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Germán Aguilar Rodrigo Riquelme Joseph Martinod José Darrozes Eric Maire 《地球表面变化过程与地形》2011,36(13):1736-1748
We quantify erosion rates in the higher sectors of the Huasco Valley, in the Main Cordillera of the semi‐arid Andes of Chile, using elevation differences between three successive geomorphic markers (pediments and paleo‐valleys) and the present day valley. Available Ar‐Ar ages of Neogene pediments are used to estimate mean erosion rates for the three periods (16 to 13 My, 13 to 8 My, and following 8 My). The landscape of the Huasco Valley is in a transient state, as indicated by well‐preserved pediment surfaces in interfluves, valleys deeply incised by fluvial and glacial erosion and scarped head‐valleys that represent the current knickzones. Higher erosion rates (45–75 m/My) are calculated for the more recent period (< 8 My) during which deep incision developed compared to previous periods (6–31 m/My). Quantitative data indicate that glaciers had a much higher erosional capability than fluvial activity in the higher sectors of the Main Cordillera. Comparison with erosion rates calculated in other drainage basins of the Chilean Andes suggests that the variability of erosion rates depends on the landscape's transient erosive state. The landscape's geomorphologic response to the uplift of the Main Cordillera results in the retreat of a knickzone, for which retreat velocity depends on precipitation rate pattern and glacial erosion intensity. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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As sediment accumulation indicates basin subsidence, erosion often is understood as tectonic uplift, but the amplitude and timing may be difficult to determine because the sedimentary record is missing. Quantification of erosion therefore requires indirect evidence, for example thermal indicators such as temperature, vitrinite reflectance and fission tracks in apatite. However, as always, the types and quality of data and the choice of models are important to the results. For example, considering only the thermal evolution of the sedimentary section discards the thermal time constant of the lithosphere and essentially ignores the temporal continuity of the thermal structure. Furthermore, the types and density of thermal indicators determine the solution space of deposition and erosion, the quantification of which calls for the use of inverse methods, which can only be successful when all models are mutually consistent. Here, we use integrated basin modelling and Markov Chain Monte Carlo inversion of four deep boreholes to show that the erosional pattern along the Sorgenfrei–Tornquist Zone (STZ) in the eastern North Sea is consistent with a tectonic model of tectonic inversion based on compression and relaxation of an elastic plate. Three wells in close proximity SW of the STZ have different data and exhibit characteristic differences in erosion estimates but are consistent with the formation of a thick chalk sequence, followed by minor Cenozoic erosion during relaxation inversion. The well on the inversion ridge requires ca. 1.7 km Jurassic-Early Cretaceous sedimentation followed by Late Cretaceous–Palaeocene erosion during inversion. No well demands thick Cenozoic sedimentation followed by equivalent significant Neogene exhumation. When data are of high quality and models are consistent, the thermal indicator method yields significant results with important tectonic and geodynamic implications. 相似文献
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The magnetic map of Slovakia used in the paper was compiled as part of a project titled Atlas of Geophysical maps and profiles in 2001. The residual magnetic data were analyzed to produce Curie point estimates. To remove distortion of magnetic anomalies
caused by the Earth’s magnetic field, reduction to pole transformation was applied to the magnetic anomalies using the magnetization
angle of the induced magnetization. Anomalies reduced to the pole tend to be better correlated with tectonic structures. We
applied a 3-km upward continuation to the residually compiled magnetic anomalies in order to remove effects of topography.
The depth of magnetic dipoles was calculated by an azimuthally averaged power spectrum method for the entire area. Such estimates
can be indicative of temperatures in the crust, since magnetic minerals lose their spontaneous magnetization according to
Curie temperature of the dominant magnetic minerals in the rocks. The computed Curie point depths in the Slovakia region vary
between 15.2 km and 20.9 km. Heat flow higher than 100 mWm−2 occurs at the central volcanics and eastern part of Slovakia, where the Curie point depths values are shallow. The correlation
between Curie point depths, heat flow and crust depth was investigated for two E-W cross sections. Heat flow and Curie point
depth values are correlated with each other however, these values could not be correlated with crust depth. The Curie point
isotherm, which separates magnetic and non-magnetic parts of the crust, is represented in two cross sections. 相似文献
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Late Miocene fluvial sediment transport from the southern Appalachian Mountains to southern Florida: An example of an old mountain belt sediment production surge 
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下载免费PDF全文 Past geomorphological models assume that erosion of sediments from old mountain belts occurred at a relatively constant rate, based on comparatively uniform isostatic adjustment caused by unloading. Late Miocene strata of the south‐eastern United States provide an example of pulsed tectonism resulting in a surge in siliciclastic sediment production and transport. Regional tectonism (uplift of the southern Appalachian Mountains) and climatic conditions during the Late Miocene resulted in the long‐distance (up to 1000 km) fluvial transport of coarse siliciclastic sediments onto a stable carbonate platform in southern Florida. The sediments are unusual in that they are significantly coarser than marine‐transported sands in southern Florida, with discoidal quartz and quartzite clasts up to 40 mm in diameter locally present, and have relatively high potassium feldspar contents (up to 16% in some sample fractions), whereas feldspar is rare in modern Florida beach sands. It is suggested that previously documented rejuvenation of the southern Appalachian Mountains during the Middle to Late Miocene time, coupled with the Messenian sea‐level low, generated the increased rate of sediment production and necessary hydraulic gradient to allow rapid transport of coarse sediments. Tectonic influence on the river pathway in Florida, as well as in the southern Appalachian Mountains, may have maintained the river on the narrow carbonate platform. The Florida Platform during the Late Miocene must also have had a sufficiently wet climate to cause episodic transport of the coarse sediments. Siliciclastic sediment transport on the Florida Platform during the Late Miocene greatly differed from Pleistocene to modern conditions, which are dominated by the transport of fine‐grained sands by longshore marine processes. 相似文献
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内蒙古中部地区高特格产出的哺乳动物化石的组合代表了该地区新近纪哺乳动物群序列中最年轻的成员，在研究蒙古高原动物群的演化与生态环境变化上有着重要意义，为此笔者等开展了对含化石地层剖面的岩石磁学和磁性地层研究。研究发现，这套地层主要携磁矿物为磁铁矿和矫顽力谱较宽的针铁矿。由于岩石的磁化强度很低，难以直接获得特征分量，然而通过低温分量的重磁化大圆弧分析，可以得到样品特征剩磁的磁极性，从而建立了该剖面的磁极性地层柱。在27．65m厚的剖面上，共获得四个正、反极性带：：N1-R1-N2-R2，R1对应于C3n．lr，N2对应于C3n．1n。高特格动物群出露在C3n．1n-C3n．1r之间，绝对年龄在4．180～4．480Ma之间，含化石层（22．65m厚）平均沉积速率为65．2m／Ma。据此推断出采样剖面的年代在4．072-4．496Ma之间。 相似文献
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