In speech production, epochs are glottal closure instants where significant energy is released from the lungs. Extracting an epoch accurately is important in speech synthesis, analysis, and pitch oriented studies. The time-varying characteristics of the source and the system, and channel attenuation of low-frequency components by telephone channels make estimation of epoch from a speech signal a challenging task. In this paper, we propose a new technique that employs a Gammatone wavelet filterbank and compute a scattering sequence whose local maxima define the candidate epochs in the speech signal. Results are presented for both normal and telephone channel speech by considering the differential electroglottograph from CMU-Arctic database as the ground-truth. The proposed method gives significant improvements with respect to multiple performance metrics when compared with state-of-the-art techniques for epoch estimation.