Modern Shelf Sedimentation Along the Apennine Coast, Adriatic Sea
Abstract
Sediment supply to the Adriatic Sea is dominated by the Po and Apennine Rivers in the northern and southern regions, respectively. The Po River is the largest point source of sediment, delivering 1.5x107 tons annually to the adjacent shelf. Investigations into the pattern of 100-y sediment accumulation using 210Pb (half-life 22.3 y) have revealed that accumulation rates are greatest in the northern portion of the dispersal system, near the Pila distributary ( ∼2 cm/y), and decreases southward toward the Apennine coast. In contrast to the Po, sedimentation in the southern region results from a series of small, distributed fluvial sources (i.e., a line source), draining the Apennine mountains. These rivers deliver approximately 2.4x107 t/y of sediment, contributing to the development of a shore-parallel shelf clinoform that has formed throughout the Holocene. Across-shelf sediment accumulation rates on the clinoform are greatest on the foreset ( ∼1 cm/y), which is characterized by the presence of seafloor crenulations in some areas. Along-shelf accumulation rates show some variability with proximity to major rivers, but a general increase is observed southward along the margin and rates are greatest near the Gargano Peninsula ( ∼1.5 cm/y). This trend differs from other line-source systems. Distinct depocenters are associated with individual fluvial sources in the Gulf of Alaska, and river inputs coalesce into a central locus of sedimentation in the Gulf of Papua. The differences among these systems lend further insight into the mechanisms controlling deposits emanating from line-source systems. Anthropogenic activities, particularly dam construction following WWII, have significantly impacted sedimentation in this region. Sediment accumulation along the Apennine region has been reduced, evidenced by changes in 210Pb profiles. However, observations during winter 2002-2003 using the short-lived radioisotopes 7Be and 234Th (half-life 53.3 d and 24.1 d, respectively) have indicated that some new sediment is delivered to the shelf during periods of elevated discharge.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2004
- Bibcode:
- 2004AGUFMOS11D..05P
- Keywords:
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- 4243 Marginal and semienclosed seas;
- 3022 Marine sediments: processes and transport