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Lenticular-bedding-like bioturbation and the onshore recognition of carbonate drifts (Oligocene, Cyprus)
Journal of Sedimentary Research ( IF 2.0 ) Pub Date : 2020-12-31 , DOI: 10.2110/jsr.2020.70
Jesús Reolid 1 , Christian Betzler 2 , Or M. Bialik 2, 3 , Nicolas Waldman 3
Affiliation  

The fine-grained carbonate deposits of the Oligocene to early Miocene of Cyprus are the most characteristic example of onshore outcropping carbonate drifts. These deposits were analyzed from a sedimentological and ichnological perspective, in order to determine the origin of the lenticular bedding characteristic of such deposits. The facies at the two study sections, Tsada and Petra Tou Romiou, consist of an alternation of thin, poorly cemented, intensely bioturbated marly limestone intervals and thick cemented wackestone intervals with abundant bioturbation and “lenticular bedding.” The ichnoassemblage, comprising Zoophycos, Thalassinoides, and Planolites is attributable to the Zoophycos Ichnofacies. The alternation of intervals with medium to well-preserved traces with completely biogenically homogenized facies reflects changes in substrate consistency related to changes in bottom-current velocity or to sedimentation. The presence of lenticular-bedding-like structures in the study deposits, traditionally considered diagnostic of bottom-current action in carbonate-drift outcrops, is shown to be exclusively the result of bioturbation. In the study sections, the “lenticular bedding” is the result of the coalescence of successive Zoophycos structures, which are readily preserved because they are constructed in the historical layer. It is proposed that the overlap of abundant isolated cone-shaped burrows of Zoophycos is the origin of the putative lenticular bedding recorded in the Oligocene fine-grained carbonate deposits of Cyprus, traditionally identified as drifts. Since this bedding is not related to currents in the study sections, the consideration of these carbonate deposits of Cyprus as drifts should be reevaluated. This has crucial implications for the recognition of carbonate drift outcrops elsewhere. Onshore carbonate drift outcrops wherein lenticular bedding is the main diagnostic criterion should be revisited and evaluated ichnologically.

中文翻译:

透镜状层状生物扰动和陆上碳酸盐漂移的识别(渐新世,塞浦路斯)

渐新世至塞浦路斯早期中新世的细粒碳酸盐矿床是陆上露头碳酸盐漂移的最典型例子。为了确定此类沉积物的透镜状层理特征的起源,从沉积学和岩石学研究的角度对这些沉积物进行了分析。Tsada和Petra Tou Romiou这两个研究部分的相由稀薄胶结,强烈生物扰动的灰质石灰岩层段和厚胶结的瓦克石层序交替组成,具有丰富的生物扰动和“透镜状层理”。鱼鳞组合,包括Zoophycos,Thhalsinoides和Planolite,可归因于Zoophycos细观。具有完全生物均质相的中度至保存完好的迹线的间隔变化反映了与底流速度或沉降有关的底物浓度变化。研究沉积物中存在类透镜层状结构,通常被认为是对碳酸盐漂移露头中的底流作用进行诊断,这完全是生物扰动的结果。在研究部分中,“柱状垫层”是连续的Zoophycos结构合并的结果,这些结构很容易保存,因为它们是在历史层中构造的。有人提出,Zoophycos大量孤立的圆锥形洞穴的重叠是塞浦路斯渐新世细粒碳酸盐矿床中记录的假定的透镜状层理的起源,传统上称为漂移。由于该层理与研究部分中的洋流无关,因此应重新评估塞浦路斯的这些碳酸盐矿床的漂移问题。这对于识别其他地方的碳酸盐漂移露头具有至关重要的意义。应重新审查以透镜状层理为主要诊断标准的陆上碳酸盐漂移露头,并对其进行地貌学评估。
更新日期:2021-02-11
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