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<p>Inherited topographies on drowned shelves post-Last Glacial Maximum (LGM) play a key role in sedimentary processes because submerged landforms create specific geomorphic habitats. This study aims to analyze the sedimentary patterns related to shallow (&lt; 30&#xa0;m) and mesophotic (30–40&#xa0;m) habitats, focusing on the geomorphic changes of the Coreaú incised valley in northeastern Brazil. The analysis is based on bathymetric, side-scan sonar, satellite images, remotely operated vehicle (ROV), and sedimentological data. Additionally, we correlate the influence of post-LGM shelf flooding with global sea-level variation curves. The Coreaú incised valley exhibits inherited morphologies categorized into three main geomorphic habitats: channelized features (incisions, walls, and troughs), paleointerfluves, and margins. Consequently, the identified sedimentary patterns are distributed in response to these geomorphic habitats. Carbonate sedimentation is predominant, characterized by poorly sorted deposits mainly composed of sand and mud fractions. Major grain components include mollusks, foraminifera, calcareous algae, and quartz. The deepest geomorphic habitats (e.g., troughs) contain higher concentrations of mud, iron element, organic matter, and molluscan grains, following the channelized morphology (axis of the valley bottom). In contrast, the valley margins exhibit coarser sediment (e.g., gravel), higher calcium content, lower organic matter, and a greater presence of calcareous algae. An increase in CaCO<sub>3</sub> content basinward was also observed. Bedform patterns identified through side-scan sonar data highlight the presence of dunes and ripples in the shallowest geomorphic habitats (e.g., paleointerfluves and margins) while plane beds associated with fine sediments were found in the troughs. Additionally, the abundant muddy carbonate sediments along the channelized valley floor (habitat rich in mollusks) appears to be influenced by seasonal along-shelf suspension transport on this siliciclastic-poor shelf. Thus, the control exerted by submerged fluvial landforms on the establishment of shallow-to-mesophotic habitats in response to shelf drowning during marine isotope stage (MIS) 1 is evident, particularly after Meltwater Pulse 1C (MWP-1C).</p>

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Shallow-to-mesophotic geomorphic habitats influenced by a drowned incised valley in the Western Equatorial Atlantic

  • 期刊论文

  • 发表日期：

    2025年9月12日

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  • Antonio Rodrigues Ximenes Neto,
  • Lidriana de Souza Pinheiro,
  • Regimário Pereira Lima Filho,
  • David Hélio Miranda de Medeiros,
  • Carlos de Araújo Farrapeira Neto,
  • Marcelo Oliveira Soares,
  • Sérgio Rossi,
  • Jáder Onofre de Morais

摘要

Inherited topographies on drowned shelves post-Last Glacial Maximum (LGM) play a key role in sedimentary processes because submerged landforms create specific geomorphic habitats. This study aims to analyze the sedimentary patterns related to shallow (< 30 m) and mesophotic (30–40 m) habitats, focusing on the geomorphic changes of the Coreaú incised valley in northeastern Brazil. The analysis is based on bathymetric, side-scan sonar, satellite images, remotely operated vehicle (ROV), and sedimentological data. Additionally, we correlate the influence of post-LGM shelf flooding with global sea-level variation curves. The Coreaú incised valley exhibits inherited morphologies categorized into three main geomorphic habitats: channelized features (incisions, walls, and troughs), paleointerfluves, and margins. Consequently, the identified sedimentary patterns are distributed in response to these geomorphic habitats. Carbonate sedimentation is predominant, characterized by poorly sorted deposits mainly composed of sand and mud fractions. Major grain components include mollusks, foraminifera, calcareous algae, and quartz. The deepest geomorphic habitats (e.g., troughs) contain higher concentrations of mud, iron element, organic matter, and molluscan grains, following the channelized morphology (axis of the valley bottom). In contrast, the valley margins exhibit coarser sediment (e.g., gravel), higher calcium content, lower organic matter, and a greater presence of calcareous algae. An increase in CaCO3 content basinward was also observed. Bedform patterns identified through side-scan sonar data highlight the presence of dunes and ripples in the shallowest geomorphic habitats (e.g., paleointerfluves and margins) while plane beds associated with fine sediments were found in the troughs. Additionally, the abundant muddy carbonate sediments along the channelized valley floor (habitat rich in mollusks) appears to be influenced by seasonal along-shelf suspension transport on this siliciclastic-poor shelf. Thus, the control exerted by submerged fluvial landforms on the establishment of shallow-to-mesophotic habitats in response to shelf drowning during marine isotope stage (MIS) 1 is evident, particularly after Meltwater Pulse 1C (MWP-1C).