise in the sub-surface and are comparatively understudied in comparison to larger, typically finer grained systems on passive margins. Short length and time scales of structural variability, high-sediment supply, and complex drainages can cause significant stratigraphic heterogeneity. A principal risk in the exploration and production of hydrocarbon resources in such settings therefore lies in understanding and accurately predicting stratigraphic architecture. Outcrop analogues can bridge the gap between understanding core and seismic scale observations to address this, however for deep-water syn-rift systems are rarely well preserved. Here we integrate outcrop fieldwork with a fully cored, research borehole in deep-water syn-rift exposures in the Gulf of Corinth, Greece. Digital outcrop, palaeomagnetic, palynological, sedimentological and structural analyses form a multi-disciplinary, and multi-scale approach address the stratigraphic architecture and core expressions of a deep-water syn-rift depositional system through extensive exposures of Mid-Pleistocene syn-rift infill of a deep-water fault terrace. This study permits the development of new conceptual models for deep-water syn-rift stratigraphy providing qualitative and quantitative investigations of the nature, distribution and evolution of conglomerate rich lobes, mass transport complexes, and coarse grained channel fills in deep-water syn-rift settings.