Asian monsoons and aridification response to Paleogene sea retreat and Neogene westerly shielding indicated by seasonality in Paratethys oysters

Asian climate patterns, characterised by highly seasonal monsoons and continentality, are thought to originate in the Eocene epoch (56 to 34 million years ago – Ma) in response to global climate, Tibetan Plateau uplift and the disappearance of the giant Proto-Paratethys sea formerly extending over Eurasia. The influence of this sea on Asian climate has hitherto not been constrained by proxy records despite being recognised as a major driver by climate models. We report here strongly seasonal records preserved in annual lamina of Eocene oysters from the Proto-Paratethys with sedimentological and numerical data showing that monsoons were not dampened by the sea and that aridification was modulated by westerly moisture sourced from the sea. Hot and arid summers despite the presence of the sea suggest a strong anticyclonic zone at Central Asian latitudes and an orographic effect from the emerging Tibetan Plateau. Westerly moisture precipitating during cold and wetter winters appear to have decreased in two steps. First in response to the late Eocene (34–37 Ma) sea retreat; second by the orogeny of the Tian Shan and Pamir ranges shielding the westerlies after 25 Ma. Paleogene sea retreat and Neogene westerly shielding thus provide two successive mechanisms forcing coeval Asian desertification and biotic crises

A Report on Arinko Club Activity, \u22Let\u27s Play in the Nature\u22 for Three Years

『自然と遊ぼう「ありんこクラブ」』は活動を始めて4年目を迎えました。保育士、学童保育指導員の経験の中から　①多くの子ども達に自然の中で体を存分に使って遊ぶ楽しさを知って欲しい②大人たちに子どもの遊びの大切さを思い出してほしい③遊び文化を絶やしたくない④地域で遊ぶことによりやがては地域の環境保全につながってほしい⑤大人たちに現在の生活や生き方を見つめなおしてほしい　このような願いから夫や仲間達とつくったクラブです。月一回の活動ですが、毎月発行している「ありんこ新聞」を読んで、都合のつく人が参加するというゆるやかな活動です。野外活動が主な為、保険の関係で会員制度にしていますが、一般の方への参加を呼びかけて環境教育学習や、上映会などにも取り組んでいます。本稿はクラブを始めた経緯から現在までの実践報告と、活動の広がりなどをまとめてみました

Etude de la saisonnalité en Asie centrale à l'éocène moyen : Apport de la sclérochronologie sur des coquilles d'huîtres

National audienc

The Cretaceous – Paleogene paleogeography of Central Asia recorded in depositional environments of the Proto-Paratethys Sea in the Tarim Basin (Western China)

The Proto-Paratethys, a shallow epicontinental sea, extended from Cretaceous to Paleogene times across Eurasia from the Mediterranean Tethys to the Tarim Basin in western China. Transgressive and regressive episodes of the Proto-Paratethys Sea have been previously recognized but their timing, extent and depositional environments remain poorly constrained especially for the Cretaceous and early Paleogene. This hampers understanding of their driving mechanisms (geodynamic and/or eustatic) and paleoclimatic consequences on regional aridification and monsoons. As part of the ERC “MAGIC” project, we report an integrated sedimentologic and stratigraphic analysis of the Proto-Paratethys from its initial Cretaceous onset to the final Paleogene retreat from multiple investigated sections in the western border of Tarim Basin. Facies associations include field observations and microfacies analyses from carbonate samples. New bio- and magneto-stratigraphic results from key intervals are also provided to testify the previously constructed regional stratigraphic framework. The previously controversial number of marine incursions in the Tarim Basin is resolved to 6 (3 Cretaceous and 3 Paleogene) also recognized in the neighboring Tajik and Turan Basins to the west and the present-day Alai Valley. The eastward extent of these marine incursions varied through time with a maximum extent during late Paleocene - early Eocene. The first marine incursion is a Cenomanian transgression recorded in the marls and calcareous mudstones of the Kukebai Formation. The next two are Coniacian and Campanian transgressions recognized in the carbonate units of the Yigeziya Formation. The first Paleogene incursion is characterized by thick evaporites of the Paleocene Aertashi Formation overlain by the marine shales of the Lower Qimugen Formation. The latter represents the maximum extent and the deepest environments of the Proto-Paratethys. The marine Kalatar limestones and silty shales of the Wulagen Formation are associated with the penultimate transgression whereas the silty shales of the Bashibulake Formation were laid down during the last smaller marine incursion. Generally, transgressive intervals are composed of restricted marine bay environments, shoal & oyster-rich bioherms giving rise to upper offshore to shoreface transition silty shales. The regressive intervals are composed of intertidal flats, supratidal sabkhas and salinas, fluvial, playa and lake environments of alluvial plain. The temporal and spatial extent of the transgressive and regressive intervals enable to discriminate the major drivers of marine fluctuations with their potential consequences on Asian aridification and monsoons