Busca avançada
Ano de início
Entree
(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Carbonate REE plus Y signatures from the restricted early marine phase of South Atlantic Ocean (late Aptian - Albian): The influence of early anoxic diagenesis on shale-normalized REE plus Y patterns of ancient carbonate rocks

Texto completo
Autor(es):
Caetano-Filho, Sergio [1] ; Paula-Santos, Gustavo M. [2] ; Dias-Brito, Dimas [3]
Número total de Autores: 3
Afiliação do(s) autor(es):
[1] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo, SP - Brazil
[2] Univ Estadual Campinas, Inst Geociencias, BR-13083870 Campinas, SP - Brazil
[3] Univ Estadual Paulista, UNESPetro, Ctr Geociencias Aplicadas Ao Petroleo, BR-13506900 Rio Claro, SP - Brazil
Número total de Afiliações: 3
Tipo de documento: Artigo Científico
Fonte: PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY; v. 500, p. 69-83, JUL 1 2018.
Citações Web of Science: 2
Resumo

Rare earth elements plus yttrium have been extensively applied in paleoenvironmental studies of ancient carbonate successions due to their fractionation in the marine environment. However, in modem marine anoxic environments, seawater REE + Y signatures can be suppressed in reducing conditions (e.g. stagnant basins and/or early diagenesis) by REE remobilization from several sedimentary components (e.g. detrital siliciclastics, oxides, organic compounds). We present the shale-normalized REE + Y signatures for a transgressive marine carbonate succession of the primitive South Atlantic Ocean (latest Aptian-Albian), in a restricted marine setting with anoxic bottom conditions, to provide and evaluate the REE + Y record deposited in such conditions. Based on well-constrained paleoenvironmental reconstruction through microfacies analysis, three shale normalized REE + Y patterns were identified, varying according to the microfacies associations (MA) and related diagenetic environments: a) light REE-enriched patterns in the more proximal MA associated with burial diagenesis at the base of section; b) flat patterns towards distal MA related to anoxic and sulfidic early diagenesis; and c) middle REE-enriched patterns in MA related to dissolution of Fe-Mn oxy-hydroxide grains under reducing early diagenesis. Cerium anomalies are absent due to stagnant water mass conditions, in accordance with previous studies for the early marine South Atlantic. Y/Ho ratios are lower than modem seawater values, with an increasing trend towards more distal facies. The ``non-seawater{''} shale-normalized REE + Y patterns of the marine carbonates from the primitive South Atlantic Ocean corroborate studies in modern marine reducing environments, in which REE can be remobilized from detrital phases, oxides and organic compounds, suppressing the primary seawater REE Y signature of authigenic minerals. Caution is suggested for the sole use of carbonate REE + Y signatures as paleoenvironmental proxies, especially in ancient successions lacking proper microfaciological components. (AU)

Processo FAPESP: 16/11496-5 - Ciclos biogeoquímicos de enxofre e carbono no Ediacarano e seu registro em sucessões sedimentares brasileiras
Beneficiário:Sergio Caetano Filho
Linha de fomento: Bolsas no Brasil - Doutorado
Processo FAPESP: 17/00399-1 - Intemperismo químico e fluxo de nutrientes para o oceano no Ediacarano superior e suas relações com a diversificação da vida
Beneficiário:Gustavo Macedo de Paula Santos
Linha de fomento: Bolsas no Brasil - Pós-Doutorado