Abstract Within the Aptian-Cenomanian formations of Sinai successions in Egypt, lateral and vertical changes occur in the numerous benthic communities. Microbenthos such as Orbitolina foraminifera and calcareous algae are widespread in the Aptian-Albian deposits in North Sinai, whereas oysters and gastropods are common in the Cenomanian siliciclastic deposits in South Sinai. In order to establish the biostratigraphy, 90 benthic and planktonic foraminifera species have been identified from the studied succession. Based on the stratigraphic distribution of the identified species the studied succession could be subdivided into three planktonic foraminiferal zones: Pseudothalmanninella ticinensis zone (Late Albian), Rotalipora cushmani zone (Middle-Late Cenomanian), and Whiteinella archaeocretacea zone (Late Cenomanian-Early Turonian). This work discusses the first record of the Albian dasycladalean alga Holosporella sugdeni (Elliott) from Sinai and reports on Montiella elitzae (Bakalova) from the Albian Risan Aneiza Formation. The occurrence of Orbitolina (Conicorbitolina) conica distinguished the Albian-Cenomanian boundary in the North Sinai sequences. The benthic communities of the studied successions indicated a faunal shift from an algal-orbitolinid foraminifera community around the Aptian-Early Albian to a rudist community during the Middle Albian and an oyster-gastropod community during the Cenomanian. This faunal shift coincided with the major sea transgression that covered North Sinai until the Middle Albian and reached South Sinai during the Cenomanian. The identified Cenomanian gastropods included Neoptyxis olisiponensis, Nerinea gemmifera, and Tylostoma bussoni. Many oyster species distinguished the Cenomanian deposits, such as Ceratostreon flabellatum, Rhynchostreon mermeti, Rhynchostreon suborbiculatum, and Costagyra olisiponensis. Identifying the benthic fauna and facies indicated a shallow inner to middle ramp environment. Stable carbon and oxygen isotope data from the Cenomanian oyster shells indicate an inner ramp environment. Comparing the carbon isotope values of the oysters with those previously recorded from the rudists may explain the different trophic levels of both groups.

中文翻译：

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埃及西奈地台白垩纪中期序列底栖群落古生态及相分析

摘要 在埃及西奈序列的 Aptian-Cenomanian 地层中，许多底栖群落发生横向和纵向变化。Orbitolina foraminifera 和钙质藻类等微型底栖动物广泛分布于北西奈半岛的 Aptian-Albian 矿床，而牡蛎和腹足类动物则常见于南西奈半岛的 Cenomanian 硅质碎屑矿床。为了建立生物地层学，已从研究的演替中鉴定了 90 种底栖和浮游有孔虫物种。根据已识别物种的地层分布，研究的演替可细分为三个浮游有孔虫区：Pseudothalmanninella ticinensis 区（晚阿尔比安）、Rotalipora cushmani 区（中-晚 Cenomanian）和 Whiteinella archaeocretacea 区（晚土马纪-Early） . 这项工作讨论了来自西奈半岛的 Albian dasycladalean 藻类 Holosporella sugdeni (Elliott) 的第一个记录，并报告了来自 Albian Risan Aneiza 组的 Montiella elitzae (Bakalova)。Orbitolina (Conicorbitolina) conica 的出现区分了北西奈序列中的 Albian-Cenomanian 边界。研究序列的底栖群落表明动物群从 Aptian-Early Albian 周围的 algal-orbitolinid foraminifera 群落到中 Albian 期间的 rudist 群落和 Cenomanian 期间的牡蛎-腹足类群落。这种动物群的转变与覆盖北西奈直到中阿尔比安并在森诺曼阶到达南西奈的主要海侵同时发生。已确定的 Cenomanian 腹足动物包括 Neoptyxis olisiponensis、Nerinea gemmifera 和 Tylostoma bussoni。许多牡蛎物种区分了 Cenomanian 沉积物，例如 Ceratostreon flabellatum、Rhynchostreon mermeti、Rhynchostreon suborbiculatum 和 Costagyra olisiponensis。识别底栖动物和相表明浅内到中间斜坡环境。来自 Cenomanian 牡蛎壳的稳定碳和氧同位素数据表明内部斜坡环境。将牡蛎的碳同位素值与先前从 rudists 记录的那些值进行比较，可以解释两组不同的营养水平。来自 Cenomanian 牡蛎壳的稳定碳和氧同位素数据表明内部斜坡环境。将牡蛎的碳同位素值与先前从 rudists 记录的那些值进行比较，可以解释两组不同的营养水平。来自 Cenomanian 牡蛎壳的稳定碳和氧同位素数据表明内部斜坡环境。将牡蛎的碳同位素值与先前从 rudists 记录的那些值进行比较，可以解释两组不同的营养水平。