Onlap stratal architectures in the Grès d’Annot: geometric models and controlling factors
Onlap stratal architectures in the Grès d’Annot: geometric models and controlling factors
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Grès d’Annot 的 Onlap 地层结构：几何模型和控制因素
DOI：
10.1144/gsl.sp.2004.221.01.21
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
P. Joseph
中科院分区：
文献类型：
--
作者：
R. Smith;P. Joseph
摘要法国东南部S地区深海海相砂岩的超覆端面呈现出一系列的样式，从突然超覆到羽化的“沉积超覆”几何形状。这些都很好地展示在蒙塔涅·德·查鲁菲的南向上覆终端的大曝光中，蒙塔涅·德·查鲁菲位于特罗伊斯·埃维什·S地块(阿尔卑斯山)的南端。这些地层结构在这里是由几何模型模拟的，这些几何模型简单地由边界坡度和同时代坡度与盆地沉积速率的比率控制。在边界坡面上没有同时代沉积的情况下，纯超覆的结果。在斜坡沉积速率相对于盆地沉积速率较高的情况下，形成羽状几何结构，连续的砂岩层与连续较年轻的斜坡覆盖层重叠。在Chalufy看到的交替的富砂和贫砂岩包的旋回性导致了连续坡基位置的阶梯式攀升轨迹，当贫泥砂流突然超覆沉积砂体时，爬升角度等于边界坡角，当坡盖沉积时，爬升幅度更大。这一结果的一个含义是，任何与边界斜坡距离有关的相变和古流摆动带都将随着时间的推移呈现出类似的垂直轨迹。这两种末端终止类型可以与墨西哥湾地下和其他地区使用的会聚-基准面和会聚-稀薄地震相进行比较。如果坡盖的存在不能通过现有地震资料的频率含量来分辨，会聚-基线覆盖地震相可能包括突然超覆和羽化叠加超覆的间隔。
Abstract Onlap terminations of deep-marine sandstones in the Grès d’Annot, SE France, exhibit a range of styles, from abrupt onlap to feathering ‘aggradational onlap’ geometries. These are well exhibited in the large exposure of southward onlap terminations at Montagne de Chalufy, on the southern end of the Trois Evêchés Massif (Alpes de Haute Provence). These stratal architectures are here simulated by geometrical models that are governed simply by bounding slope gradients and the ratio of coeval slope to basinal aggradation rates. In cases of no coeval deposition on bounding slopes, pure onlap results. In cases of high slope aggradation rates relative to basinal aggradation rates, a feathered geometry results with successive sandstone beds onlapping against successively younger slope drapes. The cyclicity of alternating sand-rich and sand-poor packets seen at Chalufy results in a stepped climbing trajectory of successive slope base positions, with climb angle equal to bounding slope angle when mud-poor sandy flows deposited sandstone bodies with abrupt onlap, and climbing more steeply when slope drapes are deposited. An implication of this result is that any zones of facies change and palaeocurrent swing that are related to distance from bounding slope will exhibit a comparable vertical trajectory through time. The two end member termination types can be compared with the convergent-baselapping and convergent-thinning seismic facies used in the Gulf of Mexico subsurface and elsewhere. The convergent-baselapping seismic facies may include both abrupt onlap and intervals of feathering aggradational onlap if the presence of slope drapes is not resolvable by the frequency content of the available seismic data.