scholarly journals Variscan structures and their control on latest to post-Variscan basin architecture; insights from the westernmost Bohemian Massif and SE Germany

2021 ◽  
Author(s):  
Hamed Fazlikhani ◽  
Wolfgang Bauer ◽  
Harald Stollhofen
Keyword(s):  
Bohemian Massif ◽  
Seismic Reflection ◽  
Shear Zones ◽  
Seismic Facies ◽  
Seismic Survey ◽  
Fault System ◽  
Variscan Orogeny ◽  
Normal Faults ◽  
Low Grade ◽  
Upper Carboniferous

Abstract. The Bohemian Massif exposes structures and metamorphic rocks remnant from the Variscan Orogeny in Central Europe and is bordered by the Franconian Fault System (FFS) to the west. Across the FFS, possible presence of Variscan units and structures are buried by Permo-Mesozoic sedimentary rocks. We integrate existing DEKORP 2D seismic reflection, well and surface geological data with the newly acquired FRANKEN 2D seismic survey to investigate the possible westward continuation of Variscan tectonostratigraphic units and structures, and their influence on latest to post-Variscan basin development. Subsurface Permo-Mesozoic stratigraphy is obtained from available wells and are tied to seismic reflection profiles using a synthetic seismogram calculated from density and velocity logs. Below the sedimentary cover, three main basement units are identified using seismic facies descriptions that are compared with seismic reflection characteristics of exposed Variscan units east of the FFS. Our results show that Upper Paleozoic low-grade metasedimentary rocks and possible Variscan nappes are bounded and transported by Variscan shear zones to ca. 65 km west of the FFS. Basement seismic facies in the footwall of the Variscan shear zones are interpreted as Saxothuringian basement. We show that the location of normal fault-bounded latest to post-Variscan Upper Carboniferous-Permian basins are controlled by the geometry of underlying Variscan shear zones. Some of these Upper Carboniferous-Permian normal faults reactivated as steep reverse faults during the regional Upper Cretaceous inversion. Our results also highlight that reverse reactivation of normal faults gradually decreases west of the FFS.

scholarly journals Seismic characteristics of polygonal fault systems in the Great South Basin, New Zealand

2020 ◽  
Vol 12 (1) ◽  
pp. 851-865
Author(s):  
Sukonmeth Jitmahantakul ◽  
Piyaphong Chenrai ◽  
Pitsanupong Kanjanapayont ◽  
Waruntorn Kanitpanyacharoen
Keyword(s):  
Three Dimensional ◽  
Late Eocene ◽  
Seismic Survey ◽  
Fault System ◽  
Normal Faults ◽  
Tier 2 ◽  
South Basin ◽  
Fault Systems ◽  
Tier 1 ◽  
Polygonal Fault

AbstractA well-developed multi-tier polygonal fault system is located in the Great South Basin offshore New Zealand’s South Island. The system has been characterised using a high-quality three-dimensional seismic survey tied to available exploration boreholes using regional two-dimensional seismic data. In this study area, two polygonal fault intervals are identified and analysed, Tier 1 and Tier 2. Tier 1 coincides with the Tucker Cove Formation (Late Eocene) with small polygonal faults. Tier 2 is restricted to the Paleocene-to-Late Eocene interval with a great number of large faults. In map view, polygonal fault cells are outlined by a series of conjugate pairs of normal faults. The polygonal faults are demonstrated to be controlled by depositional facies, specifically offshore bathyal deposits characterised by fine-grained clays, marls and muds. Fault throw analysis is used to understand the propagation history of the polygonal faults in this area. Tier 1 and Tier 2 initiate at about Late Eocene and Early Eocene, respectively, based on their maximum fault throws. A set of three-dimensional fault throw images within Tier 2 shows that maximum fault throws of the inner polygonal fault cell occurs at the same age, while the outer polygonal fault cell exhibits maximum fault throws at shallower levels of different ages. The polygonal fault systems are believed to be related to the dewatering of sedimentary formation during the diagenesis process. Interpretation of the polygonal fault in this area is useful in assessing the migration pathway and seal ability of the Eocene mudstone sequence in the Great South Basin.

Neogene and active brittle deformation on Amorgos Island (Greece)

2020 ◽  
Author(s):  
Jan Behrmann ◽  
Jakob Schneider ◽  
Benjamin Zitzow
Keyword(s):  
Moment Tensor ◽  
Spatial Relationship ◽  
Shear Zones ◽  
Fault System ◽  
Normal Faults ◽  
Small Scale ◽  
Past Century ◽  
Fault Plane Solutions ◽  
Moment Tensor Solution ◽  
Late Neogene

<p>Amorgos is the south-eastern outpost of the Cyclades Islands in the Aegean Sea, which forms part of the Neogene-Quaternary zone of crustal and lithospheric N-S upper plate extension northward of the Hellenic subduction zone and deep sea trench. Apart from subduction-related earthquakes further south, the southern Aegean is affected by frequent earthquakes sourced in the upper plate. The twin earthquakes of 9 July 1956, followed by a strong tsunami, were the strongest events of this kind in the past Century. Hypocenters are related to a NE-SW oriented normal fault bounding the Amorgos-Santorini Graben System. There are questions in the literature regarding the seismic source and fault plane solutions, especially the contribution of a transcurrent faulting component.</p><p>We have analyzed the kinematics of brittle faults exposed on Amorgos Island itself that could be related to Neogene and active extensional and/or transcurrent deformation. Seismic slip often occurs on previously existing faults. Thus, their orientations and kinematics may help shed light on the structure of seismic sources at depth. We present evidence for a complex history of faulting. Early normal detachment faults and shear zones overprint older (rare) reverse faults, and are themselves overprinted by several sets of dominantly dextral NE and SE trending strike slip faults. Youngest is a conjugate set of NE trending high-angle normal faults. These are especially frequent along the SE coast of the island, suggesting a clear spatial relationship with the 1956 rupture. They can be fitted to a moment tensor solution similar to the published solutions for the 1956 Amorgos earthquake. The kinematic solution for the population of early normal faults suggests that the whole of Amorgos Island may have experienced a 15° NNW tilt during later extension, which lets us suspect that the island could be a tilted block of a much larger fault system. Regarding long-term late Neogene to Quaternary kinematics, dextrally transtensive fault slip is required to fit the regional pattern of extensional deformation in the Aegean, and this is reflected by small-scale brittle faulting on Amorgos.</p>

Jurassic to Early Cretaceous postaccretional sinistral transpression in north-central Chile (latitudes 31–32°S)

2011 ◽  
Vol 149 (2) ◽  
pp. 208-220 ◽  
Author(s):  
UWE RING ◽  
ARNE P. WILLNER ◽  
PAUL W. LAYER ◽  
PETER P. RICHTER
Keyword(s):  
Early Cretaceous ◽  
Shear Zones ◽  
White Mica ◽  
Strike Slip ◽  
Fault System ◽  
Low Grade ◽  
North Central ◽  
Central Chile ◽  
Metamorphic Basement ◽  
Atacama Fault System

AbstractWe describe the geometry and kinematics of a Jurassic to Early Cretaceous transpressive sinistral strike-slip system within a metamorphic basement inlier of the Mesozoic magmatic arc near Bahia Agua Dulce at latitudes 31–32°S in north-central Chile and discuss possible relations with the Atacama Fault System further north. Sinistral transpression overprints structures of an accretionary system that is represented by the metamorphic basement. Sub-vertical semi-ductile NNW-striking strike-slip shear zones are the most conspicuous structures. Chlorite and sericite grew, and white mica and quartz dynamically recrystallized, suggesting low-grade metamorphic conditions during semi-ductile deformation. Folds at the 10–100 metre scale developed before and during strike-slip shearing. The folds are deforming a former sub-horizontal transposition foliation that originated during prior accretion processes. The folds have axes sub-parallel to the strike-slip shear zones and sub-vertical axial surfaces indicating a component of shortening parallel to the shear-zone boundaries, suggesting an overall transpressive deformation regime. Transpressive strike-slip deformation also affects Middle Triassic (Anisian) basal breccias of the El Quereo Formation.40Ar–39Ar laser ablation ages of synkinematically recrystallized white mica in one of the shear zones provide an age of 174–165 Ma for the waning stages of semi-ductile strike-slip shearing. The semi-ductile shear zones are cut by mafic and rhyolite dykes. Two rhyolite dykes yield40Ar–39Ar ages of 160.5 ± 1.7 Ma and 131.9 ± 1.7 Ma, respectively. The latter dyke has been affected by brittle faulting. Fault-slip analysis shows that the kinematics of the faulting event is similar to the one of the semi-ductile shearing event, suggesting that sinistral transpression continued after ~130 Ma. Timing, kinematics and geographic position suggest that the shear zones at Bahia Agua Dulce represent a southern continuation of the prominent Atacama Fault System that affected the Jurassic/Early Cretaceous arc over its ~1400 km length.

A lifetime of the Variscan orogenic plateau from uplift to collapse as recorded by the Prague Basin, Bohemian Massif

2017 ◽  
Vol 156 (3) ◽  
pp. 485-509 ◽  
Author(s):  
FRANTIŠEK VACEK ◽  
JIŘÍ ŽÁK
Keyword(s):  
Bohemian Massif ◽  
Three Dimensional ◽  
Plate Boundary ◽  
Early Carboniferous ◽  
Shear Zones ◽  
Crustal Thickening ◽  
Variscan Orogeny ◽  
Prague Basin ◽  
Lateral Extrusion ◽  
Orogenic Plateau

AbstractThe Ordovician to Middle Devonian Prague Basin, Bohemian Massif, represents the shallowest crust of the Variscan orogen corresponding toc.1–4 km palaeodepth. The basin was inverted and multiply deformed during the Late Devonian to early Carboniferous Variscan orogeny, and its structural inventory provides an intriguing record of complex geodynamic processes that led to growth and collapse of a Tibetan-type orogenic plateau. The northeastern part of the Prague Basin is a simple syncline cross-cut by reverse/thrust faults and represents a doubly vergent compressional fan accommodatingc.10–19 % ~NW–SE shortening, only minor syncline axis-parallel extension and significant crustal thickening. The compressional structures were locally overprinted by vertical shortening, kinematically compatible with ductile normal shear zones that exhumed deep crust in the orogen's interior atc. 346–337 Ma. On a larger scale, the deformation history of the Prague Syncline is consistent with building significant palaeoelevation during Variscan plate convergence. Based on a synthesis of finite deformation parameters observed across the upper crust in the centre of the Bohemian Massif, we argue for a differentiated within-plateau palaeotopography consisting of domains of local thickening alternating with topographic depressions over lateral extrusion zones. The plateau growth, involving such complex three-dimensional internal deformations, was terminated by its collapse driven by multiple interlinked processes including gravity, voluminous magma emplacement and thermal softening in the hinterland, and far-field plate-boundary forces resulting from the relative dextral motion of Gondwana and Laurussia.

Upper Carboniferous-Permian tectonics in Central Mediterranean: an updated revision

2020 ◽  
Author(s):  
Giancarlo Molli ◽  
Andrea Brogi ◽  
Alfredo Caggianelli ◽  
Enrico Capezzuoli ◽  
Domenico Liotta ◽  
...  
Keyword(s):  
Shear Zone ◽  
Regional Scale ◽  
Sedimentary Basins ◽  
Sedimentary Facies ◽  
Shear Zones ◽  
Low Grade ◽  
Central Mediterranean ◽  
Upper Carboniferous ◽  
Fold And Thrust Belt ◽  
Splay Faults

<p>An updated revision of the upper Carboniferous-Permian tectonics recorded in Corsica, Calabria and Tuscany is here proposed. We combine our and literature data to document how the sedimentary, tectono-metamorphic and magmatic upper Carboniferous-Permian record fits with a regional-scale tectonic scenario characterized by trascurrent fault systems associated with stretched crustal domains in which extensional regional structures, magmatism and transtensional basins developed. In Corsica, altogether with well-known effusive and intrusive Permian magmatism, the alpine S.Lucia nappe exposes a kilometer-scale portion of the Permian lower to mid-crust, with many similarities to the Ivrea-Verbano zone. The two distinct Mafic and Leucogranitic complexes, which characterize this crustal domain are juxtposed by an oblique-slip shear zone named as S.Lucia Shear Zone. Structural and petrological data document interaction between magmatism, metamorphism and shearing during Permian in the c. 800-400 °C temperature range. In Calabria (Sila, Serre and Aspromonte), a continuous pre-Mesozoic crustal section is exposed. The lower crust portion of such section is mainly made up of granulites and migmatitic paragneisses with subordinate marbles and metabasites. The mid-crustal section includes an up to 13 km thick sequence of granitoids of tonalitic to granitic composition, emplaced between 306 and 295 Ma and progressively deformed during retrograde extensional shearing to end with a final magmatic activity between 295 and 277 Ma, consisting in the injection of shallower dykes in a transtensional regime. The section is completed by an upper crustal portion mainly formed by a Paleozoic succession deformed as a low-grade fold and thrust belt, locally overlaying medium-grade paragneiss units, and therefore as a whole reminiscent of the external/nappe zone domains of Sardinia Hercynian orogen. In Tuscany we document, how late Carboniferous/Permian shallow marine to continental sedimentary basins characterized by unconformity and abrupt change in sedimentary facies (coal-measures, red fanglomerate deposits) and acid magmatism well fit a transtensional setting with a mid-crustal shear zone linked with a system of E-W trending (in present orientation) upper crust splay faults. We will frame the whole dataset in a regional framework of first-order transcurrent shear zones network which includes a westernmost S.Lucia Shear Zone and an easternmost East Tuscan Shear Zone, with intervening crustal domains in which extensional to transtensional shearing occured.</p>

Seismic reflection profiling studies of a buried Precambrian rift beneath the Wabash Valley fault zone

Geophysics ◽  
1986 ◽  
Vol 51 (3) ◽  
pp. 640-660 ◽  
Author(s):  
John L. Sexton ◽  
L. W. Braile ◽  
W. J. Hinze ◽  
M. J. Campbell
Keyword(s):  
Seismic Reflection ◽  
Fault System ◽  
Normal Faults ◽  
Rift System ◽  
Seismic Profiles ◽  
Seismic Reflection Data ◽  
Wabash River ◽  
Gravity And Magnetic ◽  
Wabash Valley ◽  
Wabash Valley Fault System

Sixty‐eight kilometers of 12-fold seismic reflection data were collected in the Wabash River Valley of southwestern Indiana and southeastern Illinois to investigate the configuration of a basement structure inferred from regional gravity and magnetic anomaly data. The seismic profiles were also positioned to cross faults of the Wabash Valley fault system in a number of locations. Interpretation of the seismic reflection profiles and detailed gravity and magnetic profile data provides evidence for a series of northeasterly trending grabens in the basement. These grabens are filled with pre‐Mt. Simon layered rocks and are overlain by Paleozoic sedimentary rocks of the Illinois basin. Beneath the Wabash River near Grayville, Illinois, an interpreted graben (the Grayville graben) is approximately 15 km wide and contains about 3 km of fill. Individual boundary faults for the graben cut prominent reflectors within pre‐Mt. Simon rocks and display offsets of up to 500 m. The interpreted configuration of basement faults and thickness of pre‐Mt. Simon layered rocks provide evidence of a late Precambrian rift inferred to be one arm of the New Madrid rift complex. Post‐Pennsylvanian faulting of the Wabash Valley fault system is visible on the seismic reflection record sections as small offsets (less than 100 m) on steeply dipping normal faults. The downward projection of these faults intersects the older large‐offset faults within the pre‐Mt. Simon rocks suggesting that the Wabash Valley faults represent a post‐Pennsylvanian reactivation of the rift system.

scholarly journals Evolution of a Normal Fault System, northern Graben, Taranaki Basin, New Zealand

2021 ◽  
Author(s):  
◽  
Hamish Cameron
Keyword(s):  
New Zealand ◽  
Seismic Reflection ◽  
Normal Fault ◽  
Growth Patterns ◽  
Fault System ◽  
Normal Faults ◽  
3D Seismic ◽  
Fault Evolution ◽  
Migration Pathways ◽  
Insight Into

<p>This study investigates the evolution (from initiation to inactivity) of a normal fault system in proximity to active petroleum systems within the Taranaki Basin, New Zealand. The aim of this research is to understand the evolution, interaction, and in some cases, death of normal faults in a region undergoing progressive regional extension. This research provides insight into the geometry, development, and displacement history of new and reactivated normal fault evolution through interpretation of industry standard seismic reflection data at high spatial and temporal resolution. Insight into normal fault evolution provides information on subsidence rates and potential hydrocarbon migration pathways.  Twelve time horizons between 1.2 and 35 Ma have been mapped throughout 1670 square kilometres of the Parihaka and Toro 3D seismic reflection surveys. Fault displacement analysis and backstripping have been used to determine the main phases of fault activity, fault growth patterns, and maximum Displacement/Length ratios. The timing, geometry, and displacement patterns for 110 normal faults with displacements >20 m have been interpreted and analysed using Paradigm SeisEarth and TrapTester 6 seismic interpretation and fault analysis software platforms.  Normal faults within the Parihaka and Toro 3D seismic surveys began developing at ˜11 Ma, with the largest faults accruing up to 1500 m of displacement in <10 Myr (mean throw displacement rate of 0.15mm/yr). Approximately 50% of the 110 mapped faults are associated with pre-existing normal faults and have typical cumulative displacements of ˜20 – 1000 m, with strike parallel lengths of <1 – 23 km. In contrast, new faults have typically greater displacements of 20 – 1400 m, and are generally longer with, with strike parallel lengths of ˜1 – 33 km.   New faults were the first faults within the system to become inactive when strain rates decreased from 0.06 – 0.03 between 3.6 and 3.0 Ma. Eight of the largest faults with > 1000 m cumulative displacement reach the seafloor and are potentially active at present day. An earthquake on one of these faults could be expected to produce MW 2.2 based on the maximum strike-parallel length of the fault plane.</p>

scholarly journals Revealing the deeper structure of the end-glacial Pärvie fault system in northern Sweden by seismic reflection profiling

Solid Earth ◽  
2015 ◽  
Vol 6 (2) ◽  
pp. 621-632 ◽  
Author(s):  
O. Ahmadi ◽  
C. Juhlin ◽  
M. Ask ◽  
B. Lund
Keyword(s):  
Seismic Reflection ◽  
Seismic Profile ◽  
Fault Scarp ◽  
Seismic Survey ◽  
Fault System ◽  
Earthquake Activity ◽  
Northern Sweden ◽  
Seismic Reflection Data ◽  
Scientific Drilling ◽  
Main Fault

Abstract. A new seismic reflection survey for imaging deeper levels of the end-glacial Pärvie fault system in northern Sweden was acquired in June 2014. The Pärvie fault system hosts the largest fault scarp so far documented in northern Scandinavia, both in terms of its length and calculated magnitude of the earthquake that generated it. Present-day microearthquakes occur along the length of the fault scarp on the eastern side of the scarp, in general agreement with an east-dipping main fault. In the central section of the fault system, where there is a number of subsidiary faults east of the main Pärvie scarp, it has been unclear how the earthquakes relate to the structures mapped at the surface. A seismic profile across the Pärvie fault system acquired in 2007, with a mechanical hammer as a source, showed a good correlation between the surface mapped faults and moderate to steeply dipping reflections. The most pronounced reflectors could be mapped to about 3 km depth. In the new seismic survey, for deeper penetration an explosive source with a maximum charge size of 8.34 kg in 20 m deep shot holes was used. Reflectors can now be traced to deeper levels with the main 65° east-dipping fault interpreted as a weakly reflective structure. As in the previous profile, there is a strongly reflective 60° west-dipping structure present to the east of the main fault that can now be mapped to about 8 km depth. Extrapolations of the main and subsidiary faults converge at a depth of about 11.5 km, where current earthquake activity is concentrated, suggesting their intersection has created favorable conditions for seismic stress release. Based on the present and previous seismic reflection data, we propose potential locations for future boreholes for scientific drilling into the fault system. These boreholes will provide a better understanding of the reflective nature of the fault structures and stress fields along the faults at depth.

Seismic reflection imaging of the low-angle Panamint Valley normal fault system, eastern California, USA

2020 ◽  
Author(s):  
Ryan Gold ◽  
William Stephenson ◽  
Richard Briggs ◽  
Christopher DuRoss ◽  
Eric Kirby ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Late Quaternary ◽  
Hazard Analysis ◽  
Hanging Wall ◽  
Normal Fault ◽  
Alluvial Fan ◽  
P Wave ◽  
Fault System ◽  
Normal Faults ◽  
High Angle

&lt;p&gt;A fundamental question in seismic hazard analysis is whether &lt;30&amp;#186;-dipping low-angle normal faults (LANFs) slip seismogenically. In comparison to more steeply dipping (45-60&amp;#186;) normal faults, LANFs have the potential to produce stronger shaking given increased potential rupture area in the seismogenic crust and increased proximity to manmade structures built on the hanging wall. While inactive LANFs have been documented globally, examples of seismogenically active LANFs are limited. The western margin of the Panamint Range in eastern California is defined by an archetype LANF that dips west beneath Panamint Valley and has evidence of Quaternary motion. In addition, high-angle dextral-oblique normal faults displace mid-to-late Quaternary alluvial fans near the range front. To image shallow (&lt;1 km depth), crosscutting relationships between the low- and high-angle faults along the range front, we acquired two high-resolution P-wave seismic reflection profiles. The northern ~4.7-km profile crosses the 2-km-wide Wildrose Graben and the southern ~1.1-km profile extends onto the Panamint Valley playa, ~7.5 km S of Ballarat, CA. The profile across the Wildrose Graben reveals a robust, low-angle reflector that likely represents the LANF separating Plio-Pleistocene alluvial fanglomerate and pre-Cambrian meta-sedimentary deposits. High-angle faults interpreted in the seismic profile correspond to fault scarps on Quaternary alluvial fan surfaces. Interpretation of the reflection data suggests that the high-angle faults vertically displace the LANF up to 70 m within the Wildrose Graben. Similarly, the profile south of Ballarat reveals a low-angle reflector, which appears both rotated and displaced up to 260 m by high-angle faults. These results suggest that near the Panamint range front, the high-angle faults are the dominant late Quaternary structures. We conclude that, at least at shallow (&lt;1 km) depths, the LANF we imaged is not seismogenically active today.&lt;/p&gt;

Seismic reflection imaging over a massive sulfide deposit at the Matagami mining camp, Québec

Geophysics ◽  
1999 ◽  
Vol 64 (1) ◽  
pp. 24-32 ◽  
Author(s):  
Andrew J. Calvert ◽  
Yexu Li
Keyword(s):  
Seismic Reflection ◽  
Massive Sulfide ◽  
Seismic Profile ◽  
Seismic Survey ◽  
Normal Faults ◽  
Sulfide Deposit ◽  
Seismic Reflection Profile ◽  
Massive Sulfide Deposit ◽  
Volcanic Stratigraphy ◽  
Seismic Reflections

A 2-D seismic reflection profile was shot across the southern flank of the Matagami mining camp, almost directly above the recently discovered Bell Allard massive sulfide deposit, now estimated at more than 6 million metric tons. All orebodies found in the southern part of the mining camp, including Bell Allard, are located at the contact between the primarily basaltic Wabassee Group and the underlying rhyolitic Watson Lake Group. Seismic reflections were recorded from the basalt‐rhyolite contacts of the lower Wabassee Group, as well as from gabbro sills that intrude much of the volcanic stratigraphy. A strong reflection from the top of the Bell Allard orebody was also detected, but the reflection does not extend over the full width of the deposit as defined by drilling, appearing to correlate with the lower pyrite‐rich zone. Faulting, which can be interpreted from discontinuities in the observed reflections, probably controlled the formation of the Bell Allard deposit. If the interpreted gabbro sills are accepted as isotime markers, then faulting of the deeper sill complex defines a series of half grabens within the rhyolitic Watson Lake Group. The Bell Allard deposit is found at the intersection of one of these apparently low‐angle normal faults with the top of the Watson Lake Group, indicating that sulfide mineralization may have been associated with fluid flow along the fault, which likely penetrates to the underlying mafic intrusion. Although the precise geometry of subsurface faulting cannot be estimated from a single 2-D seismic profile, these results indicate that a full 3-D seismic survey should allow the mapping of many of the subsurface fault systems and the verification of hypotheses of fault‐controlled deposit formation.

Sign in / Sign up

Export Citation Format

Share Document