东北大西洋打开后格陵兰东北部的准平原和构造

IF 2 4区 地球科学 Q1 GEOLOGY
J. Bonow, P. Japsen
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引用次数: 8

摘要

在所有气候带中,高原和深切切割的山谷都是上升的被动大陆边缘(EPCM)的特征。然而,这些特征是关于大规模景观何时以及如何形成的一个争论话题。我们调查并绘制了格陵兰东北部(70–78°N)部分冰川景观的地图。该地区由结晶基底和古生代-中生代裂谷盆地组成,由东北大西洋断裂期间喷发的古近系玄武岩覆盖。我们的地层景观分析揭示了一个典型的EPCM,由两个隆起的侵蚀面主导,东西延伸200公里,南北延伸900公里。低起伏的上平面(UPS;海拔约2km)横切基底和古近系玄武岩,表明其在后玄武岩时代被分级到大西洋定义的基准面,随后上升。UPS形成于研究区南部中新世中期熔岩沉积之前。在内部基底地形中,下平面(LPS)在海拔约1公里处形成河谷阶地,在UPS下方切割。因此LPS比UPS年轻,这意味着它形成于中新世中期之后。朝向海岸,山谷的台阶融合在一起,形成了一个连贯的表面,定义了平顶山脉。这表明LPS被分级到接近海平面,随后被抬升。因此,UPS和LPS都形成了准平原——侵蚀面分级为基准面。与LPS相关的河谷阶地进一步表明,完整的冰川条件是在上新世早期(约5 Ma)LPS抬升后才建立的。LPS的抬升导致中生代蚀刻表面的再次暴露。我们得出的结论是,晚第三纪构造隆升形成了格陵兰东北部的阶梯状景观和隆起地形。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Peneplains and tectonics in North-East Greenland after opening of the North-East Atlantic
Elevated plateaus with deeply incised valleys characterise elevated, passive continental margins (EPCMs) in all climate zones. These features are, however, a topic of debate regarding when and how the large-scale landscapes formed. We have investigated and mapped the partly glaciated landscape of North-East Greenland (70–78°N). The area consists of crystalline basement and Palaeozoic–Mesozoic rift basins, capped by Palaeogene basalts that erupted during the northeast Atlantic break-up. Our stratigraphic landscape analysis reveals a typical EPCM dominated by two elevated erosion surfaces, extending 200 km east–west and 900 km north–south. The low-relief Upper Planation Surface (UPS; c. 2 km above sea level) cuts across basement and Palaeogene basalts, indicating that it was graded to base level defined by the Atlantic Ocean in post-basalt times and subsequently uplifted. The UPS formed prior to the deposition of mid-Miocene lavas that rest on it, south of the study area. In the interior basement terrains, the Lower Planation Surface (LPS) forms fluvial valley benches at c. 1 km above sea level, incised below the UPS. The LPS is thus younger than the UPS, which implies that it formed post mid-Miocene. Towards the coast, the valley benches merge to form a coherent surface that defines flat-topped mountains. This shows that the LPS was graded to near sea level and was subsequently uplifted. Hence, both the UPS and the LPS formed as peneplains – erosion surfaces graded to base level. The fluvial valley benches associated with the LPS further indicates that full glacial conditions were only established after the uplift of the LPS in the early Pliocene (c. 5 Ma). The uplift of the LPS led to re-exposure of a Mesozoic etch surface. We conclude that episodes of late Neogene tectonic uplift shaped the stepped landscape and elevated topography in North-East Greenland.
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来源期刊
Geus Bulletin
Geus Bulletin GEOLOGY-
CiteScore
2.80
自引率
17.60%
发文量
8
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