当前位置: X-MOL 学术J. Afr. Earth Sci. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
The Maastrichtian–Danian transition in the northern Farafra Oasis, Western Desert (Egypt): Implications from foraminiferal paleobathymetry and paleoenvironmental reconstructions
Journal of African Earth Sciences ( IF 2.3 ) Pub Date : 2020-08-01 , DOI: 10.1016/j.jafrearsci.2020.103853
Amr S. Zaky , Michael A. Kaminski , Rodolfo Coccioni , Sherif Farouk , Mohamed A. Khalifa , Cesare A. Papazzoni , Mohamed M. Abu El-Hassan , Fabrizio Frontalini

Abstract Two exposed sections of the Lower/Upper Maastrichtian to Danian at northern and northeastern Farafra Oasis, Western Desert (Egypt) namely, the Farafra–Ain Dalla road and the Ain Maqfi sections have been analyzed for their planktonic and benthonic foraminifera to constrain the biostratigraphy and infer the paleoenvironmental conditions. Lithostratigraphically, the successions of the present study are classified into the Khoman Chalk and the Dakhla Shale. Biostratigraphically, six planktonic foraminiferal zones; Gansserina gansseri, Racemiguembelina powelli and Plummerita reicheli of the Maastrichtian as well as the Praemurica inconstans (P1c), Praemurica uncinata (P2) and Morozovella angulata (P3a) of the Danian are recognized. A detailed quantitative benthonic foraminiferal analysis has been performed and yields a total of 172 identified benthonic foraminiferal species belonging to 62 different genera. The various foraminiferal parameters as well as cluster analysis provide good information about the paleoenvironmental conditions and sea–level fluctuations across the Maastrichtian–Danian transition. The Maastrichtian revealed outer neritic shelf with slightly shallowing conditions recorded only at the Ain Maqfi section, well oxygenated conditions with low organic matter influx coupled with sea–level rise. During the Maastrichtian–Danian transition, a paleoenvironmental shift to inner-shallow middle neritic shelf, low oxygenated conditions with moderate organic matter influx coupled with sea–level fall is interpreted. This transition is characterized by a major hiatus due to absences of Guembelitria cretacea (P0), Parvularugoglobigerina eugubina (Pα), Parasubbotina pseudobulloides (P1a) and Subbotina triloculinoides (P1b) zones and subzones. It is well marked in the field by an irregular contact and conglomeratic phosphatic dolostone bed at the Farafra-Ain Dalla road section while the disconformity surface can be detected by planktonic foraminifera in the Ain Maqfi section. The lowermost Danian is phosphatic argillaceous chalky limestone with intensive reworking. Low oxygen and/or relatively high–moderate organic matter influx within inner–middle neritic shelf paleoenvironmental conditions can be reconstructed for the lowermost Danian associated with a slight increase in sea–level during the Praemurica inconstans (P1c) zone. The uppermost Danian reflected very well oxygenated conditions and/or low organic matter influx in middle–outer neritic shelf conditions associated with sea–level rise during ages of the planktonic foraminiferal zones P2–P3a.

中文翻译:

西部沙漠(埃及)法拉夫拉绿洲北部的马斯特里赫特-达尼亚过渡:有孔虫古水深测量和古环境重建的意义

摘要 分析了西部沙漠(埃及)法拉夫拉绿洲北部和东北部法拉夫拉绿洲北部/上马斯特里赫特至大年的两个暴露部分,即 Farafra-Ain Dalla 路段和 Ain Maqfi 路段的浮游和底栖有孔虫,以限制生物地层学并推断古环境条件。在岩性地层学上,本研究的层序被分为 Khoman Chalk 和 Dakhla 页岩。生物地层学上,六个浮游有孔虫区;马斯特里赫特的 Gansserina gansseri、Racemiguembelina powelli 和 Plummerita reicheli 以及大年的 Praemurica inconstans (P1c)、Praemurica uncinata (P2) 和 Morozovella angulata (P3a) 都得到了认可。已经进行了详细的定量底栖有孔虫分析,共产生了 172 种已鉴定的底栖有孔虫物种,属于 62 种不同的属。各种有孔虫参数以及聚类分析提供了关于马斯特里赫特-大年过渡期间古环境条件和海平面波动的良好信息。Maastrichtian 揭示了外部浅海陆架,仅在 Ain Maqfi 剖面记录到轻微变浅的条件,氧化条件良好,有机物质流入量低,海平面上升。在马斯特里赫特-大年过渡期间,古环境转变为内浅中浅海陆架,低含氧条件,中等有机质流入加上海平面下降。由于缺少 Guembelitria cretacea (P0)、Parvularugoglobigerina eugubina (Pα)、Parasubbotina pseudobulloides (P1a) 和 Subbotina triloculinoides (P1b) 区和亚区,这种转变的特点是主要中断。Farafra-Ain Dalla 路段的不规则接触面和砾岩磷酸盐白云岩层在现场得到了很好的标记,而 Ain Maqfi 路段的浮游有孔虫可以检测到不整合面。最下部的大年是经过密集改造的磷酸盐泥质白垩灰岩。内-中浅海陆架古环境条件内的低氧和/或相对高-中度有机质流入可以重建为与 Praemurica inconstans (P1c) 带期间海平面略有上升相关的最下部大年。
更新日期:2020-08-01
down
wechat
bug