Late Cenozoic uplift of the Sierra Nevada, California? A critical analysis of the geomorphic evidence
Late Cenozoic uplift of the Sierra Nevada, California? A critical analysis of the geomorphic evidence
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加州内华达山脉晚新生代隆起？
DOI：
10.2475/08.2014.03
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发表时间：
2014
影响因子：
2.9
通讯作者：
E. Gabet
中科院分区：
文献类型：
--
作者：
E. Gabet
从加州地质学的早期开始，内华达州山脉北方的斜坡状轮廓和最近切割的推定迹象被解释为该山脉是由新生代晚期刚性块体倾斜形成的证据。多年来，各种地貌分析已被用于量化隆升的幅度并确定其时间，例如分析古河道的坡度，检查沉积床的倾斜，以及重建河流的切割历史。使用这些方法的大多数研究都支持塞拉利昂最近的大幅抬升（>500米）。与此相反，基于其他来源的古地形信息，如同位素记录，热年代学和碎屑锆石地质年代学的调查发现，塞拉利昂一直在高海拔的新生代。这一系列相互矛盾的结果促使人们重新审视晚新生代隆升的地貌证据。根据新的地形分析和实地调查，对这些地貌研究进行了严格的评估，结果表明，他们的结论没有得到很好的支持。例如，有几项研究的结果是基于对古代河道的重建，这些河道本来会向上流动并越过高达190米的基岩山脊，这在物理上是不可能的。其他弱点包括不合理的假设，河流沉积物的原始倾斜，地层关系的误解，以及对岩性对河道剖面的影响认识不足。支持内华达州北方山脉最近倾斜的研究是不确定的，并且依赖于并非构造作用力所特有的观测结果。事实上，许多证据的基础上的第三纪渠道的古梯度是一致的，形成了一个早期的格状排水网络跨越交替带的抵抗和弱岩性。此外，分析表明，深北方Sierran峡谷被认为是最近切割，而不是早在始新世-渐新世。两个地貌研究从南部山脉是一致的晚新生代倾斜和隆起，虽然正在进行的构造活动可能是微不足道的。最后，我提出了一个概念模型的Sierran景观的演变，主要适用于范围的北方的一半，说明了三个不同的排水网络的发展，因为晚侏罗世。
From the earliest days of California geology, the ramp-like profile of the northern half of the Sierra Nevada mountains and putative signs of recent incision have been interpreted as evidence that the range was formed by the tilting of a rigid block in the late Cenozoic. Over the years, various geomorphic analyses have been used to quantify the magnitude of uplift and to establish its timing, such as analyzing the gradients of ancient channels, examining the tilt of sedimentary beds, and reconstructing the incisional history of rivers. Most studies that have used these methods have supported substantial (>500 m) recent uplift of the Sierra. In contrast, investigations based on other sources of paleotopographic information, such as isotope records, thermochronology, and detrital zircon geochronology, have found that the Sierra have been at high elevations for much of the Cenozoic. This set of contradictory results motivates a re-examination of the geomorphic evidence for late Cenozoic uplift. A critical assessment of these geomorphic studies, based on new topographic analyses and field investigations, reveals that their conclusions are not well supported. For example, several studies based their results on reconstructions of ancient channels that would have flowed up and over bedrock ridges as high as 190 m, a physical impossibility. Other weaknesses include unjustified assumptions regarding the original tilt of fluvial deposits, misinterpretations of stratigraphic relationships, and inadequate recognition of the effect of lithology on channel profiles. The studies supporting recent tilting in the northern Sierra Nevada are inconclusive and rely on observations not unique to tectonic forcing. Indeed, much of the evidence based on the paleogradients of the Tertiary channels is consistent with an early trellis drainage network formed across alternating bands of resistant and weak lithologies. In addition, analyses are presented to demonstrate that deep northern Sierran canyons thought to have been recently incised were, instead, cut as early as the Eocene-Oligocene. Two geomorphic studies from the southern Sierra are consistent with late Cenozoic tilting and uplift although ongoing tectonic activity may be insignificant. Finally, I present a conceptual model of the evolution of the Sierran landscape, applicable primarily to the northern half of the range, illustrating the development of three different drainage networks since the late Jurassic.
影响因子：
3.9
作者：
Hurst, Martin D.;Mudd, Simon M.;Yoo, Kyungsoo
通讯作者：
Yoo, Kyungsoo