GEOLOGY OF MT. PHULCHOKI AREA, CENTRAL NEPAL

The Nawakot and Kathmandu complexes are distributed around Kathmandu area, central Nepal and that build up the Mahabharat synclinorium. The Nawakot complex is composed of mainly weakly metamorphosed sedimentary rocks. The Kathmandu complex, which occupies the large core of the synclinorium, overlies the Nawakot Complex.. These two complexes have the thrust contact called as the Mahabharat Thrust. The Kathmandu complex is subdivided into the lower Bimphedi and the upper Phulchoki Groups. The Bimphedi Group is composed of metamorphosed sedimentary rocks and the Phulchoki Group is of weakly and non|metamorphosed sedimentary rocks. Besides its important significance, only few studies have been done in these complexes. In this paper, the present author reports preliminarily the stratigraphy of the Phulchoki Group and uppermost part of the Bimphedi Group distributed in the south of Kathmandu. In the study area, weakly to non|metamorphosed sedimentary rocks is subdivided stratigraphically into Units I to VII in ascending order. These units are characterized by the prominent composition of rock types. Most contacts observed at each adjacent units are conformable and some are transitional. Most of units show the regional variation in accompanying rock type. Unit I: coarsely crystallized marble; Unit II: black to green phyllite; Unit III: light gray quartzose fine sandstone and gray siltstone; Unit IV: well|bedded sandy argillaceous limestone; Unit V: purple siltstone; Unit VI: coarsely crystallized limestone; Unit VII: siltstone and sandstone. Correlation to the formations named by Stocklin's (1980) subdivision are as follows: Unit I might be correlated to the Markhu Formation, Units II and III to the Tistung Formation, Unit IV to the Chandragiri Formation, Unit V to the Chitlang Formation, and Units VI and VII to the Godawari Formation.From the study area, some fossils are yielded. Crinoids occur from Units IV, V, VI and VII, brachiopods from Units V, VI and VII, orthocerases from Unit VI, and trilobites from Unit V.