bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pseudo‐toplap in seismic models of the Schlern‐Raibl contact (Sella platform, northern Italy)
Authors: Stafleu JAN , Schlager WOLFGANG 
Published: November 2007

AbstractIn the Sella platform of the Dolomite Alps, the horizontal beds of the Raibl Formation directly overlie the Upper Schlern Dolomite (Cassian Dolomite of some authors). The Schlern Dolomite comprises steep clinoforms, together with a few tens of metres of horizontal topset beds in the platform interior.Two‐dimensional seismic modelling techniques were used to determine the seismic‐response of this interesting situation. To perform this, two different lithological models were constructed based on outcrops of the Sella south face. The first model is that of a rapidly prograding platform with slow aggradation in the platform interior. The second model shows clinoforms toplapping against the topset beds of the platform interior.P‐wave velocities and bulk densities were assigned to the lithostratigraphical units in accordance with values from a similar study, involving the same formations. The vertical‐incidence method was used to construct perfectly migrated time sections and depth sections of reflectivity. These were convolved with zero‐phase Ricker wavelets of different peak frequencies to produce the final synthetic seismic sections.Using conventional, low frequencies (e.g. 25 Hz), the seismic response of the two models is almost identical. The topset beds and the Schlern‐Raibl contact appear as one event. In a real seismic survey, both sections would be interpreted as toplap of Schlern clinoforms against the Raibl Formation. At higher frequencies (75 Hz), however, differences are revealed. The angle of progradation in the progradation & aggradation model becomes visible, as opposed to the horizontal surface in the progradation & toplap model. Topset beds are resolved separate from the Raibl Formation, but still appear to form a single dipping pseudo‐toplap surface.Another modelling technique, simulating unmigrated sections, shows few differences between the two models even at high frequencies. In addition, the clinoforms are disturbed by the refraction of rays. This study demonstrates that, even under ideal acquisition and processing conditions, the seismic tool can introduce a pseudo‐toplap. This implies that toplap in a seismic section is not necessarily toplap in outcrop.
The interaction between normal faulting and drainage in active extensional basins, with examples from the western United States and central Greece
Authors: Leeder M. R. , Jackson J. A. 
Published: November 2007

AbstractFaulting exerts an important control upon drainage development in active extensional basins and thus helps determine the architecture of the sedimentary infill to a synrift basin. Examples of the interaction between faulting and drainage from the western United States and central Greece may be grouped into a relatively small number of classes based upon the structural position of a drainage catchment: footwall, hangingwall, fault offset and axial. Our examples illustrate the diversity of erosional effects that might arise because of variations in the spacing, orientation and segmentation of faults and their interactions. Where basement lithology is similar, footwall catchments are generally smaller, shorter and steeper than those of the hangingwall. Footwall‐sourced alluvial fans and fan deltas are: generally smaller in area than those sourced from similar lithologies in the hangingwall. Wide fault offsets often give rise to large drainage catchments in the footwall. The development of axial drainage depends upon the breaching of transverse bedrock ridges by headward stream erosion or by lake overflow. Once breaching has occurred the direction of axial stream flow is controlled by the potential developed between basins of contrasting widths. Fault migration and propagation leads to the uplift, erosion and resedimentation of the sedimentary infill to formerly active basins, leading to the cutting of footwall unconformities. The outward sediment flux from structurally controlled catchments is modulated in an important way by lithology and runoff. The greatest contrasts in basement lithology arise when fault migration and propagation have occurred, such that the sedimentary fill to previously active basins is uplifted, incised and eroded by the establishment of large new drainage systems in the footwalls of younger faults. Drainage patterns in areas where faults interact can shed light on the relative timing of activity and therefore the occurrence of fault migration and propagation. Facies and palaeocurrent trends in ancient grabens may only be correctly interpreted when observations are made on a length scale of 10–20 km, comparable to that of the largest fault segments.
Architecture and sedimentary facies evolution of a marine, expanding outer‐arc half‐graben (Crete, late Miocene)
Authors: Postma GEORGE , Drinia HARA 
Published: November 2007

AbstractVertical trends in architecture and facies of delta systems are preserved in a clastic wedge of an expanding marine half‐graben in which tectonics, eustatic sea‐level change and climatic change are roughly known from independent evidence. The studied half‐graben is situated on Crete (Greece) and part of a larger, E‐W‐trending extensional domain situated north of the Hellenic subduction zone. The extension seems to be related to the southward migration of the trench (roll‐back) in early Late Miocene times. The infill pattern is discussed in the light of theoretical fault‐growth models for expanding half‐grabens.The geometry of the half‐graben fill is typically wedge shaped, with a thickness of nearly 1000 m near the fault scarp thinning to c. 50 m about 20 km away from the scarp. The lower part of the wedge (Stratified Prina Series) contains coarsening‐upward units representing progradational, shallow‐marine deltas. At the base of the wedge these units are thin and retrogradationally stacked. Upwards in the succession, the units become composite (coarsening‐upward subunits), thicker and finer grained. The composite structure, the thickening and the fining trend is related to progressive increase in accommodation space inherent in fault growth.Rapid deepening of the basin from the photic zone (evidenced by intercalated coral and stromatolite beds) up to a depth of 900 m started at the top of the Stratified Prina Series. The deepening continued over some tens of metres of marly sediments of the base of the Kalamavka Formation and may be related to structural collapse of the fault block. After the structural collapse, basin depth remained more or less constant and basin infilling occurred by progradation of deep‐water delta systems. These systems are characterized by a muddy delta slope with channelized conglomerates, and by mainly aggradation of prodelta turbidites deposited in small lobes at the base of slope.
Tectonic controls on base‐level variations and depositional sequences within thrust‐top and foredeep basins: examples from the Neogene thrust belt of central Sicily
Authors: Butler ROBERT W. H. , Grassot MARIO 
Published: November 2007

AbstractTectonic subsidence and uplift may be recorded by concomitant sedimentation, not only from decompacted accumulation curves but also from the evolving depositional environment relative to sea level at the time. In thrust belts there are two types of processes capable of generating vertical movements, each with different wavelengths and amplitudes. Regional subsidence is driven by flexural loading by the orogenic hinterland, the thrust belt and accumulated sediments of the underlying foreland lithosphere. Within this flexure, the foreland thrust belt will generate areas of local uplift, notably at the crests of thrust anticlines. In this contribution we examine how these processes have interacted to influence relative sea level as recorded by late Neogene sediments in an array of basins developed above and adjacent to the Maghrebian thrust belt of central Sicily. Two particular periods are addressed, the late Tortonian to early Messinian (Terravecchia Formation) and early to early late Pliocene. The earlier of these is characterized by a deltaic complex that formed prograding depositional geometries, migrating into perched basins. Collectively, however, these units are transgressive and migrate back towards the orogen. A depositional model is presented that links the migration of facies belts to subsidence caused by accentuated tectonic loading in the hinterland and break‐back thrust sequences across the basins. We infer that a palaeobathymetric profile of underfilled sub‐basins resulted and that this influenced the pattern of evaporite accumulation during Mediterranean desiccation in Messinian times. The Pliocene sediments, accumulated under renewed global sea levels, prograded towards the foreland. A waning tectonic load in the hinterland driving isostatic rebound, uplift and coastal offlap is the proposed explanation. This contribution is a case history for the depositional evolution of dominantly submarine thrust systems and their record of relative sea‐level changes.
Tectonic evolution of the Alboran Sea basin
Authors: Watts A. B. , Piatt J. P. , Buhl P. 
Published: November 2007

AbstractThe Alboran Sea is an extensional basin of Neogene age that is surrounded by highly arcuate thrust belts. Multichannel seismic (MCS) reflection profile data suggest the basin has a complex tectonic fabric that includes extensional, compressional and strike‐slip structures. The early Miocene history appears to be dominated by graben formation with border faults that are in large part contemporaneous with thrust movements in the external zones of the Betic and Rif mountains. Extension appears to have continued into the late Miocene although the main movements were probably completed by the time of the Messinian ‘salinity crisis’. The Pliocene and younger history of the basin is dominated by infilling of the Messinian topography, gentle subsidence, and extensional, compressional and strike‐slip movements. There is evidence from the sea‐floor morphology and seismicity patterns that the basin is actively deforming in response to present‐day plate motions. Backstripping of well data in the basin margin suggests that the initial extensional event was accompanied by crustal and lithospheric thinning. The depth to Moho inferred from backstripping is greater than the depth expected based on seismic and gravity modelling, suggesting that backstripping underestimates the true amount of thinning. One explanation is that some of the thinning occurred while the crust was above sea level, perhaps as a result of either crustal thickening, or a period of lithospheric heating and thinning, prior to rifting. We found that a model with a ‘normal’ crustal thickness of 31.2 km, a lithospheric thickness of 50 km, and β= 1.4 predicts 0.8 km of initial uplift. These parameters fit the well subsidence data and bring the backstripped Moho into better agreement with the seismic and gravity Moho. The origin of such a thin lithosphere is not constrained by the data, but we believe that it may be a result of the detachment of a cold lithospheric ‘root’ that formed during pre‐Neogene collisional orogeny in the region.
Geometry of trapezoidal fan deltas and their relationship to extensional faulting along the southwestern active margins of the Corinth rift, Greece
Authors: Poulimenos G. , Zelilidis A. , Kontopoulos N. , Doutsos T. 
Published: November 2007

AbstractA new subtype of Gilbert‐type fan deltas, ‘the trapezoidal fan delta’, characterized by the absence of bottomset deposits, is recognized in the south‐western active margins of the Corinth rift in central Greece. They are formed adjacent to master extensional listric faults and developed by progradation either onto a subaqueous basin escarpment or across a subaerial platform where alluvial fans have accumulated. Simultaneously with master fault activity, displacements on counter faults along intrabasinal basement highs produced fan delta foreset deposits. Furthermore, footwall imbrication and uplift along the listric faults, as well as transfer fault displacement, have strongly influenced the pattern of fan delta sedimentation.
Anomalous thermal maturities caused by carbonaceous sediments
Authors: Pollack HENRY N. , Cercone KAREN ROSE 
Published: November 2007

AbstractSedimentary rocks such as coal and carbonaceous mudstone which contain abundant carbonaceous matter are characterized by thermal conductivity much lower than that exhibited by other common rock types, by a factor of 5–10. As a result, temperature gradients in such sediments can range up to 0.25 °Cm‐1 even under conditions of average heat flow. When such steep gradients extend over a significant sedimentary thickness, temperatures of underlying rock units are elevated, causing both organic and inorganic phases to record what seem to be anomalously high levels of thermal maturity. This carbonaceous blanket insulating effect may help to explain unusual levels of maturity observed at shallow depths in the Appalachian Basin, Michigan Basin and other regions of the world with significant carbonaceous strata.
Overpressures and hydrocarbon generation in the Sable sub‐basin, offshore Nova Scotia
Authors: Williamson MARK A. 
Published: November 2007

AbstractOne of several interconnected depocentres lying offshore eastern Canada, the Sable sub‐basin preserves a thick sequence of Mesozoic‐Cenozoic clastic sediments, significant gas accumulations and an extensive development of abnormal pressures. In order to understand the basin's hydrocarbon generation, migration and accumulation history it is necessary to quantify the interplay between its burial, thermal, and maturation history, and to determine the influence on these of the basin's excess pressure history. Simple, one‐dimensional reconstructions of maturity and pore pressure histories are derived for exploration well and pseudo‐well locations on a seismic line running from the basin's structural high to its depocentre. Calibrated, where possible, by reference to measured maturity, temperature and pressures, these models provide a basic dynamic framework within which it is possible to consider the generation history of the basin's source rocks. Late Jurassic to Early Cretaceous sediments underwent an initial rapid, rift‐related subsidence. The thermal/maturation models suggest that source rocks lying within these intervals quickly matured and began generating gas and condensates. Similarly, this rapid burial was translated, through sediment compaction disequilibrium processes, into an early expression of abnormal pressures.The pore pressure/time reconstructions in the modelling assume that sediment compaction disequilibrium and gas generation are the principal causal mechanisms. Matching pore pressure reconstructions with present‐day pressure‐depth profiles is particularly sensitive to assumed seal permeability profiles. Although the seal permeabilities used as model input are based on actual measured permeabilities at the present day, this does not mean that the permeability‐time curves derived through the model's decompaction assumptions accurately reflect seal permeability evolution.
Modelling of pore pressure evolution associated with sedimentation and uplift in sedimentary basins
Authors: Luo XIAORONG , Vasseur GUY 
Published: November 2007

AbstractUnconformities, which represent either periods of interruption of sedimentation or, in most cases events characterized by deposition and subsequent erosion, are commonplace geological phenomena in sedimentary basins, and will affect the pore pressure evolution of the basin fill. The effect of unconformities on pore pressure, as well as on sediment compaction and on burial processes is studied using a numerical basin model. For coarse sediments, which are permeable so that their pore pressure always remains nearly hydrostatic, the effects of both pure deposition interruption (hiatus) and deposition‐erosion events are negligible for pore pressure evolution. However, for fine‐grained sediments, unconformities can modify the pore pressure and the stress state to varying degrees. The results show that the rate of removal of overlying sediments, the permeability of sediments and time play important roles in the pore pressure evolution. In the East Slope of the Ordos Basin (China), in which overpressure has not been detected in deep wells, the modelling results suggest that the large‐scale erosion occurring in the Late Cretaceous and in the Tertiary may have removed high overpressure existing in the basin before the erosion.
Cross formational flow in the Paris Basin
Authors: Worden R. H. , Matray J.‐M. 
Published: November 2007

AbstractCross formational flow of water has occurred across several hundred metres of Liassic mudstone from the Triassic Chaunoy Formation sandstone to the Middle Jurassic Dogger Formation carbonate in the Paris Basin, France. This has been demonstrated by chemical and isotopic data from rocks and formation waters, sampled on a basin scale, from the Dogger and Chaunoy formations. Present‐day and palaeoformation waters in the Dogger record input of exotic water in terms of salinity and carbon and strontium isotopes. The exotic water was highly saline and contained isotopically light carbon and 87Sr‐enriched strontium in comparison to the indigenous Dogger Formation water. The source of the exotic water can only have been the Chaunoy Formation. Salinity and isotope data show that present‐day Dogger Formation water contains 10–15% invasion Chaunoy water. Modelling strontium isotope ratio and concentration data from mineral cements shows that over the duration of Dogger cementation, Dogger palaeoformation waters were replaced by 1–5% Chaunoy water. Cross formational flow of water must have occurred by convective mass flow, rather than diffusion, in order to preserve the characteristics of water input from the Chaunoy. Flow probably occurred via the major Hercynian fault and fracture systems that run through the centre of the Paris Basin. Upward flow in this setting is most likely in a compressional tectonic regime, the situation during much of the Tertiary in the Paris Basin. Thermodynamic modelling indicates that cross formational flow from the Chaunoy has probably caused carbonate cementation in the Dogger.
Convective and conductive heat transfer in sedimentary basins
Authors: Vasseur G. , Demongodin L. 
Published: November 2007

AbstractIn the Earth's crust the temperature is largely controlled by heat conduction. However, under some circumstances, the thermal state is disturbed by advection of heat associated with groundwater flow. The corresponding thermal disturbance depends on the water flow velocity (modulus and direction) and therefore thermal data may be used to constrain the pattern of natural fluid flow. In this paper, some models of thermal disturbance induced by convective heat transfer are presented. They are based on the assumption that the water flow is concentrated in thin permeable structures such as aquifer or fault zones. The steady‐state and transient thermal effects associated with such scenarios are computed using a somewhat idealized model which depends on a small number of parameters: flow rate, time, aquifer geometry and thermal parameters of surrounding rocks. In order to extract the conductive and convective components of heat transfer from temperature data and to estimate the corresponding fluid flow rate, it is first necessary to estimate the thermal conductivity field. The problem of the estimation of thermal conductivity in clay‐rich rocks, based on laboratory andin‐situmeasurements, is emphasized. Then a method is proposed for the inversion of temperature data in terms of fluid flow. Vertical and lateral variations of thermal conductivity are taken into account and the fluid flow is assumed to be concentrated on a specified surface (2‐D quasi‐horizontal pattern). Thermal effects of the flow are simulated by a distribution of surface heat production which can be calculated and then inverted in terms of horizontal fluid flow pattern.
Rift basins and supradetachment basins: intracontinental extensional end‐members
Authors: Friedmann S. JULIO , Burbank DOUGLAS W. 
Published: November 2007

AbstractTwo end‐members characterize a continuum of continental extensional tectonism: rift settings and highly extended terrains. These different styles result in and are recorded by different extensional basins. Intracontinental rifts (e.g. East Africa, Lake Baikal) usually occur in thermally equilibrated crust of normal thickness. Rift settings commonly display alkali to tholeiitic magmatism, steeply dipping (45–60°) bounding faults, slip rates <1 mm yr‐1 and low‐magnitude extension (10–25%). Total extension typically requires > 25 Myr. The fault and sub‐basin geometry which dominates depositional style is a half‐graben bounded by a steeply dipping normal fault. Associated basins are deep (6–10 km), and sedimentation is predominantly axial‐ or hangingwall‐derived. Asymmetric subsidence localizes depocentres along the active basin‐bounding scarp.Highly extended continental terrains (e.g. Colorado River extensional corridor, the Cyclade Islands) represent a different tectonic end‐member. They form in back‐arc regions where the crust has undergone dramatic thickening before extension, and usually reactivate recently deformed crust. Volcanism is typically calc‐alkalic, and 80–90% of total extension requires much less time (<10 Myr). Bounding faults are commonly active at shallow dips (15–35°); slip rates (commonly > 2 mm yr‐1) and bulk extension (often > 100%) are high.The differences in extension magnitude and rate, volcanism, heat flow, and structural style suggest basin evolution will differ with tectonic setting. Supradetachment basins, or basins formed in highly extended terrains, have predominantly long, transverse drainage networks derived from the breakaway footwall. Depocentres are distal (10–20 km) to the main bounding fault. Basin fill is relatively thin (typically 1–3 km), probably due to rapid uplift of the tectonically and erosionally denuded footwall. Sedimentation rates are high (˜ 1 m kyr‐1) and interrupted by substantial unconformities. In arid and semi‐arid regions, fluvial systems are poorly developed and alluvial fans dominated by mass‐wasting (debris‐flow, rock‐avalanche breccias, glide blocks) represent a significant proportion (30–50%) of basin fill. The key parameters for comparing supradetachment to rift systems are extension rate and amount, which are functions of other factors like crustal thickness, thermal state of the lithosphere and tectonic environment. Changes in these parameters over time appear to result in changes to basin systematics.