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1.
Apatite fission track (AFT) thermochronology has been applied to a composite depth profile of Precambrian basement rocks underlying the Phanerozoic Canadian Williston Basin. Thermal histories derived from the AFT data record cycles of heating and cooling which follow the pattern of regional burial history, but which also indicate major temporal and geographic variations in the timing and degree of maximum Phanerozoic temperatures. These variations in the thermal history were not previously recognised from organic maturity indicators and subsidence models. Specifically, our study suggests a late Paleozoic heat flow anomaly with a geographic extent closer to that of Middle Devonian–Carboniferous Kaskaskia subsidence patterns than to that of the Williston Basin proper. This thermal anomaly has both economic and geodynamic significance. The recognition that potential Upper Cambrian–Lower Ordovician petroleum source rocks became fully mature during the late Paleozoic distinguishes that petroleum system from others that entered the main hydrocarbon generation stage in latest Cretaceous and Paleogene time. The late Paleozoic heat flow anomaly suggested from the AFT data implies a geodynamic coupling between inelastic Kaskaskia subsidence and previously inferred late Paleozoic lithospheric weakening. While the temporally varying heat flow model is preferred, the lack of independent constraints on the maximum thickness of upper Paleozoic strata precludes the outright rejection of the previous constant heat flow model. The AFT data provide important new constraints on the evolution of the epicratonic Williston Basin and its geodynamic models.  相似文献   

2.
The topographic evolution of the “passive” margins of the North Atlantic during the last 65 Myr is the subject of extensive debate due to inherent limitations of the geological, geomorphological and geophysical methods used for studies of uplift and subsidence. We have compiled a database of sign, time and amplitude (where possible) of topographic changes in the North Atlantic region during the Cenozoic (65–0 Ma). Our compilation is based on published results from reflection seismic studies, AFT (apatite fission track) studies, VR (vitrinite reflectance) trends, maximum burial, sediment supply studies, mass balance calculations and extrapolation of seismic profiles to onshore geomorphological features. The integration of about 200 published results reveal a clear pattern of topographic changes in the North Atlantic region during the Cenozoic: (1) The first major phase of Cenozoic regional uplift occurred in the late Palaeocene–early Eocene (ca 60–50 Ma), probably related to the break-up of the North Atlantic between Europe and Greenland, as indicated by the northward propagation of uplift. It was preceded by middle Palaeocene uplift and over-deepening of some basins of the North Sea and the surrounding areas. (2) A regional increase in subsidence in the offshore marginal areas of Norway, the northern North Sea, the northern British Isles and west Greenland took place in the Eocene (ca 57–35 Ma). (3) The Oligocene and Miocene (35–5 Ma) were characterized by regional tectonic quiescence, with only localised uplift, probably related to changes in plate dynamics. (4) The second major phase of regional uplift that affected all marginal areas of the North Atlantic occurred in the Plio-Pleistocene (5–0 Ma). Its amplitude was enhanced by erosion-driven glacio-isostatic compensation. Despite inconclusive evidence, this phase is likely to be ongoing at present.  相似文献   

3.
To study the relative and absolute timing of post-Variscan cooling and denudation processes in the Erzgebirge of the Mid-European Variscides, eight samples for apatite fission-track (AFT) analysis were collected from a ~1,300 m drill-core. The fission-track data reveal two stages of accelerated cooling through the apatite partial annealing zone (APAZ; i.e., 110±10–60 °C) in the Late Jurassic-Late Cretaceous and in the late Cenozoic, respectively. Late Jurassic-Late Cretaceous cooling corresponding to denudation of 1.5–5.9 km has been related to wrench tectonics along the Elbe Zone during Triassic-Jurassic Pangea breakup. Late Cenozoic exhumation of 2.1–5.6 km, and the increase of the geothermal gradient from 17±5 °C km–1 (Oligocene/Miocene) to 25–27 °C km–1 (recent) is likely connected to the formation of the Eger Graben starting from the Oligocene, as a result of the late Alpine orogenic phases.  相似文献   

4.
The Precambrian Aksu blueschist is located in the northwestern margin of the Tarim Block, NW China. In recent decades, many studies were carried out with focus on the metamorphic age. However, a complete understanding of the evolution of the Tarim Block requires the cooling history of the Precambrian metamorphic rocks and the time–temperature paths as determined by low-temperature thermochronometry. Therefore, apatite fission track (AFT) technique was applied on the Precambrian Aksu blueschist to reveal the thermo–tectonic evolution of the north Tarim basement. All of the six blueschist samples analysed in this study yielded AFT ages spanning 107.5–62.5 Ma, much younger than the blueschist facies metamorphic age of Neoproterozoic, and confined track lengths are between 10.46 and 12.12 µm. Based on regional stratigraphic sequences, the AFT thermal history modeling as well as previous chronological results, the thermo–tectonic evolution of the Aksu blueschist can be roughly reconstructed with four stages: (1) the Precambrain Aksu blueschist exhumed to the surface soon after its formation. Erosion during the Early Sinian is indicated by the lack of sedimentation until the Late Sinian; (2) the Late Sinian strata are continuous, while the Middle–Upper Silurian and the Lower–Middle Carboniferous strata are absent. The total thickness of the Late Sinian and Paleozoic strata probably reached 10,000 m and resulted in the total annealing and thermal resetting of AFT ages; (3) the AFT ages in the Cretaceous are related with the widespread uplift in Tian Shan and its adjacent regions that restarted the AFT clock during the Late Mesozoic. These reflect a distant effect of the collision of the Lhasa terrane with Eurasia in the Late Jurassic–Early Cretaceous; and (4) sediments of Cenozoic are documented in the Aksu area. The Aksu blueschist was heated to partial annealing zone with the overlying Cenozoic sediments. During Miocene time, the Aksu blueschist was re-exhumed which was probably a distant response to the ongoing India–Eurasia convergence.  相似文献   

5.
Apatite fission-track (AFT) dating applied to uplifted Variscan basement blocks of the Bavarian Forest is employed to unravel the low-temperature history of this segment of the Bohemian Massif. Twenty samples were dated and confined track lengths of four samples were measured. Most samples define Cretaceous APT ages between 110 and 82 Ma (Albian to Campanian) and three samples give older ~148–140 Ma (Jurassic–Cretaceous boundary) ages. No discernible regional age variations exist between the areas north-east and south-west of the Pfahl shear zone, but >500 m post-Jurassic and post-Cretaceous vertical offsets along this and other faults can be inferred from elevation profile analyses. The AFT ages clearly postdate the Variscan exhumation history of the Bavarian Forest. Thermal modeling reveals that the ages are best explained by a slight reheating of the basement rocks to temperatures within the apatite partial annealing zone during the middle and late Jurassic and/or by late Cretaceous marine transgression causing burial heating, which affected marginal low-lying areas of the Bohemian Massif and the Bavarian Forest. Late Jurassic period was followed by enhanced cooling through the 120–60 °C temperature interval during the subsequent exhumation phase for which denudation rates of ~100 m myr?1 were calculated. On a regional scale, Jurassic–Cretaceous AFT ages are ubiquitous in marginal structural blocks of the Bohemian Massif and seem to reflect the exhumation of these zones more distinctly compared to central parts.  相似文献   

6.
The Krishna–Godavari (KG) basin, a passive margin Late Carboniferous to Holocene basin along the rifted east coast of India, includes the deltaic and inter-deltaic regions of the Krishna and Godavari rivers onshore and extends into the offshore. It is one of India’s premier hydrocarbon-bearing basins. In an attempt to better understand the thermal history of the basin, apatite fission track (AFT) data has been obtained from six exploration wells (five onshore and one offshore). AFT thermal history models as well as other thermal indicators e.g. vitrinite reflectance (VR), Rock–Eval Tmax data reveal that the host rocks are currently at their maximum post-depositional temperatures and that any possible heating related to small-scale tectonism or rifting episodes in the basin bears little significance on the maturation of the sediments. In the case of one borehole (M-1) however, the organic maturity data reveals a period of Oligocene cooling across an unconformity when ∼1000 m of section was eroded due to falling sea-level. This information offers the potential for improved basin modeling of the KG basin.  相似文献   

7.
Geologic mapping and U–Pb detrital zircon geochronologic studies of (meta)sedimentary rocks in the Damxung area (90 km north of Lhasa) of the southern Lhasa terrane in Tibet provide new insights into the history of deformation and clastic sedimentation prior to late Cenozoic extension. Cretaceous nonmarine clastic rocks 10 km southeast of Damxung are exposed as structural windows in the footwall of a thrust fault (the Damxung thrust) that carries Paleozoic strata in the hanging wall. To the north of Damxung in the southern part of the northern Nyainqentanglha Range (NNQTL), metaclastic rocks of previously inferred Paleozoic age are shown to range in depositional age from Late Cretaceous to Eocene. The metaclastic rocks regionally dip southward and are interpreted to have been structurally buried in the footwall of the Damxung thrust prior to being tectonized during late Cenozoic transtension. Along the northern flank of the NNQTL, Lower Eocene syncontractional redbeds were deposited in a triangle zone structural setting. All detrital zircon samples of Cretaceous–Eocene strata in the Damxung area include Early Cretaceous grains that were likely sourced from the Gangdese arc to the south. We suggest that the that newly recognized Late Cretaceous to Early Eocene (meta)clastic deposits and thrust faults represent the frontal and youngest part of a northward directed and propagating Gangdese retroarc thrust belt and foreland basin system that led to significant crustal thickening and elevation gain in southern Tibet prior to India-Asian collision.  相似文献   

8.
Lake Teletskoye occupies a narrow graben located in the northwestern sector of the Altai fold belt in South Siberia. The lake basin is thought to have formed during the Pleistocene as a distant result of the Cenozoic collision of India and Eurasia that caused a tectonic reactivation of the Palaeozoic Gorny–Altai (GA) and West Sayan (WS) blocks.The present work reports of a pilot fission-track study performed on 13 apatite separates collected from rocks that were sampled along two profiles in close proximity of the lake. The age–length data and AFT thermochronological modelling reveal two important phases of cooling in the Altai Mountains, a first one during the Late Jurassic–Early Cretaceous and a second one that started in the Miocene–Pliocene and that persists until today. The first event is interpreted to result from uplift-induced denudation probably related to the closure of the Mongol–Okhotsk Ocean; the second event can be linked to the young Cenozoic movements that lie at the origin of the formation of the Lake Teletskoye basin.  相似文献   

9.
Geologic mapping and U–Pb detrital zircon geochronologic studies of (meta)sedimentary rocks in the Damxung area (∼90 km north of Lhasa) of the southern Lhasa terrane in Tibet provide new insights into the history of deformation and clastic sedimentation prior to late Cenozoic extension. Cretaceous nonmarine clastic rocks ∼10 km southeast of Damxung are exposed as structural windows in the footwall of a thrust fault (the Damxung thrust) that carries Paleozoic strata in the hanging wall. To the north of Damxung in the southern part of the northern Nyainqentanglha Range (NNQTL), metaclastic rocks of previously inferred Paleozoic age are shown to range in depositional age from Late Cretaceous to Eocene. The metaclastic rocks regionally dip southward and are interpreted to have been structurally buried in the footwall of the Damxung thrust prior to being tectonized during late Cenozoic transtension. Along the northern flank of the NNQTL, Lower Eocene syncontractional redbeds were deposited in a triangle zone structural setting. All detrital zircon samples of Cretaceous–Eocene strata in the Damxung area include Early Cretaceous grains that were likely sourced from the Gangdese arc to the south. We suggest that the that newly recognized Late Cretaceous to Early Eocene (meta)clastic deposits and thrust faults represent the frontal and youngest part of a northward directed and propagating Gangdese retroarc thrust belt and foreland basin system that led to significant crustal thickening and elevation gain in southern Tibet prior to India-Asian collision.  相似文献   

10.
Analysis of a 1.15 km deep apatite fission track (AFT) thermochronology profile at the Underground Research Laboratory (URL), in the southwestern Canadian Shield suggests two Phanerozoic heating and cooling episodes indicating significant, previously unsuspected, Phanerozoic heat flow variations. Phanerozoic temperature and heat flow variations are temporally associated with burial and erosion of the Precambrian crystalline shield and its overlying Phanerozoic successions, which are now eroded completely. Maximum Phanerozoic temperatures occurred in the late Paleozoic when the geothermal gradient is estimated to have been ~ 40-50 °C/km (compared to a present day gradient of ~ 14 ± 2 °C/km) and the sedimentary cover was ~ 800-1100 m thick. Our thermal history models, confirm regional stratigraphic relationships that suggest that the Paleozoic succession was completely eroded prior to beginning of Mesozoic sedimentation. A second heating phase occurred during Late Cretaceous-Paleogene burial when the geothermal gradient is estimated to have been ~ 20-25 °C/km and the Mesozoic and Cenozoic succession was ~ 1200 to 1400 m thick. The Phanerozoic thermal history at the URL site shows a pattern similar to that inferred previously for the epicratonic Williston Basin, the centre of which lies several 100 km to the west. This implies a common regional thermal history for cratonic rocks underlying both the basin and the currently exposed shield. It is suggested that the morphotectonic differences between the Williston Basin and the exposed shield at the URL are due to a dissimilar thermomechanical response to a common, but more complicated than previously inferred, Phanerozoic geodynamic history. The two Phanerozoic periods of variations in geothermal gradient (heat flow) were coeval with epeirogenic movements related to the deposition and erosion of sediments. These paleogeodynamic variations are tentatively attributed to far-field effects of orogenic processes occurring at the plate margin (i.e. the Antler and the Cordilleran orogenies) and the associated accumulation of cratonic seaway sedimentary sequences (Kaskaskia and Zuni sequences).  相似文献   

11.
The Horse Prairie basin of southwestern Montana is a complex, east-dipping half-graben that contains three angular unconformity-bounded sequences of Tertiary sedimentary rocks overlying middle Eocene volcanic rocks. New mapping of the basin and its hanging wall indicate that five temporally and geometrically distinct phases of normal faulting and at least three generations of fault-related extensional folding affected the area during the late Mesozoic (?) to Cenozoic. All of these phases of extension are evident over regional or cordilleran-scale domains. The extension direction has rotated 90° four times in the Horse Prairie area resulting in a complex three-dimensional strain field with 60% east–west and >25% north–south bulk extension. Extensional folds with axes at high angles to the associated normal fault record most of the three-dimensional strain during individual phases of extension (phases 3a, 3b, and 4). Cross-cutting relationships between normal faults and Tertiary volcanic and sedimentary rocks constrain the ages of each distinct phase of deformation and show that extension continued episodically for more than 50 My. Gravitational collapse of the Sevier fold and thrust belt was the ultimate cause of most of the extension.  相似文献   

12.
《Gondwana Research》2014,25(3):1216-1229
Fission track (FT) dating of detrital titanites, zircons and apatites combined with sandstone petrography from rocks of the Rovuma Basin was used to constrain the basin's provenance and its post depositional thermal history. A comparison of metamorphic basement and sedimentary titanite and zircon FT data indicates that erosion was localized along a zone which followed the margin of the Rovuma Basin and was the source for the late Jurassic to Cretaceous sandstones. Time–temperature models of apatite FT data show, that after the deposition, the sandstones were heated up to temperatures of ca. 60–110 °C most likely due to a combination of intensified regional heat flux and burial heating caused by fast sedimentation in a transtensional pull-apart setting and intensified by regionally elevated heat flux. The utter western part of the basin was inverted between ca. 60 and 40 Ma, concordant with the drop in the global eustatic sea level which led to a rearrangement of the source-to-sink system. Some reworked zircons were deposited in the Cenozoic strata in the eastern part of the basin.  相似文献   

13.
The apatite fission track dating of samples from the Dabashan(i.e., the Langshan in the northeastern Alxa Block) by the laser ablation method and their thermal history modeling of AFT ages are conducted in this study. The obtained results and lines of geological evidence in the study region indicate that the Langshan has experienced complicated tectonic-thermal events during the the Late Cretaceous-Cenozoic. Firstly, it experienced a tectonic-thermal event in the Late Cretaceous(~90–70 Ma). The event had little relation with the oblique subduction of the Izanagi Plate along the eastern Eurasian Plate, but was related to the Neo-Tethys subduction and compression between the Lhasa Block and Qiangtang Block. Secondly, it underwent the dextral slip faulting in the Eocene(~50–45 Ma). The strike slip fault may develop in the same tectonic setting as sinistral slip faults in southern Mongolia and thrusts in West Qinling to the southwest Ordos Block in the same period, which is the remote far-field response to the India-Eurasia collision. Thirdly, the tectonic thermal event existed in the late Cenozoic(since ~10 Ma), thermal modeling shows that several samples began their denudation from upper region of partial annealing zone(PAZ), and the denudation may have a great relationship with the growth of Qinghai-Tibetan Plateau to the northeast. In addition, the AFT ages of Langshan indicate that the main body of the Langshan may be an upper part of fossil PAZ of the Late Cretaceous(~70 Ma). The fossil PAZ were destroyed and deformed by tectonic events repeatedly in the Cenozoic along with the denudation.  相似文献   

14.
Mafic volcanic rocks have erupted in the Tianchi volcanic zone, Changbai Mountains, northeast China, since late Pliocene time. The zone formed in an extensional environment during early-middle Cenozoic time, and in a compressional environment during late Cenozoic. Crustal thickness (about 40 km) in the Changbai Mountains is larger than the regional average of 34–36 km to the northwest and southeast. The conduit for magma upwelling was not coincident with the NE-striking regional faults, but seem to be confined to a deep-seated NW–WNW-striking fault zone. Since the late Pliocene, the Tianchi volcanic zone was subjected to crustal uplift within an intracontinental, weakly compressional environment (with minor WNW–ESE shearing) related to the westward subduction of the West Pacific plate. The nature of this volcanism is not typical of active, subduction-related continental margin volcanism. The magmatic evolutionary process evolved from trachybasalt through basaltic trachyandesite, trachyte, and pantellerite.  相似文献   

15.
Formation waters of the 14 km thick late Cretaceous–Cenozoic Beaufort–Mackenzie basin were examined as part of a larger project to better understand the petroleum potential of the region, where early exploration defined petroleum reserves of 744 × 109 bbls recoverable crude oil and 11.74 tcf gas. Historical water analyses (2583 samples from 250 wells drilled up to 5 km depth) were compiled and culled to remove incomplete and poor quality samples. The resultant database shows a broad range of salinity and water chemistry that has no systematic relationship with depth. Three main water types are defined, paleo seawater, and freshwaters related to a Miocene age gravity-driven flow system, and low TDS–high alkalinity waters. High alkalinity waters are isolated in overpressured fault blocks that were rapidly buried by post-Miocene Iperk shale deposition. The high alkalinities (up to 9000 mg/L) are interpreted to be related to in situ CO2 generation through anaerobic methanogenesis in response to freshwater invasion. The dominant control on biogenic gas generation appears to be maximum burial temperature rather than the modern temperature distribution. This is consistent with the paleopasteurization model that suggests once critical burial temperatures are reached, sterilized rocks are inhibited from further biodegradation, even when temperatures subsequently drop back into the habitable zone.  相似文献   

16.
An exhumed crustal section of the Mesozoic Torlesse terrane underlies the Southern Alps collision zone in New Zealand. Since the Late Miocene, oblique horizontal shortening has formed the northeastern–southwestern trending orogen and exhumed the crustal section within it. On the eastern side, rocks are zeolite- to prehnite–pumpellyite-grade greywacke; on the western side rocks, they have the same protolith, but are greenschist to amphibolite facies of the Alpine Schist. Zircon crystals from sediments in east-flowing rivers (hinterland) have pre-orogenic fission-track ages (>80 Ma) and are dominated by pink, radiation-damaged grains (up to 60%). These zircons are derived from the upper 10 km crustal section (unreset FT color zone) that includes the Late Cenozoic zircon partial annealing zone; both fission tracks and color remain intact and unaffected by orogenesis. Many zircon crystals from sediments in west-flowing rivers (foreland) have synorogenic FT ages, and about 80% are colorless due to thermal annealing. They have been derived from rocks that originally lay in the reset FT color zone and the underlying reset FT colorless zone. The reset FT color zone occurs between 250 and 400 °C. In this zone, zircon crystals have color but reset FT ages that reflect the timing of orogenesis.  相似文献   

17.
The Shi-Hang Belt is a Mesozoic tectonic zone and has always been regarded as the boundary between the Yangtze and Cathaysia blocks. It occupies a key tectonic location and attracts considerable attention due to its dynamic formation mechanism. However, its Cenozoic dynamic process is poorly constrained. The Cenozoic activation of the Shi-Hang Belt, as well as its cooling and exhumation, aids in dating the onset time of the formation of the mountain ranges and reveals the deformation process of the South China Block. To uncover the history of its Cenozoic cooling and denudation, apatite fission-track (AFT) thermochronology was applied to batholiths and strata spread across the Shi-Hang Belt in the Hunan Province. Twenty-three samples are dated with ages ranging from 23.6 ± 1.5 to 45.8 ± 3.0 Ma. Except for two older ages (42.1 ± 2.6 and 45.8 ± 3.0 Ma), the other ages range from 23 to 36 Ma with less variation on both sides of the Chenzhou–Linwu fault. The thermochronological modelling of 15 measured samples demonstrates that rocks rapidly passed through the AFT partial annealing zone to the near surface at different onset times from 36 to 23 Ma. The regional AFT cooling pattern is unrelated to the internal structures of the Shi-Hang Belt characterized by a Mesozoic fold-thrust feature. We attribute the Cenozoic exhumation of the Shi-Hang Belt to the dynamic topography of the South China Block, which is related to mantle downwellings and upwellings due to several episodes of quick subduction of the Pacific Plate underneath Eurasia during the Late Cretaceous–early Cenozoic and the Oligocene–early Miocene. The far-field effect of the India–Tibet collision may have contributed to the exhumation of the Shi-Hang Belt.  相似文献   

18.
A fossil partial annealing zone of fission tracks in zircon is described from high pressure–low temperature (HP–LT) rocks of the Phyllite–Quartzite Unit (PQ) on the island of Crete, Greece. Correlation of regional trends in fission track age populations with independent thermobarometric and microstructural data, and with new experimental annealing results, allows a calibration of this low temperature thermochronological method to a degree hitherto not available from other field examples.The zircon fission track (FT) ages of samples from the PQ across Crete range from original detrital signature through reduced to completely reset. The annealing is the result of a single heating period related to the HP–LT metamorphism with near-peak temperatures lasting for only a few million years some time between 24±1 and 20±1 Ma. In eastern Crete, where rocks have experienced temperatures of 300±50 °C and pressures of 0.8±0.3 GPa, zircon FT ages range from 414±24 to 145±10 Ma. Ages above 300 Ma occur mostly near the east coast of the island in rocks which have not been heated to above ca. 280 °C and probably represent a pre-Variscan source. Track lengths are already indicative of a substantial annealing at this temperature. Most of the zircon FT ages from eastern Crete scatter within error around the stratigraphic age. Samples with apparent zircon FT ages significantly younger than the depositional age are only observed in areas where temperatures exceeded ca. 320 °C. Towards the west, a sudden decrease to very young ages ranging from 17±2 to 18±1 Ma reflects a complete resetting at ca. 350 °C. Short tracks, however, are still observed. Throughout the central and western part of the island, ages are consistently below 22 Ma. Thermobarometric data for this area indicate maximum temperatures of 400±50 °C and pressures of 1±0.3 GPa. Only samples from western Crete, which have been exposed to 400±50 °C, show exclusively long tracks. Consequently, the high temperature limit of the zircon partial annealing zone (ZPAZ) appears to be between 350 and 400 °C.A significant influence of elevated confining pressure on the stability of fission tracks in zircon is ruled out by the results of annealing experiments at 0.5 GPa and at different temperatures, which fit the curves previously obtained by other authors at ambient pressure.  相似文献   

19.
The Tarim Basin is a representative example of the basins developed in the northwest China that are characterized by multiple stages of heating and cooling.In order to better understand its complex thermal history,apatite fission track （AFT） thermochronology was applied to borehole samples from the Tazhong Uplift Zone （TUZ）.Twelve sedimentary samples of Silurian to Triassic depositional ages were analyzed from depths coinciding with the apatite partial annealing zone （～60-120 ℃）.The AFT ages,ranging from 132 ± 7 Ma （from a Triassic sample） to 25 ± 2 Ma （from a Carboniferous sample）,are clearly younger than their depositional ages and demonstrate a total resetting of the AFT thermometer after deposition.The AFT ages vary among different tectonic belts and decrease from the No.Ten Faulted Zone （133-105 Ma） in the northwest,the Central Horst Zone in the middle （108-37 Ma）,to the East Buried Hill Zone in the south （51 25 Ma）.Given the low magnitude of post-Triassic burial heating evidenced by low vitrinite reflectance values （Ro ＜ 0.7％）,the total resetting of the AFT system is speculated to result from the hot fluid flow along the faults.Thermal effects along the faults are well documented by younger AFT ages and unimodal single grain age distributions in the vicinity of the faults.Permian-early Triassic basaltic volcanism may be responsible for the early Triassic total annealing of those samples lacking connectivity with the fault.The above arguments are supported by thermal modeling results.  相似文献   

20.
This study assessed the hydrocarbon generation potentials/timing of the Awgu source rock horizons encountered in Igbariam-1, Iji-1 and Ajire-1 wells drilled in the southern Benue Trough; using one-dimensional (1D) Genesis Zetaware basin modelling software. This software enabled the integration of burial and thermal influences on Awgu source rocks with kinetic parameters. Thermal and burial history models indicate that the Awgu source horizons encountered at 3249m in Igbariam-1 well (northern part of the basin), expelled 85mg/gtoc of oil and 12 mg/gtoc of gas and hydrocarbon generation began in early Eocene with maximum expulsion in the mid-Eocene (52my) at the rate of 7mg/gtoc/my. To the south of the basin, the Awgu source horizons were encountered at greater depths in Iji-1 and Ajire-1 wells and hydrocarbon generation began in the mid-Palaeocene and peaked in the late Palaeocene (58my) at the rate of 32–38mg/gtoc/my. This resulted in an increase in generated hydrocarbon volume to the south due to (a) increased burial depth and early maturation, and (b) changing source lithofacies -more marine. The fault system linking potential reservoirs such as the Agbani sandstone and the overlying Owelli sandstone to the source rock suggests a possible migration of the generated hydrocarbons to those reservoirs at that time.  相似文献   

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