Biogenic calcite structures forming in Lake Fryxell, Antarctica

Abstract

Stromatolites are organosedimentary structures produced by microorganisms which have been used extensively in the interpretation of Precambrian and, to a lesser extent, Phanerozoic history^1–5. Modern stromatolites are generally restricted to hot springs or warm, hypersaline and/or alkaline aquatic environments³. Recently, however, we documented⁶ the presence of modern stromatolites in several cold, perennially ice-covered Antarctic dry valley lakes. Here, we report a finding in Lake Fryxell, Antarctica, of biogenic calcite structures not observed in our previous study of other Antarctic lakes. These structures were laminated, indurate, unbranched, and had either a vertical or horizontal orientation. We infer that these calcite structures are biogenic in origin, and hence stromatolitic based on the following evidence: (1) the presence of an actively metabolizing algal mat on their surface; and (2) an internal composition of filamentous blue-green algal cell wall fragments, diatom frustules and calcite crystals.