The role of inherited extensional fault segmentation and linkage in contractional orogenesis: a reconstruction of Lower Cretaceous inverted rift basins in the Eastern Cordillera of Colombia

Lower Cretaceous early syn‐rift facies along the eastern flank of the Eastern Cordillera of Colombia, their provenance, and structural context, reveal the complex interactions between Cretaceous extension, spatio‐temporal trends in associated sedimentation, and subsequent inversion of the Cretaceous Guatiquía paleo‐rift. South of 4°30′N lat, early syn‐rift alluvial sequences in former extensional footwall areas were contemporaneous with fan‐delta deposits in shallow marine environments in adjacent hanging‐wall areas. In general, footwall erosion was more pronounced in the southern part of the paleorift. In contrast, early syn‐rift sequences in former footwall areas in the northern rift sectors mainly comprise shallow marine supratidal sabkha to intertidal strata, whereas hanging‐wall units display rapid transitions to open‐sea shales. In comparison with the southern paleo‐rift sector, fan‐delta deposits in the north are scarce, and provenance suggests negligible footwall erosion. The southern graben segment had longer, and less numerous normal faults, whereas the northern graben segment was characterized by shorter, rectilinear faults. To the east, the graben system was bounded by major basin‐margin faults with protracted activity and greater throw as compared with intrabasinal faults to the west. Intrabasinal structures grew through segment linkage and probably interacted kinematically with basin‐margin faults. Basin‐margin faults constitute a coherent fault system that was conditioned by pre‐existing basement fabrics. Structural mapping, analysis of present‐day topography, and balanced cross sections indicate that positive inversion of extensional structures was focused along basin‐bounding faults, whereas intrabasinal faults remained unaffected and were passively transported by motion along the basin‐bounding faults. Thus, zones of maximum subsidence in extension accommodated maximum elevation in contraction, and former topographic highs remained as elevated areas. This documents the role of basin‐bounding faults as multiphased, long‐lived features conditioned by basement discontinuities. Inversion of basin‐bounding faults was more efficient in the southern than in the northern graben segment, possibly documenting the inheritance and pivotal role of fault‐displacement gradients. Our observations highlight similarities between inversion features in orogenic belts and intra‐plate basins, emphasizing the importance of the observed phenomena as predictive tools in the spatiotemporal analysis of inversion histories in orogens, as well as in hydrocarbon and mineral deposits exploration.     

The S reflector west of Galicia: the seismic signature of a detachment fault

The so-called S reflector is a group of bright, continuous reflections underlying the landward-tilted fault blocks of the west Galicia rifted margin, S has been interpreted as the brittle-ductile transition, the lop of an intrusion, a detachment fault, and the crust-mantle boundary. To constrain the internal structure of the reflector, we have carried out detailed analyses of these reflections. We compare the waveforms of the seafloor reflection and its first multiple, both to determine the amplitude of the seafloor reflection and to show (hat the seafloor is in effect a spike in the reflectivity series so that the seafloor reflection can be used as the far-field wavelet, including both source and receiver ghosts. We compare (he waveform of the seafloor and 5 and show that, within the resolution of our data, S is a reflection from a step increase in acoustic impedance. This result is confirmed through complex trace analysis, and in particular the determination of the apparent polarity of S, and the examination of the instantaneous frequency function: S is consistently positive polarity, and shows no significant frequency anomaly. Simple modelling shows that S is very unlikely to be a reflection from a thin layer. We thus conclude that S is probably a single steplike interface. From the varying frequency content of the data, we determine a value for the effective Q between S and the seafloor, and use this to assess the amplitude loss due to attenuation and scattering. We use a comparison between the seafloor and the S reflection to constrain the amplitude of S, and estimate a reflection coefficient for S of at least 0.2 in places, decreasing landwards. By analogy with structures developed in the highly extended regions of the western United States, we consider that the most likely interpretation of S is as a sharp west-dipping detachment fault separating a 'granitic' upper plate from a higher-velocity lower plate, locally probably serpentinized mantle.     

Evolution of a large Miocene growth structure in the upper plate of the Whipple detachment fault, northeastern Whipple Mountains, California

Miocene sedimentary and volcanic rocks in the north-eastern Whipple Mountains, California, and the north-western Aubrey Hills, Arizona, accumulated in the upper plate of the Whipple detachment fault during regional extension and slip on the detachment. Miocene rocks in this area can be divided into three sequences: (1) pre-18.5-Ma dominantly volcanic rocks; (2) the 18.5-Ma Peach Springs Tuff; and (3) post-18.5-Ma dominantly sedimentary rocks. Important stratigraphic markers in sequence 3 include a 100- to 14–0-m-thick basalt unit and the voluminous War Eagle landslide, both of which correlate across Lake Havasu from the north-east Whipple Mountains to the Aurbrey Hills. We divide clastic sedimentary rocks of sequence 3 into three informal members: (3a) conglomerate and sandstone stratigraphically beneath the basalt; (3b) conglomerate and sandstone above the basalt and below the War Eagle landslide; and (3c) conglomerate and sandstone that overlie the War Eagle landslide. Detailed stratigraphic analysis and field mapping reveal dramatic south-westward thickening of member 3b strata, from about 50 m in the Aubrey Hills to over 1500 m in the north-east Whipple Mountains. In the north-east Whipple Mountains, this thick dipping section is overlain by the War Eagle landslide along a major angular unconformity; in the Aubrey Hills the base of the War Eagle landslide is roughly parallel to bedding dips of underlying strata. The above stratigraphic relationships can be explained by syndepositional growth of a rollover monocline by progressive tilting of the hangingwall above a master listric normal fault (Whipple detachment fault). This phase of upper-plate deformation began shortly after deposition of the basalt and ended prior to emplacement of the War Eagle landslide. Interbedded breccias low in member 3b, about 100 m above the basalt, record the first appearance of mylonitic detritus in the section. Growth of this upper-plate rollover was thus initiated at about the same time (shortly after deposition of the basalt) that the lower plate of the Whipple detachment fault was first exposed at the earth's surface by tectonic denudation and large-scale crustal uplift. These events are interpreted to record initiation of a secondary breakaway fault on the north-east flank of the growing Whipple detachment dome shortly after deposition of the basalt at about 14.5 (±1.0) Ma.     

Exploring the reservoir potential of Lower Cretaceous Clinoforms in the Fingerdjupet Subbasin,Norwegian Barents Sea

Sandy clinothems are of interest as hydrocarbon reservoirs but there is no proven, economic, clinothem reservoir in the Norwegian Barents Sea. We used high-resolution, 2D and 3D seismic, including proprietary data, to identify a previously untested, Barremian, clinoform wedge in the Fingerdjupet Subbasin (FSB). Data from recent well 7322/7-1 plus seismic have been used to characterize this wedge and older Lower Cretaceous clinoforms in the FSB. In the latest Hauterivian – early Barremian, during post-rift tectonic quiescence, shelf-edge clinoforms (foreset height > 150 m) prograded into an under-filled basin. Increased sediment input was related to regional uplift of the hinterland (northern Barents Shelf). Early Barremian erosion in the north-western FSB and mass wasting towards the SE were followed by deposition of delta-scale (<80 m high), high-angle (c. 8°) clinoform sets seaward of older shelf-edge clinoforms. This may be the local expression of a regional, early Barremian, regressive event. By the close of the Barremian, clinoforms had prograded, within a narrow, elongate basin, across the FSB and towards the uplifted Loppa High. A seismic wedge of high-angle (10–12°), low-relief, delta-scale (25–80 m) clinoform sets occurs between shelf-edge clinoforms to the NW and the uplifted area to the SE. Well 7322/7-1, positioned on a direct hydrocarbon indicator, <1 km NNW of the high-angle, low-relief, delta-scale clinoforms, found upward coarsening siltstone-cycles linked to relative sea-level fluctuations on a marine shelf. Sand may have accumulated, offshore from the well, in high-angle, low-relief foresets of the delta-scale clinothems (which are typical geometries elsewhere interpreted as ‘delta-scale, sand-prone subaqueous clinoforms’). Deposition was controlled by the paleosurface, storms and longshore currents on an otherwise mud-dominated shelf. The study highlights challenges associated with exploration for sandstone reservoirs in seismic wedges on an outer shelf.     

Normal fault evolution and coupled landscape response: examples from the Southern Apennines,Italy

We present new data addressing the evolution, activity and geomorphic impact of three normal faults in the Southern Apennines: the Vallo di Diano, East Agri and Monti della Maddalena faults. We show that these faults have minimum total throws of ca. 1000–2000 m, and throw rates of ca. 0.7–1 mm year⁻¹ for at least the last ca. 18 ka. We demonstrate that for the Vallo di Diano and East Agri faults, the landscape is effectively recording tectonics, with relief, channel and catchment slopes varying along fault strike in the same manner as normal fault activity does, with little apparent influence of lithology. We therefore use these data to reconstruct the time‐integrated history of fault interaction and growth. From the distribution of knickpoints on the footwall channels, we infer two episodes of base level change, which we attribute to fault interaction episodes. We reconstruct the amount of throw accumulated after each of these events, and the segments involved in each, from the fault throw profiles, and use fault interaction theory to estimate the magnitude of the perturbations and past throw rates. We estimate that fault linkage events took place 0.7 ± 0.2 Ma and 1.4 ± 0.3 Ma in the Vallo di Diano fault, and 1 ± 0.1 in the East Agri Fault, and that both faults likely started their activity between 3 and 3.5 Ma. These fault linkage scenarios are consistent with the observed knickpoint heights. This method for reconstructing fault evolution could potentially be applied for any normal faults for which there is information about throw and throw rates, and in which channels are transiently responding to tectonics.     

Tectonic vs. climate forcing in the Cenozoic sedimentary evolution of a foreland basin (Eastern Southalpine system, Italy)

This paper discusses the Cenozoic interaction of regional tectonics and climate changes. These processes were responsible for mass flux from mountain belts to depositional basins in the eastern Alpine retro‐foreland basin (Venetian–Friulian Basin). Our discussion is based on the depositional architecture and basin‐scale depositional rate curves obtained from the decompacted thicknesses of stratigraphic units. We compare these data with the timing of tectonic deformation in the surrounding mountain ranges and the chronology of both long‐term trends and short‐term high‐magnitude (‘aberrant’) episodes of climate change. Our results confirm that climate forcing (and especially aberrant episodes) impacted the depositional evolution of the basin, but that tectonics was the main factor driving sediment flux in the basin up to the Late Miocene. The depositional rate remained below 0.1 mm year^?1 on average from the Eocene to the Miocene, peaking at around 0.36 mm year^?1, during periods of maximum tectonic activity in the eastern Southern Alps. This dynamic strongly changed during the Pliocene–Pleistocene, when the basin‐scale depositional rate increased to an average of 0.26 mm year^?1 (Pliocene) and 0.73 mm year^?1 (Pleistocene). This result fits nicely with the long‐term global cooling trend recorded during this time interval. Nevertheless, we note that the timing of the observed increase may be connected with the presumed onset of major glaciations in the southern flank of the Alps (0.7–0.9 Ma), the acceleration of the global cooling trend (since 3–4 Ma) and climate variability (in terms of magnitude and frequency). All these factors suggest that combined high‐frequency and high‐magnitude cooling–warming cycles are particularly powerful in promoting erosion in mid‐latitude mountain belts and therefore in increasing the sediment flux in foreland basins.     

Role of the bedrock topography in the Quaternary filling of a giant estuarine basin: the Lower St. Lawrence Estuary,Eastern Canada

The geometry of estuarine and/or incised‐valley basins and their protected character compared with open sea basins are favourable for the preservation of sedimentary successions. The Lower St. Lawrence Estuary Basin (LSLEB, eastern Canada) is characterized by a thick (>400 m in certain areas) Quaternary succession. High‐ and very high‐resolution seismic reflection data, multibeam bathymetry coverage completed by core and chronostratigraphic data as well as a 3‐D seismic stratigraphic model are used to document the geometrical relationships between the bedrock and the Quaternary units of the LSLEB. The bedrock geometry of LSLEB is characterized by two large troughs that are interpreted as resulting mainly from repeated (?) periods of glacial overdeepening of a pre‐Quaternary drainage system. However, other mechanisms with complex feedback effects such as differential glacio‐isostatic uplift, erosion, sedimentary supply, and subsidence may have contributed to the formation of bedrock troughs. The two large bedrock troughs are mostly filled by ～200 m thick Wisconsinan (Marine Isotopic Stages 2–4) and possibly older sediments. Overlying units recorded the retreat of the Laurentian Ice Sheet during the Late Wisconsinan (Marine Isotopic Stage 2) and estuarine conditions during the Holocene. The strong correlation existing between the bedrock topography and the thickness of the Quaternary succession is indicative of the effectiveness of the LSLEB as a sediment trap.     

Insights into syndepositional fault movement in a foreland basin; trends in seismites of the Upper Cretaceous,Wahweap Formation,Kaiparowits Basin,Utah, USA

The Upper Cretaceous Wahweap Formation accumulated in the active Cordilleran foreland basin of Utah. Soft‐sediment deformation structures are abundant in the capping sandstone member of the Wahweap Formation. By comparing with well‐established criteria, a seismogenic origin was determined for the majority of structures, which places these soft‐sediment deformation features in a class of sedimentary features referred to as seismites. A systematic study of the seismite trends included their vertical and horizontal distribution and a semi‐quantitative intensity analysis using a scale from 1 to 5 that is based on magnitude, sedimentary structure type, and the predominance of inferred process of hydroplastic deformation, liquefaction or fluidization. In addition, orientations of soft‐sediment fold axes were recorded. Construction of a northwest‐to‐southeast stratigraphic and seismite intensity cross‐section demonstrates: (1) reduction in stratigraphic thickness and percentage of conglomerates to the southeast, (2) the presence of lower seismite, middle nonseismite, and upper seismite zones within the capping sandstone (permitting subdivision of the capping sandstone member), and (3) elimination of the nonseismite zone and amalgamation of the lower and upper seismite zones to the southeast. Regional isoseismal contour maps generated from the semi‐quantitative analysis indicate a decrease in overall intensity from northwest to southeast in the upper and lower seismic zones and in sandstone within 5 m stratigraphically of the contact between the upper and capping sandstone members. In addition, cumulative seismite fold orientations support a west–northwest direction towards regional epicentres. Isoseismal maps are used to distinguish the effects of intrabasinal normal faulting from those of regional orogenic thrusting. Thus, this study demonstrates the utility of mapping seismites to separate the importance of regional vs. local tectonic activity influencing foreland basin sedimentation by identifying patterns that delineate palaeoepicentres associated with specific local intrabasinal normal faults vs. regional trends in soft‐sediment deformation related to Sevier belt earthquakes.     

Collapse‐induced fluidization structures in the Lower Cretaceous Athabasca Oil Sands Deposit,Western Canada

Unique vertical fluidization structures from the Lower Cretaceous Athabasca Oil Sands Deposit in Western Canada are described. The multi‐metre long structures resulted from ascending Devonian karst aquifer waters injected into the overlying unconsolidated sands of the McMurray Formation (Aptian). The dissolution removal of 100–200 m of Middle Devonian salt beds caused the collapse and fragmentation of the 200 m of Upper Devonian limestones underlying the Cretaceous sands. Hypogene karst aquifer waters fingered upwards along the faults and fractures. Disintegrated muddy wall rock sourced hydroplastic mud flows along fractures in the limestone beds below the floor of the central Bitumount Trough. These dykes widened and lengthened collapse‐induced Upper Devonian fault blocks that differentially subsided due to salt dissolution. Conduits plugged by these mud flows diverted over‐pressured aquifer waters upwards along remaining open pipes, some of which vented on the trough floor. Aquifer waters injected into the McMurray sand and mud beds accumulated on the trough floor generated several types of collapse‐induced fluidization structures: (1) stronger aquifer flows mobilized sands into tens‐of‐metres high sand dykes consisting of multiple vertical pipes of fluidized sand contorted around and intertwined with fragmented muddy wall rock; (2) smaller aquifer jets resulted in 1–2 m high sand‐rich pillars on the trough floor; and (3) narrower high‐pressure jets flowed muddy waters along multi‐metre long, 3–5 cm wide, vertical pipes that cross‐cut and wrapped around fragmented in situ beds. The velocity gradient between these narrow but multi‐metre long water pipe flows and the ambient velocity in the surrounding sediments caused water infiltration to radiate outwards. This plugged porosity along the outer wall of the pipe, diminished drainage into the wall rock, and stabilized concentric growth ring depositions along the length of the pipe. These pipe fills appear as unique striped ribbon fabrics when viewed in longitudinal section.     

Oligocene to middle Miocene basin development in the Eastern Betic Cordilleras, SE Spain (Vélez Rubio Corridor – Espuña): reflections of West Mediterranean plate-tectonic reorganizations

The suture between two West Mediterranean crustal blocks once situated several hundreds of kilometres apart can be studied in the Vélez Rubio Corridor – Espuña area of the Eastern Betic Cordilleras. This suture, or Internal–External Zone Boundary, separates the former passive southern margin of Iberia (the External Zone) from a stack of allochthonous nappe complexes (the Internal Zone), of which the highest unit is formed by the weakly or nonmetamorphosed Malaguide Complex. Analysis of the Oligocene to middle Miocene sediments of the Vélez Rubio Corridor and the Espuña, and comparison with coeval deposits elsewhere in the Western Mediterranean shows that (a) up to the middle Miocene, the southern part of the External Zone (Southern Subbetic) was positioned some 100 km more eastward; (b) up to the early Aquitanian, the Malaguide Complex, forming part of the South Sardinian block (the southern section of a West Mediterranean continental segment) was juxtaposed to the North Sardinian block (the northern part of that continental fragment), some 400 km more eastward; (c) West European extensional rifting during the late Oligocene to earliest Aquitanian resulted in deposition of rift valley sediments (Ciudad Granada and Pliego Formations) in the Malaguide realm; (d) during the Aquitanian, the West Mediterranean segment disintegrated and the West Mediterranean oceanic basins opened, resulting in, for example, the south-westward drift of the Internal Zone, with concomitant thrusting and thinning and deposition of submarine fans (Solana-Algeciras Formation) along the margin; (e) in the early Burdigalian, the allochthonous Internal Zone collided with the Iberian margin, causing the disruption of the platform-slope configuration of the External Zone; (f) after the collision a deep basin was formed upon the suture filled in with erosional products from both Internal and External Zones (Espejos–Viñuelas–Millanas Formations); (g) a strong compressive event in the late Burdigalian caused the southward thrusting of the Subbetic over the Espejos Formation, thus double-sealing the collisional contact; (h) in the latest Burdigalian to Langhian, new strongly subsiding basins were formed in the Western Mediterranean, e.g. along the Internal–External Zone Boundary; (i) dextral strike-slip faulting in the Serravallian resulted in a westward displacement of over 100 km of the southern Subbetic plus Internal Zone; (j) onset of a new pattern of strike-slip faulting induced the formation of a new suite of basins in the Tortonian.     

A major seismogenic fault in a 'silent area': the Castrovillari fault (southern Apennines, Italy)

Large historical earthquakes in Italy define a prominent gap in the Pollino region of the southern Apennines. Geomorphic and palaeoseismological investigations in this region show that the Castrovillari fault (CF) is a major seismogenic source that could potentially fill the southern part of this gap. The surface expression of the CF is a complex, 10–13 km long set of prominent scarps. Trenches across one scarp indicate that at least four surface-faulting earthquakes have occurred along the CF since Late Pleistocene time, each producing at least 1 m of vertical displacement. The length of the fault and the slip per event suggest M =6.5-7.0 for the palaeoearthquakes. Preliminary radiocarbon dating coupled with historical considerations imply that the most recent of these earthquakes occurred between 380 BC and 1200 AD, and probably soon after 760 AD; no evidence for this event has been found in the historical record. We estimate a minimum recurrence interval of 1170 years and a vertical slip rate of 0.2-0.5 mm yr^-1 for the CF, which indicates that the seismic behaviour of this fault is comparable to other major seismogenic faults of the central-southern Apennines. The lack of mention or the mislocation of the most recent event in the historical seismic memory of the Pollino region clearly shows that even in Italy, which has one of the longest historical records of seismicity, a seismic hazard assessment based solely on the historical record may not be completely reliable, and shows that geological investigations are critical for filling possible information gaps.     

Normal fault array evolution above a reactivated rift fabric; a subsurface example from the northern Horda Platform,Norwegian North Sea

The impact of a pre‐existing rift fabric on normal fault array evolution during a subsequent phase of lithospheric extension is investigated using 2‐D and 3‐D seismic reflection, and borehole data from the northern Horda Platform, Norwegian North Sea. Two fault populations are developed: (i) a population comprising relatively tall (>2 km), N‐S‐striking faults, which have >1.5 km of throw. These faults are up to 60 km long, penetrate down into crystalline basement and bound the eastern margins of 6–15 km wide half‐graben, which contain >3 km of pre‐Jurassic, likely Permo–Triassic, but possibly Devonian syn‐rift strata; and (ii) a population comprising vertically restricted (<1 km), NW‐SE‐striking faults, which are more closely spaced (0.5–5 km), have lower displacements (30–100 m) and not as long (2–10 km) as those in the N–S‐striking population. The NW‐SE‐striking population typically occurs between the N‐S‐striking population, and may terminate against or cross‐cut the larger structures. NW–SE‐striking faults do not bound pre‐Jurassic half‐graben and are largely restricted to the Jurassic‐to‐Cretaceous succession. Seismic‐stratigraphic observations, and the stratigraphic position of the fault tips in both fault populations, allow us to reconstruct the Late Jurassic‐to‐Early Cretaceous growth history of the northern Horda Platform fault array. We suggest the large, N‐S‐striking population was active during the Permo–Triassic and possibly earlier (Devonian?), before becoming inactive and buried during the Early and Middle Jurassic. After a period of relative tectonic quiescence, the N‐S‐striking, pre‐Jurassic fault population propagated through the Early‐Middle Jurassic cover and individual fault systems rapidly (within <10 Ma) established their maximum length in response to Late Jurassic extension. These fault systems became the dominant structures in the newly formed fault array and defined the locations of the main, Late Jurassic‐to‐Early Cretaceous, syn‐rift depocentres. Late Jurassic extension was also accommodated by broadly synchronous growth of the NW‐SE‐striking fault population; the eventual death of this population occurred in response to the localization of strain onto the N–S‐striking fault population. Our study demonstrates that the inheritance of a pre‐existing rift fabric can influence the geometry and growth of individual fault systems and the fault array as a whole. On the basis of observations made in this study, we present a conceptual model that highlights the influence of a pre‐existing rift fabric on fault array evolution in polyphase rifts.     

Evolution of a mixed siliciclastic‐carbonate deep‐marine system on an unstable margin: The Cretaceous of the Eastern Greater Caucasus,Azerbaijan

Mixed siliciclastic‐carbonate deep‐marine systems (mixed systems) are less documented in the geological record than pure siliciclastic systems. The similarities and differences between these systems are, therefore, poorly understood. A well‐exposed Late Cretaceous mixed system on the northern side of the Eastern Greater Caucasus, Azerbaijan, provides an opportunity to study the interaction between contemporaneous siliciclastic and carbonate deep‐marine deposition. Facies analysis reveals a Cenomanian–early Turonian siliciclastic submarine channel complex that abruptly transitions into a Mid Turonian–Maastrichtian mixed lobe‐dominated succession. The channels are entrenched in lows on the palaeo‐seafloor but are absent 10 km towards the west where an Early Cretaceous submarine landslide complex acted as a topographic barrier to deposition. By the Campanian, this topography was largely healed allowing extensive deposition of the mixed lobe‐dominated succession. Evidence for irregular bathymetry is recorded by opposing palaeoflow indicators and frequent submarine landslides. The overall sequence is interpreted to represent the abrupt transition from Cenomanian–early Turonian siliciclastic progradation to c. Mid Turonian retrogradation, followed by a gradual return to progradation in the Santonian–Maastrichtian. The siliciclastic systems periodically punctuate a more widely extensive calcareous system from the Mid Turonian onwards, resulting in a mixed deep‐marine system. Mixed lobes differ from their siliciclastic counterparts in that they contain both siliciclastic and calcareous depositional elements making determining distal and proximal environments challenging using conventional terminology and complicate palaeogeographic interpretations. Modulation and remobilisation also occur between the two contemporaneous systems making stacking patterns difficult to decipher. The results provide insight into the behaviour of multiple contemporaneous deep‐marine fans, an aspect that is challenging to decipher in non‐mixed systems. The study area is comparable in terms of facies, architectures and the presence of widespread instability to offshore The Gambia, NW Africa, and could form a suitable analogue for mixed deep‐marine systems observed elsewhere.     

Computing a hierarchy favored optimal route in a Voronoi-based road network with multiple levels of detail

This paper introduces a robust method for computing the optimal route with hierarchy. We convert a planar road network into its Voronoi-based counterpart with multiple levels of detail (LoDs), which is subsequently assigned travel times that are estimated for different times of day using taxicab trajectory data. On the basis of this network structure, we model the path-finding process in travel, as the optimal route with hierarchy is computed in a ‘coarse-to-fine’ manner. In other words, the route is iteratively constructed from roads in a low LoD network to roads in a high LoD network. To confirm the efficiency and effectiveness of our method, comparative experiments were conducted using randomly selected pairs of origins/destinations in Wuhan, China. The results indicate that our travel lengths are on average 12% longer than those computed by the Dijkstra algorithm and 15% shorter than those computed by the hierarchical algorithm (in ArcGIS). Our travel times are on average 29% longer than those computed by the Dijkstra algorithm and 31% shorter than those computed by the hierarchical algorithm (in ArcGIS). Hence, we argue that our method is situated in terms of performance between the Dijkstra algorithm and the hierarchical algorithm (in ArcGIS). Moreover, road usage patterns confirm that our algorithm is cognitively equivalent to the hierarchical algorithm (in ArcGIS) by favoring high-class roads and outperforms the Dijkstra algorithm by avoiding choosing low-class roads. Computationally, our method outperforms the Dijkstra algorithm but is on the same level as the hierarchical algorithm (in ArcGIS) in terms of efficiency. Therefore, it has the potential to be used in real-time routing applications or services.     

Normal faulting, extension and uplift in the outer thrust belt of the central Apennines (Italy): role of the Caramanico fault

The outer Adriatic zones of the central Apennines (Italy) provide good conditions for analysing geometry and kinematics of the earliest normal faults, superposed onto the thrust belt. During the latest stages of thrusting onto the Adriatic foreland (late Pliocene–early Pleistocene), the outermost imbricates of the thrust belt were subjected to normal faulting, coeval with differential uplift. Crosscutting normal faults get younger towards the foreland, thus the easternmost normal faults record the latest stages of fault propagation and growth. The Caramanico fault, on the western flank of Mt. Maiella, is the largest outcropping normal fault of the outer zones. This high‐angle fault (dip > 70°) has cumulative offsets ≤ €4.2 km, and propagated with slip rates of 2.6 mm/year in a short time interval (≤ 1.6 Ma), concomitant with intense uplift of Mt. Maiella. In contrast with normal faults in a more internal position, the Caramanico fault maintains a high‐angle planar geometry, and does not reach the major basal detachment of the thrust belt. Thus the fault did not cause large extensional displacements; its major role was rather to accommodate ongoing components of vertical uplift of the overthickened thrust wedge. Downfaulting of the thrust belt on the western flank of Mt. Maiella represents the youngest end member of the same processes that have operated since 11 Ma in the Tyrrhenian hinterland, where large extensional strains and crustal thinning of the orogenic belt were achieved by long‐lasting activity of listric normal faults detached at lower crustal depths.     

Morphology and sedimentary systems in the Central Bransfield Basin, Antarctic Peninsula: sedimentary dynamics from shelf to basin

A detailed regional characterization of the physiography, morphology and sedimentary systems of the Central Bransfield Basin (CBB) was carried out using swath bathymetry and high‐ and very high‐resolution seismic profiles. The basin margins show continental shelves with numerous glacial troughs, and continental slopes where relatively wide and flat slope platforms represent the middle domain in an atypical physiographic scenario in glaciated margins. Although the CBB is tectonically active, most of the morphologic features are sedimentary in origin, and can be classified into four sedimentary systems: (1) glacial‐glaciomarine, composed of erosional surfaces, glacial troughs, furrows and draping sheets; (2) slope‐basin, formed by trough mouth fans, slope aprons, the Gebra‐Magia instability complex and turbidity systems; (3) seabed fluid outflow system composed of pockmark fields; and (4) contourite, composed of drifts and moats. The sedimentary systems show a clear zonation from shelf to basin and their dynamics reflects the complex interplay among glacial, glaciomarine, marine and oceanographic processes involved in the entire shelf‐to‐basin sediment distribution. The CBB morphology is primarily controlled by glacial/interglacial cyclicity and physiography and to a lesser extent by tectonics and oceanography. These factors have affected the South Shetland Islands (SSI) and Antarctic Peninsula (AP) margins differently, creating a relatively starved SSI margin and a more constructional AP margin. They have also created two entire sediment‐dispersal domains: the shelf‐to‐slope, which records the glaciation history of the CBB; and the lower slope‐to‐basin, which records the imprint of local factors. This study provides a ‘source‐to‐sink’ sedimentary scheme for glaciated margins, which may be applied to the basin research in other margins, based on the characterization of sedimentary systems, their boundaries and the linkages among them. This approach proves to be adequate for the identification of global and local factors governing the CBB and may therefore be applied to other study areas.     

Tectono‐sedimentary development of early syn‐rift deposits: the Abura Graben,Suez Rift,Egypt

The thickness and distribution of early syn‐rift deposits record the evolution of structures accommodating the earliest phases of continental extension. However, our understanding of the detailed tectono‐sedimentary evolution of these deposits is poor, because in the subsurface, they are often deeply buried and below seismic resolution and sparsely sampled by borehole data. Furthermore, early syn‐rift deposits are typically poorly exposed in the field, being buried beneath thick, late syn‐rift and post‐rift deposits. To improve our understanding of the tectono‐sedimentary development of early syn‐rift strata during the initial stages of rifting, we examined quasi‐3D exposures in the Abura Graben, Suez Rift, Egypt. During the earliest stage of extension, forced folding above blind normal fault segments, rather than half‐graben formation adjacent to surface‐breaking faults, controlled rift physiography, accommodation development and the stratigraphic architecture of non‐marine, early syn‐rift deposits. Fluvial systems incised into underlying pre‐rift deposits and were structurally focused in the axis of the embryonic depocentre, which, at this time, was characterized by a fold‐bound syncline rather than a fault‐bound half graben. During this earliest phase of extension, sediment was sourced from the rift shoulder some 3 km to the NE of the depocentre, rather than from the crests of the flanking, intra‐basin extensional forced folds. Fault‐driven subsidence, perhaps augmented by a eustatic sea‐level rise, resulted in basin deepening and the deposition of a series of fluvial‐dominated mouth bars, which, like the preceding fluvial systems, were structurally pinned within the axis of the growing depocentre, which was still bound by extensional forced folds rather than faults. The extensional forced folds were eventually locally breached by surface‐breaking faults, resulting in the establishment of a half graben, basin deepening and the deposition of shallow marine sandstone and fan‐delta conglomerates. Because growth folding and faulting were coeval along‐strike, syn‐rift stratal units deposited at this time show a highly variable along‐strike stratigraphic architecture, locally thinning towards the growth fold but, only a few kilometres along‐strike, thickening towards the surface‐breaking fault. Despite displaying the classic early syn‐rift stratigraphic motif recording net upward‐deepening, extensional forced folding rather than surface faulting played a key role in controlling basin physiography, accommodation development, and syn‐rift stratal architecture and facies development during the early stages of extension. This structural and stratigraphic observations required to make this interpretation are relatively subtle and may go unrecognized in low‐resolution subsurface data sets.     

Anatomy and evolution of a Mediterranean-type fault bounded basin: the Lower Pliocene of the northern Crotone Basin (Southern Italy)

The complex development of the northern Crotone Basin, a forearc basin of the Calabrian Arc (Southern Italy), has been documented by sedimentological, stratigraphic and structural analyses. This Mediterranean‐type fault bounded basin consists of small depocentres commonly characterized by a mix of facies that grades from continental to shallow marine. The lower Pliocene infill of the Crotone Basin consists of offshore marls (Cavalieri Marl) that grade upwards into a shallow‐marine to continental succession up to 850 m thick (Zinga Formation). The succession is subdivided into three main stratal units: Zinga 1, Zinga 2, Zinga 3 bounded by major unconformities. The Zinga 1 stratal unit grades from the Cavalieri Marl to deltaic and shoreface deposits, the latter organized into several stacked progradational wedges that show spectacular thickness changes and progressive unconformities related to salt‐cored NE‐trending growth folds and listric normal faults. The Zinga 2 stratal unit records a progressive and moderate deepening of the area, marked by fluvial sedimentation at the base, followed by lagoonal deposits and by a stacking of mixed bioclastic and siliciclastic shoreface units, organized into metre‐scale high‐frequency cycles. Deposition was controlled by NE‐trending synsedimentary normal faults that dissected the basin into a series of half‐grabens. Hangingwall stratigraphic expansion was compensated by footwall condensed sedimentation. The extensional tectonic regime continued during sedimentation of the Zinga 3 stratal unit. Deposition confined within structural lows during a generalized transgressive phase led to local enhancement of tidal flows and development of sand‐wave trains. The tectonic setting testifies the generalized structural domain of a forearc region. The angular unconformity at the top of the Zinga 3 stratal unit is regional, and marks the activation of a large‐scale tectonic phase linked to strike‐slip movements.