Pine Barren Flora

[bobpbx]

Starting to get my swamp legs working again. Found an interesting stone yesterday, maybe 12" X 7" by 4". Was kicked up by a plow at one of the deer fields. Cannot figure out the pits on the surface. Seemed much heavier than sandstone, and more silicate.

 

[manumuskin]

Looks like some kind of sandstone conglomerate.I have seen rock like that around here and think it may be native but have never seen beds of it.Were you on top of a ridge?

 

[bobpbx]

Were you on top of a ridge?

No, but we are in what I call the Pine Barren Highlands here over by 539 in Greenwood Forest. Even the elevation next to the streams is 100' above sea level. I found it close to a cripple (or just a low spot), as indicated by the red line in the map below.

 

[bobpbx]

I've just read something Spung-man wrote that makes me think of what this rock really is; a silcrete rock that has been subject to intense wind-scalloping and polishing (paraphrased from his writing).

 

[Spung-Man]

Now you gone and done it...

OK, it a hard piece of sandstone? It would help to see the bottom surface, which might be a better clue to the original stone color. Is that a thick glossy skin-deep rock coating on the cobble, or is the cobble matrix glossy tan-to-orange all the way through? Provisionally this could be silcrete, which is native to the Pines.

https://forums.njpinebarrens.com/threads/about-difference-in-nj-stones.5534/#post-64755​

Silcrete is extremely dense-grained and very hard. It takes a good polish of rock coating of silica and iron, helping to facilitate deep wind-etching etching into flutes and scallops (the largest flutes). The Pine Barrens silcrete formed as a Miocene soil-derived duricrust, so some of the larger pits can be old root casts that were softer than the amorphous silica-hardened cobble matrix. Cool beans.

https://forums.njpinebarrens.com/threads/strange-stone.10230/#post-122766
https://forums.njpinebarrens.com/threads/cumberland-county-stones.10240/page-2#post-123541​

Sure looks like a cripple to me.

http://loki.stockton.edu/~demitrom/geodiversity_files/Demitroff & Nelson 2008 Poster.pdf​

S-M

 

[bobpbx]

Thanks Mark! As always, very interesting information provided by you. I took the rock, but it's under 2" of wet snow in my yard. I'll be uncovering it and giving you more information on it later this week. If I recall, yesterday when I turned it over it appears to be something sheared off an even bigger rock.

 

[Spung-Man]

This is what I had in mind—the smaller etchings look like flutes, the larger ones scallops, and the dark holes could be root casts or glaebules; pending a closer look.

 

[bobpbx]

I looked up glaebule, but what are flutes and scallops representing?

 

[Spung-Man]

Strong density-driven winds pouring off the nearby Laurentide Ice Sheet lifts grains of sand from a barren landscape. The sands leap and spin in a process called saltation. You may have been pelted by stinging sand in saltation at the beach on a very windy day. These wind-carried grains bombarded the stone's surface, slowly plucking it away, leaving behind aerodynamic dimples like flutes, grooves, and the terrestrially rare scallop form. Rare on Earth, scallop ventifacts are common on Mars. While many believe that sand is the sole ventifact abradent, I assert that dust and possibly even ice crystals also abrade rock at the cold temperatures present in the Ice Age. This stuff is at the cutting edge of our understanding of process physics.

The glossy rock coating appears to be silica dust and iron dust burnished onto the rock surface by high winds.

http://onlinelibrary.wiley.com/doi/10.1002/ppp.1860/abstract​

S-M

 

[bobpbx]

Thanks Mark. Truly fascinating!