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Fig. 7 | Journal of Palaeogeography

Fig. 7

From: Sedimentology of reefal buildups of the Xiannüdong Formation (Cambrian Series 2), SW China

Fig. 7

a Field photo of R 3 shows oolite beds onlapped the reef-mound flank with a sharp contact (red arrow). Hammer length = 30 cm; b Polished slab shows archaeocyaths (Ac) are abundant and intact. Scattered archaeocyaths were linked weakly to form a porous and loose framework. Locally adjacent archaeocyaths and their tersoids developed cavities having geopetal structure (red arrows). Micrite and siliciclastics deposited among the framework. Sample 45 in Fig. 2; c Photomicrograph (PPL) shows the close-up of rectangle area (marked as Fig. 7c) in (b). Two archaeocyathan fossils (Ac) were bound by tersoids twining (red arrow). The silty/sandy micrite (M) deposited between archaeocyaths; d Photomicrograph (PPL) shows the close-up of rectangle area (marked as Fig. 7d) in (b). A cavity was formed by adjacent archaeocyaths and possibly microbial clotted texture attached on tersoids. Geopetal structure developed in the cavity, and is comprised of spar cements (upper part, f2) and micrite sediments (lower part, f1); e The close-up of a rectangle area (marked as (Fig. 7e) in (b) shows a cavity like stromatactis which was formed by archaeocyaths and tersoids. The lower part of (e) is the tracing of the upper part

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