Review of Sedimentary Records and Stratigraphic Correlation of Indochina and Sibumasu Terranes in Southeast Asia

Mainland Southeast Asia is one of the most geologically complex regions due to its long tectonic evolution, which complicates palaeogeographic and tectonic reconstructions. The region is primarily composed of the composite Indochina Terrane in the east and the Sibumasu Terrane in the west. Over the past few decades, integrated studies combining the Palaeozoic lithostratigraphy and biostratigraphy with provenance analysis and magmatic records have significantly improved our understanding of the palaeogeographic configuration and tectonic evolution of these terranes. Within the composite Indochina Terrane, the Loei–Phetchabun and Truong Son terranes preserve important sedimentary records, including carbonate platforms developed during Givetian to earliest Tournaisian in Truong Son and from Visean to mid-Permian across both Truong Son and Loei–Phetchabun. A platform-margin coral–stromatoporoid reef formed in the Frasnian in Truong Son, coinciding with a hiatus in magmatism until renewed granite emplacement from the Pennsylvanian to Late Triassic. In the Loei–Phetchabun Terrane, Devonian siliciclastics and volcanics are overlain by Givetian limestones and patch reefs, followed by Late Devonian to earliest Tournaisian radiolarian cherts and siliciclastics. These are succeeded by Tournaisian–early Visean turbidites associated with uplift and deformation, and later by Visean terrestrial deposits with evaporites and coal and marine limestones. The Truong Son Terrane records Late Ordovician–Silurian arc magmatism along its margins, related to subduction of oceanic lithosphere, remnants of which are preserved in the Loei and Tam Ky sutures. Similar-age volcanic arcs extend into Laos. Arc magmatism along Loei–Phetchabun Terrane indicates intermittent eastward subduction from mid-Devonian to mid-Triassic. In contrast, major stratigraphic records of the Sibumasu Terrane, particularly from southern Thailand and northwestern Malaysia represented by thick sequences of Tremadocian to Sandbian shallow-marine limestones. This unit overlies the oldest sedimentary sequences of the region, the Furongian (latest Cambrian) siliciclastic successions belonging to Tarutao Group in Thailand (Satun) and the Machinchang Formation in Malaysia (Langkawi). This unit yields diverse trilobite faunas with strong affinities to South China, North China, and Australia, comparable to those from Myanmar and the Baoshan Block. Across the regions of Sibumasu, this Furongian deposits are consistently associated with felsic plutonic, volcanic, or volcaniclastic rocks. Ordovician carbonates in Langkawi and Satun record faunal shifts from North China–Australian to South China affinities, reflecting a major sea-level rise during the late Darriwilian, along with other contributing factors. Deep-water conditions prevailed during the Katian, marked by deposition of the characteristic red limestone “Pa Kae facies”, which recurs into the Silurian and Devonian. Graptolitic black shales in Hirnantian, Rhuddanian and Early Devonian support the deep-water condition. Continued deep-marine deposition persisted into the Carboniferous in parts of Sibumasu, although shallow-marine Devonian coral–stromatoporoid reef indication tropical conditions have been observed in some areas. A regional mid-Carboniferous to Pennsylvanian depositional gap is attributed to uplift associated with mantle plume activity, which led to Cisuralian rifting of Sibumasu from Gondwana. Palaeomagnetic, biogeographic, and provenance data indicate that Sibumasu remained part of the Australian margin of Gondwana until this rifting and was later deformed during its Late Triassic collision with the Indochina Terrane.