Variations In Tectonic Subsidence Research Articles

Tectonic Subsidence and Its Response to Geological Evolution in the Xisha Area, South China Sea

The evolution and mechanisms of tectonic subsidence in the Xisha area are poorly investigated, especially the spatiotemporal distribution features and reasons for the variations in tectonic subsidence. In this study, multi-channel seismic data and stratigraphic and lithologic features of wells are used to examine tectonic subsidence in the Xisha area from the Paleogene to Quaternary. The largest tectonic subsidence in the Xisha area is located in the Changchang Depression, with a maximum subsidence of 5.4 km, while the smallest tectonic subsidence is located on the Guangle Uplift and Xisha Uplift, which are close to 1.0 km and 1.5 km, respectively. Two rapid tectonic subsidence phases were mainly in the Oligocene, and from Middle to Late Miocene, with maximum subsidence rates of 0.45 m/ky and 0.32 m/ky, respectively. Five phases for the tectonic subsidence are proposed since the Paleogene based on our data. (1) The slow subsidence phase during the Eocene (53.5–32 Ma) was due to the transchronicity of the basement in the pro-rifted stage. (2) The rapid subsidence phase was common in the south and north margins of Qiongdongnan Basin, because of the faults triggered by the inherited stretched and thinned of crust in the Oligocene from 32 to 23.3 Ma. (3) The interim phase followed the rapid subsidence phase was in the Early Miocene (23.3–15.5 Ma) and marked the end of the rifted stage. (4) The accelerated rise phase started from the Middle Miocene (15.5 Ma) to the Late Miocene (5.5 Ma), and the reversal of the Red River Fault Zone may be tied to the acceleration of the tectonic subsidence. (5) The transitional phase started in the Pliocene (5.5 Ma) and lasts to the present. As the Red River Fault Zone changed from sinistral to dextral movement, the stress field of the study area has changed. Our results are helpful to better understand the spatiotemporal coupling relationship between tectonic subsidence and regional geological evolution in the Xisha area, South China Sea.

NUMERICAL MODELLING OF THE AUSTRALIA – ANTARCTICA CONJUGATE MARGINS USING THE GALO SYSTEM: PART 2. THERMAL AND MATURATION HISTORY OF THE MAWSON SEA BASIN, EAST ANTARCTICA

The thermal evolution of the Mawson Sea Basin, offshore East Antarctic, was modelled using the GALO basin modelling programme. As there exist no deep temperature or vitrinite reflectance data for the Mawson Sea Basin, the simulation was based on a limited nonthermal database. This includes the present‐day sedimentary section along a multichannel seismic profile which crosses the western part of the Mawson Sea along with geophysical assessments of the depth of the Moho. An analysis of the variations in tectonic subsidence was used to estimate the duration and magnitude of thermal activation or stretching of the lithosphere. This analysis suggested that a proportion of the lithospheric stretching took place before the start of synrift sediment deposition at about 160 Ma (Late Jurassic). This pre‐sedimentation lithospheric stretching has been ignored in previous studies, resulting in significant underestimation of the total stretching which has occurred. The analysis also suggests that the thermal maturity of Lower Jurassic potential source rocks along the profile may reach and even exceed the onset of the oil generation window, whereas source rocks in less deeply buried parts of the profile are less mature. In general, the results of the modelling indicate that the Mawson Sea Basin is a promising area for future oil and gas exploration.

The non-uniformity of fossil preservation.

The fossil record provides the primary source of data for calibrating the origin of clades. Although minimum ages of clades are given by the oldest preserved fossil, these underestimate the true age, which must be bracketed by probabilistic methods based on multiple fossil occurrences. Although most of these methods assume uniform preservation rates, this assumption is unsupported over geological timescales. On geologically long timescales (more than 10 Myr), the origin and cessation of sedimentary basins, and long-term variations in tectonic subsidence, eustatic sea level and sedimentation rate control the availability of depositional facies that preserve the environments in which species lived. The loss of doomed sediments, those with a low probability of preservation, imparts a secular trend to fossil preservation. As a result, the fossil record is spatially and temporally non-uniform. Models of fossil preservation should reflect this non-uniformity by using empirical estimates of fossil preservation that are spatially and temporally partitioned, or by using indirect proxies of fossil preservation. Geologically, realistic models of preservation will provide substantially more reliable estimates of the origination of clades.This article is part of the themed issue 'Dating species divergences using rocks and clocks'.

Change in the degree of catagenesis and hydrocarbon generation in the sedimentary rocks of the South Sumatra Basin, Indonesia

Temperature and catagenetic history of the South Sumatra Basin in Indonesia is considered by the example of the sedimentary sequence of the Limau graben during its subsidence from the Oligocene to the present time. GALO system for basin modeling was applied for numerical reconstruction of six sedimentary successions in the area of holes Pandan-81, Petanang-1, Tepus-2, Tepus-1, Gambir-1, and Lembak-8 located along the profile cutting across the Limau graben. Modeling suggests significant cooling of the basemen for the last 15–20 Ma from the high initial heat flow of 105 mW/m2, which is typical of axial zones of continental rifting, and significant heating of the basin lithosphere during the last 2–5 Ma. Examination of variations in tectonic subsidence of the basin confirms the possible extension of the lithosphere in the Oligocene-Miocene with an amplitude β increasing from 1.12 on the flanks of the Limau graben (Hole Lembak-8) to 1.32 in the central part of the graben (Tepus-1 and 2), Tectonic analysis indicates also the notable thermal activation of the basin in the Pliocene, Pleistocene, and Holocene. This activation is consistent with the high temperature gradient typical of the present-day sedimentary cover of the basin. Numerical modeling of the evolution of the organic matter maturity and hydrocarbon generation by main source formations of the basin confirms good prospects of the inferred source formations (Lemat, Talang Akar, and Gumai) of the South Sumatra basin for the generation of liquid hydrocarbons (HC) in the Limau Graben. It is also demonstrated that the source rocks of the Lemat Formation are ore-generating rocks in the main part of the Limau graben and are gas-generating rocks only in the deepest portions of the graben. The rocks at the base and roof of the Talang Akar Formation could be considered as highly oil-generating rocks, probably except for the upper horizons of the formation in the shallowest portions of the graben (Hole Lembak-8). Oil generation reached peak in the last 5–10 Ma. Modeling showed that intense oil generation by the Gumai Formation may be significant in the most part of the Limau graben and negligible only in the distant flanks of the graben (Hole Lembak-8).

Thermal regime and amplitude of lithosphere extension in the Sirte basin, Libya: Numerical estimates in the plane basin modeling system

The GALO basin modeling system has been applied for the numerical reconstruction of the subsidence history, variations in temperature, and maturity of the organic matter of sedimentary rocks composing the main tectonic structures of Sirte Basin. The reconstruction was carried out for eight sedimentary cross sections along the profile stretching from the Cyrenaica Platform on the eastern coast of the basin to the Hun Graben on its western wall. The interval of depths for temperature calculations included the sedimentary layer, consolidated crust, and the mantle to below 100 km. This extensive depth coverage made it possible to use the analysis of the variations in the tectonic subsidence of the basin for estimating the amplitudes and duration of the events of thermal activation and extension of the lithosphere of the basin in the history of its evolution. The modeling suggests that thermal activations of the lithosphere in the Albian-Cenomanian and Oligocene-Pleistocene are common for all tectonic structures of the Sirte Basin and the Cyrenaica Platform and that a relatively high temperature regime is also characteristic of the present-day conditions in the Sirte Basin and Cyrenaica Platform. To a considerable extent, such a regime is caused by the thermal activation of the lithosphere of the basin during the last 10 Ma. The intensity of this activation is highest in the western part of the basin, where it is accompanied by the highest erosion amplitudes. The analysis of the variations in tectonic subsidence of the basement also suggests a series of intervals of lithospheric extension, which accounts for the stages of relatively rapid subsidence of the basin. Two intervals of significant extension of the lithosphere in the Upper Cretaceous and Paleocene are common for all areas within the basin. Here, the total amplitudes of the crustal extension attained 1.5 in the central part of the Sirte Basin (the Ajdabiya and Maradah troughs and Zelten and Dahra platforms), was equal to 1.3 in the Hameimat and Zallah troughs, and were minimal (1.11–1.17) in the periphery of the basin (within the Hun Graben and Cyrenaica Platform).

Firmground ichnofacies recording high-frequency marine flooding events (Langhian transgression, Vallés-Penedés Basin, Spain)

The decapod burrow Spongeliomorpha sudolica occurs associated with transgressive firmgrounds in the transition between Aragonian continental red beds and Langhian marine units in some of the inner sectors of the Valles-Penedes Basin. This ichnospecies designates branching burrow systems with scratch marks in the walls produced by marine crustacean decapods. The occurrence of Spongeliomorpha represents an example of the Glossifungites ichnofacies. The several horizons where the traces are found are intercalated with continental red beds a few meters below the main transgressive surface, which is overlain by fossiliferous marine sandstones. The Spongeliomorpha-bioturbated layers record short, high frequency marine flooding surfaces that may be related either to actual sea-level changes or to variations in tectonic subsidence or sediment input. In any case, these flooding events punctuated the early phases of the Langhian transgression in the basin.

Quantitative analysis of net‐transgressive shoreline trajectories and stratigraphic architectures: mid‐to‐late Jurassic of the North Sea rift basin

ABSTRACTThis paper outlines the use of the shoreline trajectory concept to understand the controls on net‐transgressive reservoir distribution and architecture in the highly productive Middle and Late Jurassic plays in the North Sea. Two broad groups of regressive–transgressive sandstone tongue are identified, with distinctive geometries, architectures and values of net‐transgressive shoreline trajectory defined by the stacking arrangement of multiple tongues. Shoreface tongues were supplied by longshore‐transported, marine‐reworked sediment and are associated with low‐to‐moderate transgressive trajectories (typically <0.2°). These tongues have variable dip extents that decrease weakly as the angle of shoreline trajectory increases, relatively small thicknesses that increase weakly with the angle of transgressive trajectory, and partial or no overlap with underlying and overlying tongues down depositional dip. Deltaic‐to‐estuarine tongues were supplied directly by fluvial sediment and are associated with moderate‐to‐very high transgressive trajectories (typically >0.1°). These tongues have small dip extents, variable thicknesses that increase weakly with the angle of transgressive trajectory, and partial to full overlap with underlying and overlying tongues down depositional dip, although vertically stacked tongues are separated by thin mudstones over much of their extents. There is some overlap in geometry and stacking arrangement of these two groups of sandstone tongues. The temporal and spatial distribution of shoreface and deltaic‐to‐estuarine sandstone tongues reflects linked variations in tectonic subsidence and sediment routing within the evolving rift basin. Deltaic‐to‐estuarine tongues with moderate‐to‐very high transgressive trajectories were developed in rapidly subsiding fault‐bounded depocentres supplied directly by fluvial sediment, whereas shoreface tongues with low‐to‐moderate transgressive trajectories characterised slowly subsiding fault terraces and platforms that were distant from fluvial sediment supply routes. Thus, the evolving structural template of the mid‐to‐late Jurassic North Sea rift can be used to predict reservoir distribution and architecture via analysis of shoreline trajectory.

Holocene stratigraphy and depositional architecture of eastern Pozzuoli Bay (eastern Tyrrhenian Sea margin, Italy): the influence of tectonics and wave-induced currents

Pozzuoli Bay is located in the eastern Tyrrhenian Sea and is an area characterized by active tectonics and volcanism. On the basis of high-resolution seismic reflection profiles, it was possible to reconstruct the stratigraphy and three-dimensional stratal architecture of the Holocene succession. Two volcanic units and three sedimentary ones were recognized. The basal unit NC consists of volcanic deposits and dates at 10.0–8.0 ka B.P. It is followed by unit D, deposited between 8.0 and 5.5 ka B.P., which displays a backstepping configuration in the central area and a forestepping configuration in the northern area. Unit D is covered by the progradational unit B which is elongated in a SE-NW direction. Unit C is interbedded between unit B and is interpreted as the volcanic products of the Agnano-Monte Spina eruption which occurred 4.4 B.P. Unit A, the youngest unit, shows a progradational configuration and is elongated in a E-W direction. The sedimentary units record the transgressive and highstand of the eustatic sea level. They show vertical and lateral variations in the depositional architecture. Changes in the stacking pattern record variations in tectonic subsidence and hydrodynamic regimes.

Sequence stratigraphy and sea-level history of Oligocene strata of the northern Aral Sea region (Kazakhstan): Implications for glacioeustatic reconstructions

We have applied sequence stratigraphic techniques to the upper Eocene to Oligocene strata of the region north of the Aral Sea and northern Usturt Plateau (western Kazakhstan) and compared the inferred sea-level history with other records derived from different parts of the world. During late Eocene to early Miocene time, the entire region of study was within the northeastern part of the Paratethys sea. Clastic and carbonate deposition occurred in a range of environments from fluvial and lacustrine in coastal plains (northern Priaral) to relatively deep marine in the north Usturt trough. Stratal geometries and sedimentation rates indicate that the deposition of the northern Priaral sections occurred under tectonically quiet conditions, whereas noticeable syndepositional subsidence took place in the central part of the north Usturt trough. The same Oligocene sequences have been identified in these areas despite significant spatial variations in tectonic subsidence and sediment supply rates. We therefore conclude that eustasy played a major role in controlling sedimentation in the region of study, especially in the northern Priaral. Through sequence stratigraphic analysis, we identified four sequence boundaries resulting from regional sea-level falls. Two major sea-level falls are identified in the earliest Oligocene and at the early–late Oligocene boundary, and two smaller sea-level falls took place in late early Oligocene and latest Oligocene time. Each of these events can be correlated to peaks in the global δ 18 O record. In addition, paleoclimatic data from the region indicate that regional periods of cooling are coincident with the intervals of inferred sea-level falls. We therefore conclude that global glacioeustasy represents the main controlling force for the sea-level record we observe in the northern Priaral and north Usturt trough. This makes the region of study very useful for reconstruction of eustatic history for late Eocene–Oligocene time.

Temporal and spatial variations in tectonic subsidence in the Iberian Basin (eastern Spain): inferences from automated forward modelling of high-resolution stratigraphy (Permian–Mesozoic)

By subsidence analysis on eighteen surface sections and 6 wells, which cover large part of the Iberian Basin (E Spain) and which are marked by high-resolution stratigraphy of the Permian, Triassic, Jurassic and Cretaceous, we quantify the complex Permian and Mesozoic tectonic subsidence history of the basin. Backstripping analysis of the available high resolution and high surface density of the database allows to quantify spatial and temporal patterns of tectonically driven subsidence to a much higher degree than previous studies. The sections and wells have also been forward modelled with a new `automated' modelling technique, with unlimited number of stretching phases, in order to quantify variations in timing and magnitude of rifting. It is demonstrated that the tectonic subsidence history in the Iberian Basin is characterized by pulsating periods of stretching intermitted by periods of relative tectonic quiescence and thermal subsidence. The number of stretching phases appears to be much larger than found by earlier studies, showing a close match with stretching phases found in other parts of the Iberian Peninsula and allowing a clear correlation with discrete phases in the opening of the Tethys and Atlantic.

Tectonic variation in the Dniepr-Donets Basin from automated modelling of backstripped subsidence curves

The multiphase rift evolution of the Dniepr-Donets (DD) Basin is analysed by 1D backstripping and tectonic modelling of 66 stratigraphic sections, mostly from well data, distributed throughout the basin. The backstripping results illustrate strong temporal and lateral variations in tectonic subsidence. It is minor during an ‘inceptive’ pre-rift phase (Givetian-early Frasnian; 380.8-370 Ma) and does not show clear spatial correlations within the DD Basin framework. The main rift phase (Frasnian-Famennian; 370-362.5 Ma) corresponds to an acceleration in subsidence rates with tectonic subsidence up to 1500 m along the basin axis, displaying a slight increase from the northwest to the southeast. Strong lateral variations perpendicular to the basin axis reflect the effects of major basin border faults. A rift phase in the Visean (345-340 Ma) is characterised by relatively minor subsidence (up to about 500 m, except for some wells in the southeast), following a stage of extremely low rates of deposition in the earliest Carboniferous. The end of this rift phase can be taken to mark the onset of convex subsidence patterns in the later Carboniferous and Permian, typical in shape of post-rift thermal subsidence, but significantly increasing in magnitude from northwest to southeast in the basin. This trend shows no one-to-one relationship with Late Devonian syn-rift subsidence. The tectonic subsidence curves have been modelled using lithospheric stretching assumptions allowing different stretching factors for the crustal and sub-crustal lithosphere and the incorporation of finite and multiple stretching phases. A numerical technique was developed that automatically finds best fit stretching parameters for part or all of the tectonic subsidence data, given the specification of onset and duration of the various rifting events. Maps of the 1D modelling results display intrabasinal variations in terms of timing and magnitude of rifting. The results indicate that the observed spatial and temporal variations of tectonic subsidence in the DD Basin, specifically the increasing ratio of Carboniferous to Late Devonian subsidence from northwest to southeast, cannot be explained by either a uniform or depth-dependent stretching model adopting only a single Frasnian-Famennian rift phase. A two-phase model, in which a significant part of Carboniferous tectonic subsidence is related to Visean rift activity, strongly dominated by sub-crustal lithospheric attenuation, provides a satisfactory fit to the data although the tectonic implications of such a model are not easily reconcilable by independent constraints. A semi-quantitative investigation of the possible role of withdrawal of underlying Devonian salt during the Carboniferous to produce additional post-Devonian rift phase sediment accommodation space suggests that the effects of such a mechanism could be significant but that they are unlikely to preclude the necessity of the Visean rifting event to explain the Carboniferous basin evolution.

Spatial variations in tectonic subsidence during Tippecanoe I in the Michigan Basin

AbstractEpisodic tectonic subsidence can be seen from all backstripped wells from the Michigan Basin. These episodes are observed as periods of relatively rapid subsidence, contrasting with the relatively linear subsidence. Steady tectonic subsidence curves have been explained as being due to a decaying thermal anomaly in the underlying uplifted asthenosphere. Rapid episodes of subsidence require another explanation and prompt us to examine the tectonic history of surrounding areas for correlative events.The Taconic orogeny has been inferred to have influenced the development of the Michigian Basin. To analyse the extent of coupling between the Appalachian foredeep and the Michigan Basin we have used Ordovician formation tops correlated among 172 wells distributed over the whole of Michigan's Lower Peninsula. The spatial variation of tectonic subsidence over this interval supports this suggestion.Contour maps of decompacted sediment thickness and subsidence rate show substantial changes in form and magnitude during the development of the Tippecanoe I sequence. Early basin‐centred subsidence, during deposition of the Shakopee, St. Peter and Glenwood formations, was followed by tilting toward the Appalachian orogen concurrent with the early stages of the Taconic orogeny. This tilting continued, declining gradually, during deposition of the Black River, Trenton and Utica formations. Deposition during Tippecanoe I in the Michigan Basin may indicate modulation of continuing thermally driven subsidence by flexure of the lithosphere due to Taconic thrust loading, but the distinctive spatial distribution of subsidence over each interval may indicate that the important mechanisms making space available in the basin operated independently, not concurrently, invalidating the flexural model for the coupling and suggesting other regional, tectonic possibilities for models of basin initiation, evolution and filling.