Diverse thrombolites from the c. 2.4 Ga Turee Creek Group, Western Australia

Abstract

Observations from a stromatolite-thrombolite reef complex of the c. 2.4 Ga Turee Creek Group, Western Australia, indicate diversity in stromatolite and microfossil morphology, in addition to the appearance of clotted (thrombolite-like) microbialites (Barlow et al., 2016; Barlow and Van Kranendonk, 2018). Here, we document the diverse morphologies and textures of clotted microbialites from the Turee Creek Group reef complex that occur interbedded and interlayered with stromatolites and sediments in the supratidal to subtidal facies. The clotted microbialites consist of four types with distinct gross morphology, mesostructure, and microtextures, including: 1) an aggregate of isolated, millimetre-scale organic-rich clots that accumulated following storm events and were cemented by coarsely crystalline radiating carbonate; 2) domal bioherms composed of a framework of non-laminated branching columns; 3) stratiform clotted microbialites consisting of fine-grained clots that form both an interconnected framework surrounded by coarsely crystalline cement, or comprise a poorly-defined mixture of fine- and coarsely crystalline textural components; and 4) thrombolites that comprise lobate bioherms with non-layered internal textures. Variations in thrombolite texture and morphology are likely driven by a combination of environmental and biological factors, as is the case in modern microbial carbonate environments, such as Shark Bay and the Bahamas. These findings show that the Turee Creek Group clotted microbialites are significantly more diverse than first recognised, adding to previously documented expressions of microbialite complexity from this microbialite reef complex.