Nam Bay Fm
Type Locality and Naming
Established for the continental beds exposed in the south of Muong Te (Lai Chau Province) and north of Muong Nhe (Dien Bien Province). The type section is located along the car road from Na Pheo to Si Pa Phin, lying parallel with the Nam Bay Stream (Tran Dang Tuyet et al. 1994) (N = 21°48’; E = 102°56’). See Additional Information.
Synonym: Hệ tầng Nậm Bay: Trần Đăng Tuyết et al. 1994; Trịnh Dánh (in Vũ Khúc et al. 2000).
Hệ Creta (part.): Dovjikov A.E. et al. 1965. Hệ tầng Mụ Giạ (part.): Vũ Khúc, Bùi Phú Mỹ et al. 1990.
Lithology and Thickness
The characteristic section has a thickness of 221 m: (1). Lowrer 26 m begins with a basal conglomerate with angular pebbles of black-grey sandstone containing much plant humus. Grading upward into friable weathered gritstone with granules of quartz, chalcedony and chert. (2). Red-brown thick-bedded claystone and siltstone; 195 m thick. The total thickness of the formation in this section is 221 m.
Relationships and Distribution
Lower contact
Unconformably rests upon the Cretaceous Nam Ma Fm.
Upper contact
Quaternary
Regional extent
It occurs in small exposures south of Muong Te District
GeoJSON
Fossils
Oligocene spores and pollen of Pinuspollenites sp., Podocarpidites sp., Tsugapollenites sp., Piceapollenites sp., Gleichenicidites sp., Cyathecidites sp, Osmundacidites sp., Lygodiumsporites sp., Pterisisporites sp., ctc.
Age
Depositional setting
Continental deposits
Additional Information
Synonym: Hệ tầng Nậm Bay: Trần Đăng Tuyết et al. 1994; Trịnh Dánh (in Vũ Khúc et al. 2000).
Hệ Creta (part.): Dovjikov A.E. et al. 1965. Hệ tầng Mụ Giạ (part.): Vũ Khúc, Bùi Phú Mỹ et al. 1990.
Lithology and Thickness:
The characteristic section has a thickness of 221 m: (1). Lowrer 26 m begins with a basal conglomerate with angular pebbles of black-grey sandstone containing much plant humus. Grading upward into friable weathered gritstone with granules of quartz, chalcedony and chert. (2). Red-brown thick-bedded claystone and siltstone; 195 m thick. The total thickness of the formation in this section is 221 m.
Lithology-pattern: Sandy claystone
Relationships and Distribution:
Lower contact:
Unconformably rests upon the Cretaceous Nam Ma Fm.
Upper contact:
Quaternary
Regional extent:
It occurs in small exposures south of Muong Te District
GeoJSON:
Fossils:
Oligocene spores and pollen of Pinuspollenites sp., Podocarpidites sp., Tsugapollenites sp., Piceapollenites sp., Gleichenicidites sp., Cyathecidites sp, Osmundacidites sp., Lygodiumsporites sp., Pterisisporites sp., ctc.
Age:
Oligocene.
Age span:
Beginning stage: Rupelian
Fraction up in beginning stage: 0.0
Beginning date (Ma):
Ending stage: Chattian
Fraction up in ending stage: 1.0
Ending date (Ma):
Depositional setting:
Continental deposits
Depositional-pattern:
Additional information
The Nam Bay Fm has not been approved by the geological mapping (status of 2011). While waiting for results of further studies the description of Tran Dang Tuyet has been kept in the present work.