FLEXURAL ISOSTATIC MODELLING AS A CONSTRAINT ON BASIN EVOLUTION, THE DEVELOPMENT OF SEDIMENT SYSTEMS AND PALAEO-HEAT FLOW: APPLICATION TO THE VULCAN SUB-BASIN, TIMOR SEA

1997 ◽  
Vol 37 (1) ◽  
pp. 136 ◽  
Author(s):  
K. Baxter ◽  
G. T. Cooper ◽  
G. W. O'Brien ◽  
K. C. Hill ◽  
S. Sturrock

Although the petroleum industry is commonly interested in the upper few kilometres of the lithosphere, it is the deeper stretching events which may drive the development of regional thermal perturbations and which may overprint a significant thermal signature onto the shallower section. The Vulcan Sub-basin, which is located in the Timor Sea, northwestern Australia, has undergone a period of rifting during the Late Jurassic and shows a classic transition from intra-continental rifting to passive margin subsidence during the Late Jurassic to Early Cretaceous. A model has been developed of the Late Jurassic rifting history of the basin, which includes the flexural and stratigraphic response, and the development of the Cretaceous to Recent post- rift basin history. Quantification of the associated vertical motion of the lithosphere suggests that the transition is related to increased ductile extension in the lower crust and lithospheric mantle with little attendant upper crustal faulting to record the magnitude of this event in the structural history of the Vulcan Sub-basin. This lack of upper crustal deformation has resulted in an under- appreciation of the importance of this extensional event.By modelling the Jurassic to Recent basin history, a thermal model may be built allowing predictions of palaeo-heat flow during the critical time of hydrocarbon generation. The model predicts that during the Jurassic and Early Cretaceous, increased lower crust and lithospheric mantle extension produced a thermal anomaly of ~20mW/m2 across the Vulcan Sub-basin. The relaxation of this thermal anomaly in the Cretaceous and Tertiary produced a rapid post-rift subsidence which allowed flooding of the margin, with increased subsidence towards the northwest. However, the evolution of this thermal perturbation beneath the upper crust resulted in a time lag between Late Jurassic rifting and maximum basin heat flow in the Early Cretaceous of up to 30 million years after Callovian breakup Therefore, the simple relationship between upper crustal faulting and total lithosphere stretching common in intra-continental rifts is predicted to break dow n immediately preceding conti nental breakup and necessitates modelling of the transition from syn-rift to post-rift stratigraphy in order to predict the thermal history of the Vulcan Sub-basin.

2021 ◽  
Vol 62 (9) ◽  
pp. 1006-1020
Author(s):  
F.I. Zhimulev ◽  
E.V. Vetrov ◽  
I.S. Novikov ◽  
G. Van Ranst ◽  
S. Nachtergaele ◽  
...  

Abstract —The Kolyvan’–Tomsk folded zone (KTFZ) is a late Permian collisional orogen in the northwestern section of the Central Asian Orogenic Belt. The Mesozoic history of the KTFZ area includes Late Triassic–Early Jurassic and Late Jurassic–Early Cretaceous orogenic events. The earlier event produced narrow deep half-ramp basins filled with Early–Middle Jurassic molasse south of the KTFZ, and the later activity rejuvenated the Tomsk thrust fault, whereby the KTFZ Paleozoic rocks were thrust over the Early–Middle Jurassic basin sediments. The Mesozoic orogenic events induced erosion and the ensuing exposure of granitoids (Barlak complex) that were emplaced in a within-plate context after the Permian collisional orogeny. Both events were most likely associated with ocean closure, i.e., the Paleothetys Ocean in the Late Triassic–Early Jurassic and the Mongol–Okhotsk Ocean in the Late Jurassic–Early Cretaceous. The apatite fission track (AFT) ages of granitoids from the Ob’ complex in the KTFZ range between ~120 and 100 Ma (the Aptian and the Albian). The rocks with Early Cretaceous AFT ages were exhumed as a result of denudation and peneplanation of the Early Cretaceous orogeny, which produced a vast Late Cretaceous–Paleogene planation surface. The tectonic pattern of the two orogenic events, although being different in details, generally inherited the late Paleozoic primary collisional structure of the Kolyvan’–Tomsk zone.


1997 ◽  
Vol 17 (1) ◽  
pp. 363-387 ◽  
Author(s):  
W. Brian Harland ◽  
Simon R. A. Kelly

Jurassic-Cretaceous follows Triassic history with minor change. It was an interval dominated by deposition of marine muds, silts and sands, with occasional non-marine environments on advancing deltas (Parker 1967; Harland 1973a; Kelly 1988). Subdued topography contrasted with Triassic and Paleogene terrains. But there was also Late Jurassic and Early Cretaceous intrusion of basic sills and volcanism in eastern Svalbard. Figure 19.1 shows the distribution of Jurassic and Cretaceous deposits in Svalbard.The two periods (208-65 Ma) span 143 million years but the stratal record for this interval totals only 1700 m of which more than half was deposited in Albian time. The Jurassic-Cretaceous rocks of the eastern platform, presently cropping out on some islands, represent a relict of a once continuous sheet of strata, which is still preserved extensively across much of the Barents Shelf.The Triassic-Jurassic boundary is marked by seemingly continuous facies from Rhaetian to Toarcian; but then follows a contrast between the main Spitsbergen Basin (which hardly subsided) and the Eastern Platform. The contrasting areas of east and west Svalbard were divided by the continuing activity along the Billefjorden lineament. To the east, subsidence permitted a complex and variable sequence resulting from deltas from the east (marine and non-marine) through Liassic to mid-Bathonian time. To the west there was little evident subsidence and only condensed deposits of the uppermost Wilhelmoya Formation were washed by shallow seas. This part of the story concluded the history of the Kapp Toscana Group.A Late Bathonian marine transgression transformed east and


1985 ◽  
Vol 4 (1) ◽  
pp. 1-10 ◽  
Author(s):  
A. El-Arnauti ◽  
M. Shelmani

Abstract. INTRODUCTIONThe material which forms the basis of this project was obtained from a number of wells in the study area in Cyrenaica, the northeastern part of Libya. The study area, which is located between latitudes 25° and 33°N and between longitudes 20° and 25° E, covers some 365,750 square kilometres (see Fig. 1). The area extends from the Egyptian border in the east to the eastern flank of the Sirte Basin in the west and is part of the stable Saharan Shield.Since Precambrian time several phases of epeirogenic movements have produced troughs, horst blocks or platforms which have in turn influenced the subsequent sedimentological history of the area. In the southern and southeastern part of the study area, the basement is unconformably overlain by a thick, partially marine Palaeozoic sequence which is in turn unconformably overlain by sediments of Jurassic or younger age. The basement in the central and southwestern parts of the area is unconformably overlain by non-marine clastics of Late Jurassic and Early Cretaceous age or by marine sediments of Late Cretaceous and Tertiary age. In the eastern and northeastern section the basement is overlain by a wedge of eastward thickening marine Palaeozoic rocks which are in turn unconformably overlain by marine sediments of Late Cretaceous and Tertiary age. In the most northerly part of the northeastern region of the study area, a thick paralic sequence of Triassic, Jurassic and Early Cretaceous deposits is unconformably overlain by Late Cretaceous and Tertiary sediments.PALAEOZOICRocks of Cambro-Ordovician . . .


2013 ◽  
Vol 9 (4) ◽  
pp. 20130021 ◽  
Author(s):  
Valentin Fischer ◽  
Robert M. Appleby ◽  
Darren Naish ◽  
Jeff Liston ◽  
James B. Riding ◽  
...  

Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline leading to their Cenomanian extinction. We describe the first post-Triassic ichthyosaur from the Middle East, Malawania anachronus gen. et sp. nov. from the Early Cretaceous of Iraq, and re-evaluate the evolutionary history of parvipelvian ichthyosaurs via phylogenetic and cladogenesis rate analyses. Malawania represents a basal grade in thunnosaurian evolution that arose during a major Late Triassic radiation event and was previously thought to have gone extinct during the Early Jurassic. Its pectoral morphology appears surprisingly archaic, retaining a forefin architecture similar to that of its Early Jurassic relatives. After the initial latest Triassic radiation of early thunnosaurians, two subsequent large radiations produced lineages with Cretaceous representatives, but the radiation events themselves are pre-Cretaceous. Cretaceous ichthyosaurs therefore include distantly related lineages, with contrasting evolutionary histories, and appear more diverse and disparate than previously supposed.


Georesursy ◽  
2021 ◽  
Vol 23 (1) ◽  
pp. 2-16
Author(s):  
Valery I. Isaev ◽  
Margarita F. Galieva ◽  
Anna O. Aleeva ◽  
Galina A. Lobova ◽  
Vitaly I. Starostenko ◽  
...  

Study and exploration of the pre-Jurassic oil and gas complex in Western Siberia is one of the aspects of hydrocarbon raw-material base development. The main scope of this study is to locate the source of Paleozoic hydrocarbons. The problem of modeling and assessing the role of Paleozoic-Mesozoic hydrocarbon generation centers in the formation of «Paleozoic» oil deposits in the section of the Ostaninskoe oil and gas condensate field (Tomsk region) is solved. In the formation of the oil and gas content of the pre-Jurassic basement two reservoirs are involved: the weathering crust and the roof of the bed-rock Paleozoic. The first was formed during the period of 213–208 Ma, and the second is genetically determined by epigenetic processes in the weathering crust. Potential hydrocarbon sources for the weathering crust and bed-rock Paleozoic reservoirs are Domanic type rocks in the crystalline basement: Larinskaya S1lr, Mirnaya D1mr, Chuzikskaya D2cz, Chaginskaya D3cg Formations, as well as Tyumenskaya J1-2tm and Bazhenovskaya J3bg Formations in sedimentary cover. To perform joint paleotemperature modeling of sedimentary basins of the «modern» Jurassic-Cretaceous and Paleozoic «paleobasins», the Ostaninskaya 438P well was selected, which is due to the presence of measured temperatures both in the Jurassic sections and in the pre-Jurassic formations, as well as fluid inflows from the pre-Jurassic horizons into the well. At the first step, the solution of the inverse problem of geothermics was obtained using reservoir temperatures and vitrinite reflectance measurements from the Mesozoic deposits: density of deep heat flow from the base of sedimentary section was determined, which is characterized by a quasi-constant value from the Jurassic to the present. The second step was to solve the inverse problem using vitrinite reflectance measurements from Paleozoic sediments. As a result, the heat flow value was obtained for the key moments of geodynamic history of the stratigraphic section, starting from the Silurian. By solving direct problems of geothermics with the given values of heat flow, the structural-tectonic and thermal history of four Paleozoic potential oil source formations (as well as Jurassic – Bazhenov and Tyumen Formations) has been retraced. The controversial aspects of the heat transfer model in the section of the Ostaninskoe field are considered. It has been established that the Tyumen and Bazhenov oil sources (most likely Bazhenov) are syngenetic (in terms of generation, accumulation and preservation time) for the weathering crust and the Paleozoic reservoirs. The role of the Chaginskaya Formation as gas source is insignificant.


1984 ◽  
Vol 121 (5) ◽  
pp. 421-428 ◽  
Author(s):  
Marie-Françoise Brunet

AbstractThe subsidence history of the Aquitaine basin has been determined from deep exploratory well data. The contribution of sediment loading to the subsidence has been evaluated and removed, including corrections for effects of compaction, water depth and changes of sea-level but not of flexural rigidity of the lithosphere. The tectonic subsidence curves obtained indicate that the basin underwent two periods of subsidence acceleration in the Trias–Early Lias and Late Jurassic–Early Cretaceous. They are interpreted in relation to the displacements of Iberia with respect to Europe as two periods of extension followed by periods of passive subsidence due to conductive cooling of the lithosphere; the formation of the ‘flysch trough’ in the southern part of the basin is then discussed.


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