Show Us Your Erratics.

[Ludwigia]

1 hour ago, TqB said:

 

Neat little things - I mostly collect Palaeozoic ones but can't resist button corals of any age when I find them. Here's one from the Hettangian of the extreme north Yorkshire coast (where they only occur at two or three horizons - it was too muddy). They sometimes crop up as erratics further south.

Haimeicyclus ("Montlivaltia") haimei

 

The great thing about them is that they take up a minimum of space

[Plax]

Here's a somewhat different erratic. It's a root rafted erratic. Also it's quite unusual in that it shows the contact between the Eocene Castle Hayne Formation and the Paleocene Bald Head Shoals formation. Until I found this recently I had only found root rafted erratics in shell beds where their presence as root rafted erratics was known by the process of elimination. Big pieces of piedmont crystallione rocks in neogene shell beds here in the outer coastal plain of the carolinas couldn't be explained in any other way (no nearby glaciers). I have seen them in the Early Pleistocene Waccamaw Formation with Waccamaw epibionts on them. Am not talking about human transported rocks of course.

  In the case of the pictured modern erratic, the rock was dredged during river channel enlargement and dumped on a spoil island. A Tree grew around the rock and was then swept away by storms to show up as a piece of drift wood with a rock in it's roots.

Edited May 8, 2017 by Plax
clarification

[jpenn]

I found this within a cobble that was splitting apart in my new house's backyard in the summer of 2016, when I moved back to the lower Delaware Valley (Falls Twp, across from Trenton).

 

I believe this to be a Fluvial Erratic as part of the Trenton Gravel Formation which lines the bed of the nearby Delaware river for some distance from Trenton to Philadelphia. These appear to be some sort of Paleozoic molluscs in limestone. There are indeed Paleozoic formations located well upriver in Pennsylvania, New Jersey and New York with similar fauna. As the majority of the Trenton Gravel cobbles I find are quartz, diabase, and shale from Triassic/Jurassic rocks much nearer upriver, this was an interesting chance find.

 

[Peat Burns]

A cf. Gomphoceras nautiloid that I found in glacial deposits in Kalamazoo, Mich.  The rock was quite rounded from glaciers / meltwater and at some point along the way split open and exposed this little treasure inside