Kon Tum Fm

Tay Nguyen Highland area. The type section is established within the borehole drilled at Dak Cam Stream in the vicinity of Kon Tum Town (N = 14°20’; E= 108°01’). This formation bears the name of Kon Tum Town.

Synonym: Diệp Kon Turn: Trịnh Dánh (in Vù Khúc và nnk.) 1984; Trịnh Dánh 1985, 1993 (Pliocen). Hệ tầng Kon Tum: Trịnh Dánh (in Phan Cự Tiến et al. 1989; in Vũ Khúc, Bùi Phú Mỹ et al.) 1990, in Vũ Khúc et al. 2000); Trần Tinh et al. 1998 (Pliocen).

Characterized by thick beds of diatomite (siliceous chalk) and basalts: (1). Polymictic gritstone grading upward into quartz sandstone, then silty sandstone and diatomite claysíone with many intcrbeds of black-grey, compact to porous basalt and tuff, 60-80 m thick; containing plant remains, such as Arbutus elegans, Púnica planchoni and the gastropod Viviparus aff. quadratus. (2). Quartz sandstone grading upward into siltstone interbeddcd with compact and porous basalt; 30-50 m thick. Siltstone contains plant remains preserved in phytoleim form. (3). Gravel-bearing gritstone, loose silty claystone and diatomite intcrbedded with weathered basalt beds; 20-35 m thick. The total thickness of the formation in this section is 110-160 m.

1) Melosira Assemblage with Melosira praedistans, M. praeislandica, M. praegranulata, M. talica, Stephanodiscus astrea astrea, S. astrea minutulus, Cyclotella antiqua, Synedra sp. and Nitzschia sp.; 2) Stephanodiscus-Melosira Assemblage with abundant Stephanodiscus with Stephanodiscus astrea astrea, S. astrea minutulus, Melosira praedistans, M. praeislandica, M. praegranulata, Synedra sp., Nitzschia sp., and; 3) Melosira-Nitzschia Assemblage with a predominance of Melosira and Nitzschia.