tafoni #1

What are all those holes?!  That's tafoni, in Entrada sandstone in western Colorado.

Too much work right now -- three field seasons’ worth of information to describe and discuss in a report due in a few weeks.  A recurring sense of déjà vu finally focused on a time in the distant past.  This is the same scale of suffering I experienced while writing my thesis!  So for now, I’m falling back on a stash of tafoni photos in lieu of written posts.

Tafoni, natural pockets in rock, range in size from little pits to huge cavities and come in an entertaining variety of shapes and patterns.

Elongate tafoni; 52-lb dog for scale.

Sometimes there are tafoni within tafoni.

Above, nested tafoni ... not to be confused with nest in tafoni, below.

Tafoni form through weathering (decay) and erosion (transport away), though specific processes remain mysterious in many cases.  This is another one of those wonderful geo-situations where educated speculation can run wild.

An observation -- tafoni are lined up parallel to bedding planes -- leads to an idea.  Perhaps there was an interval of deposition that included coarser fragments, which fell out when exposed by erosion, opening tiny cavities that weathered with time.

Alas, around the corner there are diagonal patterns as well.

Whatever their origins, tafoni patterns are beautiful, fascinating, even mesmerizing, and for awhile I was completely lost in photographing them.  Not a bad way to spend a morning.

Sparky, ever the pragmatic dog, focused on utility instead.

I think I see something very interesting.

Yep, let's go check it out.

Black dog finds welcome respite from heat ... in tafoni.

All photos are from the McInnis Canyons National Conservation Area south of Grand Junction, Colorado, where there is a nice network of trails touring the steep fold (monocline) on the north flank of the Uncompahgre Plateau.  Tafoni are common along the Devil's Canyon Trail in Jurassic sandstone, deposited “in an eolian setting that was on the northeast margin of a large dune area, or erg, that occupied most of the Four Corners area" (Scott et al. 2001.  Geologic Map of Colorado National Monument and Adjacent Areas, Mesa County, Colorado; see the actual map here).

There is an entire website devoted to tafoni and its puzzling origins -- Jon Boxerman's TAFONI.