Significance of lherzolite at the Etang de Lherz,central Pyrenees,southern France

Geologic relationships in the central Pyrenees of southern France demonstrate that lherzolite has been emplaced, as a plastic solid, into middle or upper Cretaceous calcareous rocks; that it has been eroded and clastic peridotite debris deposited in rocks of approximately the same age as those it intruded; and that it has also been juxtaposed against Cretaceous limestone or marble along or within the North Pyrenean fault zone. There are at least three types of late Cretaceous lherzolite breccias known from this region.Metamorphism of the country rock and penetrative deformation of the lherzolite and marble took place during shearing. Shearing was accompanied by an important period of motion (perhaps 85–100 m.y. ago) along the North Pyrenean fault and an associated thermal event which involved temperatures of 400 ± 100°C. Cretaceous metamorphism along the North Pyrenean fault zone was not due to forcible primary hot intrusion of lherzolite.     

The early diagenesis of aliphatic hydrocarbons and organic matter in sedimentary particulates from Dabob Bay,Washington

Aliphatic hydrocarbon compositions were quantitatively characterized in plankton, sediment trap-collected particulate materials and sediments from Dabob Bay using high resolution glass capillary gas chromatography. The average net accumulation of individual hydrocarbons measured in a 1-yr series of sediment traps was compared with the net accumulation of corresponding compounds measured in three depth intervals of ²¹⁰Pb-dated bottom sediments. Systematic and rapid decreases in the net accumulation of individual hydrocarbons were observed from the sediment traps to the sediments. Most pronounced decreases were measured for planktonically derived hydrocarbon constituents (e.g. pristane and two unsaturated compounds) which are rapidly remineralized at or near the sediment-water interface. Consequently, the amount of each compound measured in deposited sediments is not necessarily a quantitative indication of its initial flux to the sediments. The n-alkanes (C_25,27,29,31). characteristic of terrestrial plant waxes, are the predominant hydrocarbons measured by 4–6 cm depth in these sediments and show reasonably constant net accumulation below this interval.Significant diagenetic alteration of the bulk organic matter contained in the average sediment trap particulate material is also noted through comparison with bottom sediments on the basis of organic C/N and δ¹³C measurements. Organic matter elementally similar to marine plankton is preferentially remineralized upon deposition of the sedimentary particulates. The residual organic matter remaining and buried in the bottom sediments closely resembles terrestrial organic matter.     

Sediment failure and sedimentary framework of the wilmington geotechnical corridor,U.S. atlantic continental margin

Seaward of New Jersey and the Baltimore Canyon Trough, a 7500 km² corridor across the continental margin was studied in detail using geotechnical and geophysical techniques. The objective of the study was to identify the sedimentary pattern and bottom processes which have occurred and are active on the continental margin. Delineation of a mid-Pliocene unconformity, present throughout most of the corridor, permits an evaluation of the Quaternary sedimentation pattern and its variability. Sediment failure characterized by large slide blocks and thin layer slide deposits was found on the continental slope and rise within the Quaternary sediments. Spencer and Wilmington Submarine Canyons have been active in channeling large volumes of sediment to the lower slope and rise. An increase in sediment thickness near Wilmington Canyon indicates the importance and activity of the Delaware Bay drainage system during the Pleistocene. Although both Spencer and Wilmington are as old as late Tertiary the Wilmington Valley on the lower slope and rise is a recent topographic feature. Based on geophysical data the numerous valleys that dissect the continental slope and rise appear to be active periodically in the seaward transport of sediment to the deep sea.     

Probable Neolithic footprints preserved in inter-tidal peat at Kenfig, South Wales (UK)

Holocene footprints have been reported from several locations around the UK coast preserved within inter-tidal sediments. These sediments are normally fine-grained silts, sands and clays. Here we report potential human footprints preserved in the lower of two inter-tidal peat units exposed on the foreshore at Kenfig in South Wales. The lower peat layer pre-dates 3810 ± 40 BP and its maximum age is constrained by two dates, one of 4930 ± 50 BP and another of 5110 ± 50 BP. The prints may have formed at any point within this time interval. Both peat units formed in a salt marsh, or fen environment, as indicated by the analysis of both diatoms and pollen and have been tentatively assigned to the middle Wentlooge Formation within the Holocene lithostratigraphy established for the Severn Estuary Holocene sequence. The footprints were digitised using an optical laser scanner and are compared to other Holocene human footprints exposed on the Sefton Coast in North West England. In comparison the Kenfig prints have poor anatomical form which may be the result of both the substrate and post-depositional modification. The paper demonstrates the value of using optical laser scanning in the data capture and analysis of transitory archaeological and geological trace evidence.     

青藏高原古人类的艺术创作——基于中更新世手脚印形态分析

在第二次青藏科考过程中,作者在西藏自治区拉萨市邱桑村的古泉华沉积上新发现了由5个手印和5个脚印组成 “岩面艺术” （parietal art）。对这一“岩面艺术”进行解剖学测量、3D 模型模拟、铀系测年和手脚印形态分析后,得到以下认识：① “岩面艺术”是在泉华没有成岩之前由古人类有意压上去的;② “岩面艺术”所在岩层的U/Th年代为226~169 ka B.P.,这其中包含一个手指印岩层的表面直接年龄（207~188 ka B.P.）;③ 这一发现是迄今为止发表的古人类在青藏高原上活动的最早记录之一,也为古人类适应高寒、低氧环境提供了新的证据;④ 此岩面艺术是目前世界上已知的最古老的艺术,上面的手印也是古人类留下的最早的手印;⑤ 这一原始的岩面艺术表明,创作它的古老人种可能具有一定的认知和空间感知能力,此岩面艺术的发现也将有可能改写人类艺术史,并且加深我们对已消失的古人类认知水平的认识。     

Some consequences of applying lognormal theory to pseudolognormal distributions

A logarithmic transformation may be used to improve the efficiency of estimates of the mean when observations follow the lognormal distribution. But if this transformation is applied to observations that follow another distribution, bias may be introduced. We consider some consequences of erroneously applying lognormal estimation theory and demonstrate that biased estimates may be obtained for certain classes of distributions. Illustrations of bias obtained in gold sampling are given.