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Fluid pathways within shallow-generated damage zones of strike-slip faults – evidence of map-scale faulting in a continental environment, SW Permo-Mesozoic cover of the Late Palaeozoic Holy Cross Mountains Fold Belt, Poland

Rybak-Ostrowska Barbara, Konon Andrzej, Hurai Vratislav, Bojanowski Maciej, Konon Agnieszka, Wyglądała Michał

Acta Geologica Polonica

2020

Vol. 70, no. 1

1--29

The damage zones of exhumed strike-slip faults dissecting Jurassic carbonates in the south-western part of the Late Palaeozoic Holy Cross Mountains Fold Belt reveal second-order faults and fractures infilled with syntectonic calcite. The subsequent development of a structural pattern of microscopic fault-related structures and calcite infillings reflects the activity of strike-slip faults that began in the Late Cretaceous (Late Maastrichtian) and lasted until the early Miocene (Langhian). The fabric of the syntectonic veins provides insights into the evolution of the permeable fault-related structures that were the main pathways for fluid flow during fault activity. Microstructural study of calcite veins coupled with stable isotope and fluid inclusion data indicates that calcite precipitated primarily in a rock-buffered system related to strike-slip fault movement, and secondarily in a partly open system related to the local activity of the releasing Chmielnik stepover or the uplift of the area. The presence of meteoric fluids descending from the surface into damage zones suggest that the strike-slip faulting might have taken place in a nonmarine, continental environment.

New data on the continental deposits from the Cao Bang Basin (Cao Bang-Tien Yen Fault Zone, NE Vietnam) - biostratigraphy, provenance and faciespattern

Wysocka A., Pha D. P., Durska E., Czarniecka U., Thang D. V., Filipek A., Cuong N. Q., Tuan D. M., Huyen N. X., Tha H.V.

Acta Geologica Polonica

2018

Vol. 68, no. 4

689--709

The Cao Bang Basin is the northernmost of the basins related to the Cao Bang-Tien Yen Fault Zone in northern Vietnam. The basin is filled with a thick series of continental deposits. However, the exact age of the sedimentary basin infill has been under discussion for a long time. Because of new published data, the authors have decided to revisit this basin. Palynological data has allowed us to assign the Cao Bang Basin infill to the Lower Oligocene PC1 complex of the Shangcun Fm. (southern China). Among the saccate grains of gymnosperms, the domination of Cathaya and Pinus was observed, whereas angiosperms are represented by Carya, Celtis, Hammamelidaceae, Ulmus and also Pterocarya, Quercus, the Castanea–Castanopsis–Lithocarpus group, and the Loranthaceae. Among pteridophytes occur Laevigatosporites, Osmundaceae, and Pteris. The sedimentological features of the Cao Bang Basin are distinct from those of other basins from the Cao Bang-Tien Yen Fault Zone. The basin is filled with a wide variety of clastic deposits, from some of coarse-grained, alluvial-fan origin, through sandy beds of fluvial origin up to fine, organic-rich lacustrine deposits. The coarse-grained lithofacies are built of clasts derived mainly from local sources. The sandstones from the basin equally are submature or immature. They contain a lot of lithoclasts, the composition of which depends on the sample location within the basin. The potential source area is composed of older sedimentary units and of granitic rocks. The geochemical samples studied reflect the geochemical composition of silicic source rocks with only a minor contribution of basic components. The succession that fills the basin is interpreted as a typical fill for relatively long-lasting evolving half-graben or strike-slip basins. Moreover, the basin is partly occupied by a subsequent present-day sedimentary basin of Quaternary age.