An exposed section of nearly 13 m thick was investigated in the ancient depression of Lake Eastern Juyanze, north-eastern China. The succession of lacustrine and aeolian deposits covers a period from about 5400 to 2700 cal. a BP as indicated by four radiocarbon ages of macro-plant debris. Fifteen ostracod taxa were identified of which Limnocythere inopinata and Darwinula stevensoni are by far the most abundant species. Stable isotope (O, C) data of ostracod calcite as well as ostracod species abundances and X-ray diffraction results of bulk sediment samples were used to reconstruct the history of Lake Eastern Juyanze. Highest lake levels (water depth ~10 m) occurred between 5100 and 4100 cal. a BP and were succeeded by intermediate and low levels until about 3150 cal. a BP. Three short-term events of complete desiccation were recorded between 3150 and 2900 cal. a BP. The lake experienced relatively high levels again for some decades at about 3000 cal. a BP and for at least two centuries after 2900 cal. a BP. According to the ostracod and gastropod record and the high abundance of a large diatom (Campylodiscus clypeus) in the lake sediments oligohaline to slightly mesohaline conditions were reconstructed for most of the lake periods (4-6 g/l). Geochemical and palaeontological records of Lake Eastern Juyanze reveal the retreat of the Asian monsoon after China's Hypsithermal culminating in climate instability at about 3000 cal. a BP.
Une section disponible d'environ 13 m d'epaisseur a ete analysee dans l'ancienne depression du lac Juyanze d'est, au NO de la Chine. La succession de depots lacustres et aeoliens couvre une periode comprise entre 5400 et 2700 cal. a BP, mesuree par quatre datations au radiocarbone de debris de macro-plantes. On a identifie 15 types d ostracodes, parmi lesquels Limnocythere inopinata et Darwinula stevensoni sont les plus abondantes. Pour reconstituer l'historique du lac Juyanze d'est, on a utilise les donnees d'isotopes stables (O, C) de calcite d'ostracode aussi bien que l'abondance des differentes especes d'ostracodes et la diffraction aux rayons X de volumineux echantillons de sediments. Les niveaux maxima des eaux du lac (profondeur approximative environ 10 m) ont eu lieu entre 5100 et 4100 cal. a BP et ont ete suivi par des niveaux intermediaires et bas jusqu'a environ 3150 cal. a BP. On a enregistre trois courtes periodes d'assechement complet du lac entre 3150 et 2900 cal. a BP. Le lac a encore connu des niveaux d'eau relativement eleves durant quelques decennies aux alentours de 3000 cal. a BP et pendant au moins deux siecles apres 2900 cal. a BP. Compte tenu de la presence d'ostracodes et de gasteropodes ainsi que de la grande abondance d'une grande diatomee (Campylodiscus clypeus), on a pu reconstituer les conditions de passage d'une salinite oligohaline a mesohaline pour la plus grande partie du lac (4-6 g/l). En resume, les donnees concernant le Lac Juyanze d'Est font ressortir un retrait de la mousson apres la culmination Hypsithermale chinoise avec installation d'un climat plus instable vers environ 3000 cal. a BP.