Abstract The primary objective for this study is to determine the variations of germanium (Ge) to silicon (Si) ratios in diatom shells from down core sediments off the southwestern coast of the Africa. Because Ge behaves like Si in the ocean and the major source of these two elements is rivers, Ge/Si ratios of the diatom are thus expected to record the intensity of weathering on continents. Two sediment cores (Site 1081 and 1084) were collected during the ODP Leg 175 in August, October 1997 and were analyzed for intervals between 3.1 and 1.9 Ma. Generally, the (Ge/Si)diatom ratios in this study show the similar trend with those reported from the Antarctic Ocean. The decline of Ge/Si ratios after 2.5 Ma is caused by the high opal mass accumulation rate, indicating the increasing rivers input of silica to the ocean. Relatively high Ge/Si ratios of diatom shells during warm periods shown by the depleted benthic foraminiferal £_18O values from the North and Equatorial Atlantic, suggesting a scenario of intensified chemical weathering on continent. Cold periods signified by £_18O-enriched values are associated with lower Ge/Si ratios. Very likely the reduced Ge/Si values reflect the prevailing weathering on continents was less chemical-dissolving due to the dry weather in cold stages.

Yunnan, southwestern China, represents a modern biodiversity center for Rubus (Rosaceae). The history for this high modern diversity remains poorly known due to the lack of fossil evidence. In this report, fossil pyrenes of Rubus are taxonomically studied from the late Pliocene (Piacenzian) of Lanping County, northwestern Yunnan. These pyrenes show a greater morphological variation than that of extant Rubus pyrenes within the same species, indicating that they belong to different taxa of Rubus. Based on comparisons with both modern and other fossil species, our fossil pyrenes are assigned to five taxa, including a newly established one, Rubus lanpingensis nov. sp. These fossils suggest a somewhat high species diversity of Rubus in Lanping, a small area in northwestern Yunnan, during the late Pliocene. This provides the first fossil perspective for an understanding of the historical background of the modern Rubus diversity in a limited geographic area of Yunnan. The inferred palaeobiodiversity is probably associated with a large environmental heterogeneity in a limited area of Yunnan at that time.

It is widely accepted that the late Pliocene spans a time with globally warmer conditions compared to today. Regional specifics in temperature patterns from this period, however, remain poorly known. In this study, we reconstruct quantitatively late Pliocene climates for eight sites at the southeastern border of the Qinghai-Tibet Plateau (SBTP), based on palaeobotanical data compiled from published sources using the Coexistence Approach (CoA), and analyze anomalies with respect to modern climates. The reconstructed temperatures indicate that in the late Pliocene, the northwestern part of the study area was cooler than its southern part. This spatial differentiation in temperature was largely due to differences in altitude: the northwest of the SBTP probably had higher altitudes than the south at that time. Mean annual temperatures (MATs) were around 1. °C higher than today, suggesting a cooling trend since the late Pliocene. Our data show that summer temperatures have declined significantly since the late Pliocene while winter temperatures have remained similar to those of the present, different from observations in other territories. The unexpected summer and winter temperature changes can be explained by the regional orogenic uplift plus the global cooling. The eastward extrusion of the Qinghai-Tibet Plateau might have blocked the southward cold high pressure of the winter monsoon and forced it to circumvent the eastern flank of the plateau, weakening its impact on the SBTP. The post-Pliocene mountain uplift increased the overall altitude of the region, which caused the temperature decline for both summer and winter. The reconstructed summer precipitation was lower while the winter precipitation was higher than today, suggesting a weaker monsoon climate during the late Pliocene.