Microstructures of co-axially folded vein segments and crenulation cleavage： Evidence for dissolution phenomena in the Chamba Thrust Sheet, western Himalayas

The metasediments in the Chamba region experienced three phases of deformation: DF1, DF2 and DF3.Folded quartz veins are co-folded with the F2 crenulation folds. Their geometric and tectonic significance is studied by microstructures and shortening adjacent to the discrete crenulation cleavage, S2. Microstructures of folded vein segments, their geometric changes and truncation to cleavage (S2) are mainly due to pressure-solution phenomena and the estimated volume loss from reconstructed vein segments range from 16 to 25.5%,which is closely related to volume decrease (26%) calculated from the polydeformed slates of North Wales areas.     

谈谈现代地质学的思维结构

谈谈现代地质学的思维结构吴俊华，袁训红（江西地质科学研究所南昌向塘３３０２０１）ＯｎｔｈｅＴｈｉｎｋｉｎｇＳｔｒｕｃｔｕｒｅｏｆＭｏｄｅｒｎＧｅｏｌｏｇｙＷｕＪｕｎｈｕａ；ＹｕｅｎＸｕｎｔｏｎｇ（ＪｉａｎｇｘｉＩｎｓｔｉｔｕｔｅｏｆＧｅｏｌｏｇｙ）１...     

The Geologic Time Scale and the Italian stratigraphic record

The construction of the Geologic Time Scale (GTS) is a titanic scientific challenge that has been under way for two centuries and will require much dedicated effort in the future. Italy preserves a paramount stratigraphic record of Mesozoic and Cenozoic marine sediments that have been significant in the development of the modern GTS. The Italian stratigraphic record has been histori-cally important in introducing and defining the standard Chronostratigraphic Units (CUs) of the Neogene and Quaternary. Pelagic successions from Northern Apen-nines and Southern Alps have been used in the seventies for integrating the late Cretaceous-Paleogene Geomag-netic Polarity Time Scale (GPTS) with planktonic microfossil biostratieraohv and standard CUs. This was a major contribution to the construction of a new gener-ation of GTS based on integrated magnetobiochronol-ogy. The middle Miocene to early Pleistocene marinerecord from Sicily and southern Italy has been funda-mental for establishing the recently developed Astro-nomical Time Scale (ATS). In prospect, there are many potentials still to be exploited in the Italian marine stratigraphic record for implementing the GTS by defin-ing GSSPs of various CUs, improving magneto-biochronology and extending downwards the ATS.     

The Lagoon of Venice： geological setting,evolution and land subsidence

The paper deals with the geological setting, history and subsidence of the Venetian Plain. Major attention is paid to the Pleistocene-Holocene stratigraphic sequence in the Lagoon of Venice, in relation to its origin that datesback to 6-7 kyr BP. Geological land subsidence, which played an important role in the origin and the evolution of the lagoon, and anthropogenic subsidence, that has recently assumed a major importance for the Venetian environment, are discussed. Considering also the sealevel rise, 23 cm loss in land elevation has occurred in the last century, leading to increased flooding events and environmental problems that require protective works.