Geological and hydrogeological environment in Shanghai with geohazards to construction and maintenance of infrastructures

Shanghai Administrative Region (SAR) is located on the deltaic deposit of the Yangtze River. The bed rock under SAR is generally buried in the depth of 200 m to 300 m except for several massifs, where the bed rock is exposed to the ground surface. The Quaternary deposit in Shanghai is soft sediment. The variation of palaeoclimate influenced the sea level and resulted in a very complicated sedimentary environment. The Quaternary deposit in SAR is composed of an alternated multi-aquifer-aquitard system (MAAS). The groundwater system is composed of one artesian aquifer and five confined aquifer layers with very high groundwater pressure head. The MAAS was formed mainly within the warm geological era updated to 2.6 million years ago. Between two aquifers, there is an aquitard which is composed of soft clayey soil formed mainly within the cold era. The aquitards are composed of very soft clayey silt with very high compressibility and humus content. The humus material was transformed into methane gas under a long-term geological process. With the development of economy, the infrastructures were (or are being) constructed in the top shallow soft clayey deposit, aquifer I and aquifer II. In SAR, the following geohazards occurred or possibly occur during the construction and maintenance of infrastructures: i) quicksand and piping hazards; ii) pumping-induced hazards and recharge-cutoff hazards; iii) long-term settlement due to the seasonal fluctuation of groundwater level; and iv) geohazards of methane gas.     

Late Silurian–Middle Devonian long-term shoreline shifts on the northern Gondwanan margin: eustatic versus tectonic controls

Long-term shoreline shifts reflect eustatic changes, tectonic activity, and sediment supply. Available lithostratigraphical data from northern Africa, Arabia, and the Tethys Hymalaya, coupled with facies interpretations, permit us to trace late Silurian–Middle Devonian long-term shoreline shifts across the northern Gondwanan margin and to compare them with constraints on global sea-level changes. Our analysis establishes a regression–transgression cycle. Its coincident global sea-level changes reveal the dominance of the eustatic control. A transgression–regression cycle observed in Arabia is best explained by regional subsidence. Our study highlights the importance of constraining the role of regional tectonics when interpreting shoreline shifts.     

Moderation of Cretaceous transgressions by block tectonics: An example from the north and north-west of the Paris basin

Cretaceous transgressions in the epicontinental area of western Europe, and in particular in the Paris-London Basin, were controlled, to a large extent, by the eustatic rise of sea-level in direct relation to the creation of mid-oceanic ridges.On a regional and local scale, positive and negative vertical movements of the Earth's crust have moderated the effects of transgression. These variations are revealed by changes in the nature, or thickness, of sediment deposited on the tectonic blocks which form the basin. The method used for the delimitation of blocks is supported by the presentation of paleogeographical maps from various Mesozoic epochs, as well as a NE-SW section from the Boulonnais area to Normandy which displays tectonic control on sedimentation.     

气象文苑

气象文苑慈母情□任金良母亲已逾古稀。每当我看到她那张饱经风霜、沟壑纵横的脸，心里就格外难过。母亲辛劳一生，晚年还闲不住，不干活就浑身难受。７月２８日，母亲端一大盆水洗衣服，不小心脚下一滑，重重地摔了一跤。她是被人抬进屋的。她躺在床上，不能动弹。医生说...     

Big lake records preserved in a little lake’s sediment: an example from Silver Lake,Michigan, USA

We reconstruct postglacial lake-level history within the Lake Michigan basin using soil stratigraphy, ground-penetrating radar (GPR), sedimentology and ¹⁴C data from the Silver Lake basin, which lies adjacent to Lake Michigan. Stratigraphy in nine vibracores recovered from the floor of Silver Lake appears to reflect fluctuation of water levels in the Lake Michigan basin. Aeolian activity within the study area from 3,000 years (cal yr. B.P.) to the present was inferred from analysis of buried soils, an aerial photograph sequence, and GPR. Sediments in and around Silver Lake appear to contain a paleoenvironmental record that spans the entire post-glacial history of the Lake Michigan basin. We suggest that (1) a pre-Nipissing rather than a Nipissing barrier separated Silver Lake basin from the Lake Michigan basin, (2) that the Nipissing transgression elevated the water table in the Silver Lake basin about 6,500 cal yr. B.P., resulting in reestablishment of a lake within the basin, and (3) that recent dune migration into Silver Lake is associated with levels of Lake Michigan. This is the fourth in a series of ten papers published in this special issue of Journal of Paleolimnology. These papers were presented at the 47th Annual Meeting of the International Association for Great Lakes Research (2004), held at the University of Waterloo, Waterloo, Ontario, Canada. P.F. Karrow and C.F.M. Lewis were guest editors of this special issue.     

Internal architecture and mobility of tidal sand ridges in the East China Sea

On the basis of bathymetric and seismic data and data from piston cores collected by the Chinese–French marine geology and geophysics investigation of 1996, we discuss the internal architecture and mobility of tidal sand ridges in the East China Sea (ECS). We characterized the sand ridges on the middle to outer shelf of the ECS as tide-dominated sand ridges with southwest dipping beds, indicating that the regional net sediment transport is toward the southwest. As the sand ridges gradually migrate toward the southwest, new sand ridges are continually replacing old ones, and several generations of sand ridges have developed in the study area.     

云南省会泽地区早三叠世飞仙关组沉积环境及演化特征

会泽地区早三叠世飞仙关组地层中动植物化石比较丰富,并赋存铜多金属矿产.经实测剖面对比,飞仙关组的岩性特征总体变化不大,横向上从西到东,岩石粒度变小,成熟度增高,并出现海相沉积,因此会泽地区在早三叠世时为一相对稳定的陆棚环境,随后发生一系列沉降作用,沉积环境为海陆过渡环境.     

Aspects of the marine Cretaceous of China

The marine Cretaceous of China is distributed mainly in southwestern Xinjiang, the West Kunlun Mountains, the Karakorum Mountains and most parts of Xizang (Tibet), with findings even from Taiwan.The marine Cretaceous of China may be divided into three sedimentary belts according to the lithologic and tectonic characters, biological provinces and the different modes of deposition.On the basis of recent research on the Cretaceous marine strata and faunas in China, the lithostratigraphic and biostratigraphic sequences have been preliminarily established and the division and correlation of strata and boundaries between the Jurassic and Cretaceous, Lower Cretaceous and Upper Cretaceous, as well as Cretaceous and Tertiary outlined; the position of the beach line of the Laurasian landmass in China and the events of the tectonic movement and the transgression and regression during the Cretaceous period are discussed.