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The Zanclean palaeofloras around the Mont-Dore strato-volcano: A window into upper Neogene vegetation and environments in the Massif Central (Puy de Dome, France)
Geobios ( IF 1.6 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.geobios.2020.01.001
Marie-Claude Jolly-Saad , Jean François Pastre , Sébastien Nomade

Abstract New Pliocene macrofloras and microfloras perfectly preserved from the Mont-Dore (Puy-de-Dome, Massif central, France) have been reinvestigated. Samples come from different stratigraphical levels collected from three localities, Lac Chambon, La Gratade and Pont de Chocol. The 40Ar/39Ar radiometric datings bracketing the Chambon Lake and La Gratade fossil-bearing horizons give 4.46 ± 0.05 Ma and 3.94 ± 0.04 Ma, respectively, representative of the Zanclean Stage (= Brunssumian B and C), a period of the early Pliocene (5.32 to 3.6 Ma), much older than previously thought (i.e., Piacenzian). Pont de Chocol is considered to be close biostratigraphically, or even identical in age to La Gratade. Detailed morphological evaluation of leaf morphotypes completed with pollen analysis contributed to the better taxonomic knowledge of these palaeofloras. The overview focuses on floristic and phytostratigraphical characteristics of the defined stratigraphical units and their dating and correlation with previously defined palaeofloristic units of the Massif central. The study provides detailed identifications of plants representing 11 gymnosperms among which Pinaceae (pollen and winged seeds), Cupressaceae including “Taxodioid” pollen grains and Sciadopitaceae families (only pollen). Besides, different angiosperm trees and shrubs have been determined from both micro- and macro-remains. Fagaceae is the most diversified with several foliage of beech and deciduous oaks, while diversified Juglandaceae contribute mainly as abundant leaf remains of Carya, Pterocarya and Juglans; Ulmaceae with numerous leave of two Zelkova species, and also Ulmus. Various other deciduous dicotyledonous such as Alnus, Betula, Carpinus, Populus, Acer laetum and A. interrigenum are well documented. Leguminosae are recorded by a small number of leaflet imprints. Evergreen shrubs of Buxaceae (Buxus pliocenica) are scarce. All these taxa contribute to a rich biodiversity of these Pliocene assemblages. All three sites point towards riverine forest habitats dominated by hygrophilic diversified woody plants while in the surrounding plains and slopes the thermophilic elements were scarce and mesophilic taxa abundant as temperate elements. This vegetation can be compared with mixed mesophytic forests depicting a climate cooling during the two considered periods (ca. 4.46 and 3.95 Ma).

中文翻译:

Mont-Dore 层状火山周围的 Zanclean 古植物群:了解地块中央(法国圆顶山)上新近纪植被和环境的窗口

摘要 对从 Mont-Dore(Puy-de-Dome,Massif Central,法国)保存完好的新上新世大型植物群和微生物群落进行了重新调查。样品来自不同的地层水平,采集自三个地点:Lac Chambon、La Gratade 和 Pont de Chocol。包含 Chambon Lake 和 La Gratade 化石层的 40Ar/39Ar 辐射测年分别给出了 4.46 ± 0.05 Ma 和 3.94 ± 0.04 Ma,代表了上新世早期的 Zanclean 阶段(= Brunssumian B 和 C)( 5.32 到 3.6 Ma),比以前认为的要老得多(即 Piacnzian)。Pont de Chocol 被认为在生物地层学上与 La Gratade 相近,甚至在年龄上也相同。通过花粉分析完成的叶片形态类型的详细形态学评估有助于更好地了解这些古植物群的分类学知识。概述侧重于已定义地层单元的植物区系和植物地层特征,以及它们的年代和与先前定义的地块中央古植物区系单元的相关性。该研究提供了代表 11 种裸子植物的植物的详细鉴定,其中松科(花粉和有翅种子)、柏科(包括“紫杉类”花粉粒)和 Sciadopitaceae 科(仅花粉)。此外,从微观和宏观遗骸中确定了不同的被子植物树木和灌木。山毛榉科是最多样化的,有几片山毛榉和落叶橡树的叶子,而多样化的胡桃科主要是山核桃、紫檀和胡桃的丰富叶遗物;榆树科,有两种榉树,还有榆树。各种其他落叶双子叶植物,如桤木、Betula、Carpinus、Populus、Acer laetum 和 A. interrigenum 都有很好的记录。豆科由少数传单印记记录。Buxaceae (Buxus pliocenica) 的常绿灌木稀少。所有这些分类群都为这些上新世组合的丰富生物多样性做出了贡献。所有三个地点都指向以喜湿的多样化木本植物为主的河流森林栖息地,而在周围的平原和斜坡中,高温元素稀少,而温带元素的中温分类群丰富。这种植被可以与描述在两个考虑的时期(约 4.46 和 3.95 Ma)期间气候变冷的混合中生森林进行比较。Buxaceae (Buxus pliocenica) 的常绿灌木稀少。所有这些分类群都为这些上新世组合的丰富生物多样性做出了贡献。所有三个地点都指向以喜湿的多样化木本植物为主的河流森林栖息地,而在周围的平原和斜坡中,高温元素稀少,而温带元素的中温分类群丰富。这种植被可以与描述在两个考虑的时期(约 4.46 和 3.95 Ma)期间气候变冷的混合中生森林进行比较。Buxaceae (Buxus pliocenica) 的常绿灌木稀少。所有这些分类群都为这些上新世组合的丰富生物多样性做出了贡献。所有三个地点都指向以喜湿的多样化木本植物为主的河流森林栖息地,而在周围的平原和斜坡中,高温元素稀少,而温带元素的中温分类群丰富。这种植被可以与描述在两个考虑时期(约 4.46 和 3.95 Ma)期间气候变冷的混合中生森林进行比较。
更新日期:2020-04-01
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