Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Stromatolites. (A) Modern stromatolites accreting subtidally in Shark Bay, Western Australia. (B) Columnar stromatolitic bioherm, ca. 800 Ma Inzer Formation, Russia. (C) Domal stromatolite from a coastal environment, ca. 800 Ma Grusdievbreen Formation, Spitsbergen. (D) Early Archean stromatolites, ca. 3400 Ma Warrawoona Group, Western Australia; note conoidal form in right-center. Scale bars, 20 cm (A); 12 cm (B,C); 8 cm (D).
