Precambrian fossils, oddballs, Treptichnus pedum and moving camp – fieldwork summer of 2014

written by Anette Högström

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Fig 1. From days gone, fishing cabins on our way to sections south of camp at Manndrapselva.

 

We have moved camp from the Precambrian to the Cambrian, in the midst of wind and rain after packing a weeks worth of samples and specimens that will await pickup towards next week. Results have been manifold. Our quest for the oldest macroscopic organisms on the Digermul peninsula have given us large surfaces covered with mainly Aspidella sp., they look like holdfasts or attachment structures of soft bodied animals where only the holdfasts are preserved. They appear to have been quite rigid and were preserved sitting in the sediment on an ancient sea floor whereas the remainder of the animal may have looked like a frond standing up from the bottom. We now have large numbers of discs of varying size, but no clear frond or anything similar. Our last day on the southernmost exposure of the Ediacaran beds south of Manndrapselva revealed amazing discoveries. After tracing a bed we knew to contain a number of Aspidella discs we hit upon a spot where we fortunate to excavate a larger surface. It did require removing the overlying rock or overburden with the help of long crowbars, chisels, hammers and a large portion of stubbornness. The overburden finally gave way, and the hard work paid out! The surface showed an abundant and well preserved association of Aspidella and a few more odd structures. We were not sure of what all the features represent at the moment, but no obvious fronds were seen. A smaller float (a piece of rock found loose) contains a structure, albeit poorly preserved, that actually may prove to be a frond. This could be one of the more important finds as it may be the very first discovery of this type of structure connected to these discs.

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Fig 2. Surface covered with Aspidella.

Further up from the shore in a small valley still partially filled with snow but without name (quickly nicknamed “no-name valley”) the hunt for the Precambrian – Cambrian boundary is on. Treptichnus pedum is a trace fossil distinctly Cambrian and wherever it appears we know the boundary is close. This is one of the most exciting periods in the evolution of life, huge functional changes happen and animals more similar to the ones we know from today emerge in the oceans. Animals leaving behind a multitude of traces on these shallow marine bottoms, traces we are looking for roughly 550-540 million years later. Close to where the snow still lies Treptichnus appears on an under surface worthy of showing students. However, there is one trace still eluding us, it looks a bit like series of small stacked bananas, called Palaeopascichnus.

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Fig 3. Linn at work at the Treptichnus pedum level in “no-name valley”

 

This first week in the Precambrian at Manndrapselva ends with a tired group on the beach waiting for Trygve to come pick us up and drop us off at Breidvika where our search for early life will continue in the Cambrian.

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Fig 4. Awaiting pick up on the Precambrian pebble beach at Manndrapselva.

 

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