Tectonostratigraphic Evolution Research Articles

Shelf-derived mass-transport deposits: origin and significance in the stratigraphic development of trench-slope basins

ABSTRACT Continental shelves generally supply large-scale mass-wasting events. Yet, the origin and significance of shelf-derived mass-transport deposits (MTDs) for the tectonostratigraphic evolution of subduction complexes and their trench-slope basins have not been extensively studied. Here, we present high-resolution, outcrop-scale insights on both the nature of the reworked sediments, and their mechanisms of development and emplacement along tectonically active margins, by examining the Middle Miocene shelf-derived MTDs outcropping in the exhumed southern portion of the Hikurangi subduction margin. Results show that periods of repeated tectonic activity (thrust propagation, uplift) in such compressional settings not only affect and control the development of shelfal environments but also drive the recurrent generation and destruction of oversteepened slopes, which in turn, favour the destabilisation and collapses of the shelves and their substratum. Here, these events produced both large-scale, shelf-derived sediment mass-failures and local debris flows, which eventually broke down into a series of coalescing, erosive, genetically linked surging flows downslope. The associated MTDs have a regional footprint, being deposited across several trench-slope basins. Recognition of tectonic activity as another causal mechanism for large-scale shelf failure (in addition to sea-level changes, high-sedimentation fluxes) has implications for both stratigraphic predictions and understanding the tectonostratigraphic evolution of deep-marine fold-and-thrust belts.

Sequence-stratigraphic study of Cuyo Group in the Agua del Cajón Block, Neuquén Basin, Argentina

Agua del Cajón Block is located towards the north-east flank of the Huincul High deformation belt. The Cuyo Group, one of the main hydrocarbon targets of the block, was analyzed under the sequential-stratigraphic seismic methodology, for the purpose of establishing a genetic depositional framework that guides the development of new prospective models in the area. Ages and paleoenvironmental indicators calibration were obtained from biostratigraphic sampling. In Agua del Cajón Block, the Cuyo Group was interpreted as a second-order mesosequence, composed of eight third-order seismic sequences. Seismic-stratigraphy was integrated with the structural framework of the block, allowing an interpretation of the tectono-stratigraphic evolution of the analyzed interval. It is concluded that the development of the Cuyo Group manifests eustatic control at a second-order mesosequence scale, while at the third-order scale the sequence arrangement was modified by local tectonics.

Deformation–sedimentation feedback and the development of anomalously thick aggradational turbidite lobes: Outcrop and subsurface examples from the Hikurangi Margin, New Zealand

ABSTRACT Concepts of the interaction between autogenic (e.g., flow process) and allogenic (e.g., tectonics) controls on sedimentation have advanced to a state that allows the controlling forces to be distinguished. Here we examine outcropping and subsurface Neogene deep-marine clastic systems that traversed the Hikurangi subduction margin via thrust-bounded trench-slope basins, providing an opportunity to examine the interplay of structural deformation and deep-marine sedimentation. Sedimentary logging and mapping of Miocene outcrops from the exhumed portion of the subduction wedge record heavily amalgamated, sand-rich lobe complexes, up to 200 m thick, which accumulated behind NE–SW-oriented growth structures. There was no significant deposition from low-density parts of the gravity flows in the basin center, although lateral fringes demonstrate fining and thinning indicative of deposits from low-density flows. Seismic data from the offshore portion of the margin show analogous lobate reflector geometries. These deposits accumulate into complexes up to 5 km wide, 8 km long, and 300 m thick, comparable in scale with the outcropping lobes on this margin. Mapping reveals lobe complexes that are vertically stacked behind thrusts. These results illustrate repeated trapping of the sandier parts of turbidity currents to form aggradational lobe complexes, with the finer-grained suspended load bypassing to areas downstream. However, the repeated development of lobes characterized by partial bypass implies that a feedback mechanism operates to perpetuate a partial confinement condition, via rejuvenation of accommodation. The mechanism proposed is a coupling of sediment loading and deformation rate, such that load-driven subsidence focuses stress on basin-bounding faults and perpetuates generation of accommodation in the basin, hence modulating tectonic forcing. Recognition of such a mechanism has implications for understanding the tectono-stratigraphic evolution of deep-marine fold and thrust belts and the distribution of resources within them.

Tectonostratigraphic evolution, palaeogeography and main petroleum plays of the Nuussuaq Basin: An outcrop analogue for the Cretaceous–Palaeogene rift basins offshore West Greenland

The onshore Nuussuaq Basin in central West Greenland comprises a complete Albian–Paleocene succession and as such represents the only complete rift succession outcrop analogue for the Cretaceous–Palaeogene offshore frontier basins in West Greenland. The basin fill reflects five tectonostratigraphic phases: 1) Pre-rift, 2) Albian – Early Cenomanian Early Rift, 3) Early Cenomanian – Early Campanian Thermal Subsidence, 4) Early Campanian – Early Paleocene Late Rift, and 5) Early Paleocene – Late Eocene Break-up and Drift. In addition, the succession is divided into nine tectonostratigraphic sequences (TSSs), each representing a specific configuration of depositional elements resulting mainly from tectonic events, which caused major palaeogeographic reconstruction of the basin and therefore critical to the petroleum systems. The sequences are bounded by unconformities or, in one case, by a major flooding phase. The Early Rift Phase in the Nuussuaq Basin was initiated in the Albian with development of half-grabens along N–S directed extensional faults. This phase was characterised by continued growth along extensional faults and embraces three TSSs (TSS1–3). They are characterised by alluvial fan, fan-delta and lacustrine sedimentation, wave- and tidal-dominated deltaic deposition, followed by a major fall in relative sea level and canyon incision. Oil seeps indicate presence of a lacustrine/brackish-water source rock at depth. During the following Late Cenomanian – Early Campanian Thermal Subsidence Phase a regional marine drowning of the basin took place with deposition of organic-rich mudstones, followed by re-establishment of deltaic deposition in the Coniacian–Santonian (TSS4). The Early Campanian – Early Paleocene Late Rift Phase was associated with a change in stress regime, formation of NW–SE directed extensional faults, uplift of highs and a major change in depositional environments from deltaic deposition to deposition from gravity flows in a confined system of slope channels and canyons. During the initial phase, structurally-controlled turbidite channels were established in a NW–SE trending graben-like structure that acted as conduits for sediment transport into the offshore areas (TSS5). This was followed by several phases of major uplift resulting from the rise of the Proto-Icelandic Mantle Plume prior to continental break-up eventually leading to the deposition of two structurally controlled TSSs (TSS6–7) characterised by the formation of submarine and subaerial canyons that acted as conduits for huge amounts of sediments transported into the offshore areas. The Nuussuaq Basin experienced significant subsidence during the initial phase of break-up volcanism with deposition of organic-rich Lower Paleocene marine mudstones blanketing the basin followed by a thick succession of Paleocene–Eocene volcanic rocks referred to as the West Greenland Basalt Province (TSS8–9). Volcanism gradually spread eastwards eventually blocking the connection to the sea stemming up a large lake between the prograding volcanic front and the cratonic mainland to the east. Finally, when the volcanic rocks covered the entire basin, rivers were redirected, and sediments were deposited in the offshore Sisimiut Basin to the south and the Melville Bay Basin to the north. During this latest rifting and break-up phase, the Nuussuaq Basin was aborted and terminated as a failed rift basin.Four main plays have been defined based on the tectonostratigraphic subdivision: An Early Rift Play, a Thermal Subsidence Play, a Late Rift Play and a Break-up and Drift Play. The Early Rift Play has alluvial and estuarine sandstones as reservoir, Albian lacustrine/brackish-water mudstones as source rock and Cenomanian–Turonian mudstones as seal. The Thermal Subsidence Play has deltaic and shallow marine sandstones as reservoirs, Cenomanian–Turonian mudstones as source and Campanian mudstones as seal. The Late Rift Play has incised valley, submarine canyon and turbidite sandstones as reservoirs, and Campanian and Paleocene mudstones as seal and source. The Break-up and Drift Play is subdivided into three sub-plays, including: a Lacustrine Sub-play, an Intra-basaltic Siliciclastic Sub-play and a Fractured Volcanic Sub-play. The Lacustrine Sub-play has fluvio-deltaic sandstones as reservoir and intra-formational lacustrine and delta-plain mudstones as seal. The Intra-basaltic Siliciclastic Sub-play comprise fluvial and lacustrine sandstones as reservoir and volcaniclastic or siliciclastic mudstones as seal. The Fractured Volcanic Sub-play comprises fractured, porous volcanic rocks as reservoir and intra-basaltic mudstones or tight fine-grained volcanic rocks as seal. All three sub-plays require vertical or long-distance migration of hydrocarbons from deeper-seated Cretaceous – Lower Paleocene kitchens. Because the tectonostratigraphic phases recognised in the Nuussuaq Basin can also be applied to the regional seismic mapping offshore Greenland the implications of the Nuussuaq Basin plays can be applied to the frontier offshore basins.

Punctuated Orogeny During the Assembly of Asia: Tectonostratigraphic Evolution of the North China Craton and the Qilian Shan From the Paleoproterozoic to Early Paleozoic

AbstractThe Proterozoic‐Phanerozoic evolution of the Tarim and North China cratons is integral to the construction of the Eurasian continent. Throughout the Paleozoic, these continents were bound by the Paleo‐Asian and Tethyan Oceans to the north and south, respectively, and, thus, their paleogeography is critical to reconstructions of the oceanic domains. Specifically, it remains uncertain whether the Tarim and North China cratons were contiguous during the Paleozoic. Geologic observations from the Qilian Shan and Longshou Shan of western China provide valuable information regarding the paleotectonic relationships of these continents. Here we present detailed field, geochronological, and geochemical observations from key locations in the Qilian Shan and Longshou Shan to decipher complex relationships between the Kunlun‐Qaidam, North China, and Tarim continents. Paleoproterozoic deformation might have been associated with the northern North China orogen, whereas a Neoproterozoic collisional orogen occurred between the Kunlun‐Qaidam‐South Tarim and the North China‐North Tarim. Subsequent late Neoproterozoic rifting led to the opening of the Qilian ocean as an embayed marginal sea, and the Paleo‐Asian Ocean developed along the northern margin of the North China craton. South‐dipping subduction, arc magmatism, slab rollback, and convergence between Kunlun‐Qaidam and North China continued throughout the Early Silurian, which were recorded in the Qilian Shan and Longshou Shan regions. Our updated geotectonic framework requires reevaluation of previously published paleogeographic models, including ones that suggest the North China craton was affixed to Gondwana in the early Paleozoic. It is further considered a possible connection between the North China and southern Africa at ca. 2.05 Ga.

Tectonostratigraphic evolution of the Orphan Basin and Flemish Pass region – Part 1: Results from coupled kinematic restoration and crustal area balancing

The Orphan Basin and Flemish Pass region on the Newfoundland continental margin is a frontier area in terms of oil and gas exploration and remains poorly understood in terms of structural evolution and rift development. The area has few exploration wells and, until recently, sparse seismic data coverage. Existing gravity inversion and seismic refraction data from the area suggest that stretched continental crust in the Orphan Basin is highly attenuated (locally to < 5 km) but previously published structural restorations have been unable to fully restore the continental crust below the Orphan Basin to pre-deformed thicknesses (30–32 km). Here we perform a structural restoration of a regional, WNW-ESE oriented cross-section to investigate crustal structure, rifting style, and structural evolution of the Orphan Basin and Flemish Pass region. Interpretation is constrained by modern regional depth converted broadband 2D and 3D seismic reflection data, well data, and published gravity inversion results. Present-day crustal thicknesses are used as constraints for crustal area balancing and estimation of crustal thinning across the basin. We find that low-angle extensional detachments are widespread in the area, with offsets on individual structures of up to 42 km. Zones of attenuated continental crust are coincident with the presence of low-angle detachment surfaces displaying isostatic uplift of detachment footwalls. Comparison of total extension derived from crustal area balancing vs. structural restoration suggests approximately 39% of extension across the cross-section is unresolvable in seismic data. We attribute this to (i) ductile deformation prior to brittle faulting, (ii) subseismic-scale faulting, (iii) uncertainties in detachment breakaway positions, and (iv) unresolvable later offset of detachment surfaces. Widespread and relatively evenly distributed extension across the Orphan Basin and Flemish Pass region from Middle-Late Jurassic to Early Cretaceous influences sediment distribution across the region. Calibrated regional seismic mapping of the Orphan Basin suggests that significant thicknesses of Jurassic strata exist throughout the area, including in the northwestern part of the study area, where Kimmeridgian and Tithonian strata reach combined thicknesses of up to 4.9 km.

Plio-Pleistocene to Recent tectonostratigraphic evolution of the Lalmai anticline in the western Indo-Burman Range (Bangladesh): insights from lithofacies analysis and structural synthesis

The Lalmai anticline is one of the westernmost structures within the Eastern Fold Belt of the Bengal Basin that has surficial expression. The tectonic evolution of the Eastern Fold Belt is directly linked with the development of the Indo-Burman Range in response to the late Cenozoic convergence between the Indian and Burmese plates. However, very little is known about the Plio-Pleistocene to Recent tectonic evolution of the Lalmai anticline in the context of regional tectonics. Therefore, this research is aimed at lucid understand the Plio-Pleistocene to Recent tectonostratigraphic evolution of the Lalmai anticline based on detailed lithofacies and structural observations. Results show that Plio-Pleistocene Dupitila and Pleistocene Madhupur Clay formations are exposed in the Lalmai area. Based on sedimentary texture and structures, a total of six prominent lithofacies types have been identified. These are trough cross-stratified sandstone (St), planar cross-stratified sandstone (Sp), parallel laminated sandstone (Sl), massive sandstone (Sm), laminated shale (Fl), and mudstone (Fm) facies. The facies characteristics indicate a possible fluvial depositional environment for both the formations. Structural mapping shows that the bedding surfaces are nearly horizontal. Based on the missing of strata (both the Dupitila and Madhupur Clay formations) and presence of a fault escarpment, a N-S trending east-dipping reverse fault (namely, the Mainamati Fault) has been identified on the western margin of the Lalmai anticline. The tectonostratigraphic evolutionary models show that the last major structural activation along this Mainamati Fault can be linked to late Pleistocene to Recent time. This structural activation was possibly controlled by the latest ongoing E-W crustal shortening in response to the Indo-Burman subduction processes to the far east.

Tectonostratigraphic evolution of the new frontier Foram Basin and implications for hydrocarbon potential, Western Desert, Egypt

The Western Desert of Egypt is an important hydrocarbon province as it consists of many petroliferous sedimentary basins. The researchers and petroleum companies are interested in exploring the new frontier sedimentary basins and evaluating their hydrocarbon potential. Given this point of view, the current study attempts to assess the new frontier sedimentary basin in the Western Desert of Egypt, named Foram Basin (FB), using various geophysical and geological methods, including the magnetic, gravity, and seismic methods in addition to the petroleum system and basin analysis modeling. The magnetic data analysis uses various techniques, including power spectrum and source parameter image, total magnetic intensity (TMI), reduction to the pole (RTP), regional-residual separation, and tilt derivative. The used techniques in the interpretation of gravity data include Bouguer gravity, power spectrum, regional-residual separation of Bouguer gravity, tilt derivative of the Bouguer gravity and gravity inversion, and 2D gravity modeling, in addition to the tentative basement depth based on the gravity inversion and 2D gravity modeling for the nine profiles. The main results of these techniques indicate that the main structural trend is NE-SW and the depth to the basement ranges from 1.8 to 5 km comprising two depocenters.Two-thirds of the sedimentary basin fill is a Paleozoic succession and one-third is a Mesozoic-Cenozoic succession. Therefore, the FB is thought to be a Paleozoic basin. The Paleozoic-Mesozoic stratigraphic framework of the FB was classified into six seismic sequences separated by the seven seismic boundaries. The main regional structural trend of the FB is NE-SW, the same trend as that of the Paleozoic Kufra Basin in Libya. In the FB, the major structural trend in the Early Paleozoic is NE-SW, whereas it is E-W in Late Paleozoic. Moreover, in Mesozoic Jurassic time, the dominant trends are E-W and ENE-WSW, and in Middle Cretaceous is ENE-WSW and in Upper Cretaceous are E-W and NE-SW. Regarding the tectonic subsidence rate, the FB passed three tectonic phases. The first tectonic phase has a high subsidence rate that occurred in the Paleozoic, resulting in the deposition of most of the sedimentary succession. The second and third tectonic phases occurred at a relatively low subsidence rate, resulting in the deposition of Mesozoic-Cenozoic deposits. The Paleozoic Silurian Kohla source rock passed the early generation phase in the Early Eocene (50 Ma) and reached a maximum generation rate of 2.77 (mg/gTOC^my) in Late Oligocene (27 Ma) that is considered a very low rate and did not allow for oil expulsion.

The tectono-stratigraphic evolution of the Fucino Basin (central Apennines, Italy): new insights from the geological mapping of its north-eastern margin.

ABSTRACT We present the geological map of the north-eastern margin of the Fucino Basin, which is mainly characterized by Plio-Quaternary continental deposits that show transition from deeper-water lacustrine environment, marginal lacustrine system, and fluvial facies. These deposits unconformably overlie upper Messinian Lago-Mare sediments and pre-orogenic carbonate succession. The occurrence of Caspiocypris tiberina in the Plio-Quaternary lacustrine sediments, coupled with the normal magnetic polarity of Casa Colombaia section, led to suggest the onset of the sedimentation of these continental deposits to the late Piacenzian (2.58–3.04 Ma). The upper Messinian deposits are characterized by ostracod assemblages related to the Loxocorniculina djafarovi zone, pointing to the last Lago-Mare event of the Messinian Salinity Crisis (5.40–5.33 Ma). This new stratigraphic framework may be useful to refine the long-term slip rates of the still active normal faults that affect the north-eastern margin of the Fucino Basin.

Quantifying Multiple Erosion Events in the Distal Sector of the Northern Alpine Foreland Basin (North-Eastern Switzerland), by Combining Basin Thermal Modelling with Vitrinite Reflectance and Apatite Fission Track Data

This work quantifies the amount of erosion associated with the Cretaceous and Miocene erosional unconformities recognised in the distal part of the Northern Alpine Foreland Basin (NAFB), north-eastern Switzerland. To achieve this goal, the basin thermal modelling approach is applied, calibrated by two different sets of data collected in previous studies: vitrinite reflectance (%Ro) and the temperature estimated from apatite fission tracks (AFT) data modelling. The novelty of this approach is the possibility to constrain the timing and magnitude of multiple erosion events by integrating thermal modelling with thermochronologic data. Combining these two methods allows the erosional events to be separated which would not be possible using only irreversible paleothermometers, such as vitrinite reflectance data. Two scenarios were tested, based on the data of two published thermochronology studies. For the Cretaceous unconformity, similar results are obtained for the two scenarios, both indicating that the deposition and the subsequent complete erosion of Lower Cretaceous deposits, in the order of 500–1300 m, depending on the area, are necessary, in order to attain the temperatures estimated by the thermal history modelling of AFT data. Thus, a depositional hiatus for this period is not likely. For the Miocene-Quaternary unconformity, the magnitude of erosion calculated for the two scenarios differs by 300–1400 m, depending on the AFT data considered. The two scenarios lead to a different evaluation of the subsidence and uplift rate of the study area, thus to a different interpretation of the tectono-stratigraphic evolution of this distal sector of the NAFB.

Tectono-stratigraphic evolution of a cretaceous intracontinental rift: Example from Rio do Peixe Basin, north-eastern Brazil

The Rio do Peixe Basin is part of a set of aborted rifts with NE-SW trend along the NE region of Brazil. This axis was originated in response to the stress caused by the fragmentation of Pangea during the Mesozoic, and effectively installed during the Cretaceous event that defined the Brazilian equatorial margin. The detailed structural framework allowed the recognition of the Brejo das Freiras fault zone which presents NE-SW trend and, locally, ENE-WSW. This fault zone, strongly influenced by the basement fabric, deformed the layers and originated drag folds, fault-bending folds, and fault-propagation gentle folds. The half-graben fault margin developed alluvial fans, triggered by tectonic activity and geologically instantaneous creation of accommodation space. At the central portion it predominates a lacustrine sedimentation, while fluvial systems are responsible for carrying sedimentary supply from the flexural margin towards the depocenter. Since tectonics controls sedimentation on rifts, the tectonic systems tracts correspond to an arrangement of contemporaneous depositional systems associated with basin evolutional stages. In the syn-rift sequence, corresponding to Rio do Peixe Group nine stratigraphic units were recognized, bounded by flooding surfaces and drowning unconformities which record cycles of expansion and contraction of the lacustrine system. The tectonic systems tracts related to the initial stages of the rift installation were identified, followed by moments of high and low tectonic activity. The seismic and the well data support both the tectono-sedimentary evolution of the Brejo das Freiras Sub-Basin and the seismic-stratigraphic model proposed in this work. Different correlations between accommodation and sedimentation along a half-graben basin are expected in moments of tectonic activity and quiescence. The use of seismic attributes and filters improved the visualization and extraction of geological features, in both, structural (using pseudo-relief and curvature attributes) and stratigraphic interpretations (RMS amplitude and cosine phase). The understanding of spatial and temporal distribution of depositional systems responsible for a basin filling allows predicting potential petroleum systems.

Tectonostratigraphic Evolution of the Sohar Basin, Exploration Concepts and Emerging Plays Offshore the Uae's East Coast

Tectonostratigraphic Evolution of the Sohar Basin, Exploration Concepts and Emerging Plays Offshore the Uae's East Coast

New insights into the deep-water Otway Basin – Part 3. Petroleum system modelling

The Otway Basin is a broadly northwest–southeast trending basin and forms part of a rift system that developed along Australia’s southern margin. It represents an established hydrocarbon province with mostly onshore and shallow-water offshore discoveries. However, the outboard deep-water Otway Basin, with water depths up to 6300m, is comparatively underexplored and can be considered a frontier area. Following the completion of a basin-wide seismic depth-imaging program (Part 1) and insights from the revised seismic interpretation (Part 2), we have developed a comprehensive petroleum system modelling (PSM) study by integrating these data and findings (Part 3). Together, the studies have resulted in an improved understanding of the hydrocarbon prospectivity of the deep-water areas of the basin. Given the sparsity of data outboard, almost all legacy PSM studies have been focused either on the onshore or shallow-water areas of the basin and primarily on their thick Lower Cretaceous depocentres. The limitations of legacy seismic datasets resulted in a high degree of uncertainty in the derivative interpretations used as input into PSM studies. In addition, the paucity and poor quality of data in the deep-water area reduced confidence in the understanding of the basin evolution and spatial distribution of depositional environments through time. The newly acquired 2D seismic survey and reprocessed legacy data, with calibration via several wells across the basin, have improved confidence in our understanding of the tectonostratigraphic evolution of the basin (Part 2). The study presented herein integrates products from the work in Part 2 into a petroleum system model with the primary objective being to better understand the petroleum systems across the deep-water Otway Basin.

The Barreirinhas Basin internal architecture and the evidence of transform movements along the Romanche Fracture Zone, Brazilian Equatorial Margin

The Barreirinhas Basin, located in the central part of the Brazilian Equatorial Margin, was originated by Pangea breakup during Early Cretaceous time. The Romanche Fracture Zone played an essential role during the entire tectono-stratigraphic evolution of the Barreirinhas Basin. This fracture zone divided the basin in two sub-basins to the south and north with distinct structural style printed on the basin internal geometry. This study is aimed to investigate how the tectonic and sedimentary evolution in the onshore, shallow and deep-water Barreirinhas Basin, were influenced by the Romanche Fracture Zone. Eight 2D seismic sections, subjected to seismic attributes to enhance the seismic stratigraphic horizons and structural features, and supported by five well profiles, allowed analyzing the basin infill, major faults, and the spatial relationship with the fracture zone. The basin evolution and the tectono-stratigraphic architecture are marked by structures from rift to drift stages. The rift sequences are composed of four seismic units (U1-U4) delimited on top by the horizon R4. The sag and drift sequences are composed of six seismic units (U5-U10) delimited between horizons R4-R10. The structural architectures are dominated by transtensional regimes, such as negative flower faults, tilted blocks, and wipeout zones, whereas transpressional tectonics is also present by reverse faults and positive flowers, which are fingerprints of Romanche Fracture Zone. Especially in the southern sub-basin, the transform tectonic activity deformed the entire basin from Aptian to Holocene. These structures correspond to those in Africa conjugate basins, where recurrent dextral strike-slip plate motions caused transtensional and transpressional deformations in the sedimentary pile since separation of South America and Africa. Asymmetric basin architecture, intensity and asynchrony of tectonic regimes distinguish the Atlantic Equatorial basins.

Upper Cretaceous-Paleogene stratigraphy and development of the Mímir High, Vøring Transform Margin, Norwegian Sea

Transform margins represent strike-slip type of plate boundaries that form during continental breakup and initial ocean opening. They are often characterized by margin-parallel highs with exposed pre- and syn-rift sequences. The Vøring Transform Margin, offshore mid-Norway, initiated in the earliest Eocene during the opening of the NE Atlantic. Here, 2D seismic reflection data reveal a transform margin high, the Mímir High. The western flank of this undrilled structure is a kilometer-high escarpment where seismic reflections of pre-breakup age are truncated at the seafloor. The aim of this study was to recover seabed rock samples from the outcropping or shallowly buried sedimentary sequences to provide a geological tie to the regional seismic framework, thereby constraining the basin history and tectono-stratigraphic development. Seabed samples were successfully collected from 14 gravity core and Selcore stations and 10 ROV (remotely operated vehicle) sites along a 750 m high sampling profile, recovering clay, shales, sandstones and glacial dropstones. Biostratigraphy results revealed that the ages of the sedimentary rocks follow the stratigraphic order predicted by the initial seismic interpretation, with Upper Cretaceous sediments at the base and lower Eocene sediments at the top. The integrated interpretation shows that the Mímir High area, including parts of the outer Vøring and Møre basins and the proto-Jan Mayen Microplate Complex, were characterized by the deposition of late Campanian to early Maastrichtian, near coastal and shale-dominated sequences with poor source rock qualities. The early Paleocene samples indicate deep marine conditions that abruptly ended by rapid uplift of the Mímir High in the earliest Eocene. Finally, a reworked Pliensbachian palynomorph assemblage in potential early Eocene strata indicate the presence of exposed Mesozoic sequences in the vicinity of the Mímir High. We argue that some of the lower Eocene sediments where deposited within a hypothetical drainage system sourced from Greenland (Traill Ø or Jameson Land) and/or from the Jan Mayen Ridge prior to continental separation, and not the result of recent ice-rafting.

Tectono-stratigraphic evolution and architecture of the Miocene Rio del Rey basin (Cameroon margin, Gulf of Guinea)

The Rio Del Rey basin located in the Gulf of Guinea is one of the two basins lining the Cameroonian coast. It evolved since the Cenozoic in a tectono-magmatic and seismic complex setting. During the Miocene, this evolution was controlled by tectonics, relative sea level changes, basin filling and mantle dynamics. Two deposit megasequences of second order, MS1 and MS2, were pointed out. MS1 (lower Miocene), aggradational and corresponding to the Isongo turbidites deposited during a period of relative sea level drop registered two sequences of third order differentiated by the degree of channel incision: S1a (Aquitanian–Burdigalian), hardly incised and S1b (Serravallian), moderately incised. A double extension along N–S (Burdigalian) and NE–SW (Serravallian) directions responsible for a set of horsts and grabens, high subsidence and depocentres trending NW–SE affected these sequences. MS2 (middle to upper Miocene), progradational and corresponding to deltaic alternations deposited during a period of creation of available space were controlled by the tilting, wrenching, a second stretching phase and low sedimentary filling. MS2 recorded three cycles of 3rd order: S2a (lower Tortonian), S2b (upper Tortonian) and S2c (Messinian) differentiated by their morphology in ramp for S2a and S2b and slope for S2c. The formation of grabens and horsts and the tilting of the margin coincide with the high activity of the Cameroon volcanic line interpreted as a result of deep mantle dynamics affecting the inner Congo craton lithosphere. This architecture, which differs from those of the other basins of the Gulf of Guinea, partly explains the low oil production of this basin.

Role of the Cretaceous normal faults on the formation of the Eocene (Pontide) fold-thrust belt structures in offshore Akcakoca-Amasra area, Western Black Sea basin, Turkey

The Western Black Sea basin formed during therifting of the Moesian Platform in Early Cretaceous. The closure of the Neotethys Ocean in the Middle Eocene resulted in the formation of the Pontide fold and thrust belt in northern Turkey. During this study, eight seismic reflection profiles were interpreted to determine the subsurface structural geometry and tectono-stratigraphic evolution of the offshore Akçakoca-Amasra area. The stratigraphy of the study area is determined based on a composite wireline well log of the Akçakoca-1 wildcat well, which was also used to construct a velocity model based onsonic data. We suggest that a major décollement surface was developed during the Eocene Pontide Orogeny. The decollement is located at the limestone clay-shale intraformational transition within the Late Cretaceous (Maastrichtian) - Paleocene Akveren Formation. Normal faults formed during the Cretaceous rifting in the region are located below the décollement surface. They provide tectonic ramps along the décollement surface and allow the decollement to develop ramp-flat thrust fault geometry. A well-developed duplex structure is also present along the seismic lines. The décollement surface serves as the floor thrust of the duplex structure. The roof thrust of the duplex is in the Pliocene Sarıkum formation, dominantly composed of claystone.

Constraining Basin Parameters Using a Known Subsidence History

Temperature history is one of the most important factors driving subsidence and the overall tectono-stratigraphic evolution of a sedimentary basin. The McKenzie model has been widely applied for subsidence modelling and stretching factor estimation for sedimentary basins formed in an extensional tectonic environment. Subsidence modelling requires values of physical parameters (e.g., crustal thickness, lithospheric thickness, stretching factor) that may not always be available. With a given subsidence history of a basin estimated using a stratigraphic backstripping method, these parameters can be estimated by quantitatively comparing the known subsidence curve with modelled subsidence curves. In this contribution, a method to compare known and modelled subsidence curves is presented, aiming to constrain valid combinations of the stretching factor, crustal thickness, and lithospheric thickness of a basin. Furthermore, a numerical model is presented that takes into account the effect of sedimentary cover on thermal history and subsidence modelling of a basin. The parameter fitting method presented here is first applied to synthetically generated subsidence curves. Next, a case study using a known subsidence curve from the Campos Basin, offshore Brazil, is considered. The range of stretching factors estimated for the Campos basin from this study is in accordance with previous work, with an additional estimate of corresponding lithospheric thickness. This study provides insight into the dependence of thermal history and subsidence modelling methods on assumptions regarding model input parameters. This methodology also allows for the estimation of valid combinations of physical lithospheric parameters, where the subsidence history is known.

Geology of the Epicentral Area of the November 23, 1980 Earthquake (Irpinia, Italy): New Stratigraphical, Structural and Petrological Constrains

The geology of the epicentral area of the 1980 earthquake (Irpinia-Lucania, Italy) is described with new stratigraphic, petrographic and structural data. Subsurface geological data have been collected during the studies for the excavation works of the Pavoncelli bis hydraulic tunnel, developing between Caposele and Conza della Campania in an area that was highly damaged during 1980 earthquake. Our approach includes geological, stratigraphic, structural studies, and petrological analyses of rock samples collected along the tunnel profile and in outcropping sections. Stratigraphic studies and detailed geological and structural mapping were carried out in about 200 km2 wide area. The main units cropping out have been studied and correlated in order to document the effects of tectonic changes during the orogenic evolution on the foreland basin systems and the sandstone detrital modes in this sector of the southern Apennines. The multi-disciplinary and updated datasets have allowed getting new insights on the tectono-stratigraphic evolution and stratigraphic architecture of the southern Apennines foreland basin system and on the structural and stratigraphic relations of Apennines tectonic units and timing of their kinematic evolution. They also allowed to better understand the relationships between internal and external basin units within the Apennine thrust belt and its tectonic evolution.

Precise U–Pb baddeleyite dating of the Derim Derim Dolerite, McArthur Basin, Northern Territory: old and new SHRIMP and ID-TIMS constraints

The Mesoproterozoic Roper Group of the McArthur Basin has excellent petroleum potential, but exploration has been hampered by poor constraints on its post-depositional history that has compromised understanding of the tectonostratigraphic evolution of the basin. The Derim Derim Dolerite occupies an important position in the event chronology of the McArthur Basin, having intruded the Roper Group prior to post-Roper basin inversion, and it is also a major component of Mesoproterozoic intraplate mafic magmatism in northern Australia. Since 1997, the Derim Derim Dolerite has been assigned a magmatic crystallisation age of 1324 ± 4 Ma (all uncertainties are 95% confidence), based on unpublished sensitive high-resolution ion micro probe (SHRIMP) U–Pb analyses on baddeleyite attributed to a dolerite sample from Bureau of Mineral Resources drill-hole Urapunga 5. Herein, we establish that the SHRIMP sample originated from the type locality of the Derim Derim Dolerite in outcrop 90 km northwest of Urapunga 5 and document the 207Pb/206Pb date interpreted from the 1997 dataset. New U–Pb SHRIMP reanalysis of the same grain-mounts yielded a mean 207Pb/206Pb date of 1320.1 ± 5.3 Ma, confirming the 1997 result, and isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) analysis of baddeleyites plucked from the mounts yielded a precise mean 207Pb/206Pb date of 1327.5 ± 0.6 Ma. This date is significantly older than a baddeleyite U–Pb ID-TIMS date of ca 1313 Ma recently reported elsewhere from dolerite in the Beetaloo Sub-basin 200 km to the south, indicating that magmatism attributed to the Derim Derim Dolerite spanned at least 10–15 Ma. Previously documented geochemical variation in Mesoproterozoic intraplate mafic rocks across the Northern Territory (such as the 1325 ± 36 Ma Galiwinku Dolerite in the McArthur Basin, 1316 ± 40 Ma phonolites in the Nimbuwah Domain of the eastern Pine Creek Orogen, and 1295 ± 14 Ma gabbro in the Tomkinson Province) may reflect episodic pulses of magmatism hitherto obscured by the low precision of the available isotopic dates. The timing and geochemistry of Derim Derim-Galiwinku mafic igneous activity is strikingly similar to that of the Yanliao Large Igneous Province (LIP) in the northern North China Craton, and the global paucity of 1330–1300 Ma LIPs suggests that the North Australian Craton and the North China Craton were in relatively close proximity at that time. KEY POINTS We document a previously unpublished U–Pb baddeleyite date of 1324 ± 4 Ma for the Derim Derim Dolerite in the McArthur Basin, obtained via sensitive high-resolution ion micro probe (SHRIMP), and substantiate it with an isotope dilution-thermal ionisation mass spectrometry (ID-TIMS) date of 1327.5 ± 0.6 Ma from the same sample. Our dates are significantly older than a U–Pb baddeleyite ID-TIMS date of ca 1313 Ma from dolerite in the Beetaloo Sub-basin 200 km to the south, indicating that magmatism attributed to the Derim Derim Dolerite spanned at least 10–15 Ma. Contemporaneous intraplate mafic magmatism extended hundreds of kilometres across the Northern Territory, spanning the Tomkinson Province, the McArthur Basin, and the Nimbuwah Domain of the eastern Pine Creek Orogen. The timing and geochemistry of Derim Derim Dolerite magmatism strongly resembles the Yanliao Large Igneous Province (LIP) in the northern North China Craton, which suggests that the North Australian Craton and the North China Craton were in close proximity during the Mesoproterozoic.