埃塞俄比亚下奥莫山谷Usno的热带森林和combretacae林地,3.3-3.2 Ma前

IF 1.6 4区 地球科学 Q2 PALEONTOLOGY Geobios Pub Date : 2023-02-01 DOI:10.1016/j.geobios.2023.01.003
Marie-Claude Jolly-Saad , Raymonde Bonnefille
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引用次数: 0

摘要

在本文中,我们描述了11个化石木材样本的解剖结构,这些样本收集于埃塞俄比亚下奥莫山谷的Usno组的两个地方(棕色沙和平坦沙)。根据以往的地层学研究和新的调查,特别是对插层凝灰岩的Ar/Ar定年和古地磁研究,样品的定年在3.33 ~ 3.21 Ma之间。鉴定的木材样品是在这段时间内沉积的两个不同地层中收集的。来自Brown Sands的最古老的包括Albizia sp., Entada sp.和一个可能的combretacae或Leguminosae。白沙最年轻的组合包括许多combretacae的代表,包括Combretum molle和与Erythrina sp相关的Terminalia sp.。这些组合与埃塞俄比亚已知的中新世和上新世木材组合有很大不同。所鉴定的树木类群与现存的中高地合欢林在10万年左右被Combretum/Terminalia林地所取代的亲缘关系的古环境解释。在下奥莫河谷,上新世植被的湿润特征与今天广泛分布在该地区的干旱金合欢/Commiphora草原形成鲜明对比。这些过去的植被证明了季节性气候下更为湿润和有利的气候条件。然而,在10万年的时间跨度内,树木覆盖的植物区系组成发生了重大变化,有利于气候和古环境的不稳定,当时阿法南方古猿存在于图尔卡纳盆地,并在埃塞俄比亚其他地方繁盛。
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Tropical forests and Combretaceae woodland at Usno in the Lower Omo Valley (Ethiopia), 3.3–3.2 Ma ago

In this paper, we describe anatomical structures of 11 fossil wood samples collected from two localities (Brown Sands and Flat Sands) of the Usno Formation, in the Lower Omo valley, Ethiopia. On the basis of former stratigraphy and new investigation, notably Ar/Ar dating of intercalated tuffs and palaeomagnetic studies, the samples are dated between 3.33 and 3.21 Ma. The identified wood samples have been collected within two distinct stratigraphic layers deposited during this time range. The oldest one from Brown Sands includes Albizia sp., Entada sp. and a possible Combretaceae or Leguminosae. The youngest assemblage from White Sands includes many representatives of Combretaceae including Combretum molle and Terminalia sp. associated with Erythrina sp. These assemblages strongly differ from other Miocene and Pliocene wood assemblages known from Ethiopia. Palaeoenvironmental interpretation of the identified tree taxa support affinities with the extant mid-elevation Albizia forest replaced by Combretum/Terminalia woodland in about one hundred thousand years. In the Lower Omo valley, the more humid character of the Pliocene vegetation strongly contrast with the arid Acacia/Commiphora steppe widely spread over the region today. Such past vegetation attests to much wetter and favourable climatic conditions under seasonal climate. However significant changes in the floristic composition of tree cover occurring within a timespan of hundred thousand years, plays in favour of climatic and palaeo-environmental instabilities at a time when Australopithecus afarensis existed in the Turkana basin and flourished elsewhere in Ethiopia.

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来源期刊
Geobios
Geobios 地学-古生物学
CiteScore
3.30
自引率
6.20%
发文量
28
审稿时长
6-12 weeks
期刊介绍: Geobios publishes bimonthly in English original peer-reviewed articles of international interest in any area of paleontology, paleobiology, paleoecology, paleobiogeography, (bio)stratigraphy and biogeochemistry. All taxonomic groups are treated, including microfossils, invertebrates, plants, vertebrates and ichnofossils. Geobios welcomes descriptive papers based on original material (e.g. large Systematic Paleontology works), as well as more analytically and/or methodologically oriented papers, provided they offer strong and significant biochronological/biostratigraphical, paleobiogeographical, paleobiological and/or phylogenetic new insights and perspectices. A high priority level is given to synchronic and/or diachronic studies based on multi- or inter-disciplinary approaches mixing various fields of Earth and Life Sciences. Works based on extant data are also considered, provided they offer significant insights into geological-time studies.
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