The new hominid skeleton from Sterkfontein,South Africa: age and preliminary assessment

A new hominid skeleton from Sterkfontein Member 2 attaches to foot bones recovered from loose blocks during the 1980s and first described in 1995. Several flowstone horizons are present above and below the skeleton and have given clear palaeomagnetic signatures. Five changes in magnetic polarity have been identified; when constrained by the available biostratigraphy, this sequence can be placed confidently between 3.22 and 3.58 Ma. Interpolation of sedimentation rates over the small intervals between reversals allows this range to be reduced to 3.30–3.33 Ma. The skeleton is thus the oldest yet discovered and is considered to belong to a species of Australopithecus other than africanus. Copyright © 1999 John Wiley & Sons, Ltd.     

二十世纪广西古人类学研究综述

文章回顾20世纪以来,在广西发现的重要古人类化石和文化遗物,包括4个巨猿化石地点、13个晚期智人化石地点以及一系列旧石器.对柳江人遗址等的地层和年代学进行了综合研究,对国际学术界关于现代人起源的"多地区连续演化说"将提供强有力的证据;百色盆地旧石器的综合研究,将对恢复早中更新世的环境和早期人类迁徙、扩散的模式,有着深远的意义.     

Preliminary study on enamel microstructure of Yuanmou Miocene hominoids of China

Late Miocene hominoid fossils found in Yunnan Province, China are of great importance in exploring hominid origins and hominoid phylogeny, and in recent years palaeoanthropologists have been paying great attention to them. The Yuanmou hominoid site is on…     

再论“建始人”时代

就施林峰同志对湖北建始龙骨洞“建始人”的时代提出的异议进行讨论。哺乳动物化石、古人类化石和沉积速率研究表明,龙骨洞古地磁柱的两个正极性事件应与奥都威亚时和留尼旺亚时对比。     

南京猿人洞石笋年代学研究及其古气候记录

铀系测年和石笋同位素曲线调谐年代表明,位于南京直立人头骨化石层位上之的一支石笋发育年代为３８１￣１６６ｋａ Ｂ．Ｐ．这一结果反映南京直立人生存时代早于３８１ｋａＢ．Ｐ．。从石笋方解石晶体液相包裹体δＤ测试结果定量计算了该时段内各冷、暖期的古气温,石笋显微剖面中方解石结晶习性和生长条带的特征揭示了洞穴干湿度的变化。     

Magnetostratigraphy of the lower member of the hadar formation (Ethiopia): Evidence for a short normal event in the mammoth subchron

Summary Rock magnetism and magnetostratigraphy of the lower part of the Hadar Formation (Afar, Ethiopia) is presented after analysis of multiple new collection of samples from over 84 horizons. The Hadar Formation is composed of lacustrine, lake margin, fluvial and flood plain sediments and known for important Pliocene vertebrate faunas including Australopithecus afarensis. Hysteresis measurements, thermomagnetic analysis, growth and decay of isothermal remanent magnetisation are used to unravel the complex magnetic mineralogy of the different representative lithologies. Ferrimagnetic minerals of magnetite or titanomagnetite in composition, in the stable pseudo-single domain (PSD) size range are found to be the main carriers of the remanence. In most sites the characteristic remanence was isolated using stepwise thermal demagnetisation. The overall mean direction for about 72 horizons (434 samples) is D=358·6°, I=7° (k=17·9, α₉₅=4°) implying some 14° of inclination shallowing, related to sediment compaction due to the very rapid sedimentation history of the site. Five successive polarity zones (N1-R1-N2-R2-N3) are identified and correlation with the lower Gauss chron of the astronomically calibrated geomagnetic polarity time scale (GPTS) is proposed using the existing⁴⁰Ar/³⁹Ar ages. This implies the existence of a short normal polarity event (N2), identified on six different sites, within the reversed Mammoth subchron, called the Kada-Hadar event. The age calculated for the Kada-Hadar event, using linear interpolation of the dated horizons, assuming a constant rate of sedimentation is 3.246 Ma and its duration is about 8 kyr.     

A kinematic model for the development of the Afar Depression and its paleogeographic implications

The Afar Depression is a highly extended region of continental to transitional oceanic crust lying at the junction of the Red Sea, the Gulf of Aden and the Ethiopian rifts. We analyze the evolution of the Afar crust using plate kinematics and published crustal models to constrain the temporal and volumetric evolution of the rift basin. Our reconstruction constrains the regional-scale initial 3D geometry and subsequent extension and is well calibrated at the onset of rifting (∼20 Ma) and from the time of earliest documented sea-floor spreading anomalies (∼6 Ma Red Sea; ∼10 Ma Gulf of Aden). It also suggests the Danakil block is a highly extended body, having undergone between ∼200% and ∼400% stretch. Syn-rift sedimentary and magmatic additions to the crust are taken from the literature. Our analysis reveals a discrepancy: either the base of the crust has not been properly imaged, or a (plume-related?) process has somehow caused bulk removal of crustal material since extension began. Inferring subsidence history from thermal modeling and flexural considerations, we conclude subsidence in Afar was virtually complete by Mid Pliocene time. Our analysis contradicts interpretations of late (post 3 Ma) large (∼2 km) subsidence of the Hadar area near the Ethiopian Plateau, suggesting paleoclimatic data record regional, not local, climate change. Tectonic reconstruction (supported by paleontologic and isotopic data) suggests that a land bridge connected Africa and Arabia, via Danakil, up to the Early to Middle Pliocene. The temporal constraints on land bridge and escarpment morphology constrain Afar paleogeography, climate, and faunal migration routes. These constraints (particularly the development of geographic isolation) are fundamentally important for models evaluating and interpreting biologic evolution in the Afar, including speciation and human origins.