Using basement-hosted clastic dykes as syn-rifting palaeostress indicators: an example from the basal Stoer Group, northwest Scotland

1999 ◽  
Vol 136 (3) ◽  
pp. 301-310 ◽  
Author(s):  
L. E. BEACOM ◽  
T. B. ANDERSON ◽  
R. E. HOLDSWORTH
Keyword(s):  
Sedimentary Cover ◽  
Regional Scale ◽  
Three Dimensional ◽  
Tensile Fracture ◽  
Stress Inversion ◽  
The North ◽  
Basement Rocks ◽  
Basement Faults ◽  
Half Graben ◽  
Inversion Techniques

Clastic infills of fractures (here termed clastic veins) in basement rocks immediately underlying sedimentary cover sequences can be used to date fault movements if these demonstrably occurred at the time of infilling or prior to the lithification of the entrained clastic material. This allows reconstruction of the syn-rifting palaeostress system using stress inversion techniques. During Riphean intracontinential rifting of Laurentia, the Torridonian Stoer Group sediments of northwest Scotland were deposited in half-graben basins controlled by faults, e.g. the Coigach and Clachtoll faults. At Clachtoll, northeast–southwest oblique sinistral normal faulting in the underlying basement is associated with extensive development of shear, hybrid and tensile clastic veins filled with Stoer Group sediment, infilled and deformed prior to sediment lithification. Clastic veins initially formed by gravitational infilling of sediment from above, followed by tectonically-driven, forceful hydraulic injection of fluidized sand into new fractures and reactivated pre-existing basement faults. Palaeostress axes, determined from fault lineation data and tensile fracture extension directions in the Clachtoll Fault zone, indicate west-northwest–east-southeast directed extension during rifting. On a regional scale, this implies oblique-dextral extension on the north- to north-northeast-trending Coigach Fault during Stoer Group deposition. Similar orientations, age relationships and kinematics have been obtained from pre-Torridon Group fault arrays developed in the Lewisian basement near Gairloch and Loch Maree. Overall, the faulting patterns reflect a three-dimensional strain (k≠1) formed by east-southeast–west-northwest-directed extension during deposition of the Stoer Group. More speculatitively, asymmetric density patterns of sinistral and dextral faults may indicate that rifting occurred in a regional zone of broadly north–south-oriented dextral transtension.

Folding and imbrication of the Indian crust during Himalayan collision

1988 ◽  
Vol 326 (1589) ◽  
pp. 89-116 ◽  
Keyword(s):  
Local Development ◽  
Sedimentary Cover ◽  
Three Dimensional ◽  
Indian Plate ◽  
Small Scale ◽  
Plate Convergence ◽  
The North ◽  
Basement Rocks ◽  
Wide Range ◽  
Minimum Displacement

India collided with a northern Kohistan-Asian Plate at about 50 Ma ago, the time of ocean closure being fairly accurately defined from syntectonic sediments as well as the effect on magnetic stripes on the Indian Ocean floor. Since collision, Asia has over-ridden India, developing a wide range of thrust scrapings at the top of the Indian Plate. Sections through the imbricated sedimentary cover suggest a minimum displacement of over 500 km during Eocene to recent plate convergence. This requires the Kohistan region to the north to be underlain by underthrusted middle to lower Indian crust, deformed by ductile shears and recumbent folds. These structures are well seen in the gneisses immediately south of the suture, where they are uplifted in the Indus and Nanga Parbat syntaxes. Here there are several phases of thrust-related small-scale folding and the development of a large folded thrust stack involving basement rocks, the imbrication of metamorphic zones and the local development of large backfolds. Some of the important local structures: the large late backfolds, the Salt Ranges and the Peshawar Basin, can all be related to the necessary changes in thrust wedge shape as it climbs through the crust and the three dimensional nature of the thrust movements associated with interference between the Kohistan and western Himalayan trends.

Three-Dimensional Modeling of MVT Lead-Zinc Deposit in Western Hunan and its Application

2014 ◽  
Vol 644-650 ◽  
pp. 2674-2677
Author(s):  
Kun Wang ◽  
Ke Yan Xiao
Keyword(s):  
Regional Scale ◽  
Three Dimensional ◽  
Hunan Province ◽  
Three Dimensional Model ◽  
Three Dimensional Modeling ◽  
The North ◽  
Dimensional Modeling ◽  
North Part ◽  
Lead Zinc ◽  
Fault Belt

In order to study the evolution and metallogenic regularity of MVT lead-zinc deposits in western portion of Hunan province (China), two sets of three-dimensional model are established by Minexplorer software: 3D model in typical deposit and 3Dmodel on regional scale. On the basis of synthetic analyses of two sets of models, the further prospecting should be focused on the north part of ore-bearing layer along the Huayuan-Zhangjiajie fault belt. It is effective to observe occurrence and distribution characteristics from the 3D geological model, and to provide the basis for further exploration prospecting of the concealed deposits.

Joint inversion of surface wave and gravity data reveals subbasin architecture of the Congo Basin

Geology ◽  
2021 ◽  
Author(s):  
A. Raveloson ◽  
A. Nyblade ◽  
R. Durrheim
Keyword(s):  
Joint Inversion ◽  
Gravity Data ◽  
Three Dimensional ◽  
Sedimentary Basins ◽  
Congo Basin ◽  
S Wave ◽  
African Plate ◽  
The North ◽  
Basement Faults ◽  
Structural High

We investigated the architecture of the greater Congo Basin, one of the largest and least-well-studied sedimentary basins on any continent. Seismograms from a large number of M > 4.5 earthquakes within and surrounding the African plate were used to make event-to-station Rayleigh wave group velocity measurements between periods of 5 and 100 s. Group velocities for discrete periods across the basin, obtained by inverting the event-station measurements, were jointly modeled with gravity data to obtain a three-dimensional S-wave and density model of the basin. The model corroborates the existence of two previously suggested subbasins, one to the north and one to the south, each ~8 km deep and separated by an east-west structural high. Our results favor a salt tectonics origin for the structural high but cannot rule out uplifted basement rock. The northern subbasin is offset to the west from the southern subbasin, consistent with previous studies suggesting sinistral motion along basement faults during periods of transpressional tectonics in late Neoproterozoic–early Paleozoic times.

scholarly journals ON THE NATURE AND MECHANISM OF FORMATION OF HYDROCARBON DEPOSITS ON THE SHELF OF VIETNAM

2020 ◽  
Vol 39 (5) ◽  
pp. 3-16
Author(s):  
M.G. Leonov ◽  
◽  
V.Yu. Kerimov ◽  
R.N. Mustaev ◽  
Vu Nam Hai ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Sedimentary Cover ◽  
Three Dimensional ◽  
Distribution Patterns ◽  
The Body ◽  
Oil Fields ◽  
Hydrocarbon Generation ◽  
Tectonic Model ◽  
Basement Rocks ◽  
Hydrocarbon Deposits

The paper presents the results of the study of main factors determining conditions of formation and distribution of oil and gas deposits within the Cenozoic sedimentary cover and Precenozoic granite basement of the Vietnam shelf. The structural and tectonic model of the Kyulong basin constructed by the authors allows to reveal the conditions of formation of regional and local structures in the sedimentary cover containing hydrocarbon deposits; mechanisms of hydrocarbon traps emergence and hollow space (collectors); genesis of hydrocarbons, including the hydrocarbons existed in the basement rocks; the possible mechanism of migration and accumulation of hydrocarbons in the basement rocks. The traps which are real or potential reservoirs of hydrocarbons in the body of a crystal socle are widely developed. The structural and tectonic processes in the basement itself resulted in the development of positive morfostructures (domes, protrusions) the cores of which are made of disintegrated (granulated) rocks of a crystalline cap. In order to reconstruct the chronothermobaric conditions of occurrence and evolution of hydrocarbon generation centers and to restore the conditions of formation and distribution patterns of oil and gas accumulations on the shelf of Vietnam, three-dimensional modeling of generation and accumulation hydrocarbon systems was performed using the basin modeling technology and PetroMod software (Schlumberger, Ltd, USA). Studies of hydrocarbon biomarkers of oil fields in the Kyulong basin, including those located in the crystalline basement have shown the similarity of biomarker parameters of oil and organic matter, which demonstrates the organic nature of the oil fields of the basement on the shelf of Vietnam

scholarly journals Palinspastic restoration of an exhumed deepwater system: A workflow to improve paleogeographic reconstructions

2015 ◽  
Vol 3 (4) ◽  
pp. SAA71-SAA87 ◽  
Author(s):  
Allan L. Spikings ◽  
David M. Hodgson ◽  
Douglas A. Paton ◽  
Yvonne T. Spychala
Keyword(s):  
Cross Sections ◽  
Regional Scale ◽  
Three Dimensional ◽  
Dispersal Patterns ◽  
Lower Paleozoic ◽  
Sediment Dispersal ◽  
Karoo Basin ◽  
The North ◽  
Thrust Tectonics ◽  
Palinspastic Restoration

The Permian Laingsburg depocenter, Karoo Basin, South Africa, is the focus of sedimentological and stratigraphic research as an exhumed analog for offshore hydrocarbon reservoirs in deepwater basins. Thin-skinned thrust tectonics during the Permo-Triassic Cape Orogeny result in postdepositional deformation of the Permian basin fill. Regional-scale cross sections reveal two structural domains: a southern domain in the Laingsburg depocenter comprising 8–11-km wavelength north-verging fault-propagation folding, driven by buried low-angle ([Formula: see text]) reverse faults that coalesce at depth as part of a megadetachment below the Lower Paleozoic Cape Supergroup; and a northern domain to the north of the Laingsburg depocenter of short-wavelength, low-amplitude, asymmetrical folding facilitated by a detachment within the Permian Ecca Group. Five detailed structural cross sections permit the palinspastic restoration, and a calculation of the amount of shortening, across a [Formula: see text] area in the Laingsburg depocenter. Average shortening across the study area is −16.9% (5.8 km), and it decreases south to north. Shortening estimates from the Upper Ecca Group increase from 4.3 km near Matjiesfontein in the west to 10.4 km near Prince Albert in the east. Three-dimensional restorations of stratigraphic surfaces are consistent with these figures (−17%), and they allow paleogeographic and isopach thickness maps to be resorted to their configuration at the time of deposition. Structural restoration can be routinely used in outcrop studies to improve the accuracy of dimensions (e.g., volumetrics) and reconstructions (e.g., sediment dispersal patterns) derived from ancient sedimentary systems. The workflow presented here will add value to exhumed basin analogs by presenting prekinematic configurations at the frontal margins of fold-thrust belts.

Subsurface stratigraphy and basin-fill architecture of the late Paleozoic eastern Taos trough, northern New Mexico, U.S.A.

2020 ◽  
Vol 57 (3) ◽  
pp. 149-176
Author(s):  
Nur Uddin Md Khaled Chowdhury ◽  
Dustin E. Sweet
Keyword(s):  
New Mexico ◽  
Sediment Accumulation ◽  
Late Paleozoic ◽  
North Central ◽  
The North ◽  
Basement Rocks ◽  
Basin Geometry ◽  
Deformation Event ◽  
Thrust System ◽  
Basin Fill

The greater Taos trough located in north-central New Mexico represents one of numerous late Paleozoic basins that formed during the Ancestral Rocky Mountains deformation event. The late Paleozoic stratigraphy and basin geometry of the eastern portion of the greater Taos trough, also called the Rainsville trough, is little known because the strata are all in the subsurface. Numerous wells drilled through the late Paleozoic strata provide a scope for investigating subsurface stratigraphy and basin-fill architecture of the Rainsville trough. Lithologic data obtained predominantly from petrophysical well logs combined with available biostratigraphic data from the greater Taos trough allows construction of a chronostratigraphic framework of the basin fill. Isopach- and structure-maps indicate that the sediment depocenter was just east of the El Oro-Rincon uplift and a westerly thickening wedge-shaped basin-fill geometry existed during the Pennsylvanian. These relationships imply that the thrust system on the east side of the Precambrian-cored El Oro-Rincon uplift was active during the Pennsylvanian and segmented the greater Taos trough into the eastern Rainsville trough and the western Taos trough. During the Permian, sediment depocenter(s) shifted more southerly and easterly and strata onlap Precambrian basement rocks of the Sierra Grande uplift to the east and Cimarron arch to the north of the Rainsville trough. Permian strata appear to demonstrate minimal influence by faults that were active during the Pennsylvanian and sediment accumulation occurred both in the basinal area as well as on previous positive-relief highlands. A general Permian decrease in eustatic sea level and cessation of local-fault-controlled subsidence indicates that regional subsidence must have affected the region in the early Permian.

scholarly journals Morphotectonic Analysis along the Northern Margin of Samos Island, Related to the Seismic Activity of October 2020, Aegean Sea, Greece

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 102
Author(s):  
Paraskevi Nomikou ◽  
Dimitris Evangelidis ◽  
Dimitrios Papanikolaou ◽  
Danai Lampridou ◽  
Dimitris Litsas ◽  
...  
Keyword(s):  
Fault Zone ◽  
Seismic Activity ◽  
Volcanic Rocks ◽  
Active Tectonics ◽  
Normal Fault ◽  
Aegean Sea ◽  
Northern Margin ◽  
The North ◽  
Eastern Aegean ◽  
Half Graben

On 30 October 2020, a strong earthquake of magnitude 7.0 occurred north of Samos Island at the Eastern Aegean Sea, whose earthquake mechanism corresponds to an E-W normal fault dipping to the north. During the aftershock period in December 2020, a hydrographic survey off the northern coastal margin of Samos Island was conducted onboard R/V NAFTILOS. The result was a detailed bathymetric map with 15 m grid interval and 50 m isobaths and a morphological slope map. The morphotectonic analysis showed the E-W fault zone running along the coastal zone with 30–50° of slope, forming a half-graben structure. Numerous landslides and canyons trending N-S, transversal to the main direction of the Samos coastline, are observed between 600 and 100 m water depth. The ENE-WSW oriented western Samos coastline forms the SE margin of the neighboring deeper Ikaria Basin. A hummocky relief was detected at the eastern margin of Samos Basin probably representing volcanic rocks. The active tectonics characterized by N-S extension is very different from the Neogene tectonics of Samos Island characterized by NE-SW compression. The mainshock and most of the aftershocks of the October 2020 seismic activity occur on the prolongation of the north dipping E-W fault zone at about 12 km depth.

scholarly journals Influence of the North Atlantic oscillation on the atmospheric levels of benzo[a]pyrene over Europe

2021 ◽  
Author(s):  
Pedro Jiménez-Guerrero ◽  
Nuno Ratola
Keyword(s):  
Spatial Pattern ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Transport Model ◽  
Regional Scale ◽  
The South ◽  
Climatic Fluctuations ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

AbstractThe atmospheric concentration of persistent organic pollutants (and of polycyclic aromatic hydrocarbons, PAHs, in particular) is closely related to climate change and climatic fluctuations, which are likely to influence contaminant’s transport pathways and transfer processes. Predicting how climate variability alters PAHs concentrations in the atmosphere still poses an exceptional challenge. In this sense, the main objective of this contribution is to assess the relationship between the North Atlantic Oscillation (NAO) index and the mean concentration of benzo[a]pyrene (BaP, the most studied PAH congener) in a domain covering Europe, with an emphasis on the effect of regional-scale processes. A numerical simulation for a present climate period of 30 years was performed using a regional chemistry transport model with a 25 km spatial resolution (horizontal), higher than those commonly applied. The results show an important seasonal behaviour, with a remarkable spatial pattern of difference between the north and the south of the domain. In winter, higher BaP ground levels are found during the NAO+ phase for the Mediterranean basin, while the spatial pattern of this feature (higher BaP levels during NAO+ phases) moves northwards in summer. These results show deviations up to and sometimes over 100% in the BaP mean concentrations, but statistically significant signals (p<0.1) of lower changes (20–40% variations in the signal) are found for the north of the domain in winter and for the south in summer.

Sign in / Sign up

Export Citation Format

Share Document