Sandbox Modeling of the Fault-increment Pattern in Extensional Basins

Three series of sandbox modeling experiments were performed to study the fault-increment pattern in extensional basins. Experimental results showed that the tectonic action mode of boundaries and the shape of major boundary faults control the formation and evolution of faults in extensional basins. In the process of extensional deformation, the increase in the number and length of faults was episodic, and every ＇episode＇ experienced three periods, strain-accumulation period, quick fault-increment period and strain-adjustment period. The more complex the shape of the boundary fault, the higher the strain increment each ＇episode＇ experienced. Different extensional modes resulted in different fault-increment patterns. The horizontal detachment extensional mode has the ＇linear＇ style of fault-increment pattern, while the extensional mode controlled by a listric fault has the ＇stepwise＇ style of fault-increment pattern, and the extensional mode controlled by a ramp-flat boundary fault has the ＇stepwise-linear＇ style of fault-increment pattern. These fault-increment patterns given above could provide a theoretical method of fault interpretation and fracture prediction in extensional basins.

A Quantitative Analysis System for Continental Extensional Basin

Continental extensional basin is one of the most important oil and ga s bearing basin types in the world and is main basin type in east China. The qu antitative analysis for this kind of basins has important significance for oil a nd gas exploration and development in east China. Sedimentary basin is a geodyna mic system including sedimentary basin itself, the crust and the mantle under it . Basin evolution is affected by regional structure stress field geophysical sta tus in the deep of the earth and outer condition, such as climate changes, water supplying etc. Based on the concept of basin dynamic system, the authors develo ped a geological process modeling and analyzing system-Continental Extensional B asin Quantitative Analysis System (CEBQAS). The system consists of basin geodyna mic modeling, structural modeling, sedimentary modeling, geologic analysis, data base and display subsystem. The system can reappear structural and sedimentary e volution history to an extent and provide basin geodynamic information as well a s retrieving parameter for modeling from original data such as logging, core an d seismic data .

Evolution of the Extensional Rifted Yunnan-Guizhou-Guangxi Oceanic Basin During the Late Hercynian to Middle Indosinian Stage

On the basis of exhaustive researches on the facies sequences and depositlonal evolutionary process of various depositional systems, the genetic stratigraphic framework of the extensional rifted oceanic basin, which has undergone strong structural destruction, has been reconstructed by means of dynamic genetic stratigraphic analysis. Five depositional episodes have been distinguished from various isochronous stratigraphic boundaries and stratigraphic sequences with the three-dimensional structure of each depositional episode analysed in detail. The tectonic paleogeographic environment corresponding to different stages of each depositional episode has been reconstructed for individual depositional system tracts. And the evolution history of this rifted basin has been divided into four stages' initial rifting and oceanization of continental crust, stretching and spreading of the basin, subduction and basin differentiation, and convergence and collision. A NNE-trending intracontinental soft collision suture was left after the closing of the basin.

Comparative New Insight into the Tectonic Origin of Folds and Thrust Faults of an Extensional Basin: Soke-Kusadasi Basin, Aegean, Western Turkey

The Aegean area of the western Anatolian region of Turkey,controlled by the low-angle detachment normal fault system,forms an extensional province,the West Anatolian Extensional Province(WAEP).The tectonic deformation which occurred in the Miocene Period,including the Plio–Quaternary Period has created different structures in both the basement rocks and intra-basin deposits of the crust.One of these structures,high-angle normal faults,controls the supradetachment Soke-Kusadasi Basin(SKB).Within this basin,there are folds with different axes and thrust faults with a north-northwestnortheast(N,NW,NE)trend.These folds and thrust faults in the SKB deformed the sedimentary structures of intra-basin deposits.The folds and thrust faults,which caused the rotation of beddings and imbrications in the SKB,are mainly associated with the tectonic process of the low angle detachment normal fault,which affected the SKB and the Aegean part of western Anatolia.In the SKB,during the process of extensional deformation associated with primary low angle detachment normal faulting,the ramp-flat and inversion geometry observed in the basement rocks and basin deposits of the crust caused folds and thrust faults in only intra-basin deposits.In the WAEP,it is determined for the first time that the folds and thrust faults causing limited shortening deformed the Plio–Quaternary sediments.

Tectonic and Geodynamic Setting of Oil and Gas Basins in China

About 26 sedimentary basins bearing oil and gas are developed in China. They can be classified into two main types . extensional basins and foreland basins . The former are chiefly distributed in the eastern part and the latter in the central and northwestern parts of the country . The present paper discusses the structural characteristics of these basins . including subsidence history , thermal history and structural style and kinematics . Combined with tectonic setting analysis of geophysical data and eruptive rocks , the geodynamic setting of the basins is established , and the formation mechanism of the basins is deduced to have been related to the subduction of the Izanagi and west Pacific plates and the closing of the Tethys ocean .

Mechanism of crustal extension in the Laxmi Basin,Arabian Sea

Continental rifting and magmatism has been extensively studied worldwide as it is believed that continental rifting, break up of continents and associated magmatism lead to genesis of new oceanic crust. However, various regions of the world show that these processes may lead to genesis of other types of crust than the oceanic crust. Laxmi Basin in the western continental margin of the India is one such region with an enigmatic crust.Due to its extreme strategic significance for the palaeogeographic reconstruction of continents during Cretaceous continental breakup of India, this basin has attracted various workers for more than two decades. However, still the issue of nature of crust in the basin remains controversial. In this contribution, in order to identify nature of crust, mechanism of continental extension in the Laxmi Basin has been studied for the first time through newly acquired seismic data from the basin. Here, we propose a plausible mechanism of crustal extension in the Laxmi Basin which eventually constrains the nature of crust of the Laxmi Basin. We have demonstrated that the crust in the Laxmi Basin can be categorised in two zones of stretched and transitional crust. In the stretched zone several fault bounded horst and graben structures are identified which preserve syn- and post-rift sediments along with different periods of hiatus in sedimentations as unconformities. These faults are identified as listric faults in the upper crust which sole out in the detachment faults.Detachment faults decouples the upper brittle and lower ductile crust. The transitional crust is identified as heavily intruded by sills and basaltic volcanic which were emplaced due to melting of subcontinental mantle（SCM） after hyper-stretching of crust and serpentinisation of the SCM. Panikkar Ridge is proposed to be one such basaltic volcanic body derived from melting of lower part of the SCM.

On Tectonogeomorphology of China

With the deepening of research in the tectonic evolution and stress fields of China in Meso-Cenozoic, some aspects of the Previous conclusion about the tectonogeomorphology of China are found to be open to question. The author considers that the Sichuanian stage (135-52 Ma ) is the embryonic stage for forming the recent landform in eastern China;the appearance of the mountain ranges and drainage basin areas trending in east-west are the results of the north - south directional extension during the North Sinian stage(52 - 23.3 Ma );the formation of five mega - Step landforms from the Qinghai - Xizang Plateau to Pacific ocean and the seafloor spreading basins in the eastern margin of Asian continent as well as the l- up of drainage systems of both Yangtze and Yellow rivers are related to the northward compression, cast-west trending extension and the isostatic compensation of crust during Himalayan Stage (23.3-0.73 Ma ). Through the above three Stages of tectonic processes, a framework of landform of China finally took shape in the main.

Palinspastic reconstruction and geological evolution of Jurassic basins in Mongolia and neighboring China

The important event in Jurassic tectonics in Mongolia was the subduction and closure of the Mongolia-Okhotsk ocean;correspondingly,basin evolution can be divided into two main stages,related to the orogeny and collapse of the orogenic belt,respectively.The developing of Early-Middle Jurassic basins to the north of the ocean resulted from back-arc extension.The fossil sutures,from the China-SE Asia sub-continent to the south of the ocean,were rejuvenated by subduction-related orogeny;in addition,the Yanshanian intra-continental movement occurred.Three Early-Middle Jurassic molasse basins were developed by movement in Inner Mongolia,all of which stretched westwards (or northwards) into Mongolia;therefore,the molasse basins in eastern and southern Mongolia had the same geometric and kinematic features as the basins in the Inner Mongolia.Owing to the collapse of the MongoliaOkhotsk orogenic belt,a group of rift basins developed during the Late Jurassic.In eastern Mongolia,the NE orientated extensional basins were controlled by the neogenic NE-structure.The contemporary basins in southern Mongolia and the neighboring areas in China were constrained by remobilization (inherited activation) of the latitudinal or ENE-directional basement structures.Three stages can be recognized in the evolution of the Early-Middle Jurassic basins after reversal;the basins also experienced four episodes of reformation.

Sequence architecture of a Jurassic ramp succession from Gebel Maghara(North Sinai,Egypt):Implications for eustasy

The Jurassic succession at Gebet Maghara, North Sinai, Egypt, represents a mixed carbonate-siticictastic sequence. Combining information from both fossits and rocks attowed a ptausibte reconstruction of the depositionat environments and of the basin evotution. The Ju- rassic succession of Gebel Maghara was deposited on a ramp, and the architecture of the ramp facies was strongty controtted not onty by sea-revel changes but atso by extensionat tectonics in connection with rifting of the Tethys, North Gondwana. Seven tectonicalty modified thirdorder sequences （DS 1-DS 7） have been recognized. The first three sequences （DS 1-DS 3）, ranging from the Toarcian to the Bajocian, record sea invasion （intertidat to shattow subtida[lconditions） across an intracratonic area as a resutt of eustatic sea-fever changes during a quiescent rift stage. The remaining sequences （DS 4-DS 7） reflect open marine mid to outer ramp settings. Non-marine conditions around the Bajocian-Bathonian boundary, documented by catiche, represent the maximum regression of the sea. During an active extensionat stage, horsts, which formerty acted as barriers separating the Maghara sub-basin from the main ocean, subsided. Subsequent rejuvenation and reactivation of fautts shifted the homoctinat physiography of the ramp to a distatty steepened ramp during the earty Bathonian, creating a 200-m-thick dettaic wedge. SimiLar processes during the earty Kimmeridgian created a catcirudite-catcarenite succession of stope origin. The diversity and the epifaunat/infaunat percentage of the macrofauna disptay a cyctic pattern which coincides more or tess with the sequence stratigraphic architecture.