نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشجوی کارشناسی ارشد علوم خاک دانشگاه علوم کشاورزی و منابع طبیعی گرگان
2 استاد گروه علوم خاک دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران
3 دانشیار گروه علوم خاک، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران
چکیده
وجود تناوبی از خاکهای قدیمی در رسوبات لسی شمال ایران، اشاره به دوران سرد و خشک در زمان رسوبگذاری لس و دوران گرم و مرطوب در زمان تشکیل خاکهای قدیمی دارد. از این رو، این پژوهش با هدف پژوهش میکرومورفولوژیک خاکهای لسی اوایل پلیستوسن و مقایسه آن با لسهای مدرن در مناطق آقبند، یلیبدراق و قرهآغاچ استان گلستان انجام شد. پس از مشاهدات مقدماتی و صحرایی و تعیین افقها برای هر خاکرخ در منطقه، از هر یک از افقها به مقدار کافی، نمونه خاک برای انجام آزمایشهای فیزیکوشیمیایی و همچنین نمونه دست نخورده، بهمنظور پژوهش مقاطع نازک خاک جمعآوری شد. یکی از روشهای مهم برای شناسایی و تفسیر لسهای مدرن و خاکهای قدیمی در راستای مطالعات اقلیم شناسی گذشته، بررسی میکرومورفولوژیکی خاک است. نتایج بهدست آمده از مقاطع نازک خاکهای پالئوسول و مدرن نشان میدهد که زمان و تغییرات آب و هوا، باعث تغییر در ویژگیهای میکرومورفولوژی خاک (مانند نوع و تعداد حفرات، ریزساختمان خاک، بیفابریک و پدوفیچر و ...) میشود. مشاهدههای میکرومورفولوژیکی، شواهد مختلفی از وقوع فرآیندهای پدوژنیک را در این خاکها نشان داد. بی فابریک غالب خاکها بهدلیل آبشویی آهک در افقهای آرجیلیک، لکهای و در افقهای کلسیک، بلورین میباشد. از مهمترین شاخصهای خاکسازی، وجود پوششهای رسی دور حفرات در برخی از افقهای خاکهای قدیمی است که شواهدی از شرایط اقلیمی مرطوبتر برای آبشویی و انتقال رس است. تشکیل لس و خاکهای قدیمی مورد پژوهش احتمالاً به ترتیب مربوط به دورههای یخچالی و بین یخچالی با شرایط اقلیمی متفاوت بوده است.
کلیدواژهها
موضوعات
عنوان مقاله [English]
Comparison of the micromorphology of the early Pleistocene paleosols with modern loess-derived soils
نویسندگان [English]
- masoomeh najafinia 1
- Farhad Khormali 2
- Farshad Kiani 3
- mojtaba Baranimotlagh 3
1 MSc Student of Department of Soil Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.
2 Professor., Department of Soil Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.
3 Associate Prof., Department of Soil Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
چکیده [English]
Introduction Loess sediments of northern Iran represent several cycles of climate change and evolution of the landform for the mid-to-late Quaternary. Climate change in elevations of Iran and its surrounding areas is very controversial in the mid and late Quaternary, and has been discussed in the past according to rainfall and rainfall periods and between rainfall, glacial and inter-glacial. Paleomegnatic results also indicate that Early Pliestocene loess (Reddish loess) have accumulated between, 1.8 to 2.4 million years ago. However, pedogenic processes and the effects of past climate in these soils still have not been fully investigated. The loess deposits in northern Iran are a valuable archive of regional paleoclimatic and paleoenvironmental information. Micromorphology is an important technique to identify and interpret the loess- paleosol for paleoclimate studies. Microscopy is a method of studying undisturbed soil samples with the help of microscopic techniques (and sometimes with ultramicroscopic ones), in order to identify their constituents, determine their mutual relations in space and time and interpret their formation conditions. Micromorphology uses these characteristics to make interpretations, generally on the soil formation processes. This study aimed to conduct a micromorphological investigation on the early Pleistocene loess and to compare it with the modern loess derived soils in Agh-Band, Yelli-Badrag and Qareh-Agach in loess plateau of eastern Golestan.
Materials and Methods The study area is located in semiarid climate in loess Plateau east Golestan. Six profiles were selected and studied. Physicochemical properties such as soil texture, acidity (pH), electrical conductivity (EC), saturation moisture (SP), organic carbon (OM), cationic exchange capacity (CEC) and calcium carbonate equivalent (CCE) were measured in the laboratory. Then, soil samples were prepared from each horizon for micromorphology studies. For micromorphological studies, thin sections were prepared from undisturbed, oriented and dry clods by standard methods and described under a polarizing optical microscope.
Results and Discussion Comparing the results of physicochemical properties (such as color, carbonate percentage, the cation exchange capacity, etc.) in paleosol and modern loess soils indicates that the in paleosols, soil forming processes have passed several stages. The existence of the argillic horizons and the evolved calcic in paleosols and their absence in the modern soils in which they are present, indicates the change in soil formation conditions. The change in the color of paleosols also represents the soil moisture and the more suitable conditions of the past climate (temperature, and especially rainfall) in comparison with the present climate of the region. This color change was due to activation of soil formation processes in paleosols. All paleosol samples had a higher clay content than the late modern loess soils of the Pleistocene, suggesting favorable climatic conditions for soil formation processes and the development of more ancient soil than parent materials. Reducing annual precipitation decrease soil pedogenesis.
Conclusion Comparison of the results obtained from paleosols of early Pleistocene with modern soils indicates that the time and climate change caused alterations in the soil micromorphology features (such as the type and amount of pores, soil structure and b-fabric and pedofeatures etc.). One of the most important pedofeatures was clay coating around void, presented only in buried paleosols, which is the evidence for moist climate conditions and subsequently enough leaching for clay translocation. Further, the presence of planar void caused by shrink and swell of clay is evidence for evolution in the paleosols. In argillic horizons of paleosols, dominant b-fabric is speckled due to carbonate leaching while in calcite horizon, it is crystallitic b-fabric. The micromorphological index of soil development calculated, showed that these red-colored deposits are formed under an annual precipitation of about 450- 650mm which represents more humid conditions at the time of their formation than the modern loess soils. In modern soils derived from recent loess, lack of clay coating can be a reason for weakly developed soil formation.
کلیدواژهها [English]
- Loess-paleosol
- Pleistocene
- Micromorphology
- Golestan Loess-paleosol
- Bouyoucos, G.J. 1962. Hydrometer method improved for making particle size analysis of soils. Agronomy Journal, 54: 464-465.
- Brewer, R. 1964. Fabric and mineral analysis of soils. John wily sons. Inc. Network. 442 pp.
- Brewer, R., and Sleeman, J.R. 1960. Soil structure and fabric: definition, classification and interpretation. Journal of Soil Science, 11: 172-185.
- Chapman, H.D. 1965. Cation exchange capacity. In: Black, C.A. (Ed.), Methods of Soil Analysis. Part 2: Chemical and Microbiological Properties. Soil Science Society of America and American Society of Agronomy, Madison, WI, USA, pp: 891-901.
- Dixon, J.B., and Skinner, H.C.W. 1992. Manganese minerals in surface environments. In: Skinner, H.C.W., Fitzpatrick, R.W. (Eds.), Biomineralization Processes of Iron and Manganese- Modern and Ancient Environments. Catena Verlag. Cremlingen, pp: 31-50.
- Fedoroff, N., Courty, M.A., and Thompson, M.L. 1990. Micromorphological evidence of paleoenvironmental change in Pliestocene and Holocene paleosols. In: Douglas, L. A. ed. Soil micromorphology: A basic and applied science. Developments in Soil Science, pp: 653-665.
- Fitzpatrick, E.A. 1993. Soil microscopy and micromorphology. John Wiley and Sons Pub., Chichester: John Wiley and Sons, 29.
- Gunal, H., and Ransom, M.D. 2006, b. Genesis and micromorphology of loess-derived soils from central Kansas. Catena, 65: 222-236.
- Guo, Z., Federoff, N., and An, Z.S. 1991. Genetic type of the Holocene soil and the Pleistocene paleosol in the Xifeng loess section in central China. Loess, Environment and Global Change, 93-111.
- Katswario, T., Cox, J.W., and Van Es,H. 2002. Tillage and rotation effects on soil physical properties. Agronomy Journal, 94: 299-304.
- Kemp, R.A. 1999. Micromorphology of loess-paleosol sequences: a record of paleo environmental change. Catena, 35: 179-196.
- Kemp, R.A., Toms, P.S., King, M., and Krohling, D.M. 2004. The pedosedimentry evolution and chronology of Tortugas, a late Quaternary type-site of northern Pampa, Argentina. Quaternary International, 114: 101-112.
- Kemp, R.A., Toms, P.S., Sayago, J.M., Derbyshire, E., King, M., and Wagoner, L. 2003. Micromorphology and OSL Dating of the basal part of the loessosol sequence at La Mesada in Tucuman province, Northwest Argentina. Quaternary International, 106: 111-117.
- Khormali, F., Abtahi, A., Mahmoodi, Sh., and stoops, G. 2003. Argillic horizon development in calcareous soils of arid and semiarid region of southern Iran. Catena, 776: 1-29.
- Mack, G.H., James, W.C., and Monger, H.C. 1993. Classification of paleosols. Geological Society of America Bulletin, 101: 188-203.
- McCarthy, P.J., Martini, I.P., and Leckie, D.A. 1998. Use of micromorphology for paleoenvironmental interpretation of complex alluvial paleosols: an example from the Mill Creek Formation (Albian), southwestern Alberta, Canada. Paleogeography, Paleoclimatology, Paleoecology, 143: 87-110.
- McLean, E.O. 1982. Soil pH and lime requirement. In: Page, A.L. (Ed.): Methods of soil analysis. Part 2: Chemical and microbiological properties. Soil Science Society of America and American Society of Agronomy, Madison, WI, USA, pp: 199-224.
- Muhs, D.R. 2013. The geologic records of dust in the Quaternary. Aeolian Research, 9: 3-48.
- Najafinia, M., Khormali, F., Kiani, F., and Baranimotlagh, M. 2017. Comparison of the clay micromorphology of the early Pleistocene paleosols with modern loess-derived soils. International Conference on Loess Research, pp. 80.
- Nedachi, Y., Nedachi, M., Bennett, G., and Ohmoto, H. 2005. Geochemistry and mineralogy of the 2.45 Ga Pronto paleosols, Ontario, Canada. Chemical Geology, 214: 21-44.
- Nelson, D.W., and Sommers, L.E. 1982. Total carbon, organic carbon, and organic matter, In: Buxton, D.R. (Ed.), Methods of Soil Analysis. Part 2: Chemical and Microbiological Properties. SSSA, Madison,WI, USA, pp: 539-579.
- Nelson, R.E. 1982. Carbonate and gypsum. In: Methods of Soil Analysis. Part II. Page, A.L. (Ed.). American Society of Agronomy, Madison, Wisconsin, USA, pp: 181-197.
- Nordt, L.C., Wilding, L.P., Lynn, W.C., and Crawford, C.C. 2004. Vertisol genesis in humid climate of the coastal plain of Texas, U.S.A. Geoderma, 122: 83-102.
- Page, M.C., Sparks, D.L., Noll, M.R., and Hendricks, G.J. 1987. Kinetics and mechanisms of potassium release from sandy Middle Atlantic Coastal Plain soils. Soil Science Society of America Journal, 51: 1460-1465.
- Pashaei, A. 1997. Study of physico-chemical characteristics and the source of loess deposits in Gorgan plain region. Earth Science Journal, Iranian Geology Organization, 23-24: 67-68.
- Ruhe, R.V. 1965. Quaternary and paleopedology. In wright, H.E., and D.G. Fery (Eds.). The Quaternary of the United State. Princeton University Press. Princton, NJ, pp: 755- 764.
- Segal, J.L., and Stoops, G. 1972. Pedogenic calcic accumulation in arid and semiarid region of the Indo-Gangetic alluvial plain of the erstwhile Punjab (India). Their morphology and origin. Geoderma, 8: 59-72.
- Stoops, G. 2003. Guidelines for the Analysis and Description of Soil and Regolith Thin Sections. SSSA. Madison, WI.
- Taheri, M., Khormali, F., Wang, X., Amini, A., Wei, H., Kehl, M., Frechen, M., and Chen, F. 2017. Micromorphology of the lower Pleistocene loess in the Iranian Loess Plateau and its paleoclimatic implications. Quaternary International, 429: 31-40.
- Tan, W., Liu, F., Feng, X., Huang, Q., and Li, X. 2005. Adsorption and redox reaction of heavy metals on Fe- Mn nodules from Chinese Soils. Journal of Colloid and Interface Science, 284: 600-605.
- Wang, X., Wei, H., Khormali, F., Taheri, M., Kehl, M., Frechen, M., Lauer, M., and Chen, M. 2017. Grain-size distribution of Pleistocene loess deposits in northern Iran and its palaeoclimatic implications. Quaternary International, 429: 41-51.
- Wang, X., Wei, H., Taheri, M., Khormali, F., Danukalova. G., and Chen, F. 2016. Early Pleistocene climate in western arid central Asia inferred from loess-palaeosol sequences. Scientific Reports, 1-9.
- Wider, M., and Yaalon, D.H. 1982. Micromorphological fabrics and developmental stages of carbonate nodular forms related to soil characteristics. Geoderma, 28: 203-220.
- Ziyaee, A., Pashaei, A., Khormali, F., and Roshani, M.R. 2013. Some physico-chemical, clay mineralogical and micromorphological characteristics of loess-paleosols sequences indicators of climate change in south of Gorgan. Journal of Water and Soil Conservation, 20(1): 1-27.