Morphological and petrographic analysis of newly identified stromatolitic occurrences in the Lagoa do Jacaré Formation, Bambuí Group, State of Minas Gerais, Brazil

Santos, Daniel Martins dos; Sanchez, Evelyn Aparecida Mecenero; Santucci, Rodrigo

doi:10.4072/rbp.2018.3.01

Cited by 6 publications

(5 citation statements)

References 36 publications

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“…The presence of mixed carbonate-siliciclastic facies with local evidence of subaerial exposure (e.g., mudcracks) and salt pseudomorphs indicates deposition in inter-to supratidal settings under transitory evaporitic conditions (Uhlein et al 2019). Domal and columnar stromatolites, as well as laminated microbialites, have also been described in the overlying Lagoa do Jacaré Formation (Iglesias and Uhlein 2009;Fragoso et al 2011;Santos et al 2018;Uhlein et al 2019).…”

Section: Geological Backgroundmentioning

confidence: 97%

“…Abundant stromatolites are known from the Bambuí Group, particularly the Sete Lagoas, Lagoa do Jacaré, and upper Serra da Saudade formations (Vieira et al 2007; Santos et al 2018; Uhlein et al 2020). However, eukaryotic fossils and particularly macroscopic animal fossils are rare in the Bambuí Group, either because of their poor preservation (Simonetti and Fairchild 2000; Warren et al 2014), their rarity due to ecologically stressful environment (Caetano-Filho et al 2019, 2020; Hippertt et al 2019; Caxito et al 2021), or inadequate sampling.…”

Section: Implications For the Paleobiological Record Of The Bambuí Basinmentioning

confidence: 99%

“…Recently, an occurrence of putative trace fossils identified as Treptichnus pedum in association with MISS has been described in the Três Marias Formation, the uppermost unit of the Bambuí Group (Sanchez et al 2021). Microbial structures are less conspicuous and generally poorly preserved in predominantly siliciclastic units of the Bambuí Group (Sanchez et al 2018; Santos et al 2018; Uhlein et al 2020), hampering their identification and interpretation.…”

Section: Introductionmentioning

confidence: 99%

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Simple Structures and Complex Stories: Potential Microbially Induced Sedimentary Structures in the Ediacaran Serra De Santa Helena Formation, Bambuí Group, Eastern Brazil

Okubo

Inglez

Uhlein

et al. 2023

Palaios

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Microbially induced sedimentary structures (MISS) are abundant in Ediacaran and lower Cambrian successions. However, the relationship between MISS distribution and facies has not been thoroughly explored in Ediacaran–Cambrian successions in South America. This study documents the occurrence of MISS and other potential biogenic structures from the late Ediacaran Serra de Santa Helena Formation in the Bambuí Group of eastern Brazil. This unit overlies the Cloudina-bearing Sete Lagoas Formation and is a mixed carbonate-siliciclastic succession devoid of macroscopic body fossils. Potential microbial structures include wrinkled structures such as “elephant-skin” and Kinneyia-like textures, as well as pustular structures and abundant positive epirelief discoidal structures. Another putative biogenic structure is a mm-wide meandering groove resembling a simple locomotion trail of a small vagile benthic metazoan. Microbial surface textures (i.e., “elephant skin” and Kinneyia-type wrinkles) were mainly observed in heterolithic deposits, usually at the interface between sandstone and siltstone/shale. On the other hand, discs show a facies-independent distribution, observed in heterolithic as well as carbonate and marl deposits. Petrographic analyses of these discs suggest that they have complex origins and some of them may be diagenetic structures. Thus, while facies may have strongly controlled the preservation of MISS-related structures and textures in the Serra de Santa Helena Formation, their abundance and diversity in tidal flat deposits indicate the wide distribution of matgrounds in these shallow marine paleoenvironments. Also, we demonstrate how detailed description and classification of simple features, such as discoidal structures, is an important task for paleoenvironmental reconstruction of marine ecosystems at the Ediacaran–Cambrian transition when the microbially bounded substrates played important roles in the dynamics of coastal environments.

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Section: Geological Backgroundmentioning

confidence: 97%

Section: Implications For the Paleobiological Record Of The Bambuí Basinmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simple Structures and Complex Stories: Potential Microbially Induced Sedimentary Structures in the Ediacaran Serra De Santa Helena Formation, Bambuí Group, Eastern Brazil

Okubo

Inglez

Uhlein

et al. 2023

Palaios

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“…The presence of resistive carbonate and calcareous rocks was inferred from~320 m to~480 m followed by a layer of intercalated shales and sandstones (Solon et al, 2015 [23]). This carbonate layer, which corresponds to the Lagoa do Jacaré carbonate layer, exhibits a potential karst system according to the outcrops located East of the São Francisco Basin (Dos Santos et al, 2018 [57]).…”

Section: Possible Temporary Shallow Zones Of H 2 Accumulationmentioning

confidence: 99%

Migration of Natural Hydrogen from Deep-Seated Sources in the São Francisco Basin, Brazil

et al. 2020

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Hydrogen gas is seeping from the sedimentary basin of São Franciso, Brazil. The seepages of H2 are accompanied by helium, whose isotopes reveal a strong crustal signature. Geophysical data indicates that this intra-cratonic basin is characterized by (i) a relatively high geothermal gradient, (ii) deep faults delineating a horst and graben structure and affecting the entire sedimentary sequence, (iii) archean to paleoproterozoïc basements enriched in radiogenic elements and displaying mafic and ultramafic units, and (iv) a possible karstic reservoir located 400 m below the surface. The high geothermal gradient could be due to a thin lithosphere enriched in radiogenic elements, which can also contribute to a massive radiolysis process of water at depth, releasing a significant amount of H2. Alternatively, ultramafic rocks that may have generated H2 during their serpentinization are also documented in the basement. The seismic profiles show that the faults seen at the surface are deeply rooted in the basement, and can drain deep fluids to shallow depths in a short time scale. The carbonate reservoirs within the Bambuí group which forms the main part of the sedimentary layers, are crossed by the fault system and represent good candidates for temporary H2 accumulation zones. The formation by chemical dissolution of sinkholes located at 400 m depth might explain the presence of sub-circular depressions seen at the surface. These sinkholes might control the migration of gas from temporary storage reservoirs in the upper layer of the Bambuí formation to the surface. The fluxes of H2 escaping out of these structures, which have been recently documented, are discussed in light of the newly developed H2 production model in the Precambrian continental crust.

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“…The presence of resistive carbonate and calcareous rocks was inferred from ~320 m to ~480 m followed by a layer of intercalated shales and sandstones (Solon et al, 2015 [20]). This carbonate layer which corresponds to the Lagoa do Jacaré carbonate layer, exhibits a potential karst system according to the outcrops located East of the São Francisco Basin (Dos Santos et al, 2018 [58]). Assuming a karst system at depth, this could imply a high level of porosity favorable for a massive storage volume of an aquifer.…”

Section: Possible Temporary Shallow Zones Of H2 Accumulationmentioning

confidence: 99%

Migration of Natural Hydrogen from Deep-seated Sources in the São Francisco Basin, Brazil

Donzé¹,

Truche²,

Namin³

et al. 2020

Preprint

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Hydrogen gas is seeping from the sedimentary basin of São Franciso, Brazil. The seepages of H2 are accompanied by helium whose isotopes reveal a strong crustal signature. Geophysical data indicates that this intra-cratonic basin is characterized by i) a relatively high geothermal gradient, ii) deep faults delineating a horst and graben structure and affecting the entire sedimentary sequence, iii) an archean to paleoproterozoïc basements enriched in radiogenic elements and displaying mafic and ultramafic units, and iv) a possible karstic reservoir located 400 m below the surface. The high geothermal gradient could be due to a thin lithosphere enriched in radiogenic elements, which can also contribute to a massive radiolysis process of water at depth, releasing an important amount of H2. Alternatively, ultramafic rocks that may have generated H2 during their serpentinization are also documented in the basement. The seismic profiles show that the faults seen at the surface are deeply rooted in the basement, and can drain deep fluids to shallow depths in a short time scale. The carbonate reservoirs within the Bambuí group which forms the main part of the sedimentary layers are crossed by the fault system and represent good candidates for temporary H2 accumulation zones. The formation by chemical dissolution of sinkholes located at 400 m depth might explain the presence of sub-circular depressions seen at the surface. These sinkholes might control the migration of gas from temporary storage reservoirs in the upper layer of the Bambuí formation to the surface. The very high fluxes of H2 escaping out of these structures which have been recently documented are, however, in disagreement with the newly developed H2 production model in the Precambrian continental crust. They either question the validity of these models or the measurement methodology.

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Morphological and petrographic analysis of newly identified stromatolitic occurrences in the Lagoa do Jacaré Formation, Bambuí Group, State of Minas Gerais, Brazil

Cited by 6 publications

References 36 publications

Simple Structures and Complex Stories: Potential Microbially Induced Sedimentary Structures in the Ediacaran Serra De Santa Helena Formation, Bambuí Group, Eastern Brazil

Simple Structures and Complex Stories: Potential Microbially Induced Sedimentary Structures in the Ediacaran Serra De Santa Helena Formation, Bambuí Group, Eastern Brazil

Migration of Natural Hydrogen from Deep-Seated Sources in the São Francisco Basin, Brazil

Migration of Natural Hydrogen from Deep-seated Sources in the São Francisco Basin, Brazil

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