Thrombolite microframes

Abstract ref. 1979:
Mid Cambrian reefs with microframe structure built by calcified microbes, probably cyanobacteria, are well-exposed in the Zhangxia Formation near Jinan in
Shandong Province. Members of the Epiphyton, Renalcis and Girvanella groups are almost solely responsible for a series of extensive biostromes, individually up to 15 m thick, in which metazoans are scarce. These reefs are surrounded by coarse cross-bedded oolite-pisolite, reflecting rapid growth in a high-energy environment.
The two main reef lithotypes present are: (1) matrix-rich Tarthinia-Tubomorphophyton thrombolite-dendrolite microclusters, and (2) Gordonophyton-Razumovskia thrombolite microframes. The latter were created by rectilinear arrangement of prostrate and vertical microbial filaments, and the small (millimetric) size of the cavities contributed to framework strength.
Similar, but usually less well-preserved, mid-late Cambrian reefs appear to be widespread in Asia and North America. These North China examples establish
microbial microframes as a distinctive reef-structure, and show that frame-building continued during the Cambrian despite archaeocyath demise.
