Erschienen:
Proceedings of the National Academy of Sciences, 2015
Erschienen in:
Proceedings of the National Academy of Sciences, 112 (2015) 17, Seite 5337-5341
Sprache:
Englisch
DOI:
10.1073/pnas.1422887112
ISSN:
0027-8424;
1091-6490
Entstehung:
Anmerkungen:
Beschreibung:
Significance The snowball Earth hypothesis predicts that the entire Earth was covered with ice. Snowball Earth events were suggested to have occurred several times during the Precambrian. Classic paleo-thermometers (e.g., 18 O/ 16 O in marine carbonates) are not available from snowball Earth episodes, and only a few reconstructions of 18 O/ 16 O in ancient meteoric water exist. Here we present a novel approach to reconstruct the 18 O/ 16 O composition of ancient meteoric waters using the triple oxygen isotopic composition ( 17 O/ 16 O and 18 O/ 16 O) of hydrothermally altered rocks. The inferred 18 O/ 16 O for waters that precipitated at (sub)tropical paleo-latitudes on a Paleoproterozoic (∼2.4 gigayears ago) snowball Earth are extremely low. Today, similar compositions are observed only in central Antarctica.