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The transition from diagenesis to low-grade metamorphism for the Ordovician—Early Carboniferous sequences of the Burdekin and Clarke River Basins and the Broken River—Camel Creek region is characterised by b-cell dimension and Kübler Index (KI = illite crystallinity) of K-white micas, clay-mineral assemblages and conodont colour alteration index (CAI). Data indicate that: (i) there is a regional metamorphic pattern characterised by anchizonal conditions,with consistently higher grade in the Camel Creek region (or Subprovince); (ii) anomalies are explicable in terms of location relative to areas of differing intensity of deformation (e.g. the Ruxton Formation) and inferred greater depth of burial (e.g. southern versus northern outcrop tracts of Quinton Formation); (iii) the regional pattern in the Broken River—Gray Creek area shows general alignment with the regional grain; (iv) there is a generalised north to south increase in CAI for the Broken River region (‘Top Hut’ to Broken River, <4 to >6), with higher values towards the Montgomery Range intrusions; (v) in the Burdekin Basin, there are higher CAI values north of Mt Podge and ‘Star’, and lower values (<4) in the southern part of the basin (‘Fletcher View’ to ‘Fanning River’); (vi) variation of both KI and CAI mean values through the stratigraphical sequence illustrates the existence of three metamorphic sequences, all possibly connected with interludes of orogenic activity: during the interval end-Ordovician—earliest Silurian (early Llandovery), earliest Devonian (mid-Lochkovian, broadly eurekaensis­delta Zones) and Middle Devonian (mid/late Givetian, broadly between the Middle varcus Subzone and the hermanni Zone); (vii) the relationship of KI data to CAI data from the Townsville hinterland indicates that the range of CAI values inferred for the anchizone should be enlarged to include CAI values of up to 6; and (viii) the average values of the K-white mica b-cell dimension is consistent with low­intermediate pressure­temperature metamorphic facies conditions. Distribution of the cumulative curves for the three areas indicates that metamorphism in the Camel Creek Region pelites took place under higher pressure conditions than in Broken River region or the Burdekin Basin. [ABSTRACT FROM AUTHOR]

The results of the study of the Carboniferous successions in the western part of the Northern Karakoram during three geological expeditions are summarized here. Rocks of that period are not uniformly preserved in the several thrust sheets forming the Northern Karakoram. In most of them only the basal part of the Carboniferous, up to the Visean, is preserved, whilst in the Karambar thrust sheet a more complete section—previously almost unknown—is preserved. Four new lithostratigraphic units, time-constrained by brachiopod and conodont biostratigraphy, are described, from bottom to top: (1) the Margach Formation: prevailing dark shales with subordinate fine subarkoses and quartzarenites, up to 300 m thick (mid-Famennian to middle Tournaisian); (2) the Ribat Formation: grey crinoidal limestones passing upwards to dark marly limestones and marls, at least 300 m thick (middle Tournaisian to Serpukhovian); (3) the Lupsuk Formation: subarkoses to feldspathic quartzarenites in thick beds, alternating with dark shales and siltstones, up to 400 m thick (Serpukhovian to uppermost Carboniferous); (4) within the Lupsuk Formation a local member, the Twin Valleys Member, up to 100 m thick, a bioclastic limestone intercalation of post-Moscovian age, is distinguished. The Carboniferous successions are invariably sealed by the arkoses to quartzarenites of the Gircha Formation, 133 m above the base of which, in the Karambar area, an Asselian brachiopod fauna was recovered.The Carboniferous succession is interpreted as recording the evolution of the passive margin of the Northern Karakoram Terrane, from early rifting stage in the Late Devonian to syn-rift events during the Late Carboniferous. The basal part of the Gircha Formation, of latest Carboniferous-earliest Permian age, is considered to have been deposited above a break-up unconformity, linked to the early drifting in the seaway bordering the Karakoram.In the palaeontological appendix the most significant brachiopod taxa (19 species, one new) are described. [Copyright &y& Elsevier]