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首页> 外文学位 >Paleosols as an indicator of ancient landscapes, climates and stratal response during the Triassic: The salt anticline region of Utah.
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Paleosols as an indicator of ancient landscapes, climates and stratal response during the Triassic: The salt anticline region of Utah.

机译：古土壤是三叠纪期间古代景观，气候和地层反应的指标：犹他州的盐背斜地区。

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Modern soils are excellent indicators of environmental conditions, and paleosols can be used as proxy for past conditions. This dissertation documents the response of Triassic paleosols and fluvial sediment accumulation to (1) landscape dynamics influenced by subsurface salt movement; and (2) variations in paleoclimatic conditions in eastern Utah. The first chapter is an introduction to the research. The second chapter examines the influence of salt tectonics on cyclic stratigraphy, paleosol morphology, and sedimentation rates. The distribution of paleosols are documented within a sequence stratigraphic framework to evaluate whether salt tectonics influenced patterns fluvial sediment dispersal. The Chinle Formation is divided into two sequences that are in turn composed of decameter-scale fluvial aggradational cycle sets (FACSET) and meter-scale fluvial aggradational cycles (FAC). Facies and paleosol distributions within this stratigraphic framework suggest that a minibasin initially increased and then decreased in diameter and that the axis of subsidence drifted to the northwest through the Late Triassic. The third chapter documents how ancient slopes, a geomorphic expression of halokinesis, controlled paleosol development through a traditional catena perspective. Paleoslopes on a major sequence boundary that extends across the minibasin control associated paleosol development. Pedotopographic influences included both downslope redistribution of sediment and change in soil hydrology. The fourth and final chapter utilizes a multi-proxy paleosol approach to reconstruct climatic and atmospheric conditions during the deposition of Triassic fluvial sediments and the formation of paleolandscapes associated with halokinesis. Paleoclimate reconstruction supports the occurrence of a global pluvial episode during the Carnian (late Middle Triassic) that contrasted with mostly arid climates during the Middle to Late Triassic. Arid (and near arid) episodes in the latest Moenkopi and upper Chinle contradict monsoonal seasonality, whereas the lower Chinle pluvial suggests a non-continental climate similar to the modern eastern United States. Drastic changes in rainfall and soil types indicate that the Middle to Late Triassic in eastern Utah was an interval of dynamic climate change that may partially be tied global carbon dioxide levels and tectonism.
机译：现代土壤是环境条件的极好指标，古土壤可以用作过去条件的替代。本文记录了三叠纪古土壤和河流沉积物的积累对（1）地下盐分运动影响下景观动态的响应。 （2）犹他州东部古气候条件的变化。第一章为研究导论。第二章探讨了盐构造对循环地层学，古土壤形态和沉积速率的影响。在层序地层学框架内记录了古土壤的分布，以评估盐构造是否影响了河流沉积物的扩散。 Chinle地层分为两个序列，依次由十亿级河流集水循环集（FACSET）和米级河流集水循环集（FAC）组成。在这个地层学框架内的相和古土壤分布表明，一个小盆地的直径先增大然后减小，并且沉降轴线通过三叠纪晚期向西北漂移。第三章介绍了古代斜坡，是地表运动的一种地貌表达，是如何通过传统的连环视角来控制古土壤的发育的。跨越小盆地控制的主要序列边界上的古坡与古土壤发育有关。古地形学的影响包括沉积物的下坡再分布和土壤水文学的变化。第四章也是最后一章，在三叠纪河流沉积物的沉积和与盐岩运动有关的古地貌的形成过程中，采用了多代理古土壤方法来重建气候和大气条件。古气候重建支持在卡尼期（中三叠纪晚期）发生全球一次小雨事件，这与中三叠纪至晚期的大部分干旱气候形成对比。最新的Moenkopi和上Chinle的干旱（和近干旱）事件与季风季节相矛盾，而下Chinle的小雨则表明与现代美国东部相似的非大陆性气候。降雨和土壤类型的急剧变化表明，犹他州东部的中三叠世至晚三叠世是一个动态的气候变化区间，可能部分与全球二氧化碳水平和构造运动有关。

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