The Geometry and Internal Architecture of Stream Mouth Bars in the Panther Tongue and the Ferron Sandstone Members, Utah, U.S.A.
The Geometry and Internal Architecture of Stream Mouth Bars in the Panther Tongue and the Ferron Sandstone Members, Utah, U.S.A.
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DOI：
10.2110/jsr.2010.088
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发表时间：
2010-11
影响因子：
2
通讯作者：
H. Enge;J. Howell;S. Buckley
中科院分区：
文献类型：
--
作者：
H. Enge;J. Howell;S. Buckley
摘要/ Abstract摘要/ Abstract摘要/ Abstract摘要/ Abstract摘要/ Abstract摘要/ Abstract从野外的斜地岩和地理空间受限的照片逼真的虚拟露头测量数据，用于记录斜地岩倾角、最大床层厚度和每10米的床层厚度，这些数据来自美国犹他州中部两个古老的河流三角洲序列的沉积倾向剖面。这些数据显示了河床倾角和河床变薄的系统性变化，突出了河床向河床组的离散打包，解释为三角洲前缘河口坝的进积。单个床层的特点是床层逐渐变陡，同时更迅速地变薄。利用系统采集的黑豹舌砂岩段73个独立斜层序和铁龙砂岩副层序1f的2800个位置，研究了层厚、倾角和衰减梯度参数τ之间的关系，该参数描述了下倾层减薄过程。黑豹舌中的脊岩比铁砂岩中的脊岩更长，也更平缓。在这两个系统中，层可以聚集成若干组（层组），它们的τ值系统地减小，倾角系统地增大。群之间的边界由τ值的突然增加和倾角的同时减小来定义。这些床层被解释为单独的河口坝，这些河口坝在三角洲前缘砂体内合并形成河口坝复合体。虚拟露头的使用对于收集大量厚度数据和识别非常细微（< 1°）的倾角变化至关重要，这些变化使这些解释成为可能。
Abstract Clinothems are seaward-dipping beds which are deposited during the progradation of delta-front mouth bars. Measurements taken from clinothems in the field and from geospatially constrained, photo-realistic virtual outcrops were used to record clinothem dip, maximum bed thickness, and bed thickness every 10 m along a series of depositional-dip-oriented profiles from two ancient river-dominated delta successions which crop out in central Utah, USA. These data show systematic changes in bed dip and bed thinning which highlight discrete packaging of the beds into bedsets, interpreted to represent the progradation of stream mouth bars in the delta front. Individual bedsets are characterized by a progressive steepening of beds coupled with a more rapid thinning. Systematic collection of 2800 locations along 73 separate clinothems from the Panther Tongue Sandstone Member and parasequence 1f from the Ferron Sandstone were used to study the relationship between bed thickness, dip, and decay gradient parameter (τ), which describes the down-dip bed thinning. Clinothems in the Panther Tongue are much longer and more gently dipping than the clinothems in the Ferron Sandstone. In both systems, beds can be clustered into groups (bedsets) which show a systematic decrease in τ-values and an increase in dip angle. Boundaries between the groups are defined by a sudden increase in τ-values and a concurrent decrease in dip angle. These bedsets are interpreted to represent individual stream mouth bars which amalgamate to form mouth bar complexes within the delta-front sand bodies. The use of virtual outcrops was essential for the collection of the large volumes of thickness data and the recognition of very subtle (< 1°) changes in dip angle which have made these interpretations possible.