A Living Stromatolite that Mimics Its Billion-Year-Old Precambrian Counterpart

Robert N. Ginsburg
University of Miami, Rosenstiel School of Marine and Atmospheric Science, Miami, FL

Jacutophyon, one of the most unusual and bizarre stromatolites of the Precambrian resembles a pine tree whose regularly-spaced and upward-inclined branches are shaped like the petals of an artichoke. Specimens of this stromatolite, all of which are in the range of billion years old, have been described from Siberia, the Mauritanian Sahara, Northern Norway, Brazil and Argentina. The cylindrical “trunk” of Jacutophyon from Mauritania, some 30 + cm in diameter and up to 2 m tall, consists of nested conical laminations (Conophyton).  These trunks are surrounded by regularly-spaced petals inclined upward @ 50° +, composed of convex-upward laminations that are alternations of micrite and dolomite.

Remarkably similar petals occur around the stromatolitic core of a Holocene specimen 1.5 m tall in a Bahamian tidal channel. These petals, like those of the Precambrian, consist of convex-upward laminations, but unlike their predecessors, they are composed of ooids. Living examples of these petals are common around other columnar stromatolites in the same tidal channel where they occur   preferentially on the ocean-facing sides. The similarity of the laminations in the petals with those in the stromatolites on which they develop implies that the same cyanobacteria, Schizothrix, is responsible for trapping and binding the ooid sand grains and their initial stabilization.  The nearly identical morphology of Precambrian and Holocene petals is strong support for using Holocene stromatolites as guides to interpreting the morphology and depositional environment of some Precambrian examples.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005