干旱区生态环境知识资源中心

The Karapmar playa occupies the floor of a lacustrine depression which was part of the Upper Pleistocene (23,000-17,000 yr BP) Konya palaeolake. Four sections opened in the floor of the Karaplnar depression permit the study of the stratigraphy of Holocene sequences. From the sedimentological analyses of the sand content, organic carbon content, heavy mineral inputs and molluscan fauna, associated with the sediment observation (marks of aerial weathering and plant roots), several environmental changes can be assessed during Holocene. Underneath a characteristic black marshy layer; a thick sequence of lacustrine clay shows two episodes of cencentrated unbroken shells of Dreissena polymorpha, which is a typical species of the Upper Pleistocene open lacustrine environment in the area. Between these two episodes, stem marks in the clay show that the lake dried during an unknown period, during which soil was formed and carbonatic nodules occurred on its bottom. During Early to Mid-Holocene, the development of a marshy eutrophic environment is testified by an extensive organic and molluscan-rich layer situated in all the sections at about 1 m below the surface. 14C dates obtained both on organic matter and on shells from this marshy layer are mainly distributed between two periods: 13.800-13,400 BP and 6800-6500 BP. The latter period corresponds to the end of the occupation of the Neolithic sire of Catal Huyuk in the Konya plain. Around 6500 BP. the marshes are replaced by a lake which left a 10-30 cm thick clay layer. This Mid-Holocene lacustrine readvance ended with a brutal drought marked by a change in sedimentation, with a 30 to 60 cm thick silty and sandy aeolian deposit covering the lacustrine clay. The Late Holocene is marked by arid to semi-arid processes, with wind as an important geomorphic agent. During thi uncalib. 14C), we assume that it corresponds to the arid to semi-arid dry period which followed the Mid-Holocene lacustrine stage.