scholarly journals Igneous Activity and Structural Development of the Mianhua Terrace, Offshore North Taiwan

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 303
Author(s):  
Jih-Hsin Chang ◽  
Eason Yi-Cheng Yang ◽  
Ho-Han Hsu ◽  
Tzu-Ting Chen ◽  
Char-Shine Liu ◽  
...  
Keyword(s):  
High Amplitude ◽  
Shelf Break ◽  
Normal Faults ◽  
Structural Development ◽  
Bathymetric Data ◽  
Orogenic Wedge ◽  
Igneous Activity ◽  
Fault Structures ◽  
Volcanic Influence ◽  
Northern Taiwan

Using bathymetric and multichannel seismic (MCS) data, we explored the volcanic influence on the bathymetric and stratigraphic features of the Mianhua Terrace. The Mianhua Terrace occupies the marine counterpart of the Northern Taiwan Volcanic Zone (NTVZ) along the collapsed Taiwan orogenic wedge and is dominated by post-collisional magmatism and extensional structures. The bathymetric data showed several semicircular-shaped features near the shelf break. The MCS profiles showed that the Pleistocene unconformity buried beneath the Mianhua Terrace is partly difficult to observe due to seafloor multiples, suggesting that the seafloor is dominated by physically hard lithology, probably volcanic lavas. We interpreted the high-amplitude reflectors and their projected seafloor relief as intrusive sills and associated extrusive edifice. Similarly, we interpreted high-amplitude reflectors in the vicinity of normal faults as intrusive sills emplaced and facilitated by fault structures. A volcanic or hydrothermal mound was also recognized. We propose that the Mianhua Terrace is a breached ramp in a transfer zone between the tips of two successive normal faults along the shelf break. Once the fault tips reactivate and extend toward each other, the Mianhua Terrace may continue to collapse, leading to catastrophic volcanic or associated hydrothermal events.

scholarly journals Novel Bathymetry of Lake Afdera Reveals Fault Structures and Volcano-Tectonic Features of an Incipient Transform Zone (Afar, Ethiopia)

2021 ◽  
Vol 9 ◽  
Author(s):  
Jean-Charles Schaegis ◽  
Valentin Rime ◽  
Tesfaye Kidane ◽  
Jon Mosar ◽  
Ermias Filfilu Gebru ◽  
...  
Keyword(s):  
Afar Depression ◽  
Nodal Basin ◽  
Bathymetric Data ◽  
The North ◽  
Transfer Zones ◽  
Fault Structures ◽  
Bathymetric Map ◽  
Endorheic Lake ◽  
Tectonic Features ◽  
Transfer Zone

Lake Afdera is a hypersaline endorheic lake situated at 112 m below sea-level in the Danakil Depression. The Danakil Depression is located in the northern part of the Ethiopian Afar and features an advanced stage of continental rifting. The remoteness and inhospitable environment explain the limited scientific research and knowledge about this lake. Bathymetric data were acquired during 2 weeks expeditions in January/February 2016 and 2017 using an easily deployable echosounder system mounted on an inflatable motorized boat. This study presents the first complete bathymetric map of the lake Afdera. Bathymetric results show that the lake has an average depth of 20.9 m and a total volume of 2.4 km3. The maximum measured depth is 80 m, making Lake Afdera the deepest known lake in Afar and the lowest elevation of the Danakil Depression. Comparison with historical reports shows that the lake level did not fluctuate significantly during the last 50 years. Two distinct tectonic basins to the north and the south are recognized. Faults of different orientations control the morphology of the northern basin. In contrast, the southern basin is affected by volcano-tectonic processes, unveiling a large submerged caldera. Comparison between the orientation of faults throughout the lake with the regional fault pattern indicates that the lake is part of two transfer zones: the major Alayta–Afdera Transfer Zone and the smaller Erta Ale–Tat’Ali Transfer Zone. The interaction between these Transfer Zones and the rift axis forms the equivalent of a developing nodal basin which explains the lake’s position as the deepest point of the depression. This study provides evidence for the development of an incipient transform fault on the floor of the Afar depression.

scholarly journals The abyssal giant pockmarks of the Black Bahama Escarpment: Relations between structures, fluids and carbonate physiography

2020 ◽  
Author(s):  
Thibault Cavailhes ◽  
Hervé Gillet ◽  
Léa Guiastrennec-Faugas ◽  
Thierry Mulder ◽  
Vincent Hanquiez
Keyword(s):  
Carbonate Platform ◽  
Free Edge ◽  
High Amplitude ◽  
Abyssal Plain ◽  
Tectonic Structures ◽  
Fine Grained ◽  
San Salvador ◽  
Bathymetric Data ◽  
Collapse Structures ◽  
And Control

Abstract. This study reports the discovery of spectacular abyssal giant pockmarks located at the toe of the Bahamian carbonate platform, along the Black Bahama structurally-controlled Escarpment (BBE) that exhibits up to 4 km of submarine elevation above the San Salvador Abyssal Plain (SSAP). Analysis of seismic reflection and bathymetric data collected during the CARAMBAR 2 cruise revealed the presence of 29 pockmarks; their water depths range from −4584 m to −4967 m whereas their bathymetric depressions are elliptical in shape, range in diameter from 255 m to 1819 m, and in depth from 30 m to 185 m. The pockmarks alignment trends parallel to the BBE as well as the structural lineaments of the area, exclusively between 2200 and 5000 m from its toe, and overlies a buried carbonate bench in which a high-amplitude seismic anomaly has been detected. The pockmark density interestingly increases where the recognized structural lineaments intersect the BBE. The aforementioned observations suggest an atypical relationship between the spatial occurrence of the abyssal fluid releases, the carbonate platform tectonic structures, the buried carbonate bench that underlies the hemipelagites in the San Salvador abyssal plain and the physiography of the area. Indeed, the ground water entrance during low-level stands, the dissolution of evaporites by meteoric water, the platform-scale thermal convection and the seawater entrance at the platform edge most probably act in concert to favor the circulation of brines and therefore the corrosion within the Bahamian carbonate platform. These mechanisms are particularly efficient along the structural heterogeneities (i.e. faults and fractures) which act as fluid conduits and control the physiography of the area by maintaining the location of the sedimentary pathways. The dense fluids migrate along the faults towards the BBE free edge and are subsequently trapped into the buried carbonate bench that laterally disappears below the low-permeability deep-sea hemipelagics of the SSAP. In consequence, the trapped corrosive fluids dissolve the carbonates preferentially along the tectonic structures such as the Samana Fracture Zone, at the origin of the BBE curvature and triggers collapse-structures in the overlying fine-grained deposits generating giant pockmarks. This structurally-directed process of dissolution is believed to have played a major role in the BBE 5–6 km erosional retreat and also probably explains the occurrence of plunge pools in the area.

scholarly journals The Morphotectono-Volcanic of Menoreh-Gajah-Ijo Volcanic Rock In Western Side of Yogyakarta-Indonesia

2018 ◽  
Vol 3 (3) ◽  
pp. 155
Author(s):  
Asmoro Widagdo ◽  
Subagyo Pramumijoyo ◽  
Agung Harijoko
Keyword(s):  
Volcanic Rocks ◽  
Normal Fault ◽  
Normal Faults ◽  
Body Distribution ◽  
Circular Structure ◽  
Volcanic Processes ◽  
Fault Structures ◽  
Western Side ◽  
Slope Direction ◽  
Volcanic Body

Menoreh-Gajah-Ijo have a very distinctive shape, where there are form of circular structure of volcano that is still intact and the other has not been intact. These morphologies are the morphology of the remaining volcanoes formed by tectonics and certain volcanisms. This study was conducted through a series of interpretations of volcanic body distribution, constructing a Slope Map, constructing a Slope Direction Map, constructing an alignment interpretation on satellite imagery and field mapping work. The formation of Menoreh-Gajah-Ijo morphologies are strongly influenced by tectonics and volcanic processes. The process of tectonism that produces the strike-slip fault structures, the normal faults, and the uplift have formed the lineaments of the valleys and hills with various directions patterns. The Menoreh-Gajah-Ijo volcanisms that have occurred form the structure of volcanic remains. Distribution of Menoreh-Gajah-Ijo volcanic rocks form some semicircle structures because of the normal fault structure that has occurred.

scholarly journals The structure of south Renland, Scoresby Sund. With special reference to the tectono-metamorphic evolution of a southern internal part of the Caledonides of East Greenland

1975 ◽  
Vol 112 ◽  
pp. 1-67
Author(s):  
B Chadwick
Keyword(s):  
Granulite Facies ◽  
Normal Faults ◽  
Mobile Belt ◽  
Minimum Thickness ◽  
East Greenland ◽  
North West ◽  
The North ◽  
South West ◽  
Igneous Activity ◽  
Group Form

Renland occupies an internal position within the southern extreme of the outcrop of the Caledonian mobile belt of East Greenland exposed between latitudes 70° and 82° N. In south-west Renland migmatised paragneisses derived from sediments comparable to the late Precambrian Lower Eleonore Bay Group form a multilayered sequence with a minimum thickness of 1500 m. The migmatites are interleaved with thick concordant sheets of garnetiferous augen granite, the formation of which may be linked with the low-pressure granulite or transitional amphibolite-granulite facies conditions attained during migmatisation of the paragneisses. These conditions persisted during the folding together of paragneisses and granites into regional structures of nappe dimensions which had a north or north-west direction of transport. Refolding of the nappes under continued high-grade conditions gave rise to structures locally coaxial with nappe axes. Reversals of facing of nappes occur in backfolds. Linear fabrics of sillimanite and biotite and prolate ellipsoidal augen of feldspar are parallel to fold axes and show that constrictional deformation dominated the later stages of the nappe phase and the refolding event. The constriction is attributed to compressing of rocks in south-west Renland between nappes advancing from the south and a rising mass of granite and basement gneisses in the north. Intrusion of concordant sheets of biotite-rich hypersthene monzonite (mangerite) followed the nappe deformation in south-east Renland. The principal sheet, which is 500 m thick, forms the rim to part of a lopolithic basin. Thinner sheets of monzonite injected into migmatites within the basin have been disrupted by further migmatisation and granitisation. Stable assemblages in pyribolite restite suggest this later event, which was restricted largely to the basin, attained conditions of hornblende-granulite facies. Open warps attributed to monzonite injection and the basin formation are superimposed on nappes west of the principal sheet. Normal faults with downthrow to east and west relate to the formation of troughs filled with Upper Palaeozoic and Mesozoic sediments in the Scoresby Sund region. The distribution of the faults suggests Renland was a horst area in Upper Palaeozoic times. Tertiary igneous activity in south Renland is represented by rare dykes of olivine dolerite and scattered plugs of pyroxenite which locally contain large blocks of host gneisses.

THE GULF OF CARPENTARIA—A NEW BASIN AND NEW EXPLORATION TARGETS

1993 ◽  
Vol 33 (1) ◽  
pp. 297
Author(s):  
V. L. Passmore ◽  
P. E. Williamson ◽  
T. U Mating ◽  
A.R.G. Gray
Keyword(s):  
Shallow Water ◽  
Sedimentary Rocks ◽  
High Amplitude ◽  
Source Rocks ◽  
Petroleum Potential ◽  
Basin Floor ◽  
International Boundary ◽  
Fault Structures ◽  
The One ◽  
Sag Basin

The sparsely explored Gulf of Carpentaria is a shallow water frontier area of stacked basins. The petroleum potential was not tested by the one offshore well drilled in the Gulf in 1984.Recent re-interpretation of offshore seismic in Queensland waters delineated the Bamaga Basin, a new infrabasin below the Carpentaria Basin. This new basin is a northerly trending asymmetrical sag basin that continues north of the international boundary. The Bamaga Basin, containing up to 1.8 seconds of gently folded and faulted sediments, is untested and offers a new exploration objective. Apparent high velocities make the age of the basin uncertain, but Paleozoic reservoir and source rocks, similar to sedimentary rocks in nearby basins, are inferred, although analogue basins are not readily identifiable.Bamaga Basin source rock burial is sufficient to generate hydrocarbons and could source reservoirs in the Bamaga and Carpentaria Basins via migration along faults. Possible direct hydrocarbon indicators increase support for the presence of hydrocarbons in the Gulf.Structural and stratigraphic plays in the Carpentaria Basin that provide new exploration targets include: basal sandstones onlapping areas of higher relief or filling basin floor depressions, sandstone layers within the Wallumbilla Formation draping highs and possible carbonate zones appearing as high amplitude chaotic reflectors. Within the Bamaga Basin, horst, fault structures and anticlinal features are potential structural plays, and termination of units against the main unconformity are possible stratigraphic play targets.

Mechanism of Gravity-Driven Deformation Using Sandbox Modeling: A Case Study of The Tarakan Sub-Basin, East Kalimantan

2021 ◽  
Author(s):  
B. Sapiie
Keyword(s):  
Normal Faults ◽  
Additional Information ◽  
Bathymetric Data ◽  
East Kalimantan ◽  
Tectonic Reconstruction ◽  
Gravity Driven ◽  
Sandbox Modeling ◽  
Seismic Sections ◽  
Integrated Study

Based on the observations of subsurface and bathymetric maps, various structural patterns are observed in the Tarakan Basin, especially in the Tarakan and Tidung Sub-basins. One of the hypotheses put forward in this study that the gravity-driven mechanism is responsible to generate the normal faults system and folds -thrust belt in the offshore Tarakan Basin. We conducted an integrated study using palinspatic reconstructions of several seismic sections and an analogue-sandbox modeling to observe and explain this gravity-driven. The deformation modeling, which is controlled by gravity requires special conditions that can trigger the movement. The three main parameters that cause gravity deformation to occur are lithology, loading, and slope. In the case of the Tarakan Basin, modeling was carried out by referring to the results of 2D-seismic palinspatic reconstructions. Besides, the additional information as a basis for modeling is also based on the current topographic and bathymetric data. The tectonic reconstruction is used as a reference for paleo-stress data. In theory, one of the factors determining the occurrence of this mechanism is the presence of detachment. This detachment manifests the over-pressure fluid anomaly in the rock, such as over-pressure shale and salt layers. To simulate the conditions that may closely be like the behavior in this detachment, bead materials were selected in the sandbox modeling. Twenty-two experiments were conducted to test the bead as the materials in this modeling, and more than thirty experiments were carried out to model this case. From more than ten realizations, the model with the closest results to seismic interpretation and palinspastic analyses were chosen. From the results of experiments that have been conducted, the development of thrust faults related to the development of normal faults. This evidence is in line with the deformation of gravity-driven mechanism.

Geohazard assessment of submarine salt-related thin-skinned faults: Levant Basin, offshore Israel

2020 ◽  
Author(s):  
May Laor ◽  
Zohar Gvirtzman
Keyword(s):  
High Resolution ◽  
Continental Slope ◽  
Active Faults ◽  
Normal Faults ◽  
3D Mapping ◽  
3D Seismic ◽  
Offshore Area ◽  
Bathymetric Data ◽  
Geohazard Assessment ◽  
Better Than

<p>The Israeli continental slope is dissected by numerous thin-skinned normal faults, deforming the Pliocene-Quaternary section. This extensional faulting is caused by subsurface deformation of the Messinian salt underlying Pliocene rocks. It began in the early Gelasian, at 2.6 Ma, and it is still active today, as indicated by the ruptured seabed. High-resolution bathymetric data reveal shore-parallel seabed steps reaching heights of a few tens of meters. Considering that since the beginning of faulting the average sedimentation rate (100-400 m/My) exceeds the displacement rate (50-100 m/My), the presence of numerous unburied fault scarps indicates seismic ruptures rather than slow creep. For example, considering recent sedimentation rates as measured in seabed cores (5 cm/ka = 50 m/My), if an earthquake produces a 5-m-high fault scarp, it would take about 100 ky to bury it. These preliminary considerations highlight the importance of hazard assessment for seabed infrastructures.</p><p>The recent development of gas fields offshore Israel, as well as the increasing number of planned infrastructures on the seafloor requires a risk assessment, geohazard management, and particularly accurate mapping of faults. Unlike onshore geohazard management, there is no statutory fault map for offshore Israel. Moreover, 'active' and 'potentially active' faults in the offshore area are still not defined. The purpose of this study is to prepare a fault map and discuss criteria for defining the level of fault activity in the marine environment. To accomplish this goal, we use high-resolution bathymetric data and 3D seismic surveys, allowing 3D mapping of faults much better than usually possible onshore.</p><p>For bathymetry, we developed an algorithm, which automatically calculates the height of fault scars along predefined segments. Results indicate higher faults scarps in the north, consistent with extension measurement and steepness of the continental slope that also increases northward. A 3D mapping of fault planes shows that (1) many small faults at the seabed are actually segments of a major fault. This allows reducing the total number of faults to a few large ones. (2) A significant fault can be hidden below the surface with no bathymetric expression. (3) The structure of a seismic reflector dated to 350 ka emphasizes areas with greater recent activity much better than the best available bathymetric data. This allows a quick way to focus on hazardous areas. The next stage of the research will be to measure the area of fault planes and calculate potential earthquake magnitudes. Altogether, we point out the advantage of 3D seismic mapping for geohazard assessment.</p>

scholarly journals Paleoseismic patterns of Quaternary tectonic and magmatic surface deformation in the eastern Basin and Range, USA

Geosphere ◽  
2019 ◽  
Vol 16 (1) ◽  
pp. 435-455
Author(s):  
T.A. Stahl ◽  
N.A. Niemi ◽  
M.P. Bunds ◽  
J. Andreini ◽  
J.D. Wells
Keyword(s):  
Surface Deformation ◽  
Basin And Range ◽  
Normal Faults ◽  
Structural Development ◽  
Quaternary Volcanism ◽  
Continental Extension ◽  
Exposure Dating ◽  
Late Pleistocene To Holocene ◽  
Sevier Desert

Abstract The competing contributions of tectonic and magmatic processes in accommodating continental extension are commonly obscured by a lack of on-fault paleoseismic information. This is especially true of the Sevier Desert, located at the eastern margin of the Basin and Range in central Utah (USA), where surface-rupturing faults are spatially associated with both regional detachment faults and Quaternary volcanism. Here, we use high-resolution topographic surveys (terrestrial lidar scans and real-time kinematic GPS), terrestrial cosmogenic nuclide (10Be and 3He) exposure dating, 40Ar/39Ar geochronology, and new neotectonic mapping to distinguish between modes of faulting and extension in a transect across the Sevier Desert. In the western Sevier Desert, the House Range and Cricket Mountains faults each have evidence of a single surface-rupturing earthquake in the last 20–30 k.y. and have time-integrated slip and extension rates of <0.1 and ∼0.05 mm yr−1, respectively, since ca. 15–30 ka. These rates are similar to near-negligible modern geodetic extension estimates. Despite relatively low geologic, paleoseismic, and modern extension rates, both faults show evidence of contributing to the long-term growth of topographic relief and the structural development of the region. In the eastern Sevier Desert, the intrabasin Tabernacle, Pavant, and Deseret fault systems show markedly different surface expressions and behavior from the range-bounding normal faults farther west. Pleistocene to Holocene extension rates on faults in the eastern Sevier Desert are >10× higher than those on their western counterparts. Faults here are co-located with Late Pleistocene to Holocene volcanic centers, have events temporally clustered around the timing of Pleistocene volcanism in at least one instance, and have accommodated extension ∼2×–10× above geodetic and long-term geologic rates. We propose a model whereby Pliocene to recent extension in the Sevier Desert is spatially partitioned into an eastern magma-assisted rifting domain, characterized by transient episodes of higher extension rates during volcanism, and a western tectonic-dominated domain, characterized by slower-paced faulting in the Cricket Mountains and House Range and more typical of the “Basin and Range style” that continues westward into Nevada. The Sevier Desert, with near-complete exposure and the opportunity to utilize a range of geophysical instrumentation, provides a globally significant laboratory for understanding the different modes of faulting in regions of continental extension.

scholarly journals Thick- and thin-skinned basin inversion in the Danish Central Graben, North Sea – the role of deep evaporites and basement kinematics

2020 ◽  
Author(s):  
Torsten Hundebøl Hansen ◽  
Ole Rønø Clausen ◽  
Katrine Juul Andresen
Keyword(s):  
North Sea ◽  
Ductile Deformation ◽  
Normal Faults ◽  
Rift System ◽  
Structural Development ◽  
Basin Inversion ◽  
Structural Style ◽  
Basement Faults ◽  
Half Graben ◽  
Strong Control

Abstract. Using 3D reflection-seismic data constrained by wells, we address the kinematic connections between Permian Zechstein evaporites, basin-inversion structures in the sedimentary units above, and reactivated structures in the sub-salt basement in the Danish Central Graben. The Danish Central Graben is part of the failed North Sea rift system. Where present, mobile Zechstein evaporites have played a significant role in its structural development since the Triassic, while tectonic shortening caused mild inversion in the Late Cretaceous and Paleogene. Shortening was accommodated mainly by reverse reactivation of older normal faults (i.e. fault inversion) along with folding and uplift of their hangingwalls. Within the study area, rifting generated two major W-SW-dipping basement faults with several kilometres of normal offset. The larger Coffee Soil Fault delineate the eastern boundary of the rift basins. Within its hangingwall, a broad zone is characterised by inversion-related uplift and deformation. Along the fault, buttressed growth folds in the immediate hangingwall indicate thick-skinned inversion, i.e. coupled deformation between the basement and cover units. The opposite margin of the inverted zones follows the westwards pinch-out of the Zechstein salt. Here, thin-skinned folds and faults sole out into Zechstein units on the half-graben dip slopes. The most pronounced inversion occurred directly above and in extension of salt ridges and –rollers that localized shortening in the cover above. With no apparent links to underlying basement faults, we balance thin-skinned shortening to the sub-salt basement via a triangle-zone concept. This implies that thin Zechstein units on the half-graben dip slopes formed thrust detachments during inversion, and that basement shortening was mainly accommodated by reactivation of the major rift faults further east. Ductile deformation at seismic scales accounts for thin-skinned shortening of the cover units where such a detachment did not develop. We discuss the related mechanisms. The documented structural styles are similar to those found in other inverted basins in the region, and to those produced from physical-model experiments. Our results indicate that Zechstein units imposed a strong control on structural style and kinematics during basin inversion in large parts of the Danish Central Graben. We emphasize that even thin evaporite units may act as detachments during tectonic extension and contraction if favourably orientated. Salt ridges and diapiric structures can localise shortening and generate thin-skinned faults and folds in the cover above. In mildly inverted rifts, extensive mobile salt may mask the effects of basin inversion if shortening is accommodated by salt structures without the formation of clearly defined inversion structures at the surface or significant uplift.

Post Jurassic shortening in the western Surat Basin relative to underlying basement depth and faulting

2016 ◽  
Vol 56 (2) ◽  
pp. 597 ◽  
Author(s):  
Abbas Babaahmadi ◽  
Renate Sliwa ◽  
Joan Esterle
Keyword(s):  
Gravity Data ◽  
High Amplitude ◽  
Late Triassic ◽  
Normal Faults ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Jurassic Rock ◽  
Basement Depth ◽  
Seismic Lines ◽  
Early Late

The Hutton-Wallumbilla (HWF), Merivale (MF), Kia Ora, and Injune faults are the major structures in the western Surat Basin, deforming Palaeozoic to Jurassic rock units. The authors present results from the interpretation of gridded gravity data and open-file seismic reflection data, which provide constraints on the geometry and kinematics of these faults. The interpretation of gravity data indicates that the HWF and MF are expressed by sharp lineaments in moderate to high-amplitude anomalies, indicating a deep-seated nature of the faults. The interpretation of seismic lines shows that the HWF and MF are northeast-dipping and east-dipping reverse blind faults, respectively. Some other faults also displaced and folded the rock units of the Bowen and Surat basins, such as the Kia Ora and Injune faults. The MF, Kia Ora, and the northern part of the HWF acted as normal faults during the early Permian and then have been inverted during the Late Permian–Triassic Hunter-Bowen Orogeny phases, especially during the early Late Triassic. The largest fault throws in the Bowen Basin successions are observed along the southern part of the HWF and its central splay, which are around 350 m and 480 m, respectively. The stratigraphic units of the Surat Basin above it have gently been folded over the major blind faults. The largest amount of shortening in the Surat Basin has taken place over the southern part of the HWF by 0.5%. The basement depth played an important role in the amount of contractional deformation in the Bowen and Surat basins. Where the basement is shallow, the amount of deformation along the faults in both the Bowen and Surat basins is higher.

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