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Lithofacies and terrestrial sedimentary environments in AMS measurements: case study from Neogene of Oravica River section, Čimhová, Slovakia.

Łoziński M., Ziółkowski P., Wysocka A.

Geological Quarterly

2016

Vol. 60, No. 2

259--272

The anisotropy of magnetic susceptibility (AMS) of sedimentary rocks has been used for interpreting wide range of processes: early rock deformations, palaeotransport directions, as well as the evolution of mineral content. Various sedimentary factors which may determine magnetic susceptibility within lacustrine, river, floodplain and swamp deposits have been examined in the Oravica section of the Orava-Nowy Targ Basin. Multiple components of mineral content: illite, chlorite, smectite, kaolinite, quartz and unidentified high susceptibility phase make an AMS interpretation of this content ambiguous. However, this method may be useful for tracing early diagenetic geochemical/microbial processes where iron element is involved. Some sedimentary processes may be recognized from AMS when an assemblage of parameters is studied together: bulk susceptibility, the degree and the shape of anisotropy, principal directions, and the distribution of all these parameters within a set of specimens. Debris-flow processes, as well as lacustrine and floodplain sedimentation are especially well-defined in AMS results. Palaeotransport directions are ambiguous because studied rocks have undergone weak deformation what overprints this sedimentary feature. Most specimens represent an oblate shape of anisotropy and show a good correlation of minimum susceptibility axis and normal to bedding plane.

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

Hoang V. T., Wysocka A., Phan D. P., Nguyen Q. C., Ziółkowski P.

Geology, Geophysics and Environment

2015

Vol. 41, no. 4

353--369

The Hoanh Bo Basin is a multiple period formed basin which is associated with the tectonic mechanism due to the activity of the Chi Linh-Hon Gai and Trung Luong Faults during the late Paleogene – early Neogene time. 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. The source rocks for sedimentary materials are mainly originated from rocks of the Hon Gai and Ha Coi Formations. 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. The basin is filled by gravelly, sandy and fine-grained lithofacies just covers a modest area but it represents a full of succession of 4 depositional systems including 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 (Fsm), laminated siltstones and mudstones (Fl), massive claystones (Fm) 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 (Fsm), laminated siltstones and mudstones (Fl), massive claystones (Fm) and coaly lithofacies (C).