A comparative study on the rheology and wave dissipation of kaolinite and natural Hendijan Coast mud, the Persian Gulf

The objective of this paper is to investigate the rheological behavior of kaolinite and Hendijan mud, located at the northwest part of the Persian Gulf, and the dissipative role of this muddy bed on surface water waves. A series of laboratory rheological tests was conducted to investigate the rheological response of mud to rotary and cyclic shear rates. While a viscoplastic Bingham model can successfully be applied for continuous controlled shear-stress tests, the rheology of fluid mud displays complex viscoelastic behavior in time-periodic motion. The comparisons of the behavior of natural Hendijan mud with commercial kaolinite show rheological similarities. A large number of laboratory wave-flume experiments were carried out with a focus on the dissipative role of the fluid mud. Assuming four rheological models of viscous, Kelvin-Voigt viscoelastic, Bingham viscoplastic, and viscoelastic-plastic for fluid mud layer, a numerical multi-layered model was applied to analyze the effects of different parameters of surface wave and muddy bed on wave attenuation. The predicted results based on different rheological models generally agree with the obtained wave-flume data implying that the adopted rheological model does not play an important role in the accuracy of prediction.     

Triangulation-to-GPS and GPS-to-GPS geodesy in Trinidad, West Indies: Neotectonics, seismic risk, and geologic implications

We estimated horizontal velocities at 25 sites first surveyed in a 1901-1903 British Ordnance Survey triangulation and then resurveyed with GPS in 1994-1995 to identify Trinidad's principal active on-land faults, quantify fault-slip-rates, and test for elastic locking. Our best-fit single-fault elastic dislocation model put 12 ± 3 mm/yr of dextral strike-slip on the Central Range Fault (1-2 km locking depth), an apparently aseismic active fault. The estimated motions also showed statistically insignificant horizontal motion (2.2 ± 1.8 mm/yr of right-slip; 2.7 ± 2.0 mm/yr of N-S shortening) on the eastward on-strike extension of the El Pilar Fault, known to be the active transform fault in Venezuela. Repeat GPS measurements made between 1994 and 2005 at two sites spanning the island north to south showed a 14 ± 3 mm/yr eastward (plate-motion-parallel) dextral velocity differential, consistent with our best-fit historic (1901-1995) fault-slip-rate. Paleoseismology trenching demonstrates that the Central Range Fault cuts <5000-year-old sediment and is capped by ∼550-year-old sediment, suggesting that it may be locked and may have ruptured at least once during this time interval. About ∼5 mm/yr of slip could be taken up on the Los Bajos Fault and additional faults in the offshore south of Trinidad. The existing 1901-1995 and 1994-2005 geodetic data alone cannot resolve whether the Central Range Fault is essentially creeping (≤1-2 km locking depth) or locked to a more standard depth of 10 km.     

Insights into the phylogeny of sporadotrichid ciliates (Protozoa, Ciliophora: Hypotricha) based on genealogical analyses of multiple molecular markers

The sporadotrichid ciliates are an especially diverse group. A number of investigators have studied the morphological, morphogenetic, and molecular relationships among members of this group. Despite this, a consistent classification is still lacking and several important questions about the phylogenetic relationships within this group remain unsolved. To improve our understanding of these relationships, we constructed phylogenetic trees using the nucleotide sequences of the small-subunit rRNA (SSrRNA) gene and amino acid sequences of actin I and α-tubulin. Analyses of SSrRNA gene sequences indicated that: 1) the Sporadotrichida sensu Lynn (2008) and the Oxytrichidae are polyphyletic; 2) the Uroleptus species, which are classified to urostylids, formed a sister group with the oxytrichids; 3) Halteria grandinella, which is grouped morphologically with oligotrich species, clustered within the oxytrichids. These results are congruent with previous studies based on SSrRNA gene sequences. However, the amino acid sequences of actin I and α-tubulin yielded different topologies. The main results are: 1) in all phylogenetic trees, the genus Oxytricha was paraphyletic; 2) Uroleptus was sister to a subset of Urostyla and Holosticha, albeit with low supporting values; 3) Halteria grandinella was separated distantly from the Oxytrichidae in trees inferred from actin I amino acid sequences but clustered with oligotrichids in the α-tubulin analysis. The inconsistency among the trees inferred from these different molecular markers may be caused by rapidly accumulated genetic characterizations of ciliates. Further studies with additional molecular markers and sampling of more taxa are expected to better address the relationships among sporadotrichids.     

An index to assess the propensity of landfall in Australia of a tropical cyclone

Every year, Australian oceans experience the genesis of many tropical cyclones (TCs). About 40 percent of these make landfall. Because of the enormous difference in impacts between landfalling and non-landfalling TCs on coastal communities, the benefits would be enormous if it were possible to capture early the potentiality of landfall of a TC that has undergone genesis. Published literature identifies many factors such as location, warm sea surface temperature above 26 °C, conditional instability and high relative humidity in the middle troposphere and low vertical wind shear for the genesis of cyclones. Some of these factors could hold information about the potentiality of landfall while a TC is forming. An investigation into these factors actually revealed that a landfall potential index can be developed that can capture the potentiality of making a landfall. An attractive feature of this index is that it uses values at the time and location of genesis, providing a long and useful lead time. Furthermore, it is made into a dimensionless number, which makes for easy comprehension and interpretation.     

Biostratigraphy and depositional environment evolution of the Asmari Formation at the Shajabil anticline,Iran

In the present research, biostratigraphy and paleoecology of the Asmari Formation at the Shajabil anticline, northwest Yasuj in the Izeh zone are discussed. The Asmari Formation at the studied area is Rupelian–Chattian to Burdigalian in age. In the study, 18 genera and 29 species of benthic foraminifera have been identified. Besides, the following biozones which reflect Rupelian–Chattian to Burdigalian age are identified for the Asmari Formation: (1) Lepidocyclina–Operculina–Ditrupa; (2) Archaias asmaricus–Archaias hensoni–Miogypsinoides complanatus; (3) Peneroplis farsenensis_Elphidium sp.14–Miogypsina sp.; (4) Borelis melo–Borelis melo curdica. Relying on fossils, Coral and Corallinacea have been detected depositional environment. The paleo-ecological factors are identified for the Asmari Formation at the study area: water salinity, 34 to more than 50 psu; water depth of 90 to 0 m; water temperature of 14 °C to more than 27 °C in a subtropical to tropical environment, oligotrophoic to mesotrophic conditions.     

Geochemical constraints on the provenance of Oligocene–Miocene siliciclastic deposits (Zivah Formation) of NW Iran: implications for the tectonic evolution of the Caucasus

In this study, the whole-rock geochemistry of 35 Oligocene–Miocene sandstone and shale samples from the Zivah Formation, Moghan area (NW Iran) were collected and analyzed for evaluation of their provenance, tectonic setting and the intensity of paleo-weathering. Low to moderate values of the chemical index of alteration (mean CIA?=?53/68 for sandstones/shales) and relatively high values of index of compositional variability (mean ICV?=?1.23/1.08 for sandstones/shales) suggest weak chemical weathering and an immature source. These results support for the semi-arid and semi-humid paleoclimate conditions in the source area. The geochemistry results reveal that the sediments were deposited in a basin related to the island arc and active continental margin tectonic settings, probably indicating the time of initial collision between Arabia and Eurasia. The enrichment of Cr, Ni and V in the sandstone and shales are consistent with mafic input from the source area. However, La/Th vs. Hf and La/Sc vs. Co/Th plots reveal mixed source of felsic and intermediate volcanic rocks. The data indicate that the sediments most likely originated from a mixture of mafic, intermediate and felsic igneous source areas, possibly as the erosional products of localized topography of the Talysh and the Lesser Caucasus mountains (south to southwest), created by compression in the Moghan region during the syn-collisional development of the Caucasus.     

Microfacies and environmental study of the lower cretaceous yamama formation in Ratawi field

The Yamama Formation is the main Lower Cretaceous (late Berriasian–Valangenian) carbonate reservoir in southern Iraq. Petrographic study from thin-section examination shows that the skeletal grains included calcareous algae from both red and green algae. Red algae is concentrated in the upper part of the Formation, and the most important of this algae species is Permocalculus ssp. Green algae is less common, and its concentration is in the middle part of the Formation. The most species found in the Yamama Formation is dasycladeans, and both small and large species of benthonic foraminifera such as Nautiloculina, Textularia, Trocholina, Pseudocyclammina, and Everticyclammina are also present. The non-skeleton grains included oolites, pellets, and micrite. Six cyclic type microfacies have been recognized for Yamama Formation in Ratawi-3 (Rt-3) and Ratawi-4 (Rt-4) Wells, namely peloidal packstone–grainstone, algal wackestone–packstone, oolitic–peloidal grainstone, bioclastic wackestone–packstone, foraminiferal wackestone, and mudstone microfacies. The latter has been divided into two submicrofacies: argillaceous lime mudstone and fossiliferous lime mudstone. The lateral extension of these microfacies has been identified by integrating the thin-section data and well logs’ character variations with similar characteristic for microfacies. The Yamama Formation was affected by five diagenetic processes, which are micritization, cementation, recrystallization, silicification, and stylolites. The Yamama Formation was deposited during a regressive period within the outer ramp, shoal, and inner ramp setting.     

Detailed ground radiometric surveys on Gabal El Sela,Southeastern Desert,Egypt

Gabal El Sela area lies in the extreme southeastern part of the eastern desert in Egypt. It is covered by basement rocks of different compositions. The detailed work in this area covers about 4 km² and it is represented mainly by coarse younger granite as a curved shape extended in NE–SW direction and dissected by many faults in various trends; some of them are invaded by dykes especially the lamprophyre dykes in the ENE–WSW trend. Detailed geological, structural, and radiometric investigations are carried out on the area. The radiometric data are statistically analyzed and the results show that the total count radiometric map reflects six separate anomalies. The field work revealed that four anomalies are related to lamprophyre dykes, the other two anomalies are structurally controlled by NE–SW and E–W faults. These anomalies are followed by some trenches which traced and measured in detail exhibiting the possible extension of these anomalies with depth. These measurements show that lamprophyre dyke has the highest reading of radioactivity, it reaches 270 Ur in the surface and to 6,300 in the trenches. While the granite of the sela area is considered possesses high level of radioactivity, where its radioactivity ranges from 19.9 to 81 Ur with an average of about 32 Ur.     

Mean runoff coefficient estimation for ungauged streams in the Kingdom of Saudi Arabia

Runoff coefficient estimation in ungauged watersheds has a priority for rain water harvesting and management of runoff water, for domestic and agriculture activities, in semi-arid and arid regions. To estimate mean runoff coefficient (C _Re) for ungauged streams, Pearson's coefficient of linear correlation (r) was measured. The method of linear regression (y?=?mx?+?c) was applied for 16 gauged catchments representing several regions in the Kingdom of Saudi Arabia, such as Al Qassim, Al Madinah, Riyadh, Asir, Makkah, and Jazan. The studied catchments were equally divided into two groups based on their main streams slopes; group A includes eight gauged streams having main stream slope less than 0.01, where group B includes eight gauged streams having main stream slope equal to or greater than 0.01. The result yields the constant of the linear regression for each group and the mean runoff coefficient of basin by an independent value (basin slope) for group A and an independent value (stream slope) for group B. The results indicate that the measured runoff coefficient (C _Rm) and the estimated runoff coefficient (C _Re) are almost equal to each other.