The famous microbialite deposits within Hamelin Pool (Shark Bay, Western Australia) provide important modern analogues for understanding the processes involved in the formation of Deep Time microbialite reefs. Here, we extend the potential for analogous study by comparison of the effects of Tropical Cyclone (TC) Olwyn (March, 2015) on Shark Bay microbialites to potential storm deposits from a c. 2.4 Ga microbialite reef complex from the Turee Creek Group (TCkG) of Western Australia. Previous studies of Deep Time microbialite reef complexes have identified the effect of past storms in the form of flat pebble (or edgewise) conglomerates in very shallow water (peritidal, or lacustrine shoreline) settings, yet recent observations of the effects of TC Olwyn on Shark Bay microbialites indicate that a higher number of facies in ancient deposits may relate to storm events than has been previously recognised. A key feature relating to TC Olwyn is the formation of a number of different types of benthic microbial mucilage deposits from storm generated floc. This relatively unknown storm process drove a biogeomorphic response by the benthic microbial ecosystem that contributed to the development of microbial mats and structures with the capacity to form stromatolites (Morris et al., 2022). The TCkG microbialite reef complex consists of five shallow- to deep-water facies associations, one of which occurs at the transition from shallow to deep water facies and includes an average of 40 m thick of “clotted, thrombolite-like microbialite” (Barlow et al., 2016) or “clotted microbialite aggregate” (Nomchong and Van Kranendonk, 2020). While (Barlow et al., 2016) regarded this unit as having formed as thrombolite-like microbialite in a low-energy, low-sediment subtidal environment, Nomchong and Van Kranendonk (2020) suggested an origin of the clots as “…ripped-up fragments of semi-lithified, non-laminated microbialite derived from intertidal to subtidal environments where they would be more susceptible to erosion by storm events”. Here, we collectively explore these interpretations in light of the subsequently reported impacts of TC Olwyn. Given the differences in the hydrochemistry of the Archean and Proterozoic times compared to today, rapid organomineralisation and/or silicification of benthic mucilage aggregates may have contributed to granular and clotted textures between stromatolitic structures such as those observed in the TCkG. 

Reference(s)

Barlow, E., Van Kranendonk, M., Yamaguchi, K., Ikehara, M. and Lepland, A.J.G., 2016. Lithostratigraphic analysis of a new stromatolite–thrombolite reef from across the rise of atmospheric oxygen in the Paleoproterozoic Turee Creek Group, Western Australia. 14(4): 317-343. 

Morris, T.E., Morris, S., Fearns, P.R.C.S., Chopra, A., Aspandair, M.F., Collins, L.B., O'Leary, M.J. and Visscher, P.T., 2022. Impacts of Severe Tropical Cyclone Olwyn and the biogeomorphic response, Hamelin Pool, Shark Bay, Western Australia. The Depositional Record.

Nomchong, B.J. and Van Kranendonk, M.J.J.P.R., 2020. Diverse thrombolites from the c. 2.4 Ga Turee Creek Group, Western Australia. 338: 105593.