SPP2 Project - Switching pro- and retro-wedges in the Eastern Alps and their peripheral basins - clues to a change in subduction polarity?

该项目将面临确定东阿尔卑斯山之下是否发生了新近纪俯冲极性转换的挑战。此外，它将回答新近纪压痕亚得里亚板块的运动如何转移到阿尔卑斯山造山地壳的问题，并将确定压痕、板片运动与阿尔卑斯山以北和南部的莫拉斯和威尼托(东坡)盆地动力学之间的相互作用。这将通过利用阿尔卑斯山造山带的结构和盆地历史作为俯冲极性的替代来完成。据预测，这种转变将使北部造山带前锋的行为发生变化，从前楔型(通过交替顺次和无序推覆而幕式推进)到反向楔型(缓慢推进、顺次逆冲和停滞交替)。这种截然不同的行为预计将反映在莫拉塞盆地碎屑沉积的数量和性质上。北阿尔卑斯山前缘从前向后楔形构造的转变，可以说是在莫拉斯盆地东部持续下沉到约16 Ma期间，逆冲前缘在~21 Ma停滞。在南阿尔卑斯山前缘，随着新近纪的逆冲和威尼托盆地近端在21-22 Ma的变形开始，逆楔行为可能已经转变为顺楔行为。该项目结合了使用最先进的地震学、盆地分析和构造地质学的3个工作包。地震学工作包将使用尖端技术(重新)处理Transalp实验的地震反射数据。多维相干分析将大大减少噪音，改善地下重建，对与地质相关的特征有更清晰的定义。盆地分析工作包将利用工业地震和钻孔数据重建北部造山前缘的结构、沿其走向的莫拉斯盆地东部的第三纪沉降史，以及造山前缘附近的沉积模式的变化。构造地质学一揽子工作将使用这些新图像以及东非地质学和SWATH-D实验中出现的图像，以建立和构造平衡从莫拉塞盆地通过东部阿尔卑斯山的基底核心到达南部威尼托盆地的新的综合地质-地球物理剖面。交付成果包括：(1)陶恩窗区下方断层的三维高分辨率图像，该图像划分了亚得里亚海压痕和侧向逃逸过程中的应变；(2)莫拉塞盆地东部的4维模型，记录了沿造山前缘从西至东阿尔卑斯山过渡带到东阿尔卑斯山交界处的逆冲运动的进退；(3)东阿尔卑斯山的综合4维模型，从板块撕裂和断裂到亚得里亚海的压痕。

This project will meet the challenge of determining whether or not a Neogene switch in subduction polarity occurred beneath the Eastern Alps. Further, it will answer the question of how Neogene motion of the indenting Adriatic plate was transferred to the Alpine orogenic crust and will identify the interactions between indentation, slab motions and the dynamics of the Molasse and Veneto (eastern Po) Basins, respectively, north and south of the Alpine Orogen.This will be done by using the structure and basin histories of the Alpine orogen as proxies for subduction polarity. Such a switch is predicted to effect change in the behaviour of the northern orogenic front from pro-wedge type (episodic advance by alternating in- and out-of-sequence thrusting) to retro-wedge type (slower advance, alternating in-sequence thrusting and stagnation). This contrasting behavior is expected to be reflected in the amount and nature of clastic deposits in the Molasse Basin. The transition of the northern Alpine front from pro- to retro-wedge behavior is arguably manifested by stagnation of the thrust front at ~21 Ma during prolonged subsidence of the eastern Molasse Basin until ~16 Ma. Along the southern Alpine front, retro-wedge behaviour may have changed to pro-wedge behaviour with the onset of Neogene thrusting and deformation of proximal parts of the Veneto Basin at 21-22 Ma. The project combines 3 work packages using state-of-the-art seismology, basin analysis and structural geology. The seismological work package will (re)process seismic reflection data from the TRANSALP experiment using cutting-edge techniques. Multi-dimensional coherence analysis will drastically reduce noise and improve subsurface reconstructions with a clearer definition of geologically relevant signatures. The basin analysis work package will use industry seismics and borehole data to reconstruct the structural of the northern orogenic front, the Tertiary subsidence history of the eastern Molasse Basin along and across its strike, and variations in sedimentation patterns next to the orogenic front. The structural geology work package will use these new images as well as those emerging from the EASI and SWATH-D experiments to construct and tectonically balance new integrated geological-geophysical cross sections reaching from the Molasse Basin through the basement core of the Eastern Alps to the Veneto Basin in the south. Deliverables include (1) a 3D high-resolution image of faults beneath the Tauern Window area that partitioned strain during Adriatic indentation and lateral escape; (2) a 4D model of the eastern Molasse Basin that documents advances and retreats of thrusting along the orogenic front, from the Central-Eastern Alps transition in the west to the Alps-Carpathians junction in the east; (3) an integrated 4D model of the Eastern Alps, from slab tearing and breakoff to Adriatic indentation.