Middle Cambrian Stromatolites?

[JesseKoz]

Hi Everyone,

 

I've recently returned from a weekend trip to a fossil site in central Australia. The location contains siltstone laid from the ancient ocean once in the middle of Australia during the middle Cambrian. Both John R. Laurie and Dr P.D. Kruse have completed work on the site and have some publications accessible online. Along with a good collection of trilobites I came across a number of what I believe to be stromatolite fossils.

 

The first image (1.1) was found on the way to the location about 150km before we reached it, the road cut through a much lighter shade of rock outcropping than we had previously seen. The formation appeared identical to the Arthur Creek formation, and judging from the geological surveys I have checked it should be part of the same formation. So keep in mind the first image is not from a known fossil bed, but is only from my best judgement part of the same formation.

 

The remaining fossils in 1.2 are all from the known fossil bed, part of the Arthur Creek formation dating to the Templetonia (middle Cambrian).

 

Top-left looks to me like a very typical stromatolite, similar to what is still seen today in Western Australia. The other fossils seem to me to be either the same stomatolite but seen at a different stage of weathering, or another type of stromatolite. I am interested to hear the opinions of those more knowledgeable! Thanks in advance.

 

Trip Post:

 

The fossil site is found in the location below

https://www.google.com/maps/place/21%C2%B042'53.0%22S+135%C2%B039'38.9%22E/@-21.71473,135.66081,1873m/data=!3m1!1e3!4m5!3m4!1s0x0:0x0!8m2!3d-21.71473!4d135.66081

 

In the publication below, NTGS Elk 3 bore samples refer to the location visited.

 

Quote

Biostratigraphy of the Arthur Creek Formation and Thorntonia Limestone, Georgina Basin

by John R. Laurie

https://www.researchgate.net/publication/236858748_Biostratigraphy_of_the_Arthur_Creek_Formation_and_Thorntonia_Limestone_Georgina_Basin

 

NTGS Elk 3

Arthur Creek Formation

6.80-9.60 m: Xystridura altera (Templetonian)

57.15 m: Pentagnostus rectus (Templetonian P. shergoldi Zone)

64.85-65.12 m (Shergold sample): Pentagnostus shergoldi

(Templetonian P. shergoldi Zone)

66.87-85.13 m: Pentagnostus praecurrens (Templetonian P.

praecurrens Zone)

99.20-99.27 m: Pentagnostus anabarensis (Templetonian P.

anabarensis Zone)

Stromatolite and bioturbated sea floor 1.1

 

Stromatolites 1.2

[Johannes]

Material you show are mostly arthropod trace fossils, the lower ones in "Stromatolites 1.2" are Rusophycus isp. (nice ones, by the way).

 

For identifying the upper left, we need pictures showing more details. Doesn't look like a stromatolite following this picture.

[JesseKoz]

Thank you Johannes!

 

Very interesting, sorry stromatolites but having the imprints of trilobites seems much more exciting. I am wondering are the lines created from athropod plates / legs imprints left behind in the sea floor? Also, is the give-away the fact they have a groove down the center? Looking at the same large trilobites I found at the location I see how their bottom plates would make a trace fossil like this.

[westcoast]

2 hours ago, Johannes said:

Material you show are mostly arthropod trace fossils, the lower ones in "Stromatolites 1.2" are Rusophycus isp. (nice ones, by the way).

 

For identifying the upper left, we need pictures showing more details. Doesn't look like a stromatolite following this picture.

+1