Search published articles


Showing 3 results for Gypsiferous Soils
Geologic Sources of Gypsum in Soils of Northwest of Isfahan, Iran
N. Tomanian, A. Jalalian, A. Zolanvar,
Volume 3, Issue 3 (10-1999)
Abstract

Gypsiferous soils, as the most characteristic soil in arid and semi-arid regions, are widespread in Isfahan Province. The north-west region of Isfahan is a closed basin and is surrounded by geologic formations. This area is a part of Zayandehrood watershed. The origin of gypsum in this area was investigated in this study. Considering the geologic distribution of gypsum, twenty-two locations, suspected to have been affected by gypsum, were selected for sampling. Natural and artificial excavations were used to discover their relationships. To distinguish the differences between fresh and weathered shales, some fresh samples were taken from the depth of Shemshak formations (a lead mine).

Field observations showed that in Shemshak and Nayband formations, gypsic crystals were present within the layers of weathered shales, and pyrite was observed only in the mine shales. In weathered red conglomerates (Lower Cretaceous), considerable amounts of gypsum had accumulated. In the hydrothermal veins of Shemshak and Nayband formations, gypsic crystals were found in matrix or between rock layers. In some parts, the Qom formation (Evaporate sediments) contained plenty of gypsum.

From field observations and analytical data, such as mineralogy of untreated and floated rock powders, determination of residual sulfides in shales, and the examination of thin and polished sections of rocks, we conclude that the origin and main resources of gypsum in our study area are as follows:

1. Gypsum being released from Cretaceous limes particularly from red conglomerates

2. Oxidation of pyrite and any sulfidic minerals existing in shales

3. Gypsum being released from evaporates (Qom formation and Oligomiocenic Marls)

4. Gypsum formed through hydrothermal reactions during late Tertiary.


Genesis and Micromorphology of Saline and Gypsiferous Aridisols on Different Geomorphic Surfaces in Nough Area, Rafsanjan
M. H. Farpour, M. K. Eghbal, H. Khademi,
Volume 7, Issue 3 (10-2003)
Abstract
Gypsiferous Aridisols are of great importance and extent in arid and semi-arid environments. There is a close relationship between soil genesis and landscape positions. This study aimed to determine the genesis and classification of gypsiferous soils and to investigate the relationship between micro-and macro-morphology of gypsum crystals and geomorphic positions in Rafsanjan area. The study area is located in Nough, 30 km north of Rafsanjan with a mean annual precipitation of 60 mm. Seven representative pedons were selected on different geomorphic positions. Physico-chemical, micromorphological, XRD, and SEM observations were performed on soil samples. Rock pediment geomorphic surfaces, that are in fact peripheries of old closed water bodies in central Iran, are the source of gypsum in the area. Large gypsum pendants and microforms of lenticular, vermiform, platy, and interlocked gypsum plates are found in rock pediment. The amount of gypsum and the size of pendants decrease moving down the slope. Lenticular and interlocked gypsum plates are found in a transition of pediment and playa. Puffy ground is observed on the saline surface of playa. Lenticular and vermiform gypsum crystals increase down the slope, but alabastrine gypsum is the most dominant form of gypsum in the playa surface. Large amounts of soft gypsum nodules are found on the rock pediment surface (western slope). In addition, spindle form of gypsum and palycrete bundles are observed in this position. Wind action played a significant role in the genesis and development of soil in rock pediment. A close relationship was found between morphology of gypsum crystals and geomorphic positions.
The Effect of Topography and Irrigation on Soil Development and Clay Mineral Diversity of Khuzestan's Gypsic Soils
Y. Abdoli, S. Jafari,
Volume 22, Issue 1 (6-2018)
Abstract
This study was done to evaluate the effect of topography, water table, and irrigation on gypsc soil development and clay mineral diversity in Ram-Hormuz Plain, Khuzestan Province. To localize, 10 profiles in this region that covered all purpose irrigation and topography situation were described. The results showed that the soils could be classified in Entisols, Inceptisols and Aridisols orders. All soil epipedons were ochric and subsurface horizons were cambic, gypsic, and salic. The salic horizons were formed under a low water table. The XRD results showed that smectite, kaolinite, illite, chlorite, palygorskite, vermiculite and sepiolite were the dominant minerals, respectively. Kaolinite and illite were inherited from the parent material, but chlorite was the result of both inheritance and transformation of other clay minerals except uncultivated or non-irrigated soils. Sepiolite was decreased in gypsic horizons, but palygorskite was increased in these horizons. Sepiolite was raised with increasing the depth under the good drainage class; this could be related to neoformation, but it was decreased with depth under the weak drainage class. These results could be due to the instability of this mineral in high moisture and its low Mg activity. There was also a negative correlation correlation between Palygorskite and smectite; this was such that most palygorskite was observed in the surface horizons, but smectite was in the subsurface. Smectite was the dominant clay mineral in the studied soils; it was formed from the weathering of other minerals as well as from neoformed ones in the lowlands. Vermiculite was formed in these soils due to k depletion by leaching or plant absorption. This happened in the illite to smectite transformation process. Therefore, topography and irrigation could be regarded as the main factors putting these soils in high category; also, clay mineral assemblage was different under this situation in these soils.

Page 1 from 1     

© 2024 CC BY-NC 4.0 | JWSS - Isfahan University of Technology

Designed & Developed by : Yektaweb