Process-Driven Architectural Variability In Mouth-Bar Deposits: A Case Study From A Mixed-Process Mouth-Bar Complex, Drumheller, Alberta, Canada
Process-Driven Architectural Variability In Mouth-Bar Deposits: A Case Study From A Mixed-Process Mouth-Bar Complex, Drumheller, Alberta, Canada
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口坝沉积物中工艺驱动的结构变异性：加拿大阿尔伯塔省德兰赫勒混合工艺口坝综合体的案例研究
DOI：
10.2110/jsr.2016.23
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发表时间：
2016
影响因子：
2
通讯作者：
S. Dashtgard
中科院分区：
文献类型：
--
作者：
R. Ainsworth;B. Vakarelov;J. Maceachern;R. Nanson;T. Lane;Franklin Rarity;S. Dashtgard
河口沙洲可以在河流分流河道向海岸线输送粗泥沙的地方发育。因此，在默认情况下，它们通常被认为是受河流支配的。然而，根据河流、波浪和潮汐能量在任何给定海岸线位置的相对平衡，保存下来的沉积结构、几何形状和河口坝的内部结构将反映这些能量的相对平衡。因此，河口坝可能是河流、波浪或潮汐主导的，也可能表现出由以上一种作用形成的沉积结构。识别和预测这些混合过程系统结构的能力对于准确解释古代记录非常重要，并对油气勘探和开发策略具有重要意义。本文对形成加拿大阿尔伯塔省坎帕尼亚地区不对称三角洲系统的一部分的混合过程河口-坝复合体进行了详细的描述和解释。这个河口-沙洲复合体被解释为一个混合影响、波浪主导的系统，从侧面过渡到混合影响、河流主导的系统。河口坝复合体代表了一个单一的沉积前积阶段，厚度可达8米，可以在露头和地下面积约60平方公里的范围内追踪到。它包括多个千米尺度的叶状几何结构（元素、元素集和元素复合体），在两个尺度（元素内和元素间集）上具有内部倾斜、泥岩和碳覆盖的斜形表面。波瓣的几何形状与海岸线近平行。潮汐对该体系的影响体现在元素内河口坝斜状地层中的潮汐束序列、潮汐过深、泥岩填充的分流河道网络以及在波浪主导的河口坝序列顶部发育的显著厚度（高达3.5 m）的冲积带沉积物。据估计，河口坝复合体的沉积构造单元是由自生事件产生的，从每日（潮汐对联），经过十年（元素）到百年（元素集）和千年（元素复合体和元素复合体）时间框架。澳大利亚卡奔塔利亚湾提出了一种全新世的部分类似沉积体系。这些混合过程河口坝复合体的几何形状、纵横比和相关系与已发表文献中描述的以河流为主的河口坝的原型有很大不同。
Abstract Mouth bars can develop in locations where fluvial distributary channels deliver coarse sediment to the shoreline. As a consequence, they are typically considered, by default, to be fluvially dominated. However, depending upon the relative balance of fluvial, wave, and tidal energies at any given shoreline location, the preserved sedimentary structures, geometry, and internal architecture of the mouth bar will reflect the relative balance of these energies. Hence, mouth bars can be fluvial-, wave-, or tide-dominated and can also exhibit sedimentary structures formed by more than one of these processes. The ability to recognize, and to predict the architecture of these mixed-process systems is important for accurately interpreting the ancient record and has implications for hydrocarbon exploration and exploitation strategies. A detailed description and interpretation is given herein of a mixed-process mouth-bar complex which forms part of an asymmetrical delta system from the Campanian of Alberta, Canada. This mouth-bar complex is interpreted as a mixed-influence, wave-dominated system that transitions laterally into a mixed-influence, fluvially dominated system. The mouth-bar complex represents a single progradational phase of deposition, is up to 8 m thick, and can be traced over an area of approximately 60 km2 in both outcrop and the subsurface. It comprises multiple, kilometer-scale lobe geometries (elements, element sets, and element complexes) with internal dipping, mudstone- and carbonaceous-draped clinoform surfaces at two scales (intra-element and inter-element set). The lobe geometries are oriented subparallel to the coastline. The influence of tides on the system is illustrated by tidal bundle sequences in intra-element mouth-bar clinoform bedsets, networks of tidally overdeepened, mudstone-filled distributary channels, and the development of significant thicknesses (up to 3.5 m) of swash-zone deposits at the tops of the wave-dominated mouth-bar successions. Depositional architectural units of the mouth-bar complex are estimated to have been generated by autogenic events from daily (tidal couplets), through decadal (elements) to centennial (element sets) and millennial (element complex and element complex set) time frames. A Holocene partial analog for these types of depositional systems is suggested from the Gulf of Carpentaria, Australia. Geometries, aspect ratios, and facies relationships of these mixed-process mouth-bar complexes vary significantly from the archetypal fluvial-dominated mouth bars described in the published literature.