Contributions to the Post‐Silurian geology of Burma (Northern Shan States and Karen State)

Publisher Website
Google Scholar
Abstract
Antiquated stratigraphic and tectonic concepts on non‐metamorphic upper Palaeozoic and Mesozoic sequences in eastern Burma are revised. Post‐Silurian of Northern Shan States: The misleading traditional term Plateau Limestone ('Devonian‐Permian') is abandoned. The Devonian part is to be known as Shan Dolomite—with the Eifelian Padaukpin Limestone and the Givetian Wetwin Shale as subordinate member formations—and the disconformable Permian as Tonbo Limestone. Carboniferous formations are absent. Upper Palaeozoic of Karen State: The sequence begins with the fossiliferous Middle to Upper Carboniferous Taungnyo Group resting unconformably on the epimetamorphic Mergui ‘Series’ (probably Silurian) and on older metamorphics. There is no evidence of Devonian rocks. The Permian is represented by widespread, but discontinuous, reef complexes, known as Moulmein Limestone, which rest unconformably on the moderately folded Carboniferous. The earliest beds of the Permian are of the Artinskian Epoch. No Mesozoic sequence is known west of the Dawna Range. Mesozoic of Northern Shan States: Triassic and Jurassic are present, but the Cretaceous is absent. The Bawgyo Group (Upper Triassic and Rhaetic) rests unconformably on the Palaeozoic and consists of the Pangno Evaporites (below) and the Napeng Formation. The Jurassic Namyau Group, consisting of the Tati Limestone (Bathonian‐Callovian) and the Hsipaw Redbeds (Middle to Upper Jurassic) follows unconformably. Origin of folding of Mesozoic: The intense primary folding of the Triassic and Jurassic sequences in the Hsipaw region is due to gravity‐sliding (Gleittektonik) on the Upper Triassic evaporites. Secondary complications were introduced by diapiric displacements which are probably continuing. Neither of these tectonic phases shows a significant causal relationship with the Alpine Orogeny sensu stricto. The latter is at best responsible for minor overprinting, chiefly through broad warping and horst‐and‐graben fracturing of the Shan Dolomite with locally considerable vertical displacements. There are no Alpine fold structures in the region. Geotectonically, it was a well‐consolidated frontal block of the Alpidic hinterland.

This publication has 2 references indexed in Scilit: