Stromatolites then ... wildflowers now

Even though my blog is called In the Company of Plants and Rocks, I managed to get away with having no rocks whatsoever in the header photo for almost a year.  The problem has been fixed.  The new header features alpine wildflowers growing on two-billion-year-old metadolomite in the Snowy Range of southeast Wyoming.

Varileaf cinquefoil (yellow; Potentilla diversifolia) and alpine clover (white/pink; Trifolium dasyphyllum) in a planter of ancient metadolomite.

Fossil stromatolite and alpine clover.

The metadolomite of the Nash Fork Formation contains abundant fossil stromatolites, among the oldest records of life on earth.  Two billion years ago, these were domes and reefs made of marine algal mats and trapped sediment.  In spite of continental collision and several mountain-building episodes, the rocks have undergone only low-grade metamorphism and stromatolite structures are easy to discern.

Sparky found quite a nice fossilized stromatolite.

From Knight, S.H.  1968.  Precambrian stromatolites, bioherms and reefs in the lower half of the Nash [Fork] Formation, Medicine Bow Mountains.  Rocky Mountain Geology 7:73-116.

Several stromatolitic “reefs” of the Nash Fork Formation are well-exposed in the Snowy Range (Medicine Bow Mountains) a short distance north of US Highway 130 and east of Libby Lake.  When we were there in mid-July, the old marine reefs were brightly decorated with wildflowers.

Yellow flowers of common stonecrop (Sedum lanceolatum).

A mass of alpine phlox flowers (Phlox pulvinata).

Colorado columbine (Aquilegia coerulea) and greenleaf bluebells (Mertensia viridis; on left, click to view).

Alpine clover sprawls over remains of ancient algal mats.

Rock art of the Nash Fork Formation.

In the company of plants and rocks.  Photo by Jim LoCascio.