scholarly journals Tectonic Influence on Speleogenesis of Sea Caves on Biševo Island (UNESCO Global Geopark Vis Archipelago, Adriatic Sea, Croatia)

Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 341
Author(s):  
Ivan Mišur ◽  
Marko Budić ◽  
Tomislav Kurečić ◽  
Tvrtko Korbar
Keyword(s):  
Host Rock ◽  
Adriatic Sea ◽  
Strike Slip ◽  
Main Channel ◽  
Fault System ◽  
Quaternary Sediments ◽  
Tidal Zone ◽  
Tectonic Regime ◽  
Side Channels ◽  
Host Rocks

A geological and speleological investigation was conducted in the famous Blue Cave (Modra špilja) and the Monk Seal Cave (Medvidina špilja) on Biševo Island (Croatia) to promote the island’s geoheritage through the new Visitor Centre. The island is mainly composed of Cretaceous to Paleogene neritic carbonates, which form the bedrock, whereas parts of the island are covered with thin Quaternary sediments. The caves are of small dimensions and a simple layout, composed of the main channel and few shorter side channels, all positioned in the tidal zone. Thus, the caves are semi-submerged sea caves located along the coastline. The Blue Cave and the Monk Seal Cave developed within the bedrock limestones and dolostones, respectively, within a zone of left-lateral NNE–SSW striking strike-slip faults that belong to the Biševo fault system. Conjugated discontinuities within the carbonate bedrock indicate a specific strike-slip tectonic regime. Additionally, the host rocks were probably also deformed and fractured during the rise of salt diapirs that characterise this part of the Adriatic foreland. Tectonic and bedding discontinuities form the fragments of the host rock, that combined with the impacts of the strong southern waves, significantly influenced the genesis of the caves.

The Miocene plutonic event of the Patagonian Batholith at 44° 30′ S: thermochronological and geobarometric evidence for melting of a rapidly exhumed lower crust

2000 ◽  
Vol 91 (1-2) ◽  
pp. 169-179 ◽  
Author(s):  
M. A. Parada ◽  
A. Lahsen ◽  
C. Palacios
Keyword(s):  
Late Miocene ◽  
Lower Crust ◽  
Fission Track ◽  
Strike Slip ◽  
Fault System ◽  
Apatite Fission Track ◽  
Axial Zone ◽  
Exhumation Rates ◽  
Fission Track Ages ◽  
Host Rocks

The Patagonian Batholith was formed by numerous plutonic events that took place between the Jurassic and the Miocene. North of 47° S, the youngest plutons occupy the axial zone adjacent to the Liquiñe-Ofqui Fault Zone, which is a major intra-arc strike-slip fault system active since the Miocene. The Queulat Complex, located at 44° 30′ S, includes two Miocene plutonic units: the Early Miocene Queulat diorite (QD) and the Late Miocene Puerto Cisnes granite (PCG). The QD includes hornblende + clinopyroxene diorites and tonalites, whereas the PCG includes slightly peraluminous garnet ± sillimanite granites and granodiorites.Eleven mineral Ar–Ar ages and three apatite fission track ages were obtained from the Queulat Complex and surrounding host rocks. Hornblende and biotite Ar–Ar ages of c. 16-18 Ma and 9-10 Ma, respectively, were obtained for the QD. The youngest ages of the QD are similar to the age of emplacement of the PCG as previously determined. Ar–Ar ages for muscovites and biotites of 6·6 ± 0·3 Ma and 5·6 ± 0·1 Ma, respectively, were obtained for the PCG. Biotites and muscovites from mylonites and pelitic hornfelses adjacent to the PCG yielded Ar—Ar ages between 5·1 Ma and 5·5 Ma. The apatite fission track ages of the QD and PCG overlap within the error margin (2•2 ± 1·1-3·3 ± 1·4 Ma).The Al-in-hornblende geobarometer yielded pressures for the QD emplacement equivalent to depths in the 19-24 km range, which is substantially higher than the 10 km depth estimated previously for the PCG emplacement. Exhumation rates (v) up to 2·0mm/yr were calculated for the time elapsed between the QD and PCG emplacements. A v value of 1·0mm/yr was calculated for the PCG subsequent to its emplacement. Using the silica—Ca-tschermak-anorthite geobarometer, we estimate the QD magma generation to be at c. 33 km, which is similar to the current crustal thickness. Melting of mafic and metapelitic lower crust was possible at > 30km depth during a period when v was between 1·0mm/yr and 2·0mm/yr.

scholarly journals Magma Mixing Genesis of the Mafic Enclaves in the Qingshanbao Complex of Longshou Mountain, China: Evidence from Petrology, Geochemistry, and Zircon Chronology

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 195 ◽  
Author(s):  
Wenheng Liu ◽  
Xiaodong Liu ◽  
Jiayong Pan ◽  
Kaixing Wang ◽  
Gang Wang ◽  
...  
Keyword(s):  
Host Rock ◽  
Inductively Coupled Plasma ◽  
Magma Mixing ◽  
Coarse Grained ◽  
Calc Alkaline ◽  
Quartz Crystals ◽  
Alkaline Rocks ◽  
Mafic Enclaves ◽  
Normal Zoning ◽  
Host Rocks

The Qingshanbao complex, part of the uranium metallogenic belt of the Longshou-Qilian mountains, is located in the center of the Longshou Mountain next to the Jiling complex that hosts a number of U deposits. However, little research has been conducted in this area. In order to investigate the origin and formation of mafic enclaves observed in the Qingshanbao body and the implications for magmatic-tectonic dynamics, we systematically studied the mineralogy, petrography, and geochemistry of these enclaves. Our results showed that the enclaves contain plagioclase enwrapped by early dark minerals. These enclaves also showed round quartz crystals and acicular apatite in association with the plagioclase. Electron probe analyses showed that the plagioclase in the host rocks (such as K-feldspar granite, adamellite, granodiorite, etc.) show normal zoning, while the plagioclase in the mafic enclaves has a discontinuous rim composition and shows instances of reverse zoning. Major elemental geochemistry revealed that the mafic enclaves belong to the calc-alkaline rocks that are rich in titanium, iron, aluminum, and depleted in silica, while the host rocks are calc-alkaline to alkaline rocks with enrichment in silica. On Harker diagrams, SiO2 contents are negatively correlated with all major oxides but K2O. Both the mafic enclaves and host rock are rich in large ion lithophile elements such as Rb and K, as well as elements such as La, Nd, and Sm, and relatively poor in high field strength elements such as Nb, Ta, P, Ti, and U. Element ratios of Nb/La, Rb/Sr, and Nb/Ta indicate that the mafic enclaves were formed by the mixing of mafic and felsic magma. In terms of rare earth elements, both the mafic enclaves and the host rock show right-inclined trends with similar weak to medium degrees of negative Eu anomaly and with no obvious Ce anomaly. Zircon LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry) U-Pb concordant ages of the mafic enclaves and host rock were determined to be 431.8 5.2 Ma (MSWD (mean standard weighted deviation)= 1.5, n = 14) and 432.8 4.2 Ma (MSWD = 1.7, n = 16), respectively, consistent with that for the zircon U-Pb ages of the granite and medium-coarse grained K-feldspar granites of the Qingshanbao complex. The estimated ages coincide with the timing of the late Caledonian collision of the Alashan Block. This comprehensive analysis allowed us to conclude that the mafic enclaves in the Qingshanbao complex were formed by the mixing of crust-mantle magma with mantle-derived magma due to underplating, which caused partial melting of the ancient basement crust during the collisional orogenesis between the Alashan Block and Qilian rock mass in the early Silurian Period.

Is the North Altyn fault part of a strike-slip duplex along the Altyn Tagh fault system?

Geology ◽  
2000 ◽  
Vol 28 (3) ◽  
pp. 255 ◽  
Author(s):  
Eric Cowgill ◽  
An Yin ◽  
Wang Xiao Feng ◽  
Zhang Qing
Keyword(s):  
Strike Slip ◽  
Fault System ◽  
Altyn Tagh Fault ◽  
The North ◽  
Altyn Tagh

Microearthquake seismicity and tectonics of Coastal Northern California

1970 ◽  
Vol 60 (5) ◽  
pp. 1669-1699 ◽  
Author(s):  
Leonardo Seeber ◽  
Muawia Barazangi ◽  
Ali Nowroozi
Keyword(s):  
High Frequency ◽  
Fault Plane ◽  
San Andreas Fault ◽  
High Gain ◽  
Strike Slip ◽  
Fault System ◽  
Northern California ◽  
Fault Plane Solutions ◽  
Sharp Bend ◽  
San Andreas

Abstract This paper demonstrates that high-gain, high-frequency portable seismographs operated for short intervals can provide unique data on the details of the current tectonic activity in a very small area. Five high-frequency, high-gain seismographs were operated at 25 sites along the coast of northern California during the summer of 1968. Eighty per cent of 160 microearthquakes located in the Cape Mendocino area occurred at depths between 15 and 35 km in a well-defined, horizontal seismic layer. These depths are significantly greater than those reported for other areas along the San Andreas fault system in California. Many of the earthquakes of the Cape Mendocino area occurred in sequences that have approximately the same magnitude versus length of faulting characteristics as other California earthquakes. Consistent first-motion directions are recorded from microearthquakes located within suitably chosen subdivisions of the active area. Composite fault plane solutions indicate that right-lateral movement prevails on strike-slip faults that radiate from Cape Mendocino northwest toward the Gorda basin. This is evidence that the Gorda basin is undergoing internal deformation. Inland, east of Cape Mendocino, a significant component of thrust faulting prevails for all the composite fault plane solutions. Thrusting is predominant in the fault plane solution of the June 26 1968 earthquake located along the Gorda escarpement. In general, the pattern of slip is consistent with a north-south crustal shortening. The Gorda escarpment, the Mattole River Valley, and the 1906 fault break northwest of Shelter Cove define a sharp bend that forms a possible connection between the Mendocino escarpment and the San Andreas fault. The distribution of hypocenters, relative travel times of P waves, and focal mechanisms strongly indicate that the above three features are surface expressions of an important structural boundary. The sharp bend in this boundary, which is concave toward the southwest, would tend to lock the dextral slip along the San Andreas fault and thus cause the regional north-south compression observed at Cape Mendocino. The above conclusions support the hypothesis that dextral strike-slip motion along the San Andreas fault is currently being taken up by slip along the Mendocino escarpment as well as by slip along northwest trending faults in the Gorda basin.

Erosion rates of the New Zealand Southern Alps reflect long-term tectonics and transient climate

2021 ◽  
Author(s):  
Duna Roda-Boluda ◽  
Taylor Schildgen ◽  
Hella Wittmann-Oelze ◽  
Stefanie Tofelde ◽  
Aaron Bufe ◽  
...  
Keyword(s):  
New Zealand ◽  
Strike Slip ◽  
Southern Alps ◽  
Fault System ◽  
Tectonic Deformation ◽  
Seismic Cycle ◽  
Erosion Rates ◽  
Alpine Fault ◽  
Oblique Convergence

<p>The Southern Alps of New Zealand are the expression of the oblique convergence between the Pacific and Australian plates, which move at a relative velocity of nearly 40 mm/yr. This convergence is accommodated by the range-bounding Alpine Fault, with a strike-slip component of ~30-40 mm/yr, and a shortening component normal to the fault of ~8-10 mm/yr. While strike-slip rates seem to be fairly constant along the Alpine Fault, throw rates appear to vary considerably, and whether the locus of maximum exhumation is located near the fault, at the main drainage divide, or part-way between, is still debated. These uncertainties stem from very limited data characterizing vertical deformation rates along and across the Southern Alps. Thermochronology has constrained the Southern Alps exhumation history since the Miocene, but Quaternary exhumation is hard to resolve precisely due to the very high exhumation rates. Likewise, GPS surveys estimate a vertical uplift of ~5 mm/yr, but integrate only over ~10 yr timescales and are restricted to one transect across the range.</p><p>To obtain insights into the Quaternary distribution and rates of exhumation of the western Southern Alps, we use new <sup>10</sup>Be catchment-averaged erosion rates from 20 catchments along the western side of the range. Catchment-averaged erosion rates span an order of magnitude, between ~0.8 and >10 mm/yr, but we find that erosion rates of >10 mm/yr, a value often quoted in the literature as representative for the entire range, are very localized. Moreover, erosion rates decrease sharply north of the intersection with the Marlborough Fault System, suggesting substantial slip partitioning. These <sup>10</sup>Be catchment-averaged erosion rates integrate, on average, over the last ~300 yrs. Considering that the last earthquake on the Alpine Fault was in 1717, these rates are representative of inter-seismic erosion. Lake sedimentation rates and coseismic landslide modelling suggest that long-term (~10<sup>3</sup> yrs) erosion rates over a full seismic cycle could be ~40% greater than our inter-seismic erosion rates. If we assume steady state topography, such a scaling of our <sup>10</sup>Be erosion rate estimates can be used to estimate rock uplift rates in the Southern Alps. Finally, we find that erosion, and hence potentially exhumation, does not seem to be localized at a particular distance from the fault, as some tectonic and provenance studies have suggested. Instead, we find that superimposed on the primary tectonic control, there is an elevation/temperature control on erosion rates, which is probably transient and related to frost-cracking and glacial retreat.</p><p>Our results highlight the potential for <sup>10</sup>Be catchment-averaged erosion rates to provide insights into the magnitude and distribution of tectonic deformation rates, and the limitations that arise from transient erosion controls related to the seismic cycle and climate-modulated surface processes.</p><p> </p><p> </p>

Inversion of regional surface-wave spectra for source parameters of aftershocks from the 1992 Petrolia earthquake sequence

1995 ◽  
Vol 85 (3) ◽  
pp. 705-715
Author(s):  
Mark Andrew Tinker ◽  
Susan L. Beck
Keyword(s):  
Surface Wave ◽  
Focal Mechanism ◽  
Source Parameters ◽  
Strike Slip ◽  
Earthquake Sequence ◽  
Fault System ◽  
Accretionary Wedge ◽  
Wave Spectra ◽  
The North ◽  
Gorda Plate

Abstract Regional distance surface waves are used to study the source parameters for moderate-size aftershocks of the 25 April 1992 Petrolia earthquake sequence. The Cascadia subduction zone had been relatively seismically inactive until the onset of the mainshock (Ms = 7.1). This underthrusting event establishes that the southern end of the North America-Gorda plate boundary is seismogenic. It was followed by two separate and distinct large aftershocks (Ms = 6.6 for both) occurring at 07:41 and 11:41 on 26 April, as well as thousands of other small aftershocks. Many of the aftershocks following the second large aftershock had magnitudes in the range of 4.0 to 5.5. Using intermediate-period surface-wave spectra, we estimate focal mechanisms and depths for one foreshock and six of the larger aftershocks (Md = 4.0 to 5.5). These seven events can be separated into two groups based on temporal, spatial, and principal stress orientation characteristics. Within two days of the mainshock, four aftershocks (Md = 4 to 5) occurred within 4 hr of each other that were located offshore and along the Mendocino fault. These four aftershocks comprise one group. They are shallow, thrust events with northeast-trending P axes. We interpret these aftershocks to represent internal compression within the North American accretionary prism as a result of Gorda plate subduction. The other three events compose the second group. The shallow, strike-slip mechanism determined for the 8 March foreshock (Md = 5.3) may reflect the right-lateral strike-slip motion associated with the interaction between the northern terminus of the San Andreas fault system and the eastern terminus of the Mendocino fault. The 10 May aftershock (Md = 4.1), located on the coast and north of the Mendocino triple junction, has a thrust fault focal mechanism. This event is shallow and probably occurred within the accretionary wedge on an imbricate thrust. A normal fault focal mechanism is obtained for the 5 June aftershock (Md = 4.8), located offshore and just north of the Mendocino fault. This event exhibits a large component of normal motion, representing internal failure within a rebounding accretionary wedge. These two aftershocks and the foreshock have dissimilar locations in space and time, but they do share a north-northwest oriented P axis.

Seismic attribute for characterization and prediction of carbonate faulted karst reservoirs in Tarim Basin, China

2021 ◽  
pp. 1-36
Author(s):  
Zhiwei Xiao ◽  
Li Wang ◽  
Ruizhao Yang ◽  
Dewei Li ◽  
Lingbin Meng
Keyword(s):  
Tarim Basin ◽  
Oil And Gas ◽  
Prediction Method ◽  
Strike Slip ◽  
Fault System ◽  
Bright Spot ◽  
Upper Ordovician ◽  
Reservoir Prediction ◽  
Seismic Attribute ◽  
Gas Field

An ultradeep, faulted karst reservoir of Ordovician carbonate was discovered in the Shunbei area of the Tarim Basin. Fractured-cavity reservoirs buried beneath the large thickness of upper Ordovician mudstone were formed along the fault-karst belts. The hydrocarbon accumulation in these reservoirs is controlled by the fault system, and the oil-gas accumulation was affected by karstification and hydrothermal reformation. Previous studies and 2D modeling revealed that the reservoirs had “bright spot” amplitude responses like “string beads,” and they have developed along the strike-slip faults. However, describing such a complex fault-controlled karst system is still a difficult problem that has not been well addressed. We have sought to instruct the attribute expression of faulted karst reservoirs in the northern part of the Tarim Basin. We applied coherence and fault likelihood (FL) seismic attributes to image faults and fractures zones. We then used a trend analysis method to calculate the residual impedance from the impedance of the acoustic inversion, using the fact that residual impedance has higher lateral resolution in reservoir predictions. Finally, we integrated the coherence, FL, and residual impedance attributes into a new seismic attribute, the “fault-vuggy body,” with a certain fusion coefficient. The fault-vuggy body attribute establishes a connection between faults and karst cavities. This method could help in the characterization and prediction of carbonate faulted karst reservoirs. Available drilling data were used to validate that the fused fault-vuggy body attribute was an effective reservoir prediction method. As the seismic sections and slices along the layer help delineate, the distribution of bright spots and strike-slip faults indicates that the main strike-slip fault zones are the most favorable reservoirs in the Shunbei Oil and Gas Field.

A strike-slip core complex from the Najd fault system, Arabian shield

Terra Nova ◽  
2014 ◽  
Vol 26 (5) ◽  
pp. 387-394 ◽  
Author(s):  
Sven Erik Meyer ◽  
Cees Passchier ◽  
Tamer Abu-Alam ◽  
Kurt Stüwe
Keyword(s):  
Strike Slip ◽  
Fault System ◽  
Arabian Shield ◽  
Core Complex ◽  
Najd Fault System
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