Basin-fill Architecture Research Articles

Fucino Basin structure revealed by the tomography and the reusing of the CROP11 seismic data

The refraction reprocessing of the CROP11-1999 seismic reflection data, which were acquired for deep seismic exploration using a split-spread long offset geometry, provides valuable new insights into the main geological structures of the central Apennines. In this study, we present the geophysical interpretation of a sub-transect of the CROP11 seismic profile, crossing the Piani Palentini and Fucino basins carried out using an integrated approach based on the refraction tomography, the stacked refraction convolution section, and the seismic reflection. The reprocessing allowed us to obtain, for the first time, a high resolution (about 15 m in distance and depth) P-waves seismic velocity 2D model and the imaging of the refractor interface of the basin up to the depth of the Meso-Cenozoic carbonate substratum. The outcomes, combined with the interpretation of a CROP11 seismic reflection sub-transect and a subparallel commercial seismic reflection profile, allowed us to highlight a complex basin-fill architecture and stratigraphy. Four seismo-facies, characterized by different Vp velocity values, were recognized above the Meso-Cenozoic carbonate substratum. In particular, a low-velocity zone (LVZ) was evidenced in both basins. The geophysical interpretation and the comparison with the outcropping sequences allowed us to associate it with an upper Messinian thrust-top deposit.The obtained model constitutes an essential geophysical-geological informative base for future investigations on seismic wave propagation and site response studies at the large scale of the Fucino Basin, one of the areas of the Italian territory with a high seismic hazard.

Dryland avulsion sequences: Insights from data-model comparison of a terminal dryland river system

An advection–diffusion model of fluvial processes was used to analyze the stratigraphic expression of avulsions in terminal river systems and understand their control on basin-fill architecture. The initial and boundary conditions of the model runs (i.e., catchment area, smoothed initial topographic surface, grain-size distribution and sediment supply rates) were extracted from the modern Rio Colorado dryland terminal river system in the Altiplano Basin (Bolivia). Water-discharge and sediment-load values were derived from global regression curves and the BQART equation, respectively. To evaluate the robustness of the simulations, the model was tested under increasing sediment-load scenarios ranging from 0.003 m3/s to 0.095 m3/s. Data-model comparison provided insights into the role of avulsions in the geomorphological evolution of terminal river systems. The observed stacking of sediments, as captured by geospatial and geochronological data from the Rio Colorado, is consistent with the high sediment-load scenarios, which start with a single-thread fluvial channel that in time radially expands over the floodplain by successive river avulsions on account of alluvial-ridge aggradation and channel-floor elevation above the surrounding floodplain. The model output shows a laterally extensive, convex-upwards lobate topography which is in agreement with the lateral and longitudinal geomorphology in the upper and lower coastal plain of the Rio Colorado. The simulated inter-avulsion period, which is the time period between two successive full (or stabilized) avulsions in the model, varies from 0.18 to 1.2 kyr and is consistent with the OSL-age determination in the Rio Colorado with inter-avulsion periods up to 1.28 ± 0.34 kyr.

Subsurface stratigraphy and basin-fill architecture of the late Paleozoic eastern Taos trough, northern New Mexico, U.S.A.

The greater Taos trough located in north-central New Mexico represents one of numerous late Paleozoic basins that formed during the Ancestral Rocky Mountains deformation event. The late Paleozoic stratigraphy and basin geometry of the eastern portion of the greater Taos trough, also called the Rainsville trough, is little known because the strata are all in the subsurface. Numerous wells drilled through the late Paleozoic strata provide a scope for investigating subsurface stratigraphy and basin-fill architecture of the Rainsville trough. Lithologic data obtained predominantly from petrophysical well logs combined with available biostratigraphic data from the greater Taos trough allows construction of a chronostratigraphic framework of the basin fill. Isopach- and structure-maps indicate that the sediment depocenter was just east of the El Oro-Rincon uplift and a westerly thickening wedge-shaped basin-fill geometry existed during the Pennsylvanian. These relationships imply that the thrust system on the east side of the Precambrian-cored El Oro-Rincon uplift was active during the Pennsylvanian and segmented the greater Taos trough into the eastern Rainsville trough and the western Taos trough. During the Permian, sediment depocenter(s) shifted more southerly and easterly and strata onlap Precambrian basement rocks of the Sierra Grande uplift to the east and Cimarron arch to the north of the Rainsville trough. Permian strata appear to demonstrate minimal influence by faults that were active during the Pennsylvanian and sediment accumulation occurred both in the basinal area as well as on previous positive-relief highlands. A general Permian decrease in eustatic sea level and cessation of local-fault-controlled subsidence indicates that regional subsidence must have affected the region in the early Permian.

Three-dimensional Reduced-Complexity Simulation of Fluvio-Deltaic Clastic Stratigraphy

Abstract A novel reduced-complexity approach to 3D forward modeling of siliciclastic stratigraphy is presented for the simulation of erosion, transport, and sedimentation in continental, transitional, and marine depositional domains. The numerical model is based on defining centerlines that connect sediment input points to the shoreline. For each centerline, erosional and depositional surfaces bound depositional domains, and sand and mud proportions are assigned to each domain. The position of each depositional surface follows a set of geologic rules and ensures mass balance with sediment input. The numerical model is tested by simulating the basin-fill architecture of the XES02 laboratory experiment run at the University of Minnesota, which generates stratigraphy mimicking a passive-margin basin fill. Automatic calibration is used to test multiple combinations of uncertain model input parameters to find those that produce scenarios consistent with the experimental stratigraphy. Calibrated models accurately reproduce shoreline and mass-balance centroid migration, marine sediment proportions, and shoreline trajectories measured in the XES02 experiment. The models also provide reasonable approximations of sand distribution. Of interest, falling shoreline trajectories in the experiment and the calibrated models develop coeval to topset aggradation or topset incision depending on rate of base-level fall. The results reported herein validate the numerical approach for simulating sand distribution in an experimental basin, representing a first step towards the application of the numerical model in fluvio-deltaic settings. For field applications, analogue data can be used to independently constrain the geometry of surfaces bounding depositional domains and their composition. The simplicity of the numerical model then enables multiple realizations by quickly varying uncertain boundary conditions, allowing probabilistic predictions in settings with limited data constraints.

Sedimentology, rhythmicity and basin-fill architecture of a carbonate ramp depositional system with intermittent terrigenous influx: The Albian Kharfot Formation of the Jeza-Qamar Basin, Dhofar, Southern Oman

The Albian Kharfot Formation is preserved in the eastern margin of the Jeza-Qamar Basin which straddles across the Oman–Yemen border. This study addresses the sedimentological attributes of the formation and deduces its depositional setting, cyclicity and relative sea level changes in local (within the basin) and regional (Arabian) contexts. The interaction among siliciclastic influxes, in-situ carbonate production and tectono-climatic controls on the stacking nature of the various lithofacies that build-up the formation is discussed. In the study area, the formation lies unconformably over Barremian–Aptian Qishn Formation and conformably under late Albian–?Turonian Dhalqut Formation. The Kharfot Formation thickens from ~140m in the eastern side of the study area to ~300m at the Oman–Yemen border. It consists of eight lithofacies: Orbitolina-rich marls, peloidal bioclastic packstone, bioclastic mudstone to wackestone, argillaceous, bioclastic floatstone to rudstone, bioclastic rudstone, sandy, peloidal, bioclastic mudstone to packstone, peloidal, bioclastic grainstone and dolostone. The vertical arrangement of these lithofacies defines recurring meter- to decameter-scale, shallowing-upward units deposited on a westward-deepening inner- to outer-ramp setting. Tectonic rejuvenation of the siliciclastic source area was accompanied by warm, humid climatic conditions as suggested by high kaolinitic marls of the Kharfot Fm. and coeval quartz-rich sandstone units (Harshiyat Fm.). The shallowing-upward rhythmic sedimentation of the formation has close resemblance with cycles of the Nahr Umr Formation in northern Oman and partially comparable with the global sea level changes. The Kharfot basin was an intrashelf depression that was part of the much larger Arabian epeiric platform. The latter is defined by a rimmed margin in northern Oman where Al-Hassanat Formation represents platform margin deposits and Nahr Umr Formation representing back-rim intrashelf depression which received fine-grained siliciclastic influx from the land (westward). In southern Oman where Kharfot Formation accumulated, the platform was unrimmed ramp type basin with high fine clastic influx along with elevated carbonate production.

A Quantitative Approach To Linking Drainage Area and Distributive-Fluvial-System Area In Modern and Ancient Endorheic Basins

Abstract Regression relationships are derived relating the areal extent of large distributive fluvial systems (DFSs) (> 30 km in length) formed in endorheic basins to contributing drainage area. The resulting correlation coefficients vary between 79% and 98%. Derived correlation values are strikingly similar when stratified by climate, large-scale tectonic regime, and basin context. Regression-equation exponent values range from 0.41 to 0.75, indicating a strong positive relationship between drainage area and DFS area, while coefficients account for the influence of external parameters on the derived relationships. Analysis of the dataset using planform morphology and drainage-basin slope as additional variables reveals that regressions for braided bifurcating DFS produce a highly significant relationship. The relationship suggests that drainage-basin relief influences sediment supply to the sedimentary basin in terms of volume or caliber, which in turn affects the depositional gradient of the DFS surface and resultant channel planform. An evaluation of the predictive capability of the regression equations reveals that the relationships derived from braided bifurcating DFSs perform best, with 80% of the predicted values falling within ± 25% of the measured DFS area value, with a third of the predicted values within ± 10% of the measured DFS area value. Application of the regression relationships derived here to rock-record examples of fluvial deposits interpreted as large DFSs show that DFS area can be used as a proxy to predict the surface area of fluvially transported sediment deposited in a sedimentary basin from the contributing drainage-basin area. The regression relationships for modern drainage areas and corresponding DFS areas from a range of tectonic and climatic settings suggest a measurable link between source and sink in the sedimentary rock record. The results provide a potential tool for more accurate reconstruction and prediction of preserved fluvial deposits and basin-fill architecture within basin-scale climatic and tectonic contexts.

Tectonosedimentary evolution of the Karacasu and Bozdoğan basins in the Central Menderes Massif, W Anatolia

The Karacasu and Bozdogan basins, which trend obliquely to modern grabens in the Central Menderes Massif, are investigated in terms of morphology, basinfill architecture, and structure. Evaluation of the previous geophysical and new structural data indicates that the basins are symmetrical grabens mostly running in a N-S direction. Analysis of sedimentary facies of the basins' infill supports the simple graben model by revealing lateral alluvial/colluvial fans in basin margins and axial fluvial/lacustrine environments in a central trough. The long-term changes between fluvial and lacustrine conditions in the basins are attributed to paleoclimatic origin. Paleostress analysis of slickensides substantiates that the basins were deformed under E-W extension and related N-S compression in the Late Miocene times, and this stress field would have been started in early Miocene times parallel to the Buyuk Menderes Graben (BMG). Following a basin-wide unconformity related to a short-lived compression in mid-Pliocene times, the stress field changed to a N-S extension as a result of the onset of the Buyuk Menderes Detachment in the north in the Late Pliocene-Early Quaternary. Emergence of the modern BMG bounded by high-angle normal faults in the north caused a progressive drop of base level and resulted in southward-developing fluvial incision since the Late Quaternary in the studied basins.

Controls on forearc basin architecture from seismic and sequence stratigraphy of the Upper Cretaceous Great Valley Group, central Sacramento Basin, California

Seismic and sequence stratigraphic analysis of deep-marine forearc basin fill (Great Valley Group) in the central Sacramento Basin, California, reveals eight third-order sequence boundaries within the Cenomanian to mid-Campanian second-order sequences. The third-order sequence boundaries are of two types: Bevelling Type, a relationship between underlying strata and onlapping high-density turbidites; and Entrenching Type, a significantly incised surface marked by deep channels and canyons carved during sediment bypass down-slope. Condensed sections of hemipelagic strata draping bathymetric highs and onlapped by turbidites form a third important type of sequence-bounding element, Onlapped Drapes. Five tectonic and sedimentary processes explain this stratigraphic architecture: (1) subduction-related tectonic tilting and deformation of the basin; (2) avulsion of principal loci of submarine fan sedimentation in response to basin tilting; (3) deep incision and sediment bypass; (4) erosive grading and bevelling of tectonically modified topography by sand-rich, high-density turbidite systems; and (5) background hemipelagic sedimentation. The basin-fill architecture supports a model of subduction-related flexure as the principal driver of forearc subsidence and uplift during the Late Cretaceous. Subduction-related tilting of the forearc and growth of the accretionary wedge largely controlled whether and where the Great Valley turbiditic sediments accumulated in the basin. Deeply incised surfaces of erosion, including submarine canyons and channels, indicate periods of turbidity current bypass to deeper parts of the forearc basin or the trench. Fluctuations in sediment supply likely also played an important role in evolution of basin fill, but effects of eustatic fluctuations were overwhelmed by the impact of basin tectonics and sediment supply and capture. Eventual filling and shoaling of the Great Valley forearc during early Campanian time, coupled with dramatically reduced subsidence, correlate with a change in plate convergence, presumed flat-slab subduction, cessation of Sierran arc volcanism, and onset of Laramide orogeny in the retroarc.

Provenance of the northern part of the Kahramanmaraş Peripheral Foreland Basin (Miocene, S Turkey)

The Miocene Kahramanmaraş Peripheral Foreland Basin (KPFB) resemble to classic foreland basin model, with small differences. In the classic model, both the accretionary wedge and foredeep extend lengthways parallel to the plate margin. In addition, accretionary wedge includes wedge top basin or piggy back basin that extends parallel to foredeep. However, the accretionary wedge of the KPFB contains small half-graben type basins that obliquely intersect the plate margin between the Arabian Plate and the Anatolide–Taurides Platform (due to the irregular shape of the plate boundary). Tectonic lineaments controlled the shape and orientation of these basins and larger main depocentre of the KFPB, which were predominantly filled with deep-sea sediments. This paper focuses on the provenance of features of the KFPB, predominantly was fed from the northern basin margin, while also aiming to resolve the complex basin evolution that occurred during the Miocene. Clasts of Palaeozoic and Mesozoic limestone and ophiolites are common components of the confined deep-water clastic systems, which evolved as elongated trenches in the north-western sector of the KPFB during the Early-Middle Miocene. During the Middle Miocene, continuous thrusting of the northern basin margin to south caused depocentre migration to south-east, through the basin interior. At that time, the north-east and central depocentres of the KPFB were filled primarily by clasts of ophiolite and metamorphic units. The tectonic control on basin fill architecture can be observed anywhere in the KFPB. The principal tectonic features controlled the geometry and orientation of the canyon, the channel geometry of the deep-water slope on the northern basin margin, the frequency and distribution of slump-slide-debris flows and the overall pattern of sedimentation cycles in the stratigraphy of the slope and the central basin floor. Some basin sectors have continuously reactivated and as a result, different sediment entry points with substantial local accumulation of sediment and deformation have evolved on the slope and basin floor. Three scales of provenance were used to investigate the source rock: (a) field-based observation and analysis of conglomerate clasts, (b) modal analysis of sandstone facies and (c) geochemical analysis, all of which were in agreement.

Inner-Forearc Sequence Architecture in Response to Climatic and Tectonic Forcing Since 150 ka: Hawke's Bay, New Zealand

The influence of eustasy, tectonic deformation, and sediment flux as controlling parameters on basin stratigraphy and depositional sequence development are largely accepted. Eustasy is usually considered as the dominant mechanism of sequence generation, especially for Pleistocene successions. In active subduction-margin settings, the high rates of tectonic deformation are expected to have a stronger influence on basin-fill architecture, while sediment flux is generally less well constrained, and therefore less frequently considered. The active Hikurangi subduction margin in New Zealand offers the opportunity to quantitatively assess the relative roles of tectonic, climatic, and eustatic drivers. We present a quantitative source-to-sink-like study of the late Pleistocene succession from the Hawke's Bay sector of the inner forearc domain (c. 150 ka to present). The interpretation of a grid of high-resolution marine seismic data, onland and offshore core and well descriptions, and the integration of geomorphic studies enabled identification of system tracts. In turn these comprise two sea-level-cycle depositional sequences (LPS1 and LPS2), including one complete 100 ka sequence (LPS1). Isopach maps of both sequences reveal changes in sediment distribution and preservation that reflect the relative roles of tectonic deformation and eustasy. Eustasy dominates development of sequence architecture at relatively short time scales (i.e., 100 kyrs). Four long-lasting depocenters are identified over the inner forearc domain and located in four subsiding basins (Kidnappers, Mahia, Lachlan, and Motu-o-Kura basins). Significant shifts of the depocenter location in the basins are correlated with eustatic sea-level changes. Estimates of sediment volumes and masses from isopach maps indicate higher mass accumulation rates during climato-eustatic extremes, which we correlated to the onland erosional response. Sediment distribution and landscape evolution are strongly influenced by the interaction of the structural deformation and sediment flux. We present paleogeographic reconstructions for the inner forearc domain coincident with two paleoclimatic extremes (Last Glacial Maximum and Holocene Optimum). These illustrate the importance of eustatic changes, structural deformation, and sediment flux on the pattern of sediment distribution, accumulation, and sequence architecture.

Sub-grid parameterisation of fluvio-deltaic processes and architecture in a basin-scale stratigraphic model

We present a parameterisation of fluvio-deltaic drainage network evolution and alluvial architecture in a basin-scale 2-DH model. The model setup is capable of producing convergent and divergent channel networks. Major elements are the alluvial-ridge aggradation and the coupled overbank deposition, the dimension and style of the channel belt and the sub-grid stratigraphic expression. Avulsions are allowed to develop out of randomly instigated crevasses. Channel stability is modelled one dimensionally by calculating the flow and sediment transport at prospective avulsion nodes. The ultimate fate of crevasses (failed avulsion, successful avulsion, stable bifurcation) depends on the ratio of cross-valley and in-channel gradients in the local neighbourhood of the grid cell under consideration and on the amount and distribution of the suspended sediment load in the water column. The sub-grid parameterisation yields implicit knowledge of the alluvial architecture, which may be analysed stochastically. Stochastic realisations of the alluvial architecture allow us to investigate the relationship between basin-fill architecture and small-scale alluvial architecture, which is likely to improve geological reservoir modelling of these notoriously complex deposits. Modelling results under conditions of time-invariant forcing indicate significant quasi-cyclic autogenic behaviour of the fluvio-deltaic system. Changes in the avulsion frequency are correlated with the number and length of distributary channels, which are in turn related to alternating phases of progradational and aggradational delta development. The resulting parasequences may be difficult to distinguish from their allogenically induced counterparts.

Deformation style and basin-fill architecture of the offshore Limón back-arc basin (Costa Rica)

The Limón back-arc basin, located at the eastern coast of Costa Rica, is part of the southern Central American arc-trench system. Basin evolution started in Late Cretaceous times as response to the onset of the subduction of the Farallón Plate below the Caribbean Plate. The Limón Basin can be subdivided into a northern and a southern sub-basin separated by the E–W trending Trans Isthmic Fault System. A regional grid of offshore seismic lines allows the comparative analysis of the basin-fill architecture and the deformation style in both sub-basins. The northern sub-basin shows exclusively normal faults. The basin-fill architecture resembles a passive continental margin setting showing a distinct wedge-shaped geometry and seaward propagating depositional units. The area of the Rio San Juan Delta is characterized by gravity-driven, deltaic deformation exhibiting a series of listric growth faults both on the shelf and in slope areas. In contrast to the northern basin, the southern sub-basin is characterized by the development of thin-skinned fold-and-thrust belt tectonics best recorded in concentric or asymmetric hangingwall anticlines separated by listric or planar southwestward dipping thrust faults. Due to the pronounced NE-propagating of folding the shelf is broader and the slopes are steeper in the southern sub-basin, compared with the northern sub-basin. Thus both sub-basins show a very different tectonic style. In the North Limón Basin an extensional regime established, whereas in the South Limón Basin compression dominated. However, in both sub-basins the basal detachment is probably controlled by a lithological change from limestone to shale.

Facies architecture of the Grès de Peïra Cava, SE France: landward stacking patterns in ponded turbiditic basins

Basins in which turbidity currents are completely or partially trapped are common in many tectonically active, deep-water settings. Field study of an Eocene–Oligocene turbiditic system in the Peïra Cava area, a sub-basin of the Alpine foreland in southeastern France, allows spatial characterization of a ponded basin fill on the basis of a correlation framework derived from measured outcrop sections and photomosaics. The basin-fill architecture comprises a sand-rich, proximal scour-and-fill facies and a downstream transition to mud-rich, basin-plain turbidite sheet facies. The proximal facies is interpreted to have formed directly downstream of a slope break, where currents were highly erosional during some periods and highly depositional during other periods, as a result of the interacting effects of turbulence enhancement and rapid deceleration. Both the proximal facies and the downstream transition to distal basin-plain facies occur in progressively landward positions at higher stratigraphic levels. The landward shift in depositional facies is likely to have resulted from the basin-floor aggradation and a landward migration of the slope break. This ‘back-stepping’ process may be expected to occur in many ponded turbiditic basins and to produce a similar type of sedimentary architecture.

Palaeoenvironmental analysis of a Miocene basin in the high Taurus Mountains (southern Turkey) and its palaeogeographical and structural significance

Determination of the relationships between the southern, marine-dominated Miocene basins of south central Turkey and their continental hinterland in southern Turkey has traditionally been frustrated by the apparent absence of basin remnants within the Taurus Mountains. The Dikme basin, which seems to be an enclave of basin remnants within the Aladağ Mountains (Eastern Taurides), consists mainly of coarse-grained continental sediments of various facies. These mostly early–middle Miocene sediments were studied to determine the depositional environments and the factors controlling the basin formation and basin fill architecture, to attempt to close the information gap between the Adana Basin to the south and central Anatolian Miocene further to the north. A generally southwest-flowing axial fluvial system and interfingering coarse-grained marginal alluvial clastics derived from northwest and southeast were identified. The marginal facies to the northwest is bounded by a N 55° E-running structural lineament, that starts from the Ecemiş Fault Zone and in digital elevation models extends toward the north of the study area. Along this lineament, Miocene sediments onlap steep fault-line escarpments. Certain Miocene levels are tectonically disrupted, and an intraformational unconformity and boulder conglomerates are also well-developed in the Miocene sequence. The southeast boundary is similarly defined by a NE-trending fault that periodically elevated the adjacent Tufanbeyli autochthon, producing coarse clastics from this area. This boundary fault also induced fining-upwards vertical patterns and synsedimentary deformation in the marginal facies. Additionally, the central part of the basin exhibits a distinct fault-defined morphology characterized by small-scale (tens of metres to 150 m high) valley-and-sill topography. A thin marine interval was also encountered in the southernmost part of the basin, indicating that the clastic system originating around this area debouched into a Miocene sea situated further to the south. The proposed palaeogeography and basin fill model suggests that the Dikme basin and similar Miocene remnants, all controlled mainly by a northeast-running extensional or transtensional fault system, may have been parts of the terrestrial hinterland that supplied sediment to rapidly subsiding marine areas further south, such as the Adana Basin.

Large-Scale Cycle Architecture in Continental Strata, Hornelen Basin (Devonian), Norway

ABSTRACT Nine large-scale stratigraphic cycles, each about 100 m thick, along the northern margin of the Hornelen basin, western Norway, record systematic expansions and contractions of alluvial-fan, braidplain, and lake facies tracts. The braidplain facies tract occupies the basin center, from time to time expanding toward the margins, and constitutes the deposits of axial or longitudinal drainage from an eastern source. The alluvial-fan facies tract, which comprises the deposits of high-gradient transverse drainages, occupies a narrow belt close to the fault-bounded basin margin. The lake facies tract is between the alluvial-fan and braidplain facies tracts. Physical correlation of strata shows that the large-scale cycles are symmetric in all facies tracts. The symmetry of the large-scale cycles, in which the base-level rise and fall hemicycles of each cycle are of approximately the same thickness, indicates that sediment accumulated in all environments during the entire base-level cycle. Absence of regional unconformities (sequence boundaries) also indicates approximately continuous sediment accumulation in the basin during base-level cycles. The base-level fall-to-rise turnaround is represented by an interval of strata, rather than by a sequence boundary, at the maximum expansion of the alluvial-fan facies tract. Condensed sections are also absent. They are represented mainly by intervals of lake strata at base-level rise-to-fall turnarounds. Strata in the base-level fall hemicycle (decreasing accommodation) accumulated as the braidplain and alluvial-fan facies tracts expanded from the basin center and the northern basin margin, respectively. Expansions of these two facies tracts filled the basin, while the lake facies tract contracted. Strata in the base-level rise hemicycle accumulated as the alluvial-fan and braidplain facies tracts contracted sourceward, respectively toward the northern and eastern basin margins, during times of increasing accommodation. This sourceward retreat of the alluvial-fan and braidplain facies tracts was coincident with expansion of the lake facies tract. At the rise-to-fall turnarounds, alluvial-fan and braidplain sediments are stored near their respective sources toward the basin margins, and the centers of mass of these facies tracts are at basin-margin positions. During base-level fall time, the centers of mass of the alluvial-fan and braidplain facies tracts migrate basinward. The alluvial-fan and braidplain facies tracts usually expand toward each other simultaneously, and then move away from each other simultaneously. This in-phase relationship is replaced by a reciprocal stacking pattern when the two facies tracts abut each other near base-level fall-to-rise turnarounds. When the two facies tracts are in contact, the higher-gradient alluvial-fan facies tract initially blocks expansion of the braidplain. As the alluvial-fan facies tract retreats toward the basin margin and fan-margin gradients are reduced, however, the braidplain expands across former fan margins. In the reciprocal configuration, the two facies tracts move in tandem in the same direction. This reciprocal pattern plus changes in aggradation-to-progradation ratio of the alluvial-fan facies tract suggest that alluvial-fan morphology changes during base-level cycles. Large-scale cycle stacking patterns show significant changes in basin-fill architecture through time, including syndepositional structural changes accompanied by changes in stratal geometries, a change from ephemeral to permanent lakes, permanent increase in alluvial-fan gradients, and permanent reduction of alluvial-fan radii and volume at the northern basin margin. Consideration of these changes and the largely in-phase relationships between facies tracts sourced by two separate sediment supplies suggest that an interplay of climate, self-regulatory, and tectonic factors controlled sedimentary accumulation within the Hornelen basin.

Interaction between faulting, drainage and sedimentation in extensional hanging-wall syncline basins: example of the Oligocene Matelles basin (Gulf of Lion rifted margin, SE France)

Abstract A tectono-sedimentary model for hanging-wall syncline basins emphasizing the role of erosion in the basin architecture is proposed, based on the well-exposed Matelles basin. Detailed geological mapping is the base for the analysis of the extensional double ramp-flat Matelles fault system, hanging-wall deformation and relationships between faulting/drainage/sedimentation. Displacement of the hanging-wall above the fault resulted in the formation of (a) upper and lower rollovers associated with the upper and lower rampflat couples, (b) a hanging-wall ramp syncline above the lower ramp and (c) a half graben associated with the emergent ramp and upper flat couple. Only the hanging-wall ramp syncline and the lower rollover are preserved. Ramp syncline basin-fill architecture is characterized by progressive unconformity and faultward migration of the growth synclines ‘climbing up’ the monoclinal prerift strata corresponding to the ramp-side limb of the ramp syncline. Clast composition analysis of the synrift deposits indicates that sediments were mainly supplied from the hanging-wall flat, and allows to propose palinspastic reconstructions of the hanging wall in order to establish the palaeo-drainage system and its evolution. ‘Upper hanging-wall flat catchments’ and ‘lower rollover catchments’ are proposed as main features of the drainage system in extensional hanging-wall syncline basins.

Mechanical aspects of sedimentary basin formation: development of integrated models for lithospheric and surface processes

Different assumptions for the thermo-mechanical properties of the lithosphere strongly affect predictions inferred from quantitative sedimentary basin modeling. Examples from various basins, selected as natural laboratories, illustrate the importance of incorporating a finite strength of the extending lithosphere in forward stratigraphic modeling of large-scale basin stratigraphy. Current models can effectively couple erosion at uplifted rift shoulders of extensional basins with the basin fill architecture of the subsiding basin compartments. Modeling of the synrift strata integrates spatial scales characteristic for subbasins, such as the Oseberg field in the North Sea, with large-scale lithospheric properties characterizing the bulk strength of extending lithosphere. Modeling of compressional basins in foreland fold-and-thrust-belt settings can effectively link lithospheric flexure with surface processes. Scales pertinent to short-term spatial and temporal variations in basin fill and basin deformation can now be addressed, allowing the quantitative investigation of consequences of different modes of thrusting for basin fill geometry and facies characteristics.

Abstract: Sequence Stratigraphy and Forearc Basin Fill Architecture, Upper Cretaceous Great Valley Group, North-Central Sacramento Basin, California 

Abstract: Sequence Stratigraphy and Forearc Basin Fill Architecture, Upper Cretaceous Great Valley Group, North-Central Sacramento Basin, California 

Lacustrine fan-deltaic sedimentation in a Proterozoic rift basin: the Sopa-Brumadinho Tectonosequence, southeastern Brazil

The Sopa-Brumadinho Tectonosequence (100 to 200 m thick) is the fourth unit in ascending order of the up-to-2000 m thick Mesoproterozoic Espinhaço Supergroup, representing the depositional products of the third and main phase of the rift stage of the Espinhaço basin. The Sopa-Brumadinho Tectonosequence in the study area consists of diamond-bearing lacustrine fan-delta deposits, bounded by prominent angular and erosional unconformities. Detailed lithofacies studies were carried out in the central part of the southern Serra do Espinhatço, southeastern Brazil, to characterize the paleogeography and basin-fill architecture of the Sopa-Brumadinho Tectonosequence. Thirteen lithofacies are present: massive clast-supported conglomerates (lithofacies UGCS), inversely graded clastsupported conglomerates (lithofacies IGCS), normally graded clast-supported conglomerates (lithofacies NGCS), massive to crudely stratified clast-supported conglomerates (lithofacies CSCS), sandy matrix-supported conglomerates (lithofacies S-MS), muddy matrix-supported conglomerates (lithofacies M-MS), talus-breccia clast-supported conglomerates (lithofacies TB-CS), massive sandstones (lithofacies Sm), horizontal stratified sandstones (lithofacies Sh), trough cross-stratified sandstones (lithofacies St), planar cross-stratified sandstones (lithofacies Sp), graded-stratified sandstones (lithofacies Sg), and pelites (lithofacies P). They represent the products of several types of subaerial and subaqueous sediment gravity flows (ranging from turbidity currents to cohesive debris flows) and ephemeral braided streams. The deposits are usually arranged in coarsening- to fining-upward tectono-depositional intervals. Each tectono-depositional interval represents a progradational lobe, which starts at the base with lacustrine pelites and evolves with time from distal (subaqueous) to proximal (subaerial) characteristics. The fining-upward part represents the abandonment phase of the depositional lobes. The origin, characteristics, distribution and spatial arrangement of the various lithofacies, the interbedding of gravityflow and stream-flow deposits, the predominance of debris-flow conglomerates over aqueous current-formed ones, the semi-radial, fan-like dispersion pattern of the paleocurrents, and the recognition of associated subaerial and subaqueous depositional settings are all indicative of a lacustrine alluvial-fan/fan-delta environment, or a fan-delta system. An interplay between several intrabasinal and extrabasinal controls probably determined the fan evolution. The sedimentation of the lacustrine fan-delta systems of the Sopa-Brumadinho Tectonosequence probably took place in a N-S elongated continental rift basin, compartmentalized by N-S trending normal faults and W-E trending transfer faults, under a tropical semi-arid climate. The basin-fill architecture was probably determined by episodic subsidence, clockwise block tilting and asymmetric-graben evolution, as well as by inherited characteristics of the source area. Additionally, a new descriptive scheme for classification of conglomerate lithofacies is here proposed.

Introduction to Special Issue on Integrated Basin Studies (IBS) — a European Commission (DGXII) project

This issue contains papers issued from the Integrated Basin Studies Project (IBS) which is part of a larger program of the European Commission DGXII, entitled Geosciences II. The IBS project (EC contract JOU2 CT92 0110) originated in Geosciences consultation meetings, the first of them being held in Strasbourg in June 1989 under the auspices of Mr Hubert Curien, former French Minister for Research and Technology, and the subsequent meeting being held in Brussels. These consultation meetings have resulted in the conclusion that a main axis of future research in Geosciences should be the study of sedimentary basins, upstream of industrial activities, mainly the oil and gas industry but also water resources management, the mining industry, the storage of undesirable products and coastal engineering. They also resulted in the conclusion that future research on sedimentary basins should fulfill two requirements: integration of disciplines and modelling. Such a conclusion may now seem trivial but was not so generally accepted at that time. In this spirit, the IBS project was designed to provide the oil and gas industry with a new generation of models for basin formation, basin evolution and basin fill architecture from basin scale to reservoir scale. Its main objectives are the linkage of crust thermomechanical behaviour to basin formation and deformation mechanics and the corresponding modelling, the quantification of tectonic control on the sedimentary record and the analysis of compaction and mass and heat transfer. The IBS strategy is to link subsurface data to field data, and an important part of the project is devoted to thematic field studies in European sedimentary basins of different tectonic styles, taken as natural laboratories. Basin research has gone through a rapid evolution during the last decade, in particular through the development of new acquisition and processing methods for seismic data and advances in drilling technology. Modelling provides an important tool to analyse different aspects of basin formation processes and find their tectonic expression in the basin fill. The need for 3-D modelling techniques and models capable of linking processes operating on basinwide to subbasin scales is increasingly recognized and a significant effort has been made in the IBS project to develop a new generation of basin formation models coping with these needs (see also Cloetingh et al., 1993a; Van Wees and Cloetingh, 1994). As many data required to test these models reside in industrial companies, IBS has promoted a closer link between academic research and basin studies carried out by industry. The participation of the petroleum industry has been vital in this project and IBS has been able to establish a well functioning system of cooperation that not only facilitated data access, but most important, guaranteed the suitability of the end products of the project. This has led to an intensive exchange of modelling concepts and data sets between industry and academia. The IBS project has also used extensively the International Lithosphere Program Task Force Origin of Sedimentary Basins (See Cloetingh, Sassi and Task Force Team, 1994; Cloetingh et al., 1993a,b; 1994) to implement planning and to discuss preliminary results. It also builds partly on joint research through the European Commission TEMPUS and PECO Programs on Pannonian basin studies (Horvath, 1993; Van Balen and Cloetingh, 1995; Van Balen et al., 1995; Horvath and Cloetingh, 1995). A stimulating aspect of the activity of the IBS group is the creation of a research network in the corresponding field of knowledge which comprises now 30 teams belonging to eight European countries (England, France, Germany, Hungary, Norway, Spain, Switzerland and The Netherlands). This demonstrates the capacity of the procedures used by the DGXII of the European community to formulate a really European research space. PhD students and young researchers form an important component of the research groups