Writers : Pashai,A.
Refference : Geosciences Scientific Quarterly Journal,No.:19,P.:42
Publishing Year : 1375

Abstract :
To understand the climatical and pedological changes In north- east Iran during the Holocene two different methods has been attempted. The first one were sedimentological studies in the Atrak valley and the second one were pedological studies in the loses sedimentation area of Gorgan- Plains.
The sedimentological studies at different river- cuts from korand to Gosheh- Tappeh villages indicate
four alternated eolian and pluvial sedimentation periods, the lowest sedimentation layer of all of them is a thick and loose conglomeratic layer of black Sanganeh materials. This means that the climatic changes during the Holocene in this area, started with a post- pluvial period, followed by four alternated bess sedimentations with a dry and hot climate, as well as three other much thinner fluvial sedimentation layers with warm and moist climate. By pedological investigation in this area, two different profiles were found, one in Agh- Emam peak with 1370m elevation and another in Minoo- Dasht plain with 150 m elevation.
According to the knage- Galdi section in the Atrak- Valley, after post- pluvial period, four different bess sedimentations with hot and dry climate, alternated with humification periods were found in the Minoo- Dashi profile. The lowest one had warm and wet climate while the other three had warm and woist climate.
The lowest humification period occurred in 5860 B.C. during Atlantic time. The pedobogical process in
this time was hydromorphism. The second and third humificatlon period occurred In 940 and 610 B.C. respectively during sub-Boreal; while the last one in 200 B,C. during sub- Atlantic time. The pedobogical process in all of them was Melanization.
On the other hands the Agh- Emam profile indicates three bess sedimentation periods as well as having hot and dry climates. This being interrupted by two oxidation periods with tropical climate. The twa horizons, Bir 1 and BIr 2 in this case were probably formed in 12000- 6000 B.C. during pre- Boreal or Boreal period as well as during post- pluvial time.
Subject List : Paleogeography