A Pleistocene (MIS 5e) mollusk assemblage from Ezeiza (Buenos Aires Province,Argentina)

A fossil assemblage collected around 3.5 m amsl from Ezeiza, Buenos Aires province, have AMS ¹⁴C ages of ca. 33,000 to ca. 40,000 yr BP, whereas in the literature is a report of a conventional ¹⁴C age of >43,000 yr BP. An OSL age from the overlying deposit corresponds to ca. 22,000 yr. The samples contain marine fossils: mollusks, balanids and corals (Astrangia). La Coronilla (Uruguay, attributed to MIS 5e) is the locality most related to Ezeiza faunistically, despite is not the nearest one. In consequence, the relationship should be addressed to a more similar age and environment than others. The fauna indicates a higher water temperature than today. In Ezeiza exclusively cold water taxa are absent, and we found seven warm taxa with their southern distribution limit displaced northwards today, plus other six at their southern distribution limit. Around 60% of all the species and more than 70% of the individuals are of warm-temperate waters. In sum, although prima facie the numerical ages would locate the deposit in MIS3, faunistic, temperature, and height evidences show that the Ezeiza mollusk assemblage belong to MIS5e. A stronger than presently Brazil warm current, reaching Southern latitudes, may explain the changes in geographical ranges.     

The border as an engine for mobility and spatial integration: A study of commuting in a Swedish–Norwegian context

The purpose of the study was to analyse how cross-border commuting differed from intranational commuting in Sweden, and how cross-border mobilities affected spatial integration. The authors analysed patterns and spatial flows of cross-border commuting by comparing them with characteristics of intranational commuting. In the article, they explore the assumption that the border constitutes an ‘engine’ for work-related mobility, which affects processes of spatial integration in cross-border areas. The empirical material comprised data from surveys of commuting from the Swedish county of Värmland to Norway and commuting within Värmland. The findings showed that cross-border commuting shared common features with intranational commuting, including how the frequency of commuting was dependent on distance. The motives for commuting differed, and the reasons for working in Norway were economic rather than professional. In terms of spatial integration, cross-border commuting was mainly one-directional, from Sweden to Norway, while leisure mobility and migration tended to be in the opposite direction. The authors conclude that the border region is characterised by integration through specialisation, which involves a permanent state of ‘transient’ mobility. Thus, a win-win situation can be distinguished, in which the border serves as a resource and an ‘engine’ for cross-border integration, mobility and economic activities.     

Perihelion motion of small irregular dust particles due to radiation forces

Perihelion motion, i.e. a secular change of longitude of perihelion, of interplanetary dust particles is investigated under the action of solar gravity and solar electromagnetic radiation. As for spherical particle [Kla?ka, J., 2004. Electromagnetic radiation and motion of a particle. Cel. Mech. Dynam. Astron. 89, 1-61]: (i) perihelion motion is of the order ( is heliocentric velocity of the meteoroid and c is the speed of light in vacuum), if a component of electromagnetic radiation acceleration is considered as a part of central acceleration; (ii) perihelion motion is of the first order in if the total electromagnetic radiation force is considered as a disturbing force. The new facts presented in this paper concern irregular dust particles. Detailed numerical calculations were performed for the grains ejected at aphelion of comet Encke. Perihelion motion for irregular interplanetary dust particles exists already in the first order in for both cases of central accelerations. Moreover, perihelion motion of irregular particles exhibits both positive and negative directions during the particle orbital motion. Irregularity of the grains causes not only perihelion motion, but also dispersion of the dust in various directions, also normal to the orbital plane of the parent body.     

Architecture and evolution of the Kushiro submarine canyon in the Kurile Trench forearc slope,North‐western Pacific

An air‐gun survey, conducted over a total distance of 4356 km in the western end of the Kurile Arc offshore, has revealed the architecture and evolution of the Kushiro submarine canyon and Tokachi submarine channels of the Tokachi‐oki forearc basin. The Kushiro submarine canyon, which runs along the eastern margin of the forearc basin, is characterized by an entrenchment of up to several hundred metres in depth. The Tokachi submarine channels, by contrast, occupy the centre of the basin and consist of small, branching and levéed channels. The Kushiro submarine canyon is not connected to the Tokachi River, which has the largest drainage area in eastern Hokkaido, with a catchment area of approximately 9010 km² that includes high mountains and a volcanic region. Instead, the Kushiro submarine canyon exhibits an offset connection/quasi‐connection (probably having been connected during a prior sea‐level lowstand) with the Kushiro River (drainage area of 2500 km²) which contains the Kushiro Swamp at its mouth. To understand this unusual arrangement of rivers and submarine channels, acoustic facies analysis was undertaken to establish the seismic stratigraphy of the area. Subsurface strata can be divided into six seismic units of Miocene to Recent age. Analyses of seismic facies and isopach maps indicate that: (i) the palaeo‐Kushiro submarine canyon, which was ancestral to the Kushiro submarine canyon, was an aggradational levéed channel; and (ii) the palaeo‐Tokachi submarine channel was much larger than the present‐day channel and changed its course several times. Both the palaeo‐Kushiro submarine canyon and palaeo‐Tokachi submarine channel were fed predominantly by the ancestral Tokachi River, whereas the present‐day channels are no longer connected or quasi‐connected to the Tokachi River. Entrenchment of the Kushiro submarine canyon began in its distal reaches during the Early Pleistocene and propagated landward over time, which was possibly caused by base‐level fall (i.e. subsidence of the trench floor) or uplift of the forearc basin. Entrenchment of the upper part of the Kushiro submarine canyon began during the Middle Pleistocene, which may have been related to: (i) depositional progradation; (ii) uplift of the coastal area; or (iii) a change in source area from the ancestral Tokachi River to the Kushiro River.     

The last interglacial sea-level high stand on the southern Cape coastline of South Africa

The continental margin of southern South Africa exhibits an array of emergent marginal marine sediments permitting the reconstruction of long-term eustatic sea-level changes. We report a suite of optical luminescence ages and supplementary amino acid racemization data, which provide paleosea-level index points for three sites on this coastline. Deposits in the Swartvlei and Groot Brak estuaries display tidal inlet facies overlain by shoreface or eolian facies. Contemporary facies relations suggest a probable high stand 6.0-8.5 m above modern sea level (amsl). At Cape Agulhas, evidence of a past sea-level high stand comprises a gravel beach (ca. 3.8 m amsl) and an overlying sandy shoreface facies (up to 7.5 m amsl). OSL ages between 138 ± 7 ka and 118 ± 7 ka confirm a last interglacial age for all marginal marine facies. The high stand was followed by a sea-level regression that was associated with the accumulation of eolian dunes dating to between 122 ± 7 ka and 113 ± 6 ka. These data provide the first rigorous numerical age constraints for last interglacial sea-level fluctuations in this region, revealing the timing and elevation of the last interglacial high stand to broadly mirror a number of other far-field locations.     

宇宙探索与钻探技术

钻探技术已成为人类探索宇宙的首批技术之一。以月球钻探为例,论述了外星球钻探的特点和难点;介绍了美国、前苏联钻探专家与航天专家合作研制的轻便、高可靠性、全自动月表取样钻机及其钻进工艺的现状;分析了各种钻进方案的优缺点;结合我国将要实施的“嫦娥3期”工程,就月球自动采样并返回技术提出了设想。     

受控石油定向井技术初步实践

通过石油定向井技术初步实践，为今后的定向井施工奠定了基础，并取得了显著的经济效益。     

复合片取心钻头的研制及其应用

由金刚石共晶体与硬质合金基座制成的复合体是一种新型超硬研磨材料，用它和特制的钻头胎体制成的复合片取心钻头适用于可钻性小于Ⅶ级岩石的钻进，它的应用可大大提高煤系地层（特别是煤心）的采取率。