Regional Environmental Gis-based Decision Support System And Its Urban And Suburban Areas In Beijing

Timing, tectonic setting and sedimentary evironment of the GuanjiagouGroup, located in the Motianling area of the southwestern Qinling, stillremains controversial although having many different interpretations byprevious work.Based on our field observation, combined with the previous results, theSedimentary characteristics, facies associations changes of the GuanjiagouGroup were studied in the paper. As well as, timing and tectonic setting ofthe Guanjiagou Group by means of petrology, geochemistry and isotopicgeochronology are also explored.1. Our rusults show that sediment association of the Guanjiagou Groupis characterized by increasing coarsening upwards sequence. The bottom ofthe Guanjiagou GrOup is deep basin facies, which consists mainly of modelturbidity current deposit, lts grain-sizes change coarse upwards and theconglomerate stratum becomes thick in the middle part. Tht upper part isthicker conglomerate with lamella massive sandstone. The content of gravelin conglomerate and granularity adds and augments respectively. By way ofstudy, the Guanjiagou Group is marine sediments which were transported byturbidite current. Therefore, it is deduced that the Guanjiagou Group ismarine fan.2. The statistic analyses of graywackes of the Guanjiagou Group wereindicated that the detritus mainly came from the source of island. Thegeochemistry of siltstone and muddy siltstone makes know that the data ofLa,Ce,∑REE,Eu of the Guanjiagou Group are similar to those of islandarc.3. By the tilted lay of stratum, the excellent trend of gravel and thechange of gravel in orientation, the current on the Guanjiagou Group isanalysed synthetically and it is deduced that the direction of paleocurrentis 230°—356°, most are eastwest; while the gravel excellent trend is 228°—338°, most north west north. From south to north, the size of gravelbecomes small gradually, gravel round increasing, and gravel excellent trendis disorderâ†'order by field statistic for gravel. With previous results, theGuanjiagou Group is in Bekou forearc basin and it is presumed that thesedimentary detritus was from eastsouthern island arc.4. Fossils indicated that the age of the Guanjiagou Group is Late Carboniferous period or Late Permian. The ⁴⁰Ar/³⁹Ar thermochronology ofthe granitic and volcanic gravels from the Guanjiagou Group suggests thatage of the Guanjiagou Group is Late Triassic. Therefore, its age is perhapslate Paleozoic or Mesozoic.