Terraces, reefs, and valleys along the Brazil northeast outer shelf: deglacial sea-level archives?

Gomes, Moab Praxedes; Vital, Helenice; Droxler, André W.

doi:10.1007/s00367-020-00666-4

Cited by 26 publications

(10 citation statements)

References 103 publications

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“…Finally the southern GoP shelf‐edge reef provides another case study on the edification of transgressive reefs and barrier reefs on a fluvio‐deltaic substrate. Along with other case studies reported from Belize barrier reef (Ferro et al., 1999; Droxler & Jorry, 2013), the Gulf of Mexico (Rezak & Bright, 1976; Belopolsky & Droxler, 1999), the north‐east Brazilian outer shelf (Gomes et al., 2020), the Calabrian continental shelf of Italy (Franchi et al., 2018) and the Gulf of Elat/Aqaba in the Red Sea (Hartman et al., 2015), all of these Quaternary case studies may constitute relevant analogues to interpret geometries and facies heterogeneities in the subsurface. Recently, it has been demonstrated that at least two Miocene palaeodeltas in the South China Sea provided favourable substratum of elevated sand bars for the emergence of transgressive carbonate build ups (Mathew et al., 2020).…”

Section: Discussionsupporting

confidence: 65%

Timescale dependent sedimentary record during the past 130 kyr from a tropical mixed siliciclastic–carbonate shelf edge and slope: Ashmore Trough (southern Gulf of Papua)

et al. 2021

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In tropical and sub-tropical mixed siliciclastic-carbonate depositional systems, fluvial input and in situ neritic carbonate interact over space and time. Despite being the subject of many studies, controls on partitioning of mixed sediments remains controversial. Mixed sedimentary records, from Ashmore Trough shelf edge and slopes (southern Gulf of Papua), are coupled with global sea-level curves and anchored to Marine Isotope Stage stratigraphy to constrain models of sediment accumulation at two different timescales for the past 130 kyr: (i) 100 kyr scale for last glacial cycle; and (ii) millennial scale for last deglaciation. During the last glacial cycle, carbonate production and accumulation were primarily controlled by sea-level fluctuations. Export of neritic carbonate to the slopes was initiated during re-flooding of previously exposed reefs and continued during Marine Isotope Stage 5e and 1 interglacial sea-level highs. Siliciclastic fluxes to the slope were controlled by interplay of sea level, shelf physiography and oceanic currents. Heterogeneous accumulation of siliciclastic mud on the slope, took place during Marine Isotope Stage 5d to Marine Isotope Stage 3 sea-level fall. Siliciclastics reached adjacent depocentres during Marine Isotope Stage 2. Coralgal reef and oolitic-skeletal sand resumed at the shelf edge during the subsequent stepwise sea-level rise of the last deglaciation. Contemporaneous, abrupt

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Section: Discussionsupporting

confidence: 65%

Timescale dependent sedimentary record during the past 130 kyr from a tropical mixed siliciclastic–carbonate shelf edge and slope: Ashmore Trough (southern Gulf of Papua)

et al. 2021

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“…Although the geological composition of these hard substrates was not determined in most of these studies, three articles reported CaCO 3 -cemented sandstones, most likely submerged beachrock, and one described a limestone covered by a well-developed coral assemblage (the Açu reefs), thus confirming the occurrence of biogenic reefs along the SAC (Supplementary Table S1 ). It is important to note that only primary studies are being reported here, and the nature of both the sandstone and limestone formations have been supported by subsequent studies 29 – 31 , 38 , 46 – 49 . Another two studies 32 , 36 mentioned large coral assemblages on unspecified substrates, but only one 32 quantified the benthic cover, reporting a dominance by seaweeds and sponges, with live corals and calcareous algae covering together 9.2% of the substrate.…”

Section: Resultsmentioning

confidence: 73%

“…Such flat seascapes are not typical of reef environments, which, by definition, have three-dimensional profiles. Nevertheless, ROV data is localized, and sandy and rocky flats are a known feature of reefs along the SAC 32 , 38 , 46 . In fact many formations along the ARS 8 , 10 and ERS 64 are flat and largely covered by marine sediment.…”

Section: Discussionmentioning

confidence: 99%

“…Biological and geological characterizations of these substrates are only beginning, but many sustain a diverse reef-associated biota (i.e., reef fishes and epilithic benthos), which play an important role in the economy and ecology of the region 32 , 35 – 37 . Furthermore, there are similarities between the SAC hard substrates and the biogenic reefs from the ARS and ERS 2 , 33 , 34 , 38 .…”

Section: Introductionmentioning

confidence: 95%

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Interconnected marine habitats form a single continental-scale reef system in South America

Carneiro¹,

Neto

Jucá-Queiroz

et al. 2022

Sci Rep

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Large gaps in reef distribution may hinder the dispersal of marine organisms, interrupting processes vital to the maintenance of biodiversity. Here we show the presence and location of extensive reef habitats on the continental shelf between the Amazon Reef System (ARS) and the Eastern Brazilian Reef System (ERS), two reef complexes off eastern South America. Formations located 20–50 m deep include both biogenic and geogenic structures. The presence of diverse reef assemblages suggests the widespread occurrence of rocky substrates below 50 m. These habitats represent an expansion of both the ARS and ERS and the closure of the only remaining large-scale gap (~ 1000 km) among West Atlantic reef environments. This indicates that the SW Atlantic harbors a single, yet heterogeneous, reef system that stretches for about 4000 km, and thus, represents one of the largest semi-continuous tropical marine ecosystems in the world.

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“…Although the cement may be contaminated by carbonate particles other than the calcite cement, the use of radiocarbon 14 C is still the most appropriate method for dating beachrocks. Various calcareous cement dates have already been undertaken for Holocene beachrocks, and used to reconstitute sea level changes (Ramsay and Cooper 2002;Desruelles et al 2009).…”

Section: Materials Methodsmentioning

confidence: 99%

Beachrocks of the last low sea level, substrate of the barrier reef system along the outer Guiana shelf

Giresse

Loncke

Heuret

et al. 2022

Preprint

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The Great Amazon Reef System is a living biogenic mesophotic reef ecosystem that has been recently described along the shelf break of Brazil. An exploration mission was carried out in 2019 along the outer edge of the French Guiana Shelf. A side-scan sonar survey was conducted to locate reef outcrops and allowed twelve in situ 80 to 120 m depth dives and sampling of the reef rocks and peripheral sands. The majority of the hard-rocks are composed of biological concretions. However several fragments revealed the inside presence of sandstone clasts. These clasts, more or less enveloped by biogenic coatings, probably represent destroyed clasts of underlying or neighboring beachrock banks. Their dominant cement is micritic (high-magnesian calcite); the intergranular or extragranular porous field was later filled with low-magnesian sparry calcite. The sand or gravel that accumulated near the barrier mainly consist of the blunt debris of coastal fauna and flora associated with different carbonate or ferruginous neoformed ooids. At 104 m depth, ooids extracted from Dive 11 samples dated from the start of MIS2 (27,370 cal yr BP) and attest to the presence of a significant coastal accumulation. At this same site, cementing did not take place until about 3,500 years later (23,990 cal yr BP). The cement of a nearby beachrock indicates a much more recent age (16,170 cal yr BP). Lastly, the age of 4,100 year BP measured on the barnacles attached to the top of the reef attests to the late Holocene reef's biological activity.

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Terraces, reefs, and valleys along the Brazil northeast outer shelf: deglacial sea-level archives?

Cited by 26 publications

References 103 publications

Timescale dependent sedimentary record during the past 130 kyr from a tropical mixed siliciclastic–carbonate shelf edge and slope: Ashmore Trough (southern Gulf of Papua)

Timescale dependent sedimentary record during the past 130 kyr from a tropical mixed siliciclastic–carbonate shelf edge and slope: Ashmore Trough (southern Gulf of Papua)

Interconnected marine habitats form a single continental-scale reef system in South America

Beachrocks of the last low sea level, substrate of the barrier reef system along the outer Guiana shelf

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