Classification of the Sibumasu and Paleo‐Tethys tectonic division in Thailand using chert lithofacies

Abstract

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.

The role of strike-slip faults in the displacement of the Palaeotethys suture zone in Southeast Thailand

“…She does state that a Permian age for her Yaang Formation cannot be ruled out, and this writer takes the view that the Khao Wang Chik sections of both authors are of latest Permian age. Sashida et al (2000b) interpreted the facies of their Sections I and II as deep-marine, pelagic, and this interpretation was accepted by Kamata et al (2009) who, however, had not examined the rocks in the field. On examining the rocks at outcrop Kamata later noted the terrigenous clastic intercalations in the chert successions, which caused him to modify his earlier interpretation to hemipelagic (Y.…”

Nd isotopic composition of Late Devonian seawater in western Thailand: Geotectonic implications for the origin of the Sibumasu terrane

“…It is widely accepted that the two principal microcontinents, Sibumasu in the west and Indochina in the east, had formerly been a part of Gondwana. There is, however, still an ongoing debate on the overall plate tectonic model and the position of the Paleotethys suture (e.g., Ueno and Hisada, 2001;Hisada et al, 2004;Ferrari et al, 2008;Kamata et al, 2009;Metcalfe, 2009). The tectonic framework of Thailand is formed of four units (Fig.…”

“…It is characterized by various types of rocks, including Devonian-Triassic deep-water radiolarian cherts, Carboniferous-Permian carbonates deposited on seamounts, and basaltic rocks. Because the Inthanon Zone also contains metamorphic rocks of the Precambrian basement and preDevonian sedimentary rocks (Cambrian sandstones and Ordovician limestones), it is suggested that the Sibumasu Terrane structurally underlies the Paleotethys accretionary complex along a low-angle thrust (e.g., Ueno and Hisada, 2001;Kamata et al, 2009). The Sukhothai Terrane (Barr and Macdonald, 1991) is interpreted to be a magmatic island arc which developed along the margin of the Indochina terrane (Sone and Metcalfe, 2008).…”

“…2). This fault zone is interpreted to represent the boundary between Sibumasu and the Inthanon Zone, and thus the biogeographic Gondwana-Paleotethys divide (e.g., Hisada et al, 2004;Ferrari et al, 2008;Kamata et al, 2009). According to Metcalfe (2006Metcalfe ( , 2009, however, the entire Mae Sariang area belongs to the Inthanon Zone and the Mae Yuam Fault, because of its Tertiary age, cannot be related to the destruction of the Paleotethys.…”

Late Devonian sedimentary record of the Paleotethys Ocean – The Mae Sariang section, northwestern Thailand

“…Early Paleozoic fossils of this block strongly suggest a connection to Australian Gondwana, from which Indochina separated during the Early Devonian by the opening of the Paleotethys Ocean. Various continental blocks occur in Thailand and their paleogeographic affinities are still in discussion (Ferrari et al, 2008;Kamata et al, 2009;Metcalfe, 2009Metcalfe, , 2011.…”