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Category: Mineral Article
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Abstract

New occurrence of Late Silurian radiolarian cherts were reported from a large abandoned pit and a small quarry in the Sepon mining district, central Lao PDR, including the Huai Yang Pit and the 'chert quarry' sections. This occurrence  together with new localities of Late Devonian radiolarian chert and siliceous shale outcrops observed in the region which include the Vilabouly section, indicate the existence of deep marine environment in the Truong Son foldbelt east of the Indochina Terrane.

The cherts from the Huai Yang Pit section is maroon color and contains Futobari morishitai Furutani, 1990, Zadrappolus sp., Secuicollacta sp. and others. Futobari morishitai was first described from the Yoshiki Formation, Fukuji area by Furutani, 1990 in the Zadrappolus yoshikiensis Assemblage. The genus Futobari has its first appearance in the latest Silurian and its acme in the Early Devonian on the basis of radiolarian biostratigraphy in the Kurosegawa Belt (Umeda, 1997).