Differential Subsidence Rates Research Articles

Luminescence dating of neotectonic activity on the southwestern coastal plain, Taiwan

The southwestern coastal plain of Taiwan is heavily urbanised, with a population of more than 6 million. The area is known to be subsiding, and the resulting basin is filled with thick fluvial deposits, of at least 200 m thickness. In the past century, three large earthquakes have occurred in the area; two caused surface ruptures, and resulted in large property loss and more than 2000 casualties. There is an urgent need for an understanding of the dynamics and recurrence intervals of this neotectonic activity, but little is known of the chronology of the late Pleistocene deposits. Recently more than 20 cores longer than 250 m were taken from the coastal plain as part of a large hydrogeological investigation, and basic data on lithology, hydrogeology and palaeobiology were collected. The base of these cores is beyond the 14C age limit, and so the application of luminescence dating to these sediments has been investigated. Optically stimulated luminescence methods have been applied to quartz sand-sized grains extracted from 29 samples. Dosimetry based on gamma spectrometry is also compared with ICP-MS and XRF analyses. In the age range up to ∼40 ka, radiocarbon ages are compared with the luminescence results, to give confidence that the initial bleaching of these sediments was sufficient. The luminescence ages are then discussed and differential rates of basin subsidence are deduced. It is clear from these data that the study area is tectonically active, and it may be that regions of similar subsidence rate correlate with identifiable geological structures.

Evidence of a tectonically driven sequence succession in the Middle Ordovician Taconic foredeep

The late Mohawkian through early Cincinnatian (Ordovician) Trenton Group carbonates and coeval siliciclastic succession of the central Mohawk Valley, New York State, were deposited in a foreland basin during the Taconic orogeny. Development of this facies mosaic records changes in stacking patterns that took place during episodic basin deepening and simultaneous carbonate-ramp shallowing along a ramp to basin transect located on the distal slope of the foreland basin. Differential rates of subsidence across the region produced accommodation rates that increased by an order of magnitude from west to east. High rates of siliciclastic sediment supply and even higher subsidence rates resulted in a thick, deep-water succession in the eastern part of the study region. The coeval Trenton Group succession in the west formed under conditions of moderate sediment supply and lower subsidence rate, resulting in a net shallowing-upward succession. These relationships suggest that active margin tectonism was the proximate cause of the Mohawk Valley facies architecture.

Structural controls on Quaternary depocentres within the Chotts Trough region of southern Tunisia

The Chotts Trough of southern Tunisia is a sedimentary basin that lies immediately north of the Saharan platform. Within this basin there exist several structurally controlled depocentres, which were created by Miocene to Early Pleistocene compression associated with the Atlas orogeny. One of these depocentres, the Chott Djerid basin, has an average Quaternary subsidence rate of 0.01–0.27 mm yr 1. Additional structural features within the Chotts Trough include east-west trending anticlines and synclines, at least some of which are controlled by east-west striking subsurface faults and northwest striking right-lateral strike-slip faults. Present movement along the northwest striking faults is a direct consequence of the Africa-Europe collision. The northwest striking faults and the east-west striking faults have cut the Chotts Trough into numerous smaller structural blocks, which experience different rates of subsidence. For the Quaternary, subsidence is caused by local extension associated with movement along the various strike-slip faults.

Cycle Stacking and Long-Term Sea-Level History in the Lower Cretaceous (Gavrovo Platform, NW Greece)

ABSTRACT The stacking pattern of peritidal shallowing-upward cycles of a continuously exposed Barremian to upper Albian section from an isolated carbonate platform in the Gavrovo-Tripolitza Zone (NW Greece) has been analyzed. The 541 m thick succession is located in an intraplatform setting with an overall mud-dominated facies development. It comprises 252 peritidal cycles, which show a systematic increase in cycle thickness from the Barremian to Albian. Comparison of the cycle stacking pattern of the section, which spans 35 m.y., and several published curves of long-term eustatic sea-level history show striking similarities. Comparison of cycle stacking pattern in Greece with a time-equivalent section measured near Potrero Garcia in Mexico suggests preservation of similar trends in Fischer pl ts in the two areas even though a difference in mean cycle thickness indicates different rates of subsidence in Greece and Mexico. This implies that the shallow-water carbonates of the Gavrovo platform are recording second-order eustatic sea-level variations. Closely spaced samples throughout the section allow evaluation of the degree of early diagenetic alteration of depositional facies within the shallowing-upward cycles. The degree of vadose diagenetic overprinting of intertidal and subtidal facies and multiple overprinting of individual cycles support a predominantly allocydic control of deposition by low-amplitude, high-frequency sea-level fluctuations during Early Cretaceous greenhouse climate. However, expected time gaps of different lengths in the succession during sea-level lows ands may bias the direct translation of cycle stacking pattern into third-order sea-level curves.

Comparison of Upper Cretaceous and Paleogene Depositional Sequences in the Eastern Gulf Coastal Plain: ABSTRACT

ABSTRACT Genetic depositional sequences representing durations of 0.5 to 11 million years, their component systems tracts and associated physical surfaces have been identified and mapped in Upper Cretaceous and Paleogene strata of the eastern Gulf Coastal Plain. The time duration in which these sequences were deposited appears to have little impact on sequence development in that the component systems tracts can be recognized in all of the sequences. However, the Upper Cretaceous sequences represent longer periods of time, resulted from slower sedimentation rates, experienced lower subsidence rates, and, generally, reflect more marine paleoenvironmental conditions. In the eastern Gulf Coastal Plain, the Late Cretaceous was characterized by warm climates, relatively high sea levels, and stable depositional conditions. Conversely, Paleogene sequences represent shorter durations of time and were greatly affected by differential rates of sedimentation and subsidence. In Paleogene sequences, usually only the transgressive systems tracts were characterized by marine depositional conditions. In the eastern Gulf Coastal Plain, the Paleogene was typified by widely fluctuating climates and dynamic changes in depositional conditions. Generally, Upper Cretaceous sequences span more than one biozone, whereas Paleogene sequences usually are restricted to a single biozone. The sedimentation rates and patterns, the stable depositional conditions, and high biologic productivity during the Late Cretaceous results in a stratigraphic section that is useful for high resolution sequence analysis. Thus, the diachroneity of sequence boundaries and first transgressive surfaces and the synchroneity of maximum flooding surfaces are more easily discerned by mapping Upper Cretaceous system tracts and associated physical surfaces in the eastern Gulf Coastal Plain. The study of Upper Cretaceous depositional sequences, therefore, is potentially more helpful in identifying the factors affecting global sea level change.

Pleistocene glaciolacustrine sedimentation in a tectonically active zone, Kleszczów Graben, central Poland

ABSTRACTThe Kleszczów Graben in central Poland was formed by late Oligocene to Middle Pleistocene extensional tectonics. During the Pleistocene it was infilled with a 200 m thick sequence of predominantly glacial sediments. Four distinct formations of Elsterian and Saalian age are identified, each containing 15–40 m of glaciolacustrine strata. The boundaries between formations are marked by erosional surfaces and, in part, by angular discordances caused by tectonism. Glaciolacustrine sedimentation was tectonically controlled: the thickness of the sequences in the graben are three to five times greater than outside the area of fault‐controlled subsidence. Deposition in the proglacial lakes was controlled by differential subsidence rates within the basin: deep‐lake facies (varved clays) were deposited in sub‐basins with high subsidence rates and deltaic to shallow‐water facies accumulated in areas of moderate subsidence or occasional uplift. These variations led to the development of a very complex, ‘mosaic’ of lateral facies relationships, suggesting that several sub‐basins with differing subsidence rates were present. The Vertical successions show proximal‐distal sequences typical of glacier‐fed lakes that have limited contact with the ice sheet. However, gravity flow facies are very common, and occur both in the shallow‐ and deep‐water deposits. These deposits are interpreted to have been formed adjacent to active fault scarps which bordered the lake basin. Although several distinct phases of glaciolacustrine sedimentation occurred during the history of trough infilling, the location of the areas of high subsidence varied through time.

Tertiary flexural evolution of the Beaufort-Mackenzie Basin, Canada

Seismic reflection data indicate that more than 14–16 km of clastic materials are preserved in the Beaufort-Mackenzie Basin. These correspond to tectonic activity and sediment loading from the Upper Cretaceous to the present day. To understand better how the basement movement responds to the thick sediment loading, an inverse flexural model has been used to simulate the evolutionary process. The results of the inverse flexural model simulation show that the basin subsidence developed dominantly as an elastic flexural response to sediment loading, with a minor component due to lateral compressive stress. The forward model results show that the Late Eocene to Pleistocene subsidence of the basin included three stages with different rates of subsidence. The Koponoar, Kugmallit and Iperk sequences represent products of two rapid subsidence stages, whereas the Mackenzie Bay and Akpak sequences reflect the products of a more stable and slower subsidence stage.

Application of Seismic Sequence Concepts to Basin Evolution and Petroleum Exploration, Pletmos Basin, Offshore South Africa: ABSTRACT

As a result of excellent seismic data, shallow burial depths, and slow subsidence rates, 67 type 1 and type 2 unconformities were identified in the postrift Cretaceous section of the Pletmos subbasins. The purpose of this study was to develop a seismic sequence-stratigraphic framework for the mid-Valanginian to mid-Campanian sequences as a basis for future petroleum exploration. The study further developed the recent stratigraphic techniques proposed by Exxon. Sixteen of the 67 type 1 and type 2 unconformities could be correlated directly with Exxon's global third-order cycles; the remaining 51, interpreted to be fourth- and fifth-order cycles, could be grouped into megasequences comprising 2 to 6 sequences, bounded by major third-order type 1 unconformities. The study demonstrates the complex interplay of variations in sea level fluctuation, differential subsidence rates, sediment supply, and tectonic stability and the resultant wide range of geometries and styles in depositional environments. By using seismic sequence concepts, these variables can be accounted for and can be made with greater assurance. Further analyses of lowstand systems tracts are underway to localize stratigraphic trap prospects to be drilled in the near future.

Tidally influenced coal-bearing sediments in the Tertiary Bering River Coalfield, south-central Alaska

Tertiary coal-bearing sediments of the Tokun Formation in the structurally complex Bering River Coalfield, south-central Alaska, comprise stacked, glauconitic, fining- and rare coarsening-upward sequences up to 7 m thick. Fining-upward sequences consist of a scoured base, overlain by shale pellet conglomerate, coarse- to medium-grained, well-sorted, planar and trough cross-bedded sandstone, containing skeletal remnants of crabs and bivalves, and carbonaceous shale and coal beds. Coarsening-upward sequences are the inverse of the fining-upward sequences; stacking of these sequences produces megasequences up to 50 m thick. The fining- and coarsening-upward sequences are interpreted to have been deposited in tidal inlet and back barrier lagoon, and marsh environments that formed part of a mesotidal barrier island-estuarine complex. Seaward migration of inlet channels and flood tidal deltas produced fining-upward sequences capped by back barrier lagoon and marsh deposits. Vertical stacking of sequences is attributed to a series of transgressive-regressive events controlled by differential rates of sediment supply and subsidence. Consideration of the plate tectonic setting of the Bering River Coalfield and the established tectonic control on Tertiary sedimentation in Alaska, suggests that megasequence deposition was most probably related to longer term regional tectonic events, such as fault-controlled basin subsidence.

Type 1 and Type 2 Unconformity Development in Response to Differential Subsidence Rates and Eustatic Sea Level Fluctuations, Pletmos Basin, Offshore South Africa: ABSTRACT

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Controls on Early Cretaceous Carbonate Platform Margin Development: Northeastern Gulf of Mexico: ABSTRACT

A seismic stratigraphic analysis of approximately 3000 km of multifold reflection data correlated to available geologic information documents the development of an Early Cretaceous carbonate platform margin in the De Soto Canyon area of the northeastern Gulf of Mexico. During the Jurassic(.), inferred oceanic and thin transitional crust underlying the Gulf subsided and formed a flexure zone on which the Early Cretaceous margin developed. By the late Aptian to late Albian, two types of margin morphologies evolved in response to different paleogeographic settings. Northwest of De Soto Canyon, a gently dipping accretionary slope morphology formed as a result of its proximity to a terrigenous clastic province. Seawater turbidity and chemistry probably inhibited buildup formation on this leeward margin, thus allowing both carbonate and siliciclastic sediments to be transported from the platform interior to the adjacent slope. Southeast of De Soto Canyon, the carbonate province was cleaner and a steeply dipping bypass slope morphology formed due to the development of robust buildups that probably limited downslope deposition of platform-derived sediments, thereby gradually starving the adjacent basin. Total tectonic subsidence profiles across both types of margin morphologies show steeper gradients associated with the bypass slope morphology, suggesting that differential subsidence rates contributedmore » to the development of the margin's morphology and may reflect the margin's proximity to the oceanic-continental crust boundary. In the late Albian, the platform interior drowned in response to a pronounced fluctuation in short-term eustatic sea level superimposed on a long-term rise. Buildups continued to form at the margin, however, until they drowned in the middle Cenomanian due to another big change in short-term eustatic sea level combined with down-to-basin faulting and the continuing long-term rise.« less

Cenozoic Differential Subsidence of North Sea

The structural evolution of the central North Sea has been dominated by subsidence throughout the last 65 m.y., which occurred at different rates in various segments of the basin. The bulk of the Tertiary sediments accumulated in a relatively narrow, elongate basin in the central North Sea. The base of the Tertiary today is deeper than 3,250 m in the axis of the Central graben. The overall shape of the basin is well defined by contours decreasing in depth northward to the Norwegian Sea, and landward in all other directions. Different rates of subsidence of the various subbasins are evident by comparison of isopach maps. During the Paleocene and Eocene, the main depocenter was located in the northwest part of the North Sea (the Viking graben), whereas the Oligocene and Miocene depocenters are observed to have been in the southern part of the Central graben. In addition, two ancillary depocenters have been identified for other intervals of the Tertiary: the Moray Firth and the Central Jutland portion of the Danish subbasin.

The rate of Pleistocene subsidence and sedimentation in the Hula Basin as compared with those of other time spans in other Israeli tectonic regions

Absolute dating of Quaternary sediments in the Hula Basin, northern Israel, by means of radiocarbon and 230Th/234U gives the rate of subsidence of the basin. The rate of sedimentation, which can be obtained by adding the calculated compaction, is quite a bit higher. From the Hula Basin and other parts of the country it is evident that different rates of subsidence and vertical displacements are obtained for different time spans. Rates become higher as the time span becomes shorter and the age younger. Rates calculated for time spans since the Neogene, since the Quaternary, and for the last decades are on the order of magnitude of 10−1 mm/y, 100 mm/y and 101 mm/y, respectively.

Adell Field and Vicinity--Sheridan and Decatur Counties, Kansas: ABSTRACT

The Adell field in northeastern Sheridan County, Kansas, and other smaller fields in the area, produce oil from multiple zones of the Lansing-Kansas City. Porous zones of this age are shoal deposits consisting of rounded carbonate grains, many of which have superficial oolitic coating. Carbonate grain distribution was controlled by water turbulence and relief on the sea floor. The Jennings anticline existed during Lansing-Kansas City deposition and provided the necessary relief on the sea floor for shoals to occur. Differential rates of sea-floor subsidence and cyclic nature of sediment accumulation account for the multiple porous pay zones which are stacked on top of each other. End_of_Article - Last_Page 1323------------

Middle Triassic carbonate margin development: Hochstaufen-Zwieselmassif, northern Calcareous Alps, Germany

The Middle Triassic carbonate series of the Hochstaufen-Zwieselmassif reflect the last stage of a northward progradation of a wide southern reef platform extending into the attached northern basin. Regional facies differentiation was caused by differences in the morphology of the basin. A massive central reef core, exhibiting clear ecological zonation, developed along the slope of the slightly deeper eastern part of the basin. The shallower western parts, however, were quickly filled up by forereef debris and overlain by sediments of the rapidly spreading lagoon. A typical grapestone facies includes intercalations of vadose pisolitic crusts, thus indicating a shallow marine platform environment, which was sporadically interrupted by areas of subaerial exposure. Various sediment types occurring along the platform margin reflect synsedimentary mass movements. These were induced by tectonic disturbances caused by different rates of subsidence between the rapidly subsiding platform and the slowly subsiding basin. Forereef rocks which have been entirely lithified were affected by various stages of internal brecciation during this process. In contrast, basinal sediments which were semilithified or patchily cemented exhibit plastic deformation (slumping) and subsequent disintegration into intraformational breccias and debris flows. Turbidites were induced in cases of higher pore water saturations. All these mass mobilisations took place on gentle slopes. This assumption is supported by the observation of initial reef growth flourishing on protected areas of the foreslope. Along a gentle slope, differential rates of subsidence can easily be balanced by plastic deformation and dislocation of basinal material. This is supported by the fact that no prominent synsedimentary fault system could be observed along the platform margin. The facies differentiation of the central reef core is substantiated by a clear eclogical zonation of organisms. The lower, more protected portions of the central reef belt were occupied by theTubiphytes zones. Along the reef front the Coral-Solenoporacean biocoenoses found favorable living conditions. The high energy sediments of the reef flat exhibit a highly diverse Calcisponge—Hydrozoan—Coral community. Towards backreef areas a small belt was inhabited by a typicalThecosmilia —Thaumatoporella biocenosis.

Tectonic Effects on Meandering River Deposits, Carboniferous, Nova Scotia, Canada: ABSTRACT

Sediments of the Boss Point, Port Hood, and Parrsboro Formations (Carboniferous) of Nova Scotia were deposited on alluvial plains in tectonically active basins bounded by strike-slip faults. Some basins contain over 1 km of strata of this age. Fining-upward fluvial channel sandstones are about 20 m thick and are composed of a vertical sequence of basal conglomerate, trough cross-beds, ripple lamination, and siltstone. Large-scale lateral accretion surfaces are present and the sandstones are interpreted as meandering river deposits. Flood-plain sediments include crevasse splay sandstones, rooted mudrocks, thin coals, and lacustrine deposits. The channel sandstones are stacked vertically and many form thick sandstone packages. One 1-km thick sequence, for example, consists of over 75% channel sandstone. There are similarly thick, laterally equivalent, sequences of flood-plain sediment with few or no channel sandstones. It appears, therefore, that meander belts were restricted in their positions for long periods, allowing the unusually thick sequences of channel and coeval overbank sediment to accumulate. The variation from the classic meander-belt model, in which avulsion randomly distributes the meander belts across the alluvial plain through time, was presumably due to differential subsidence rates which caused the meander belts to be restricted to the areas of higher subsidence, thus retarding avulsion frequency. End_of_Article - Last_Page 955------------

Oceanic transform structures and the development of Atlantic continental margin sedimentary basins—a review

Atlantic sedimentary basins are classified into 3 types: (1) tensional rift basins (simple elongate basins and fracture zone end basins), (2) sheared margin basins (fracture zone parallel and fracture ridge dammed basins), and (3) taphrogenic basins. During the early phase of ocean opening, wrench tectonics occur ams offset continential margins, producing splay faulting relative to some transform directions; this influences the formation of fracture zones end and fracture zone parallel basins. Dammed basins develop against fracture zone ridges along large offset sheared margins. In taphrogenic basins of southern S America extant fracture zones follow Palaeozoic lines of weakness across the continent. Basement structures influence the location of some transform directions, particularly in the equatorial Atlantic, and there is some evidence to suggest a link between changes in subsidence rates and the shift in location of poles of opening on sedimentation rates. The asymmetry of basin development on opposing sides of the Atlantic is partially ascribed to the grain of the coastal geology and partly to differential subsidence rates caused by anomalous or asymmetric development of the adjacent ocean floor.

Concepts of Micropaleontology Applied to Petroleum Geology: ABSTRACT

Micropaleontologic correlations by means of planktonic microfossil zones, defined on either an evolutionary or paleoceanographic basis, show that there are major time-transgressive features for paleontologic zones based upon benthic forams. This problem is especially acute in tectonically active basins where rapid sedimentation is combined with differential subsidence rates. Stage boundaries based on benthic species may occur progressively down-section toward submarine fans; conversely, such boundaries are progressively higher in the section toward deep-water depositional areas that are far from sediment sources. Thus, the misidentification of stratigraphic objectives can lead to drilling errors of many hundreds of meters in exploring different depositional centers within a basin. This aspect of correlation precision is especially acute in areas of continental margins. Paleoenvironmental logging of sections and wells, employing primarily benthic foram faunas, makes possible (1) definition of paleobathymetric cycles, (2) detection of areas with truncated cycles, (3) definition of principal depositional centers and their migration in time, (4) proper evaluation of sediment bodies such as turbidites and submarine landslides, and (5) definition of paleotectonic rates which lead to the definition of structural trends developing within a basin. End_of_Article - Last_Page 602------------

Paleontological Guides to Depositional Environments: ABSTRACT

Foraminiferal-environmental relations provide criteria for (1) the reconstruction of marine basins of the geologic past, (2) the determination of structural trends based on differential subsidence rates, and (3) the identification of important producing trends within the sediment and environmental framework. One of the primary guides to depositional environments is the patent foraminiferal zonation from marsh to deep-sea environments. This may be summarized for southern California as follows: (1) marsh, Jadammina-Miliammina fauna; (2) euryhaline lagoon, Ammonia beccarii tepida fauna; (3) intertidal zone, Rotorbinella fauna; (4) open ocean 0-20 m., Buliminella elegantissima type of fauna; (5) 20-100 m., Florilus-Nonionella fauna; (6) 100 m. upper depth limit, Bolivina acuminata-Uvigerina peregrina fauna; (7) 400 m. upper depth limit, Bolivina argentea-Bolivina spissa fauna; (8) 700 m. upper depth limit, Bulimina striata mexicana fauna; (9) 1,000 m. upper depth limit, Uvigerina hispida fauna; and (10) 2,400 m. upper depth limit, Melonis pompilioides-Uvigerina senticosa fauna. Bathyal specie such as Uvigerina peregrina, hispida, senticosa, and Melonis pompilioides are essentially isobathyal showing little if any evidence of temperature control in their distribution patterns in different oceanic areas. Other guides to depositional environments include the bathyal bolivine trend within the general oxygen minimum zone (0.3-0.7 ml./l.); specimens of this group become larger and more abundant with increasing organic content and depth. Oxygen values of about 0.1 ml./l. or less result in an absence of larger invertebrates and a concentration of depositional laminae with very fragile hyaline bolivines and other Foraminifera. The largest benthic bathyal Foraminifera (measuring several millimeters in length) require oxygen values of more than 1.5 ml./l. and nitrogen values of more than 0.15 per cent; these occur in homogeneous or disturbed sediments, characteristics resulting from the activities of larger invertebrates. Displacement processes may produce intercalations of these various facie ; variations in water masses may result in somewhat similar fluctuations of facies. Planktonic foraminiferal abundance and diversity increase seaward into the bathyal zone. Although most planktonic Foraminifera live in the photic zone, some such as Globigerina pachyderma (typical form) and Sphaeroidinella are characteristic of the bathyal zone when they are fully developed. Many planktonic Foraminifera add a crystalline crust to their test as they descend into deeper waters of the bathyal zone. Radiolarians are of primary importance in middle bathyal-to-abyssal depths. End_of_Article - Last_Page 453------------

Study of Proterozoic (Jatulian) facies in Central Karelia

Jatulian (middle Proterozoic) deposits in Karelia form isolated synclinoria, trending northwest and surrounded by blocks of granitic rocks and schists. Individual zones are 70-250 km long by 5-130 km wide. They have been traced 600 km from south to north. Jatulian deposits consist of metamorphosed sedimentary and volcanic rocks. Sedimentary rocks in central Karelia consist of polymictic conglomerates, sericitic sandstones and carbonate-bearing sandstones. Facies change gradually away from the central parts of Jatulian troughs from lacustrine to shallow-water shore facies and then to those of streams and mountain slopes. The intervals thin in the same basins. The lateral facies sequence is repeated vertically. Variations in thickness and facies were determined by contemporaneous Jatulian tectonic activity. There resulted a system of relatively narrow zones with different rates of subsidence, sedimentation and uplift.—C. G. Tillman.