Mineralogical and paleobotanical investigations of Oligo-Miocene petrified wood from the southwest of Thrace Basin (NW Turkey)

Authors: BURCU ÜNER, SABAH YILMAZ ŞAHİN, ÜNAL AKKEMİK

Abstract: Petrified wood samples are found within terrestrial sediments belonging to the Late Oligocene-Early Miocene Danişmen Formation in Malkara-Keşan located in the southwest of the Thrace Basin. The petrified wood in both regions is usually silicified and partly coalified. The silicification of the Tertiary wood in the Malkara-Keşan region is associated with volcanic activity and coeval sedimentation. Thin sections from petrified wood samples were taken as transverse, tangential, and radial sections. The mineralogicalpetrographic- botanical studies were carried out under a polarizing and botanical microscope. Opal-moganite-chalcedony-quartz, which are different polymorphs of silica, were detected under the microscope in the petrified wood. Results were supported by X-Ray Diffractometer (XRD), Confocal Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR) analysis, and measurement of density in a total of five samples. In addition, scanning electron microscopy (SEM/EDS) was performed for textures and to determine the average elementary composition of wood samples. Results showed that while crystalline quartz and chalcedony were well defined, opal-A and other polymorphs of silica could be partly examined due to isotropic features. As a result of XRD studies of petrified wood samples from the Keşan and Malkara regions, the peaks of the crystalline types of silica were well defined in the diffractogram patterns. As a result of FT-IR analysis, polymorphs of silica such as quartz-chalcedony-moganite and mineralogical elements similar to carbon and graphite were detected. In two samples, the densities of chalcedony and quartz composition were 2.35 and 2.27 g/cm³, respectively. Furthermore, the average elementary composition was detected with SEM-EDS analysis as O, Si, S, Ca, Cr, and Fe elements in the Keşan region samples and O, Si, S, and Fe elements in the Malkara region samples. The results of all investigations and analyses were interpreted to understand the geodynamic evolution and paleobotanical properties of the region.

Keywords: Petrified wood, Thrace, mineralogy, geochemistry, paleobotany

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