Nerding out on Some Old Bugs

This incredible trackway - in the Permian Collingham Fm., Ecca Group - Maybe it's a eurypterid trackway? It doesn't look like the other eurypterid trackways on the internet. Hilde? Help? Whatever made this was something huge! Here's paleontologist John Almond sitting on the same outcrop for a SABC show about the Dwyka glaciation / Ecca Sea.

A bit of paleo-environmental background and a few questions:
The Dwyka Group (Carboniferous-Permian) contains a minimum of 3 regressive sequences - mostly glaciomarine diamictite, laminated or massive. There is some weird shiznit in there, including Banded Iron Formation boulders (which I have only collected one large hand sample of but must get more!) The warming sequence is the Ecca Group - brackish to marine, transgressive sequence - begins with a silt/shale unit of variable colour and fresh water del18O (Prince Albert Fm) which is gleefully structurally destroyed in the Laingsburg area but my guess is no more than a few 10s meters thick. More on that later. That is overlain by gypsum-bearing black anoxic shales (only a few meters): the Whitehill Fm. The Collingham Fm. where these trackways are found is more normal looking turbiditic sequence with blackish shales and gray siltstones. Not sure about salinity. Above that we get coarser and more sandy turbidites for hundreds, more like thousands of meters. There's not much published on these formations - and the work is quite old. From a shallow survey of the eurypterid literature, it looks like by the Permian most of the big guys are showing up in brackish-fresh anoxic lagoons and sometimes hypersaline lagoons.

This leads to my big question about the whole Ecca Group, and indeed the Dwyka Group as well - aren't these to some degree marginal environments? Where on earth today can one find a place like this? The Black Sea perhaps if it were near to the South Pole, as the inland Ecca Sea was during the Carboniferous-Permian? What about the Dwyka - how are the massive diamictites deposited, and are they in fact true tillites? Both the massive (aka "coarse") and laminated subunits have dropstones and are mostly rock flour except for the 1c-2c "Boulder Bed" (See John Rogers' photo here). I guess I should read the papers before I get on my soap box but doesn't this sound like sub-ice sheet deposition, with maybe varve cycles developing during times of thinning and/or increased seasonal sensitivity in the basin?

Finally, the Burgess Shale mystery animal Hallucigenia has been positively identified and is extant in the Succulent Karoo. This is going to be bigger than the coelocanth.
The Cambrian fossil

My photo

**** sorry for the nerdy jokes, I am tired from the trip ****
****** I hope Al Curren is proud that I recognized Hallucigenia on sight ******

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