The Geology and Geomorphology of the Fenho Drainge Basin
This paper deals with the structural characteristics, Pleistocene sediments,recent active tectonics, and physiographic development of the Fenho basin. Thevalley of Fenho is situated in the middle of the Shansi plateau, which is a por-tion of the North China platform. Major rock divisions in this area consist ofpre-Sinian metamorphics, Sinian quartzose sandstones, shales, and siliceous lim-estones, middle Ordovician limestones, Carboniferous and Permian coal series,Permian purple shales and sandstones, and Cretaceous alkaline intrusives. TheSinian and post-Sinian sediments lie unconformably upon the pre-Sinian crys-talline rocks. Structurally, the Shansi plateau is marked by a number of open foldsand long-extending, longitudinal faults. The well-known Fenho graben, situatedin the middle of the plateau, is an outstanding feature. The Yenshanian folds areassociated with high-angle thrusts, transverse and oblique faults, and differentsets of joint systems. This area has been affected by the Himalayan movementsand is still the site of rather powerful crustal movement. The Pontien red clay (Pliocene), Pleistocene Nihowan sands and gravelswith interbedded sandstones, Choukoutien basal conglomerates, sandy beds andreddish loess, Malan loess, and Holocene alluvium are well developed and pre-served. The Pliocene and Pleistocene sediments have been affected by recentactive tectonics. Many different streams of geological investigation have contributed much to our knowledge about the origin of the North China loess. But as far as theFenho basin is concerned, the present writers, according to their field observa-tion together with laboratory work, are inclined to attribute the origin of theloess, as it is in the present state, to fluvial and pluvial processes. Eolianorigin is probably of minor importance. Along the course of Fenho there are river terraces pertaming to six diff-erent elevations, The two lower terraces are of fill types, while the four higherterraces are of composite erosion and fluvial types. Along the foot of theHoshan, there is an abandoned channel of the ancieut Fenho. On the basis of the depositonal environment of the Pleistocene sediments,neotectonics, and geomorphological features, the writers tackle the problem ofthe evolutlonal history of the Fenho basin, and propose their concept in rela-tion to deciphering the geomorphological development of this well--known river,which has been described in detail in the Chinese text.