The middle-upper Cenomanian of Zilly (Sachsen-Anhalt, northern Germany) with remarks on the Pycnodonte Event
The middle-upper Cenomanian of Zilly (Sachsen-Anhalt, northern Germany) with remarks on the Pycnodonte Event
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齐利 (德国北部萨克森-安哈尔特州) 的中上塞诺曼阶人对 Pycnodonte 事件的评论
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发表时间：
2006
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通讯作者：
T. Voigt
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作者：
M. Wilmsen;T. Voigt
介绍了Zilly （Sachsen-Anhalt）地区28 m厚的Cenomanian演替的详细地层测井资料。该演替由11米的中塞诺曼尼亚半远洋泥灰岩交替（“Planer石灰石”）和15米的上塞诺曼尼亚钙质上长岩（“Poor rhotomagense石灰石”）组成，不整合地覆盖1.5米的红色泥质粘土和石灰石（“Rotplaner”）。11 m的Pycnodonte事件区域间标志层、26 m的相变层和26.9 m的plenus层基底的证据，使这些层位的生物/年代地层对比分别与中/上Acanthoceras jukesbrownei带（中Cenomanian）、Calycoceras (Proeucalycoceras) guerangeri / Metoicoceras geslinianum带过渡和下Metoicoceras geslinianum带（中Cenomanian）进行对比。岩性/微相和层序地层学分析表明，在相变化之前，远洋影响总体上有所增加。这一倒退趋势在短时间内被碧诺洞特事件打断，其基础与中诺曼晚期层序边界SB Ce IV及其后的海侵面有关。相变化表明，Cenomanian中晚期海平面明显下降（层序边界SB Ce V），随后是更多的浅水Rotplaner沉积。Pycnodonte事件在Zilly非常厚且近端。它的单种牡蛎动物群由小的pycnodonteines组成，属于Pycnodonte (Phygraea) vesicularis (LAMARCK) vesiculosa (J. SOWERBY)，一种二级自由躺着的牡蛎，生活在“杯状躺椅”上。牡蛎的零星分布、在最终掩埋前的分选和部分损伤以及大量陆源物质的供应表明，在Pycnodonte事件沉积期间，水能偶尔升高，环境压力强烈。这种情况促进了牡蛎在海底的定居和繁殖的成功。碧诺多特事件是一个典型的“重叠生物事件”，其形成受到海平面上升、陆源涌入、环境压力和优先保存等多种因素的控制。
A detailed stratigraphic log of the 28 m thick Cenomanian succession at Zilly (Sachsen-Anhalt) is presented. The succession is composed of 11 m of middle Cenomanian hemi-pelagic marl–limestone alternations (‘Planer Limestones’) grading into 15 m of upper Cenomanian calcareous pelagites (‘Poor rhotomagense Limestones’) unconformably overlain by 1.5 m of red-coloured marly clays and limestones (‘Rotplaner’). The proof of the interregional marker beds of the Pycnodonte Event at the 11 m level, the Facies Change at 26 m, and the base of the plenus Bed at 26.9 m allow a bio-/chronostratigraphic correlation of these levels with the middle/upper Acanthoceras jukesbrownei Zone (upper middle Cenomanian), the Calycoceras ( Proeucalycoceras ) guerangeri / Metoicoceras geslinianum Zone transition, and the lower Metoicoceras geslinianum Zone, respectively (middle upper Cenomanian). Litho-/microfacies and sequence stratigraphic analyses indicate an overall increase of pelagic influence up to the Facies Change. This retrogradational trend was shortly interrupted by the Pycnodonte Event, the base of which correlates with the late middle Cenomanian sequence boundary SB Ce IV and the succeeding transgressive surface. The Facies Change indicates a significant mid-late Cenomanian sea-level fall (sequence boundary SB Ce V), followed by more shallow water Rotplaner deposition. The Pycnodonte Event is very thick and proximal in character at Zilly. Its monospecific oyster fauna consists of small pycnodonteines assigned to Pycnodonte ( Phygraea ) vesicularis (LAMARCK) vesiculosa (J. SOWERBY), a secondarily free-lying oyster which lived as a ‘cup-shaped recliner’. The patchy occurrence of the oysters, the sorting and partial damage of valves prior to final burial along with significant supply of terrigenous materials suggest episodically elevated water energy and strong environmental stress during deposition of the Pycnodonte Event. This situation promoted colonization of the sea-floor by, and reproductive success of the inferred eurytopic oyster. The Pycnodonte Event is a classic example of an ‘onlapping bioevent’, the formation of which was controlled by different factors such as sea-level rise, terrigenous influx, environmental stress, and preferential preservation.