Subsidence Curves Research Articles

Filling sequence in Late Paleozoic continental basins: A chimera of climate change? A new light shed given by the Graissessac–Lodève basin (SE France)

The characteristics of sedimentary deposits in continental basins, especially those controlled by extension, are often used to infer global climatic changes. We question the relevance of such an approach because the stratigraphic pattern of those basins are mostly similar whatever their latitudes/paleolatitudes (i.e. their general climatic conditions), namely the transition from (1) an ancestral drainage network to (2) deep lake with a dominance of black and grey shale deposits, (3) shallow oxic lake with a dominance of red pelites deposits and to eventually (4) a new drainage network. Such transitions observed in Late Palaeozoic continental basins throughout Laurasia and Gondwana are generally interpreted as evidence of global change from a wet climate to an arid climate. From the sedimentological and structural analysis of a Late Palaeozoic basin, the Graissessac–Lodève basin, in the south of the Variscan French Massif Central, we proposed a new tectono-stratigraphic sequence of this basin from the Late Carboniferous to the Early Trias. We estimate the paleo-area (from 295–450 km 2 to 880–1150 km 2) of the basin and we deduce a subsidence curve from the Late Carboniferous to the Late Permian (from 600 ± 200 m/My to 100 ± 10 m/My). We conclude that the Graissessac–Lodève basin stratigraphic pattern corresponds to a classical continental rift sequence controlled by tectonics. In order to assess a possible control of the stratigraphic sequence by the climate, we have reconstructed the paleo-depth of the lake with (1) the morphometric analysis of the wave ripples and (2) with an estimation of the lacustrine slope considering the tectonic origin of the lake. We find that the maximum lacustrine depth has evolved from a range of 80–300 m during the Late Carboniferous to 40–45 m during the Late Permian. From our estimates of the different configurations of the basin, we show that the volume of the water in the lake has remained nearly constant between 10 and 30 km 3, from the Late Carboniferous (300 My) to the Late Permian (250 My). Eventually, we conclude that the sedimentological indicators of shallowing and episodic drying observed from the Late Carboniferous to Late Permian in this basin, and probably in all the Pangea basins of the same type, are the consequence of the basin enlargement by tectonics and its sedimentary filling rather than climatic change.

Basin analysis study of block 10 in the Say'un-Masilah Basin, Yemen, using a 1D backstripping method

Geohistory analysis was carried out on block 10 in the Say’un-Masilah Basin. The present study is based on the analysis of the well logs of six exploration wells. In the Middle Jurassic to the Middle Eocene, Say’un-Masilah Basin exhibited a complex subsidence history over a period of about 155 Ma. Backstripped subsidence curves are constructed by removing the effects of decompaction to the water column and sediment loads. In the Middle Jurassic, slow subsidence was driven under the effect of sediment load as Kuhlan and Shuqra Formations were deposited as pre-rift deposits. The average total subsidence value of the basement during the deposition of Shuqra Formation was 276 m. The highest subsidence rates during this time are observed northeast of the study area. Rapid subsidence initiated in the Upper Jurassic driven by mechanical extension of the rift, resulting in the deposition of Madbi and Safer Formations, or the so-called Syn-rift deposits. The average tectonic subsidence value of the basements during the deposition of Madbi Formation was 368 m. The highest subsidence rates during this time are observed southwest of the study area. Mechanical extension ceased at about 145 Ma, being replaced by a phase of post-rift subsidence, resulting in more widespread uniform sedimentation, with reduced tectonic subsidence rates forming post-rift deposits represented by Nayfa Formation, Sa’ar Formation, Biyad Formation, and Mahra Group. The total subsidence value of the basement during the deposition of the post-rift sediments increases gradually due to the increase of the sediment load as the rate of deposition was high especially northeast of the area.

Evolution of the Cordilleran foreland basin system in northwestern Montana, U.S.A.

New lithostratigraphic and chronostratigraphic, geochronologic, and sedimentary petrologic data illuminate the history of development of the North American Cordilleran foreland basin system and adjacent thrust belt from Middle Jurassic through Eocene time in northwestern Montana. The oldest deposits in the foreland basin system consist of relatively thin, regionally tabular deposits of the marine Ellis Group and fluvial-estuarine Morrison Formation, which accumulated during Bajocian to Kimmeridgian time. U-Pb ages of detrital zircons and sandstone modal petrographic data indicate that by ca. 170 Ma, miogeoclinal strata were being deformed and eroded in hinterland regions. Sandstones of the Swift and Morrison Formations contain detrital zircons derived from the Intermontane belt. The Jurassic deposits probably accumulated in the distal, back-bulge depozone of an early foreland basin, as suggested by the slow rates of tectonic subsidence and tabular geometry. A regional unconformity separates the Jurassic strata from late Barremian(?) foredeep deposits. This unconformity possibly resulted as a combined effect of forebulge migration, decreased dynamic subsidence, and eustatic sea-level fall. The late Barremian(?)-early Albian Kootenai Formation is the first unit that consistently thickens westward, as would be expected in a foredeep depozone. The subsidence curve at this time begins to show the convex-upward pattern characteristic of foredeeps. By Albian time, the fold-and-thrust belt had propagated to the east and incorporated Proterozoic rocks of the Belt Supergroup, as indicated by sandstone compositions, detrital zircon ages in the Blackleaf Formation, and by crosscutting relationships in thrust sheets involving Belt Supergroup rocks in the thrust belt. A major episode of marine inundation and black shale deposition (Marias River Shale) occurred between the Cenomanian and mid-Santonian, and was followed by a regressive succession represented by the Upper Santonian–mid-Campanian Telegraph Creek, Virgelle, and Two Medicine Formations. Provenance data do not resolve the timing of individual thrust displacements during Cenomanian–early Campanian time. The Upper Campanian Bearpaw Formation represents the last major marine inundation in the foreland basin. By latest Campanian time, a major episode of slip on the Lewis thrust system had commenced, as recorded in the foreland by the Willow Creek and St. Mary River Formations in the proximal foredeep depozone. The final stage in the evolution of the Cordilleran fold-and-thrust belt and foreland basin system is recorded by the Paleocene–early Eocene Fort Union and Wasatch Formations, which were preserved in the distal foreland region. Regional extensional faulting along the fold-and-thrust belt began during the middle Eocene. The results presented here enable the establishment of links between previous geological work in Canada and the better known parts of the Cordilleran foreland basin in the United States.

Lithospheric cooling and thickening as a basin forming mechanism

Widely accepted basin forming mechanisms are limited to flexure of the lithosphere, and lithospheric stretching followed by cooling and thermal subsidence. Neither of these mechanisms works for a group of large basins, sometimes known as “intracontinental sags”. In this paper we investigate cooling and thickening of initially thin lithosphere as a basin forming mechanism, by a combination of forward modelling and a backstripping study of two Palaeozoic North African basins: Ghadames and Al Kufrah. These are two of a family of basins, once unified, which lie over the largely accretionary crust of North Africa and Arabia. Such accretionary crust tends to be juvenile, consisting of amalgamated island arcs, accretionary prisms and melanges, and typically has near-normal crustal thicknesses but initially thin mantle lithosphere. Post-accretion subsidence is modelled using a plate cooling model similar to cooling models for oceanic lithosphere. The crustal composition and thickness used in the models are varied around average values of accretionary crust to represent likely heterogeneity. The model allows the lithosphere to thicken as it cools and calculates the resulting isostatic subsidence. Water-loaded tectonic subsidence curves from these forward models are compared to tectonic subsidence curves produced from backstripped wells from Al Kufrah and Ghadames Basins. A good match between the subsidence curves for the forward model and backstripping is produced when the best estimates for the crustal structure, composition and the present day thickness of the lithosphere for North Africa are used as inputs for the forward model. The model produces sediment loaded basins of 2–7 km thickness for the various crustal assemblies over ~ 250 Myr. This shows that lithospheric cooling provides a viable method for producing large basins with prolonged subsidence, without the need for initial extension, provided the condition of initially thin mantle lithosphere is met.

Geohistory Analysis of the Tabas Block (Abdoughi-Parvadeh Basins) as Seen from the Late Triassic through Early Cretaceous Subsidence Curves

The study area is situated in the Middle part of the Tabas Block. It contains outcrops of rocks that formed along longitudinal faults in Early Cimmerian orogenic phase. The basin subsided along these faults from the Late Triassic to Early Cretaceous, which include two sedimentary cycles. A sedimentary cycle, related to Upper Triassic to Bajocian is known as Shemshak group. Another sedimentary cycle, related to Bathonian to Upper Jurassic, is known as MAGU group. The Cretaceous rock units include red coarse-grained sandstone, at the base changing upward into red gypsifferous marl, rudist limestone and conglomerate, which deposited in a shallow marine environment. Subsidence analysis is applied to geologically disconnected objects in a manner that departs from its traditional use in basin analysis. However, as it introduces quantified data on the behavior of the crust in response to tectonics, it was shown to be an efficient tool in sorting out the major events amongst various local evidences for crustal instability. Based on the subsidence curves plotted for tectonic domain of the Tabas Block , the major obtained results include: - subsidence curves shown a relatively high subsidence rate in the Upper Triassic to the Middle Cretaceous, that coupled with rifting environment in this time; - this rifting was rapidly ceased in the Late Cretaceous to form Aulacogen( Failed Rift) and caused to generate oceanic crust and overriding of Sabzevar-Nain-Baft Ophiolites in this time; - subsidence rate in this part of Tabas Block was increasing towards the west and the north.

Cratonic basins and the long-term subsidence history of continental interiors

Abstract: Cratonic basins form within stable regions of the continental interior and initiate during periods of break-up and dispersal of supercontinental assemblies, when the continental lithosphere may experience tensional stress. We investigate the subsidence of cratonic basins using a 1D forward model of protracted stretching at low strain rates of thick continental lithosphere. At low strain rates, subsidence history departs from the uniform instantaneous model, as supported by calculations of the thermal Péclet number. Cooling as a result of upward advection is matched by thermal diffusion, producing a subsidence trajectory with a near-constant slope and a slight elbow when stretching ceases. The model is used to evaluate the subsidence history of boreholes in cratonic basin-fills. Marked accelerations and decelerations of subsidence, attributed to secondary mechanisms such as the dynamic response to mantle convection, are removed from the backstripped, water-loaded subsidence curves to obtain the ‘reduced' subsidence. Fits to the reduced curves indicate strain rates of c . 10 −16 s −1 , stretching durations of 50 Ma, and stretch factors of as little as 1.1–1.3, despite the extreme longevity of subsidence. Cratonic basins are therefore part of the rift–drift suite, occupying a portion of the existence field at low stretch factors and low extensional strain rate.

Subsidence history from a backstripping analysis of the Permo‐Mesozoic succession of the Central Southern Alps (Northern Italy)

ABSTRACTSeven tectonic subsidence curves, based on outcrop data, have been calculated in order to constrain the geodynamic evolution of the Permian–Mesozoic sedimentary succession (up to 10 km thick) of the Central Southern Alps basin (Italy). The analysis of the tectonic subsidence curves, covering a time span of about 200 Ma, allowed us to quantify the subsidence rates, to document the activity of syndepositional fault systems and calculate their slip rates. Different stages, in terms of duration and magnitude of subsidence‐uplift trends, have been identified in the evolution of the basin. The fault activity, reconstructed by comparing subsidence curves from adjacent sectors, resulted as highly variable both temporally and spatially. Strike‐slip tectonics was coeval to Permian sedimentation, as suggested by the strong differences in the subsidence rates in the sections. The evolution and subsidence rates suggest a continental shelf deposition from Early Triassic to Carnian, when subsidence came to a stop. A rapid resumption of subsidence is observed from the Norian, with a subsidence pulse in the Late Norian, followed by the regional uplift, in the Late Rhaetian. The following Early Jurassic subsidence is characterized by tectonic subsidence similar to that of the Norian. The Norian and Early Jurassic pulses were characterized by the highest slip rates along growth faults and are identified as two distinct tectonic events. The Norian–Rhaetian event is tentatively related to transtensional tectonics whereas the Early Jurassic event is related to crustal extension. The Early Jurassic subsidence records a shift in space an time of the beginning of the extensional stage, from Late Hettangian to the east to Late Pliensbachian–Toarcian to the west. From the Toarcian to the Aptian, the curves are compatible with regional thermal subsidence, later followed (Albian–Cenomanian) by uplift pulses in a retrobelt foreland basin (from Cenomanian onward).

Feedbacks of sedimentation on crustal heat flow: New insights from the Vøring Basin, Norwegian Sea

ABSTRACTBasement heat flow is one of the key unknowns in sedimentary basin analysis. Its quantification is challenging not in the least due to the various feedback mechanisms between the basin and lithosphere processes. This study explores two main feedbacks, sediment blanketing and thinning of sediments during lithospheric stretching, in a series of synthetic models and a reconstruction case study from the Norwegian Sea. Three types of basin models are used: (1) a newly developed one‐dimensional (1D) forward model, (2) a decompaction/backstripping approach and (3) the commercial basin modelling software TECMOD2D for automated forward basin reconstructions. The blanketing effect of sedimentation is reviewed and systematically studied in a suite of 1D model runs. We find that even for moderate sedimentation rates (0.5 mm year−1), basement heat flow is depressed by ∼25% with respect to the case without sedimentation; for high sedimentation rates (1.5 mm year−1), basement heat flow is depressed by ∼50%. We have further compared different methods for computing sedimentation rates from the presently observed stratigraphy. Here, we find that decompaction/backstripping‐based methods may systematically underestimate sedimentation rates and total subsidence. The reason for this is that sediments are thinned during lithosphere extension in forward basin models while there are not in backstripping/decompaction approaches. The importance of sediment blanketing and differences in modelling approaches is illustrated in a reconstruction case study from the Norwegian Sea. The thermal and structural evolution of a transect across the Vøring Basin has been reconstructed using the backstripping/decompaction approach and TECMOD2D. Computed total subsidence curves differ by up to ∼3 km and differences in computed basement heat flows reach up to 50%. These findings show that strong feedbacks exist between basin and lithosphere processes and that resolving them require integrated lithosphere‐scale basin models.

Subsidence history and basin phases of the Bowen, Gunnedah and Surat Basins, eastern Australia

The Early Permian to Middle Triassic Bowen and Gunnedah Basins and the Early Jurassic to Early Cretaceous Surat Basin exhibit a complex subsidence history over a period of about 200 Ma. Backstripped tectonic subsidence curves, constructed by removing the effects of processes such as sediment loading, loading due to the water column and sediment compaction, allow the subsidence histories of the basin to be examined in terms of the tectonic drivers that caused the subsidence of the basins. In the Early Permian, rapid subsidence was driven by mechanical extension, forming a series of half-grabens along the western margin of the Bowen and Gunnedah Basins. Mechanical extension ceased at about 280 Ma, being replaced by a phase of passive thermal subsidence, resulting in more widespread, uniform sedimentation, with reduced tectonic subsidence rates. At the start of the Late Permian, the passive thermal subsidence phase was interrupted by the onset of lithospheric flexure during a foreland basin phase, driven by convergence and thrust loading to the east in the New England Orogen. Initially, dynamic loading, caused by viscous corner flow in the asthenospheric wedge above the west-dipping subducting plate, led to limited tectonic subsidence. Later in the Late Permian, the dynamic loading was overwhelmed by static loading, caused by the developing retroforeland thrust belt in New England, leading to very high rates of tectonic subsidence, and the development of a major retroforeland basin. Peneplanation in the Late Triassic was followed by sedimentation at the start of the Jurassic, forming the Surat Basin, where the tectonic subsidence can again be interpreted in terms of dynamically induced platform tilting. Subduction ceased at about 95 Ma, resulting in rapid uplift, due to the rebound of the lithosphere following either cessation of subduction, or it stepping well to the outboard of Australia.

Subsidence and crustal roughness of ultra-slow spreading ridges in the northern North Atlantic and the Arctic Ocean

SUMMARY Five basin-wide seismic reflection profiles of up to 550 km each were acquired in the Arctic Ocean and the northern North Atlantic in 2001 and 2002. The main objective was to investigate the depth to the basement and to analyse the crustal structure, morphology and roughness of ultra-slow spreading ridges of the Gakkel, Molloy and Knipovich ridges. To date, little is known to date of the ultra-slow spectrum of such spreading ridges. The seismic profiles of all investigated ridges show similar morphological characteristics with deep axial valleys and rough basement topography. Magnetic data compilation and interpretation suggests that the ultra-slow spreading systems are fairly stable and existed during the entire evolution of the basins to the north of the Greenland Fracture Zone. The thermal subsidence curve was calculated and corrected for sediment loads, and crustal roughness values are estimated for all five profiles. The resulting roughness values append the global roughness data set for ultra-slow spreading systems. The results are higher than those predicted by interpolating existing global roughness. This study confirms the presence of a global relationship between crustal roughness, ridge morphology and spreading rates. New curve fits, supporting the global relationship, are discussed. Data on present spreading rates, ridge morphology, subsidence and roughness provide a better insight into the development of the axial ridge morphology in the study area. The results show that the basins to the north of the Greenland Fracture Zone were formed at ultra-slow spreading axial rift valleys and continued spreading at ultra-slow rates to the present day configuration.

Change in tectonic force inferred from basin subsidence: Implications for the dynamical aspects of back-arc rifting in the western Mediterranean

A method has been developed that allows temporal changes in tectonic force during rift basin formation to be inferred from observed tectonic subsidence curves and has been applied to the Gulf of Lions (the Provençal Basin) and the Valencia Trough in order to gain some understanding of the dynamical aspects of back-arc basin rifting in the western Mediterranean Sea. Two distinct tectonic force regimes active at different times during the evolution of each of these back-arc basins are identified. The first, which can be seen in both basins, is characterized by tensional forces that gradually abate with time to vanish some ∼ 20 my after the onset of rifting. The magnitude of tectonic force required to initiate the rifting process is significantly greater in the Valencia Trough than in the Provençal Basin. Subsequently, the dynamic development of these back-arc basins differs. In the Provençal Basin, there is a renewal of force, with extensional deformation concentrated in the central part of the rift whereas, in the Valencia Trough, the second tectonic force regime is inferred to be one that causes compression that subsequently relaxes. Such temporal patterns of tectonic force are interpreted to be related to the causative driving processes, allowing constraints to be placed on the transient interaction between the overriding and subducting plates in a back-arc setting. The models also allow inferences to be made about the rheological structure of the lithosphere. A significant variation of initial crustal thickness is inferred for the Provençal Basin but not for the Valencia Trough. In both basins, a wet rheology is required in order to initiate rifting given currently accepted bounds on tectonic force magnitudes; adoption of a dry rheology leads to insufficiently high strain rates for significant lithosphere extension in both cases.

Late Carboniferous foreland basin formation and Early Carboniferous stretching in Northwestern Europe: inferences from quantitative subsidence analyses in the Netherlands

ABSTRACTThe large thickness of Upper Carboniferous strata found in the Netherlands suggests that the area was subject to long‐term subsidence. However, the mechanisms responsible for subsidence are not quantified and are poorly known. In the area north of the London Brabant Massif, onshore United Kingdom, subsidence during the Namurian–Westphalian B has been explained by Dinantian rifting, followed by thermal subsidence. In contrast, south and east of the Netherlands, along the southern margin of the Northwest European Carboniferous Basin, flexural subsidence caused the development of a foreland basin. It has been proposed that foreland flexure due to Variscan orogenic loading was also responsible for Late Carboniferous subsidence in the Netherlands. In the first part of this paper, we present a series of modelling results in which the geometry and location of the Variscan foreland basin was calculated on the basis of kinematic reconstructions of the Variscan thrust system. Although several uncertainties exist, it is concluded that most subsidence calculated from well data in the Netherlands cannot be explained by flexural subsidence alone. Therefore, we investigated whether a Dinantian rifting event could adequately explain the observed subsidence by inverse modelling. The results show that if only a Dinantian rifting event is assumed, such as is found in the United Kingdom, a very high palaeowater depth at the end of the Dinantian is required to accommodate the Namurian–Westphalian B sedimentary sequence. To better explain the observed subsidence curves, we propose (1) an additional stretching event during the Namurian and (2) a model incorporating an extra dynamic component, which might well explain the very high wavelength of the observed subsidence compared with the wavelength of the predicted flexural foreland basin.

Buoyancy of tunnels in soft soils

INTRODUCTION The construction of bored tunnels in soft soils is one of the major achievements of civil engineering in the 20th century. The process minimises the disturbance in the environment, especially in built-up areas, but there may still be some disturbance of the stress field, and some deformation of the soil surrounding the tunnel. In particular, some subsidence above the tunnel may occur, because of the excavation process at the front of the tunnel, and because the dimensions of the tunnel-boring machine are necessarily somewhat larger than the tunnel constructed in its interior. The latter effect is often reduced by the injection of grout between the tunnel elements and the soil, but experience shows that there is usually some subsidence above the tunnel. The simplest problem for theoretical analysis arises when considering the ground loss problem: the deformations caused by a uniform reduction of the radius of a cylindrical cavity. For the surface subsidence due to ground loss, various methods of analysis have been suggested, ranging from analytic solutions assuming elastic or elasto-plastic behaviour to numerical solutions using advanced material modelling of soil behaviour, and empirical methods using some assumed subsidence curve (Peck, 1969). In most of the elastic methods (Sagaseta, 1987; Verruijt & Booker, 1996) the problem considered is an imposed deformation of a circular ring in a half-plane, ignoring other effects. It has been observed (e.g. Loganathan & Poulos, 1998) that the subsidence curve predicted by such elastic solutions is wider than the subsidence curve observed in engineering practice, with the observed subsidence curves being some 50% narrower than the curves predicted from elastic solutions for the ground loss problem. To improve the predictions, various improved methods of analysis have been suggested. Loganathan & Poulos (1998) considered the possible ovalisation of the tunnel and, preferably, the addition of a semi-empirical correction factor. Other possible causes for deviations from an elastic solution are differences between the excavation face pressure and the in situ stresses, plastic deformations of the soil (Osman et al., 2006), and consolidation or creep of the soil after the construction process of the soil. Perhaps the ultimate solution is to use a numerical method, for instance based upon the finite element method, in which elasto-plastic soil behaviour and creep can be incorporated, and even the effect of grouting (Van Jaarsveld et al., 1999; Brinkgreve et al., 2006). Buoyancy will automatically be included in such a model if it starts with an initial state of stress due to gravity of the soil, and then considers the construction of the tunnel as a removal of the soil, the installation of the tunnel, and consolidation or creep of the soil after the construction process, taking into account the effective weight of the various components. If desired, the grouting process can also be included. The effect to be considered in this paper is the difference in weight of the completed tunnel and the excavated soil, to be denoted as the buoyancy effect (Strack, 2002; Strack & Verruijt, 2002). Because the weight of the tunnel is usually less than the weight of the excavated soil, an upward force is exerted on the surrounding soil, and this will affect the deformation and stress field, including a reduced subsidence. The purpose of the present paper is to investigate the influence of the buoyancy effect on the subsidence curve at the surface, and in particular the width of this curve, using a simple homogeneous isotropic elastic model for the soil. Of course, other effects, such as plasticity, consolidation and creep, may also influence the shape of the subsidence curve, but this paper considers the ground loss and buoyancy effects only.

Tectonics and subsidence evolution of the Sirt Basin, Libya

A backstripping analysis of 225 wells located within the Sirt Basin, Libya, provides new constraints on the development of the Sirt Basin. Four tectonic phases are identified from Late Jurassic to present. The presentation of contour maps of subsidence and crustal stretching allows spatial and temporal variations in stretching to be visualized. A close match is observed with stretching phases documented for other African basins, consistent with discrete phases in the opening of the Tethys and Atlantic. Rifting and reactivation appear to be primarily controlled by the orientation of the basin and the underlying basement structure with respect to stress directions. The tectonic subsidence curves have also been forward modeled with an automated modeling technique to quantify the variation in timing and the magnitude of rifting. The tectonic subsidence history of the Sirt Basin is characterized by periods of stretching, alternating with periods of relative tectonic quiescence and thermal subsidence. Stretching started at the centers of the troughs and migrated toward the platform crests.

The birth of the Rheic Ocean — Early Palaeozoic subsidence patterns and subsequent tectonic plate scenarios

New plate-tectonic reconstructions of the Gondwana margin suggest that the location of Gondwana-derived terranes should not only be guided by the models, but should also consider the possible detrital input from some Asian blocks (Hunia), supposed to have been located along the Cambrian Gondwana margin, and accreted in the Silurian to the North-Chinese block. Consequently, the Gondwana margin has to be subdivided into a more western domain, where the future Avalonian blocks will be separated from Gondwana by the opening Rheic Ocean, whereas in its eastern continuation, hosting the future basement areas of Central Europe, different periods of crustal extension should be distinguished. Instead of applying a rather cylindrical model, it is supposed that crustal extension follows a much more complex pattern, where local back-arcs or intra-continental rifts are involved. Guided by the age data of magmatic rocks and the pattern of subsidence curves, the following extensional events can be distinguished: – During the early to middle Cambrian, a back-arc setting guided the evolution at the Gondwana margin. Contemporaneous intra-continental rift basins developed at other places related to a general post-Pan-African extensional phase affecting Africa – Upper Cambrian formation of oceanic crust is manifested in the Chamrousse area, and may have lateral cryptic relics preserved in other places. This is regarded as the oceanisation of some marginal basins in a context of back-arc rifting. These basins were closed in a mid-Ordovician tectonic phase, related to the subduction of buoyant material (mid-ocean ridge?) – Since the Early Ordovician, a new phase of extension is observed, accompanied by a large-scale volcanic activity, erosion of the rift shoulders generated detritus (Armorican Quartzite) and the rift basins collected detrital zircons from a wide hinterland. This phase heralded the opening of Palaeotethys, but it failed due to the Silurian collision (Eo-Variscan phase) of an intra-oceanic arc with the Gondwana margin. During this time period, at the eastern wing of the Gondwana margin begins the drift of the future Hunia microcontinents, through the opening of an eastern prolongation of the already existing Rheic Ocean. The passive margin of the remaining Gondwana was composed of the Galatian superterranes, constituents of the future Variscan basement areas. Remaining under the influence of crustal extension, they will start their drift to Laurussia since the earliest Devonian during the opening of the Palaeotethys Ocean.

DeCompactionTool: Software for subsidence analysis including statistical error quantification

Subsidence analysis based on decompaction of the sedimentary record is a standard method for reconstructing the evolution of sedimentary basins. For such an analysis, data on strata thickness, lithology, age constraints, lithological properties, porosity, palaeobathymetry, sea-level changes and heat flux, amongst others, are required. The uncertainties associated with this wide range of input parameters have a major effect on the shape of the resulting subsidence curve, particularly because errors at successive points are not independent. The program DeCompactionTool (DCT) combines 1D-subsidence calculations, including backstripping, with error quantification, based on the principles of Monte Carlo simulation (MCS). In this, the range of possible input values (minimum, maximum, most likely number) is assigned to each of the parameters used. The parameter age has been implemented for the first time. A random number generator chooses values within the defined intervals and calculates results for every combination. The probability that a number is selected by the generator may follow a uniform distribution, a power distribution, a symmetric normal distribution or an asymmetric normal distribution. The results are mean values with two extreme values quantifying the error range. To demonstrate the program's capabilities, an example of subsidence calculation based on well-data from the Vienna Basin is presented.

Tectonic control on the architecture of a Miocene carbonate ramp in the Central Apennines (Italy): Insights from facies and backstripping analyses

Analyses of facies associations and biotic assemblages integrated with backstripping analysis are presented to improve understanding of the development of a shallow water Miocene carbonate ramp in the Central Apennines (Italy), with special reference to the relationships between tectonic subsidence and the internal architecture of the ramp. Subsidence curves were calculated for six measured sections located in different sectors of the platform. Dating is derived from Sr isotope analyses (from previous studies) and regional correlations. Corrections for eustasy and paleobathymetry were deduced from biota and facies analyses. The subsidence curves show rates that vary both in space and time. By analysing the vertical motions in different sectors of the ramp over a fixed time span (Burdigalian to Tortonian), it was possible to evaluate the control on platform architecture exerted by tectonically induced changes in sea-floor bathymetry and highlight the effects of tectonic migration. Most analysed sites experienced a short period of tectonic uplift or stability followed by a period of slow subsidence. This preceded increased subsidence which resulted in drowning of the shallow-water carbonate platform. The stability/uplift is progressively younger towards the north-eastern sectors that correspond to progressively more external zones of the foreland relative to the Apenninic orogenic belt. The subsequent drowning is related to the diachronous down-flexure of the Adriatic lithosphere due to its eastward retreating subduction under the Apennines. The small magnitude of the uplift suggests that the formation of a foreland bulge due to subduction-related flexure of the Adriatic plate was probably not the responsible mechanism. Hence, this uplift is related to the development of proto-thrusts or to the propagation of compressive stresses in the foreland. These vertical motions influenced the geometry of the platform during the 17.5–16 Ma stage. During this period the platform was characterised by exceptional progradation of the bryomol-dominated proximal outer ramp facies belt. This rapid spreading may be induced by the combined effect of increased eutrophic conditions and a contemporaneous decrease in the sea-floor bathymetry resulting from the tectonic uplift. From the Tortonian onwards, when the platform became involved in the eastward migrating foredeep system, the tectonic subsidence curve records a short period of fast tectonic subsidence rates followed by a period of slow subsidence or slight uplift during basin drowning and infilling, respectively.

Mesozoic transtensional basin history of the Eastern Cordillera, Colombian Andes: Inferences from tectonic models

Backstripping analysis and forward modeling of 162 stratigraphic columns and wells of the Eastern Cordillera (EC), Llanos, and Magdalena Valley shows the Mesozoic Colombian Basin is marked by five lithosphere stretching pulses. Three stretching events are suggested during the Triassic–Jurassic, but additional biostratigraphical data are needed to identify them precisely. The spatial distribution of lithosphere stretching values suggests that small, narrow (<150 km), asymmetric graben basins were located on opposite sides of the paleo-Magdalena–La Salina fault system, which probably was active as a master transtensional or strike-slip fault system. Paleomagnetic data suggesting a significant (at least 10°) northward translation of terranes west of the Bucaramanga fault during the Early Jurassic, and the similarity between the early Mesozoic stratigraphy and tectonic setting of the Payandé terrane with the Late Permian transtensional rift of the Eastern Cordillera of Peru and Bolivia indicate that the areas were adjacent in early Mesozoic times. New geochronological, petrological, stratigraphic, and structural research is necessary to test this hypothesis, including additional paleomagnetic investigations to determine the paleolatitudinal position of the Central Cordillera and adjacent tectonic terranes during the Triassic–Jurassic. Two stretching events are suggested for the Cretaceous: Berriasian–Hauterivian (144–127 Ma) and Aptian–Albian (121–102 Ma). During the Early Cretaceous, marine facies accumulated on an extensional basin system. Shallow-marine sedimentation ended at the end of the Cretaceous due to the accretion of oceanic terranes of the Western Cordillera. In Berriasian–Hauterivian subsidence curves, isopach maps and paleomagnetic data imply a (>180 km) wide, asymmetrical, transtensional half-rift basin existed, divided by the Santander Floresta horst or high. The location of small mafic intrusions coincides with areas of thin crust (crustal stretching factors >1.4) and maximum stretching of the subcrustal lithosphere. During the Aptian–early Albian, the basin extended toward the south in the Upper Magdalena Valley. Differences between crustal and subcrustal stretching values suggest some lowermost crustal decoupling between the crust and subcrustal lithosphere or that increased thermal thinning affected the mantle lithosphere. Late Cretaceous subsidence was mainly driven by lithospheric cooling, water loading, and horizontal compressional stresses generated by collision of oceanic terranes in western Colombia. Triassic transtensional basins were narrow and increased in width during the Triassic and Jurassic. Cretaceous transtensional basins were wider than Triassic–Jurassic basins. During the Mesozoic, the strike-slip component gradually decreased at the expense of the increase of the extensional component, as suggested by paleomagnetic data and lithosphere stretching values. During the Berriasian–Hauterivian, the eastern side of the extensional basin may have developed by reactivation of an older Paleozoic rift system associated with the Guaicáramo fault system. The western side probably developed through reactivation of an earlier normal fault system developed during Triassic–Jurassic transtension. Alternatively, the eastern and western margins of the graben may have developed along older strike-slip faults, which were the boundaries of the accretion of terranes west of the Guaicáramo fault during the Late Triassic and Jurassic. The increasing width of the graben system likely was the result of progressive tensional reactivation of preexisting upper crustal weakness zones. Lateral changes in Mesozoic sediment thickness suggest the reverse or thrust faults that now define the eastern and western borders of the EC were originally normal faults with a strike-slip component that inverted during the Cenozoic Andean orogeny. Thus, the Guaicáramo, La Salina, Bitúima, Magdalena, and Boyacá originally were transtensional faults. Their oblique orientation relative to the Mesozoic magmatic arc of the Central Cordillera may be the result of oblique slip extension during the Cretaceous or inherited from the pre-Mesozoic structural grains. However, not all Mesozoic transtensional faults were inverted.

The relationships between tectonics and sedimentation in the Late Cretaceous series of the eastern Atlasic Domain (Algeria)

Our study of the Late Cretaceous series in the eastern Atlasic Domain of Algeria is intended to show the geometry of the sedimentary deposits and the sequential palaeogeographic evolution of the region’s basins. The Late Cretaceous series consist of four transgressive–regressive sedimentary megasequences corresponding to 2nd order cycles, noted as I–IV. Each megasequence is made up of three or four sequences that have been correlated with 3rd order cycles. The beginning of megasequences I and II mark a rapid tectonic deepening concomitant with an acceleration of sea-level rise which allowed the deposition of pelagic sediments at their initiation, during the latest Albian and early Turonian times. This tectonism reflects the reactivation of basement faults resulting in extension and block-tilting. The succeeding sequences, showing alternating marls and carbonate beds with benthic facies were deposited in a homoclinal ramp and are indicative of a gradual development of shallow marine conditions. In the megasequences III (Coniacian to Santonian) and IV (Campanian to Maastrichtian) the sequences were wholly deposited on a homoclinal ramp. The major basement faults are NE-SW trending transtensional strike-slip faults, which delimit the margins of the basins, and WNW-ESE and NW-SE trending normal faults that led to block tilting during the Late Cretaceous. Both types of faults strongly influenced palaeogeography and sedimentation. The evolution of the subsidence through the Late Cretaceous shows a progressive sagging of these basins, interrupted by short phases of extension highlighted by accelerations on the subsidence curves. These phases constitute, after the Jurassic extension, a new extensional episode occurring during the latest Albian and Early Turonian, which led to a tilting of basement blocks. The Late Cretaceous extension phases reflect reorientations of the stress in the African plate, during its northeastwardly directed drift, and rifting processes on its northeastern margin. A first compressive phase, which was relatively localized, is registered at the end of the Maastrichtian, leading to palaeogeographic reorganization of the Atlasic basins.

Plate tectonics and basin subsidence history

Research Article| January 01, 2009 Plate tectonics and basin subsidence history Xiangyang Xie; Xiangyang Xie † 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA *Present address: Institute for Geophysics, University of Texas at Austin, 10100 Burnet Road Building 196, Austin, Texas 78758, USA. †E-mail: xiangyang@utig.ig.utexas.edu Search for other works by this author on: GSW Google Scholar Paul L. Heller Paul L. Heller 1Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2009) 121 (1-2): 55–64. https://doi.org/10.1130/B26398.1 Article history received: 31 Dec 2007 rev-recd: 15 Jun 2008 accepted: 18 Jun 2008 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Xiangyang Xie, Paul L. Heller; Plate tectonics and basin subsidence history. GSA Bulletin 2009;; 121 (1-2): 55–64. doi: https://doi.org/10.1130/B26398.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Tectonic setting exerts first-order control on basin formation as reflected in basin subsidence history. While our approach ignores the effects of flexural loading and eustatic sea-level change, consistency of backstripped subsidence histories (i.e., with local loading effects of sediment removed) suggests consistent tectonic driving mechanisms in each tectonic setting, with the possible exception of forearc basins.Based on published subsidence curves and open-file stratigraphic data, we show the subsidence characteristics of passive margins, strike-slip basins, intracontinental basins, foreland basins, and forearc basins. Passive margin subsidence is characterized by two stages, rapid initial, synrift subsidence and slow post-rift thermal subsidence, with increasing subsidence rates toward the adjacent ocean basin. Subsidence of intracontinental basins is similar in magnitude to that seen in passive margin settings, but the former is generally slower, longer lived, and lacks initial subsidence. Long-lived subsidence for many intracontinental basins is consistent with cooling following thermal perturbation of thick lithosphere found beneath old parts of continents. Basins associated with strike-slip faults are usually short lived with very rapid subsidence. Changes in local stress regimes as strike-slip faults evolve, and migrate over time, coupled with three-dimensional heat loss in these small basins likely explain this subsidence pattern. Foreland basin subsidence rates reflect the flexural response to episodic thrust loading. Resultant subsidence curves are punctuated by convex-up (accelerating) segments. Forearc basins have the least consistent subsidence patterns. Subsidence histories of these basins are complex and may reflect multiple driving mechanisms of subsidence in forearc settings.Second-order deviations in subsidence suggest reactivation or superimposed tectonic events in many basin settings. The effects of eustatic sea-level change may also explain some deviations in curves. For many of these settings, subsidence histories are sufficiently distinctive to be used to help determine tectonic setting of ancient basin deposits. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.