Evaluating iron as a biomarker of rhythmites - An example from the last Paleozoic ice age of Gondwana

Autor(es):Mostrar menos -

Callefo, F. ^[1] ; Ricardi-Branco, F. ^[1] ; Hartmann, G. A. ^[1] ; Galante, D. ^[2] ; Rodrigues, F. ^[3] ; Maldanis, L. ^[2] ; Yokoyama, E. ^[4] ; Teixeira, V. C. ^[2] ; Noffke, N. ^[5] ; Bower, D. M. ^{[6, 7]} ; Bullock, E. S. ^[8] ; Braga, A. H. ^[3] ; Coaquira, J. A. H. ^[9] ; Fernandes, M. A. ^[10]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Inst Geociencias, UNICAMP, BR-13083855 Campinas, SP - Brazil

^[2] Brazilian Ctr Res Energy & Mat CNPEM, Brazilian Synchrotron Light Lab LNLS, BR-13083970 Campinas, SP - Brazil

^[3] Univ Sao Paulo, Inst Chem, Dept Fundamental Chem, BR-05508000 Sao Paulo - Brazil

^[4] Univ Brasilia, Inst Geociencias, BR-70910900 Brasilia, DF - Brazil

^[5] Old Dominion Univ, Dept Ocean Earth & Atmospher Sci, Norfolk, VA 23529 - USA

^[6] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 - USA

^[7] Univ Maryland, Dept Astron, College Pk, MD 20742 - USA

^[8] Carnegie Inst Sci, Geophys Lab, 5251 Broad Branch Rd NW, Washington, DC 20015 - USA

^[9] Univ Brasilia, Inst Fis, BR-70919970 Brasilia, DF - Brazil

^[10] Univ Fed Sao Carlos, Dept Ecol & Biol Evolut, Lab Paleoecol & Paleoicnol, BR-13565905 Sao Carlos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: SEDIMENTARY GEOLOGY; v. 383, p. 1-15, APR 1 2019.
• Citações Web of Science: 2

Resumo

Microorganisms play a significant role in mineral precipitation, but detecting them in the fossil record is still a challenge. Here we offer an example of how the detection of biological activity in the sedimentary environment can modify a classical depositional model. This study describes the activity of microorganisms in sedimentary structures and the iron mineral formation during the last Paleozoic Ice Age in southwestern Gondwana, recorded by the ``Itu rhythmites{''}, Parana Basin, Brazil. The Itu rhythmites have been considered to be varve-type deposits that present alternating dark laminae (clay/silt-size sediments) and light layers (sand/gravel-size sediments) of varied thickness, forming couplets. Earlier studies focused on abiotic processes of these structures. We applied different techniques and analytical approaches were used, such as synchrotron-based techniques and rock magnetic techniques, in order to test the biogenicity of iron minerals contained in putative microbially-induced sedimentary structures. By detecting biominerals in this rock succession, the depositional model had to be reconsidered, taking into account the biological activity, the limitations on the specific conditions for bacterial growth, and for mineral precipitation. Therefore, we offer a new depositional model that considers the role of microorganisms in formation of these laminae, and this model can be considered for other iron-rich rhythmic deposits in other places of the world. Considering the effects of temperature and other factors in the bacterial productivity, the deposition of the latest couplets in the outcrop occurred in different seasons and by different depositional processes, corroborating with the non-periodicity of 1 year per lithological couplet. (C) 2019 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 16/06114-6 - O Sistema Terra e a evolução da vida durante o Neoproterozoico
• Beneficiário: Ricardo Ivan Ferreira da Trindade
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 16/20927-0 - Estudos de acumulações modernas e fósseis de bioclastos em ambientes continentais e costeiros.
• Beneficiário: Fresia Soledad Ricardi Torres Branco
• Modalidade de apoio: Auxílio à Pesquisa - Regular