Rosselia in core from the Canadian oil sands. I took this photo during an Applied Ichnology course at an AAPG ACE meeting in Calgary. There are amazing courses offered at conferences, and students get crazy discounts!
These organisms were likely attempting to keep up with sedimentation, the oldest traces are towards the bottom of the picture and the youngest towards the top.
This image gives you a unique look at the concentric nature of the mudball tops and the sandy core!
ROSSELIA (OURCROP 1)
This picture is from the Fox Hills Sandstone near Casper, WY. These organisms were pretty happy colonizing the top of this bed. Notice how they are large and their are many of them. Some of the traces show multiple "stories" as the organism moved up through the sediment. In this photo the tops of the mudballs are lopped off for several of the traces. The overlying beds are stormwave deposits. You can still identify the rosselia traces from their tapered shape, concentric mud-packed exteriror, and their sandy cores.
Rosselia (OUTCROP 2)
This picture is from the Fox Hills Sandstone near Casper, WY. This image gives a nice view of the sandy core. Note that from picture to picture the mudball tops have different geometries and are preserved differently. Here the stem of the trace was poorly preserved, but you can see its imprint in the sand.