4.4 Summary (Adjacent Seas)
4.4
Summary (Adjacent Seas)
The water circulation systems, salinities, and
redox conditions of adjacent seas connected with
the open ocean largely vary with time and from
basin to basin. These properties are mainly
controlled by the inflow of river water and the
dimension of their opening to a neighboring
ocean.
Estuarine circulation with predominating surface
outflow favors the accumulation of black shales
(Black Sea, Gulf of Califomia, Baltic Sea). Antiestuarine circulation with strong subsurface inflow
produces well-oxygenated bottom water and the
tendency for increased salinity in shallow parts of
the "arid" basin (Red Sea, Persian Gulf).
181
Shallow and narrow sills generate either brackish
or hypersaline basins; this effect is reinforced by
relative sea-Ievel fall or closure of gateways,
transforming adjacent seas into lakes or evaporite
basins.
These general rules, however, are modified by other
factors controlling basin evolution and sediments.
Distinct, but weaker effects on sedimentary
characteristics are also observed in marginal ocean
basins with horizontally separated inflow and
outflow (e.g. Caribbean Sea, northem North
Atlantic).