Abstract Architectural elements of fluvial multi-storey sandbodies provide principal controls on the distribution of meso-scale (100–101 m scale) heterogeneity and reservoir quality. Consequently, it is valuable to understand the deposition and preservation of sedimentary architecture in such systems in relation to autogenic (stream capture and avulsion) and allogenic controls (subsidence rates, climate and sediment supply). The aims of this study are to quantify the architectural and erosional nature of a fluvial multi-storey sandbody and to establish the effects of downstream distance and subsidence rates upon the preservation of architectural elements, using the Lower Castlegate Sandstone, Utah, USA, as an example. Quantitative architectural element analysis and palaeodischarge reconstructions were undertaken from eight locations using sedimentary logs and three terrestrial photogrammetric outcrop datasets along a 150 km down-dip profile. These observations were supplemented by burial history analysis of ten wells across the same profile. Results show the Lower Castlegate comprises channel-fill, downstream accretion, lateral accretion, upstream accretion and overbank elements. From these observations, calculations of sinuosity and flow depths along with architectural geometric analysis provide evidence of stream capture contemporaneous with foreland basin subsidence. The preservation of lateral accretion and overbank elements is limited within the distal portion of the multi-storey sandbody, as a result of local avulsion and limited subsidence rates. Results demonstrate that complex sedimentary architecture can form in fluvial multi-storey sandbodies as a product of variable discharge rates, the fluvial graded profile and spatially variable aggradation rates, driven principally by subsidence rates. The use of meso-scale architectural analysis, with analysis of in-channel sinuosity and hydrodynamics, along with erosional bounding surfaces, has helped to complemented basin-scale interpretations of fluvial architecture.

中文翻译：

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控制河流多层砂体内建筑元素的沉积和保存

摘要 河流多层砂体的建筑元素为中尺度（100-101 m 尺度）非均质性和储层质量的分布提供了主要控制。因此，了解与自生（河流捕获和撕脱）和同种异体控制（沉降率、气候和沉积物供应）相关的此类系统中沉积结构的沉积和保存是很有价值的。本研究的目的是量化河流多层砂体的建筑和侵蚀性质，并确定下游距离和沉降速率对建筑元素保护的影响，使用美国犹他州的下卡斯尔盖特砂岩作为例子。使用沉积测井和三个陆地摄影测量露头数据集沿着 150 公里的下倾剖面从八个地点进行了定量建筑元素分析和古地貌重建。对同一剖面上的 10 口井的埋藏历史分析补充了这些观察结果。结果表明，Lower Castlegate 包括河道填充、下游增生、横向增生、上游增生和堤岸元素。根据这些观察结果，计算曲率和水流深度以及建筑几何分析提供了与前陆盆地沉降同时发生的河流捕获的证据。由于局部剥脱和有限的沉降速率，在多层砂体的远端部分，侧向堆积和堤岸元素的保存受到限制。结果表明，复杂的沉积结构可以在河流多层砂体中形成，这是可变排放率、河流分级剖面和空间可变的聚集率的产物，主要由沉降率驱动。中尺度建筑分析的使用，以及对河道内曲折和流体动力学的分析，以及侵蚀边界面，有助于补充对河流建筑的盆地尺度解释。