Lateral extrusion in the eastern Alps, PArt 2: Structural analysis
Lateral extrusion in the eastern Alps, PArt 2: Structural analysis
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DOI：
10.1029/90tc02623
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发表时间：
1991-04
期刊：
影响因子：
4.2
通讯作者：
L. Ratschbacher;W. Frisch;H. Linzer;O. Merle
中科院分区：
文献类型：
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作者：
L. Ratschbacher;W. Frisch;H. Linzer;O. Merle
阿尔卑斯山晚渐新世-中新世构造样式沿造山带沿着走向变化。在阿尔卑斯山脉的西部和中部，前陆叠瓦状、逆冲推覆和后褶作用占主导地位。在东阿尔卑斯山脉，走滑和正断层占主导地位。这些差异是由于东阿尔卑斯山脉的横向挤压造成的。横向挤压包括构造逃逸（由作用于其边界的力驱动的构造楔的平面应变水平运动）和伸展塌陷（重力从造山带的地形高点向外扩散）。以下因素促成了东阿尔卑斯山侧向挤压的形成：（1）坚硬的前陆，（2）由凹陷和早期碰撞形成的厚地壳，（3）由于热松弛导致的地壳强度降低，（4）从东阿尔卑斯山到喀尔巴阡山脉的地壳厚度梯度，以及（5）可能的岩石圈根的扰动。南阿尔卑斯山向北的压痕导致增厚和前面的压头和构造逃逸。重力扩张使地壳厚度差异减小。锯齿状构造出现在东阿尔卑斯山脉西部，包括褶皱、逆冲断层和走滑断层。这些结构横向进入扩张结构，其中包括东阿尔卑斯山东部的张扭断层和正断层。整体构造格局主要是由逃逸结构，即一套走滑断层，约束连续挤压楔。构造的复杂性源于（1）主要断层组的干扰，（2）东阿尔卑斯山脉与其前缘和腹地之间位移差异的调节，（3）位移从东阿尔卑斯山脉向喀尔巴阡山脉转移，喀尔巴阡山脉充当横向不受约束的边缘，以及（4）地壳解耦，将挤压分为脆性上板块和韧性下板块变形。侧向挤压的运动学近似推覆构造的挤压扩张模型。
The late Oligocene-Miocene tectonic style of the Alps is variable along strike of the orogen. In the Western and Central Alps, foreland imbrication, backthrusting, and backfolding dominate. In the Eastern Alps, strike-slip and normal faults prevail. These differences are due to lateral extrusion in the Eastern Alps. Lateral extrusion encompasses tectonic escape (plane strain horizontal motion of tectonic wedges driven by forces applied to their boundaries) and extensional collapse (gravitational spreading away from a topographic high in an orogenic belt). The following factors contributed to the establishment of lateral extrusion in the Eastern Alps: (1) a rigid foreland, (2) a thick crust created by indentation and earlier collision, (3) a decrease in strength in the crust due to thermal relaxation, (4) a crustal thickness gradient from the Eastern Alps to the Carpathians, and, possibly, (5) a disturbance of the lithospheric root. Northward indentation by the Southern Alps causes thickening in and in front of the indenter and tectonic escape. Gravitational spreading attenuates crustal thickness differences. Indentation structures occur in the western Eastern Alps and comprise folds, thrusts, and strike-slip faults. These structures pass laterally into spreading structures, which encompass transtensional and normal faults in the eastern Eastern Alps. The overall structural pattern is dominated by escape structures, namely, sets of strike-slip faults that bound serially extruding wedges. Structural complexity arises from (1) interference of major fault sets, (2) accommodation of displacement differences between the Eastern Alps and their fore- and hinterland, (3) displacement transfer from the Eastern Alps toward the Carpathians which act as a lateral unconstrained margin, and (4) crustal decoupling, which partitions extrusion into brittle upper plate and ductile lower plate deformation. The kinematics of lateral extrusion is approximated by an extrusion-spreading model proposed for nappe tectonics.