NUMERICAL-STUDIES OF BOTTOM SHEAR-STRESS AND SEDIMENT DISTRIBUTION ONTHE AMAZON CONTINENTAL-SHELF

Citation
Pw. Jewell et al., NUMERICAL-STUDIES OF BOTTOM SHEAR-STRESS AND SEDIMENT DISTRIBUTION ONTHE AMAZON CONTINENTAL-SHELF, Journal of sedimentary petrology, 63(6), 1993, pp. 734-745
Citations number
57
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geology
Journal title
ISSN journal
0022-4472
Volume
63
Issue
6
Year of publication
1993
Supplement
S
Pages
734 - 745
Database
ISI
SICI code
0022-4472(1993)63:6<734:NOBSAS>2.0.ZU;2-B
Abstract
The relation between bottom shear stress and the distribution of botto m sediments on the Amazon continental shelf has been studied using a t hree-dimensional, primitive-equation computer model that incorporates the turbulence-closure scheme of Mellor and Yamada (1982) for calculat ing eddy diffusivity and a simple algorithm for computing nonlinear wa ve-current influences on bottom shear stress. Model results compare re asonably well with salinity data sets for the Amazon plume. Model resu lts on distribution of bottom currents and bottom shear stresses help explain some of the observed sedimentological features of the Amazon c ontinental shelf. High concentrations of suspended sediment in the Ama zon River are transported outward over the continental shelf and north ward by the North Brazil Coastal Current. As this sediment settles out of the water column, it forms the prograding, subaqueous delta descri bed by Nittrouer et al. (1986). Accumulation rates are greatest shorew ard of the 40-m isobath due to a zone of convergent, cross-shelf resid ual tidal velocities. Little sediment is deposited in the shallow part s of the shelf, where bottom shear stress exceeds 10 dynes/cm2 over a diurnal tidal cycle. Zones of laminated sand and mud on the Amazon con tinental shelf coincide with areas of high interseasonal differences i n bottom shear stress. Our results suggest that our model may be usefu l in interpreting sedimentation in ancient sedimentary basins as well.