Classification of the Sibumasu and Paleo-Tethys tectonic division in Thailand using chert lithofacies
Article first published online: 17 FEB 2009
© 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Asia Pty Ltd
Volume 18, Issue 1, pages 21–31, March 2009
How to Cite
Kamata, Y., Ueno, K., Hara, H., Ichise, M., Charoentitirat, T., Charusiri, P., Sardsud, A. and Hisada, K.-i. (2009), Classification of the Sibumasu and Paleo-Tethys tectonic division in Thailand using chert lithofacies. Island Arc, 18: 21–31. doi: 10.1111/j.1440-1738.2008.00652.x
- Issue published online: 17 FEB 2009
- Article first published online: 17 FEB 2009
- Received 12 May 2007; accepted for publication 7 March 2008.
Two types of chert are defined in Thailand based on lithology, faunal content, and stratigraphy. ‘Pelagic chert’ consists of densely packed radiolarian tests in a microcrystalline quartz matrix with no terrigenous material and is found as blocks embedded within sheared matrix. ‘Hemipelagic chert’ also has a microcrystalline quartz matrix, and contains not only scattered radiolarian tests, but also calcareous organisms such as foraminifers. The pelagic cherts range in age from Devonian to Middle Triassic, whereas hemipelagic chert is only from the Early to the Late Triassic. Lithological and stratigraphic characteristics indicate that the pelagic chert originated in the Paleo-Tethys, whereas the hemipelagic chert accumulated on the eastern margin of the Sibumasu Block. The hemipelagic and pelagic chert are exposed in two north-trending belt-like zones. The western zone includes the hemipelagic chert, as well as glaciomarine and other Paleozoic to Mesozoic successions, overlying a Precambrian basement that consists exclusively of Sibumasu elements. The eastern zone contains pelagic chert and limestone and should be correlated to the Inthanon Zone. The Inthanon Zone is characterized by the presence not only of Paleo-Tethyan sedimentary rocks, but also of Sibumasu Block elements that structurally underlie the Paleo-Tethyan rocks. The boundary between the Sibumasu and Paleo-Tethys zones is a north-trending, low-angle thrust that resulted from the collision of the Sibumasu and Indochina blocks.