A
palynofacies
analysis
was
carried
out
on
thirty
ditch-cuttings
from
the
Upper
Cretaceous
sequences
drilled
by
the
Salam-60
well
in
the
Shushan
Basin, north-western Egypt. Quantitative vertical distributions of palynomorphs and particulate organic matter exhibit two palynofacies (PF) types.
PF-1 suggests deposition of the clastic-carbonate section of upper Bahariya and the lowermost “G” Member of Abu Roash in a brackish, proximal
inner shelf environment of prevailing reducing (suboxic-anoxic) conditions that witnessed occasional local oxic-dysoxic conditions. A slight shift
from
a
proximal
to
a
distal
inner
shelf
environment
that
witnessed
notable
fluctuations
resulted
in
deposition
of
the
mainly
carbonate
section
of
the
uppermost “G” and “F” to “C” members, during a late Cenomanian-Turonian marine transgression, under the same suboxic-anoxic conditions. This
relative sea level rise was mostly connected to the global late Cenomanian marine transgression. PF-2 represents the rest of the carbonate section
(“B” and “A” members) of Abu Roash and Khoman formations, which was deposited in middle shelf environments of prominent suboxic-anoxic
conditions during a major regional marine transgression that was mostly connected to the global Turonian-Maastrichtian eustatic sea level rise.
Nevertheless, minor fluctuations in the local Turonian sea level may have occurred. Regional comparison indicates Bahariya and the “G” Member
of Abu Roash formations have similar marginal to inner shelf depositional settings across most of the northern Western Desert. Except at western
Matruh Basin, where they have a deeper open marine, middle shelf setting. The “F” to “C” members have an outer inner shelf setting in the coastal
basins (Shushan and Matruh basins) and a deeper, inner middle shelf setting at the central basinal area (Abu Gharadig Basin). This interbasinal
difference in their depositional settings is mostly related to the late Cretaceous tectonic differentiation of Abu Gharadig Basin. The “B” and “A”
members of Abu Roash and Khoman formations were deposited in central Abu Gharadig and at southern Matruh basins in deeper, outer shelf and
upper to middle slope settings in comparison to their suggested inner middle and outer middle shelf settings in Shushan Basin. This was due to
the progressive late Cretaceous tectonic development of Abu Gharadig and Matruh basins. Local pteridophytes on wet lowlands and conifers on
elevated hinterlands were growing near Salam-60 under a regional warm and relatively dry palaeoclimate.
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