نوع مقاله : مقاله پژوهشی
نویسندگان
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
The Quaternary mapping of central North Iran has provided the first documentation of the loess deposits of the area. The loess is derived from the adjoining flood plains and has been transported by winds over relatively short distances at low altitudes. An accumulation rate of about 12 cm/1000 years has been assumed which implies that the investigated Nowdeh loess section, Mazandaran province, spans the last 208000 years. Paleoclmatic evidence indicates the loess of central North Iran was deposited under cold, dry and windy conditions interrupted by short, warm periods represented by paleosol formation.
The loess-paleosol sequence of the Nowdeh section corresponds to the Riss Glaciation, Riss-wilrm interglacial, wilrm Glaciation and the present interglacial. The reflection of world-wide paleoclimatic fluctuations in the loess record is demonstrated by a fairly good correlation with deep sea core data. Both the loess- paleosol stratigraphy and the reconstructed kd/cl (coarse silt/ clay ratio) curve seem to reflect the 20/000-year and the 100/000-year cycles which, tentatively, permit the prediction that the inception of the next windy, cold and dry phase will be in approximately 6/000 years time, while its major peak will be in 56000 years time.
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