{"title":"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","authors":"Marie-Claude Jolly-Saad , Raymonde Bonnefille","doi":"10.1016/j.geobios.2023.01.003","DOIUrl":null,"url":null,"abstract":"<div><p><span>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 </span><em>Albizia</em> sp., <em>Entada</em> sp. and a possible Combretaceae or Leguminosae. The youngest assemblage from White Sands includes many representatives of Combretaceae including <em>Combretum molle</em> and <em>Terminalia</em> sp. associated with <em>Erythrina</em><span> sp. These assemblages strongly differ from other Miocene<span> and Pliocene wood assemblages known from Ethiopia. Palaeoenvironmental interpretation of the identified tree taxa support affinities with the extant mid-elevation </span></span><em>Albizia</em> forest replaced by <em>Combretum/Terminalia</em> 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 <em>Acacia/Commiphora</em><span> 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 </span><em>Australopithecus afarensis</em> existed in the Turkana basin and flourished elsewhere in Ethiopia.</p></div>","PeriodicalId":55116,"journal":{"name":"Geobios","volume":null,"pages":null},"PeriodicalIF":1.6000,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Tropical forests and Combretaceae woodland at Usno in the Lower Omo Valley (Ethiopia), 3.3–3.2 Ma ago\",\"authors\":\"Marie-Claude Jolly-Saad , Raymonde Bonnefille\",\"doi\":\"10.1016/j.geobios.2023.01.003\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p><span>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 </span><em>Albizia</em> sp., <em>Entada</em> sp. and a possible Combretaceae or Leguminosae. The youngest assemblage from White Sands includes many representatives of Combretaceae including <em>Combretum molle</em> and <em>Terminalia</em> sp. associated with <em>Erythrina</em><span> sp. These assemblages strongly differ from other Miocene<span> and Pliocene wood assemblages known from Ethiopia. Palaeoenvironmental interpretation of the identified tree taxa support affinities with the extant mid-elevation </span></span><em>Albizia</em> forest replaced by <em>Combretum/Terminalia</em> 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 <em>Acacia/Commiphora</em><span> 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 </span><em>Australopithecus afarensis</em> existed in the Turkana basin and flourished elsewhere in Ethiopia.</p></div>\",\"PeriodicalId\":55116,\"journal\":{\"name\":\"Geobios\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.6000,\"publicationDate\":\"2023-02-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Geobios\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0016699523000037\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"PALEONTOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geobios","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0016699523000037","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"PALEONTOLOGY","Score":null,"Total":0}
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.
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.