Date of Issue : 2 Aug 1991
Postmark : Beijing
Denomination : 20 fēn
Stamp Size : 40 mm x 30 mm
Printing Process : Photogravure
The Convention of the Federation of the 13th International Quaternary Period Research was held in Beijing, China from 2 to 9 Aug 1991. The Quaternary Period is the most recent of the three periods within the Cenozoic Era. It began approximately 2.58 million years ago and continues to the present day. The Quaternary Period is characterised by the cyclic growth and decay of continental ice sheets, influenced by Milankovitch cycles. The study of the Quaternary Period is one of multipurpose comprehensive science. Commemorating this event, the single stamp in this issue features the prehistoric human, with a Wooly Mammoth and Wooly Rhinoceros in the background.