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Located on the northern Vietnam onshore/offshore transition, the Hoanh Bo Trough is an excellently exposed terrestrial Palaeogene sedimentary sequence that may be treated as an analogue for regional interpretations of the sedimentary and structural evolution of the northern Song Hong Basin. The Hoanh Bo Trough lies to the north of the northern Song Hong Basin and to the west of the Beibuwan Basin, the origin and evolution of which are linked with Palaeogene South China Sea rifting. Field and archival well sedimentological observations were made throughout the Palaeogene succession of the Hoanh Bo Trough, and samples were collected for palynological, petrographical, and geochemical analysis. Based on the coexistence of particular lithofacies, proximal alluvial fan, distal alluvial fan, fluvial alluvial plain with channels, alluvial plain and/or lake margin, and lacustrine facies associations were distinguished. Palynological analyses suggest the sedimentary infill of the Hoanh Bo Trough is of the Late Eocene–Early Oligocene age and was deposited in a very warm tropical/subtropical climate. In turn, geochemical results demonstrate that the deposits have intermediate chemical maturity and were probably reworked from older sedimentary rock sources. Moreover, it is suggested to combine the Dong Ho and Tieu Giao formations and synonymize them as the Dong Ho Formation. The sedimentary pattern, age, climatic conditions, and structural evolution of the Hoanh Bo Trough align well with the rift initiation, rift development, and rift termination tectonic system tracts. Moreover, the Hoanh Bo Trough could be treated as a landward keyhole for the offshore basins: for instance, the Kien An Basin in the northern Song Hong Basin. [ABSTRACT FROM AUTHOR]

Studies of Miocene sediments in the Fore-Carpathian Basin, conducted by geologists from the University of Warsaw have provided new insights on the distribution of the facies infilling the basin, particularly in the forebulge and back-bulge zones. The origin of the large-scale sand bodies, evaporitic deposits and large-scale organic buildups is discussed, described and verified. These deposits originated in variable, shallow marine settings, differing in their water chemistry and the dynamics of sedimentary processes, and are unique with regard to the fossil assemblages they yield. Many years of taxonomic, biostratigraphic, palaeoecologic and ecotaphonomic investigations have resulted in the identification of the fossil assemblages of these sediments, their age, sedimentary settings and post-mortem conditions. Detailed studies were focused on corals, polychaetes, most classes of molluscs, crustaceans, echinoderms, and fishes. [ABSTRACT FROM AUTHOR]

Ground-penetrating radar (GPR) surveys and sedimentological outcrop analyses were combined in order to determine the reflection patterns and internal architecture of terrace deposits of the Vistula River at Kępa Zawadowska in the southern part of Warsaw (central Poland). The sedimentary analyses concerned the granulometric composition and lithofacies analysis. The 34 GPR profiles, which were obtained in two outcrops, using a Malå RAMAC/GPR system with 500-MHz and 250-MHz shielded antennas, were up to 100 m long. The most characteristic ground-penetrating radar profiles are presented; they show a high-resolution data set of radar facies. The GPR data suggest the presence of three geophysically different units, namely with high-angle inclined reflections (radar facies 1), with discontinuous undulating or trough-shaped reflections (radar facies 2), and with low-angle reflections (radar facies 3). The internal structure of the fluvial deposits was obtained by integration of the GPR and sedimentological data, which combination provides a more accurate visualisation of sedimentary units than do reconstructions that are based only on standard lithologic point data. [ABSTRACT FROM AUTHOR]

Abstract: The Lao Cai, Yen Bai and Bao Yen Basins connected with the Red River Fault Zone (RRFZ) are filled with over 1000m thick Neogene (Miocene) clastic deposits of different type and origin. Coarse-grained alluvial deposits predominate along the south-western margin of the Lao Cai and Yen Bai Basins, while different types of conglomerates and sandstones, even siltstones occur in their central and along their north-eastern parts. Such asymmetry in the cross-section basin fill points to the south-western active margin of these basins. Three main facies associations composed of 12 lithofacies have been recognized in the Miocene succession filling the studied basins: (1) debris-flow dominated alluvial fan association, (2) sheetflood dominated alluvial fan association, and (3) lacustrine association. Both alluvial fan facies associations are broadly spread in the studied basins, especially along their south-western margins. The debris-flow dominated deposits are represented by decimetre to several meters thick, sand- and mud-supported disorganized pebble- to cobble-size, occasionally boulder breccia and conglomerate beds. The sheetflood dominated deposits are represented by alternating planar-bedded pebble and cobble gravel couplets. The occurrence of conglomerate bodies within and overlapping fine deposits of the lacustrine facies association may suggest deposition in a debris-flow and sheetflood dominated alluvial-fan setting associated with narrow, elongated basins that could be occupied by lakes and bordered by active fault scarps. The facies pattern of the particular basins is connected with the evolution of the RRFZ. The origin of these basins may be correlated with a sinistral transtensional regime which occurred in the Early to Middle Miocene. Moreover, the high-grade metamorphic core of the Day Nui Con Voi Massif, presently the main structural element of the RRFZ, was probably not exposed during sedimentation of most of the strata in the studied basins. [Copyright &y& Elsevier]