Stable carbon and oxygen isotopes of four planktonic foraminiferal species from core-top sediments of the Indonesian throughflow region and their significance

Horizontal and vertical distributions of δ^(18)O and δ^(13)C were investigated in shells of four planktonic foraminiferal species, Globigerinoides ruber, Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquedrina dutertrei, from a total of 62 core-top sediment samples from the Indonesian throughflow region. Results were compared to modern hydrologic conditions in order to explore potential of proxies in reconstructing fluvial discharge and upper ocean water column characteristics in this region. Our results show that, in the Makassar Strait, both of depleted δ^(18)O and δ^(13)C of these four species were linked to freshwater input. In the Bali Sea,however, depleted δ^(18)O and δ^(13)C for these species may be due to different reasons. Depleted δ^(18)O was a result of freshwater input and as well influenced by along-shore currents while depleted δ^(13)C was more likely due to the Java-Sumatra upwelling. Comparison of shell δ^(18)O records and hydrographic data of World Ocean Atlas 2005 suggests that G. ruber and G. sacculifer calcify within the mixed-layer, respectively at 0–50 m and 20–75 m water depth, and P. obliquiloculata and N. dutertrei within the upper thermocline, both at 75–125 m water depth. N.dutertrei calcifies at slightly deeper water depth than P. obliquiloculata does. In general, δ^(13)C values of both G.ruber and G. sacculifer are larger than those of P. obliquiloculata and N. dutertrei at all sites, possibly related to depth habitats of these species and vertical distribution of nutrients in the Indonesian throughflow region.

Geochemical characteristics from tests of four modern planktonic foraminiferal species in the Indonesian Throughflow region and their implications

Test geochemistry of planktonic foraminifera is an indispensable tool in reconstructing past ocean hydrological changes. It is essential to investigate region-specific implications of test geochemistry,although those established from other regions can be broadly applied. In this study, characteristics of6180 and Mg/Ca from tests of four planktonic foraminiferal species, Globigerinoides ruber sensu stricto(s.s.), Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, from 60 coretop sediment samples retrieved from the Indonesian Throughflow(ITF) region were studied. These geochemical data were compared with modern hydrographic profiles in order to assess their relations and to investigate potential implications of test geochemical parameters in reconstructing past oceanographic change in the ITF region. Calcification depths of these four species were first estimated based on comparison between measured test δ180 and predicted calcite δ^(18)O that was calculated from modern temperature and salinity. The results indicate that G. ruber s.s. and G. sacculifer calcify within the mixedlayer at 0-50 m and 20-75 m, respectively, whereas P. obliquiloculata and N. dutertrei calcify within the thermocline at around 75 to 125 m. A combined study of excess Mg/Ca(difference between measured and predicted Mg/Ca) and salinity suggests that salinity exerts a negligible impact on test Mg/Ca of these foraminiferal species in the ITF region. Comparison of test Mg/Ca-derived temperatures with temperature profiles of the upper 200 m of the water column from the seas of the ITF region also indicate calcification depths of these species, which match well with the above estimations using test δ^(18)O. It further indicates that G. sacculifer may be more sensitive in reflecting changes in the depth of the mixedlayer, highlighting a potential use of Mg/Ca temperature difference between G. ruber s.s. and G. sacculifer in reconstructing the depth of the mixed-layer in the ITF region.

A New Model for Correlation between the Marine Benthic Oxygen Isotope and Red Clay Magnetic Susceptibility on the Chinese Loess Plateau

Objective Aeolian sediments on the Chinese Loess Plateau contain some of the best continental archives of palaeoclimate change in the Late Cenozoic.The consensus that alternating MS in loess-paleosols in China was due to the strengthening and weakening of the East Asian palaeomonsoon provides an excellent climate record when correlated with global ice volume.Significantly,new basal dates from the red clay underlying the loess-paleosol sequence indicate that wind-blown dust began to accumulate on the Chinese Loess Plateau at least

New Discovery of Oligocene Gastropod Opercula from the Yehucheng Formation in Northwestern China

Fourteen species of nonmarine gastropod opercula are found to be in high abundance in the Oligocene upper member of the Yehucheng Formation,Lanzhou Basin,northwest China.They are attributed to two families,namely Bithyniidae and Assimineidae,and four genera,namely Pseudemmericia,Bithynia,Mirolaminatus and Assiminea.Among them,three species are new,and they are Bithynia paramonolithic sp.nov.,B.obliquus sp.nov.,and B.disregularis sp.nov.Some of these species were first discovered in Paleogene strata of the vast Northwest China and can be compared with the opercula recovered from the Paleogene deposits in East and South China.It is inferred from the paleontology and sediment associations that the climate was slightly humid and the fauna probably inhabited the fresh or brackish water of a shallow lake in the Lanzhou Basin during the late early Oligocene period.

Nanpoping fauna of the Lanzhou Basin and its environmental significance

季风干旱的环境系统开始在渐新世期间开发了的亚洲人，而是干旱地区边界的准确位置在渐新世是不明确的。石块哺乳动物集合能被用来估计一个区域的环境。有在从 Lanzhou 盆的渐新世阶层的 Nanpoping 动物志的哺乳动物的二种尺寸：小的是象 Ctenodactylidae 那样的草地啮齿类动物；大的是象 Paraceratherium 和 Paraentelodon 那样的森林居民。在 Nanpoping 动物志识别的哺乳动物的 23 种类， ~40% 是森林居民和剩余的(~60%) 是草地 taxa。Nanpoping 动物志在到南方的 Linxia 区域与在到北方和 Jiaozigou 动物志的 Danghe 区域的同时期的 Dingdanggou 动物志相比。Nanpoping 动物志包含两另外的动物志的元素并且因此代表在森林和草地之间的一个过渡集合。那么，在中国的干旱地区的南部的边界可能在渐新世期间在 Lanzhou 盆附近，这能被推断。

Discovery and chronological division of the Hipparion fauna in Laogaochuan Village, Fugu County, Shaanxi

Over two hundred species of the Hipparion fauna belonging to the Baode Stage havebeen found in more than a hundred localities in China. All of these fossils had beenthought to come from the same horizon by most scientists till the end of the 1950s.Since 1960, the Hipparion fauna has been discovered from different horizons and differentecologic groups, and extensive studies of taxonomy and evolution of some mammals

Change of Indonesian Throughflow outflow in response to East Asian Monsoon and ENSO activities since the Last Glacial

上面的海洋西方太平洋和印度洋浇，调制在这些海洋之间的热和新鲜的水预算，并且接着起在全球气候的一个重要作用的印度尼西亚的 Throughflow (ITF ) 连接变化。气候的现象象东方亚洲季风和 El Ni 那样 ?o 南部的摆动(ENSO ) 对流动，水性质和 ITF 的垂直层化施加强烈影响。这个工作学习了在 Timor 海从 ITF 的流出方面被检索以便自从最后，调查 ITF 的反应到季风和 ENSO 活动的核心 SO18462 的沉积冰川。在 planktonic 的壳把比率和氧同位素基于 Mg/Ca 有孔虫目的表面和 thermocline 种类，海水温度和表面和 thermocline 水和 ITF 流出的垂直热坡度的咸度被重建。核心 SO18462 的记录当时与从从西方的和平的温暖的水池(WPWP ) 被恢复的核心 3cBX 的那些相比。结果显示了那类似的表面水在最后期间发生在 Timor 海和 WPWP 冰川。自从 16 ka，在这二个区域之间的表面水里的明显的差别在咸度存在，比在 WPWP 在 Timor 海由新鲜得多的水显示了。相反，处于海表面温度(SST ) 的差别有小变化。关于 thermocline 温度(TT ) ，自从最后，它增加了直到 11.5 ka 冰川，然后在 WPWP 仍然是一个全面未改变的趋势，但是连续地向迟了的 Holocene 在 Timor 海减少了。自从 6 ka， thermocline 水趋于在 Timor 海和 WPWP 之间接近对方。由于东方亚洲季风和显著地添的表面在印度尼西亚的海上浇的可能的 ENSO 冷阶段加强了降水，这被显示，阻碍 ITF 表面流动并且接着在 Holocene 期间提高了 thermocline 流动。因而， ITF 流出的 thermocline 水正在冷却， thermocline 向迟了的 Holocene 正在变浅。除了东方亚洲冬季季风加强，多半在迟了的 Holocene 期间增加 ENSO 事件在影响 ITF 流出的 thermocline 深度起了一个重要作用，这被推测。