Use of altered volcanic ash falls in stratigraphic studies of coal-bearing sequences: An example from the Upper Cretaceous Ferron Sandstone Member of the Mancos Shale in central Utah
Use of altered volcanic ash falls in stratigraphic studies of coal-bearing sequences: An example from the Upper Cretaceous Ferron Sandstone Member of the Mancos Shale in central Utah
复制标题
在含煤层序地层学研究中使用蚀变火山灰落：以犹他州中部曼科斯页岩上白垩统 Ferron 砂岩段为例
DOI：
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发表时间：
1980
期刊：
影响因子：
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通讯作者：
R. M. Pollastro
中科院分区：
文献类型：
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作者：
T. A. Ryer;R. Phillips;B. Bohor;R. M. Pollastro
煤层最常出现在以快速横向相变化为特征的地层单元中，因此确定时间关系和相对比是困难的。犹他州中部Mancos页岩的Ferron砂岩段就是这样一个单元。Ferron记录了一个三角洲系统的活动，该系统在晚Turonian时期向东北方向推进进入内白垩纪海道。铁龙由五个三角洲旋回组成，每个三角洲旋回包括一个煤带。每个煤带至少包含一个，通常是几个，横向持久的高岭石粘土岩分异。对分离物的实验室研究表明，它们代表了变质的火山灰落下。事实证明，这些分体对重建金刚砂煤田C煤层的沉积史特别有用。它们允许将C煤层划分为四个等时单元。在铁龙三角洲第三次旋回的构造和破坏阶段，煤层聚集在与三角洲平原沉降同时发育的盆地中。在以煤为代表的时间间隔内，泥炭的聚集面积向海向和向陆向扩展。泥炭沉积的海侵终止了泥炭沉积的向海部分，此时第四三角洲旋回的前三角洲和三角洲前缘地层不整合地覆在煤上。在其向陆地的部分，C煤层被第四旋回的三角洲-平原地层覆盖，没有侵蚀的迹象。
Coal beds most commonly occur in stratigraphic units characterized by rapid lateral facies changes for which determination of time relationships and correlation of facies are difficult. The Ferron Sandstone Member of the Mancos Shale in central Utah is such a unit. The Ferron records the activity of a delta system that prograded in a northeasterly direction into the Interior Cretaceous seaway during late Turonian time. The Ferron consists of five delta cycles, each of which includes one coal zone. Each of the coal zones contains at least one, and usually several, laterally persistent kaolinitic claystone partings. Laboratory study of the partings demonstrates that they represent altered volcanic ash falls. These partings have proven particularly useful in reconstructing the depositional history of the C coal bed of the Emery coal field. They permit division of the C coal bed into four isochronous units. The coal bed accumulated in a basin that developed concurrently with subsidence of the delta plain during both the constructive and destructive phases of the third delta cycle of the Ferron. The area of peat accumulation expanded in both seaward and landward directions during the interval of time represented by the coal. Peat accumulation was terminated by transgression of the sea across the seaward part of the peat deposit, where prodelta and delta-front strata of the fourth delta cycle now disconformably overlie the coal. In its landward part, the C coal bed is overlain, with no evidence of erosion, by delta-plain strata of the fourth cycle.