In this study, we investigated the high-pressure (HP) metamorphism of the Precambrian continental crust exposed in the Zheltau terrane in South Kazakhstan (Koyandy complex) and the Chu-Kendyktas terrane in the North Tien Shan of Kyrgyzstan (Aktyuz, Kemin and Kokdzhon complexes) within the SW part of the Central Asian Orogenic Belt. HP quartz–feldspar lithologies of the Koyandy complex consist of migmatized kyanite-bearing garnet–mica paragneisses, garnet–kyanite paragneisses and their derivatives associated with eclogites. Paragneisses demonstrate prograde evolution involving mica dehydration melting and producing magnesium-rich garnet, kyanite and K-feldspar at the near-peak to retrograde stages at pressures of 15–18.5 kbar and temperatures of 800–870°C. The widespread growth of micas in these rocks reflects lower stages of retrogression at P = 10–12 kbar and T = 720–770°C. The age distributions of the cores of detrital zircon grains from the paragneisses indicate a predominance of Neoproterozoic and minor occurrence of Mesoproterozoic and Palaeoproterozoic sources of their protoliths. The ages of ∼487–485 Ma obtained from the zircon rims of the paragneisses reflect the timing of their HP metamorphic re-equilibration. These age clusters are consistent with the age estimates obtained from the rims of zircons in the eclogite-bearing garnet gneisses of the adjacent Aktyuz complex in the North Tien Shan. The P–T paths and zircon ages obtained from the high-grade quartz–feldspar gneisses of the Zheltau and Chu-Kendyktas terranes are thus interpreted to indicate involvement of the crustal material derived from the Precambrian basement (magmatic zircons aged ca. 844 Ma) and its Ediacaran–Cambrian sedimentary cover (detrital zircons with maxima at 1 Ga and 800–600 Ma) in the latest Cambrian subduction processes induced by the closure of the oceanic basins assigned to the Palaeo-Asian Ocean.

The episode of widespread organic carbon deposition marked by peak black shale sedimentation during the Palaeoproterozoic is also reflected in exceptionally abundant graphite deposits of this age. Worldwide anoxic/euxinic sediments were preserved as a deep crustal reservoir of both organic carbon, and sulphur in accompanying pyrite, both commonly >1 wt %. The carbon- and sulphur-rich Palaeoproterozoic crust interacted with mafic magma to cause Ni–Co–Cu–PGE mineralization over the next billion years, and much uranium currently produced is from Mesoproterozoic deposits nucleated upon older Palaeoproterozoic graphite. Palaeoproterozoic carbon deposition has thus left a unique legacy of both graphite deposits and long-term ore deposition.

Beothukis mistakensis from the Ediacaran System of Newfoundland, Canada demonstrates complex fractal-like morphology through the development of primary-, secondary- and tertiary-order Rangea-like units. The primary-order rangeomorph units observed in B. mistakensis are tightly juxtaposed, show no evidence of being independent of one another and are made up of chamber-like secondary-order – probably mesoglea-filled – units. The growth of these rangeomorph units demonstrates that the frond developed from the tip towards the basal region through ontogeny. The tertiary-order units of Beothukis are considered to represent surface morphology on the secondary-order units. This is in contrast to palaeobiological reconstructions of Beothukis that invoke three-dimensional fractal-like branches with independent units, which has been used to infer an osmotrophic mode of life. It is considered here that the fractal-like morphology of the lower surface of B. mistakensis was an adaptation to increase surface area to volume ratio. The quilted morphology of Beothukis proposed here is consistent with a sessile, reclining, phagocytotic and/or chemosymbiotic mode of life similar to that invoked for the reclining rangeomorph Fractofusus.

The phase petrology of two bodies of basic granulites occurring in association with supracrustal sequences within a dextral oblique-slip shear complex in the high-grade terrain of south India, have been studied. Some metabasites are characterized by garnet + clinopyroxene assemblages such as Grt + Cpx + PI ± Hbl ± Opx ± Qtz + Fe-Ti oxide(s) which are high-pressure granulites (garnet-clinopyroxene subfacies) transitional between the intermediate-pressure granulites (orthopyroxene-plagioclase subfacies) and eclogite. Mineralogical characteristics suggest that metamorphic conditions did not reach the eclogite facies but certainly approached that level. Close spatial association of the garnetiferous varieties with garnet-free assemblages (Opx + Hbl + Pl ± Cpx) and intimate juxtaposition of anhydrous and hydrous assemblages indicate a complex interplay of variable μH2O and bulk composition, especially αSiO2. Due to variable and low closure temperature of Fe-Mg exchange reactions between coexisting pyroxene and garnet, reliable estimation of peak temperatures during this near eclogite-facies metamorphism is problematic. A combination of a garnet-clinopyroxene barometer and various temperature estimates suggests P-T conditions of 875 ± 25°C and 8 ± 1 kbar for the Mettuppalaiyam samples and 900 ± 50°C and 14 ± 2 kbar for the Kanjamalai samples. Bulk rock chemical differences in terms of SiO2-content can account for the development of similar mineral assemblages along a near adiabatic metamorphic gradient between these two localities. These assemblages represent some of the highest grade granulite facies rocks in south India. The high-pressure granulites are not in situ samples of ancient lower continental crust, but low-pressure protoliths buried at depth. Textural features suggest that the high-pressure garnet-clinopyroxene subfacies rocks evolved from an amphibolitic assemblage by formation of garnet at the expense of hornblende and plagioclase and this high-pressure assemblage underwent an isothermal decompression indicating a clockwise P-T-t path resulting from crustal thickening and exhumation. A later isobaric cooling, possibly accompanying shearing and high H2O influx (aH2O≈0.78) gave rise to the coexisting orthopyroxeneplagioclase subfacies rocks (intermediate pressure granulites).

The Central Asian Orogenic Belt is an accretionary orogen with many distinct terranes including the Chinese Central Tianshan, whose Precambrian tectonic affinity is not yet clearly known. We present Precambrian age spectra of inherited/xenocrystic zircons from magmatic rocks in the Chinese Central Tianshan, collected from published papers. The age patterns are dominated by zircons with ages ranging from 3261 to 541 Ma. These spectra provide robust clues regarding the Precambrian affinity of the Chinese Central Tianshan. The age spectra record two major tectonothermal events, represented by salient age peaks of c. 950 and 900 Ma within the ‘Grenville Orogeny’ period, and age peaks at c. 750 and 630 Ma, synchronous with magmatic events corresponding to Rodinia break-up. These results are consistent with the hypothesis that the Chinese Central Tianshan was part of the Tarim craton during Precambrian time as well as documenting its incorporation into, and separation from the Rodinia landmass.

Precambrian rocks comprise nearly one-quarter of the surface of Brazil and range from Paleoarchean (ca. 3.6 Ga) to the latest Ediacaran (0.542 Ga) in age. Except for controversial phosphatized ‘embryo-like’ microfossils like those from the lower Ediacaran Doushantuo Formation, China and complex rangeomorphs, Brazilian research has revealed all major categories of Precambrian life forms described elsewhere – microbialites, biomarkers, silicified microfossils, palynomorphs, vase-shaped microfossils, macroalgae, metazoans, vendobionts and ichnofossils – but the paleobiological significance of this record has been little explored. At least four occurrences of these fossils offer promise for increased understanding of the following aspects of Precambrian biospheric evolution: (i) the relationship of microbialites in 2.1–2.4 Ga old carbonates of the Minas Supergroup in the Quadrilátero Ferrífero, Minas Gerais (the oldest Brazilian fossils) to the development of the early oxygenic atmosphere and penecontemporaneous global tectonic and climatic events; (ii) the evolutionary and biostratigraphic significance of Mesoproterozoic to Ediacaran organic-walled microfossils in central–western Brazil; (iii) diversity and paleoecological significance of vase-shaped heterotrophic protistan microfossils in the Urucum Formation (Jacadigo Group) and possibly the Bocaina Formation (Corumbá Group), of Mato Grosso do Sul; and (iv) insights into the record of skeletogenesis and paleoecology of latest Ediacaran metazoans as represented by the abundant organic carapaces of Corumbella and calcareous shells of the index fossil Cloudina, of the Corumbá Group, Mato Grosso do Sul. Analysis of the Brazilian Precambrian fossil record thus holds great potential for augmenting paleobiological knowledge of this crucial period on Earth and for developing more robust hypotheses regarding possible origins and evolutionary pathways of biospheres on other planets.

Zoophycos-group burrows are prevalent elements of the post-Cambrian trace fossil record. Here we report the oldest specimens of Zoophycos from Lower Cambrian strata of the Lower Member Wood Canyon Formation in southeastern California. In addition to these being the oldest examples of this well-known trace fossil, the discovery of these specimens also reveals the presence of deposit feeding considerably earlier than has been suggested for the advent of this feeding style. This type of activity may have had a significant impact on sediment mixing during the Precambrian–Cambrian transition, though the rarity and shallow tier position of these specimens suggests otherwise.

Carbon isotopic data from the Selinde section in the southeastern part of the Siberian platform area are correlated with the reference isotopic profile from the Lower Cambrian stratotype sections of the Lena–Aldan region, but also show additional δ13C excursions unrecognized there. The chemostratigraphic correlation suggests that the geological and fossil record of the lower Pestrotsvet Formation in the Selinde section has a deeper history than the stratotype region. This conclusion is important for both constraining the age of the earliest Cambrian marine transgression on the Siberian platform and providing a clearer understanding of the pace and order of early Cambrian geochemical and biological events.

The cyanobacterial fossil record is among the oldest for any group of organisms, possibly reaching back to 3500 Ma ago. The molecular phylogeny of cyanobacteria is complementary to the fossil findings, confirming the antiquity of the group, the role of cyanobacteria in the evolution of planetary primary production, and the symbiotic origins of plastids in algae and plants from cyanobacterial ancestors. The study of fossil cyanobacteria followed the discovery of Precambrian microbial fossils by S.A Tyler and E.S. Barghoorn in 1954, and is still developing. Most fossil cyanobacteria are preserved in permineralized conditions in cherts and phosphorites or as organic compressions in shales. The interpretation of fossil cyanobacteria is aided by the study of modern counterparts, preferably within their natural habitats. These comparisons include the post mortem degradation of cellular remains. The fortuitous preservation and fossilization of ancient cyanobacterial communities in growth position, i.e. in the synsedimentary context, allows one to draw conclusions about their palaeoenvironment, including interactions between cyanobacteria and ancient sediments. These relations are based on cyanobacterial ecological requirements, and they compare well with behavioural responses of modern cyanobacteria in microbial mats and modern stromatolites. The general trend in the evolution of cyanobacteria is one of gradually increasing complexity and diversity, but the group shows a conservative maintenance of morphological adaptations to successful ecological niches. Accordingly, a large proportion of ancient morphological types is still represented among modern cyanobacteria. Fossil to Recent counterparts are identified for several coccoid and filamentous cyanobacteria. Evidence for heterocystous cyanobacteria is indirect, through identification of fossil akinetes.

The first section of the paper is concerned with a detailed account of the structure of the classic Schiehallion area. The account is extended to the flat belt via the Glen Lyon-Ben Lawers area. It is demonstrated that major D1 folds involve the whole of the Appin and Argyll groups and now face SE. However, the original D1 folds were probably open upward-facing folds which have been refolded and modified by the dominant D2 deformation. D2 is represented by an antiformal complex which culminates downwards in the Boundary Slide, a zone of strong deformation associated with NW translation of Dalradian over the ‘young Moine’ rocks. D3 has been responsible for the rotation of the originally flat D2 structures into their present ‘steep’ attitudes N of Glen Lyon. D4 is represented by the strike-swing of the lower Dalradian formations, possibly related to early movements on the two major faults that bound the area. The concept of a D1 Tay Nappe which roots in the ‘young Moine’ to the N is retained, although the scale and flat attitude of that fold is regarded as in part a product of D2.

Approximately 700 samples from five slate, three marble and five quartzite units have been analysed for 26 elements to determine the use of geochemistry in stratigraphic correlation. Statistical treatment of the data has established that for all the slates and marbles, and certain of the quartzites, geochemistry is a viable method of distinguishing units of similar lithology. The most useful elements for distinguishing the four main slate units are P, Cr. Zn, Cu and, to a lesser extent, Rb, Sr, Y, Nb, Ba, La and Ce. Sr may indicate climatic changes or variable organic activity. The three marble units were considered as three limestone and three dolostone types. Dolostones are distinguished by high insoluble residue contents and the elements that distinguish between the dolostones are heavily influenced by these. Limestones, however, have very large differences in Sr. SiO2, Al2O3, K2O, Cr, Mn, Cu, Rb, Sr, Y and Zr have been used in discrimint function analysis. These parameters are strongly controlled by the insoluble residue with Al2O3, K2O, Cr and Rb being correlated with shaley impurities and SiO2, TiO2 and Zr with sandy impurities. Sr, Pb, Y and Zn, and to a lesser extent S and Mn, appear to be associated with the carbonate fraction.

The quartzites were found to be of three major types: (1) a very variable deltaic deposit (Appin Quartzite Formation), (2) marine bodies of immature quartz sands (Glen Coe and Eilde Quartzite formations) and (3) highly mature quartz sands (Binnein Quartzite Formation and northerly outcrops of the Glen Coe Quartzite Formation). It is possible to distinguish these three types on the basis of some trace elements (Zn, Rb, Sr, Y, Ba, La, Ce) but it is not feasible to distinguish between the Glen Coe and Eilde quartzites purely on geochemistry. The Eilde Flags, an immature estuarine sandstone, has a geochemistry intermediate between that of the quartzites and the pelites, although with higher CaO, Zr and Ba than either.

In spite of the structural complexity of polyphase deformed gneisses and migmatites and the absence of distinctive marker horizons, these rocks are amenable to structural investigation and interpretation with resolution of their tectonic history possible, particularly in regions of reasonable exposure. Although methods such as those employing interpretation of stereo-plots can seldom be used, direct observation of refold relationships on the outcrop using all available structural, igneous and metamorphic features will ultimately lead to the resolution of the deformational history. This is achieved by determining the relationships of fold sets observed at the various localities examined throughout the field of investigation and then combining these by correlation according to basic stratigraphical principles. The effects of weak deformation normally not discernible in complicated successions may be detected by the simple form of folded planar and linear structures in igneous masses emplaced in complex structures at intermediate stages in the deformational history.

Synthesis of the total succession and determination of the overall sequence of deformation in particularly complex terranes is made easier if at least one distinctive set of structures can be recognised throughout the area. These key structures have the effect of subdividing the long succession into two in which refold relationships are generally more easily determined. An example of the method is given using photographs from the migmatite terrane in southern Finland.