Weathering and soils formation on different parent materials in Golestan Province,Northern Iran

Geochemical, mineralogical, and micromorphological characteristics of soils and their relevant parent rocks including loess, ignimbrite, sandstone and limestone were investigated to identify the soil-parent material uniformity and the weathering degree of soils in Golestan Province, northern Iran. Highly developed Calcixerolls and moderately developed Haploxerepts were formed on loess and limestone, respectively. In contrast, the soils formed on ignimbrite and sandstone were non-developed Entisols. Illite was the dominant clay mineral found in ignimbrite and sandstone in both the A horizon and parent material. In loess derived soils however, smectite was dominant especially in the Bt horizon compared to its parent material indicating partly to its pedogenic formation. In limestone, illite and vermiculite were dominant both in the A and C horizons. Ti/Zr ratio proved that the studied soils were closely related to their underlying parent materials geochemically. Chemical index of alteration (CIA), micromorphological index of soil development (MISECA), smectite/illite+chlorite ratio and magnetic susceptibility were applied to investigate the degree of soil development. Results showed that the most and the least developed soils were those formed on loess deposits and limestone, respectively. Application of the different geochemical and pedogenetic approaches was proved to be useful in identifying the relevance of soils to their underlying parent materials and also their degree of development.     

Experimental Study on the Sand of Bandar-e Anzali Using Shaking Table

Geotechnical and Geological Engineering - Due to the economic and tourist importance of Bandar-e Anzali coastal zone and also the high seismic risk in this area, this article provides an...     

Mass balance of major elements in relation to weathering in soils developed on igneous rocks in a semiarid region, northwestern Iran

This study was conducted to evaluate the weathering intensity of the major soils developed on igneous rocks in semiarid region of northwestern Iran.Eight parent materials were selected including monzodiorite,alkali granite,granodiorite,syenite,pyroxene diorite,hornblende andesite,pyroxene andesite,and dacite.Representative soil profiles were described and soil samples were collected and analyzed for selected chemical and physical properties and total concentrations of major elements and Zr,V,Ti and Y.Bulk densities as well as Ti,Zr and V concentrations were used to estimate the strain factors and mass balance equations were used to quantify the net result of pedogenic weathering,i.e.elemental loss and gain.The results of clay content and pedogenic iron variability as well as index of compositional variability(ICV),chemical index of alteration(CIA) and,A-CN-K and MFW ternary plots showed that the soils developed on volcanic rocks(hornblende andesite> pyroxene andesite> dacite) were more weathered than those on the plutonic parent rocks(alkali granite,granodiorite,monzodiorite,syenite,pyroxene diorite).The results of mass balance calculations based on the strain factors revealed that the Ca and Na depleted during weathering progress mostly from plagioclase grains.In the semiarid regions Ca is precipitated as pedogenic calcite in the soil horizons.K and Mg depletion is less than Ca and Na especially in the profiles on the hornblende andesite with the highest clay and LOI content.The results of this study clearly suggest that the behavior of K and Mg during the weathering cannot only be explained by the disintegration of the primary minerals,since they are fixed on the secondary clay minerals.Iron did not change in the soils compared to the parent material and was precipitated as the pedogenic iron and conserved in the soil horizons.Overall,the results on the weathering indicators and major elements mass balance enrichment/depletion in the study area confirmed that the soil profiles developed on volcanic rocks are more weathered than those on the plutonic igneous rocks.     

In-situ zircon U-Pb age and Hf-O isotopic constraints on the origin of the Hasan-Robat A-type granite from Sanandaj–Sirjan zone,Iran: implications for reworking of Cadomian arc igneous rocks

Mineralogy and Petrology - The Lower Permian Hasan-Robat syenogranite occurs as a single pluton and intruded the Upper Carboniferous–Lower Permian sandstones and dolomitic limestones in the...     

Variations in crab claw morphology and diet across contrasting inter‐tidal habitats

Crabs are important predators of inter‐tidal ecosystems, controlling the abundance and distribution of their prey populations. Often the same crab species occupies several habitats and, although their effects on prey have been quantified across habitats, crabs’ dietary and morphological responses to differing environmental influences have been overlooked. Here, we used the crabs Eriphia verrucosa and Pachygrapsus marmoratus as model species to examine differences in claw morphometry – size and wear – and diet between rocky shore and heterogeneous sand flat habitats. We predicted that, intra‐specifically, crabs from rocky shores would consume more hard‐shelled prey owing to their high availability and consequently, would display chelipeds with the following claw characteristics: a higher degree of claw damage, stronger musculature (higher propel height) and increased mechanical advantage (defined as the ratio of input lever length to output lever length) than crabs in the heterogeneous sand flat habitats. Sampling was performed in heterogeneous sand flat habitats and rocky shores of the Central Portuguese coast. For each crab species, carapace width, diet composition and several claw morphometric measures were recorded, revealing significant intra‐specific differences (using multivariate analysis) between shore types. We found that E. verrucosa and P. marmoratus consumed more hard prey on rocky shore than on sand flat habitats, which resulted in rocky shore crabs having more accentuated dentition wear and larger musculature than their sand flat habitat counterparts. We suggest that the strong response of crab claw morphometry to environmentally induced diet variations is an important mechanism in the successful adaptation of crab species to inhabit differing habitats. A major implication is that the impact of the same species on prey may vary largely with habitat type as a result of predation efficiency varying with claw condition.     

Quantitative pore-type characterization from well logs based on the seismic petrophysics in a carbonate reservoir

Quality, availability and consistency of the measured and interpreted well log data are essential in the seismic reservoir characterization methods, and seismic petrophysics is the recommended workflow to achieve data consistency between logs and seismic domains. This paper uses seismic petrophysics workflow to improve well logs and pore geometry interpretations for an oil carbonate reservoir in the Fahliyan Formation in the southwest of Iran. The petrophysical interpreted well logs, rock physics and well-to-seismic tie analysis are integrated into the proposed workflow. Our implementation incorporates revising petrophysical well log interpretations and updating pore geometry characteristics to obtain a better well-tie quality. We first propose an improved pore-type characterization approach based on both P- and S-wave velocities for quantifying pore geometry. Then, seismic logs are estimated accordingly, and the results are used in the well-to-seismic analysis. The quality of the well-tie is improved, furthermore, by iterating on the petrophysical interpreted well logs as well as the calculated pore geometries. For the intervals with high-quality data, our workflow improves the consistency between the results of measured and modelled seismic logs. For the intervals with problematic well logs, the application of our proposed workflow results in the successful replacement of the poor data and subsequently leads to an improved wavelet estimation and well-tie results. In both cases, a higher quantification of pore geometries is achieved, which in turn is confirmed by the core images and formation micro-imager analysis.