北京古蓟城城址古地貌环境演变研究——以广义大厦工程剖面为例

广安门地区是北京最早的城址——古蓟城所在地。对广安门内的广义大厦工程地层剖面进行的古地貌复原研究表明,当地在2.2万年前为永定河河道,全新世以来发育成河旁高地,成为古代蓟城的选址地。经历了由晚更新世晚期较冷湿的疏林草地、较干旱的草原植被景观、全新世较暖湿的疏林草地及较凉湿的草甸植被环境的演变过程。     

早更新世甘肃省临夏盆地的环境演化

以孢粉分析为主,结合ω(CaCO3),c(Cl-)和粒度指标,建立了临夏盆地早更新世的环境演化序列.临夏盆地早更新世环境演化大致经历了干(2.50～1.91 Ma)-湿(1.91～1.80 Ma)-干(1.80～1.76 Ma)三个阶段,其中在1.89～1.87 Ma期间云杉孢粉含量占绝对主导地位(77.8%～89.4%),是临夏盆地早更新世气候最湿润期.通过将孢粉资料同北大西洋深海底栖有孔虫氧同位素曲线和南海浮游有孔虫氧同位素曲线对比以及孢粉波谱分析发现,1.95 Ma前后是临夏盆地气候转型的重要时期.在此之前,气候变化主要受热带季风控制,之后受高纬冰盖变化的驱动.根据前人相关研究结果推测,青藏高原在早更新世的强烈隆升可能是造成这一气候转型的原因之一.     

粤东华林第四纪断层初析

 首次报道粤东地区发现的第四纪断层华林断层。该断层切割了时代可能属晚更新世的沉积;断面总体走向300°,倾向北东,倾角75°,下盘尚发育多个向下收敛的分枝裂面,其上的擦痕指示断裂下盘上升。断面向下与基岩中的断裂相连,表明其形成是基底断裂继承性活动引起。     

High lake levels on Alxa Plateau during the Late Quaternary

Field investigations including lake shoreline measurement and ¹⁴C chronology have been carried out on the Alxa Plateau to better understand the formation and evolution of the high lake levels in northwest China during the late Pleistocene. Comprehensive field investigations show that there are at least ten shorelines at different elevations at Juyan Lake, at least four on the northwest side of the Jilantai Salt Lake, and nine shorelines and one terrace on the northeast margin of Zhuye Lake. Stratigraphic correlations and chronological evidence indicate that the paleo-lakes have the highest lake levels in Marine Isotope Stage (MIS) 3. Though the optically stimulated luminescence (OSL) results which have been reported by some scholars do not support this view, the fact that the paleo-lakes have the highest lake levels in MIS 3 can not be denied. Differences between OSL and ¹⁴C results from this work might indicate that high lake levels existed on the Alxa Plateau during two different periods. It also suggests that the high lake levels may exist in both MIS 5 and early MIS 3. This paper also provides the basic hydrological information for further water resources research in this arid region.     

张坪洞穴群中田鼠类臼齿形态研究

目的 探讨田鼠类臼齿的形态变化和种类演替.方法 运用经典的古生物学方法,包括化石标本的形态学分析和测量统计等.结果 田鼠齿列中M3和ml的长宽比值是其中最大的,其第5齿峡Is5相应的由宽变窄,趋于封闭,第6齿峡Is6从无到有,逐步变小.结论 在田鼠臼齿中,M3和ml由于特殊的形态及位置使它们容易延伸变化而成为形态学分析的重点,其形态具有由简单到复杂的变化趋势,研究区及其附近,田鼠类更新世以来的演替顺序分析为Allophaiomys(Q1)-Predromys(Q1)-Microtus(Q2).