Geohistory Analysis Research Articles

Quantitative geo-history analysis of the Luconia-Balingian provinces, Malaysia with emphasis on the tectonic subsidence signatures.

This paper presents the subsidence analysis in Luconia-Balingian Province using 22 wells, including an onshore well in neighbouring province. It aims to refine the basin evolution for Luconia-Balingian by integrating tectonic signatures from 37 Ma to Present. Tectonic subsidence was calculated using BasinVis 2.0, a Matlab based program with input prepared for each of the wells analysed. The tectonic subsidence rates for Luconia-Balingian provinces can be divided into five stages, which are (i) 37 to 23 Ma: A uniform, increasing but steady subsidence is recorded with higher tectonic subsidence rate in the central to west of Luconia-Balingian and moderate tectonic subsidence in the north and south. The average tectonic subsidence rate for 37 to 23 Ma in the study area is 1.976 mm/yr. (ii) 23-18 Ma: Increase in total and tectonic subsidence for most parts in Luconia-Balingian with minor decrease in total tectonic subsidence recorded in some of the wells. The average tectonic subsidence rate for 23 to 18 Ma is 2.568 mm/yr. (iii) 18 to 15.5 Ma: Delayed in subsidence within the central and northern parts of Luconia-Balingian with evidence of minor uplift in the northern section. However, the southern part experienced increased in the total and tectonic subsidence rates. (iv) 15.5 to 11.8 Ma: Overall decrease in tectonic subsidence rate, coincide with the prolific growth of Middle to Upper Miocene limestone. (v) 11.8 to recent: Increase in tectonic subsidence rate particularly in the wells within the southern part of Luconia-Balingian. The stretching factors ranges from 1.3 to 1.95, indicative of foreland basin with moderate extension experience by the crust. This study had quantitatively presented the variation in tectonic subsidence rates for this area and characterized major and minor tectonic influences at different timing of the basin growth.

Basin Geohistory Analysis of the Mishrif Formation in Southern Iraq

Basin Geohistory Analysis of the Mishrif Formation in Southern Iraq

Carbonate Reservoir Quality Variations in Basins with a Variable Sediment Influx: A Case Study from the Balkassar Oil Field, Potwar, Pakistan.

The carbonate reservoir quality is strongly reliant on the compaction process during sediment burial and other processes such as cementation and dissolution. Porosity and pore pressure are the two main factors directly affected by mechanical and chemical compactions. Porosity reduction in these carbonates is critically dependent on the overburden stress and subsidence rate. A variable sediment influx in younger basins may lead to changes in the reservoir quality in response to increasing lithostatic pressure. Deposition of molasse sediments as a result of the Himalayan orogeny caused variations in the sedimentation influx in the Potwar Basin of Pakistan throughout the Neogene times. The basic idea of this study is to analyze the carbonate reservoir quality variations induced by the compaction and variable sediment influx. The Sakesar Limestone of the Eocene age, one of the proven carbonate reservoirs in the Potwar Basin, shows significant changes in the reservoir quality, specifically in terms of porosity and pressure. A 3D seismic cube (10 km2) and three wells of the Balkassar field are used for this analysis. To determine the vertical and lateral changes of porosity in the Balkassar area, porosity is computed from both the log and seismic data. The results of both the data sets indicate 2-4% porosities in the Sakesar Limestone. The porosity reduction rate with respect to the lithostatic pressure computed with the help of geohistory analysis represents a sharp decrease in porosity values during the Miocene times. Pore pressure predictions in the Balkassar OXY 01 well indicate underpressure conditions in the Sakesar Limestone. The Eocene limestones deposited before the collision of the Indian plate had enough time for fluid expulsion and show underpressure conditions with high porosities.

Overpressures Induced by Compaction Disequilibrium Within Structural Compartments of Murree Formation, Eastern Potwar, Pakistan

Overpressure conditions in Potwar Basin of Pakistan pose significant drilling and completion problems. Specifically, in eastern Potwar, abnormally high pressures are observed within structural compartments of Murree Formation of Neogene age. Compaction disequilibrium and tectonic stresses are considered as two major factors, controlling pore pressures in this foreland basin. Undercompaction of sediments due to high sediment influx affects the porosity-depth relationship as the rock deviates from the normal compaction trend. Demarcation of structural geometries is critical in understanding abnormal pressure conditions within thick molasse deposits of Murree Formation. Eastern Potwar is divided into three zones on the basis of structural geometries, including duplex thrust sheets, salt-cored anticlines, and triangular zones. Geohistory analysis and pore pressure prediction have been performed for determining the overpressuring mechanism. Log-based pressure prediction in different oil fields of eastern Potwar depicts anomalous pressure conditions in some of the wells. High-sedimentation rate during Miocene times resulted in a low porosity reduction rate due to the inability of fluid to escape out of the pores. Eaton’s method was used to predict the pore pressure, and these pressure curves were calibrated against measured pressure to validate the results. Pressures predicted in Qazian-1X well showed very good correlation with measured pressure data. Most of the wells with overpressure intervals exhibited high porosity values, showing deviation from the normal compaction trend. This pressure prediction revealed that compaction disequilibrium is the primary cause of overpressure conditions within Murree Formation, resulted in response to the rapid rate of sedimentation. The deformation mechanism and presence of different structural geometries also contributed in the development of abnormal pressures.

Controls on Early Miocene carbonate and siliciclastic deposition in eastern Java and south Makassar Straits, Indonesia

The Early Miocene stratigraphy of NE Java and the southern Makassar Straits is examined in the context of siliciclastic sediment supply and subsidence (creation of accommodation space), as indicated by biohermal carbonate growth. Stratigraphic variation is examined geographically and assessed quantitatively, using geohistory analysis. During the Oligocene through to basal Miocene times, basin development had been dominated by extension with local transtension. This changed within the Early Miocene to regional compression, increasing in magnitude with time. Three tectonic events, at about 24 Ma (base of section studied), at 21 Ma, and roughly 16 Ma are described in terms of the influence they had on stratigraphy. Most significant was the concentration of siliciclastics on the proximal side of the Oligo-Miocene axis of subsidence, which caused isostatic loading and nearby pinnacle reefs to achieve high relief, but ultimately an acceleration in siliciclastic input at about 16 Ma caused simultaneous reef extinction. Carbonates of Early Miocene age are important hydrocarbon reservoirs, and the siliciclastics are a geographically variable part of the overburden and seal, as well as causing the thermal maturation of hydrocarbon source rocks. The stratigraphic framework described here will have implications for facies and exploration risk prediction into under-explored regions around the study area. The tectono-stratigraphic framework is carefully constrained for age and facies inputs, and the resulting palaeogeographic history indicates a new model of basin development. This dynamic framework correlates to coeval tectonic processes over a large region and has important implications for Sundaland plate tectonics.

Latest Eocene and Oligocene tectonic controls on carbonate deposition in eastern Java and the south Makassar Straits, Indonesia

This review examines the development of carbonates and their enclosing siliciclastic sediments, from the Late Eocene until the end of the Oligocene, in eastern Java and the southern Makassar Straits. Five genetic sedimentary sequences are recognised, which correlate to other studies in the area, and points to an episodic sedimentary history controlled by tectonism. An additional intra Late Miocene uplift and unconformity is also described as it illustrates the speed at which tectonic transitions occurred. These genetic sedimentary sequences are part of a regional stratigraphic framework that describes the tectonic evolution of Sundaland. Two unconformities, in mid-Oligocene and at terminal Oligocene times, correlating across the entire eastern margin of Sundaland, are highlighted as part of a new regional tectonic model. Quantitative approaches such as geohistory analysis are used to integrate stratigraphy with tectonic controls on accommodation space, and closely spaced wells are correlated to show abrupt facies shifts during tectono-stratigraphic transitions. A zone under the modern island of Java and continuing northeast through the centre of the Makassar Straits is, by far, the most tectonically active region, and also is the site of the largest hydrocarbon discoveries, yet is the least understood area. Measurement and mapping of the highly variable unconformities appears to be the key to understanding the development of this dynamic plate margin, and reaching a better understanding of carbonate reservoirs, all elements of petroleum systems, and the tectonic development of Sundaland.

Sedimentary Basin Reconstruction and Tectonic Development of Paleocene-Eocene Succession, Southern Iraq, by Geohistory Analysis

The Paleocene-Early Eocene sequence is represented by Aliji and Umm Er Radhuma formations, while the Middle-Late Eocene sequence is represented by Jaddala and Dammam formations. The Rus Formation has been described and its basin was analyzed separately because it was deposited during the regression period (Middle Eocene), which is a transitional period between these two cycles. 
 This study includes analysis of the geohistory of this succession, interpretation of the changes of the accumulation, and calculation of subsidence rates. The results were compared with the space available to explain the basin development. The study site included the boreholes of Garraf-84 and 92, Halfaya-1, Nasirya-13 and 40, and Noor-5 at the Mesopotamian Block, in addition to the Ratawi-8, Tuba-15, Rumaila-217, Zubair-45, and West Qurna-60 at the Basra Block.
 The Aliji basin was characterized by the decrease in accommodation values to the northeast direction and the increase in all the other parts of the study area. A comparison of the setting of this basin with the Umm Er Radhuma basin gives a clear evidence of the tectonic impact coming from the northeast. During the Middle Eocene stage, we notice that the basin was affected by comprehensive uplifting processes. This led to the generation of a very shallow basin (Rus basin) with the exposure of the northern part of the basin during the regression stage.
 The Middle-Late Eocene basin is represented by a transgression stage with high subsidence, where the sea level had been raised and covered the northeastern and eastern parts of the studied area by deep sea deposits (Jaddala Formation). While the other parts of the study area were characterized by shallow sediments of Dammam Formation. This period ended with a clear tectonic uplift occurring in the northeastern parts and decreasing towards the southwest. This confirms the reactivation of the tectonic action from the northeast, represented by the continental collision.
 All these sources of evidence indicate that the study area is divided into a northern part and a southern part. Both of these parts are separated by a major tectonic lineament extending from the West Qurna oil field to the Nasiriya oil field, which confirms the presence of the tectonic boundary between the Mesopotamian block and the Basra block. In addition, there exists a secondary tectonic boundary that divides the Mesopotamian block into two parts, the first is to the east and the other is to the west. The results showed that the eastern side was most affected by the collision of the Iranian Plate with the Arabian Plate, which led to its uplift, while the western side was less affected by this tectonics evidence.

Using basin thermal history to evaluate the role of Miocene–Pliocene flat‐slab subduction in the southern Central Andes (27° S–30° S)

AbstractStudies in both modern and ancient Cordilleran‐type orogenic systems suggest that processes associated with flat‐slab subduction control the geological and thermal history of the upper plate; however, these effects prove difficult to deconvolve from processes associated with normal subduction in an active orogenic system. We present new geochronological and thermochronological data from four depositional areas in the western Sierras Pampeanas above the Central Andean flat‐slab subduction zone between 27° S and 30° S evaluating the spatial and temporal thermal conditions of the Miocene–Pliocene foreland basin. Our results show that a relatively high late Miocene–early Pliocene geothermal gradient of 25–35 °C km−1 was typical of this region. The absence of along‐strike geothermal heterogeneities, as would be expected in the case of migrating flat‐slab subduction, suggests that either the response of the upper plate to refrigeration may be delayed by several millions of years or that subduction occurred normally throughout this region through the late Miocene. Exhumation of the foreland basin occurred nearly synchronously along strike from 27 to 30° S between ca. 7 Ma and 4 Ma. We propose that coincident flat‐slab subduction facilitated this wide‐spread exhumation event. Flexural modelling coupled with geohistory analysis show that dynamic subsidence and/or uplift associated with flat‐slab subduction is not required to explain the unique deep and narrow geometry of the foreland basin in the region implying that dynamic processes were a minor component in the creation of accommodation space during Miocene–Pliocene deposition.

Basin modeling analysis and organic maturation for selected wells from different oil fields, Southern Iraq

One dimension petroleum system modeling was performed on selected wells located within four oil fields in Southern Iraq, these are: Rumila, Subba, Tuba and Ratawi. The geo history analysis was applied for the studied fields; and it shows that the stratigraphic section contains many periods which are different in the tectonic and sedimentary subsidence, burial history, sedimentary, and erosion rates. It was seen that the burial depth was greater in the Ratawi oil field than the other fields. There is a different period of subsidence, which ranges from high to moderate subsidence, occurred at upper Jurassic to Mid-Cretaceous. Also, special uplift occurred in the Miocene and moderate subsidence occurred during the Paleogene. Four unconformities took place during the geological history of the Mesopotamian basin. In general, there is similarity to the burial histories that indicates all formations were deposited in the same basin of the studied oil fields, which was effected by the tectonic and sedimentary subsidence. Heat flow is in range (27–70 mW/m2) which influence in the thermal maturity.

Oroclinal bending of the Juan Fernández Ridge suggested by geohistory analysis of the Bahía Inglesa Formation, north-central Chile

The stratigraphy of the Bahía Inglesa Formation in the Caldera Basin west of Copiapó, (north-central Chile) is revised, based on hitherto unpublished stratigraphic sections and 87Sr/86Sr dating. The depositional environment varied from a rocky shoreline to the upper continental slope, with sea-level oscillations and tectonic movements causing numerous local unconformities as well as lateral and vertical facies changes. Geohistory and sedimentological analyses show that the area was close to the concurrent sea level at about 15.3Ma, but at the same time being elevated about 100m above the present sea level. Although the basin then subsided at least 350m until around 6Ma, marine deposition was only recorded after 10.4Ma. This suggests that the sea level initially dropped faster than the rate of subsidence so that subaerial erosion occurred. The period of subaerial exposure before 10.4Ma can be attributed to the presence of a NE-trending branch of the Juan Fernández Ridge below the continental crust at this time, whereas the ensuing subsidence was due to subduction erosion and crustal accommodation in its wake as it migrated south along the South American coastline. The subsequent uplift of at least 250m can be explained by an acceleration in plate expansion and isostatic rebound of the continental crust after being partially submerged in the upper mantle. The uplift–subsidence–uplift pattern mirrors those recorded around the Nazca Ridge in Peru, as well as in similar basins to the south of Caldera. However, a higher southward migration rate of the Juan Fernández Ridge against the edge of the South American Plate and less intense uplift–subsidence–uplift cycles are recorded in the latter basins. This can possibly be attributed to oroclinal bending of the ridge due to friction with the overlying continental plate, which diminished the angle of incidence and the intensity of the stress field, but increased the migration velocity of the ridge relative to the coastline.

Present-Day Heat Flow, Thermal History, and Tectonic Subsidenceof the Jianghan Basin

Thermal gradient distribution of the Jianghan Basin is obtained based on systematic steady-state and oil-test temperature data. The present geothermal gradient and terrestrial heat flow of 18 wells are calculated in the Jianghan Basin. A total of 9 measured terrestrial heat flow values are reported based on detailed thermal conductivity data and systematic steady-state temperature data. These values vary from 41.9 to 60.9 mW/m2, with a mean value of 52.3 ± 6.3 mW/m2. However, thermal history analyses, derived from vitrinite reflectance (RO) and apatite fission track (AFT) data, indicate that the Jianghan Basin was at a stable stage before the Indosinian movement. The heat flow increased and reached its maximum value of ∼68 mW/m2 during the Late Indosinian to Early Yanshan period. Since the Late Himalayan period, rapidly decreasing basement heat flow made the Jianghan Basin cool down. Furthermore, geohistory analysis reveals that the tectonic subsidence of the Jianghan Basin from the Cretaceous to Early Miocene was characterized by initial synrift subsidence followed by thermal subsidence. The thermal and tectonic subsidence history have directly effects on petroleum source rock maturation, so their analyses are of great significance forpetroleum exploration and hydrocarbon source assessment in the Jianghan Basin.

Upper Cretaceous Sequence Stratigraphy of the Rock Springs Uplift, Wyoming

Three scales of sedimentary cyclicity are observed in the Campanian to Maastrichtian-aged strata of southwestern Wyoming based on sedimentary stacking patterns, facies successions, paleontological data and geometric criteria from outcrop, and subsurface data. The largest scale of sequence stratigraphic interpretation is of 10-15 million years duration per cycle and is designated as second order. Second-order cyclicity is represented by profound sequence boundaries and maximum-flooding surfaces that are related to regional tectono-subsidence drivers. The 2nd-order sequence boundaries at the base of the Ericson Formation (Moxa Unconformity) and the base of the Fort Union Formation (Laramide Unconformity) locally erode thousands of feet of section on discrete structural highs, but also show evidence of uplift on a broader scale. Both unconformities terminate long successions of marine shoreline progradation. Second-order maximum flooding surfaces are present within thick marine mudstone successions of the Baxter-Niobrara and Lewis formations. These intervals represent the deepest water deposits in the Upper Cretaceous and are associated with important regional seals and source rocks. The large-scale tectono-cyclicity is composed of an aggregate of smaller-scale, 3rd- and 4th-order sequences and their component systems tracts. In addition to the second-order sequences described above, third-order sequence boundaries are interpreted at the base of the Blair Formation, base of the Chimney Rock Member of the Rock Springs Formation, and at the base of the Canyon Creek Member of the Ericson Formation. Third-order maximum flooding surfaces are in the middle Blair Formation, middle Black Butte Member of the Rock Springs Formation, and in the upper part of the Rusty Member of the Ericson Formation. At least 7 additional 4th-order sequences can be interpreted within these successions. The higher-order cycles are shorter in duration and smaller in magnitude (i.e., thinner and with a smaller degree of change in environments or bathymetry within a cycle). The sequence stratigraphic interpretation approach is observationally based and consistent across these scales. However, finer-scale sequence stratigraphic interpretations, especially at the 4th-order scale, are subject to additional subjectivity. An important challenge is to separate apparent cyclicity related to factors such as local to regional shifting of depocenters (autocyclicity) from regionally correlative cyclicity (allocyclicity) within the high-frequency sequences. Examples of this are provided, most clearly for the lower portion of the Blair Formation. Such considerations are important economically, as this is the scale that controls sandstone reservoir and mudstone seal architecture within petroleum fields. Standard systems tracts criteria using parasequence stacking patterns are extended to non-marine strata by use of the degree of amalgamation (net/gross) of the fluvial sandstones. This approach is demonstrated to be plausible via physical ties to shoreline systems using regional correlations and paleontology, and via estimates of accommodation change from geohistory analysis.

The Friulian-Venetian Basin II: paleogeographic evolution and subsidence analysis from micropaleontological constraints

During the Cenozoic, the Friulian-Venetian Basin (FVB, NE Italy) underwent a complex evolution, related to the inherited Mesozoic sea-bottom topography and the load exerted by the main tectonic phases which affected the three surrounding belts: the Dinarides to the east, the Southern Alps to the north and the Northern Apennines to the south-west. The study of the foraminiferal assemblages from over 500 samples collected from 13 key wells provides important constraints on the paleobathymetric changes which occurred into the basin through time. Moreover, the defined bathymetric ranges, together with information on both thickness of the different depositional units and depositional geometries (derived from 2D seismic), were used as input in geohistory analysis in order to reconstruct the subsidence/uplift trends occurred in different sectors of the basin, as a response to collisional tectonics acting along basin boundaries. The collected results show that the overall depositional architecture of the FVB is the result of six main tectono-depositional phases (Lutetian, Chattian, Langhian, Tortonian, Piacenzian and Quaternary) characterised by paleobathymetric variations and subsidence/uplift trends reflecting the change in the tectonic control of the basin and the balance between subsidence and sediment supply. In particular, the easternmost sector of the FVB evolved as a Dinaric foredeep during Lutetian time. Since Chattian time (Cavanella Group), a moderate subsidence phase characterised by faint flexure to the north occurred, which was followed by a Langhian accentuated subsidence phase, consistent with the development of a Southalpine system. The accommodation space was progressively outpaced by the sediment flux during Serravallian-Messinian time as demonstrated by an overall shallowing upward trend recorded in this stratigraphic interval. A new basin configuration occurred during Piacenzian, when a complex geometry was developed due to the concurrent flexural load of the Southern Alps, to the North, and of the Apennines, to the South. Unlike the previous stratigraphic intervals, the Quaternary sedimentary sequence eventually shows a broadly symmetrical geometry with fast and relatively homogeneous subsidence all over the basin, overbalanced by the sedimentary supply. The observed symmetrical subsidence distribution could be interpreted as a consequence of both vanishing tectonic control and increase of sedimentary input related to increasing climatic variability.

Foredeep palaeobathymetry and subsidence trends during advancing then retreating subduction: the Northern Apennine case (Oligocene‐Miocene, Italy)

AbstractThe Northern Apennines provide an example of long‐term deep‐water sedimentation in an underfilled pro‐foreland basin first linked to an advancing orogenic wedge and then to a retreating subduction zone during slab rollback. New palaeobathymetric and geohistory analyses of turbidite systems that accumulated in the foredeep during the Oligocene‐Miocene are used to unravel the basin subsidence history during this geodynamic change, and to investigate how it interplayed with sediment supply and basin tectonics in controlling foredeep filling. The results show an estimated ca. 2 km decrease in palaeowater depth at ca. 17 Ma. Moreover, a change in basin subsidence is documented during Langhian time, with an average decompacted subsidence rate, during individual depocentre life, that increased from <0.3 to 0.4–0.6 mm y−1, together with the appearance of a syndepositional backstripped subsidence bracketed between 0.1 and 0.2 mm y−1. This change prevented the basin from complete filling during late Miocene and is interpreted as the foredeep response to initial rollback of the downgoing Adriatic slab. Thus, the Northern Apennine system provides an example of a pro‐foreland basin that experienced both a slow‐ and high‐subsidence regime as a consequence of the advancing then retreating evolution of the collisional system.

Geohistory analysis and basin development of the Neogene succession, NE Iraq

The Neogene succession in the studied area is represented by seven formations (Serikagni, Euphrates, Dhiban, Jeribe, Fatha, Injana, and Muqdadiya formations). The area of study is located in the Unstable Shelf within the Low Folded Zone and the north part of the Stable Shelf (Mesopotamian Zone). This study included the geohistory analysis of the Neogene succession and interpretation the changes of the accumulation and subsidence rates and compared them with the space available to explanation the basin development. At The Early Miocene (Aquitanian age), the Sirekagni and Euphrates formations was deposited during a major transgression with high rates of subsidence and accumulation in the Himreen, Makhul, and north of Tigris subzones, while the Chemchemal–Arbil and Butmah–Mosul subzones were positive areas. This period ended with a sea withdrawal to the southeast to generate the Dhiban lagoonal basin which was characterized by low accumulation and subsidence rates. During the Early Burdigalian, the Jeribe Formation was deposited during another sea level rise that covered the area except the Chemchemal–Arbil and Butmah–Mosul subzones representing the uplifted positive area. The sea level rise continued to the early Langhian age where the transition beds for the Fatha Formation was deposited to mark the maximum flooding surface covering all the study area. The Fatha Formation was deposited at the Late Langhian to the Early Serravallian during sea level stillstand with high accumulation and subsidence rates in the Himreen subzone and the Chemchemal–Arbil subzone. This period ended without a clear tectonic activity. The period from Late Miocene to Pliocene was characterized by high tectonic activity and sea level fall where fluvial–lacustrine environment prevailed to deposit the Injana and Muqdadiya formations. The Injana Formation was deposited during the Late Serravallian–Tortonian in the Himreen and Chemchemal–Butmah subzones; in addition to the northern part of Tigris subzone. The areas of high rates of accumulation and subsidence were located near Jambour while the southwestern part was affected by an uplift generating the Himreen structure. The Chemchemal–Butmah subzones was characterized by a high uplift in the southeast part where Kirkuk and Chemchemal structures were forming, while The northeastern part (from Bi Hassan to the borehole Kirkuk-117) was with low accumulation and subsidence rates. The linear region between these parts (Khabaz oil field) showed an abnormal values for accumulation and subsidence rates (very high); this region corresponds to the location and direction of Anah–Fatha–Qalat Dizah Fault which suggest that the fault was active during that time. The tectonic activity continued to uplift all the north of the study area as well as the West and the East during the Late Tortonian to the Piacenzian where the Muqdadiya Formation was deposited in the area between Jambour to Khabaz oilfields. Then the succession was deformed and uplifted to approximately 800 m above the sea level as in the present day.

Tectonic and climatic controls on the sequential arrangement of an alluvial fan/fan‐delta complex (Montserrat, Eocene, Ebro Basin, NE Spain)

AbstractA magnetostratigraphy‐based chronological framework has been constructed in the Eocene sediments of the Montserrat alluvial fan/fan‐delta complex (southeast Ebro Basin), in order to unravel forcing controls on their sequential arrangement and to revise the tectonosedimentary history of the region. The palaeomagnetic study is based on 403 sites distributed along an 1880‐m‐thick composite section, and provides improved temporal constraints based on an independent correlation to the geomagnetic polarity time scale. The new chronological framework together with sequence stratigraphy and geohistory analysis allow us to investigate the interplay between factors controlling the sequential arrangement of the Montserrat complex at the different temporal scales and to test for orbitally driven climate forcing. The results suggest that the internal stacking pattern in transgressive and regressive sequences sets within the more than 1000‐m‐thick Milany Composite Megasequence can be explained as the result of subsidence‐driven accommodation changes under a general increase of sediment supply. Composite sequences (tens to hundreds of metres thick) likely reflect orbitally forced cyclicity related to the 400‐kyr eccentricity cycle, possibly controlled by climatically induced sea‐level fluctuations. This study also provides new insights on the deformational history of the area, and shows a correlation between (tectonic) subsidence and forelimb rotation measured on basin‐margin deformed strata. Integration of subsidence curves from different sectors of the eastern Ebro Basin allows us to estimate the variable contribution of tectonic loads from the two active basin margins: the Catalan Coastal Ranges and the Pyrenees. The results support the presence of a double flexure from Late Lutetian to Late Bartonian, associated with the two tectonically active margins. From Late Bartonian to Early Priabonian the homogenization of subsidence values is interpreted as the result of the coupling of the two sources of tectonic load.

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.

Stratigraphic record of basin development within the San Andreas fault system: Late Cenozoic Fish Creek-Vallecito basin, southern California

The Fish Creek–Vallecito basin contains a 5.5-km-thick section of late Miocene to early Pleistocene sedimentary rocks exposed in the hanging wall of the West Salton detachment fault. These deposits preserve a high-fidelity record of late Cenozoic subsidence and basin filling that resulted from deformation in the San Andreas fault system of southern California. Existing and new paleomagnetic data, combined with new U-Pb zircon ages of two tuffs high in the section, show that the section ranges in age from ca. 8.0 ± 0.4 Ma at the base to ca. 0.95 Ma at the top. Geohistory analysis reveals: (1) moderate subsidence (0.46 mm/yr) from ca. 8.0 to 4.5 Ma; (2) rapid subsidence (2.1 mm/yr) from 4.5 to 3.1 Ma; (3) moderate subsidence (0.40 mm/yr) from 3.1 to 0.95 Ma; and (4) rapid uplift and erosion that has exhumed the section since ca. 1 Ma. Onset of sedimentation at ca. 8.0 ± 0.4 Ma records earliest extension or transtension in the area, possibly related to localization of the Pacific–North America plate boundary in the Salton Trough and Gulf of California. Alternatively, marine incursion at 6.3 Ma may be the earliest record of plate-boundary deformation in the Gulf of California–Salton Trough region. A thick interval higher in the section records progradation of the Colorado River delta into and across the basin starting ca. 4.9 Ma. Progradation continued during an abrupt increase in subsidence rate at 4.5 Ma, and fluvial-deltaic conditions persisted for 1.4 m.y. during the rapid-subsidence phase, indicating that delta progradation was driven by a large increase in rate of sediment input from the Colorado River. Uplift and inversion of the basin starting ca. 1.0 Ma record initiation of strike-slip faults that define the modern phase of dextral wrench tectonics in the western Salton Trough.

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.

Natural subsidence of the Venice area during the last 60 Myr

ABSTRACTIntegrated geohistory analysis performed on high‐resolution stratigraphy of Venezia 1 and Lido 1 wells (Quaternary–Pliocene interval) and low‐resolution stratigraphy of a simulated well extending Lido 1 down to the base of Cenozoic (Palaeocene–Miocene interval) is used to reconstruct the interplay between subsidence and sedimentation that occurred in the Venice area (eastern Po Plain) during the last 60 Myr, and to discuss the relationships between calculated subsidence rates and time resolution of stratigraphic data. Both subsidence and sedimentation are mostly related to the tectonic evolution of the belts that surround the Venice basin, influencing the lithosphere vertical motions and the input of clastic sediments through time. In particular, two subsidence phases are recorded between 40–33.5 and 32.5–24 Myr (0.13 and 0.14 mm year−1, respectively), coeval with tectonic phases in the Dinaric belt. Vice versa, during the main South‐Alpine orogenic phase (middle–late Miocene), quiescence or little uplift (−0.03 mm year−1) reflects the location of the Venice area close to the peripheral bulge of the South‐Alpine foreland system. Early Pliocene evolution is characterised by a number of subsidence/uplift events, among which two uplifts occurred between 5–4.5 and 3–2.2 Myr (at −0.4 and −0.2 mm year−1, respectively) and can be correlated with tectonic motions in the Apennines. During the last million years, the Venice area was initially characterised by uplift (−0.6 mm year−1 rising to −1.5 mm year−1 between 0.4 and 0.38 Myr), eventually replaced by subsidence at a rate ranging between 1.6 and 1.0 mm year−1 up to 0.12 Myr and then decreased to 0.4 mm year−1, as an average, up to present. Our results highlight that time resolution of the stratigraphic dataset deeply influences the order of magnitude obtained for the calculated subsidence rate. This is because subsidence seems to have worked through short‐lived peaks (in the order of 105 years), alternating with long relatively quiescent intervals. This suggests caution when components of subsidence are deduced by subtracting long‐term to short‐term subsidence rate.