Department of Geosciences, University of Tübingen, Tübingen, Germany.
Faculty of Science, Geology Department, Mansoura University, Mansoura, Egypt.
PLoS One. 2023 Jan 30;18(1):e0281008. doi: 10.1371/journal.pone.0281008. eCollection 2023.
Changes in terrestrial vegetation during the mid-Cretaceous and their link to climate and environmental change are poorly understood. In this study, we use plant macrofossils and analysis of fossil pollen and spores from the Western Desert, Egypt, to assess temporal changes in plant communities during the Cenomanian. The investigated strata have relatively diverse sporomorph assemblages, which reflect the nature of parent vegetation. Specifically, the palynofloras represent ferns, conifers, monosulcate pollen producers, Gnetales, and a diverse group of angiosperms. Comparisons of both, dispersed palynoflora and plant macrofossils reveal different characteristics of the palaeoflora owing to a plethora of taphonomical and ecological biases including the depositional environment, production levels, and discrepancies between different plant organs. A combination of detailed records of sporomorphs, leaves, and charcoal from the studied successions provide new understandings of the palaeoclimate and palaeogeography during the Cenomanian and Albian-Cenomanian transition in Egypt. The mixed composition of the palynofloral assemblages reflects the presence of different depositional situations with a weak marine influence, as evidenced by a minor dinoflagellate cysts component. The local vegetation comprised various categories including herbaceous groups including ferns and eudicots, fluvial, open environments, and xeric arboreal communities dominated by Cheirolepidiaceae and perhaps including drought- and/or salt-tolerating ferns (Anemiaceae) and other gymnosperms (Araucariaceae, Ginkgoales, Cycadales, and Gnetales) as well as angiosperms. The presence of riparian and freshwater wetland communities favouring aquatic and/or hygrophilous ferns (of Salviniaceae and Marsileaceae), is noted. The wide variation of depositional settings derived from the palynological data may be attributed to a prevalent occurrence of producers in local vegetation during the early Cenomanian of Egypt. For the purpose of this work on the studied Bahariya Formation and its equivalent rock units, where iconic dinosaurs and other fossil fauna roamed, we attempt to improve the understanding of Egypt's Cenomanian climate, which is reconstructed as generally warm and humid punctuated by phases of considerably drier conditions of varying duration.
中生代中期陆地植被的变化及其与气候和环境变化的关系还知之甚少。在这项研究中，我们使用植物大化石和来自埃及西部沙漠的化石花粉和孢子分析，评估白垩纪中期植物群落的时间变化。研究的地层具有相对多样化的孢子形态组合，反映了母体植被的性质。具体来说，花粉组合代表蕨类植物、针叶树、单沟花粉生产者、买麻藤植物和多样化的被子植物群。分散的孢粉组合和植物大化石的比较揭示了由于大量的埋藏学和生态学偏见，包括沉积环境、生产水平以及不同植物器官之间的差异，古植被的不同特征。对研究序列中的孢粉、叶片和木炭的详细记录的组合为埃及白垩纪和阿尔比阶-白垩纪过渡期的古气候和古地理提供了新的认识。孢粉组合的混合组成反映了不同沉积情况的存在，海洋影响较弱，这一点可以从少量的沟鞭藻化石组分得到证明。当地植被包括各种类别，包括草本植物群，包括蕨类植物和真双子叶植物，河流、开阔环境和以 Cheirolepidiaceae 为主的干旱林地群落，可能包括耐旱和/或耐盐蕨类植物（凤尾蕨科）和其他裸子植物（南洋杉科、银杏科、苏铁科和买麻藤科）以及被子植物。注意到存在河岸和淡水湿地群落，有利于水生和/或喜湿蕨类植物（水龙骨科和满江红科）的生长。从孢粉数据中得出的沉积环境的广泛变化可能归因于埃及早白垩世当地植被中生产者的普遍存在。为了研究 Bahariya 组及其等效的岩石单元，这里有标志性的恐龙和其他化石动物群出没，我们试图提高对埃及白垩纪气候的理解，该气候被重建为总体温暖潮湿，但有几个不同持续时间的干燥阶段。
