黄山逍遥溪地区第四纪沉积环境研究

QUATERNARY SEDIMENTARY FEATURES FROM XIAOYAOXI PROFILE, HUANGSHAN MOUNTAIN

根据对黄山逍遥溪剖面１７个样品的分析，得出下述见解：１．粒度参数和ＣＭ图象反映，该处沉积物大都未经改造就进入新环境，反映了近源沉积和多变的环境．２．Ｆｅ３＋／Ｆｅ２＋含量测定表明，该处第四纪期间最低年均气温并未低于０℃，因此不具备冰川发育的条件．３．该剖面ＣａＯ的淋溶强于黄土发育区，氧化物比值反映出多数情况下较高年均气温与多雨期一致，反之亦然．４．孢粉样品揭示中更新世至少经历过从温暖→干凉→湿热的沉积环境．５．伊利石（ｄ００１）衍射峰显示：开形指数Ｎｓ值自下而上逐渐被动增大，长宽比Ｈｗ指数正相反，表明风化度有逐渐增大的趋势．６．重矿和扫描电镜分析均发现磁铁矿和绿帘石表面的强烈溶蚀现象，证实了中更新世经历过湿热风化沉积环境．７．古地磁测试发现该剖面主要属布容正极性世，地层年代应属Ｑ２－Ｑ４。８．磁化率、粒度等综合分析表明：该处在中更新世既经历过湿热和干热过程，也有过暖千与暖湿及干凉环境；晚更新世以冰缘坡面重力堆积环境为主控新世以湿热坡积环境为主．

Since the 1930's, the problem of the Huangshan Quaternary sedimental environment has been argued. J. S. Lee (1936) had even suggested that the Huangshan had a paleo-glacier history and paleo-glacial landform as well as paleo-glacial deposits during Quaternary. However, according to the analyses of 17 samples from Xiaoyaoxi, profile,Huangshan Mountain, the authors obtained the following new results and discoveries:1. Size parameter and C-M map show, most of the sediments have not been reformed more a new place for sedimentation. This phenomenon indicates that there was a proximal and diverse depositional environment here. 2. By using volumetric analysis method to test thee Fe3+ and Fe2+ contents of the samples, the Fe3+/ Fe2+(formula: tpaleo-temperature; T-local present mean annual air-temperature; M-difference of Fe3+/ Fe2+ between single sample and mean value; X-mean value of all samples for Fe3+ / Fe2+) the data did not show the lowest annual air-temperature during Quaternary to reach below 0℃, in fact, the lowest value was 11.42℃, and the highest was 20.29℃. Gladers, therefore, could not have developed here. 3. By using ICP-AES method, the leachingof CaO for the profile is stronger than the loess-land. The oxide ratio here shows that in most cases the higher annual mean air-temperature is synchronous with the pluvial period,contrary to the lower annual air-temperature. 4. Pollen assemblage reveals at least that the place had undergone the sedmentary environment, i.e from warm→cool dry→humid hot during the Mid-pleistocene. 5. Illite (d001) X ray diffraction indicates that open index Ns is gradually increscent (1.4-1 .6) from lower to upper on the profile; conversely for the ratio index (Hw: 2.3-1.95) of long and width, this illustrates that the weathering intensity has a gradual increscent trend. 6. Both panning and scanning electron microscope reveal that the surface of magnetite and epidote in the samples have stronger solution phenomena, which confirms that the place had undergone the humid-hot weathering enviroment during the Mid-Pleistocene. 7. Paleomagnetic dating finds that the profile belongs to Brunhes normal epoch, its stratigraphical time table should be Q2-Q4. 8. In the strata of the Q2, Q3 and the Q4, most low susceptibility values are correspondence with the fine grain size of the samples, on the contrary for their high susceptibility values. Comprehensive an,alyses of susceptibility and granularity, etc. show that the place had undergone the environments of humid-hot, dry-hot, and warm-dry, warm-humid as well as dry-cool during the Mid-Pleistocene; periglacial slope-gravity deposition for the Late-Pleistocene, and humid-hot slope deposition (sliderock) for the Holocene epoch.