Geology of Khorassan

Kopeh- Dagh sedimentary region (basin) This region extends from Sarakhs (extremely North-east of Iran) to Gorgan and Gonabad. This mountainous area has been developed due to the latest Alpine orogenic which was followed by an erosion, has provided a relatively thick middle Jurassic sedimentaries of 8000 m which extends to the present age. (Afshar harb 1970) The width of this area is 30 to 70 km and it extends approximately 350 km. In eastern areas it has proceeded from north-west to south-east and in western parts it has proceeded almost from east to west. The tectonicall movements in Kopeh-Dogh region has caused facies changes in interval stages. These movements have been both orogenic and epirogenic movements. The two large structural and sedimentrial cycles in northern and central parts of Iran show the periodic time between the late Triassic and earlier cretaceous. Each cycle is accompanied with a sea transgression which is followed by on orogenic and an uplifting afterward. Earlier cycle started in norian and continued to the end of earlier Bajocian. This cycle is followed by a relatively long uplifting in Carnian and Caused by blockage of Paleo tethys and connection of northern and central parts of Iran, (part of cimmerid continent, Shengor.1990) to the southern border of laurasia super continent. (Turan or plate) .the existence of latheritic soils and erosional evidence and karst in the base of Shemshak formation or Nayband Formation (shemshak group) are clear evidence of presence of this old land. First cycle started in Norian with transgression of Shemshak sea and with elastic sediments and mollas and ended with lutian movements (middle Cimmerian). The recent event is very important aspect of future evaluation in central and northern part of Iran. Formation of some of these new sedimentary like North Alborz and Koppeh dagh are probably related to the extentional process following this event. The second cycle has aiso started with sea transgression in late Bajocian and has ended with late Cimmerian event. (K,Seyed Emami, Shayrer- Behrouzi ) This area is bordered to turkemaria from north and to paleo tethys sutare zone from south (Alavi. 1995) and huge gas fields have been discovered in this area.

Binalood zone Binalood zone is restricted to Paleotethys remnants and Metamorphic rocks and Permian turbiditic sediments from the north, and to neo-telhys ophiolitic rocks in the south. (Sabzevar- South Fariman ophiolitic). Binalood mountain range with approximately North west- south east trend is composed from thiclc seqwence of slate and phillitic rocks of Triassic Jurassic age, and over thrusted slices of Paleozoic sedimentary rocks (mainly Camberian Silurian and Devonian rocks). (figure in page 92 report 52)

Geology of Khorassan contains :