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1、Chapter 6 Fault setsKeywordsExtensional structurelistic faultdomino faultsDetachmentThrust structure伸展构造犁式断层多米诺断层拆离断层逆冲（推覆）构造Roll-over anticlinesdecollementNappeKlippe旋转褶皱挤离断层，滑脱断层，基底逆掩断层推覆体飞来峰duplexmetamorphic core complexesFlat and Rampwindow双重逆冲构造变质核杂岩断坪，断坡构造窗Hinter land, fore landBedding-step th
2、rustingPull-apart BasinHorst， Graben后陆，前陆台阶式逆冲断层拉分盆地地垒，地堑“Pop -Up” Structureimbricated splay faultsback-thrustsoverturned anticlines冲起构造叠瓦状断层（叠瓦扇）反冲断层反转背斜1. Extensional structureExtensional structure is usually composed of series normal faults due to the streching of the lithosphere. Consequently th
3、ey are the chief structural components of many sedimentary rift basins where they have major significance for hydrocarbon exploration. They can also be found in deltas, at the rear edges of huge gravitation slumps and slides. The extensional structure can occur in different scale , at different dept
4、h and under different geological condition. The main structure patterns will be shown in following:(1) listic faultIn some situations the faults can become gently dipping at depth so that they have a spoon (or listric) shape. Listric faults can be defined as curved normal faults in which the fault s
5、urface is in concave upwards; its dip decreases with depth. These faults also occur in extension zones where there is a main detachment fracture following a curved path rather than a planar path. Hanging wall blocks may either rotate and slide along the fault plane (eg slumps), or they may pull away
6、 from the main fault, slipping instead only along the low dipping part of the fault. Roll-overanticlines will often form between bedding planes and the main fault plane as a result of thelistric fault collapsesflexing between the two.Example of listric faults known as slumps. Hanging wall blocks rot
7、ate and slide along the entire fault plane.(2) grabens and horsts.The structures are the product of several normal faults forming in close proximity and dippingin opposite directions. This leads to the subsidence of a hanging wall (graben) between two foot walls (horst). A horst is a raised elongate
8、d block of the earths crust lying between two normal faults, and a graben is an elongated block of earths crust lying between two normal faults. When a horst and graben are beside each other, they are considered to be a horst and graben structuralsystem.This diagram illustrates the formation of a ho
9、rst and graben system. The development of opposite dipping normal faults leads to the subsidence of grabens in between horst blocks.Diagram illustrating the formation of half grabens from a series of normal faults dipping in the same direction. These structures look like fallen dominoesDetachment nn
10、odel for CyctadesNaxos - ParosAnti panos30 kmSection through the Hornelen Basrn, Norway(3) Domino faultsNormal faults may not always dip in opposite directions when they form. Instead, they may actually dip in similar directions. This will lead to a domino structure in which adjacent faults will sli
11、p down relative to the fault next to it. These structures are also known as half-grabens and are accompanied by a tiling of the fault blocks. Sedimentary layers may also bend towards the fault plane.(4) Detachments and metamorphic core complexesAlthough most active normal faults can be shown to dip
12、at angles steeper than 50 degrees, there are examples of very low-angle normal faults. These are often termed detachments - although this is a pretty vague term! Detachment faulting is associated with large-scale extensional tectonics. Detachments show gentle dips and often expose high grade metamor
13、phic rocks in their footwalls. These footwalls can be termed metamorphic core complexes.2. Thrust structureThrusts are reverse faults and commonly dominate the structure of collision mountain belts. Some thrusts have moved a long way - many mountain belts have thrusts that have moved many tens of ki
14、lometers. Thrust faults often move older rocks on top of younger rock and influence the positions of ore deposits and hydrocarbons.Nappe is a large sheetlike body of rock that has been moved older rocks on top of younger rocks far from its original position due to the thrust movement. Windows are ho
15、les eroded into the older rocks in the hanging wall, down through the fault plane, and into the younger rocks of the footwall on a map. The exposure of younger rocks is surrounded by older rocks. Klippe, the opposite of a window, erosion through the hanging wall and the fault plane, isolates a piece
16、 of the hanging wall (older) at the top of a hill of younger rocks (older and younger rocks are separated by a segment of the thrust fault cutting through the hill).Thrust faults develop when one block of earth collides with and compresses another block. Thrust fault deformation comes in two varieties, decollement and imbricated splays
