The Turee Creek Group, is a geologic group in Western Australia, and is a part of the wider Mount Bruce Supergroup. It preserves a number of fossils dating back to the Siderian period, some of which are amongst the oldest known microfossil communities.
The Turee Creek Group is made up of three formations. The basal-most formation within the group is the Kungarra Formation, which is primarily composed of siltstone, with a layer of diamictite rock in the upper sections of the formation, which go under the name of the "Meteorite Bore Member". This is overlain by the middle Koolbye Formation, which is the thinnest of the three, and is predominately composed of sandstone. Finally, the upper-most formation within the group is the Kazput Formation, with dolomite and sandstone at its base, which then turns into just sandstone further towards the top. The group itself is overlain by the basalt composed Wyloo Group, and is underlain by the banded iron dominated Hamersley Group. Alongside the latter group, the Turee Creek Group is a part of the Mount Bruce Supergroup.
Through U-Pb dating of zircon samples collected from the base and top of the group, the group was confidentially placed into the Siderian period, although its true deposition age is still contended.
Zircon samples from the base of the group recovered a date of , whilst samples from the top of the group recovered a date of . Although, other studies have put forward other dates, for example in 2017, a deposition date of â was recovered from zircon crystals based on Detrital zircon geochronology, hinting at a general deposition age of when combining all the dates.
The Turee Creek Group contains a small number of important fossil localities, although the exact placement of a majority of these localities in relations to the formal formations remains difficult to figure out, but some studies note that even then all researchers agree that the following localities are within the Turee Creek Group.
The Turee Creek Group is home to many stromatolites and thrombolites, with the most well known stromatoliteâÂÂthrombolite locality being in the Kazput Syncline. This locality, known as the "Kazput Reef Complex" and only discovered in 2016, is composed of a thick and long dolomitic microbialite reef complex, which has been purposed to be a part of either the upper Kazput Formation or lower Kungarra Formation, with the latter seeming more likely in recent studies. Dating of the area has recovered a date between â , which would make the Kazput Reef Complex the oldest known Proterozoic reef complex yet, predating previous examples by some â .
The Kazput Reef Complex contains up to five distinct facies associations, which are as follows, in ascending age:
Within the Kazput Reef Complex, microfossils of varying shapes and sizes had been also recovered, numbering up to eighteen distinct morphotypes, two of which were previously unknown, and gave evidence to the fact that microbial communities were already quickly diversifying after the end of the Archean. These microfossils can be split into two distinct communities, which are as follows: