302
C. G. ST. C. Kendall· A. Sen
from 15.5 to 13.8 Ma; from 13.8 to 12.5 Ma; from 12.5 to lO.5 Ma; from lO.5 to 6.2
Ma; from 6.2 to 5.5 Ma; from 5.5 to 3.8 Ma; and from 3.8 to the present day. It can
be seen on the seismic that the geometries associated with each sea level event
match the simulation with remarkable resolution (Fig. 6).
The illustrations in Fig. 6 track the geometry and timing of the evolving sedimentary fill of the Neogene sedimentary fill of the West Andros channel.
30-28.5 Ma. The geometry of this sequence was the product of the low subsidence rates of 0.09 m/ka and high rates of shallow water benthic carbonate accumulation. The initial rise in sea level on the Haq et.al. (1987) chart at this
time caused aggradation on and onlap across the shelf margin which was followed by progradation during a sea -level fall. At this time the accommodation
was reduced, and the shallower water depths caused faster accumulation
rates.
28.5-25.5 Ma. The low subsidence rate, as well as the carbonate accumulation
rate, were maintained. Aggradation and progradation matched the sequence associated with the time interval 30-28.5 Ma on the seismic interpretation. The accommodation produced by this sea-level event was reduced, since the sea level
was unable to rise far across the shelf margin.
25.5-22.5 Ma. A larger rise in the sea level at the beginning of this interval caused
carbonate aggradation. The subsidence and carbonate accumulation rates (both
benthic and pelagic) matched those of the previous interval. The extensive carbonate on lap of the shelf was driven by a sea-level rise.
22.5-21 Ma. The same rates for subsidence and carbonate accumulation rates
were maintained. The sea level shows a slight fall at the end of this period, thus
producing a little progradation of the carbonate margin. The ramps produced
are steeper than those we have on the seismic, but the amount of progradation
was the same.
21-17.5 Ma. The same rates for subsidence and benthic carbonate depositional
rates were maintained. The sea level slowly rose and both progradation and
aggradation took place. A wide lowstand wedge was produced, because the sea
level did not rise sufficiently to onlap the shelf and enable sediment to accumulate here.
17.5-16.5 Ma. The initial half of this sequence was marked by a sharp increase in
sea level followed by a sharp decrease in the later half. As a result, the simulation
shows an aggradation and onlap of the shelf followed by progradation. The same
rates for subsidence was maintained. The deep water benthic carbonate rate remained the same, but the shallow water rate started to decline. The basin was too
deep for much progradation to take place, and this also produced a steeper
ramp.
C. G. ST. C. Kendall· A. Sen
from 15.5 to 13.8 Ma; from 13.8 to 12.5 Ma; from 12.5 to lO.5 Ma; from lO.5 to 6.2
Ma; from 6.2 to 5.5 Ma; from 5.5 to 3.8 Ma; and from 3.8 to the present day. It can
be seen on the seismic that the geometries associated with each sea level event
match the simulation with remarkable resolution (Fig. 6).
The illustrations in Fig. 6 track the geometry and timing of the evolving sedimentary fill of the Neogene sedimentary fill of the West Andros channel.
30-28.5 Ma. The geometry of this sequence was the product of the low subsidence rates of 0.09 m/ka and high rates of shallow water benthic carbonate accumulation. The initial rise in sea level on the Haq et.al. (1987) chart at this
time caused aggradation on and onlap across the shelf margin which was followed by progradation during a sea -level fall. At this time the accommodation
was reduced, and the shallower water depths caused faster accumulation
rates.
28.5-25.5 Ma. The low subsidence rate, as well as the carbonate accumulation
rate, were maintained. Aggradation and progradation matched the sequence associated with the time interval 30-28.5 Ma on the seismic interpretation. The accommodation produced by this sea-level event was reduced, since the sea level
was unable to rise far across the shelf margin.
25.5-22.5 Ma. A larger rise in the sea level at the beginning of this interval caused
carbonate aggradation. The subsidence and carbonate accumulation rates (both
benthic and pelagic) matched those of the previous interval. The extensive carbonate on lap of the shelf was driven by a sea-level rise.
22.5-21 Ma. The same rates for subsidence and carbonate accumulation rates
were maintained. The sea level shows a slight fall at the end of this period, thus
producing a little progradation of the carbonate margin. The ramps produced
are steeper than those we have on the seismic, but the amount of progradation
was the same.
21-17.5 Ma. The same rates for subsidence and benthic carbonate depositional
rates were maintained. The sea level slowly rose and both progradation and
aggradation took place. A wide lowstand wedge was produced, because the sea
level did not rise sufficiently to onlap the shelf and enable sediment to accumulate here.
17.5-16.5 Ma. The initial half of this sequence was marked by a sharp increase in
sea level followed by a sharp decrease in the later half. As a result, the simulation
shows an aggradation and onlap of the shelf followed by progradation. The same
rates for subsidence was maintained. The deep water benthic carbonate rate remained the same, but the shallow water rate started to decline. The basin was too
deep for much progradation to take place, and this also produced a steeper
ramp.