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Classification of soft-sediment deformation in carbonates based on the Lower Cretaceous Vigla Formation, Kastos, Greece
International Journal of Earth Sciences ( IF 1.8 ) Pub Date : 2020-08-14 , DOI: 10.1007/s00531-020-01919-4
Nicolina Bourli , Angelos G. Maravelis , Avraam Zelilidis

Soft-sediment deformation (SSD) structures are widespread within the Lower Cretaceous Vigla Formation (limestones and shales) that are exposed in a 7–10 km long and 100 m high section along the east coast of Kastos Island in the Ionian Sea. SSD was observed both in limestones and in shales, and formed during or immediately after deposition, during the first stage of sediment consolidation. They are classified into six (6) different types of deformations: (1) Thick synclines and anticlines, formed due to strong synsedimentary deformation, that were produced mostly from N-S directed normal faults or from the interaction between normal and transfer faults, and are situated between undeformed horizons. (2) Thin slumps ascribed to normal fault activity and especially slumping in the footwall of the active fault, prograding orthogonal to the fault direction. (3) Thin to medium slumps produced from the synsedimentary interaction of N–S normal faults and E–W directed transfer faults, showing multiply directions of progradation. (4) Thin SSD related to diapiric intrusions that also associated with fault activity. (5) Thick slump horizons displaying erosional contacts with the neighboring undeformed limestones in the same horizon, resulting from gravity-driven mass-transport deposits that flowed across inclined basin floors. (6) Thin slumps, with chert nodules, within a slumped horizon, resulting from a slumping phase both after the sedimentation and after early diagenesis in carbonates deposits, but during the sedimentation of the lower Cretaceous Vigla limestones. All the above categories were characterized as seismites or deformation due to fault activity. This tectonism resulting in tilted blocks, the creation of space in hangingwall downthrown blocks, and changes of inclination of the basin floor, outcrops with high lateral extent in different directions adds constraints to the geometry of slumps. The transition zone between Vigla limestones and shales showed particularly abundant deformation structures. Although the Vigla Formation limestones have low primary porosity, the presence of many SSD horizons could increase secondary porosity in this formation.



中文翻译:

基于希腊白垩纪下白垩统维格拉组的碳酸盐岩中软沉积变形的分类

软沉积变形(SSD)结构广泛分布在下白垩统维格拉组(石灰岩和页岩)中,沿爱奥尼亚海的卡斯托斯岛东海岸长7-10 km,高100 m。在沉积物固结的第一阶段,无论是在石灰岩还是在页岩中都观察到了SSD,并且在沉积过程中或沉积之后立即形成了SSD。它们分为六(6)种不同类型的变形:(1)由于强烈的同沉积变形而形成的粗斜向斜线和背斜线,它们主要是由NS定向正断层或正断层与传递断层之间的相互作用产生的,且位于在未变形的视界之间。(2)归因于正常断层活动的薄塌陷,尤其是活动断层下盘的塌陷,与断层方向正交。(3)由N–S正常断层和E–W定向转移断层的同沉积作用产生的薄至中型塌陷,显示了多个扩展方向。(4)与非主动入侵相关的精简SSD,它也与故障活动有关。(5)坍落度较厚的地层显示出与同一地层中相邻未变形石灰岩的侵蚀接触,这是由于重力驱动的大量沉积物流经倾斜的盆地底板所致。(6)在碳酸盐矿床沉积后和早期成岩后,但在下白垩统维拉石灰岩沉积期间,由于处于塌陷阶段,在塌陷的地平线内出现了薄薄的塌陷,有节结节。以上所有类别的特征都是由于断层活动引起的地震或变形。这种构造导致了倾斜的块体,在下垂的悬壁壁块中创造了空间,以及盆地底部的倾斜度发生了变化,在不同方向上具有高横向延伸的露头增加了塌陷的几何形状的限制。Vigla石灰岩和页岩之间的过渡带显示出特别丰富的变形结构。尽管Vigla地层石灰岩的初级孔隙度低,但许多SSD层的存在可能会增加该地层的次级孔隙度。Vigla石灰岩和页岩之间的过渡带显示出特别丰富的变形结构。尽管Vigla地层石灰岩的初级孔隙度低,但许多SSD层的存在可能会增加该地层的次级孔隙度。Vigla石灰岩和页岩之间的过渡带显示出特别丰富的变形结构。尽管Vigla地层石灰岩的初级孔隙度低,但许多SSD层的存在可能会增加该地层的次级孔隙度。

更新日期:2020-08-14
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