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Slump folds within mid-Miocene crevasse-splay deposits: a unique example from the Tomisławice lignite opencast mine in central Poland
Geological Quarterly ( IF 1 ) Pub Date : 2020-09-07 , DOI: 10.7306/gq.1545
Marek WIDERA

Non-tectonic, soft-sediment deformation structures occur in mid-Miocene crevasse-splay deposits exposed in the Tomislawice lignite opencast mine in central Poland. The crevasse-splay cross-stratified siliciclastic deposits are underlain by continuously folded and relatively thick lignite beds, and overlain by a thin undisturbed layer of lignite. Only the middle part of the crevasse-splay succession is deformed plastically in the form of folds, while the lower and uppermost beds are undeformed. Most of the intraformational deformation structures are recumbent folds, while only a few can be classified as upright folds in the initial stage of their evolution. The origin of these folds is associated here with a penecontemporaneous slumping process caused by liquefaction of sandy-muddy sediments. The slumping was triggered by an increase in the inclination of heterolithic layers caused by the compactional subsidence of an organic-rich substrate – peat. This type of subsidence occurred following a sudden siliciclastic load on top of the underlying and poorly-compacted peat/lignite seam. The initiation and development of the slump folds can be explained by differentiated loading, compaction and liquefaction processes, and the introduction of a tectonic agent is unnecessary.

中文翻译:

中中新世裂隙张开型矿床中的塌陷褶皱:波兰中部托米斯瓦维采褐煤露天矿的一个独特例子

波兰中部 Tomislawice 褐煤露天矿出露的中中新世裂隙张开沉积物中出现非构造软沉积物变形结构。裂隙-展开交叉层状硅质碎屑沉积物的下方是连续折叠且相对较厚的褐煤层,上方是薄的未受干扰的褐煤层。只有裂隙-展开序列的中间部分以褶皱的形式塑性变形,而下层和最上层未变形。地层内变形构造多为横卧褶皱,只有少数在演化初期可归类为直立褶皱。这些褶皱的起源与由砂质泥质沉积物液化引起的准同期坍塌过程有关。这种坍塌是由富含有机物的基质——泥炭的压实下沉引起的异质层倾斜度增加引起的。这种类型的沉降发生在下伏且压实性差的泥炭/褐煤接缝顶部突然发生硅质碎屑负载之后。坍塌褶皱的产生和发展可以通过不同的加载、压实和液化过程来解释,并且没有必要引入构造剂。
更新日期:2020-09-07
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