Ediacaran-Cambrian microbialites of the Southern Amazon Craton: relation with the metazoan rise, sea-level changes, and global tectonics

Nogueira, Afonso César Rodrigues; Santos, Renan Fernandes dos; Romero, Guilherme Raffaeli; Bandeira, José; Riccomini, Cláudio; Barrera, Ivan Alfredo Romero; Silva, Pedro Augusto Santos da; Soares, Joelson Lima; Fairchild, Thomas R.; Nogueira, Anna Andressa Evangelista; Góes, Ana Maria; Oliveira, Rick Souza de; Medeiros, Renato Sol Paiva de; Andrade, Luís Jesuíno de Oliveira; Brito, Alba Regina Monteiro Souza; Oliveira, Pedro Guilherme Assunção; Sodré, Argel de Assis Nunes; Carvalho, Davi Ferreira de; Truckenbrodt, Werner

doi:10.1590/2317-4889202220210065

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“…A significative erosive gap has been detected between the Araras and Alto Paraguai groups in the study region (ca. 610–540 Ma), based on the δ 13 C global isotopic curve, Cambrian fossil assemblage at the base of the siliciclastic sequence and evolution of stromatolite communities along the succession (Figure 2a) (Nogueira et al, 2019, 2022; Santos et al, 2017).…”

Section: Geologic Settingmentioning

confidence: 99%

“…It is the basal unit of the Araras Group (cap carbonate sequence), which immediately overlies the Puga diamictite and is unconformably superimposed by Cambrian siliciclastics of the Alto Paraguai Group (Figure 2a). A foreland setting has been proposed (Bandeira et al, 2012;McGee et al, 2014McGee et al, , 2015Trompette et al, 1998), but more recent structural and paleoenvironmental data indicate transtensional tectonics in epicontinental setting following the formation of the Paraguai belt and amalgamation of Western Gondwana (<650 Ma;Santos et al, 2020;Nogueira et al, 2019Nogueira et al, , 2022.…”

Section: G Eolog I C S E T Tingmentioning

confidence: 99%

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Constraining the diagenesis of the Puga cap carbonate from U–Pb in‐situ dating of seafloor crystal fans, southern Amazonian craton, Brazil

et al. 2023

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Massive cap carbonates punctuate the aftermath of two long lived global glaciations (Sturtian: ca. 717-659 Ma; and Marinoan: ca. 650/639-635 Ma;Hoffman et al., 2017). It is predicted that their precipitation resulted from alkalinity oversaturation of seawater due to rapid global ice melting and weathering of exposed continental shelves (Hoffman & Schrag, 2002). Oxygenation of the ocean in the recovery from this disturbed state may have promoted the earliest diversification of animals (Sahoo et al., 2012). Nevertheless, due to lack of fossil content and lithologies suitable for precise dating, the chronostratigraphy of these successions is poorly defined.Marinoan cap carbonates are recognized in more than 10 paleocontinents by well-developed decameter-thick cap dolostone and limestone with typical anomalous lithofacies and geochemistry (δ 13 C carb ca. −7 to −3‰ and 87 Sr/ 87 Sr carb ca. 0.7071-0.7073; et al., 2010). Their synchronicity is tested by U-Pb zircon ages (ca. 635 Ma) from volcanic ash layers within deglacial deposits from Australia, China, and Africa (Hoffman et al., 2017). HalversonNevertheless, timescale for cap carbonates deposition is unknown.Carbon cycling under ultra-high pCO 2 conditions would have led to "fast" carbonate precipitation (10 3 -10 4 years, Higgins & Schrag, 2003;Yu et al., 2018), however multiple paleomagnetic reversals in the cap dolostone implies 10 5 -10 6 years of deposition (Trindade et al., 2003).

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Section: Geologic Settingmentioning

confidence: 99%