Topography of the Magura floor thrust and morphotectonics of the Outer West Carpathians in Poland

Neotectonic (Pliocene-Quaternary) elevations and depressions detected on maps of subenvelope surfaces of the topography of the Outer West Carpathians of Poland are, to a certain extent, portrayed on the map showing topography of the Magura floor thrust, particularly in the western segment of the study area. The floor thrust of the Magura Nappe is highly uneven, its position changing from 725 m a.s.l. to more than 7,000 m b.s.l. The most prominent depression is located in the medial (S of Dunajec and Poprad confluence) segment of the Polish Outer Carpathians (2-7 km b.s.l.), and its axis trends NW-SE from the eastern margin of the Mszana Dolna tectonic window to the Poprad River valley. Another, much more shallower, Jordanów depression (2 km b.s.l.) is to be found NW of the Mszana Dolna tectonic window, shortly north of the Skawa River valley. Elevated structures, in turn, include the Mszana Dolna tectonic window, Sól-Skomielna (on the west), and Limanowa (on the east) elevations of subparallel orientation. Still farther to the east, a longitudinal elevation extending between the Klęczany-Pisarzowa and Świątkowa tectonic windows is to be seen some 10-15 km south of the Magura frontal thrust. South of this area, the Magura floor thrust slopes steeply down to more than 4 km b.s.l. A comparison between the pattern of elevated and subsided structures of the Magura floor thrust and subenvelope surfaces of different orders shows that in the western part of the Polish Outer Carpathians the highest-elevated neotectonic structures (in the southern portion of that area) coincide with depressions of the Magura thrust, whereas farther north a reverse pattern becomes dominant: neotectonic elevations coincide either with the Magura frontal thrust or with elevations of its surface. This is particularly true for an area comprised between 20° and 20°30’E meridians. The origin of such relationships is difficult to explain. We infer that one of possible factors could be Pliocene-Quaternary reactivation of faults cutting the Magura floor thrust, and particularly that one, which appears to separate the western-medial segment of the Outer Carpathians from their more eastern portion

Jointing in the Dukla Nappe (Outer Carpathians, Poland) : an attempt at palaeostress reconstruction

The joint network in the portion of the Dukla Nappe studied originated in two stages showing different orientations of the stress field axes. The older, compressive stage I was characterized by a N45^{\circ}E-orientated (at present coordinates) horizontal s1 and formation of the diagonal, shear (SL and SR) joint system. The younger, extensional stage II was characterized by vertical s1 and horizontal, N35^{\circ}E-orientated (also at present coordinates) s3 suitable for formation of the fold-parallel joints. At the turn of the first stage, under diminishing horizontal compression (s1 trending N35^{\circ}E), the cross-fold T joints developed. The orientation of the maximum compression axis changed between stages I and II. The first stage probably commenced while strata which were not fully lithified underwent shortening, and lasted until the termination of nappe emplacement. The second stage, in turn, is associated with pat-orogenic collapse of the Carpathians, whose onset in the study region began at least in Late Miocene times

Cainozoic evolution of Lower Silesia, SW Poland : a new interpretation in the light of sub-Cainozoic and sub-Quaternary topography

An analysis of the youngest tectonic movements by the use of either morphometric or instrumental techniques should take into account both exposed and buried fault zones. The sub-Cainozoic and sub-Quaternary surface maps presented in this study display buried palaeotopography whose interpretation proves helpful in identification of tectonic dislocations. Such a kind of analysis has been conducted for the area of Lower Silesia, including the Sudetes, Fore-Sudetic Block, and Fore-Sudetic Monocline. The maps have been constructed on the basis of well-bore data, vertical geoelectrical soundings, and detailed mapping of exposures of pre-Quaternary rocks. Well-bore data have been reinterpreted with a view to reconstruct the original depth to the top of the crystalline basement. Many archival borehole descriptions place the boundary between Tertiary strata and the Proterozoic-Palaeozoic substratum at the top of poorly weathered rocks, including regoliths of the crystalline substratum into the Tertiary cover. The presented maps portray for the first time the actual morphology of the sub-Cainozoic surface. A comparison between the sub-Cainozoic and sub-Quaternary surface maps enables us to document changes in tectonic mobility throughout Cainozoic times. An additional source of information is provided by the attached thickness maps of individual time-slices of the Cainozoic

Młode uskoki w północnym Wietnamie : przykład ze strefy uskoku Rzeki Czerwonej

Strefa uskoku Rzeki Czerwonej wyznacza granicę pomiędzy blokami Chin południowych i Indochinami. Była ona ukształtowana w dwóch fazach: podczas lewoskrętnego ścinania w warunkach podatnych, w okresie 27-16 Ma z późniejszym wypiętrzeniem i ekshumacją z głębokości 20-25 km, a następnie w warunkach kruchego ścinania prawoskrętnego w plio-czwartorzędzie. Wielkość post-mioceńskiego przemieszczenia prawoskrętnego była rekonstruowana na 20 do 57 km, podczas gdy rozmiar przemieszczenia czwartorzędowych dolin był szacowany na 9 m do blisko 2 km. Dlatego ruch ten odpowiada tempu 1 do 9 mm/rok lub 1 do 4 mm/rok. Strefa uskokowa spełnia więc warunki umożliwiające w przyszłości generowanie silnych trzęsień ziemi.The Red River Fault Zone marks the boundary between the South China and Indochina blocks. It was shaped in two phases: during sinistral, ductile shear active 27-16 Ma, followed by exhumation and uplift from depths of 20-25 km, and then as dextral, predominantly brittle shear active in Plio-Quaternary times. The amount of post-Miocene dextral offset has been variously reconstructed as 20 to 57 km, whereas the size of individual offset of Quaternary valleys has been calculated as 9 m to nearly 2 km. Therefore, the corresponding rates of Quaternary dextral slip range between 1 and 9 mm/yr or 1 and 4 mm/yr. The fault zone is capable of generating relatively strong earthquakes in the future

Morphotectonic properties of the Lo River Fault near Tam Dao in North Vietnam

International audienceThe Lo River fault near Tam Dao, North Vietnam, is a young, right-lateral, normal fault which has been active throughout the Quaternary. Rates of dextral slip range between 1 and 2 mm/yr whereas rates of uplift can be estimated roughly at 0.1?1 mm/yr. The drainage deflection and arrangement of shutter ridges suggest 1.5?2.0 km of dextral offset during the past 1?2 millions of years (m. y.), and the height of the youngest faceted spurs averages at 170 m. Analysis of morphometric parametres of the mountain front at Tam Dao indicates that this segment shows properties typical for nearly rectilinear, young normal scarps that belong to class I or II of relative tectonic activity and that are capable of generating strong earthquakes in the future

Late Miocene to present day structural development of the Polish segment of the Outer Carpathians

This paper presents a few pieces of evidence on neotectonic structural evolution of the Polish segment of the Outer Carpathians. During the Late Neogene, structural development was largely controlled by normal faulting and block uplift. However, there are also indications of compressional stress setting, at least during the Pliocene and particularly within the medial and eastern parts of the belt. In the Quaternary, in turn, structural development has been mainly controlled by compressional stress arrangement, with \sigma _{1} orientated roughly perpendicular to the belt. The Pliocene-Quaternary tectonic mobility of the Polish Outer Carpathians has been relatively weak and mostly of thin-skinned character. Normal faults were formed on the margins of intramontane basins and in the western part of the belt. Rates of uplift of individual structures were variable and the amount of uplift was the greatest in the Late Pliocene and Early Quaternary times. Geomorphologically-detected zones of uplift are relatively narrow and arranged subparallel or under small angle in respect to the strike of principal thrusts and frontal parts of large slices. Such an arrangement is interpreted as resulting from the steepening of frontal thrusts due to horizontal compression within the overthrust flysch nappes. This hypothesis is confirmed by the results of recent break-out and GPS studies, as well as by focal solutions of some Outer Carpathian earthquakes