Late Jurassic to Early Cretaceous red beds of the Phuquoc Formation were sampled at 33 sites from... more Late Jurassic to Early Cretaceous red beds of the Phuquoc Formation were sampled at 33 sites from the Sihanoukville and Koah Kong areas of the Phuquoc-Kampot Som Basin, southwestern Cambodia. Two high-temperature remanent components with unblocking temperature ranging 650 •-670 • C and 670-690 • C were identified. The magnetization direction for the former component (D = 5.2 • , I = 18.5 • with α 95 = 3.1 • in situ) reveals a negative fold test that indicates a post-folding secondary nature. However, the latter component, carried by specular hematite, is recognized as a primary remanent magnetization. A tilt-corrected mean direction of D = 43.4 • , I = 31.9 • (α 95 = 3.6 •) was calculated for the primary component at 11 sites, corresponding to a paleopole of 47.7 • N, 178.9 • E (A 95 = 3.6 •). When compared with the 130 Ma East Asian pole, a southward displacement of 6.0 • ± 3.5 • and a clockwise rotation of 33.1 • ± 4.0 • of the Phuquoc-Kampot Som Basin (as a part of the Indochina Block) with respect to East Asia were estimated. This estimate of the clockwise rotation is ∼15 • larger than that of the Khorat Basin, which we attribute to dextral motion along the Wang Chao Fault since the mid-Oligocene. The comparison of the herein estimated clockwise rotation with the counterclockwise rotation reported from the Da Lat area in Vietnam suggests the occurrence of a differential tectonic rotation in the southern tip of the Indochina Block. During the southward displacement of the Indochina Block, the non-rigid lithosphere under its southern tip moved heterogeneously, while the rigid lithosphere under the Khorat Basin moved homogeneously.
Paleomagnetic samples of Paleocene-Eocene red sandstones were collected at 36 sites from the Jian... more Paleomagnetic samples of Paleocene-Eocene red sandstones were collected at 36 sites from the Jiangdihe-4 and Zhaojiadian formations around the Yongren (26.1jN, 101.7jE) and Dayao areas (25.7jN, 101.3jE). These areas are located in the Chuxiong basin of the Chuan Dian Fragment, southwestern part of the Yangtze block. After stepwise thermal demagnetization, a hightemperature component with unblocking temperature of about 680 jC is isolated from 26 sites. The primary nature of this magnetization is ascertained through positive fold and reversal tests at 95% confidence level. The tilt-corrected mean paleomagnetic directions for the Yongren and Dayao areas are D = 17.2j, I = 26.6j with a 95 = 5.8j and D = 16.5j, I = 31.1j with a 95 = 4.8, respectively. Easterly deflected declinations from this study are consistent with those reported from other areas of the Chuxiong basin, indicating its wide presence in the Cretaceous-Eocene formations of the said basin. Comparison with declination values expected from the Cretaceous-Eocene APWP of Eurasia indicates that the magnitude of clockwise rotation systematically increases toward the southeast within the Chuxiong basin as well as in the Chuan Dian Fragment. This trend of the differential tectonic rotation in the Chuan Dian Fragment is consistent with curvature of the Xianshuihe-Xiojiang fault system. Deformation of the Chuxiong basin can fairly be associated with the formation of eastward bulge in the southern part of the Chuan Dian fragment. During southward displacement, the Chuan Dian Fragment was probably subjected to tectonic stresses as a result interaction with the Yangtze and Indochina blocks, which resulted into east-west extension and north-south shortening.
Abstract A primary remanent magnetization is identified in the Jurassic-Cretaceous red bed sandst... more Abstract A primary remanent magnetization is identified in the Jurassic-Cretaceous red bed sandstones of the Tembeling Group in Peninsular Malaysia. This high-temperature magnetic component is unblocked at 680–690 °C, revealing a clockwise deflected direction of D s = 56.8°, I s = 31.6° (where k s = 8.5, α 95 = 11.3° and N = 22) in stratigraphic coordinates. The primary origin of this component is ascertained by a positive fold test and a geomagnetic polarity reversal in the Kuala Wau section. Secondary remanent magnetizations are identified in the rocks of the Tembeling and Bertangga basins, which indicate a counter-clockwise deflection in the geographic coordinates (D g = 349.1°, I g = 15.3° where k g = 11.8, α 95 = 5.1°, N = 72). The comparison with the expected paleomagnetic directions from the 130 Ma and 40 Ma Eurasian poles indicates two-stages of tectonic movement in the southern Malay Peninsula: (1) a clockwise rotation of 61.1° ± 11.9° accompanied by a 13.3° ± 8.1° southward displacement after the Cretaceous; and (2) a subsequent counter-clockwise rotation of 18.5° ± 5.0° to the present day position. The first stage of rotation is ascribed to tectonic deformation caused by the indentation of India into Asia after 55 Ma, while the second stage is attributed to the collision of the Australian Plate with SE Asia after 30–20 Ma. The present paleomagnetic results from the Jurassic-Cretaceous Tembeling Group thus reveal impacts of both of these collisions on SE Asia in general and on Peninsular Malaysia in particular.
Journal of the Indian Society of Remote Sensing, 2015
ABSTRACT Geological and structural mappings of Tayyib Al-Ism area were carried out using the rock... more ABSTRACT Geological and structural mappings of Tayyib Al-Ism area were carried out using the rocks finite strain data, the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) data and the field based observations. To analyze the finite strain in the studied rocks, the Rf /ϕ and Fry methods are applied to feldspar porphyroclasts and mafic grains from nine metavolcano-sedimentary samples (Hegaf Formation), four diorite-gabbros suite samples (Sawawin Complex), two meta-granite samples (Ifal suite) and five Zuhd alkali granite samples. The obtained data indicate traces of high to moderate level of deformation in the meta-granite and metavolcano-sedimentary rocks. The axial ratios along the XZ section range from 1.70 to 4.80 for the Rf/ϕ method and from 1.50 to 4.50 for the Fry method. A sub-vertical trend of short axes in association with sub-horizontal foliation is also observed. These informations allow us to conclude that a finite strain in the deformed granitic rocks is of the same order of magnitude as in the metavolcano-sedimentary rocks. The contacts between the metavolcano-sedimentary and granitic rocks in Tayyib al Ism area were formed during the granitic intrusions along some of the faults under brittle to semi-ductile deformation conditions. These faults have significantly influenced the geometry and style of rifting in the Red Sea during the Neogene. The finite strain was accumulated in the area during the process of deformation, which superimpose the already existed nappe structure. It indicates that the nappe contacts formed during the accumulation of finite strain. In addition to finite strain analysis, band ratio images (3/1, 5/3, 7/5) and Principal Component Analysis (PCA) technique have been used, which proved effective in mapping geological and structural features of various rock bodies exposed in the study area
Introduction During the past few decades rock magnetic and paleomagnetic techniques have been inc... more Introduction During the past few decades rock magnetic and paleomagnetic techniques have been increasingly used to study magnetic behavior of sedimentary rocks, particularly red beds of various ages. Widespread secondary magnetization in sedimentary rocks has been reported from many parts of the world with migration of hot exotic fluids assumed to be the cause of remagnetization (Turner
Shallow palaeomagnetic inclinations have been frequently reported from the red beds of central an... more Shallow palaeomagnetic inclinations have been frequently reported from the red beds of central and southeast Asia. To trace the origin of this phenomenon, inclination variation in southeast Asia is examined on lithological to locality scale. Lithological aspect of this variation has been studied using the Early Cretaceous Bailong and Cangxi formations of the Bazhong area (32.1 • N, 106.7 • E), the northern Sichuan Basin. Samples from 36 sites, consisting 18 pairs of successive sandstones and mudstones layers, were collected for this purpose from a synclinal structure. Stepwise thermal demagnetization of most samples revealed the presence of stable characteristic remanent magnetization, which is generally unblocked by 680 • C. Positive fold and reversal tests suggest a primary origin for this component, yielding the Early Cretaceous palaeomagnetic direction of declination/inclination = 20.9 • /26.5 • (ks = 37.2, α 95 = 4.4 • , N = 30). 10 pairs of sandstone and mudstone layers show almost identical inclinations (I sandstones = 23.3 • ± 3.7 • and I mudstones = 24.7 • ± 2.4 •), but 27 • shallower than that expected from the Eurasian apparent polar wander paths (APWPs), indicating that no lithological variation in inclination has occurred. Location-wise variation in inclination shallowing is examined through palaeomagnetic data from Late Jurassic to Eocene red beds distributed around southeast Asia. Based on these investigations, no inclination shallowing is observed in the eastern part of the South China Block (SCB), whereas large degree of shallowing is observed in the Sichuan and Xining-Ninhe basins. Variation in inclination shallowing from one sedimentary basin to another could probably be caused by changes in the depositional environment. The eastern part of the SCB, where no inclination shallowing have been observed, is characterized by Basin and Range type tectono-geological setting. In contrast, the foreland basins are bounded to the north by east-west striking high altitude orogenic belt. Swift development of these basins as a result of flexural subsidence is the most likely reason for inclination shallowing.
This study presents microscopic results of 50 samples and 5 in situ magnetic susceptibility profi... more This study presents microscopic results of 50 samples and 5 in situ magnetic susceptibility profiles, field investigations and bedrock characteristics of northern Harrat Rahat Quaternary volcanic rocks, located in the southern part of Al-Madinah city. The petrographic data of volcanic rocks show mainly aphanitic (fine-grained) holocrystalline basaltic units, rich in olivine depicting porphyritic, glomeroporphyritic, ophitic, subophitic, dictytaxitic, seriatic, interstitial, and trachytic textures. Field observations and petrographic studies reveal 9 rock units, from oldest to youngest: olivine basalt, hawaiite, vesicular olivine basalt, alkali olivine basalt, mugearite, benmoreite, scoriaceous basalt, trachytoid basalt and pyroclastic rocks. The magnetic susceptibility data vary from one rock to another based on texture, alteration, grain size, opaque minerals content, and weathering. The Fe-rich and massive basaltic rocks generally reveal higher susceptibility, while basaltic scoria and vesicular, fractured and weathered basaltic rocks generally reveal lower susceptibility. Occurrence of highly mature opaque minerals might suggest an associated sulphide mineralization.
The Early Miocene sandstone of the Burqan Formation from Midyan Basin is considered an oil-bearin... more The Early Miocene sandstone of the Burqan Formation from Midyan Basin is considered an oil-bearing unit. The outcrops of this sandstone, which are exposed in the northwestern part of the basin, have been studied through field and laboratory-based investigations. During the field work, 81 surface samples were collected for reservoir characterization. Laboratory analyses were undertaken to determine the effect of the diagenesis on the reservoir quality using integrated sedimentological, petrological, and petrophysical analyses. According to these analyses, the sandstone of Burqan Formation is predominately subarkosic and sublitharenite in nature, medium to course grained in size, rounded to subangular in shape, and poor to moderately sorted. Porosity of the studied sandstone, which is both syndepositional and diagenetic in origin, has been determined as poor to very high, with an average value of 22.73%. The observed permeability is moderate to very high, with an average estimate of 2444.2 millidarcy. Cementation coupled with compaction had an important effect on the porosity destruction after sedimentation and burial. The reservoir quality of the studied sandstone is reduced by clay minerals (kaolinite and smectite), calcite, and silica cementations, but, on other hand, it is increased by alteration and dissolution of the unstable grains, in addition to partial dissolution of calcite cements. The potential of the studied sandstone to serve as a reservoir is strongly related to sandstone diagenesis.
The stability of a granitic rock cut located within a densely populated residential area in Madin... more The stability of a granitic rock cut located within a densely populated residential area in Madinah, Saudi Arabia, was investigated to avoid rock failure consequences. Based on the field inspection, this cut is characterized by a very irregular face leading to the occurrence of rock sliding and rockfall events in the area. Moreover, this cut lacks any type of stabilization or protection measurements. Kinematic analysis was used to analyze rock sliding events while RocFall software was used to analyze the mechanism of rockfall incidents. The results indicated to the high probability of wedge failures to take place (≈ 67%) as well as the toppling failures but with lower probability (< 10%). Furthermore, it was found that some large loose rock blocks on the cut surface could be easily triggered and fallen down reaching all onto the road and causing loss of life and damages to properties. As a result, this research recommended immediate scaling for loose rocks as well as constructing effective catch ditch in addition to anchoring large intact rocks.
Paleomagnetic samples of Paleocene-Eocene red sandstones were collected at 36 sites from the Jian... more Paleomagnetic samples of Paleocene-Eocene red sandstones were collected at 36 sites from the Jiangdihe-4 and Zhaojiadian formations around the Yongren (26.1jN, 101.7jE) and Dayao areas (25.7jN, 101.3jE). These areas are located in the Chuxiong basin of the Chuan Dian Fragment, southwestern part of the Yangtze block. After stepwise thermal demagnetization, a hightemperature component with unblocking temperature of about 680 jC is isolated from 26 sites. The primary nature of this magnetization is ascertained through positive fold and reversal tests at 95% confidence level. The tilt-corrected mean paleomagnetic directions for the Yongren and Dayao areas are D = 17.2j, I = 26.6j with a 95 = 5.8j and D = 16.5j, I = 31.1j with a 95 = 4.8, respectively. Easterly deflected declinations from this study are consistent with those reported from other areas of the Chuxiong basin, indicating its wide presence in the Cretaceous-Eocene formations of the said basin. Comparison with declination values expected from the Cretaceous-Eocene APWP of Eurasia indicates that the magnitude of clockwise rotation systematically increases toward the southeast within the Chuxiong basin as well as in the Chuan Dian Fragment. This trend of the differential tectonic rotation in the Chuan Dian Fragment is consistent with curvature of the Xianshuihe-Xiojiang fault system. Deformation of the Chuxiong basin can fairly be associated with the formation of eastward bulge in the southern part of the Chuan Dian fragment. During southward displacement, the Chuan Dian Fragment was probably subjected to tectonic stresses as a result interaction with the Yangtze and Indochina blocks, which resulted into east-west extension and north-south shortening.
A research project on the Saudi Gulf of Aqaba was initiated in January 2012 to evaluate, protect,... more A research project on the Saudi Gulf of Aqaba was initiated in January 2012 to evaluate, protect, and develop a proper management plan for sustainable use of water resources in the coastal region. Within the framework of this project, a total of 85 surface water samples was collected and investigated to document the surface distribution of the hydrographical parameters (including water temperature, salinity, density, hydrogen ion concentration, and dissolved oxygen) as well as concentration of the nutrient salts (ammonium, nitrite, nitrate, phosphate, and silicate). The results show no thermocline or thermal pollution in the studied water and that they are mostly well oxygenated. In addition, no significant variations in the pH and salinity values have been observed. Relatively low levels of nitrogen, phosphorus (in the dissolved and total forms), and reactive silicate are observed. Inorganic nitrogen is found in the order of NO 3 -N . NO 2 -N . NH 4 -N. On the basis of the relatively low level of nutrient salts, the Gulf of Aqaba coastal water is classified as oligotrophic to mesotrophic in nature, and the study area is not yet seriously affected by contamination in spite of rapid population growth and fast infrastructural/recreational development during the past decade.
We present palaeomagnetic results from Lower Cretaceous rocks in Bikin area of the Alchan basin (... more We present palaeomagnetic results from Lower Cretaceous rocks in Bikin area of the Alchan basin (46.5 • N, 134.7 • E), Sikhote Alin orogenic belt, Far Eastern Russia. A high-temperature magnetization component with maximum unblocking temperatures at about 590 • C was isolated from six sites of dacite welded tuffs in the Albian Alchanskaya Formation. The fold tests for these six sites are positive, suggesting that primary magnetization is preserved in the studied rocks. The tilt-corrected mean direction of D = 309.3 • , I = 68.7 • (α 95 = 10.1 • ), with a corresponding palaeopole position at 57.0 • N, 76.8 • E (A 95 = 15.1 • ), indicates a counter-clockwise (CCW) rotation for the studied area. CCW rotation is also indicated from west-directed declinations (D = 249.1 • , I = 64.1 • , α 95 = 11.2 • ) obtained from secondary magnetization of the Berriasian Kultukha Formation. Combining with the previously reported studies, the westdirected Cretaceous palaeomagnetic directions cover widely the eastern part of the Mongolia block. Comparison with 100 Ma palaeomagnetic pole for Eurasia shows that the eastern part of the Mongolia block experienced a CCW rotation of over 36 • with respect to the Eurasian continent later than Late Cretaceous. This rotation is ascribed to post-Late Cretaceous extension that affected the continental basins (the Middle Amur, Sanjiang, Razdolnian, Amur-Zeya and Songliao basins) of the northeast Chinese Plain along the eastern margin of the Mongolia block. Contemporaneous with this CCW rotation, similar extension resulted in clockwise rotation of the eastern part of the North China block.
We present paleomagnetic results from Middle Jurassic red sandstones of the Sangba Formation. Ori... more We present paleomagnetic results from Middle Jurassic red sandstones of the Sangba Formation. Orientated samples were collected at 14 sites on north side of the Basu (30.1°N, 96.9°E), northeastern border of the Lhasa Block. After stepwise thermal demagnetization, high-temperature component with unblocking level of 680°C is isolated from 7 sites. Primary nature of this magnetization is ascertained through positive fold and reversal tests at 95% confidence level. Combined with previously reported paleomagnetic results, tilt-corrected mean direction of D =353.4°, I =15.1°, α 95 =14.1°, N = 8 is calculated, indicating that during Middle Jurassic the study area was located at 7.7°N ± 7.4°. Comparison with the Jurassic paleomagnetic data reported from eastern Tibet indicates that the Lhasa Block was located south of the Qiangtang Block at a latitudinal difference of 31 ± 11°. Compilation of paleomagnetic data further suggest that until the Cretaceous large spatial gap of more than 1200 km remained open between the Lhasa Block and the Qiangtang Block of eastern Himalayan syntaxis and eventually vanished during Tertiary. Cretaceous paleolatitude corresponding to this gap (13.0°N-31.0°N) is almost identical to that reported from Shan-Thai Block (25.4°N ± 5.2°). Furthermore, the Permo-Carboniferous sequences of Gondwanic affinity are distributed in western part of the Shan-Thai block as well as in the Lhasa and Qiangtang blocks. Keeping in view these similarities, we propose a new pre-collision (India vs. Asia) reconstruction model in which the Lhasa, Shan-Thai and Qiangtang blocks are shown in their respective order from south to north along southern margin of the Asian continent. The aftermath of gigantic India-Asia collision however introduced north-south compressional regime in the Asian Continent that eventually played a role in eastward extrusion of the Shan-Thai Block from an area between the Qiangtang and Lhasa blocks.
In order to describe features of tectonic deformation in the Indochina Peninsula, Early Jurassic ... more In order to describe features of tectonic deformation in the Indochina Peninsula, Early Jurassic to Early Cretaceous red sandstones were sampled at three localities in the Shan-Thai and Indochina blocks. Stepwise thermal treatment of most samples revealed the presence of characteristic remanent magnetization, which is generally unblocked by 680 • C. This component from Phong Saly (21.6 • N, 101.9 • E) and Borikhanxay (18.5 • N, 103.8 • E) localities yield positive fold tests with Late Jurassic-Early Cretaceous directions of Dec/Inc = 28.8 , respectively. Additionally, a syn-folding mid-Cretaceous characteristic magnetization is observed in the samples of Muang Phin locality (16.5 • N, 106.1 • E), which gave a mean direction of Dec/Inc = 30.8 • /39.9 • , k = 102.6, α 95 = 3.0 • , N = 23. This reliable Late Jurassic to Mid-Cretaceous palaeomagnetic directions from three different localities are incorporated into a palaeomagnetic database for Shan-Thai and Indochina blocks. Based on these compilations, tectonic deformation of the Shan-Thai and Indochina blocks is summarized as follows: (1) the Shan-Thai and Indochina blocks experienced a clockwise rotation of about 10 • as a composite unit in the early stage of India-Asia collision and (2) following this, the Shan-Thai Block underwent an internal tectonic deformation, whereas the Indochina Block behaved as a rigid tectonic unit during the same period. Comparison of our palaeomagnetic results with seismic tomographic images suggests that the strength of continental lithosphere beneath these blocks played an important role in the process of deformation rather than any other tectonic regime. In contrast to the Shan-Thai Block, an existence of continental roots beneath the Indochina Block prevented its internal deformation.
This study presents a newly discovered geomagnetic excursion in the andesitic lava sequence of th... more This study presents a newly discovered geomagnetic excursion in the andesitic lava sequence of the Kamegaoka Mountain (31 • 21'N, 130 • 13'E), Noma Peninsula, Kyushu Island. About 170 oriented samples were collected from 13 consecutive lava flows, covering an area from mountain top to sea shore. Thermal and alternating field demagnetizations of the studied samples generally revealed a univectorial magnetization, however, two components structure with minor viscous overprints is also observed in some samples. Remanent magnetization is generally unblocked between 560 and 590 • C, indicating magnetite as dominant remanence carrier. Reversed polarity directions are detected in the bottom and uppermost parts of the sequence, whereas anomalous directions with positive inclination are observed in the middle part of the sequence. This newly discovered anomalous palaeomagnetic direction, named as Noma excursion (C3Ar-1), has a well-defined K-Ar age of 6.66 ± 0.45 Ma. Comparison with the geomagnetic polarity timescale allow us to place this event within the polarity subchron C3Ar, in which no such cryptochron has been observed before by high resolution ODP study of the sedimentary cores. The virtual geomagnetic poles estimated for the studied lava sequence moved from Antarctica to Kamchatka Peninsula (60 • N), swung back to New Guinea equatorial region and then followed a path to Antarctica again. These poles followed a swath between the 90 • E and 140 • E longitudes, which are almost identical to one of the preferred longitudinal bands for transitional poles at the times of polarity reversals and excursions in the Brunhes and Matuyama chrons. According to this study, this preferred pathway may have started prior to 6.7 Ma. If properly emphasized, identification of Noma excursion in the studied lava flows can facilitate more such discoveries in the Late Miocene.
Late Jurassic to Early Cretaceous red beds of the Phuquoc Formation were sampled at 33 sites from... more Late Jurassic to Early Cretaceous red beds of the Phuquoc Formation were sampled at 33 sites from the Sihanoukville and Koah Kong areas of the Phuquoc-Kampot Som Basin, southwestern Cambodia. Two high-temperature remanent components with unblocking temperature ranging 650 •-670 • C and 670-690 • C were identified. The magnetization direction for the former component (D = 5.2 • , I = 18.5 • with α 95 = 3.1 • in situ) reveals a negative fold test that indicates a post-folding secondary nature. However, the latter component, carried by specular hematite, is recognized as a primary remanent magnetization. A tilt-corrected mean direction of D = 43.4 • , I = 31.9 • (α 95 = 3.6 •) was calculated for the primary component at 11 sites, corresponding to a paleopole of 47.7 • N, 178.9 • E (A 95 = 3.6 •). When compared with the 130 Ma East Asian pole, a southward displacement of 6.0 • ± 3.5 • and a clockwise rotation of 33.1 • ± 4.0 • of the Phuquoc-Kampot Som Basin (as a part of the Indochina Block) with respect to East Asia were estimated. This estimate of the clockwise rotation is ∼15 • larger than that of the Khorat Basin, which we attribute to dextral motion along the Wang Chao Fault since the mid-Oligocene. The comparison of the herein estimated clockwise rotation with the counterclockwise rotation reported from the Da Lat area in Vietnam suggests the occurrence of a differential tectonic rotation in the southern tip of the Indochina Block. During the southward displacement of the Indochina Block, the non-rigid lithosphere under its southern tip moved heterogeneously, while the rigid lithosphere under the Khorat Basin moved homogeneously.
Paleomagnetic samples of Paleocene-Eocene red sandstones were collected at 36 sites from the Jian... more Paleomagnetic samples of Paleocene-Eocene red sandstones were collected at 36 sites from the Jiangdihe-4 and Zhaojiadian formations around the Yongren (26.1jN, 101.7jE) and Dayao areas (25.7jN, 101.3jE). These areas are located in the Chuxiong basin of the Chuan Dian Fragment, southwestern part of the Yangtze block. After stepwise thermal demagnetization, a hightemperature component with unblocking temperature of about 680 jC is isolated from 26 sites. The primary nature of this magnetization is ascertained through positive fold and reversal tests at 95% confidence level. The tilt-corrected mean paleomagnetic directions for the Yongren and Dayao areas are D = 17.2j, I = 26.6j with a 95 = 5.8j and D = 16.5j, I = 31.1j with a 95 = 4.8, respectively. Easterly deflected declinations from this study are consistent with those reported from other areas of the Chuxiong basin, indicating its wide presence in the Cretaceous-Eocene formations of the said basin. Comparison with declination values expected from the Cretaceous-Eocene APWP of Eurasia indicates that the magnitude of clockwise rotation systematically increases toward the southeast within the Chuxiong basin as well as in the Chuan Dian Fragment. This trend of the differential tectonic rotation in the Chuan Dian Fragment is consistent with curvature of the Xianshuihe-Xiojiang fault system. Deformation of the Chuxiong basin can fairly be associated with the formation of eastward bulge in the southern part of the Chuan Dian fragment. During southward displacement, the Chuan Dian Fragment was probably subjected to tectonic stresses as a result interaction with the Yangtze and Indochina blocks, which resulted into east-west extension and north-south shortening.
Abstract A primary remanent magnetization is identified in the Jurassic-Cretaceous red bed sandst... more Abstract A primary remanent magnetization is identified in the Jurassic-Cretaceous red bed sandstones of the Tembeling Group in Peninsular Malaysia. This high-temperature magnetic component is unblocked at 680–690 °C, revealing a clockwise deflected direction of D s = 56.8°, I s = 31.6° (where k s = 8.5, α 95 = 11.3° and N = 22) in stratigraphic coordinates. The primary origin of this component is ascertained by a positive fold test and a geomagnetic polarity reversal in the Kuala Wau section. Secondary remanent magnetizations are identified in the rocks of the Tembeling and Bertangga basins, which indicate a counter-clockwise deflection in the geographic coordinates (D g = 349.1°, I g = 15.3° where k g = 11.8, α 95 = 5.1°, N = 72). The comparison with the expected paleomagnetic directions from the 130 Ma and 40 Ma Eurasian poles indicates two-stages of tectonic movement in the southern Malay Peninsula: (1) a clockwise rotation of 61.1° ± 11.9° accompanied by a 13.3° ± 8.1° southward displacement after the Cretaceous; and (2) a subsequent counter-clockwise rotation of 18.5° ± 5.0° to the present day position. The first stage of rotation is ascribed to tectonic deformation caused by the indentation of India into Asia after 55 Ma, while the second stage is attributed to the collision of the Australian Plate with SE Asia after 30–20 Ma. The present paleomagnetic results from the Jurassic-Cretaceous Tembeling Group thus reveal impacts of both of these collisions on SE Asia in general and on Peninsular Malaysia in particular.
Journal of the Indian Society of Remote Sensing, 2015
ABSTRACT Geological and structural mappings of Tayyib Al-Ism area were carried out using the rock... more ABSTRACT Geological and structural mappings of Tayyib Al-Ism area were carried out using the rocks finite strain data, the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) data and the field based observations. To analyze the finite strain in the studied rocks, the Rf /ϕ and Fry methods are applied to feldspar porphyroclasts and mafic grains from nine metavolcano-sedimentary samples (Hegaf Formation), four diorite-gabbros suite samples (Sawawin Complex), two meta-granite samples (Ifal suite) and five Zuhd alkali granite samples. The obtained data indicate traces of high to moderate level of deformation in the meta-granite and metavolcano-sedimentary rocks. The axial ratios along the XZ section range from 1.70 to 4.80 for the Rf/ϕ method and from 1.50 to 4.50 for the Fry method. A sub-vertical trend of short axes in association with sub-horizontal foliation is also observed. These informations allow us to conclude that a finite strain in the deformed granitic rocks is of the same order of magnitude as in the metavolcano-sedimentary rocks. The contacts between the metavolcano-sedimentary and granitic rocks in Tayyib al Ism area were formed during the granitic intrusions along some of the faults under brittle to semi-ductile deformation conditions. These faults have significantly influenced the geometry and style of rifting in the Red Sea during the Neogene. The finite strain was accumulated in the area during the process of deformation, which superimpose the already existed nappe structure. It indicates that the nappe contacts formed during the accumulation of finite strain. In addition to finite strain analysis, band ratio images (3/1, 5/3, 7/5) and Principal Component Analysis (PCA) technique have been used, which proved effective in mapping geological and structural features of various rock bodies exposed in the study area
Introduction During the past few decades rock magnetic and paleomagnetic techniques have been inc... more Introduction During the past few decades rock magnetic and paleomagnetic techniques have been increasingly used to study magnetic behavior of sedimentary rocks, particularly red beds of various ages. Widespread secondary magnetization in sedimentary rocks has been reported from many parts of the world with migration of hot exotic fluids assumed to be the cause of remagnetization (Turner
Shallow palaeomagnetic inclinations have been frequently reported from the red beds of central an... more Shallow palaeomagnetic inclinations have been frequently reported from the red beds of central and southeast Asia. To trace the origin of this phenomenon, inclination variation in southeast Asia is examined on lithological to locality scale. Lithological aspect of this variation has been studied using the Early Cretaceous Bailong and Cangxi formations of the Bazhong area (32.1 • N, 106.7 • E), the northern Sichuan Basin. Samples from 36 sites, consisting 18 pairs of successive sandstones and mudstones layers, were collected for this purpose from a synclinal structure. Stepwise thermal demagnetization of most samples revealed the presence of stable characteristic remanent magnetization, which is generally unblocked by 680 • C. Positive fold and reversal tests suggest a primary origin for this component, yielding the Early Cretaceous palaeomagnetic direction of declination/inclination = 20.9 • /26.5 • (ks = 37.2, α 95 = 4.4 • , N = 30). 10 pairs of sandstone and mudstone layers show almost identical inclinations (I sandstones = 23.3 • ± 3.7 • and I mudstones = 24.7 • ± 2.4 •), but 27 • shallower than that expected from the Eurasian apparent polar wander paths (APWPs), indicating that no lithological variation in inclination has occurred. Location-wise variation in inclination shallowing is examined through palaeomagnetic data from Late Jurassic to Eocene red beds distributed around southeast Asia. Based on these investigations, no inclination shallowing is observed in the eastern part of the South China Block (SCB), whereas large degree of shallowing is observed in the Sichuan and Xining-Ninhe basins. Variation in inclination shallowing from one sedimentary basin to another could probably be caused by changes in the depositional environment. The eastern part of the SCB, where no inclination shallowing have been observed, is characterized by Basin and Range type tectono-geological setting. In contrast, the foreland basins are bounded to the north by east-west striking high altitude orogenic belt. Swift development of these basins as a result of flexural subsidence is the most likely reason for inclination shallowing.
This study presents microscopic results of 50 samples and 5 in situ magnetic susceptibility profi... more This study presents microscopic results of 50 samples and 5 in situ magnetic susceptibility profiles, field investigations and bedrock characteristics of northern Harrat Rahat Quaternary volcanic rocks, located in the southern part of Al-Madinah city. The petrographic data of volcanic rocks show mainly aphanitic (fine-grained) holocrystalline basaltic units, rich in olivine depicting porphyritic, glomeroporphyritic, ophitic, subophitic, dictytaxitic, seriatic, interstitial, and trachytic textures. Field observations and petrographic studies reveal 9 rock units, from oldest to youngest: olivine basalt, hawaiite, vesicular olivine basalt, alkali olivine basalt, mugearite, benmoreite, scoriaceous basalt, trachytoid basalt and pyroclastic rocks. The magnetic susceptibility data vary from one rock to another based on texture, alteration, grain size, opaque minerals content, and weathering. The Fe-rich and massive basaltic rocks generally reveal higher susceptibility, while basaltic scoria and vesicular, fractured and weathered basaltic rocks generally reveal lower susceptibility. Occurrence of highly mature opaque minerals might suggest an associated sulphide mineralization.
The Early Miocene sandstone of the Burqan Formation from Midyan Basin is considered an oil-bearin... more The Early Miocene sandstone of the Burqan Formation from Midyan Basin is considered an oil-bearing unit. The outcrops of this sandstone, which are exposed in the northwestern part of the basin, have been studied through field and laboratory-based investigations. During the field work, 81 surface samples were collected for reservoir characterization. Laboratory analyses were undertaken to determine the effect of the diagenesis on the reservoir quality using integrated sedimentological, petrological, and petrophysical analyses. According to these analyses, the sandstone of Burqan Formation is predominately subarkosic and sublitharenite in nature, medium to course grained in size, rounded to subangular in shape, and poor to moderately sorted. Porosity of the studied sandstone, which is both syndepositional and diagenetic in origin, has been determined as poor to very high, with an average value of 22.73%. The observed permeability is moderate to very high, with an average estimate of 2444.2 millidarcy. Cementation coupled with compaction had an important effect on the porosity destruction after sedimentation and burial. The reservoir quality of the studied sandstone is reduced by clay minerals (kaolinite and smectite), calcite, and silica cementations, but, on other hand, it is increased by alteration and dissolution of the unstable grains, in addition to partial dissolution of calcite cements. The potential of the studied sandstone to serve as a reservoir is strongly related to sandstone diagenesis.
The stability of a granitic rock cut located within a densely populated residential area in Madin... more The stability of a granitic rock cut located within a densely populated residential area in Madinah, Saudi Arabia, was investigated to avoid rock failure consequences. Based on the field inspection, this cut is characterized by a very irregular face leading to the occurrence of rock sliding and rockfall events in the area. Moreover, this cut lacks any type of stabilization or protection measurements. Kinematic analysis was used to analyze rock sliding events while RocFall software was used to analyze the mechanism of rockfall incidents. The results indicated to the high probability of wedge failures to take place (≈ 67%) as well as the toppling failures but with lower probability (< 10%). Furthermore, it was found that some large loose rock blocks on the cut surface could be easily triggered and fallen down reaching all onto the road and causing loss of life and damages to properties. As a result, this research recommended immediate scaling for loose rocks as well as constructing effective catch ditch in addition to anchoring large intact rocks.
Paleomagnetic samples of Paleocene-Eocene red sandstones were collected at 36 sites from the Jian... more Paleomagnetic samples of Paleocene-Eocene red sandstones were collected at 36 sites from the Jiangdihe-4 and Zhaojiadian formations around the Yongren (26.1jN, 101.7jE) and Dayao areas (25.7jN, 101.3jE). These areas are located in the Chuxiong basin of the Chuan Dian Fragment, southwestern part of the Yangtze block. After stepwise thermal demagnetization, a hightemperature component with unblocking temperature of about 680 jC is isolated from 26 sites. The primary nature of this magnetization is ascertained through positive fold and reversal tests at 95% confidence level. The tilt-corrected mean paleomagnetic directions for the Yongren and Dayao areas are D = 17.2j, I = 26.6j with a 95 = 5.8j and D = 16.5j, I = 31.1j with a 95 = 4.8, respectively. Easterly deflected declinations from this study are consistent with those reported from other areas of the Chuxiong basin, indicating its wide presence in the Cretaceous-Eocene formations of the said basin. Comparison with declination values expected from the Cretaceous-Eocene APWP of Eurasia indicates that the magnitude of clockwise rotation systematically increases toward the southeast within the Chuxiong basin as well as in the Chuan Dian Fragment. This trend of the differential tectonic rotation in the Chuan Dian Fragment is consistent with curvature of the Xianshuihe-Xiojiang fault system. Deformation of the Chuxiong basin can fairly be associated with the formation of eastward bulge in the southern part of the Chuan Dian fragment. During southward displacement, the Chuan Dian Fragment was probably subjected to tectonic stresses as a result interaction with the Yangtze and Indochina blocks, which resulted into east-west extension and north-south shortening.
A research project on the Saudi Gulf of Aqaba was initiated in January 2012 to evaluate, protect,... more A research project on the Saudi Gulf of Aqaba was initiated in January 2012 to evaluate, protect, and develop a proper management plan for sustainable use of water resources in the coastal region. Within the framework of this project, a total of 85 surface water samples was collected and investigated to document the surface distribution of the hydrographical parameters (including water temperature, salinity, density, hydrogen ion concentration, and dissolved oxygen) as well as concentration of the nutrient salts (ammonium, nitrite, nitrate, phosphate, and silicate). The results show no thermocline or thermal pollution in the studied water and that they are mostly well oxygenated. In addition, no significant variations in the pH and salinity values have been observed. Relatively low levels of nitrogen, phosphorus (in the dissolved and total forms), and reactive silicate are observed. Inorganic nitrogen is found in the order of NO 3 -N . NO 2 -N . NH 4 -N. On the basis of the relatively low level of nutrient salts, the Gulf of Aqaba coastal water is classified as oligotrophic to mesotrophic in nature, and the study area is not yet seriously affected by contamination in spite of rapid population growth and fast infrastructural/recreational development during the past decade.
We present palaeomagnetic results from Lower Cretaceous rocks in Bikin area of the Alchan basin (... more We present palaeomagnetic results from Lower Cretaceous rocks in Bikin area of the Alchan basin (46.5 • N, 134.7 • E), Sikhote Alin orogenic belt, Far Eastern Russia. A high-temperature magnetization component with maximum unblocking temperatures at about 590 • C was isolated from six sites of dacite welded tuffs in the Albian Alchanskaya Formation. The fold tests for these six sites are positive, suggesting that primary magnetization is preserved in the studied rocks. The tilt-corrected mean direction of D = 309.3 • , I = 68.7 • (α 95 = 10.1 • ), with a corresponding palaeopole position at 57.0 • N, 76.8 • E (A 95 = 15.1 • ), indicates a counter-clockwise (CCW) rotation for the studied area. CCW rotation is also indicated from west-directed declinations (D = 249.1 • , I = 64.1 • , α 95 = 11.2 • ) obtained from secondary magnetization of the Berriasian Kultukha Formation. Combining with the previously reported studies, the westdirected Cretaceous palaeomagnetic directions cover widely the eastern part of the Mongolia block. Comparison with 100 Ma palaeomagnetic pole for Eurasia shows that the eastern part of the Mongolia block experienced a CCW rotation of over 36 • with respect to the Eurasian continent later than Late Cretaceous. This rotation is ascribed to post-Late Cretaceous extension that affected the continental basins (the Middle Amur, Sanjiang, Razdolnian, Amur-Zeya and Songliao basins) of the northeast Chinese Plain along the eastern margin of the Mongolia block. Contemporaneous with this CCW rotation, similar extension resulted in clockwise rotation of the eastern part of the North China block.
We present paleomagnetic results from Middle Jurassic red sandstones of the Sangba Formation. Ori... more We present paleomagnetic results from Middle Jurassic red sandstones of the Sangba Formation. Orientated samples were collected at 14 sites on north side of the Basu (30.1°N, 96.9°E), northeastern border of the Lhasa Block. After stepwise thermal demagnetization, high-temperature component with unblocking level of 680°C is isolated from 7 sites. Primary nature of this magnetization is ascertained through positive fold and reversal tests at 95% confidence level. Combined with previously reported paleomagnetic results, tilt-corrected mean direction of D =353.4°, I =15.1°, α 95 =14.1°, N = 8 is calculated, indicating that during Middle Jurassic the study area was located at 7.7°N ± 7.4°. Comparison with the Jurassic paleomagnetic data reported from eastern Tibet indicates that the Lhasa Block was located south of the Qiangtang Block at a latitudinal difference of 31 ± 11°. Compilation of paleomagnetic data further suggest that until the Cretaceous large spatial gap of more than 1200 km remained open between the Lhasa Block and the Qiangtang Block of eastern Himalayan syntaxis and eventually vanished during Tertiary. Cretaceous paleolatitude corresponding to this gap (13.0°N-31.0°N) is almost identical to that reported from Shan-Thai Block (25.4°N ± 5.2°). Furthermore, the Permo-Carboniferous sequences of Gondwanic affinity are distributed in western part of the Shan-Thai block as well as in the Lhasa and Qiangtang blocks. Keeping in view these similarities, we propose a new pre-collision (India vs. Asia) reconstruction model in which the Lhasa, Shan-Thai and Qiangtang blocks are shown in their respective order from south to north along southern margin of the Asian continent. The aftermath of gigantic India-Asia collision however introduced north-south compressional regime in the Asian Continent that eventually played a role in eastward extrusion of the Shan-Thai Block from an area between the Qiangtang and Lhasa blocks.
In order to describe features of tectonic deformation in the Indochina Peninsula, Early Jurassic ... more In order to describe features of tectonic deformation in the Indochina Peninsula, Early Jurassic to Early Cretaceous red sandstones were sampled at three localities in the Shan-Thai and Indochina blocks. Stepwise thermal treatment of most samples revealed the presence of characteristic remanent magnetization, which is generally unblocked by 680 • C. This component from Phong Saly (21.6 • N, 101.9 • E) and Borikhanxay (18.5 • N, 103.8 • E) localities yield positive fold tests with Late Jurassic-Early Cretaceous directions of Dec/Inc = 28.8 , respectively. Additionally, a syn-folding mid-Cretaceous characteristic magnetization is observed in the samples of Muang Phin locality (16.5 • N, 106.1 • E), which gave a mean direction of Dec/Inc = 30.8 • /39.9 • , k = 102.6, α 95 = 3.0 • , N = 23. This reliable Late Jurassic to Mid-Cretaceous palaeomagnetic directions from three different localities are incorporated into a palaeomagnetic database for Shan-Thai and Indochina blocks. Based on these compilations, tectonic deformation of the Shan-Thai and Indochina blocks is summarized as follows: (1) the Shan-Thai and Indochina blocks experienced a clockwise rotation of about 10 • as a composite unit in the early stage of India-Asia collision and (2) following this, the Shan-Thai Block underwent an internal tectonic deformation, whereas the Indochina Block behaved as a rigid tectonic unit during the same period. Comparison of our palaeomagnetic results with seismic tomographic images suggests that the strength of continental lithosphere beneath these blocks played an important role in the process of deformation rather than any other tectonic regime. In contrast to the Shan-Thai Block, an existence of continental roots beneath the Indochina Block prevented its internal deformation.
This study presents a newly discovered geomagnetic excursion in the andesitic lava sequence of th... more This study presents a newly discovered geomagnetic excursion in the andesitic lava sequence of the Kamegaoka Mountain (31 • 21'N, 130 • 13'E), Noma Peninsula, Kyushu Island. About 170 oriented samples were collected from 13 consecutive lava flows, covering an area from mountain top to sea shore. Thermal and alternating field demagnetizations of the studied samples generally revealed a univectorial magnetization, however, two components structure with minor viscous overprints is also observed in some samples. Remanent magnetization is generally unblocked between 560 and 590 • C, indicating magnetite as dominant remanence carrier. Reversed polarity directions are detected in the bottom and uppermost parts of the sequence, whereas anomalous directions with positive inclination are observed in the middle part of the sequence. This newly discovered anomalous palaeomagnetic direction, named as Noma excursion (C3Ar-1), has a well-defined K-Ar age of 6.66 ± 0.45 Ma. Comparison with the geomagnetic polarity timescale allow us to place this event within the polarity subchron C3Ar, in which no such cryptochron has been observed before by high resolution ODP study of the sedimentary cores. The virtual geomagnetic poles estimated for the studied lava sequence moved from Antarctica to Kamchatka Peninsula (60 • N), swung back to New Guinea equatorial region and then followed a path to Antarctica again. These poles followed a swath between the 90 • E and 140 • E longitudes, which are almost identical to one of the preferred longitudinal bands for transitional poles at the times of polarity reversals and excursions in the Brunhes and Matuyama chrons. According to this study, this preferred pathway may have started prior to 6.7 Ma. If properly emphasized, identification of Noma excursion in the studied lava flows can facilitate more such discoveries in the Late Miocene.
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Papers by Haider Zaman