The processes and deposits of tide-dominated river deltas and estuaries are well-understood, but the sedimentary dynamics of tide-dominated straits and seaways are relatively little studied. Although recent depositional models have started to fill this gap, many aspects of tidal strait sedimentation such as interaction with strait-margin alluvial fans and marginal marine systems remain poorly understood. This paper presents a study of the late Miocene basal carbonate member of the Bouse Formation exposed along the lower Colorado River, where prior studies have suggested a tidal influence on deposition. This study explores the applicability of tidal strait models in a continental oblique-rift setting, and tests hypotheses for depositional processes and environments through detailed analysis of sedimentary facies, cross-bedding architecture and palaeocurrent data. Mixed carbonate–siliciclastic facies on the west margin of the southern Blythe Basin record sedimentation in alluvial fans and fan-fringing tidal flats at the retreating margin of a transgressive tidal strait. Pre-Bouse normal faults established a narrow, tectonically confined basin architecture that led to amplification of tidal currents. Basin-margin deposits pass laterally and up-section into high-energy cross-bedded grainstone facies that record southward migration of compound dunes in the dune-bedded strait zone of a shallow (ca 25 m) tidal strait. These findings provide the basis for recognition of strait-margin facies in other settings where complex facies associations result from along-strike variations in palaeobathymetry and current velocity. The results support a tidal origin for the southern Bouse Formation and provide new evidence for post-Miocene uplift of the lower Colorado River Valley and adjacent areas.

中文翻译：

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美国西南部科罗拉多河下游中新世晚期潮汐海峡边缘的碳酸盐-硅质碎屑混合沉积

潮汐主导的河流三角洲和河口的过程​​和沉积物已被很好地理解，但潮汐主导的海峡和航道的沉积动力学研究相对较少。尽管最近的沉积模型已开始填补这一空白，但潮汐海峡沉积的许多方面仍知之甚少，例如与海峡边缘冲积扇和边缘海洋系统的相互作用。本文介绍了对沿科罗拉多河下游暴露的 Bouse 地层的晚中新世基底碳酸盐岩成员的研究，先前的研究表明潮汐对沉积的影响。本研究探讨了潮汐海峡模型在大陆斜裂谷环境中的适用性，并通过对沉积相的详细分析来检验沉积过程和环境的假设，跨层结构和古海流数据。布莱斯盆地南部西缘的混合碳酸盐岩-硅质碎屑相记录了海侵潮汐海峡后退边缘冲积扇和扇缘潮滩的沉积。Pre-Bouse 正断层建立了一个狭窄的、受构造限制的盆地结构，导致潮汐流的放大。盆地边缘沉积物横向和上剖面进入高能交错颗粒岩相，记录了浅层沙丘层海峡带中复合沙丘的南移。构造受限的盆地结构导致潮汐流放大。盆地边缘沉积物横向和上剖面进入高能交错颗粒岩相，记录了浅层沙丘层海峡带中复合沙丘的南移。构造受限的盆地结构导致潮汐流放大。盆地边缘沉积物横向和上剖面进入高能交错颗粒岩相，记录了浅层沙丘层海峡带中复合沙丘的南移。约25 m) 潮汐海峡。这些发现为在其他环境中识别海峡边缘相提供了基础，在这些环境中，复杂的相关联是由古水深测量和水流速度的沿走向变化引起的。结果支持南部 Bouse 组的潮汐起源，并为科罗拉多河下游河谷和邻近地区的后中新世隆起提供了新的证据。