Writers : Fateh Bahari, Leili; Mahmoudi Gharaei, Mohammad Hossein; Mahboubi, Asadollah; Moussavi Harami, Seyed Reza
Refference : 27th Symposium on geosciences and the 13th symposium on geological society of Iran-Tehran
Publishing Year : 1388

Abstract :

The Upper Cretaceous Ab-Deraz Formation mainly consists of carbonate-siliciclastic sequence of marine deposits in Kopet-Dagh basin in north-east Iran. Carbonate lithofacies are mainly formed as rhythmic alternation of chalk and chalky-marl. They represent two types of carbonate-rich (80-95 % carbonate) and carbonate-poor (65-80 % carbonate) beds, which are one of prominent features in Mesozoic sedimentary interval and in particular Cretaceous rocks. Cycles are in decimeter-decameter scale in both Hamam-Qale and Padeha stratigraphic sections and also in Khangiran well no.56 in Sarakhs area.
Variations in the earth orbital parameters caused climate fluctuation resulting in rhythmic sedimentation patterns. Three dominant frequencies have been identified in the natural gamma-ray log of Khangiran well no.56. They are attributed to three Millankovitch cycles of precession (21-23 ka). eccentricity (100 ka) and long eccentricity (413 ka) cycles. Counted eccentricity cycles are in agree with established biostratigraphic age determination. These variations are confirmed by calcimetery of chalky and marly beds in both Hamam-Qale and Padeha sections.

Subject List : Millankovitch cycles