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The Cambrian Series 3 thrombolites from the Changhia Formation, at the Jiulongshan section in Shandong Province, northern China, provide an excellent example for studying the development of calcimicrobial structures. Thrombolites constructed by calcimicrobes have particular stacking patterns, which are controlled by their environments and are reflected in the relationships between micro-, meso- and macroscopic structures, requiring an approach we term “multiscopic”. Under high-energy conditions, Epiphyton A (with dense micritic bifurcating thalli) grew sporadically and adapted to the environment by taking a bushy-lateral form, because the bushy-upward form is more likely to be broken by waves or currents. Epiphyton A was fused with each other to form spotted frameworks at the mesoscopic level. The weak baffling of spotted frameworks led to the formation of low-relief tabular/lentoid macrostructures via preferential lateral accretion. In low-energy, deep-subtidal settings, Epiphyton A and Epiphyton B (with microsparry segments in the bifurcating thalli) coexisted with Hedstroemia A (with a wide terminal) and B (with a narrow terminal). These calcimicrobes grew abundantly in both the vertical and lateral directions, fusing together to form meshed frameworks, or dendritic frameworks if vertical fusion of bushy-upward calcimicrobes was predominant. The preferential vertical stacking of meshed and dendritic mesostructures highlights the ability of these frameworks to actively baffle lime mud, and ultimately to form large-domed macrostructures. Stacking patterns in these multiscopic structures help to inform environmental interpretations of thrombolites. The thrombolitic growth model we present here provides important insights into the environmental interpretations of thrombolites in other cases, especially the calcimicrobe-dominated early and middle Palaeozoic thrombolites. [ABSTRACT FROM AUTHOR]

Abstract: The archaeocyath-bearing reefs that first appeared in South China in the Atdabanian were last seen in the lower Toyonian (e.g., in the Tianheban and Jindingshan formations). The upper Toyonian–lower Amgan Qingxudong Formation of Hunan Province examined in this study includes large-sized reefs formed solely by calcimicrobes of Epiphyton, Kordephyton, Girvanella, Hedstroemia, and Renalcis. During the middle and upper Cambrian, small-scale stromatolite reefs were formed. The Qingxudong reefs are therefore interpreted to be the most well-developed microbial reefs of the post archaeocyath-bearing reefs in the late early Cambrian. The transition from archaeocyath-bearing to purely microbial reefs was caused by a decline in the diversity of metazoans, and was accompanied by a reduction in the abundance of reefs, possibly related in part to late early Cambrian regression. The late early Cambrian reefs of South China contain a well-preserved record of reef succession, and provide important insights into the factors that led to the demise of archaeocyath-bearing reefs and the subsequent long-lasting hindrances to the development of skeletal-dominated reefs during the middle and late Cambrian. [Copyright &y& Elsevier]