Tectonic Subsidence Patterns Research Articles

Tectonic subsidence patterns in the multi-stage extension systems: Insights from quantitative backstripping analysis and modelling of the margins of Dahra and Beda Platforms, Sirt Basin, Libya

Quantitative analysis of tectonic subsidence patterns of 13 wells from the margins of Dahra and Beda Platforms provides new insights into the development of two major fault blocks in a tectonically active region of the western Sirt Basin. Backstripped subsidence curves and tectonic subsidence rates reveal four different tectonic stages (I–IV) from the Late Cretaceous to Middle Eocene. Continental rifting was initiated during the Cenomanian-Turonian period. Model curves predict maximum crustal stretching factor is 1.11 for this stage. From Campanian to Maastrichtian an exponentially decaying subsidence behaviour is described in the backstripped curves, indicating a stage of thermal sagging associated with the widespread distribution of Maastrichtian shallow-marine sediments according to a regional transect that crosses the margins of both platforms. Rapid short-term subsidence alterations from thermally driven long-term sagging, were recognised during the Palaeocene. The stretching factors for this third stage are about 1.3 for the southeastern margin of the Dahra Platform and >1.21 for the Amin High. The termination of subsidence during the Eocene is defined as a thermal subsidence stage. The stretching factor possibly decreased to an average 1.18 on both platforms. However, well data indicate that the Middle Eocene sediments exposed along the margins of Dahra and Beda Platforms, indicating that the sedimentary rocks of the post-Eocene succession, were whether not deposited or were mostly removed by erosion in the study area, due to a subsequent regional phase of differential uplift during the Oligocene-Miocene. This uplift phase is clearly distinguished on the tectonic subsidence curve from the Middle Maradah Trough.

Estimating stratal completeness of carbonate deposition via process-based stratigraphic forward modeling

Hiatuses are ubiquitous in stratigraphic records at various temporal scales, but they cannot be easily identified and quantified owing to the lack of adequate methods in determining the duration of hiatuses or stratal completeness. Here a process-based stratigraphic forward modeling (SFM) approach was used to effectively estimate the completeness of carbonate strata in three dimensions and at basin-scale. By using information derived from both spatial and temporal domains in the SFM outputs for five grid locations (pseudo wells) under different depositional settings, we were able to delineate basin-wide hiatuses of various temporal scales and determine their durations and stratal completeness quantitatively. The stratal completeness appears to be controlled by sea level changes, depositional environments, carbonate growth rates and tectonic subsidence patterns in various ways.

Spatio-temporal evolution of strain accumulation derived from multi-scale observations of Late Jurassic rifting in the northern North Sea: A critical test of models for lithospheric extension

We integrate observations of lithospheric extension over a wide range of spatial and temporal scales within the northern North Sea basin and critically review the extent to which existing theories of lithospheric deformation can account for these observations. Data obtained through a prolonged period of hydrocarbon exploration and production has yielded a dense and diverse data set over the entire Viking Graben and its flanking platform areas. These data show how syn-rift accommodation within the basin varied in space and time with sub-kilometer-scale spatial resolution and a temporal resolution of 2–3 Myr. Regional interpretations of 2D seismic reflection, refraction and gravity data for this area have also been published and provide an image of total basin wide stretching for the entire crust. These image data are combined with published strain rate inversion results obtained from tectonic subsidence patterns to constrain the spatio-temporal evolution of strain accumulation throughout the lithosphere during the 40 Myr (170–130 Ma) period of Late Jurassic extension across this basin. For the first 25–30 Myr, strain localisation dominated basin development with strain rates at the eventual rift axis increasing while strain rates over the flanking areas declined. As strain rates across the whole basin were consistently very low (< 3 × 10 - 16 s - l ), thermally induced strength loss cannot explain this phenomenon. The strain localisation is manifest in the near-surface by a systematic migration of fault activity. The pattern and timing of this migration are inconsistent with flexural bending stresses exerting an underlying control, especially when estimates of flexural rigidity for this area are considered. The best explanation for what is observed in this time period is a coupling between near-surface strain localisation, driven by brittle (or plastic) failure, and the evolving thermal structure of the lithosphere. We demonstrate this process using a continuum mechanics model for normal fault growth that incorporates the strain rate-dependence of frictional strength observed in laboratory studies. During the final 10 Myr of basin formation, strain accumulation was focused within the axis and strain rates declined rapidly. Replacement of weak crust by stronger mantle material plus crustal buoyancy forces can adequately explain this decline.

Fault activity and sedimentation in a marine rift basin (Upper Jurassic, Wessex Basin, UK)

Shallow‐marine carbonates and siliciclastics of the Corallian Formation (Oxfordian–Early Kimmeridgian) accumulated on and around an intrabasinal high in the extensional Wessex Basin. Four sequences can be recognized. Sequences 1–3 accumulated under conditions of thermal subsidence on a ramp‐type margin. The initial sequence was siliciclastic. Highstand sedimentation in this sequence reflects the supply of sandy mud from a recently emergent intrabasinal high. During transgression and regression this muddy sediment was reworked into cleaner sandstone bodies by landward or basinward migrating zones of shoreface erosion. Carbonates dominate the second and third sequences when rising sea level increased the area of carbonate production and reduced siliciclastic input. Oolite bodies developed as both transgressive barrier bars and highstand sheets. The forth sequence formed during the activation of major normal faults. This caused the breakdown of the ramp system, and patterns of sediment accumulation were strongly controlled by tectonic subsidence patterns.

Late Vendian–Early Palæozoic tectonic evolution of the Baltic Basin: regional tectonic implications from subsidence analysis

Subsidence analysis was performed on 43 boreholes penetrating the Upper Vendian–Lower Palaeozoic sedimentary succession of the Baltic Basin. The results were related to lithofacial and structural data to elucidate subsidence mechanisms and the regional tectonic setting of basin development. Tectonic subsidence patterns are consistent throughout the basin for the time period studied. An extensional tectonic subsidence event, possibly of two phases, is indicated from the Late Vendian to the beginning of the Middle Cambrian. This event is seen in the southwestern part of the Baltic Basin (Peri-Tornquist zone) until the earliest Cambrian after which it is also observed in the SW–NE-trending Baltic Depression part of the basin. Basin development during this time is interpreted as recording the latest stages of break-up of the Precambrian super-continent Rodinia and ultimately the formation of the Tornquist Sea. The late Middle Cambrian to Middle Ordovician tectonic subsidence pattern of the Baltic Basin is characteristic of post-rift thermal subsidence of the newly formed passive continental margin of Baltica, developed along its southwestern edge. A gradual increase in subsidence rate is observed from the (Middle?) Late Ordovician and throughout the Silurian (particularly for Ludlow and Pridoli times) creating subsidence curves with convex shapes typical of foreland basin development. The rate of Late Silurian tectonic subsidence increases significantly towards the southwest margin of the Baltic basin, adjacent to the present location of the North German–Polish Caledonides. The Baltic Basin therefore appears to have developed primarily as a flexural foreland basin during Silurian oblique collision of Baltica and Eastern Avalonia. A foreland setting is supported by the influx of distal turbidites into the basin from southwest sources in the Late Silurian. Compressional deformation structures of Early Devonian (Lochkovian) age are seen in seismic sections in the central part of the Baltic Basin (Lithuania). These, together with a change in subsidence pattern, mark the end of the Caledonian stage of basin development of the Baltic Basin.

Early Cretaceous sedimentary and tectonic development of the Dauphinois Basin (SE France)

A subsidence analysis is applied to two Valanginian-Albian composite columns of the Dauphinois Basin (SE France); one for the deeper part of the Dauphinois Basin (Vocontian Basin) and one for its marginal setting (Vercors Area). Within the Valanginian-Albian interval of both sequences, three phases of subsidence are recognized: (1) a Valanginian-Hauterivian phase characterized by relatively uniform tectonic subsidence patterns; (2) a Barremian-Gargasian phase characterized by profound shifts in subsidence; (3) a Clansayesian-Albian phase characterized by relatively small rates of tectonic subsidence or uplift. The Barremian-Gargasian phase can be further subdivided in three subphases viz. (1) uplift during the Early Barremian; (2) subsidence during the Late Barremian to early Bedoulian; (3) virtually no subsidence of the Vercors Area and subsidence of the Vocontian Basin during the late Bedoulian to Gargasian. This Barremian-Gargasian phase is related to compressional stress built up as a result of the changing tectonic regime of the Piemonte-Ligurian Ocean from extension to compression. As a consequence the Barremian-Gargasian tectonic phase forced the onset, progradation and eventual disappearance of extensive carbonate platforms at the margin of the Dauphinois Basin. It implies that these carbonate platforms document the very first sedimentary response to the changing tectonic regime. Vertical motions induced by such a changing tectonic regime in particular determine the regional sea-level curves established for these carbonate platforms and related basinal facies rather than global sea-level changes.

Application of organic facies studies to sedimentary basin analysis: a case study from the Yitong Graben, China

An organic facies is defined in this paper as a mappable stratigraphic unit containing organic matter (OM) of a particular genetic type in certain abundance. Several concepts concerning organic facies are proposed, and their significance in basin analysis is discussed in detail. A combined sedimentological and organic geochemical investigation has been carried out in the Yitong Graben and four organic facies and one organic parafacies have been recognized. Distinct Organic Basin-Fill Sequences (OBFS) and Organic Facies Association (OFA) were developed in different sub-units of this graben, which indicates that the Yitong Graben had undergone two tectonic subsidence cycles. Such tectonic subsidence patterns could not have been found out without detailed organic facies analysis, confirming that organic facies, especially OBFS and OFA study, is a very useful tool, not only for prediction and three-dimensional mapping of petroleum source rocks, but also for sedimentary basin analysis.

Depositional System Evolution within Paleogene Supply-Dominated Genetic Stratigraphic Sequences, Northwest Gulf of Mexico Basin

The Paleogene fill of the northwest Gulf Coast basin consists of eight genetic stratigraphic sequences that record a succession of major and minor depositional episodes. The major sequences were characterized by very high rates of deposition during their periods of maximum continental-margin outbuilding; in contrast, periods of retrogressive deposition and continental-margin flooding were times of decreasing and minimal sediment input and accumulation. Each sequence consists of a unique paleogeographic array of six generic depositional systems: fluvial, streamplain, delta, shore-zone, shelf, and slope. Paleogeographic reorganization of the array of depositional systems composing each sequence occurs during the periods of transgressive flooding. During each episode, the depositional systems evolved in response to the changing balance among sediment supply, marine energy flux, potential for gravity redistribution, and patterns of subsidence. Calculation of sediment accumulation rates along profiles through each of four subbasins shows that regionally correlative 5- to 10-fold changes of average rate occurred at time spans of 1 to 3 Ma. The component depositional systems within sequences, such as the Oligocene Frio, reflect this recurrent motif of accelerating supply and outbuilding, followed by waning sediment input and retrogradation. Progradational shelf and shelf-edge deltas as well as retrogradational deltas each display distinctive patternsmore » of depositional geometry and facies development. Shorezone and shelf systems evolve from progradational to retrogressive/transgressive types. Fluvial systems respond to changing coastal-plain width, base-level change, and load-induced tectonic subsidence patterns.« less

Quantitative Paleobathymetric Analysis from Subsidence Data: Example from Middle Ordovician of Michigan Basin: ABSTRACT

Quantitative paleobathymetry is difficult to determine for any rock sequence with a significant subtidal component. Water depth estimates are traditionally obtained from detailed sedimentology and paleontology, but this type of data is seldom available in subsurface work. Further, a good geological data base may be inconclusive for paleobathymetry in subtidal or substorm-wave base environments. More accurate facies prediction would be possible if paleobathymetry could be determined from the conventional subsurface data normally available to explorationists. Subsidence analysis of sedimentary basins has the potential to provide precise paleobathymetric estimates for a variety of depositional settings. This technique is illustrated using the Middle Ordovician carbonates of the Michigan basin. Tectonic subsidence patterns established from stratigraphic and subsidence modeling of the Lower-Middle Ordovician Prairie du Chien Group in Michigan are projected forward through the Middle Ordovician. Isopach thicknesses of the Black River and Trenton carbonates are superimposed on the tectonic subsidence patterns to provide a quantitative basin-fill model. The model paleobathymetry is then compared with core data from exploration wells to evaluate the model facies interpretation. An excellent fit is achieved for the shallow to deep subtidal platform and basinal Trenton carbonates. This technique allows paleobathymetry to be calculated in many basins wheremore » tectonic subsidence patterns can be accurately modeled.« less