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31.
32.
Development of ground-shaking maps for the Sultanate of Oman 总被引:1,自引:1,他引:0
33.
Turbidites and their association with past earthquakes in the deep Çınarcık Basin of the Marmara Sea
Two gravity cores (CAG-3 and C-15) from the tectonically active, 1,276-m deep Çınarcık Basin of the Marmara Sea each include three sandy turbiditic mud units (1 mm–2 cm thick) with sharp basal contacts. The high benthic foraminifer content of these units suggests that the sediments were transported by turbidity currents from the upper slope region. These units represent the thin edges of turbidites thickening towards the subsiding north-eastern part of the basin, and contain quartz, detrital calcite, intact shells and shell fragments, smectite, pyrite framboids, muscovite, biotite, epidote and garnet. Their clay fractions are more enriched in smectite than those of adjacent layers. AMS 14C ages (957±43 a.d. and 578±31 a.d.) of two upper and middle turbiditic units in core C15 overlap with the historical İstanbul-Thrace (intensity=10) and İstanbul-Kocaeli (intensity=9) earthquakes of 26 October 986 and 15 August 553, respectively. This overlap, together with sedimentological characteristics, strongly suggests that the turbiditic units are related to the tectono-seismic activity of the North Anatolian Fault. The age of the lowest turbiditic unit in core C-3 was found to be 6,573±87 a b.p. (calendar) by AMS 14 C. In terms of chronostratigraphic relationships and lithological composition, the turbiditic units in core CAG-3 cannot be correlated with those in C15. This can be explained by gravity-controlled sedimentation causing wedging out of turbidites towards the edge of the basin. 相似文献
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36.
Mete Çetinkaplan Osman Candan Roland Oberhänsli Masafumi Sudo Bénédicte Cenki-Tok 《Journal of Metamorphic Geology》2020,38(4):379-419
Eclogite and blueschist facies rocks occurring as a tectonic unit between the underlying Menderes Massif (MM) and the overlying Afyon Zone/Lycian Nappes and the Bornova Flysch Zone in western Anatolia represent the eastward continuation of the Cycladic Blueschist Unit (CBU) in Turkey. This high-P unit is attributed to the closure of the Pindos Ocean and consists of (a) a Triassic to Upper Cretaceous coherent series derived from passive continental margin sediments and (b) the tectonically overlying Upper Cretaceous Selçuk mélange with eclogite blocks embedded in a pelitic epidote-blueschist matrix. The coherent series has experienced epidote-blueschist facies metamorphism (490 ± 25°C/11.5 ± 1.5 kbar; 38 km depth). 40Ar/39Ar white mica and 206Pb/238U monazite dating of quartz metaconglomerate from coherent series yielded middle Eocene ages of 44 ± 0.3 and 40.1 ± 3.1 Ma for epidote-blueschist facies metamorphism, respectively. The epidote-blueschist facies metamorphism of the matrix of the Selçuk mélange culminates at 520 ± 15°C/13 ± 1.5 kbar, 43 km depth, and is dated at 57.5 ± 0.3–54.5 ± 0.1 Ma (40Ar/39Ar phengite). Eclogite facies metamorphism of the blocks (570 ± 30°C/18 ± 2 kbar, 60 km depth) is early Eocene and dated at 56.2 ± 1.5 Ma by 206Pb/238U zircon. Eclogites experienced a nearly isothermal retrogression (490 ± 40°C/~6 to 7 kbar) during their incorporation into the Selçuk mélange. The retrograde overprints of the coherent series (410 ± 15°C/7 ± 1.5 kbar from Dilek Peninsula and 485 ± 33°C/~6 to 7 kbar from Selçuk–Tire area) and the Selçuk mélange (510 ± 15°C/6 ± 1 kbar) are dated at 35.8 ± 0.5–34.3 ± 0.1 Ma by 40Ar/39Ar white mica and 31.6 ± 6.6 Ma by 206Pb/238U allanite dating methods, respectively. Regional geological constrains reveal that the contact between the MM and the CBU originally formed a lithosphere-scale transform fault zone. 40Ar/39Ar white mica age from the contact indicates that the CBU and the MM were tectonically juxtaposed under greenschist facies conditions during late Eocene, 35.1 ± 0.3 Ma. 相似文献
37.
The origin of Neogene tectonic rotations in the Galatean volcanic massif, central Anatolia 总被引:1,自引:1,他引:0
A paleomagnetic study was carried out on Neogene volcanic rocks at 30 sites within the Galatean massif (40.4°N, 31.5°E) to
determine possible block rotations due to stress variations. Two phases of rotation could be characterized as the result of
Neogene volcanic activity. We suggest that the first stage of rotation was isolated in Early Middle Miocene calc-alkali rocks,
with a relative counterclockwise rotation of R ± ΔR = −20.2 ± 9.3° with respect to Eurasia. This accommodates the south-westward rotational collapse of the Western Anatolia
peninsula across a pole on the Bitlis suture. In the neotectonic period, on other hand, a relative clockwise rotation of R ± ΔR = 27.3 ± 6.4° with respect to Eurasia is predicted. In contrast to the uniform clockwise rotations, extremely large clockwise
rotations up to 264° are restricted in a narrow zone between two dextral faults. We believe that the second stage rotations
support the idea of individual microblock rotations due to deformation along the North Anatolian Fault zone. 相似文献
38.
Abstract An attempt was made to compensate for the lack of long hydrological time series and the lack of information on maximum streamflow in the Alzette River basin (Luxembourg) via the regionalization of stormflow coefficients. Streamflow data recorded since 1995 with a very dense streamgauge network allowed the determination of maximum stormflow coefficients in 18 sub-basins of the Alzette. The stormflow coefficients were then regionalized via stepwise multiple regression analysis for 83 different sub-basins of the Alzette. Combined with 10-year daily rainfall heights (statistical estimation), this regionalization allowed the spatial variability of storm runoff in the Alzette basin to be mapped, thus providing a view of hazard and risk-producing areas, as well as of risk-exposed areas. In a basin with little historical hydrological information this technique can help identify areas where storm runoff reducing measures should be applied from the outset. 相似文献
39.
The aim of this study was to investigate long-term seasonal trends and decadal change patterns of monthly mean water vapor
pressure (WVP) observation series at 16 meteorological stations scattered point-wisely over the Southeastern Anatolian Project (GAP) area in Turkey, where large-scale soil and water development projects have been put into practice since the 1970s. The record
length of WVP observation series of each station varied between 31- and 41-years between 1962 and 2002. The monthly mean WVP
observation series of each station was rearranged on seasonal basis. Sequential Mann–Kendall trend test, Sen’s slope estimator,
and Spearman’s rank–order correlation tests were employed for detection of likely trends, and Kruskall–Wallis test was used
to detect decadal variations in WVP series of each observation station. A possible area of representation for each meteorological
station was determined by using the Thiessen polygons technique in a geographical information systems media. It was found
that 15 seasonal WVP series have a positive trend covering 97% of the GAP area in the summer season; although one WVP series
has a negative trend direction. However, in the spring season, 33% of the area had a positive trend, and a negative trend
did not appear in any stations. WVP records in the winter season showed an increasing trend over 19% of the GAP area, whereas
a decreasing trend prevailed in 9% of the area. The study results led us to conclude that the substantial increase of WVP
observations in summer season could be attributed to both the shift from rain-fed agriculture to irrigated agriculture being
made increasingly spacious year by year and building large water reservoirs in the GAP located in a semi-arid region. The
results also indirectly suggested that the historical trends in the WVP parameters might be related to global climate change
phenomenon. 相似文献
40.