The age of two calcrete nodules (C1 and C2) from the Bala section in the region of Ankara, Turkey, is determined by the Electron Spin Resonance (ESR) method. Three radiation-induced ESR signals at g=2.0056 (A signal), g=2.0006 (C signal) and g=2.0038 (broad signal, BL) were observed. The broad signal (BL) intensity was used as a dating signal. The properties of this dating signal are described in this manuscript. The calcrete nodules were irradiated with a Co-60 gamma source and measured with an ESR spectrometer (X-band) to obtain the signal intensity vs. dose curve and fitted well with the single exponential saturation functions. Based on this model, accumulated dose (D-E) values for dating are obtained using the multiple-aliquot additive dose method. The D-E values of C1 and C2 calcretes are 1880 +/- 207 and 671 +/- 67 Gy, respectively. The ESR ages of the two calcrete samples are obtained by assessing the annual dose rate (D) from the content of U-238, Th-232 and K2O determined by wavelength dispersive X-ray fluorescence (XRF) spectrometry. The results are 761 +/- 120 and 419 +/- 64 ka, respectively, falling into the Middle Pleistocene Epoch in the geological time scale in agreement with the positions of the stratigraphical record. (C) 2010 Elsevier Ltd. All rights reserved.