Sedimentology
Alireza Vaezi; Vahid Tavakoli; Abdolmajid Naderi-Beni
Abstract
In the present study, in order to reconstruct the paleoenvironmental and climatic changes of Jiroft during the last 4000 years, several evidences of sedimentology and biogeochemistry on a sedimentary core have been investigated. Around. 3950 cal yr BP, low values of Ti/Al, Si/Al, C/N and CPI along with ...
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In the present study, in order to reconstruct the paleoenvironmental and climatic changes of Jiroft during the last 4000 years, several evidences of sedimentology and biogeochemistry on a sedimentary core have been investigated. Around. 3950 cal yr BP, low values of Ti/Al, Si/Al, C/N and CPI along with high values of δ13COM, and Paq indicate a wet period in Jiroft. evidence indicates a relative decrease in humidity between about 3900 and 3293 cal yr BP. Between 3293 and 2897 cal yr BP, Jiroft was dry and dusty. The results show very dry conditions with a significant increase in the amount of dust around 3200 cal yr BP. A long-wet period from about 2897 to 2302 cal yr BP can be recognized with high Paq values. The highest Ti/Al values along with the lowest δ13COM values indicate increased wind activity and dry conditions between 2100 and 1650 cal yr BP. Jiroft experienced wet conditions between 1540 and 1315 cal yr BP. With the relative decrease of rainfall, a semi-humid climate prevailed in Jiroft between 1315 and 854 cal yr BP.
N Hashemi; A.R Ashouri; M Aliabadian; M.H Mahmoudi Gharaie
Abstract
Paleozoology of Yafteh and Kani Mikaiel caves in center and northwest of Zagros Mountains led to the identification of small mammals' assemblage. Taxonomic determination revealed inclusion of four orders of small mammals including: order Rodentia with families of Muridea, Cricetidae, Calomyscidae, ...
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Paleozoology of Yafteh and Kani Mikaiel caves in center and northwest of Zagros Mountains led to the identification of small mammals' assemblage. Taxonomic determination revealed inclusion of four orders of small mammals including: order Rodentia with families of Muridea, Cricetidae, Calomyscidae, Dipodidae; order Lagomorpha with two families of Ochotonidae and Leporidae; order Soricomorpha with family Talpidae, and order Carnivores with family Mustelidae. These remains were recovered after systematic excavation in these caves. Radiocarbon analysis of these remains showed the oldest sample belonged to Yafteh cave with 35,000 BP. and Pleistocene period, whereas, Kani Mikaiel cave covered the periods from lat Pleistocene (19,000 BP.) to Holocene (17, 00 BP.). Geochronology analysis of Kani Mikaiel sediments showed that the lower layers of this cave belonged to the last glacial age in Pleistocene which gradually has been replaced by the warm weather in Holocene period. With continuing of this weathering varying, faunal spectrum of Pleistocene and Holocene periods has been migrated in cold and warm phases or more spread. The aim of this research, are the study of small mammal remains of Yafteh and Kani Mikaiel caves in center and northwest of Zagros mountains and the research about the study of paleobiodiversity, paleoenvironment conditions and the evolution of microvertebrate on the Iranian plateau.
R Lak; M Taghizadeh
Abstract
The Persian Gulf has an area about 240000 km2, considered as the northern part of the counterclockwise movement of Arabian Plate and as a recent example of Holocene carbonated sedimentary environment in dry (arid) climate. The basin volume, regarding to its average depth (36m), is estimated about 87,000km3. ...
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The Persian Gulf has an area about 240000 km2, considered as the northern part of the counterclockwise movement of Arabian Plate and as a recent example of Holocene carbonated sedimentary environment in dry (arid) climate. The basin volume, regarding to its average depth (36m), is estimated about 87,000km3. The present study was done in order to examine the sea level changes and determine the rate of sedimentation of Holocene deposits in the northeast of Persian Gulf. A complete and undisturbed core from the Holocene deposits (1070 cm length) located in the south of Rajaee port in theHormozgan province was prepared. Following the exact description of this core, based on the objective observations, 52 samples were taken according to the facies divisions and they were sedimentologically and geochemically tested. The granulometric analysis, mineralogy by XRD method, abundance percentage of elements by ICP-OEC device and polarograph, percentage of organic matter by the Rock Eval device, percentage determination of carbonates by automatic calcimeter device were done for all samples and 10 samples were dated by 14C AMS method. The granulometric results indicated that most of the deposits are mud containing sand and gravel. The gravels are mainly related to shell fragments. The amount of carbonates varies from 17 to 84 percent. The silisiclastic deposits include quartz, feldspar, muscovite, pyroxene and clay minerals such as kaolinite, chlorite, montmoryonite, illite and paligorskite. The chemical and biochemical sediments are mainly calcite, dolomite and aragonite. The percentage of organic matter contained in the sediments varies from 0.02 to 0.13. The variation curve of calcium and strontium, which indicates intrabasinal sediments, is correlated to sea level changes in combination with objective evidences such as grain size, sediment type, and amount of organic matter, texture and structure of sediments. The abundance of most elements especially Al, Mg, Mn, Cr, Ba with continental origin, revealed a reversed relation with the sea level variations. In addition, two significant phases of rapid transgression have occurred from 6800 to 3700 and from 9300 to 7900 years ago. The dating results showed that the average rate of sedimentation in the study area is about 1mmper year(966mm/ka).
M Foroutan; H Nazari; B Meyer; M Sébrier; M Fattahi; K Le Dortz; M Ghorashi; Kh Hessami; M. R Ghassemi; M Talebian
Abstract
The Dehshir fault system (DFS) including six fault segments forms the western border of NS-striking active dextral strike-slip fault cutting the Sanandaj-Sirjan, Uromieh-Dokhtar magmatic arc, and Central Iran. This active fault system right-laterally offset Eocene volcanic rocks and Quaternary alluvial ...
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The Dehshir fault system (DFS) including six fault segments forms the western border of NS-striking active dextral strike-slip fault cutting the Sanandaj-Sirjan, Uromieh-Dokhtar magmatic arc, and Central Iran. This active fault system right-laterally offset Eocene volcanic rocks and Quaternary alluvial fans. Geomorphic evidence imply the activity of the DFS in the Late Quaternary, and paleoseismic investigations revealed seismic movements along the Marvast fault segment during the Late Pleistocene and Holocene timescales. In order to unravel the seismic history of the DFS over the intermediate geologic (103 -105 yr) time scale, and based on the morphotectonics and sedimentary-stratigraphic properties, three paleoseismic sites have been selected along the 35-km-long stretch of the Marvast fault segment. The southern site (Harabarjan) shows steep fault branches of N140±10º strike with sub-horizontal striations in dextral component. Another trench has been excavated at the North Marvast site whitin the Late Pleistocene-Holocene alluvial and colluvial deposits. OSL analysis of loose quartz rich deposits yielded an age of ~72 ka for the oldest exposed sediments. Paleoseismic stduies along the Marvast fault segment provide evidence for the occurrence of several large seismic events associated with surface ruptures along the DFS. The chronology of paleoearthquakes on the Marvast segment indicates that at least 7 large (≈Mw > 7) earthquakes occurred in the last 43 ka with an average recurrence time of 3650±150 years. The most recent earthquake, event I, occurred ~2200 years ago, which associated with 2-4 m of dextral slip and >40 km surface rupture along the Marvast fault segment. These investigations are compatible with the lack of destruction in the Marvast historical (~1300 years) castle, located
A. Pouresmaeil; F. Hadavi; R. Lak
Abstract
In this study, a core with 10.5 m lenght and in shallow water in Bandar Abbas (Shahid Rajaee Port area) was studied based on calcareous nannoplankton. In this study, 52 samples of sediment cores were taken and prepared. Most species were photographed by light microscope. For the first time 21 genera ...
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In this study, a core with 10.5 m lenght and in shallow water in Bandar Abbas (Shahid Rajaee Port area) was studied based on calcareous nannoplankton. In this study, 52 samples of sediment cores were taken and prepared. Most species were photographed by light microscope. For the first time 21 genera and 35 species introduced in this area. In the core mentioned Gephyrocapsa oceanica and Emiliania huxleyi are the dominant taxa, based on the abundant presence of these species can be concluded that the Persian Gulf basin is a marginal sea in the lower latitudes and shallow areas have been formed and in this area productivity of nannoplankton is high.
M Foroutan; H. Nazari; B. Meyer; M. Sébrier; M. Fattahi; K. Le Dortz; M. Ghorashi; Kh. Hessami; M. R. Ghassemi; M. Talebian
Abstract
The evaluation of seismic potential along the Dehshir fault with 550-km length (by count of northern and southern splays) is critical considering that more than 3.5 million people live in cities and towns located at vicinity of the fault. The Dehshir fault is considered as westernmost limit ...
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The evaluation of seismic potential along the Dehshir fault with 550-km length (by count of northern and southern splays) is critical considering that more than 3.5 million people live in cities and towns located at vicinity of the fault. The Dehshir fault is considered as westernmost limit of N-striking dextral strike-slip faults set that slice Central and eastern Iran. Due to the lack of large recorded earthquakes (instrumental and historical) in Central Iran, access to seismic potential of active faults by studying the earthquake catalogs seems to be impossible. No instrumental earthquake has been recorded greater than mb 4.7 around the Dehshir fault and also historical data shows no evidence for occurrence of large earthquake around the fault. No sign of destruction in Marvast historical castle (at a less than 10 km far from the Dehshir fault) built in Islamic period (~700-1250), shows any remarkable seismic activity until 750-1300 years ago. However, several evidence of geomorphologic markers such as drainages, gullies, streams and alluvial fans offsets, represent activity of the Dehshir fault in Late Quaternary. Of Geomorphic evidence at Marvast and Harabarjan sites record dextral - slip on the Dehshir fault during the Late Pleistocene-Holocene as major movement with minor dip - slip component. Rake of the fault movement has been considered for assessing to amount of horizontal and vertical slip rate on the Dehshir fault. This value in the North Marvast site has been calculated ~10 degrees and according to right bank offset on the Marvast river is ~7 degrees with horizontal and vertical displacements of 13 m and 1.5 m, respectively. Combining cumulative offset markers with OSL dating implies the Dehshir fault in Late Pleistocene-Holocene time period slips at horizontal and vertical components about 1±0.3 and 0.1 mm yr-1, respectively. We observed a minimum dextral offset along the Marvast fault segment in west of Harabarjan about 2 m that allow us assuming the related magnitude and date of last large paleoearthquake on the Dehshir fault is about Mw 7 and 2000 years ago, respectively.
