Abstract The Baling formation of eastern Kedah and northern-most Perak, Peninsular Malaysia has long been proposed for group rank. This proposal is adopted here although it is still not possible to formalize fully this rock unit. The Baling group extends across the international frontier into Thailand (as the Bannang Sata group) where it evidently attains its maximum development, at least in terms of areal extent, but it has not yet been studied in detail in that country. The Baling consists of arenite and carbonate of the Papalut quartzite below, and black siliceous argillite, with minor calcareous rocks, of the Kroh formation, above. A thick sequence of rhyolitic pyroclastic rocks (the Grik tuff) occurs around the passage between two foregoing formations in the Grik area of Perak. Review of age criteria and regional relationships indicates that the Papulut is closely related to a (?) Mid Cambrian to Lower Ordovician shelf sequence in parts of the coastal tract of NW Peninsular Malaysia and the adjacent portion of Thailand (Jerai formation, Machinchang Formation, Tarutao Formation). Minor amounts of acid pyroclastic rocks in all these rock units are correlated with the initial phase of the Grik tuffs. The Kroh formation is part of a hitherto unrecognised but widespread association of Mid Palaeozoic black shale facies including the Mahang Formation to the west and the upper part of the Foothills group (“Bentong group”) to the east and southeast. This facies seems to have been initiated in the Ordovician and is characterized by Lower to Mid Silurian and Lower Devonian graptolites, the latter accompanied in the Baling and Mahang by numerous Lower to Mid Devonian tentaculites. No fossils of uppermost Wenlock, Ludlow or Pridoli ages have been determined in these rocks. Counter to earlier palaeogeographic reconstructions no evidence of a confining sill or barrier or contemporary subduction zone can be detected within the outcrop of this black siliceous argillite association. If such features formerly existed they must have lain to the east of the present outcrop. The Grik tuff may correspond in time with another faunal hiatus, Mid to Late Ordovician in date, recently recognised in the former shelf area, to the west of the auxinites, and to a metamorphic/tectonic event within the Foothills group succession.