Paleoenvironmental insights by stable isotopes and phytoliths at Simbiro III Monumental Section (~1.2-1.3 Ma) (Melka Kunture, Upper Awash, Ethiopia) (Abstract)

Depto. de Prehistoria, Historia Antigua y ArqueologíaFac. de Geografía e HistoriaTRUEpu

The ACER pollen and charcoal database: a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period

Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid climate change in the past are the warming events associated with the Dansgaard–Oeschger (D–O) cycles during the last glacial period, which were sufficiently large to have had a potential feedback through changes in albedo and greenhouse gas emissions on climate. Previous reconstructions of vegetation and fire changes during the D–O cycles used independently constructed age models, making it difficult to compare the changes between different sites and regions. Here, we present the ACER (Abrupt Climate Changes and Environmental Responses) global database, which includes 93 pollen records from the last glacial period (73–15 ka) with a temporal resolution better than 1000 years, 32 of which also provide charcoal records. A harmonized and consistent chronology based on radiometric dating (14C, 234U∕230Th, optically stimulated luminescence (OSL), 40Ar∕39Ar-dated tephra layers) has been constructed for 86 of these records, although in some cases additional information was derived using common control points based on event stratigraphy. The ACER database compiles metadata including geospatial and dating information, pollen and charcoal counts, and pollen percentages of the characteristic biomes and is archived in Microsoft AccessTM at https://doi.org/10.1594/PANGAEA.870867

Atlas des pollens d\u27\uc9thiopie. Pollens actuels de la basse vall\ue9e de l\u27Omo, r\ue9coltes botaniques 1968

Volume: 11Start Page: 463End Page: 51

Pollen-inferred precipitation time-series from equatorial mountains, Africa, the last 40 kyr BP

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Precipitation signal in pollen rain from tropical forests, South India

International audienceWe have analyzed the pollen content of 51 surface soil samples collected in tropical evergreen and deciduous forests from the Western Ghats of South India sampled along a west to east gradient of decreasing rainfall (between 11 degrees 30-13 degrees 20 'N and 75 degrees 30-76 degrees 30 'E). Values of mean annual precipitation (Pann, mm/yr) have been calculated at each of the 51 sampling sites from a great number of meteorological stations in South India, using a method of data interpolation based on artificial neural network. Interpolated values at the pollen sites of Pann range from 1200 to 5555 mm/yr, while mean temperature of the coldest month (MTCO) remains > 15 degreesC and humidity factor (AET/PET, the actual evapotranspiration to potential evapotranspiration ratio) remains also included between 65 and 72%. Results are presented in the form of percentage pollen diagrams where samples are arranged according to increasing values of annual precipitation. They indicate that the climatic signal of rainfall is clearly evidenced by distinct pollen associations. Numerical analyses show that annual precipitation is an important parameter explaining the modern distribution of pollen taxa in this region. Pollen taxa markers of high rainfall (Pann > 2500 mm/yr) are Mallotus type, Elaeocarpus, Syzygium type, Olea dioica, Gnetum ula, and Hopea type, associated with Ixora type and Caryota. Pollen taxa markers of low rainfall (Pann < 2500 mm/yr) are Melastomataceae/Combretaceae, Maytenus type, Lagerstroemia and Grewia. The proportions of evergreen taxa and of arboreal taxa vary according to rainfall values. Indeed, when rainfall is < 2500 mm/yr, percentage of arboreal pollen (AP) is < 50% and proportion of evergreen taxa is < 20%. When rainfall exceeds 2500 mm/yr, AP values average 70%, and proportion of evergreen taxa increases from 60 to 90%. Moreover, a,good correlation between precipitation and proportion of evergreen taxa (0.85) presumes that precipitation can be estimated from pollen data

Lower to Mid-Pliocene pollen data from East African hominid sites, a review

International audienceThis paper presents fossil pollen data (39 samples) available for the Lower Pliocene outcrops at five hominid sites in East Africa located within the intertropical region between 3° South to 11° North. They are dated from 4.2 to 2.95 millions years (Ma). Most of these data were obtained many years ago, except one additional pollen assemblage recently obtained in the Woranso-Mille area of the Lower Awash valley, Ethiopia. In East Africa, Plio-Pleistocene sedimentary sequences are internationally renowned for the continuous palaeo-anthropological researches pursued for decades, following the discoveries of preserved remains of fossil hominins associated to a rich, diversified and abundant mammalian fauna. As a result of these new discoveries, geological studies have continued, being connected to following field expeditions and exploration of new sites in the Ethiopian Rift. We present here the revised geological context, adding chronological precision to previous age constraints of the original pollen data. For each terrestrial Pliocene site, we also include some comments regarding the significance of pollen counts and briefly discuss their interpretation for reconstructing past vegetation, environment, and inferred climatic parameters at the studied hominin sites

&lt;i&gt;Ficoxylon&lt;/i&gt; sp., un bois fossile de 4,4 Ma (vallée moyenne de l’Awash, Éthiopie)

Cet article décrit les structures microscopiques d’un fragment de bois fossile, silicifié, récolté dans la vallée moyenne de l’Awash (Éthiopie). Le bois fossilisé a été trouvé dans des dépôts datés avec précision de 4,4 Ma. Son attribution en tant que Ficoxylon sp. est basée sur la comparaison du bois de quelques espèces modernes du genre Ficus, connues en Afrique et la présence de caractères décrits pour les spécimens de bois fossiles d’Afrique de l’Ouest, de Libye, d’Égypte et d’Éthiopie, antérieurement attribués à Ficoxylon.In this article we describe the microscopic structures of a silicified piece of wood collected in the Middle Awash Valley (Ethiopia). The fossil wood was extracted from sediment precisely dated 4.4 Ma. Its attribution to the Ficoxylon species is based upon detailed comparison with published data and with comparisons of some modern species of the genus Ficus and similar characters encountered in fossil woods from West Africa, Egypt, Libya and Ethiopia previously described and attributed to this taxon.</p

Fruits fossiles d\u27Antrocaryon dans la vall\ue9e de l\u27Omo (\uc9thiopie)

Volume: 16Start Page: 65End Page: 8

Fossil woods from the Usno Formation (Lower Omo Valley, Ethiopia) document humid tropical forests ca. 3.3 Ma ago.

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