Two research cruises were conducted by CNR (formerly Institute of Marine Geology, now ISMAR, Bologna) in 1979 (R/V Salernum) and 1983 (R/V Bannock), in the Red Sea transitional region, between 22.5N and 24.5N. These cruises gave insights into four closely spaced deeps (from south to north: Thetis, Nereus, Bannock and Vema) that seem to be younger and less evolved from south to north. From these observations, it was proposed that transition from a continental to an oceanic rift occurs in the Red Sea by initial emplacement of oceanic crust in regularly spaced cells or deeps, which serve as nuclei for axial propagation into segments of oceanic crust accretion and for initiation of seafloor spreading [Bonatti (1985)]. This segmentation could be derived either from regularly spaced diapirs of upwelling astenosphere [Bonatti (1985)], or from an initial structural segmentation of the rift in the continental stage, with transfer zones probably exploiting pre-existing structural discontinuities as observed in East African Rift [Rosendahl (1987)] and in the Gulf of Suez [Younes and McClay (2002),Khalil and McClay (2002)]. The northward propagation of the oceanization seems to end at the intersection with a major fracture zone (Zabargad Fracture Zone [Bonatti et al.(1984)], striking almost N-S and offsetting the axial valley in the Red Sea. The island of Zabargad, an uplifted block of sub-Red Sea lithosphere, lies along this important structure [Bonatti et al.(1981),Bonatti et al.(1984)]. It is hypothesized that the Zabargad Fracture Zone is a 'prototransform' that, if the Red Sea would continue its opening trend, might develop into an 'initial' major oceanic transform, similar to those offsetting today the equatorial Mid Atlantic Ridge.
The above cited 'Deeps' of the Red Sea, other than being peculiar geological structures reflecting and providing insights into the tectonic processes, present bottom water stratification with brines that are warmer, saltier, acidic and nearly saturated with respect to NaCl and highly enriched over normal RSDW composition. Moreover, they are strictly anaerobe and Fe and Mn oxides are precipitated above the chemocline of metal-rich brines [Schmidt et al.(2003)].
The salty brines are mainly formed by seawater dissolving Miocene evaporites which build up to several kilometers thick deposits under the normal pelagic/terrigeneous sediments. They are separated from normal RSDW by several meters thick interfaces, and transport across the brine-seawater interface is mainly controlled by diffusion [Anschutz and Blanc (1996),Schmidt et al.(2003)].
High gas concentrations (CO
, hydrocarbons) were determined in the
brines reaching saturation conditions in the Kebrit Deep brine [Faber (1998)].
Stable carbon and hydrogen isotope analyses of dissolved
hydrocarbons in Red Sea water and brines clearly indicated a thermogenic
origin of the gases due to locally high heat flows and the presence of
sedimentary organic matter in the subsurface of the Red Sea deeps [Faber (1998)].
The brine/seawater interface, however, represents a zone of
complex biogeochemical reactions causing highly effective methane oxidation
(indicated by strong secondary isotope fractionation of residual methane
having most positive 
C values up to +47 % PDB; [Faber (1998)]) while
methane is diffusing upwards from the brine into Red Sea bottom water.
There is geochemical evidence that the biogeochemical methane oxidation
process which increases brine-seawater methane fluxes most likely are
combined with a reduction of Mn-oxides/ hydroxides [Schmidt et al.(2003)].
The Red Sea water is controlled by high evaporation rates, low rainfall and low runoff waters from wadis (seasonal streams), which yields to an average salinity of 40.5 PSU and temperatures ranging between 23-32°C in surface waters. Strong currents and atmospheric pressure gradients control the influx of less saline and colder water from the Gulf of Aden through the Strait of Bab al Mandeb during winter. The north-heading current mixes with a south-heading wind-driven surface current from the northern Red Sea. A thermocline at a water depth of about 200-400m separates the mixing water zone from Red Sea Deep Water at relatively stable temperature and salinity conditions. The nutrient distribution in the Red Sea is not well known and surface waters are generally depleted in nutrients [Ross (1983)]. As waters from the Gulf of Aden are also depleted in nutrients a possible scenario of nutrient supply in winter is the turbulent mixing of the above described currents and an uplift of nutrient-enriched deeper waters. The maximum turbulent mixing zone is probably in the central Red Sea.