Abstract
In areas of the continental shelf where sediment supply is greater than the sediment dispersion capacity, an extensive terrigenous deposits and consequently submerged deltas can be formed. The Eastern Brazilian shelf is characterized by the occurrence of river feed deltas in between starving coasts. Herein, modern sedimentary processes acting along the Doce river adjacent continental shelf are investigated. The main objective was to understand the shelf sediment distribution, recognizing distinct sedimentary patterns and the major influence of river sediment discharge in the formation of shelf deposits. The study used 98 surficial samples that were analyzed for grain size, composition and bulk density. Results revealed 3 distinct sectors: south - dominated by mud fraction with a recent deposition from riverine input until 30 m deep and from this depth bioclastic sands dominate; central north - sand mud dominated, been recognized as a bypass zone of resuspended sediment during high energy events; and north - relict sands with high carbonate content. The modern sedimentation processes along the Doce river continental shelf is dominated by distinct sedimentary regimes, showing a strong fluvial influence associated with wave/wind induced sediment dispersion and a carbonate regime along the outer shelf. These regimes seem to be controlled by the distance from the river mouth and bathymetric gradients.
Highlights
Modern shelf morphology and sediment distribution is strongly influenced by processes acting in different time scales
Three sectors were recognized based upon distinct sed‐ iment characteristics along the Doce River Inner Shelf (DRIS): south ‐ from the Doce river mouth to the southern boundary of the study area; central‐north ‐ on the stretch from the Doce river mouth up to 25 km northward; and north ‐ extending for approximately 28 km from the central‐north sector limit (Fig. 2)
The results revealed that the continental shelf adjacent to the Doce river mouth presents different sedimentary patterns in terms of both depth and distance from the coast
Summary
Modern shelf morphology and sediment distribution is strongly influenced by processes acting in different time scales. In low‐latitude regions, biogenic carbonate sedimenta‐ tion dominates, but, in some cases, terrigenous sediment supply may supplant this regime, leading to differentia‐ tion in the sedimentation pattern (Nittrouer et al 2007). These situations are common in areas where fluvial pro‐ cesses control the sediment supply to the shelf. In areas where sediment supply is greater than sediment dispersion capacity, extensive terrigenous deposits and submerged deltas can be formed. Episodic events, such as heavy flooding, may lead to an uneven supply. In addition to river supply control, the sedimentary pat‐ tern can still be influenced by the coastal dynamics itself (Nitrouer et al 2007)
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