华东喀斯特地貌发育过程与古地理背景

PROCESS AND PALEOGEOGRAPHIC ENVIRONMENT OF KARST GEOMORPHOLOGIC DEVELOPMENT IN EAST CHINA

本文探讨古地理环境与喀斯特发育的关系。认为本区喀斯特地貌发育过程的特点是:从行星风型到季风型喀斯特,具有不同强度的多期性,造成南北方喀斯特形态归并与兼容,以及南北过渡性与区域分异。

The karst geomorphology is generated and developed in the system of natural environment, karst process and relevant karst landforms in the area. It is sculptured by the translation of karstificational energy and material in the long history of various paleoenvironment in the system.The characteristics of karst geomorphic process in the region have been studied by the authors. For example, the processes pass from the planetary winds karst to monsoon karst, and multiple stages of various karstific intensity statued out different types of karst landforms, and they synthesize and coexist in the area.The results of sedimentary analysis suggest that the paleoclimate was frequently fluctuated.For instance, the red clastic sediment with evaporite rocks interlayer reflect a dry and not environment with wetter and hot environment some time at the Eogene; the reticulated leterite is with the lower SiO2 /R2O3 ratio of 1.8-2.1, and kaolinite and wood plants dominant in the clay mineral and spore-pollen assemblage suggest a more humid and hotter environ ment in the period of middle Pleistocene; while the xiasu loess with2.7-4.0 of SiO2/Al2O3 ratio and illites as the dominant clay mineral, means a dry and cool climate at the later period of the late Pleistocene. Therefore, the development has experienced six strong stages and several weak stages. The former includes, 1, From middle Eocene to early Oligocene a stronger karstification period; 2 , From middle Miocene to middle Pliocene a strong karstif ication period; 3 , The middle of early Pleistocane stronger karstification period; 4 , The middle and later middle Pleistocene, a strong karstification period- 5 , The middle of late Pleistocene, a stronger karst ification period; 6 , The middle Holocene, stronger and shorter karstification period.The natural zones have been shifted northward or southward several times in Cenozoic, so that the karst landforms in East China is characterized by the transitional features from the Fenglin in the south China to the karstified hills and dry valleys in the north. Therefore, karst geomorphology .in the studied are might be divided rnto three regions and several subregions.