Lithofacies and depositional environments of the Paleogene / Neogene sediments in the Hoanh Bo Basin (Quang Ninh province, NE Vietnam)

Hoang Tha,Anna Wysocka,Phan Pha,Nguyen Cuong,Piotr Ziółkowski

doi:10.7494/geol.2015.41.4.353

Hoang Tha, Anna Wysocka + Show 3 more

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https://doi.org/10.7494/geol.2015.41.4.353

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Abstract

The Hoanh Bo Basin is a multiple period formed basin which is associated with the tectonic mechanism due to the activities of the Chi Linh - Dong Trieu and Trung Luong faults. The basin is filled with continental sediments, comprising mainly polymictic conglomerates, sandstones, siltstones, claystones and shales. Coarser-grained polymictic deposits predominate along the northern and western margins of the basin, while different types of siltstones, claystones, even sandstones occur in its center, as well as along its southern and eastern parts toward the Ha Long Bay. Based on the dominant grain-size class, texture, stratification, degree of clast rounding and sorting, 17 lithofacies were determined in the Hoanh Bo Basin infill, accumulating in alluvial fan, fluvial, deltaic and lacustrine environments. Alluvial fan and fluvial environments are characterized by an assemblage of lithofacies such as sand- and mud-supported disorganized breccias (Gb), clast- to sand-supported conglomerates (Gmm), clast-supported inverse-graded conglomerates (Gig), planar-cross-bedded conglomerates (Gp), trough cross-bedded conglomerates (Gt), horizontally stratified conglomerates (Gh), planar cross-bedded sandstones (Sp), trough cross-bedded sandstones (St), ripple cross-laminated sandstones (Sr), horizontally bedded sandstones (Sh), massive sandstones (Sm), massive mudstones, siltstones (Fm), laminated siltstones and mudstones (Fl), massive claystones (Fsm) and coaly lithofacies (C); the deltaic assemblage is dominated by planar-cross-bedded conglomerates (Gp), horizontally stratified conglomerates (Gh), planar cross-bedded sandstones (Sp), horizontally bedded sandstones (Sh), low-angle cross-bedded sandstones (Sl); while the lacustrine assemblage consists of ripple cross-laminated sandstones (Sr), horizontally bedded sandstones (Sh), normally graded sandstones (Sng), massive mudstones, siltstones (Fm), laminated siltstones and mudstones (Fl), massive claystones (Fsm) and coaly lithofacies (C).

Highlights

IntroductionThis area spreads over the territory of the Hoanh Bo district and Ha Long city, the Quang Ninh province
Main goal of our study is to describe in details the sedimentological features and to interpret the sedimentary environments of the Hoanh Bo Basin during the Paleogene/ Neogene periods
The study of the sedimentary sequence of Paleogene/Neogene age from the Hoanh Bo Basin (Quang Ninh province, NE Vietnam) revealed the following results: 1. The Hoanh Bo Basin is filled with continental sediments, mainly composed of polymictic conglomerates, sandstones, siltstones, claystones and shales

Summary

Introduction

This area spreads over the territory of the Hoanh Bo district and Ha Long city, the Quang Ninh province. In the aspect of tectonics, the Hoanh Bo Basin is situated in the eastern part of the Red River Fault Zone, where the Day Nui Con Voi Massif is present, and it has key significance for understanding of the Paleogene-Neogene geodynamic evolution of the southeast Asia (Cuong & Zuchiewicz 2001, Cuong 2007). Tertiary basins were formed with the geometry of small, elongated, narrow grabens and half-grabens. They occur along main fault zones of northern Vietnam. Lithofacies and depositional environments of the Paleogene/Neogene sediments in the Hoanh Bo Basin tectonically-controlled basins (Wysocka & Świerczewska 2005, 2010)

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