TY - JOUR
T1 - Large and robust lenticular microorganisms on the young Earth
AU - Oehler, Dorothy Z.
AU - Walsh, Maud M.
AU - Sugitani, Kenichiro
AU - Liu, Ming Chang
AU - House, Christopher H.
N1 - Funding Information:
DZO was supported by NASA Mars Science Laboratory Participating Scientist Grant #10-MSLPSP10-0094, by Astromaterials Research and Exploration Science at Johnson Space Center, and by the Planetary Science Institute. MWW was supported by the Louisiana State University Council for Research, the Louisiana Space Consortium and the Board of Regents Support fund, and the NASA Space Grant Program under NGT5-40035. G.F. Worrell collected and made available samples from the Kromberg Formation. G.R. Byerly and D.R. Lowe provided MMW guidance in field and laboratory studies. CHH was funded by the NASA Astrobiology Institute (cooperative agreement #NNA09DA76A) and NASA Exobiology #NNX14AJ9OA. KS was supported by the Japanese Society for the Promotion of Science (Grant-in-Aid #’s 22340149 and 24654162) and by N. Takagi for thin section preparation. M-CL was partially supported by a grant from the Instrumentation and Facilities Program, Division of Earth Sciences, National Science Foundation which partly supports the UCLA SIMS facility.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/7/1
Y1 - 2017/7/1
N2 - In recent years, remarkable organic microfossils have been reported from Archean deposits in the Pilbara craton of Australia. The structures are set apart from other ancient microfossils by their complex lenticular morphology combined with their large size and robust, unusually thick walls. Potentially similar forms were reported in 1992 from the ∼3.4 Ga Kromberg Formation (KF) of the Kaapvaal craton, South Africa, but their origin has remained uncertain. Here we report the first determination of in situ carbon isotopic composition (δ13C) of the lenticular structures in the KF (obtained with Secondary Ion Mass Spectrometry [SIMS]) as well as the first comparison of these structures to those from the Pilbara, using morphological, isotopic, and sedimentological criteria. Our results support interpretations that the KF forms are bona fide, organic Archean microfossils and represent some of the oldest morphologically preserved organisms on Earth. The combination of morphology, occurrence, and δ13C values argues that the lenticular forms represent microbes that had planktonic stages to their life cycles. The similarity in morphology, δ13C, and facies associations among specimens from Australia and South Africa suggests that the lenticular microfossils on the two continents represent related organisms. The biological success of these organisms is demonstrated by their abundance, widespread distribution, and the fact that, as a group, they appear to have been present at least 400 million years. This success may be due in part to their robust structure and planktonic habit, features that may have contributed to survival on a young planet. Isotopic results further suggest that the lenticular organisms were autotrophs, an interpretation supporting the view that autotrophic metabolisms developed early on the young Earth.
AB - In recent years, remarkable organic microfossils have been reported from Archean deposits in the Pilbara craton of Australia. The structures are set apart from other ancient microfossils by their complex lenticular morphology combined with their large size and robust, unusually thick walls. Potentially similar forms were reported in 1992 from the ∼3.4 Ga Kromberg Formation (KF) of the Kaapvaal craton, South Africa, but their origin has remained uncertain. Here we report the first determination of in situ carbon isotopic composition (δ13C) of the lenticular structures in the KF (obtained with Secondary Ion Mass Spectrometry [SIMS]) as well as the first comparison of these structures to those from the Pilbara, using morphological, isotopic, and sedimentological criteria. Our results support interpretations that the KF forms are bona fide, organic Archean microfossils and represent some of the oldest morphologically preserved organisms on Earth. The combination of morphology, occurrence, and δ13C values argues that the lenticular forms represent microbes that had planktonic stages to their life cycles. The similarity in morphology, δ13C, and facies associations among specimens from Australia and South Africa suggests that the lenticular microfossils on the two continents represent related organisms. The biological success of these organisms is demonstrated by their abundance, widespread distribution, and the fact that, as a group, they appear to have been present at least 400 million years. This success may be due in part to their robust structure and planktonic habit, features that may have contributed to survival on a young planet. Isotopic results further suggest that the lenticular organisms were autotrophs, an interpretation supporting the view that autotrophic metabolisms developed early on the young Earth.
UR - http://www.scopus.com/inward/record.url?scp=85019120272&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85019120272&partnerID=8YFLogxK
U2 - 10.1016/j.precamres.2017.04.031
DO - 10.1016/j.precamres.2017.04.031
M3 - Article
AN - SCOPUS:85019120272
SN - 0301-9268
VL - 296
SP - 112
EP - 119
JO - Precambrian Research
JF - Precambrian Research
ER -