Cenozoic relief evolution of the Eastern Alps - con- straints from apatite fission track age-provenance of Neogene intramontane sediments
Cenozoic relief evolution of the Eastern Alps - con- straints from apatite fission track age-provenance of Neogene intramontane sediments
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东阿尔卑斯山新生代地貌演化——磷灰石裂变径迹的制约——新近纪山内沉积物的年龄来源
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
W. Frisch
中科院分区：
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作者：
I. Dunkl;J. Kuhlemann;J. Reinecker;W. Frisch
东阿尔卑斯山内盆地中中新世砂岩碎屑磷灰石的裂变径迹（FT）年龄反映了阿尔卑斯山前演化阶段的地表分布。用磷灰石碎屑热年代学方法描述了东阿尔卑斯东部新生代发掘阶段的意义和分布。此外，我们还完成了对东阿尔卑斯新近系盆地残余物源区的认识，并将这些沉积学特征整合到对磷灰石FT年龄分布的解释中。根据碎屑磷灰石的裂变径迹年龄谱，中中新世可划分出3个时代地形：(1)北部和中部以白垩纪、古新世和始新世磷灰石FT年龄为主的源区；(2)东阿尔卑斯南缘以渐新世FT年龄为主的区域；(3)快速发掘的Pohorje （Bacher）山脉中新世的小源区。根据砾石岩性、输运指标和沉积相资料，对研究区中中新世沉积输运和埋藏模式进行了重建。早中新世至中中新世盆地形成时期，沉积物覆盖在陶恩窗和潘诺尼亚盆地之间的东阿尔卑斯山脉，覆盖范围比今天更广。主要的沉积遗迹带（enstal、Noric洼地和Drau山谷）代表了中中新世古enns、古muri - murz和古Drau三大河流的流域。他们的位置与现在的河流情况或多或少相似。我们认为这些古河流的山谷填充物是潘诺尼亚/斯蒂里亚盆地体系的西部延续。东阿尔卑斯陶恩窗以东的变质基底和浮雕建筑的发掘，经历了晚白垩世、中始新世、渐新世、早至中中新世和上新世五个不同的旋回。在这些时期之间，缓慢甚至停滞的垂直运动使得地形破坏、夷平和沉积成为可能。后戈索挤压事件在中始新世产生了发掘。从这一事件开始，变质区表面以始新世磷灰石FT时代为主，记录在新近系砂岩的碎屑磷灰石中。渐新世后挖掘阶段的垂直偏移有限，始新世磷灰石FT时代仍然保存在陶恩窗以东的变质地块的峰顶和隆起的古表面残余物中。
Fission track (FT) ages of detrital apatites from Middle Miocene sandstones of the intramontane basins of the Eastern Alps register the surface distribution of FT ages of the Alps in its former stage of evolution. We have used the apatite detrital thermochronology method to describe the significance and distribution of Cenozoic exhumation phases of the eastern part of the Eastern Alps. Additionally we have completed the knowledge on the provenance indicators of the Neogene basin remnants of the Eastern Alps and integrated these sedimentological features in the interpretation of the apatite FT age distributions. According to the fission track age spectra of the detrital apatites, three age terrains can be characterized for the Middle Miocene: (1) a northern and central source area with Cretaceous, Paleocene and Eocene apatite FT ages, (2) a region along the southern margin of the Eastern Alps, dominated by Oligocene FT ages, and (3) a small source area of Miocene ages in the rapidly exhuming Pohorje (Bacher) mountains. On the basis of pebble lithologies, transport indicators and facies data, we propose a reconstruction on the sediment transport and burial pattern for the study area in Middle Miocene time. During the Early-Middle Miocene basin formation period sediments covered the Eastern Alps between the Tauern Window and the Pannonian basin more widely than preserved today. The dewatering trend was usually from west to east and we suppose that the major belts of sediment remnants (Ennstal, Noric depression and Drau valley) indicate the valleys of three major rivers during Middle Miocene: Paleo-Enns, Paleo-Mur-Murz and Paleo-Drau. Their positions were more-or-less similar to the present situation of the rivers. We consider the valley fillings of these paleo-rivers as the western continuation of the Pannonian/Styrian basin system. The exhumation of the metamorphic basement and relief building in the Eastern Alps east of the Tauern Window occurred in five distinct cycles in Late Cretaceous, Middle Eocene, Oligocene, Early to Middle Miocene and Pliocene times. Between these periods slow or even stagnating vertical movements allowed relief destruction, planation and sedimentation. The post-Gosau compressional event generated exhumation in the Middle Eocene. From this event on, the surface of the metamorphic areas was dominated by Eocene apatite FT ages as recorded in detrital apatites in Neogene sandstones. The vertical offsets during post-Oligocene exhumation phases were limited and Eocene apatite FT ages are still preserved at the summits and in elevated paleosurface remnants of the metamorphic blocks east of the Tauern Window.