Journal of Earth Sciences and Geotechnical Engineering

Age Estimation of Alqosh Main Landslide, North Iraq Using Exposure Dating Method

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• Abstract

   

  Alqosh town is located in the central part of north Iraq, along the southern limb of Alqosh anticline, a rugged mountain with maximum elevation of 837 m (a.s.l.) in the study area. The exposed formation is Pila Spi (Eocene), it consists of thickly well bedded and hard dolostone, dolomitic limestone with some marl intercalations. The dip amount varies from (15 – 45) southwards. The southern limb of Alqosh anticline is densely dissected by deep valleys; some of them are in canyon form. The spacing between valleys ranges from (115 – 235) m, they all run almost in straight courses downslope, with some slight meandering. Alqosh town is one of the old towns in the vicinity, it dates back to 1000 years B.C. with population of about 11 000 inhabitants. In the old part of the town, the houses are built of large blocks of dolostone and dolomitic limestone quarried from the Pila Spi Formation. Due to north of the town, a large and very old landslide exists, the toe has reached the extreme northern part of the town. Tens of houses are built on the toe area; indicating that the landslide is very old. The involved area by the landslide is about 50 000 m2 with length and width of 500 m and (62 – 144) m, respectively. To estimate the age of the landslide, field work was carried out to map the toe area, check about the slid materials and to measure the size of the existing slid blocks and any other evidence of the landslide. The exposure dating method is used to estimate the age of the landslide. The old living people in the town were asked about the age of the houses that are built on the toe to estimate the age of the landslide. Moreover, the covered materials of the toe and other parts of the landslide were carefully inspected to find indications for age estimation. Some archaeological data also were used for age estimation. Depending on all available data, the age of the landslide is estimated to be about 3000 (three thousand) years.